Association of insulin resistance with serum ferritin and aminotransferases-iron hypothesis

AIM: To investigate the relationship of iron indices with diabetes mellitus(DM) in those without hemochromatosis.METHODS: This cross-sectional study examined data collected during the Third National Health and Nutrition Examination Survey(NHANES III). Only those who fasted properly and were not anemic with transferrin saturation < 45% were included(n = 6849). Insulin sensitivity and beta cell function were calculated from fasting glucose and insulin concentrations. Indices of iron metabolism were examined in the presence or absence of DM. We examined the relationship of insulin sensitivity and beta cell function with serum ferritin concentration. The influence of C-reactive protein and liver enzymes was also investigated.RESULTS: Serum ferritin concentration was significantly higher in diabetic subjects(P = 0.0001 to< 0.000001). The difference remained significant after adjustment for age, body mass index, alcohol consumption, and mineral/iron supplement(P = 0.03 to< 0.000001). In those who did not take insulin, serum ferritin concentration was negatively associated with insulin sensitivity(P = 0.05 to 0.00001), but not with beta cell function. The alanine aminotransferase was correlated with serum ferritin concentration(P = 0.02 to< 0.000001) but not with insulin sensitivity, suggesting the role of the liver in iron-associated insulin resistance.CONCLUSION: As most of diabetes is type 2 diabetes and insulin resistance is a cardinal feature of type 2diabetes, disordered iron metabolism could play a role in the pathogenesis of insulin resistance and type 2diabetes through its effect on liver function.

Conundrum of vitamin D on glucose and fuel homeostasis

As an endocrine hormone,vitamin D plays an important role in bone health and calcium homeostasis.Over the past two decades,the non-calcemic effects of vitamin D were extensively examined.Although the effect of vitamin D on beta cell function were known for some time,the effect of vitamin D on glucose and fuel homeostasis has attracted new interest among researchers.Yet,to date,studies remain inconclusive and controversial,in part,due to a lack of understanding of the threshold effects of vitamin D.In this review,a critical examination of interventional trials of vitamin D in prevention of diabetes is provided.Like use of vitamin D for bone loss,the benefits of vitamin D supplementation in diabetes prevention were observed in vitamin D-deficient subjects with serum 25-hydroxyvitamin D<50 nmol/L(20 ng/mL).The beneficial effect from vitamin D supplementation was not apparent in subjects with serum 25-hydroxyvitamin D>75 nmol/L(30 ng/mL).Furthermore,no benefit was noted in subjects that achieved serum 25-hydroxyvitamin D>100 nmol/L(40 ng/mL).Further studies are required to confirm these observations.

Role of hepatitis A virus in diabetes mellitus

BACKGROUND Although much information is available regarding hepatitis C virus infection and diabetes,less is known about the relationship between hepatitis A virus(HAV)infection and diabetes.AIM To examine the roles of HAV in diabetes risk.METHODS This cross-sectional study population included data from the National Health and Nutrition Examination Survey collected between 2005-2012.Adult subjects(≥20 years old)with available body mass index measurements,defined diabetes status,history of HAV vaccination,and HAV serology were included.HAV vaccination was based on self-reported history.Successful HAV immunization was defined as the presence of both vaccination and anti-HAV antibody.HAV infection was defined by the absence of vaccination but presence of anti-hepatitis A antibody.The odds ratio(OR)for diabetes with 95%confidence intervals(95%CI)was calculated for each HAV status and then adjusted for covariates.Sensitivity tests,based on different definitions of diabetes,were performed to verify the results.RESULTS Among 19942 subjects,4229 subjects(21.21%)received HAV vaccination and HAV antibody was present in 9224 subjects(46.25%).Although HAV infection was associated with an increased risk of diabetes(OR:1.13;95%CI:1.08-1.18),HAV vaccination was not associated with diabetes(OR:1.06;95%CI:0.95-1.18),and successful HAV immunization had no impact on the risk of diabetes(OR:1.11;95%CI:0.97-1.27).Thus,HAV infection was an unlikely cause of diabetes.Alternatively,in non-vaccinated subjects,diabetes increased the risk of HAV infection by 40%(OR:1.40,95%CI:1.27-1.54).CONCLUSION An association between HAV infection and diabetes is observed which is best explained by an increased risk of HAV infection in diabetic patients.Diabetic subjects are more susceptible to HAV.Thus,HAV vaccination is highly recommended in diabetic patients.