Obesity is one of the most prevalent chronic diseases worldwide, and dysregulated adipocyte function plays an important role in obesity-associated metabolic disorder. The level of plasma plasminogen activator inhibitor-1 (PAI-1) is increased in obese subjects, and PAI-1 null mice show improved insulin sensitivity when subjected to high-fat and high-sucrose diet-induced metabolic stress, suggesting that a best-in-class PAI-1 inhibitor may become a novel therapeutic agent for obesity-associated metabolic syndrome. TM5441 is a novel orally active PAI-1 inhibitor that does not cause bleeding episodes. Hence, in the present study we examined the preventive effect of TM5441 on high-fat diet (HFD)-induced adipocyte dysfunction. EXPERIMENTAL APPROACHTen-week-old C57BL/6J mice were fed a normal diet (18% of total calories from fat) or HFD (60% of total calories from fat) for 10 weeks, and TM5441 (20 mg·kg À1 oral gavage) was administered daily with the initiation of HFD. KEY RESULTSTM5441 prevented HFD-induced body weight gain and systemic insulin resistance. TM5441 normalized HFD-induced dysregulated JNK and Akt phosphorylation, suggesting that it prevents the insulin resistance of adipocytes. TM5441 also attenuated the macrophage infiltration and increased expression of pro-inflammatory cytokines, such as inducible nitric oxide synthase, induced by the HFD. In addition, TM5441 prevented the HFD-induced down-regulation of genes involved in mitochondrial biogenesis and function, suggesting that it may prevent adipocyte inflammation and dysregulation by maintaining mitochondrial fitness. CONCLUSION AND IMPLICATIONSOur data suggest that TM5441 may become a novel therapeutic agent for obesity and obesity-related metabolic disorders.Abbreviations ATGL, adipose triglyceride lipase; Cox, cytochrome c oxidase; FAS, fatty acid synthase; FFA, free fatty acid; GTT, glucose tolerance test; H&E, haematoxylin and eosin; HFD, high-fat diet; HSL, hormone-sensitive lipase; iNOS, inducible nitric oxide synthase; ITT, insulin tolerance test; KO, knockout; MCP-1, monocyte chemotactic protein-1; mtDNA, mitochondrial DNA; ND, normal diet; PAI-1, plasminogen activator inhibitor-1; PGC1α, PPARγ coactivator-1α; Tfam, mitochondrial transcription factor A; TG, triglyceride; TM5275, 5-chloro-2- [({2-[4-(diphenylmethyl)piperazin-1-yl]-2-oxoethoxy}acetyl) amino]benzoate; TM5441, 5-chloro-2 {[(2-{[3-(furan-3-yl)phenyl]amino}-2-oxoethoxy) acethyl]amino} benzoic acid; UCP, uncoupling protein; WAT, white adipose tissue

Recent evidences showed that elevation of plasminogen activator inhibitor 1 (PAI-1) was responsible in mediating obesity-induced non-alcoholic fatty liver disease (NAFLD) and metabolic disorders. Here, we investigated the effect of TM5441, an oral PAI-1 inhibitor that lacks of bleeding risk, on high-fat diet (HFD)-induced NAFLD. HFD-fed C57BL/6J mice was daily treated with 20 mg/kg TM5441. To examine the preventive effect, 10-week-treatment was started along with initiation of HFD; alternatively, 4-week-treatment was started in mice with glucose intolerance in the interventional strategy. In vivo study showed that early and delayed treatment decreased hepatic steatosis. Particularly, early treatment prevented the progression of hepatic inflammation and fibrosis in HFD mice. Interestingly, both strategies abrogated hepatic insulin resistance and mitochondrial dysfunction, presented by enhanced p-Akt and p-GSK3β, reduced p-JNK signaling, along with p-AMPK and PGC-1α activation. Consistently, TM5441 treatment in the presence of either PAI-1 exposure or TNF-α stimulated-PAI-1 activity showed a restoration of mitochondrial biogenesis related genes expression on HepG2 cells. Thus, improvement of insulin sensitivity and mitochondrial function was imperative to partially explain the therapeutic effects of TM5441, a novel agent targeting HFD-induced NAFLD.

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