Peripheral ghrelin stimulates feeding behavior and positive energy balance in a sciurid hibernator

Healy, Jessica E.; Bateman, Jenna L.; Ostrom, Cara E.; Florant, Gregory L.

doi:10.1016/j.yhbeh.2011.01.013

Cited by 24 publications

(16 citation statements)

References 34 publications

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“…In ground squirrels, ghrelin levels are low during hibernation relative to the active season (252), which may contribute to the suppression of appetite during winter fasting. During summer, fasts of 1, 3, or 5 days increased circulating ghrelin levels relative to controls, although concentrations did not vary with length of the fast (254).…”

Section: Adiponectin Leptin and Ghrelinmentioning

confidence: 99%

Integrative Physiology of Fasting

Secor

Carey

2016

Comprehensive Physiology

150

144

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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.

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Section: Adiponectin Leptin and Ghrelinmentioning

confidence: 99%

Integrative Physiology of Fasting

Secor

Carey

2016

Comprehensive Physiology

150

144

View full text Add to dashboard Cite

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“…It also appears to be regulated at different levels during different seasons, low in the spring upon emergence from hibernation, gradually increasing in the summer, high during the autumnalhyperphagic period, and extremely low during the winter (Healy et al 2010(Healy et al , 2011a. Peripheral injection of ghrelin causes an increase in food intake during all seasons, even in normally aphagic hibernators (Healy et al 2011a).…”

Section: Ghrelin and Its Role In Food Intakementioning

confidence: 99%

The regulation of food intake in mammalian hibernators: a review

Florant

Healy

2011

J Comp Physiol B

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One of the most profound hallmarks of mammalian hibernation is the dramatic reduction in food intake during the winter months. Several species of hibernator completely cease food intake (aphagia) for nearly 7 months regardless of ambient temperature and in many cases, whether or not food is available to them. Food intake regulation has been studied in mammals that hibernate for over 50 years and still little is known about the physiological mechanisms that control this important behavior in hibernators. It is well known from lesion experiments in non-hibernators that the hypothalamus is the main brain region controlling food intake and therefore body mass. In hibernators, the regulation of food intake and body mass is presumably governed by a circannual rhythm since there is a clear seasonal rhythm to food intake: animals increase food intake in the summer and early autumn, food intake declines in autumn and actually ceases in winter in many species, and resumes again in spring as food becomes available in the environment. Changes in circulating hormones (e.g., leptin, insulin, and ghrelin), nutrients (glucose, and free fatty acids), and cellular enzymes such as AMP-activated protein kinase (AMPK) have been shown to determine the activity of neurons involved in the food intake pathway. Thus, it appears likely that the food intake pathway is controlled by a variety of inputs, but is also acted upon by upstream regulators that are presumably rhythmic in nature. Current research examining the molecular mechanisms and integration of environmental signals (e.g., temperature and light) with these molecular mechanisms will hopefully shed light on how animals can turn off food intake and survive without eating for months on end.

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“…Previous studies in hibernating species suggest involvement of AMPK and SIRT1 in the metabolic adjustments during seasonal adaptation. In marmots (Marmota flaviventris) and ground squirrels (Callospermophilus lateralis) hypothalamic AMPK participates in the regulation of food intake during hibernation season (Florant et al 2010;Healy et al 2011a). In peripheral tissues, such as white adipose tissues (WAT) and brown adipose tissues (BAT) and liver, AMPK expression and phosphorylation vary in response to different stages of the torpor bout and also between the summer-and winteracclimatized euthermic ground squirrels (C. lateralis and Ictidomys tridecemlineatus; Horman et al 2005;Healy et al 2011b;Lanaspa et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Expression of AMPK, SIRT1, and ACC Differs between Winter- and Summer-Acclimatized Djungarian Hamsters

Kinnunen

Mänttäri

Saarela

2017

Physiological and Biochemical Zoology

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The wintering strategy of the Djungarian hamster (Phodopus sungorus) includes a naturally occurring decrease in food intake and body mass. Our aim was to investigate the conceivable role of the metabolic regulators, AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1), in the seasonal adaptation of the Djungarian hamster. In addition, a rate-limiting enzyme in fatty acid synthesis and oxidation, acetyl CoA carboxylase (ACC), was studied. Relative protein expressions and phosphorylated forms (pAMPK and pACC) were determined by Western blot from subcutaneous white adipose tissues (sWAT), abdominal white adipose tissues (aWAT), interscapular brown adipose tissues (iBAT), skeletal muscle, and hypothalamus of winter- and summer-acclimatized hamsters. The winter group had higher AMPK expression in sWAT, aWAT, and iBAT, but the relative amount of phosphorylated protein (pAMPK/AMPK ratio) was lower in these tissues. Furthermore, ACC expression was higher in sWAT and iBAT of the winter animals. pACC (inactive form) levels were higher in all adipose tissues, yet a lower pACC/ACC ratio was detected in iBAT of the winter hamsters. Muscle AMPK expression was lower but pAMPK/AMPK ratio higher in the winter group. SIRT1 expression was higher in muscle and all adipose tissues of the winter hamsters. Hypothalamic protein expressions did not differ between the groups. Higher expressions of AMPK, ACC, and SIRT1 in WAT and iBAT of the winter hamsters suggest a role in the regulation of lipid reserves and increased thermogenic capacity characteristic to the winter-adapted Djungarian hamsters.

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Peripheral ghrelin stimulates feeding behavior and positive energy balance in a sciurid hibernator

Cited by 24 publications

References 34 publications

Integrative Physiology of Fasting

Integrative Physiology of Fasting

The regulation of food intake in mammalian hibernators: a review

Expression of AMPK, SIRT1, and ACC Differs between Winter- and Summer-Acclimatized Djungarian Hamsters

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