- About this Journal ·
- Abstracting and Indexing ·
- Aims and Scope ·
- Annual Issues ·
- Article Processing Charges ·
- Author Guidelines ·
- Bibliographic Information ·
- Citations to this Journal ·
- Contact Information ·
- Editorial Board ·
- Editorial Workflow ·
- Free eTOC Alerts ·
- Publication Ethics ·
- Recently Accepted Articles ·
- Reviewers Acknowledgment ·
- Submit a Manuscript ·
- Subscription Information ·
- Table of Contents
International Journal of Endocrinology
Volume 2014 (2014), Article ID 105168, 7 pages
The TG/HDL-C Ratio Might Be a Surrogate for Insulin Resistance in Chinese Nonobese Women
Department of Cardiovascular Medicine, West China Hospital, Sichuan University, Chengdu 610041, China
Received 17 May 2014; Accepted 23 June 2014; Published 21 July 2014
Academic Editor: Giovannella Baggio
Copyright © 2014 Jiyun He 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.
Obejective. To examine the discriminatory power of triglyceride (TG) and triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C) for insulin resistance (IR) in a normoglycaemic Chinese population. Methods. The data were collected from 711 individuals. The normoglycaemic individuals were eventually included in the study (n = 533, age: 62.8 ± 6.6 years, male: 56.8%), who were with a fasting plasma glucose < 6.1 mmol/L and without a history of diabetes. IR was defined as the upper quintile (≥1.6) of homeostasis model assessment of IR. Area under the receiver operating characteristic curve (AROC) was used to examine the discriminatory power. Results. The discriminatory power of TG/HDL-C for IR was acceptable in women with a BMI < 24 kg/m2 or waist circumference < 80 cm (AROCs: 0.718 and 0.713, resp.); however, the discriminatory power was not acceptable in the obese women. TG/HDL-C was not an acceptable marker of IR in men. The discriminatory power of TG for IR was not acceptable in both men and women. Conclusions. The discriminatory power of TG/HDL-C for IR differs by gender and obesity index in the normoglycaemic Chinese population, and TG/HDL-C could discriminate IR in the nonobese and normoglycaemic women.
Insulin resistance is characterized by a decrease in the ability of insulin to stimulate the use of glucose by muscles and adipose tissues and to suppress hepatic glucose production and output . Insulin resistance plays an important pathogenic role in causation of diabetes and cardiovascular diseases (CVD). Therefore, identification of insulin resistance would facilitate selection of high-risk individuals for primary preventions of these interrelated diseases. Currently, the standard methods of measuring insulin resistance includes the glucose clamp, the insulin suppression test, and the frequently sampled intravenous glucose tolerance test [2–4], but these tests are not routinely measured in most clinical practices owing to the time and cost involved. Some simple methods of measuring insulin resistance includes fasting insulin, fasting plasma glucose (FPG)/fasting insulin (FINS), homeostasis model assessment method of insulin resistance (HOMA-IR), and 1/(FPG × FINS). These methods all include insulin, but plasma insulin is not routinely measured in most clinical laboratories. So, identification of insulin resistance by simple surrogates would be useful in clinical practices.
Recently, some studies [2, 5–7] gave us some hopes, and these studies showed that in patients without diabetes, triglyceride (TG) and triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C) were closely and positively related to insulin resistance, and the two variables were recommended as surrogates for insulin resistance. However, not all studies found TG and TG/HDL-C to be associated with insulin resistance. For example, some studies [8–11] showed that TG and TG/HDL-C were not reliable markers of insulin resistance in some populations. These previous results were inconsistent, and further studies are still necessary. On the other hand, these previous studies mainly focused on non-Asian populations. Therefore, the aims of our study were to examine the discriminatory power of TG and TG/HDL-C for insulin resistance in a normoglycaemic Chinese population.
