Postprandial triglyceride levels rather than fat distribution may reflect early signs of disturbed fat metabolism in Iraqi immigrants

PURPOSE

Previous studies have shown that at a similar body mass index, Middle Eastern immigrants are more insulin resistant and at higher risk for type 2 diabetes (T2D) than native Europeans. Insulin resistance is strongly associated with disturbed fat metabolism and cardiovascular disease (CVD). However, fat metabolism is poorly investigated comparing Middle Eastern and European ethnicities.

METHODS

This observational study included 26 Iraqi and 16 Swedish-born men without T2D or clinical risk factors for CVD. An oral fat tolerance test (OFTT) was performed, where plasma triglycerides (p-TG) were measured for 6 h. mRNA expression and adipocyte size were measured in subcutaneous adipose tissue biopsies collected prior to OFTT, and magnetic resonance imaging was conducted to assess body fat distribution.

RESULTS

The median p-TG accumulation was higher and the clearance slower among Iraqis than Swedes. None of the groups reached their fasting p-TG (Iraqis 1.55 mmol/l; Swedes 0.95 mmol/l) after 6 h (Iraqis p-TG 3.10 mmol/l; Swedes p-TG 1.50 mmol/l). Adipocyte size, mRNA expression, and fat accumulation in the liver, muscle and abdomen were similar in both groups.

CONCLUSION

Postprandial p-TG levels rather than fat distribution may reflect early signs of disturbed fat metabolism in Iraqi immigrants without CVD risk factors.

ANGPTL8 promotes the ability of ANGPTL3 to bind and inhibit lipoprotein lipase

OBJECTIVE

Several members of the angiopoietin-like (ANGPTL) family of proteins, including ANGPTL3 and ANGPTL8, regulate lipoprotein lipase (LPL) activity. Deficiency in either ANGPTL3 or ANGPTL8 reduces plasma triglyceride levels and increases LPL activity, whereas overexpression of either protein does the opposite. Recent studies suggest that ANGPTL8 may functionally interact with ANGPTL3 to alter clearance of plasma triglycerides; however, the nature of this interaction has remained elusive. We tested the hypothesis that ANGPTL8 forms a complex with ANGPTL3 and that this complex is necessary for the inhibition of vascular LPL by ANGPTL3.

METHODS

We analyzed the interactions of ANGPTL3 and ANGPTL8 with each other and with LPL using co-immunoprecipitation, western blotting, lipase activity assays, and the NanoBiT split-luciferase system. We also used adenovirus injection to overexpress ANGPTL3 in mice that lacked ANGPTL8.

RESULTS

We found that ANGPTL3 or ANGPTL8 alone could only inhibit LPL at concentrations that far exceeded physiological levels, especially when LPL was bound to its endothelial cell receptor/transporter GPIHBP1 (glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1). Physical interaction was observed between ANGPTL3 and ANGPTL8 when the proteins were co-expressed, and co-expression with ANGPTL3 greatly enhanced the secretion of ANGPTL8. Importantly, ANGPTL3-ANGPTL8 complexes had a dramatically increased ability to inhibit LPL compared to either protein alone. Adenovirus experiments showed that 2-fold overexpression of ANGPTL3 significantly increased plasma triglycerides only in the presence of ANGPTL8. Protein interaction assays showed that ANGPTL8 greatly increased the ability of ANGPTL3 to bind LPL.

CONCLUSIONS

Together, these data indicate that ANGPTL8 binds to ANGPTL3 and that this complex is necessary for ANGPTL3 to efficiently bind and inhibit LPL.

Angiopoietin-like 4 directs uptake of dietary fat away from adipose during fasting

Objective

Angiopoietin-like 4 (ANGPTL4) is a fasting-induced inhibitor of lipoprotein lipase (LPL) and a regulator of plasma triglyceride metabolism. Here, we examined the kinetics of Angptl4 induction and tested the hypothesis that ANGPTL4 functions physiologically to reduce triglyceride delivery to adipose tissue during nutrient deprivation.

Methods

Gene expression, LPL activity, and triglyceride uptake were examined in fasted and fed wild-type and Angptl4^−/− mice.

