Catalase activity, allelic variations in the catalase gene and risk of kidney complications in patients with type 1 diabetes

Rs4862705 in the melatonin receptor 1A gene is associated with renal function decline in type 1 diabetes individuals

Aim

The pathogenesis of chronic diabetes complications has oxidative stress as one of the major elements, and single-nucleotide polymorphisms (SNPs) in genes belonging to antioxidant pathways modulate susceptibility to these complications. Considering that melatonin is a powerful antioxidant compound, our aim was to explore, in a longitudinal cohort study of type 1 diabetes (T1D) individuals, the association of microvascular complications and SNPs in the gene encoding melatonin receptor 1A (MTNR1A).

Methods

Eight SNPs in MTNR1A were genotyped in 489 T1D individuals. Besides cross-sectional analyses of SNPs with each one of the microvascular complications (distal polyneuropathy, cardiovascular autonomic neuropathy, retinopathy, and diabetic kidney disease), a longitudinal analysis evaluated the associations of SNPs with renal function decline in 411 individuals followed up for a median of 8 years. In a subgroup of participants, the association of complications with urinary 6-sulfatoxymelatonin (aMT6s) concentration was investigated.

Results

The group of individuals with a renal function decline ≥ 5 mL min-1 1.73 m-2 year-1 presented a higher frequency of the A allele of rs4862705 in comparison with nondecliners, even after adjustment for confounding variables (OR = 1.84, 95% CI = 1.20-2.82; p = 0.0046). No other significant associations were found.

Conclusions

This is the first study showing an association between a variant in a gene belonging to the melatonin system and renal function decline in the diabetic setting.

Association of a single nucleotide polymorphism in SOD2 with susceptibility for the development of diabetic nephropathy in patients with type 2 diabetes: A Saudi population study

INTRODUCTION

One of the complications of diabetes mellitus (DM) is diabetic nephropathy (DN), which plays a significant role in the progression of end-stage renal disease. Oxidative stress is implicated in DN pathogenesis, and genetic variations in antioxidant enzymes such as superoxide dismutase 2 (SOD2) and catalase (CAT) may contribute to the susceptibility. This study aimed to investigate the potential association between single nucleotide polymorphisms (SNPs) in antioxidant enzymes, specifically SOD2 rs4880 and CAT rs769217, and the risk of T2D and susceptibility to DN within the Saudi population.

METHODS

This case-control study included 150 participants, comprising 50 patients with T2D without DN (group 1), 50 patients with T2D with DN (group 2), and 50 healthy participants (group 3). The samples were genotyped using real-time PCR for SOD2 rs4880 and CAT rs769217 SNPs. Sanger sequencing was used for validation. Statistical analyses were performed to explore associations between these SNPs and T2D with or without DN.

RESULTS

No significant difference was observed in CAT rs769217 expression between the groups. However, a significant difference was observed in SOD2 rs4880 expression between the healthy controls and patients with T2D with DN (p = .028). Furthermore, SOD2 rs4880 was associated with approximately threefold increased risk of DN in patients with T2D compared to that in healthy participants (odds ratio [OR] = 2.99 [1.31-6.83]). Validation through Sanger sequencing further confirmed these findings.

CONCLUSIONS

The findings of this study provide evidence that SOD2 rs4880 SNP may contribute to inadequate defence by the antioxidant enzyme, SOD2, against DM-induced oxidative stress and thus cause DN in Saudi patients with T2D. Therefore, SOD2 rs4880 may serve as a predictive marker to prevent the development and progression of DN in patients with T2D.

Redox Genetic Risk Score and the Incidence of End-Stage Kidney Disease in People with Type 1 Diabetes

End-stage kidney disease (ESKD) is a multifactorial condition influenced by genetic background, but the extent to which a genetic risk score (GRS) improves ESKD prediction is unknown. We built a redox GRS on the base of previous association studies (six polymorphisms from six redox genes) and tested its relationship with ESKD in three cohorts of people with type 1 diabetes. Among 1012 participants, ESKD (hemodialysis requirement, kidney transplantation, eGFR < 15 mL/min/1.73 m²) occurred in 105 (10.4%) during a 14-year follow-up. High redox GRS was associated with increased ESKD risk (adjusted HR for the upper versus the lowest GRS tertile: 2.60 (95% CI, 1.51-4.48), p = 0.001). Each additional risk-allele was associated with a 20% increased risk of ESKD (95% CI, 8-33, p < 0.0001). High GRS yielded a relevant population attributable fraction (30%), but only a marginal enhancement in c-statistics index (0.928 [0.903-0.954]) over clinical factors 0.921 (0.892-0.950), p = 0.04). This is the first report of an independent association between redox GRS and increased risk of ESKD in type 1 diabetes. Our results do not support the use of this GRS in clinical practice but provide new insights into the involvement of oxidative stress genetic factors in ESKD risk in type 1 diabetes.

