ORCID Profile
0000-0002-9235-7079
Current Organisation
University of Veterinary Medicine
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Publisher: The Royal Society
Date: 10-2019
Abstract: We experimentally tested the costs of deep torpor at low temperatures by comparing telomere dynamics in two species of rodents hibernating at either 3 or 14°C. Our data show that hibernators kept at the warmer temperature had higher arousal frequencies, but maintained longer telomeres than in iduals hibernating at the colder temperature. We suggest that the high-energy demand of frequent arousals is counteracted by a lower temperature differential between torpid and euthermic body temperature and that telomere length is restored during arousals when the body temperature is returned to normothermic values. Taken together, our study shows that hibernation at low body temperatures comes with costs on a cellular level and that hibernators need to actively counterbalance the shortening of telomeres.
Publisher: University of Chicago Press
Date: 11-2015
DOI: 10.1086/683039
Abstract: Endothermy, high basal metabolic rates (BMRs), and high locomotor-related metabolism were important steps in the evolution of mammals. It has been proposed that the composition of membrane phospholipid fatty acids plays an important role in energy metabolism and exercise muscle physiology. In particular, the membrane pacemaker theory of metabolism suggests that an increase in cell membrane fatty acid unsaturation would result in an increase in BMR. We aimed to determine whether membrane phospholipid fatty acid composition of heart, liver, and gastrocnemius muscles differed between lines of bank voles selected for high swim-induced aerobic metabolism-which also evolved an increased BMR-and unselected control lines. Proportions of fatty acids significantly differed among the organs: liver was the least unsaturated, whereas the gastrocnemius muscles were most unsaturated. However, fatty acid proportions of the heart and liver did not differ significantly between selected and control lines. In gastrocnemius muscles, significant differences between selection directions were found: compared to control lines, membranes of selected voles were richer in saturated C18:0 and unsaturated C18:2n-6 and C18:3n-3, whereas the pattern was reversed for saturated C16:0 and unsaturated C20:4n-6. Neither unsaturation index nor other combined indexes of fatty acid proportions differed between lines. Thus, our results do not support the membrane pacemaker hypothesis. However, the differences between selected and control lines in gastrocnemius muscles reflect chain lengths rather than number of double bonds and are probably related to differences in locomotor activity per se rather than to differences in the basal or routine metabolic rate.
Publisher: Wiley
Date: 27-01-2019
Publisher: The Company of Biologists
Date: 2016
DOI: 10.1242/JEB.137828
Abstract: Basking can substantially reduce thermoregulatory energy expenditure of mammals. We tested the hypothesis that the largely white winter fur of hamsters (Phodopus sungorus), originating from Asian steppes, may be related to camouflage to permit sun basking on or near snow. Winter-acclimated hamsters in our study were largely white and had a high proclivity to bask when resting and torpid. Resting hamsters reduced metabolic rate (MR) significantly (& %) when basking at ambient temperatures (Ta) of ∼15 and 0°C. Interestingly, body temperature (Tb) also was significantly reduced from 34.7±0.6°C (Ta 15°C not basking) to 30.4±2.0°C (Ta 0°C basking), which resulted in an extremely low (& % of predicted) apparent thermal conductance. Induced torpor (food withheld) during respirometry at Ta 15°C occurred on 83.3±36.0% of days and the minimum torpor MR was 36% of basal MR at an average Tb of 22.0±2.6°C movement to the basking l occurred at Tb& .0°C. Energy expenditure for rewarming was significantly reduced (by & %) during radiant heat-assisted rewarming, however, radiant heat per se without an endogenous contribution by animals did not strongly affect metabolism and Tb during torpor. Our data show that basking substantially modifies thermal energetics in hamsters, with a drop of resting Tb and MR not previously observed and a reduction of rewarming costs. The energy savings afforded by basking in hamsters suggest that this behaviour is of energetic significance not only for mammals living in deserts where basking is common, but also for P. sungorus and likely other cold-climate mammals.
Publisher: Springer Science and Business Media LLC
Date: 23-04-2019
DOI: 10.1038/S41598-019-42756-Z
Abstract: Muscle nonshivering thermogenesis (NST) was recently suggested to play an important role in thermoregulation of species lacking brown adipose tissue (BAT). The mechanism, which is independent of muscle contractions, produces heat based on the activity of an ATPase pump in the sarcoplasmic reticulum (SERCA1a) and is controlled by the protein sarcolipin. To evaluate whether muscle NST could indeed play an important role in thermoregulation in species lacking BAT, we investigated the thermogenic capacities of newborn wild boar piglets. During cold exposure over the first 5 days of life, total heat production was improved while shivering intensity decreased, indicating an increasing contribution of NST. S ling skeletal muscle tissue for analyses of SERCA activity as well as gene expression of SERCA1a and sarcolipin, we found an age-related increase in all three variables as well as in body temperature. Hence, the improved thermogenesis during the development of wild boars is not due to shivering but explained by the observed increase in SERCA activity. Our results suggest that muscle NST may be the primary mechanism of heat production during cold stress in large mammals lacking BAT, strengthening the hypothesis that muscle NST has likely played an important role in the evolution of endothermy.
