3. Discussion
overweight or obese, metabolic syndrome, gout, satiety
METABOLIC SYNDROME, OXIDATIVE STRESS, GOUT, DNA STRAND BREAK
It is well known that polyphenols possess a plethora of beneficial properties. The aim of the present human intervention study was to investigate the effects of PRB consumption on different biomarkers regarding lipid metabolism, such as blood lipids or PDE activity. In addition, nutrient intake, hunger, and satiety hormones as well as uric acid concentrations were monitored. Supplementary, parameters of oxidative stress such as DNA strand breaks were examined. The participants consumed either 750 mL of the PRB on a daily basis over an eight-week intervention period, which was produced from different red fruit juices/concentrates (chokeberry, cranberry, and pomegranate) or 750 mL of the placebo drink. These three different fruit varieties were chosen here based on preliminary in vitro studies on lipid accumulation, lipolysis, and PDE activity [Evaluation of the food and beverage records pointed out that only PRB consumption was found to decrease fat and protein intakes significantly compared to the washout period. No modulation in carbohydrate intake might be observed, since the PRB consumed during the intervention period was rich in carbohydrates, especially glucose and fructose. Although the participants consumed isocaloric study beverages, energy and nutrient intake did not alter in placebo group after uptake of placebo drink. The trend we identified in the present study towards reducing energy intake, caused by the consumption of the polyphenol-rich drink, might help to improve the satiating capacity and, thus, support body weight management. In C57BL/6J mice a decreased food intake in proportion to the concentration of cyanidin-3-galactoside enriched chokeberry extract treatment was found [In the current study, we provide evidence of the beneficial effects of PRB consumption (containing chokeberry, cranberry, and pomegranate juice; total phenolics = 3.0 g LRegarding the impact of PRB consumption on the regulation of lipid metabolism in terms of hormonal signaling, GLP-1 and leptin play a central role. GLP-1 is secreted by pancreatic cells and is involved in the reducing gastric emptying and food intake, thus promoting satiety but also in lowering blood glucose [In general, many studies have discussed the effects of polyphenols on blood lipid profiles [In the present study, we investigated the PDE activity in platelets as another important parameter for monitoring the biological effects of PRB consumption on lipid metabolism. Especially the enzyme PDE 3B is essential for the regulation of pathways mediated by the second messenger cAMP and thus, can influence lipid metabolism via stimulation of lipolysis when PDE activity is inhibited [In addition to the above mentioned parameters, the plasma uric acid concentrations were determined as indicator in the frame of clinical trials, since overproduction of uric acid can indicate the prevalence of the metabolic syndrome and can lead to the occurrence of gout [Many studies reported the antioxidant potential of polyphenols in vitro as wells as in vivo [In conclusion, this study demonstrated the beneficial effects of a PRB (containing chokeberry, cranberry, and pomegranate juice) on human health. The focus of the study was on parameters of the lipid metabolism, and we could observe an influence on reduced energy intake, which was correlated by a decrease in fat and protein intake. Furthermore, an inhibited PDE activity might be partly responsible for the stimulation of lipolysis and consequently, a modulation of body weight and composition. In addition, the beverage rich in polyphenols tended to improve DNA integrity. We are aware that our study is only a pilot intervention study since it has a limited number of participants. Future studies with an extended number of volunteers should be performed. Since we had the main focus in this study on the lipid metabolism, investigations with overweight or obese people should be performed to confirm the observed effects, respectively. Complementary, follow up studies could aim to focus more on single food compounds utilising controlled-feeding trials. To have a closer look at gender-specific effects, intervention studies with men and women could be conducted.