Inter-relationships between DNA damage, ascorbic acid and glycaemic control in Type 2 diabetes mellitus.

AIMS: The onset of complications in Type 2 diabetes mellitus (DM) patients cannot be predicted in individuals. Evidence suggests a link between complications and hyperglycaemia, oxidative stress and antioxidants, but causality is unclear. This study investigated baseline (entry) fasting plasma ascorbic acid, lymphocytic DNA damage and glycaemic control in Type 2 DM as part of a long-term study, the aim of which is to explore a biomarker profiling approach to identify and improve outcome in high-risk subjects. METHODS: A cross-sectional study, in which DNA damage, glycated haemoglobin (HbA(1c)), fasting plasma glucose (FPG) and ascorbic acid (AA) were measured on fasting blood samples collected from 427 Type 2 DM subjects. RESULTS: DNA damage was significantly (P < 0.0001) and directly correlated to both FPG (r = 0.540) and HbA(1c) (r = 0.282), and was significantly (P < 0.0001), independently and inversely correlated to plasma AA (r = -0.449). In those subjects with both poor glycaemic control and low AA (< 48 microm, the overall mean value for the study group), DNA damage was significantly (P < 0.005) higher compared with those subjects with a similar degree of hyperglycaemia but with AA above the mean. CONCLUSIONS: The novel finding of a significant inverse relationship between plasma AA and DNA damage in Type 2 DM indicates that poorly controlled diabetic subjects might benefit from increased dietary vitamin C. The data also have important implications for biomarker profiling to identify those subjects who might benefit most from intensive therapy. Longer-term follow-up is underway.     

Reduced plasma ascorbic acid levels in recipients of myeloablative conditioning and hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) conditioned using myeloablative conditioning (MAC) is complicated by end organ injury due to endothelial dysfunction and graft versus host disease. Mucositis and oxidant injury results in micronutrient deficiency. Ascorbic acid (AA) levels were measured in 15 patients undergoing HCT conditioned with MAC (11 allogeneic and four autologous HCT). Ascorbate levels declined postconditioning to 27.3 μMol/L (±14.1) by day 0 (P = .03 compared with pretransplant baseline), reaching a nadir level of 21.5 (±13.8) on day 14 (P = .003) post‐transplant. Patients undergoing allogeneic HCT continued to have low AA levels to day 60 post‐transplant. The role of AA in maintaining endothelial function and hematopoietic as well as T‐cell recovery is provided, developing the rationale for repletion of vitamin C following HCT.     

Silymarin and Vitamin E do not Attenuate and Vitamin E Might Even Enhance the Antiarrhythmic Activity of Amiodarone in a Rat Reperfusion Arrhythmia Model

Oxidative stress and lysosomal phospholipoidosis, which also might be partly attributed to free radicals induced by amiodarone (AM), may be involved in AM toxicity, which can be prevented by antioxidants. Our aim was to study if vitamin E (E) or silymarin (S), a lipid and a water-soluble antioxidant, modified the antiarrhythmic efficacy of AM in a rat reperfusion arrhythmia test. The following groups of male Sprague-Dawley rats (15 rats/group) were treated by gavage once a day for 4 weeks: 1. methylcellulose (MC, 0.4%), 2. sunflower seed oil (SSO), 3. AM, suspended in MC (30 mg/kg), 4. E, dissolved in SSO (100 mg/kg), 5. AM + E, 6. S, suspended in MC (80 mg/kg), 7. AM + S. The mean duration of ventricular tachycardia + fibrillation (MDVT + VF) and sinus rhythm (MDSR) the incidence of ventricular fibrillation (VF) and ventricular tachycardia (VT) and mortality were measured during a 10-min reperfusion after a 5-min coronary artery occlusion in anaesthetized rats. An arrhythmia score, representing the combined incidence and duration of different types of ventricular arrhythmia, was calculated. Compared with the MC group, MDSR was longer and MDVT + VF was shorter in all drug treated groups and in the SSO group. In the AM + E treated group MDSR was prolonged more and MDVT + VF was shortened more than in the AM, E or SSO groups. Compared with the MC group, the incidence of VF and mortality was similarly decreased in the SSO group and in most drug treated groups. No significant difference in the incidence of VT was found among all groups. The arrhythmia score was reduced by all drug treatments. Combined treatment with AM + E decreased arrhythmia score more than treatment with AM or SSO alone, but arrhythmia score was similar in the AM + E and E groups. In conclusion, both AM and antioxidant treatments alone or together resulted in a marked reduction of reperfusion arrhythmias in this model. SSO also exerted a moderate antiarrhythmic effect. Antioxidants administered together with AM did not attenuate and E might have even enhanced the antiarrhythmic effect of AM, therefore the combination of antioxidants with AM may be advantageous to reduce AM toxicity.     

