PPARα activation by MHY908 attenuates age-related renal inflammation through modulation of the ROS/Akt/FoxO1 pathway

2-[4-(5-Chlorobenzothiazothiazol-2-yl)phenoxy]-2-methyl-propionic acid (MHY908) has been shown to prevent insulin resistance-induced hyperinsulinemia in aged rats. However, the mechanism underlying MHY908-mediated amelioration of renal inflammation with insulin resistance during aging remains unknown. This study investigated the effects of MHY908 on age-related changes in the IRS/Akt/forkhead box (FoxO) 1 signaling pathway in the kidneys of aged rats and HEK293T cells. Experiments were performed in young, old, and MHY908-fed old rats (1mg or 3mg/kg/day MHY908 for 4 weeks). We found that MHY908-fed old rats suppressed phosphorylation of IRS/Akt and induced FoxO1 activation, leading to increased expression of MnSOD and catalase. In addition, in insulin-treated cells, MHY908 prevented the FoxO1 inactivation and increased the expression of MnSOD and catalase by inactivating IRS and Akt. In contrast, NF-κB signaling pathway decreased with MHY908 treatment in insulin-treated cells. Furthermore, MHY908 exclusively activated peroxisome proliferator-activated receptor (PPAR) α in the kidneys, leading to the inhibition of insulin-induced NADPH oxidase subunit 4 (NOX4)-derived reactive oxygen species (ROS) generation and FoxO1 inactivation. In conclusion, MHY908 improved the hyperinsulinemia-induced pro-inflammatory response through NF-κB inactivation and FoxO1 activation in aged rat kidneys. These phenomena suggest that PPARα activation by MHY908 attenuates NOX4-derived ROS generation in response to insulin.

Effects of MHY908, a New Synthetic PPARα/γ Dual Agonist, on Inflammatory Responses and Insulin Resistance in Aged Rats

Insulin resistance is common with aging and is associated with the inflammatory response in both humans and rodents. A number of peroxisome proliferator-activated receptor (PPAR) α/γ dual agonists have been tested for their abilities to attenuate insulin resistance and type 2 diabetes. However, there is no study on the effects of PPARα/γ dual agonists on inflammation and insulin resistance during aging. In the present study, we investigated the ability of 2-[4-(5-chlorobenzothiazothiazol-2-yl)phenoxy]-2-methyl-propionic acid (MHY908), a newly synthesized novel PPARα/γ dual agonist, to suppress the inflammatory response and attenuate insulin resistance in aged rats. Twenty-month-old rats were divided into four groups: ad libitum fed, ad libitum fed supplemented with MHY908 (1 mg and 3 mg/kg/day for 4 weeks), and 40% calorie restricted. Six-month-old ad libitum fed rats were used as an age control. The aged rats supplemented with MHY908 showed reduced serum glucose, triglyceride, and insulin levels, as well as reduced liver triglyceride levels. MHY908 brought about a reduction in endoplasmic reticulum stress and activation of the c-Jun N-terminal kinase in the livers of aged rats, which consequently improved insulin signaling. In the kidneys of aged rats, the efficacy of MHY908 as a potent anti-inflammatory agent was shown by its suppression of NF-κB activation through inhibition of the Akt/IκB kinase signaling pathway. Therefore, the major finding of this study is that MHY908 acts as a therapeutic agent against age-related inflammation associated with insulin resistance by activating PPARα and PPARγ, thus attenuating endoplasmic reticulum stress.