Dietary intake of micronized avian eggshell membrane in aged mice reduces circulating inflammatory markers, increases microbiota diversity, and attenuates skeletal muscle aging.

Introduction: Avian eggshell membrane (ESM) is a complex extracellular matrix comprising collagens, glycoproteins, proteoglycans, and hyaluronic acid. We have previously demonstrated that ESM possesses anti-inflammatory properties in vitro and regulates wound healing processes in vivo. The present study aimed to investigate if oral intake of micronized ESM could attenuate skeletal muscle aging associated with beneficial alterations in gut microbiota profile and reduced inflammation. Methods: Elderly male C57BL/6 mice were fed an AIN93G diet supplemented with 0, 0.1, 1, or 8% ESM. Young mice were used as reference. The digestibility of ESM was investigated using the static in vitro digestion model INFOGEST for older people and adults, and the gut microbiota profile was analyzed in mice. In addition, we performed a small-scale pre-clinical human study with healthy home-dwelling elderly (>70 years) who received capsules with a placebo or 500 mg ESM every day for 4 weeks and studied the effect on circulating inflammatory markers. Results and discussion: Intake of ESM in elderly mice impacted and attenuated several well-known hallmarks of aging, such as a reduction in the number of skeletal muscle fibers, the appearance of centronucleated fibers, a decrease in type IIa/IIx fiber type proportion, reduced gene expression of satellite cell markers Sdc3 and Pax7 and increased gene expression of the muscle atrophy marker Fbxo32. Similarly, a transition toward the phenotypic characteristics of young mice was observed for several proteins involved in cellular processes and metabolism. The digestibility of ESM was poor, especially for the elderly condition. Furthermore, our experiments showed that mice fed with 8% ESM had increased gut microbiota diversity and altered microbiota composition compared with the other groups. ESM in the diet also lowered the expression of the inflammation marker TNFA in mice and in vitro in THP-1 macrophages. In the human study, intake of ESM capsules significantly reduced the inflammatory marker CRP. Altogether, our results suggest that ESM, a natural extracellular biomaterial, may be attractive as a nutraceutical candidate with a possible effect on skeletal muscle aging possibly through its immunomodulating effect or gut microbiota.

Oxidized Dietary Oil, High in Omega-3 and Omega-6 Polyunsaturated Fatty Acids, Induces Antioxidant Responses in a Human Intestinal HT29 Cell Line.

When oxidized, dietary oils generate products which have the potential to cause adverse effects on human health. The objective of the study was to investigate whether lipid oxidation products in an oxidized dietary oil can be taken up in intestinal cells, induce antioxidant stress responses and potentially be harmful. The in vitro cell model HT29 was exposed to camelina oil with different extents of oxidation, or only 4-hydroxy-2-hexenal (HHE) or 4-hydroxy-2-nonenal (HNE). The cellular content of HHE increased with an increasing extent of oxidation of the camelina oil added to the cell's growth media, whereas HNE did not show a similar trend. Deuterated HHE was taken up by the HT29 cells, with 140 µM HHE metabolized within 0.5-1 h. The low oxidation degree of the camelina oil increased the gene expression of antioxidant markers (GPX, ATF6, XBP1). The increase in the gene expression of SOD at medium oxidation levels of the oil might indicate different regulation mechanisms. Highly oxidized camelina oil and a low concentration of HHE, over time, induced SOD and catalase enzyme activity in HT29 cells. Oxidized camelina oil contains multiple oxidation products which can be responsible for the intracellular responses observed in HT29 cells, while HHE and HNE in combination with other oxidation products induce antioxidant defence responses.

Ellagic acid and urolithin A modulate the immune response in LPS-stimulated U937 monocytic cells and THP-1 differentiated macrophages.

Dietary polyphenols are subjected, following ingestion, to an extensive metabolism, and the molecules that act at the cellular and tissue level will be, most likely, metabolites rather than native polyphenols. The mechanisms behind the positive effects exerted by polyphenols are not yet completely elucidated, since most in vitro studies use unmetabolised polyphenols rather than the metabolites present in the body. The aim of this study was to investigate and compare the potential effect of phenolic metabolites on the immune response using U937 monocyte and THP-1 macrophage cell cultures. Of the 16 metabolites tested, urolithins (Uro), and Uro A, in particular were the most potent, showing a modest increase in basal NF-κB activity and a reduction in lipopolysaccaride (LPS)-induced NF-κB activity, gene expression and secretion of pro-inflammatory cytokines. Protocatechuic acid and its sulfate/glucuronide metabolites reduced LPS-induced NF-κB activity, but not IL-6 and TNF-α cytokine secretion. Interestingly, both ellagic acid and its metabolite Uro A had immunomodulating effects, although they regulated the immune response differently, and both reduced LPS-induced NF-κB activity in U937 cells. However, while Uro A dramatically reduced IL-6 and IL-10 mRNA expression, no effect could be observed with ellagic acid. In THP-1 cells, treatment with ellagic acid dramatically reduced the expression of Toll-like receptor 4, while Uro A had no effect. The dual role observed for Uro A, showing both a modest increase in basal NF-κB activity and a reduction in LPS-induced NF-κB activity, as well as a reduction in LPS-induced pro-inflammatory cytokine secretion, makes this metabolite particularly interesting for further studies in animals and humans.