Intestinal fatty acid binding protein polymorphism at codon 54 is not associated with postprandial responses to fat and glucose tolerance tests in healthy young Europeans. Results from EARS II participants

Association between Genotype and the Glycemic Response to an Oral Glucose Tolerance Test: A Systematic Review

The inter-individual variability of metabolic response to foods may be partly due to genetic variation. This systematic review aims to assess the associations between genetic variants and glucose response to an oral glucose tolerance test (OGTT). Three databases (PubMed, Web of Science, Embase) were searched for keywords in the field of genetics, OGTT, and metabolic response (PROSPERO: CRD42021231203). Inclusion criteria were available data on single nucleotide polymorphisms (SNPs) and glucose area under the curve (gAUC) in a healthy study cohort. In total, 33,219 records were identified, of which 139 reports met the inclusion criteria. This narrative synthesis focused on 49 reports describing gene loci for which several reports were available. An association between SNPs and the gAUC was described for 13 gene loci with 53 different SNPs. Three gene loci were mostly investigated: transcription factor 7 like 2 (TCF7L2), peroxisome proliferator-activated receptor gamma (PPARγ), and potassium inwardly rectifying channel subfamily J member 11 (KCNJ11). In most reports, the associations were not significant or single findings were not replicated. No robust evidence for an association between SNPs and gAUC after an OGTT in healthy persons was found across the identified studies. Future studies should investigate the effect of polygenic risk scores on postprandial glucose levels.

Genetic polymorphism of fatty acid binding protein-2 in hyperlipidemic Asian Indians in North India

BACKGROUND

Fatty acid binding protein-2 (FABP-2) is involved in the metabolism of lipids in the intestine. FABP-2 Ala54Thr polymorphism involves a transition of G to A at codon 54 of FABP-2, resulting in an amino acid substitution Ala54 to Thr54 and is associated with elevated fasting triglycerides in some hyperlipidemic populations. In current genome builds and gene databases the variant of the Ala54Thr FABP-2 (rs 1 799 883) is annotated as c.163A>G (p. Thr55Ala).

AIM AND OBJECTIVE

The status of this polymorphism in hyperlipidemic Asian Indians from North India has not been investigated. This study was aimed to evaluate the distribution of the polymorphic variants of the Ala54Thr FABP-2 and their association with lipids in hyperlipidemic subjects.

METHODS

Ala54Thr FABP-2 polymorphism in both hyperlipidemic (n = 210) and normolipidemic (n = 342) subjects was assessed by PCR-RFLP.

RESULTS

Ala54Thr genotypes and alleles distribution did not differ between the hyperlipidemic and normolipidemic groups. The heterozygous genotype FABP-2 Ala/Thr was significantly associated with higher levels of triglycerides and very low-density lipoproteins as compared to the homozygous variant (Thr/Thr) genotype and the wild type homozygous (Ala/Ala) genotype.

CONCLUSIONS

The heterozygous genotype FABP-2 Ala54Thr is a risk factor for the development of hypertriglyceridemia and increased levels of VLDL-c in Asian Indians from North India.

Quantile-dependent expressivity of postprandial lipemia

Purpose

“Quantile-dependent expressivity” describes an effect of the genotype that depends upon the level of the phenotype (e.g., whether a subject’s triglycerides are high or low relative to its population distribution). Prior analyses suggest that the effect of a genetic risk score (GRS) on fasting plasma triglyceride levels increases with the percentile of the triglyceride distribution. Postprandial lipemia is well suited for testing quantile-dependent expressivity because it exposes each individual’s genotype to substantial increases in their plasma triglyceride concentrations. Ninety-seven published papers were identified that plotted mean triglyceride response vs. time and genotype, which were converted into quantitative data. Separately, for each published graph, standard least-squares regression analysis was used to compare the genotype differences at time t (dependent variable) to average triglyceride concentrations at time t (independent variable) to assess whether the genetic effect size increased in association with higher triglyceride concentrations and whether the phenomenon could explain purported genetic interactions with sex, diet, disease, BMI, and drugs.

Results

Consistent with the phenomenon, genetic effect sizes increased (P≤0.05) with increasing triglyceride concentrations for polymorphisms associated with ABCA1, ANGPTL4, APOA1, APOA2, APOA4, APOA5, APOB, APOC3, APOE, CETP, FABP2, FATP6, GALNT2, GCKR, HL, IL1b, LEPR, LOX-1, LPL, MC4R, MTTP, NPY, SORT1, SULF2, TNFA, TCF7L2, and TM6SF2. The effect size for these polymorphisms showed a progressively increasing dose-response, with intermediate effect sizes at intermediate triglyceride concentrations. Quantile-dependent expressivity provided an alternative interpretation to their interactions with sex, drugs, disease, diet, and age, which have been traditionally ascribed to gene-environment interactions and genetic predictors of drug efficacy (i.e., personalized medicine).

Conclusion

Quantile-dependent expressivity applies to the majority of genetic variants affecting postprandial triglycerides, which may arise because the impaired functionalities of these variants increase at higher triglyceride concentrations. Purported gene-drug interactions may be the manifestations of quantile-dependent expressivity, rather than genetic predictors of drug efficacy.

Postprandial Hypertriglyceridemia Is Associated with the Variant 54 Threonine FABP2 Gene

Purpose: Fasting or postprandial hypertriglyceridemia is considered an independent cardiovascular disease (CVD) risk factor. The intestinal fatty acid binding protein (FABP2) is involved in the intracellular transport and metabolism of fatty acids. The presence of the Ala54Thr polymorphism of the FABP2 gene appears to be involved in postprandial hypertriglyceridemia. We explored the possible association of the Ala54Thr polymorphism with fat intolerance in apparently healthy, fasting, normolipidemic subjects with normal body-mass index and without diabetes. Methodology: A total of 158 apparently healthy individuals were classified as fat tolerant (n = 123) or intolerant (n = 35) according to their response (plasma triglycerides) to an oral abbreviated tolerance test with blood samples taken at 0, 2 and 4 h. At 0 h, all subjects ingested 26.3 g of fats. Presence of the Ala54Thr polymorphism of the FABP2 gene was evaluated by polymerase chain reaction⁻restriction fragment length (PCR⁻RFLP). Results: The group with fat intolerance (postprandial hypertriglyceridemia group) showed an increased frequency of the Thr54Thr genotype when compared with the group with normal fat tolerance (control group) (23% vs. 4%, respectively, OR: 16.53, 95% CI: 4.09⁻66.82, p: 0.0001, pc: 0.0003). Carriers of at least one Thr54 allele were up to six times more prevalent in the fat intolerant group than in the non-carriers. (OR: 6.35; 95% CI: 1.86⁻21.59, p: 0.0003, pc: 0.0009). The levels of plasma triglycerides (Tg) at 4 h after the test meal were higher in carriers of at least one 54Thr allele than in carriers of the Ala54 allele (p < 0.05). Conclusions: There is a significant association between postprandial hypertriglyceridemia and the presence of at least one 54Thr allele of the FABP2 gene. In addition, subjects with this genotype showed an increased ratio of Tg/HDL-cholesterol. This parameter is a marker of increased CVD risk and insulin resistance.

