Increase In Nonshivering Thermogenesis Research Articles

1501-P: Deletion of miR-494 Induces Adipocyte Browning and Slows Aging in Mice

Adipocyte browning is a potent therapeutic strategy for obesity and metabolic disorders. We previously reported that miR-494 served as a negative regulator of mitochondrial biogenesis during browning in cultured adipocytes. However, the in vivo evidence has not been provided. In this study, we examined the role of miR-494 in adipocyte browning and aging using miR-494 knockout (KO) mice. KO mice were generated using CRISPR/Cas9 system. KO mice had equivalent energy expenditure, physical activity, food intake and body weight compared to wild-type (WT) mice; had lower resting respiratory quotient (0.95±0.006 vs 0.91±0.004), less visceral fat (16.3±1.08 vs 13.4±0.96 g/kg body weight) and 3.7-fold increased expression of Ucp1 in subcutaneous fat. In addition, KO mice showed cold tolerance during 3 hours exposure to 4ºC and increased oxygen consumption than WT mice after administration of a β3 agonist in thermoneutral condition, indicating an increase in non-shivering thermogenesis. In adipose tissues of KO mice, increased expression of Pgc-1α, a target gene of miR-494, and tendency to increase in mitochondrial DNA were observed. Primary adipocytes derived from KO mice showed enhanced mitochondrial respiration driven by fatty acids as determined by extracellular flux analysis. Finally, KO mice showed an extended median lifespan 29% relative to WT mice (from 113.7 to 146.7 weeks). Aged KO mice (≥ 2 years old) showed reduced age-related changes, such as hair graying and low physical activity. In conclusion, deletion of miR-494 demonstrated increased adipocyte browning and survival advantage in mice. Although there are numerous studies that focused on promoting adipocyte browning, its long-term effect has not been well evaluated. Thus, our data showing the association among miR-494, adipocyte browning and longevity provide a novel insight into adipocyte biology and aging study. The gene sequence of miR-494 and its binding site to Pgc-1α are conserved from mice to humans; it is expected to be applied to human research. Disclosure L.Sugawara: None. K.Morino: Research Support; AstraZeneca, Astellas Pharma Inc., Sanwa Kagaku Kenkyusho, Ono Pharmaceutical Co., Ltd. H.Iwasaki: None. S.Ida: None. T.Yanagimachi: None. M.Lemecha: None. H.Maegawa: None. Y.Fujita: Research Support; Terumo Corporation, Boehringer Ingelheim Japan, Inc., Japan Society for the Promotion of Science, Mitsubishi Tanabe Pharma Corporation, Sumitomo Dainippon Pharma Co., Ltd. S.Kume: Research Support; Boehringer Ingelheim International GmbH, Japan Society for the Promotion of Science. Funding Grants-in-Aid for Scientific Research (22K08650)

Effect of the sympathetic nervous system co-transmitters ATP and norepinephrine on thermoregulatory response to cooling

The existence of co-transmitters of the sympathetic nervous system norepinephrine (NE) and ATP implies variations in the neuromodulator mechanisms of physiological processes. The role of ATP, as a transmitter of the peripheral part of sympathetic nervous system in the formation of thermoregulatory response is not clear. Whether ATP modulates any parameters of thermoregulatory response to cold; if yes, whether co-transmitters of sympathetic nervous system ATP and NE differently modulate thermoregulatory response and on which parameters of cold-defense response the influence of ATP is more pronounced. Experiments were carried out on rats. ATP (10−6), NE (10−3), and their mixture introduced iontophoretically into skin. Their effects on thermoregulatory parameters (temperature parameters, total oxygen consumption, carbon dioxide release, muscle activity, respiratory coefficient) were studied in thermoneutral conditions (without cold load) and under the cooling. In thermoneutral conditions both ATP and NE enhance total metabolism through increase in metabolic rate of lipids, NE effect being more expressed. It was shown that ATP and NE influence predominantly on the different components of the metabolic response to cold. ATP affects to the greatest extent on cold muscular thermogenesis by increasing shivering almost twofold and lowering its initiation temperature thresholds, whereas NE mainly promotes increase in non-shivering thermogenesis. When introducing the mixture of these biological substances the effect of NE is more expressed and the ATP effect is weakened. The obtained results allow to suggest that in vivo the NE effects can be more expressed when the sympathetic nervous system is stimulated by cold. Thus, NE and ATP being co-transmitters and predominantly acting on the different processes of cold thermogenesis (ATP on shivering and NE on non-shivering) may organize the certain sequence of cold defense responses.

