Post-load hyperglycemia more accurately predicts type 2 diabetes

By Laura Newman

NEW YORK (Reuters Health) - One-hour post-load hyperglycemia is better than impaired fasting glucose for predicting type 2 diabetes, Italian researchers say.

They found that individuals with normal glucose tolerance but blood glucose of 155 mg/dl (8.6 mmol/l) or greater at one-hour post-load (NGT-1h-high) were at higher risk for diabetes than individuals with impaired fasting glucose or lower one-hour glucose loads (NGT-1h-low).

As reported online August 14 in the Journal of Clinical Endocrinology & Metabolism, Dr. Giorgio Sesti and colleagues from University Magna Graecia of Catanzaro, Italy, analyzed data from two groups. The first consisted of 595 nondiabetic white adults who underwent oral glucose tolerance testing (OGTT) and euglycemic hyperinsulinemic clamp as part of the European Network on Functional Genomics of type 2 Diabetes project. Each had one parent with type 2 diabetes.

A second group of 392 adults were part of the ongoing longitudinal CATAMERI study of individuals at elevated risk for metabolic and cardiovascular outcomes. Mean follow-up came to 5.2 years.

On Cox proportional hazard regression analysis, the hazard raio for developing type 2 diabetes was 4.02 for individuals in the NGT-1h-high group, compared with 6.67 for impaired glucose tolerance individuals and 1.91 for the impaired fasting glucose group.

"Individuals of the NGT 1h-high group have a significant reduction in peripheral insulin sensitivity, evaluated by the hyperinsulinemic euglycemic clamp, as compared with individuals of the NGT 1h-low group," the researchers noted.

For the second group, the incidence rates of new-onset diabetes during follow up were 2.9%, 16.7%, 12.5%, and 31.4%, respectively, in the NGT-1h-low, NGT-1h-high, isolated impaired fasting glucose, and impaired glucose tolerance groups.

The NGT-1h-high group had a high proportion of males compared with the NGT-1h-low group, as well as a high proportion of older individuals and individuals with significantly higher FPG, the researchers wrote.

"Our results are consistent with two longitudinal studies in Mexican-American and Scandinavian Caucasian populations, as well as a retrospective study carried out in Asian Indians," Dr. Sesti told Reuters Health. "Taken together, these data suggest that one-hour post-load hyperglycemia may be a useful tool, in addition to fasting glucose, two-hour post-load glucose, and (hemoglobin A1c), to identify individuals at higher risk to develop diabetes."

Dr. David M. Nathan, director of the Massachusetts General Hospital Diabetes Center and Clinical Research Center, Boston, told Reuters Health by email, "The current paper only follows a relatively small cohort over about five years. Sample 1 is well described with regard to its make-up - all white - but sample 2 is poorly described, so we can't even conclude whether these results are generalizable. Moreover, note the difference in composition of the different glycemia groups (with large differences in gender and age."

Dr. Sesti acknowledged that generalizing to other nonwhite ethnic groups should be done with caution. "Nevertheless, higher risk for future type 2 diabetes in individuals with NGT and 1 hour post-load glucose 155 mg/dl has been observed in Mexican-American, Scandinavian, Caucasian, and Asian Indian populations," he said.

As for the large differences in gender and age distribution in the various glycemia groups, he explained, "It is well known that glucose intolerance varies according to age and gender."

SOURCE: http://bit.ly/1JaLbkg

J Clin Endocrinol Metab 2015.

(c) Copyright Thomson Reuters 2015. Click For Restrictions - http://about.reuters.com/fulllegal.asp