Genetic variation of the intestinal fatty acid-binding protein 2 gene in carotid atherosclerosis

The alanine (A) to threonine (T) substitution at codon 54 of the intestinal fatty acid-binding protein 2 (FABP2) has been associated with dyslipidaemia and other characteristics of the metabolic syndrome, which in turn is a risk factor for cerebrovascular disease. The aim of this study was to investigate whether the A54T polymorphism in the FABP2 gene is associated with internal carotid artery (ICA) stenosis in stroke patients. Swedish subjects initially diagnosed with acute cerebrovascular disease (n = 196) that had been assessed with ultrasound of the carotid arteries were identified and grouped depending on whether a stenosis was found. The subjects were genotyped for the A54T polymorphism using a PCR-RFLP method. In a multivariate logistic-regression analysis, where known risk factors for atherosclerosis were fixed (diabetes, systolic blood pressure, age and smoking), having the FABP2 T allele was a significant risk factor for ICA stenosis (odds ratio 2.9; 95% confidence interval, 1.1-7.7; p = 0.04) together with diabetes (odds ratio 4.9; 95% confidence interval, 1.8-14; p < 0.01). Age, smoking and blood pressure did not reach statistical significance. In conclusion, our result supports the hypothesis that the FABP2 A54T polymorphism is associated with ICA stenosis.

Association of angiotensin-converting enzyme (ACE) and fatty acid binding protein 2 (FABP2) genes polymorphism with type 2 diabetes mellitus in Northern India

BACKGROUND

Type 2 diabetes mellitus (T2DM) is growing in an epidemic manner across the world with an expected doubling of the incidence to millions of affected individuals in the last decades. At present, adequate data are not available regarding the ACE and FABP2 polymorphisms and their susceptibility with T2DM cases in the North Indian population. Thus we conceived the need for further study of ACE (I/D) and FABP2 (Ala54Thr) genes polymorphism and its susceptibility to T2DM in the North Indian population.

MATERIALS AND METHODS

In this study, a total of 300 subjects (including 190 T2DM cases and 110 controls) participated. ACE and FABP2 gene polymorphisms in the cases and controls were evaluated by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

The frequencies of ACE I/I, I/D and D/D genotypes in T2DM cases and controls were 28.73%, 55.17%, 16.09% and 13.63%, 57.95%, 28.40%, respectively. The frequencies of FABP2 Ala54Ala, Ala54Thr and Thr54Thr in T2DM cases were 18.39%, 66.66%, 14.94% and 22.72%, 61.36%, 15.90% in controls, respectively. ACE I/I genotype was significantly more frequent in cases as compared to controls (p = 0.003, χ(2) = 9.13).

CONCLUSION

It appears that the ACE I/I genotype frequency was significantly higher in the T2DM cases as compared to the controls.

Higher cardiorespiratory fitness attenuates arterial stiffening associated with the Ala54Thr polymorphism in FABP2

Fatty acid binding protein 2 (FABP2) Ala54Thr polymorphism is a candidate gene associated with the risk of cardiovascular disease. Habitual exercise brings higher cardiorespiratory fitness and results in the improvement of cardiovascular disease risk. However, the effect of cardiorespiratory fitness level and FABP2 Ala54Thr polymorphism on the risk of cardiovascular diseases remains unclear. In the present study, a cross-sectional investigation of 837 Japanese men and women was performed to clarify the effects of cardiorespiratory fitness on the relationship between risk of cardiovascular disease and FABP2 Ala54Thr gene polymorphism. The study subjects were divided into high-cardiorespiratory fitness (High-Fit) and low-cardiorespiratory fitness (Low-Fit) groups based on the median value of peak oxygen uptake in each sex and decade. The FABP2 Ala54Thr polymorphism did not significantly affect carotid β-stiffness or blood pressure. In the Low-Fit group, carotid β-stiffness, systolic blood pressure, and diastolic blood pressure were higher for individuals with the Ala/Ala genotype compared with those with the Ala/Thr or Thr/Thr genotype, whereas no differences were observed in the High-Fit group. Additionally, serum triglyceride and plasma glucose levels were lower and serum high-density lipoprotein cholesterol levels were higher in the High-Fit group compared with the Low-Fit group; the FABP2 Ala54Thr polymorphism did not significantly affect these parameters. These results suggest that the higher cardiorespiratory fitness may attenuate the changes in central arterial stiffness and blood pressure that are associated with the FABP2 genotype.

Meta-analysis on the effect of the Ala54Thr polymorphism of the fatty acid-binding protein 2 gene on body mass index

BACKGROUND AND AIM

The results from studies published on the association of fatty acid-binding protein 2 (FABP2) Ala54Thr polymorphism with body mass index (BMI) are conflicting. In this meta-analysis, we investigated the association of the FABP2 Ala54Thr polymorphism with BMI.

