Comparison of triacylglycerol synthesis in rat brown and white adipocytes. Effects of hypothyroidism and streptozotocin-diabetes on enzyme activities and metabolic fluxes.
نویسندگان
چکیده
1. Adipocytes were isolated from the interscapular brown fat and the epididymal white fat of normal, streptozotocin-diabetic and hypothyroid rats. 2. Measurements were made of the maximum rate of triacylglycerol synthesis by monitoring the incorporation of [U-14C]glucose into acylglycerol glycerol in the presence of palmitate (1 mM) and insulin (4 nM) and of the activities of the following triacylglycerol-synthesizing enzymes: fatty acyl-CoA synthetase (FAS), mitochondrial and microsomal forms of glycerolphosphate acyltransferase (GPAT), dihydroxyacetonephosphate acyltransferase (DHAPAT), monoacylglycerol phosphate acyltransferase (MGPAT), Mg2+-dependent phosphatidate phosphohydrolase (PPH) and diacylglycerol acyltransferase (DGAT). 3. FAS activity in brown adipocytes was predominantly localized in the mitochondrial fraction, whereas a microsomal localization of this enzyme predominated in white adipocytes. Subcellular distributions of the other enzyme activities in brown adipocytes were similar to those shown previously with white adipocytes [Saggerson, Carpenter, Cheng & Sooranna (1980) Biochem. J. 190, 183-189]. 4. Relative to cell DNA, brown adipocytes had lower activities of triacylglycerol-synthesizing enzymes and showed lower rates of metabolic flux into acylglycerols than did white adipocytes isolated from the same animals. 5. Diabetes decreased both metabolic flux into acylglycerols and the activities of triacylglycerol-synthesizing enzymes in white adipocytes. By contrast, although diabetes decreased metabolic flux into brown-adipocyte acylglycerols by 80%, there were no decreases in the activities of triacylglycerol-synthesizing enzymes, and the activity of PPH was significantly increased. 6. Hypothyroidism increased metabolic flux into acylglycerols in both cell types, and increased activities of all triacylglycerol-synthesizing enzymes in brown adipocytes. By contrast, in white adipocytes, although hypothyroidism increased the activities of FAS, microsomal GPAT and DGAT, this condition decreased the activities of mitochondrial GPAT and PPH. 7. It was calculated that the maximum capabilities for fatty acid oxidation and esterification are approximately equal in brown adipocytes. In white adipocytes esterification is predominant by approx. 100-fold. 8. Diabetes almost abolished incorporation of [U-14C]glucose into fatty acids in both adipocyte types. Hypothyroidism increased fatty acid synthesis in white and brown adipocytes by 50% and 1000% respectively.
منابع مشابه
Enzymes involved in adenosine metabolism in rat white and brown adipocytes. Effects of streptozotocin-diabetes, hypothyroidism, age and sex differences.
1. Adipocytes were isolated from epididymal white fat and interscapular brown fat of male rats, and activities of 5'-nucleotidase, adenosine deaminase and adenosine kinase were measured in cell extracts. 2. 5'-Nucleotidase activity in white adipocytes was increased in streptozotocin-diabetes, decreased in hypothyroidism and increased with age. That activity in brown adipocytes was unchanged in ...
متن کاملVARIATIONS OF GLUCOSE 6-PHOSPHATE DEHYDROGENASE ACTIVITY IN VARIOUS TISSUES INDUCED BY METABOLIC ALKALOSIS, ACIDOSIS AND DIABETES
The effects of chronic metabolic acidosis, alkalosis and alloxan-induced ketoacidosis on G6PD activity of rat kidney, liver and erythrocytes were studied. Metabolic acidosis significantly increased the activity of kidney enzyme (55%) but decreased the liver (43%) and erythrocyte (38%) enzyme activities. Alkalosis did not make a significant change in the kidney or liver enzyme activity but ...
متن کاملComparative Study on Antihyperglycemic and Antihyperlipidemic Effects of Separate and Composite Extract of Seed of Eugenia Jambolana and Root of Musa Paradisiaca in Streptozotocin-Induced Diabetic Male Albino Rat
Herbal medicine development against the non-communicable disease like diabetes is one of the thrust area of research in the field of global medicine. Here we have studied the separate and composite methanolic extract of seed of Eugenia jambolana and root of Musa paradisiaca for the management of streptozotocin-induced diabetes mellitus. We have measured the fasting blood glucose level and glyco...
متن کاملEffects of streptozotocin-diabetes and insulin administration in vivo or in vitro on the activities of five enzymes in the adipose-tissue triacylglycerol-synthesis pathway.
At 2 days after administration of streptozotocin (100 mg/kg), activities in rat epididymal fat-pads of the following enzymes were significantly decreased: fatty acyl-CoA synthetase (FAS), mitochondrial and microsomal forms of glycerolphosphate acyltransferase (GPAT), monoacylglycerolphosphate acyltransferase (MGPAT) and Mg2+-dependent phosphatidate phosphohydrolase (PPH). There were no signific...
متن کاملANTICALMODULIN DRUGS DUE TO THE NET EFFECTS CANNOT ANTAGONIZE DIBUTYRYL-CAMP-MEDIATED SUPPRESSION OF DE NOVO SYNTHESIZED LIPID SECRETION IN BOTH CULTURED MCARDLE CELLS AND RAT HEPATOCYTES
The effects and interaction between cAMP-analogue dibutyryl-cAMP and calmodulin antagonists were investigated on de novo synthesis and secretion of lipids in cultures of hepatoma McArdle-RH7777 cells and normal rat hepatocytes. Dibutyryl cAMP caused a significant decrease in the secretion of de novo synthesized triacyl [3H] glycerol in both cultures of McArdle cells and rat hepatocytes. The ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- The Biochemical journal
دوره 250 2 شماره
صفحات -
تاریخ انتشار 1988