Association of postprandial and fasting triglycerides with traits of the metabolic syndrome in the Metabolic Intervention Cohort Kiel

Metabolic and inflammatory postprandial effect of a highly saturated fat meal and its relationship to abdominal obesity

Introduction: The postprandial stage is associated with the increase of markers related to cardiovascular risk, and its intensity depends on the metabolic state. Objective: To determine the impact of a high-fat meal intake on the metabolic and inflammatory profile, and its relationship to abdominal obesity. Materials and methods: This clinical trial included 42 individuals (21 with abdominal obesity). We measured glucose, insulin, lipid profile, reactive C protein, lipopolysaccharides, and interleukin 6 in fasting blood, and four hours after eating. Results: Besides obesity, we found insulin resistance and higher levels of fasting triacylglycerides and C-reactive protein. There were higher postprandial responses to glucose, insulin, and triacylglycerides. Interleukin 6 decreased in the non-obese group, and lipopolysaccharides increased in both groups. Conclusions: A saturated high-fat food intake produced a greater impact on the glycemic variables in the group with obesity, while it affected the lipids in both groups. However, the increase of triacylglycerides was higher in the presence of a high basal concentration, and it promoted the increase of lipopolysaccharides. The basal and postprandial inflammatory state affected the group with obesity more. The postprandial moment reflected the most frequent state of the individuals on a normal day and evidenced the capacity of the metabolic response to food intake, as well as early metabolic risk states.

Genetic background in nonalcoholic fatty liver disease: A comprehensive review

In the Western world, nonalcoholic fatty liver disease (NAFLD) is considered as one of the most significant liver diseases of the twenty-first century. Its development is certainly driven by environmental factors, but it is also regulated by genetic background. The role of heritability has been widely demonstrated by several epidemiological, familial, and twin studies and case series, and likely reflects the wide inter-individual and inter-ethnic genetic variability in systemic metabolism and wound healing response processes. Consistent with this idea, genome-wide association studies have clearly identified Patatin-like phosholipase domain-containing 3 gene variant I148M as a major player in the development and progression of NAFLD. More recently, the transmembrane 6 superfamily member 2 E167K variant emerged as a relevant contributor in both NAFLD pathogenesis and cardiovascular outcomes. Furthermore, numerous case-control studies have been performed to elucidate the potential role of candidate genes in the pathogenesis and progression of fatty liver, although findings are sometimes contradictory. Accordingly, we performed a comprehensive literature search and review on the role of genetics in NAFLD. We emphasize the strengths and weaknesses of the available literature and outline the putative role of each genetic variant in influencing susceptibility and/or progression of the disease.

Effect of quercetin on traits of the metabolic syndrome, endothelial function and inflammation in men with different APOE isoforms

BACKGROUND AND AIMS

The polyphenol quercetin may prevent cardiovascular diseases due to its vasorelaxant and anti-oxidative properties. We investigated the effects of quercetin on risk factors of atherosclerosis, biomarkers of inflammation and oxidative stress, depending on the apolipoprotein E (APOE) genotype.

METHODS AND RESULTS

In a double-blind crossover study 49 healthy male subjects with APOE genotype 3/3 (n = 19), 3/4 (n = 22) and 4/4 (n = 8) consumed 150 mg/d quercetin or placebo for 8 weeks each, intermitted by a three-week washout phase. After each intervention, endothelial function, anthropometry, metabolic and inflammatory parameters were measured in the fasting and postprandial state following a standardized lipid-rich meal. Endothelial function was not changed. In all subjects combined, quercetin significantly decreased waist circumference (P = 0.004) and postprandial systolic blood pressure (P = 0.044). Postprandial triacylglycerol concentrations were significantly decreased and HDL-cholesterol concentrations increased after quercetin as compared to placebo consumption (P = 0.025). Quercetin also moderately increased levels of TNFα (P = 0.024). There was a significant gene-diet interaction for waist circumference and for body mass index (BMI).

CONCLUSIONS

Quercetin supplementation improved some risk factors of cardiovascular disease, yet exerted slightly pro-inflammatory effects. Genotype-dependent effects were seen only on waist circumference and BMI.

A common haplotype of carnitine palmitoyltransferase 1b is associated with the metabolic syndrome

The carnitine palmitoyltransferase (CPT) enzyme system facilitates the transport of long-chain fatty acids into mitochondria to provide substrates for β-oxidation. We performed an analysis including three coding SNP in the muscle isoform of the CPT1b gene (rs3213445, rs2269383 and rs470117) and one coding SNP in the CPT2 gene (rs1799821) to find associations with traits of the metabolic syndrome (MetS). Male participants (n 755) from the Metabolic Intervention Cohort Kiel were genotyped and phenotyped for features of the MetS. Participants underwent a glucose tolerance test and a postprandial assessment of metabolic variables after a standardised mixed meal. Carriers of the rare CPT1b 66V (rs3213445) allele had significantly higher γ-glutamyl transpeptidase (GGT), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvate transaminase (GPT) activities (P< 0·0001, P= 0·03 and P= 0·048, respectively) and a higher fatty liver index (FLI, P= 0·026). Fasting and postprandial TAG (P= 0·007 and P= 0·009, respectively) and fasting glucose (P= 0·012) were significantly higher in 66V-allele carriers. The insulin sensitivity index determined after a glucose load was lower in those subjects (P= 0·005). Total cholesterol (P= 0·051) and LDL-cholesterol (P= 0·062) tended to be higher in 66V-allele carriers when compared with I66I homozygotes. Homozygosity of the rare K531E allele presented with lower GGT and GOT activities (P= 0·011 and P= 0·027, respectively). E531E homozygotes tended to have lower GPT and FLI (P= 0·078 and P= 0·052, respectively). CPT2 V368I (rs1799821) genotypic groups did not differ in the investigated anthropometric and metabolic parameters. The present results confirm the association of CPT1b coding polymorphisms with the MetS, with a deleterious effect of the CPT1b I66V and a protective impact of the CPT1b K531E SNP, whereas haplotype analysis indicates a relevance of the E531K polymorphism only.