Evaluation of the hepatic reduction of a nitroxide radical in rats receiving ascorbic acid, glutathione or ascorbic acid oxidase by in vivo electron spin resonance study

BACKGROUND: A nitroxide radical, 4-hydroxyl-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL), is directly reduced to hydroxylamine by ascorbic acid (AsA). Ascorbic acid is oxidized to dehydroascorbic acid (DHA) by ascorbic acid oxidase (AAOx), and DHA is reduced to AsA by glutathione (GSH). In the present study, in vivo and ex vivo reduction of TEMPOL in the rat liver under various conditions of AsA supply was investigated using an electron spin resonance (ESR) spectrometer equipped with a surface coil-type resonator. METHODS: To investigate in vivo hepatic reduction of TEMPOL, an ESR study of the liver of living rats which orally received AsA or intravenously received GSH or AAOx was made. To investigate direct interactions between TEMPOL and GSH or AAOx, an in vitro ESR study was conducted. To investigate TEMPOL reduction in the hepatic homogenate, an ex vivo ESR study was performed. RESULTS: Ascorbic acid and GSH administration increased the in vivo hepatic reducing ability of TEMPOL. In contrast, AAOx administration decreased the reducing ability. In vitro TEMPOL was not reduced by GSH and hydroxylamine was not oxidized by AAOx. Reducing ability in the hepatic homogenate of AAOx-treated rats decreased, but that for GSH-treated rats was unchanged. CONCLUSION: Ascorbic acid administration directly increases hepatic reducing ability. Ascorbic acid, which increased in the plasma due to GSH administration, entered the liver and enhanced the hepatic reducing ability. Administration of AAOx impaired the hepatic reducing ability by oxidizing AsA in the plasma and/or the liver.     

Oxidative Stress and DNA Single Strand Breaks in Skeletal Muscle of Aged Rats: Role of Carnitine and Lipoicacid

The exposure of biological system to various conditions of oxidative stress is the major contributor for aging process. Oxidative stress in turn increases the cellular levels of oxidatively modified proteins, lipids and nucleic acids resulting in a loss of physical activity and metabolic integrity. In this study, we evaluated the role of l-carnitine and dl-α-lipoic acid in minimizing oxidant generation and macromolecular damage in skeletal muscle of aged rats. We found that the oxidant generation was increased in aged rat skeletal muscle when compared to young rats. There was a simultaneous increase in the levels of lipid peroxidation, protein carbonyl content and DNA strand breaks in aged rat skeletal muscle. Administration of l-carnitine (300 mg/kg body wt/day) and dl-α-lipoic acid (100 mg/kg body wt/day) to aged rats for 30 days, decreased the oxidant generation, lipid peroxidation, protein carbonylation and DNA strand breaks. We concluded that co-administration of carnitine and lipoic acid to aged rats has the potential to prevent oxidative stress mediated macromolecular damage in skeletal muscle of aged rats by their putative role as efficient antioxidants.     

Efficacy and safety of melphalan, arsenic trioxide and ascorbic acid combination therapy in patients with relapsed or refractory multiple myeloma: a prospective, multicentre, phase II, single-arm study

We assessed the safety and efficacy of melphalan, arsenic trioxide (ATO) and ascorbic acid (AA) (MAC) combination therapy for patients with multiple myeloma (MM) who failed more than two different prior regimens. Patients received melphalan (0.1 mg/kg p.o.), ATO (0.25 mg/kg i.v.) and AA (1 g i.v) on days 1-4 of week 1, ATO and AA twice weekly during weeks 2-5 and no treatment during week 6 of cycle 1; during cycles 2-6, the schedule remained the same except ATO and AA were given twice weekly in week 1. Objective responses occurred in 31 of 65 (48%) patients, including two complete, 15 partial and 14 minor responses. Median progression-free survival and overall survival were 7 and 19 months respectively. Twenty-two patients had elevated serum creatinine levels (SCr) at baseline, and 18 of 22 (82%) showed decreased SCr levels during treatment. Specific grade 3/4 haematological (3%) or cardiac adverse events occurred infrequently. Frequent grade 3/4 non-haematological adverse events included fever/chills (15%), pain (8%) and fatigue (6%). This steroid-free regimen was effective and well tolerated in this heavily pretreated group. These results indicate that the MAC regimen is a new therapeutic option for patients with relapsed or refractory MM.     

