Vitamin E and adiponectin: proposed mechanism for vitamin E-induced improvement in insulin sensitivity.

Insulin resistance and type 2 diabetes have been treated with the PPARγ agonists thiazolidinediones, or TZDs, since the 1990s. One mechanism by which these drugs may work is through PPARγ-mediated upregulation of adiponectin, an endogenous adipokine that has been shown to increase insulin sensitivity. Interestingly, α- and γ-tocopherol, two vitamin E vitamers, have structural similarities to the TZDs and have also been linked to enhanced insulin sensitivity. A recent study identified a novel function of α- and γ-tocopherol in 3T3-L1 preadipocytes: upregulation of an endogenous ligand involved in activating PPARγ. This study also found that tocopherols dramatically enhanced adiponectin expression and that this effect was mediated through a PPARγ-dependent process. These findings illustrate a possible mechanistic link between vitamin E and insulin sensitivity.