Oxytocin (OT) is a hypothalamic neuropeptide synthesized and secreted by OT neurons. In addition to its conventional role in reproductive physiology, central OT also regulates various social behaviors, such as care, trust, and emotions. Central and subcutaneous OT infusions stimulate lipid metabolism in mice and rats when fed standard or high fat diets. Mice lacking the OT receptor (OTR) or OT peptide develop late-onset obesity with greater fat pad weights, larger adipocyte size and elevated plasma levels of leptin. To study the effects of OT on lipid metabolism, we examined the effects of serial OT doses (0, 10, 30, 100, 150, 300 nM) on 3T3L1 adipocytes, together with long (144 hours, 6 days) and short (24 hours, 1 day) term treatments. The short-term treatment with 150 nM OT increased triacylglycerol (TAG) accumulation and decreased mRNA expressions of carnitine palmitoyltransferase 1α (CPT-1α) and fatty acid binding protein 4 (FABP4). After long-term incubation with 150 nM OT, only the CPT-1α mRNA was decreased. In differentiated adipocytes derived from pig adipose tissue stem cells, only hormone sensitive lipase mRNA was decreased after short- or long-term treatment with OT. To obtain further insight into the underlying mechanism of OT induction, we tested the involvement of the AKT/PKB pathway;however, AKT phosphorylation was decreased after treatment with 150 nM OT, suggesting that OT effects may be independent from the AKT/PKB pathway. Taken together, OT effects on adipocyte glucose and lipid metabolism are probably through mechanisms other than the AKT/PKB pathway.
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