Reactive oxygen species activity and lipid peroxidation in Helicobacter pylori associated gastritis: relation to gastric mucosal ascorbic acid concentrations and effect of H pylori eradication

Centre for Digestive Diseases, The General Infirmary at Leeds, Leeds, UK

Correspondence to: Dr I M Drake, c/o Department of Gastroenterology,Leeds General Infirmary, Great George Street,Leeds LS1 3EX, UK.

Accepted for publication 19 January 1998

Background—Helicobacter pylori is an independent risk factor for gastric cancer, and this association may be due to the bacterium causing reactive oxygen species mediated damage to DNA in the gastric epithelium. High dietary ascorbic acid intake may protect against gastric cancer by scavenging reactive oxygen species.
Aims—To assess reactive oxygen species activity and damage in gastric mucosa in relation to gastric pathology and mucosal ascorbic acid level, and to determine the effect of H pylori eradication on these parameters.
Patients—Gastric biopsy specimens were obtained for analysis from 161 patients undergoing endoscopy for dyspepsia.
Methods—Reactive oxygen species activity and damage was assessed by luminol enhanced chemiluminescence and malondialdehyde equivalent estimation respectively. Ascorbic acid concentrations were measured using HPLC.
Results—Chemiluminescence and malondialdehyde levels in gastric mucosa were higher in patients with H pylori gastritis than in those with normal histology. Successful eradication of the bacterium led to decreases in both parameters four weeks after treatment was completed. Gastric mucosal ascorbic acid and total vitamin C concentrations were not related to mucosal histology, but correlated weakly with reactive oxygen species activity (chemiluminescence and malodialdehyde levels).
Conclusions—Data suggest that reactive oxygen species play a pathological role in H pylori gastritis, but mucosal ascorbic acid is not depleted in this condition.
(GUT 1998;:768-771)

Keywords: Helicobacter pylori;  gastric cancer;  reactive oxygen species;  ascorbic acid

     

Evidence for a role of free radicals by synthesized scavenger, 2-octadecylascorbic acid,in cerulein-induced mouse acute pancreatitis

To define the role of free radicals and of lipid peroxide involvement during the progress of cerulein-induced acute pancreatitis in mice, we evaluated the effect of a novel free radical scavenger, 2-octadecylascorbic acid (CV-3611), on pancreatic edema formation, and the levels of serum enzymes (amylase, lipase) and of lipid peroxide in pancreatic tissue. Mice were divided into three groups: control group, intraperitoneal injection of saline only; pancreatitis group, cerulein 50 g/kg injected intraperitoneally six times at 1-hr intervals; treatment group, CV-3611 10 mg/kg subcutaneously just after intraperitoneal cerulein injection. After the cerulein injection, the degree of pancreatic edema formation, serum amylase and lipase levels, and the amount of lipid peroxide in pancreatic tissue increased significantly during the observation period of 12 hr. Treatment with CV-3611 resulted in significant reduction in pancreatic edema formation at 3.5 hr (P<0.05) and 9 hr (P<0.05), serum amylase and lipase levels at 3.5 hr (P<0.05) and 12 hr (P<0.05), and lipid peroxide levels at 3.5 hr (P<0.05), 6 hr (P<0.05) and 12 hr (P<0.05). These results indicate that a novel free radical scavenger, CV-3611, has a strong therapeutic effect during the development of acute pancreatitis and suggest that oxygenderived free radicals play an important role in the pathogenesis of acute pancreatitis.     