ACE I/D Polymorphism, Plasma ACE Levels, and Long-term Kidney Outcomes or All-Cause Death in Patients With Type 1 Diabetes

OBJECTIVE

The deletion (D) allele of the ACE insertion/deletion (I/D) polymorphism is a risk factor for diabetic kidney disease. We assessed its contribution to long-term kidney outcomes and all-cause death in patients with long-standing type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 1,155 participants from three French and Belgian cohorts were monitored for a median duration of 14 (interquartile range 13) years. The primary outcome was the occurrence of end-stage kidney disease (ESKD) or a 40% drop in the estimated glomerular filtration rate (eGFR). Secondary outcomes were the individual components of the primary outcome, rapid decline in eGFR (steeper than -3 mL/min/1.73 m² per year), incident albuminuria, all-cause death, and a composite ESKD or all-cause death. Hazard ratios (HRs) for XD versus II genotype and for baseline plasma ACE levels were computed by Cox analysis. Genotype performance in stratifying the primary outcome was tested.

RESULTS

Genotype distribution was 954 XD and 201 II. The primary outcome occurred in 20% of XD and 13% of II carriers: adjusted HR 2.07 (95% CI 1.32-3.40; P = 0.001). Significant associations were also observed for rapid decline in eGFR, incident albuminuria, ESKD, all-cause death, and ESKD or all-cause death. Baseline plasma ACE levels were higher in XD carriers and significantly associated with an increased risk of the primary outcome. The ACE genotype enhanced net reclassification improvement (0.154, 95% CI 0.007-0.279; P = 0.04) and integrated discrimination improvement (0.012, 95%CI 0.001-0.021; P = 0.02) for primary outcome stratification.

CONCLUSIONS

The D-allele of the ACE I/D polymorphism was associated with an increased risk of major kidney events and all-cause death in patients with long-standing type 1 diabetes.

Oxidative Stress Markers in Chronic Kidney Disease with Emphasis on Diabetic Nephropathy

Diabetes prevalence is increasing worldwide, especially through the increase of type 2 diabetes. Diabetic nephropathy occurs in up to 40% of diabetic patients and is the leading cause of end-stage renal disease. Various factors affect the development and progression of diabetic nephropathy. Hyperglycaemia increases free radical production, resulting in oxidative stress, which plays an important role in the pathogenesis of diabetic nephropathy. Free radicals have a short half-life and are difficult to measure. In contrast, oxidation products, including lipid peroxidation, protein oxidation, and nucleic acid oxidation, have longer lifetimes and are used to evaluate oxidative stress. In recent years, different oxidative stress biomarkers associated with diabetic nephropathy have been found. This review summarises current evidence of oxidative stress biomarkers in patients with diabetic nephropathy. Although some of them are promising, they cannot replace currently used clinical biomarkers (eGFR, proteinuria) in the development and progression of diabetic nephropathy.

Relationship between renal capacity to reabsorb glucose and renal status in patients with diabetes

AIMS

Interindividual variability in capacity to reabsorb glucose at the proximal renal tubule could contribute to risk of diabetic kidney disease. Our present study investigated, in patients with diabetes, the association between fractional reabsorption of glucose (FR_GLU) and degree of renal disease as assessed by urinary albumin excretion (UAE) and estimated glomerular filtration rate (eGFR).

METHODS

FR_GLU [1-(glucose clearance/creatinine clearance)] was assessed in 637 diabetes patients attending our tertiary referral centre, looking for correlations between FR_GLU and UAE (normo-, micro-, macro-albuminuria) and Kidney Disease: Improving Global Outcomes (KDIGO) eGFR categories: >90 (G1); 90-60 (G2); 59-30 (G3); and<30-16 (G4) mL/min/1.73 m². Patients were stratified by admission fasting plasma glucose (FPG) into three groups: low (<6mmol/L); intermediate (6-11mmol/L); and high (>11mmol/L).

