Metabolic syndrome, Mediterranean diet, and polyphenols

Metabolic syndrome (MetS) is defined as the co- occurrence of metabolic risk factors that include insulin resistance, hyperinsulinemia, impaired glucose tolerance, type 2 diabetes mellitus, dyslipidemia, and visceral obesity. The clinical significance of MetS consists of identifying a subgroup of patients sharing a common physiopathological state predisposing to chronic diseases. Clinical and scientific studies pinpoint lifestyle modification as an effective strategy to reduce several features accountable for the risk of MetS onset.
In a review published in the Journal of Cell Physiology, the authors state that current evidence highlights the protective effect exerted by the MedDiet on the different components of MetS. Interestingly, the effect exerted by polyphenols contained within the representative MedDiet components (i.e., olive oil, red wine, and nuts) seems to be accountable for the beneficial properties associated with this dietary pattern. In their paper, the authors summarise the principal evidence regarding the effectiveness of MedDiet polyphenols in preventing or delaying the physiopathological components accountable for MetS onset.
Because wine is made using yeast fermentation of grape juice chemical modification occurs in many phytochemicals that are initially present in the fresh fruit. Over 500 compounds have been identified in red wine including major bioactive components ethanol and polyphenols. Polyphenols are particularly concentrated in red wine, coming from the skin and seeds of the grape. In a glass of red wine there are is almost 200mg of polyphenols compared to 30mg in a glass of white wine. Principal red wine polyphenols include flavonols (catechin and myrucetin), flavanols (catechin and epicatechin) and anthocyanin and stilbenes (resveratrol). The abundance of polyphenols in a wine will vary depending on factors such as soil characteristics and other environmental variations and biological effects.
The authors state that growing evidence in vitro and in vivo studies suggest that red wine polyphenols (RWPs), in particular, could help protect against MetS development.
Research has shown that resveratrol activates the Sirt1gene, and it is thought that this phytochemical could mimic the protective effect exerted by calorific restriction against MetS development. Other studies have found that resveratrol administration is effective in counteracting the effects of calorific excess and helps prevent MetS development, having a positive action on bodyweight, fat mass and BMI.
There is also evidence that resveratrol enhances the activation of AMPK (adenosine monophosphate- activated protein kinase) and has been found to increase insulin sensitivity and metabolic profiles.
The beneficial activity of resveratrol on mitochondria has also been described. The protective role exerted by resveratrol on the biogenesis, function, and oxidative capacity of mitochondria is an important feature, limiting their dysfunction (which is responsible for predisposition toward MetS). Resveratrol has also been demonstrated to exert an anti-inflammatory action, showing a protective effect on the endothelium in mice.
Other antioxidant properties and cardiovascular protective effects of RWPs have also been described. Catechin and quercetin administration was found to slow atherosclerosis progression in mice. Evidence suggest that RWPs promote endothelial-dependent vasodilation by acting on nitric oxide enhancement and release. This is an area of promising potential for RWPs on MetS, as there is evidence that eNOS deficient mice are most likely to suffer from MetS and its related features, such as Insulin resistance, dyslipidemia, and meta- inflammation.
RWPs have also been demonstrated to counteract the activation of monocyte and leukocytes adhesion to the endothelium, a hallmark of the inflammatory process, by down regulating the expression of pro- atherosclerotic and prothrombotic factors.
The authors comment that these findings support the effectiveness of RWPs in playing a role protecting against the development of many of the key features that predispose or enhance MetS onset.
Source: Metabolic syndrome, Mediterranean diet, and polyphenols: Evidence and perspectives. Finicelli M, Squillaro T, Di Cristo F, Di Salle A, Melone MAB, Galderisi U, Peluso G. J Cell Physiol. 2019 May;234(5):5807-5826.