Manganese superoxide dismutase alanine to valine polymorphism and risk of neuropathy and nephropathy in Egyptian type 1 diabetic patients

Concentration/activity of superoxide dismutase isozymes and the pro-/antioxidative status, in context of type 2 diabetes and selected single nucleotide polymorphisms (genes: INS, SOD1, SOD2, SOD3) - Preliminary findings

The alterations in concentration/activity of superoxide dismutase isozymes in the context of type 2 diabetes or obesity are well-described. Moreover, many hereditary factors, including single-nucleotide polymorphisms (SNPs) of genes for coding insulin, insulin receptors, or insulin receptor substrates (INS, INSR, IRS1, IRS2) or superoxide dismutase isozymes (SOD1, SOD2, SOD3), have been linked with the incidence of obesity and diabetes. However, the underlying changes in the plasma concentration/activity of superoxide dismutase isozymes and their potential connection with the said hereditary factors remain unexplored. Previously, we have observed that the plasma concentration/activity of superoxide dismutase isozymes differs in the context of obesity and/or rs2234694 (SOD1) and rs4880 (SOD2) and that the concentrations of SOD1, SOD2, SOD3 are correlated with each other. Intersexual variability of SOD1 concentration was detected regardless of obesity. In this study, the variability of concentration/activity of superoxide dismutase isozymes in plasma is considered in the context of type 2 diabetes and/or SNPs: rs2234694 (SOD1), rs5746105 (SOD2), rs4880 (SOD2), rs927450 (SOD2), rs8192287 (SOD3). Genotypic variability of SNP rs3842729 (INS), previously studied in the context of insulin-dependent diabetes, is investigated in terms of selected clinical parameters associated with type 2 diabetes. This study revealed higher SOD1 concentration in diabetic men compared to women, and extremely high SOD1 concentration, higher total superoxide dismutase, and copper-zinc superoxide dismutase activity, and lower superoxide dismutase and copper-zinc superoxide dismutase activity (when adjusted for the concentration of SODs) in the diabetic group regardless of sex. Multiple logistic regression, applied to explore possible links between the studied SNPs and other factors with the odds of type 2 diabetes or obesity, revealed that the genotypic variability of rs4880 (SOD2) could affect these odds, supporting the findings of several other studies.

Single-nucleotide polymorphisms (SNPs) of antioxidant enzymes SOD2 and GSTP1 genes and SLE risk and severity in an Egyptian pediatric population

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease associated with increased oxidative stress that participates in immune dysregulation, and injury resulting in loss of immune tolerance and increased auto-antibody production. This study was designed to investigate the effects of genetic polymorphisms of the antioxidant enzymes genes that code for SOD2 (rs2758332) and GSTP1 (rs1695) on SLE risk and severity in Egyptian children and adolescents cohort from Delta region.

METHODS

The frequencies of these genes polymorphic variants were compared between 100 SLE children and adolescents and 100 healthy control subjects. Single-nucleotide polymorphisms (SNPs) of the two antioxidants were determined using TaqMan SNP genotyping assay.

RESULTS

Individuals with the TT and CT genotypes of rs2758332 in the SOD2 gene were of significant risk for SLE patients (OR = 1.831, 95% CI = 1.082-3.101, P = 0.024) and (OR = 1.864, 95% CI = 1.136-3.059, P = 0.014), respectively. Cases who have combined CT + TT genotype were of significant higher risk of SLE (OR = 1.851, 95% CI = 1.156 - 2.962, P = 0.010). While, they did not show any significant association between SOD2 genotypes or alleles with SLE clinical features. In case of the SNP rs1695 in the GSTP1 gene, no significant associations of genotypes or alleles with SLE risk or with SLE clinical features were detected.

CONCLUSIONS

This study among Egyptian children and adolescents showed a strong association of the SOD2 rs2758332 not GSTP1 rs1695 polymorphism with the risk of SLE disease.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Prevalence of nephropathy in type 1 diabetes in the Arab world: A systematic review and meta-analysis

