Insulin resistance is a key pathophysiologic feature of the "metabolic syndrome" and is strongly associated with co-existing cardiovascular risk factors and accelerated atherosclerosis. Due to the clinical consequences associated with insulin resistance in subjects with metabolic syndrome and type 2 diabetes, clinical regimens directed at increasing insulin sensitivity in vivo remain one of the most desirable goals of treatment. Although it is well established that lifestyle modification can improve insulin resistance and effectively improve many of the risk factors associated with the metabolic syndrome, the success of maintaining lifestyle changes in humans over a chronic period is poor. Therefore, strategies to improve insulin resistance by pharmacological means have represented the traditional approach for clinical medicine. However, because of the widespread use of dietary supplements by the general public, nutritional supplementation with the use of botanical extracts that effectively increase insulin sensitivity represent a very attractive and novel approach.

Unfortunately, considerable controversy exists regarding the effect of botanical supplements on the metabolic syndrome in large part because efficacy data for many of the supplements used for this purpose consists of only uncontrolled studies and anecdotal reports. As such, there is a paucity of data in humans in regard to the effect of botanicals to improve measures of insulin action in vivo or on cellular aspects of insulin action. However, several lines of evidence in both in vitro and in vivo models suggest that botanicals may modulate intracellular pathways of glucose metabolism. Specifically, preclinical data with use of extracts from grapes and blueberries suggest that components of these botanical mixtures, e.g. anthocyanins and resveratrol, may play a role in enhancing cellular pathways of insulin action. On a clinical level, if cellular pathways of insulin action are enhanced, e.g. PI-3 kinase activity, this should be associated with an increase in whole body glucose disposal as reflected in measures assessing insulin sensitivity. However, there is limited experience in human studies for which insulin sensitivity has been assessed with use of "gold standard" techniques assessing in vivo insulin action. Therefore, this project's overall objective is to examine the role of a specific botanical (i.e., blueberry powder) on insulin action in vivo with use of hyperinsulinemic-euglycemic clamps. This pilot trial is designed to evaluate a fixed consumption of blueberry powder and to provide data of the effect so that a larger, more comprehensive study can be planned. To accomplish our goal, we will conduct a randomized, placebo-controlled pilot clinical study with blueberry powder designed to assess insulin sensitivity in subjects who are obese and insulin resistant. We hypothesize that blueberry powder will be effective, when compared to placebo, to increase insulin action in vivo. If so, this pilot trial will provide the necessary background to progress to studies in subjects with Type 2 diabetes. An increase in insulin sensitivity in patients with Type 2 diabetes will be expected to markedly reduce glucose levels.