DGAT2-MOGAT2 SNPs and Gene-Environment Interactions on Serum Lipid Profiles and the Risk of Ischemic Stroke

Background: The genetic susceptibility to ischemic stroke (IS) is still not well-understood. Recent genome-wide association studies (GWASes) found that several single nucleotide polymorphisms (SNPs) in the Diacylglycerol acyltransferase 2 gene (DGAT2) and monoacylglycerol O-acyltransferase 2 (MOGAT2) cluster were associated with serum lipid levels. However, the association between the DGAT2-MOGAT2 SNPs and serum lipid phenotypes has not yet been verified in the Chinese people. Therefore, the present study was to determine the DGAT2-MOGAT2 SNPs and gene-environment interactions on serum lipid profiles and the risk of IS. Methods: Genotyping of 5 SNPs (DGAT2 rs11236530, DGAT2 rs3060, MOGAT2 rs600626, MOGAT2 rs609379, and MOGAT2 rs10899104) in 544 IS patients and 561 healthy controls was performed by the next-generation sequencing technologies. The association between genotypes and serum lipid data was determined by analysis of covariance, and a corrected P-value was adopted after Bonferroni correction. Unconditional logistic regression analysis was performed to assess the association between genotypes and the risk of IS after adjustment of potential confounders. Results: The rs11236530A allele was associated with increased risk of IS (CA/AA vs. CC, OR = 1.45, 95%CI = 1.12-1.88, P = 0.0044), whereas the rs600626G-rs609379A-rs10899104G haplotype was associated with decreased risk of IS (adjusted OR = 0.67, 95% CI = 0.48-0.93, P = 0.018). The rs11236530A allele carriers had lower high-density lipoprotein cholesterol (HDL-C) concentrations than the rs11236530A allele non-carriers (P < 0.001). The interactions of rs11236530-smoking, rs3060-smoking and rs10899104-smoking influenced serum apolipoprotein B levels, whereas the interactions of rs11236530- and rs3060-alcohol affected serum HDL-C levels (P _I < 0.004-0.001). The interaction of rs600626G-rs609379A-rs10899104G-alcohol (OR = 0.41, 95% CI = 0.22-0.76) and rs600626G-rs609379C-rs10899104T-alcohol (OR = 0.12, 95% CI = 0.04-0.36) decreased the risk of IS (P _I < 0.0001). Conclusions: The rs11236530A allele was associated with decreased serum HDL-C levels in controls and increased risk of IS in patient group. The rs600626G-rs609379A-rs10899104G haplotype, the rs600626G-rs 609379A-rs10899104G-alcohol and rs600626G-rs609379C-rs10899104T-alcohol interactions were associated with decreased risk of IS. The rs11236530 SNP may be a genetic marker for IS in our study populations.

Risperidone-induced metabolic dysfunction is attenuated by Curcuma longa extract administration in mice

Antipsychotics, such as risperidone, increase food intake and induce alteration in glucose and lipid metabolism concomitantly with overweight and body fat increase, these biological abnormalities belong to the metabolic syndrome definition (high visceral adiposity, hypertriglyceridemia, hyperglycemia, low HDL-cholesterol and high blood pressure). Curcumin is a major component of traditional turmeric (Curcuma longa) which has been reported to improve lipid and glucose metabolism and to decrease weight in obese mice. We questioned the potential capacity of curcumin, contained in Curcuma longa extract (Biocurcuma™), to attenuate the risperidone-induced metabolic dysfunction. Two groups of mice were treated once a week, for 22 weeks, with intraperitoneal injection of risperidone (Risperdal) at a dose 12.5 mpk. Two other groups received intraperitoneal injection of the vehicle of Risperdal following the same schedule. Mice of one risperidone-treated groups and of one of vehicle-treated groups were fed a diet with 0.05% Biocurcuma™ (curcumin), while mice of the two other groups received the standard diet. Curcumin limited the capacity of risperidone to reduce spontaneous motricity, but failed to impede risperidone-induced increase in food intake. Curcumin did not reduce the capacity of risperidone to induce weight gain, but decreased visceral adiposity and decreased the risperidone-induced hepatomegaly, but not steatosis. Furthermore, curcumin repressed the capacity of risperidone to induce the hepatic over expression of enzymes involved in lipid metabolism (LXRα, FAS, ACC1, LPL, PPARγ, ACO, SREBP2) and decreased risperidone-induced glucose intolerance and hypertriglyceridemia. Curcumin decreased risperidone-induced increases in serum markers of hepatotoxicity (ALAT, ASAT), as well as of one major hepatic pro-inflammatory transcription factor (NFκB: p105 mRNA and p65 protein). These findings support that nutritional doses of curcumin contained in Curcuma longa extract are able to partially counteract the risperidone-induced metabolic dysfunction in mice, suggesting that curcumin ought to be tested to reduce the capacity of risperidone to induce the metabolic syndrome in human.

