Effect of pioglitazone on progression of subclinical atherosclerosis in non-diabetic premenopausal Hispanic women with prior gestational diabetes.

The Pioglitazone in the Prevention of Diabetes (PIPOD) study was a single arm 3-year open-label pioglitazone treatment to determine the effects of pioglitazone in women with prior gestational diabetes mellitus (GDM) who had completed the troglitazone in the Prevention of Diabetes (TRIPOD) study. Here we report the results on progression of subclinical atherosclerosis, measured by carotid intima-media thickness (CIMT) in non-diabetic women. Data were analyzed to compare CIMT progression rates during pioglitazone treatment to rates that had been observed during either placebo or troglitazone treatment in the TRIPOD study. Sixty-one women met the entry criteria with mean age of 40 years. In the 30 women who came to PIPOD from the placebo arm of TRIPOD, the CIMT rate was 69% lower during pioglitazone treatment than it had been during placebo (0.0031 vs. 0.0100mm/yr, p=0.006). In the 31 women who came to PIPOD from the troglitazone arm of TRIPOD, CIMT rate was 38% lower during pioglitazone than it had been during troglitazone, a difference that was not statistically significant (0.0037 vs. 0.0060mm/year; p=0.26). Adjustment for differences in baseline characteristics and potential on-trial confounders did not alter the conclusion but did increase the CIMT rates differences slightly. We conclude that treatment with pioglitazone slowed CIMT progression in women who had been on placebo in the TRIPOD study and maintained a relatively low rate of progression in women who had been on troglitazone. Pioglitazone slows progression of subclinical atherosclerosis in young Hispanic women at increased risk for type 2 diabetes.

Effect of pioglitazone on pancreatic beta-cell function and diabetes risk in Hispanic women with prior gestational diabetes.

The Pioglitazone In Prevention Of Diabetes (PIPOD) study was conducted to evaluate beta-cell function, insulin resistance, and the incidence of diabetes during treatment with pioglitazone in Hispanic women with prior gestational diabetes who had completed participation in the Troglitazone In Prevention Of Diabetes (TRIPOD) study. Women who completed the TRIPOD study were offered participation in the PIPOD study for a planned 3 years of drug treatment and 6 months of postdrug washout. Oral glucose tolerance tests were performed annually on pioglitazone and at the end of the postdrug washout. Intravenous glucose tolerance tests (IVGTTs) for assessment of insulin sensitivity and beta-cell function were conducted at baseline, after 1 year on pioglitazone, and at the end of the postdrug washout. Of 95 women who were not diabetic at the end of the TRIPOD study, 89 enrolled in the PIPOD study, 86 completed at least one follow-up visit, and 65 completed all study visits, including the postdrug tests. Comparison of changes in beta-cell compensation for insulin resistance across the TRIPOD and PIPOD studies revealed that pioglitazone stopped the decline in beta-cell function that occurred during placebo treatment in the TRIPOD study and maintained the stability of beta-cell function that had occurred during troglitazone treatment in the TRIPOD study. The risk of diabetes, which occurred at an average rate of 4.6% per year, was lowest in women with the largest reduction in total IVGTT insulin area after 1 year of treatment. The similarity of findings between the PIPOD and TRIPOD studies support a class effect of thiazolidinedione drugs to enhance insulin sensitivity, reduce insulin secretory demands, and preserve pancreatic beta-cell function, all in association with a relatively low rate of type 2 diabetes, in Hispanic women with prior gestational diabetes.

Effect of thiazolidinedione treatment on progression of subclinical atherosclerosis in premenopausal women at high risk for type 2 diabetes.

We tested the effects of treatment with a thiazolidinedione drug on rates of progression of carotid intima-media thickness (CIMT) and some putative determinants of CIMT in young women at high risk for type 2 diabetes. A total of 266 nondiabetic, Hispanic women with recent gestational diabetes were randomized to placebo or troglitazone. CIMT measurements were made at baseline, annually, and at study end, together with measurements of obesity, serum lipids, and glucose and insulin levels during oral glucose tolerance tests. Insulin sensitivity (minimal model analysis) was measured at baseline and 3 months later. Data were analyzed to compare CIMT progression rates between treatment groups and investigate potential determinants of differences in CIMT progression. One hundred ninety-two women had a CIMT measurement at baseline and at least one follow-up visit. The mean rate of CIMT change was 31% lower in women assigned to troglitazone (P = 0.048). This intergroup difference was not explained by baseline or on-trial differences in obesity, lipids, glucose, or insulin. The reduction in CIMT progression developed gradually, occurred only in women who had an increase in insulin sensitivity, and was unrelated to the presence of the metabolic syndrome at baseline. Troglitazone reduced the progression of subclinical atherosclerosis via a mechanism that involved unmeasured mediators of atherosclerosis, either in the circulation or directly in the arterial wall.

Pharmacological treatment of insulin resistance at two different stages in the evolution of type 2 diabetes: impact on glucose tolerance and beta-cell function.

