Thyroid hormone resistance in hibernating ground squirrels, Spermophilus richardsoni

Magnus, T. H.; Henderson, Nancy

doi:10.1016/0016-6480(88)90025-1

Cited by 39 publications

(21 citation statements)

References 25 publications

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“…THE JOURNAL OF EXPERIMENTAL BIOLOGY 4648 concentration in hibernating ground squirrels results from reduced TH metabolism, accompanied by a reduction in nuclear receptors, suggesting that TH function is suppressed despite the increase in circulating levels (i.e. cryptically hyperthyroid) (Magnus and Henderson, 1988a;Magnus and Henderson, 1988b). Such variability in the regulation of TH levels and function in food-deprived mammals demonstrates the diversity of TH physiology during periods of acute or chronic food deprivation, and highlights the necessity to perform more comprehensive studies into the functional relevance of these differences.…”

Section: Discussionmentioning

confidence: 99%

“…Alternatively, metabolically quiescent hibernators such as the ground squirrel respond to hibernation-associated food deprivation differently: reducing TH metabolism, which results in elevated TH levels (Demeneix and Henderson, 1978a; Demeneix and Henderson, 1978b). However, in the presence of reduced receptor number and binding affinity (Magnus and Henderson, 1988a;Magnus and Henderson, 1988b), these elevated levels make these animals cryptically hyperthyroid and render these TH concentrations essentially non-functional. Furthermore, unlike humans and rodents, T 3 levels remain constant while T 4 levels decrease during fasting in the house musk shrew ( THE JOURNAL OF EXPERIMENTAL BIOLOGY 4650 deiodination and T 3 utilization are increased, and subsequently cellular metabolism.…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, circulating levels of TH decreased in wintering bears (Azizi et al, 1979). However, in hibernating ground squirrels, T 3 levels increased (Demeneix and Henderson, 1978a; Demeneix and Henderson, 1978b) because of a decrease in metabolic clearance from circulation, and in the presence of reduced TH receptor number and binding affinity (Magnus and Henderson, 1988a;Magnus and Henderson, 1988b). This increase in plasma T 3 is characteristic of cryptic hyperthyroidism, reducing the functionality of the elevated circulating levels.…”

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confidence: 99%

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Prolonged food deprivation increases mRNA expression of deiodinase 1 and 2, and thyroid hormone receptor β-1 in a fasting-adapted mammal

Martinez

Soñanez‐Organis

Vázquez‐Medina

et al. 2013

Journal of Experimental Biology

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SUMMARYFood deprivation in mammals is typically associated with reduced thyroid hormone (TH) concentrations and deiodinase content and activity to suppress metabolism. However, in prolonged-fasted, metabolically active elephant seal pups, TH levels are maintained, if not elevated. The functional relevance of this apparent paradox is unknown and demonstrates variability in the regulation of TH levels, metabolism and function in food-deprived mammals. To address our hypothesis that cellular TH-mediated activity is upregulated with fasting duration, we quantified the mRNA expression and protein content of adipose and muscle deiodinase type I (DI1) and type II (DI2), and TH receptor beta-1 (THrβ-1) after 1, 3 and 7 weeks of fasting in northern elephant seal pups (N=5-7 per week). Fasting did not decrease the concentrations of plasma thyroid stimulating hormone, total triiodothyronine (tT 3 ), free T 3 , total thyroxine (tT 4 ) or free T 4 , suggesting that the hypothalamic-pituitary-thyroid axis is not suppressed, but rather maintained during fasting. Mean mRNA expression of adipose DI1 and DI2 increased threefold and fourfold, respectively, and 20-and 30-fold, respectively, in muscle. With the exception of adipose DI1, protein expression of adipose DI2 and muscle DI1 and DI2 increased twofold to fourfold. Fasting also increased adipose (fivefold) and muscle (fourfold) THrβ-1 mRNA expression, suggesting that the mechanisms mediating cellular TH activity are upregulated with prolonged fasting. The data demonstrate a unique, atypical mechanism of TH activity and regulation in mammals adapted to prolonged food deprivation in which the potential responsiveness of peripheral tissues and cellular TH activity are increased, which may contribute to their lipid-based metabolism.Key words: lipid metabolism, reverse T3, seal, thyroxine, triiodothyronine. THE JOURNAL OF EXPERIMENTAL BIOLOGY 4648 concentration in hibernating ground squirrels results from reduced TH metabolism, accompanied by a reduction in nuclear receptors, suggesting that TH function is suppressed despite the increase in circulating levels (i.e. cryptically hyperthyroid) (Magnus and Henderson, 1988a;Magnus and Henderson, 1988b). Such variability in the regulation of TH levels and function in food-deprived mammals demonstrates the diversity of TH physiology during periods of acute or chronic food deprivation, and highlights the necessity to perform more comprehensive studies into the functional relevance of these differences.Northern elephant seals, Mirounga angustirostris (Gill 1866), naturally fast from food and water for up to 3 months while on land (Ortiz et al., 1978; Crocker et al., 1998;Le Boeuf and Laws, 1994), and during the post-weaning fast, oxidation of non-esterified fatty acids (NEFAs) accounts for approximately 95% of the pup's metabolic rate (Ortiz et al., 1978;Viscarra et al., 2012). The fasting metabolism of seals is primarily dependent on lipid oxidation (Crocker et al., 1998;Pramfalk et al., 2011; Crocker et al., 2012a; Crocker et al., 2012...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Prolonged food deprivation increases mRNA expression of deiodinase 1 and 2, and thyroid hormone receptor β-1 in a fasting-adapted mammal