2.1. Study Population
In 2007, a health examination was performed in 711 individuals in an urban community located in Chengdu, Sichuan province, China. The cohort was a part of a study supported by megaprojects of science research for the 11th five-year plan, China (Trends in the incidence of metabolic syndrome and integrated control in China). The detailed information of the study has been reported elsewhere . We included normoglycaemic individuals in the study, who were with a FPG < 6.1 mmol/L and without a medical history of diabetes . In addition, we excluded individuals using any medication known to influence insulin resistance or lipid metabolism (such as corticosteroids and lipid-lowering drugs). Because estrogen exposure could lead to an elevation of TG levels, women receiving exogenous estrogens also were excluded. Therefore, 533 individuals with complete data (age: years, range: 45.0~83.0, male: 56.8%) were available for analysis. The study was approved by Ministry of Health of China, as well as by the Ethics Committee of West China Hospital of Sichuan University. The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki as reflected in a priori approval by the institution’s human research committee. All participants provided written informed consent.
2.2. Data Collection
In 2007, medical professionals conducted a survey of CVD risk factors according to the MONICA protocol. The survey content included standardized questionnaire, physical examination, and laboratory tests. The questionnaire included sex, age and CVD risk factors, such as smoking status, alcohol consumption levels, physical activity, and CVD family history. Physical examination included blood pressure, height, weight, waist circumference, and hip circumference. Laboratory tests included FPG, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), HDL-C, TG, high sensitivity creactive protein (hsCRP), and insulin. Blood was drawn from the antecubital vein in the morning after a 12 h fasting. Fasting serum insulin was measured by radioimmunoassay (XH-6010, Xi’an, China). Fasting glucose, TG, and HDL-C were measured enzymatically using a MODULAR P800 Analyzer (Roche Diagnostics). These chemistries were measured at the laboratory of West China Hospital (Chengdu, China).
2.3. Related Definitions
Insulin resistance was defined by using HOMA-IR, which was calculated as (fasting glucose mmol/L × fasting insulin mU/L)/22.5. Insulin resistant individuals were defined as those who had the highest quintile value of the HOMA-IR (≥1.6), according to the previous studies [14, 15]. Smoking is the average cigarette consumption ≥ one/day. Alcohol intake is the average intake of alcohol ≥ 50 g/day. Those with hypertension were defined as having systolic blood pressure (SBP) ≥ 140 mmHg and/or diastolic blood pressure (DBP) ≥ 90 mmHg and/or currently taking antihypertensive medications. Body mass index (BMI) was calculated as weight (in kg)/height .
2.4. Statistical Analysis
Data are presented as means ± standard deviation (SD) for normal variables or median + interquartile range for skewed variables. Smoking and alcohol intake were used as dummy variables. Comparisons between groups were performed by independent t test for normally distributed variables and by the nonparametric Mann-Whitney test for skewed variables. Interactions between categorical variables were evaluated with the Pearson test. Area under the receiver operating characteristic curve (AROC) was used to examine the discriminatory power of TG and TG/HDL-C for insulin resistance: AROC of 0.5 = no discrimination, 0.7 ≤ AROC < 0.8 = acceptable, 0.8 ≤ AROC < 0.9 = excellent, AROC ≥ 0.9 = outstanding . For statistical analysis, SPSS (version 10.0; SPSS, Chicago, IL) software was used. Statistical significance was defined as .
3.1. Demographic Data
Demographic data are presented in Table 1. Age, waist circumference, waist circumference/hip circumference, prevalence of smoking and alcohol intake, SBP, DBP, and TC/HDL-C were significantly higher in men; however, HDL-C, TG, insulin and HOMA-IR were significantly lower. TG/HDL-C, hsCRP, FPG, LDL-C, BMI, hip circumference, and prevalence of hypertension were similar in both groups. The prevalence of insulin resistance was 20.5% in the population, and the prevalence was higher in women than in men (27.4% versus 15.2%, , Table 1).
3.2. Discriminatory Power of TG/HDL-C and TG for Insulin Resistance in Different Population
The correlations between TG and TG/HDL-C with HOMA-IR were not similar in different groups (r for TG and HOMA-IR: all individuals = 0.343, men = 0.316 and women = 0.339; TG/HDL-C and HOMA-IR: all individuals = 0.376, men = 0.360 and women = 0.401; all associations, ).
