Codon 54 polymorphism of the fatty acid binding protein 2 gene is associated with increased fat oxidation and hyperinsulinemia, but not with intestinal fatty acid absorption in Korean men

The alanine to threonine substitution at codon 54 (Ala54Thr) of the fatty acid binding protein 2 (FABP2) gene has been reported to be associated with increased fat oxidation and insulin resistance in several populations. It has been hypothesized that Ala54Thr substitution results in enhanced intestinal uptake of fatty acids and thereby an impairment of insulin action, but this hypothesis has not been proven in vivo. We studied the association between the Ala54Thr polymorphism of the FABP2 gene and intestinal (3)H-oleic acid absorption, as well as basal insulin level, basal metabolic rate, and fat oxidation rate in 96 healthy young Korean men. Among our subjects, the allele frequency of the Ala54Thr substitution was 0.34. Subjects with Thr54-encoding allele were found to have a higher mean fasting plasma insulin concentration and a higher basal fat oxidation rate compared with the subjects who were homozygous for the Ala54-encoding allele. However, there was no significant difference in basal metabolic rate or (3)H-oleic acid absorption according to the FABP2 gene polymorphism. These results suggest that the Ala54Thr substitution in the FABP2 gene is associated with increased fat oxidation and hyperinsulinemia in normal Korean men, but these effects are not mediated by an increase in the intestinal fatty acid absorption.     

Variation of the fatty acid binding protein 2 gene is not associated with obesity and insulin resistance in Japanese subjects.

An alanine to threonine substitution at codon 54 of the fatty acid binding protein 2 (FABP2) gene has been associated with insulin resistance in Pima Indians and with obesity in aboriginal Canadians. We investigated whether this polymorphism contributes to obesity and insulin resistance in 258 Japanese subjects. Thirty-six subjects (13.9%) were homozygous for the Thr54 allele, 106 (41.1%) were heterozygous for the Ala54/Thr54 allele, and 116 (45.0%) were homozygous for the Ala54 allele. The frequency of the Thr54 allele was 0.34 and did not differ significantly between men and women. The incidence of non-insulin-dependent diabetes mellitus (NIDDM) was not different among the three genotypes. The variation at codon 54 of the FABP2 gene was not associated with obesity, hypertension, dyslipidemia, hyperuricemia, or hyperinsulinemia. These results suggest that the polymorphism at codon 54 of the FABP2 gene is not a major contributing factor to obesity and insulin resistance in Japanese subjects.     

Codon 54 polymorphism of the fatty acid binding protein gene and insulin resistance in the Japanese population.

AIM: To determine the relationship of the polymorphism at codon 54 of the intestinal fatty acid binding protein gene (FABP2) with insulin resistance and susceptibility to Type 2 diabetes mellitus (DM) in the Japanese population. METHODS: We evaluated the polymorphism by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 150 Type 2 DM patients and 147 healthy control subjects. The frequency of alleles encoding threonine (Thr54) and alanine (Ala54) at codon 54 of FABP2 in Type 2 DM patients was compared with that of healthy controls. Insulin sensitivity was assessed by the hyperinsulinaemic euglycaemic clamp in Type 2 DM patients with Ala54 homozygotes, Ala54/Thr54 heterozygotes and Thr54 homozygotes and by homeostasis model assessment (HOMA) in the nondiabetic group. RESULTS: The frequency of alleles encoding Ala54 and Thr54 was 0.59 and 0.41 in Type 2 DM patients, respectively, similar to that observed in nondiabetic controls (0.64 for Ala54 and 0.36 for Thr54). Insulin sensitivity was not significantly different between subjects with and without Thr54 allele either within the DM group or healthy controls. CONCLUSIONS: The allele encoding threonine in the FABP2 does not predispose to Type 2 DM or insulin resistance in the Japanese population.     

Lack of association between the fatty acid binding protein 2 (FABP2) polymorphism with obesity and insulin resistance in two aboriginal populations from Chile

Abstract The aim of this study was to assess the frequency of fatty acid binding protein 2 (FABP2) Ala54Thr genetic polymorphism and to evaluate its association with obesity and insulin resistance in Chilean aboriginal populations. A sample of 96 urban Aymara and 111 urban Mapuche subjects aged 20–80 years were recruited for this cross-sectional study. Glucose, insulin and lipid profile were measured in fasting plasma samples. Insulin resistance was estimated through the HOMA-IR model. FABP2 Ala54Thr genotypes were determined by PCR followed by RFLP analysis. The allele frequency of Thr54 variant was estimated as 18.2% in Aymara subjects, which is one of the lowest reported to date. The corresponding frequency in Mapuche subjects was 31.9% (p<0.002). Regarding genotype–phenotype associations, no significant differences were found in any of the anthropometric or metabolic variables according to Ala54Thr genotypes. After adjustment by BMI and metabolic variables through a logistic regression analysis, the association of the FABP2 polymorphism with ethnic group persisted (Mapuche group: OR=2.37, 95% CI 1.319–4.277, p=0.004) It is unlikely that Ala54Thr polymorphism of the FABP2 gene plays a relevant role in obesity and insulin resistance in Chilean ethnic groups.     

