Adipose and skeletal muscle thermogenesis: studies from large animals

• Published in: Journal of endocrinology Vol. 237; no. 3; pp. R99 - R115
• Main Authors: Fuller-Jackson, John-Paul, Henry, Belinda A
• Format: Journal Article
• Language: English
• Published: England Bioscientifica Ltd 01.06.2018; Portland Press Ltd The Biochemical Society
• Subjects: Adipocytes; Adipose tissue; Adipose tissue (brown); Body fat; Body weight; Calcium; Clavicle; Creatine; Energy expenditure; Energy intake; Heat; Metabolic rate; Mitochondria; Musculoskeletal system; Neck; Physical activity; Protons; Review; Skeletal muscle; Thermogenesis; Uncoupling protein 1; pigs; thermogenesis; adipose tissue; weight loss; skeletal muscle; obesity; sheep
• ISSN: 0022-0795; 1479-6805
• DOI: 10.1530/JOE-18-0090

The balance between energy intake and energy expenditure establishes and preserves a ‘set-point’ body weight. The latter is comprised of three major components including metabolic rate, physical activity and thermogenesis. Thermogenesis is defined as the cellular dissipation of energy via heat production. This process has been extensively characterised in brown adipose tissue (BAT), wherein uncoupling protein 1 (UCP1) creates a proton leak across the inner mitochondrial membrane, diverting protons away from ATP synthesis and resulting in heat dissipation. In beige adipocytes and skeletal muscle, thermogenesis can occur independent of UCP1. Beige adipocytes have been shown to produce heat via UCP1 as well as via both futile creatine and calcium cycling pathways. On the other hand, the UCP1 homologue UCP3 is abundant in skeletal muscle and post-prandial thermogenesis has been associated with UCP3 and the futile calcium cycling. This review will focus on the differential contributions of adipose tissue and skeletal muscle in determining total thermogenic output and energy expenditure in large mammals. Sheep and pigs do not have a circumscribed brown fat depot but rather possess white fat depots that contain brown and beige adipocytes interspersed amongst white adipose tissue. This is representative of humans, where brown, beige and white adipocytes have been identified in the neck and supraclavicular regions. This review will describe the mechanisms of thermogenesis in pigs and sheep and the relative roles of skeletal muscle and adipose tissue thermogenesis in controlling body weight in larger mammals.