The circadian clock regulates metabolic homeostasis and its disruption predisposes to obesity and other metabolic diseases. However, the effect of phase shifts on metabolism is not completely understood. We examined whether alterations in the circadian rhythm caused by phase shifts induce metabolic changes in crucial genes that would predispose to obesity. Three-month-old rats were maintained on a standard diet under lighting conditions with chronic phase shifts consisting of advances, delays or advances plus delays. Serum leptin, insulin and glucose levels decreased only in rats subjected to advances. The expression of the clock gene Bmal 1 increased in the hypothalamus, white adipose tissue (WAT), brown adipose tissue (BAT) and liver of the advanced group compared to control rats. The advanced group showed an increase in hypothalamic AgRP and NPY mRNA, and their lipid metabolism gene profile was altered in liver, WAT and BAT. WAT showed an increase in inflammation and ER stress and brown adipocytes suffered a brown-to-white transformation and decreased UCP-1 expression. Our results indicate that chronic phase advances lead to significant changes in neuropeptides, lipid metabolism, inflammation and ER stress gene profile in metabolically relevant tissues such as the hypothalamus, liver, WAT and BAT. This highlights a link between alteration of the circadian rhythm and metabolism at the transcriptional level.

Conspecific vocalisations have an important ecological role for marmosets and likely modulate the circadian timing system. However, the effect of this specific cue on circadian activity rhythm (CAR) has not been evaluated. To analyse the synchroniser effect of conspecific vocalisations on CAR in marmosets, the motor activity of five isolated adult males was continuously recorded in rooms with constant dim light (~2 lx) and attenuated sound. All animals presented positive masking, four presented relative coordination and three presented temporary entrainment associated with the daily pattern of vocalisations from animals kept outdoors, similarly to previous studies that assessed social cues. Furthermore, most animals displayed a shortened circadian period in response to conspecific vocalisation pulses that were reproduced daily for 30 days under total darkness. This is evidence that a non-photic cue with ecological significance can modulate the CAR, reinforcing the role of conspecific vocalisation as an important zeitgeber for marmosets.

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