Radioglucose utilization by active, hibernating, and arousing ground squirrels

Tashima, LS; Adelstein, S. James; Cp, Lyman

doi:10.1152/ajplegacy.1970.218.1.303

Cited by 67 publications

(32 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Inhibition of pyruvate dehydrogenase by PDK-4 offers a mechanism for the wellestablished findings of Lyman and colleagues (15), who showed that glycolytic intermediates were blocked from entering the tricarboxylic acid cycle during hibernation. Arrest of carbohydrate oxidation by phosphorylation of pyruvate dehydrogenase is reversed by a phosphatase which restores the conversion of pyruvate to Ac-CoA (reviewed in ref.…”

Section: Resultsmentioning

confidence: 92%

“…16). The reversibility of this inhibition resembles the reversibility of hibernation itself, because it allows for the resumption of glucose oxidation seen shortly after arousal (15).…”

Section: Resultsmentioning

confidence: 93%

“…We propose that the inhibition of glucose oxidation by PDK-4 impedes carbohydrate catabolism and contributes to the observed metabolic rate depression. The resulting anaerobic glycolysis (21) generates three-carbon molecules such as lactate and dihydroxyacetone phosphate that can participate in gluconeogenesis (15,22) and cardiac triglyceride synthesis, respectively. Gluconeogenic activity is enhanced during hibernation (23,24) and is additionally fueled by the release of glycerol from the hydrolysis of triglycerides in adipose tissue (22,25).…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Low-temperature carbon utilization is regulated by novel gene activity in the heart of a hibernating mammal

Andrews

Squire

Bowen

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

143

126

View full text Add to dashboard Cite

Hibernation is a physiological adaptation characterized by dramatic decreases in heart rate, body temperature, and metabolism, resulting in long-term dormancy. Hibernating mammals survive for periods up to 6 mo in the absence of food by minimizing carbohydrate catabolism and using triglyceride stores as their primary source of fuel. The cellular and molecular mechanisms underlying the changes from a state of activity to the hibernating state are poorly understood; however, the selective expression of genes offers one level of control. To address this problem, we used a differential gene expression screen to identify genes that are responsible for the physiological characteristics of hibernation in the heart of the thirteen-lined ground squirrel (Spermophilus tridecemlineatus). Here, we report that genes for pancreatic lipase and pyruvate dehydrogenase kinase isozyme 4 are up-regulated in the heart during hibernation. Pancreatic lipase is normally expressed exclusively in the pancreas, but when expressed in the hibernating heart it liberates fatty acids from triglycerides at temperatures as low as 0°C. Pyruvate dehydrogenase kinase isozyme 4 inhibits carbohydrate oxidation and depresses metabolism by preventing the conversion of pyruvate to Ac-CoA. The resulting anaerobic glycolysis and low-temperature lipid catabolism provide evidence that adaptive changes in cardiac physiology are controlled by the differential expression of genes during hibernation.Maintenance of normal physiological function in mammals usually requires a constant body temperature of approximately 37°C. Lowering body temperature 10-15°C for an extended period of time often leads to hypothermic dysfunction of several organ systems, while lowering the temperature 30°C below the optimum usually results in death (1). An exception is seen in hibernating mammals. Certain ''deep'' hibernators lower their body temperature to 2-7°C, reduce their heart rate from 300 beats/min to 2-10 beats/min, and lessen their O 2 consumption as much as 50-fold (2). This amazing transformation of whole-animal physiology is completely reversible and serves as an adaptation to conserve energy reserves during extended periods of harsh climate and little or no food. Energy reserves in the form of fat sustain vital functions during long bouts of torpor and support periodic rewarming to euthermic temperatures during interbout arousals. Despite years of work on the ecology and physiology of hibernation in mammals, the underlying molecular genetic basis of this adaptation has received little attention.The reduction in metabolism that accompanies the hypothermia of hibernation is not only a function of thermodynamics, but also the result of precisely regulated metabolic reactions (3). Hibernating mammals survive the entire winter without feeding by limiting their carbohydrate catabolism and using fat stores as their primary source of fuel (reviewed in ref.2). We have begun to address the genetic control of this process by using a differential gene expression screen (4) ...

show abstract

Section: Resultsmentioning

confidence: 92%

“…16). The reversibility of this inhibition resembles the reversibility of hibernation itself, because it allows for the resumption of glucose oxidation seen shortly after arousal (15).…”

Section: Resultsmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Low-temperature carbon utilization is regulated by novel gene activity in the heart of a hibernating mammal

