About this Journal Submit a Manuscript Table of Contents
Journal of Obesity
Volume 2011 (2011), Article ID 168659, 17 pages
http://dx.doi.org/10.1155/2011/168659
Review Article

Variations in Adipokine Genes AdipoQ, Lep, and LepR are Associated with Risk for Obesity-Related Metabolic Disease: The Modulatory Role of Gene-Nutrient Interactions

1Department of Physiology, University of Manitoba and Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, 351 Tache Ave, Winnipeg, Manitoba, R2H 2A6, Canada
2Departments of Human Nutritional Sciences and Physiology, University of Manitoba, 351 Tache Ave, Winnipeg, Manitoba, R2H 2A6, Canada
3Departments of Physiology and Human Nutritional Sciences, University of Manitoba and Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, 351 Tache Ave, Winnipeg, Manitoba, R2H 2A6, Canada

Received 9 January 2011; Accepted 10 March 2011

Academic Editor: P. Trayhurn

Copyright © 2011 Jennifer Emily Enns et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Obesity rates are rapidly increasing worldwide and facilitate the development of many related disease states, such as cardiovascular disease, the metabolic syndrome, type 2 diabetes mellitus, and various types of cancer. Variation in metabolically important genes can have a great impact on a population's susceptibility to becoming obese and/or developing related complications. The adipokines adiponectin and leptin, as well as the leptin receptor, are major players in the regulation of body energy homeostasis and fat storage. This paper summarizes the findings of single nucleotide polymorphisms in these three genes and their effect on obesity and metabolic disease risk. Additionally, studies of gene-nutrient interactions involving adiponectin, leptin, and the leptin receptor are highlighted to emphasize the critical role of diet in susceptible populations.

1. Introduction

Obesity is the result of an imbalance in energy homeostasis and is characterized by increased adipose tissue mass, chronic low-grade inflammation, insulin resistance, and endothelial dysfunction. Obesity is a major risk factor for type 2 diabetes mellitus (T2DM), cardiovascular disease (CVD), and several types of cancer [13], and lies at the core of a cluster of metabolic abnormalities defined as the metabolic syndrome, which includes insulin resistance and hyperinsulinemia, hypertension, impaired glucose tolerance, and T2DM [4]. According to the National Health and Nutrition Examination Survey (NHANES), 33.8% of American adults are obese (BMI ≥ 30) and 68.0% are considered overweight or obese (BMI ≥ 25) [5]. Dietary choices (and overeating) in combination with low physical activity are typically attributed as the root cause of the rapid spread of the obesity epidemic in the modern world [6], but genetic factors are a strong determinant of individual susceptibility to obesity. The growing prevalence of obesity and obesity-related pathologies has spurred the search for greater insight into the mechanisms that contribute to the development of obesity and its complications.

Adipose tissue plays multiple important roles in body weight regulation and energy homeostasis. Adipose functions as an energy storage organ, storing fat primarily in the form of triglycerides and releasing free fatty acids as the body’s energy demands change. Adipose tissue is also an active endocrine organ, secreting many cytokines, chemokines, and hormone-like factors. These molecules, which are produced and secreted primarily by adipocytes, are known as adipokines [7]. Adipokines constitute a diverse group of bioactive peptides with many and varied roles, including mediation of glucose and lipid metabolism, blood pressure regulation, and modulation of inflammation and immune function [8]. While over 100 adipokines have been identified [9], the specific functions of many of these molecules are poorly understood. Regardless, it has been clearly established that in obesity, adipocytes undergo hypertrophy and become dysfunctional [10, 11]. As a result, the adipokine profile they express and secrete is altered, leading to a proinflammatory environment both locally and systemically, and contributing to the pathological effects of obesity.

Since many critical metabolic functions are influenced by adipokines, genetic variations that affect their efficacy may contribute to various pathophysiological states. For instance, genetic variation in adipokine genes has been shown to modulate circulating adipokine levels and thus could predispose carriers of single nucleotide polymorphisms (SNPs) to developing obesity or other metabolic illnesses in which adipokines play a prominent role, or alternatively, provide them some protection against disease. Studying the impact of such gene polymorphisms in human populations can provide insight into the roles specific adipokines play in obesity and related pathologies. This paper will discuss the association of SNPs in the protein-coding genes for two well-studied adipokines, adiponectin and leptin, as well as the leptin receptor, in the context of obesity-related metabolic disease. In addition, due to the profound effect that diet can have on weight gain and regulation, the recent literature on nutrient-gene interaction studies involving adipokines and dietary factors will be highlighted.

2. Methods

Articles for this review were identified using the PubMed/Medline databases. Search terms included “single gene polymorphism”, “gene variant”, “adiponectin”, “AdipoQ”, “leptin”, “leptin receptor”, and “obesity” or “metabolic disease”. An emphasis was placed on studies published in the last decade, but the search was not limited to a specific time interval. The articles were chosen by scanning the abstract to ensure relevancy. Only studies in human populations and in English were included.

3. Adiponectin

Adiponectin is an important anti-inflammatory and insulin-sensitizing hormone and promotes lipid oxidation in tissues such as skeletal muscle and liver [12, 13]. Adiponectin also has direct antiatherosclerotic properties, as it strongly inhibits expression of adhesion molecules and growth factors [14]. Adiponectin serum levels are inversely correlated with body fat percentage in obese subjects, as well as in those afflicted with T2DM or coronary heart disease [15, 16]. Due to the protective nature of adiponectin in many types of cardiovascular and metabolic disease states, low serum levels of this adipokine are thought to contribute to the pathogenesis of these conditions. Several excellent reviews on the various roles of adiponectin are available [1720]. The adiponectin gene AdipoQ has been identified as a susceptibility locus for the metabolic syndrome, T2DM and CVD [21, 22]. AdipoQ is located on chromosome 3q27. The gene is 15.8 kb long and contains three exons.

3.1. Adiponectin Levels and Obesity-Related Metabolic Disease Parameters

It is estimated that a 30–70% variation in normal circulating adiponectin levels can be attributed to genetic factors [2329]. A total of 42 SNPs in AdipoQ and its regulatory region with a minor allele frequency of >1.5% have been identified [30]. Table 1 lists AdipoQ SNPs studied in the last decade and their relation (if any) to adiponectin levels and other obesity-related metabolic disease parameters. Since changes in adiponectin due to genetic variation are of particular interest in this paper, the table highlights the percent change in adiponectin levels in those studies that reported this parameter. Four SNPs (−11391 G > A, −11377 C > G, +45 T > G and +276 G > T) were analyzed with far greater frequency than any others and will be the focus of the following discussion.

tab1
Table 1: SNPs in the adiponectin gene AdipoQ.

The majority of studies analyzing the SNP −11391 G > A found a favourable increase in circulating adiponectin levels in those subjects carrying the A allele. A recent meta-analysis determined that SNP −11391 G>A was associated with adiponectin levels according to a dominant model with A allele carriers (GA and AA genotypes) having higher adiponectin levels compared with GG carriers [29]. An in vitro study supports these data, reporting a biological function of this SNP with the A allele enhancing AdipoQ promoter activity [31]. Despite the prevalence of the high adiponectin finding, most studies did not report any association with improved health in their subjects. Only one study, an analysis of a Caucasian population from Italy, showed a decrease in obesity-related risk factors (BMI, weight, and waist and hip circumference) [32]. Three studies had conflicting findings. In a study of European children carrying the A allele, adiponectin levels were found to be higher, similar to the situation in adults; however, the SNP showed an obesity-mediated detrimental association with fasting serum insulin and HOMA-IR [33]. A second study involving obese and morbidly obese French Caucasians found the SNP to be associated with lower adiponectin levels, but similarly accompanied by lower insulin sensitivity and a higher risk of T2DM [32]. In a third study, there was also an association between the GA genotype and risk of hyperglycemia in a population of French Caucasians [34]. While it is clear that most carriers of the A allele have raised adiponectin levels and could expect to be protected from metabolic disease, in certain populations the increase in adiponectin observed in GA and AA carriers appears to be too small to impart any appreciable metabolic advantage, where it fails to counterbalance the metabolic damages of obesity. In fact, it may contribute to the increased risk for childhood obesity and related insulin resistance.

