Lifelong calorie restriction affects indicators of colonic health in aging C57Bl/6J mice

Diminished colonic health is associated with various age-related pathologies. Calorie restriction (CR) is an effective strategy to increase healthy lifespan, although underlying mechanisms are not fully elucidated. Here, we report the effects of lifelong CR on indicators of colonic health in aging C57Bl/6J mice. Compared to an ad libitum control and moderate-fat diet, 30% energy reduction was associated with attenuated immune- and inflammation-related gene expression in the colon. Furthermore, expression of genes involved in lipid metabolism was higher upon CR, which may point towards efficient regulation of energy metabolism. The relative abundance of bacteria considered beneficial to colonic health, such as Bifidobacterium and Lactobacillus, increased in the mice exposed to CR for 28 months as compared to the other diet groups. We found lower plasma levels of interleukin 6 and lower levels of various metabolites, among which bile acids, in the colonic luminal content of CR-exposed mice as compared to the other diet groups. Switching from CR to an ad libitum moderate-fat diet at old age (24 months) revealed remarkable phenotypic plasticity in terms of gene expression, microbiota composition and metabolite levels, although expression of a subset of genes remained CR-associated. This study demonstrated in a comprehensive way that CR affects indicators of colonic health in aging mice. Our findings provide unique leads for further studies that need to address optimal and feasible strategies for prolonged energy deprivation, which may contribute to healthy aging

Akkermansia muciniphila ameliorates the age-related decline in colonic mucus thickness and attenuates immune activation in accelerated aging Ercc1(-/7) mice

BackgroundThe use of Akkermansia muciniphila as potential therapeutic intervention is receiving increasing attention. Health benefits attributed to this bacterium include an improvement of metabolic disorders and exerting anti-inflammatory effects. The abundance of A. muciniphila is associated with a healthy gut in early mid- and later life. However, the effects of A. muciniphila on a decline in intestinal health during the aging process are not investigated yet. We supplemented accelerated aging Ercc1(-/7) mice with A. muciniphila for 10weeks and investigated histological, transcriptional and immunological aspects of intestinal health.ResultsThe thickness of the colonic mucus layer increased about 3-fold after long-term A. muciniphila supplementation and was even significantly thicker compared to mice supplemented with Lactobacillus plantarum WCFS1. Colonic gene expression profiles pointed towards a decreased expression of genes and pathways related to inflammation and immune function, and suggested a decreased presence of B cells in colon. Total B cell frequencies in spleen and mesenteric lymph nodes were not altered after A. muciniphila supplementation. Mature and immature B cell frequencies in bone marrow were increased, whereas B cell precursors were unaffected. These findings implicate that B cell migration rather than production was affected by A. muciniphila supplementation. Gene expression profiles in ileum pointed toward a decrease in metabolic- and immune-related processes and antimicrobial peptide production after A. muciniphila supplementation. Besides, A. muciniphila decreased the frequency of activated CD80(+)CD273(-) B cells in Peyer's patches. Additionally, the increased numbers of peritoneal resident macrophages and a decrease in Ly6C(int) monocyte frequencies in spleen and mesenteric lymph nodes add evidence for the potentially anti-inflammatory properties of A. muciniphila.ConclusionsAltogether, we show that supplementation with A. muciniphila prevented the age-related decline in thickness of the colonic mucus layer and attenuated inflammation and immune-related processes at old age. This study implies that A. muciniphila supplementation can contribute to a promotion of healthy aging.Peer reviewe

Vitamin B-12 deficiency stimulates osteoclastogenesis via increased homocysteine and methylmalonic acid

The risk of nutrient deficiencies increases with age in our modern Western society, and vitamin B(12) deficiency is especially prevalent in the elderly and causes increased homocysteine (Hcy) and methylmalonic acid (MMA) levels. These three factors have been recognized as risk factors for reduced bone mineral density and increased fracture risk, though mechanistic evidence is still lacking. In the present study, we investigated the influence of B(12), Hcy, and MMA on differentiation and activity of bone cells. B(12) deficiency did not affect the onset of osteoblast differentiation, maturation, matrix mineralization, or adipocyte differentiation from human mesenchymal stem cells (hMSCs). B(12) deficiency caused an increase in the secretion of Hcy and MMA into the culture medium by osteoblasts, but Hcy and MMA appeared to have no effect on hMSC osteoblast differentiation. We further studied the effect of B(12), Hcy, and MMA on the formation of multinucleated tartrate-resistant acid phosphatase-positive osteoclasts from mouse bone marrow. We observed that B(12) did not show an effect on osteoclastogenesis. However, Hcy as well as MMA were found to induce osteoclastogenesis in a dose-dependent manner. On the basis of these results, we conclude that B(12) deficiency may lead to decreased bone mass by increased osteoclast formation due to increased MMA and Hcy levels

Folate and epigenetics : Why we should not forget bacterial biosynthesis

Folate, together with other B-vitamins, plays a crucial role in epigenetic regulation. Folate-mediated one-carbon metabolism refers to a complex network of interconnected metabolic pathways, which ultimately result in a supply of methyl groups for DNA, RNA or protein methylation. These epigenetic marks, particularly DNA methylation, have been proposed as plausible mechanisms underlying associations between folate and various disease outcomes, such as neural tube defects (NTDs), asthma, cardiometabolic disorders and cancer. However, evidence for the impact of folate on most of these disease outcomes, except for NTDs, is hampered by inconsistencies, with studies investigating the relationship between folate, DNA methylation and disease being subject to further complexities (i.e. identification of specific genomic loci affected, directions of differential methylation, and timing of epigenetic changes throughout the life course). Folate is closely related to other key role players in one-carbon metabolism (i.e. vitamin B12, homocysteine, methionine and choline) and therefore compensatory changes in interrelated metabolic pathways may account for inconsistent reports. Moreover, estimated folate intake does not necessarily correspond to circulating levels (correlations ranging from r=0.05–0.54), pointing towards methodological issues or other genetic, physiological or environmental factors determining folate levels. One particular aspect that remains unexplored is the contribution of bacterial folate biosynthesis to folate status and DNA methylation patterns

