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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Brown adipocytes were isolated from the interscapular depot of male rats maintained at approx. 21 degrees C. In some experiments parallel studies were made with white adipocytes from the epididymal depot. 2. Insulin increased and noradrenaline decreased [U-14C]glucose incorporation into fatty acids by brown adipocytes. Brown adipocytes differed from white adipocytes in that exogenous fatty acid (palmitate) substantially decreased fatty acid synthesis from glucose. Both noradrenaline and insulin increased lactate + pyruvate formation by brown adipocytes. Brown adipocytes converted a greater proportion of metabolized glucose into lactate + pyruvate and a smaller proportion into fatty acids than did white adipocytes. 3. In brown adipocytes, when fatty acid synthesis from [U-14C]glucose was decreased by noradrenaline or palmitate, incorporation of 3H2O into fatty acids was also decreased to an extent which would not support proposals for extensive recycling into fatty acid synthesis of acetyl-CoA derived from fatty acid oxidation. 4. In the absence of glucose, [U-14C]lactate was a poor substrate for lipogenesis in brown adipocytes, but its use was facilitated by glucose. When brown adipocytes were incubated with 1 mM-lactate + 5 mM-glucose, lactate-derived carbon generally provided at least 50% of the precursor for fatty acid synthesis. 5. Both insulin and noradrenaline increased [U-14C]glucose conversion into CO2 by brown adipocytes (incubated in the presence of lactate) and, in combination, stimulation of glucose oxidation by these two agents showed synergism. Rates of 14CO2 formation from glucose by brown adipocytes were relatively small compared with maximum rates of oxygen consumption by these cells, suggesting that glucose is unlikely to be a major substrate for thermogenesis. 6. Brown adipocytes from 6-week-old rats had considerably lower maximum rates of fatty acid synthesis, relative to cell DNA content, than white adipocytes. By contrast, rates of fatty acid synthesis from 3H2O in vivo were similar in the interscapular and epididymal fat depots. Expressed relative to activities of fatty acid synthase or ATP citrate lyase, however, brown adipocytes synthesized fatty acids as effectively as did white adipocytes. It is suggested that the cells most active in fatty acid synthesis in the brown adipose tissue are not recovered fully in the adipocyte fraction during cell isolation. Differences in rates of fatty acid synthesis between brown and white adipocytes were less apparent at 10 weeks of age.
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PMID:Lipogenesis in rat brown adipocytes. Effects of insulin and noradrenaline, contributions from glucose and lactate as precursors and comparisons with white adipocytes. 313 22

1. The effects of intragastric glucose feeding and L-tri-iodothyronine (T3) administration on rates of hepatic and brown-fat lipogenesis in vivo were examined in fed and 48 h-starved rats. 2. T3 treatment increased hepatic lipogenesis in the fed but not the starved animals. Brown-fat lipogenesis was unaffected or slightly decreased by T3 treatment of fed or starved rats. 3. Intragastric glucose feeding increased hepatic lipogenesis in control or T3-treated fed rats, but did not increase hepatic lipogenesis in starved control rats. Glucose feeding increased hepatic lipogenesis if the starved rats were treated with T3. Glucose feeding increased rates of brown-fat lipogenesis in all experimental groups. The effects of glucose feeding on liver and brown-fat lipogenesis were mimicked by insulin injection. 4. The increase in hepatic lipogenesis in T3-treated 48 h-starved rats after intragastric glucose feeding was prevented by short-term insulin deficiency, but not by (-)-hydroxycitrate, an inhibitor of ATP citrate lyase. The increase in lipogenesis in brown adipose tissue in response to glucose feeding was inhibited by both short-term insulin deficiency and (-)-hydroxycitrate. 5. The results tend to preclude pyruvate kinase and acetyl-CoA carboxylase as the sites of interaction of insulin and T3 in the regulation of hepatic lipogenesis in 48 h-starved rats. Other potential sites of interaction are discussed.
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PMID:Interactions between insulin and thyroid hormone in the control of lipogenesis. 613 16