Butyrate regulates leptin expression through different signaling pathways in adipocytes

Leptin is an adipocytokine that regulates body weight, and maintains energy homeostasis by promoting reduced food intake and increasing energy expenditure. Leptin expression and secretion is regulated by various factors including hormones and fatty acids. Butyrate is a short-chain fatty acid that acts as source of energy in humans. We determined whether this fatty acid can play a role in leptin expression in fully differentiated human adipocytes. Mature differentiated adipocytes were incubated with or without increasing concentrations of butyrate. RNA was extracted and leptin mRNA expression was examined by Northern blot analysis. Moreover, the cells were incubated with regulators that may affect signals which may alter leptin expression and analyzed with Northern blotting. Butyrate stimulated leptin expression, and stimulated mitogen activated protein kinase (MAPK) and phospho-CREB signaling in a time-dependent manner. Prior treatment of the cells with signal transduction inhibitors as pertusis toxin, Gi protein antagonist, PD98059 (a MAPK inhibitor), and wortmannin (a PI3K inhibitor) abolished leptin mRNA expression. These results suggest that butyrate can regulate leptin expression in humans at the transcriptional level. This is accomplished by: 1) Gi protein-coupled receptors specific for short-chain fatty acids, and 2) MAPK and phosphatidylinositol-3-kinase (PI3K) signaling pathways.

Role of protease inhibitors and acylation stimulating protein in the adipogenesis in 3T3-L1 cells

Treatment of AIDS (HIV) and hepatitis C virus needs protease inhibitors (PI) to prevent viral replication. Uses of PI in therapy are usually associated with a decrease in body weight and dyslipidemia. Acylation stimulating protein (ASP) is a protein synthesized in adipocytes to increase triglycerides biosynthesis, for that the relation of PI and ASP to adipogenesis is tested in this work. ASP expression was increased during 3T3-L1 differentiation and reached a peak at day 8 with cell maturation. Addition of PI during adipocytes differentiation dose dependently and significantly (p < 0.5) inhibited the degree of triglycerides (TG) accumulation. Moreover, presence of ASP (450 ng/mL) in media significantly (p < 0.5) stimulated the degree of TG accumulation and there was additive stimulation for ASP when added with insulin (10 microgram/mL). Finally, when ASP in different doses (Low, 16.7; Medium, 45 and High, 450 ng/mL) incubated with a dose of x150 PI, ASP partially inhibited the PI-inhibited adipogenesis and TG accumulation. The results in this study show that PI inhibit lipids accumulation and confirm role of ASP in TG biosynthesis and adipogenesis.