METHODS AND RESULTS

We searched for articles published prior to June 2009 using PubMed, HugeNavigator and China National Knowledge Internet. The languages were limited to English and Chinese. Data on BMI were collected. A pooled weighted mean difference (WMD), together with 95% confidence interval (CI), was used for this meta-analysis. A total of 27 studies with 10 974 subjects were included in this meta-analysis. The pooled effect for dominant, recessive and co-dominant model comparisons did not suggest the significant association between the FABP2 Ala54Thr polymorphism and BMI in overall populations: WMD(fixed effects)=-0.00, 95% CI: (-0.16 to 0.15), p=0.99, WMD(random effects)=-0.00, 95% CI: (-0.16 to 0.15), p=0.99, p(Q)=0.77, I(2)=0%, WMD(fixed effects)=-0.12, 95% CI: (-0.39 to 0.14), p=0.35, WMD(random effects)=-0.12, 95% CI: (-0.39 to 0.14), p=0.35, p(Q)=0.47, I(2)=0% and WMD(fixed effects)=0.07, 95% CI: (-0.11 to 0.25), p=0.45, WMD(random effects)=0.07, 95% CI: (-0.11 to 0.25), p=0.45, p(Q)=0.90, I(2)=0%, respectively. The results from the comparisons of ThrThr versus AlaAla and AlaThr versus AlaAla showed no evidence that the FABP2 Ala54Thr polymorphism is significantly associated with BMI in overall populations (p>0.05). All the results from the subgroup analyses for these genetic models comparisons were not significant (p>0.05).

CONCLUSIONS

Our meta-analysis does not support the association between the FABP2 Ala54Thr polymorphism and BMI.

Liver fatty acid-binding protein and obesity

While low levels of unesterified long chain fatty acids (LCFAs) are normal metabolic intermediates of dietary and endogenous fat, LCFAs are also potent regulators of key receptors/enzymes and at high levels become toxic detergents within the cell. Elevated levels of LCFAs are associated with diabetes, obesity and metabolic syndrome. Consequently, mammals evolved fatty acid-binding proteins (FABPs) that bind/sequester these potentially toxic free fatty acids in the cytosol and present them for rapid removal in oxidative (mitochondria, peroxisomes) or storage (endoplasmic reticulum, lipid droplets) organelles. Mammals have a large (15-member) family of FABPs with multiple members occurring within a single cell type. The first described FABP, liver-FABP (L-FABP or FABP1), is expressed in very high levels (2-5% of cytosolic protein) in liver as well as in intestine and kidney. Since L-FABP facilitates uptake and metabolism of LCFAs in vitro and in cultured cells, it was expected that abnormal function or loss of L-FABP would reduce hepatic LCFA uptake/oxidation and thereby increase LCFAs available for oxidation in muscle and/or storage in adipose. This prediction was confirmed in vitro with isolated liver slices and cultured primary hepatocytes from L-FABP gene-ablated mice. Despite unaltered food consumption when fed a control diet ad libitum, the L-FABP null mice exhibited age- and sex-dependent weight gain and increased fat tissue mass. The obese phenotype was exacerbated in L-FABP null mice pair fed a high-fat diet. Taken together with other findings, these data suggest that L-FABP could have an important role in preventing age- or diet-induced obesity.

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.

The emerging functions and mechanisms of mammalian fatty acid-binding proteins

Fatty acid-binding proteins (FABPs) are abundant intracellular proteins that bind long-chain fatty acids with high affinity. Nine separate mammalian FABPs have been identified, and their tertiary structures are highly conserved. The FABPs have unique tissue-specific distributions that have long suggested functional differences among them. In the last decade, considerable progress has been made in understanding the specific functions of the FABPs and, in some cases, their mechanisms of action at the molecular level. The FABPs appear to be involved in the extranuclear compartments of the cell by trafficking their ligands within the cytosol via interactions with organelle membranes and specific proteins. Several members of the FABP family have been shown to function directly in the regulation of cognate nuclear transcription factor activity via ligand-dependent translocation to the nucleus. This review will focus on these emerging functions and mechanisms of the FABPs, highlighting the unique functional properties of each as well as the similarities among them.

Influence of Ala54Thr polymorphism of fatty acid-binding protein 2 on weight loss and insulin levels secondary to two hypocaloric diets: a randomized clinical trial

OBJECTIVE

A transition G to A at codon 54 of FABP2 was associated with high insulin resistance and different dietary response. The aim of our study was to investigate the influence of this polymorphism on weight loss and metabolic changes secondary to two hypocaloric diets.

SUBJECTS AND METHODS

A sample of 204 obesity patients was analyzed. Before and after 2 months of hypocaloric diet, a nutritional evaluation was performed. Patients were randomly allocated to diet I (low-fat diet) or II (low carbohydrate diet).

RESULTS

With diet Type I and in the wild group (Ala54/Ala54), BMI, weight, fat mass, waist circumference, waist to hip ratio, systolic and diastolic blood pressures, total cholesterol, triglyceride and insulin levels decreased. In the mutant group (Ala54/Thr54 and Thr54/Thr54), BMI, weight, waist circumference and fat mass decreased. In the wild group with diet Type II, the same parameters that group I decreased and glucose levels, too. In the mutant group, BMI, weight, waist circumference and fat mass decreased. Only leptin levels have a significant decrease in the wild group with both diets (diet I: 30.7%; p<0.05 and diet II: 15.85%; p<0.05).

CONCLUSION

Similar weight loss is associated with different changes, depending on the FABP genotype with both diets. Weight loss is associated with a more deep decrease in serum leptin concentration with low-fat diet.

Influence of genetic factors in the modulation of postprandial lipemia

Postprandial lipemia is traditionally defined by the extent and duration of the increase in plasma triglycerides in response to a fat-enriched meal. The relationship between alimentary lipemia and coronary disease is of great interest in view of the epidemiological and experimental evidence that underlies it. The rate of synthesis of triglyceride-rich lipoproteins, lipoprotein lipase-mediated triglyceride hydrolysis, and the hepatic capture of chylomicron remnants via the interaction of the lipoprotein receptor with APOE and LPL, are the fundamental pillars of the metabolism and modification of these lipoproteins. The modulation of such phenomena is influenced by both genetic and environmental factors, thus explaining their extraordinary individual variance. This review presents the current evidence linking a number of candidate genes to the modulation of postprandial lipid metabolism.

Sex-specific association of fatty acid binding protein 2 and microsomal triacylglycerol transfer protein variants with response to dietary lipid changes in the 3-mo Medi-RIVAGE primary intervention study

BACKGROUND

The dietary guidelines targeted at reducing cardiovascular risk lead to largely heterogeneous responses in which genetic determinants are largely involved.

