Effect of induced hypoglycemia on inflammation and oxidative stress in type 2 diabetes and control subjects

Abstract

Intensive diabetes control has been associated with increased mortality in type 2 diabetes (T2DM); this has been suggested to be due to increased hypoglycemia. We measured hypoglycemia-induced changes in endothelial parameters, oxidative stress markers and inflammation at baseline and after a 24-hour period in type 2 diabetic (T2DM) subjects versus age-matched controls. Case-control study: 10 T2DM and 8 control subjects. Blood glucose was reduced from 5 (90 mg/dl) to hypoglycemic levels of 2.8 mmol/L (50 mg/dl) for 1 hour by incremental hyperinsulinemic clamps using baseline and 24 hour samples. Measures of endothelial parameters, oxidative stress and inflammation at baseline and at 24-hours post hypoglycemia were performed: proteomic (Somalogic) analysis for inflammatory markers complemented by C-reactive protein (hsCRP) measurement, and proteomic markers and urinary isoprostanes for oxidative measures, together with endothelial function. Between baseline and 24 -hours after hypoglycemia, 15 of 140 inflammatory proteins differed in T2DM whilst only 1 of 140 differed in controls; all returned to baseline at 24-hours. However, elevated hsCRP levels were seen at 24-hours in T2DM (2.4 mg/L (1.2-5.4) vs. 3.9 mg/L (1.8-6.1), Baseline vs 24-hours, P < 0.05). In patients with T2DM, between baseline and 24-hour after hypoglycemia, only one of 15 oxidative stress proteins differed and this was not seen in controls. An increase (P = 0.016) from baseline (73.4 ng/mL) to 24 hours after hypoglycemia (91.7 ng/mL) was seen for urinary isoprostanes. Hypoglycemia resulted in inflammatory and oxidative stress markers being elevated in T2DM subjects but not controls 24-hours after the event.While type 2 diabetes (T2DM) is associated with an increased risk of cardiovascular disease 1 , strict glycemic control does not result in obvious cardiovascular benefit in people with T2DM 2-4 . A link between strict glycemic control, hypoglycemia and increased cardiovascular morbidity and mortality has been observed in clinical studies 5,6 . Although the underlying mechanism remains unclear, increased inflammatory cytokines and a leukocytosis are reported after hypoglycemia 7,8 , suggesting a link between hypoglycemia and inflammation.It is well recognized that oxidative stress leads to damage of proteins and deoxyribonucleic acid (DNA) 9 and contributes to the diabetic complications of retinopathy, nephropathy, neuropathy and cardiovascular disorders 10-13 , and is directly linked to vascular inflammation, precipitating both endothelial cell dysfunction and vascular damage 14 . Oxidative stress results from excessive generation of free radicals and/or deficient defense mechanisms 15 , and leads to a disturbance of the physiological redox state 16 . The membrane associated 1

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