The microbiome: A heritable contributor to bone morphology?

Energy and macronutrient intake heritability: A systematic review and meta-analysis of twin and family-based studies

BACKGROUND/AIMS

The current meta-analysis aimed to examine the heritability and familial resemblance of dietary intakes, including energy and macronutrients in both twin and family-based studies.

METHODS

The online literature databases, including PubMed, Scopus, and Web of Science were searched comprehensively until 2023 to identify the relevant studies. The heritability index in family studies was h2 and the heritability indices for twin studies were h2, A2, and E2. Three weighted methods were used to calculate the mean and SE of heritability dietary intakes.

RESULTS

Eighteen papers including 8 studies on familial population and 12 for twin population studies were included in the present meta-analysis. The heritability of dietary intakes in twin studies (range of pooled estimated h2, A2, and E2 was 30-55%, 14-42%, and 52-79%, respectively) was higher than family studies (range of pooled estimated h2 = 16-39%). In family studies, the highest and lowest heritability for various nutrients was observed for the fat (%Kcal) (h2 range:36-38%) and carbohydrate in g (h2 range:16-18%), respectively. In twin studies, based on mean h2, the highest and lowest heritability for various nutrients was reported for the fat (%Kcal) (h2 range:49-55%) and protein intake in g (h2 range:30-35%), respectively. Also, based on the mean of A2, the highest and lowest heritability was observed for carbohydrates (% Kcal) (A2 range:42-42%), and protein (% Kcal) (A2 range:14-16%), respectively. Furthermore, in twin studies, the highest and lowest mean of E2 was shown for saturated fats (E2 range:74-79%) and energy intake (E2 range:52-57%), respectively.

CONCLUSION

Our analysis indicated that both environmental factors and genetics have noticeable contributions in determining the heritability of dietary intakes. Also, we observed higher heritability in twins compared to family studies.

Beneficial effects of arketamine on the reduced bone mineral density in susceptible mice after chronic social defeat stress: Role of the gut-microbiota-bone-brain axis

Patients with depression exhibit reduced bone mineral density (BMD). We previously reported that the new antidepressant arketamine improved the reduced BMD seen in chronic social defeat stress (CSDS) susceptible mice and ovariectomized mice. Considering the role of the gut microbiota in maintaining bone health, the current study investigated whether the gut microbiota, along with metabolites derived from the microbiome, play a role in the beneficial actions of arketamine with respect to the anhedonia-like behavior and reduced BMD seen in CSDS susceptible mice. A single administration of arketamine (10 mg/kg) ameliorated anhedonia-like behavior and decreased femoral neck cortical (and total) BMD in CSDS susceptible mice. There was a negative correlation between anhedonia-like behavior and BMD. Furthermore, significant differences in the abundance of microbiota (and plasma metabolites) were found between the CSDS + saline and CSDS + arketamine groups. Correlations were observed between the abundance of certain microbiota (and plasma metabolites) and cortical (and total) BMD. These data suggest that, in addition to its anti-anhedonia effect, arketamine might ameliorate the reduced cortical (and total) BMD seen in CSDS susceptible mice through the gut-microbiota-bone-brain axis. Therefore, arketamine could serve as a drug therapy for depressed patients with low BMD. This article is part of the Special Issue on "Ketamine and its Metabolites".

Transcriptome-wide association study identifies novel genes associated with bone mineral density and lean body mass in children

OBJECTIVE

To identify novel candidate genes whose expression is associated with bone mineral density (BMD) and body lean mass (LM) in children.

METHODS

A tissue-specific transcriptome-wide association study (TWAS) was conducted utilizing a large-scale genome-wide association study (GWAS) dataset associated with BMD and LM and involving 10,414 participants. The measurement of BMD and LM phenotypes was made based on total-body dual-energy X-ray absorptiometry (TB-DXA) scans. TWAS was conducted by using FUSION software. Reference panels for muscle skeleton (MS), peripheral blood (NBL) and whole blood (YBL) were used for TWAS analysis. Functional enrichment and protein-protein interaction (PPI) analyses of the genes identified by TWAS were performed by using the online tool Metascape ( http://metascape.org ).

RESULTS

For BMD, we identified 174 genes with P < 0.05, such as IKZF1 (P = 1.46 × 10^-9) and CHKB (P = 8.31 × 10^-7). For LM, we identified 208 genes with P < 0.05, such as COPS5 (P = 3.03 × 10^-12) and MRPS33 (P = 5.45 × 10^-10). Gene ontology (GO) enrichment analysis of the BMD-associated genes revealed 200 GO terms, such as protein catabolic process (Log P = -5.09) and steroid hormone-mediated signaling pathway (Log P = -3.13). GO enrichment analysis of the LM-associated genes detected 287 GO terms, such as the apoptotic signaling pathway (Log P = -8.08) and lipid storage (Log P = -3.55).

CONCLUSION

This study identified several candidate genes for BMD and LM in children, providing novel clues to the genetic mechanisms underlying the development of childhood BMD and LM.

Effects of (R)-ketamine on reduced bone mineral density in ovariectomized mice: A role of gut microbiota

Depression is a high risk for osteoporosis, suggesting an association between depression and low bone mineral density (BMD). We reported that the novel antidepressant (R)-ketamine could ameliorate the reduced BMD in the ovariectomized (OVX) mice which is an animal model of postmenopausal osteoporosis. Given the role of gut microbiota in depression and bone homeostasis, we examined whether gut microbiota plays a role in the beneficial effects of (R)-ketamine in the reduced BMD of OVX mice. OVX or sham was operated for female mice. Subsequently, saline (10 ml/kg/day, twice weekly) or (R)-ketamine (10 mg/kg/day, twice weekly) was administered intraperitoneally into OVX or sham mice for the six weeks. The reduction of cortical BMD and total BMD in the OVX mice was significantly ameliorated after subsequent repeated intermittent administration of (R)-ketamine. Furthermore, there were significant changes in the α- and β-diversity between OVX + saline group and OVX + (R)-ketamine group. There were correlations between several OTUs and cortical (or total) BMD. There were also positive correlations between the genera Turicibacter and cortical (or total) BMD. Moreover, there were correlations between several metabolites in blood and cortical (or total) BMD. These data suggest that (R)-ketamine may ameliorate the reduced cortical BMD and total BMD in OVX mice through anti-inflammatory actions via gut microbiota. Therefore, it is likely that (R)-ketamine would be a therapeutic drug for depressed patients with low BMD or patients with osteoporosis.

The Microbiota-Bone-Allergy Interplay

Emerging knowledge suggests an increasing importance of gut microbiota in health and disease. Allergy and bone metabolism are closely interconnected, and the possible negative effects of common therapies are not the only aspects of this relationship. The immune system is influenced by the microbiota-host interactions, and several pieces of evidence suggest the existence of an interplay between microbiota, bone metabolism, and allergies. Understanding these inter-relationships is essential for the development of new potential strategies of treatment and prevention targeting microbiota. A wide range of substances and germs, prebiotics and probiotics, are capable of influencing and modifying the microbiota. Prebiotics and probiotics have been shown in several studies to have different actions based on various factors such as sex, hormonal status, and age. In this review, we summarize the latest knowledge on the topic, and we discuss practical implications and the need for further studies.