Sustained Consumption of a Decaffeinated Green Coffee Nutraceutical Has Limited Effects on Phenolic Metabolism and Bioavailability in Overweight/Obese Subjects.

Knowledge on the bioavailability of coffee (poly)phenols mostly come from single dose postprandial studies. This study aimed at investigating the effects of regularly consuming a green coffee phenolic extract (GCPE) on the bioavailability and metabolism of (poly)phenols. Volunteers with overweight/obesity consumed a decaffeinated GCPE nutraceutical containing 300 mg hydroxycinnamates twice daily for two months. Plasma and urinary pharmacokinetics, and fecal excretion of phenolic metabolites were characterized by LC-MS-QToF at weeks 0 and 8. Fifty-four metabolites were identified in biological fluids. Regular consumption of the nutraceutical produced certain changes: reduced forms of caffeic, ferulic and coumaric acids in urine or 3-(3'-hydroxypenyl)propanoic, and 3,4-dihydroxybenzoic acids in feces significantly increased (p < 0.05) after 8 weeks; in contrast, coumaroylquinic and dihydrocoumaroylquinic acids in urine decreased (p < 0.05) compared to baseline excretion. The sum of intestinal and colonic metabolites increased after sustained consumption of GCPE, without reaching statistical significance, suggesting a small overall effect on (poly)phenols' bioavailability.

Influence of 8-week daily consumption of a new product combining green coffee hydroxycinnamates and beta-glucans on polyphenol bioavailability in subjects with overweight and obesity.

Nutraceuticals based on plant extracts rich in polyphenols, as well as dietary fibres, are new means to fight overweight/obesity and associated diseases. However, to understand the potential effects of polyphenols on health it is critical to study their bioavailability and metabolic fate. Consumption of a green coffee phenolic extract (GCPE) in combination with oat beta-glucan (BG) could affect the pharmacokinetic profile of the main polyphenols present in coffee (hydroxycinnamates). Moreover, the regular intake of the combination could also induce changes. Nine overweight men and women consumed a novel nutraceutical product containing 300 mg of green coffee hydroxycinnamic acids and 2.5 g of BG twice a day for 8 weeks. A pharmacokinetic study was carried out in blood and urine samples taken before (baseline) and at week 8 after the nutraceutical intervention, collecting samples at different times in a 0-24 h interval. Faecal samples were also obtained at 0 and 24 h after the intake of the nutraceutical at baseline and week 8. Phenolic metabolites were analysed by LC-MS-QToF. Results showed that polyphenols were differentially absorbed and extensively metabolized throughout the gastrointestinal tract. An apparent reduction in the excretion of small intestinal metabolites was accompanied by a tendency to increase colonic metabolites after sustained intake (p = 0.052). In conclusion, continued consumption of the GCPE/BG nutraceutical appears to enhance the absorption of hydroxycinnamates by increasing the colonic bioavailability of their derived metabolites compared to baseline, although the regular intake of the nutraceutical did not modify the metabolite profile in any of the biological samples.

Knockout of PRDX6 induces mitochondrial dysfunction and cell cycle arrest at G2/M in HepG2 hepatocarcinoma cells.

Peroxiredoxin 6 (PRDX6) has been associated with tumor progression and cancer metastasis. Its acting on phospholipid hydroperoxides and its phospholipase-A2 activity are unique among the peroxiredoxin family and add complexity to its action mechanisms. As a first step towards the study of PRDX6 involvement in cancer, we have constructed a human hepatocarcinoma HepG2PRDX6-/- cell line using the CRISPR/Cas9 technique and have characterized the cellular response to lack of PRDX6. Applying quantitative global and redox proteomics, flow cytometry, in vivo extracellular flow analysis, Western blot and electron microscopy, we have detected diminished respiratory capacity, downregulation of mitochondrial proteins and altered mitochondrial morphology. Autophagic vesicles were abundant while the unfolded protein response (UPR), HIF1A and NRF2 transcription factors were not activated, despite increased levels of p62/SQSTM1 and reactive oxygen species (ROS). Insulin receptor (INSR), 3-phosphoinositide-dependent protein kinase 1 (PDPK1), uptake of glucose and hexokinase-2 (HK2) decreased markedly while nucleotide biosynthesis, lipogenesis and synthesis of long chain polyunsaturated fatty acids (LC-PUFA) increased. 254 Cys-peptides belonging to 202 proteins underwent significant redox changes. PRDX6 knockout had an antiproliferative effect due to cell cycle arrest at G2/M transition, without signs of apoptosis. Loss of PLA2 may affect the levels of specific lipids altering lipid signaling pathways, while loss of peroxidase activity could induce redox changes at critical sensitive cysteine residues in key proteins. Oxidation of specific cysteines in Proliferating Cell Nuclear Antigen (PCNA) could interfere with entry into mitosis. The GSH/Glutaredoxin system was downregulated likely contributing to these redox changes. Altogether the data demonstrate that loss of PRDX6 slows down cell division and alters metabolism and mitochondrial function, so that cell survival depends on glycolysis to lactate for ATP production and on AMPK-independent autophagy to obtain building blocks for biosynthesis. PRDX6 is an important link in the chain of elements connecting redox homeostasis and proliferation.