RESULTS

Median (interquartile range, IQR) FR_GLU levels were blood glucose-dependent: 99.90% (0.05) for low (n=106); 99.90% (0.41) for intermediate (n=288); and 96.36% (12.57) for high (n=243) blood glucose categories (P<0.0001). Also, FR_GLU increased with renal disease severity in patients in the high FPG group: normoalbuminuria, 93.50% (17.74) (n=135); microalbuminuria, 96.56% (5.94) (n=77); macroalbuminuria, 99.12% (5.44) (n=31; P<0.001); eGFR G1, 94.13% (16.24) (n=111); G2, 96.35% (11.94) (n=72); G3 98.88% (7.59) (n=46); and G4, 99.11% (2.20) (n=14; P<0.01). On multiple regression analyses, FR_GLU remained significantly and independently associated with UAE and eGFR in patients in the high blood glucose group.

CONCLUSION

High glucose reabsorption capacity in renal proximal tubules is associated with high UAE and low eGFR in patients with diabetes and blood glucose levels>11mmol/L.

Importance of intensive blood pressure control in type 2 diabetes: Mechanisms, treatments and current guidelines

Observational and interventional studies have shown that intensified blood pressure (BP) reduction can benefit people with diabetes. Because of their special haemodynamic properties, renin-angiotensin-aldosterone system (RAAS) blockers are recommended. The results of the BP arm of the ADVANCE study strongly support the recently updated European Society of Cardiology/European Association of Diabetes recommendations for the treatment of BP in people with diabetes, which recommend a target systolic/diastolic BP of 130/80 mmHg with few exceptions, and a fixed combination of an RAAS blocker with a diuretic or a calcium channel blocker as first-line treatment.

Germacrone cooperates with dexmedetomidine to alleviate high-fat diet-induced type 2 diabetes mellitus via upregulating AMPKα1 expression

The aim of the present study was to investigate the effects of germacrone (GM) and dexmedetomidine (DEX) in treating type 2 diabetes mellitus (T2DM). A high-fat diet (HFD)-induced T2DM rat model was established. The experimental rats were divided into the control group, HFD group, GM treatment group, DEX treatment group and GM + DEX treatment group. In addition, adenosine monophosphate-activated protein kinase (AMPK) inhibitor compound C (CC) was used to inhibit AMPKα1 expression. All rats received their respective treatment daily for 21 days. Blood glucose and lipid levels, apoptosis of hepatic cells, and levels of inflammatory factors and oxidative stress indicators in serum samples were evaluated. Protein expression of AMPKα1 and its downstream targets were also investigated. Results demonstrated that blood glucose concentration, blood lipid indicators (endothelin, total cholesterol, triglyceride and low density lipoprotein cholesterol), cell apoptosis in liver tissues, total oxidant status, malondialdehyde, interleukin (IL)-6, tumor necrosis factor-α (TNF-α) and IL-1β levels in serum were increased in the high-fat group compared to the control but decreased following GM and/or DEX treatment. By contrast, high-density lipoprotein cholesterol and antioxidative stress indicator superoxide dismutase (SOD) were decreased in the high-fat group but increased following GM and/or DEX treatment. Protein expression of AMPKα1 and the catabolic genes carnitine palmitoyltransferase-1, peroxisome proliferator-activated receptor-α and acyl coenzyme A were decreased whilst anabolic genes, including sterol regulatory element binding protein-1c, fatty acid synthase and diacylglycerol acyltransferase-2, were increased in the HFD group. These effects were attenuated by GM and/or DEX treatment. AMPKα1 inhibition resulted in decreased SOD and increased cell apoptosis in liver tissues as well as increased IL-6, TNF-α and IL-1β levels compared with the HFD group. However, these effects were abolished following treatment with CC, GM and DEX together. Taken together these results indicated that GM worked synergistically with DEX to attenuate symptoms of high-fat-induced T2DM, with the effect potentially involving an increase in AMPKα1 expression.

Plasma concentrations of 8-hydroxy-2'-deoxyguanosine and risk of kidney disease and death in individuals with type 1 diabetes

AIMS/HYPOTHESIS

Oxidative stress is involved in the pathogenesis of diabetic kidney disease. We evaluated the association between 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of DNA oxidative damage, and end-stage renal disease (ESRD) or death in individuals with type 1 diabetes.

