Silencing of ultradian rhythms and metabolic depression during spontaneous daily torpor in Djungarian hamsters.

Ultradian rhythms of metabolism, body temperature and activity are attenuated or disappear completely during torpor in Djungarian hamsters, for all three ultradian periodicities (URsmall, URmedium and URlarge). URsmall and URmedium disappear during entrance into torpor, whereas URlarge disappear later or continue with a low amplitude. This suggests a tight functional link between torpor and the expression of ultradian rhythms, i.

Multiple ultradian rhythms of metabolism, body temperature and activity in Djungarian hamsters.

Djungarian hamsters (Phodopus sungorus) living at constant 15 °C T in short photoperiod (8:16 h L:D) showed pronounced ultradian rhythms (URs) of metabolic rate (MR), body temperature (T) and locomotor activity. The ultradian patterns differed between individuals and varied over time. The period length of URs for MR, T and activity was similar although not identical.

Could Chronic Hypothermia in a Human Affect the Clock System?

AbstractHibernation-like episodes would be particularly interesting for clinical and spatial use if they could be observed and induced in humans. As animal hibernation differs from hypothermia with its control by a temperature-dependent clock, we undertook to find evidence that human hypothermia might affect the circadian clock system. We revisited Siffre's 1962 abyss experiment.

European space agency's hibernation (torpor) strategy for deep space missions: Linking biology to engineering.

Long-duration space missions to Mars will impose extreme stresses of physical and psychological nature on the crew, as well as significant logistical and technical challenges for life support and transportation. Main challenges include optimising overall mass and maintaining crew physical and mental health. These key scopes have been taken up as the baseline for a study by the European Space Agency (ESA) using its Concurrent Design Facility (CDF).

Hibernating astronauts-science or fiction?

For long-duration manned space missions to Mars and beyond, reduction of astronaut metabolism by torpor, the metabolic state during hibernation of animals, would be a game changer: Water and food intake could be reduced by up to 75% and thus reducing payload of the spacecraft. Metabolic rate reduction in natural torpor is linked to profound changes in biochemical processes, i.e.

Seasonal Control of Mammalian Energy Balance: Recent Advances in the Understanding of Daily Torpor and Hibernation.

Endothermic mammals and birds require intensive energy turnover to sustain high body temperatures and metabolic rates. To cope with the energetic bottlenecks associated with the change of seasons, and to minimise energy expenditure, complex mechanisms and strategies are used, such as daily torpor and hibernation. During torpor, metabolic depression and low body temperatures save energy.

Torpor at high ambient temperature in a neotropical didelphid, the grey short-tailed opossum (Monodelphis domestica).

The grey short-tailed opossum, Monodelphis domestica, has been an established research animal for more than five decades, but relatively, little is known about its thermophysiology. Here we studied core body temperature (T b) and metabolic rate (MR) of female adult M. domestica housed in the laboratory at an ambient temperature (T a) of 26 °C.

Brown adipose tissue dynamics in wild-type and UCP1-knockout mice: in vivo insights with magnetic resonance.

We used noninvasive magnetic resonance imaging (MRI) and magnetic resonance spectroscopy to compare interscapular brown adipose tissue (iBAT) of wild-type (WT) and uncoupling protein 1 (UCP1)-knockout mice lacking UCP1-mediated nonshivering thermogenesis (NST). Mice were sequentially acclimated to an ambient temperature of 30°C, 18°C, and 5°C. We detected a remodeling of iBAT and a decrease in its lipid content in all mice during cold exposure.

Metabolic depression during warm torpor in the Golden spiny mouse (Acomys russatus) does not affect mitochondrial respiration and hydrogen peroxide release.

Small mammals actively decrease metabolism during daily torpor and hibernation to save energy. Recently, depression of mitochondrial substrate oxidation in isolated liver mitochondria was observed and associated to hypothermic/hypometabolic states in Djungarian hamsters, mice and hibernators. We aimed to clarify whether hypothermia or hypometabolism causes mitochondrial depression during torpor by studying the Golden spiny mouse (Acomys russatus), a desert rodent which performs daily torpor at high ambient temperatures of 32°C.

Depression of mitochondrial respiration during daily torpor of the Djungarian hamster, Phodopus sungorus, is specific for liver and correlates with body temperature.

Small mammals actively decrease metabolism during daily torpor and hibernation to save energy. Increasing evidence suggests depression of mitochondrial respiration during daily torpor of the Djungarian hamster but tissue-specificity and relation to torpor depth is unknown. We first confirmed a previous study by Brown and colleagues reporting on the depressed substrate oxidation in isolated liver mitochondria of the Djungarian hamster (Phodopus sungorus) during daily torpor.