Melatonin,xanthurenic acid,resveratrol, EGCG,vitamin C and alpha-lipoic acid differentially reduce oxidative DNA damage induced by Fenton reagents: a study of their individual and synergistic actions

DNA damage generated by oxygen-derived free radicals is related to mutagenesis, carcinogenesis and aging. In the last several years, hundreds of publications have confirmed that melatonin is a potent endogenous free radical scavenger. In the present in vitro study, we have examined the efficacy of three polyphenolic antioxidants, i.e. xanthurenic acid, resveratrol (3,4',5-trihydroxy-trans-stilbene) and (-)-epigallocatechin-3-gallate (EGCG) and two classical non-polyphenolic antioxidants, i.e. vitamin C (ascorbic acid) and alpha-lipoic acid (LA, 1,2-dithiolane-3-pentanoic acid) in inhibiting *OH-induced oxidative DNA damage. We compared the efficacy of these five antioxidants with the effectiveness of melatonin (N-acetyl-5-methoxytryptamine) and we also investigated the possible synergistic effects of melatonin with the other five molecules. Using high performance liquid chromatography (HPLC), the formation of 8-hydroxy-2-deoxyguanosine (8-OH-dG) in purified calf thymus DNA treated with the Fenton reagents, chromium(III) (as CrCl3) plus hydrogen peroxide (H2O2) (Cr(III)/H2O2), was measured in the presence or absence of the antioxidants alone or in combination with melatonin. 8-OH-dG is considered a biomarker of oxidative DNA damage. Among the antioxidants tested, melatonin was the most effective of these with an IC50 = 3.6 +/- 0.1 micro m. For the other antioxidants the IC50 values were as follows: xanthurenic acid (IC50 = 7.9 +/- 0.3), resveratrol (IC50 = 10.9 +/- 0.3), EGCG (IC50 = 5.7 +/- 0.3), vitamin C (IC50 = 16.9 +/- 0.5) and LA (IC50 = 38.8 +/- 0.7). These values differ from that of melatonin with a P < 0.01. Melatonin (1 micro M) reversed the pro-oxidant effect of resveratrol (0.5 micro M) and vitamin C (0.5 micro M), had an antagonistic effect when used in combination with EGCG (1 micro M) and it exhibited synergism in combination with vitamin C (0.5 micro M) and with LA (5 micro M).     

Insulin effect on serum potassium and auto-inhibition of insulin secretion is intact in a patient with leprechaunism despite severe impairment of substrates metabolism

BACKGROUND: The effect of insulin on glucose, protein metabolism, circulating fatty acids (FFA), potassium (K(+)) and C-peptide concentrations were investigated in a 12-year-old girl with leprechaunism. The mutations do not affect the insulin-receptor binding affinity and insulin-stimulated auto-phosphorylation of the receptor. METHODS: The subject was studied with a primed-continuous infusion of [6,6 - (2)H(2)] glucose and [1-(13)C] leucine during a basal period followed by two steps of insulin infusion (1 and 10 mU/kg/min) of 2 h each, during which plasma glucose level decreased from 131 to 115 and then to 95 mg/dL. RESULTS: Whole body glucose disposal was virtually unaffected by insulin, slightly decreasing from 21 micromol/kg/min in the basal period to 20 and to 19 micromol/kg/min during the two steps of insulin infusion, respectively. The endogenous leucine flux, an index of proteolysis, was completely insensitive to insulin, being 182, 189 and 180 micromol/kg/min, in the three periods, respectively. The FFA concentration (an indirect index of lipolysis) decreased from 1135 to 799 during step 1. During step 2 the FFA concentration rebounded to 917 micromol/L. The concentration of K(+) decreased from 4.2 to 3.2 mmol/L and an infusion of 20 mEq/h of KCl was necessary to prevent further hypokalemia (final value 3.3 mmol/l). The C-peptide concentration declined from 1.85 to 0.97 and then to 0.29 pmol/mL. CONCLUSIONS: The dissociation of control exerted by insulin on K+ uptake and on beta-cell secretion may rely on a differential expression and folding of the mutated receptors in the different insulin target tissues.     

