Manganese-containing superoxide dismutase signal sequence polymorphism associated with sporadic motor neuron disease

Association of Val16Ala Polymorphism of Manganese Superoxide Dismutase (MnSOD) with Food Intake and Cardiometabolic Risk Factors in the Elderly in Primary Care in Porto Alegre

BACKGROUND

The aging process causes physiological changes on its own. The combination of an unhealthy lifestyle with the presence of genetic polymorphisms, such as the Val16Ala of the antioxidant enzyme manganese-dependent superoxide dismutase (MnSOD) may contribute to a greater occurrence of cardiometabolic risk factors.

OBJECTIVE

This study aimed to verify the association of Val16Ala-MnSOD polymorphism with food intake, caloric expenditure, and cardiometabolic risk factors in the elderly.

METHODS

A cross-sectional study with a sample size of 270 elderly individuals assisted in primary health care in the city of Porto Alegre, RS, Brazil. Val16Ala polymorphism, glucose, lipid profile, insulin, HOMA-IR, blood pressure, waist circumference, PCR-us, IL-6, food consumption, and caloric expenditure were evaluated.

RESULTS

The average age of the elderly was 68.6 ± 7.6 years. There were statistically significant differences regarding the consumption of two or more servings of fruits and vegetables daily between the elderly VV versus AV (P=0.017). There were also statistically significant differences regarding the consumption of two or more daily servings of legumes and eggs between the elderly AA versus VV (P=0.002). The median of insulin was higher in the elderly AA versus AV (P=0.025) and the median of HOMA-IR was higher in the elderly VV versus AV (P=0.029). AA elderly individuals had higher means of high-density lipoprotein (HDL-c) compared to AV (P=0.029).

CONCLUSION

The results suggest that Val16Ala -MnSOD polymorphism is associated with the consumption of fruits, vegetables, legumes, and eggs, as well as with cardiometabolic risk factors in the elderly.

Association of SOD2 p.V16A polymorphism with Parkinson's disease: A meta-analysis in Han Chinese

BACKGROUND

Oxidative stress could participate in the pathogenesis of Parkinson's disease (PD). However, the role of genetic variation of superoxide dismutase 2 (SOD2), an important regulator against oxidative stress, in PD remains to be elucidated.

METHODS

We screened SOD2 gene variation by sequencing cDNA from 72 patients with early onset PD. A cohort of PD (n = 609) and ethnically matched controls (n = 681) were further examined for the identified sequence variant by PCR and NaeI restriction analysis.

RESULTS

Only a reported c.47T>C polymorphism (rs4880, SOD2 p.V16A) was found by cDNA sequencing. Case-control study of c.47T>C revealed that genotype and allele frequencies were in Hardy-Weinberg equilibrium in both patients and healthy controls. In a recessive model, those with CC genotype had a 2.61-fold increased risk of PD (95% CI: 1.08-6.30, P = 0.03) compared to subjects with TT and TC genotypes. Significant association between CC genotype and PD in non-smokers was also observed after stratification according to the history of smoking (3.54-fold increased risk of PD, 95% CI: 1.17-10.72, P = 0.02). Meta-analysis by combining studies of Chinese in China, Singapore, and Taiwan (total 2302 cases and 2029 controls) consistently showed CC genotype with increased risk of PD (OR = 1.77, 95% CI: 1.15-2.71, P = 0.01).

CONCLUSION

Our findings demonstrate that SOD2 p.V16A may play a role in the susceptibility of PD in Han Chinese.

Vulnerability of white matter tracts and cognition to the SOD2 polymorphism: A preliminary study of antioxidant defense genes in brain aging

Oxidative stress is a key mechanism of the aging process that can cause damage to brain white matter and cognitive functions. Polymorphisms in the superoxide dismutase 2 (SOD2) and catalase (CAT) genes have been associated with abnormalities in antioxidant enzyme activity in the aging brain, suggesting a risk for enhanced oxidative damage to white matter and cognition among older individuals with these genetic variants. The present study compared differences in white matter microstructure and cognition among 96 older adults with and without genetic risk factors of SOD2 (rs4880) and CAT (rs1001179). Results revealed higher radial diffusivity in the anterior thalamic radiation among SOD2 CC genotypes compared to CT/TT genotypes. Further, the CC genotype moderated the relationship between the hippocampal cingulum and processing speed, though this did not survive multiple test correction. The CAT polymorphism was not associated with brain outcomes in this cohort. These results suggest that the CC genotype of SOD2 is an important genetic marker of suboptimal brain aging in healthy individuals.

Targeted exon capture and sequencing in sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that results in progressive degeneration of motor neurons, ultimately leading to paralysis and death. Approximately 10% of ALS cases are familial, with the remaining 90% of cases being sporadic. Genetic studies in familial cases of ALS have been extremely informative in determining the causative mutations behind ALS, especially as the same mutations identified in familial ALS can also cause sporadic disease. However, the cause of ALS in approximately 30% of familial cases and in the majority of sporadic cases remains unknown. Sporadic ALS cases represent an underutilized resource for genetic information about ALS; therefore, we undertook a targeted sequencing approach of 169 known and candidate ALS disease genes in 242 sporadic ALS cases and 129 matched controls to try to identify novel variants linked to ALS. We found a significant enrichment in novel and rare variants in cases versus controls, indicating that we are likely identifying disease associated mutations. This study highlights the utility of next generation sequencing techniques combined with functional studies and rare variant analysis tools to provide insight into the genetic etiology of a heterogeneous sporadic disease.

Amyotrophic lateral sclerosis (ALS), also known as Charcot disease or Lou Gehrig's disease, is one of the most common neuromuscular diseases worldwide. This disease is characterized by a progressive degeneration of motor neurons, leading to patient death within a few years after onset. Despite the fact that most ALS cases are sporadic, most of the ALS genetic studies have focused on familial forms, leading to the genetic determination of cause for 70% of cases of familial ALS but for only 10% of sporadic ALS cases. This, coupled with the dearth of families available for study, suggests that researchers should begin tapping into the relatively untouched reservoir of available sporadic samples to identify novel genetic causes of sporadic ALS. Here we take advantage of high-throughput target sequencing techniques to test four different hypotheses about the genetic causes of ALS in sporadic ALS and uncover new candidate genes and pathways implicated in ALS.

Association of RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms with diabetic retinopathy in T2DM patients from north India

AIMS

The present study aimed to examine the association of RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms with diabetic retinopathy (DR) in north Indian T2DM patients.

METHODS

In this case-control association study, 758 T2DM patients were recruited. 446 with retinal neovascularization, microneurysms and hemorrhages were considered as cases (DR) and 312 patients with T2DM and no clinical signs of retinopathy (DNR), were recruited as controls. Genotypes for RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms were generated by direct sequencing of amplified products.

