Curcumin modulation of high fat diet-induced atherosclerosis and steatohepatosis in LDL receptor deficient mice

Objective

Consuming curcumin may benefit health by modulating lipid metabolism and suppressing atherogenesis. Fatty acid binding proteins (FABP-4/aP2) and CD36 expression are key factors in lipid accumulation in macrophages and foam cell formation in atherogenesis. Our earlier observations suggest that curcumin's suppression of atherogenesis might be mediated through changes in aP2 and CD36 expression in macrophages. Thus, this study aimed to further elucidate the impact of increasing doses of curcumin on modulation of these molecular mediators on high fat diet-induced atherogenesis, inflammation, and steatohepatosis in Ldlr^−/− mice.

Methods

Ldlr^−/− mice were fed low fat (LF) or high fat (HF) diet supplemented with curcumin (500 HF + LC; 1000 HF + MC; 1500 HF + HC mg/kg diet) for 16 wks. Fecal samples were analyzed for total lipid content. Lipids accumulation in THP-1 cells and expression of aP2, CD36 and lipid accumulation in peritoneal macrophages were measured. Fatty streak lesions and expression of IL-6 and MCP-1 in descending aortas were quantified. Aortic root was stained for fatty and fibrotic deposits and for the expression of aP2 and VCAM-1. Total free fatty acids, insulin, glucose, triglycerides, and cholesterol as well as several inflammatory cytokines were measured in plasma. The liver's total lipids, cholesterol, triglycerides, and HDL content were measured, and the presence of fat droplets, peri-portal fibrosis and glycogen was examined histologically.

Results

Curcumin dose-dependently reduced uptake of oxLDL in THP-1 cells. Curcumin also reduced body weight gain and body fat without affecting fat distribution. During early intervention, curcumin decreased fecal fat, but at later stages, it increased fat excretion. Curcumin at medium doses of 500–1000 mg/kg diet was effective at reducing fatty streak formation and suppressing aortic expression of IL-6 in the descending aorta and blood levels of several inflammatory cytokines, but at a higher dose (HF + HC, 1500 mg/kg diet), it had adverse effects on some of these parameters. This U-shape like trend was also present when aortic root sections were examined histologically. However, at a high dose, curcumin suppressed development of steatohepatosis, reduced fibrotic tissue, and preserved glycogen levels in liver.

Conclusion

Curcumin through a series of complex mechanisms, alleviated the adverse effects of high fat diet on weight gain, fatty liver development, dyslipidemia, expression of inflammatory cytokines and atherosclerosis in Ldlr^−/− mouse model of human atherosclerosis. One of the mechanisms by which low dose curcumin modulates atherogenesis is through suppression of aP2 and CD36 expression in macrophages, which are the key players in atherogenesis. Overall, these effects of curcumin are dose-dependent; specifically, a medium dose of curcumin in HF diet appears to be more effective than a higher dose of curcumin.     

Conjugated linoleic acid isomers have no effect on atherosclerosis and adverse effects on lipoprotein and liver lipid metabolism in apoE-/- mice fed a high-cholesterol diet

Dietary supplementation with conjugated linoleic acid (CLA) has been shown, in several animal models, to decrease the development of atherosclerosis. The mechanism behind the anti-atherogenic properties of CLA is not clear. The objectives of this study were to determine the effect of CLA on atherosclerosis, lipoprotein and liver lipid metabolism, and plasma adiponectin and insulin in apoE^−/− mice fed an atherogenic (16%, w/w fat; 1.25%, w/w cholesterol) diet. Mice were fed the diet with or without supplementation of linoleic acid (LA), c-9,t-11 CLA, t-10,c-12 CLA, or a 1:1 mixture of the two CLA isomers, at a concentration of 0.5% (w/w), for 12 weeks. Relative to the LA group, CLA supplementation had no significant effect on the lesion area in either en face preparations of the aorta or in aortic root cross-sections. Plasma triacylglycerol and cholesterol concentrations were higher in the t-10,c-12 CLA group than all other treatment groups and liver weight was also increased in this group due to a three-fold increase in liver triacylglycerol. Supplementation with t-10,c-12 CLA or mixed CLA reduced plasma adiponectin levels, whereas t-10,c-12 CLA increased plasma insulin levels. Liver triglycerides correlated directly with blood glucose and plasma insulin and inversely with plasma adiponectin. We conclude that dietary supplementation with CLA does not affect atherosclerosis of the apoE^−/− mouse on a high-cholesterol diet. Furthermore, t-10,c-12 CLA causes adverse changes in adipocyte function and plasma and liver lipid metabolism, which are partially ameliorated by the inclusion of the c-9,t-11 CLA isomer.     

