Efficacy and safety of the combined metabolic medication, containing inosine, nicotinamide, riboflavin and succinic acid, for the treatment of diabetic neuropathy: a multicenter randomized, double-blind, placebo-controlled parallel group clinical trial (CYLINDER).

INTRODUCTION: Antioxidants may have positive impact on diabetic polyneuropathy (DPN), presumably due to alleviation of oxidative stress. We aimed to evaluate the efficacy and safety of combination of antioxidants: succinic acid, inosine, nicotinamide, and riboflavin (SINR) in the treatment of DPN. RESEARCH DESIGN AND METHODS: In a double-blind, placebo-controlled clinical trial, men and women aged 45-74 years with type 2 diabetes and symptomatic DPN, with initial Total Symptom Score (TSS) ˃5, were randomized into experimental (n=109) or placebo (n=107) group. Patients received study medication/placebo intravenously for 10 days, followed by oral administration for 75 days. Statistical significance was defined as a two-tailed p<0.05. RESULTS: In SINR group, mean TSS change after 12 weeks was -2.65 (±1.46) vs -1.73 (±1.51) in the placebo group (p<0.0001; t-test). Reduction of symptoms in the SINR group was achieved regardless of hemoglobin A1c levels, but better results were observed in patients with initial TSS <7.5. The analysis of TSS subscores revealed statistically significant between-group differences by dynamics of the intensity of paresthesia and of numbness starting from day 11 (p=0.035 and p=0.001, respectively; mixed model); by day 57, statistically significant between-group differences were detected also by dynamics of burning intensity (p=0.005; mixed model). Study limitations are small effect size, moderate proportion of patients with severe DPN symptoms, subjective assessment of outcomes, exclusion of participants who received injectable glucose-lowering medications other than insulins, and patients with uncontrolled and type 1 diabetes. CONCLUSIONS: The combination of SINR effectively alleviates DPN symptoms in patients with type 2 diabetes. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT04649203; Unique Protocol ID: CTF-III-DM-2019).

Predictors of response to treatment with actovegin for 6 months in patients with type 2 diabetes and symptomatic polyneuropathy.

AIMS: To evaluate two definitions of response and the predictive value of baseline covariates for response to actovegin treatment in type 2 diabetic patients with symptomatic diabetic sensorimotor polyneuropathy (DSPN). METHODS: Response to 6-months treatment with actovegin or placebo was defined as a clinically meaningful decline from baseline to 6months in (1) both Neuropathy Impairment Score of Lower Limbs (NIS-LL) ≥2 points and Total Symptom Score (TSS) >50% and (2) NIS-LL ≥2 points only. Nineteen baseline covariates were evaluated using separate logistic regression models and either both NIS-LL and TSS or NIS-LL response definitions. RESULTS: Intention-to-treat analysis included 567 patients. Actovegin treatment compared to placebo was associated with better odds of response (OR [95% CI] of 1.73 [1.21-2.48] for definition 1 and 1.94 [1.33-2.84] for definition 2). Significant interaction with actovegin treatment was noted only for baseline use of angiotensin receptor blockers (ARBs)/angiotensinogen converting enzyme inhibitors (ACEIs), resulting in a reduced treatment response (P=0.03). CONCLUSIONS: Actovegin treatment was associated with a clinically meaningful response in neuropathic symptoms and/or impairments in patients with symptomatic DSPN. Since only one predictor of response to actovegin treatment was identified, this drug seems an appropriate therapy for the majority of patients with DSPN.

The Role of Oxidative Stress in Diabetic Neuropathy: Generation of Free Radical Species in the Glycation Reaction and Gene Polymorphisms Encoding Antioxidant Enzymes to Genetic Susceptibility to Diabetic Neuropathy in Population of Type I Diabetic Patients.