The aim of this study was to conduct a systematic review and meta-analysis and determine the prevalence of diabetic nephropathy (DN) among Arab patients with T1D. A systematic literature search was conducted using 4 different literature databases (PubMed, ScienceDirect, Web of Science, and Embase) to capture all relevant data about Arab patients with T1D that had DN. Meta-analysis and systematic review were performed using the random effect model, and the heterogeneity of the studies was assessed using the Q-test, I2, and Tau-squared statistics. Publication bias was assessed using the funnel-plot test. Our search strategy captured 372 studies in only 10 out of the 22 Arab countries in a period of 48 years (1969-2017); of which, 41 met our inclusion criteria for full article analysis, of those, 15 were eligible for meta-analysis. We estimated the prevalence of DN among Arab people with T1D to be 18.2% (95% confidence interval 13.1%-24.8%). In conclusion, DN prevalence is underexplored among Arab patients with T1D and represents a significant risk for the well-being of Arab patients with T1D. Therefore, there is an urgent need for comprehensive epidemiological studies for DN among Arab patients with T1D.

Role of Superoxide Dismutase 2 Gene Ala16Val Polymorphism and Total Antioxidant Capacity in Diabetes and its Complications

Diabetes Mellitus (DM) is a chronic heterogeneous disorder and oxidative stress is a key participant in the development and progression of it and its complications. Anti-oxidant status can affect vulnerability to oxidative damage, onset and progression of diabetes and diabetes complications. Superoxide dismutase 2 (SOD2) is one of the major antioxidant defense systems against free radicals. SOD2 is encoded by the nuclear SOD2 gene located on the human chromosome 6q25 and the Ala16Val polymorphism has been identified in exon 2 of the human SOD2 gene. Ala16Val (rs4880) is the most commonly studied SOD2 single nucleotide polymorphism (SNP) in SOD2 gene. This SNP changes the amino acid at position 16 from valine (Val) to alanine (Ala), which has been shown to cause a conformational change in the target sequence of manganese superoxide dismutase (MnSOD) and also affects MnSOD activity in mitochondria. Ala16Val SNP and changes in the activity of the SOD2 antioxidant enzyme have been associated with altered progression and risk of different diseases. Association of this SNP with diabetes and some of its complications have been studied in numerous studies. This review evaluated how rs4880, oxidative stress and antioxidant status are associated with diabetes and its complications although some aspects of this line still remain unclear.

Association investigation of BACH2 rs3757247 and SOD2 rs4880 polymorphisms with the type 1 diabetes and diabetes long-term complications risk in the Polish population

Genetic factors are indicated in the development of type 1 diabetes (DM1). Recently, nucleotide variants of BACH2 and SOD2 have been associated with this chronic condition. Therefore, the purpose of the present study was to investigate the contribution of BACH2 rs3757247 and SOD2 rs4880 (Ala16Val) polymorphisms to the risk of DM1 and diabetes long-term complications. Selected polymorphic variants of BACH2 and SOD2 were investigated in a group of 141 patients with DM1 and in a group of age, gender-matched healthy subjects (n=369) using a high-resolution melting curve method. There was no evidence for either allelic or genotypic association with the risk of DM1 and diabetes chronic complications for analysed polymorphisms. In addition, no interaction between BACH2 and SOD2 variants in the development of this condition was observed. However, the frequency of BACH2 rs3757247 AG and AA genotypes was statistically different between DM1 patients with retinopathy and healthy individuals (odds ratio, 2.455; 95% confidence interval, 0.999-6.035; P=0.044), but this result did not survive multiple testing corrections. The present study did not confirm the involvement of BACH2 rs3757247 and SOD2 rs4880 polymorphisms in the development of DM1 and diabetes long-term complications. Further studies in a larger population sample are required.

Review of Genetic Association in the SOD2 Gene with Chronic Kidney Disease: Case-Control Studies and Meta-Analysis Confirm Association with Diabetic Nephropathy

The SOD2 gene encodes a mitochondrial protein that is involved with response to oxidative stress and cellular proliferation. The diabetic milieu, in particular hyperglycemia, results in the overproduction of superoxide and formation of secondary reactive oxygen species contributing to the accumulation of DNA, protein and cellular damage. Functional genetic variants within the SOD2 gene are postulated to influence renal injury. We sought to resolve the inconsistent conclusions of several studies examining the SOD2 gene for association with chronic kidney disease, in particular diabetic nephropathy. We genotyped a total of 3,913 individuals with diabetic nephropathy, glomerulonephritis and/or end-stage renal disease, reviewed published literature, and conducted a subsequent meta-analysis. Using χ2 test, our independent case-control study for diabetic nephropathy revealed evidence for association of rs4880 (P=0.01). However, this was ameliorated by adjusting for age at diagnosis, duration, sex and recruitment centre in the logistical model. Genotype counts were obtained for all published studies having genotyped this SNP and a meta-analysis was performed on a total of 3,949 individuals with type 1 diabetes mellitus (cases n=2,184; controls, n=1,765). No significant heterogeneity was observed (P=0.5) and association with diabetic nephropathy was supported by P=0.005 (odds ratio 0.87, 95% confidence interval: 0.79–0.96). There is biological evidence that this amino-acid changing SNP, rs4880, directly influences enzymatic activity of the SOD2 gene product. We conclude that the functional, clinically associated rs4880 is important in the pathogenesis of diabetic nephropathy.