Effects of phenotypic and genotypic factors on the lipid responses to niacin in Chinese patients with dyslipidemia

The acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes DGAT1 and DGAT2 catalyze the final step in triglycerides biosynthesis. This study examined the relationships of baseline phenotypes and the common polymorphisms in DGAT1 and DGAT2 with the lipid responses to niacin.Lipid responses in Chinese patients with dyslipidemia treated with the extended release (ER) niacin/laropiprant combination 1000/20 mg for 4 weeks and then 2000/40 mg for 8 weeks (n = 121, the primary study) or with ER niacin 1500 mg for at least 4 weeks (n = 68, the replication study) were analyzed according to genotypes of DGAT1 rs7003945 T>C and DGAT2 rs3060 T>C polymorphisms.Treatment with ER niacin improved all lipid parameters in both studies. Absolute and percentage changes in lipids were related to their baseline levels, particularly for low-density lipoprotein cholesterol (LDL-C). The DGAT2 rs3060 T>C polymorphism was associated with lower baseline LDL-C, apoB, high-density lipoprotein cholesterol (HDL-C), and apoAI in patients on statin therapy in the primary study. Subjects with the DGAT2 rs3060 T>C variant had less reduction in LDL-C in the primary study and smaller changes in triglyceride and HDL-C in the replication study but these associations became non-significant after adjusting for baseline lipid values. The DGAT1 rs7003945 T>C polymorphism was not related to lipid baseline values or changes in either study. Concomitant statin therapy and lower body weight were also associated with greater reduction in LDL-C.Baseline lipid levels were the main determinants of lipid responses especially for LDL-C. The DGAT2 rs3060 polymorphism might influence the lipid responses depending on baseline phenotype, but this association did not persist after adjustment for the baseline lipid levels.

Serum lipoprotein changes in dogs with renal disease

Background

People with renal disease develop a dyslipidemia that contributes to progression of renal injury and development of cardiovascular disease. Lipoproteins in dogs with renal disease have not been investigated.

Hypothesis

Dogs with chronic kidney disease (CKD) have dyslipidemia characterized by increased lower density lipoproteins and decreased high‐density lipoproteins (HDLs). The degree of dyslipidemia is positively correlated with severity of disease, as reflected by serum creatinine concentration.

Animals

Prospective study of client‐owned dogs presented to the Cornell University Hospital for Animals: 29 dogs with confirmed CKD, 5 dogs with nephrotic syndrome (NS), and 12 healthy control dogs presented for routine vaccinations, dental cleaning, or owned by students.

Methods

Lipoprotein electrophoresis was used to quantify relative proportions of the 3 main classes of lipoproteins in canine serum: low‐density lipoproteins (LDL), very low‐density lipoproteins (VLDL), and HDL. Serum cholesterol and creatinine concentrations; urinalysis and urine protein‐to‐creatinine ratio were measured by standard methods.

Results

Dyslipidemia was consistently found in dogs with CKD and NS and was characterized by a decrease in HDL and variable increases in LDL and VLDL. Dogs with NS had a proportionately greater increase in the VLDL fraction, as compared with dogs with CKD.

Conclusion and Clinical Importance

Dyslipidemia similar to that documented in people with renal disease occurs in dogs with CKD, despite serum cholesterol concentrations often being within the reference interval. The contribution of altered lipoproteins to the pathogenesis of renal disease in dogs warrants additional study.

Dietary nicotinic acid supplementation ameliorates chronic alcohol-induced fatty liver in rats

BACKGROUND

Alcohol abuse frequently causes niacin deficiency in association with the development of alcoholic liver disease. The objective of the present study was to determine whether dietary nicotinic acid (NA) deficiency exaggerates and whether dietary NA supplementation alleviates alcohol-induced fatty liver.

