Chronic β3-AR stimulation activates distinct thermogenic mechanisms in brown and white adipose tissue and improves systemic metabolism in aged mice.

Duraipandy Natarajan, Bhuvana Plakkot, Kritika Tiwari, Shoba Ekambaram, Weidong Wang, Michael Rudolph, Mahmoud A Mohammad, Shaji K Chacko, Madhan Subramanian, Stefano Tarantini, Andriy Yabluchanskiy, Zoltan Ungvari, Anna Csiszar, Priya Balasubramanian

Vascular Cognitive Impairment, Neurodegeneration, and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA. · pubmed

Paper

Abstract

Adipose thermogenesis has been actively investigated as a therapeutic target for improving metabolic dysfunction in obesity. However, its applicability to middle-aged and older populations, which bear the highest obesity prevalence in the United States (approximately 40%), remains uncertain due to age-related decline in thermogenic responses. In this study, we investigated the effects of chronic thermogenic stimulation using the β3-adrenergic (AR) agonist CL316,243 (CL) on systemic metabolism and adipose function in aged (18-month-old) C57BL/6JN mice. Sustained β3-AR treatment resulted in reduced fat mass, increased energy expenditure, increased fatty acid oxidation and mitochondrial activity in adipose depots, improved glucose homeostasis, and a favorable adipokine profile. At the cellular level, CL treatment increased uncoupling protein 1 (UCP1)-dependent thermogenesis in brown adipose tissue (BAT). However, in white adipose tissue (WAT) depots, CL treatment increased glycerol and lipid de novo lipogenesis (DNL) and turnover suggesting the activation of the futile substrate cycle of lipolysis and reesterification in a UCP1-independent manner. Increased lipid turnover was also associated with the simultaneous upregulation of proteins involved in glycerol metabolism, fatty acid oxidation, and reesterification in WAT. Further, a dose-dependent impact of CL treatment on inflammation was observed, particularly in subcutaneous WAT, suggesting a potential mismatch between fatty acid supply and oxidation. These findings indicate that chronic β3-AR stimulation activates distinct cellular mechanisms that increase energy expenditure in BAT and WAT to improve systemic metabolism in aged mice. Considering that people lose BAT with aging, activation of futile lipid cycling in WAT presents a novel strategy for improving age-related metabolic dysfunction.

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Research summary

The paper investigates the effects of chronic β3-adrenergic stimulation on metabolic dysfunction in aged mice, which is relevant to understanding mechanisms that could potentially mitigate age-related metabolic decline. However, while it presents solid findings regarding thermogenic mechanisms in adipose tissues, the impact is limited as it primarily focuses on a specific treatment in a mouse model without broader implications for longevity or lifespan extension. The findings contribute to the understanding of metabolic processes but do not address root causes of aging or significant breakthroughs that could transform the field.

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