Leu54Phe and Val762Ala polymorphisms in the poly(ADP-ribose)polymerase-1 gene are associated with diabetic polyneuropathy in Russian type 1 diabetic patients

Diabetic peripheral neuropathy: pathogenetic mechanisms and treatment

Diabetic peripheral neuropathy (DPN) refers to the development of peripheral nerve dysfunction in patients with diabetes when other causes are excluded. Diabetic distal symmetric polyneuropathy (DSPN) is the most representative form of DPN. As one of the most common complications of diabetes, its prevalence increases with the duration of diabetes. 10-15% of newly diagnosed T2DM patients have DSPN, and the prevalence can exceed 50% in patients with diabetes for more than 10 years. Bilateral limb pain, numbness, and paresthesia are the most common clinical manifestations in patients with DPN, and in severe cases, foot ulcers can occur, even leading to amputation. The etiology and pathogenesis of diabetic neuropathy are not yet completely clarified, but hyperglycemia, disorders of lipid metabolism, and abnormalities in insulin signaling pathways are currently considered to be the initiating factors for a range of pathophysiological changes in DPN. In the presence of abnormal metabolic factors, the normal structure and function of the entire peripheral nervous system are disrupted, including myelinated and unmyelinated nerve axons, perikaryon, neurovascular, and glial cells. In addition, abnormalities in the insulin signaling pathway will inhibit neural axon repair and promote apoptosis of damaged cells. Here, we will discuss recent advances in the study of DPN mechanisms, including oxidative stress pathways, mechanisms of microvascular damage, mechanisms of damage to insulin receptor signaling pathways, and other potential mechanisms associated with neuroinflammation, mitochondrial dysfunction, and cellular oxidative damage. Identifying the contributions from each pathway to neuropathy and the associations between them may help us to further explore more targeted screening and treatment interventions.

A Drosophila model of diabetic neuropathy reveals a role of proteasome activity in the glia

Diabetic peripheral neuropathy (DPN) is the most common chronic, progressive complication of diabetes mellitus. The main symptom is sensory loss; the molecular mechanisms are not fully understood. We found that Drosophila fed a high-sugar diet, which induces diabetes-like phenotypes, exhibit impairment of noxious heat avoidance. The impairment of heat avoidance was associated with shrinkage of the leg neurons expressing the Drosophila transient receptor potential channel Painless. Using a candidate genetic screening approach, we identified proteasome modulator 9 as one of the modulators of impairment of heat avoidance. We further showed that proteasome inhibition in the glia reversed the impairment of noxious heat avoidance, and heat-shock proteins and endolysosomal trafficking in the glia mediated the effect of proteasome inhibition. Our results establish Drosophila as a useful system for exploring molecular mechanisms of diet-induced peripheral neuropathy and propose that the glial proteasome is one of the candidate therapeutic targets for DPN.

Poly (ADP-ribose) polymerase 1-mediated defective mitophagy contributes to painful diabetic neuropathy in the db/db model

Studies have shown that poly (ADP-ribose) polymerase 1 (PARP1) was involved in the pathological process of diabetes. Mitophagy is widely acknowledged to be a key regulatory process in maintaining reactive oxygen species homeostasis via lysosome degradation of damaged mitochondria. However, the regulatory role of PARP1 in mitophagy-related mitochondrial oxidative injury and progression of painful diabetic neuropathy (PDN) is unclear. In this study, we studied the in vitro and in vivo mechanisms of PARP1-mediated mitophagy blockade in a leptin gene-mutation (db/db) mouse model of PDN. Db/db mice models of PDN were established by assessing the sciatic nerve conduction velocity (SNCV), mechanical withdrawal threshold (MWT), and thermal withdrawal latency (TWL). The results showed that PARP1 activity and mitochondrial injury of dorsal root ganglion (DRG) neurons were increased, and mitophagy was impaired in PDN mice. PARP1 was found to mediate the impairment of mitophagy in DRG neurons isolated from PDN mice. PARP1 inhibitors (PJ34 or AG14361) attenuated diabetes-induced peripheral nerve hyperalgesia, restored DRG neuron mitophagy function and decreased mitochondrial oxidative injury. Mitophagy impairment induced by lysosome deacidificant (DC661) aggravated diabetes-induced DRG neuron mitochondrial oxidative stress and injury. Taken together, our data revealed that PARP1 induced defective mitophagy of DRG neurons is a key mechanism in diabetes-induced peripheral neuropathic injury. Inhibition of PARP1 and restoration of mitophagy function are potential therapeutic targets for PDN.

Genetics of diabetic neuropathy: Systematic review, meta-analysis and trial sequential analysis

OBJECTIVE

Diabetic neuropathy (DN) is one of the most common complications of diabetes that occurs in more than 67% of individuals with diabetes. Genetic polymorphisms may play an important role in DN development. However, until now, the association between genetic polymorphisms and DN risk has remained unknown. We performed a systematic review, meta-analysis, and trial sequential analysis (TSA) of the association between all genetic polymorphisms and DN risk.

