Folate and Colorectal Cancer in Rodents: A Model of DNA Repair Deficiency

Table 2

Impact of experimental design on blood and tissue folate.

Animal model	Experimental diet	Abx	Wire cages	Length of feeding	In vivo folate levels	Citation
Rat studies quantifying impact of dietary intervention on blood and/or tissue folate status
Sprague-Dawley rats	Amino acid defined (Dyets); Control group: 8 mg/kg folate; Experimental group: 0 mg/kg folate	No	Yes	25 weeks	Folate levels (nmol/g); Control group: Liver 27.11; Kidney 11.69; Spleen 3.74; Brain 0.65; Experimental group: Liver 11.10; Kidney 4.79; Spleen 1.29; Brain 0.60	[71]
Sprague-Dawley rats	Amino acid defined (Dyets); Control group: 2 mg/kg folate; Experimental groups: 0 mg/kg folate; 8 mg/kg folate; 20 mg/kg folate	No	Yes	8 weeks	Control group: Plasma folate (ng/mL) ~50; Colonic folate (ng/mL) ~650; Experimental groups: Deficient; Plasma folate (ng/mL) ~25; Colonic folate (ng/mL)  ~480; Supplemented (8 mg/kg); Plasma folate (ng/mL)  ~80; Colonic folate (ng/mL)  ~975; Supplemented (20 mg/kg); Plasma folate (ng/mL)  ~140; Colonic folate (ng/mL)  ~975	[83]
Sprague-Dawley rats	AIN-76 semipurified diet; Control group: 8 mg/kg folate, no abx; Experimental groups: 0 mg/kg folate, no abx; 0 mg/kg folate, with abx first 4 weeks of feeding; 0 mg/kg folate, with abx last 4 weeks of feeding	Yes and no	Yes	12 weeks	Whole blood folate; Control group: 657 ng/mL; Experimental group: 125 ng/mL (no abx); 114 ng/mL (abx first 4 weeks); 61 ng/mL (abx last 4 weeks)	[72]
Sprague-Dawley rats	AIN-76 semipurified diet; Control group: 8 mg/kg folate, no abx; Experimental groups: 0 mg/kg folate, no abx; 0 mg/kg folate, with abx first 4 weeks of feeding; 0 mg/kg folate, with abx 4 weeks after AOM	Yes and no	Yes	26 weeks	Whole blood folate; Control group: 684 ng/mL; Experimental groups: 694 ng/mL (control + abx); 99 ng/mL (0 mg/kg, no abx); 100 ng/mL (0 mg/kg, abx first 4 weeks); 96 ng/mL (0 mg/kg, abx 4 weeks after AOM); Colon folate; Control group: 9.6 ug/mg; Experimental groups: 8.0 ug/mg (control + abx); 2.7 ug/mg (0 mg/kg, no abx); 3.1 ug/mg (0 mg/kg, abx first 4 weeks); 4.3 ug/mg (0 mg/kg, abx 4 weeks after AOM)	[73]
Sprague-Dawley rats	AIN93 (G or M not Specified); Control group: 2 mg/kg folate; Experimental group: 0 mg/kg folate	No	No	20 weeks	Hepatic folate (nmol/g); Control group: 17 nmol/g (weanling); 17 nmol/g (12 month old); Experimental group: 2.7 nmol/g (weanling); 1.8 nmol/g (12 month old)	[74]
Sprague Dawley rats	AIN93 purified diet (G or M not specified); Control group; 2 mg/kg (folate-replete); Experimental groups: 0 mg/kg; folate; 8 mg/kg	No	Yes	20 weeks	Plasma folate; Young Old; Control group: (umol/L) 34.1 30.6; [(ng/mL) 15.1 13.5]; Experimental group: Deficient; (umol/L) 1.5, 0.9; [(ng/mL) 0.7 0.04]; Supplemented: (umol/L)  53.9 55.5; [(ng/mL 23.8 24.6]; Colon (nmol/g); Young Old; Control; 4.7 3.0; Deficient; 1.3 0.7; Supplemented; 5.6 4.4	[75]
Fischer-344 rats	AIN-93 diet; Control group: 2 mg/kg folate; Experimental group: 0 mg/kg folate; Note: selenium assessed in this paper, not evaluated here.	No	Yes	11 weeks	Plasma folate; Control group: 277.4 nmol/L; [122.44 ng/mL]; Experimental group: 12.0 nmol/L; [5.30 ng/mL]	[85]
