AMPK x Adiponectin receptors

Obesity and imbalance in lipid homeostasis contribute greatly to heart failure with preserved ejection fraction (HFpEF), the dominant form of heart failure. Few effective therapies exist to control metabolic alterations and lipid homeostasis.

We aimed to investigate the cardioprotective roles of AdipoRon, the adiponectin receptor agonist, in regulating lipid accumulation in the two-hit HFpEF model.

HFpEF mouse model was induced using 60 % high-fat diet plus L-NAME drinking water. Then, AdipoRon (50 mg/kg) or vehicle were administered by gavage to the two-hit HFpEF mouse model once daily for 4 weeks. Cardiac function was evaluated using echocardiography, and Postmortem analysis included RNA-sequencing, untargeted metabolomics, transmission electron microscopy and molecular biology methods.

Our study presents the pioneering evidence that AdipoR was downregulated and impaired fatty acid oxidation in the myocardia of HFpEF mice, which was associated with lipid metabolism as indicated by untargeted metabolomics. AdipoRon, orally active synthetic adiponectin receptor agonist, could upregulate AdipoR1/2 (independently of adiponectin) and reduce lipid droplet accumulation, and alleviate fibrosis to restore HFpEF phenotypes. Finally, AdipoRon primarily exerted its effects through restoring the balance of myocardial fatty acid intake, transport, and oxidation via the downstream AMPKα or PPARα signaling pathways. The protective effects of AdipoRon in HFpEF mice were reversed by compound C and GW6471, inhibitors of AMPKα and PPARα, respectively.

AdipoRon ameliorated the HFpEF phenotype by promoting myocardial fatty acid oxidation, decreasing fatty acid transport, and inhibiting fibrosis via the upregulation of AdipoR and the activation of AdipoR1/AMPKα and AdipoR2/PPARα-related downstream pathways. These findings underscore the therapeutic potential of AdipoRon in HFpEF. Importantly, all these parameters get restored in the context of continued mechanical and metabolic stressors associated with HFpEF.

This study investigated the ameliorative effects of Yinchen lipid-lowering tea (YCLLT) on Non-alcoholic fatty liver disease (NAFLD), the specific mechanism involved was also studied. We modeled hepatocellular steatosis with HepG2 cells and intervened with different concentrations of YCLLT-containing serum. Lipid deposition was assessed by oil red O staining and AdipoR1 expression was analyzed by Western blot. The hepatocyte steatosis model was further treated with YCLLT-containing serum and/or silencing AdipoR1. Lipid deposition was observed by oil red O staining. Flow cytometry was used to detect apoptosis and mitochondrial membrane potential. The levels of TNF-α, IL-6, MDA, 8-OHdG, and ATP were analyzed by ELISA or the corresponding kits. The mitochondrial structure was observed by transmission electron microscopy. The expression of AdipoR1/AMPK/SIRT1 signaling pathway factors was analyzed by Western blot, and co-localization of SIRT1 and immunofluorescence. The results revealed that YCLLT attenuated lipid deposition, inhibited the levels of inflammatory factors TNF-α and IL-6, reduced the levels of MDA and 8-OHdG, up-regulated the ATP content and mitochondrial membrane potential, and promoted the expression of AdipoR1, p-LKB1, p-AMPKα, SIRT1, and PGC-1a in a cellular model of NAFLD. Further, silencing of AdipoR1 inhibited the ameliorative effect of YCLLT in the NAFLD cell model. Altogether, Yinchen lipid-lowering tea attenuates lipid deposition in a fatty liver model by improving mitochondrial function via activating AdipoR1/AMPK/ SIRT1 signaling.

The dipeptide Tyr-Pro, a novel natural agonist of adiponectin receptor 1 (AdipoR1), promotes glucose uptake in skeletal muscle cells. This study investigated the antidiabetic effect of orally administered Tyr-Pro in spontaneously diabetic Torii (SDT) rats. Oral administration of Tyr-Pro (1 mg/kg/day) improved glucose intolerance in SDT rats at 22 weeks of prediabetic age. By 29 weeks of age, fasting blood glucose levels (BGLs) increased to 142 ± 14 mg/dL in the control group, whereas those in the Tyr-Pro group remained within the normal range (80-99 mg/dL), demonstrating a novel antidiabetic effect in vivo. Substantially increased levels of AdipoR1 and p-AMPK/AMPK were observed in the skeletal muscle of Tyr-Pro-administrated SDT rats. The intake of Tyr-Pro also enhanced insulin secretion and inhibited p-IRS-1(Ser) in skeletal muscle. These findings demonstrate that Tyr-Pro prevented the onset of diabetes and improved impaired insulin signaling pathways in SDT rats by inducing AdipoR1-mediated AMPK activation.