Methylenetetrahydrofolate reductase and methionine synthase reductase gene polymorphisms and protection from microvascular complications in adolescents with type 1 diabetes

A NOS3 polymorphism determines endothelial response to folate in children with type 1 diabetes or obesity

OBJECTIVE

To determine the effect of polymorphisms in NOS3 and folate pathway enzymes on vascular function and folate status and endothelial response to folate in children with diabetes or obesity.

STUDY DESIGN

A total of 244 subjects (age 13.8 ± 2.8 years, 125 males) were studied for NOS3 and/or folate pathway polymorphisms using polymerase chain reaction/restriction fragment length polymorphism, including at baseline: 139 with type 1 diabetes; 58 with obesity; and 47 controls. The effect of NOS3 genotype on endothelial response to folate (5 mg) was assessed in 85 subjects with diabetes and 28 obese subjects who received active treatment during intervention trials. Vascular function (flow-mediated dilatation [FMD] and glyceryl trinitrate-mediated dilatation), clinical, and biochemical measurements were assessed at baseline and 8 weeks in folate intervention studies.

RESULTS

Folate pathway enzyme and NOS3 polymorphisms did not significantly affect baseline vascular function. The polymorphism in intron 4 of endothelial nitric oxide synthase altered endothelial response to folate significantly: in subjects with diabetes FMD improved by 6.4 ± 5% (insertion carriers) vs 2.3 ± 6.6% (deletion carriers), P = .01; in obese subjects FMD improved by 1.8 ± 5.4% (insertion carriers) and deteriorated by -3.2 ± 7.2% (deletion carriers), P = .05. More subjects carrying the insertion normalized FMD after folate supplementation (insertion 64% vs deletion 28%, χ(2) = 10.14, P = .001).

CONCLUSIONS

A NOS3 polymorphism predicts endothelial response to folate in children with diabetes or obesity, with implications for vascular risk and folate intervention studies.

Current trends in the monitoring and treatment of diabetic retinopathy in young adults

The diagnosis and treatment of diabetic retinopathy (DR) in young adults have significantly improved in recent years. Research methods have widened significantly, for example, by introducing spectral optical tomography of the eye. Invasive diagnostics, for example, fluorescein angiography, are done less frequently. The early introduction of an insulin pump to improve the administration of insulin is likely to delay the development of diabetic retinopathy, which is particularly important for young patients with type 1 diabetes mellitus (T1DM). The first years of diabetes occurring during childhood and youth are the most appropriate to introduce proper therapeutic intervention before any irreversible changes in the eyes appear. The treatment of DR includes increased metabolic control, laserotherapy, pharmacological treatment (antiangiogenic and anti-inflammatory treatment, enzymatic vitreolysis, and intravitreal injections), and surgery. This paper summarizes the up-to-date developments in the diagnostics and treatment of DR. In the literature search, authors used online databases, PubMed, and clinitrials.gov and browsed through individual ophthalmology journals, books, and leading pharmaceutical company websites.

MTHFR 677T variant contributes to diabetic nephropathy risk in Caucasian individuals with type 2 diabetes: a meta-analysis

OBJECTIVE

Previous studies regarding the association between 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and diabetic nephropathy (DN) risk in Caucasian individuals with type 2 diabetes reported conflicting results. To derive a more precise estimation of this association, a meta-analysis was performed.

MATERIALS/METHODS

Odds ratios (ORs) with corresponding 95% confidence intervals (95% CIs) were pooled to assess the association between MTHFR C677T polymorphism and DN risk. Finally, 10 case-control studies with a total of 1590 DN cases and 1555 type 2 diabetic controls without DN were included.

RESULTS

Overall, there was an association between MTHFR C677T polymorphism and increased risk of DN under four comparison models (OR T vs. C=1.50, 95% CI 1.07-2.02, P=0.02; OR TT vs. CC=2.09, 95% CI 1.07-4.08, P=0.03; OR TT vs. TC+CC=1.70, 95% CI 1.10-2.63, P=0.017; OR TC+TT vs. CC=1.85, 95% CI 1.19-2.88, P=0.006). Sensitivity analysis suggested exclusion of any single study did not materially alter the overall pooled ORs above.

CONCLUSIONS

This meta-analysis supports that there is an association between MTHFR C677T polymorphism and DN risk, and MTHFR 677T variant contributes to increased risk of DN in Caucasian individuals with type 2 diabetes.

Hyperhomocysteinemia is independently associated with albuminuria in the population-based CoLaus study

Background

Increased serum levels of homocysteine and uric acid have each been associated with cardiovascular risk. We analyzed whether homocysteine and uric acid were associated with glomerular filtration rate (GFR) and albuminuria independently of each other. We also investigated the association of MTHFR polymorphisms related to homocysteine with albuminuria to get further insight into causality.

