Effect of Methionine Restriction on Bone Density and NK Cell Activity

Long term methionine restriction: Influence on gut microbiome and metabolic characteristics

The Methionine restriction (MR) diet has been shown to delay aging and extend lifespan in various model organisms. However, the long-term effects of MR diet on the gut microbiome composition remain unclear. To study this, male mice were started on MR and control diet regimens at 6 months and continued until 22 months of age. MR mice have reduced body weight, fat mass percentage, and bone mineral density while having increased lean mass percentage. MR mice also have increased insulin sensitivity along with increasing indirect calorimetry markers such as energy expenditure, oxygen consumption, carbon dioxide production, and glucose oxidation. Fecal samples were collected at 1 week, 18 weeks, and 57 weeks after the diet onset for 16S rRNA amplicon sequencing to study the gut microbiome composition. Alpha and beta diversity metrics detected changes occurring due to the timepoint variable, but no changes were detected due to the diet variable. The results from LEfSe analysis surprisingly showed that more bacterial taxa changes were linked to age rather than diet. Interestingly, we found that the long-term MR diet feeding induced smaller changes compared to short-term feeding. Specific taxa changes due to the diet were observed at the 1 or 18-week time points, including Ileibacterium, Odoribacter, Lachnoclostridium, Marinifilaceae, and Lactobacillaceae. Furthermore, there were consistent aging-associated changes across both groups, with an increase in Ileibacterium and Erysipelotrichaceae with age, while Eubacterium_coprostanoligenes_group, Ruminococcaceae, Peptococcaceae, and Peptococcus decreased with age.

Dietary Intake and Circulating Amino Acid Concentrations in Relation with Bone Metabolism Markers in Children Following Vegetarian and Omnivorous Diets

Scientific studies reported that most vegetarians meet the total protein requirements; however, little is known about their amino acid intakes. We aimed to assess dietary intake and serum amino acid levels in relation to bone metabolism markers in prepubertal children on vegetarian and traditional diets. Data from 51 vegetarian and 25 omnivorous children aged 4–9 years were analyzed. Dietary intake of macro- and micronutrients were assessed using the nutritional program Dieta 5®. Serum amino acid analysis was performed using high-pressure liquid chromatography technique, 25-hydroxyvitamin D and parathormone–electrochemiluminescent immunoassay, and bone metabolism markers, albumin, and prealbumin levels using enzyme-linked immunosorbent assay. Vegetarian children had a significantly lower intake of protein and amino acids with median differences of about 30–50% compared to omnivores. Concentrations of four amino acids (valine, lysine, leucine, isoleucine) in serum varied significantly by diet groups and were lower by 10–15% in vegetarians than meat-eaters. Vegetarian children also had lower (p < 0.001) serum albumin levels compared to omnivores. Among bone markers, they had higher (p < 0.05) levels of C-terminal telopeptide of collagen type I (CTX-I) than omnivores. Correlation patterns between amino acids and bone metabolism markers differed in the vegetarian and omnivore groups. Out of bone markers, especially osteoprotegerin was positively correlated with several amino acids, such as tryptophan, alanine, aspartate, glutamine, and serine, and ornithine in vegetarians. Vegetarian children consumed apparently sufficient but lower protein and amino acids compared to omnivores. In circulation these differences were less marked than in the diet. Significantly lower amino acid intake and serum levels of valine, lysine, leucine, and isoleucine as well as the observed correlations between serum amino acids and biochemical bone marker levels indicated the relations between diet, protein quality, and bone metabolism.

The cortical bone metabolome of C57BL / 6J mice is sexually dimorphic

Cortical bone quality, which is sexually dimorphic, depends on bone turnover and therefore on the activities of remodeling bone cells. However, sex differences in cortical bone metabolism are not yet defined. Adding to the uncertainty about cortical bone metabolism, the metabolomes of whole bone, isolated cortical bone without marrow, and bone marrow have not been compared. We hypothesized that the metabolome of isolated cortical bone would be distinct from that of bone marrow and would reveal sex differences. Metabolite profiles from liquid chromatography–mass spectrometry (LC‐MS) of whole bone, isolated cortical bone, and bone marrow were generated from humeri from 20‐week‐old female C57Bl/6J mice. The cortical bone metabolomes were then compared for 20‐week‐old female and male C57Bl/6J mice. Femurs from male and female mice were evaluated for flexural material properties and were then categorized into bone strength groups. The metabolome of isolated cortical bone was distinct from both whole bone and bone marrow. We also found sex differences in the isolated cortical bone metabolome. Based on metabolite pathway analysis, females had higher lipid metabolism, and males had higher amino acid metabolism. High‐strength bones, regardless of sex, had greater tryptophan and purine metabolism. For males, high‐strength bones had upregulated nucleotide metabolism, whereas lower‐strength bones had greater pentose phosphate pathway metabolism. Because the higher‐strength groups (females compared with males, high‐strength males compared with lower‐strength males) had higher serum type I collagen cross‐linked C‐telopeptide (CTX1)/procollagen type 1 N propeptide (P1NP), we estimate that the metabolomic signature of bone strength in our study at least partially reflects differences in bone turnover. These data provide novel insight into bone bioenergetics and the sexual dimorphic nature of bone material properties in C57Bl/6 mice. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Network pharmacology integrated with experimental validation reveals the regulatory mechanism of plastrum testudinis in treating senile osteoporosis

ETHNOPHARMACOLOGICAL RELEVANCE

Plastrum testudinis (PT) has been used in traditional Chinese medicine to treat bone diseases such as senile osteoporosis (SOP) for thousands of years. However, the underlying mechanisms remain largely unknown.