The findings on the −11377 G > C SNP are inconsistent, but the general trend links the G allele to various detrimental conditions, including lower adiponectin levels [23, 42, 43, 45, 48], risk for developing hypertension [43], and, in some cases, risk for developing colorectal cancer [46]. On the other hand, the presence of the C allele has also been associated with higher BMI and obesity risk [31, 36], increased fasting glucose levels and T2DM risk [35, 42]. For example, a study that investigated genetic variations in adiponectin in individuals with metabolic syndrome found that SNP −11377 G > C was a determinant of HOMA-IR, where CC homozygotes had significantly lower HOMA-IR scores [77]. There is evidence that the presence of the minor G allele decreases the affinity of the transcription factor Sp1 to its binding site within the AdipoQ promoter [78], and a recent study showed that this allele had altered DNA-binding activity, leading to lower basal and inducible AdipoQ promoter activity in mouse 3T3-L1 adipocytes [79]. The mechanism by which the C allele might contribute to disease remains unclear.

The silent +45 T > G SNP is strongly associated with detrimental health effects including lower adiponectin levels [55, 57], higher BMI and lower insulin sensitivity [34, 55], higher risk for developing hyperglycemia and T2DM [34, 52, 53, 56, 57, 62], and higher levels of blood lipids (triglycerides, LDL cholesterol, and total cholesterol) [55, 57]. In contrast, the T allele generally appeared to afford the carrier some protection, being associated with higher adiponectin levels [53] and lower body weight [55, 63]. A few studies obtained results that differed, and some found no significant associations with these parameters at all; however, the overall trends remained apparent even across such diverse populations as Iranians, Japanese, and European Caucasians [34, 52, 56]. The mechanisms by which these genetic variations exert effects on adiponectin levels and metabolic disease parameters have not been fully elucidated. Yang et al. [80] showed that the silent +45 T > G mutation may alter RNA splicing or stability, suggesting an allele-specific differential expression of adiponectin. It is thus possible that SNPs with no apparent biological significance may have an effect on gene expression, although in this case it is likely that SNP +45 is in linkage disequilibrium with some other functional genetic alterations, resulting in the difference in mRNA expression of its two alleles. Other research has indicated that the +45 T > G SNP is in linkage disequilibrium with the +276 G > T SNP and that the haplotype defined by the two together is strongly associated with many components of the metabolic syndrome [61, 62, 81].

The G allele of the +276 G > T SNP is primarily associated with lower insulin sensitivity and increased T2DM risk, lower adiponectin levels, and increased blood lipids. Conversely, many carriers of the T allele have higher adiponectin levels and a lower BMI. Two notable exceptions to this trend are the studies authored by Beebe-Dimmer et al. [67] and Bouatia-Naji et al. [31], in which the presence of the T allele corresponded with severe obesity. The first of these occurred in African American men, and so the conflicting results may be attributed to the racial composition of the populations studied. The second was a study of lean and obese French Caucasians. The authors suggest that while the higher adiponectin levels seen in the obese T allele carriers may protect them against insulin resistance and T2DM, hyperadiponectinemia may actually predispose these patients to weight gain due to the insulin-sensitizing effects of adiponectin, which could promote lipid uptake and storage [31, 82]. This mechanism may also explain why some populations have higher adiponectin levels despite being in an obese state. The T allele also appears to be an important determinant of CVD risk; however, this may correlate directly with the tendency of T allele carriers to have increased adiponectin levels, as demonstrated in one study in which the diabetic participants with the TT genotype had lower risk of CVD, while those without CVD had higher adiponectin levels [71]. Several other studies identified the T allele as a determinant of cardiovascular risk [65, 72].

Overall, the magnitude of change in adiponectin levels varies considerably between studies. This is not surprising, since the studies examine populations that are very different in ethnicity, age, and health condition. However, it is worth noting that several studies show quite substantial changes in adiponectin levels and therefore provide convincing evidence that seemingly minute variations in the genetic code can produce large changes in adipokine levels, and thus significantly affect health status.

3.2. AdipoQ Nutrient-Gene Interactions

Subtle genetic variations can have a large impact on important obesity-related disease determinants, as demonstrated by many of studies discussed above. Individuals with SNPs in genes such as AdipoQ can be subject to greater sensitivity to dietary factors, due to the critical role adiponectin plays in maintaining metabolic balance. Several recent studies have investigated the nutrient-gene interactions that take place between dietary factors and AdipoQ SNPs. Pérez-Martínez et al. [83] investigated the influence of dietary fat on insulin resistance in C allele carriers of the −11377 G > C SNP in Caucasian men and women. Only men who were homozygous for the C allele had significantly lower IR after consuming monounsaturated (MUFA-) and carbohydrate-rich diets than after consuming an SFA-rich diet. In a population of European Caucasian ancestry with MUFA intake above the median, lower BMI and decreased obesity risk were observed in carriers of the −11391 A allele [84]. The +45, +276, and −11377 SNPs were examined in 363 subjects with impaired fasting glucose or newly diagnosed type 2 diabetes following a dietary intervention (replacement of cooked refined rice with whole grains and an increase in vegetable intake) and regular walking for 12 weeks without any medication. Fasting glucose levels declined in all genotype groups of the +45 T > G SNP, and TT homozygotes had increased adiponectin levels and lower HOMA-IR indexes [85]. In another study, obese Japanese women with the +276 SNP were placed on a low-calorie diet for 8 weeks. At the study conclusion, those with a GT or TT genotype had a greater decrease in waist circumference, and those with the TT genotype in the +45 SNP had lower plasma triglycerides. In the same population, the participants with CG and GG genotypes at SNP −11377 enjoyed a greater decrease in systolic blood pressure and fasting plasma glucose than those with CC [86]. Each of these studies used appropriate statistical testing to determine significant interactions between the gene polymorphisms and metabolic parameters. These findings correspond with the trends in metabolic disease discussed in the previous section.

4. Leptin

Leptin regulates body weight and energy expenditure, and plays important roles in the modulation of glucose and lipid metabolism, angiogenesis, immunity, and blood pressure homeostasis. Leptin is also a critical signalling molecule in the hypothalamus, where it influences appetite and satiety. The circulating levels of leptin correlate directly with adipocyte number and size [87], thus, leptin levels are elevated in obesity and are thought to exacerbate many of the negative effects of weight gain, such as contributing to the local inflammatory response [88] and creating a positive feedback loop for feeding behaviour through leptin resistance [89]. More details on the many roles of leptin in metabolic disease can be found in recent reviews [9092].

The study of leptin began when mice homozygous for single-gene mutations in the leptin gene (ob/ob) and the leptin receptor gene (db/db) were identified [93]. The absence of leptin or its receptor leads to uncontrolled eating, and mice with either defect become massively obese. Treatment of ob/ob mice with leptin injections brings about a reduction in body weight to that of a normal mouse. For this reason, leptin was once believed to be the solution to the Western world’s epidemic of obesity. Unfortunately, it was soon determined that such monogenic mutations occur very rarely in humans. In fact, severe obesity due to a single mutation in the leptin gene has been observed in only 12 human cases in the entire world [94]. It is now clear that multiple genes and gene variants are involved in the development of human obesity. SNPs in the human leptin gene (Lep) and the leptin receptor gene (LepR) can have a profound impact on body weight, insulin resistance and other metabolic disease parameters. The literature describing the effects of these SNPs is summarized in Table 2.

tab2
Table 2: SNPs in the Leptin (Lep) and Leptin Receptor (LepR) Genes.
4.1. Leptin and Leptin Receptor Gene Variants: Risk for Obesity-Related Metabolic Disease

The Lep gene is located on chromosome 7q31 and encompasses approximately 20 kb. It contains 3 exons, the first of which is noncoding. Its sequence is highly conserved and contains very little reported variation. Only one leptin SNP, +19 G > A, has been investigated in detail for its effects on obesity-related metabolic disease. A recent study found that the A allele was significantly associated with lower body weight, lower BMI, lower circulating leptin levels, and consequently, a lower risk for obesity in Caucasian and African-American women [100]. Another reported that the presence of the A allele was linked to higher leptin levels and lower BMI in obese Caucasian females compared to GG homozygotes, suggesting that carriers of this allele may experience better sensitivity to satiety signals via the leptin protein [99]. Several other publications failed to find any significant associations between this SNP and BMI or blood lipid levels [9698]. The Lep +19 A > G variant lies within the first untranslated exon of the gene, and it is not known how such an alteration might modify protein function. However, it is has been suggested that the Lep +19 A > G SNP is in disequilibrium with promoter region variation that may have an effect on gene transcription [100].

