Regulation of phosphoenolpyruvate carboxykinase and fatty acid synthetase in brown fat of suckling rats

Ten kilobases of 5'-flanking region confers proper regulation of the mouse alcohol dehydrogenase-1 (Adh-1) gene in kidney and adrenal of transgenic mice

The expression profile of the mouse Adh-1 gene, which encodes class I alcohol dehydrogenase enzyme (ADH), is complex and includes tissue specificity and differential hormone responsiveness. Whereas kidney Adh-1 transcription rate is stimulated six- to sevenfold by testosterone treatment, adrenal gland ADH-1 mRNA is reduced to less than 5% of control level within 18 h following hormone administration. Androgen receptor is required for both responses since neither occurs in Tfm mutant mice lacking receptor. Hormonal and tissue-specific aspects of Adh-1 regulation were studied in transgenic mice harboring either of two constructs containing either -2.5 kb or -10 kb of 5'-flanking sequence attached to an Adh-1 minigene. The minigene transcript was expressed in kidney and adrenal tissues, but not liver, in five independent lines harboring a transgene with -2.5 kb of 5'-flanking sequence. Androgen treatment repressed the level of the minigene transcript in adrenal gland, but did not cause induction in kidney. In four lines of transgenic mice carrying the construct with -10 kb of 5'-flanking sequence, the minigene transcript was both repressed in adrenal and induced in kidney by testosterone. These lines have no detectable transgene expression in liver tissue. The -10 kb region in the mouse Adh-1 gene contains necessary controlling regions for proper tissue expression and hormonal regulation in kidney and adrenal; however, this region does not contain all essential elements necessary for expression in liver.

Fatty acid synthesis and ketone body utilization by brown adipose tissue of the rat. Response to cold or nutritional state?

The effects of cold adaptation (exposure to 2-4 degrees C for 2-3 weeks) on the incorporation of 3H from 3H2O and of D-3-hydroxy [3- 14C]butyrate into fatty acid in vivo in interscapular brown adipose tissue of the rat were examined. Fatty acid synthesis, measured with 3H2O, was increased in brown adipose tissue of cold-adapted rats pair-fed ad libitum but not in cold-adapted rats pair-fed to the same food intake as rats maintained at 18-20 degrees C. Incorporation of D-3-hydroxybutyrate into fatty acid was increased in brown adipose tissue of cold-adapted rats, both when rats were fed ad libitum and when they were deprived of food for 48 h. Ketone bodies may be an important substrate for brown adipose tissue in the cold-adapted rat.

Effect of insulin and prednisolone on cyclic nucleotides and phosphoenolpyruvate carboxykinase activity in brown fat and liver of developing rats

The concentrations of cyclic AMP and cyclic GMP in brown fat and liver of both suckling and adult rats at fixed times after injection of insulin (2.5 U/100 g body weight) or prednisolone (2.5 mg/100 g body weight) were compared with the activity of phosphoenolpyruvate carboxykinase assayed 24 h after the injections. A stimulus that produced an increase in cyclic AMP content also produced an increase in the enzyme activity. If the content of cyclic GMP was also increased there was no rise in phosphoenolpyruvate carboxykinase activity. A rise in the content of cyclic GMP alone was associated with a reduction in the activity of the enzyme. These preliminary results indicate that cyclic AMP could be involved in the induction of phosphoenolpyruvate carboxykinase and that cyclic GMP may somehow be related to its repression. The known differences in the response of phosphoenolpyruvate carboxykinase activity to insulin and prednisolone in different tissues and at different stages of ontogenic development may thus be linked to differences in the responsiveness of enzymes concerned with the metabolism of cyclic nucleotides.