Cold acclimation recruits human brown fat and increases nonshivering thermogenesis

In recent years, it has been shown that humans have active brown adipose tissue (BAT) depots, raising the question of whether activation and recruitment of BAT can be a target to counterbalance the current obesity pandemic. Here, we show that a 10-day cold acclimation protocol in humans increases BAT activity in parallel with an increase in nonshivering thermogenesis (NST). No sex differences in BAT presence and activity were found either before or after cold acclimation. Respiration measurements in permeabilized fibers and isolated mitochondria revealed no significant contribution of skeletal muscle mitochondrial uncoupling to the increased NST. Based on cell-specific markers and on uncoupling protein-1 (characteristic of both BAT and beige/brite cells), this study did not show "browning" of abdominal subcutaneous white adipose tissue upon cold acclimation. The observed physiological acclimation is in line with the subjective changes in temperature sensation; upon cold acclimation, the subjects judged the environment warmer, felt more comfortable in the cold, and reported less shivering. The combined results suggest that a variable indoor environment with frequent cold exposures might be an acceptable and economic manner to increase energy expenditure and may contribute to counteracting the current obesity epidemic.

Nonshivering thermogenesis capacity associated to mitochondrial DNA haplotypes and gender in the greater white‐toothed shrew, Crocidura russula

A selection gradient was recently suggested as one possible cause for a clinal distribution of mitochondrial DNA (mtDNA) haplotypes along an altitudinal transect in the greater white-toothed shrew, Crocidura russula (Ehinger et al. 2002). One mtDNA haplotype (H1) rare in lowland, became widespread when approaching the altitudinal margin of the distribution. As H1 differs from the main lowland haplotype by several nonsynonymous mutations (including on ATP6), and as mitochondria play a crucial role in metabolism and thermogenesis, distribution patterns might stem from differences in the thermogenic capacity of different mtDNA haplotypes. In order to test this hypothesis, we measured the nonshivering thermogenesis (NST) associated with different mtDNA haplotypes. Sixty-two shrews, half of which had the H1 haplotype, were acclimated in November at semioutdoor conditions and measured for NST throughout winter. Our results showed the crucial role of NST for winter survival in C. russula. The individuals that survived winter displayed a higher significant increase in NST during acclimation, associated with a significant gain in body mass, presumably from brown fat accumulation. The NST capacity (ratio of NST to basal metabolic rate) was exceptionally high for such a small species. NST was significantly affected by a gender x haplotype interaction after winter-acclimation: females bearing the H1 haplotype displayed a better thermogenesis at the onset of the breeding season, while the reverse was true for males. Altogether, our results suggest a sexually antagonistic cyto-nuclear selection on thermogenesis.

Thermal acclimation and non-shivering thermogenesis in three species of South American rodents: a comparison between arid and mesic habitats

Non-hibernating mammals that live in seasonal and arid environments change their non-shivering thermogenesis (NST) capacity to maintain homeothermy. Metabolic capabilities of animals, such as NST, are considered adaptive plastic traits because they have a broad range of possible phenotypes with different ambient temperatures (i.e. the reaction norm). Consequently, we determined the reaction norm for NST in Octodon degus (Bennett, 1832; mb=189 g) andPhyllotis darwini (Waterhouse, 1837; mb=61 g) from the mesic habitat of central Chile, and inPhyllotis xanthopygus (Waterhouse, 1837; mb=67 g) from the high Andean plains of northern Chile, an arid and seasonal habitat. Octodon degus showed a 22% increase in NST with thermal acclimation, whereas P. xanthopygus showed a 112% increase, and P. darwini showed a 117% increase in NST, being the largest change observed. These results are in agreement with our hypothesis of evolutionary inertia, which states that observed metabolic plasticity in Phyllotis species is consequence of their high Andean origin, in spite of the fact the actual habitat ofP. darwini is the less seasonal central valley of Chile.

Cold adaptive thermogenesis in small mammals from different geographical zones of China