Influence of different CLA isomers on insulin resistance and adipocytokines in pre-diabetic, middle-aged men with PPARγ2 Pro12Ala polymorphism

Conjugated linoleic acids (CLAs) are natural PPARγ ligands, which showed conflicting effects on metabolism in humans. We examined metabolic effects of different isomers of CLA in subjects with PPARγ2 Pro12Ala polymorphisms. A total of 35 men underwent four intervention periods in a crossover study design: subjects with either genotypes received c9, t11 CLA or t10, c12 CLA, a commercially available 1:1 mix of both isomers or reference oil (linoleic acid (LA)). Adipocytokines, insulin, glucose and triglycerides were assessed in the fasting state and after a standardized mixed meal. Across all genotypes, there was a significant (p = 0.025) CLA treatment effect upon postprandial (pp) HOMA-IR values, with c9, t11 CLA and CLA isomer mix improving, but t10, c12 CLA isomer worsening. In Ala12Ala subjects, the t10, c12 isomer caused weight gain (p = 0.03) and tended to increase postprandial insulin levels (p = 0.05). In Pro12Pro subjects, t10, c12 resulted in reduction in waist circumference (p = 0.03). The comparison of the different genotype groups revealed statistically different changes in fasting and postprandial insulin, HOMA-IR and leptin after intervention. c9, t11 CLA and the commercial CLA mix showed beneficial effects on insulin sensitivity compared with LA, while t10, c12 CLA adversely affects body weight and insulin sensitivity in different PPAR genotypes. CLA isomers have different effects on metabolism in Ala and Pro carriers.

The effect of FABP2 promoter haplotype on response to a diet with medium-chain triacylglycerols

The fatty-acid-binding protein-2 (FABP2) gene has been proposed as a candidate gene for diabetes because the encoded protein is involved in fatty acid absorption and therefore may affect insulin sensitivity and glucose metabolism. The rare haplotype (B) of its promoter was shown to be associated with a lower risk for type 2 diabetes. The aim of this study was to investigate whether a polymorphism in the FABP2 promoter does affect the metabolic response to either an medium-chain triacylglycerol (MCT) or an long-chain triacylglycerol (LCT) diet, which were suggested to differ in transport mechanisms, in affinity to FABP2, in activating transcription factors binding to the FABP2 promoter and in their effects on insulin sensitivity. We studied 82 healthy male subjects varying in the FABP2 promoter (42 homozygous for common haplotype (A), 40 homozygous for the rare haplotype (B)) in an interventional study with either an MCT or LCT diet over 2 weeks to examine gene-nutrient interaction. The saturation grade of MCT was adjusted to that of the LCT fat. We determined glucose, insulin, triacylglycerols (TGs), chylomicron triacylglycerols and cholesterol before and after a standardised mixed meal before and after the intervention. HDL cholesterol increased in all groups, which was most pronounced in subjects homozygous for the common promoter haplotype A who received MCT diet (P = 0.001), but not significant in homozygous rare haplotype B subjects who received MCT fat. Subjects homozygous for FABP2 haplotype A showed a significant decrease in fasting and postprandial glucose (P = 0.01, 0.04, respectively) and a decrease in insulin resistance (HOMA-IR, P = 0.04) during LCT diet. After correction for multiple testing, those effects did not remain significant. Fasting and postprandial triacylglycerols, LDL cholesterol, chylomicron TGs and cholesterol were not affected by genotype or diet. MCT diet increased HDL cholesterol dependent on the FABP2 promoter haplotype. The effects of the promoter haplotype B could be mediated by PPARγ, which is upregulated by medium-chain fatty acids.

A variant in the heart-specific fatty acid transport protein 6 is associated with lower fasting and postprandial TAG, blood pressure and left ventricular hypertrophy

Fatty acid transport protein 6 (FATP6) is primarily expressed in the heart and seems to be involved in cardiac fatty acid uptake. Therefore, we investigated whether a variation in the 5'-untranslated region of the FATP6 gene is associated with features of the metabolic syndrome and signs of myocardial alteration or heart failure. A total of 755 male participants from a Metabolic Intervention Cohort Kiel were genotyped for the FATP6-7T>A polymorphism (rs2526246) and phenotyped for features of the metabolic syndrome. Participants underwent a glucose tolerance test and the postprandial assessment of metabolic variables after a standardised mixed meal. Left ventricular heart function was evaluated in fifty-four participants. Fasting (P = 0·01) and postprandial (P = 0·02) TAG concentrations were significantly lower in AA homozygotes when compared with wild-type carriers. Homozygosity of allele A was associated with significantly lower postprandial insulin concentrations after a glucose load and significantly lower systolic (P = 0·01) and diastolic (P = 0·01) blood pressure values compared with wild-type carriers. Accordingly, left ventricular heart mass was significantly lower in twenty-seven AA homozygotes in comparison with twenty-seven TT homozygotes, matched for BMI (P = 0·04). In conclusion, the effects of the FATP6 polymorphism on TAG are mediated by affluent dietary fat. The FATP6-7T>A polymorphism may protect from traits of the metabolic syndrome and CVD.