Comparison of Glycemic and Lipid Response to Pioglitazone Treatment in Mexican-Americans and Non-Hispanic Caucasians With Type 2 Diabetes

The risk of type 2 diabetes in Mexican-Americans is almost twice that of non-Hispanic Caucasians (1). Mexican-Americans are also, in general, more likely to have insulin resistance, impaired fasting glucose, and impaired glucose tolerance than non-Hispanic Caucasians (1,2). Given these increased risks of type 2 diabetes in the Mexican-American population and the fact that poor glycemic control is more common in diabetic Mexican-Americans than in non-Hispanic Caucasians (3), it is important to consider the efficacy of diabetes therapy in this specific population.

In a retrospective chart review, our clinic identified patients with type 2 diabetes who had been treated with pioglitazone 45 mg/day for 6 or more months without interruption. Patient charts were then selected if HbA_1c and lipids were available within 4 weeks of starting treatment and ∼4 months into treatment. Patients whose lipid-lowering medication was changed during this same time period were excluded. In total, data from 98 non-Hispanic Caucasians and 81 Mexican-Americans were reviewed.

The majority of patients (>75%) were taking pioglitazone in combination with metformin, sulfonylurea, or insulin, with the remainder of the patients receiving pioglitazone as monotherapy. The percentage of patients on monotherapy was the same in both groups. Fifty-three percent of non-Hispanic and 31% of Mexican-American patients were taking statin medication (P = 0.002). One patient in the Mexican-American group and three in the non-Hispanic group were taking a fibrate. Baseline characteristics (duration of diabetes, BMI, C-peptide, and male-to-female ratio) for the two groups were similar with the exception of age. The mean and standard deviation for age was 61.2 ± 12.8 years in the non-Hispanic Caucasian population and 52.7 ± 15.2 in the Mexican-American population (P < 0.001). The younger age in the Mexican-American population is consistent with the younger age of onset of diabetes that has been reported elsewhere for this population (4). The mean duration of treatment, at which time the laboratory data were obtained, was 3.9 months in the Mexican-American patients and 4.4 months in the non-Hispanic Caucasians (P = 0.312).

Our analysis showed that mean reduction in HbA_1c was similar between the two populations. Mean baseline HbA_1c was 8.0 ± 1.9% for non-Hispanics and 8.2 ± 1.9% for Mexican-Americans. At 3 months, the mean reductions from baseline were 1.2 ± 1.8% and 1.1 ± 1.4%, respectively (the difference between two populations was not statistically significant, P = 0.616).

Similarly, there was no difference between the two populations in terms of lipid effects. Baseline triglyceride levels were 216 and 207 mg/dl, respectively; baseline HDL cholesterol levels were 41.6 and 43.1 mg/dl, respectively; and baseline LDL cholesterol levels were 106 and 113 mg/dl, respectively. Mean reductions in triglycerides from baseline were 10.1 ± 47.1% in non-Hispanic Caucasians and 8.4 ± 47.3% in Mexican-Americans (P = 0.802 for two populations). Mean increases in HDL cholesterol were 17.0 ± 21.0 and 16.0 ± 18.8%, respectively (P = 0.748), and mean increases in LDL cholesterol were 5.1 ± 25.2 and 6.5 ± 48.1%, respectively (P = 0.826). In a subanalysis, there was no significant (P > 0.05) difference within each ethnic group in the lipid response to pioglitazone regardless of whether the patient was concurrently taking a statin.

Also of interest was the fact that weight gain was similar in both groups. Baseline BMI was practically identical between the two population groups (33.9 and 33.1 kg/m², respectively, for non-Hispanics Caucasians vs. Mexican-Americans), although overall, the Caucasians weighed more at baseline than the Mexican-Americans (mean weight 99.6 and 89.2 kg, respectively). Mean weight gain at 3 months was 1.64 and 1.41 kg, respectively (P = 0.540).

Although Mexican-Americans have a higher incidence of type 2 diabetes and an earlier age of onset, our analysis suggests that their response to treatment with pioglitazone is similar to that seen in non-Hispanic Caucasians in terms of HbA_1c and lipid changes. Such a comparison of pioglitazone treatment between these two ethnic groups has not previously been conducted, and thus these data provide some interesting and encouraging insights. Certainly, good glycemic control can greatly reduce the risk for diabetic complications in all ethnic groups; however, because of the increased risk in Mexican-Americans, treatments that improve glycemic control potentially offer a greater benefit in this population (5). Further prospective comparative studies in Mexican-American populations should be conducted to confirm and expand upon our results.