RESULTS

Genotype distribution of p.Gly82Ser (RAGE) and p.Val16Ala (MnSOD) polymorphisms were significantly different between DR and DNR (p<0.05) whereas distribution of allele frequency did not differ significantly (p>0.05). A significantly higher frequency of homozygous Ser82 genotype in DR patients was detected compared with DNR (2.4% vs 0.64%) for p.Gly82Ser (RAGE) polymorphism whereas there was a higher frequency of homozygous Ala16 genotype for p.Val16Ala (MnSOD) polymorphism in DR patients compared with DNR (22.6% vs 19.3%). Binary logistic analyses showed an association of homozygous recessive genotype Ser82 with DR (OR: 2.63%, 95% CI: 0.16-15.88, p<0.033) for p.Gly82Ser (RAGE) polymorphism. However, we did not find a significant association of p.Val16Ala polymorphism in MnSOD with retinopathy.

CONCLUSIONS

The findings indicate a statistically significant association of p.Gly82Ser polymorphism in RAGE with DR in T2DM patients.

Oxidative stress and genetic markers of suboptimal antioxidant defense in the aging brain: a theoretical review

Normal aging involves a gradual breakdown of physiological processes that leads to a decline in cognitive functions and brain integrity, yet the onset and progression of decline are variable among older individuals. While many biological changes may contribute to this degree of variability, oxidative stress is a key mechanism of the aging process that can cause direct damage to cellular architecture within the brain. Oligodendrocytes are at a high risk for oxidative damage due to their role in myelin maintenance and production and limited repair mechanisms, suggesting that white matter may be particularly vulnerable to oxidative activity. Antioxidant defense enzymes within the brain, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferase (GST), are crucial for breaking down the harmful end products of oxidative phosphorylation. Previous studies have revealed that allele variations of polymorphisms that encode these antioxidants are associated with abnormalities in SOD, CAT, GPx, and GST activity in the central nervous system. This review will focus on the role of oxidative stress in the aging brain and the impact of decreased antioxidant defense on brain integrity and cognitive function. Directions for future research investigations of antioxidant defense genes will also be discussed.

Involvement of superoxide dismutase isoenzymes and their genetic variants in progression of and higher susceptibility to vitiligo

Oxidative stress has been implicated as the initial triggering event in vitiligo pathogenesis leading to melanocyte destruction. Here, we report a significant increase in oxidative stress in vitiligo patients as evidenced by high lipid peroxidation levels suggesting an imbalance in the antioxidant enzyme system as reported in our previous studies. This study examined the role of the enzymatic antioxidant SOD, which converts the pro-oxidant superoxide into H2O2, in vitiligo pathogenesis. The activity of three isoforms of SOD, i.e., SOD1, SOD2, and SOD3, was significantly higher in vitiligo patients. To identify the underlying mechanism for the increase in activities of SOD isoforms, we explored the SOD1, SOD2, and SOD3 genes for their genetic variations and transcript levels. The SOD2 Thr58Ile (rs35289490) and Leu84Phe (rs11575993) polymorphisms were significantly associated with vitiligo patients, and the Val16Ala (rs4880) polymorphism was associated with active vitiligo patients. Interestingly, SOD2 activity was contributed by these polymorphisms along with its increase in transcript levels in patients. SOD3 activity was associated with the Arg213Gly (rs8192291) polymorphism. The SOD3 transcript levels were also increased in patients, which might contribute to the increased SOD3 activity. However, we could not establish the genotype-phenotype correlation for SOD1 as we could not detect any novel or reported SNPs in SOD1. In addition, both transcript and protein levels of SOD1 were unchanged between patients and controls, though SOD1 activity was increased in patients. Activities of SOD isoforms also correlated with progression of the disease as the activity was higher in active cases of vitiligo compared to stable cases. Here, we report that SOD2 and SOD3 polymorphisms may be genetic risk factors for susceptibility and progression of vitiligo and hence the genetic makeup of an individual may form a basis for the effective treatment of the disease. Overall, our results suggest that increased activity of SOD isoforms under the influence of genetic factors may lead to accumulation of H2O2 in cytoplasmic, mitochondrial, and extracellular compartments resulting in oxidative damage to the melanocytes.

Effects of 47C allele (rs4880) of the SOD2 gene in the production of intracellular reactive species in peripheral blood mononuclear cells with and without lipopolysaccharides induction

Challenging of peripheral blood mononuclear cells (PBMCs) with lipopolysaccharides (LPS) has been shown to activate monocytes and macrophages, leading to the production of pro-inflammatory cytokines and reactive oxygen species (ROS). Manganese superoxide dismutase (MnSOD) is an important enzyme that may play a central role in the response to oxidative stress. 47C> T SNP of the SOD2 gene, the -9Val MnSOD is less efficient than the -9Ala version. We have previously characterized the cellular redox status of human PBMCs expressing either -9Ala (CC) or -9Val (TT) SOD2 and analyzed the responses of these cells to oxidative stress induced by LPS. Due to the observed alterations in the activities of these antioxidant enzymes, we decided to investigate their immunocontent and analyze the production of intracellular oxidants, as well as any resulting DNA damage. PBMCs were isolated from the blood of 30 healthy human volunteers (15 volunteers per allele). We then analyzed levels of nitrite, DNA damage by comet assay, TNF-α, carboxymethyl lysine and nitrotyrosine and assessed production of intracellular reactive species by the DCFH-DA-based assay and western blots were used to analyze protein levels. Our results show that there occurs an increase in nitric oxide production in both allele groups after challenge with LPS. A significant increase in DNA damage was observed in PBMCs after an 8-h LPS challenge. Cells expressing the SOD2 47C allele quickly adapt to a more intense metabolism by upregulating cellular detoxification mechanisms. However, when these cells are stressed over a long period, they accumulate a large quantity of toxic metabolic byproducts.

Genetic polymorphisms of antioxidant enzymes as risk factors for oxidative stress-associated complications in preterm infants

We aimed to identify specific polymorphisms of genes encoding for superoxide dismutase (SOD) 1 (cytoplasmic Cu/ZnSOD), SOD2 (mitochondrial MnSOD), SOD3 (extracellular Cu/ZnSOD) and CAT in a cohort of preterm infants and correlate their presence to the development of respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), intraventricular haemorrhage (IVH) and retinopathy of prematurity (ROP). We carried out a retrospective study to evaluate the allele frequency and the genotype distribution of polymorphisms of SODs and CAT in a population of preterm neonates (n = 152) with a gestational age ≤ 28 weeks according to the presence or absence of RDS, BPD, IVH and ROP. Moreover, we evaluated through the haplotype reconstruction analysis whether combinations of the selected polymorphisms are related to the occurrence of RDS, BPD, IVH and ROP. We found that rs8192287 SOD3 polymorphism is an independent protective factor for all grade IVH, while rs4880 and rs5746136 SOD2 polymorphisms are associated with a lower gestational age (rs4880, rs5746136) and birth weight (rs4880). Haplotypes reconstruction showed that SOD1 (GG) decreased the risk of RDS, IVH and ROP; SOD2 (GT) increased the risk of BPD and decreased the risk of RDS, IVH and ROP; SOD3 (TGC) decreased the risk of BPD and IVH; and 4) CAT (CTC) decreased the risk of RDS. The rs8192287 SOD3 polymorphism is per se an independent predictor of a decreased risk of developing IVH. Different SOD2 polymorphisms are associated per se with a lower gestational age and/or birth weight, and haplotypes of SOD1, SOD3 and CAT genes may be independent protecting or risk markers for prematurity complications.

