Effect and Metabolism of lignans on gut microbiota and their impact on health

Abstract

The World Health Organization (WHO) 1 says that CVDs are number one cause of death globally. An estimated 17.7 million people died from CVDs in 2015, representing 31% of all global deaths. Over three quarters of CVD deaths take place in low- and middle-income countries. Some of the risk factors are raised blood pressure, raised blood glucose, raised blood lipids, and overweight and obesity. A large number of epidemiological studies have associated the consumption of polyphenols with a decreased risk of CV or coronary heart disease. Lignans are a class of polyphenols formed by 2 phenylpropane units, also referred as plant phytoestrogens. When ingested, they can be metabolized by the gastrointestinal microbiota to their bioactive forms, the enterolignans enterodiol (ED) and enterolactone (EL)2,3 . The presence of ED and EL in the body has been correlated with the prevention of some chronic disease like cardiovascular disease, osteoporosis, and hyperlipidemia, and some cancers like colon cancer, breast cancer, prostate cancer and menopausal syndrome2,4,5. Moreover, since in the last consensus International Scientific Association for Probiotics and Prebiotics (ISAPP) concluded that plant polyphenols can also meet the criteria of prebiotics; lignans could act as a prebiotic. Although, still more studies in the target host are required6. Malnutrition is estimated to contribute to more than one third of all child deaths, although it is rarely listed as the direct cause7. From WHO sources7 we know that in 2014, approximately 462 million adults worldwide were underweight, while 1.9 billion were either overweight or obese. In 2016, an estimated 155 million children under the age of 5 years were suffering from stunting, while 41 million were overweight or obese. Around 45% of deaths among children under 5 years of age are linked to undernutrition. These mostly occur in low- and middle-income countries. At the same time, in these same countries, rates of childhood overweight and obesity are rising. It is becoming increasingly apparent that gut microbiota play a pivotal role in the development and etiology of malnutrition8–10. The microbiota influence host metabolism, nutrient absorption, inflammation and even hormonal signaling, leading to changes in linear growth and weight gain in mice and humans11,12. In this thesis I aim to study the impact of dietary lignans and yogurts on cardiovascular risk parameters, deepen on knowledge of lignans metabolism by gut microbiota and evaluate the impact of lignans in health and malnourishment.