Quercetin, a polyphenolic compound and a major bioflavonoid in the human diet, has anti-inflammatory properties and has been postulated to enhance energy expenditure (EE). We sought to determine whether quercetin alters body weight, body composition, EE, and circulating markers of inflammation. At 6 weeks (W) of age, 2 cohorts of C57BL/6J mice (N = 80) were placed on one of 2 diets for 3W or 8W: (1) high fat (HF) (45% kcal fat) or (2) high fat + quercetin (HF + Q) (45% kcal fat + 0.8% quercetin). Quercetin concentrations in the diet and plasma were evaluated using mass spectrometry. Body weight, composition (nuclear magnetic resonance), and food consumption were measured weekly. Energy expenditure was measured by indirect calorimetry at 3 and 8W, and inflammatory markers were measured in plasma obtained at 8W. The presence of quercetin in the HF diet did not alter food consumption over time in the HF + Q group and did not differ from the HF group at any time point. However, circulating plasma quercetin concentrations declined between 3 and 8W. At 3W, EE was higher during both day and night phases (P < .0001) in the HF + Q group compared with the HF group; but this difference was not detected at 8W and did not translate into significant differences between the HF + Q and HF groups with respect to body weight or body composition. During the night phase, concentrations of the inflammatory markers (interferon-gamma, interleukin-1alpha, and interleukin-4) were significantly lower when compared with HF treatment group (P < .05). Dietary supplementation with quercetin produces transient (3W) increases in EE that are not detected after 8W on the diet. A corresponding decrease in circulating quercetin between 3 and 8W suggests that metabolic adaptation may have diminished the impact of quercetin's early effect on EE and diminished its overall effect on nutrient partitioning and adiposity. However, quercetin at the levels provided was effective in reducing circulating markers of inflammation observed in animals on an HF diet at 8W.

Grape polyphenols have previously been shown to improve gut health and attenuate the symptoms of metabolic syndrome; however, the mechanism of these beneficial effects is still debated. In this study, we investigated the protective effect of proanthocyanidin-rich grape seed extract (GSE) on bacterial lipopolysaccharide (LPS)-induced oxidative stress, inflammation, and barrier integrity of human Caco-2 colon cells. GSE significantly reduced the LPS-induced intracellular reactive oxygen species (ROS) production and mitochondrial superoxide production, and upregulated the expression of antioxidant enzyme genes. GSE also restored the LPS-damaged mitochondrial function by increasing mitochondrial membrane potential. In addition, GSE increased the expression of tight junction proteins in the LPS-treated Caco-2 cells, increased the expression of anti-inflammatory cytokines, and decreased pro-inflammatory cytokine gene expression. Our findings suggest that GSE exerts its beneficial effects on metabolic syndrome by scavenging intestinal ROS, thus reducing oxidative stress, increasing epithelial barrier integrity, and decreasing intestinal inflammation.

This study aims to document the dual mode of pharmacological action of moringa isothiocyanate-1 (MIC-1) derived from seeds of Moringa oleifera Lam. Oral administration of chemically stable MIC-1 (80 mg/kg) significantly reduced the expression of inflammatory markers (Tnf-α, Ifn-α, IL-1β, IL-6) in the liver, kidney, spleen, and colon and decreased spleen weight in the lipopolysaccharide (LPS)-induced sepsis / acute inflammation model in mice. Transcriptomic analysis of the effect of MIC-1 on the liver and in the LPS-induced RAW264.7 murine macrophage showed that MIC-1 decreases inflammation via inflammation, immunity, and oxidative stress pathways. These results are supported by the immunocytochemical observations that MIC-1 increased the nuclear accumulation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) transcription factor and decreased the nuclear accumulation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in the LPS-induced macrophages. Transcriptional activation of antioxidant genes by MIC-1 translated into a reduction of reactive oxygen species (ROS) in the cytoplasm, decrease of mitochondrial superoxide content, and restoration of the mitochondrial membrane potential in the LPS-induced macrophages. Our data indicate that MIC-1 affects inflammation and oxidative stress, two key processes involved in the etiology of many chronic diseases. These effects involve upstream regulation of two key transcriptional factors regulating responses to these processes at a gene expression level.