The LepR gene is found on chromosome 1p31, spans about 100 kb, and contains 20 exons. Numerous analyses of LepR SNPs have been published over the last decade, as the role of these genetic variants as determinants of adiposity and related conditions has become clear. The SNP Gln223Arg A > G has been studied extensively in a wide range of populations. The G allele is primarily associated with increased adiposity, BMI and percent fat mass, as well as higher circulating insulin and leptin levels. Larger adipocyte size has also been observed in individuals with the GG genotype. A couple of studies revealed varying results, with the G allele linked to a lean phenotype [103] and lower blood pressure [115], or no association whatsoever with weight-related parameters [96, 113]. Conversely, the A allele has also been found to be associated with total abdominal fat mass, increased insulin and leptin levels, and higher risk of developing T2DM [117].

The Lys656Asn G > C SNP was analyzed in several different populations, but no consistent trends were identified—both alleles are associated with increased fat mass in different ethnic groups [112, 121], whereas the C allele has also been linked to increased fasting glucose and fasting insulin [122]. Two studies also reported no association between this SNP and blood pressure, BMI, leptin levels, insulin and serum glucose [115, 117].

The A allele of the Arg109Lys G > A SNP is associated with increased T2DM risk [118], higher leptin levels [112], and higher BMI [123]. Several studies reported no association between this SNP and obesity-related disease parameters [96, 107, 113], while one study found the GG, but not AA, genotype to be linked to lower blood pressure and BMI [115].

Functional data on these polymorphisms is scarce, and the mechanisms by which the genetic variation influences metabolism and obesity are largely speculative at this point in time. The increased fat mass and leptin levels in many of the LepR SNP carriers points toward a possible change in binding affinity for the leptin receptor. The receptor functions in a dimeric form both in serum and at the cell surface. The genetic variations in the coding gene for the receptor may alter the ability of subunits to form dimers, leading to the phenotypic differences observed. Quinton et al. [105] measured the leptin-binding activity of the soluble leptin receptor in study participants who were carriers of the Gln223Arg SNP and found significantly higher activity in individuals homozygous for the G allele than for the A allele. These authors suggest the change in binding affinity might also result in an evolutionarily significant tendency to higher fat mass, contributing to the fixation of these alleles in human populations.

4.2. Gene-Nutrient Interactions with Lep and LepR

Most of the literature on gene-nutrient interactions involving leptin or the leptin receptor focuses on fetal nutrition and leptin levels in breast-feeding mothers. Recent evidence suggests that early prenatal and postnatal nutrition has an impact on susceptibility to chronic disease later in life. Leptin in breast milk has been identified as a key protective factor against several metabolic and physiological changes at an older age, such as obesity and related medical complications [124]. Several recent reviews on this topic are available [125, 126].

There is scant research on the interactions of leptin or leptin receptor gene SNPs with dietary factors. One study analyzed the effects of leptin receptor polymorphisms and PUFA consumption in relation to insulin resistance and metabolic syndrome [127]. The findings revealed that participants in the lowest median of plasma (n-3) PUFA and LCPUFA with the GG genotype of the rs3790433 SNP were at higher risk for hyperinsulinemia and insulin resistance, whereas in individuals with the same genotype but high plasma (n-3) PUFA and LCPUFA the risk of developing hyperinsulinemia and insulin resistance was effectively eliminated. Moreover, a high-plasma (n-6) PUFA profile accentuated the risk of these same conditions in GG homozygotes. The study concluded that homozygous carriers of this SNP may be predisposed to metabolic syndrome compared with the A allele carriers, especially if the plasma fatty acid profile was unfavourable. Another study assessed the influence of the LepR Lys656Asn polymorphism on the leptin response secondary to a low fat or low carbohydrate diet in obese people [128]. Leptin levels were significantly lower in the Lys656/Lys656 cohort on a low fat diet than on a low carbohydrate diet. The Lys656/Lys656 group also enjoyed a decrease in several obesity-related disease parameters (BMI, weight, fat mass, blood pressure, total cholesterol, triglycerides, blood insulin, and glucose) on a low fat diet, while significant changes in only BMI, weight and fat mass were observed in Asn656 carriers on the same diet. These studies indicate that polymorphisms in the leptin receptor genes can play an influential role in the body’s physiological response to diet. There is a need for more research in this important area.

5. Concluding Remarks

In summary, the current literature demonstrates that SNPs in the genes for adiponectin, leptin, and the leptin receptor can to a great degree influence the carriers’ susceptibility to obesity and related complications. While epidemiological studies have reported associations between adipokine levels and metabolic disease parameters, the evidence compiled here provides a compelling argument for the causality of adipokine levels in disease. In many of the studies cited here, changes in adipokine levels were observed in individuals with gene polymorphisms, and thus, the change in adipokine levels precedes the occurrence of pathological conditions. Varied downstream effects on parameters of health are to be expected, since the adipokines examined here play diverse roles in many organ systems, as recently reviewed by DeClercq et al. [129]. The genetic variants included in this review by no means constitute an exhaustive list, and further investigation of adipokine SNPs and their impact on human health is warranted. Furthermore, population differences are also a factor in the strength of genetic determinants of disease. The gene-nutrient interaction studies discussed emphasize the role of diet in the modification of risk for developing metabolic disease. Future research in this field is needed to confirm and expand the findings presented here.

Abbreviations

adn:Adiponectin
BMI:Body mass index
CAD:Coronary artery disease
CRC:Colorectal cancer
CVD:Cardiovascular disease
FSI:Fasting serum insulin
HOMA-IR:Homeostatic model assessment of insulin resistance
IR:Insulin resistance
LCPUFA:Long chain polyunsaturated fatty acid
LDL:Low density lipoprotein
MUFA:Monounsaturated fatty acid
PUFA:Polyunsaturated fatty acid
SNP:Single nucleotide polymorphism
T2DM:Type 2 diabetes mellitus
WHR:Waist-to-hip ratio.

Acknowledgment

This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada.

