Ciprofibrate increases cholesteryl ester transfer protein gene expression and the indirect reverse cholesterol transport to the liver.

BACKGROUND: CETP is a plasma protein that modulates atherosclerosis risk through its HDL-cholesterol reducing action. The aim of this work was to examine the effect of the PPARalpha agonist, ciprofibrate, on the CETP gene expression, in the presence and absence of apolipoprotein (apo) CIII induced hypertriglyceridemia, and its impact on the HDL metabolism. RESULTS: Mice expressing apo CIII and/or CETP and non-transgenic littermates (CIII, CIII/CETP, CETP, non-Tg) were treated with ciprofibrate during 3 weeks. Drug treatment reduced plasma triglycerides (30-43%) and non-esterified fatty acids (19-47%) levels. Cholesterol (chol) distribution in plasma lipoprotein responses to ciprofibrate treatment was dependent on the genotypes. Treated CIII expressing mice presented elevation in VLDL-chol and reduction in HDL-chol. Treated CETP expressing mice responded with reduction in LDL-chol whereas in non-Tg mice the LDL-chol increased. In addition, ciprofibrate increased plasma post heparin lipoprotein lipase activity (1.3-2.1 fold) in all groups but hepatic lipase activity decreased in treated CETP and non-Tg mice. Plasma CETP activity and liver CETP mRNA levels were significantly increased in treated CIII/CETP and CETP mice (30-100%). Kinetic studies with 3H-cholesteryl ether (CEt) labelled HDL showed a 50% reduction in the 3H-CEt found in the LDL fraction in ciprofibrate treated compared to non-treated CETP mice. This means that 3H-CEt transferred from HDL to LDL was more efficiently removed from the plasma in the fibrate treated mice. Accordingly, the amount of 3H-CEt recovered in the liver 6 hours after HDL injection was increased by 35%. CONCLUSION: Together these data showed that the PPARalpha agonist ciprofibrate stimulates CETP gene expression and changes the cholesterol flow through the reverse cholesterol transport, increasing plasma cholesterol removal through LDL.

Effects of diabetes and CETP expression on diet-induced atherosclerosis in LDL receptor-deficient mice.

The role of CETP expression and diabetes in atherogenesis was investigated in mice with heterozygous disruption of the LDL receptor gene (LDLR1). LDLR1 mice with and without CETP expression were treated with streptozotocin (STZ) and maintained on a standard diet for one month before switching to an atherogenic diet for an additional month. STZ-sensitive mice had approximately 2.5-fold higher glycemia and 7.5- to 8.0-fold higher cholesterolemia. Factorial analysis of variance showed no significant effect of diabetes, CETP or diabetes-CETP interaction on the size of the atherosclerotic lesions. CETP expression in non-diabetic mice resulted in a 50% reduction in the area of the atherosclerotic lesions. Multiple regression analysis showed a positive and independent atherogenic effect of triglyceridemia in LDLR1 mice and of cholesterolemia in diabetic mice. Logistic analysis showed that elevated plasma cholesterol level significantly increased the risk of developing large lesion size (>75th percentile). In conclusion, CETP expression did not alter the lesion formation in response to diabetes, although it may be protective in the euglycemic state; the triglyceride level was an independent risk factor for LDL receptor-deficient mice but not for CETP-expressing mice; and elevated plasma cholesterol levels increased the risk of developing large atherosclerotic lesions, independently of CETP and diabetes.

Chronic treatment with bark infusion from Croton cajucara lowers plasma triglyceride levels in genetic hyperlipidemic mice.

Aqueous infusion and preparations containing dehydrocrotonin (DHC) and essential oil from Croton cajucara bark were tested for plasma lipid-lowering effects in genetically modified hyperlipidemic mice. Two mouse models were tested: 1) primary hypercholesterolemia resulting from the LDL-receptor gene knockout, and 2) combined hyperlipidemia resulting from crosses of LDL-receptor knockout mice with transgenic mice overexpressing apolipo protein (apo) CIII and cholesteryl ester-transfer protein. Mice treated with bark infusion, DHC, essential oil, or placebos for 25 days showed no signals of toxicity as judged by biochemical tests for liver and kidney functions. The bark infusion reduced triglyceride plasma levels by 40%, while essential oil and DHC had no significant effects on plasma lipid levels. The bark infusion treatment promoted a redistribution of cholesterol among the lipoprotein fractions in combined hyperlipidemic mice. There was a marked reduction in the VLDL fraction and an increase in the HDL fraction, in such a way that the (VLDL + LDL)/HDL ratio was reduced by half. The bark infusion treatment did not modify cholesterol distribution in hypercholesterolemic mice. In conclusion, C. cajucara bark infusion reduced plasma triglycerides levels and promoted a redistribution of cholesterol among lipoproteins in genetically combined hyperlipidemic mice. These changes modify risk factors for the development of atherosclerotic diseases.

Hypertriglyceridemia increases mitochondrial resting respiration and susceptibility to permeability transition.

High plasma level of triglycerides (TGs) is a common feature in atherosclerosis, obesity, diabetes, alcoholism, stress, and infection. Since mitochondria have been implicated in cell death under a variety of metabolic disorders, we examined liver mitochondrial functions in hypertriglyceridemic transgenic mice. Hypertriglyceridemia increased resting respiration and predisposed to mitochondrial permeability transition (MPT). Ciprofibrate therapy reduced plasma TG levels, normalized respiration, and prevented MPT. The higher resting respiration in transgenic mitochondria remained in the presence of the adenine nucleotide carrier inhibitor, carboxyatractyloside, bovine serum albumin, and the uncoupling proteins (UCPs) inhibitor, GDP. UCP2 content was similar in both control and transgenic mitochondria. We propose that faster resting respiration represents a regulated adaptation to oxidize excess free fatty acid in the transgenic mice.