METHODS

Relevant published studies examining the relationship between all genetic polymorphisms and DN were obtained based on a designed search strategy up to 28 February 2019. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess overall pooled effects of genetic models as well as in subgroup analyses. Sensitive analysis and publication bias were applied to evaluate the reliability of the study. Moreover, TSA was conducted to estimate the robustness of the results.

RESULTS

We conducted a systematic review of a total of 1256 articles, and then 106 publications reporting on 136 polymorphisms of 76 genes were extracted. We performed 107 meta-analyses on 36 studies involving 12,221 subjects to derive pooled effect estimates for eight polymorphisms. We identified that ACE I>D, MTHFR 1298A/C, GPx-1 rs1050450, and CAT -262C/T were associated with DN, while MTHFR C677T, GSTM1, GSTT1, and IL-10 -1082G/A were not. Sensitivity analysis, funnel plot, and Egger's test displayed robust results. Furthermore, the results of TSA indicated sufficient sample size in studies of ACE, GPx-1, GSTM1, and IL-10 polymorphisms.

INTERPRETATION

Our study assessed the association between ACE I>D, MTHFR C677T, MTHFR 1298A/C, GPx-1 rs1050450, CAT -262C/T, GSTM1, GSTT1, and IL-10 -1082G/A polymorphisms and DN risk. We hope that the data in our research study are used to study DN genetics.

Constrained maximum entropy models to select genotype interactions associated with censored failure times

We propose a novel screening method targeting genotype interactions associated with disease risks. The proposed method extends the maximum entropy conditional probability model to address disease occurrences over time. Continuous occurrence times are grouped into intervals. The model estimates the conditional distribution over the disease occurrence intervals given individual genotypes by maximizing the corresponding entropy subject to constraints linking genotype interactions to time intervals. The EM algorithm is employed to handle observations with uncertainty, for which the disease occurrence is censored. Stepwise greedy search is proposed to screen a large number of candidate constraints. The minimum description length is employed to select the optimal set of constraints. Extensive simulations show that five or so quantile-dependent intervals are sufficient to categorize disease outcomes into different risk groups. Performance depends on sample size, number of genotypes, and minor allele frequencies. The proposed method outperforms the likelihood ratio test, Lasso, and a previous maximum entropy method with only binary (disease occurrence, non-occurrence) outcomes. Finally, a GWAS study for type 1 diabetes patients is used to illustrate our method. Novel one-genotype and two-genotype interactions associated with neuropathy are identified.

Risk Factors and Comorbidities in Diabetic Neuropathy: An Update 2015

Distal symmetric sensorimotor polyneuropathy (DSPN) is the most common neurological manifestation in diabetes. Major risk factors of DSPN include diabetes duration, hyperglycemia, and age, followed by prediabetes, hypertension, dyslipidemia, and obesity. Height, smoking, insulin resistance, hypoinsulinemia, and others represent an additional risk. Importantly, hyperglycemia, hypertension, dyslipidemia, obesity, and smoking are modifiable. Stringent glycemic control has been shown to be effective in type 1, but not to the same extent in type 2 diabetes. Antilipidemic treatment, especially with fenofibrate, and multi-factorial intervention have produced encouraging results, but more experience is necessary. The major comorbidities of DSPN are depression, autonomic neuropathy, peripheral arterial disease, cardiovascular disease, nephropathy, retinopathy, and medial arterial calcification. Knowledge of risk factors and comorbidities has the potential to enrich the therapeutic strategy in clinical practice as part of the overall medical care for patients with neuropathy. This article provides an updated overview of DSPN risk factors and comorbidities.

The role of base excision repair in the development of primary open angle glaucoma in the Polish population

Glaucoma is a leading cause of irreversible blindness in developing countries. Previous data have shown that progressive loss of human TM cells may be connected with chronic exposure to oxidative stress. This hypothesis may suggest a role of the base excision repair (BER) pathway of oxidative DNA damage in primary open angle glaucoma (POAG) patients. The aim of our study was to evaluate an association of BER gene polymorphism with a risk of POAG. Moreover, an association of clinical parameters was examined including cup disk ratio (c/d), rim area (RA) and retinal nerve fiber layer (RNFL) with glaucoma progression according to BER gene polymorphisms. Our research included 412 patients with POAG and 454 healthy controls. Gene polymorphisms were analyzed by PCR-RFLP. Heidelberg Retinal Tomography (HRT) clinical parameters were also analyzed. The 399 Arg/Gln genotype of the XRCC1 gene (OR 1.38; 95% CI 1.02-1.89 p = 0.03) was associated with an increased risk of POAG occurrence. It was indicated that the 399 Gln/Gln XRCC1 genotype might increase the risk of POAG progression according to the c/d ratio (OR 1.67; 95% CI 1.07-2.61 P = 0.02) clinical parameter. Moreover, the association of VF factor with 148 Asp/Glu of APE1 genotype distribution and POAG progression (OR 2.25; 95% CI 1.30-3.89) was also found. Additionally, the analysis of the 324 Gln/His MUTYH polymorphism gene distribution in the patient group according to RNFL factor showed that it might decrease the progression of POAG (OR 0.47; 95% CI 0.30-0.82 P = 0.005). We suggest that the 399 Arg/Gln polymorphism of the XRCC1 gene may serve as a predictive risk factor of POAG.

