Comparison of the glucose oxidase method for glucose determination by manual assay and automated analyzer

In experimental models of diabetes, glucose levels in plasma and blood are commonly determined by colorimetric assay and by automated analyzers based on the glucose oxidase conversion of glucose and O2 to gluconate and H2O2. We have compared the glucose levels obtained by these two methods in control Wistar rats, streptozotocin diabetic Wistar rats, Zucker fa/fa fatty rats and Zucker Diabetic Fatty rats. We found that the manual glucose assay and the glucose analyzer produced comparable values up to concentrations of about 25 mM. Above this level, samples should be diluted.     

A prospective study of prepregnancy dietary iron intake and risk for gestational diabetes mellitus

OBJECTIVE

It is important to identify modifiable factors that may lower gestational diabetes mellitus (GDM) risk. Dietary iron is of particular interest given that iron is a strong prooxidant, and high body iron levels can damage pancreatic β-cell function and impair glucose metabolism. The current study is to determine if prepregnancy dietary and supplemental iron intakes are associated with the risk of GDM.

RESEARCH DESIGN AND METHODS

A prospective study was conducted among 13,475 women who reported a singleton pregnancy between 1991 and 2001 in the Nurses’ Health Study II. A total of 867 incident GDM cases were reported. Pooled logistic regression was used to estimate the relative risk (RR) of GDM by quintiles of iron intake controlling for dietary and nondietary risk factors.

RESULTS

Dietary heme iron intake was positively and significantly associated with GDM risk. After adjusting for age, BMI, and other risk factors, RRs (95% CIs) across increasing quintiles of heme iron were 1.0 (reference), 1.11 (0.87–1.43), 1.31 (1.03–1.68), 1.51 (1.17–1.93), and 1.58 (1.21–2.08), respectively (P for linear trend 0.0001). The multivariate adjusted RR for GDM associated with every 0.5-mg per day of increase in intake was 1.22 (1.10–1.36). No significant associations were observed between total dietary, nonheme, or supplemental iron intake and GDM risk.

CONCLUSIONS

These findings suggest that higher prepregnancy intake of dietary heme iron is associated with an increased GDM risk.Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications affecting approximately 7% of all pregnancies and up to 14% of pregnancies in high-risk populations (1). Overweight and obesity are the major modifiable risk factors of GDM. However, the overall population attributable fraction among the general U.S. population because of overweight and obesity is estimated to be less than 50% (2), implying the need to identify additional risk factors, particularly modifiable risk factors, that may help lower GDM risk.Although the underlying mechanism remains unclear, available evidence suggests that the main defect in the pathogenesis of GDM is relatively diminished insulin secretion coupled with pregnancy-induced insulin resistance (3). Iron, a redox-active transitional metal, is a strong prooxidant. Accumulating evidence from experimental studies has demonstrated that iron overload can lead to β-cell toxicity, β-cell dysfunction, and impaired glucose metabolism (4). Moreover, several epidemiological studies have documented a positive association of circulating levels of ferritin (a marker of body iron stores) with circulating levels of glucose and insulin, and risk of type 2 diabetes melletus (T2DM) (5) and GDM (6–9). The major source of body iron is from the diet. Dietary iron exists as heme (mainly from meat and meat products) or nonheme iron. A positive association has been observed between dietary heme iron intake and T2DM (10). However, to our knowledge, there are no published studies evaluating dietary iron intake and GDM risk. Studies of supplemental iron and GDM risk are also scarce, and findings are inconsistent (11,12). The aim of this study was to evaluate the association between iron intake, including varying sources of iron (heme, nonheme, and supplemental) and GDM risk in a large prospective cohort.     

Neuromyelitis optica spectrum disorders and anti-myelin oligodendrocyte glycoprotein positive optic neuropathies

AIM: To describe the clinical characteristics and treatments associated with antibody positive optic neuropathies including anti-myelin oligodendrocyte glycoprotein (MOG) and anti-aquaporin 4 (AQP4), alongside diagnostic modalities, investigations, and outcomes. METHODS: A cross-sectional single-centre retrospective case series consisting of 16 patients including 12 anti-MOG positive patients and 4 anti-AQP4 positive patients. Each of these patients had clinical signs and symptoms of optic neuritis and consisted of all patients who had a positive blood antibody result in our centre. Clinical findings including presence of a relative afferent pupillary defect, colour vision and disc assessment were recorded. Structured clinical exam and multimodal imaging was undertaken sequentially on each. Optical coherence tomography (OCT) scanning was preformed to examine the correlation between ganglion cell layer (GCL) thickness and visual acuity (VA) at presentation and as a determinant of final visual outcome in both groups. Initial and long-term treatment is also summarised. RESULTS: A total of 16 patients were included in the study consisting of 12 anti-MOG and 4 anti-AQP4 positive patients. Nine of the 16 patients were female and the average age of onset was 29.2y in the MOG group and 42y in the AQP4 group. There was no statistically significant correlation (Pearson correlation) between GCL thickness and presenting and final VA [r(10)=0.081, P=0.08 and r(10)=0.089, P=0.34 respectively]. The same statistical analysis was performed for the correlation between retinal nerve fibre layer (RNFL) and VA and similar outcomes were observed [r(10)=0.04, P=0.22 and r(10)=0.09, P=0.04]. No correlation was seen for initial RNFL thickness and final visual outcome in this group either [r(2)=0.19, P=0.38]. Visual field testing and radiological findings for each group are described. CONCLUSION: No correlation between initial VA or RNFL and final visual outcome is identified. A broad range of visual field and radiographic findings are identified, a consensus on treatment of neuromyelitis optica spectrum disorders and anti-MOG positive optic neuropathies has yet to be accepted but initial high dose immunosuppression followed by low dose maintenance therapy is favoured.