Relationships between single nucleotide polymorphisms of antioxidant enzymes and disease

The presence and progression of numerous diseases have been linked to deficiencies in antioxidant systems. The relationships between single nucleotide polymorphisms (SNPs) arising from specific antioxidant enzymes and diseases associated with elevated oxidative stress have been studied with the rationale that they may be useful in screening for diseases. The purpose of this narrative review is to analyse evidence from these studies. The antioxidant enzyme SNPs selected for analysis are based on those most frequently investigated in relation to diseases in humans: superoxide dismutase (SOD2) Ala16Val (80 studies), glutathione peroxidise (GPx1) Pro197Leu (24 studies) and catalase C-262T (22 studies). Although the majority of evidence supports associations between the SOD2 Ala16Val SNP and diseases such as breast, prostate and lung cancers, diabetes and cardiovascular disease, the presence of the SOD2 Ala16Val SNP confers only a small, clinically insignificant reduction (if any) in the risk of these diseases. Other diseases such as bladder cancer, liver disease, nervous system pathologies and asthma have not been consistently related to this SOD SNP genotype. The GPx1 Pro197Leu and catalase C-262T SNP genotypes have been associated with breast cancer, but only in a small number of studies. Thus, currently available evidence suggests antioxidant enzyme SNP genotypes are not useful for screening for diseases in humans.

Clinical genetics of amyotrophic lateral sclerosis: what do we really know?

Hereditary amyotrophic lateral sclerosis (ALS) encompasses a group of genetic disorders characterized by adult-onset loss of the lower and upper motor neuron systems, often with involvement of other parts of the nervous system. Cases of hereditary ALS have been attributed to mutations in 12 different genes, the most common being SOD1, FUS and TARDBP-mutations in the other genes are rare. The identified genes explain 25-35% of cases of familial ALS, but identifying the remaining genes has proved difficult. Only a few genes seem to account for significant numbers of ALS cases, with many others causing a few cases each. Hereditary ALS can be inherited in an autosomal dominant, autosomal recessive or X-linked manner, and families with low disease penetrance are frequently observed. In such families, the genetic predisposition may remain unnoticed, so many patients carry a diagnosis of isolated or sporadic ALS. The only clinical feature that distinguishes recognized hereditary from apparently sporadic ALS is a lower mean age of onset in the former. All the clinical features reported in hereditary cases (including signs of extrapyramidal, cerebellar or cognitive involvement) have also been observed in sporadic cases. Genetic counseling and risk assessment in relatives depend on establishing the specific gene defect and the disease penetrance in the particular family.

Single-nucleotide polymorphisms within the antioxidant defence system and associations with aggressive prostate cancer

OBJECTIVE

To study the effects of oxidative stress on prostate cancer development as the exact biological mechanisms behind the relationship remain uncertain. We previously reported a statistically significant interaction between circulating selenium levels, variants in the superoxide dismutase 2 gene (SOD2; rs4880), and risk of developing prostate cancer and presenting with aggressive prostate cancer.

PATIENTS AND METHODS

We genotyped men with localized/regional prostate cancer for 26 loci across eight genes that are central to cellular antioxidant defence: glutathione peroxidase (GPX1, GPX4), peroxisome proliferator-activated receptor γ coactivator (PPARGC1A, PPARGC1B), SOD1, SOD2, and SOD3, and 'X-ray repair complementing defective repair in Chinese hamster cell 1' (XRCC1). Among 489 men, we examined the relationships between genotypes, circulating selenium levels, and risk of presenting with aggressive prostate cancer at diagnosis, as defined by stage, grade and prostate-specific antigen (PSA) level (213 aggressive cases).

RESULTS

Two variants in SOD2 were significantly associated with the risk of aggressive prostate cancer (rs17884057, odds ratio 0.83, 95% confidence interval 0.70-0.99; and rs4816407, 1.27, 1.02-1.57); men with A alleles at rs2842958 in SOD2 had lower plasma selenium levels (median 116 vs 121.8 µg/L, P= 0.03); and the association between plasma selenium levels and risk of aggressive prostate cancer was modified by SOD1 (rs10432782) and SOD2 (rs2758330).

CONCLUSION

While this study was cross-sectional and these associations might be due to chance, further research is warranted on the potential important role of antioxidant defence in prostate cancer.

Polymorphism of the superoxide dismutase gene family in the bay scallop (Argopecten irradians) and its association with resistance/susceptibility to Vibrio anguillarum

The superoxide dismutases (SODs) are a family of enzymes that function as the first line of antioxidant defense against highly reactive superoxide radicals. The bay scallop Argopecten irradians contains three unique superoxide dismutases: Ai-icCuZnSOD, Ai-MnSOD and Ai-ecCuZnSOD, which were characterized in our previous studies. qRT-PCR was also performed to characterize the temporal expression of SODs in the hemocytes of bay scallops injected with the bacterium Vibrio anguillarum. To characterize the SOD family in A. irradians completely, we evaluated the polymorphism in the SOD genes and investigated the association of this polymorphism with resistance/susceptibility to V. anguillarum. Fifty-nine SNPs were identified in the promoter, exon and partial intron sequences of the three SOD genes. AiECSOD contained the most SNPs, as compared to AiCuZnSOD and AiMnSOD, and the majority of these were located in the promoter. Among them, the genotypes of -1739 T-C SNP in the AiCuZnSOD promoter and alleles of the -498 A-T and -267 G-A SNPs in the AiECSOD promoter showed a significant association with resistance/susceptibility to V. angullarum (P<0.05). The only non-synonymous SNP that was identified, E1-38 C-A in Ai-ecCuZnSOD, was a dimorphism caused by a C to A transition that resulted in a Thr to Lys substitution at position 13 in the signal peptide. The Thr allele was associated with increased susceptibility to V. anguillarum (P<0.05). To confirm the presumption, another independent challenge experiment was performed, in which the cumulative mortality of Ai-icCuZnSOD Q-1739 genotype TT was significantly lower than TC (P<0.05). Ai-ecCuZnSOD Q-498 genotype AA and AT were significantly lower than TT (P<0.05), Ai-ecCuZnSOD E1-3 genotype AA was significantly higher than CA and CC (P<0.05). The results suggested that these three polymorphic loci could be potential gene markers for the future molecular selection of strains that are resistant to diseases caused by V. anguillarum.

