Role of Essential Amino Acids in Age-Induced Bone Loss

Biomolecule-grafted GO enhanced the mechanical and biological properties of 3D printed PLA scaffolds with TPMS porous structure

Graphene oxide (GO) exhibits excellent mechanical strength and modulus. However, its effectiveness in mechanically reinforcing polymer materials is limited due to issues with interfacial bonding and dispersion arising from differences in the physicochemical properties between GO and polymers. Surface modification using coupling agents is an effective method to improve the bonding problem between polymer and GO, but there may be biocompatibility issues when used in the biomedical field. In this study, the biomolecule L-lysine, was applied to improve the interfacial bonding and dispersion of GO in polylactic acid (PLA) without compromising biocompatibility. The PLA/L-lysine-modified GO (PLA/L-GO) bone scaffold with triply periodic minimal surface (TPMS) structure was prepared using fused deposition modeling (FDM). The FTIR results revealed successful grafting of L-lysine onto GO through the reaction between their -COOH and -NH2 groups. The macroscopic and microscopic morphology characterization indicated that the PLA/L-GO scaffolds exhibited an characteristics of dynamic diameter changes, with good interlayer bonding. It was noteworthy that the L-lysine modification promoted the dispersion of GO and the interfacial bonding with the PLA matrix, as characterized by SEM. As a result, the PLA/0.1L-GO scaffold exhibited higher compressive strength (13.2 MPa) and elastic modulus (226.8 MPa) than PLA/0.1GO. Moreover, PLA/L-GO composite scaffold exhibited superior biomineralization capacity and cell response compared to PLA/GO. In summary, L-lysine not only improved the dispersion and interfacial bonding of GO with PLA, enhancing the mechanical properties, but also improved the biological properties. This study suggests that biomolecules like L-lysine may replace traditional modifiers as an innovative bio-modifier to improve the performance of polymer/inorganic composite biomaterials.

Nutrition and Bone Marrow Adiposity in Relation to Bone Health

Bone remodeling is energetically demanding process. Energy coming from nutrients present in the diet contributes to function of different cell type including osteoblasts, osteocytes and osteoclasts in bone marrow participating in bone homeostasis. With aging, obesity and osteoporosis the function of key building blocks, bone marrow stromal cells (BMSCs), changes towards higher accumulation of bone marrow adipose tissue (BMAT) and decreased bone mass, which is affected by diet and sex dimorphism. Men and women have unique nutritional needs based on physiological and hormonal changes across the life span. However, the exact molecular mechanisms behind these pathophysiological conditions in bone are not well-known. In this review, we focus on bone and BMAT physiology in men and women and how this approach has been taken by animal studies. Furthermore, we discuss the different diet interventions and impact on bone and BMAT in respect to sex differences. We also discuss the future perspective on precision nutrition with a consideration of sex-based differences which could bring better understanding of the diet intervention in bone health and weight management.

Multi-omics analysis of kidney, bone and bone marrow explored potential mechanisms of Erzhi Wan against osteoporosis with kidney-Yin deficiency

Osteoporosis (OP) is a metabolic bone disease that can lead to major health challenges. The theory of Traditional Chinese medicine believes that kidney-Yin deficiency (KYD) is the main cause of postmenopausal osteoporosis. This study was aimed to investigate the effect of EZW on anti-osteoporosis with KYD, and explore potential mechanisms from the perspective of the kidney, bone and bone marrow through analysis of metabolomics and proteomics. The model of OP with KYD was established by rats treated with bilateral ovariectomy (OVX), and then given intragastric administration of thyroid and reserpine to induce. Micro-CT was applied to determine the microstructures of bone. Serum levels associated with bone turnover markers and kidney-Yin deficiency were detected by enzyme-linked immunosorbent (ELISA) assay. The differential metabolites in the kidney, bone and bone marrow were analyzed by metabolomics. The differentially expressed proteins in these three tissues were detected via proteomics. The findings suggested that EZW could alleviate a variety of metabolites and proteins among the kidney, bone and bone marrow, primarily in amino acid metabolism, carbohydrate metabolism, nucleotide metabolism and lipid metabolism, thus leading to improvements of OP with KYD, which provided theoretical basis for clinical treatment of EZW on OP with KYD.