METHODS

Plasma 8-OHdG concentrations were measured at baseline in participants with type 1 diabetes from GENEDIAB (n = 348) and GENESIS (n = 571) cohorts. A follow-up was conducted in 205 and 499 participants for a mean ± SD duration of 8.9 ± 2.3 years and 5.2 ± 1.9 years, respectively. We tested associations between 8-OHdG concentrations and urinary albumin concentration (UAC) or eGFR at baseline, and the risk of ESRD or all-cause mortality during follow-up. Analyses were performed in pooled cohorts.

RESULTS

The highest UAC (geometric mean [95% CI]) was observed in the third 8-OHdG tertile (tertile 1, 9 [6, 13] mg/l; tertile 2, 10 [7, 16] mg/l; tertile 3, 16 [10, 25] mg/l; p = 0.36 for tertile 1 vs tertile 2 and p = 0.003 for tertile 3 vs tertile 1) after adjustment for potential confounding covariates. The lowest eGFR (mean [95% CI]) was observed in the third tertile (tertile 1, 87 [82, 93] ml min^-1 1.73 m^-2; tertile 2, 88 [82, 94] ml min^-1 1.73 m^-2; tertile 3, 74 [68, 80] ml min^-1 1.73 m^-2; p = 0.61 for tertile 1 vs tertile 2; p < 0.001 for tertile 3 vs tertile 1). ESRD and death occurred in 48 and 64 individuals, respectively. The HR for ESRD, but not death, was higher in the third tertile than in the first (tertile 2 vs tertile 1, 1.45 [0.45, 5.04], p = 0.54; tertile 3 vs tertile 1, 3.05 [1.16, 9.60], p = 0.02) after multiple adjustments.

CONCLUSIONS/INTERPRETATION

Higher plasma concentrations of 8-OHdG were independently associated with increased risk of kidney disease in individuals with type 1 diabetes, suggesting that this marker can be used to evaluate the progression of diabetic kidney disease.

Glutathione peroxidase-1 gene (GPX1) variants, oxidative stress and risk of kidney complications in people with type 1 diabetes

BACKGROUND AND AIM

Glutathione peroxidase (GPX) is a class of antioxidant enzymes that catalyze the reduction of hydrogen peroxide to water. GPX1 is the most abundant isoform and is expressed in all kidney cells. Isoprostane and advanced oxidation protein products (AOPP) were identified as markers of oxidative stress in patients with kidney disease. We investigated associations of GPX1 genotypes with kidney complications, and with plasma concentrations of isoprostane and AOPP in type 1 diabetic patients.

METHODS

Four SNPs in the GPX1 gene region were genotyped in SURGENE (n=340; 10-year follow-up); GENEDIAB (n=461) and GENESIS (n=584) cohorts of type 1 diabetic patients. Subsets of GENEDIAB (n=237) and GENESIS (n=466) participants were followed up for 9 and 5years, respectively. Plasma concentrations of isoprostane and AOPP were measured at baseline in GENEDIAB. Hazard ratios (HR) were estimated for incidence of kidney complications.

RESULTS

In SURGENE, 98 renal events (new cases of microalbuminuria or progression to more severe stage of diabetic nephropathy) occurred during follow-up. The minor T-allele of rs3448 was associated with the incidence of renal events (HR 1.81, 95% CI 1.16-2.84, p=0.008). In GENESIS/GENEDIAB pooled study, end stage renal disease (ESRD) occurred during follow-up in 52 individuals. The same variant was associated with the incidence of ESRD (HR 3.34, 95% CI, 1.69-6.98, p=0.0004). The variant was also associated with higher plasma isoprostane concentration in GENEDIAB cohort: 2.02±0.12 (TT+CT) vs 1.75±0.13 (CC) ng/mL (p=0.009), and with higher plasma AOPP in the subset of participants with the baseline history of ESRD (TT+CT 67±6 vs CC 48±6μmol/L, p=0.006).

CONCLUSIONS

The minor T-allele of rs3448 was associated with kidney complications (incidences of microalbuminuria, renal events and ESRD) in patients with type 1 diabetes. The risk allele was associated with higher plasma concentrations of isoprostane and AOPP. Our results are consistent with the implication of GPX1 in the mechanism of renal protection against oxidative stress in type 1 diabetic patients.

