Thermoregulatory adaptations to cold in C3H/HeJ mice are independent of ADRB3 signaling

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Housing conditions and mouse strain significantly influence metabolic phenotypes, affecting the translational relevance of preclinical studies. Although C57BL/6J (C57) mice are widely used, their thermogenic and adrenergic profiles may not fully reflect human physiology. This study compared thermogenic responses to cold exposure between male C57 and C3H/HeJ (C3H) mice. Animals were housed in a Promethion indirect calorimetry system and exposed to varying ambient temperatures. Thermoneutral points during the light phase were nearly identical (C57: 29.26 ± 0.28 °C; C3H: 29.46 ± 0.17 °C), yet C3H mice exhibited significantly higher energy expenditure (EE) during both acute and chronic cold exposure. Gene expression analysis revealed a stronger induction of thermogenic genes in brown adipose tissue (BAT) of C3H mice. Notably, β3-adrenergic receptor (Adrb3) expression was minimal in BAT and white adipose tissue (WAT) of C3H mice and unaffected by cold exposure. Consistent with impaired β3 signaling, the β3 agonist CL 316,243 markedly increased EE in C57 mice but had only modest effects in C3H mice. In contrast, norepinephrine elicited EE responses in both strains, and propranolol pretreatment (a β1/β2 antagonist) abolished these strain differences, suggesting that C3H mice depend on β1/β2 or non-canonical pathways. In conclusion, C3H mice exhibit enhanced cold-induced thermogenesis through ADRB3-independent mechanisms. Despite similar thermoneutral point, C3H and C57 mice display distinct metabolic and adrenergic adaptations, underscoring the importance of strain selection in metabolic research. C3H mice may represent a model to study alternative thermogenic mechanisms applicable to human physiology.

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