Glu298Asp polymorphism influences the beneficial effects of fish oil fatty acids on postprandial vascular function

Glu298Asp (rs1799983) Polymorphism Influences Postprandial Vascular Reactivity and the Insulin Response to Meals of Varying Fat Composition in Postmenopausal Women: Findings from the Randomized, Controlled Dietary Intervention and VAScular function (DIVAS)-2 Study

BACKGROUND

Previous acute studies suggest the Glu298Asp polymorphism (rs1799983) may influence vascular reactivity in response to long-chain n-3 PUFA intake. However, the effects of this genotype on postprandial vascular function after meals rich in SFAs, n-6 PUFAs, and MUFAs are unclear.

OBJECTIVES

This study determined the impact of the Glu298Asp polymorphism on changes in vascular function and cardiometabolic risk biomarkers in response to sequential meals of varying fat composition.

METHODS

In a randomized, double-blind, crossover, acute study, 32 postmenopausal women (mean ± SD age: 58 ± 5 y; BMI: 25.9 ± 4.1 kg/m2) consumed mixed meals (breakfast: 0 min, 50 g fat; lunch: 330 min, 30 g fat) containing SFAs, n-6 PUFAs, or MUFAs on 3 occasions. Blood samples for cardiometabolic disease risk markers and real-time measures of vascular reactivity [including flow-mediated dilatation (FMD; primary outcome)] were collected/performed before and regularly for 480 min after breakfast. Participants were retrospectively genotyped for the Glu298Asp (rs1799983) polymorphism. Data were analyzed using linear mixed models.

RESULTS

For the postprandial %FMD response, a test fat × genotype interaction was observed for the AUC (P = 0.019) but not incremental AUC (IAUC), with the AUC being ∼24% greater after MUFA- than after SFA- and n-6 PUFA-rich meals in the Glu298 homozygotes (P ≤ 0.026). Test fat × genotype interactions were also evident for postprandial insulin (P ≤ 0.005), with the MUFA-rich meals demonstrating significantly higher AUC (12.8%/14.9%), IAUC (14.6%/20.0%), and maximum concentration (20.0%/34.5%) than the SFA- and n-6 PUFA-rich meals, respectively, in Asp298 carriers (P < 0.05). Genotype did not influence other study outcome measures in response to the test fats.

CONCLUSIONS

Our findings suggest the Glu298Asp polymorphism may represent a potential determinant of the inter-individual variability in postprandial responsiveness of %FMD and insulin to acute meal fat composition in postmenopausal women. Further studies are required to confirm these observations.This trial was registered at clinicaltrials.gov as NCT02144454.

Replication of a Gene-Diet Interaction at CD36, NOS3 and PPARG in Response to Omega-3 Fatty Acid Supplements on Blood Lipids: A Double-Blind Randomized Controlled Trial

BACKGROUND

Modulation of genetic variants on the effect of omega-3 fatty acid supplements on blood lipids is still unclear.

METHODS

In a double-blind randomized controlled trial, 150 patients with type 2 diabetes (T2D) were randomized into omega-3 fatty acid group (n = 56 for fish oil and 44 for flaxseed oil) and control group (n = 50) for 180 days. All patients were genotyped for genetic variants at CD36 (rs1527483), NOS3 (rs1799983) and PPARG (rs1801282). Linear regression was used to examine the interaction between omega-3 fatty acid intervention and CD36, NOS3 or PPARG variants for blood lipids.

FINDINGS

Significant interaction with omega-3 fatty acid supplements was observed for CD36 on triglycerides (p-interaction = 0.042) and PPAGR on low-density lipoprotein-cholesterol (p-interaction = 0.02). We also found a significant interaction between change in erythrocyte phospholipid omega-3 fatty acid composition and NOS3 genotype on triglycerides (p-interaction = 0.042), total cholesterol (p-interaction = 0.013) and ratio of total cholesterol to high-density lipoprotein cholesterol (p-interaction = 0.015). The T2D patients of CD36-G allele, PPARG-G allele and NOS3-A allele tended to respond better to omega-3 fatty acids in improving lipid profiles. The interaction results of the omega-3 fatty acid group were mainly attributed to the fish oil supplements.

INTERPRETATION

This study suggests that T2D patients with different genotypes at CD36, NOS3 and PPARG respond differentially to intervention of omega-3 supplements in blood lipid profiles.

Consumption of Fish Oil Providing Amounts of Eicosapentaenoic Acid and Docosahexaenoic Acid That Can Be Obtained from the Diet Reduces Blood Pressure in Adults with Systolic Hypertension: A Retrospective Analysis

BACKGROUND

Although many randomized controlled trials (RCTs) have examined the effects of the n-3 (ω-3) fatty acids eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) on blood pressure (BP) and vascular function, the majority have used doses of EPA+DHA of >3 g/d, which are unlikely to be achieved by dietary manipulation.

OBJECTIVE

The objective was to examine, by using a retrospective analysis from a multicenter RCT, the impact of recommended EPA+DHA intakes achievable through diet on systolic and diastolic BPs and microvascular function in adults in the United Kingdom.

