Differential regulation of uncoupling protein gene homologues in multiple tissues of hibernating ground squirrels

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 1998-10, Vol.275 (4), p.1232-R1238
• Main Authors: Boyer, Bert B, Barnes, Brian M, Lowell, Bradford B, Grujic, Danica
• Format: Article
• Language: English
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.1998.275.4.r1232

1  Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775; and 2  Division of Endocrinology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215 Nonshivering thermogenesis in brown adipose tissue (BAT) provides heat through activation of a mitochondrial uncoupling protein (UCP1), which causes futile electron transport cycles without the production of ATP. Recent discovery of two molecular homologues, UCP2, expressed in multiple tissues, and UCP3, expressed in muscle, has resulted in investigation of their roles in thermoregulatory physiology and energy balance. To determine the expression pattern of Ucp homologues in hibernating mammals, we compared relative mRNA levels of Ucp 1, -2, and -3 in BAT, white adipose tissue (WAT), and skeletal muscle of arctic ground squirrels ( Spermophilus parryii ) hibernating at different ambient and body temperatures, with levels determined in tissues from ground squirrels not in hibernation. Here we report significant increases in mRNA levels for Ucp 2 in WAT (1.6-fold) and Ucp 3 in skeletal muscle (3-fold) during hibernation. These results indicate the potential for a role of UCP2 and UCP3 in thermal homeostasis during hibernation and indicate that parallel mechanisms and multiple tissues could be important for nonshivering thermoregulation in mammals. nonshivering thermogenesis; Spermophilus ; uncoupling protein 1; uncoupling protein 2; uncoupling protein 3