Mitochondrial dysfunction and mitophagy: the beginning and end to diabetic nephropathy?

Diabetic nephropathy (DN) is a progressive microvascular complication arising from diabetes. Within the kidney, the glomeruli, tubules, vessels and interstitium are disrupted, ultimately impairing renal function and leading to end-stage renal disease (ESRD). Current pharmacological therapies used in individuals with DN do not prevent the inevitable progression to ESRD; therefore, new targets of therapy are urgently required. Studies from animal models indicate that disturbances in mitochondrial homeostasis are central to the pathogenesis of DN. Since renal proximal tubule cells rely on oxidative phosphorylation to provide adequate ATP for tubular reabsorption, an impairment of mitochondrial bioenergetics can result in renal functional decline. Defects at the level of the electron transport chain have long been established in DN, promoting electron leakage and formation of superoxide radicals, mediating microinflammation and contributing to the renal lesion. More recent studies suggest that mitochondrial-associated proteins may be directly involved in the pathogenesis of tubulointerstitial fibrosis and glomerulosclerosis. An accumulation of fragmented mitochondria are found in the renal cortex in both humans and animals with DN, suggesting that in tandem with a shift in dynamics, mitochondrial clearance mechanisms may be impaired. The process of mitophagy is the selective targeting of damaged or dysfunctional mitochondria to autophagosomes for degradation through the autophagy pathway. The current review explores the concept that an impairment in the mitophagy system leads to the accelerated progression of renal pathology. A better understanding of the cellular and molecular events that govern mitophagy and dynamics in DN may lead to improved therapeutic strategies.

Association of the C47T polymorphism in SOD2 with diabetes mellitus and diabetic microvascular complications: a meta-analysis

AIMS/HYPOTHESIS

A meta-analysis was performed to assess the association of C47T (rs4880) (also called Val16Ala) polymorphism in SOD2 gene with reduced risk of diabetes mellitus, including type 1 and type 2 diabetes, and diabetic microvascular complications (DMI) including diabetic nephropathy, diabetic retinopathy and diabetic polyneuropathy.

METHODS

A comprehensive search was conducted to identify all case-control or cohort design studies of the above-mentioned associations. The fixed or random effect pooled measure was selected on the basis of homogeneity test among studies. Heterogeneity among studies was evaluated using the I (2). Meta-regression and the 'leave one out' sensitive analysis of Patsopoulos et al. were used to explore potential sources of between-study heterogeneity. Publication bias was estimated using modified Egger's linear regression test as proposed by Harbord et al.

RESULTS

Seventeen articles were included. After excluding articles that deviated from Hardy-Weinberg equilibrium in cases and/or in controls, and were also the key contributors to between-study heterogeneity, the meta-analysis showed a significant association of the C allele with reduced risk of DMI in dominant (OR 0.788, 95% CI 0.680-0.914), recessive (OR 0.808, 95% CI 0.685-0.953) and codominant (OR 0.828, 95% CI 0.751-0.913) models. It also showed a significant association with reduced risk of diabetic nephropathy in the dominant model (OR 0.801, 95% CI 0.664-0.967), and reduced risk of diabetic retinopathy in the dominant (OR 0.601, 95% CI 0.423-0.855), recessive (OR 0.548, 95% CI 0.369-0.814) and codominant (OR 0.651, 95% CI 0.517-0.820) models.

CONCLUSIONS/INTERPRETATION

The meta-analysis suggested that C allele of C47T polymorphism in SOD2 gene has protective effects on risk of DMI, diabetic nephropathy and diabetic retinopathy. This risk needs to be confirmed by further studies.

