Évolution de la teneur en lipides de Leptosphaeria typhae en fonction de sa croissance et de sa reproduction sexuée : activité de synthèse et étude des lipides neutres et polaires

When perithecia appear (on the 7th day of growth), the mycelial lipid content falls and the degree of fat insaturation increases; fatty acid synthetase activity greatly increases. Lipid turnover is therefore accelerated. Among neutral lipids, triglycerides constitute the largest pool and their proportion increases when perithecia appear. Free fatty acids also increase, confirming the lipid turnover's acceleration. Polar lipids especially disappear; the phosphatidylcholine/phosphatidylethanolamine ratio increases when the fungus ascosporulates.

Development of fatty acid-synthetic capacity in interscapular brown adipose tissue during suckling in genetically obese Zucker rats

The development of the lipogenic capacity in brown adipose tissue was studied in suckling lean (Fa/fa) and obese (fa/fa) Zucker pups aged from 7 to 22 days. In both lean and obese pups, activities of the two key lipogenic enzymes, fatty acid synthetase and acetyl-CoA carboxylase, and of citrate cleavage enzyme rose from the early to the late suckling period. Compared with lean pups, 7-day-old fa/fa pups showed a 35% increase in fat accumulation in interscapular brown adipose tissue and a 25% increase in fatty acid synthetase activity. By 10 days of age, fat deposition, lipogenesis in vivo (assessed by the incorporation of 3H from 3H2O into fatty acids) and fatty acid synthetase activity were 1.5-2-fold higher in pre-obese than in lean pups. Compared with lean pups, the increased lipogenesis in vivo observed in brown adipose tissue of 10-day-old pre-obese pups could not entirely account for the difference in fat deposition observed in this tissue, suggesting that additional mechanisms are at play to explain the increased fat content of this tissue.