References

  1. K. B. Schelbert, “Comorbidities of Obesity,” Primary Care, vol. 36, no. 2, pp. 271–285, 2009. View at Publisher · View at Google Scholar · View at Scopus
  2. E. E. Calle, C. Rodriguez, K. Walker-Thurmond, and M. J. Thun, “Overweight, obesity, and mortality from cancer in a prospectively studied cohort of U.S. Adults,” New England Journal of Medicine, vol. 348, no. 17, pp. 1625–1638, 2003. View at Publisher · View at Google Scholar · View at Scopus
  3. C. Samanic, W. H. Chow, G. Gridley, B. Jarvholm, and J. F. Fraumeni Jr., “Relation of body mass index to cancer risk in 362,552 Swedish men,” Cancer Causes and Control, vol. 17, no. 7, pp. 901–909, 2006. View at Publisher · View at Google Scholar · View at Scopus
  4. O. Ukkola and C. Bouchard, “Clustering of metabolic abnormalities in obese individuals: the role of genetic factors,” Annals of Medicine, vol. 33, no. 2, pp. 79–90, 2001. View at Scopus
  5. K. M. Flegal, M. D. Carroll, C. L. Ogden, and L. R. Curtin, “Prevalence and trends in obesity among US adults, 1999–2008,” Journal of the American Medical Association, vol. 303, no. 3, pp. 235–241, 2010. View at Publisher · View at Google Scholar
  6. P. G. Kopelman, “Obesity as a medical problem,” Nature, vol. 404, no. 6778, pp. 635–643, 2000. View at Scopus
  7. P. Trayhurn and I. S. Wood, “Adipokines: inflammation and the pleiotropic role of white adipose tissue,” British Journal of Nutrition, vol. 92, no. 3, pp. 347–355, 2004. View at Publisher · View at Google Scholar · View at Scopus
  8. F. Y. Li, K. K. Cheng, K. S. Lam, P. M. Vanhoutte, and A. Xu, “Cross-talk between adipose tissue and vasculature: role of adiponectin,” Acta Physiologica. In press.
  9. H. Hauner, “Secretory factors from human adipose tissue and their functional role,” Proceedings of the Nutrition Society, vol. 64, no. 2, pp. 163–169, 2005. View at Publisher · View at Google Scholar · View at Scopus
  10. M. Bluher, “Adipose tissue dysfunction in obesity,” Experimental and Clinical Endocrinology and Diabetes, vol. 117, no. 6, pp. 241–250, 2009. View at Publisher · View at Google Scholar · View at Scopus
  11. H. E. Bays, J. M. González-Campoy, G. A. Bray et al., “Pathogenic potential of adipose tissue and metabolic consequences of adipocyte hypertrophy and increased visceral adiposity,” Expert Review of Cardiovascular Therapy, vol. 6, no. 3, pp. 343–368, 2008. View at Publisher · View at Google Scholar · View at Scopus
  12. T. Yamauchi, J. Kamon, H. Waki et al., “The fat-derived hormone adiponectin reverses insulin resistance associated with both lipoatrophy and obesity,” Nature Medicine, vol. 7, no. 8, pp. 941–946, 2001. View at Publisher · View at Google Scholar · View at Scopus
  13. T. Yamauchi, J. Kamon, Y. Minokoshi et al., “Adiponectin stimulates glucose utilization and fatty-acid oxidation by activating AMP-activated protein kinase,” Nature Medicine, vol. 8, no. 11, pp. 1288–1295, 2002. View at Publisher · View at Google Scholar · View at Scopus
  14. T. Kadowaki and T. Yamauchi, “Adiponectin and adiponectin receptors,” Endocrine Reviews, vol. 26, no. 3, pp. 439–451, 2005. View at Publisher · View at Google Scholar
  15. J. J. Díez and P. Iglesias, “The role of the novel adipocyte-derived hormone adiponectin in human disease,” European Journal of Endocrinology, vol. 148, no. 3, pp. 293–300, 2003. View at Publisher · View at Google Scholar
  16. K. Hotta, T. Funahashi, Y. Arita et al., “Plasma concentrations of a novel, adipose-specific protein, adiponectin, in type 2 diabetic patients,” Arteriosclerosis, Thrombosis, and Vascular Biology, vol. 20, no. 6, pp. 1595–1599, 2000. View at Scopus
  17. P. Trayhurn and I. S. Wood, “Signalling role of adipose tissue: adipokines and inflammation in obesity,” Biochemical Society Transactions, vol. 33, no. 5, pp. 1078–1081, 2005. View at Publisher · View at Google Scholar · View at Scopus
  18. G. R. Hajer, T. W. Van Haeften, and F. L. J. Visseren, “Adipose tissue dysfunction in obesity, diabetes, and vascular diseases,” European Heart Journal, vol. 29, no. 24, pp. 2959–2971, 2008. View at Publisher · View at Google Scholar
  19. E. Maury and S. M. Brichard, “Adipokine dysregulation, adipose tissue inflammation and metabolic syndrome,” Molecular and Cellular Endocrinology, vol. 314, no. 1, pp. 1–16, 2010. View at Publisher · View at Google Scholar · View at Scopus
  20. Y. Matsuzawa, “Adiponectin: a key player in obesity related disorders,” Current Pharmaceutical Design, vol. 16, no. 17, pp. 1896–1901, 2010. View at Publisher · View at Google Scholar
  21. N. Vionnet, E. H. Hani, S. Dupont et al., “Genomewide search for type 2 diabetes-susceptibility genes in French whites: evidence for a novel susceptibility locus for early-onset diabetes on chromosiome 3q27-qter and independent replication of a type 2-diabetes locus on chromosome 1q21-q24,” American Journal of Human Genetics, vol. 67, no. 6, pp. 1470–1480, 2000. View at Publisher · View at Google Scholar · View at Scopus
  22. S. Francke, M. Manraj, C. Lacquemant et al., “A genome-wide scan for coronary heart disease suggests in Indo-Mauritians a susceptibility locus on chromosome 16p13 and replicates linkage with the metabolic syndrome on 3q27,” Human Molecular Genetics, vol. 10, no. 24, pp. 2751–2765, 2001. View at Scopus
  23. F. Vasseur, N. Helbecque, C. Dina et al., “Single-nucleotide polymorphism haplotypes in the both proximal promoter and exon 3 of the APM1 gene modulate adipocyte-secreted adiponectin hormone levels and contribute to the genetic risk for type 2 diabetes in French Caucasians,” Human Molecular Genetics, vol. 11, no. 21, pp. 2607–2614, 2002. View at Scopus
  24. B. V. De Courten, R. L. Hanson, T. Funahashi et al., “Common polymorphisms in the adiponectin gene ACDC are not associated with diabetes in Pima Indians,” Diabetes, vol. 54, no. 1, pp. 284–289, 2005. View at Publisher · View at Google Scholar
  25. L. M. Chuang, Y. F. Chiu, W. H. H. Sheu et al., “Biethnic comparisons of autosomal genomic scan for loci linked to plasma adiponectin in populations of chinese and Japanese origin,” Journal of Clinical Endocrinology and Metabolism, vol. 89, no. 11, pp. 5772–5778, 2004. View at Publisher · View at Google Scholar · View at Scopus
  26. A. G. Comuzzie, T. Funahashi, G. Sonnenberg et al., “The genetic basis of plasma variation in adiponectin, a global endophenotype for obesity and the metabolic syndrome,” Journal of Clinical Endocrinology and Metabolism, vol. 86, no. 9, pp. 4321–4325, 2001. View at Publisher · View at Google Scholar · View at Scopus
  27. X. Guo, M. F. Saad, C. D. Langefeld et al., “Genome-wide linkage of plasma adiponectin reveals a major locus on chromosome 3q distinct from the adiponectin structural gene: the IRAS Family Study,” Diabetes, vol. 55, no. 6, pp. 1723–1730, 2006. View at Publisher · View at Google Scholar · View at Scopus
  28. R. S. Lindsay, T. Funahashi, J. Krakoff et al., “Genome-wide linkage analysis of serum adiponectin in the Pima Indian population,” Diabetes, vol. 52, no. 9, pp. 2419–2425, 2003. View at Publisher · View at Google Scholar · View at Scopus
  29. C. Menzaghi, V. Trischitta, and A. Doria, “Genetic influences of adiponectin on insulin resistance, type 2 diabetes, and cardiovascular disease,” Diabetes, vol. 56, no. 5, pp. 1198–1209, 2007. View at Publisher · View at Google Scholar · View at Scopus