Association of three SNPs in the PARP-1 gene with Hashimoto's thyroiditis

Poly(ADP-ribose) polymerase-1 (PARP-1) has a vital role in the progression of the inflammatory response, and its inhibition confers protection in various models of inflammatory disorders. Therefore, we investigated the effect of promoter and exon variations of the PARP-1 gene on the risk for the inflammatory disease Hashimoto's thyroiditis (HT). This case-control association study was comprised of 141 HT patients and 150 controls from a group of women in a Turkish population. Two polymorphisms in the promoter region of the PARP-1 gene, rs2793378 and rs7527192, were analyzed using the PCR-RFLP method. In addition, single nucleotide polymorphism (SNP) rs1136410, which is located at codon 762, was analyzed using bidirectional sequencing. The combined genotype and haplotype analyses of these polymorphisms were performed using SPSS 18 and Haploview 4.2. The results were statistically analyzed by calculating the odds ratios and 95% confidence interval using Pearson's χ (2)-test and Fisher's exact test (two-sided). Although we had a number of significant results, the associations became nonsignificant following a Bonferroni correction for multiple comparisons. Nonetheless, a protective factor against HT was still observed for the heterozygous genotype (TC) of SNP rs1136410 (P=0.001), even following Bonferroni correction, and according to the rs2793378-rs7527192 combined analysis, the occurrence of the TT/GA combined genotype was significantly higher in the controls (P=0.007). These results prove that the heterozygosity of SNP rs1136410 provides a protective effect against HT disease in a group of women in a Turkish population.

Therapeutic applications of PARP inhibitors: anticancer therapy and beyond

The aim of this article is to describe the current and potential clinical translation of pharmacological inhibitors of poly(ADP-ribose) polymerase (PARP) for the therapy of various diseases. The first section of the present review summarizes the available preclinical and clinical data with PARP inhibitors in various forms of cancer. In this context, the role of PARP in single-strand DNA break repair is relevant, leading to replication-associated lesions that cannot be repaired if homologous recombination repair (HRR) is defective, and the synthetic lethality of PARP inhibitors in HRR-defective cancer. HRR defects are classically associated with BRCA1 and 2 mutations associated with familial breast and ovarian cancer, but there may be many other causes of HRR defects. Thus, PARP inhibitors may be the drugs of choice for BRCA mutant breast and ovarian cancers, and extend beyond these tumors if appropriate biomarkers can be developed to identify HRR defects. Multiple lines of preclinical data demonstrate that PARP inhibition increases cytotoxicity and tumor growth delay in combination with temozolomide, topoisomerase inhibitors and ionizing radiation. Both single agent and combination clinical trials are underway. The final part of the first section of the present review summarizes the current status of the various PARP inhibitors that are in various stages of clinical development. The second section of the present review summarizes the role of PARP in selected non-oncologic indications. In a number of severe, acute diseases (such as stroke, neurotrauma, circulatory shock and acute myocardial infarction) the clinical translatability of PARP inhibition is supported by multiple lines of preclinical data, as well as observational data demonstrating PARP activation in human tissue samples. In these disease indications, PARP overactivation due to oxidative and nitrative stress drives cell necrosis and pro-inflammatory gene expression, which contributes to disease pathology. Accordingly, multiple lines of preclinical data indicate the efficacy of PARP inhibitors to preserve viable tissue and to down-regulate inflammatory responses. As the clinical trials with PARP inhibitors in various forms of cancer progress, it is hoped that a second line of clinical investigations, aimed at testing of PARP inhibitors for various non-oncologic indications, will be initiated, as well.