Thr-encoding allele homozygosity at codon 54 of FABP 2 gene may be associated with impaired delta 6 desatruase activity and reduced plasma arachidonic acid in obese children

BACKGROUND: Alanine-for-threonine substitution at codon 54 (A54T polymorphism) in the fatty acid-binding protein 2 gene (FABP2) has been associated with hypertriglyceridemia and insulin resistance. Impairment in the activity of delta 6 and 5 desaturases is also supposed to be a factor predisposing the development of insulin resistance syndrome. AIM: We investigated the relationship between A54T polymorphism in FABP2 and the impairment of long-chain polyunsaturated fatty acid metabolism in obese children. METHODS: Thirty-two obese children participated. During the study, the children continued their habitual diet, which was documented in a 3-day food record using household measures. Anthropometry was performed, and serum lipid and fatty acid composition in plasma were analyzed. The polymorphism of codon 54 in the FABP 2 gene was analyzed. RESULTS: The allele frequency was 0.66 and 0.34 for Ala54 and Thr54, respectively. There were no significant differences in age, body mass index, fasting serum glucose, insulin or serum lipoproteins among the three polymorphism groups. These were also no significant differences in the intake of energy, the percentage of energy nutrients or in the dietary lipid composition. The content of arachidonic acid (AA) in plasma was lowest in Thr/Thr54 (p < 0.05). The indices of delta-6 desaturase (D6D) activity in Thr/Thr54 were significantly lower than in Thr/Ala54 or Ala/Ala54 (p < 0.05, p < 0.01, respectively). CONCLUSIONS: In obese children, Thr/Thr54 of the FABP 2 gene is associated with impaired activation of D6D and reduced AA content. The results in the LCPUFA profile suggest that Thr/Thr54 may predispose the to development of insulin resistance.     

Ala54Thr polymorphism of the fatty acid binding protein 2 gene and saturated fat intake in relation to lipid levels and insulin resistance: the Coronary Artery Risk Development in Young Adults (CARDIA) study

The Thr54 allele of the intestinal fatty acid–binding protein Ala54Thr functional polymorphism (FABP2) is associated with increased fat oxidation and insulin resistance. We determined the cross-sectional associations of the FABP2 gene with lipid levels and insulin resistance in 2148 participants who completed the year-20 examination of the Coronary Artery Risk Development in Young Adults (CARDIA) study. No significant difference in total cholesterol, low-density or high-density lipoprotein cholesterol, triglycerides, high-density lipoprotein cholesterol to total cholesterol ratio, or homeostasis model assessment of insulin resistance (HOMA-IR) was found between FABP2 genotypes. However, in the presence of a high–saturated fat diet (≥53.2 g/d, the 90th percentile for the population), the AA/AG genotypes (carriers of the Thr54 allele) of FABP2 had statistically significantly higher levels of log(HOMA-IR) (P = .006) and a lower high-density lipoprotein cholesterol to total cholesterol ratio (P = .03), and borderline statistically significantly higher levels of total cholesterol, low-density lipoprotein cholesterol, and log(triglycerides) (P values = .08, .07, and .05, respectively) compared with those with the GG genotype (Ala54 homozygotes). Lipid levels and log(HOMA-IR) did not vary by genotype with saturated fat intake less than 53.2 g/d. Limiting dietary saturated fat intake may be particularly important among carriers of the A allele of FABP2.     

Thr54 allele of the FABP2 gene affects resting metabolic rate and visceral obesity

We investigated the relationship between Ala54Thr variant allele of the fatty acid-binding protein 2 (FABP2) gene (Ala54Thr) and development of obesity in Japanese obese women. FABP2 genotypes were determined with a fluorescent allele-specific DNA primer assay system. Body weight, waist and hip circumference, amounts of visceral and subcutaneous white adipose tissue measured by computed tomography (CT) were compared between subjects with Thr allele and without Thr allele before and after the diet and exercise therapy in 80 Japanese obese women. The frequency of the Thr54 allele did not differ between obese and control subjects (0.388 versus 0.329, respectively). In subjects with Ala/Thr and Thr/Thr genotype, adjusted resting metabolic rate (RMR) was significantly lower than the subjects with Ala/Ala genotype. Subjects with the Thr54 allele showed significantly greater waist circumference after diet and exercise therapy than subjects with Ala/Ala genotype. They also demonstrated greater body weight at 20 years of age compared to subjects with Ala/Ala genotype. In conclusion, Thr54 allele of FABP2 has associations with lower adjusted resting metabolic rate, resistance in reducing visceral white adipose tissue (WAT) and early onset of obesity in Japanese obese women.     

