scholarly journals Dietary antioxidants and DNA damage in patients on long-term acid-suppression therapy: a randomized controlled study

2002 ◽  
Vol 88 (3) ◽  
pp. 265-271 ◽  
Author(s):  
K. L. M. White ◽  
D. M. Chalmers ◽  
I. G. Martin ◽  
S. M. Everett ◽  
P. M. Neville ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Dna Damage ◽  
Ascorbic Acid ◽  
Vitamin E ◽  
Vitamin C ◽  
Gastric Juice ◽  
Proton Pump ◽  
Dietary Antioxidants ◽  
Total Vitamin

Free radicals and reactive species producedin vivocan trigger cell damage and DNA modifications resulting in carcinogenesis. Dietary antioxidants trap these species limiting their damage. The present study evaluated the role of vitamins C and E in the prevention of potentially premalignant modifications to DNA in the human stomach by supplementing patients who, because of hypochlorhydria and possible depletion of gastric antioxidants, could be at increased risk of gastric cancer. Patients undergoing surveillance for Barrett's oesophagus (n100), on long-term proton pump inhibitors were randomized into two groups: vitamin C (500 mg twice/d) and vitamin E (100 mg twice/d) for 12 weeks (the supplemented group) or placebo. Those attending for subsequent endoscopy had gastric juice, plasma and mucosal measurements of vitamin levels and markers of DNA damage. Seventy-two patients completed the study. Plasma ascorbic acid, total vitamin C and vitamin E were elevated in the supplemented group consistent with compliance. Gastric juice ascorbic acid and total vitamin C levels were raised significantly in the supplemented group (P=0·01) but supplementation had no effect on the mucosal level of this vitamin. However, gastric juice ascorbic acid and total vitamin C were within normal ranges in the unsupplemented group. Mucosal malondialdehyde, chemiluminescence and DNA damage levels in the comet assay were unaffected by vitamin supplementation. In conclusion, supplementation does not affect DNA damage in this group of patients. This is probably because long-term inhibition of the gastric proton pump alone does not affect gastric juice ascorbate and therefore does not increase the theoretical risk of gastric cancer because of antioxidant depletion.

scholarly journals Ascorbic acid and total vitamin C concentrations in plasma, gastric juice, and gastrointestinal mucosa: effects of gastritis and oral supplementation.

Gut ◽  
1996 ◽  
Vol 38 (2) ◽  
pp. 171-176 ◽  
Author(s):  
A J Waring ◽  
I M Drake ◽  
C J Schorah ◽  
K L White ◽  
D A Lynch ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Gastric Juice ◽  
Gastrointestinal Mucosa ◽  
Total Vitamin ◽  
Oral Supplementation

Role of vitamin C in gastric cancer

2018 ◽  
Vol 01 (1) ◽  
Author(s):  
Takalkar U Vidyadhar
Keyword(s):  
Gastric Cancer ◽  
Vitamin C ◽  
Gastric Juice ◽  
Oxidative Dna Damage ◽  
Preventive Measure ◽  
Dietary Factors ◽  
Preventive Strategy ◽  
H Pylori

Gastric cancer is a multifactorial disease with complex interplay of environmental and genetic factors. Helicobacter pylori (H. pylori) infestation has been identified as the most important etiological agent in the pathogenesis of gastric cancer. Also, the role of dietary factors that is low consumption of fruits and vegetables have been found to be associated with gastric cancer. Among the dietary factors, antioxidants especially vitamin C has been found to confer the strongest protection against gastric cancer. Its anti-proliferative and pro-apoptotic action has been suggested in vitro. Because of its antioxidant activity, it protects cells against oxidative DNA damage caused by toxic effects of reactive oxygen species. It also inhibits production of carcinogenic N-nitroso compound in the stomach. The person with H. pylori infection has low levels of vitamin C in their gastric juice and levels of vitamin C normalizes on eradication of H. pylori. Vitamin C levels are high in gastric mucosa and gastric juice, sometimes more than that of in plasma. But gastric pathological conditions cause lowered secretion of vitamin C into gastric juice. Effect of H. pylori on vitamin C in gastric juice is reversible and on eradication of H. pylori, it returns to normal level. Hence, eradication of H. pylori and chemoprevention with antioxidant supplementation will be an effective preventive strategy to reduce the incidence of gastric cancer and related mortality. Vitamin C and gastric cancer is an area of potential interest for researchers as a preventive measure. Keywords: Vitamin C, H. pylori, gastric cancer.

