Mechanisms of ketamine action on lipid metabolism in rats.

BACKGROUND AND OBJECTIVE: This study was conducted to determine the effect of ketamine on metabolic homoeostasis and particularly in lipoprotein lipase (LPL) activity in adipose tissue. METHODS: Sixty male Wistar rats were divided into six groups of 10 each. Group A served as controls, while Groups B-F received, respectively, ketamine 60, 80, 100, 120 and 140 mg kg(-1) intraperitoneally. The animals were sacrificed 20 min after the administration of ketamine. Insulin concentrations in plasma and total cholesterol, triglyceride, high-density lipoprotein (HDL) and free fatty acid (FFA) concentrations in serum were measured. LPL activity in adipose tissue and medium-chain acyl-CoA dehydrogenase (MCAD) content in muscle were determined. RESULTS: FFA concentrations in serum significantly increased from the second lowest dose of ketamine. Insulin concentrations in plasma did not exhibit any significant difference between groups. MCAD levels were 0.5-fold more in Group F than in Group A, while there were no significant differences between control group and Groups B-E. Furthermore, high concentrations (120 and 140 mg kg(-1)) of ketamine interfered with in metabolic homoeostasis by significantly reducing LPL activity, thus elevating triglyceride concentrations in serum without affecting cholesterol and HDL metabolism. CONCLUSIONS: Ketamine induces various metabolic effects due to changes in adipose LPL activity and MCAD levels in muscles. These findings seem to be significant only at high doses.

Ligand-induced expression of peroxisome proliferator-activated receptor alpha and activation of fatty acid oxidation enzymes in fatty liver.

BACKGROUND: Peroxisome proliferator-activated receptor alpha (PPARalpha) regulates lipid metabolism upon activation by ligands. Peroxisome proliferator-activated receptor alpha may play a role in the pathogenesis of fatty liver disease. The aim of this study was to assess the PPARalpha expression pattern and mitochondrial/peroxisomal enzyme activities in response to high fat diet (HFD) and clofibrate, a well known PPARalpha ligand. MATERIALS AND METHODS: Four groups of Wistar-Albino rats were included: (1) rats fed a control diet (CD) for 6 weeks, (2) rats fed CD (6 weeks) plus clofibrate (last 2 weeks), (3) rats fed HFD for 6 weeks, and (4) rats fed HFD (6 weeks) plus clofibrate (last 2 weeks). Peroxisome proliferator-activated receptor alpha expression was evaluated by immunohistochemistry. Fatty acid beta-oxidation (peroxisomal-acyl-CoA-oxidase and mitochondrial-acyl-CoA-dehydrogenase) and catalase enzyme activities, and malondialdehyde and glutathion levels were measured spectrophotometrically in liver tissues. RESULTS: All animals were fed HFD but only 2/12 animals were fed HFD plus clofibrate-developed fatty liver. Both HFD and clofibrate induced PPARalpha expression, clofibrate induction being more prominent than HFD. Clofibrate plus HFD did not further increase PPARalpha expression. Activities of peroxisomal-acyl-CoA-oxidase and mitochondrial-acyl-CoA-dehydrogenase enzymes were not induced by HFD alone. Clofibrate increased the activity of these enzymes in both CD- and HFD-fed animals. However, an increase of acyl-CoA-oxidase activity was blunted in rats fed HFD. Catalase activity and malondialdehyde levels were increased but glutathion levels were unchanged in rats fed HFD plus clofibrate. CONCLUSIONS: Clofibrate was a more potent inducer of PPARalpha expression than HFD in our rat fatty liver model. The finding of blunted peroxisomal enzyme response to clofibrate in fatty livers suggests that alterations in postreceptor events may exist and further contribute to liver steatosis. Clofibrate seems to stabilize glutathion content and this might contribute to the prevention of liver steatosis.