The Mn-superoxide dismutase single nucleotide polymorphism rs4880 and the glutathione peroxidase 1 single nucleotide polymorphism rs1050450 are associated with aging and longevity in the oldest old

The free radical theory of aging states that reactive oxygen species (ROS) play a key role in age-related accumulation of cellular damage, and consequently influence aging and longevity. Therefore, variation in genes encoding proteins protecting against ROS could be expected to influence variation in aging and life span. The rs4880 and rs1050450 SNPs in the manganese superoxide dismutase (MnSOD) and glutathione peroxidase 1 (GPX1) genes, respectively, are associated with age-related diseases and appear to affect the activities of the encoded variant proteins. In this study we genotyped these SNPs in 1650 individuals from the Danish 1905 cohort (follow-up time: 1998-2008, age at intake: 92-93 years, number of deaths: 1589 (96.3%)) and investigated the association with aging and longevity. We found decreased mortality of individuals holding either the MnSOD rs4880 C or the GPX1 rs1050450 T alleles (HR (MnSOD(CC/CT))=0.91, P=0, p=0.002 and HR (GPX1(TT/TC))=0.93, p=0.008). Furthermore, a synergetic effect of the alleles was observed (HR=0.76, p=0.001). Finally, moderate positive associations with good self rated health, decreased disability and increased cognitive capacity were observed. Our results thus indicate that genetic variation in MnSOD and GPX1 may be associated with aging and longevity.

Manganese superoxide dismutase Ala-9Val mitochondrial targeting sequence polymorphism in systemic lupus erythematosus in Poland

Systemic lupus erythematosus (SLE) is a chronic and progressive autoimmune disease in which reactive oxygen species contribute to pathogenesis. We analysed the distribution of manganese superoxide dismutase (MnSOD2) 47C>T (Ala-9Val) functional polymorphic variants within the mitochondrial targeting sequence in SLE patients (n = 102) and controls (n = 199). We did not find significant differences in the distribution of MnSOD2 47C>T polymorphic variants in SLE patients and controls. However, we found that MnSOD2 Val/Val genotype (recessive model) showed a significant association with Raynaud's phenomenon, odds ratio (OR) = 12.000 [95% confidence interval (CI) = 2.315-62.193], p = 0.0015. We also found that the MnSOD2 Val/Val genotype contributes to immunologic manifestations, OR = 2.957 (95% CI = 1.207-7.243), p = 0.0222, and anti-dsDNA antibody presence OR = 3.365 (95% CI = 1.364-8.304), p = 0.0107, in patients. Our observations indicate that MnSOD2 Val/Val variant can be linked to some clinical manifestations in patients with SLE.

Polymorphism in the manganese superoxide dismutase gene

Oxidative stress and mitochondrial damage occur in sepsis. Manganese superoxide dismutase (MnSOD) provides the main defence against oxidative stress within mitochondria. Ala9Val is a single nucleotide polymorphism (SNP) in the MnSOD gene, predicted to affect intra-mitochondrial transport of the enzyme. We found a significant difference in the genotype frequency between healthy subjects (n = 100) and patients with sepsis (n = 40, p = 0.009). For assessment of functionality ten healthy subjects of each homozygous genotype (A/A or V/V) were studied. Peripheral blood mononuclear cells were separated and incubated for 18 h with lipopolysaccharide (LPS), followed by analysis of mitochondrial and cytosolic fractions. There was no difference between genotypes in MnSOD activity and cytochrome c concentration, and minor differences in total antioxidant capacity (TAC) and mitochondrial membrane potential, which did not affect response to LPS. Despite predictions from structural enzyme studies that mitochondrial trafficking would be affected by the Ala9Val polymorphism of the MnSOD gene had little functional effect.

Genetic polymorphisms of manganese superoxide dismutase, NAD(P)H:quinone oxidoreductase, glutathione S-transferase M1 and T1, and the susceptibility to drug-induced liver injury

BACKGROUND/AIMS

Drug metabolizing enzymes may be related to drug-induced liver injury (DILI). Manganese superoxide dismutase (MnSOD), NAD(P)H:quinone oxidoreductase (NQO1), and glutathione S-transferase (GST) are important drug metabolizing enzymes. We aimed to elucidate the relationship between genetic polymorphisms of these enzymes and the susceptibility to DILI.

METHODS

A total of 115 patients with DILI and 115 drug-, sex-, and age-matched controls were enrolled. Their genetic polymorphisms of MnSOD, NQO1, GSTM1, and GSTT1 were assayed.

RESULTS

Sixty-three (54.8%) of DILI patients were incriminated to anti-tuberculosis drugs. Subjects with a mutant C allele (T/C or C/C genotype) of MnSOD had a higher risk of DILI than those with MnSOD T/T genotype, both in overall drugs studied (adjusted OR: 2.44, 95% C.I.: 1.38-4.30, P=0.002), and in sub-category of anti-tuberculosis drugs (adjusted OR: 2.47, 95% C.I.: 1.13-5.39, P=0.02). In addition, subjects carrying GSTM1 null genotype had increased risk of anti-tuberculosis DILI (adjusted OR: 2.23, 95% C.I.: 1.07-4.67, P=0.03).

CONCLUSIONS

The MnSOD mutant C allele may increase the susceptibility to DILI, and GSTM1 null genotype may be related to anti-tuberculosis drug-induced hepatotoxicity. Determination of the MnSOD and GSTM1 genotypes may help identify patients at high risk for DILI.

Association between the MnSOD Ala-9Val polymorphism and development of schizophrenia and abnormal involuntary movements in the Xhosa population

Reactive oxygen species (ROS)-mediated damage has been hypothesized to play a role in the development and poor outcome of schizophrenia, as well as the development of neuroleptic-induced abnormal involuntary movements. Recently, the functional polymorphism (Ala-9Val) in the manganese superoxide dismutase (MnSOD) gene (part of the antioxidant defense mechanism) was found to be associated with schizophrenia in a Turkish population. This study was aimed at replicating this finding in a Xhosa population. In addition, the role of Ala-9Val in abnormal involuntary movement and tardive dyskinesia development in the Xhosa population was also investigated. The schizophrenic patient group (n=286) and a healthy control group (n=243) were genotyped for the Ala-9Val polymorphism using heteroduplex-single stranded conformational polymorphism (HEX-SSCP) analysis. No significant difference in genotype or allele frequency could be observed between the schizophrenia and control group (P=0.294 and P=0.528 respectively). In addition no association could be found between the polymorphism and symptom severity (SANS and SAPS). The Xhosa schizophrenia patient group with abnormal involuntary movements (n=54) and a subgroup with tardive dyskinesia (n=30) was found to significantly differ in Ala-9Val genotype frequency (P=0.008 and P=0.011 respectively) compared to the Xhosa schizophrenia patient group without abnormal involuntary movements (n=204). However, no significant difference was found for the allele frequencies (P=0.955 and P=0.161). Further, using ANCOVA no association was found between AIMS score and genotype in the group with abnormal involuntary movements (P=0.1234). However, in the patient group with tardive dyskinesia an association was observed between genotype and AIMS score (P=0.0365). These results do not support a major role of the MnSOD Ala-9Val polymorphism in the development of schizophrenia or symptom severity in the Xhosa population. Yet it seems to be involved in the development of abnormal involuntary movements and tardive dyskinesia and may even modulate the severity of tardive dyskinesia.