The Association of the Essential Amino Acids Lysine, Methionine, and Threonine with Clinical Outcomes in Patients at Nutritional Risk: Secondary Analysis of a Randomized Clinical Trial

Lysine, methionine, and threonine are essential amino acids with vital functions for muscle and connective tissue health, metabolic balance, and the immune system. During illness, the demand for these amino acids typically increases, which puts patients at risk for deficiencies with harmful clinical consequences. In a secondary analysis of the Effect of Early Nutritional Support on Frailty, Functional Outcomes, and Recovery of Malnourished Medical Inpatients Trial (EFFORT), which compared individualized nutritional support to usual care nutrition in patients at nutritional risk, we investigated the prognostic impact of the lysine, methionine, and threonine metabolism. We had complete clinical and amino acid data in 237 patients, 58 of whom reached the primary endpoint of death at 30 days. In a model adjusted for comorbidities, sex, nutritional risk, and trial intervention, low plasma methionine levels were associated with 30-day mortality (adjusted HR 1.98 [95% CI 1.16 to 3.36], p = 0.01) and with a decline in functional status (adjusted OR 2.06 [95% CI 1.06 to 4.01], p = 0.03). The results for lysine and threonine did not show statistically significant differences regarding clinical outcomes. These findings suggest that low levels of methionine may be critical during hospitalization among patients at nutritional risk. Further studies should investigate the effect of supplementation of methionine in this patient group to improve outcomes.

Identification of Amino Acids and Polyphenolic Metabolites in Human Plasma by UHPLC-ESI-QTOF-MS/MS, after the Chronic Intake of a Functional Meal in an Elderly Population

Novel foods especially formulated and targeted for the elderly population should provide sufficient nutrients and bioactive ingredients to counteract the natural age-related deterioration of various organs and tissues. Dietary protein and phenolic compounds achieve this goal; however, older adults have alterations in their gastrointestinal system that may impact their bioavailability and few studies have been aimed at this population. Since phenolic compounds are the subject of multiple biotransformations by host and microbiome enzymes during the digestion process, identification of their bioavailable forms in human plasma or tissues represents a considerable analytical challenge. In this study, UHPLC-ESI-QTOF/MS-MS, chemometrics, and multivariate statistical methods were used to identify the amino acids and phenolic compounds that were increased in the plasma of elderly adults after a 30-day intervention in which they had consumed an especially formulated muffin and beverage containing Brosimum alicastrum Sw. seed flour. A large interindividual variation was observed regarding the amino acids and phenolic metabolites identified in the plasma samples, before and after the intervention. Three phenolic metabolites were significantly increased in the population after the intervention: protocatechuic acid, 5-(methoxy-4'-hydroxyphenyl) valerolactone, and phloretic acid. These metabolites, as well as others that were not significantly increased (although they did increase in several individuals), are probably the product of the microbiota metabolism of the major phenolic compounds present in the B. alicastrum Sw. seed flour and other food ingredients. A significant decrease in 4-ethyl-phenol, a biomarker of stress, was observed in the samples. Results showed that the incorporation of foods rich in phenolic compounds into the regular diet of older adults contributes to the increase in bioactive compounds in plasma, that could substantially benefit their mental, cardiovascular, and digestive health.

Ageing-related bone and immunity changes: insights into the complex interplay between the skeleton and the immune system

Ageing as a natural irreversible process inherently results in the functional deterioration of numerous organ systems and tissues, including the skeletal and immune systems. Recent studies have elucidated the intricate bidirectional interactions between these two systems. In this review, we provide a comprehensive synthesis of molecular mechanisms of cell ageing. We further discuss how age-related skeletal changes influence the immune system and the consequent impact of immune system alterations on the skeletal system. Finally, we highlight the clinical implications of these findings and propose potential strategies to promote healthy ageing and reduce pathologic deterioration of both the skeletal and immune systems.

Metabolic factors are not the direct mediators of the association between type 2 diabetes and osteoporosis

Objective

The causal relationship between type 2 diabetes mellitus (T2DM) and osteoporosis (OS) remains unclear. This study aims to investigate the causal relationship and explore the potential metabolic mechanism and its mediating role.

Methods

We conducted a comprehensive study, gathering data on 490,089 T2DM patients from the genome-wide association study (GWAS) database and selecting OS data from FinnGen and MRC-IEU sources, including 212,778 and 463,010 patients, respectively, for causal analysis. Simultaneously, we explored the potential roles of three obesity traits and 30 metabolic and inflammation-related mediating variables in the causal relationship.

Results

There is a strong causal relationship between T2DM and OS. The data from our two different database sources appeared in the same direction, but after correcting for body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR), the direction became the same. T2DM may increase the risk of OS [odds ratio (OR) > 1.5, p < 0.001]. Steiger's test results show that there is no reverse causality. No risk factors related to glycolipid metabolism, amino acid metabolism, and inflammation were found to mediate the causal relationship.