OBJECTIVES

We evaluated the effect of fatty acid binding protein 2 (FABP2) Ala54Thr and microsomal triacylglycerol transfer protein (MTTP) -493G/T allelic variations on plasma lipid markers, at baseline and on the response to the 3-mo Medi-RIVAGE primary prevention study.

DESIGN

Subjects with moderate cardiovascular disease risk (n = 169) were advised to reduce total and saturated dietary fats and to increase intake of monounsaturated and polyunsaturated fats. They were genotyped for FABP2 Ala54Thr and MTTP -493G/T allelic variations, and plasma was processed for cardiovascular risk marker analyses.

RESULTS

At baseline, men and women homozygous for Thr54 presented a significant opposite profile for plasma oleic acid (18:1), triacylglycerol-rich lipoprotein (TRL) cholesterol, and TRL phospholipids. In addition, all Thr/Thr men presented higher 18:1 values than did women. For the MTTP -493G/T polymorphism, although all TT subjects presented high apolipoprotein B-48, a genotype x sex interaction was present for palmitic acid, linolenic acid, eicosatrienoic acid, and insulin. The prudent diet clearly improved plasma lipid markers. FABP2 genotype did not interact much with the amplitude of the response. However, for MTTP polymorphism, men homozygous for the T allele displayed a significantly more pronounced response than did men carrying the G allele, which is particularly evident by their larger decrease in the Framingham score.

CONCLUSIONS

These 2 polymorphic loci are thus differently associated with the baseline lipid markers as well as with the response to nutritional recommendations, but both presented a marked sex-specific profile, with the response to diet being particularly efficient in men homozygous for the MTTP -493T allele.

Dietary, physiological, genetic and pathological influences on postprandial lipid metabolism

Most of diurnal time is spent in a postprandial state due to successive meal intakes during the day. As long as the meals contain enough fat, a transient increase in triacylglycerolaemia and a change in lipoprotein pattern occurs. The extent and kinetics of such postprandial changes are highly variable and are modulated by numerous factors. This review focuses on factors affecting postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and risk of CHD. Postprandial lipoprotein metabolism is modulated by background dietary pattern as well as meal composition (fat amount and type, carbohydrate, protein, fibre, alcohol) and several lifestyle conditions (physical activity, tobacco use), physiological factors (age, gender, menopausal status) and pathological conditions (obesity, insulin resistance, diabetes mellitus). The roles of many genes have been explored in order to establish the possible implications of their variability in lipid metabolism and CHD risk. The postprandial lipid response has been shown to be modified by polymorphisms within the genes for apo A-I, A-IV, A-V, E, B, C-I and C-III, lipoprotein lipase, hepatic lipase, fatty acid binding and transport proteins, microsomal triglyceride transfer protein and scavenger receptor class B type I. Overall, the variability in postprandial response is important and complex, and the interactions between nutrients or dietary or meal compositions and gene variants need further investigation. The extent of present knowledge and needs for future studies are discussed in light of ongoing developments in nutrigenetics.

Polymorphism of the FABP2 gene: a population frequency analysis and an association study with cardiovascular risk markers in Argentina

BACKGROUND

The FABP2 gene encodes for the intestinal FABP (IFABP) protein, which is expressed only in intestinal enterocytes. A polymorphism at codon 54 in exon 2 of the FABP2 gene exchanges an Alanine (Ala), in the small helical region of the protein, for Threonine (Thr). Given the potential physiological role of the Ala54Thr FABP2 polymorphism, we assess in this study the local population frequency and analyze possible associations with five selected markers, i.e. glycemia, total cholesterol, body mass index (BMI), hypertension, and high Cardiovascular Risk Index (CVR index).

METHODS

We studied 86 men and 116 women. DNA was extracted from a blood drop for genotype analysis. Allele frequencies were calculated by direct counting. Hardy Weinberg Equilibrium was evaluated using a Chi-square goodness of fit test. For the polymorphism association analysis, five markers were selected, i.e. blood pressure, Framingham Risk Index, total cholesterol, BMI, and glycemia. For each marker, the Odds Ratio (OR) was calculated by an online statistic tool.

RESULTS

Our results reveal a similar population polymorphism frequency as in previous European studies, with q = 0.277 (95% confidence limits 0.234-0.323). No significant association was found with any of the tested markers in the context of our Argentine nutritional and cultural habits. We did, however, observe a tendency for increased Cholesterol and high BMI in Thr54 carriers.

CONCLUSION

This is the first study to look at the population frequency of the Thr54 allele in Argentina. The obtained result does not differ from previously reported frequencies in European populations. Moreover, we found no association between the Thr54 allele and any of the five selected markers. The observed tendency to increased total cholesterol and elevated BMI in Thr54 carriers, even though not significant for p < 0.1 could be worth of further investigation to establish whether the Thr54 variant should be taken into consideration in cardiovascular prevention strategies.

FABP2 Ala54Thr genotype is associated with glucoregulatory function and lipid oxidation after a high-fat meal in sedentary nondiabetic men and women

BACKGROUND

A common functional missense mutation [Ala54Thr of the fatty acid-binding protein 2 gene (FABP2)] has previously been studied for associations with glucoregulation, postprandial lipemia, and lipid oxidation rates. However, most of those studies have not accounted for the interactive and potentially confounding effects of habitual physical activity and diet.

OBJECTIVE

We tested the hypothesis that, in sedentary nondiabetic subjects following a low-fat diet, Thr54 FABP2 carriers have lower glucoregulatory function, greater postprandial lipemia, and greater lipid oxidation rates than do their Ala54 FABP2-homozygous counterparts.

DESIGN

Men and women (n = 122) aged 50-75 y who were following a low-fat diet were genotyped and underwent oral-glucose-tolerance tests. A subgroup (n = 36) also underwent postprandial lipemia tests with lipid oxidation rate measurements.

RESULTS

Thr54 carriers were less likely to have normal glucose tolerance (P = 0.05) and had higher fasting glucose concentrations (P = 0.003) than did Ala54 homozygotes. In Thr54 carriers, the insulin sensitivity index was lower (P = 0.02), and the fasting insulin and the oral-glucose-tolerance test insulin area under the curve were higher (P = 0.05 and 0.03, respectively) than in Ala54 homozygotes. FABP2 genotype was not associated with fasting or postprandial lipemia test triacylglycerol or free fatty acids (P > or = 0.22 for all), but postprandial lipid oxidation rates were higher (P = 0.01), which suggests that fat absorption is higher in Thr54 carriers than in Ala54 homozygotes.