Allelic variations in the CYBA gene of NADPH oxidase and risk of kidney complications in patients with type 1 diabetes

Oxidative stress plays a pivotal role in the pathophysiology of diabetic nephropathy, and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system is an important source of reactive oxygen species in hyperglycemic conditions in the kidney. Plasma concentration of advanced oxidation protein products (AOPP), a marker of oxidative stress, is increased in patients with diabetic nephropathy. We investigated associations of variants in the CYBA gene, encoding the regulatory subunit p22(phox) of NADPH oxidase, with diabetic nephropathy and plasma AOPP and myeloperoxidase (MPO) concentrations in type 1 diabetic patients. Seven SNPs in the CYBA region were analyzed in 1357 Caucasian subjects with type 1 diabetes from the SURGENE (n=340), GENEDIAB (n=444), and GENESIS (n=573) cohorts. Duration of follow-up was 10, 9, and 6 years, respectively. Cox proportional hazards and logistic regression analyses were used to estimate hazard ratios (HR) or odds ratios (OR) for incidence and prevalence of diabetic nephropathy. The major G-allele of rs9932581 was associated with the incidence of renal events defined as new cases of microalbuminuria or the progression to a more severe stage of nephropathy during follow-up (HR 1.59, 95% CI 1.17-2.18, P=0.003) in SURGENE. The same allele was associated with established/advanced nephropathy (OR 1.52, 95% CI 1.22-1.92, P=0.0001) and with the incidence of end-stage renal disease (ESRD) (HR 2.01, 95% CI 1.30-3.24, P=0.001) in GENEDIAB/GENESIS pooled studies. The risk allele was also associated with higher plasma AOPP concentration in subsets of SURGENE and GENEDIAB, with higher plasma MPO concentration in a subset of GENEDIAB, and with lower estimated glomerular filtration rate (eGFR) in the three cohorts. In conclusion, a functional variant in the promoter of the CYBA gene was associated with lower eGFR and with prevalence and incidence of diabetic nephropathy and ESRD in type 1 diabetic patients. These results are consistent with a role for NADPH oxidase in the pathophysiology of kidney complications of diabetes.

Manganese superoxide dismutase (SOD2) polymorphisms, plasma advanced oxidation protein products (AOPP) concentration and risk of kidney complications in subjects with type 1 diabetes

Aims

Oxidative stress is involved in the pathophysiology of diabetic nephropathy. Manganese superoxide dismutase (SOD2) catalyses the dismutation of superoxide, regulates the metabolism of reactive oxygen species in the mitochondria and is highly expressed in the kidney. Plasma concentration of advanced oxidation protein products (AOPP), a marker of oxidative stress, was found to be increased in patients with kidney disease. We investigated associations of SOD2 allelic variations, plasma SOD activity and AOPP concentration with diabetic nephropathy in type 1 diabetic subjects.

Methods

Eight SNPs in the SOD2 region were analysed in 1285 Caucasian subjects with type 1 diabetes from the SURGENE prospective study (n = 340; 10-year follow-up), GENESIS (n = 501) and GENEDIAB (n = 444) cross-sectional studies. Baseline plasma concentration of AOPP and SOD activity were measured in GENEDIAB participants. Hazard ratio (HR) and odds ratio (OR) were determined for incidence and prevalence of nephropathy. Analyses were adjusted or stratified by retinopathy stages.

Results

In the SURGENE cohort, the T-allele of rs4880 (V16A) was associated with the incidence of renal events (new cases, or the progression to a more severe stage of nephropathy; HR 1.99, 95% CI 1.24–3.12, p = 0.004) and with the decline in estimated glomerular filtration rate (eGFR) during follow-up. Similar associations were observed for rs2758329 and rs8031. Associations were replicated in GENESIS/GENEDIAB cohorts, in the subset of participants without proliferative retinopathy, and were confirmed by haplotype analyses. Risk allele and haplotype were also associated with higher plasma AOPP concentration and lower SOD activity.

Conclusions

SOD2 allelic variations were associated with the incidence and the progression of diabetic nephropathy, with a faster decline in eGFR and with plasma AOPP concentration and SOD activity in subjects with type 1 diabetes. These results are consistent with a role for SOD2 in the protection against oxidative stress and kidney disease in type 1 diabetes.