2012 Annual Report
1a.Objectives (from AD-416):
Poor muscle fat combustion is a hallmark of reduced insulin sensitivity, pre-diabetes, and propensity toward development of type 2 diabetes mellitus. Identifying persons who display this phenotype, however, has been difficult and requires in-depth specialized and costly clinical evaluation (i.e., muscle biopsies, analysis of blood parameters across the muscle bed using dual catheterization). The lack of a facile, inexpensive technique to characterize muscle fat utilization hinders strategies to optimally apply nutritional and physical activity regimens to thwart insulin resistance and diabetes, since markers are unavailable to identify at-risk persons who may benefit most from said interventions, and to use in order to track efficacy of the interventions. Our objective is to identify blood metabolites or metabolite signatures reflective of skeletal muscle fat combustion, and to test whether said patterns shift in response to a diet and exercise regimen in overweight to obese persons.
1b.Approach (from AD-416):
We will use unique organelle (mitochondria), cell, and animal models which display altered muscle fat utilization to derive biofluids that will be tested using state-of-the-art metabolomics technologies--these studies will identify specific metabolites or metabolite signatures reflective of fat combustion in this tissue. In addition, we will analyze the plasma of human subjects who display a disruptive genetic polymorphism in a muscle protein involved in mitochondrial fatty acid metabolism (UCP3) to assess whether metabolomic patterns differ from people without the polymorphism. Finally, we will evaluate whether overweight to obese persons with insulin resistance have plasma metabolite patterns reflective of poor muscle fat burning, and test whether a diet and exercise intervention strategy normalizes these patterns concurrent with improvements in insulin action.
This research contributes to objectives 3 and 6 of the in-house parent project. The team examined lipid-related metabolites through “targeted oxylipid/endocannabinoid” metabolite profiling of archived blood plasma of 44 obese diabetic women and 12 non-diabetic obese control subjects to identify novel metabolic markers. It was discovered that metabolites reflective of modulation of the chemical bonds in fats are altered in diabetes, and may provide a unique set of markers that can be tested in the broader population to help detect pre-diabetes and diabetes phenotypes. Other studies looking at broad metabolite patterns in the blood of human subjects have indicated that in type 2 diabetes, amino acid metabolites that likely reflect inhibition of proper amino acid catabolism are associated with blood sugar control. Follow up work is illustrating that in the obese, insulin-resistant state, key enzymes of amino acid metabolism are down-regulated in the fat tissue, which may contribute to the dysregulated protein metabolism of pre-diabetes and diabetes. This raises the possibility that strategies to improve amino acid and protein metabolism could improve health and metabolic homeostasis in persons at-risk for developing diabetes.