Methods

This was a cross-sectional population-based study in Caucasians (n = 5913). Hyperhomocysteinemia was defined as total serum homocysteine ≥ 15 μmol/L. Albuminuria was defined as urinary albumin-to-creatinine ratio > 30 mg/g.

Results

Uric acid was associated positively with homocysteine (r = 0.246 in men and r = 0.287 in women, P < 0.001). The prevalence of albuminuria increased across increasing homocysteine categories (from 6.4% to 17.3% in subjects with normal GFR and from 3.5% to 14.5% in those with reduced GFR, P for trend < 0.005). Hyperhomocysteinemia (OR = 2.22, 95% confidence interval: 1.60-3.08, P < 0.001) and elevated serum uric acid (OR = 1.27, 1.08-1.50, per 100 μmol/L, P = 0.004) were significantly associated with albuminuria, independently of hypertension and type 2 diabetes. The 2-fold higher risk of albuminuria associated with hyperhomocysteinemia was similar to the risk associated with hypertension or diabetes. MTHFR alleles related to higher homocysteine were associated with increased risk of albuminuria.

Conclusions

In the general adult population, elevated serum homocysteine and uric acid were associated with albuminuria independently of each other and of renal function.

Microalbuminuria in the paediatric age: current knowledge and emerging questions

The prevalence of microalbuminuria (MA) in children and adolescents differs from the one in adults, and it is estimated to be about 5.7-7.3% in boys and 12.7-15.1% in girls. The percentage is greater in smaller age group, whereas a positive association is found between albumin excretion rate and pubertal development stage in nondiabetic subjects. The data so far suggest that impairment of glucose metabolism, obesity-related proatherosclerotic pathways and the impact of haemodynamic load constitute major determinants of albuminuria development in the early years of life. In everyday practice if persistent MA is present at a young age, especially in the setting of diabetes, further investigation of cardiovascular risk factors, a more careful follow-up and dietary/lifestyle interventions are needed.

CONCLUSION

Although the significance of MA in paediatric essential hypertension has yet to be determined, its role in diabetic children and adolescents is established and albuminuria assessment has been utilized as a screening test for the presence of diabetes-related kidney disease.

Fenofibrate treatment enhances antioxidant status and attenuates endothelial dysfunction in streptozotocin-induced diabetic rats

Diabetic endothelial dysfunction is accompanied by increased oxidative stress and upregulated proinflammatory and inflammatory mediators in the vasculature. Activation of peroxisome proliferator-activated receptor-alpha (PPAR-α) results in antioxidant and anti-inflammatory effects. This study was designed to investigate the effect of fenofibrate, a PPAR-α activator, on the endothelial dysfunction, oxidative stress, and inflammation in streptozotocin diabetic rats. Diabetic rats received fenofibrate (150 mg kg⁻¹ day⁻¹) for 4 weeks. Fenofibrate treatment restored the impaired endothelium-dependent relaxation and increased basal nitric oxide availability in diabetic aorta, enhanced erythrocyte/liver superoxide dismutase and catalase levels, ameliorated the abnormal serum/aortic thiobarbituric acid reactive substances, and prevented the increased aortic myeloperoxidase without a significant change in serum total cholesterol and triglyceride levels. It did not affect the decreased total homocysteine level and the increased tumor necrosis factor-α level in the serum of diabetic rats. Fenofibrate-induced prevention of the endothelial function seems to be related to its potential antioxidant and antiinflammatory activity.

Albuminuria in children

PURPOSE OF REVIEW

Albuminuria is a marker of present and future cardiovascular and renal morbidity, and mortality, in adults. Because the roots of these diseases extend back into childhood, assessment of albuminuria has become relevant to child and adolescent clinical care.

RECENT FINDINGS

Normal levels of albumin excretion in children are well below the cut-off for microalbuminuria. In healthy children, albuminuria relates to fasting insulin, but not blood pressure, BMI, lipid levels, fasting glucose, or insulin resistance. In obese children, albuminuria relates to multiple measures of insulin resistance. In children with type 1 diabetes, hemoglobin A1c seems to be the most consistent clinical predictor of microalbuminuria although multiple mechanisms seem to be involved, including genetic polymorphisms. Children with type 2 diabetes and hypertension already exhibit microalbuminuria.

SUMMARY

When considering the population as a whole, children make ideal subjects in which to study the natural history of albuminuria given their relative lack of multiple morbidities commonly seen in adults. The unfortunate rise in 'adult' diseases in the pediatric age group makes this especially relevant. There is a need for longitudinal studies examining predictors of elevated urinary albumin levels as well as potential treatment strategies.