Proceedings of The Physiological Society
AstraZeneca (2010) Proc Physiol Soc 18, PC19
Long day length potentiates leptin secretion in female Wistar rats
H. Kelestimur1, M. Ozcan1, E. Alcin1, B. Yilmaz2, E. Kilic2, A. Ayar3
1. Firat University, Elazig, Turkey. 2. Yeditepe University, Istanbul, Turkey. 3. Karadeniz Technical University, Trabzon, Turkey.
Leptin is predominantly secreted by adipocytes and plays a central role in the regulation of energy homeostasis and food intake. Additionally, leptin is implicated in other physiological processes, including mainly reproductive functions by providing a link between metabolic status and related hypothalamic areas. It is proposed that leptin provides information to the brain that there are enough energy stores for reproductive functions, and may be a major determinant or only a permissive factor of the timing of puberty. Our previous studies showed that serum leptin levels were significantly elevated in the pinealectomised rats, and were suppressed by exogenous administration of melatonin. Day length (DL) can affect leptin secretion by modulating melatonin secretion and therefore leptin-regulated physiological functions. The aim of this study was to investigate the effect of a long DL cycle on serum leptin levels and puberty onset in female rats fed high-fat. For this aim, the groups were fed diets that contained 24%, 4.3% or 2.4% fat by weight. The groups were reared under conditions of 12-h light/dark or 18-h light/6-h dark cycles from day 21 when the rats were weaned. Body weight and food intake were daily determined, and vaginal opening was daily monitored starting from day 26. The animals were decapitated when the first estrus, which was determined by vaginal smears, was observed. Puberty onset was advanced only in the rats fed a high-fat (24%) diet. Serum leptin levels were found to be higher (P<0.05) in the groups fed the diets with 24% and 4.3% fat compared to the rats fed the diet with 2.4% fat. Under long DL, serum leptin levels increased significantly (P<0.05), and puberty onset was delayed in the three groups. The results of the present experiment show that photoperiod affects leptin secretion and the onset of puberty independent of metabolic status in the female rats. (The experimental protocol was approved by the Firat University Ethical Committee).
Where applicable, experiments conform with Society ethical requirements