The Impact of Photoperiod on the Leptin Sensitivity and Course of Inflammation in the Anterior Pituitary.

Leptin has a modulatory impact on the course of inflammation, affecting the expression of proinflammatory cytokines and their receptors. Pathophysiological leptin resistance identified in humans occurs typically in sheep during the long-day photoperiod. This study aimed to determine the effect of the photoperiod with relation to the leptin-modulating action on the expression of the proinflammatory cytokines and their receptors in the anterior pituitary under physiological or acute inflammation. Two in vivo experiments were conducted on 24 blackface sheep per experiment in different photoperiods. The real-time PCR analysis for the expression of the genes , , , , , , , and was performed. Expression of all examined genes, except and , was higher during short days. The leptin injection increased the expression of all examined genes during short days. In short days the synergistic effect of lipopolysaccharide and leptin increased the expression of , , , , and and decreased expression of . This mechanism was inhibited during long days for the expression of and The obtained results suggest the occurrence of leptin resistance during long days and suggest that leptin modulates the course of inflammation in a photoperiod-dependent manner in the anterior pituitary.