AIM OF THE STUDY

This study aims to investigate the possible molecular mechanism of PT in the treatment of SOP using an integrated strategy of network pharmacology and experimental validation.

MATERIALS AND METHODS

The compounds of PT and its targets were identified through the BATMAN-TCM database. The SOP-related targets were retrieved from the GeneCards database. Protein-protein interaction information was obtained by inputting the intersection targets into the STRING database. Cytoscape software was used to construct a protein-protein interaction network and a PT-compound-target-SOP network. Using Cytoscape and R software, we conducted GO function and KEGG pathway enrichment analyses. We also conducted in vivo and in vitro experiments to verify the network pharmacology findings.

RESULTS

In total, 6 active compounds and 342 targets of PT were screened, of which 57 common targets were related to SOP. The GO biological process enrichment analysis identified 880 entries, mainly relating to the regulation of hormone response, the cell apoptotic process, the apoptotic signaling pathway, NF-kappaB transcription factor activity, fatty acid transportation, osteoclast differentiation, macrophage activation, and inflammatory response. The KEGG pathway enrichment analysis identified 52 entries, including 14 related signaling pathways, which mainly involved the TNF, MAPK, IL-17, AGE-RAGE, estrogen, relaxin, and other signaling pathways. Our in vivo experiments confirmed that PT alleviates SOP, while the in vitro experiments demonstrated that PT exerts a suppressive effect on osteoclast differentiation and bone resorption in a concentration-dependent manner. Furthermore, we observed that PT downregulates the expression of osteoclast-specific genes, including C-FOS, TNF, and BDNF, in the MAPK signaling pathway.

CONCLUSION

Through network pharmacology and experimental validation, this study is the first to report that PT downregulates the expression of osteoclast-specific genes, including C-FOS, TNF, and BDNF, in the MAPK signaling pathway, thus exerting a suppressive effect on osteoclast differentiation and bone resorption, which may be the molecular mechanism for PT treatment of SOP.

Perspective: Methionine Restriction-Induced Longevity-A Possible Role for Inhibiting the Synthesis of Bacterial Quorum Sensing Molecules

Methionine restriction (MR) extends lifespans in multiple species through mechanisms that include enhanced oxidative stress resistance and inhibition of insulin/insulin-like growth factor I (IGF-I) signaling. Methionine and S-adenosylmethionine (SAM) are the essential precursors of bacterial quorum sensing (QS) molecules, and therefore, MR might also affect bacterial communication to prevent enteric bacterial infection as well as chronic inflammation, which contributes to lifespan prolongation. Here, we discuss the influence of MR on oxidative stress resistance and inhibition of insulin/IGF-I cell signaling and further propose a potential mechanism involving bacterial QS inhibition for lifespan extension. Unraveling the connection between MR and inhibition of QS provides new strategies for combating infectious diseases, resulting in enriched understanding of MR-induced lifespan extension.

Liver X Receptor Inverse Agonist SR9243 Suppresses Nonalcoholic Steatohepatitis Intrahepatic Inflammation and Fibrosis

Abnormal metabolism of cholesterol may be a contributing factor in nonalcoholic steatohepatitis (NASH) pathogenesis. Accumulating evidence has shown that liver X receptor (LXR) is closely related to intrahepatic inflammation and fibrosis. In this study, we evaluated the effects of a novel liver-specific LXR inverse agonist, SR9243, on antifibrosis in NASH mice. A high-cholesterol diet was employed to induce NASH in BALB/c mice by either carbon tetrachloride (CCL4) administration or bile-duct ligation (BDL). Once NASH was induced, mice were treated with SR9243 for one month by intraperitoneal (i.p.) injection. Liver tissues were collected to determine the degree of fibrosis and intrahepatic inflammation via pathological examination and QPCR; serum was collected to analyze the plasma lipid levels and liver function by clinical biochemistry. The mice developed hepatic steatosis, severe hepatic inflammation, and fibrosis by BDL or CCL4. Treatment with SR9243 significantly reduced the severity of hepatic inflammation and ameliorated hepatic fibrosis; simultaneously, body weight, serum glucose, and plasma lipid levels were controlled effectively. Our data demonstrate that SR9243 exerts an antifibrotic and anti-inflammatory effect in NASH mice; hence these findings highly suggest that LXR inverse agonist could be therapeutically important in NASH treatment.