Amperometric assay of vitamin C using an ascorbate oxidase enzyme electrode

1979 ◽  
Vol 44 (11) ◽  
pp. 3395-3404 ◽  
Author(s):  
Pavel Posádka ◽  
Lumír Macholán
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Oxygen Electrode ◽  
Ascorbate Oxidase ◽  
Current Response ◽  
Reaction Conditions ◽  
Long Term Storage ◽  
Oxidase Enzyme ◽  
Optimal Reaction

An oxygen electrode of the Clark type, coated by a thin, active layer of chemically insolubilized ascorbate oxidase from squash peelings specifically detects by measuring oxygen uptake 10 to 400 μg of ascorbic acid in 3 ml of phosphate buffer. The record of current response to substrate addition lasts 1-2 min. The ascorbic acid values determined in various samples of fruit juices are in good agreement with the data obtained by titration and polarography. The suitable composition of the membrane and its lifetime and stability during long-term storage are described; optimal reaction conditions of vitamin C determination and the possibilities of interference of other compounds are also examined. Of the 35 phenols, aromatic amines and acids tested chlorogenic acid only can cause a positive error provided that the enzyme membrane has been prepared from ascorbate oxidase of high purity.

scholarly journals Long-term proton pump inhibitors and risk of gastric cancer development after treatment for Helicobacter pylori: a population-based study

Gut ◽  
2017 ◽  
Vol 67 (1) ◽  
pp. 28-35 ◽  
Author(s):  
Ka Shing Cheung ◽  
Esther W Chan ◽  
Angel Y S Wong ◽  
Lijia Chen ◽  
Ian C K Wong ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Helicobacter Pylori ◽  
Proton Pump Inhibitors ◽  
Proton Pump ◽  
Proportional Hazards Model ◽  
Absolute Risk ◽  
Eradication Therapy ◽  
Cox Proportional Hazards ◽  
Cox Proportional Hazards Model

ObjectiveProton pump inhibitors (PPIs) is associated with worsening of gastric atrophy, particularly in Helicobacter pylori (HP)-infected subjects. We determined the association between PPIs use and gastric cancer (GC) among HP-infected subjects who had received HP therapy.DesignsThis study was based on a territory-wide health database of Hong Kong. We identified adults who had received an outpatient prescription of clarithromycin-based triple therapy between year 2003 and 2012. Patients who failed this regimen, and those diagnosed to have GC within 12 months after HP therapy, or gastric ulcer after therapy were excluded. Prescriptions of PPIs or histamine-2 receptor antagonists (H2RA) started within 6 months before GC were excluded to avoid protopathic bias. We evaluated GC risk with PPIs by Cox proportional hazards model with propensity score adjustment. H2RA was used as a negative control exposure.ResultAmong the 63 397 eligible subjects, 153 (0.24%) developed GC during a median follow-up of 7.6 years. PPIs use was associated with an increased GC risk (HR 2.44, 95% CI 1.42 to 4.20), while H2RA was not (HR 0.72, 95% CI 0.48 to 1.07). The risk increased with duration of PPIs use (HR 5.04, 95% CI 1.23 to 20.61; 6.65, 95% CI 1.62 to 27.26 and 8.34, 95% CI 2.02 to 34.41 for ≥1 year, ≥2 years and ≥3 years, respectively). The adjusted absolute risk difference for PPIs versus non-PPIs use was 4.29 excess GC (95% CI 1.25 to 9.54) per 10 000 person-years.ConclusionLong-term use of PPIs was still associated with an increased GC risk in subjects even after HP eradication therapy.

Streamlined three step total vitamin C analysis by HILIC-UV for laboratory testing

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Michael Fitzpatrick ◽  
Paul Bonnitcha ◽  
Van Long Nguyen
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Laboratory Testing ◽  
Potassium Phosphate ◽  
Internal Standard ◽  
Good Precision ◽  
Hydrophilic Interaction ◽  
Reverse Phase Hplc ◽  
Reverse Phase ◽  
Total Vitamin

Abstract Objectives In the clinical setting, the analysis and quantification of vitamin C (ascorbic acid) poses several challenges including analyte instability and poor retention by reverse phase HPLC systems. In this article we describe a rapid hydrophilic interaction chromatography ultraviolet method for the measurement of total vitamin C in plasma which overcomes these issues. Methods Ascorbic acid and the internal standard were separated under isocratic conditions using a Waters BEH-Amide column and a mobile phase containing 0.005 M potassium phosphate in 80% acetonitrile. Results The proposed method was validated and showed good precision (coefficient of variation <5%), accuracy (>99%), and analyte stability after extraction (>24 h). Conclusions The simple sample preparation allows full automation and rapid analytical run times of the assay and is therefore suitable for a high-throughput clinical chromatography laboratory.

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