Objective The effect of pioglitazone on high-density lipoprotein cholesterol (HDL-C) has been attracting attention. However, there are limited data on the characteristics of patients who are likely to respond to pioglitazone in terms of the improvement in HDL-C levels (lipid responders). In the present study, the characteristics of lipid responders were investigated. Methods Five hundred and sixty-three patients with type 2 diabetes who started pioglitazone treatment were followed for six

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... . They were divided into two groups according to the response to pioglitazone. Subjects whose HDL-C levels increased by 10% or more from the baseline were defined as lipid responders. The odds ratios (OR) for becoming lipid responders were calculated using logistic regression. Results Significant patients' characteristics of lipid responders were age, HbA1c, HDL-C and low-density lipoprotein cholesterol (LDL-C), yielding adjusted ORs of 0.76 [95% confidence interval (CI) =0.61-0.93] for an increment of 10 years, 0.79 (95% CI=0.66-0.95) for an increment of 1 %, 0.83 (95% CI=0.72-0.96) for an increment of 10 mg/dL and 0.93 (95% CI=0.87-1.00) for an increment of 10 mg/dL, respectively. Patients with sulfonylurea treatment and those with both sulfonylurea and metformin treatment were less likely to become lipid responders than diet-treated patients with ORs of 0.32 (95% CI=0.15-0.69) and 0.41 (95% CI= 0.19-0.87), respectively. Conclusion Pioglitazone could be beneficial especially for patients with young age, low HbA1c, low HDL-C or low LDL-C levels at baseline in terms of the improvement in HDL-C levels. Use of sulfonylureas at baseline could attenuate the effect of pioglitazone on HDL-C.