Entry #: 16
Date: 20 October 2017
Section: Oxidative stress
Topic: Polyphenols and chronic ethanol addiction
Type: In vivo model
OliveNetTM Journal Club
Expert review of literature related to olives and olive oil
D. Elizabeth McCord, Nancy B. Ray and Tom C. Karagiannis
Olive polyphenol effects in a mouse model of chronic ethanol addiction
Carito V et al
Citation / Year
(1) / 2017
Olive polyphenols, hydroxytyrosol, chronic ethanol addiction, oxidative stress, reactive oxygen species
Essentially using two well-characterised kits, the overall the aim of this experiment was to determine whether olive polyphenols could attenuate ethanol-induced oxidative stress in a chronic murine model of ethanol addiction. This study represents a neat experiment in which three month old mice (CD-1 outbred; n=10 per group) were randomly assigned to one of four groups, namely: 1) control group (sucrose dissolved in water), 2) ethanol group (11% ethanol in water for 90 days), 3) polyphenol group (20 mg per kg per day dissolved in sucrose), and 4) polyphenol + ethanol group (20 mg per kg per day polyphenols dissolved in 11% ethanol). Importantly, the caloric intake of the sucrose and ethanol groups was balanced and ethanol was administered following a habituation period. The ethanol was of analytical grade and a well-characterised (2) blend of olive phenolic compounds derived from olive pulp (5% total polyphenols including 30% hydroxytyrosol and 20% hydroxytyrosol derivatives as well as other phenolics), was used. Following a two month period, ethanol blood levels, body weight, serum hydroxytyrosol and metabolite concentrations and oxidative stress parameters were measured. As anticipated, a range of ethanol was detected in the blood of relevant groups and interestingly, the findings indicated a slight increase in food and liquid consumption in the two groups receiving polyphenols however, this was not accompanied by significant changes in body weight. Another interesting finding was the detection of two hydroxytyrosol sulphate isomers in the serum of mice receiving polyphenols, with more than a 2-fold increase in the polyphenol + ethanol group compared to the polyphenol only group. As described by the authors, this phenomenon, at least in part, may relate to the endogenous hydroxytyrosol production through the dopamine pathway which has been shown to be accentuated by alcohol consumption (3-5); however, this does require further clarification.
Key points and implications
The key findings from this experiment are derived from two kits which designed to evaluate oxidative stress using serum samples (n=5 per group were used for each). The first kit, referred to as the free oxygen radical defence kit is designed to measure antioxidant capacity in serum samples. The findings were largely unremarkable using this assay when comparing the ethanol only and polyphenol + ethanol groups. However, a significant change was observed when comparing the control and the polyphenol only group, suggesting polyphenols may increase the natural oxygen radical defences. The other kit, known as the free oxygen radical test was utilised to directly measure free radical levels in the serum for each of the groups. The findings indicated a marked increase in serum free radicals the ethanol groups compared to the other three groups. Baseline levels were observed in the control and polyphenol groups and compared to the ethanol only group, a significant reduction in free oxygen radicals (approximately halved), was found when olive polyphenols were administered with ethanol. To re-iterate, these findings highlight that olive polyphenols can attenuate alcohol-induced oxidative stress by reducing free oxygen radicals in the serum and overall, provide the basis for further investigation in the broader field involving the role of polyphenols and human addiction.
- V. Carito et al., Olive polyphenol effects in a mouse model of chronic ethanol addiction. Nutrition 33, 65-69 (2017).
- S. De Nicolo et al., Effects of olive polyphenols administration on nerve growth factor and brain-derived neurotrophic factor in the mouse brain. Nutrition 29, 681-687 (2013).
- C. Perez-Mana et al., Ethanol induces hydroxytyrosol formation in humans. Pharmacological research 95-96, 27-33 (2015).
- V. E. Davis, M. J. Walsh, Y. Yamanaka, Augmentation of alkaloid formation from dopamine by alcohol and acetaldehyde in vitro. The Journal of pharmacology and experimental therapeutics 174, 401-412 (1970).
- H. Schroder et al., Alcohol consumption is associated with high concentrations of urinary hydroxytyrosol. The American journal of clinical nutrition 90, 1329-1335 (2009).