  30. H. F. Gu, “Biomarkers of adiponectin: plasma protein variation and genomic DNA polymorphisms,” Biomarker Insights, vol. 4, pp. 123–133, 2009.
  31. N. Bouatia-Naji, D. Meyre, S. Lobbens et al., “ACDC/adiponectin polymorphisms are associated with severe childhood and adult obesity,” Diabetes, vol. 55, no. 2, pp. 545–550, 2006. View at Publisher · View at Google Scholar
  32. C. Menzaghi, T. Ercolino, L. Salvemini et al., “Multigenic control of serum adiponectin levels: evidence for a role of the APM1 gene and a locus on 14q13,” Physiological Genomics, vol. 19, pp. 170–174, 2005. View at Publisher · View at Google Scholar · View at Scopus
  33. A. Morandi, C. Maffeis, S. Lobbens et al., “Early detrimental metabolic outcomes of rs17300539-A Allele of ADIPOQ gene despite higher adiponectinemia,” Obesity, vol. 18, no. 7, pp. 1469–1473, 2010. View at Publisher · View at Google Scholar · View at Scopus
  34. F. Fumeron, R. Aubert, A. Siddiq et al., “Adiponectin gene polymorphisms and adiponectin levels are independently associated with the development of hyperglycemia during a 3-year period: the epidemiologic data on the insulin resistance syndrome prospective study,” Diabetes, vol. 53, no. 4, pp. 1150–1157, 2004. View at Publisher · View at Google Scholar
  35. M. Yang, C. C. Qui, W. Chen, L. L. Xu, M. Yu, and H. D. Xiang, “Identification of a regulatory single nucleotide polymorphism in the adiponectin (APM1) gene associated with type 2 diabetes in Han nationality,” Biomedical and Environmental Sciences, vol. 21, no. 6, pp. 454–459, 2008. View at Publisher · View at Google Scholar · View at Scopus
  36. H. F. Gu, A. Abulaiti, C.-G. Östenson et al., “Single nucleotide polymorphisms in the proximal promoter region of the adiponectin (APM1) gene are associated with type 2 diabetes in Swedish Caucasians,” Diabetes, vol. 53, supplement 1, pp. S31–S35, 2004.
  37. F. Gibson and P. Froguel, “Genetics of the APM1 locus and its contribution to type 2 diabetes susceptibility in French Caucasians,” Diabetes, vol. 53, no. 11, pp. 2977–2983, 2004. View at Publisher · View at Google Scholar · View at Scopus
  38. P. Henneman, Y. S. Aulchenko, R. R. Frants et al., “Genetic architecture of plasma adiponectin overlaps with the genetics of metabolic syndrome-related traits,” Diabetes Care, vol. 33, no. 4, pp. 908–913, 2010. View at Publisher · View at Google Scholar · View at Scopus
  39. T. Kyriakou, L. J. Collins, N. J. Spencer-Jones et al., “Adiponectin gene ADIPOQ SNP associations with serum adiponectin in two female populations and effects of SNPs on promoter activity,” Journal of Human Genetics, vol. 53, no. 8, pp. 718–727, 2008. View at Publisher · View at Google Scholar · View at Scopus
  40. J. G. Woo, L. M. Dolan, R. Deka et al., “Interactions between noncontiguous haplotypes in the adiponectin gene ACDC are associated with plasma adiponectin,” Diabetes, vol. 55, no. 2, pp. 523–529, 2006. View at Publisher · View at Google Scholar · View at Scopus
  41. M. F. Hivert, A. K. Manning, J. B. McAteer et al., “Common variants in the adiponectin gene (ADIPOQ) associated with plasma adiponectin levels, type 2 diabetes, and diabetes-related quantitative traits: the framingham offspring study,” Diabetes, vol. 57, no. 12, pp. 3353–3359, 2008. View at Publisher · View at Google Scholar · View at Scopus
  42. F. Vasseur, N. Helbecque, S. Lobbens et al., “Hypoadiponectinaemia and high risk of type 2 diabetes are associated with adiponectin-encoding (ACDC) gene promoter variants in morbid obesity: evidence for a role of ACDC in diabesity,” Diabetologia, vol. 48, no. 5, pp. 892–899, 2005. View at Publisher · View at Google Scholar · View at Scopus
  43. K. L. Ong, M. Li, A. W. K. Tso et al., “Association of genetic variants in the adiponectin gene with adiponectin level and hypertension in Hong Kong Chinese,” European Journal of Endocrinology, vol. 163, no. 2, pp. 251–257, 2010. View at Publisher · View at Google Scholar
  44. S. L. Prior, D. R. Gable, J. A. Cooper et al., “Association between the adiponectin promoter rs266729 gene variant and oxidative stress in patients with diabetes mellitus,” European Heart Journal, vol. 30, no. 10, pp. 1263–1269, 2009. View at Publisher · View at Google Scholar · View at Scopus
  45. G. Hoefle, A. Muendlein, C. H. Saely et al., “The -11377 C>G promoter variant of the adiponectin gene, prevalence of coronary atherosclerosis, and incidence of vascular events in men,” Thrombosis and Haemostasis, vol. 97, no. 3, pp. 451–457, 2007. View at Publisher · View at Google Scholar · View at Scopus
  46. S. Pechlivanis, J. L. Bermejo, B. Pardini et al., “Genetic variation in adipokine genes and risk of colorectal cancer,” European Journal of Endocrinology, vol. 160, no. 6, pp. 933–940, 2009. View at Publisher · View at Google Scholar · View at Scopus
  47. L. G. Carvajal-Carmona, S. Spain, D. Kerr, R. Houlston, J. B. Cazier, and I. Tomlinson, “Common variation at the adiponectin locus is not associated with colorectal cancer risk in the UK,” Human Molecular Genetics, vol. 18, no. 10, pp. 1889–1892, 2009. View at Publisher · View at Google Scholar · View at Scopus
  48. V. G. Kaklamani, K. B. Wisinski, M. Sadim et al., “Variants of the adiponectin (ADIPOQ) and adiponectin receptor 1 (ADIPOR1) genes and colorectal cancer risk,” Journal of the American Medical Association, vol. 300, no. 13, pp. 1523–1531, 2008. View at Publisher · View at Google Scholar · View at Scopus
  49. LU. Qi, A. Doria, J. E. Manson et al., “Adiponectin genetic variability, plasma adiponectin, and cardiovascular risk in patients with type 2 diabetes,” Diabetes, vol. 55, no. 5, pp. 1512–1516, 2006. View at Publisher · View at Google Scholar · View at Scopus
  50. C. L. Wassel, J. S. Pankow, D. R. Jacobs Jr., M. W. Steffes, NA. Li, and P. J. Schreiner, “Variants in the Adiponectin Gene and Serum Adiponectin: The Coronary Artery Development in Young Adults (CARDIA) Study,” Obesity, vol. 18, no. 12, pp. 2333–2338, 2010. View at Publisher · View at Google Scholar · View at Scopus
  51. S.-M. Ruchat, R. J. F. Loos, T. Rankinen et al., “Associations between glucose tolerance, insulin sensitivity and insulin secretion phenotypes and polymorphisms in adiponectin and adiponectin receptor genes in the Quebec Family Study,” Diabetic Medicine, vol. 25, no. 4, pp. 400–406, 2008. View at Publisher · View at Google Scholar
  52. G. Mohammadzadeh and N. Zarghami, “Associations between single-nucleotide polymorphisms of the adiponectin gene, serum adiponectin levels and increased risk of type 2 diabetes mellitus in Iranian obese individuals,” Scandinavian Journal of Clinical and Laboratory Investigation, vol. 69, no. 7, pp. 764–771, 2009. View at Publisher · View at Google Scholar · View at Scopus
  53. C. F. Low, E. R. Mohd Tohit, P. P. Chong, and F. Idris, “Adiponectin SNP45TG is associated with gestational diabetes mellitus,” Archives of Gynecology and Obstetrics. In press. View at Publisher · View at Google Scholar · View at Scopus
  54. L. Melistas, C. S. Mantzoros, M. Kontogianni, S. Antonopoulou, J. M. Ordovas, and N. Yiannakouris, “Association of the +45T>G and +276G>T polymorphisms in the adiponectin gene with insulin resistance in nondiabetic Greek women,” European Journal of Endocrinology, vol. 161, no. 6, pp. 845–852, 2009. View at Publisher · View at Google Scholar · View at Scopus