Diabetic neuropathy (DN) represents the main cause of morbidity and mortality among diabetic patients. Clinical data support the conclusion that the severity of DN is related to the frequency and duration of hyperglycemic periods. The presented experimental and clinical evidences propose that changes in cellular function resulting in oxidative stress act as a leading factor in the development and progression of DN. Hyperglycemia- and dyslipidemia-driven oxidative stress is a major contributor, enhanced by advanced glycation end product (AGE) formation and polyol pathway activation. There are several polymorphous pathways that lead to oxidative stress in the peripheral nervous system in chronic hyperglycemia. This article demonstrates the origin of oxidative stress derived from glycation reactions and genetic variations within the antioxidant genes which could be implicated in the pathogenesis of DN. In the diabetic state, unchecked superoxide accumulation and resultant increases in polyol pathway activity, AGEs accumulation, protein kinase C activity, and hexosamine flux trigger a feed-forward system of progressive cellular dysfunction. In nerve, this confluence of metabolic and vascular disturbances leads to impaired neural function and loss of neurotrophic support, and over the long term, can mediate apoptosis of neurons and Schwann cells, the glial cells of the peripheral nervous system. In this article, we consider AGE-mediated reactive oxygen species (ROS) generation as a pathogenesis factor in the development of DN. It is likely that oxidative modification of proteins and other biomolecules might be the consequence of local generation of superoxide on the interaction of the residues of L-lysine (and probably other amino acids) with α-ketoaldehydes. This phenomenon of non-enzymatic superoxide generation might be an element of autocatalytic intensification of pathophysiological action of carbonyl stress. Glyoxal and methylglyoxal formed during metabolic pathway are detoxified by the glyoxalase system with reduced glutathione as co-factor. The concentration of reduced glutathione may be decreased by oxidative stress and by decreased in situ glutathione reductase activity in diabetes mellitus. Genetic variations within the antioxidant genes therefore could be implicated in the pathogenesis of DN. In this work, the supporting data about the association between the -262T > C polymorphism of the catalase (CAT) gene and DN were shown. The -262TT genotype of the CAT gene was significantly associated with higher erythrocyte catalase activity in blood of DN patients compared to the -262CC genotype (17.8 ± 2.7 × 10(4) IU/g Hb vs. 13.5 ± 3.2 × 10(4) IU/g Hb, P = 0.0022). The role of these factors in the development of diabetic complications and the prospective prevention of DN by supplementation in formulations of transglycating imidazole-containing peptide-based antioxidants (non-hydrolyzed carnosine, carcinine, n-acetylcarcinine) scavenging ROS in the glycation reaction, modifying the activity of enzymic and non-enzymic antioxidant defenses that participate in metabolic processes with ability of controlling at transcriptional levels the differential expression of several genes encoding antioxidant enzymes inherent to DN in Type I Diabetic patients, now deserve investigation.

A splice variant of GNB3 and peripheral polyneuropathy in type 1 diabetes.

Abnormalities in G protein-mediated signal transduction could be involved in the pathogenesis of diabetic polyneuropathy (DPN). Here we test whether the GNB3 C825T variant confers susceptibility to DPN in type 1 diabetes (T1D) mellitus. The C825T marker of GNB3 was genotyped in genomic DNA from blood isolated from a total of 213 Russian T1D patients 100 of whom had DPN. Compared to carriers of the wild-type genotype C/C, diabetic subjects with genotypes T/T had significantly increased risk to develop DPN (Odds Ratio (OR) of 4.4 (p = 0.001). The adjustment for confounders (age, sex, body mass index, cigarette smoking, and level of reduced glutathione) resulted in increase of the OR value up to 4.72 (p = 8.9 x 10;{-3}). The further adjustment for hypertension abolished the association between the GNB3 C825T variant and DPN (OR = 1.95, p = 0.18). Non-complicated subjects homozygous for T/T showed decreased levels of reduced glutathione (T/T: 69 +/- 19 vs. C/T: 74 +/- 19 vs. C/C: 77 +/- 17 micromol/l, p = 0.009). Compared to other GNB3 variants, carriers of the T/T genotype had elevated systolic blood pressure (SBP) in complicated (T/T: 115.8 +/- 9.1 vs. C/T: 113.3 +/- 8.2 vs. C/C: 109.5 +/- 8.7 mm/Hg, p = 0.036) and non-complicated T1D patients (T/T: 118.1 +/- 8.4 vs. C/T: 116.9 +/- 7.9 vs. C/C: 112.1 +/- 7.2 mm/Hg, p = 0.02). However, the significance of association between the C825T polymorphism was lost after adjustment for confounding risk factors. In conclusion, the 825T allele of GNB3 is likely to accelerate the development of DPN through primary effects to SBP and hypertension in subgroups of diabetic patients with impaired neurovascular function and advanced oxidative stress.

Treatment of symptomatic polyneuropathy with actovegin in type 2 diabetic patients.