Bcl-2 in endothelial cells is increased by vitamin E and alpha-lipoic acid supplementation but not exercise training

Atherosclerotic plaque contains apoptotic endothelial cells with oxidative stress implicated in this process. Vitamin E and alpha-lipoic acid are a potent antioxidant combination with the potential to prevent endothelial apoptosis. Regular exercise is known to increase myocardial protection, however, little research has investigated the effects of exercise on the endothelium. The purpose of these studies was to investigate the effects of antioxidant supplementation and/or exercise training on proteins that regulate apoptosis in endothelial cells. Male rats received a control or antioxidant-supplemented diet (vitamin E and alpha-lipoic acid) and were assigned to sedentary or exercise-trained groups for 14 weeks. Left ventricular endothelial cells (LVECs) were isolated and levels of the anti-apoptotic protein Bcl-2 and the pro-apoptotic protein Bax were measured. Antioxidant supplementation caused a fourfold increase in Bcl-2 (P < 0.05) with no change in Bax (P > 0.05). Bcl-2:Bax was increased sixfold with antioxidant supplementation compared to non-supplemented animals (P < 0.05). Exercise training had no significant effect on Bcl-2, Bax or Bcl-2:Bax either alone or combined with antioxidant supplementation (P > 0.05) compared to non-supplemented animals. However, Bax was significantly lower (P < 0.05) in the supplemented trained group compared to non-supplemented trained animals. Cultured bovine endothelial cells incubated for 24 h with vitamin E and/or alpha-lipoic acid showed the combination of the two antioxidants increased Bcl-2 to a greater extent than cells incubated with the vehicle alone. In summary, vitamin E and alpha-lipoic acid increase endothelial cell Bcl-2, which may provide increased protection against apoptosis.     

A study on the action of vitamin E supplementation on plasminogen activator inhibitor type 1 and platelet nitric oxide production in type 2 diabetic patients

Background and aimType 2 diabetic (T2DM) patients show decreased fibrinolysis, mainly linked to high plasminogen activator inhibitor type 1 (PAI-1) production, together with a reduced bioavailability of nitric oxide and an impairment in Na⁺/K⁺-ATPase activity possibly involved in increased cardiovascular risk. Vitamin E is the major natural lipid-soluble antioxidant in human plasma. The present work was conducted in order to measure PAI-1, ICAM and VCAM-1 plasma levels, platelet nitric oxide production and membrane Na⁺/K⁺-ATPase activity in type 2 diabetic subjects treated with vitamin E (500 IU/day) for 10 weeks and then followed for other 20 weeks.Methods and resultsThirty-seven T2DM patients (24 males and 13 females) were studied. None of them were affected by any other disease or diabetic complications. Significant differences were detected for PAI-1 antigen (p < 0.001), PAI-1 activity (p < 0.001), nitric oxide (NO) production (p < 0.001), and Na⁺/K⁺-ATPase activity (p < 0.001) among the 4 phases of the study. A significant decrease both in ICAM and VCAM-1 plasma levels was also found at the 10th week compared with baseline (respectively p < 0.001 and p < 0.05).ConclusionOur data suggest that vitamin E counteracts endothelial activation in T2DM patients possibly representing a new tool for endothelial protection.