CONCLUSIONS

In sedentary nondiabetic persons following a low-fat diet, FABP2 Thr54 carriers have lower glucose tolerance and lower insulin action than do Ala54-homozygous persons. Furthermore, FABP Thr54 carriers have higher lipid oxidation rates, which may be the mechanism of glucoregulatory dysfunction.

Influence of ALA54THR Polymorphism of Fatty Acid Binding Protein 2 on Lifestyle Modification Response in Obese Subjects

BACKGROUND/AIM

It has been found that the expression of fatty acid binding protein 2 (FABP2) mRNA is under dietary control. A G-to-A transition at codon 54 of FABP2 results in an amino acid substitution (from Ala 54 to Thr 54). This polymorphism was associated with high insulin resistance and high fasting insulin concentrations. The aim of our study was to investigate the influence of Thr54 polymorphism in the FABP2 protein on the response to a lifestyle modification (Mediterranean hypocaloric diet and exercise) in obese patients.

METHODS

A population of 69 obese (body mass index > 30) nondiabetic outpatients was analyzed in a prospective way. Before and after 3 months of the lifestyle modification program, indirect calorimetry, tetrapolar electrical bioimpedance measurement, blood pressure recording, serial assessment of the nutritional intake (3 days of written food records), and biochemical analysis were performed. The lifestyle modification program consisted of a hypocaloric diet (1,520 kcal; 52% carbohydrates, 25% lipids, and 23% proteins). The exercise program consisted of aerobic exercise for at least three times/week (60 min each). Statistical analysis was performed for combined Ala54/Thr54 and Thr54/Thr54 as a mutant group and wild-type Ala54/Ala54 as second group.

RESULTS

The mean age was 45.5 +/- 16.7 years, the mean body mass index was 34.1 +/- 5.1, and there were 14 males (20.3%) and 55 females (79.7%) with a weight loss of 3.17 +/- 3.5 kg (3.5%). Thirty-seven patients (53.6%) had the genotype Ala54/Ala54 (wild-type group) and 32 (46.4%) patients either the genotype Ala54/Thr54 (26 patients, 30.2%) or the genotype Thr54/Thr54 (6 patients, 16.2%). The percentage of responders (weight loss) was similar in both groups (89.2 vs. 90.6%). In the wild-type group, body mass index, weight, fat mass, low-density lipoprotein cholesterol level, and waist circumference decreased, whereas the VO2 (oxygen consumption) increased. In the mutant group, glucose, body mass index, weight, waist circumference, and systolic blood pressure decreased, and VO2 increased. No differences were detected between basal values in both groups. Only the leptin levels showed a significant decrease in the wild-type group (23.85%; p < 0.05), with no statistically significant difference in the mutant group (2.59%; NS). Resistin, tumor necrosis factor alpha, interleukin 6, insulin, and C-reactive protein remained without changes in both groups.

CONCLUSIONS

Weight loss is associated with different changes, depending on the FABP2 genotype. Carriers of the Thr54 allele have a different response than wild-type obese subjects, with a significant decrease of systolic blood pressure and glucose levels in Thr54 carriers and a significant decrease in fat mass, low-density lipoprotein cholesterol, and leptin in wild-type patients.

Additive effects of the PPARgamma, APOE, and FABP-2 genes in increasing daylong triglycerides of normolipidemic women to concentrations comparable to those in men

BACKGROUND

Fasting and postprandial triglyceride (TG) concentrations vary considerably among individuals. TG metabolism is more efficient in women than in men, which may partly explain why females are protected against atherosclerosis. Our aim was to identify gender-specific genetic influences on fasting and postprandial TG concentrations under typical living conditions in healthy, lean, normolipidemic women.

METHODS

We studied 40 women and 48 men. Diurnal capillary TG profiles were calculated as the integrated area under the capillary TG curve averaged over 3 days. Genotypes of the FABP-2, HL, LPL, APOE, and PPARgamma genes and the APOC-III, APOC-III/A-IV intergenic region were determined.

RESULTS

Three genes (FABP-2, APOE, and PPARgamma) had a significant additive effect only in women. Mean TG concentrations were fourfold higher in women carriers of the PPARgamma wild-type allele (P = 0.044), threefold higher in carriers of the rare FABP-2 allele (P = 0.006), and fivefold higher in carriers of the E2 allele of the APOE gene (P = 0.037) than in noncarriers. None of these effects was observed in men. The presence of two or more of these adverse alleles increased TG concentrations in a dose-dependent manner. Women carriers of three adverse alleles had postprandial TG values comparable to those for men.

CONCLUSIONS

An adverse combination of common alleles of the FABP-2, APOE, and PPARgamma genes in women increases their TG concentrations to values comparable to those seen in men. Although this influence is not appreciable when studying fasting plasma TGs, it becomes apparent with use of a more sensitive index such as measurements made throughout the day.

The FABP2 gene polymorphism in cerebrovascular disease

OBJECTIVE

Earlier studies have shown that the fatty acid binding protein 2 (FABP2) T54 allele is associated with dyslipidemia, which in turn correlates with the incidence of cerebrovascular disease (CVD). To assess whether the FABP2 gene A54T polymorphism is associated with an increased risk of CVD we undertook a case-control study.

MATERIALS AND METHODS

A total of 407 patients diagnosed with acute CVD and 158 control subjects were genotyped for the A54T polymorphism using a PCR-RFLP method.

RESULTS

Allele and genotype frequencies of the FABP2 A54T polymorphism did not differ between subjects with acute CVD (TT, 9.6%; TA, 41.0%; AA, 49.4%) and controls (TT, 7.6%; TA, 41.1%; AA, 51.3%; P = ns) or in the following subgroups of CVD compared with controls: non-cardioembolic infarction (n = 252), intracerebral hemorrhage (n = 23), and cardioembolic infarction (n = 91). In transient ischemic attacks (TIAs) (n = 41) the combined TT and TA genotype frequency (TT + TA, 65.9%) was more frequent than in controls (48.7%) (P = 0.05). Furthermore, the TT genotype was more frequent in non-smoking patients under the age of 70 (n = 77) with a non-cardioembolic infarction (TT, 18.2%) compared with controls (7.6%) (P = 0.024).

