INSULIN SENSITIVITY AND ACUTE INSULIN-RESPONSE IN AFRICAN-AMERICANS, NON-HISPANIC WHITES, AND HISPANICS WITH NIDDM - THE INSULIN-RESISTANCEATHEROSCLEROSIS STUDY

NIDDM is usually characterized by beta-cell failure and decreased insu lin sensitivity, It has been reported that a high proportion of Africa n-American NIDDM subjects are insulin sensitive, To examine this issue , we determined insulin sensitivity (S-1) in 479 NIDDM subjects by min imal model analyses of frequently sampled intravenous glucose toleranc e (FSIGT) from the Insulin Resistance Atherosclerosis Study (IRAS), a large multicenter study of insulin sensitivity and cardiovascular risk in African-Americans, Hispanics, and non-Hispanic whites, The African -Americans and non-Hispanic whites were sampled in Los Angeles and Oak land, California, The non-Hispanic whites and Hispanics were sampled i n San Antonio, Texas, and San Luis Valley, Colorado, We defined the pr oportion of insulin-sensitive (S-1) subjects as greater than or equal to 1.61 min(-1) . pU(-1) . ml(-1), which is above the median for nondi abetic subjects of all ethnic groups in the IRAS, Using this definitio n, the proportion of insulin-sensitive diabetic subjects was very low in all ethnic groups (non-Hispanic whites [14.3%] vs, African-American s [6.5%], P = 0.039 in Los Angeles and Oakland; non-Hispanic whites [6 .8%] vs, Hispanics [4.9%], P = 0.737 in San Luis Valley and San Antoni o). These results were also similar in newly diagnosed mildly hypergly cemic diabetic subjects. In addition, these results were not affected by the adjustment for differences in obesity, body fat distribution, a nd severity of hyperglycemia. Even in nonobese subjects (with BMI <30 kg/m(2)), the proportion of insulin-sensitive subjects (S-1 greater th an or equal to 1.61 min(-1) . mu U-1 . ml(-1)) was low (3.6-9.7%). The acute insulin response (AIR) was significantly higher in African-Amer icans than in non-Hispanic whites; there were no ethnic differences in AIR between Hispanics and non-Hispanic whites, There were no signific ant ethnic differences for non-insulin-mediated glucose disposal (S-G) . We conclude that the number of insulin-sensitive NIDDM subjects is l ow and similar among non-Hispanic whites, Hispanics, and African-Ameri cans in the U.S.