Role of KATP Channel Loss in Type 2 Diabetes

NCT ID: NCT06830096

Last Updated: 2025-07-04

Basic Information

• Recruitment Status: RECRUITING
• Clinical Phase: NA
• Total Enrollment: 40 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-03-07
• Study Completion Date: 2026-07-01

Brief Summary

Insulin is a hormone that is made by β-cells in the pancreas and when released into the bloodstream helps control blood sugar levels. Insulin release is regulated by electrical activity in the β-cell which is generated by the ATP-sensitive potassium (KATP) channel. While reduced KATP activity is associated with increased insulin secretion, animals lacking KATP exhibit reduced secretion. This crossover from hypersecretion to undersecretion with KATP loss mirrors insulin secretion during type 2 diabetes. Intriguingly, evidence from cell and animal models suggest that chronically stimulated β-cells can lose KATP revealing a possible role for KATP loss in the failure of insulin secretion and poor control of blood sugar observed in type 2 diabetes. This study will therefore examine insulin responses following ingestion of a single dose of a sulfonylurea called glipizide that inhibits KATP channels in people with and without type 2 diabetes. The goal is to determine whether KATP channel activity is reduced during type 2 diabetes progression.

Detailed Description

The worldwide epidemic of obesity has developed alongside, and is causally linked to, the epidemic of insulin resistance and type 2 diabetes mellitus (T2DM). Plasma insulin concentrations are typically elevated in people with insulin resistance attributable to an increase in insulin secretion rate by pancreatic β-cells; however, in people with T2DM, β-cells eventually fail to 'keep up' and there is a crossover from insulin hypersecretion to undersecretion.

In the β-cell, KATP channels serve as the link between rising glucose and insulin secretion. Unlike other cells in the body, the uptake of glucose by the β-cell is directly proportional to the amount of glucose in the blood, so increasing blood glucose results in increased metabolism and production of ATP. This ATP closes the KATP channel, depolarizing the cell and driving an increase in intracellular Ca2+, which stimulates the secretion of insulin. The critical role of KATP channels in control of insulin secretion is clearly demonstrated by Gain-of-function (GOF) mutations that increase channel activity, preventing glucose mediated depolarization and secretion of insulin. Such mutations underlie neonatal diabetes mellitus (NDM) in humans and severe diabetes in experimental NDM mice that express transgenic GOF mutant KATP channels. While this paradigm implies that loss of KATP should cause the opposite effect, i.e. hypersecretion of insulin, mice with complete knockout (KO) of KATP show little evidence of hyperinsulinism, instead developing reduced secretion and impaired glucose tolerance from a very early age. Intriguingly, loss of function (LOF) mutations in mice have been shown to result increased insulin secretion, but these "crossover" to the under secreting KO phenotype when challenged with a high fat diet, mirroring the progression of T2DM from hypersecretion to undersecretion. In humans, LOF mutations have been associated with congenital hyperinsulinism, characterized by hypersecretion of insulin and hypoglycemia from a young age. However, despite this early hyperinsulinism, children from with CHI generally remit, losing insulin secretion and even progressing to diabetes with time. Counter to the simple model directly coupling KATP inhibition to insulin secretion, these observations from humans and mouse models suggest a more complex regulation wherein acute depolarization induces insulin secretion but when prolonged, secretion begins to fail.

Electrical measurements from β-cells of isolated islets have demonstrated that incubation in high glucose results in a reduction in KATP activity, and mouse models of obesity and diabetes show increased electrical activity and a loss of KATP in proportion to their loss of glycemic control. These observations have led us to develop the hypothesis that β-cells subjected to chronic stimulation due to increased insulin resistance will progressively lose KATP, eventually causing the "crossover" to undersecretion that is observed in T2DM. In this study our goal is to test this hypothesis, administering a single dose of the KATP antagonist glipizide (10 mg) and using the resulting insulin secretion to indirectly assess KATP channel activity in the islets of volunteers from the following four cohorts, lean and normoglycemic (Lean NGT), obese with normoglycemia (Obesity NGT), obese with impaired fasting glucose (Obesity IFG) and obese type 2 diabetes (Obesity T2DM).

Conditions

Obesity and Type 2 Diabetes

Study Design

• Allocation Method: NON_RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

Lean with normal glucose tolerance

Body mass index ≥18.5 and \<25.0 kg/m², fasting plasma glucose concentration \<95 mg/dl, 2-hr oral glucose tolerance test plasma glucose concentration ≤140-mg/dl, and hemoglobin A1C (HbA1C) ≤5.6%.

