Effect of thyroid hormone on metabolic adaptation to fasting

Carter, William J.; Shakir, K.M. Mohamed; Hodges, S Konnar; Faas, Fred H.; Wynn, James

doi:10.1016/0026-0495(75)90154-7

Cited by 60 publications

(13 citation statements)

References 23 publications

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“…A general energy conserving physiological adaptation to starvation is a lowering of RMR (Keys et al, 1950;Kleiber, 1975;Fuglei and Øritsland, 1999b). It is thought that a reduction of fT 3 may explain the reduction of RMR observed during starvation (Carter et al, 1975). The decline in fT 3 during starvation in the present study coincided with a starvation-induced lowering of RMR found in arctic foxes (Fuglei and Øritsland, 1999a), which implies an association between fT 3 and RMR in arctic foxes during starvation.…”

Section: Discussionsupporting

confidence: 66%

Hormones and metabolites of arctic foxes (Alopex lagopus) in response to season, starvation and re-feeding

Fuglei

Aanestad

Berg

2000

Comparative Biochemistry and Physiology Part A: Molecular &

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Svalbard's arctic foxes experience large seasonal variations in light, temperature and food supply throughout the year, which may result in periods of starvation. The aim of this work is to investigate if there are seasonal variations in post-absorptive plasma thyroid hormones (free thyroxin (fT 4 ), free triiodothyronine (fT 3 ) and reverse triiodothyronine (rT 3 )) and metabolites (free fatty-acids (FFA) and b-hydroxybutyrate (b-OHB)) with season and their response to starvation and re-feeding. The concentrations of post-absorptive free triiodothyronine were significantly higher in November than May, while those of thyroxin, reverse triiodothyronine, free fatty-acids and b-hydroxybutyrate remained unchanged. Possible explanations for the seasonal variations in free triiodothyronine are discussed. There were no significant changes from post-absorptive concentrations of thyroxin and reverse triiodothyronine in starved and re-fed foxes. However, free triiodothyronine concentrations decreased during starvation and increased again with re-feeding both in May and November. Starvation induced high levels of free fatty acids in both May and November, indicating increased lipolysis. There was a significant increase in b-hydroxybutyrate in November only, indicating that arctic foxes are capable of protein conservation during starvation.

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Section: Discussionsupporting

confidence: 66%

Hormones and metabolites of arctic foxes (Alopex lagopus) in response to season, starvation and re-feeding

Fuglei

Aanestad

Berg

2000

Comparative Biochemistry and Physiology Part A: Molecular &

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“…This is surprising given the strong evidence for impacts of thyroid hormones on protein degradation in other animal systems (e.g. Carter et al, 1975). Ortiz and colleagues found that thyroid hormones increased across the fast in developing weaned pups and suggested that these changes were associated with mobilization of protein and synthesis of respiratory pigments (Ortiz et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

Sex differences in fuel use and metabolism during development in fasting juvenile northern elephant seals

Kelso

Champagne

Tift

et al. 2012

Journal of Experimental Biology

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SUMMARYMany polygynous, capital breeders exhibit sexual dimorphism with respect to body size and composition. Sexual dimorphism is often facilitated by sex differences in foraging behavior, growth rates and patterns of nutrient deposition during development. In species that undergo extended fasts during development, metabolic strategies for fuel use have the potential to influence future reproductive success by directly impacting somatic growth and acquisition of traits required for successful breeding. We investigated sexual dimorphism associated with metabolic strategies for fasting in developing northern elephant seals. Thirty-one juvenile seals of both sexes were sampled over extended fasts during annual autumn haul-outs. Field metabolic rate (FMR) and the contribution of protein catabolism to energy expenditure were estimated from changes in mass and body composition over 23±5days of fasting (mean ± s.d.). Protein catabolism was assessed directly in a subset of animals based on urea flux at the beginning and end of the fast. Regulatory hormones and blood metabolites measured included growth hormone, cortisol, thyroxine, triiodothyronine, insulin, glucagon, testosterone, estradiol, glucose, urea and -hydroxybutyrate. Males exhibited higher rates of energy expenditure during the fast but spared body protein stores more effectively than females. Rates of protein catabolism and energy expenditure were significantly impacted by hormone levels, which varied between the sexes. These data suggest that sex differences in fuel metabolism and energy expenditure during fasting arise early in juvenile development and may play an important role in the development of adult traits associated with reproductive success.

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“…The studies were performed in the morning after an overnight fast (12)(13)(14) [3][4] cm from the wedge position. Patency of the catheters was maintained by intermittent flushing with saline.…”

Section: Methodsmentioning

confidence: 99%

“…Such data would be of particular interest in that thyrotoxicosis has been reported to result in depletion of muscle (12) as well as hepatic glycogen stores (13). Furthermore, changes in thyroid hormone availability (specifically a reduction in triiodothyronine) have been implicated in the regulation of gluconeogenesis and protein catabolism during starvation (14,15). The present study was consequently undertaken to evaluate the effects of hyperthyroidism on splanchnic exchange of glucose and gluconeogenic substrate metabolism.…”

Section: Introductionmentioning

confidence: 99%

Influence of hyperthyroidism on splanchnic exchange of glucose and gluconeogenic precursors.

Wahren¹,

Wennlund²,

Nilsson³

et al. 1981

J. Clin. Invest.

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A B S T R A C T Arterial concentrations and splanchnic exchange ofglucose, amino acids, lactate, pyruvate, and glycerol were determined in 14 hyperthyroid patients and 12 healthy controls. Seven of the patients were restudied after 5-12 mo of medical management at which time there was chemical and clinical evidence of a euthyroid state.The arterial level of glucose was slightly higher (+ 10%) in the patient group and the glycerol concentration was three times greater among the patients. The plasma levels of the glycogenic amino acids, alanine, glycine, and serine were decreased by 20-30%, while the concentrations of leucine, isoleucine, and tyrosine were increased by 20-80%. The levels of lactate and pyruvate were similar in patients and controls as were insulin and glucagon concentrations.Splanchnic glucose output in the patient group was 35% lower than in controls. However, total splanchnic uptake of glucogenic precursors was 100% higher than in controls and showed a direct linear correlation with serum triiodothyronine. Total precursor uptake could account for 75% of splanchnic glucose output in the patients, compared to 26% in controls. The increase in uptake of lactate, alanine, and other amino acids was due to a 35-80% rise in splanchnic fractional extraction plus a 20% rise in estimated hepatic blood flow. When the patients were restudied after medical treatment splanchnic exchange of glucose and glucose precursors had reverted to normal values.The present findings demonstrate that in hyperthyroidism (a) total splanchnic glucose output is reduced in relation to controls, (b) splanchnic uptake of gluconeogenic precursors is accelerated, largely due to a rise in fractional extraction ofprecursor substrates and

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Effect of thyroid hormone on metabolic adaptation to fasting

Cited by 60 publications

References 23 publications

Hormones and metabolites of arctic foxes (Alopex lagopus) in response to season, starvation and re-feeding

Hormones and metabolites of arctic foxes (Alopex lagopus) in response to season, starvation and re-feeding

Sex differences in fuel use and metabolism during development in fasting juvenile northern elephant seals

Influence of hyperthyroidism on splanchnic exchange of glucose and gluconeogenic precursors.

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