Andrews

Squire

Bowen

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

143

126

View full text Add to dashboard Cite

show abstract

“…Rather, the high rates of protein breakdown and net protein degradation in bats aroused from hibernation are comparable to those seen in short term fasting, when tissue protein is rapidly degraded to supply the increased gluconeogenic demand (Adibi 1976;Pozefsky et al 1976;Chang and Goldberg 1978a, b;Li et al 1979;Snell 1980). Glucose oxidation appears to account for a significantly greater proportion of metabolism during periodic arousals than during torpor bouts in hibernating mammals (South and House 1967;Tashima et al 1970;Yacoe 1982). Since glycogen stores are small (Dodgen and Blood 1956;Leonard and Wimsatt 1959;Yacoe 1982) and the contribution of glycerol is coupled to the rate of fat oxidation, the increased demand for glucose might be met by gluconeogenesis from tissue protein.…”

Section: Discussionmentioning

confidence: 97%

Protein metabolism in the pectoralis muscle and liver of hibernating bats,Eptesicus fuscus

Yacoe

1983

J Comp Physiol B

View full text Add to dashboard Cite

Summary. Seasonal variations in protein metabolism of the pectoralis muscle and liver of the big brown bat, Eptesicus fuscus, are examined in relation to seasonal changes in physiological status. A technique is described for the determination of protein synthetic rates in vivo in animals too small for conventional methods. The results indicate no detectable rates of protein synthesis in hibernating bats during torpor bouts ( Table 2). Rates of synthesis in hibernating bats during periods of arousal are comparable to those of active summer bats (Table 2), despite the fact that the hibernating bats had not eaten in over 2 months. Rates of protein degradation were calculated from the rate of urea formation in torpid bats (Figs. 4, 5), the overall loss of pectoralis muscle and liver protein mass during hibernation (Table 3), the proportion of the total time of hibernation spent in torpor and arousal (Table 1), and the observed rates of protein synthesis (Table 2). These estimates (Table 4) indicate negligible rates of protein degradation in torpid bats. However, protein degradation during periodic arousals is comparable to that of summer bats after an overnight fast. These findings are consistent with earlier observations suggesting that significant gluconeogenesis from tissue protein occurs during spontaneous arousals from hibernation.

show abstract

“…6A), lactating northern elephant seals, and of 8 months for the subterranean salamander P. anguinus (98,101,231,259,261,272,420,433,567). In general, blood glucose levels likewise remain relatively stable during hibernation for mammals, with any drop during torpor reversed during interbout arousals via gluconeogenesis (310,505,544). In other species, plasma glucose concentrations have been observed to: (1) decline early in a fast and largely remain stable thereafter; (2) decline gradually throughout the fast; or, (3) remain stable for an extended period before significantly decreasing (Fig.…”

Section: Glucosementioning

confidence: 99%

Integrative Physiology of Fasting

Secor

Carey

2016

Comprehensive Physiology

149

144

View full text Add to dashboard Cite

Extended bouts of fasting are ingrained in the ecology of many organisms, characterizing aspects of reproduction, development, hibernation, estivation, migration, and infrequent feeding habits. The challenge of long fasting episodes is the need to maintain physiological homeostasis while relying solely on endogenous resources. To meet that challenge, animals utilize an integrated repertoire of behavioral, physiological, and biochemical responses that reduce metabolic rates, maintain tissue structure and function, and thus enhance survival. We have synthesized in this review the integrative physiological, morphological, and biochemical responses, and their stages, that characterize natural fasting bouts. Underlying the capacity to survive extended fasts are behaviors and mechanisms that reduce metabolic expenditure and shift the dependency to lipid utilization. Hormonal regulation and immune capacity are altered by fasting; hormones that trigger digestion, elevate metabolism, and support immune performance become depressed, whereas hormones that enhance the utilization of endogenous substrates are elevated. The negative energy budget that accompanies fasting leads to the loss of body mass as fat stores are depleted and tissues undergo atrophy (i.e., loss of mass). Absolute rates of body mass loss scale allometrically among vertebrates. Tissues and organs vary in the degree of atrophy and downregulation of function, depending on the degree to which they are used during the fast. Fasting affects the population dynamics and activities of the gut microbiota, an interplay that impacts the host's fasting biology. Fasting-induced gene expression programs underlie the broad spectrum of integrated physiological mechanisms responsible for an animal's ability to survive long episodes of natural fasting.

show abstract

Radioglucose utilization by active, hibernating, and arousing ground squirrels

Cited by 67 publications

References 0 publications

Low-temperature carbon utilization is regulated by novel gene activity in the heart of a hibernating mammal

Low-temperature carbon utilization is regulated by novel gene activity in the heart of a hibernating mammal

Protein metabolism in the pectoralis muscle and liver of hibernating bats,Eptesicus fuscus

Integrative Physiology of Fasting

Contact Info

Product

Resources

About