The mechanisms of thermogenesis and thermoregulation were studied in the tree shrew ( Tupaia belangeri) and greater vole ( Eothenomys miletus) of the subtropical region, and Brandt's vole ( Microtus brandti), Mongolian gerbil ( Meriones unguiculatus), Daurian ground squirrel ( Spermophilus dauricus) and plateau pika ( Ochotona curzoniae) of the northern temperate zone. Resting metabolic rate (RMR) and non-shivering thermogenesis (NST) increased significantly in T. belangeri, E. miletus, M. brandti and M. unguiculatus after cold acclimation (4°C) for 4 weeks. In T. belangeri, the increase in RMR and thermogenesis at liver cellular level were responsible for enhancing the capacity of enduring cold stress, and homeothermia was simultaneously extended. Stable body temperature in M. brandti, E. miletus, M. unguiculatus and O. curzoniae was maintained mainly through increase in NST, brown adipose tissue (BAT) mass and its mitochondrial protein content, and the upregulation of uncoupling protein (UCP1) mRNA, as well as enhancement of the activity of cytochrome C oxidase, α-glycerophosphate oxidase and T 4 5′-deiodenase in BAT mitochondria. The RMR in O. curzoniae and euthermic S. dauricus was not changed, while NST significantly increased during cold exposure; the former maintained their stable body temperature and mass, while body temperature in the latter declined by 4.8°C. The serum T 3 concentration or ratio of T 3/T 4 in all the species was enhanced after cold acclimation. Results indicated that: (1) the adaptive mechanisms of T. belangeri residing in the subtropical region to cold are primarily by increasing RMR and secondly by increasing NST, and the mechanisms of thermogenesis are similar to those in tropical mammals; (2) in small mammals residing in northern regions, the adaptation to cold is chiefly to increase NST; (3) the mechanism of cold-induced thermogenesis in E. miletus residing in subtropical and high mountain regions is similar to that in the north; (4) a low RMR in warm environments and peak RMR and NST in cold environments enabled M. unguiculatus to tolerate a semi-desert climate; (5) O. curzoniae has unusually high RMR and high NST, acting mainly via increasing NST to adapt to extreme cold of the Qinghai–Tibet Plateau; (6) the adaptation of euthermic S. dauricus to cold is due to an increase in NST and a relaxed homeothermia; and lastly (7) the thyroid hormone is involved in the regulation of cold adaptive thermogenesis in all the species studied.

Role of body temperature in seasonal acclimatization: Photoperiod‐induced rhythms and heat production in Meriones crassus

AbstractHeat production by means of nonshivering thermogenesis (NST) and food consumption were compared in individuals of the fat jird Meriones crassus, acclimated to 8L:16D and 16L:8D cycles at an ambient temperature of 28°C. Daily rhythms of body temperature were compared at the same time.A significant (P < 0.05 and P < 0.005) increase in NST and food consumption was noted in fat jirds acclimated to short photoperiod 8L:16D when compared with those acclimated to a long photoperiod 16L:8D. A clear difference in rhythms of body temperature was observed between the two groups.In light of these results it is reasonable to assume that seasonal acclimatization in the fat jird can be partly induced by the change of photoperiod. Rhythms of body temperature in the fat jird are entrained by photoperiod and appear to be adjusted to the different metabolic demands of summer and winter.

Hypothermia and abnormalities in thermoregulation in patients with anorexia nervosa

Hypothermia and other persisting disturbances in thermoregulation among weight-recovered anorexia nervosa patients are reviewed. Possible neurobiological mechanisms that might explain these clinical features are presented along with evidence supporting the hypothesis that an increase in nonshivering thermogenesis and an underlying autonomic nervous system imbalance may contribute to the persistence of certain abnormal thermo-regulatory responses to cold in anorectics.

Effects of cold, short day and melatonin on thermogenesis, body weight and reproductive organs in Alaskan red-backed voles

This study examined whether cold, short day or melatonin causes reproductive regression and stimulates nonshivering thermogenesis in a subarctic rodent Clethrionomys rutilus. Red-backed voles born and raised at 23 degrees C and 22 h light per day (LD 22:2) at Fairbanks, Alaska (65 degrees N) were exposed in one of six groups to: 1) long day (LD 22:2), 23 degrees C, injected daily with melatonin or saline 2 h before lights out, 2) long day, 3 degrees C, injected daily with melatonin or saline, 3) short day (LD 8:16), 23 degrees C or 3 degrees C. Voles were tested for nonshivering thermogenesis (NST) prior to and after 8 wk exposure. Body weight, testes weight and female reproductive tract weight were assessed after 8 wk in long day and 12 wk in short day. NST was not altered by short day or melatonin but cold (3 degrees C) caused an increase in NST which was similar in long day and short day. Body weight of males and females was not affected by short day but was decreased by melatonin. Short day did not alter mean testes weight (about 20% voles regressed) but reduced mean female reproductive tract weight (more than 40% voles regressed). Melatonin reduced testes weight and female reproductive tract weight (more than 50% of voles of both sexes regressed). The results suggest that in northern red-backed voles: the pineal does not mediate seasonal changes in thermogenic capacity, the pineal may mediate reduction of body weight and regression of reproductive organs but, in addition to day-length, other cues or factors may be important, populations may exhibit variability in sensitivity of reproduction to photoperiod which could allow for opportunistic breeding.