METHODS

In a double-blind, placebo-controlled RCT, healthy men and women (n = 312) consumed a control oil or fish oil (FO) providing 0.7 or 1.8 g EPA+DHA/d, in random order, each for 8 wk. Fasting BP and microvascular function (using laser Doppler iontophoresis) were assessed and plasma collected for the quantification of markers of vascular function. Participants were retrospectively genotyped for the endothelial nitric oxide synthase (eNOS) rs1799983 variant.

RESULTS

No effects of n-3 fatty acid treatment or any treatment × eNOS genotype interactions were evident in the group as a whole for any of the clinical or biochemical outcomes. Assessment of response according to hypertension status at baseline indicated a significant (P = 0.046) FO-induced reduction (mean: 5 mm Hg) in systolic BP, specifically in those with isolated systolic hypertension (n = 31). No dose response was observed.

CONCLUSIONS

These findings indicate that in adults with isolated systolic hypertension, daily doses of EPA+DHA as low as 0.7 g show clinically meaningful BP reductions, which, at a population level, could be associated with lower cardiovascular disease risk. Confirmation of findings in an RCT in which participants are prospectively recruited on the basis of BP status is required to draw definite conclusions.

Endothelial function and insulin sensitivity during acute non-esterified fatty acid elevation: Effects of fat composition and gender

BACKGROUND AND AIMS

We have reported that adverse effects on flow-mediated dilation of an acute elevation of non-esterified fatty acids rich in saturated fat (SFA) are reversed following addition of long-chain (LC) n-3 polyunsaturated fatty acids (PUFA), and hypothesised that these effects may be mediated through alterations in insulin signalling pathways. In a subgroup, we explored the effects of raised NEFA enriched with SFA, with or without LC n-3 PUFA, on whole body insulin sensitivity (SI) and responsiveness of the endothelium to insulin infusion.

METHODS AND RESULTS

Thirty adults (mean age 27.8 y, BMI 23.2 kg/m(2)) consumed oral fat loads on separate occasions with continuous heparin infusion to elevate NEFA between 60 and 390 min. For the final 150 min, a hyperinsulinaemic-euglycaemic clamp was performed, whilst FMD and circulating markers of endothelial function were measured at baseline, pre-clamp (240 min) and post-clamp (390 min). NEFA elevation during the SFA-rich drinks was associated with impaired FMD (P = 0.027) whilst SFA + LC n-3 PUFA improved FMD at 240 min (P = 0.003). In males, insulin infusion attenuated the increase in FMD with SFA + LC n-3 PUFA (P = 0.049), with SI 10% greater with SFA + LC n-3 PUFA than SFA (P = 0.041).

CONCLUSION

This study provides evidence that NEFA composition during acute elevation influences both FMD and SI, with some indication of a difference by gender. However our findings are not consistent with the hypothesis that the effects of fatty acids on endothelial function and SI operate through a common pathway. This trial was registered at clinical trials.gov as NCT01351324 on 6th May 2011.

Fish-oil supplementation alters numbers of circulating endothelial progenitor cells and microparticles independently of eNOS genotype

BACKGROUND

Emerging cellular markers of endothelial damage and repair include endothelial microparticles (EMPs) and endothelial progenitor cells (EPCs), respectively. Effects of long-chain (LC) n-3 (omega-3) polyunsaturated fatty acids (PUFAs) and the influence of genetic background on these markers are not known.

OBJECTIVE

We investigated effects of fish-oil supplementation on both classical and novel markers of endothelial function in subjects prospectively genotyped for the Asp298 endothelial nitric oxide synthase (eNOS) polymorphism and at moderate risk of cardiovascular disease (CVD).

DESIGN

A total of 84 subjects with moderate risk of CVD (GG: n = 40; GT/TT: n = 44) completed a randomized, double-blind, placebo-controlled, 8-wk crossover trial of fish-oil supplementation that provided 1.5 g LC n-3 PUFAs/d. Effects of genotype and fish-oil supplementation on the blood lipid profile, inflammatory markers, vascular function (by using peripheral artery tonometry), and numbers of circulating EPCs and EMPs (by using flow cytometry) were assessed.

RESULTS

There was no significant effect of fish-oil supplementation on blood pressure, plasma lipids, or plasma glucose, although there was a trend (P = 0.069) toward a decrease in the plasma triglyceride concentration after fish-oil supplementation compared with placebo treatment. GT/TT subjects tended to have higher concentrations of total cholesterol and low-density lipoprotein cholesterol, but vascular function was not affected by either treatment or eNOS genotype. Biochemical markers of endothelial function were also unaffected by treatment and eNOS genotype. In contrast, there was a significant effect of fish-oil supplementation on cellular markers of endothelial function. Fish-oil supplementation increased numbers of EPCs and reduced numbers of EMPs relative to those with placebo treatment, which potentially favored the maintenance of endothelial integrity. There was no influence of genotype for any cellular markers of endothelial function, which indicated that effects of fish-oil supplementation were independent of eNOS genotype.

CONCLUSION

Emerging cellular markers of endothelial damage, integrity, and repair appear to be sensitive to potentially beneficial modification by dietary n-3 PUFAs. This trial was registered at www.controlled-trials.com/isrctn as ISRCTN76272133.