Increased incidence of FMO1 gene single nucleotide polymorphisms in sporadic amyotrophic lateral sclerosis

Flavin-containing monooxygenases (FMO) represent a gene family involved in the oxidative metabolism of a variety of xenobiotics, pesticides and drugs. A new function for FMO proteins has been recently uncovered: yeast FMO has been demonstrated to take part in maintaining the redox balance, catalysing the oxidation of reduced glutathione (GSH) to glutathione disulfide (GSSG). The GSSG/GSH balance is an important buffering system for reactive oxygen species and its involvement has been documented in ALS and other neurodegenerative disorders. Human FMO genes present different mutations, which may be related to ethnicity, altered metabolic activity and, in some cases, specific diseases. The human FMO1 gene presents 20 single nucleotide polymorphisms (SNPs) located in coding regions, intronic sequences and untranslated regions. The FMO1 gene has also recently been found underexpressed in spinal cord of ALS patients. Using SSCP and direct sequencing, we studied the allelic and genotypic frequency of two 3'UTR SNPs of the FMO1 gene in sporadic ALS patients compared to a healthy control population. We found a significantly higher frequency of these two polymorphisms, exclusive of the female population, in SALS patients compared to controls (p<0.01), suggesting that specific allelic variants of the FMO1 gene might be associated to susceptibility to develop ALS.

Glia cells in amyotrophic lateral sclerosis: New clues to understanding an old disease?

In classic neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), the pathogenic concept of a cell-autonomous disease of motor neurons has been challenged increasingly in recent years. Macro- and microglial cells have come to the forefront for their role in multistep degenerative processes in ALS and respective disease models. The activation of astroglial and microglial cells occurs early in the pathogenesis of the disease and seems to greatly influence disease onset and promotion. The role of oligodendrocytes and Schwann cells remains elusive. In this review we highlight the impact of nonneuronal cells in ALS pathology. We discuss diverse glial membrane proteins that are necessary to control neuronal activity and neuronal cell survival, and summarize the contribution of these proteins to motor neuron death in ALS. We also describe recently discovered glial mechanisms that promote motor neuron degeneration using state-of-the-art genetic mouse technology. Finally, we provide an outlook on the extent to which these new pathomechanistic insights may offer novel therapeutic approaches.

Association analysis of SOD2 variants with methamphetamine psychosis in Japanese and Taiwanese populations

SOD2 (superoxide dismutase 2) plays a crucial role in protecting the cells against damage caused by free radicals, by catalyzing their detoxification. On the other hand, cell damage caused by free radical generation following methamphetamine administration has been postulated as one of the possible pathophysiological mechanisms for methamphetamine psychosis. Hence, we investigated the association of SOD2 polymorphisms with the development of methamphetamine psychosis, in two independent populations of Japan and Taiwan. We recruited 116 patients with methamphetamine psychosis and 189 controls in Japan, and 135 patients with methamphetamine psychosis and 204 controls in Taiwan. The methamphetamine group was divided into two clinical subtypes: a transient type of psychosis (i.e., good prognosis) and a prolonged type of psychosis (i.e., poor prognosis), according to the course of the manifestation of psychosis. With reference to the genotypic and allelic frequencies of Ala/Val functional polymorphism in exon 2, we found significant differences between individuals with prolonged methamphetamine psychosis and control samples from Japan and Taiwan in the genotypic (P value 0.014 and 0.016, respectively) and in the allelic (P value 0.004 and 0.047, respectively) frequencies. Our results suggest that Ala/Val polymorphism of the SOD2 gene could be associated with the risk of developing methamphetamine psychosis.

The manganese superoxide dismutase Ala16Val dimorphism modulates both mitochondrial import and mRNA stability

A genetic dimorphism incorporates either alanine (Ala) or valine (Val) in the mitochondrial targeting sequence (MTS) of manganese superoxide dismutase (MnSOD). The Ala-MTS confers a 40% higher MnSOD activity than the Val-MTS after import into isolated mitochondria in vitro. The present study aimed to characterize functional consequences in whole cells. HuH7 human hepatoma cells were transfected with vectors encoding for the human Ala- or Val-MnSOD variants fused to a Myc-His-tag. The Ala-variant resulted in four-fold higher levels of the mature exogenous protein and MnSOD activity than the Val-variant. Studies with a proteasome inhibitor indicated that precursor proteins are either imported into the mitochondria or degraded by the proteasome. Despite identical levels 8 h after transfection, mRNA levels at 36 h were two-fold higher for the Ala-encoding mRNA than the Val-mRNA. Decreasing the mitochondrial membrane potential decreased both MnSOD mitochondrial import and its mRNA levels. Much larger differences in the activity of the human Val- and Ala-MnSOD variants are observed in whole cells rather than after import experiments performed in vitro. First, the slowly imported Val-MnSOD is degraded by the proteasome in cells. Second, the slower mitochondrial import of the Val-variant may be associated with decreased mRNA stability, possibly due to impaired cotranslational import.

Lack of association between MnSOD gene polymorphism and sporadic Alzheimer's disease

BACKGROUND AND AIMS

Substantial evidence supports the hypothesis that impairment of mitochondrial function and increased oxidative damage are involved in the pathogenesis of several neurodegenerative disorders including Alzheimer's disease (AD). Manganese superoxide dismutase (MnSOD) plays a major role in protecting the mitochondrion from oxidative damage due to superoxide radicals and other excited oxygen species. Recent studies have indicated that MnSOD mRNA levels are significantly increased in the lymphocytes of AD patients, supporting the role of oxidative alterations in the pathogenetic mechanism underlying this neurodegeneration. A potentially functional amino acid polymorphism (Ala-9Val) has been described in the signal sequence of enzymes associated with decreased defense capacity against oxidative stress. The object of this study was to investigate the association between this polymorphism of the MnSOD gene and AD in the Italian population.

METHODS

The Ala-9Val polymorphism was genotyped by PCR amplification and SSCP analysis in 227 AD patients and 198 healthy controls.

RESULTS

No significant differences in genotype or allele frequencies between cases and controls, even after stratification for APOE carrier status, were observed.

CONCLUSIONS

Our data suggest that the Ala-9Val polymorphism in the MnSOD gene is not associated with genetic susceptibility in AD patients.

MnSOD polymorphisms in sensitized patients with delayed-type hypersensitivity reactions to the chemical allergen para-phenylene diamine: A case–control study

Dyes such as para-phenylene diamine (PPD) or related para-compounds are very common contact sensitizers in man. The corresponding contact dermatitis in sensitized individuals is a complex and common illness associated with considerable morbidity and social cost. It has been found that oxidative stress from reactive oxygen species (ROS) may play an important role in the pre-immunological phase of allergic contact dermatitis to PPD. Manganese superoxide dismutase (MnSOD) is one of the primary enzymes that directly scavenge potential harmful oxidizing species. A valine (Val) to alanine (Ala) substitution at amino acid -9, occurring in the MnSOD gene, has been associated with various disease risk. The aim of our study was to investigate possible associations of the MnSOD 47 T>C genotype in exon 2 (Ala-9Val) and the 339 T>C genotype in exon 3 (Ile58Thr) with contact sensitization to PPD in humans in a case-control study. The study was performed in 157 unrelated cases and 201 age- and gender-matched controls. The MnSOD genotypes were determined using LightCycler allele discrimination assays. No heterozygous (CT) or homozygous carriers (TT) for the Ile58Thr polymorphism were found. The frequency for the C allele of the Ala-9Val polymorphism was 51% (79/157) in cases and 49% (107/201) in controls. Homozygous CC carriers (Ala/Ala) were 27% (43/157) in cases and 23% (46/201) in controls (odds ratio [OR], 1.3; 95% confidence interval [CI], 0.8-2.1). Stratification into subgroups based on gender and age limited the association to females. Increased risk among homozygous CC carriers (Ala/Ala) was only found in the group of older females (over 45 years, 25% versus 18%; OR, 1.5; 95% CI, 0.7-2.34). These data suggest that the C (Ala) allele of MnSOD modifies contact dermatitis risk among older females, but is not an independent susceptibility factor for contact sensitization to PPD.

