Abstract
ABSTRACTBrandt's voles have an annual cycle of body weight and adiposity. These changes can be induced in the laboratory by manipulation of photoperiod. In the present study, male captive-bred Brandt's voles aged 35 days were acclimated to a short day (SD) photoperiod (8L:16D) for 70 days. A subgroup of individuals (n=16) were implanted with transmitters to monitor physical activity and body temperature. They were then randomly allocated into long day (LD=16L:8D) (n=19, 8 with transmitters) and SD (n=18, 8 with transmitters) groups for an additional 70 days. We monitored aspects of energy balance, glucose and insulin tolerance (GTT and ITT), body composition and organ fat content after exposure to the different photoperiods. LD voles increased in weight for 35 days and then re-established stability at a higher level. At the end of the experiment LD-exposed voles had greater white adipose tissue mass than SD voles (P=0.003). During weight gain they did not differ in their food intake or digestive efficiency; however, daily energy expenditure was significantly reduced in the LD compared with SD animals (ANCOVA, P<0.05) and there was a trend to reduced resting metabolic rate RMR (P=0.075). Physical activity levels were unchanged. Despite different levels of fat storage, the GTT and ITT responses of SD and LD voles were not significantly different, and these traits were not correlated to body fatness. Hence, the photoperiod-induced obesity was independent on disruptions to glucose homeostasis, indicating a potential adaptive decoupling of these states in evolutionary time. Fat content in both the liver and muscle showed no significant difference between LD and SD animals. How voles overcome the common negative aspects of fat storage might make them a useful model for understanding the phenomenon of ‘healthy obesity’.
Highlights
The world is currently faced by two health epidemics
We have shown previously that in short-tailed field voles (Microtus agrestis) that the long-photoperiod-induced weight increase is driven by an increase in digestive efficiency (Król et al, 2005), whereas in collared lemmings (Dicrostonyx groenlandicus) the photoperiod-induced weight increase is achieved by a suppression of resting energy expenditure linked to reduced levels of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) (Powell et al, 2002)
Differences in body mass and body composition between long day (LD) and short day (SD) groups For the first 6 days after the photoperiod change there was no difference in the body mass between the SD and LD groups, but thereafter the mass of the LD animals increased and diverged from that of the SD animals and reached maximal levels after 35 days of LD exposure
Summary
The first is the expansion in levels of obesity, and the second is the increase in. Obesity and type 2 diabetes are closely linked with one another the association is not inevitable (Scheen, 1999; Schwartz and Porte, 2005; Blüher, 2010). There are many patients who develop obesity but do not develop any metabolic complications. This population has been generally called the ‘healthy obese’ (Blüher, 2010). Given the failure of our attempts to solve the obesity problem, stemming the translation from obesity to type 2 diabetes could be a more effective option
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
