Capillary pressure in subjects with type 2 diabetes and hypertension and the effect of antihypertensive therapy

Raised capillary pressure has been implicated in the formation of diabetic microangiopathy in type I diabetes, in which it is elevated in those with the earliest signs of diabetic kidney disease but remains normal in those without complications. In subjects with type 2 diabetes without complications, capillary pressure is normal, although alterations in the pressure waveforms suggested enhanced wave reflections. The nature of skin capillary pressure in subjects with type 2 diabetes and hypertension remains to be elucidated, as does the effect of blood pressure-lowering therapy on capillary pressure in these subjects. Three studies were performed in well-matched groups. First, capillary pressure was elevated in hypertensive subjects with type 2 diabetes compared with normotensive subjects with type 2 diabetes (20.2 [17.4 to 22.7] mm Hg versus 17.7 [16.1 to 18.9] mm Hg, respectively, P<0.03, Mann-Whitney U test). Second, no significant difference was detected between hypertensive subjects with type 2 diabetes and hypertensive subjects without type 2 diabetes (19.4 [15.8 to 21.3] mm Hg versus 17.2 [15.1 to 19.8] mm Hg, respectively, P=0.5, Mann-Whitney U test). Finally, patients with type 2 diabetes were recruited to a case-control study. Seven subjects received blood pressure-lowering therapy and 8 did not. Therapy reduced capillary pressure from 18.2 [15.8 to 20.1] mm Hg to 15.9 [15.4 to 17.0] mm Hg (P=0.024 ANOVA), in contrast to the lack of effect of time alone. Mean arterial pressure was reduced from 110 [102 to 115] mm Hg to 105 [101 to 111] mm Hg (P=0.006, ANOVA). These findings provide a plausible mechanism by which reducing arterial hypertension may reduce the risk of microangiopathy in type 2 diabetes.