Brown fat thermogenesis in cold-acclimated rats is not abolished by the suppression of thyroid function.
The effects of long-term cold exposure on brown adipose tissue (BAT) thermogenesis in hypothyroid rats have been examined. Thyroid ablation was performed in normal rats after 2 mo of exposure to 4 degrees C, when BAT hypertrophy and thermogenic activity were maximal. After ablation, hypothyroid and normal controls remained in the cold for 2 additional months. At the end of the 4-mo cold exposure, all untreated hypothyroid rats were alive, had normal body temperature, and had gained an average 12.8% more weight than normal controls. Long-term cold exposure of hypothyroid rats markedly increased BAT weight, mitochondrial proteins, uncoupling protein (UCP)-1, mRNA for UCP-1, and oxygen consumption to levels similar to those seen in cold-exposed normal rats. The results indicate that thyroid hormones are required for increased thermogenic capacity to occur as an adaptation to long-term cold exposure. However, cold adaptation can be maintained in the absence of thyroid hormone.
Zaninovich
Angel A
AA
Thyroid Research Laboratory, Nuclear Medicine Center, University Hospital, 1120 Buenos Aires, Argentina. azaninovich@sinectis.com.ar
Raíces
Marcela
M
Rebagliati
Inés
I
Ricci
Conrado
C
Hagmüller
Karl
K
D000064:Acclimatization; D002001:Adipose Tissue, Brown / Q000502:physiology* / Q000503:physiopathology; D000818:Animals; D013956:Antithyroid Agents / Q000494:pharmacology; D001835:Body Weight; D002352:Carrier Proteins / Q000378:metabolism; D003080:Cold Temperature; D005260:Female; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D007037:Hypothyroidism / Q000378:metabolism / Q000503:physiopathology; D007473:Ion Channels; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008713:Methimazole / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D010101:Oxygen Consumption; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D022722:Thermogenesis; D013961:Thyroid Gland / Q000502:physiology* / Q000503:physiopathology; D013997:Time Factors; D000071256:Uncoupling Protein 1
D013956:Antithyroid Agents; D002352:Carrier Proteins; D007473:Ion Channels; D007527:Isoenzymes; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; C000604373:Ucp1 protein, rat; D000071256:Uncoupling Protein 1; D008713:Methimazole; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases