Inhibition of Grb14, a negative modulator of insulin signaling, improves glucose homeostasis without causing cardiac dysfunction.

Insulin resistance increases patients' risk of developing type 2 diabetes (T2D), non-alcoholic steatohepatitis (NASH) and a host of other comorbidities including cardiovascular disease and cancer. At the molecular level, insulin exerts its function through the insulin receptor (IR), a transmembrane receptor tyrosine kinase. Data from human genetic studies have shown that Grb14 functions as a negative modulator of IR activity, and the germline Grb14-knockout (KO) mice have improved insulin signaling in liver and skeletal muscle. Here, we show that Grb14 knockdown in liver, white adipose tissues, and heart with an AAV-shRNA (Grb14-shRNA) improves glucose homeostasis in diet-induced obese (DIO) mice. A previous report has shown that germline deletion of Grb14 in mice results in cardiac hypertrophy and impaired systolic function, which could severely limit the therapeutic potential of targeting Grb14. In this report, we demonstrate that there are no significant changes in cardiac function as measured by echocardiography in the Grb14-knockdown mice fed a high-fat diet for a period of four months. While additional studies are needed to further confirm the efficacy and to de-risk potential negative cardiac effects in preclinical models, our data support the therapeutic strategy of inhibiting Grb14 to treat diabetes and related conditions.