  55. Z. L. Wang, B. Xia, U. Shrestha et al., “Correlation between adiponectin polymorphisms and non-alcoholic fatty liver disease with or without metabolic syndrome in Chinese population,” Journal of Endocrinological Investigation, vol. 31, no. 12, pp. 1086–1091, 2008. View at Scopus
  56. K. Hara, P. Boutin, Y. Mori et al., “Genetic variation in the gene encoding adiponectin is associated with an increased risk of type 2 diabetes in the Japanese population,” Diabetes, vol. 51, no. 2, pp. 536–540, 2002. View at Scopus
  57. L. L. Li, X. L. Kang, X. J. Ran et al., “Associations between 45T/G polymorphism of the adiponectin gene and plasma adiponectin levels with type 2 diabetes,” Clinical and Experimental Pharmacology and Physiology, vol. 34, no. 12, pp. 1287–1290, 2007. View at Publisher · View at Google Scholar · View at Scopus
  58. B. S. Sutton, S. Weinert, C. D. Langefeld et al., “Genetic analysis of adiponectin and obesity in Hispanic families: the IRAS Family Study,” Human Genetics, vol. 117, no. 2-3, pp. 107–118, 2005. View at Publisher · View at Google Scholar · View at Scopus
  59. Y. Y. Lee, N. S. Lee, Y. M. Cho et al., “Genetic association study of adiponectin polymorphisms with risk of Type 2 diabetes mellitus in Korean population,” Diabetic Medicine, vol. 22, no. 5, pp. 569–575, 2005. View at Publisher · View at Google Scholar · View at Scopus
  60. V. Mackevics, I. M. Heid, S. A. Wagner et al., “The adiponectin gene is associated with adiponectin levels but not with characteristics of the insulin resistance syndrome in healthy Caucasians,” European Journal of Human Genetics, vol. 14, no. 3, pp. 349–356, 2006. View at Publisher · View at Google Scholar · View at Scopus
  61. J. L. González-Sánchez, C. A. Zabena, M. T. Martínez-Larrad et al., “An SNP in the adiponectin gene is associated with decreased serum adiponectin levels and risk for impaired glucose tolerance,” Obesity Research, vol. 13, no. 5, pp. 807–812, 2005. View at Scopus
  62. J. Zacharova, J. -L. Chiasson, and M. Laakso, “The common polymorphisms (Single Nucleotide Polymorphism [SNP] +45 and SNP +276) of the adiponectin gene predict the conversion from impaired glucose tolerance to type 2 diabetes: the STOP-NIDDM trial,” Diabetes, vol. 54, no. 3, pp. 893–899, 2005. View at Publisher · View at Google Scholar
  63. K. Nakatani, K. Noma, J. Nishioka et al., “Adiponectin gene variation associates with the increasing risk of type 2 diabetes in non-diabetic Japanese subjects,” International Journal of Molecular Medicine, vol. 15, no. 1, pp. 173–177, 2005. View at Scopus
  64. O. Ukkola, E. Ravussin, P. Jacobson, L. Sjöström, and C. Bouchard, “Mutations in the adiponectin gene in lean and obese subjects from the Swedish obese subjects cohort,” Metabolism: Clinical and Experimental, vol. 52, no. 7, pp. 881–884, 2003. View at Publisher · View at Google Scholar · View at Scopus
  65. S. Bacci, C. Menzaghi, T. Ercolino et al., “The +276 G/T single nucleotide polymorphism of the adiponectin gene is associated with coronary artery disease in type 2 diabetic patients,” Diabetes Care, vol. 27, no. 8, pp. 2015–2020, 2004. View at Publisher · View at Google Scholar · View at Scopus
  66. C. Lacquemant, P. Froguel, S. Lobbens, P. Izzo, C. Dina, and J. Ruiz, “The adiponectin gene SNP+45 is associated with coronary artery disease in Type 2 (non-insulin-dependent) diabetes mellitus,” Diabetic Medicine, vol. 21, no. 7, pp. 776–781, 2004. View at Publisher · View at Google Scholar · View at Scopus
  67. J. L. Beebe-Dimmer, K. A. Zuhlke, A. M. Ray, E. M. Lange, and K. A. Cooney, “Genetic variation in adiponectin (ADIPOQ) and the type 1 receptor (ADIPOR1), obesity and prostate cancer in African Americans,” Prostate Cancer and Prostatic Diseases, vol. 13, no. 4, pp. 362–368, 2010. View at Publisher · View at Google Scholar
  68. MC Huang, TN Wang, KT Lee, et al., “Adiponectin gene SNP276 variants and central obesity confer risks for hyperglycemia in indigenous Taiwanese,” The Kaohsiung Journal of Medical Sciences, vol. 26, pp. 227–236, 2010.
  69. F. Mousavinasab, T. Tähtinen, J. Jokelainen et al., “Common polymorphisms (single-nucleotide polymorphisms SNP+45 and SNP+276) of the adiponectin gene regulate serum adiponectin concentrations and blood pressure in young Finnish men,” Molecular Genetics and Metabolism, vol. 87, no. 2, pp. 147–151, 2006. View at Publisher · View at Google Scholar · View at Scopus
  70. E. Verduci, S. Scaglioni, C. Agostoni et al., “The relationship of insulin resistance with SNP 276G>T at adiponectin gene and plasma long-chain polyunsaturated fatty acids in obese children,” Pediatric Research, vol. 66, no. 3, pp. 346–349, 2009. View at Publisher · View at Google Scholar · View at Scopus
  71. LU. Qi, T. Li, E. Rimm et al., “The +276 polymorphism of the APM1 gene, plasma adiponectin concentration, and cardiovascular risk in diabetic men,” Diabetes, vol. 54, no. 5, pp. 1607–1610, 2005. View at Publisher · View at Google Scholar · View at Scopus
  72. E. Filippi, F. Sentinelli, S. Romeo et al., “The adiponectin gene SNP+276G>T associates with early-onset coronary artery disease and with lower levels of adiponectin in younger coronary artery disease patients (age ≤50 years),” Journal of Molecular Medicine, vol. 83, no. 9, pp. 711–719, 2005. View at Publisher · View at Google Scholar · View at Scopus
  73. Y. Jang, J. H. Lee, J. S. Chae et al., “Association of the 276G→T polymorphism of the adiponectin gene with cardiovascular disease risk factors in nondiabetic Koreans,” American Journal of Clinical Nutrition, vol. 82, no. 4, pp. 760–767, 2005. View at Scopus
  74. Y. Iwashima, T. Katsuya, K. Ishikawa et al., “Hypoadiponectinemia is an independent risk factor for hypertension,” Hypertension, vol. 43, no. 6, pp. 1318–1323, 2004. View at Publisher · View at Google Scholar · View at Scopus
  75. K. S. Vimaleswaran, V. Radha, K. Ramya et al., “A novel association of a polymorphism in the first intron of adiponectin gene with type 2 diabetes, obesity and hypoadiponectinemia in Asian Indians,” Human Genetics, vol. 123, no. 6, pp. 599–605, 2008. View at Publisher · View at Google Scholar · View at Scopus
  76. C. Specchia, K. Scott, P. Fortina, M. Devoto, and B. Falkner, “Association of a polymorphic variant of the adiponectin gene with Insulin resistance in African Americans,” Clinical and Translational Science, vol. 1, no. 3, pp. 194–199, 2008. View at Publisher · View at Google Scholar · View at Scopus
  77. J. F. Ferguson, C. M. Phillips, A. C. Tierney et al., “Gene-nutrient interactions in the metabolic syndrome: single nucleotide polymorphisms in ADIPOQ and ADIPOR1 interact with plasma saturated fatty acids to modulate insulin resistance,” American Journal of Clinical Nutrition, vol. 91, no. 3, pp. 794–801, 2010. View at Publisher · View at Google Scholar · View at Scopus
  78. D. Zhang, J. Ma, K. Brismar, S. Efendic, and H. F. Gu, “A single nucleotide polymorphism alters the sequence of SP1 binding site in the adiponectin promoter region and is associated with diabetic nephropathy among type 1 diabetic patients in the Genetics of Kidneys in Diabetes Study,” Journal of Diabetes and its Complications, vol. 23, no. 4, pp. 265–272, 2009. View at Publisher · View at Google Scholar · View at Scopus
