Activity/inactivity circadian rhythm shows high similarities between young obesity-induced rats and old rats

Abstract

The objective of the present study was to compare differences between elderly rats and young obesity-induced rats in their activity/inactivity circadian rhythm. The investigation was motivated by the differences reported previously for the circadian rhythms of both obese and elderly humans (and other animals), and those of healthy, young or mature individuals. Three groups of rats were formed: a young control group which was fed a standard chow for rodents; a young obesity-induced group which was fed a high-fat diet for four months; and an elderly control group with rats aged 2.5 years that was fed a standard chow for rodents. Activity/inactivity data were registered through actimetry using infrared actimeter systems in each cage to detect activity. Data were logged on a computer and chronobiological analysis were performed. The results showed diurnal activity (sleep time), nocturnal activity (awake time), amplitude, acrophase, and interdaily stability to be similar between the young obesity-induced group and the elderly control group, but different in the young control group. We have concluded that obesity leads to a chronodisruption status in the body similar to the circadian rhythm degradation observed in the elderly.

Learning From Human Responses to Deconditioning Environments: Improved Understanding of the “Use It or Lose It” Principle

“…Humans experience daily circadian rhythms, where there are periods of activity and inactivity (usually sleep) that are accompanied by variations in chemicals (i.e., corticosteroids, melatonin) (Majidinia et al, 2018 ) and controlled by neural loci such as the suprachiasmatic nucleus (SCN) and the hypothalamus (discussed in Hut and Van der Zee, 2011 ). Interestingly, such cycles are disrupted in young rats with obesity, similar to what is seen on old normal weight rats (discussed in Bravos Santos et al, 2016 ). While inactivity during sleep is normally considered restorative, from a mechanical loading perspective such acute periods of physical inactivity could be also considered an acute period of “deconditioning.” Thus, evolutionarily, such alternating periods of activity/inactivity were deemed important for system integrity and likely should be considered as part of the 24-h activity cycle (discussed in Rosenberger et al, 2019 ).…”

“…While inactivity during sleep is normally considered restorative, from a mechanical loading perspective such acute periods of physical inactivity could be also considered an acute period of “deconditioning.” Thus, evolutionarily, such alternating periods of activity/inactivity were deemed important for system integrity and likely should be considered as part of the 24-h activity cycle (discussed in Rosenberger et al, 2019 ). With the disruption of these periods of activity/inactivity in the elderly (discussed in Bravos Santos et al, 2016 ), there may also be increased risk for the development of chronicity regarding disease development (Lazarus and Harridge, 2017 ). However, more robust periods of activity could lead to restoration of aspects of the circadian rhythms.…”

Actigraphy-Derived Daily Rest–Activity Patterns and Body Mass Index in Community-Dwelling Adults

“…38 In animal studies, inducing obesity in young rats via a high-fat diet disrupts rest-activity patterns in a manner similar to aging, suggesting the relationship of rest-activity patterns to BMI could be bi-directional or mutually reinforcing. 39,40 In humans, rest-activity measures (including a more flattened pattern measured as magnitude from cosinor, a higher fragmentation of rest-activity patterns determined by higher IV, and lower amplitude) each predicted less response to a weight loss intervention; in contrast, total activity rates did not predict weight loss. 22 RA derived from nonparametric analysis of rest-activity patterns has been examined extensively in the psychology literature, where it is positively correlated with cognitive functioning in schizophrenia 41 and inversely correlated with risk of relapse in bi-polar disorder.…”

Chronic Timed Sleep Restriction Attenuates LepRb-Mediated Signaling Pathways and Circadian Clock Gene Expression in the Rat Hypothalamus

“…The transcription factors BMAL1 and CLOCK usually exist as heterodimers and induce the expression of the repressors CRY1, CRY2, PER1, and PER2 via E-box sequences in their promoters. CRYs and PERs translocate into the nucleus and suppress CLOCK:BMAL1-mediated transcription after translation, thereby forming a negative feedback loop (Vogel et al, 2015;Bravo Santos et al, 2016;Rácz et al, 2018). Therefore, the reduction of BMAL1 and CLOCK mRNA levels observed in our study could be the initial contributors to depletion of circadian clock expression in the hypothalamus.…”