Sprague-Dawley rats	Amino acid defined (Dyets); All animals fed same diet (2 mg/kg folate) for first 10 weeks; 5 weeks following completion of carcinogen exposure, experimental diets began.; Control group: 2 mg/kg folate; Experimental groups: 0 mg/kg folate; 5 mg/kg folate; 8 mg/kg folate	Yes	No	24 weeks	Plasma folate; Control group: 32.2 ng/mL; Experimental groups: Deficient; 6.0 ng/mL; Supplemented (5 mg/kg); 72.8 ng/mL; Supplemented (8 mg/kg); 78.2 ng/mL; Hepatic folate; Control group: 7.7 ug/g; Experimental groups: Deficient; 5.0 ug/g; Supplemented (5 mg/kg); 8.5 ug/g; Supplemented (8 mg/kg); 9.9 ug/g	[76]
Male Hooded-Lister; rats	AIN-93G purified diet with vitamin-free casein; Control group: 5 mg/kg folate; Experimental group: 0 mg/kg folate	No	Yes	6 weeks	Folate value, ng/mg protein; Lymphocytes; Control: 0.45; Experimental: 0.27; Liver; Control: 136.2; Experimental: 93.9; Colon (descending); Control: 24.6; Experimental: 9.9; Spleen; Control: 16.5; Experimental: 7.9; Kidney; Control: 58.6; Experimental: 26.6; Brain; Control: 20.4; Experimental: 15.3; Heart; Control: 9.2; Experimental: 3.4	[82]
Mouse studies quantifying impact of dietary intervention on blood and/or tissue folate status
C57bl/6J mice, APC^Min	Amino acid defined (Dyets); Control group: 2 mg/kg folate; Experimental group: 0 mg/kg folate; 8 mg/kg folate*; 20 mg/kg folate	No	No	3 months; 6 months	Serum folate (ng/mL): Control group: 39.0 (3 months); 35.4 (6 months); Experimental group: Depleted; 12.1 (3 months); 10.8 (6 months); Supplemented; 56.0 (3 months); 46.0 (6 months); Hypersupplemented; 49.9 (3 months); 43.3 (6 months)	[77]
C57bl/6 mice, β-pol^+/−	AIN-93G purified diet with vitamin-free casein; Control group: 2 mg/kg folate; Experimental group: 0 mg/kg folate	Yes	No	8 weeks	Serum folate; Control group: 60 ng/mL; Experimental group: <5 ng/mL	[21]
C57bl/6 mice, Aag^−/−	AIN-93G purified diet with vitamin-free casein; Control group: 2 mg/kg folate; Experimental group: 0 mg/kg folate	Yes	Yes	4 weeks	Liver folate; Control group; 27.0 μg/g; Experimental group; 1.2 μg/g	[39]
					Apc ^+/+ crossed to SHMT genotype as indicated ^(+/+, +/−, −/−); Control group: (5 weeks); Plasma (ng/mL); 58.56 (+/+); 58.34 (+/−); 40.82 (−/−); Liver (fmol/ug pro); 51.80 (+/+); 56.65 (+/−); 50.77 (−/−)
C57bl/6 mice,; Apc ^min/+ Shmt1 (^+/− and ^−/−)	AIN-93G purified diet; Control group: 2 mg/kg folate; 2.5 g/kg choline; Experimental group: 0 mg/kg folate; 0 g/kg choline	No	Yes	5 weeks (Apc^+/+); 11 weeks (Apc^min/+)	Colon (fmol/ugpro); 35.14 (+/+); 21.46 (+/−); 17.09 (−/−); Experimental group: (5 weeks); Plasma (ng/mL); 20.60 (+/+); 38.95 (+/−); 8.52 (−/−); Liver (fmol/ug pro); 47.26 (+/+); 44.30 (+/−); 48.88 (−/−); Colon (fmol/ugpro); 9.15 (+/+); 18.04 (+/−); 14.89 (−/−); Apc ^min/+ crossed to Shmt genotype indicated ^(+/+, +/−, −/−); Control group: (11 weeks); Plasma (ng/mL); 24.68 (+/+); 20.91 (+/−); 26.44 (−/−); Liver (fmol/ug pro); 45.72 (+/+); 40.00 (+/−); 41.50 (−/−); Experimental group: (11 weeks); Plasma (ng/mL); 11.79 (+/+); 8.37 (+/−); 9.97 (−/−); Liver (fmol/ug pro); 28.49 (+/+); 23.25 (+/−); 29.44 (−/−)	[68]
