Long-term Effect of Metformin on Blood Glucose Control in Non-obese Patients with Type 2 Diabetes

The study demonstrated the long-term beneficial effect of metformin in non-obese (BMI < 25 kg/m²) diabetic patients….

A retrospective study was performed in 213 patients with Type 2 diabetes under the administration of metformin for more than one year. 

The clinical parameters were investigated for 3 years. The obese and non-obese individuals were defined as a body mass index (BMI) of 25 kg/m² or over (n = 105) and a BMI of less than 25 kg/m² (n = 108), respectively.

The results showed that, HbA1c levels were significantly decreased compared with those at the baseline time. The course of HbA1c was similar between the non-obese and the obese groups, while the dose of metformin required to control blood glucose was significantly lower in the non-obese group than in the obese group. The reductions in HbA1c were 1.2% and 1.1% at 12 months, 0.9% and 0.9% at 24 months, and 0.8% and 1.0% at 36 months in the non-obese and obese groups, respectively. BMI did not change during the observation periods. Approximately half of all patients required no additional antidiabetic agents or a reduction in other treatments after the initiation of metformin in either of the two groups.

Metformin appears to maintain the glucose-lowering effect even after the observation period of this study had concluded, because the dose in the non-obese group was limited to 677 mg at 36 months of this study. The worsening in glycemic control over time observed in many patients with Type 2 diabetes mellitus can probably be attenuated by increasing the dose of metformin because metformin reduces the HbA1c levels in a dose-related manner. Metformin is a tolerable drug for patients if the dosage of the first year is completed, because no patients were omitted from this study due to side effects caused by metformin.

The levels of HbA1c were maintained within less than 7% during the 3-year observation period of this study. Additional OHAs or insulin treatment was necessary in 46 (43%) non-obese and 37 (35%) obese patients. It may also be caused by the attenuation of endogenous insulin secretion. However, approximately half of patients required no addition or reduction of other treatments after the initiation of metformin in either group. Although the present study was not performed using metformin monotherapy, the results clinically demonstrated the advantage of metformin either in combination with the other antidiabetic agents or as a single therapy without any change in the treatment.

From the results it was concluded that the present study demonstrated the long-term beneficial effect of metformin in non-obese (BMI < 25 kg/m²) diabetic patients. This effect appears to be maintained even after the observation period of this study, because metformin was limited to a relatively low dose in the non-obese group and the observed worsening in glycemic control over time can probably be attenuated by increasing the dose of metformin.