Relationship between Glycosylated Hemoglobin, Serum Nitric Oxide and Mean Arterial Blood Pressure

BACKGROUND: Hypertension is about twice as frequent in individuals with diabetes as in those without diabetes. Formation of glycosylated conjugates like HbA1c is implicated to have many effects on the vascular endothelium which leads to the development of hypertension in diabetes. Nitric oxide (NO)-dependent vasodilatation has been shown to be an important factor in the maintenance and regulation of peripheral vascular tone. Studies correlating these parameters give conflicting results. Hence the present study was designed to correlate HbA1c, Serum NO & mean arterial blood pressure. AIMS: To study the relationship between glycosylated hemoglobin, serum nitric oxide & mean arterial blood pressure. SETTINGS AND DESIGN: It is a case control study with 28 type 2 diabetic hypertensives, 32 type 2 diabetic normotensives and 51 controls (non diabetic normotensives). MATERIALS & METHODS: The study subjects included 28 type 2 diabetic hypertensives, 32 type 2 diabetic normotensives and 51 controls (non diabetic normotensives) [ADA 2010 and JNC7]. FBS, PPBS, PCV, Hb, HbA1c & serum NO estimation and BP recording was done in all the study subjects. Normalised mean arterial blood pressure (MAPn) and calculated glycosylated hemoglobin (cHbA1c) were calculated from mean arterial BP (MAP) and HbA1c respectively. STATISTICAL ANALYSIS: was done using R commander software. The difference in the distribution of cHbA1c, MAPn & NO levels between all 3 groups was measured using ANOVA and Kruskal-Wallis test. Correlation between the parameters was measured by Correlation coefficient and logistic regression (Spearman linear regression) analysis (univariate and multivariate). RESULTS: There was a significant difference in the distribution of cHbA1c, MAPn & NO levels (p<0.001) between all 3 groups, whether measured by ANOVA or Kruskal-Wallis test. On univariate analysis, there was a positive correlation between cHbA1c & MAPn (ρ= +0.26), a negative correlation between NO & MAPn (ρ = -0.54) and cHbA1c & NO (ρ= -0.66) .On multivariate analysis, not only NO, but contrary to univariate analysis, cHbA1c also showed a negative association with MAPn. CONCLUSION: As the severity of diabetes increases, there is increase in BP, which is mainly due to the marked decrease in NO level which masks the negative correlation between HbA1c on MAPn.