For discriminating insulin resistance, TG and TG/HDL-C were not acceptable in the whole population (AROCs: 0.634 and 0.654, resp.). When applied to men or women, AROCs were also not acceptable (men: 0.627 for TG, 0.657 for TG/HDL-C; women: 0.614 for TG, 0.652 for TG/HDL-C, resp.).
When women were divided into different subgroups according to BMI (<24, ≥24 kg/m2) or waist circumference (<80, ≥80 cm), the discriminatory power of TG/HDL-C for insulin resistance was acceptable in the nonobese women (Table 2; Figures 1(a) and 1(c)). However, the discriminatory power of TG/HDL-C for insulin resistance was not acceptable in the obese women (Table 2; Figures 1(b) and 1(d)). When men were divided into different subgroups according to BMI (<24, ≥24 kg/m2) or waist circumference (<90, ≥90 cm), the discriminatory power of TG/HDL-C for insulin resistance was not acceptable in each subgroup (Table 2). In addition, TG was not an acceptable marker of insulin resistance in each subgroup (Table 2, Figures 1(a)–1(d)). Further, we categorized the population into different subgroups according to the combination of BMI and waist circumference, and the discriminatory power was not improved, even lower than the single standard of classification (data not shown)
3.3. Other Potential Markers of Insulin Resistance
Table 3 shows AROCs for some other potential markers of insulin resistance. For men, the best surrogate for insulin resistance was waist circumference, followed by waist circumference/hip circumference, BMI, and hip circumference (Table 3). For women, BMI was the best surrogate for insulin resistance, followed by waist circumference, waist circumference/hip circumference, and hip circumference (Table 3). AROCs of all clinical variables were acceptable, and AROCs of all biological variables were not acceptable (Table 3).
Our findings showed that the discriminatory power of TG/HDL-C for insulin resistance differs by gender and obesity index in normoglycaemic Chinese population, and the discriminatory power of TG for insulin resistance is not acceptable in both men and women. Its presence has been demonstrated in two ways. First, the discriminatory power of TG/HDL-C for insulin resistance was acceptable in the nonobese women (all AROCs > 0.700 in each subgroup). However, TG/HDL-C could not discriminate insulin resistance in the obese women, and in men (all AROCs < 0.700 in each subgroup). Second, the discriminatory power of TG for insulin resistance is not acceptable in both men and women (all AROCs < 0.700 in each subgroup).
The study showed that there were more significant associations between insulin resistance and TG, as well as TG/HDL-C, in women than in men, the same as a previous study . While, Masharani et al.  had a different result: in women, there was no significant association between insulin resistance and TG. The current inconsistent results might be caused by sexual and racial differences in lipid profiles. Usually, women show a more favorable metabolic risk profile than men, including lower TG and higher HDL-C levels . Després et al.  have also shown that in African Americans and white women, lipoprotein lipase (LPL) activity, which is responsible for clearing TG-containing lipoproteins from the circulation, was higher and this might induce a lower TG levels, and then further causing a weak association between TG levels and insulin resistance in those population. Along with these characteristics, some studies have shown that TG and TG/HDL-C were not reliable markers of insulin resistance in African Americans [8, 9, 11]. However, our study did not draw similar conclusions in Chinese women, and further studies should be warranted. Although sexual and racial differences might influence the associations between insulin resistance and TG, as well as TG/HDL-C, many studies have shown that increasing TG and decreasing HDL-C could deteriorate insulin sensitivity. When TG persists at high levels, heparin activates lipoprotein lipase to increase intravascular lipolysis of circulating TG, thus increasing tissue exposure to free fatty acids (FFA). High FFA may deteriorate insulin sensitivity though oxidative stress pathway [21, 22]. On the other hand, oxidation and inflammation could cause insulin resistance. Since HDL-C has the ability of anti-oxidation and anti-inflammation, decreasing HDL-C might lead to insulin resistance.
