Effect of Dietary Glycemic Index on Beta-cell Function

Summary

The study will determine if increasing the highs and lows of blood glucose levels (glycemic variability) impairs insulin secretion in people with impaired glucose tolerance and/or impaired fasting glucose who are at risk for developing type 2 diabetes. Furthermore, the study will determine whether changes in beta-cell function are associated with glycemic variability and whether they are mediated by oxidative stress. To decrease or increase glycemic variability the study will provide subjects with special diets containing either low or high glycemic index foods respectively for 4 weeks. To determine if oxidative stress is a mediator, subjects on the high glycemic index diet will take either placebo or the anti-oxidant N-acetylcysteine. The study will address the hypothesis that increased glycemic variability results in increased oxidative stress and thereby exacerbates beta-cell dysfunction in individuals with impaired glucose tolerance and/or impaired fasting glucose. The findings may have important implications for the development of effective strategies aimed at the prevention and treatment of type 2 diabetes. In addition, understanding the contribution of dietary glycemic index to beta-cell dysfunction in subjects with pre-diabetes may have a significant public health impact, including changes to dietary counseling and promotion of healthier eating patterns.

Conditions

• Impaired Glucose Tolerance
• Oxidative Stress
• Prediabetes
• Impaired Fasting Glucose

Interventions

OTHER

low glycemic index (LGI) diet

Following a 2 week medium glycemic index control diet (glycemic index 50-55), subjects will be provided with a weight stable low glycemic index diet (glycemic index \<35) for 4 weeks with all food provided by the Human Nutrition Lab

OTHER

high glycemic index (HGI) diet plus placebo (PLAC)

Following a 2 week medium glycemic index control diet (glycemic index 50-55), subjects will be provided with a weight stable high glycemic index diet (glycemic index \>70) for 4 weeks, all food provided by the Human Nutrition Lab. They will take placebo capsules (matching for active N-acetylcysteine (NAC) in arm 3) twice daily for the 4 weeks on the high GI diet. The NAC vs. placebo arms (arms 2 and 3) will be double-blinded.

DRUG

high glycemic index diet plus N-acetylcysteine

Following a 2 week medium glycemic index control diet (glycemic index 50-55), subjects will be provided with a weight stable high glycemic index diet (glycemic index \>70) for 4 weeks, all food provided by the Human Nutrition Lab. They will take N-acetylcysteine (NAC) two 600 mg capsules twice daily for the 4 weeks on the high GI diet. The NAC vs. placebo arms (arms 2 and 3) will be double-blinded.

Sponsors & Collaborators

• VA Puget Sound Health Care System

  collaborator FED

• Seattle Institute for Biomedical and Clinical Research

  lead OTHER

Principal Investigators

• Kristina M Utzschneider, MD · VA Puget Sound Health Care System

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

65 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2011-07-31

Primary Completion

2019-08-01

Completion

2019-08-01

Countries

• United States

Study Locations