Role of hepatitis C virus substitutions and interleukin‐28B polymorphism on response to peginterferon plus ribavirin in a prospective study of response‐guided therapy

Recent studies have indicated that amino acid (aa) substitutions in the core region and NS5A interferon sensitivity‐determining region (ISDR) of hepatitis C virus (HCV) as well as genetic polymorphisms in the interleukin‐28B (IL‐28B) locus affect the outcome of interferon (IFN)‐based therapies. We aimed to investigate the role of these factors on response to peginterferon plus ribavirin in a prospective study of response‐guided therapy. The aa sequences in core region and ISDR and rs12979860 genotypes were analysed in 115 HCV‐1 patients. The treatment was 24 weeks for patients achieving a rapid virological response (RVR), 48 weeks for those with an early virological response (EVR) and early terminated in those without an EVR. A sustained virological response (SVR) was achieved in 82% of 34 RVR patients, 45% of 74 EVR patients and 0% of seven non‐EVR patients. Logistic regression analysis showed that ISDR mutation (≥2) [odds ratio(OR): 6.024], double core 70/91 mutations (OR: 0.136), and platelet counts ≥ 15 × 10⁴/μL (OR: 3.119) were independent pretreatment factors associated with SVR. Apart from rs12979860 CC genotype, low viral load and ISDR mutation (≥2) were significant factors predictive of RVR. Combination of rs12979860 genotype and baseline viral characteristics (viral load and core/ISDR mutations) could predict RVR and SVR with positive predictive value of 100% and 91%, and negative predictive value of 80% and 54%, respectively. In conclusion, pretreatment screening rs12979860 genotype and aa substitutions in the core region and ISDR could help identifying patients who are good candidates for peginterferon plus ribavirin therapy.     

Treatment of myelodysplastic syndromes with retinoic acid and 1 alpha-hydroxy-vitamin D3 in combination with low-dose ara-C is not superior to ara-C alone. Results from a randomized study. The Scandinavian Myelodysplasia Group (SMG)

63 evaluable patients with myelodysplastic syndromes (MDS) and 15 with acute myelogenous leukemia (AML) were randomized between low-dose ara-C (arm A) and low dose ara-C in combination with 13-cis-retinoic acid (13-CRA) and 1 alpha-hydroxy-vitamin D3 (1 alpha D3) (arm B). 69 patients were evaluable and 18 (26.1%) responded to therapy. The addition of 13-CRA and 1 alpha D3 had no positive influence on survival of the patients, remission rates or duration of remissions. 12/27 patients in arm A and 6/29 patients in arm B progressed from MDS to AML during the course of the study (p = 0.0527). Arm B gave significantly more side-effects than arm A (p = 0.005). Therapeutic effects of 13-CRA and 1 alpha D3 on MDS is not supported by this study. However, an inhibiting effect on AML development in some MDS subgroups cannot be excluded.     

Design and rationale of a randomized study to compare amiodarone and Class IC anti-arrhythmic drugs in terms of atrial fibrillation treatment efficacy in patients paced for sinus node disease: the PITAGORA trial.

AIMS: Many sinus node disease (SND) patients suffer from atrial fibrillation (AF). Anti-arrhythmic drugs (AADs) are the therapeutic mainstay for AF prophylaxis. The PITAGORA trial has a multicentre, prospective, randomized, single blind design to compare amiodarone with Class IC AADs in patients who have an AF history and are paced for SND. METHODS AND RESULTS: Starting from January 2001, 176 patients received a Medtronic AT500 pacemaker. AADs were randomly assigned with a 3 : 2 ratio between Class III and Class IC. Randomization was stratified in order to assign two patients to amiodarone and one patient to sotalol every three Class III AAD patients. After a 5-month observational period, Ramp or Burst+ ATP therapies were enabled in a randomized way, maintained for 4 months, and then crossed over. Total follow-up period is 21 months. The primary long-term objective is to show the non-inferiority of IC AADs compared with amiodarone in terms of time to first occurrence of a composite endpoint (death, atrial cardioversion, hospitalizations due to AF or heart failure, or change of AADs). Data will be analysed on an intention-to-treat basis. The primary short-term objective is to compare Ramp vs. Burst+ efficacy in terminating atrial tachyarrhythmias treated by the device. Secondary endpoints are major clinical events, medication toxicity, symptoms, AF burden, and quality-of-life. CONCLUSION: Given the high morbidity and healthcare costs associated with AF, new therapeutic strategies are needed. The results of the PITAGORA trial may help in guiding AADs therapy and ATP programming in SND patients suffering from AF.