Association between the rs4880 superoxide dismutase 2 (C>T) gene variant and coronary heart disease in diabetes mellitus

Mitochondrial superoxide dismutase 2 (SOD2) is an endogenous anti-oxidant enzyme. The rs4880 gene variant results in a C>T substitution, influencing SOD enzymatic activity. This variant has been associated with micro- and macro-vascular complications in diabetes mellitus. Our aim was to examine the association between this variant and coronary heart disease (CHD) risk in a cross-sectional sample of subjects with diabetes. 776 Caucasian subjects with diabetes were genotyped. CHD risk, oxidised-LDL and plasma total anti-oxidant status (TAOS) were analysed in relation to genotype. In females, the TT genotype was associated with CHD (CC/CT/TT: No CHD vs. CHD: 22.4/56.0/21.6% vs. 12.0/50.0/38.0%, p=0.03; for CC/CT vs. TT, p=0.01). The odds ratio for CHD associated with the TT genotype compared to CC/CT was 2.22 [95%CI: 1.17-4.24], p=0.01. The TT genotype was also associated with significantly lower plasma TAOS. In males, no association was observed between genotype and CHD risk, but CHD was significantly associated with age, lower HDL, higher triglycerides, higher BMI and cigarette smoking. The TT genotype of this variant is associated with increased CHD risk and lower plasma anti-oxidant defences in females with diabetes. This modest genotype-effect is not apparent in males where traditional risk factors may play a greater role.

Association between SOD2 T-9C and MTHFR C677T polymorphisms and longevity: a study in Jordanian population

BACKGROUND

Aging in animals is associated with high body oxidative stress, which might affect susceptibility and onset of age-related diseases, and the subsequent life span. Therefore, genes that modulate oxidative stress might play a role in determining longevity. In this study, we investigated whether the gene pool relevant to the SOD2-9T/C and MTHFR 677C/T polymorphisms changes as the Jordanian population ages.

METHODS

Polymorphisms were genotyped in 130 elderly subjects (57 females and 73 males, mean age: 90.01 years) and 135 young control subjects (67 females and 68 males, mean age: 33.43 years).

RESULTS

No significant differences were found in the genotype and allele frequencies of examined SOD2 and MTHFR gene variants between the elderly group and young controls (P > 0.05), nor when each gender was considered separately (P > 0.05).

CONCLUSION

SOD2-9T/C and MTHFR 677C/T gene polymorphisms do not seem to be important in Jordanian population for longevity phenotype.

Age-dependent dichotomous effect of superoxide dismutase Ala16Val polymorphism on oxidized LDL levels

We investigated the association between superoxide dismutase (SOD) Ala16Val polymorphism and the levels of oxidized LDL lipoprotein-C (ox-LDL-C) in two age-different Greek cohorts. Four hundred fifteen middle-aged (n=147 females: 43.2+/-13 years, n=268 males: 43.3+/-14 years) Caucasian Greek subjects consisted the middle aged cohort. One hundred seventy five elderly (n=88 females: 79.9+/-4 years; n=87 males: 80.6+/-4 years) were selected from the elderly cohort. Genotype data were obtained for all of them. Multiple linear regression analysis, stratified by gender and adjusted for age, smoking habits and body mass index as covariates, showed higher ox-LDL-C levels for the middle aged men with the Val/Val genotype, compared to the other allele (Ala/Ala and Ala/Val) carriers (65.9+/-25.7 vs. 55.7+/-20.5 mg/dl; standardized beta coefficient=0.192, P=0.012). On the contrary, elderly women with the Val/Val genotype occurred with lower ox-LDL-C levels compared to the Ala/Ala or Ala/Val genotype (74.2+/-22.1 vs. 86.5+/-26.6 mg/dl; standardized beta coefficient= -0.269, P=0.015). The same trend was also recorded in elderly men, however without reaching statistical significance (standardized beta coefficient= -0.187, P=0.077). Moreover, elderly men and women with the Ala/Ala or Ala/Val genotype presented higher triglycerides levels compared to Val/Val (women: 145.2+/-68.7 vs. 114.3+/- 34.3 mg/dl, P= 0.027; men: 147.8+/-72.4 vs. 103.7 +/-38.0 mg/dl, P=0.002). Additionally, middle aged men with the Val/Val genotype had higher HDL-C levels compared to the Ala allele carriers. The results suggest that SOD Ala16Val polymorphism is an age-dependent modulator of ox-LDL-C levels in middle-aged men and elderly women.