CONCLUSIONS

Our findings suggest an involvement of the FABP2 (A54T) gene polymorphism in the pathogenesis of CVD. The FABP2 T54 allele appears to be a genetic susceptibility marker for TIA and non-cardioembolic infarction at younger onset.

Genetic polymorphisms affecting the phenotypic expression of familial hypercholesterolemia

The clinical expression of heterozygous familial hypercholesterolemia (FH) is highly variable even in patients carrying the same LDL receptor (LDL-R) gene mutation. This variability might be due to environmental factors as well as to modifying genes affecting lipoprotein metabolism. We investigated Apo E (2, 3, 4), MTP (-493G/T), Apo B (-516C/T), Apo A-V (-1131T/C), HL (-514C/T and -250G/A), FABP-2 (A54T), LPL (D9N, N291S, S447X) and ABCA1 (R219K) polymorphisms in 221 unrelated FH index cases and 349 FH relatives with defined LDL-R gene mutations. We found a significant and independent effect of the following polymorphisms on: (i) plasma LDL-C (Apo E, MTP and Apo B); (ii) plasma HDL-C (HL, FABP-2 and LPL S447X); (iii) plasma triglycerides (Apo E and Apo A-V). In subjects with coronary artery disease (CAD+), the prevalence of FABP-2 54TT genotype was higher (16.5% versus 5.2%) and that of ABCA1 219RK and KK genotypes lower (33.0% versus 51.5%) than in subjects with no CAD. Independent predictors of increased risk of CAD were male sex, age, arterial hypertension, LDL-C level and FABP-2 54TT genotype, and of decreased risk the 219RK and KK genotypes of ABCA1. These findings show that several common genetic variants influence the lipid phenotype and the CAD risk in FH heterozygotes.

Postprandial lipemia in subjects with the threonine 54 variant of the fatty acid-binding protein 2 gene is dependent on the type of fat ingested

BACKGROUND

The 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. Obese and diabetic T54 carriers have greater postprandial lipemia than do A54 homozygotes. The T54 protein isoform is also associated with increased triacylglycerol secretion in vitro.

OBJECTIVE

We investigated diet-gene interactions by measuring postprandial lipids, glucose, insulin, and C-peptide in healthy, nonobese A54 homozygotes and T54 carriers after ingestion of 3 different fats.

DESIGN

Eleven A54 homozygotes and 11 T54 carriers were given 3 oral-fat-tolerance tests (butter, safflower oil, and olive oil). Cholesterol and triacylglycerol were measured in plasma and in chylomicron fractions.

RESULTS

There was no main effect of FABP2 genotype for chylomicron triacylglycerol, glucose, or C-peptide. The area under the insulin curve and the ratio of insulin to C-peptide were lower in T54 carriers than in A54 homozygotes [312 +/- 29 ( +/- SEM) compared with 425 +/- 31 pmol. h/L (P = 0.05) and 0.23 +/- 0.03 compared with 0.40 +/- 0.05 (P = 0.04), respectively], which suggests greater hepatic insulin clearance in T54 carriers. An association between genotype and chylomicron cholesterol was seen only after olive oil: values were higher (P = 0.02) in T54 carriers (0.087 +/- 0.006 mmol. h/L) than in A54 homozygotes (0.058 +/- 0.004 mmol. h/L). The main effect of fat was significant for the areas under the chylomicron cholesterol and chylomicron triacylglycerol curves [higher values for safflower (0.635 +/- 0.053 and 2.48 +/- 0.30 mmol. h/L, respectively) and olive (0.592 +/- 0.052 and 2.48 +/- 0.32 mmol. h/L, respectively) oils than for butter (0.425 +/- 0.043 and 1.69 +/- 0.20 mmol. h/L, respectively); P < 0.05].

CONCLUSIONS

The A54T polymorphism results in a diet-gene interaction: the T54 group had increased chylomicron cholesterol after olive oil only. Nevertheless, the greater hepatic insulin clearance in T54 carriers suggests that the polymorphism may not be deleterious in nonobese subjects.

The A54T polymorphism of fatty acid-binding protein 2 may entail a reduction in fat-stimulated secretion of GIP that potentiates the adverse impact of fatty diets on insulin sensitivity

A common polymorphism of the 54th codon of fatty acid-binding protein 2 (FABP2), in which threonine substitutes for alanine (T54), has been linked to insulin resistance and/or increased postprandial triglycerides in various studies. I propose that, in subjects expressing T54, the secretion of gastric inhibitory polypeptide (GIP) evoked by fatty meals is subnormal, such that adipocytes are less efficient in converting chylomicrons to stored triglyceride. The increased postprandial free fatty acid flux which this may imply could be expected to exacerbate insulin resistance syndrome--thus accounting for the association of T54 with insulin resistance in epidemiological studies. If this thesis proves to be correct, it will help to clarify the importance of appropriate GIP secretion to maintenance of insulin sensitivity in the context of fatty diets.

Obesity, Type II diabetes and the Ala54Thr polymorphism of fatty acid binding protein 2 in the Tongan population

Genetic variation of fatty acid binding protein 2 (FABP2) may contribute to the high prevalence of obesity and Type II diabetes in Tonga. To explore this we assessed the frequency of the FABP2 Ala54Thr polymorphism, obesity, and Type II diabetes in Tongans and possible inter-relationships. We investigated 1022 Tongan subjects, 433 men and 589 women aged 15-85 years, to identify possible associations between the FABP2 Ala54Thr polymorphism, obesity, Type II diabetes, BMI, glucose tolerance and standard lipid variables. The prevalence of the polymorphism was compared with that reported for other ethnic populations (studies from: Japanese, Finnish, African American, Native Canadian and Inuit, Swedish, Guadeloupe Indians, European males, and Caucasian populations). We found that 84% of the Tongan men and 93% of the Tongan women were overweight or obese (BMI> or =25kg/m2). The mean BMI+/-SD was not significantly different among those who were and were not carrying the Thr allele (males: Ala/Ala 30.4+/-5.4 and Thr carriers 29.8+/-5.1; females: Ala/Ala 33.8+/-6.4 and Thr carriers 33.6+/-5.1). The genotype frequencies were 76.2% Ala/Ala, 22.8% Ala/Thr, and 1.0% Thr/Thr. The Alal/Ala frequency is higher than the prevalences reported for all populations studied. The Thr allele was significantly associated with lower total cholesterol and LDL cholesterol in both sexes and in women also with lower HDL cholesterol. We conclude that there is a high prevalence of the FABP2 Ala54Thr polymorphism in Tongans. The polymorphism may be involved in lipid metabolism as the Thr allele is associated with low total and LDL cholesterol levels in this population.