Publisher: Springer Science and Business Media LLC
Date: 24-11-2016
DOI: 10.1038/SREP36856
Abstract: Telomere shortening is thought to be an important biomarker for life history traits such as lifespan and aging, and can be indicative of genome integrity, survival probability and the risk of cancer development. In humans and other animals, telomeres almost always shorten with age, with more rapid telomere attrition in short-lived species. Here, we show that in the edible dormouse ( Glis glis ) telomere length significantly increases from an age of 6 to an age of 9 years. While this finding could be due to higher survival of in iduals with longer telomeres, we also found, using longitudinal measurements, a positive effect of age on the rate of telomere elongation within older in iduals. To our knowledge, no previous study has reported such an effect of age on telomere lengthening. We attribute this exceptional pattern to the peculiar life-history of this species, which skips reproduction in years with low food availability. Further, we show that this “sit tight” strategy in the timing of reproduction is associated with an increasing likelihood for an in idual to reproduce as it ages. As reproduction could facilitate telomere attrition, this life-history strategy may have led to the evolution of increased somatic maintenance and telomere elongation with increasing age.
Publisher: The Company of Biologists
Date: 15-08-2016
DOI: 10.1242/JEB.140871
Abstract: We studied the impact of hibernation and food supply on relative telomere length (RTL), an indicator for aging and somatic maintenance, in free-living edible dormice. Small hibernators such as dormice have ∼50% higher maximum longevity than non-hibernators. Increased longevity could theoretically be due to prolonged torpor directly slowing cellular damage and RTL shortening. However, although mitosis is arrested in mammals at low body temperatures, recent evidence points to accelerated RTL shortening during periodic re-warming (arousal) from torpor. Therefore, we hypothesized that these arousals during hibernation should have a negative effect on RTL. Here, we show that RTL was shortened in all animals over the course of ∼1 year, during which dormice hibernated for 7.5–11.4 months. The rate of periodic arousals, rather than the time spent euthermic during the hibernation season, was the best predictor of RTL shortening. This finding points to negative effects on RTL of the transition from low torpor to high euthermic body temperature and metabolic rate during arousals, possibly because of increased oxidative stress. The animals were, however, able to elongate their telomeres during the active season, when food availability was increased by supplemental feeding in a year of low natural food abundance. We conclude that in addition to their energetic costs, periodic arousals also lead to accelerated cellular damage in terms of RTL shortening. Although dormice are able to counteract and even over-compensate for the negative effects of hibernation, restoration of RTL appears to be energetically costly.
Publisher: The Royal Society
Date: 23-04-2013
Abstract: Small hibernating rodents have greater maximum lifespans and hence appear to age more slowly than similar-sized non-hibernators. We tested for a direct effect of hibernation on somatic maintenance and ageing by measuring seasonal changes in relative telomere length (RTL) in the edible dormouse Glis glis . Average RTL in our population did not change significantly over the hibernation season, and a regression model explaining in idual variation in post-hibernation RTL suggested a significant negative effect of the reduction in body mass over the inactive hibernation period (an index of time spent euthermic), supporting the idea that torpor slows ageing. Over the active season, RTL on average decreased in sub-adults but increased in adults, supporting previous findings of greater telomere shortening at younger ages. Telomere length increase might also have been associated with reproduction, which occurred only in adults. Our study reveals how seasonal changes in physiological state influence the progress of life-history traits, such as somatic maintenance and ageing, in a small hibernating rodent.
Publisher: Springer Science and Business Media LLC
Date: 11-2018
Publisher: Wiley
Date: 15-08-2014
DOI: 10.1111/BRV.12137
Publisher: Springer Science and Business Media LLC
Date: 08-08-2017
DOI: 10.1038/S41598-017-07946-7
Abstract: Mammals typically keep their body temperature (T b ) within a narrow limit with changing environmental conditions. There are indications that some wild ungulates can exhibit certain forms of energy saving mechanisms when ambient temperatures are low and/or food is scarce. Therefore, the aim of the study was to determine if the llama, one of the most extensively kept domestic livestock species, exhibits seasonal adjustment mechanisms in terms of energy expenditure, T b and locomotion. For that purpose llamas (N = 7) were kept in a temperate habitat on pasture. Locomotor activity, T b (measured in the rumen) and the location of each animal were recorded continuously for one year using a telemetry system. Daily energy expenditure was measured as field metabolic rate (FMR). FMR fluctuated considerably between seasons with the lowest values found in winter (17.48 ± 3.98 MJ d −1 , 402 kJ kg −0.75 d −1 ) and the highest in summer (25.87 ± 3.88 MJ d −1 , 586 kJ kg −0.75 d −1 ). Llamas adjusted their energy expenditure, T b and locomotor activity according to season and also time of day. Thus, llamas seem to have maintained the ability to reduce their energy expenditure and adjust their T b under adverse environmental conditions as has been reported for some wild ungulates.
