Dietary Polyphenols and Obesity: A Review of Polyphenol Effects on Lipid and Glucose Metabolism, Mitochondrial Homeostasis, and Starch Digestibility and Absorption.

Obesity is a major global public health concern, limiting socio-economic development and human productivity. As studies focus on finding sustainable solutions to this challenge, polyphenols have shown promising results and have become a research focus. This is mainly because of associated lower risks of side effects with their use, compared to synthetic pharmaceuticals. In this study, the anti-obesity potentials of dietary polyphenols have been reviewed. Using a narrative approach, the biological activities of polyphenols and their influence on energy metabolism and mechanisms are discussed. Specifically, their roles in insulin-dependent glucose uptake, insulin sensitivity, lipid metabolism and storage in adipocytes, starch digestibility, and regulation of mitophagy and mitogenesis in muscle cells and adipocytes, were considered. After considering the major findings of many related studies, it was confirmed that polyphenols can prevent and ameliorate obesity by fighting insulin resistance (IR) induced by pro-inflammatory cytokines, scavenging reactive oxygen species (ROS) and limiting their effects, and by regulating the expression and/or activity of key enzymes along relevant pathways. More human studies are needed to reveal more about the anti-obesity effects of dietary polyphenols and their effective doses in humans.

Uptake and accumulation of pyrrolizidine alkaloids in the tissues of maize (Zea mays L.) plants from the soil of a 4-year-old Chromolaena odorata dominated fallow farmland.

In an attempt to maximize yields of food crops, smallholder farmers have, over the years, increasingly employed agricultural practices such as slash-and-burn and slash-and-mulch on Chromolaena odorata dominated fallow farmlands. However, owing to recently introduced "Horizontal Natural Product Transfer" concept, concerns have been raised over how these common agricultural practices could potentially lead to toxic pyrrolizidine alkaloids (PAs), from decaying or burnt C. odorata residues, taken up by food crops and subsequently accumulate in the food chain. A field experiment was therefore conducted to analyze the PA contents in the tissues of maize (Zea mays L.) plants grown on slash-and-burn and slash-and-mulch plots, previously dominated with Chromolaena odorata, using liquid chromatography mass spectroscopy (LC-ESI-MS/MS). The results revealed, in general, trace amounts of PAs in the maize tissues (i.e. roots, leaves and grains) at maturity while significantly higher levels were detected in the surface soils sampled before sowing (for both plots), 45 days after sowing (slash-and-burn plot) and 90 days after sowing (slash-and-mulch plot). These findings demonstrate, for the first time, the leaching out of PAs from C. odorata residues (e.g. mulch and ash particles) and taken up by maize tissues. In spite of its air polluting and farmland degrading effects, slash-and-burn agricultural practices could lead, in the long term, to relatively lower accumulation of PAs in maize cultivated on PA-plant dominated fallow farmlands, hence smallholder farmers are encouraged to frequently employ this farming system.