Thermoneutral housing worsens MASLD and reveals defective brown adipose tissue response to β3-adrenergic stimulation

Metabolic dysfunction-associated steatotic liver disease (MASLD), and its more advanced stage metabolic dysfunction-associated steatohepatitis, is the most common chronic liver disease, constituting a major public health issue. Relevant preclinical models are needed to define molecular mechanisms underlying MASLD pathogenesis and evaluate therapeutic approaches. The majority of the lipids accumulating in the liver upon MASLD originate from adipose tissue and appropriate models to study the liver-adipose tissue dialog are also needed. Here, we demonstrated that, compared to standard temperature housing, thermoneutral housing aggravated western diet (WD)-induced obesity, diabetes, and steatosis in male mice, which was associated with increased hepatic expression of inflammation- and fibrosis-related genes. Accordingly, thermoneutral-housed WD-fed mice developed more severe hepatic inflammation and fibrosis compared to standard-housed mice. We next used thermoneutral-housed WD-fed mice to question the effect of MASLD during β3-adrenergic stimulation. We found that diet-induced MASLD is associated with defective inter-organ metabolic cross-talk which leads to impaired activation of brown adipose tissue.