CAPILLARY-PRESSURE IN PATIENTS WITH NIDDM

The hemodynamic hypothesis suggests that raised capillary pressure may play a role in the pathogenesis of diabetic microangiopathy. Although patients with noninsulin-dependent diabetes mellitus (NIDDM) and insulin-dependent diabetes mellitus (IDDM) develop a similar range of microvascular complications, differences in their expression and prevalence suggest that different pathogenic mechanisms may be operational. Capillary pressure is elevated in IDDM; the aim of this study was to assess whether capillary pressure was also elevated in NIDDM. Twenty-one patients with NIDDM (15 men) and 21 healthy control subjects matched for age, sex, and skin temperature were investigated supine with the hand at heart level. Finger nailfold capillary pressure was measured after direct cannulation at the summit of the capillary loops using glass micropipettes. The groups were matched for skin temperature (30.4 [24.2-33.8]degrees C, median [95% confidence interval], NIDDM patients vs. 30.0 [23.4-33.6]degrees C control subjects), age (62.0 [39.4-72.7] years NIDDM patients vs. 62.0 [39.4-72.0] years control subjects), and both systolic (sBP) and diastolic (dBP) blood pressures (133.0 [111.0-167.3]/78.0 [57.0-89.5] mmHg NIDDM patients vs. 133.0 [114.1-158.9]/80.0 [68.2-88.9] mmHg control subjects). Capillary pressure did not differ in the two groups (17.6 [13.1-21.2] mmHg NIDDM patients vs. 19.1 [14.1-23.6] mmHg control subjects [NS]). There was no correlation of capillary pressure with either HbA(1c) or glucose; however, there was a negative association between capillary pressure and diabetes duration (R(s) = -0.50, P = 0.020). Although these data provide no evidence of capillary hypertension in patients with NIDDM, at least under resting conditions, they raise the possibility that diabetes of long duration might modify the normal mechanisms controlling capillary pressure.