The effect of ribose-cysteine on heart disease biomarkers

This study proposes an intervention with ribose-cysteine [2(R,S)-D-ribo-(1',2',3',4'-tetrahydroxybutyl)-thiazolidine-4(R)-carboxylic acid], a dietary supplement sold in 14 countries that has been developed to boost the levels of glutathione, an important antioxidant in the body. Ribose-cysteine is listed with Australia’s Therapeutic Goods Administration as a permissible ingredient and is sold by the network marketing company, Max International. While a few animal studies have been performed on its glutathione enhancing and lipid-lowering properties, no study has been conducted to establish the potential cardio-protective effects of ribose-cysteine in humans. We propose an intervention study of healthy, non-smoking, post menopausal women between the ages of 45 and 65 that are not currently on ribose cysteine supplementation or lipid-lowering medication. Men and women have significantly different lipid levels and their results are normally analysed separately in large clinical trials where lipids are a main outcome. This is particularly important in genetic studies looking at associations with lipids as associations are often different between genders. As our trial is very small (and lipids are one of our primary outcomes) accommodating both genders would seriously underpower our study. Postmenopausal women were chosen for the study due to them having higher LDL levels and being more at risk of CVD than premenopausal women, however, the results should be generalizable to all women. As the trial is a "first in humans" trial and not a therapeutic trial, we need to recruit healthy people. The inclusion of people not suffering existing heart or liver conditions is to ensure recruitment of healthy individuals. The exclusion criteria (smoking, obesity, diabetes and excessive alcohol consumption) is also to ensure recruitment of healthy individuals. Furthermore, all of these exclusion criteria are associated with alterations in lipid levels and antioxidant status which would add unnecessary variability to our primary outcomes making it difficult to dissect real differences due to ribose-cysteine treatment. We will also exclude participants on medications that affect lipid levels i.e. statins, as this would confound any effect of ribose-cysteine on lipid levels. The trial will be conducted in a simple randomized crossover design with participants receiving either ribose-cysteine or placebo followed by a 6 week washout period before crossover. Participants will be supplied with either a daily supplement of 500 mg ribose-cysteine for 3 months or placebo (both to be taken as oral capsules which will be supplied by Max International).They will be adviced to follow a regular diet for the duration of the trial. The trial will be double-blinded with both the study investigators and participants blinded as to which treatment arm participants are in. The Research Nurse who will dispense the capsules to the study participants at the end of each visit will hold the codes for unblinding which will be revealed after all data analysis has been completed. Participants will be instructed to return empty containers at the end of each arm of the study to monitor compliance. Blood samples (40 ml) will be collected at the beginning and the end of each treatment arm and the plasma, blood cells and genomic DNA isolated. Blood pressure, body weight and height will be measured along with the collection of diet, supplement, medication and physical activity information at each sampling. Participants will be instructed to report any noticeable side effects throughout the study. Adverse side effects will be reported. Blood samples will be measured for ribose-cysteine, glutathione (GSH), cysteine, F2-isoprostanes (an oxidative stress marker), glucose, total cholesterol, triglycerides, HDL cholesterol, apoA1, LDL cholesterol, apoB and Lp(a). The activity of the antioxidant enzyme, glutathione peroxidase and selenium levels (Se is a cofactor for glutathione peroxidase) will also be measured. Alanine transferase (ALT) will be measured to check the supplementation has no effect on liver function. Genomic DNA will be subject to genotyping of common single nucleotide polymorphisms (SNPs) in genes involved in GSH and lipid metabolism.