Insulin therapy may increase blood pressure levels in type 2 diabetes mellitus

OBJECTIVE: To assess the effects of insulin therapy on blood pressure levels in type 2 diabetes mellitus (T2 DM). MATERIAL AND METHODS: This is a retrospective analysis of clinical records of 313 T2DM patients (125 men and 188 women), excluding those with proteinuria or hypertensive diseases and those taking drugs that may influence blood pressure levels except antihypertensive therapy. Mean age was 56.3 +/- 11.7 years and mean duration of diabetes was 7.1 +/- 5.5 years. After one week of observation under diet and maximal doses of oral antidiabetic drugs, patients who did not improve their glucose control were changed towards insulin therapy (n=129) and formed the insulin treated group (ITG), those who improved their glucose levels were maintained under oral therapy (n=184) and formed the orally treated group (OTG). Blood pressure levels were compared between the two groups at baseline and after a mean follow-up period of 12.1 +/- 6.1 months. Hypertension was considered if patients were known and treated or if SBP >=140 mmHg and/or DBP >=90 mmHg. RESULTS: At baseline, patients in ITG were moderately older (58.4 +/- 11 vs 54.9 +/- 12.1 years, p<0.05), had a longer duration of diabetes (9.2 +/- 6.2 vs 5.7 +/- 5 years, p<0.01), a lower BMI (24.6 +/- 4.6 vs 28.8 +/- 6.6 kg/m(2), p<0.01) and a higher frequency of retinopathy (44% vs 31.1%, p<0.05). There was no significant difference regarding sex ratio, WHR, family history of hypertension, plasma levels of creatinine and lipid parameters. SBP, DBP and frequency of hypertension were similar in both groups at baseline. After follow up, insulin treated group exhibited higher levels of SBP (150 +/- 25.7 vs 138.6 +/- 27.1 mmHg, p<0.001) and DBP (84.1 +/- 13 vs 75.8 +/- 14.9 mmHg, p<0.001) than orally treated group. Progression rate of hypertension frequency was mildly but not significantly higher in ITG than in OTG (+21% vs +12%, p=0.08) and was associated with weight gain in ITG only. SBP increase was mildly correlated with weight gain (p=0.06). In ITG, higher values of BMI (> 27 kg/m(2)) at baseline were associated with the highest increases of blood pressure levels under insulin therapy. No significant relationship was found with insulin doses. CONCLUSION: Insulin therapy may contribute to the development of hypertension in T2DM obese patients. Additional prospective randomised studies are required for a better appreciation of such influence.