OBJECTIVE To evaluate the efficacy and safety of actovegin in patients with diabetic polyneuropathy. RESEARCH DESIGN AND METHODS In this multicenter, randomized, double-blind trial, 567 patients with type 2 diabetes received 20 intravenous infusions of actovegin (2,000 mg/day) (n = 281) or placebo (n = 286) once daily followed by three tablets of actovegin (1,800 mg/day) or placebo three times daily for 140 days. Total symptom score (TSS) of the lower limbs and vibration perception threshold (VPT) were used as coprimary outcome measures, computed as the area under the curve (AUC) from repeated scores and divided by duration of exposure. Secondary end points included individual TSS symptoms, neuropathy impairment score of the lower limbs (NIS-LL), and quality of life (short form [SF]-36). RESULTS TSS was significantly improved during actovegin treatment compared with placebo, as assessed by AUC (-0.56 points [95% CI -0.85 to -0.27]; P = 0.0003), and from baseline to 160 days (-0.86 points [-1.22 to -0.50]; P < 0.0001). VPT (five sites per foot) decreased by 3% (95% CI 0-6; P = 0.084) with actovegin than placebo, as assessed by AUC, and by 5% (1-9; P = 0.017) after 160 days. NIS-LL sensory function, as assessed by AUC, was significantly improved with actovegin versus placebo (-0.25 [95% CI -0.46 to -0.04]; P = 0.021), as was the SF-36 mental health domain. There were no differences in the incidence of adverse events between the groups. CONCLUSIONS Sequential intravenous and oral actovegin treatment over 160 days improved neuropathic symptoms, VPT, sensory function, and quality of life in type 2 diabetic patients with symptomatic polyneuropathy.

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

Poly(ADP-ribose) polymerase-1 (PARP-1) is an ubiquitous DNA-binding protein involved in the cellular response to various genotoxic agents. Excessive PARP-1 activation is known to lead to the depletion of intracellular NAD+ and ATP pools and hence to threat cell survival. Therefore, PARP-1 could be involved in neuronal death and contribute to the development of diabetic polyneuropathy (DPN). This study addressed the association of Leu54Phe and Val762Ala polymorphisms of PARP-1 with DPN in Russian type 1 diabetic (T1D) patients. Eighty-six T1D patients with severe DPN and 93 T1D patients with no clinical signs of DPN have been studied by a polymerase chain reaction restriction fragment length polymorphism approach. Using Fisher's exact test revealed the association of the Phe54 and Val762 variants of PARP-1 (odds ratio (OR), 1.66 and 2.88, respectively) with increased risk of DPN in T1D. These results suggest that the PARP1 gene is involved in the pathogenesis of diabetic neuropathy in a Russian population. Additionally, a logistic regression analysis revealed a significant association between the neurological variances such as vibration detection threshold (OR, 2.08), vibration and temperature perception thresholds (OR, 1.32 and 1.67, respectively), and sensory and motor nerve conduction velocities (OR, 2.34 and 2.58, respectively), with DPN.

The sensory symptoms of diabetic polyneuropathy are improved with alpha-lipoic acid: the SYDNEY trial.

OBJECTIVE: Because alpha-lipoic acid (ALA), a potent antioxidant, prevents or improves nerve conduction attributes, endoneurial blood flow, and nerve (Na(+) K(+) ATPase activity in experimental diabetes and in humans and may improve positive neuropathic sensory symptoms, in this report we further assess the safety and efficacy of ALA on the Total Symptom Score (TSS), a measure of positive neuropathic sensory symptoms. RESEARCH DESIGN AND METHODS: Metabolically stable diabetic patients with symptomatic (stage 2) diabetic sensorimotor polyneuropathy (DSPN) were randomized to a parallel, double-blind study of ALA (600 mg) (n = 60) or placebo (n = 60) infused daily intravenously for 5 days/week for 14 treatments. The primary end point was change of the sum score of daily assessments of severity and duration of TSS. Secondary end points were sum scores of neuropathy signs (NIS), symptoms (NSC), attributes of nerve conduction, quantitative sensation tests (QSTs), and an autonomic test. RESULTS: At randomization, the groups were not significantly different by the criteria of metabolic control or neuropathic end points. After 14 treatments, the TSS of the ALA group had improved from baseline by an average of 5.7 points and the placebo group by an average of 1.8 points (P < 0.001). Statistically significant improvement from baseline of the ALA, as compared with the placebo group, was also found for each item of the TSS (lancinating and burning pain, asleep numbness and prickling), NIS, one attribute of nerve conduction, and global assessment of efficacy. CONCLUSIONS: Intravenous racemic ALA, a potent antioxidant, rapidly and to a significant and meaningful degree, improved such positive neuropathic sensory symptoms as pain and several other neuropathic end points. This improvement of symptoms was attributed to improved nerve pathophysiology, not to increased nerve fiber degeneration. Because of its safety profile and its effect on positive neuropathic sensory symptoms and other neuropathic end points, this drug appears to be a useful ancillary treatment for the symptoms of diabetic polyneuropathy.