ESPE Abstracts

Introduction: Leptin, an adipokine secreted mainly by adipose tissue, is a regulator of energy balance acting through central mechanisms on the hypothalamus. However, leptin has many functions regulating e.g., immune system and reproduction. Leptin exerts its biological effects through its receptor, the expression of which has been demonstrated in several tissues. There are several leptin receptor isoforms, but activation of only one of them, the long form, results in signaling pathway activation. Nevertheless, there are conflicting results about peripheral effects of leptin on adipocytes.

Aim of the study: Our purpose was to investigate how leptin affects the physiology of adipose progenitor cells.

Methods: Experiments were conducted on adipose progenitor cells (LipPD1) incubated with recombinant leptin (0-100 nM). We assessed cell proliferation after Hoechst staining. Cell viability was studied by incubating cells with WST-1 (water-soluble tetrazolium salt). Intracellular lipid content was measured using Oil Red O and Nile Red. To examine whether exogenous leptin can reverse the effects of leptin deficiency, we used siRNA to introduce leptin knockdown. The expression of leptin and leptin receptor isoforms was studied by qPCR.

Results: Leptin and leptin receptors were present in preadipocytes and adipocytes with higher expression in differentiated cells (respectively 1.6-fold and. 2-fold change compared to. preadipocytes). Leptin treatment (10, 100 nM) in the presence of 10% FCS in the culture medium decreased preadipocyte viability (approx. 0.8-fold change vs. control group, on day 1). No effect was observed after an incubation in a medium containing 0.1% BSA or 0.1% and 1% FCS. In addition, incubation with leptin (0-100 nM) did not affect preadipocyte number (on day 1 and 7) in medium with 0.1% BSA, 0.1%, 1% and 10% FCS. Leptin treatment did not alter lipid accumulation measured on day 8 (after differentiation onset) – demonstrated by Oil Red O and Nile Red staining. However, leptin incubation (1 nM) partially reversed the decreased lipid accumulation observed after leptin knockdown (1.6-fold change compared to leptin knockdown group).

Conclusion: Leptin receptor expression occurs in preadipocytes and adipocytes, suggesting that leptin may act directly on adipose tissue. Leptin treatment affects preadipocyte physiology by lowering their viability (in culture medium with 10% FCS conditions), without impacting their expansion. Moreover, leptin does not stimulate adipocyte differentiation but can restore this process in the presence of leptin deficiency.