Correlation of lipolytic and lipogenic actions of synthetic peptides with structure

The effects of various synthetic peptides on basal and ACTH-stimulated lipolysis in fat cells were examined. Glu-Arg-Gly-Phe-Phe-Phe possessed lipolytic activity and increased ACTH-stimulated lipolysis at concentrations higher than 0.5 mumol/ml. Glu-Arg-Gly-Phe-Phe-Tyr did not cause any release of FFA from fat cells. Glu-Arg-Gly-Leu-Leu-Leu had no lipolytic activity but inhibited ACTH-stimulated lipolysis at concentrations higher than 0.25 mumol/ml. Glu-Arg-Gly-Leu-Leu-Leu also inhibited epinephrine-stimulated lipolysis. The effects of the peptides on basal and insulin-stimulated lipogenesis in fat cells were examined. Glu-Arg-Gly-Phe-Phe-Tyr increased both basal and insulin-stimulated lipogenesis. A tripeptide, Glu-Arg-Gly, inhibited both basal and insulin-stimulated lipogenesis. Glu-Arg-Gly-Leu-Leu-Leu had no effect on either basal or insulin-stimulated lipogenesis. Glu-Arg-Gly-Phe-Phe-Phe and ACTH, which elicit FFA release from fat cells, also stimulated formation of [14C]triglyceride from [14C]glucose.