Genetic determinants of plasma lipoprotein levels and their dietary response

Chronic Real-Ambient PM2.5 Exposure Exacerbates Cardiovascular Risk via Amplifying Liver Injury in Mice Fed with a High-Fat and High-Cholesterol Diet

Epidemiology has associated fine particulate matter (PM2.5) exposure with an increased cardiovascular risk. However, the underlying mechanism, particularly from the liver perspective, remains unclear. Here, the influence of chronic PM2.5 exposure on cardiovascular risk in mice fed a high-fat and high-cholesterol diet (HFCD) was studied by using a real-world PM2.5 exposure system. Results showed that PM2.5 exposure elevated the serum levels of nonhigh-density lipoprotein cholesterol (non-HDL-C) and oxidized low-density lipoprotein (oxLDL) in HFCD-fed mice, demonstrating increased cardiovascular risk. To investigate the molecular mechanism, lipidomics and metabolomics analyses were conducted and revealed that PM2.5 exposure enhanced lipid accumulation and disturbed purine metabolism and glutathione metabolism in the liver of HFCD-fed mice, contributing to the elevated non-HDL-C levels and intensified oxidative stress. Moreover, PM2.5 exposure increased total cholesterol levels by upregulating Hmgcr expression and downregulating Cyp7a1 expression in the livers of HFCD-fed mice. The HDL-C level was reduced by inhibiting the hepatic Abca1 and Abcg1 expression and decreasing the levels of ApoA-I and LCAT. Additionally, the PM2.5-induced pro-oxidative environment impeded the oxLDL clearance and further triggered inflammation, in turn exacerbating oxidative stress and oxLDL production. This study demonstrated a synergy of PM2.5 and HFCD on cardiovascular risk and illuminated the molecular mechanism in PM2.5-susceptible populations.

In vivo biochemical and gene expression analyses of the antioxidant activities and hypocholesterolaemic properties of Tamarindus indica fruit pulp extract

BACKGROUND

Tamarindus indica (T. indica) is a medicinal plant with many biological activities including anti-diabetic, hypolipidaemic and anti-bacterial activities. A recent study demonstrated the hypolipidaemic effect of T. indica fruit pulp in hamsters. However, the biochemical and molecular mechanisms responsible for these effects have not been fully elucidated. Hence, the aims of this study were to evaluate the antioxidant activities and potential hypocholesterolaemic properties of T. indica, using in vitro and in vivo approaches.

METHODOLOGY/PRINCIPAL FINDINGS

The in vitro study demonstrated that T. indica fruit pulp had significant amount of phenolic (244.9 ± 10.1 mg GAE/extract) and flavonoid (93.9 ± 2.6 mg RE/g extract) content and possessed antioxidant activities. In the in vivo study, hamsters fed with high-cholesterol diet for ten weeks showed elevated serum triglyceride, total cholesterol, HDL-C and LDL-C levels. Administration of T. indica fruit pulp to hypercholesterolaemic hamsters significantly lowered serum triglyceride, total cholesterol and LDL-C levels but had no effect on the HDL-C level. The lipid-lowering effect was accompanied with significant increase in the expression of Apo A1, Abcg5 and LDL receptor genes and significant decrease in the expression of HMG-CoA reductase and Mtp genes. Administration of T. indica fruit pulp to hypercholesterolaemic hamsters also protected against oxidative damage by increasing hepatic antioxidant enzymes, antioxidant activities and preventing hepatic lipid peroxidation.

CONCLUSION/SIGNIFICANCE

It is postulated that tamarind fruit pulp exerts its hypocholesterolaemic effect by increasing cholesterol efflux, enhancing LDL-C uptake and clearance, suppressing triglyceride accumulation and inhibiting cholesterol biosynthesis. T. indica fruit pulp has potential antioxidative effects and is potentially protective against diet-induced hypercholesterolaemia.

Modulation of the regression of atherosclerosis in the hamster by dietary lipids: comparison of coconut oil and olive oil

The Golden Syrian hamster (Mesocricetus auratus) has been shown to be a useful model of both human lipoprotein metabolism and the development of atherosclerosis. We report the effects of dietary lipids on the progression and regression of atherosclerosis in this model. In the first study, hamsters fed on coconut oil (150 g/kg diet) and cholesterol (30 g/kg diet) developed lipid-rich lesions in the ascending aorta (0.28 (SD 0.14) mm2) and aortic arch (0.01 (SD 0.01) mm2) after 4 weeks that continued to progress over the next 8 weeks (0.75 (SD 0.41) mm2 and 0.12 (SD 0.11) mm2 for the ascending aorta and aortic arch respectively). Removal of cholesterol from the diet halted this progression. Furthermore, in animals fed on olive oil in the absence of added cholesterol, plasma LDL-cholesterol concentrations were lower (P < 0.05) and the extent of atherosclerotic lesions was reduced (P < 0.001 for both regions of the aorta) compared with animals fed on coconut oil (with no added cholesterol). In a second study, animals were fed on the atherogenic diet for 10 weeks, transferred to diets containing either coconut oil (150 g/kg diet) or olive oil (150 g/kg diet) without added cholesterol and monitored for up to 16 weeks. In the ascending aorta, lesion size doubled in animals fed on coconut oil but stabilized in those fed on olive oil. In the aortic arch, lesion size decreased linearly (P < 0.05, P < 0.001 for coconut oil and olive oil respectively) with the greatest reduction being seen in the olive-oil-fed animals (P < 0.05). Again, progression and regression of atherosclerosis appeared to reflect the relative concentrations of LDL-cholesterol and HDL-cholesterol in the plasma. We conclude that the male Golden Syrian hamster represents a useful model of dietary induced regression as well as progression of atherosclerosis.