Thyroid function testing in elephant seals in health and disease

Yochem, Pamela K.; Gulland, Frances M. D.; Stewart, Brent S.; Haulena, Martin; Mazet, Jonna A. K.; Boyce, Walter M.

doi:10.1016/j.ygcen.2007.11.012

Cited by 13 publications

(10 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Values of tT3 in fasting adult male elephant seals are comparable to values observed in non-molting, adult members of other species of phocid seal, regardless of whether they are fasting or intermittently feeding (see Haulena et al, 1998 for a table providing thyroid hormone values for phocid seals by age and reproductive condition). However, fed yearling elephant seals demonstrated tT3 levels nearly half, and tT4 levels nearly double, that observed in fasting adult male elephant seals (Yochem et al, 2008). Studies in weaned elephant seals undergoing long-term fasts revealed relatively stable tT 3 across the fast, but an increase in tT 4 between the first 2 weeks of fasting and the eighth week of fasting (Ortiz et al, 2001a;2003).…”

Section: Discussionmentioning

confidence: 80%

“…Individuals with higher DEE exhibited elevations of thyroid across the fast and this was associated with reductions in protein sparing. Thyroid hormones have been demonstrated to vary as a function of age and physiological condition in phocid seals (Boily, 1996;Haulena et al, 1998;Sormo et al, 2005;Stokkan et al, 1995;Woldstad and Jenssen, 1999;Yochem et al, 2008;Bennett et al 2012). Values of tT3 in fasting adult male elephant seals are comparable to values observed in non-molting, adult members of other species of phocid seal, regardless of whether they are fasting or intermittently feeding (see Haulena et al, 1998 for a table providing thyroid hormone values for phocid seals by age and reproductive condition).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Hormone and metabolite changes associated with extended breeding fasts in male northern elephant seals (Mirounga angustirostris)

Crocker

Ortiz

Houser

et al. 2012

Comparative Biochemistry and Physiology Part A: Molecular &

View full text Add to dashboard Cite

We measured metabolic hormones and several key metabolites in breeding adult male northern elephant seals to examine the regulation of fuel metabolism during extended natural fasts of over 3 months associated with high levels of energy expenditure. Males were sampled twice, early and late in the fast, losing an average of 23% of body mass and 47% of adipose stores between measurements. Males exhibited metabolic homeostasis over the breeding fast with no changes in glucose, non-esterified fatty acids, or blood urea nitrogen. Ketoacids increased over the fast but were very low when compared to other fasting species. Changes within individuals in total triiodothyronine (tT 3 ) were positively related to daily energy expenditure (DEE) and protein catabolism. Differences in levels of thyroid hormones relative to that observed in weaned pups and females suggest a greater deiodination of T 4 to support the high DEE of breeding males. Relative levels of leptin and ghrelin were consistent with the suppression of appetite but a significant reduction in growth hormone across the fast was contrary to expectation in fasting mammals. The lack of the increase in cortisol during fasting found in conspecific weaned pups and lactating females may contribute to the ability of breeding males to spare protein despite high levels of energy expenditure. Together these findings reveal significant differences with conspecifics under varying nutrient demands, suggesting metabolic adaptation to extended high energy fasts.

show abstract

Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Hormone and metabolite changes associated with extended breeding fasts in male northern elephant seals (Mirounga angustirostris)

Crocker

Ortiz

Houser

et al. 2012

Comparative Biochemistry and Physiology Part A: Molecular &

View full text Add to dashboard Cite

show abstract

“…TH function has important implications in northern elephant seal health and disease (Yochem et al. ). In fasting adult northern elephant seals, THs levels are unchanged (Crocker et al.…”

Section: Introductionmentioning

confidence: 99%

“…Although this highlights the potential link between TH and SIRT1, the mechanism behind this signaling pathway is poorly understood. TH function has important implications in northern elephant seal health and disease (Yochem et al 2008). In fasting adult northern elephant seals, THs levels are unchanged (Crocker et al 2012b); however, studies examining SIRT1 activity in mammals that undergo a natural and prolonged fasting period are lacking.…”

Section: Introductionmentioning

confidence: 99%

Fasting increases the phosphorylation of AMPK and expression of sirtuin1 in muscle of adult male northern elephant seals ( Mirounga angustirostris )

et al. 2017

View full text Add to dashboard Cite

Fasting typically suppresses thyroid hormone (TH)‐mediated cellular events and increases sirtuin 1 (SIRT1) activity. THs may regulate metabolism through nongenomic pathways and directly through activation of adenosine monophosphate‐activated protein kinase (AMPK). Adult male elephant seals (Mirounga angustirostris) are active, hypermetabolic, and normothermic during their annual breeding fast, which is characterized by stable TH levels. However, the contribution of TH to maintenance of their fasting metabolism is unknown. To investigate the fasting effects on cellular TH‐mediated events and its potential association with SIRT1 and AMPK, we quantified plasma TH levels, mRNA expressions of muscle SIRT1 and TH‐associated genes as well as the phosphorylation of AMPK in adult, male northern elephant seals (n = 10/fasting period) over 8 weeks of fasting (early vs. late). Deiodinase type I (DI1) expression increased twofold with fasting duration suggesting that the potential for TH‐mediated cellular signaling is increased. AMPK phosphorylation increased 61 ± 21% with fasting suggesting that cellular metabolism is increased. The mRNA expression of the TH transporter, monocarboxylate transporter 10 (MCT10), increased 2.4‐fold and the TH receptor (THrβ‐1) decreased 30‐fold suggesting that cellular uptake of T4 is increased, but its subsequent cellular effects such as activation of AMPK are likely nongenomic. The up‐regulation of SIRT1 mRNA expression (2.6‐fold) likely contributes to the nongenomic activation of AMPK by TH, which may be necessary to maintain the expression of PGC‐1α. These coordinated changes likely contribute to the up‐regulation of mitochondrial metabolism to support the energetic demands associated with prolonged fasting in adult seals.

show abstract

“…Patchy to extensive alopecia and ulcerative skin lesions are frequently observed in northern elephant seals (Mirounga angustirostris) and although the syndrome has been extensively investigated, its etiology remains obscure (Beckmen et al 1997;Yochem et al 2008). Patchy alopecia is observed in Steller sea lions (Eumetopias jubatus) and California sea lions (Zalophus californianus) in western North American waters and extensive alopecia is seen in gray seals (Halichoerus grypus) around the Farne Isles, United Kingdom (Gulland et al 2001a).…”

mentioning

confidence: 99%

Characterization and causal investigations of an alopecia syndrome in Australian fur seals (Arctocephalus pusillus doriferus)

Lynch¹,

Kirkwood²,

Gray³

et al. 2012

J Mammal

View full text Add to dashboard Cite

Thyroid function testing in elephant seals in health and disease

Cited by 13 publications

References 32 publications

Hormone and metabolite changes associated with extended breeding fasts in male northern elephant seals (Mirounga angustirostris)

Hormone and metabolite changes associated with extended breeding fasts in male northern elephant seals (Mirounga angustirostris)

Fasting increases the phosphorylation of AMPK and expression of sirtuin1 in muscle of adult male northern elephant seals ( Mirounga angustirostris )

Characterization and causal investigations of an alopecia syndrome in Australian fur seals (Arctocephalus pusillus doriferus)

Contact Info

Product

Resources

About