Proteomic Mechanisms of Hepatic- and Cardio-Protection of a Food-Hoarding Hibernator, Tamias sibiricus.

SIZE MATTERS

The pygmy marmoset (Cebuella pygmaea) is the smallest New World Monkey and presents an interesting primate comparison to evolutionary experiments in body size evolution. Previous research has been suggested that pygmy marmosets exhibit a lower basal metabolism relative to mammals of similar size, with the adaptive reasons involving dietary constraints. Indeed, this hypometabolism hypothesis has been evoked as a correlate to the pygmy marmoset’s proposed phyletic dwarfism. However, these earlier assessments of basal metabolic rates were conducted on sleeping animals. Pygmy marmosets are capable of quite pronounced diurnal changes in body temperature (4–5°C), with consequent effects on estimates of basal metabolism. Since comparison of a particular species’ metabolism to standard mammalian curves for basal metabolism requires similar assessment parameters, I chose to re-evaluate these measurements in the context of the changes in metabolism that accompany the onset and maintenance of the diurnal inactive period when marmosets typically sleep. \(\dot{V}_{{\rm o}_{2}} \) estimates at thermoneutrality in captive raised pygmy marmosets ranged from 34 to 11 ml O2 kg−1 min−1 during active periods to sleep periods. During this same time period, body temperature ranged from 39.2 to 35.5°C. Q10 for metabolism, assessed at similar thermal conductances, during these natural transitions was ~4.6, which suggests that the process of sleep and subsequent metabolic adjustments are associated with a suppression of metabolism below the normothermic basal value. These results have implications for the understanding of primate metabolism, and reinforce the notion that large diurnal changes in body temperature and metabolism are common strategies for energy conservation in small mammals.

Niemann-Pick C1-like 1 protein (NPC1L1), a transporter crucial in intestinal cholesterol absorption, is expressed in human liver but not in murine liver. To elucidate the role of hepatic NPC1L1 on lipid metabolism, we overexpressed NPC1L1 in murine liver utilizing adenovirus-mediated gene transfer. C57BL/6 mice, fed on normal chow with or without ezetimibe, were injected with NPC1L1 adenovirus (L1-mice) or control virus (Null-mice), and lipid analyses were performed five days after the injection. The plasma cholesterol levels increased in L1-mice, and FPLC analyses revealed increased cholesterol contents in large HDL lipoprotein fractions. These fractions, which showed α-mobility on agarose electrophoresis, were rich in apoE and free cholesterol. These lipoprotein changes were partially inhibited by ezetimibe treatment and were not observed in apoE-deficient mice. In addition, plasma and VLDL triglyceride (TG) levels decreased in L1-mice. The expression of microsomal triglyceride transfer protein (MTP) was markedly decreased in L1-mice, accompanied by the reduced protein levels of forkhead box protein O1 (FoxO1). These changes were not observed in mice with increased hepatic de novo cholesterol synthesis. These data demonstrate that cholesterol absorbed through NPC1L1 plays a distinct role in cellular and plasma lipid metabolism, such as the appearance of apoE-rich lipoproteins and the diminished VLDL-TG secretion.

Comparison of natural and pharmacological hypothermia in animals: Determination of activation energy of metabolism.

Change in Temperature Profile May Precede Fever and be an Early Indicator of Sepsis

Changes in Body Temperature and Basal Metabolic Rate of the Ama— A Commentary

> George Somero discusses Scholander et al.'s classic paper ‘Adaptation to cold in Arctic and tropical mammals and birds in relation to body temperature, insulation and basal metabolic rate’, published in The Biological Bulletin in 1950. It is unusual to re-visit a paper a half-century after

The thermoregulatory hypothesis proposes that endothermy in mammals and birds evolved as a thermoregulatory mechanism per se and that natural selection operated directly to increase body temperature and thermal stability through increments in resting metabolic rate. We experimentally tested this hypothesis by measuring the thermoregulatory consequences of increased metabolic rate in resting lizards (Varanus exanthematicus). A large metabolic increment was induced by feeding the animals and consequent changes in metabolic rate and body temperature were monitored. Although metabolic rate tripled at 32 degrees C and quadrupled at 35 degrees C, body temperature rose only about 0.5 degrees C. The rate of decline of body temperature in a colder environment did not decrease as metabolic rate increased. Thus, increasing the visceral metabolic rate of this ectothermic lizard established neither consequential endothermy nor homeothermy. These results are inconsistent with a thermoregulatory explanation for the evolution of endothermy.

Naked mole rats (Heterocephalus glaber) are poikilothermic, eusocial mammals in which the single dominant female breeds continuously throughout the year, producing approximately every 76 d litters of up to 27 young, with a mean litter size of 9 ± 1. We investigated the changes in metabolic rate (n = 8) and body temperature (n = 8) in breeding naked mole rat females throughout the 10-wk gestation period and during the first week of lactation. Metabolic rate from week 2 of pregnancy to parturition (1.9 ± 0.1 mL O2 ․ g⁻¹ ․ h⁻¹) was 1.4-fold higher than that of nonreproductive animals. Oxygen consumption increased in a biphasic manner, with the nadir at week 8, similar to the O₂ consumption observed in nonpregnant and very early pregnant females and statistically no different than the high rates associated with pregnancy. Oxygen consumption was maximal during lactation (3.0 ± 0.3 mL O₂ ․ g⁻¹ ․ h⁻¹) and was 160.3% of that during the initial week of pregnancy. Body temperature in early pregnancy was similar to ...