  79. H. Laumen, A. D. Saningong, I. M. Heid et al., “Functional characterization of promoter variants of the adiponectin gene complemented by epidemiological data,” Diabetes, vol. 58, no. 4, pp. 984–991, 2009. View at Publisher · View at Google Scholar · View at Scopus
  80. W. S. Yang, P. L. Tsou, W. J. Lee et al., “Allele-specific differential expression of a common adiponectin gene polymorphism related to obesity,” Journal of Molecular Medicine, vol. 81, no. 7, pp. 428–434, 2003. View at Publisher · View at Google Scholar · View at Scopus
  81. C. Menzaghi, T. Ercolino, R. D. Paola et al., “A haplotype at the adiponectin locus is associated with obesity and other features of the insulin resistance syndrome,” Diabetes, vol. 51, no. 7, pp. 2306–2312, 2002. View at Scopus
  82. F. Abbasi, J. W. Chu, C. Lamendola et al., “Discrimination between obesity and insulin resistance in the relationship with adiponectin,” Diabetes, vol. 53, no. 3, pp. 585–590, 2004. View at Publisher · View at Google Scholar · View at Scopus
  83. P. Pérez-Martínez, J. López-Miranda, C. Cruz-Teno et al., “Adiponectin gene variants are associated with insulin sensitivity in response to dietary fat consumption in caucasian men,” Journal of Nutrition, vol. 138, no. 9, pp. 1609–1614, 2008. View at Scopus
  84. D. Warodomwichit, J. Shen, D. K. Arnett et al., “ADIPOQ polymorphisms, monounsaturated fatty acids, and obesity risk: the GOLDN study,” Obesity, vol. 17, no. 3, pp. 511–517, 2009. View at Publisher · View at Google Scholar · View at Scopus
  85. H. K. Chung, J. S. Chae, Y. Hyun et al., “Influence of adiponectin gene polymorphisms on adiponectin level and insulin resistance index in response to dietary intervention in overweight-obese patients with impaired fasting glucose or newly diagnosed type 2 diabetes,” Diabetes Care, vol. 32, no. 4, pp. 552–558, 2009. View at Publisher · View at Google Scholar · View at Scopus
  86. K. Tsuzaki, K. Kotani, N. Nagai et al., “Adiponectin gene single-nucleotide polymorphisms and treatment response to obesity,” Journal of Endocrinological Investigation, vol. 32, no. 5, pp. 395–400, 2009. View at Scopus
  87. T. Skurk, C. Alberti-Huber, C. Herder, and H. Hauner, “Relationship between adipocyte size and adipokine expression and secretion,” Journal of Clinical Endocrinology and Metabolism, vol. 92, no. 3, pp. 1023–1033, 2007. View at Publisher · View at Google Scholar · View at Scopus
  88. G. Fantuzzi, “Adipose tissue, adipokines, and inflammation,” Journal of Allergy and Clinical Immunology, vol. 115, no. 5, pp. 911–920, 2005. View at Publisher · View at Google Scholar · View at Scopus
  89. P. J. Scarpace and Y. Zhang, “Elevated leptin: consequence or cause of obesity?” Frontiers in Bioscience, vol. 12, pp. 3531–3544, 2007. View at Publisher · View at Google Scholar · View at Scopus
  90. T. A. Dardeno, S. H. Chou, H. S. Moon, J. P. Chamberland, C. G. Fiorenza, and C. S. Mantzoros, “Leptin in human physiology and therapeutics,” Frontiers in Neuroendocrinology, vol. 31, no. 3, pp. 377–393, 2010. View at Publisher · View at Google Scholar · View at Scopus
  91. A. Stofkova, “Leptin and adiponectin: from energy and metabolic dysbalance to inflammation and autoimmunity,” Endocrine Regulations, vol. 43, no. 4, pp. 157–168, 2009. View at Scopus
  92. J. P. Thaler and M. W. Schwartz, “Minireview: inflammation and obesity pathogenesis: the hypothalamus heats up,” Endocrinology, vol. 151, no. 9, pp. 4109–4115, 2010. View at Publisher · View at Google Scholar
  93. D. L. Coleman, “Obese and diabetes: two mutant genes causing diabetes-obesity syndromes in mice,” Diabetologia, vol. 14, no. 3, pp. 141–148, 1978. View at Scopus
  94. S. A. Ranadive and C. Vaisse, “Lessons from extreme human obesity: monogenic disorders,” Endocrinology and Metabolism Clinics of North America, vol. 37, no. 3, pp. 733–751, 2008. View at Publisher · View at Google Scholar · View at Scopus
  95. Y. Friedlander, G. Li, M. Fornage et al., “Candidate molecular pathway genes related to appetite regulatory neural network, adipocyte homeostasis and obesity: results from the CARDIA Study,” Annals of Human Genetics, vol. 74, no. 5, pp. 387–398, 2010. View at Publisher · View at Google Scholar
  96. N. Y. Souren, A. D. Paulussen, A. Steyls et al., “Common SNPs in LEP and LEPR associated with birth weight and type 2 diabetes-related metabolic risk factors in twins,” International Journal of Obesity, vol. 32, no. 8, pp. 1233–1239, 2008. View at Publisher · View at Google Scholar · View at Scopus
  97. A. Meirhaeghe, D. Cottel, P. Amouyel, and J. Dallongeville, “Lack of association between certain candidate gene polymorphisms and the metabolic syndrome,” Molecular Genetics and Metabolism, vol. 86, no. 1-2, pp. 293–299, 2005. View at Publisher · View at Google Scholar · View at Scopus
  98. R. Lucantoni, E. Ponti, M. E. Berselli et al., “The A19G polymorphism in the 5' untranslated region of the human obese gene does not affect leptin levels in severely obese patients,” Journal of Clinical Endocrinology and Metabolism, vol. 85, no. 10, pp. 3589–3591, 2000. View at Scopus
  99. J. Hager, K. Clement, S. Francke et al., “A polymorphism in the 5' untranslated region of the human ob gene is associated with low leptin levels,” International Journal of Obesity, vol. 22, no. 3, pp. 200–205, 1998.
  100. M. L. Hart Sailors, A. R. Folsom, C. M. Ballantyne et al., “Genetic variation and decreased risk for obesity in the Atherosclerosis Risk in Communities Study,” Diabetes, Obesity and Metabolism, vol. 9, no. 4, pp. 548–557, 2007. View at Publisher · View at Google Scholar · View at Scopus
  101. Y. Jiang, J. B. Wilk, I. Borecki et al., “Common variants in the 5′ region of the leptin gene are associated with body mass index in men from the National Heart, Lung, and Blood Institute Family Heart Study,” American Journal of Human Genetics, vol. 75, no. 2, pp. 220–230, 2004. View at Publisher · View at Google Scholar · View at Scopus
  102. O. Mammès, D. Betoulle, R. Aubert, B. Herbeth, G. Siest, and F. Fumeron, “Association of the G-2548A polymorphism in the 5′ region of the LEP gene with overweight,” Annals of Human Genetics, vol. 64, no. 5, pp. 391–394, 2000. View at Publisher · View at Google Scholar · View at Scopus
  103. O. Portolés, J. V. Sorlí, F. Francés et al., “Effect of genetic variation in the leptin gene promoter and the leptin receptor gene on obesity risk in a population-based case-control study in Spain,” European Journal of Epidemiology, vol. 21, no. 8, pp. 605–612, 2006. View at Publisher · View at Google Scholar
  104. D. Murugesan, T. Arunachalam, V. Ramamurthy, and S. Subramanian, “Association of polymorphisms in leptin receptor gene with obesity and type 2 diabetes in the local population of Coimbatore,” Indian Journal of Human Genetics, vol. 16, pp. 72–77, 2010.
  105. N. D. Quinton, A. J. Lee, R. J. M. Ross, R. Eastell, and A. I. F. Blakemore, “A single nucleotide polymorphism (SNP) in the leptin receptor is associated with BMI, fat mass and leptin levels in postmenopausal Caucasian women,” Human Genetics, vol. 108, no. 3, pp. 233–236, 2001. View at Publisher · View at Google Scholar · View at Scopus
