Chromium Effects in Impaired Glucose Tolerance

Impaired glucose tolerance(IGT) often precedes Type II diabetes and is a cardiac risk. Chromium (Cr) is an insulin co-factor. This study will investigate the effects of daily Chromium for 6 months at two doses on serum measures of glucose tolerance and endothelial function in adults with IGT.

Official Title

Conditions

– Obesity

Study Type

Interventional

Study Design

Prevention, Randomized, Double-Blind, Placebo Control, Crossover Assignment, Pharmacokinetics/Dynamics Study

Further Details

Impaired glucose tolerance (IGT) is often a prelude to type II diabetes mellitus (DM) and its sequelae, and is a cardiac risk factor in its own right. The worsening epidemic of DM in the US, along with the increasing prevalence of obesity, insulin resistance, and IGT, render the identification of promising interventions for these states a matter of some urgency. While lifestyle interventions based on dietary pattern and physical activity can delay or prevent the onset of diabetes, and reduce cardiovascular risk, adherence at the population level is severely limiting. Pharmacotherapy offers promise for diabetes prevention, but with associated high costs, unacceptability to many patients, and potential toxicity. In this context, the potential role of chromium (Cr), an insulin co-factor, in IGT is of great interest. Chromium use is widespread, but evidence of any therapeutic effect is limited. This study is a randomized, double-blind, placebo controlled pilot trial conducted at the Yale Prevention Research Center, to investigate the effects of daily Cr for 6 months at two dose levels on serum measures of glucose tolerance, and on endothelial function, in adults with IGT. A modified crossover design will allow for paired and unpaired analyses including comparison of both 500 mcg and 1,000 mcg of Cr daily to placebo; comparison between 500 mcg and 1000 mcg of chromium; and evaluation of Cr washout time. The study is powered to detect a clinically meaningful effect of Cr supplementation at either dose on glucose control, and to compare the two doses for equivalence. The study will investigate effects of Cr on both measures of glucose tolerance (glucose, insulin, OGTT) and brachial artery endothelial function, thus combining serum measures with a physiologic test of Cr effects on the vasculature. The study will generate much needed data regarding the efficacy of Cr in IGT and offers the promise of guiding practice, as well as directing future study. By contributing to knowledge related to potential diabetes prevention strategies, this study addresses one of the more pressing public health issues in the US today.

Study Start

Eligibility & Criteria

Ages Eligible for Study: 18 Years and above, Genders Eligible for Study: Both Criteria Inclusion Criteria:Adults 18 years or older with Impaired Glucose tolerance (IGT) IGT defined as: 1) Plasma glucose two hours after 75g glucose is at least 140mg/dl but below 200mg/dl [7.8 mmol/l to 11.1 mmol/l] 2) Fasting plasma glucose is <126 mg/dl [7.0 mmol/l Exclusion Criteria:Known diabetes Known diabetes defined as: 1) Fasting Blood glucose > 126/mg/dl 2) 2 hour 75g OGTT plasma glucose > 200 mg/dl 3) Previous diagnosis by MD Hospitalization for heart disease in last 6 months Impaired renal function: [creatinine clearance < 80ml/min., urinary albumin excretion >300mcg/mg CR] Pancreatitis, Inflammatory bowel disease Recent or significant abdominal surgery Pregnancy Polycystic ovarian syndrome or irregular menses NOTE: Individuals taking multi-vitamins containing chromium will be asked to change to vitamins which do not contain chromium. Those that will not change will not be eligible to participate. Subjects taking the following medications will be excluded: drugs that affect insulin sensitivity, antihypertensive drugs, lipid lowering agents, glucocorticoids, antineoplastic agents, psychoactive agents, bronchodilators

Total Enrolment

60

Contact Details

[1] The Yale-Griffin Prevention Research Center, Derby, Connecticut