Publisher: The Royal Society
Date: 14-09-2011
Abstract: Ageing can progress at different rates according to an in idual's physiological state. Natural hypothermia, including torpor and hibernation, is a common adaptation of small mammals to survive intermittent or seasonal declines in environmental conditions. In addition to allowing energy savings, hypothermia and torpor have been associated with retarded ageing and increased longevity. We tested the hypothesis that torpor use slows ageing by measuring changes in the relative telomere length (RTL) of Djungarian hamsters, Phodopus sungorus , a highly seasonal rodent using spontaneous daily torpor, over 180 days of exposure to a short-day photoperiod and warm (approx. 20°C) or cold (approx. 9°C) air temperatures. Multi-model inference showed that change in RTL within in iduals was best explained by positive effects of frequency of torpor use, particularly at low body temperatures, as well as the change in body mass and initial RTL. Telomere dynamics have been linked to future survival and proposed as an index of rates of biological ageing. Our results therefore support the hypothesis that daily torpor is associated with physiological changes that increase somatic maintenance and slow the processes of ageing.
Publisher: Wiley
Date: 15-10-2013
Publisher: University of Chicago Press
Date: 11-1995
Publisher: Springer Science and Business Media LLC
Date: 24-05-2023
DOI: 10.1186/S12983-023-00498-9
Abstract: Torpor is an energy saving strategy achieved by substantial reductions of metabolic rate and body temperature that enables animals to survive periods of low resource availability. During hibernation (multiday torpor), the frequency of periodic rewarming—characterised by high levels of oxidative stress—is associated with shortening of telomeres, a marker of somatic maintenance. In this study, we determined the impact of ambient temperature on feeding behaviour and telomere dynamics in hibernating garden dormice ( Eliomys quercinus ) over winter. This obligate hibernator prepares for hibernation by accumulating fat stores but can also feed during hibernation. Food intake, torpor pattern, changes in telomere length, and body mass change were assessed in animals housed at experimentally controlled temperatures of either 14 °C (i.e., a mild winter) or 3 °C (i.e., a cold winter) over 6 months. When hibernating at 14 °C, dormice experienced 1.7-fold more frequent and 2.4-fold longer inter-bout euthermia, and spent significantly less time torpid, compared to animals hibernating at 3 °C. Higher food intake enabled in iduals to compensate for increased energetic costs when hibernating at milder temperatures (14 °C vs. 3 °C), to buffer body mass loss and thus increase winter survival. Interestingly, we observed a significant increase of telomere length over the entire hibernation period, irrespective of temperature treatment. We conclude that higher temperatures during winter, if associated with sufficient food availability, can have a positive effect on the in idual’s energy balance and somatic maintenance. These results suggest that winter food availability might be a crucial determinant for the survival of the garden dormouse in the context of ever-increasing environmental temperatures.
Publisher: Wiley
Date: 06-11-2021
DOI: 10.1111/JEB.13954
Abstract: Life‐history theory predicts a trade‐off between growth rates and lifespan, which is reflected by telomere length, a biomarker of somatic state. We investigated the correlation between telomere length and early‐life growth of wild boar piglets, Sus scrofa , kept under semi‐natural conditions with high food availability to examine our hypothesis that increased pre‐ and postnatal growth will lead to telomere length attrition, but that a high supply of nutrient may provide the possibility to compensate telomere loss via telomere repair mechanisms. As predicted, our data showed a clear negative correlation between birth body mass and initial telomere length: heavier neonates had shorter telomeres at birth, and we did not find an influence of the mother on initial telomere length. Body mass at birth correlated with body mass later in life and postnatal growth rate did not affect telomere length. We observed an increase in telomere length during postnatal development, suggesting that high food availability allowed piglets to invest into both, growth and telomere restoration. The increase in telomere length over the duration of the study was not accompanied by telomerase activity thus, telomere elongation was caused either by alternative mechanisms or by short pulses of telomerase activity that we missed. Taken together, this study suggests a trade‐off between investment into growth and telomere maintenance even before birth and the possibility to compensate telomere attrition during growth under high amounts of available energy.
No related grants have been discovered for Thomas Ruf.