Although TG/HDL-C could discriminate insulin resistance in nonobese women, it couldn’t work in obese women. A study  also showed that the association of TG/HDL-C with insulin resistance was stronger among people with a BMI < 25 kg/m2 than those with a BMI ≥ 30 kg/m2. Some studies [8, 10] also showed TG/HDL-C was not a reliable marker of insulin resistance in the obese. These current data might suggest that TG/HDL-C is most clinically useful for the discrimination of insulin resistance in individuals with normal weight. However, McLaughlin et al.  showed TG/HDL-C could discriminate insulin resistance in the subjects with a BMI ≥ 25 kg/m2. Current studies have different results, and confirmatory studies might be warranted. In the present study, all clinical variables were acceptable markers of insulin resistance (Table 3), and those should be recommended to be used in most clinical practices. However, all biological variables were not acceptable (Table 3).
Insulin resistance expressed by HOMA-IR is generally accepted as a valid method in epidemiological surveys. However, there is hardly any consensus on the cut-off points. Values based on 50th percentile [24, 25], 75th percentile , 90th percentile , lower boundary of the top quintile [14, 15], or tertile [2, 3] of HOMA-IR have been used previously. We defined insulin resistance as HOMA-IR greater than the 80th percentile (≥1.60), which was commonly practiced [14, 15]. In addition, when we performed a separate analyses with insulin resistance defined by the top quartile of HOMA (>1.47) or 90th percentile (>2.02), we obtained similar results (data not shown). Further, insulin resistance is reported to occur at HOMA levels that range from 2.00 to 4.00 in non-Asians, even greater [28, 29], and the threshold levels are lower in Asians, from 1.38 to 2.00 [14, 30, 31]. Our HOMA threshold of 1.6 is within this range. Although we defined insulin resistance a little arbitrarily, it might be accepted in clinical practices.
The study also had several limitations. Firstly, the major limitation of our study was failure to use a glucose clamp, an insulin suppression test, or a frequently sampled intravenous glucose tolerance test. However, those methods for all individuals over the course of our study were not feasible for pragmatic reasons and logistics. Secondly, the absence of an oral glucose tolerance test might miss some patients with diabetes. Thirdly, because of the relatively small sample size, the results of our study might have limited statistical power. No comparisons between different races might be another limitation.
In conclusion, the discriminatory power of TG/HDL-C for insulin resistance differs by gender and obesity index in the normoglycaemic Chinese population, and the discriminatory power of TG for insulin resistance is not acceptable in both men and women. TG/HDL-C could discriminate insulin resistance in the nonobese and normoglycaemic women, and it should be recommended in clinical practices. TG might not be recommended for clinical practices. Further studies should include different ethnic backgrounds, and the gold standard test for evaluating insulin resistance should be used.
Conflict of Interests
The authors declare that there is no conflict of interests regarding the publishing of this paper.
Jiyun He and Sen He equally contributed to the paper.
The authors thank the contributions of Dr. Qing’s team at the Hospital of Chengdu Guoguang Eectron Tube Plant (Chengdu, CN). This study was supported by Megaprojects of Science Research for the 11th Five-Year Plan, China (Grant no. 2006BAI01A01).
- S. Matthaei, M. Stumvoll, M. Kellerer, and H. Häring, “Pathophysiology and pharmacological treatment of insulin resistance,” Endocrine Reviews, vol. 21, no. 6, pp. 585–618, 2000.
- T. McLaughlin, F. Abbasi, K. Cheal, J. Chu, C. Lamendola, and G. Reaven, “Use of metabolic markers to identify overweight individuals who are insulin resistant,” Annals of Internal Medicine, vol. 139, no. 10, pp. 802–809, 2003.
- K. L. Cheal, F. Abbasi, C. Lamendola, T. McLaughlin, G. M. Reaven, and E. S. Ford, “Relationship to insulin resistance of the Adult Treatment Panel III diagnostic criteria for identification of the metabolic syndrome,” Diabetes, vol. 53, no. 5, pp. 1195–1200, 2004.