C57bl/6J mice, Shmt (^+/− and ^−/−)	AIN-93G purified diet; Control group: 2 mg/kg folate; 2.5 g/kg choline; Experimental group: 0 mg/kg folate; 0 g/kg choline	No	No	32 weeks	Control group: Plasma folate (ng/mL); (wt)  36.3; (Tg)  46.8; Liver folate (fmol/ug pro); (wt)  43.1; (Tg)  51.3; Experimental group: Plasma folate (ng/mL); (wt)  7.4; (Tg)  5.5; Liver folate (fmol/ug pro); (wt)  36.1; (Tg)  34.0	[68]
C57bl/6 mice, APC^1638N	Amino acid defined (Dyets); Control group: 2 mg/kg folate; B-vitamin adequate; Experimental group: 0 mg/kg folate; B12, B6, and riboflavin deficient	No	No	16 weeks	Control group: Plasma folate (ng/mL) ~170; Colon folate (ng/g) ~500; Experimental group: Plasma folate (ng/mL) ~110; Colon folate (ng/g) ~300	[84]
C57bl/6 mice, APC^1638N	Maternal diet: AIN93M (Dyets); Control and experimental; Offspring diet: AIN93G during first 16 weeks of life; AIN93M during last 16 weeks of life (Dyets); Control and experimental; Control group: 2 mg/kg folate; 6 mg/kg riboflavin; 7 mg/kg B6; 50 ug/kg B12; Experimental groups: Deficient; 0.5 mg/kg folate; 2 mg/kg riboflavin; 2 mg/kg B6; 10 ug/kg B12; Supplemented; 8 mg/kg folate; 24 mg/kg riboflavin; 28 mg/kg B6; 200 ug/kg B12	No	No	Maternal diet: Fed 4 weeks preconception through weaning; Offspring diet: 32 weeks	Maternal; Control group: Plasma folate (ng/mL) 84.7; Hepatic folate (ug/g) 13.2; Experimental group: Deficient; Plasma folate (ng/mL) 81.4; Hepatic folate (ug/g) 11.1; Supplemented; Plasma folate (ng/mL) 104.4; Hepatic folate (ug/g) 13.3; Offspring; Control group: Plasma folate (ng/mL) 52.5; Hepatic folate (ug/g) 14.1; Sm Int folate (ng/g) 1205.9; Experimental group: Deficient; Plasma folate (ng/mL) 59.3; Hepatic folate (ug/g) 12.9; Sm Int folate (ng/g) 1264.7; Supplemented; Plasma folate (ng/mL) 50.2; Hepatic folate (ug/g) 13.3; Sm Int folate (ng/g) 1172.4	[78]
Folate depletion studies presenting critical colorectal cancer endpoints, but without folate status information
Fisher 344 rats	AIN93G; Control group: 2 mg/kg folate, −abx; Experimental groups: 0 mg/kg folate, −abx; 0 mg/kg folate, +abx	Yes and no	No	5 weeks	ND	[15]
Fisher 344 rats	NIH-31; Control group: 0.4% methionine; 0.3% choline; 2 mg/kg folate; Experimental group: Low methionine; 0% choline; 0 mg/kg folate	No	No	36 weeks; 54 weeks	ND	[79]
C57bl/6J mice	Casein/soy based; Control group: 2 mg/kg folate; Experimental group: 0 mg/kg folate	No	No	10 weeks	ND	[80]
BALB/cAnNCrlBR mice	Amino acid defined (Harlan Teklad); Control group: 2 mg/kg folate; Experimental group: 0.3 mg/kg folate	Yes	No	12 to 14 months	ND	[81]
C57bl/6 mice Bpol^+/−	AIN93G (Dyets); Control group: 2 mg/kg folate; Experimental group: 0 mg/kg folate	Yes	No	12 weeks total; (6 pre-DMH; 6 post-DMH)	ND	[59]
Albino rats	AIN93M; Control group: 2 mg/kg folate; Experimental groups: 8 mg/kg folate; 40 mg/kg folate	No	No	6 weeks total (4 weeks pre-AOM; 2 weeks post-AOM)	ND	[86]

Values in brackets [] have been calculated from published values for ease of comparison across studies; +/+, +/− and −/− refer to wildtype, heterozygous and null genotypes; ND: not determined.