Interesting article: Medical News: ADA: Diabetes Prevention Hopes Revived for Thiazolidinedione - in Meeting Coverage, ADA from MedPage Today
SAN FRANCISCO, June 11 -- Pioglitazone (Actos) may prevent or delay progression to diabetes for patients with insulin resistance, researchers found.

At an average 2.6 years of follow-up, the thiazolidinedione extended time to occurrence of diabetes by 81% for patients with impaired glucose tolerance compared with placebo in the large randomized ACT NOW trial.

The number needed to treat to prevent one case of type 2 diabetes was 3.5 for one year, "a pretty favorable number," reported Ralph A. DeFronzo, M.D., of the University of Texas Health Science Center at San Antonio, at the at the American Diabetes Association meeting here.

If replicated, these findings put pioglitazone in the lead for prevention, commented Saul Genuth, M.D., of Case Western Reserve in Cleveland, who was a chair of the late-breaking clinical trials session at which the results were reported.