Changes in plasma cortisol during acute cold exposure in euthermic European hedgehogs: thermoregulatory role of the hypothalamo-pituitary-adrenal axis

During acute cold exposure regulatory heat production of European hedgehogs was significantly increased with a simultaneous rise in the plasma cortisol level. Soon after cold exposure, at the time when standard metabolic rate was measured, the plasma cortisol level was reduced again. This finding indicates a highly reactive hypothalamo-pituitary-adrenal axis in euthermic hedgehogs exposed to a cold environment. Two effects of the adrenocorticostatic agent metopirone ditartrate were observed: (1) A metopirone-induced increase in nonshivering thermogenesis (NST) starting 18 min after application, reaching a maximum after 43 min and disappearing after 90 min (Fig. 1, Table 1). Simultaneously a profound long lasting hyperglycemia was observed (Fig. 2). (2) In contrast to untreated hedgehogs, animals which were given metopirone did not show an increase in the plasma cortisol level, when exposed to cold within 2 to 3 h (Fig. 6). When animals were pretreated with dexamethasone the metopirone-induced NST was suppressed, indicating that the effect of metopirone is mediated by the hypothalamo-pituitary-adrenal system (Fig. 4). The effect of metopirone at doses used in this study was reversible. It is suggested that a combined action of corticosteroids and catecholamines is involved in the control of regulatory heat production.

Increased contribution of brown adipose tissue to nonshivering thermogenesis in the Djungarian hamster during cold-adaptation.

The effect of cold-adaptation was investigated on the brown adipose tissue of Djungarian hamsters. Animals maintained at 23 degrees C and 16 hours light per day (controls) were exposed to 5 degrees C. The wet weight of the total brown fat is reduced by some 40% within 4 days of cold-exposure, as a result of extensive triacylglycerol depletion of the tissue with no reduction in DNA; the tissue mass remains constant under persistent cold influence. The total amount of tissue mitochondria is doubled by 24 h and increases by a factor of 3 under persistent cold-stimulus, the specific respiratory capacity of the organelles remaining unchanged. The amount of 32 kDa regulatory protein per mg mitochondrial protein quantified from high-affinity GDP-binding, is increased by a factor of 2.7 after 21 days of cold-adaptation; a 9-fold increment is found of the total mitochondrial GDB-binding capacity. Comparison of nonshivering thermogenesis and the maximal thermogenic capacity of brown fat, estimated from the maximal respiration of the isolated mitochondria and the total amount of mitochondria in the tissue, suggests that brown fat may contribute about 20% to the whole-body nonshivering thermogenesis in warm-adapted controls and 45% in cold-adapted hamsters. The estimated increase in thermogenic capacity of the tissue in response to 21 days of cold-adaptation corresponds to the increase in nonshivering thermogenesis, suggesting a central thermoregulatory role of brown fat during cold-adaptation.

Adrenergic beta-receptors and non-shivering thermogenesis.

Sellers, Scott and Thomas1 demonstrated that after prolonged cold exposure (cold acclimatization) heat production through shivering is gradually replaced by an increase in non-shivering thermogenesis. It is often assumed that muscle tissue is an important site of non-shivering thermogenesis. Recently, Himms-Hagen2 has suggested that acceleration of the triglyceride cycle of brown adipose tissue is a major mechanism of non-shivering thermogenesis in cold-acclimatized rats. As lipid metabolism of adipose tissue is under β-adrenergic control, a study of the effect of β-adrenergic blockade on electrical muscle activity in rats exposed to about 4° C after acclimatization to 23° C or 4° C would be expected to yield valuable information. This communication presents preliminary data of such an investigation. Cold-acclimatized rats were removed from the cold room, anaesthetized with urethane (1 to 1.25 g/kg)—a drug known to alter only the degree, not the type, of the electrical response of muscle activity1—and exposed to a temperature of 4° C. Needle electrodes were inserted into a leg muscle and electrical activity was measured with a Grass model 5 polygraph3. Rectal temperature was monitored throughout the experiment. Each rat was tested at least twice, once when given drug treatment, and once when given saline or nothing. The β-adrenergic blocking agent, propranolol (AY 64043) (kindly donated by Ayerst, McKenna and Harrison, Ltd., Montreal), was used at doses of 0.3 or 0.9 mg/kg intraperitoneally every 30 min. Fig. 1 shows rectal temperature, duration of exposure to 4° C and the effect of the drug on electrical muscle activity in six cold-acclimatized rats. None of the animals shivered during an experimental period of 2.5 h when treated with saline. A seventh rat showed signs of shivering and was therefore excluded from this series. After treatment with propranolol, all six rats showed a marked increase of electrical muscle activity. Representative tracings of the muscle activity before and after propranolol are shown in Fig. 1: no effort was made to quantitate accurately the observed increase.