Defective Atypical Protein Kinase C (PKC) Activation in Diabetes and Metabolic Syndrome

VA Office of Research and Development

Status: Completed

Conditions: Diabetes Mellitus, Type 2

Study type: Observational

Funder types: Other U.S. Federal agency

Identifiers

NCT00690755

ENDA-037-04F

Details and patient eligibility

About

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.

Full description

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.

Enrollment: 157 patients

Sex: All

Ages: 18 to 75 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• Stable uncomplicated type 2 diabetes
• Able to be off oral treatments for 2 months

Exclusion criteria

• Diabetic complications related to heart, eye, nerve problems
• Renal impairment
• Cardiovascular disease
• Hepatic disease
• Prior history of other disorders or complications caused by diseases
• Insulin therapy needed

Trial design

157 participants in 7 patient groups

Group 1

Description:

type 2 diabetic individuals

Group 2

Description:

type 1 diabetic individuals or those with diabetes secondary to pancreatic disease

Group 3

Description:

non-diabetic individuals who are not considered to be overweight

Group 4

Description:

non-diabetic individuals who are considered to be overweight

Group 5

Description:

non-diabetic and type 2 diabetic individuals who will be subjected to an exercise study

Group 6

Description:

individuals who have or are suspected of having glucose intolerance, including patients who have a history of gestational diabetes and patients who have polycystic ovary syndrome

Group 7

Description:

healthy non-diabetic subjects who will receive one dose of metformin orally 1-2 hours before performing procedures