That's hot: golden spiny mice display torpor even at high ambient temperatures.

Golden spiny mice (Acomys russatus) living in the Judean desert are exposed to extended periods of food and water shortage. We investigated their thermal and metabolic response to three weeks of 50% food reduction at ambient temperatures of 23, 27, 32 and 35 °C by long term records of metabolic rate and body temperature in the laboratory. At all ambient temperatures, A.

Photoperiod-dependent regulation of carboxypeptidase E affects the selective processing of neuropeptides in the seasonal Siberian hamster (Phodopus sungorus).

The production of bioactive peptides from biologically inactive precursors involves extensive post-translational processing, including enzymatic cleavage by proteolytic peptidases. Endoproteolytic prohormone-convertases initially cleave the precursors of many neuropeptides at specific amino acid sequences to generate intermediates with basic amino acid extensions on their C-termini. Subsequently, the related exopeptidases, carboxypeptidases D and E (CPD and CPE), are responsible for removing these amino acids before the peptides achieve biological activity.

The dietary flavonoids naringenin and quercetin acutely impair glucose metabolism in rodents possibly via inhibition of hypothalamic insulin signalling.

Secondary metabolites of herbs and spices are widely used as an alternative strategy in the therapy of various diseases. The polyphenols naringenin, quercetin and curcumin have been characterised as anti-diabetic agents. Conversely, in vitro, naringenin and quercetin are described to inhibit phosphoinositide-3-kinase (PI3K), an enzyme that is essential for the neuronal control of whole body glucose homoeostasis.

Seasonal changes in thermogenesis of a free-ranging afrotherian small mammal, the Western rock elephant shrew (Elephantulus rupestris).

We report on the seasonal metabolic adjustments of a small-sized member of the phylogenetically ancient Afrotheria, the Western rock elephant shrew (Elephantulus rupestris). We recorded body temperature (T (b)) patterns and compared the capacity for adrenergically induced nonshivering thermogenesis (NST) in E. rupestris captured in the wild in summer and winter.

Phylogenetic differences of mammalian basal metabolic rate are not explained by mitochondrial basal proton leak.

Metabolic rates of mammals presumably increased during the evolution of endothermy, but molecular and cellular mechanisms underlying basal metabolic rate (BMR) are still not understood. It has been established that mitochondrial basal proton leak contributes significantly to BMR. Comparative studies among a diversity of eutherian mammals showed that BMR correlates with body mass and proton leak.

Induction of torpor: mimicking natural metabolic suppression for biomedical applications.

Mammalian hibernation consists of periods of depressed metabolism and reduced body temperature called "torpor" that are interspersed by normothermic arousal periods. Numerous cellular processes are halted during torpor, including transcription, translation, and ion homeostasis. Hibernators are able to survive long periods of low blood flow and body temperature followed by rewarming and reperfusion without overt signs of organ injury, which makes these animals excellent models for application of natural protective mechanisms to human medicine.

Adaptive thermogenesis and thermal conductance in wild-type and UCP1-KO mice.

We compared maximal cold-induced heat production (HPmax) and cold limits between warm (WA; 27°C), moderate cold (MCA; 18°C), or cold acclimated (CA; 5°C) wild-type and uncoupling-protein 1 knockout (UCP1-KO) mice. In wild-type mice, HPmax was successively increased after MCA and CA, and the cold limit was lowered to -8.3°C and -18.

Torpor patterns, arousal rates, and temporal organization of torpor entry in wildtype and UCP1-ablated mice.

In eutherian mammals, uncoupling protein 1 (UCP1) mediated non-shivering thermogenesis from brown adipose tissue (BAT) provides a mechanism through which arousal from torpor and hibernation is facilitated. In order to directly assess the magnitude by which the presence or absence of UCP1 affects torpor patterns, rewarming and arousal rates within one species we compared fasting induced torpor in wildtype (UCP1(+/+)) and UCP1-ablated mice (UCP(-/-)). Torpor was induced by depriving mice of food for up to 48 h and by a reduction of ambient temperature (T (a)) from 30 to 18°C at four different time points after 18, 24, 30 and 36 h of food deprivation.

Seasonal changes of myostatin expression and its relation to body Mass acclimation in the Djungarian hamster, Phodopus sungorus.

The Djungarian hamster is an animal that is prominent for distinct seasonal adaptations. Cued by shortening day length in autumn they spontaneously exhibit reductions in food intake, body mass (BM), fat mass and also in lean mass (LM). The mechanisms behind the seasonal regulation of body composition are only partly resolved.