insulin resistance is the principle step towards the progression of type 2 diabetes, and has been linked to increased circulating levels of cytokines, leading to chronic low-grade inflammation. specifically, in chronic disease states increased interleukin-6 (il-6) is thought to play a critical role in the regulation of insulin resistance in peripheral tissues, and has been used as a marker of insulin resistance. there is also an endogenous up-regulation of il-6 in response to physical activity, which has been linked to improved insulin sensitivity. this leads to the question “how can elevated il-6 lead to the development of insulin resistance, and yet also lead to increased insulin sensitivity?” resolving the dual role of il-6 in regulating insulin resistance/sensitivity is critical to the development of potential therapeutic interventions. this study was designed to investigate the role of il-6 on high fat diet (hfd) induced glucose intolerance, and the response to voluntary physical activity in the prevention of insulin resistance. six-week old wild type (wt) and il-6 knockout (ko) mice with (run) or without (sed) access to running wheels were fed a hfd (60% from kcal) for 4 weeks. a glucose tolerance test revealed that blood glucose levels were 25-30% higher in ko run compared to all other groups after 30 minutes. in wt run, weight gain was positively correlated with total caloric intake; however, this correlation was absent in ko run, which may be attributed to impaired glycogen breakdown or increased the nuogenesis in these mice. in soleus muscle, there was a 2-fold increase in socs3 expression in ko run compared to all other groups. in gastrocnemius/plantaris muscles, akt phosphorylation was 31% higher in wt run compared to wt sed, but this effect of running was absent in ko mice. additionally, there was a 2.4-fold increase in leptin expression in ko run compared to ko sed in the gastrocnemius/plantaris muscles. in the liver, there was a 2-3.8-fold increase in socs3 expression in ko sed compared to all other groups, and ampka phosphorylation was 27% higher in wt mice (both run and sed) compared to ko mice (both run and sed). these findings provide new insight into the role of the il-6 in metabolism and energy storage, and highlights tissue specific changes in early signaling pathways in response to hfd for 4 weeks. the collective findings suggest that endogenous il-6 is important for the prevention of insulin resistance leading to type 2 diabetes.