RAGE and CYBA polymorphisms are associated with microalbuminuria and end-stage renal disease onset in a cohort of type 1 diabetes mellitus patients over a 20-year follow-up

Elevated ALOX12 in renal tissue predicts progression in diabetic kidney disease

Diabetic kidney disease (DKD) is one of the major causes of end-stage renal disease and one of the significant complications of diabetes. This study aims to identify the main differentially expressed genes in DKD from transcriptome sequencing results and analyze their diagnostic value. The present study sequenced db/m mouse and db/db mouse to determine the ALOX12 genetic changes related to DKD. After preliminary validation, ALOX12 levels were significantly elevated in the blood of DKD patients, but not during disease progression. Moreover, urine ALOX12 was increased only in macroalbuminuria patients. Therefore, to visualize the diagnostic efficacy of ALOX12 on the onset and progression of renal injury in DKD, we collected kidney tissue from patients for immunohistochemical staining. ALOX12 was increased in the kidneys of patients with DKD and was more elevated in macroalbuminuria patients. Clinical chemical and pathological data analysis indicated a correlation between ALOX12 protein expression and renal tubule injury. Further immunofluorescence double staining showed that ALOX12 was expressed in both proximal tubules and distal tubules. Finally, the diagnostic value of the identified gene in the progression of DKD was assessed using receiver operating characteristic (ROC) curve analysis. The area under the curve (AUC) value for ALOX12 in the diagnosis of DKD entering the macroalbuminuria stage was 0.736, suggesting that ALOX12 has good diagnostic efficacy. During the development of DKD, the expression levels of ALOX12 in renal tubules were significantly increased and can be used as one of the predictors of the progression to macroalbuminuria in patients with DKD.

Association of ALOX12 gene polymorphism with all-cause and cardiovascular mortality in diabetic nephropathy

PURPOSE

Cardiovascular (CV) events are the first cause of death in patients with chronic renal disease (CKD) and in patients with type 2 diabetes mellitus (DM2). The combination of CKD and DM2 elevates the risk of both cardiovascular disease (CVD) and death in this high-risk population. Besides traditional risk factors, such as dyslipidemia, smoking, obesity, and carotid atherosclerosis, novel factors are under investigation such as genetic polymorphisms. Lipoxygenases (LOXs) and their genes are of critical importance in oxidative stress, inflammation, and atherosclerosis. The aim of the study is to clarify a potential ALOX12 role in CVD presence and progress of diabetic patients in different stages of nephropathy.

METHODS

We studied 145 patients with a documented history of DM2 for at least 10 years and diabetic nephropathy (DN), mean age 68 ± 9 years, body mass index 31 ± 5 kg/m², and different stages of renal disease, depending on glomerular filtration rate. The sample population consisted of two groups: 108 DM2 patients with DN in all five stages of CKD and 37 DM2 patients as controls. Anthropometric and clinical characteristics, interview for history of previous CV event, and assessment of carotid intima-media thickness (cIMT) were recorded at baseline. All patients were genotyped for ALOX12 polymorphisms with focus on rs14309. Genotypes (AA, AG, and GG) were evaluated for any possible role in CVD, and grouping was performed on A genotype, which is the dominant model. All participants were followed over a period of 7 years, and the end points studied were all-cause mortality, CV mortality, and CV events. CV events were defined as myocardial infarction (MI), stroke, or peripheral artery disease.

RESULTS

The GG genotype has been significantly associated with cIMT levels above 0.86 mm and with history of MI. Regarding the presence of an atherosclerotic plaque in either carotid artery, no significant association was found when the genotypes were assessed on their own. After grouping, though, GG genotype revealed a significant association between carotid plaque formation and atheromatosis. Kaplan-Meier analysis revealed that ALOX12 gene GG genotype predicted all-cause mortality, CV mortality, and CV events. Similarly, when AA and AG genotypes were grouped, Kaplan-Meier analysis showed that patients with GG genotype presented an even more significant higher all-cause mortality, CV mortality, and CV events compared with AA and AG genotypes combined. After adjustment for several traditional risk factors, multivariate Cox proportional hazard analysis showed that patients with the GG genotype had a significant higher risk of all-cause mortality, a threefold increase in CV mortality, and a twofold increased risk for CV events compared to patients with the AA or the AG genotype.

CONCLUSION

ALOX12 rs14309 GG genotype expression was found to be significantly associated with MI, higher cIMT, increased CV events, CV, and overall mortality. This phenomenon could be partially explained by the increased platelet proaggregatory activity of AA products and the control they exert in thrombotic occurrence and plaque formation.

NADPH oxidase p22phox C242T polymorphism is associated with macroalbuminuria in diabetic patients: A meta-analysis

AIMS

Previous studies suggested an association between C242T polymorphism in NADPH Oxidase p22phox and diabetic nephropathy (DN) risk, but the results were inconsistent. To obtain a more precise estimation, we carried out a meta-analysis to analyze the effect of C242T polymorphism in NADPH Oxidase p22phox on DN risk.

METHODS

We searched PubMed, ISI Web of Science, and China National Knowledge Infrastructure for all eligible case-control studies through May 2016. The odds ratios (ORs), together with the 95% confidence intervals (CIs), were calculated to evaluate the strength of association between C242T SNP in NADPH Oxidase p22phox on DN risk.

RESULTS

Overall, ten eligible studies involving a total of 1894 cases and 1746 controls were included in our meta-analysis. The results showed that there was no statistical evidence of association between NADPH oxidase p22phox C242T polymorphism and DN in all genetic models (T vs. C: OR 1.16, 95% CI 0.85-1.59, p=0.34; TT vs. CC: OR 1.49, 95% CI 0.80-2.76, p=0.21; TT/CT vs. CC: OR 1.18, 95% CI 0.81-1.72, p=0.40; TT vs.

CT/CC

OR 1.31, 95% CI 0.82-2.11, p=0.26). However, significant association was found in diabetic patients with macroalbuminuria.

CONCLUSION

This meta-analysis indicates that NADPH oxidase p22phox C242T polymorphism is associated with macroalbuminuria in diabetic patients. However, this conclusion should be interpreted with caution due to the small sample size. Larger sample-size studies with homogeneous patients and well-matched controls are required.

CYBA encoding p22(phox), the cytochrome b558 alpha polypeptide: gene structure, expression, role and physiopathology

P22(phox) is a ubiquitous protein encoded by the CYBA gene located on the long arm of chromosome 16 at position 24, containing six exons and spanning 8.5 kb. P22(phox) is a critical component of the superoxide-generating nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs). It is associated with NOX2 to form cytochrome b558 expressed mainly in phagocytes and responsible for the killing of microorganisms when bacterial and fungal infections occur. CYBA mutations lead to one of the autosomal recessive forms of chronic granulomatous disease (AR22(0)CGD) clinically characterized by recurrent and severe infections in early childhood. However, p22(phox) is also the partner of NOX1, NOX3 and NOX4, but not NOX5, which are analogs of NOX2, the first identified member of the NOX family. P22(phox)-NOX complexes have emerged as one of the most relevant sources of reactive oxygen species (ROS) in tissues and cells, and are associated with several diseases such as cardiovascular and cerebrovascular diseases. The p22(phox)-deficient mouse strain nmf333 has made it possible to highlight the role of p22(phox) in the control of inner ear balance in association with NOX3. However, the relevance of p22(phox) for NOX3 function remains uncertain because AR22(0)CGD patients do not suffer from vestibular dysfunction. Finally, a large number of genetic variations of CYBA have been reported, among them the C242T polymorphism, which has been extensively studied in association with coronary artery and heart diseases, but conflicting results continue to be reported.