Gaseous Metabolism and Water Relations of the Zebra Finch, Taeniopygia castanotis

Thermal changes during dialysis strongly influence intra-dialytic hemodynamics. The mechanisms behind the increase in body temperature during hemodialysis (HD) are still not completely understood. The objective of this retrospective observational cohort study is to assess the effect of circadian variation on body temperature changes during HD by comparing results in patients treated on different treatment shifts. Data from the Renal Research Institute, New York, clinical database encompassing patients treated in six states in the USA were used. Data from January and August 2008 were used for analysis. Body temperature changes during HD were categorized by dialysis shifts. Patients with morning shifts (n = 1064), afternoon shifts (n = 730) and evening shifts (n = 210) were compared. Pre-dialysis body temperatures were significantly different among the different shifts [morning, 36.41 (95% confidence interval: 36.39-36.43°C), afternoon, 36.47 (36.45-36.49°C), evening, 36.67 (36.64-36.70°C), P < 0.001]. In August, but not in January, intra-dialytic increases in body temperature were significantly different between patients treated during morning [0.07 (0.058-0.082°C)], afternoon [0.03 (0.016-0.044°C)] and evening shifts [-0.01 (-0.032 to 0.012°C); P < 0.001 analysis of variance], although in January, treatment shift was a significant predictor of the intra-dialytic increase in body temperature. The intra-dialytic change in body temperature was related not only to the pre-dialysis body temperature (r(2) = 0.31; P < 0.001) but also to microbiological dialysate quality, treatment time and dialysate temperature. The intra-dialytic change in blood pressure (BP) was significantly related to changes in intra-dialytic body temperature irrespective of the study month. Both pre-dialytic body temperature as well as changes in body temperature are significantly related to the timing of the dialysis shifts, in phase with the circadian body temperature rhythm. Due to the relationship between body temperature changes and changes in intra-dialytic BP, these findings might be of additional relevance in the pathogenesis of intra-dialytic hypotension.

The durations of the intervals of torpor and euthermia during mammalian hibernation were found to be dependent on body mass. These relationships support the concept that the timing of body temperature changes is controlled by some metabolic process. Data were obtained from species spanning nearly three orders of magnitude in size, that were able to hibernate for over six months without food at 5 degrees C. The timing of body temperature changes was determined from the records of copper-constantan thermocouples placed directly underneath each animal. Because all species underwent seasonal changes in their patterns of hibernation, animals were compared in mid-winter when the duration of euthermic intervals was short and relatively constant and when the duration of torpid intervals was at its longest. Large hibernators remained euthermic longer than small hibernators (Fig. 2). This was true among and within species. The duration of euthermic intervals increased with mass at the same rate (mass 0.38) that mass-specific rates of euthermic metabolism decrease, suggesting that hibernators remain at high body temperatures until a fixed amount of metabolism has been completed. These data are consistent with the theory that each interval of euthermia is necessary to restore some metabolic imbalance that developed during the previous bout of torpor. In addition, small species remained torpid for longer intervals than large species (Fig. 3). The absolute differences between different-sized species were large, but, on a proportional basis, they were comparatively slight.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic water restriction resulted in a 30% decrease in metabolic rate and an over 50% decrease in evaporative loss in jackrabbits with no change in body temperature. Thus, evaporative cooling as a means of maintaining body temperature was minimized. Accommodation to measuring technique may account for part of the decrease in O2 consumption. Fractional water content increased, and solids decreased associated with a 10.6% weight loss due to chronic restriction, whereas plasma and extracellular volume decreased in proportion to weight loss. The biological half-life of water, T½, was increased from 5.8 to 11.6 days while water exchange decreased from 13.0% to 5.9% of the body water per day. In acutely dehydrated jackrabbits (3–5 days without water at 25 C), all body fluid compartments lost equal proportions (10.7%) with no change in metabolic rate. Similarly, oxygen consumption was unaffected, and plasma volume decreased in proportion to weight loss (5.5%) in jackrabbits acutely dehydrated in hyperthermic conditions (12–14 h at 35–40 C). The jackrabbit is similar to several other desert species in that it minimizes the loss of plasma volume when exposed to dehydration. Evans Blue space of 8.6% of body weight was shown to be a 36% overestimation of plasma volume as measured with iodinated (125I) albumin (6.3% of body weight).

People over the age of 60 have, on average, a lower temperature than the accepted 'normal' value of 37°C. There is also less variability in temperature, which means that older people may have little fever response to severe infection. People with cognitive impairment may have either higher or lower temperature; this may be due to loss of appropriate behavioural response to changes in temperature. Those with Alzheimer's disease sometimes have a modest increase in core body temperature, suggesting that change in basic metabolic rate may be responsible.

A novel role for interleukin 32 in cholestasis.