Variation in the FABP2 promoter alters transcriptional activity and is associated with body composition and plasma lipid levels

The fatty acid-binding proteins (FABPs) are cytoplasmic proteins involved in intracellular fatty acid transport and metabolism. FABP2, the intestinal-type FABP, is expressed exclusively in enterocytes in the small intestine. In previous studies of an Ala54Thr substitution in FABP2, the Thr-allele showed association with increased lipid oxidation, elevated plasma lipids, and impaired insulin sensitivity. We screened roughly 1 kb 5' of the FABP2 initiation codon and identified three insertion/deletion polymorphisms and four single nucleotide polymorphisms (SNPs). Three of the SNPs were in complete linkage disequilibrium with the three insertion/deletion polymorphisms, defining exactly two haplotypes (FABP2p-ID). We tested the hypothesis that this variation alters gene expression by transfecting Caco-2 cells with pGL3-Basic constructs containing opposite FABP2p-ID haplotypes. Luciferase assays showed a statistically significant two-fold increase in gene expression of the pGL3-insertion construct over the pGL3-deletion construct (P<0.001; n=5). We also tested for association between three FABP2 variants and measurements of body composition, plasma lipids, and insulin sensitivity in non-diabetic control subjects from the San Luis Valley Diabetes Study (n=714). The only informative variant, FABP2p-ID, was statistically significantly associated with body mass index (P=0.042) and marginally associated with fat mass (P=0.084), cholesterol (P=0.066), and HOMA IR (a derived measure of insulin resistance; P=0.062) in the entire cohort. Similar associations were seen only in non-Hispanics when the analysis was stratified by ethnicity. Within the non-Hispanic subgroup, the effects of FABP2p-ID on plasma lipids were sex-specific. These results suggest that genetic variation in the 5' region of FABP2 affects transcriptional activity, presumably leading to alterations in body composition and lipid processing.

Fatty acid binding protein-2 gene variants and insulin resistance: gene and gene-environment interaction effects

The intestinal fatty acid binding protein (FABP2) gene is proposed as a candidate gene for diabetes because the protein it codes is involved in fatty acid (FA) absorption and metabolism and may, therefore, affect insulin sensitivity and glucose metabolism. Numerous studies have assessed FABP2 gene variants and their association with insulin resistance and type 2 diabetes. Some weak evidence indicates that the silent variants and those in the noncoding regions of the gene (codon 118, 3' noncoding region, intron 2 trinucleotide repeat) might be associated with insulin resistance/type 2 diabetes. The most extensively studied variant is the missense Ala54Thr variation, which is common in diverse populations and results in increased FA absorption in vivo. Some evidence indicates that this variant may be associated with insulin sensitivity/type 2 diabetes. However, the large majority of studies assessing the potential association between the Ala54Thr FABP2 variant and insulin resistance/type 2 diabetes did not account for the independent and substantial effects of body composition, habitual physical activity (PA) levels, and diet on insulin resistance. We recently reported that there was an association between Ala54Thr FABP2 genotypes and insulin sensitivity after accounting for the independent effects of body composition and habitual PA levels on insulin sensitivity. Furthermore, others have demonstrated that Ala54Thr FABP2 may associate with insulin sensitivity, but only if individuals are consuming a high-fat diet. These results highlight the importance of including behavioral and environmental factors in the design of studies seeking to assess the impact of genes on physiological and clinical outcome phenotypes.

Disordered fat storage and mobilization in the pathogenesis of insulin resistance and type 2 diabetes

The primary genetic, environmental, and metabolic factors responsible for causing insulin resistance and pancreatic beta-cell failure and the precise sequence of events leading to the development of type 2 diabetes are not yet fully understood. Abnormalities of triglyceride storage and lipolysis in insulin-sensitive tissues are an early manifestation of conditions characterized by insulin resistance and are detectable before the development of postprandial or fasting hyperglycemia. Increased free fatty acid (FFA) flux from adipose tissue to nonadipose tissue, resulting from abnormalities of fat metabolism, participates in and amplifies many of the fundamental metabolic derangements that are characteristic of the insulin resistance syndrome and type 2 diabetes. It is also likely to play an important role in the progression from normal glucose tolerance to fasting hyperglycemia and conversion to frank type 2 diabetes in insulin resistant individuals. Adverse metabolic consequences of increased FFA flux, to be discussed in this review, are extremely wide ranging and include, but are not limited to: 1) dyslipidemia and hepatic steatosis, 2) impaired glucose metabolism and insulin sensitivity in muscle and liver, 3) diminished insulin clearance, aggravating peripheral tissue hyperinsulinemia, and 4) impaired pancreatic beta-cell function. The precise biochemical mechanisms whereby fatty acids and cytosolic triglycerides exert their effects remain poorly understood. Recent studies, however, suggest that the sequence of events may be the following: in states of positive net energy balance, triglyceride accumulation in "fat-buffering" adipose tissue is limited by the development of adipose tissue insulin resistance. This results in diversion of energy substrates to nonadipose tissue, which in turn leads to a complex array of metabolic abnormalities characteristic of insulin-resistant states and type 2 diabetes. Recent evidence suggests that some of the biochemical mechanisms whereby glucose and fat exert adverse effects in insulin-sensitive and insulin-producing tissues are shared, thus implicating a diabetogenic role for energy excess as a whole. Although there is now evidence that weight loss through reduction of caloric intake and increase in physical activity can prevent the development of diabetes, it remains an open question as to whether specific modulation of fat metabolism will result in improvement in some or all of the above metabolic derangements or will prevent progression from insulin resistance syndrome to type 2 diabetes.