Variation in the<Emphasis Type="Italic"> FABP2</Emphasis> promoter affects gene expression: implications for prior association studies

Aims/hypothesis An Ala54Thr polymorphism in the FABP2 gene has previously been associated with insulin resistance and lipid oxidation rates in Pima Indians. Ala54Thr functionally alters the proteins ability to bind and transport dietary fatty acids. In the current report, we sought additional functional variation in FABP2 by sequencing putative regulatory regions.Methods More than 1.2 Kb of the putative promoter of FABP2 was sequenced in 20 Pima subjects. Variations were genotyped in 84 additional Pima Indian subjects to assess haplotype combinations. Functional activities of variant and nonvariant promoters were compared in Caco-2 cells transfected with luciferase reporter constructs.Results Seven variations were identified in the FABP2 promoter in Pima Indians. Genotypes of these variants were in complete concordance with each other, and were in complete concordance with Ala54Thr. Therefore, only two promoter alleles were observed in Pima Indians, an Ala54-associated promoter and a Thr54-associated promoter. In contrast, genotyping of these variants in Caucasian DNA showed multiple genotypic combinations. In vitro reporter assays indicated that the Thr54-associated promoter in Pima Indians resulted in a threefold reduction in promoter activity as compared to Ala54-associated promoter.Conclusion/interpretation Two functional variations exist in FABP2—the coding Ala54Thr and the variant promoter. In the Pima Indian population, but not the Caucasian population, these two functional variants are always carried on the same allele. Therefore, some of the in vivo phenotypic associations previously attributed to the Ala54Thr substitution, which alters binding characteristics of the protein, could instead be due to promoter variation, which alters expression levels.Abbreviations A, Adenosine - Ala, alanine - CEPH, genomic DNA set, originating from Caucasians from Utah, USA - FABP2, intestinal fatty acid binding protein gene - G, guanosine - IFABP, intestinal fatty acid binding protein - PCR, polymerase chain reaction - Thr, threonine     

The type 2 deiodinase A/G (Thr92Ala) polymorphism is associated with decreased enzyme velocity and increased insulin resistance in patients with type 2 diabetes mellitus

The single-nucleotide polymorphism A/G in the type 2 deiodinase (D2) gene predicts a threonine (Thr) to alanine (Ala) substitution at codon 92 (D2 Thr92Ala) and is associated with insulin resistance in obese patients. Here, this association was investigated in 183 patients with type 2 diabetes mellitus, using homeostasis model assessment. The median fasting plasma insulin in Ala/Ala individuals was significantly higher than in patients with Ala/Thr or Thr/Thr genotypes (19.6 vs. 12.0 vs. 14.8 mIU/ml, respectively; P = 0.004). Assuming a recessive model, the homeostasis model assessment index was higher in the Ala/Ala group when compared with Ala/Thr-Thr/Thr group (8.50 vs. 4.85, P = 0.003). Although this polymorphism has not been associated with changes in D2 kinetics as measured in HEK-293 cells transiently expressing D2 Thr92Ala, we investigated whether such association could be detected in human tissue samples. Remarkably, in thyroid and skeletal muscle samples from subjects homozygous for the Ala allele, D2 velocity was significantly lower than in subjects with Ala/Thr-Thr/Thr genotypes (P = 0.05 and 0.04, respectively). In conclusion, the A/G polymorphism is associated with greater insulin resistance in type 2 diabetes mellitus patients and with lower D2 velocity in tissue samples. These findings suggest that the D2-generated T(3) in skeletal muscle plays a role in insulin resistance.     

Variation in the fatty acid binding protein 2 gene is not associated with markers of metabolic syndrome in patients with coronary heart disease

BACKGROUND AND AIM: It has been suggested that the threonine (Thr) 54 allele of the intestinal fatty acid binding protein 2 (FABP2) gene is associated with insulin resistance and affects the fatty acid composition of serum lipids. Our aim was to investigate the frequency of the alanine (Ala) 54Thr polymorphism of the FABP2 gene in patients with coronary heart disease (CHD), and the association between the polymorphism and the markers of metabolic syndrome, serum lipid levels and the fatty acid profile of serum lipids. METHODS AND RESULTS: A total of 414 CHD patients (mean age 61 years, range 33-74) participated in the cross-sectional EUROASPIRE (European Action on Secondary Prevention through Intervention to Reduce Events) Study. Markers of metabolic syndrome included fasting plasma glucose concentration, serum high-density lipoprotein cholesterol and triglycerides (TG), waist circumference, the waist/hip ratio, body mass index (BMI) and blood pressure (BP). The frequency of the Thr54 allele was similar in the CHD patients (27.2%) and control subjects from two independent studies (27.8% and 28.7%). There were no significant differences in plasma glucose, serum lipids, BP, BMI, waist circumference or waist/hip ratio among the genotypes. Genotype frequency was not associated with the prevalence of diabetes or metabolic syndrome, but metabolic syndrome (as defined by National Cholesterol Education Program criteria) tended to be more frequent in subjects with the Thr/Thr genotype (p = 0.095). There were no differences in the fatty acid profiles of serum cholesteryl esters, TG or phospholipids among the genotypes. CONCLUSIONS: The Ala54Thr polymorphism of the FABP2 gene is not associated with CHD, markers of the metabolic syndrome, or the fatty acid profile of serum lipids in Finnish CHD patients.