Differences in effects of insulin glargine or pioglitazone added to oral anti-diabetic therapy in patients with type 2 diabetes: what to add--insulin glargine or pioglitazone?

BACKGROUND: While metformin is the first line treatment in type 2 diabetes, the best way to escalate therapy is not always clear, particularly whether to add one or two oral agents or to introduce insulin.

METHODS: Thirty-six patients inadequately controlled on metformin and sulfonylurea/meglitinide were randomized to receive add-on therapy with insulin glargine or pioglitazone for 26 weeks. Insulin was up-titrated to achieve fasting plasma glucose <6 mmol/l. Pioglitazone was increased to 45 mg/day after 16 weeks if HbA1c>6.2%. beta-Cell function and insulin sensitivity were assessed by measuring insulin, proinsulin and adiponectin, and in a subgroup using a combined glucagon-stimulated C-peptide test and insulin tolerance test (GITT). Lipids and natriuretic peptides were measured at start and end of study.

RESULTS: The reduction in HbA1c was slightly greater in the insulin glargine group and used as co-variate when analysing other variables. The effect on beta-cell function was more favourable with insulin glargine measured by proinsulin (42+/-48 to 19+/-16, p=0.01 vs. 36+/-26 to 27+/-16 p=0.04) while the improvement in insulin sensitivity measured by adiponectin (7.5+/-3.7 to 15+/-10, p<0.01 vs. 8.7+/-4 to 7.6+/-3, p=0.04) and HDL cholesterol (1.10+/-0.24 to 1.24+/-0.3, p<0.01 vs. 1.08+/-0.35 to 1.04+/-0.33, ns) (all p between groups <0.01) was more favourable in pioglitazone group. Pioglitazone caused significant increase in natriuretic peptides (BNP pmol/l 6.6+/-5.2 to 13.7+/-16.1, p=0.04 vs. 8.8+/-11.6 to 8.6+/-10.6, ns, p between groups 0.028).

CONCLUSIONS: The results demonstrate characteristic differences in the effects of insulin glargine vs. pioglitazone on measures of beta-cell function and insulin sensitivity as well as cardiac load.