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Nondiabetic Mexican-Americans do not have reduced insulin responses relative to nondiabetic non-Hispanic whites
S M Haffner1, H Miettinen, M P Stern
1Department of Medicine, University of Texas Health Science Center at San Antonio, TX 78284-7873, USA.
Objective:
To study why Mexican-Americans have a threefold increase in NIDDM relative to non-Hispanic whites. The etiology of NIDDM is still controversial, with both insulin resistance and decreased insulin secretion proposed as precursors of NIDDM.
Research Design And Methods:
We examined possible ethnic differences in fasting insulin (as a marker of insulin resistance) and change in insulin-to-change in glucose ratio (delta I30:delta G30) during the first 30 min after oral glucose ingestion (as a marker of abnormal whites from the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Fasting insulin and delta I30:delta G30 were evaluated as continuous variables.
Results:
Mexican-Americans had increased insulin concentrations at fasting and 30, 60, and 120 min after an oral glucose load as well as an increased 0- to 30-min increment in insulin and delta I30:delta G30 relative to non-Hispanic whites. These results remained unchanged after adjustment for age, sex, obesity, body fat distribution, and glucose tolerance.
Conclusions:
These results suggest that increased insulin resistance rather than decreased insulin secretion is characteristic of nondiabetic Mexican-Americans, a high-risk population for NIDDM.