  106. V. S. Mattevi, V. M. Zembrzuski, and M. H. Hutz, “Association analysis of genes involved in the leptin-signaling pathway with obesity in Brazil,” International Journal of Obesity, vol. 26, no. 9, pp. 1179–1185, 2002. View at Publisher · View at Google Scholar
  107. N. Yiannakouris, M. Yannakoulia, L. Melistas, J. L. Chan, D. Klimis-Zacas, and C. S. Mantzoros, “The Q223R polymorphism of the leptin receptor gene is significantly associated with obesity and predicts a small percentage of body weight and body composition variability,” Journal of Clinical Endocrinology and Metabolism, vol. 86, no. 9, pp. 4434–4439, 2001. View at Publisher · View at Google Scholar · View at Scopus
  108. N. Stefan, B. Vozarova, A. Del Parigi et al., “The Gln223Arg polymorphism of the leptin receptor in Pima Indians: influence on energy expenditure, physical activity and lipid metabolism,” International Journal of Obesity, vol. 26, no. 12, pp. 1629–1632, 2002. View at Publisher · View at Google Scholar
  109. K. C. Chiu, A. Chu, L. M. Chuang, and M. F. Saad, “Association of leptin receptor polymorphism with insulin resistance,” European Journal of Endocrinology, vol. 150, no. 5, pp. 725–729, 2004. View at Publisher · View at Google Scholar · View at Scopus
  110. G. M. Van Der Vleuten, L. A. Kluijtmans, A. Hijmans, H. J. Blom, A. F. H. Stalenhoef, and J. De Graaf, “The Gln223Arg polymorphism in the leptin receptor is associated with familial combined hyperlipidemia,” International Journal of Obesity, vol. 30, no. 6, pp. 892–898, 2006. View at Publisher · View at Google Scholar · View at Scopus
  111. S. F. Pimentel Duarte, E. A. Francischetti, V. Genelhu-Abreu et al., “p.Q223R leptin receptor polymorphism associated with obesity in Brazilian multiethnic subjects,” American Journal of Human Biology, vol. 18, no. 4, pp. 448–453, 2006. View at Publisher · View at Google Scholar · View at Scopus
  112. M. Wauters, I. Mertens, M. Chagnon et al., “Polymorphisms in the leptin receptor gene, body composition and fat distribution in overweight and obese women,” International Journal of Obesity, vol. 25, no. 5, pp. 714–720, 2001. View at Publisher · View at Google Scholar
  113. T. Ogawa, H. Hirose, Y. Yamamoto et al., “Relationships between serum soluble leptin receptor level and serum leptin and adiponectin levels, insulin resistance index, lipid profile, and leptin receptor gene polymorphisms in the Japanese population,” Metabolism, vol. 53, no. 7, pp. 879–885, 2004. View at Publisher · View at Google Scholar
  114. U. L. Fairbrother, L. B. Tankó, A. J. Walley, C. Christiansen, P. Froguel, and A. I. F. Blakemore, “Leptin receptor genotype at Gln223Arg is associated with body composition, BMD, and vertebral fracture in postmenopausal Danish women,” Journal of Bone and Mineral Research, vol. 22, no. 4, pp. 544–550, 2007. View at Publisher · View at Google Scholar · View at Scopus
  115. R. Rosmond, Y. C. Chagnon, G. Holm et al., “Hypertension in obesity and the leptin receptor gene locus,” Journal of Clinical Endocrinology and Metabolism, vol. 85, no. 9, pp. 3126–3131, 2000. View at Scopus
  116. Y. C. Chagnon, W. K. Chung, L. Pérusse, M. Chagnon, R. L. Leibel, and C. Bouchard, “Linkages and associations between the leptin receptor (LEPR) gene and human body composition in the Quebec Family Study,” International Journal of Obesity, vol. 23, no. 3, pp. 278–286, 1999.
  117. J. M. Guízar-Mendoza, N. Amador-Licona, S. E. Flores-Martínez, M. G. López-Cardona, R. Ahuatzin-Trémary, and J. Sánchez-Corona, “Association analysis of the Gln223Arg polymorphism in the human leptin receptor gene, and traits related to obesity in Mexican adolescents,” Journal of Human Hypertension, vol. 19, no. 5, pp. 341–346, 2005. View at Publisher · View at Google Scholar · View at Scopus
  118. T. Salopuro, L. Pulkkinen, J. Lindström et al., “Genetic variation in leptin receptor gene is associated with type 2 diabetes and body weight: the Finnish Diabetes Prevention Study,” International Journal of Obesity, vol. 29, no. 10, pp. 1245–1251, 2005. View at Publisher · View at Google Scholar · View at Scopus
  119. L. Gallicchio, H. H. Chang, D. K. Christo et al., “Single nucleotide polymorphisms in obesity-related genes and all-cause and cause-specific mortality: a prospective cohort study,” BMC Medical Genetics, vol. 10, article no. 103, 2009. View at Publisher · View at Google Scholar · View at Scopus
  120. O. Mammès, R. Aubert, D. Betoulle et al., “LEPR gene polymorphisms: associations with overweight, fat mass and response to diet in women,” European Journal of Clinical Investigation, vol. 31, no. 5, pp. 398–404, 2001. View at Publisher · View at Google Scholar · View at Scopus
  121. Y. J. Liu, S. M. S. Rocha-Sanchez, P. Y. Liu et al., “Tests of linkage and/or association of the LEPR gene polymorphisms with obesity phenotypes in Caucasian nuclear families,” Physiological Genomics, vol. 17, pp. 101–106, 2004. View at Publisher · View at Google Scholar · View at Scopus
  122. M. Wauters, I. Mertens, T. Rankinen, M. Chagnon, C. Bouchardt, and L. Van Gaal, “Leptin receptor gene polymorphisms are associated with insulin in obese women with impaired glucose tolerance,” Journal of Clinical Endocrinology and Metabolism, vol. 86, no. 7, pp. 3227–3232, 2001. View at Publisher · View at Google Scholar · View at Scopus
  123. K. S. Park, H. D. Shin, B. L. Park et al., “Polymorphisms in the leptin receptor (LEPR)—putative association with obesity and T2DM,” Journal of Human Genetics, vol. 51, no. 2, pp. 85–91, 2006. View at Publisher · View at Google Scholar · View at Scopus
  124. A. Palou, J. Sánchez, and C. Picó, “Nutrient-gene interactions in early life programming: leptin in breast milk prevents obesity later on in life,” Advances in Experimental Medicine and Biology, vol. 646, pp. 95–104, 2009. View at Publisher · View at Google Scholar · View at Scopus
  125. F. Savino and S. A. Liguori, “Update on breast milk hormones: leptin, ghrelin and adiponectin,” Clinical Nutrition, vol. 27, no. 1, pp. 42–47, 2008. View at Publisher · View at Google Scholar · View at Scopus
  126. S. G. Bouret, “Leptin, nutrition, and the programming of hypothalamic feeding circuits,” Nestle Nutrition Workshop Series: Pediatric Program, vol. 65, pp. 25–39, 2010. View at Publisher · View at Google Scholar
  127. C. M. Phillips, L. Goumidi, S. Bertrais et al., “Leptin receptor polymorphisms interact with polyunsaturated fatty acids to augment risk of insulin resistance and metabolic syndrome in adults,” Journal of Nutrition, vol. 140, no. 2, pp. 238–244, 2010. View at Publisher · View at Google Scholar · View at Scopus
  128. D. A. De Luis, R. Aller, O. Izaola, M. Gonzalez Sagrado, and R. Conde, “Influence of Lys656Asn polymorphism of leptin receptor gene on leptin response secondary to two hypocaloric diets: a randomized clinical trial,” Annals of Nutrition and Metabolism, vol. 52, no. 3, pp. 209–214, 2008. View at Publisher · View at Google Scholar · View at Scopus
  129. V. DeClercq, D. Stringer, R. Hunt, C. G. Taylor, and P. Zahradka, “Adipokine production by adipose tissue: a novel target for treating metabolic syndrome and its sequelae,” in Metabolic Syndrome: Underlying Mechanisms and Drug Therapies, M. Wang, Ed., pp. 73–131, John Wiley & Sons, Hoboken, NJ, USA, 2011.