- R. N. Bergman, I. D. Hope, Y. J. Yang, et al., “Assessment of insulin sensitivity in vivo: a critical review,” Diabetes/Metabolism Research and Reviews, vol. 5, pp. 411–429, 1989.
- T. McLaughlin, G. Reaven, F. Abbasi et al., “Is there a simple way to identify insulin-resistant individuals at increased risk of cardiovascular disease?” The American Journal of Cardiology, vol. 96, no. 3, pp. 399–404, 2005.
- P. Bovet, D. Faeh, A. Gabriel, and L. Tappy, “The prediction of insulin resistance with serum triglyceride and high-density lipoprotein cholesterol levels in an East African population,” Archives of Internal Medicine, vol. 166, no. 11, pp. 1236–1237, 2006.
- C. Snehalatha, K. Satyavani, S. Sivasankari, V. Vijay, and A. Ramachandran, “Serum triglycerides as a marker of insulin resistance in non-diabetic urban Indians,” Diabetes Research and Clinical Practice, vol. 69, no. 2, pp. 205–206, 2005.
- A. E. Sumner, K. B. Finley, D. J. Genovese, M. H. Criqui, and R. C. Boston, “Fasting triglyceride and the triglyceride-HDL cholesterol ratio are not markers of insulin resistance in African Americans,” Archives of Internal Medicine, vol. 165, no. 12, pp. 1395–1400, 2005.
- S. Kim-Dorner, P. A. Deuster, S. A. Zeno, A. T. Remaley, and M. Poth, “Should triglycerides and the triglycerides to high-density lipoprotein cholesterol ratio be used as surrogates for insulin resistance?” Metabolism, vol. 59, no. 2, pp. 299–304, 2010.
- Y. M. C. Huguette, A. K. G. Boris, N. F. Raïssa, et al., “Prevalence of insulin resistance in obese Cameroonian Women,” Journal of Diabetes and Endocrinology, vol. 1, pp. 19–26, 2010.
- M. G. Knight, J. H. Goedecke, M. Ricks et al., “The TG/HDL-C ratio does not predict insulin resistance in overweight women of African descent: a study of South African, African American and West African women,” Ethnicity and Disease, vol. 21, no. 4, pp. 490–494, 2011.
- J. Ren, S. M. Grundy, J. Liu et al., “Long-term coronary heart disease risk associated with very-low-density lipoprotein cholesterol in Chinese: the results of a 15-Year Chinese Multi-Provincial Cohort Study (CMCS),” Atherosclerosis, vol. 211, no. 1, pp. 327–332, 2010.
- World Health Organization, Definition and Diagnosis of Diabetes Mellitus and Intermediate Hyperglycaemia. Report of a World Health Organization/International Diabetes Federation Consultation, World Health Organization, 2006.
- E. Bonora, S. Kiechl, J. Willeit et al., “Prevalence of insulin resistance in metabolic disorders: the Bruneck study,” Diabetes, vol. 47, no. 10, pp. 1643–1649, 1998.
- S. Tabata, S. Yoshimitsu, T. Hamachi, H. Abe, K. Ohnaka, and S. Kono, “Waist circumference and insulin resistance: a cross-sectional study of Japanese men,” BMC Endocrine Disorders, vol. 9, article 1, 2009.
- D. Hosmer and S. Lemeshow, Applied Logistic Regression, John Wiley & Sons, New York, NY, USA, 2nd edition, 2000.
- R. Lichnovská, S. Gwozdziewiczová, and J. Hrebícek, “Gender differences in factors influencing insulin resistance in elderly hyperlipemic non-subjects,” Cardiovascular Diabetology, vol. 1, article 4, 2002.
- U. Masharani, I. D. Goldfine, and J. F. Youngren, “Influence of gender on the relationship between insulin sensitivity, adiposity, and plasma lipids in lean nondiabetic subjects,” Metabolism: Clinical and Experimental, vol. 58, no. 11, pp. 1602–1608, 2009.