Racial and tissue-specific cancer risk associated with PARP1 (ADPRT) Val762Ala polymorphism: a meta-analysis

The Val762Ala polymorphism poly [ADP-ribose] polymerase 1 (PARP1) gene [ADPRT (adenosine diphosphate ribosyltransferase) gene] affects enzymatic activity, which modulates cancer susceptibility among human populations. Individual data on 13,745 cases and 16,947 controls from 28 published case-control studies were re-evaluated. Odds ratios (OR) were estimated for ethnic group, cancer type, smoking joint effects and studies confined to the Hardy-Weinberg equilibrium. We applied subgroup, sensitivity and outlier analyses as well as the Bonferroni correction for multiple testing. The results show strong evidence that the variant (C) allele confers significant increased risk in the Chinese (OR 1.20-1.44, P < 0.0001-0.002), exacerbated by smoking (OR 1.66-2.53, P < 0.0001) and joint interaction with XRCC1 Arg399Gln (OR 1.39, P < 0.0001) as well as adjustment for tumor type (gastric carcinoma ORs 1.39-2.01, P < 0.0001). These significant effects were unaltered following conservative correction for multiple tests. By contrast, this procedure erased the protective significance in Caucasians, but not in two American subgroups, (i) those in the brain tumor category (0.77-0.79, P < 0.0001) and (ii) smokers in the dominant model (OR 0.86, P < 0.0001). These differential findings between the two ethnicities maybe correlated with significantly (P < 0.0001) greater allele frequency of the variant allele (C) among the Chinese compared to Caucasians. Our racial and tissue-specific summary estimates imply consideration of the Val762Ala polymorphism as candidate gene marker for screening cancer patients' best suited for PARP inhibitor therapy.

HIV-associated sensory neuropathy: risk factors and genetics

HIV-associated sensory neuropathy (HIV-SN) remains a common neurological complication of HIV infection despite the introduction of effective antiretroviral therapies. Exposure to neurotoxic antiretroviral drugs and increasing age have consistently been identified as risk factors for HIV-SN, while comorbid conditions with underlying predisposition to cause peripheral neuropathy (eg, diabetes mellitus, malnutrition, isoniazid exposure), ethnicity, and increasing height also have been implicated. Genetic association studies have identified genes affecting mitochondrial function and genes involved in the inflammatory response that modify the risk for HIV-SN among patients exposed to neurotoxic antiretrovirals. However, there is a lack of data on clinical, demographic, and genetic risk factors for HIV-SN in the modern era, with the rate of HIV-SN remaining unacceptably high despite the introduction of safer medications. Thus, more work is required to identify the principal factors that increase an individual's risk for HIV-SN so that effective preventative or therapeutic strategies can be implemented.

Poly ADP-ribose polymerase-1 and health

Niacin (vitamin B(3)) is required to form nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are involved in scores of anabolic and catabolic redox reactions throughout metabolism. It is now understood that NAD(+) is also a substrate for several families of ADP-ribosylation reactions, which control processes like DNA repair, replication and transcription, the activity of G-proteins, chromatin structure and intracellular calcium signalling. Poly(ADP-ribose)polymerase-1 (PARP-1) is the most active of the PARP enzymes, and it has been implicated in both prevention and aggravation of disease processes. Inhibition of poly-ADP-ribose formation will tend to cause genomic instability and tumorigenesis in chronic models of DNA damage, but the same inhibition can prevent many acute disease processes, such as stroke, myocardial infarction and septic shock. In models of acute stress, PARP-1 inhibition may protect cellular NAD pools and prevent nuclear factor-kappaB-dependent inflammatory signalling, while long-term protective roles for PARP-1 include DNA repair and regulation of chromatin structure. Promising new PARP-1 inhibitors may display interactions with dietary niacin status and may have long-term deleterious effects on genomic stability, but may be extremely valuable for the treatment of acute inflammatory conditions.

The Ala allele at Val762Ala polymorphism in poly(ADP-ribose) polymerase-1 (PARP-1) gene is associated with a decreased risk of asthma in a Turkish population

BACKGROUND AND OBJECTIVE

It has been suggested that inhibition of poly (ADP-ribose) polymerase-1 (PARP-1), either pharmacologically or by a gene knockout provides significant protection against systemic or tissue inflammation in animal models. The aim of this study was to analyze the association of the PARP-1 Val762Ala polymorphism, which has beenreported to be associated with decreased enzymatic activity, in Turkish patients with adult asthma.

METHODS

A total of 112 subjects with stable asthma and 180 normal controls from the same geographic region were studied and polymerase chain reaction-based restriction analysis was used to identify Val762Ala polymorphism of the PARP-1.

RESULTS

In univariate analysis, PARP-1 762 AA genotype conferred a 3.4 fold reduction in risk (OR = 0.297, 95% CI = 0.105-0.813; P = 0.014), while heterozygous VA genotype conferred an even greater level of protection (OR = 0.06; 95%CI, 0.026-0.14; P < 10(-6)). In addition, wild type PARP-1 762 V allele had 5 times the risk of developing asthma than those without the allele (OR 0.199, CI 0.118-0.334, P = 10(-6)).

CONCLUSIONS

These findings suggest that PARP-1 V762A variants may be one of the factors participating in protection or susceptibility to asthma in our population.