Conclusion

This study's findings indicate a robust causal relationship between T2DM and OS, influenced by relevant factors such as BMI. Our results shed light on the pathogenesis of OS and underscore the importance for clinicians to treat metabolic disorders to prevent osteoporosis.

Discussion on protein recommendations for supporting muscle and bone health in older adults: a mini review

Muscle and bone tissues are interconnected, and both rely on an adequate protein intake. Recommendations for protein intake for older adults specifically vary across countries. The purpose of this narrative review is to discuss the existing evidence for protein recommendations for supporting muscle and bone health in older adults and to evaluate if a protein intake above the current population reference intake (PRI) for older adults would be scientifically justified. First, this review summarizes the protein recommendations from bodies setting dietary reference values, expert groups, and national health organizations. Next, relevant studies investigating the impact of protein on muscle and bone health in older adults are discussed. In addition, the importance of protein quality for muscle and bone health is addressed. Lastly, a number of research gaps are identified to further explore the added value of a protein intake above the PRI for older adults.

Absorption and transport properties of a codfish-derived peptide and its protective effect on bone loss in ovariectomized mice

A potential osteogenic tetradecapeptide with the amino acid sequence GETNPADSKPGSIR (P-GM-2) was identified from Gadus morhua. The present study aimed to elucidate its absorption and transport properties using Caco-2/HT29-MTX co-culture monolayers and to evaluate its osteogenic activity using an ovariectomized mouse model. The results showed that P-GM-2 could cross Caco-2/HT29-MTX co-culture barriers intactly with an apparent permeability coefficient of 4.02 × 10-6 cm s-1via the TJ-mediated passive paracellular pathway. Pharmacokinetic results revealed that P-GM-2 was detectable in the blood of mice within 5 min of oral administration and reached its maximum concentration at 30 min. Furthermore, the oral administration of P-GM-2 for a duration of three months has been found to effectively regulate the secretion of key markers of bone turnover, thereby protecting against bone microstructure degeneration and bone loss in ovariectomized mice. Importantly, no toxicity related to the treatment was observed. Taken together, these findings offer valuable insights into the absorption and transport mechanisms of P-GM-2, highlighting its potential as a safe and effective active ingredient for preventing osteoporosis.

Association between amino acids and recent osteoporotic fracture: a matched incident case-control study

Context

Osteoporotic fracture is a major public health issue globally. Human research on the association between amino acids (AAs) and fracture is still lacking.

Objective

To examine the association between AAs and recent osteoporotic fractures.

Methods

This age and sex matched incident case-control study identified 44 recent x-ray confirmed fracture cases in the Second Hospital of Jilin University and 88 community-based healthy controls aged 50+ years. Plasma AAs were measured by high performance liquid chromatography coupled with mass spectrometry. After adjusting for covariates (i.e., body mass index, milk intake >1 time/week, falls and physical activity), we conducted conditional logistical regression models to test the association between AAs and fracture.

Results

Among cases there were 23 (52.3%) hip fractures and 21 (47.7%) non-hip fractures. Total, essential, and non-essential AAs were significantly lower in cases than in controls. In the multivariable conditional logistic regression models, after adjusting for covariates, each standard deviation increase in the total (odds ratio [OR]: 0.304; 95% confidence interval [CI]: 0.117-0.794), essential (OR: 0.408; 95% CI: 0.181-0.923) and non-essential AAs (OR: 0.290; 95%CI: 0.107-0.782) was negatively associated with recent fracture. These inverse associations were mainly found for hip fracture, rather than non-hip fractures. Among these AAs, lysine, alanine, arginine, glutamine, histidine and piperamide showed the significantly negative associations with fracture.

Conclusion

There was a negative relationship between AAs and recent osteoporotic fracture; such relationship appeared to be more obvious for hip fracture.

Dietary protein levels during 12 to 26 wk improve the growth performance, bone quality, and testosterone in Pearl Gray male guinea fowl (Numida meleagris)

Guinea fowl (Numida meleagris), although native to Africa and despite its many potentials, does not represent the dominant species on the continent because of its seasonal reproductive nature and high keets mortality. This study was conducted to assess the effect of crude protein levels on growth performance, bone characteristics and reproductive activity of Pearl Gray male breeder guinea fowl from 12 to 26 wk of age. A total of 120 twelve-wk-old guinea fowls were randomly allotted to 3 dietary treatments with 8 replicates each and 5 birds per replicate using a completely randomized design. The dietary treatments comprised low level (LL), normal level (NL), and high level (HL) with diets respectively containing 15, 17, and 19% crude protein (CP). The results showed that guinea fowl in the HL treatment had a significantly lower feed conversion ratio (P = 0.008) than those in the other treatments. The birds fed the HL diet had significantly higher concentrations of testosterone (P < 0.05) than in the other treatments. High levels of calcium and phosphorus were observed in the femur of the HL group relative to the LL group. The birds in the LL treatment had a significantly higher (P = 0.007) femur robusticity index than those in the HL treatment. In conclusion, feeding 19% crude protein to Pearl Gray male guinea fowl from 12 to 26 wk of age improves growth performance, the density and strength of the femur and tibia and the reproductive tract. The CP level for the best performance of male guinea fowl from 12 to 26 wk of age is 19%.