Results

Angptl4 was strongly induced early in fasting, and this induction was suppressed in mice with access to food during the light cycle. Fasted Angptl4^−/− mice manifested increased LPL activity and triglyceride uptake in adipose tissue compared to wild-type mice.

Conclusions

Angptl4 is induced early in fasting to divert uptake of fatty acids and triglycerides away from adipose tissues.

•Angptl4 is induced within the first few hours of fasting.

•Angptl4 expression is driven by fasting rather than circadian rhythms.

•Fasted Angptl4^−/− mice have increased triglyceride uptake in adipose tissue.

•Angptl4^−/− mice also have increased LPL activity specifically in adipose tissue.

•Data support a model where ANGPTL4 acts locally in adipose during fasting.

Long chain polyunsaturated fatty acids (LCPUFAs) and nordihydroguaiaretic acid (NDGA) modulate metabolic and inflammatory markers in a spontaneous type 2 diabetes mellitus model (Stillman Salgado rats)

BACKGROUND

Diabetes mellitus (DM) is a complex disease with alterations in metabolic and inflammatory markers. Stillman Salgado rats (eSS) spontaneously develop type 2 DM by middle age showing progressive impairment of glucose tolerance with hyperglycemia, hypertriglyceridemia and hyperinsulinemia. We analyzed the effects of supplementation of ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) with or without nordihydroguaiaretic acid (NDGA) added, an antioxidant and lipoxygenase inhibitor, on metabolic and inflammatory parameters in eSS rats to evaluate whether they can delay development and/or prevent progression of DM.

METHODS

After weaning, eSS rats received, intraperitoneally, once a month ω-3 (EPA 35% and DHA 40%-6.25 mg/Kg) or ω-6 (90% arachidonic acid- 6. 25 mg/Kg) for twelve months. Two additional groups of rats received 1.9 mg/kg NDGA added to ω-3 and ω-6 fatty acids. Blood samples were collected at day 40, and at the end of the 6th month and 12th month of age to determine plasma triglycerides (TGs), total plasma fatty acids (FA), A1C hemoglobin (HbA1C), C-reactive protein (CRP), gamma glutamyl transpeptidase (GGT), lipo and hydro peroxides, nitrites and IL-6 (in plasma and liver, kidney, and pancreas) and underwent oral glucose tolerance test (OGTT) as well. Wistar and eSS rats that received saline solution were used as controls.

RESULTS

Plasma lipids profile, TG, fasting and post-prandial blood glucose levels, and glycosylated HbA1C showed significant improvements in ω-3 and ω-3 + NDGA treated animals compared to eSS control group. ω-3 and ω-3 + NDGA groups showed an inverse correlation with fasting blood glucose and showed lower plasma levels of GGT, TG, and CRP. eSS rats treated with ω-3 LCPUFAs showed reduced level of inflammatory and oxidative indices in plasma and liver, kidney and pancreas tissues in comparison with eSS control (non-treated) and ω-6 treated groups.

CONCLUSIONS

eSS rats are a useful model to study type 2 DM pathophysiology and related inflammatory indices. ω-3 + NDGA supplementation, at the doses tested, ameliorated inflammatory, metabolic and oxidative stress markers studied.

A randomized, placebo-controlled, double-blind study on the effects of (-)-epicatechin on the triglyceride/HDLc ratio and cardiometabolic profile of subjects with hypertriglyceridemia: Unique in vitro effects

BACKGROUND

Cardiometabolic disruptions such as insulin resistance, obesity, high blood pressure, hyperglycemia, and dyslipidemias, are known to increase the risk for cardiovascular and metabolic diseases such as type 2 diabetes mellitus and atherosclerosis. Several screening tools for assessing cardiometabolic risk have been developed including the TG/HDLc ratio, which has been, demonstrated to possess a strong association with insulin resistance and coronary disease. Dietary modifications, together with regular moderate exercise have proven to be effective in attenuating cardiometabolic disruptions. However, they often exhibit poor long-term patient compliance. Nutraceutics, including (-)-epicatechin (EPI), have gained increasing interest as coadjuvant effective and safe therapies that are able to attenuate hypertension, hyperglycemia, hyperinsulinemia, hypertriglyceridemia and hypoalphalipoproteinemia.