- S. Lemieux, J. P. Després, S. Moorjani et al., “Are gender differences in cardiovascular disease risk factors explained by the level of visceral adipose tissue?” Diabetologia, vol. 37, no. 8, pp. 757–764, 1994.
- J. P. Després, C. Couillard, J. Gagnon, et al., “Race, visceral adipose tissue, plasma lipids, and lipoprotein lipase activity in men and women: the health, risk factors, exercise training, and genetics (HERITAGE) family study,” Arteriosclerosis, Thrombosis, and Vascular Biology, vol. 20, no. 8, pp. 1932–1938, 2000.
- T. K. T. Lam, A. Carpentier, G. F. Lewis, G. van de Werve, I. G. Fantus, and A. Giacca, “Mechanisms of the free fatty acid-induced increase in hepatic glucose production,” The American Journal of Physiology—Endocrinology and Metabolism, vol. 284, no. 5, pp. E863–E873, 2003.
- G. F. Lewis, A. Carpentier, K. Adeli, and A. Giacca, “Disordered fat storage and mobilization in the pathogenesis of insulin resistance and type 2 diabetes,” Endocrine Reviews, vol. 23, no. 2, pp. 201–229, 2002.
- C. Li, E. S. Ford, Y. X. Meng, A. H. Mokdad, and G. M. Reaven, “Does the association of the triglyceride to high-density lipoprotein cholesterol ratio with fasting serum insulin differ by race/ethnicity?” Cardiovascular Diabetology, vol. 7, article 4, 2008.
- H. Yeni-Komshian, M. Carantoni, F. Abbasi, and G. M. Reaven, “Relationship between several surrogate estimates of insulin resistance and quantification of insulin-mediated glucose disposal in 490 healthy nondiabetic volunteers,” Diabetes Care, vol. 23, no. 2, pp. 171–175, 2000.
- M. T. Ghiringhello, J. G. Vieira, T. T. Tachibana, et al., “Distribution of HOMA-IR in brazilian subjects with different body mass indexes,” Arquivos Brasileiros de Endocrinologia, vol. 50, pp. 573–574, 2006.
- B. Hedblad, P. Nilsson, L. Janzon, and G. Berglund, “Relation between insulin resistance and carotid intima-media thickness and stenosis in non-diabetic subjects. Results from a cross-sectional study in Malmo, Sweden,” Diabetic Medicine, vol. 17, no. 4, pp. 299–307, 2000.
- Y. Nakai, M. Fukushima, S. Nakaishi et al., “The threshold value for insulin resistance on homeostasis model assessment of insulin sensitivity,” Diabetic Medicine, vol. 19, no. 4, pp. 346–347, 2002.
- L. U. Monzillo and O. Hamdy, “Evaluation of insulin sensitivity in clinical practice and in research settings,” Nutrition Reviews, vol. 61, no. 12, pp. 397–412, 2003.
- J. F. Ascaso, P. Romero, J. T. Real, R. I. Lorente, J. Martínez-Valls, and R. Carmena, “Abdominal obesity, insulin resistance, and metabolic syndrome in a Southern European population,” European Journal of Internal Medicine, vol. 14, no. 2, pp. 101–106, 2003.
- H. Ohnishi, S. Saitoh, S. Takagi et al., “Incidence of insulin resistance in obese subjects in a rural Japanese population: the Tanno and Sobetsu study,” Diabetes, Obesity and Metabolism, vol. 7, no. 1, pp. 83–87, 2005.
- Y. Park, H. Kwon, S. Y. Lim et al., “Optimal waist circumference cutoff value reflecting insulin resistance as a diagnostic criterion of metabolic syndrome in a nondiabetic korean population aged 40 years and over: the chungju metabolic disease cohort (cmc) study,” Yonsei Medical Journal, vol. 51, no. 4, pp. 511–518, 2010.