Martinez

Soñanez‐Organis

Vázquez‐Medina

et al. 2013

Journal of Experimental Biology

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“…These mammals can reduce dramatically their basal metabolic, heart, and respiratory rates as well as their body temperature during hibernation (Magnus and Henderson, 1988;Weekley, 1995). Among mammalian hibernators, Jaculus orientalis is an excellent model for hibernation research due to its small body size and distinct behavioural pattern in relation to hibernation.…”

Section: Discussionmentioning

confidence: 99%

Prehibernation and hibernation effects on D-3-hydroxybutyrate dehydrogenase of heavy and light mitochondria from liver of jerboa (Jaculus orientalis) and related metabolism

Mountassif¹,

Kabine²,

Latruffe³

et al. 2007

Comparative Biochemistry and Physiology Part B: Biochemistry an

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Kebbaj To cite this version:Driss Mountassif, Mostafa Kabine, Norbert Latruffe, M'Hammed Saïd El Kebbaj. Prehibernation and hibernation effects on the D-3-hydroxybutyrate dehydrogenase of the heavy and light mitochondria from liver jerboa (Jaculus orientalis) and related metabolism.. Biochimie, Elsevier, 2007, 89 (8) Abstract:The D-3-hydroxybutyrate dehydrogenase (BDH) (EC 1.1.1.30) from liver jerboa (Jaculus orientalis), a ketone body converting enzyme in mitochondria, in two populations of mitochondria (heavy and light) has been studied in different jerboa states (euthermic, prehibernatingand hibernating). The results reveal: (1) important variations between states in terms of ketones bodies, glucose and lipid levels; (2) significant differences between the BDH of the two mitochondrial populations in term of protein expression and kinetic properties. These results suggest that BDH leads an important conformational change depending on the physiological state of jerboa. This BDH structural change could be the consequence of the lipid composition modifications in inner mitochondrial membrane leading to changes in BDH catalytic properties.

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“…Observations of enhanced binding of T 4 by thyroid binding globulin (TBG) in hibernating ground squirrels and wood chuck have led to the suggestion that elevated TBG levels are partially responsible for winter associated increase in serum concentration of thyroid hormones (Magnus & Henderson, 1988;Young et al, 1986). The hibernating bat, Myotis lucifugus also showed high TBG levels during winter (Damassa at al., 1995).…”

Section: Discussionmentioning

confidence: 99%

Changes in the thyroid gland during the reproductive cycle of the male vespertilionid bat, Scotophilus heathi

Krishna

Singh

1998

Rev. Bras. Biol.

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The aim of present study was to compare the changes in thyroid gland with the reproductive cycle of S. heathi. Thyroid showed marked seasonal variation in weight, quantity of colloid and follicular epithelial height, suggesting the thyroid gland to be inactive during quiescence and winter dormancy and active during the time of recrudescence and breeding similarly to the testicular cycle. Plasma thyroxin (T 4 ) concentration showed a significant seasonal change with high concentration during breeding and post-breeding and low concentration during quiescence. However, the T 4 concentration increased from breeding to post-breeding phase, when the testes weight was declining. It is suggested that in S. heathi the positive correlation between thyroid and testicular cycles occurs only during the phases of the reproductive cycle when the body weight and testicular activity are also closely correlated.Key words: Thyroid, thyroxin, testes, bat, body weight, reproduction. RESUMO Mudanças na glândula tireóide durante o ciclo reprodutivo masculino em um morcego vespertilionídeo Scotophilus heathiO objetivo do presente estudo foi comparar as mudanças na glândula tireóide com o ciclo reprodutivo de S. heathi. A tireóide mostrou variação sazonal marcada em peso, quantidade de colóide e altura do epitélio folicular, sugerindo que esta glândula está inativa durante a quiescência e o torpor de inverno e ativa durante o tempo de recrudescência e acasalamento, similarmente ao ciclo testicular. A concentração de tiroxina (T 4 ) do plasma mostrou significantes mudanças sazonais com alta concentração durante o acasalamento e pós-acasalamento e baixa concentração durante a quiescência. Entretanto, a concentração plasmática de T 4 aumentou da fase reprodutiva à pós-reprodutiva, quando o peso dos testículos estava se reduzindo. Sugere-se que, em S. heathi, a estreita correlação entre os ciclos testicular e tireóideo durante algumas fases do ciclo reprodutivo esteja relacionada à sensibilidade aumentada no período reprodutivo e à atividade metabólica.

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Thyroid hormone resistance in hibernating ground squirrels, Spermophilus richardsoni

Cited by 39 publications

References 25 publications

Prolonged food deprivation increases mRNA expression of deiodinase 1 and 2, and thyroid hormone receptor β-1 in a fasting-adapted mammal

Prolonged food deprivation increases mRNA expression of deiodinase 1 and 2, and thyroid hormone receptor β-1 in a fasting-adapted mammal

Prehibernation and hibernation effects on D-3-hydroxybutyrate dehydrogenase of heavy and light mitochondria from liver of jerboa (Jaculus orientalis) and related metabolism

Changes in the thyroid gland during the reproductive cycle of the male vespertilionid bat, Scotophilus heathi

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