METHODS

The aims of this study were: 1) to compare the in vitro effect of EPI vs. (+)-catechin on fructose induced triglyceride accumulation and mitochondrial function in Hep2 cells in culture, 2) to evaluate the efficacy of EPI treatment in reducing fasting blood triglycerides and improving the TG/HDLc ratio in hypertriglyceridemic patients with a total daily dose of 100mg of EPI. Secondary clinical variables included total cholesterol, LDLc, fructosamine, glucose, insulin, and high sensitivity C-reactive protein blood levels.

RESULTS AND CONCLUSION

Our results provide preliminary evidence as to favorable effects of EPI on glycemia homeostasis, lipid profile and systemic inflammation such bioactive actions are not class-effects (i.e. limited to their antioxidant potential) but instead, may result from the specific activation of associated downstream signaling pathways since catechin has no effects.

Effects of anacetrapib on plasma lipids in specific patient subgroups in the DEFINE (Determining the Efficacy and Tolerability of CETP INhibition with AnacEtrapib) trial

BACKGROUND

In the Determining the Efficacy and Tolerability of cholesteryl ester transfer protein (CETP) INhibition with AnacEtrapib (DEFINE) trial, anacetrapib added to statin produced robust low-density lipoprotein cholesterol (LDL-C)-lowering and high-density lipoprotein cholesterol (HDL-C)-raising vs placebo in patients with coronary heart disease (CHD). Predictors of the degree of LDL-C and HDL-C responses to anacetrapib, however, are poorly understood.

OBJECTIVE

Lipid effects of anacetrapib in patient subgroups within the DEFINE trial (clinicaltrials.gov: NCT00685776) are reported.

METHODS

The percent of placebo-corrected changes from baseline for LDL-C (estimated by Friedewald calculation [Fc-LDL-C]) and HDL-C after 24 weeks of anacetrapib 100 mg/day were compared among patients by age, gender, race, diabetes status, type of concomitant statin with or without other lipid therapies, and baseline HDL-C, Fc-LDL-C, and triglyceride (TG) levels.

RESULTS

Percent decreases in Fc-LDL-C and increases in HDL-C with anacetrapib were similar (magnitude of difference generally <1/5 of the overall treatment effect) across subgroups by age, gender, diabetes status, lipid-modifying regimen, and baseline Fc-LDL-C, HDL-C, or TG. On the other hand, anacetrapib effects on Fc-LDL-C (-24% vs -41%) and HDL-C (+75% vs +139%) appeared to be less in black vs white patients, respectively.

CONCLUSION

Effects of anacetrapib on Fc-LDL-C and HDL-C were generally comparable across subgroups, including being relatively independent of baseline Fc-LDL-C, HDL-C, or TG levels. The clinical impact of the lipid-modifying effects of anacetrapib is being evaluated in the cardiovascular disease outcomes trial, Randomized EValuation of the Effects of Anacetrapib though Lipid-modification (REVEAL).

Evaluation of thiazole containing biaryl analogs as diacylglycerol acyltransferase 1 (DGAT1) inhibitors

Biphenyl carboxylic acids, exemplified by compound 5, are known potent inhibitors of diacylglycerol acyltransferase, DGAT1, an enzyme involved in the final committed step of triglyceride biosynthesis. We have synthesized and evaluated 2-phenylthiazole, 4-phenylthiazole, and 5-phenylthiazole analogs as DGAT1 inhibitors. The 5-phenylthiazole series exhibited potent DGAT1 inhibition when evaluated using an in vitro enzymatic assay and an in vivo fat tolerance test in mice. Compound 33 (IC50 = 23 nM) exhibiting promising oral pharmacokinetic parameters (AUCinf = 7058 ng h/ml, T1/2 = 0.83 h) coupled with 87 percent reduction of plasma triglycerides in vivo may serve as a lead for developing newer anti-obesity agents.