Facultative nonshivering thermogenesis in regulation of body temperature in endotherms

Facultative (regulatory) nonshivering thermogenesis (NST) is a very effective way to generate heat, especially in small animals exposed to cold. It is energetically much cheaper response to cold than shivering thermogenesis or the increase in maximum metabolic rate. The thermogenic capacity of NST undergoes seasonal changes, being the highest in winter and the lowest in summer. The main cues for seasonal improvement of the capacity for NST are short photoperiod and low ambient temperature. However, not only seasonal but also daily variations in the NST capacity are possible. The latter depend on the circadian rhythm of body temperature. The NST is very important for heterotherms since it plays a fundamental role during the arousal from torpor (daily or seasonal), allowing for rapid elevation of body temperature. In placental mammals, the major source of NST is the brown adipose tissue (BAT). Thermogenic capacity of BAT depends on the species, the ability to enter torpor, photoperiodic and thermal history of animals and ambient temperature. The mechanism of NST in BAT requires a special and unique feature of BAT mitochondria, i.e. The presence of the uncoupling protein UCP1, that uncouples - under the control of fatty acids - oxidative phosphorylation from ATP synthesis. Nevertheless, not only placental mammals but also marsupials and birds are able to increase heat production by means of NST. They need extra heat to maintain a constant body temperature in the cold or during arousal from torpor. However, most of these animals lack functional BAT (it was found only in a few species of marsupials) and their mechanism(-s) of NST is (are) entirely different. NST here is attributable to skeletal muscles and may involve other members of the UCP family, like UCP2 or UCP3 or avian ucps. Another possible mechanisms are based on the translocation of CA2+ between the lumen of sarcoplasmic reticulum (SR) and the cytosol, mediated by the SR CA2+-ATPase. The energy derived from a CA2+ gradient may be converted into heat. Independently of BAT- or muscle-origin, NST is an important source of heat in the face of cold. Different mechanisms could evolve concomitantly as a response to changes in the environment, mainly due to a decrease in ambient temperature. Both, seasonal and daily changes in the capacity of NST reflect different demands for heat dependently on the time of the year and time of day

Photoresponsiveness affects life history traits but not oxidative status in a seasonal rodent

Abstract Background Shortening photoperiod triggers seasonal adjustments like cessation of reproduction, molting and heterothermy. However there is a considerable among-individual variation in photoresponsiveness within one population. Although seasonal adjustments are considered beneficial to winter survival, and natural selection should favor the individuals responding to changes in photoperiod (responders), the phenotype non-responding to changes in day length is maintained in population. Assuming the same resource availability for both phenotypes which differ in strategy of winter survival, we hypothesized that they should differ in life history traits. To test this we compared reproductive traits of two extreme phenotypes of Siberian hamster Phodopus sungorus – responding and non-responding to seasonal changes in photoperiod. We bred individuals of the same phenotype and measured time to first parturition, time interval between litters, offspring body mass 3, 10 and 18 days after birth and their growth rate. We also analyzed nest-building behavior. Additionally, we estimated the correlation between reproduction, and basal metabolic rate (BMR) and oxidative status in both phenotypes to infer about the effect of reproductive output on future investments in somatic maintenance. Results Prior to reproduction responding individuals were smaller than non-responding ones, but this difference disappeared after reproduction. Responding pairs commenced breeding later than non-responding ones but there was no difference in time interval between consecutive litters. Responders delivered smaller offspring than non-responders and more out of responding individuals built the nest during winter than non-responding ones. Reproduction did not affect future investments in somatic maintenance. Phenotypes did not differ in BMR and oxidative status after reproduction. However, concentration of reactive oxygen metabolites (ROM) was highest in responding males, and biological antioxidant potential (BAP) was higher in males of both phenotypes than in females. Conclusions Delayed breeding in responding Siberian hamsters and high ROM concentration in male responders support our hypothesis that differences in adjustment to winter result in different life history characteristics which may explain coexistence of both phenotypes in a population. We propose that polymorphism in photoresponsiveness may be beneficial in stochastic environment, where environmental conditions differ between winters. We suggest that non-responding phenotype may be particularly beneficial during mild winter, whereas responders would be favored under harsh conditions. Therefore, none of the phenotypes is impaired when compared to the other

Dataset: Warm spells raw data.xlsx

Dataset from: Warm spells in winter affect the equilibrium between winter phenotypes published at the Journal of Thermal Biology, Volume 120, February 2024, 103811, https://doi.org/10.1016/j.jtherbio.2024.103811</p

Influence of Algae Supplementation on the Concentration of Glutathione and the Activity of Glutathione Enzymes in the Mice Liver and Kidney

Algae are potential and natural source of long-chain polyunsaturated fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The diatom Pinnularia borealis accumulates high levels of EPA and may be considered as a source for commercial production of dietary supplements. In this study we asked the question whether diet supplementation with P. borealis may augment antioxidant defense and ameliorate risk factors for cardiovascular diseases. We fed mice (Mus musculus) with lyophilized diatom solutions of different concentrations (1%, 3%, and 5%) for 7 days. Then we measured glutathione content and the activity of glutathione redox system enzymes, total cholesterol and triacylglycerol concentrations, and malondialdehyde concentration in the liver and kidney. We found that cholesterol and triacylglycerol concentrations in the liver and kidneys were the lowest in mice who were fed with the highest concentration of Pinnularia borealis, suggesting protective properties of algae. Additionally, the lowest concentration of Pinnularia borealis was sufficient to improve antioxidant capacity. Our results suggest that P. borealis may be used as a source for dietary supplements rich in EPA, but the amount supplied to the organism should be limited