Sex‐dependent differences in voluntary physical activity

Abstract

There are increasing numbers of overweight and obese individuals in the US and globally, and correspondingly, the associated healthcare costs are rising dramatically. More than one-third of children are currently considered obese with a predisposition to type 2 diabetes, and it is likely that their metabolic conditions will worsen with age. Physical inactivity has also risen to be the leading cause of many chronic, non-communicable diseases (NCD). Children are more physically inactive now than they were in past decades, which may be due to intrinsic and extrinsic factors. In rodents, the amount of time engaged in spontaneous activity within the home cage is a strong predictor of later adiposity and weight gain. Thus, it is important to understand primary motivators stimulating physical activity (PA). There are normal sex differences in PA levels in rodents and humans. The perinatal environment can induce sex-dependent differences in PA disturbances. This review will consider the current evidence that there are sex differences in PA in rodents and humans. The rodent studies showing that early exposure to environmental chemicals can shape later adult PA responses will be discussed. Next, an exploration of whether there are different motivators stimulating exercise in male vs. female humans will be examined. Finally, the brain regions, genes, and pathways, that modulate PA in rodents, and possibly by translation humans, will be described. A better understanding of why each sex remains physically active through the lifespan could open up new avenues to prevent and treat obesity in children and adults.

Re-evaluating the effect of age on physical activity over the lifespan

“…We found that during adolescence and early adulthood, males generally have higher PA than females, particularly, within the MVPA range. These findings are consistent with prior work (e.g., 18,36,37 ). However, from midlife to older adulthood, males show sharper lowering in PA by age compared with females, and actually have lower total PA measured by TLAC during older adulthood, including lower LiPA and higher SePA.…”

Female pups receive more maltreatment from stressed dams

“…We did not find any differences in nurturing (p = 0.164) or adverse behavior (p = 0.3822) received by pups in the normal maternal care and crossfoster care conditions. Consistent with other reports using this model (Blaze et al, 2015, 2017Doherty et al, 2017Doherty et al, , 2016Roth et al, 2009Roth et al, , 2014, these analyses demonstrate that pups placed in the maltreatment conditions receive more adverse and less nurturing behavior relative to pups in the two control conditions.…”

“…Because this behavior helps to recycle resources back to the dam, it is advantageous for the dam to focus anogenital licking on the male pups. Another potential explanation could involve the increased locomotor activity observed in female as opposed to male rodents (Rosenfeld, ). We speculate that enhanced locomotor activity typical of female rodents could place the female pup in contact with the dam more frequently, which in turn results in more adverse behaviors directed toward the female pup.…”

“…The scarcity-adversity model of low nesting resources outside the home cage was used, as has been done previously by our laboratory , 2017Doherty et al, 2017;Doherty, Forster, & Roth, 2016;Hill, Warren, & Roth, 2014;Roth et al, 2009Roth et al, , 2014Walker et al, 2017). This model employs a within litter design such that 1/3 of the litter remains with the biological dam in the home cage, 1/3 of the litter is placed with a cross-foster dam in a novel environment, and 1/3 of the litter is exposed to maltreatment in a novel environment ( Figure 1).…”

“…Our lab utilizes the scarcity-adversity model of low nesting resources outside the home cage, which capitalizes on resource deprivation to experimentally induce caregiver maltreatment Blaze, Scheuing, & Roth, 2013;Doherty et al, 2017;Roth, Lubin, Funk, & Sweatt, 2009;Roth et al, 2014;Walker et al, 2017). Using this model, we have uncovered a number of sex-specific outcomes of maltreatment in the domains of both neurobiology and behavior, with females typically exhibiting more consequences relative to male subjects , 2017Doherty et al, 2017;Roth et al, 2014). For example, in the realm of behavior, female rats exposed to the scarcity-adversity model exhibit altered behavior on the novel object recognition and forced-swim tests not present in maltreated males, while males show deficits in fear extinction that are not exhibited by females subjected to maltreatment (Doherty et al, 2017).…”