Acute changes in blood glucose do not alter blood glutathione synthesis in adolescents with poorly controlled type 1 diabetes mellitus

Improved glycemic control either alone, or combined with antioxidant supplementation, fails to restore blood glutathione or markers of oxidative stress in adolescents with poorly controlled type 1 diabetes

In earlier studies, we showed that adolescents with type 1 diabetes mellitus (T1DM) have significant glutathione (GSH) depletion and that GSH is reciprocally related to glycemic control. In both the general population and in those with diabetes, the use of over-the-counter antioxidant supplements is widespread. We hypothesized that improved glycemic control, alone or in combination with dietary antioxidants, would restore blood GSH pool. The study included 41 participants who were 15.8 ± 2.4 years of age (mean ± standard deviation) and with poorly controlled T1DM (hemoglobin A1c [HbA1c] 8.2 ± 0.6%). Erythrocyte GSH, and 3-nitrotyrosine, F2-isoprostane, and 8-hydroxy-2'-deoxy-guanosine (as markers of protein, lipid, and DNA oxidative stress, respectively) were determined in the postabsorptive state after blood glucose was maintained overnight near euglycemia. Participants were then randomized to a mix of antioxidants (vitamin C, selenium, zinc, vitamin E, β-carotene) or placebo for 3 to 6 months, and diabetes management was intensified using CSII (n = 30) or multiple daily injections (n = 11) coupled with CDE phone calls and visits with a Nutritionist. A second, identical study was performed when/if a drop in HbA1c ≥0.5% was achieved. HbA1c levels dropped similarly in both groups (from 8.9 ± 1.0% to 7.9 ± 0.9% and 8.5 ± 0.6% to 7.7 ± 0.7% in placebo and antioxidant group, respectively). Neither total nor reduced GSH was altered by improved metabolic control. Markers of protein, lipid, and DNA oxidation remained unaltered. We conclude that, in youngsters with T1DM, neither a significant improvement in diabetes control over a 3-month period nor the regimen of dietary antioxidant supplied in the current study can mitigate oxidative stress. These findings suggest that, in adolescents with T1DM, (1) more sustained improvement of diabetes control may be needed to alleviate oxidative stress and (2) the putative benefit of antioxidant supplements remains to be proven.

Glutathione metabolism in type 2 diabetes and its relationship with microvascular complications and glycemia

Aims/Hypotheses

We hypothesized that there is decreased synthesis of glutathione (GSH) in type 2 diabetes (T2DM) especially in the presence of microvascular complications, and this is dependent on the degree of hyperglycemia.

Methods

In this case-control study, we recruited 16 patients with T2DM (7 without and 9 with microvascular complications), and 8 age- and sex-matched non-diabetic controls. We measured GSH synthesis rate using an infusion of [²H₂]-glycine as isotopic tracer and collection of blood samples for liquid chromatography mass spectrometric analysis.

Results

Compared to the controls, T2DM patients had lower erythrocyte GSH concentrations (0.90 ± 0.42 vs. 0.35 ± 0.30 mmol/L; P = 0.001) and absolute synthesis rates (1.03 ± 0.55 vs. 0.50 ± 0.69 mmol/L/day; P = 0.01), but not fractional synthesis rates (114 ± 45 vs. 143 ± 82%/day; P = 0.07). The magnitudes of changes in patients with complications were greater for both GSH concentrations and absolute synthesis rates (P-values ≤ 0.01) compared to controls. There were no differences in GSH concentrations and synthesis rates between T2DM patients with and without complications (P-values > 0.1). Fasting glucose and HbA1c did not correlate with GSH concentration or synthesis rates (P-values > 0.17).

Conclusions

Compared to non-diabetic controls, patients with T2DM have glutathione deficiency, especially if they have microvascular complications. This is probably due to reduced synthesis and increased irreversible utilization by non-glycemic mechanisms.

Acute blood glucose fluctuations can decrease blood glutathione and adiponectin levels in patients with type 2 diabetes

INTRODUCTION

Glutathione appears to have apparent antioxidant activity to counter regulate hyperglycemia induced oxidative stress. Adiponectin also plays a role in the suppression of the metabolic derangements in type 2 diabetes mellitus (DM). The aim of this study was to determine whether blood glucose fluctuations can alter blood levels of glutathione and adiponectin.

METHODS

We enrolled 34 patients with type 2 DM. As a measure of short-term glycemic variability, the mean amplitude of glycemic excursions (MAGE) was computed from a continuous glucose monitor system (CGMS), and data were recorded over 72 h. For long-term glycemic variability, we calculated the standard deviation (SD) of HbA1c over a 2-year period. Glutathione and adiponectin levels were measured after completing the 72-h CGMS data collection.

RESULTS

The blood levels of glutathione were significantly and negatively correlated with MAGE (r = -0.543; P < 0.001), but not with HbA1c and SD of HbA1c. Adiponectin levels were also significantly and negatively correlated with MAGE and SD of HbA1c (r = -0.64 and r = -0.55, respectively; P < 0.001). Using generalized estimating equations, multivariate regression analysis revealed that MAGE is an independent predictor of serum levels of adiponectin (P = 0.002) and glutathione (P = 0.004).

CONCLUSIONS

We found strong associations between acute blood glucose variability, glutathione, and adiponectin in type 2 diabetic patients treated with oral hypoglycemic agent therapy.