METHODS

Male Sprague-Dawley rats were pair-fed with 4 isocaloric liquid diets: control, ethanol (EtOH), EtOH with dietary NA deficiency, and EtOH with dietary NA supplementation, respectively, for 8 weeks. The control and EtOH diets contained normal levels of NA (7.5 mg/l). Dietary NA deficiency (0 mg NA/l) was achieved by removing NA from the vitamin mix, while NA was added to the liquid diet at 750 mg/l for dietary NA supplementation.

RESULTS

Chronic EtOH feeding induced significant lipid accumulation in the liver, which was not worsened by dietary NA deficiency, but was ameliorated by dietary NA supplementation. Liver total NAD, NAD(+) , and NADH levels were remarkably higher in the NA supplemented group than the NA deficient or EtOH alone groups. Dietary NA supplementation to EtOH-fed rats increased the protein levels of hepatic cytochrome P450 4A1 (CYP4A1) and acyl-coenzyme A oxidase 1 without affecting their mRNA levels. Interestingly, we found dietary NA supplementation reduced the ubiquitination level of CYP4A1. In addition, hepatic fatty acid synthase expression was reduced, while the serum β-hydroxybutyrate and adiponectin concentrations were significantly elevated by dietary NA supplementation. Moreover, dietary NA supplementation modulated EtOH-perturbed liver and serum metabolite profiles.

CONCLUSIONS

These results demonstrate that alcoholic fatty liver was not exaggerated by dietary NA deficiency, but was ameliorated by dietary NA supplementation. Increased hepatic fatty acid oxidation and decreased hepatic de novo lipogenesis contribute to the effects of dietary NA supplementation.

Supplementing obese Zucker rats with niacin induces the transition of glycolytic to oxidative skeletal muscle fibers

In the present study, we tested the hypothesis that niacin increases the oxidative capacity of muscle by increasing the oxidative type I muscle fiber content. Twenty-four obese Zucker rats were assigned to 2 groups of 12 rats that were fed either a control diet (O group) or a diet supplemented with 750 mg/kg diet niacin (O+N group) for 4 wk. In addition, one group of lean rats (L group) was included in the experiment and fed the control diet for 4 wk. Plasma and liver concentrations of TG were markedly greater in obese groups than in the L group but markedly lower in the O+N group than in the O group (P < 0.05). Rats of the O+N group had a higher percentage of oxidative type I fibers and higher mRNA levels of genes encoding regulators of muscle fiber composition (Ppard, Ppargc1a, Ppargc1b), angiogenic factors (Vegfa, Vegfb), and genes involved in fatty acid utilization (Cpt1b, Slc25a20, Slc22a4, Slc22a5, Slc27a1) and oxidative phosphorylation (Cox4i1, Cox6a2) and a higher activity of the mitochondrial oxidative enzyme succinate dehydrogenase in muscle than rats of the O and L groups (P < 0.05). These niacin-induced changes in muscle metabolic phenotype are indicative of an increased capacity of muscle for oxidative utilization of fatty acids and are likely mediated by the upregulation of Ppard, Ppargc1a, and Ppargc1b, which are key regulators of muscle fiber composition, mitochondrial biogenesis, angiogenesis, and genes involved in fatty acid catabolism and oxidative phosphorylation. The increased utilization of fatty acids by muscle might contribute to the strong TG-lowering effect of niacin treatment.

Nonalcoholic fatty liver disease and lipids

PURPOSE OF REVIEW

This article reviews the mechanisms leading to the development of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) and the effects of hypoglycaemic and lipid-lowering therapies on NAFLD/NASH.

RECENT FINDINGS

The interaction of lipogenesis, fatty acid oxidation, inflammation, endoplasmic reticulum stress and hepatic insulin resistance contribute to the pathogenesis of NAFLD/NASH. Few large scale clinical trials exist with biopsy or magnetic resonance endpoints as opposed to ultrasonographic and transaminase endpoints. Trial evidence that exists supports the utility of weight loss, metformin, thiazolidinediones, fibrates, niacin, ezetimibe and statins in improving the steatosis component of NAFLD/NASH though with less or minimal effects on the fibrotic component of NASH.