Cytoplasmic fatty acid-binding proteins: emerging roles in metabolism and atherosclerosis

Cytoplasmic fatty acid-binding proteins (FABPs) are a family of proteins, expressed in a tissue-specific manner, that bind fatty acid ligands and are involved in shuttling fatty acids to cellular compartments, modulating intracellular lipid metabolism, and regulating gene expression. Several members of the FABP family have been shown to have important roles in regulating metabolism and have links to the development of insulin resistance and the metabolic syndrome. Recent studies demonstrate a role for intestinal FABP in the control of dietary fatty acid absorption and chylomicron secretion. Heart FABP is essential for normal myocardial fatty acid oxidation and modulates fatty acid uptake in skeletal muscle. Liver FABP is directly involved in fatty acid ligand signaling to the nucleus and interacts with peroxisome proliferator-activated receptors in hepatocytes. The adipocyte FABP (aP2) has been shown to affect insulin sensitivity, lipid metabolism and lipolysis, and has recently been shown to play an important role in atherosclerosis. Interestingly, expression of aP2 by the macrophage promotes atherogenesis, thus providing a link between insulin resistance, intracellular fatty acid disposition, and foam cell formation. The FABPs are promising targets for the treatment of dyslipidemia, insulin resistance, and atherosclerosis in humans.

Postprandial plasma ApoB-48 levels are influenced by a polymorphism in the promoter of the microsomal triglyceride transfer protein gene

The microsomal triglyceride transfer protein (MTP) plays a key role in the secretion of apolipoprotein B (apoB)-containing lipoproteins. The rare variant of a functional polymorphism in the promoter region of the MTP gene has been associated with elevated transcriptional activity of the gene in vitro (MTP-493G/T). With use of a "recruit-by-genotype" approach, we investigated one of the potentially complex phenotypes of this polymorphism, the appearance in plasma of apoB-48 after a meal intake. A total of 12 homozygous carriers of the rare MTP-493T variant were identified from a population-based screening of 50-year-old healthy white men. All subjects were of the apoE3/3 genotype. Along with 48 baseline well-matched heterozygotes (n=24) plus homozygotes (n=24) for the common variant, they were given a standardized oral fat meal. Postprandial plasma concentrations of apoB-48 were determined by the combination of density gradient ultracentrifugation and analytical SDS-PAGE. The postprandial plasma concentrations of triglycerides did not differ between the groups, but homozygous carriers of the rare MTP-493T variant showed a >100% greater increase in apoB-48 in the smallest (Svedberg flotation rate constant 20 to 60) triglyceride-rich lipoprotein fraction (P=0.005). These data support the notion that elevated transcriptional activity of MTP leads to an increased generation of the smallest triglyceride-rich lipoprotein from the intestine.

Effects of the FABP2 A54T mutation on triglyceride metabolism of viscerally obese men

OBJECTIVE

Viscerally obese individuals are frequently characterized by a proatherogenic condition. A missense mutation (A54T) in the fatty acid binding protein type 2 (FABP2) gene has been associated with insulin resistance and obesity. This study examined the effect of this mutation on lipoprotein levels in viscerally obese hyperinsulinemic condition.

RESEARCH METHODS AND PROCEDURES

A total of 217 men were assigned to one of two groups based on their FABP2 A54T polymorphism.

RESULTS

The two genotypic groups showed no difference in either physiological characteristics or lipoprotein/lipid profile, before or after statistical adjustment for age. From this initial sample, 50 men accepted to have their postprandial lipid response assessed and 10 T54/A54 heterozygotes were then individually matched for visceral adipose tissue accumulation and fasting plasma triglyceride (TG) levels with 10 A54/A54 homozygotes. High-density lipoprotein (HDL)-TG levels were significantly increased in the fasting state as well as 4 hours after the test meal (p = 0.04 and p = 0.0008, respectively) in men bearing the A54T mutation. In addition, the area under the curve of postprandial HDL-TG levels was also significantly higher among T54/A54 heterozygotes than among A54/A54 homozygotes (p = 0.04). Interestingly, fasting TG concentrations in large TG-rich lipoproteins (large-TRL; S(f) > 400) were correlated with HDL-TG levels at 4 (r = 0.74, p = 0.01) and 8 hours (r = 0.73, p = 0.01) after the test meal in T54/A54 heterozygotes only.

DISCUSSION

The FABP2 A54T missense mutation may contribute to the TG enrichment of HDL in the postprandial state that, in turn, may alter the risk of atherosclerotic vascular disease.

Association of the Ala54-Thr polymorphism in the intestinal fatty acid-binding protein with 2-h postchallenge insulin levels in the Framingham Offspring Study

OBJECTIVE

To investigate the association of variants of the intestinal fatty acid-binding protein gene (FABP2) with fasting and postchallenge glucose and insulin levels, HbA(1c), and prevalence of type 2 diabetes in a separate sample of men and women.

RESEARCH DESIGN AND METHODS

Subjects were participants in the Framingham Offspring Study, a long-term community-based prospective observational study of risk factors for cardiovascular disease. The study sample consisted of 762 men and 922 women.

RESULTS

In women, carriers of the Thr54 allele had significantly higher 2-h postchallenge insulin levels than noncarriers (104.4 +/- 73.0 vs. 93.4 +/- 61.5 microU/ml; P = 0.0139). This relationship remained significant after adjustment for familial relationship, age, BMI, triglycerides, APOE genotype, smoking, alcohol intake, the use of beta-blockers, menopausal status, and estrogen therapy. No such significant association was observed in men. In both men and women, there were no statistical associations between the FABP2 polymorphism and BMI, fasting glucose, fasting insulin, 2-h postchallenge glucose levels, HbA(1c), and prevalence of type 2 diabetes.

CONCLUSIONS

These results suggest that the FABP2 Thr54 allele may have a minor contribution to the insulin resistance syndrome in a white general population.

Unravelling the significance of cellular fatty acid-binding proteins

Cellular long-chain fatty acid (FA) transport and metabolism are believed to be regulated by membrane-associated and soluble proteins that bind and transport FAs. Several different classes of membrane proteins have been proposed as FA acceptors or transmembrane FA transporters. New evidence from in-vitro and whole-animal studies supports the existence of protein-mediated transmembrane transport of FAs, which is likely to coexist with passive diffusional uptake. The trafficking of FAs by intracellular fatty acid-binding proteins may involve their interaction with specific membrane or protein targets. Evidence is also emerging for concerted actions between the membrane and cytoplasmic fatty acid-binding proteins that allow for efficient regulation of FA transport and metabolism.