The purpose of this study was to compare the impact of treating insulin resistance with a thiazolidinedione drug before vs. at the onset of diabetes on glucose levels and beta-cell function. Nondiabetic Hispanic women of Mexican or Central American descent with prior gestational diabetes mellitus (GDM) were randomized to troglitazone (early intervention), 400 mg/d, or placebo (later intervention). Women who developed diabetes were placed on open-label troglitazone. Glucose tolerance, insulin resistance, and beta-cell function were measured at randomization, at the diagnosis of diabetes, and 8 months post trial to determine the long-term impact of the two treatment strategies on glucose levels and beta-cell function. During a mean follow-up of 4.3 yr between baseline and posttrial tests, glucose tolerance (oral glucose tolerance test glucose area, P = 0.04) and insulin resistance (MINMOD SI, P = 0.02) worsened more in women randomized to late intervention (n = 69) than to early intervention (n = 57). Insulin secretion (acute insulin response in the iv glucose tolerance test, P = 0.09) and beta-cell compensation for insulin resistance (disposition index, P = 0.07) also tended to worsen more in the late intervention group. Among women in the late intervention group who developed diabetes, oral glucose tolerance test glucose area (P = 0.0001) and beta-cell function (P < or = 0.04) deteriorated significantly during development of diabetes on placebo and then did not change significantly (P > 0.50) during treatment with troglitazone and posttreatment washout. In high-risk Hispanic women, amelioration of insulin resistance can stabilize glycemia at the time diabetes develops. These findings highlight the role of insulin resistance in the genesis of progressive beta-cell dysfunction during the evolution of type 2 diabetes.

Changes in insulin sensitivity in response to troglitazone do not differ between subjects with and without the common, functional Pro12Ala peroxisome proliferator-activated receptor-gamma2 gene variant: results from the Troglitazone in Prevention of Diabetes (TRIPOD) study.

OBJECTIVE: We have tested whether the Pro12Ala variant of the peroxisome proliferator-activated receptor (PPAR)-gamma nuclear receptor involved in thiazolidinedione (TZD) action accounted for the failure of troglitazone to increase insulin sensitivity in nondiabetic Hispanic women with previous gestational diabetes treated in the Troglitazone in Prevention of Diabetes (TRIPOD) study. RESEARCH DESIGN AND METHODS: Ninety-three women assigned to troglitazone had intravenous glucose tolerance tests at randomization and after 3 months of treatment with troglitazone, 400 mg/day, and were genotyped for the Pro12Ala variant of the PPAR-gamma gene. Subjects were divided into tertiles based on their change in minimal model insulin sensitivity (S(i)) during the first 3 months of troglitazone treatment. RESULTS: The mean changes in S(i) in the bottom, middle, and top tertiles of S(i) response were -0.21 +/- 0.57, 0.91 +/- 0.26, and 2.58 +/- 1.32 min(-1) per microU/ml. 10(-4), respectively. Frequencies of the Ala/- genotype were 30, 22, and 26% in the same three tertiles (P = 0.77). Analysis of phenotypes by genotype revealed only small differences between the Pro/Pro and Ala/- groups, respectively, in baseline S(i) (2.76 +/- 0.19 vs. 2.33 +/- 0.33 x 10(-4) min(-1) per microU/ml; P = 0.27), the change in S(i) after 3 months of troglitazone treatment (1.19 +/- 0.17 vs. 0.93 +/- 0.30; P = 0.46), and the cumulative incidence of diabetes during a median follow-up of 30 months (13 vs. 17%; P = 0.66). CONCLUSIONS: Among young Hispanic women at high risk for type 2 diabetes, the Pro12Ala variant of the PPAR-gamma receptor gene did not explain the failure of approximately 1/3 of subjects to increase their insulin sensitivity when placed on troglitazone at a dose of 400 mg/day.

Preservation of pancreatic beta-cell function and prevention of type 2 diabetes by pharmacological treatment of insulin resistance in high-risk hispanic women.

Type 2 diabetes frequently results from progressive failure of pancreatic beta-cell function in the presence of chronic insulin resistance. We tested whether chronic amelioration of insulin resistance would preserve pancreatic beta-cell function and delay or prevent the onset of type 2 diabetes in high-risk Hispanic women. Women with previous gestational diabetes were randomized to placebo (n = 133) or the insulin-sensitizing drug troglitazone (400 mg/day; n = 133) administered in double-blind fashion. Fasting plasma glucose was measured every 3 months, and oral glucose tolerance tests (OGTTs) were performed annually to detect diabetes. Intravenous glucose tolerance tests (IVGTTs) were performed at baseline and 3 months later to identify early metabolic changes associated with any protection from diabetes. Women who did not develop diabetes during the trial returned for OGTTs and IVGTTs 8 months after study medications were stopped. During a median follow-up of 30 months on blinded medication, average annual diabetes incidence rates in the 236 women who returned for at least one follow-up visit were 12.1 and 5.4% in women assigned to placebo and troglitazone, respectively (P < 0.01). Protection from diabetes in the troglitazone group 1) was closely related to the degree of reduction in endogenous insulin requirements 3 months after randomization, 2) persisted 8 months after study medications were stopped, and 3) was associated with preservation of beta-cell compensation for insulin resistance. Treatment with troglitazone delayed or prevented the onset of type 2 diabetes in high-risk Hispanic women. The protective effect was associated with the preservation of pancreatic beta-cell function and appeared to be mediated by a reduction in the secretory demands placed on beta-cells by chronic insulin resistance.