Association between Ala-9Val polymorphism of Mn-SOD gene and schizophrenia

Reactive oxygen species (ROS) have been suggested to play an important role in physiopathology of schizophrenia. The major intracellular antioxidant enzymes, copper-zinc superoxide dismutase in the cytoplasm and manganese superoxide dismutase (Mn-SOD) in the mitochondria, rapidly and specifically reduce superoxide radicals to hydrogen peroxide. Polymorphisms in the genes encoding antioxidant enzymes should therefore result in predisposition to schizophrenia. The present study was performed to assess whether there is a genetic association between a functional polymorphism (Ala-9Val) in the human Mn-SOD gene in schizophrenic patients (n=153) and healthy controls (n=196) using a PCR/RFLP method. Significant differences in the genotypic distribution between schizophrenics and controls were observed. Genotypic distribution with 14 (9.2%) Ala/Ala, 106 (69.3%) Ala/Val and 33 (21.6%) Val/Val subjects in schizophrenia was different from those of controls with 46 (23.5%), 83 (42.3%) and 67 (34.2%), respectively (p<0.0001). When the patients with schizophrenia were divided into the subgroups as disorganized, paranoid and residual, there was a significant difference in genotypic distribution among the subgroups (chi2=11.35, df=4, p=0.023). This association between -9Ala Mn-SOD allele and schizophrenia suggests that -9Ala variant may have a contribution in the physiopathogenesis of schizophrenia. Further investigations are warranted in larger populations with other susceptible genes that might be associated with schizophrenia.

Toxicity of Familial ALS-Linked SOD1 Mutants from Selective Recruitment to Spinal Mitochondria

One cause of amyotrophic lateral sclerosis (ALS) is mutation in ubiquitously expressed copper/zinc superoxide dismutase (SOD1), but the mechanism of toxicity to motor neurons is unknown. Multiple disease-causing mutants, but not wild-type SOD1, are now demonstrated to be recruited to mitochondria, but only in affected tissues. This is independent of the copper chaperone for SOD1 and dismutase activity. Highly preferential association with spinal cord mitochondria is seen in human ALS for a mutant SOD1 that accumulates only to trace cytoplasmic levels. Despite variable proportions that are successfully imported, nearly constant amounts of SOD1 mutants and covalently damaged adducts of them accumulate as apparent import intermediates and/or are tightly aggregated or crosslinked onto integral membrane components on the cytoplasmic face of those mitochondria. These findings implicate damage from action of spinal cord-specific factors that recruit mutant SOD1 to spinal mitochondria as the basis for their selective toxicity in ALS.

PCR/RFLP-based cost-effective identification of SOD2 signal (leader) sequence polymorphism (Ala–9Val) using NgoM IV: a detailed methodological approach

BACKGROUND

Superoxide dismutases (SOD) play an important role in the protection of cells and extracellular space from the products of oxidative stress. Two allelic variants have been described for the SOD2 gene (Ile58Thr involves a C to T substitution at nucleotide residue 339 and Ala-9Val involves a T to C substitution at nucleotide residue 1183). The enzyme proteins encoded by the different alleles have been suggested to have different activity patterns.

METHODS

The SOD2 polymorphism was determined using a polymerase chain reaction (PCR) and RFLP techniques with restriction endonuclease NgoM IV.

RESULTS

The most available results were obtained from with 20 pmol primer final concentration in PCR reaction. A total of 20 pmol seems the cost-effective primer concentration with maximum quality. There were no difference between the band quality of 1-5 units of restriction endonucleases. On the other hand, short and long incubation times seem to be similar in order to obtain sharp bands on agarose gel.

CONCLUSIONS

We have extended a method of SOD2 polymorphism (Ala-9Val) in mitochondrial sequence. This method provides the ability to genotype of SOD2, and it represents a fast, reliable, cost-effective and semi-automated methodology to determine SOD2 polymorphism in order to perform large-scale population studies.

Association of antioxidant enzyme gene polymorphisms and glutathione status with severe acute pancreatitis

BACKGROUND & AIMS

Genetic variations in antioxidant metabolism may explain varying biological responses to acute pancreatitis (AP). We studied the contribution of oxidative stress to the pathogenesis of severe pancreatitis by examining the prevalence of functional gene polymorphisms of antioxidant enzymes and evidence of heightened oxidative stress.

METHODS

DNA from 320 patients with AP (90 severe) and 263 controls was genotyped for glutathione S-transferase (Mu-1 [M-1], theta-1 [T-1], and pi-1 [P-1: Ile-105Val]), manganese superoxide dismutase (Ala-9Val), and catalase (C-260T) polymorphisms. Erythrocyte reduced glutathione (GSH) concentration was determined 24 and 72 hours after the onset of pain in 46 patients (11 severe). Disease severity was assessed using Atlanta clinical criteria, Acute Physiology Scores (APS), and peak serum C-reactive protein levels.

RESULTS

The functional GSTT-1*A genotype was more prevalent in severe (96%) compared with mild attacks of AP (78%; odds ratio [OR], 5.9; 95% confidence interval [CI ], 2-17; P < 0.0001) and controls (76%; OR, 6.6; 95% CI, 2.3-18.7; P < 0.0001). Compared with null genotype, GSTT-1*A was associated with higher peak C-reactive protein levels (184 vs. 94 g/dL; P = 0.0005) and APS (24 hours, P = 0.04; 48 hours, P = 0.015). Reduced glutathione (GSH) at 24 hours was lower in mild (median, 382 nmol/g) and severe attacks (median, 407 nmol/g) compared with controls (median, 3685 nmol/g; P < 0.001). Levels increased at 72 hours in mild (P = 0.012) but not severe attacks and inversely correlated with APS (r = -0.49; P = 0.04).

CONCLUSIONS

The functional GSTT-1*A genotype was associated with severe attacks of pancreatitis. Heightened oxidative stress characterized by glutathione depletion may be of importance in mediating the progression from mild to severe pancreatitis.

Two functional variants of the superoxide dismutase genes in Finnish families with asthma

BACKGROUND

Functional polymorphisms in the genes encoding superoxide dismutases (SOD)-that is, superoxide scavenging antioxidant enzymes-may play an important role in the development of inflammatory airway diseases such as asthma.

