Abstract:

Brown Adipose Tissue (BAT) present only in mammals play a significant role in maintaining body temperature through non-shivering thermogenesis during the early days of extra-uterine life. “Metabolic Winter Hypothesis”, suggests that cold exposure is one the most powerful and physiological stimulus for BAT activation resulting in weight loss through increased thermogenesis. The objective of this study was to review the relationship between cold stress (metabolic winter hypothesis) and related factors in energy metabolism through activation of brown adipose tissue. Literature search was conducted using Science direct, Medline, Scopus data bases, 59 studies were included in this review. Mitochondrion rich BAT are unique in the sense that they bypass adenosine triphosphate (ATP) production and instead create heat by activating uncoupling protein 1 (UCP-1). Repeated stimulation by cold (16-18◦C) few hours per day for a period of 6 weeks in human adults resulted in hyperplasia of brown adipocytes and increased tissue mass. Increased stimulation from sympathetic nerve endings also resulted in increased UCP-1 activity as found in studies performed with rodents and humans. Melatonin, a hormone associated with sleep, acting to lower the core body temperature, increased BAT activity and improved glucose metabolism. New studies suggest that Sirtuins (Sır-2) proteins and exercise-induced production of Irisin causes an increase in BAT activity by stimulating mitochondrial biogenesis in brown adipocytes leading to increased energy expenditure. Further studies are required to elucidate the novel relationship between cold stress and altered energy metabolism, promising a solution to obesity related progressive metabolic diseases.

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