The effect of EGCG on hepatic steatosis may contribute to its
effects on insulin resistance. Hepatic steatosis is associated with
insulin resistance in humans and studies in rodent models have
shown that suppression of hepatic steatosis improved hepatic
insulin sensitivity (32). These effects may be mediated through
the activation of protein kinase C, which is stimulated by fatty
acids and contributes to the phosphorylation of the insulin
receptor substrate at Ser-307, resulting in inhibition of normal
insulin signaling (32,33). EGCG has been shown to both inhibit
protein kinase C and increase insulin receptor substrate-mediated
downstream signaling in cell line studies (31).