Macrophages Produce Heat from Brown Adipose Tissue in Response to Cold

Maintaining body temperature in cold environments is critical for survival. However, the detailed mechanisms remain elusive. The body employs two methods for heat production: shivering-mediated heat production by skeletal muscle and non-shivering thermogenesis by brown adipose tissue. The latter is particularly significant for long-term adaptation to cold. Recently, researchers from the University of Tsukuba, Japan, and colleagues investigated the role of the transcription factor MAFB in macrophages—an immune cell type involved in non-shivering thermogenesis within brown adipose tissue. This tissue can generate heat to increase the body temperature in response to cold, primarily regulated by the sympathetic nervous system. Therefore, the researchers bred Mafb-deficient mice and exposed them to cold conditions, monitoring their body temperature changes. They found that heat production by brown adipose tissue was reduced in Mafb-deficient mice, leading to a decrease in body temperature. Additionally, the density of sympathetic nerve fibers in the brown adipose tissue of Mafb-deficient mice was notably lower than that in wild-type mice. Further analysis revealed that MAFB inhibits the expression of the inflammatory cytokine IL-6, consequently reducing the expression of nerve growth factor in brown adipose tissue and impairing the development of sympathetic nerve fibers. These results suggest that MAFB-mediated regulation of sympathetic nerve fiber density plays a key role in the thermogenic capacity of brown adipose tissue.

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