High-fat diet (HFD)-induced leaky gut syndrome combined with low-grade inflammation increase reactive oxygen species (ROS) in the intestine and may contribute to dysbiosis and metabolic syndrome (MetS). Poorly bioavailable and only partially metabolizable dietary polyphenols, such as proanthocyanidins (PACs), may exert their beneficial effects on metabolic health by scavenging intestinal ROS. To test this hypothesis, we developed and validated a novel, noninvasive, in situ method for visualizing intestinal ROS using orally administered ROS-sensitive indocyanine green (ICG) dye. C57BL/6J mice fed HFD for 10 weeks accumulated high levels of intestinal ROS compared to mice fed low-fat diet (LFD). Oral administration of poorly bioavailable grape polyphenol extract (GPE) and β-carotene decreased HFD-induced ROS in the gut to levels comparable to LFD-fed mice, while administration of more bioavailable dietary antioxidants (α-lipoic acid, vitamin C, vitamin E) did not. Forty percent of administered GPE antioxidant activity was measured in feces collected over 24 h, confirming poor bioavailability and persistence in the gut. The bloom of beneficial anaerobic gut bacteria, such as Akkermansia muciniphila, associated with improved metabolic status in rodents and humans may be directly linked to protective antioxidant activity of some dietary components. These findings suggest a possible mechanistic explanation for the beneficial effects of poorly bioavailable polyphenols on metabolic health.

Globalization facilitated the spread of invasive alien species (IAS), undermining the stability of the world’s ecosystems. We investigated the metabolomic profiles of three IAS species: Chromolaena odorata (Asteraceae) Datura stramonium (Solanaceae), and Xanthium strumarium (Asteraceae), comparing metabolites of individual plants in their native habitats (USA), to their invasive counterparts growing in and around Kruger National Park (South Africa, ZA). Metabolomic samples were collected using RApid Metabolome Extraction and Storage (RAMES) technology, which immobilizes phytochemicals on glass fiber disks, reducing compound degradation, allowing long-term, storage and simplifying biochemical analysis. Metabolomic differences were analyzed using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) of samples eluted from RAMES disks. Partial Least Squares-Discriminant Analysis (PLS-DA) of metabolomes of individual plants allowed statistical separation of species, native and invasive populations of each species, and some populations on the same continent. Invasive populations of all species were more phytochemically diverse than their native counterparts, and their metabolomic profiles were statistically distinguishable from their native relatives. These data may elucidate the mechanisms of successful invasion and rapid adaptive evolution of IAS. Moreover, RAMES technology combined with PLS-DA statistical analysis may allow taxonomic identification of species and, possibly, populations within each species.

Obesity and metabolic dysfunction have been shown to be associated with overproduction of reactive oxygen species (ROS) in the gastrointestinal (GI) tract, which contributes to dysbiosis or imbalances in the gut microbiota. Recently, the reversal of dysbiosis has been observed as a result of dietary supplementation with antioxidative compounds including polyphenols. Likewise, dietary polyphenols have been associated with scavenging of GI ROS, leading to the hypothesis that radical scavenging in the GI tract is a potential mechanism for the reversal of dysbiosis. The objective of this study was to investigate the relationship between GI ROS, dietary antioxidants and beneficial gut bacterium Akkermansia muciniphila. The results of this study demonstrated A. muciniphila to be a discriminant microorganism between lean (n = 7) and obese (n = 7) mice. The relative abundance of A. muciniphila was also found to have a significant negative correlation with extracellular ROS in the GI tract as measured using fluorescent probe hydroindocyanine green. The ability of the dietary antioxidants ascorbic acid, β-carotene and grape polyphenols to scavenge GI ROS was evaluated in tandem with their ability to support A. muciniphila bloom in lean mice (n = 20). While the relationship between GI ROS and relative abundance of A. muciniphila was conserved in lean mice, only grape polyphenols stimulated the bloom of A. muciniphila. Analysis of fecal antioxidant capacity and differences in the bioavailability of the antioxidants of interest suggested that the poor bioavailability of grape polyphenols contributes to their superior radical scavenging activity and support of A. muciniphila in comparison to the other compounds tested. These findings demonstrate the utility of the GI redox environment as a modifiable therapeutic target in the treatment of chronic inflammatory diseases like metabolic syndrome.