Defective Atypical Protein Kinase C (PKC) Activation in Diabetes and Metabolic Syndrome
The investigators are examining the activation of insulin signaling factors in skeletal muscles of human diabetics. The investigators are characterizing the defects in signaling, and are examining the effects of anti-diabetic agents and exercise on signaling to glucose transport biochemical machinery and whole body glucose disposal.
Diabetes Mellitus, Type 2
|Study Design:||Observational Model: Cohort
Time Perspective: Cross-Sectional
|Official Title:||Defective Atypical PKC Activation in Diabetes and Metabolic Syndrome|
- Improved insulin signaling with combined metformin-thiazolidinedione treatment. [ Time Frame: Insulin signaling in muscle evaluated 6 weeks after combined Met-TZD treatmentall muscle samples obtained by 9/30/07final date for examination of samples 9/30/08 ] [ Designated as safety issue: No ]
Biospecimen Retention: None Retained
Muscle biopsies taken before and after insulin stimulation in euglycemic clamp studies
|Study Start Date:||October 2005|
|Study Completion Date:||September 2008|
|Primary Completion Date:||September 2008 (Final data collection date for primary outcome measure)|
We have provided clear evidence that insulin activation of all three signaling components, Viz., IRS-1-dependent PI 3-Kinase, atypical protein kinase C (aPKC) and PKB/Akt is defective in diabetic muscle. These defects are best seen when insulin activation is conducted at both half-maximal and maximal stimulation. Moreover, whereas previous studies had shown that treatment with metformin (Met) alone improves aPKC activation, or that treatment with thiazolidinedione (TZD) alone produces increases in activation of IRS-1/PI3K and aPKC when evaluated at maximal insulin stimulation, we have recently found that combined treatment with Met plus TZD for 6 weeks provokes marked increases in insulin effects on all three signaling factors at both half-maximal and maximal insulin stimulation. This work is being prepared for submission for publication.
We have also evaluated the improvement in insulin signaling in diabetic muscle 4 hours after acute endurance (one-legged) exercise and found that the responsiveness of aPKC to the lipid PI3K-derived activator, PIP3, was improved. Also increased was the activation by insulin of IRS-2-dependent PI3K, ERK1/2, and downstream protein synthesis machinery, viz., p70S6 kinase and eukaryotic elongation factor eEF2. These effects of exercise would be expected to enhance glucose transport and utilization by muscle, and promote protein synthesis, i.e., an anabolic response.
|United States, Florida|
|VA Medical Center|
|Tampa, Florida, United States, 33612|
|Principal Investigator:||Robert V Farese, MD||Department of Veterans Affairs|