METHODS

The allele frequencies of two missense polymorphisms of SOD genes (Ala16Val in MnSOD (SOD2) and Arg213Gly in ECSOD (SOD3)) were investigated in Finnish patients with asthma and compared with family based controls. Both variants have been shown to be functionally interesting in the lung. The polymorphism at the exon-intron 3 boundary of a third SOD, CuZnSOD (SOD1), was also included in the analysis.

RESULTS

None of the SOD genetic variants studied appeared to be major genetic regulators in the development of asthma. We could exclude all models of inheritance that increased the risk of asthma more than 1.2 fold for MnSOD*Val (frequency of allele 0.74 in the population) and more than 6.6 fold for ECSOD*Gly213 (frequency of allele 0.03 in the population) compared with non-carriers. For the intronic polymorphism in CuZnSOD, a relative risk of more than 3.3 (frequency of allele 0.10 in the population) could be excluded.

CONCLUSIONS

It is highly unlikely that the functionally important genetic variants Ala16Val and Arg213Gly of SODs play a major role in the genetic susceptibility of asthma.

VEGF is a modifier of amyotrophic lateral sclerosis in mice and humans and protects motoneurons against ischemic death

Amyotrophic lateral sclerosis (ALS) is an incurable degenerative disorder of motoneurons. We recently reported that reduced expression of Vegfa causes ALS-like motoneuron degeneration in Vegfa(delta/delta) mice. In a meta-analysis of over 900 individuals from Sweden and over 1,000 individuals from Belgium and England, we now report that subjects homozygous with respect to the haplotypes -2,578A/-1,154A/-634G or -2,578A/-1,154G/-634G in the VEGF promoter/leader sequence had a 1.8 times greater risk of ALS (P = 0.00004). These 'at-risk' haplotypes lowered circulating VEGF levels in vivo and reduced VEGF gene transcription, IRES-mediated VEGF expression and translation of a novel large-VEGF isoform (L-VEGF) in vivo. Moreover, SOD1(G93A) mice crossbred with Vegfa(delta/delta) mice died earlier due to more severe motoneuron degeneration. Vegfa(delta/delta) mice were unusually susceptible to persistent paralysis after spinal cord ischemia, and treatment with Vegfa protected mice against ischemic motoneuron death. These findings indicate that VEGF is a modifier of motoneuron degeneration in human ALS and unveil a therapeutic potential of Vegfa for stressed motoneurons in mice.

Genetic epidemiology of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a late onset, rapidly progressive and ultimately fatal neurological disorder, caused by the loss of motor neurons in the brain and spinal cord. Familial aggregation of ALS, with an age-dependent but high penetrance, is a major risk factor for ALS. Familial ALS (FALS) is clinically and genetically heterogeneous. Three genes and linkage to four additional gene loci have been identified so far and may either predominantly lead to ALS (ALSI-ALS6) or cause multisystem neurodegeneration with ALS as an occasional symptom (tauopathies, ALS-dementia complex). This review presents a tentative classification of the "major" ALS genes and ALS "susceptibility" genes, that may act as susceptibility factors for neurodegeneration in interaction with other genetic or environmental risk factors. Considering that mutations in ALS genes explain approximately 10% of familial as well as sporadic ALS, and most remaining cases of the discase are thought to result form the interaction of several genes and environmental factors, ALS is a paradigm for multifactorial discases.

Common denominator of Cu/Zn superoxide dismutase mutants associated with amyotrophic lateral sclerosis: decreased stability of the apo state

More than 100 point mutations of the superoxide scavenger Cu/Zn superoxide dismutase (SOD; EC ) have been associated with the neurodegenerative disease amyotrophic lateral sclerosis (ALS). However, these mutations are scattered throughout the protein and provide no clear functional or structural clues to the underlying disease mechanism. Therefore, we undertook to look for folding-related defects by comparing the unfolding behavior of five ALS-associated mutants with distinct structural characteristics: A4V at the interface between the N and C termini, C6F in the hydrophobic core, D90A at the protein surface, and G93A and G93C, which decrease backbone flexibility. With the exception of the disruptive replacements A4V and C6F, the mutations only marginally affect the stability of the native protein, yet all mutants share a pronounced destabilization of the metal-free apo state: the higher the stability loss, the lower the mean survival time for ALS patients carrying the mutation. Thus organism-level pathology may be directly related to the properties of the immature state of a protein rather than to those of the native species.

The increased activity of plasma manganese superoxide dismutase in tardive dyskinesia is unrelated to the Ala-9Val polymorphism

That tardive dyskinesia (TD) may have its origins in free-radical toxicity has stimulated investigations into one enzyme important in the control of oxidative free radicals: superoxide dismutase (SOD). The manganese-containing form of this enzyme (MnSOD) is the major superoxide scavenger in mitochondria; a weak association between a functional genetic polymorphism (Ala-9Val) in the mitochondrial targeting sequence (MTS) of this enzyme and TD has been reported in a Japanese population. We have undertaken to determine both the plasma activity of MnSOD and the association of the Ala-9Val polymorphism in a well-matched series of male Chinese schizophrenic patients with (n=42) and without (n=59) TD, and normal male controls (n=50). MnSOD activity was elevated in the TD subjects over those without TD (P<0.05) and normal controls (P<0.05), an effect that was independent of age, age at first antipsychotic treatment, drug dosage and duration of illness. A significant positive correlation between total AIMS score and MnSOD activity was also observed (P<0.0001). No significant reduction in the frequency of the Ala allele was observed in the TD group (0.14) below non-TD (0.18) or control subjects (0.17); nor was there any relationship between MnSOD activity and the polymorphism. There was no difference between the mean AIMS scores for the two genotypes (V/V and A/V) in the TD group. We conclude that while we have further evidence of a disturbance in the mechanisms regulating oxidative free radicals in TD, this effect is not under the control of the genetic polymorphism investigated here.

Superoxide dismutase multigene family: a comparison of the CuZn-SOD (SOD1), Mn-SOD (SOD2), and EC-SOD (SOD3) gene structures, evolution, and expression

Superoxide dismutases are an ubiquitous family of enzymes that function to efficiently catalyze the dismutation of superoxide anions. Three unique and highly compartmentalized mammalian superoxide dismutases have been biochemically and molecularly characterized to date. SOD1, or CuZn-SOD (EC 1.15.1.1), was the first enzyme to be characterized and is a copper and zinc-containing homodimer that is found almost exclusively in intracellular cytoplasmic spaces. SOD2, or Mn-SOD (EC 1.15.1.1), exists as a tetramer and is initially synthesized containing a leader peptide, which targets this manganese-containing enzyme exclusively to the mitochondrial spaces. SOD3, or EC-SOD (EC 1.15.1.1), is the most recently characterized SOD, exists as a copper and zinc-containing tetramer, and is synthesized containing a signal peptide that directs this enzyme exclusively to extracellular spaces. What role(s) these SODs play in both normal and disease states is only slowly beginning to be understood. A molecular understanding of each of these genes has proven useful toward the deciphering of their biological roles. For example, a variety of single amino acid mutations in SOD1 have been linked to familial amyotrophic lateral sclerosis. Knocking out the SOD2 gene in mice results in a lethal cardiomyopathy. A single amino acid mutation in human SOD3 is associated with 10 to 30-fold increases in serum SOD3 levels. As more information is obtained, further insights will be gained.