SUMMARY

Hypoglycaemic and lipid-lowering therapies may have a role in the treatment of NAFLD/NASH but large scale endpoint trials remain to be performed.

New lipid-lowering drugs: an update

Lipid lowering is established as a proven intervention to reduce atherosclerosis and its complications. Statins form the basis of care but are not able to treat all aspects of dyslipidaemia. Many novel therapeutic compounds are being developed. These include additional therapeutics for low-density lipoprotein cholesterol, for example, thyroid mimetics (thyroid receptor beta-agonists), antisense oligonucleotides or microsomal transfer protein inhibitors (MTPI); triglycerides, for example, novel peroxosimal proliferator activating receptors agonists, MTPIs, diacylglycerol acyl transferase-1 inhibitors and high-density lipoprotein cholesterol (HDL-C), for example, mimetic peptides; HDL delipidation strategies and cholesterol ester transfer protein inhibitors and modulators of inflammation, for example, phospholipase inhibitors. Gene therapy for specific rare disorders, for example, lipoprotein lipase deficiency using alipogene tiparvovec is also in clinical trials. Lipid-lowering drugs are likely to prove a fast-developing area for novel treatments as possible synergies exist between new and established compounds for the treatment of atherosclerosis.

Liver fat reduction with niacin is influenced by DGAT-2 polymorphisms in hypertriglyceridemic patients

Niacin reduces plasma triglycerides, but it may increase free fatty acids and insulin resistance during long-term treatment. We examined the effect of extended-release niacin on liver fat content in Chinese patients with dyslipidemia and whether the common diacylglycerol acyltransferase-2 (DGAT2) polymorphisms influenced this effect. The 39 patients (baseline liver fat content: 12.8 ± 7.6%, triglycerides: 3.30 ± 1.67 mmol/l) were treated with niacin, gradually increasing the dose to 2 g/day for a total of 23 weeks. The liver fat content and visceral/subcutaneous fat was measured before and after treatment. Subjects were genotyped for the DGAT2 rs3060 and rs101899116 polymorphisms. There were significant (P < 0.001) reductions in plasma triglycerides (-34.9 ± 37.6%), liver fat content (-47.2 ± 32.8%), and visceral fat (-6.3 ± 15.8%, P < 0.05) after niacin treatment. Mean body weight decreased by 1.46 ± 2.7% (1.17 ± 2.44 kg, P < 0.001) during the study, but liver fat changes remained significant after adjustment for age, gender, and body weight changes [mean absolute change (95% CI): -6.1% (-8.0, -4.3), P < 0.001]. The DGAT2 variant alleles were associated with a smaller reduction in liver fat content in response to niacin after adjustment for other covariates (P < 0.01). These findings suggest that niacin treatment may reduce liver fat content in Chinese patients with dyslipidemia and that the mechanism may involve inhibition of DGAT2. However, the findings might have been confounded by the small but significant reductions in body weight during the study. Future large randomized controlled trials are needed to verify these findings.

Effects of nicotinic acid on gene expression: potential mechanisms and implications for wanted and unwanted effects of the lipid-lowering drug

CONTEXT

Nicotinic acid (NA), or niacin, lowers circulating levels of lipids, including triglycerides, very low-density lipoprotein-cholesterol, and low-density lipoprotein-cholesterol. The lipid-lowering effects have been attributed to its effect to inhibit lipolysis in adipocytes and thus lower plasma free fatty acid (FFA) level. However, evidence accumulates that the FFA-lowering effect may account for only a fraction of NA effects on plasma lipids, and other mechanisms may be involved. Recent studies have reported NA effects on gene expression in various tissues in vivo and in cultured cells in vitro.

EVIDENCE ACQUISITION

We reviewed articles reporting NA effects on gene expression, identified by searching PubMed, focusing on potential underlying mechanisms and implications for unexplained NA effects.

CONCLUSION

The effects of NA on gene expression may be mediated directly via the NA receptor in the affected cells, indirectly via changes in circulating FFA or hormone levels induced by NA, or by activating the transcription factor FOXO1 in insulin-sensitive tissues. NA effects on gene expression provide new insights into previously unexplained NA effects, such as FFA-independent lipid-lowering effects, FFA rebound, and insulin resistance observed in clinics during NA treatment.