Short photoperiod reverses obesity in Siberian hamsters via sympathetically induced lipolysis and Browning in adipose tissue

Abstract

Changes in photoperiod length are transduced into neuroendocrine signals by melatonin (MEL) secreted by the pineal gland triggering seasonally adaptive responses in many animal species. Siberian hamsters, transferred from a long-day 'summer-like' photoperiod (LD) to a short-day 'winter-like' photoperiod (SD), exhibit a naturally-occurring reversal in obesity. Photoperiod-induced changes in adiposity are mediated by the duration of MEL secretion and can be mimicked by exogenously administered MEL into animals housed in LD. Evidence suggests that MEL increases the sympathetic nervous system (SNS) drive to white adipose tissue (WAT). Here, we investigated whether MEL-driven seasonally adaptive losses in body fat are associated with WAT lipolysis and browning. Hamsters were subcutaneously administered vehicle (LD+VEH) or 0.4mg/kg MEL (LD+MEL) daily for 10weeks while animals housed in SD served as a positive control. MEL and SD exposure significantly decreased the retroperitoneal (RWAT), inguinal (IWAT), epididymal (EWAT) WAT, food intake and caused testicular regression compared with the LD+VEH group. MEL/SD induced lipolysis in the IWAT and EWAT, browning of the RWAT, IWAT, and EWAT, and increased UCP1 expression in the IBAT. Additionally, MEL/SD significantly increased the number of shared MEL receptor 1a and dopamine beta-hydroxylase-immunoreactive neurons in discrete brain sites, notably the paraventricular hypothalamic nucleus, dorsomedial hypothalamic nucleus, arcuate nucleus, locus coeruleus and dorsal motor nucleus of vagus. Collectively, these findings support our hypothesis that SD-exposed Siberian hamsters undergo adaptive decreases in body adiposity due to SNS-stimulated lipid mobilization and generalized WAT browning.

Consumption of out-of-season orange modulates fat accumulation, morphology and gene expression in the adipose tissue of Fischer 344 rats

“…These changes were dependent on the photoperiod, because only the animals that ate orange in the short day had their parameters altered, but it was also dependent on the season in which the fruit was harvested, because no differences were obtained with the orange from the northern hemisphere. Numerous studies in small rodents have shown that a long photoperiod increases fat accumulation or body weight, while the opposite was observed for a short photoperiod [30][31][32][33][34]. Our data show a similar effect on OSSD animals, which are in a short photoperiod but consuming fruit harvested in the spring.…”

“…The reason why rodents increase their body mass in an LD photoperiod is not fully understood. Some authors report an increase in calorie intake or a change in diet preferences with longer photoperiods [31,32], while other studies attribute the changes to a decrease in BAT activity [35] or to activation of WAT lipolysis and browning during the SD [33]. In our study, the possibility of an increase in the fat content of the OSSD group due to diet was discarded, because no significant changes were observed in food intake or plasmatic parameters.…”

Mitochondria: the birth place, battle ground and the site of melatonin metabolism in cells

“…Some studies have shown that long term melatonin administration to rats or mice makes the white adipose tissue differentiate to brite (brown-in-white)/beige adipocytes which characteristically express UCP1 in their mitochondria (124)(125)(126). The classic brown and brite adipocytes have different origin (127).…”

Influence of morning and evening melatonin administration on the mucosa and crypts of a small intestine in rats with obesity

“…Крім того, варто враховувати тривалість фотоперіоду, адже середньодобова концентрація мелатоніну відрізняється залежно від тривалості дня і ночі. Вплив фотоперіоду на процеси ожиріння був, наприклад, показаний для сибірських хом'ячків [13]. Для того, щоб визначити характер впливу мелатоніну на тонку кишку при ожирінні та оцінити ефективність його впливу при різних термінах введення цього гормона за умов весняно-осіннього фотоперіоду і була проведена ця робота.…”