ABSTRACT: Type 2 diabetes (T2D) is a growing global health crisis, largely driven by rising obesity rates. Untreated T2D leads to severe complications such as cardiovascular disease, nephropathy, retinopathy, neuropathy, and hepatic dysfunction. Current therapies primarily manage hyperglycemia but often fail to address core pathophysiological drivers like insulin resistance and obesity. This highlights an urgent need for novel therapeutics with distinct mechanisms, particularly those targeting energy metabolism and insulin sensitivity, to improve long-term T2D outcomes. Modulating mitochondrial respiration through mild uncoupling has emerged as a promising strategy to promote negative energy balance. SR4, a small-molecule mitochondrial uncoupler, represents a novel class of fatty acid-activated proton transporters. In this study, we investigated the metabolic effects of oral SR4 administration in male db/db mice model of T2D. SR4 significantly reduced body weight gain and improved body composition by selectively decreasing fat mass without affecting lean mass. Indirect calorimetry confirmed that SR4 treatment increased oxygen consumption and total energy expenditure, independent of food intake. Importantly, SR4 substantially improved glycemic control, reduced insulin resistance, and prevented dyslipidemia, hepatic steatosis, and liver injury. Mechanistically, SR4 activated hepatic AMP-activated protein kinase (AMPK), enhanced mitochondrial respiration, and mitigated oxidative stress. Liver transcriptomic profiling further demonstrated broad metabolic reprogramming, including downregulation of lipogenesis and peroxisome proliferator-activated receptor γ (PPARγ) signaling, concurrently with upregulation of genes involved in energy metabolism and antioxidant defense. Collectively, these findings demonstrate that SR4 ameliorates multiple aspects of metabolic dysfunction in an obese T2D mouse model by targeting key pathways in energy regulation and lipid metabolism. Our results provide additional mechanistic insights into the effects of mitochondrial uncouplers in the liver and support further investigation of SR4 and related fatty acid anion transporters as a novel therapeutic class for metabolic diseases.
