Clinical Trial: Contribution of Hyperinsulinemia vs. Hyperglycemia to Insulin Resistance in Type 1 Diabetes and Maturity Onset Diabetes of the Young, Type 2 (MODY2)

Study Status: Recruiting
Recruit Status: Recruiting
Study Type: Interventional

Official Title: A Novel Cross-sectional Analysis of Insulin Sensitivity Among Adolescents and Young Adults With Type 1 Diabetes, MODY2, and Normal Controls: the Contribution of Hyperinsul

Brief Summary:

The purpose of this study is to determine the key factors influencing insulin sensitivity in type 1 diabetes (T1DM) and maturity onset diabetes of the young, type 2 (MODY2).

Our study tests the hypothesis that decreased insulin sensitivity is primarily driven by chronically elevated insulin levels in the blood rather than chronic elevations in blood sugar.

Detailed Summary:

This research will determine whether insulin resistance (IR) in T1DM is predominantly an effect of chronic hyperglycemia, as is commonly accepted, or a consequence of iatrogenic hyperinsulinemia in the peripheral circulation, as alternatively hypothesized. IR is a consistent but under-recognized finding in T1DM. Despite its independent contribution to micro- and macrovascular disease, its underlying cause has not been established nor have strategies to mitigate it been developed. This research will also characterize IR in maturity onset diabetes of the young, type 2 (MODY2), a population for whom IR has been inadequately studied to date.

Insulin therapy in T1DM attempts to achieve euglycemia but does so in an "unphysiologic" way, by delivering insulin into the subcutaneous tissue as compared to physiologic delivery directly into the hepatic portal circulation. Although life-saving, peripheral insulin delivery in T1DM results in a loss of the normal insulin distribution; the physiologic state maintains insulin at 3-fold higher concentrations in the portal circulation compared with the peripheral circulation. IR in T1DM could therefore occur in response to peripheral hyperinsulinemia, a mechanism that would protect against hypoglycemia and ensure adequate glucose delivery to the central nervous system.

MODY2 is a condition that results a mutation in the gene encoding glucokinase (GCK), which in turn causes a defect in β-cell sensitivity to glucose due to reduced glucose phosphorylation. This effectively raises the "set point" for insulin secretion in response to increased glycemia. Because MODY2 patients retain pancreatic insulin secretion, they usually require no insulin therapy and have a normal insulin distribution between the portal and peripheral circulations.

The primary outcome is the degree to which Rd (determined using isotopic glucose tracer techniques) during maximal insulin stimulation differs between cohorts.