Sex-dependent variation in endogenous period and energy homeostasis during high fat diet-induced obesity in free-running mice

High-fat diet (HFD)-induced obesity is known to affect the reproductive cycle in mammals both through the hypothalamus-pituitary axis as well as timed cues from the suprachiasmatic nucleus (circadian clock). Recent studies have independently shown the effects of age-related changes in tau in female and male mice. However, there is the absence of a systematic study on the sex-dependent changes in HFD-induced obesity on the endogenous period (tau) and energy homeostasis in mammals. We hypothesize that there is a gender-dependent variation in energy expenditure and tau in HFD-fed mice. We evaluated gender-dependent variations in tau and energy homeostasis of low-fat diet (LFD) and HFD-fed mice held under constant darkness (DD). Circadian locomotor activity rhythm and energy homeostasis in C56BLJ/6 male and female mice were evaluated. Importantly, notable gender-dependent variations in circadian locomotor activity rhythm and energy homeostasis-related parameters were noted in HFD-fed mice. HFD resulted in an immediate deceleration in the endogenous circadian rhythm of locomotor activity compared to LFD-fed mice in both the sex. These findings suggest the importance of considering the sex-related variations in the circadian system and energy homeostasis in manipulating the lighting regime of the environment while feeding on HFD ad-libitum.