Insulin resistance does not inhibit the ability of overload to induce hypertrophy in the obese Zucker rat (Lepr fa ) plantaris

Skeletal muscle is capable of displaying remarkable plasticity enabling it to adapt to alterations in contractile activity. How insulin resistance may affect the ability of skeletal muscle to adapt to an increase in muscle loading is not well understood. Here, we compare the ability of the lean (LZ) and obese (insulin resistant) Zucker (OZ) rat plantaris muscle to undergo hypertrophy following 8 weeks of muscle overload induced by synergistic ablation of the gastrocnemius muscle. Compared to the unloaded contralateral control muscle, synergistic ablation increased OZ plantaris wet weight (WW), total protein (TP) content, myofibrillar protein (MP) content, muscle cross sectional area (CSA), and mean fiber area (MFA) by 41%, 43%, 52%, 41%, and 42%, respectively (P<0.05). Similarly, overload in the LZ animals increased plantaris WW, TP content, MP content, muscle CSA, and MFA by 40%, 37%, 46%, 34%, and 42%, respectively (P<0.05). Taken together, these data indicate that insulin resistance does not affect the ability of the rat plantaris muscle to hypertrophy during 8 weeks of muscle overload.