Environmental exposure to trace elements and risk of amyotrophic lateral sclerosis: a population-based case-control study

We analyzed the association between the environmental exposure to trace elements and the risk of sporadic amyotrophic lateral sclerosis (ALS) in a population-based case-control study in the Emilia-Romagna region in northern Italy. We evaluated exposure to selected trace elements by measuring toenail concentrations of the same by means of inductively coupled plasma optical spectrometry and instrumental neutron activation analysis. The final number enrolled in the study was 22 patients and 40 controls. Disease progression, assessed through a clinical score, was generally unassociated with toenail trace element levels, with the exception of an inverse relation with zinc and selenium content and a direct correlation with copper concentration. In logistic regression analysis, we found no evidence of an association between ALS risk and toenail content of cadmium, lead, copper, zinc, manganese, selenium, chromium, cobalt, iron, and aluminum. This investigation does not suggest a major role in sporadic ALS etiology of environmental exposure to these trace elements, though results for zinc, selenium, and copper should be evaluated with caution due to the potential limitations of toenails as biomarkers of chronic exposure in patients.

Mutation screening of manganese superoxide dismutase in amyotrophic lateral sclerosis

Seventy-seven cases of ALS were screened for mutations in the manganese superoxide dismutase gene (SOD2). DNA was extracted from CNS tissue and screened using single stranded conformation polymorphism and heteroduplex analysis. No mutations were identified in the entire coding region of the SOD2 gene. The known polymorphism in the mitochondrial targeting sequence was identified. No association was found between this polymorphism and ALS. A further polymorphism was detected in the intronic sequence upstream of exon 4, though no association with ALS was demonstrated. We therefore conclude that mutations in SOD2 do not appear to cause ALS.

Oxidative stress, human genetic variation, and disease

Oxidative stress has been implicated in numerous pathophysiological conditions and also aging. The tools for studying oxidative stress are now expanding as a result of the human genome effort and, in particular, expanding knowledge on human genetic variation. A few genetic variants, mostly in the form of single nucleotide polymorphisms of relevance to oxidative stress are already studied by a molecular epidemiologic approach. A review of the current knowledge on variant human genes that are directly implicated in human protection against oxidative stress is presented.

Homozygosity for alanine in the mitochondrial targeting sequence of superoxide dismutase and risk for severe alcoholic liver disease

BACKGROUND & AIMS

For similar ethanol consumption, some subjects only develop macrovacuolar steatosis whereas others develop severe liver lesions. A genetic dimorphism encodes for either alanine or valine in the mitochondrial targeting sequence of manganese superoxide dismutase and could modulate its mitochondrial import.

METHODS

The DNA of 71 white patients with alcoholic liver disease and 79 white blood donors was amplified and genotyped.

RESULTS

The frequency of the alanine-encoding allele and the percentage of alanine homozygotes were higher in all patients than in controls and increased with the severity of liver lesions. The percentage of alanine homozygotes was 19% in controls, 17% in alcoholic patients with macrovacuolar steatosis, 43% in patients with microvesicular steatosis, 58% in patients with alcoholic hepatitis, and 69% in patients with cirrhosis. Alcohol consumption in alcoholics was similar whatever the genotype. Alanine homozygosity did not change the risk of developing macrovacuolar steatosis in alcoholics, but increased by 3-fold that of microvesicular steatosis, and 6- and 10-fold that of alcoholic hepatitis and cirrhosis.

CONCLUSIONS

Homozygosity for alanine in the mitochondrial targeting sequence of manganese superoxide does not modify alcohol consumption and the risk of macrovacuolar steatosis in alcoholics but is a major risk factor for severe alcoholic liver disease.

Polymorphisms in the Mn-SOD and EC-SOD genes and their relationship to diabetic neuropathy in type 1 diabetes mellitus

BACKGROUND

Oxidative stress, resulting in a marked increase in the level of oxygen free radicals (OFR), has been implicated in the etiology of diabetic neuropathy (DN). Antioxidant enzymes may protect against the rapid onset and progression of DN, by reducing the excess of OFR and peroxide. Mutations and polymorphisms in the genes encoding such enzymes may therefore result in predisposition to DN. We investigated the role of genes encoding two antioxidant enzymes, mitochondrial (Mn-SOD) and extracellular (EC-SOD) superoxide dismutase, in DN pathogenesis in a Russian population. We studied Ala(-9)Val and Ile58Thr polymorphisms of the Mn-SOD gene and Arg213Gly dimorphism of the EC-SOD gene in type 1 diabetic patients with (n = 82) and without DN (n = 84).

RESULTS

We developed and used a new polymerase chain reaction (PCR) assays for rapid detection of polymorphisms. These assays involved the use of mismatch PCR primers to create restriction sites in the amplified product only in presence of the polymorphic base. The PCR product was than digested with BshTI, Eco32I or Eco52I to detect Ala(-9)Val, Ile58Thr or Arg213Gly polymorphic site respectively. The frequencies of the Ala allele (50.6% vs. 68.5%, p < 0.002) and the Ala/Ala genotype (17.1% vs. 39.3%, p < 0.005) of the Mn-SOD gene were significantly lower in DN patients than in diabetic subjects without DN. In contrast, the Val allele (49.4% vs. 31.5%, p < 0.002) and the Val/Val genotype (15.9% vs. 2.4%, p < 0.01) were significantly more frequent in the DN patients than in the control group.

CONCLUSIONS

Ala(-9)Val substitution in the Mn-SOD gene was associated with DN in a Russian population

Genetics of sporadic ALS

The only known gene to be involved in ALS is the CuZn-superoxide dismutase (CuZn-SOD) gene. Since 1993, 89 disease-associated mutations have been found in this gene, 14 of them in cases with apparently sporadic ALS. Most frequent are the D90A (most often with recessive inheritance, but a few with dominant inheritance) and the I113T (dominant inheritance with variable penetrance). Statistical and genealogical evidence suggest that quite a number of diagnosed sporadic cases may in fact be familial cases in pedigrees with very low disease penetrance.

Genetic factors in the early diagnosis of ALS

The frequency of familial amyotrophic lateral sclerosis (ALS) is usually reported as 5-10% of all ALS cases. This figure is probably an underestimate, primarily due to inadequate recording of family history in the patients' charts, and to the not infrequent occurrence of reduced disease penetrance in pedigrees with familial ALS. The true familial ALS frequency may be at least double this. Familial ALS is heterogenetic. The only known ALS-causing gene is the CuZn-superoxide dismutase gene (CuZn-SOD). Mutations in this gene account for a fifth of all familial ALS cases and a few percent of apparent sporadic ALS cases. Genetic testing for CuZn-SOD mutations can help confirm a diagnosis of ALS, especially in cases with atypical features that have been reported in some cases with CuZn-SOD mutations. Genetic testing should only be performed after thorough clinical examination and in cases with a proven or uncertain family history of ALS. It is not warranted in cases with no proven family history for three generations, unless the patient shows the characteristic phenotype associated with recessive inheritance of the D90A CuZn-SOD mutation.