Characterization of the molecular mechanisms underlying increased mucus production of HT29-MTX-E12 cells grown on a semi-wet interface with mechanical stimulation

The multifunctional intestinal mucus layer plays a crucial role in human health. Our understanding of the human colonic mucus layer in terms of structure, function and has been largely dependent on expensive and advanced ex vivo or in vitro models, which often require high expertise. The mucus-producing intestinal cell line HT29-MTX-E12 has been commonly used in more simple in vitro models, but produces only low amounts of the intestine-specific MUC2. It has been shown previously that HT29-MTX-E12 cells cultured in Semi-Wet interface with Mechanical Stimulation (SWMS) produced higher amounts of MUC2 and had a thicker mucus layer compared to conventional culturing methods. However, it remains unknown which underlying pathways are involved. Therefore, we aimed to further explore the cellular processes underlying the increased mucus production by HT29-MTX-E12 cells grown under SWMS conditions. Cells grown on Transwell inserts for 15 days were subject to transcriptome analysis to investigate underlying molecular pathways at gene expression level. We also further characterized the model by measuring transepithelial resistance and pH and lactate production of the conditioned medium. We confirmed higher MUC2 production under SWMS conditions and demonstrated that this culturing method primarily stimulated cell growth. In addition, we also found evidence for a more aerobic cell metabolism under SWMS, as shown previously for similar models. In summary, we suggest different mechanisms in which mucus production is enhanced under SWMS and propose potential applications of this model in future studies. Overall design: HT29-MTX-E12 and Caco-2 cells were seeded on Transwell membranes. One day after seeding, cells were further cultured for 14 days under either SWMS conditions (i.e. low apical volume and continuous shaking at 65 rpm) or static conditions (similar conditions as during seeding). After harvesting, RNA isolated from cells was subjected to microarray analysis

Characterization of the molecular mechanisms underlying increased mucus production of HT29-MTX-E12 cells grown on a semi-wet interface with mechanical stimulation

The multifunctional intestinal mucus layer plays a crucial role in human health. Our understanding of the human colonic mucus layer in terms of structure, function and has been largely dependent on expensive and advanced ex vivo or in vitro models, which often require high expertise. The mucus-producing intestinal cell line HT29-MTX-E12 has been commonly used in more simple in vitro models, but produces only low amounts of the intestine-specific MUC2. It has been shown previously that HT29-MTX-E12 cells cultured in Semi-Wet interface with Mechanical Stimulation (SWMS) produced higher amounts of MUC2 and had a thicker mucus layer compared to conventional culturing methods. However, it remains unknown which underlying pathways are involved. Therefore, we aimed to further explore the cellular processes underlying the increased mucus production by HT29-MTX-E12 cells grown under SWMS conditions. Cells grown on Transwell inserts for 15 days were subject to transcriptome analysis to investigate underlying molecular pathways at gene expression level. We also further characterized the model by measuring transepithelial resistance and pH and lactate production of the conditioned medium. We confirmed higher MUC2 production under SWMS conditions and demonstrated that this culturing method primarily stimulated cell growth. In addition, we also found evidence for a more aerobic cell metabolism under SWMS, as shown previously for similar models. In summary, we suggest different mechanisms in which mucus production is enhanced under SWMS and propose potential applications of this model in future studies. Overall design: HT29-MTX-E12 and Caco-2 cells were seeded on Transwell membranes. One day after seeding, cells were further cultured for 14 days under either SWMS conditions (i.e. low apical volume and continuous shaking at 65 rpm) or static conditions (similar conditions as during seeding). After harvesting, RNA isolated from cells was subjected to microarray analysis

A weekly alternating diet between caloric restriction and medium fat protects the liver from fatty liver development in middle-aged C57BL/6J mice

We investigated whether a novel dietary intervention consisting of an every-other-week calorie-restricted diet could prevent nonalcoholic fatty liver disease (NAFLD) development induced by a medium-fat (MF) diet

Persistent organic pollutants alter DNA methylation during human adipocyte differentiation

Ubiquitous persistent organic pollutants (POPs) can accumulate in humans where they might influence differentiation of adipocytes. The aim of this study was to investigate whether DNA methylation is one of the underlying mechanisms by which POPs affect adipocyte differentiation, and to what extent DNA methylation can be related to gene transcription. Adipocyte differentiation was induced in two human cell models with continuous exposure to different POPs throughout differentiation. From the seven tested POPs, perfluorooctanesulfonic acid (PFOS) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) decreased lipid accumulation, while tributyltin (TBT) increased lipid accumulation. In human mesenchymal stem cells (hMSCs), TCDD and TBT induced opposite gene expression profiles, whereas after PFOS exposure gene expression remained relatively stable. Genome-wide DNA methylation analysis showed that all three POPs affected DNA methylation patterns in adipogenic and other genes, possibly related to the phenotypic outcome, but without concomitant gene expression changes. Differential methylation was predominantly detected in intergenic regions, where the biological relevance of alterations in DNA methylation is unclear. This study demonstrates that POPs, at environmentally relevant levels, are able to induce differential DNA methylation in human differentiating adipocytes.</p

Cover Image, Volume 117, Number 12, December 2016

Cover: The cover image, by Myrthe W. van den Dungen et al., is based on the Article Comprehensive DNA Methylation and Gene Expression Profiling in Differentiating Human Adipocytes, DOI: 10.1002/jcb.25568.</p