Serum Leptin, Energy Budget, and Thermogenesis in Striped Hamsters Exposed to Consecutive Decreases in Ambient Temperatures

Abstract

Leptin has been found to be a direct participant in the regulation of both energy intake and energy expenditure in small mammals showing seasonal declines in body mass (M(b)) and fat mass, but its roles in an animal exhibiting seasonally increased thermogenesis and unchanged M(b) remain unclear. Serum leptin levels, energy budget, and thermogenesis were measured in striped hamsters exposed to consecutive decreases in ambient temperatures ranging from 23° to -23°C. Cold-exposed hamsters had significant increases in gross energy intake (GEI), the rate of basal metabolism, nonshivering thermogenesis, and activity of cytochrome c oxidase (COX) in brown adipose tissue (BAT), compared with control hamsters, indicating a cold-induced elevation of thermogenesis. Body mass and fat content were decreased in cold-exposed animals, and serum leptin levels were increased in hamsters exposed to temperatures of -8°C and below in inverse proportion to body fat content. Serum leptin levels were positively correlated with GEI and BAT COX activity in cold-exposed hamsters, but no such relationships were observed in control animals. These findings suggest that cold-exposed hamsters increase food consumption to meet the energy requirements for increased BAT thermogenesis. The increases in serum leptin levels are likely involved in increased thermogenesis in hamsters under cold stress. Cold-exposed hamsters may become leptin resistant, which is associated with impaired regulation of food intake. This new natural model of leptin resistance may also provide insight into the dynamic long-term control of energy homeostasis for animals that do not exhibit seasonal decline in M(b).

Effect of food restriction on energy budget in warm-acclimated striped hamsters

“…T a has significant effects on both BMR and NST max in many small mammals including striped hamsters [9,[17][18][19][20][21]40,41]. In the present study, striped hamsters significantly decreased BMR and NST max after being acclimated to a warm condition (30°C), which were lower by 30.3% and 53.8% at 30°C than those at 21°C, respectively.…”

“…Animals usually increase energy intake in cold conditions, while less food is consumed after being acclimated to warm conditions [17][18][19][20][21]. In the previous study on striped hamsters, we observed that a consecutive decrease in T a induced a significant increase in food intake [21].…”

“…It has been well established that the metabolic rate of mammals is affected by T a , and a decrease in T a induces elevations of both basal metabolic rate (BMR) and nonshivering thermogenesis (NST) [17][18][19][20][21]. In contrary, mammals usually decrease the energy expended on BMR and NST after they are exposed to warm conditions, and reach a constant lowest rate of energy metabolism when they are in the thermal neutral zone (TNZ) [19,22,23].…”

Thermogenic properties of Yunnan red-backed voles (Eothenomys miletus) from the Hengduan mountain region

“…Different correlations have been shown between serum leptin levels and body mass in many small mammals under cold acclimation. For example, positive correlation were reported for Meriones unguiculatus (Li et al, 2004), E. miletus (Zhu et al, 2010a(Zhu et al, , 2010b(Zhu et al, , 2012b and A. chevrieri (Zhu et al, 2011b(Zhu et al, , 2012c, but tree shrews showed a negative correlation (Zhang et al, 2011), while Cricetulus barabensis showed no variation (Zhao, 2011). Consequently, the exact role of leptin in regulating body mass remains largely unknown and complex in wild mammals (Zhang & Wang, 2007).…”

Effect of temperature and food restriction on immune function in striped hamsters (Cricetulus barabensis)

“…It was not affected by cold stress or food restriction, and it was also not correlated with all the immunological parameters detected, implying glucose was not the reason for the changes of immune function in striped hamsters. Cold exposure increases thermogenic capacity and metabolic rate across many species, including striped hamsters (Li et al, 2001;Liu et al, 2009;Chi and Wang, 2011;Zhao et al, 2010;Zhao, 2011;Zhou et al, 2015). Although thermogenic capacity and metabolic rate were not measured in the present study, the competition for energy resources between immune responses and thermogenesis might also account for the suppression of humoral immunity in striped hamsters (Yang et al, 2011;Odegaard and Chawla, 2013;Evans et al, 2015).…”