Group Type: EXPERIMENTAL

10 mg glipizide ingestion

Intervention Type: DRUG

A single dose of 10 mg glipizide will be ingested

Obesity with normal glucose tolerance

Body mass index ≥30 and \<50 kg/m², fasting plasma glucose concentration \<95 mg/dl, 2-hr oral glucose tolerance test plasma glucose concentration ≤140 mg/dl, and hemoglobin A1C (HbA1C) ≤5.6%.

Group Type: EXPERIMENTAL

10 mg glipizide ingestion

Intervention Type: DRUG

A single dose of 10 mg glipizide will be ingested

Obesity with impaired fasting glucose

Body mass index ≥30 and \<50 kg/m², fasting plasma glucose concentration 100-125 mg/dl, and 2-hr oral glucose tolerance test plasma glucose concentration \<200 mg/dl.

Group Type: EXPERIMENTAL

10 mg glipizide ingestion

Intervention Type: DRUG

A single dose of 10 mg glipizide will be ingested

Obesity with type 2 diabetes

Body mass index ≥30 and \<50 kg/m²; HbA1C 6.5-9.5%, fasting plasma glucose ≥126 mg/dl, 2-hr oral glucose tolerance test plasma glucose concentration ≥200 mg/dl and/or medical history of type 2 diabetes and currently using anti-diabetic medications.

Group Type: EXPERIMENTAL

10 mg glipizide ingestion

Intervention Type: DRUG

A single dose of 10 mg glipizide will be ingested

Interventions

10 mg glipizide ingestion

A single dose of 10 mg glipizide will be ingested

Intervention Type: DRUG

Eligibility Criteria

Inclusion Criteria

• Lean-normoglycemic group (n=10): BMI ≥18.5 and <25.0 kg/m², fasting plasma glucose concentration <95 mg/dl, 2-hr oral glucose tolerance test plasma glucose concentration ≤140-mg/dl, and hemoglobin A1C (HbA1C) ≤5.6%.
• Obesity-normoglycemic group (n=10): BMI ≥30 and <50 kg/m², fasting plasma glucose concentration <95 mg/dl, 2-hr oral glucose tolerance test plasma glucose concentration ≤140 mg/dl, and hemoglobin A1C (HbA1C) ≤5.6%.
• Obesity-impaired fasting glucose group (n=10): BMI ≥30 and <50 kg/m², fasting plasma glucose concentration 100-125 mg/dl, and 2-hr oral glucose tolerance test plasma glucose concentration <200 mg/dl.
• Obesity-type 2 diabetes group (n=10): BMI ≥30 and <50 kg/m²; HbA1C 6.5-9.5%, fasting plasma glucose ≥126 mg/dl, 2-hr oral glucose tolerance test plasma glucose concentration ≥200 mg/dl and/or medical history of T2DM and currently using anti-diabetic medications.

Exclusion Criteria

• Diabetes therapy with insulin at >0.5 units/kg/day.
• Any change in diabetes medication in previous 3 months.
• Unstable weight (>2% change during the last 2 months before entering the study).
• Evidence of significant organ system dysfunction or disease other than obesity and T2D.
• Regular use of tobacco products.
• Excessive consumption of alcohol (≥3 drinks/day for men and ≥2 drinks/day for women).
• Use of medications that are known to affect the study outcome measures (e.g., steroids, non-statin lipid-lowering medications) or increase the risk of study procedures (e.g., anticoagulants) and that cannot be temporarily discontinued for this study.
• Anemia (Hemoglobin <10.0 g/dL).
• Pregnant or breastfeeding.
• Unable or unwilling to follow the study protocol or for any reason the research team believes the volunteer is not an appropriate candidate for this study, including non-compliance with screening appointments or previous medical visits.

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 65 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

NIH

Sponsor Role: collaborator

Washington University School of Medicine

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Locations

Washington University in St. Louis

St Louis, Missouri, United States

Site Status: RECRUITING

Countries

United States

Central Contacts

Kyle Timmons

Role: CONTACT

nutritionresearch@wustl.edu

314-273-1879

Facility Contacts

Kyle Timmons

Role: primary

timmons@wustl.edu

314-362-8699

Other Identifiers

5P30DK056341

Identifier Type: NIH

Identifier Source: secondary_id

View Link

202406075

Identifier Type: -

Identifier Source: org_study_id