Evidence of increased inflammation and microcirculatory abnormalities in patients with type 1 diabetes and their role in microvascular complications

Abstract

Objective: Type 1 diabetes is associated with increased microvascular complications and inflammation. The monocyte-macrophage is a pivotal cell in atherogenesis. There are scanty data on noninvasive measures of microvascular abnormalities and inflammation in type 1 diabetic subjects with microvascular complications. Thus, we examined systemic and cellular biomarkers of inflammation in type 1 diabetic patients with microvascular complications (T1DM-MV patients) and type 1 diabetic patients without microvascular complications (T1DM patients) compared with matched control subjects and determined the microcirculatory abnormalities in the T1DM and T1DM-MV patients using computer-assisted intravital microscopy (CAIM).

Research design and methods: Fasting blood, 24-h urine, and CAIM measurements were obtained from the T1DM and T1DM-MV patients and matched control subjects. C-reactive protein, E-selectin, nitrotyrosine, monocyte superoxide, and cytokines were elevated in the T1DM and T1DM-MV patients compared with control subjects (P < 0.01).

Results: Severity index, as assessed by CAIM, was significantly increased in the T1DM and T1DM-MV patients compared with the control subjects (P < 0.001). There was a significant increase in C-reactive protein, nitrotyrosine, vascular cell adhesion molecule and monocyte superoxide anion release, and interleukin-1 release in T1DM-MV compared with T1DM patients (P < 0.05). T1DM-MV patients had significantly increased CAIM severity index and microalbumin-to-creatinine ratio compared with T1DM patients (P < 0.05). Furthermore, pp38MAPK, pp65, and pERK activity were significantly increased in monocytes from the T1DM and T1DM-MV patients compared with those from the controls subjects, and pp38MAPK and pp65 activity were significantly increased in the T1DM-MV compared with the T1DM patients (P < 0.01).

Conclusions: T1DM-MV patients have increased inflammation compared with T1DM patients. CAIM provides an effective biomarker of microvascular complications, since it is significantly elevated in T1DM-MV compared with T1DM patients and can be monitored following therapies targeted at improving inflammation and/or microvascular complications of type 1 diabetes.

FIG. 1

Increased microvascular abnormalities in T1DM-MV compared with T1DM patients and control subjects (C). Severity index was computed from CAIM measurements of the bulbar conjunctiva from control subjects and T1DM and T1DM-MV patients, as described in RESEARCH DESIGN AND METHODS. *P < 0.001 by one-way ANOVA compared with control subjects, and #P < 0.05 compared with T1DM patients.

FIG. 2

Nitrotyrosine levels in control subjects (C) and T1DM and T1DM-MV patients. Levels of plasma nitrotyrosine were assessed in T1DM-MV and T1DM patients and matched control subjects as described in RESEARCH DESIGN AND METHODS. *P < 0.001 by one-way ANOVA compared with control subjects, and #P < 0.05 compared with T1DM patients.

FIG. 3

Monocyte proatherogenic activity in T1DM-MV compared with T1DM patients and control subjects (C). Monocytes were isolated from fasting heparinized blood and superoxide anion release (A). IL-1β release (B) was measured in LPS-activated monocytes from control subjects and T1DM and T1DM-MV patients, as described in RESEARCH DESIGN AND METHODS. *P < 0.01 by one-way ANOVA compared with control subjects, and #P < 0.05 compared with T1DM patients.

FIG. 4

Activation of MAPK in monocytes of T1DM patients. Monocyte lysates were prepared, and activity of phosphor-to-total p38MAPK, ERK, and JNK were measured in control subjects (C) and T1DM and T1DM-MV patients, as described in RESEARCH DESIGN AND METHODS. Also, nuclear extracts of monocytes from these three groups were prepared, and pp65 activity to total p65 was assessed as described in RESEARCH DESIGN AND METHODS. *P < 0.01 by one-way ANOVA compared with control subjects, and #P < 0.05 compared with T1DM patients.