Acute hyperglycemia reduces cerebrovascular reactivity: the role of glycemic variability.

Abstract

Cerebral vasomotor reactivity (CVR) is reduced in patients with diabetes mellitus (DM), and glucose variability (GV) might be responsible for cerebrovascular damage. Studying patients with insulin resistance without DM, we explored the role of GV in impairing CVR. We studied 18 metabolic syndrome (MS) patients without DM, 9 controls (C), and 26 patients with DM. Groups were compared in terms of CVR, GV, and 24-hour blood pressure. To evaluate the impact of acute hyperglycemia on CVR, a hyperglycemic clamp was performed in MS patients and controls. Baseline CVR was reduced in DM vs C and MS (C vs DM = 20.2, 95% CI = 3.5-36.9, P = .014; and MS vs DM = 22.2, 95% CI = 8.6-35.8, P = .001), but similar between MS and C (MS vs C = 2.0, 95% CI = -14.7 to 18.7, P = .643). During acute hyperglycemia, CVR fell in MS and C to values comparable to DM. GV progressively increased from C to MS to DM. In MS, CVR at 120 minutes and GV displayed a negative correlation (r = -0.48, P = .043), which did not change after controlling for mean 24-hour systolic and diastolic blood pressure. In MS, the CVR reduction was significantly correlated to GV (r = 0.55, P = .02). GV is increased in patients with MS but without DM and is the major predictor of CVR reduction induced by acute hyperglycemia, possibly representing the earliest cause of cerebrovascular damage in DM.