Integrated Amino Acids and Transcriptome Analysis Reveals Arginine Transporter SLC7A2 Is a Novel Regulator of Myogenic Differentiation

Skeletal muscle differentiation is a precisely coordinated process. While many of the molecular details of myogenesis have been investigated extensively, the dynamic changes and functions of amino acids and related transporters remain unknown. In this study, we conducted a comprehensive analysis of amino acid levels during different time points of C2C12 myoblast differentiation using high-performance liquid chromatography (HPLC). Our findings revealed that the levels of most amino acids exhibited an initial increase at the onset of differentiation, reaching their peak typically on the fourth or sixth day, followed by a decline on the eighth day. Particularly, arginine and branched-chain amino acids showed a prominent increase during this period. Furthermore, we used RNA-seq analysis to show that the gene encoding the arginine transporter, Slc7a2, is significantly upregulated during differentiation. Knockdown of Slc7a2 gene expression resulted in a significant decrease in myoblast proliferation and led to a reduction in the expression levels of crucial myogenic regulatory factors, hindering the process of myoblast differentiation, fusion, and subsequent myotube formation. Lastly, we assessed the expression level of Slc7a2 during aging in humans and mice and found an upregulation of Slc7a2 expression during the aging process. These findings collectively suggest that the arginine transporter SLC7A2 plays a critical role in facilitating skeletal muscle differentiation and may hold potential as a therapeutic target for sarcopenia.

Effect of a New Hyaluronic Acid Hydrogel Dermal Filler Cross-Linked With Lysine Amino Acid for Skin Augmentation and Rejuvenation

BACKGROUND

Hyaluronic acid (HA) fillers are the most popular filler agents for skin rejuvenation. Although 1,4-butanediol diglycidyl ether is regarded as a relatively safe cross-linker, it still exhibits certain cytotoxicity.

OBJECTIVES

We presented here an amino acid-cross-linked HA (ACHA) which was obtained by an amidation reaction with lysine and HA. This study aimed to investigate ACHA's efficacy and safety for skin augmentation and rejuvenation.

METHODS

Rheology, compressive tests, and swelling experiments were conducted to investigate ACHA's mechanical and viscoelastic properties. The effects of ACHA on the human keratinocytes (HaCaT) cells and the human dermal fibroblast (HDF) were investigated by Transwell and wound healing assays. Its impacts on the epithelial thickness and collagen synthesis were further examined in a mouse experimental model. We recruited 50 patients with moderate to severe nasolabial folds (NLFs). The patients were randomly allocated to receive ACHA or Restylane injections. The resulting retention rates of HA and the Wrinkle Severity Rating Scale and Global Aesthetic Improvement Scale outcomes were evaluated and compared.

RESULTS

ACHA exhibited good viscoelasticity. It not only promoted migration and proliferation of HaCat and HDF and secretion of various growth factors but also increased skin thickness and promoted the generation of collagen. Patients who received ACHA had more residual volume 12 months after treatment. ACHA exhibited a promising augmentation effect in NLF correction with few adverse reactions.

CONCLUSIONS

ACHA has shown promise as a biomaterial with excellent biocompatibility and viscoelastic characteristics in both research and the clinic.See the abstract translated into Hindi, Portuguese, Korean, German, Italian, Arabic, Chinese, and Taiwanese online here: https://doi.org/10.1093/asj/sjad169.

LEVEL OF EVIDENCE: 2

Glycometabolic reprogramming in cementoblasts: A vital target for enhancing cell mineralization

Cementum, a constituent part of periodontal tissues, has important adaptive and reparative functions. It serves to attach the tooth to alveolar bone and acts as a barrier delimit epithelial growth and bacteria evasion. A dynamic and highly responsive cementum is essential for maintaining occlusal relationships and the integrity of the root surface. It is a thin layer of mineralized tissue mainly produced by cementoblasts. Cementoblasts are osteoblast-like cells essential for the restoration of periodontal tissues. In recent years, glucose metabolism has been found to be critical in bone remodeling and osteoblast differentiation. However, the glucose metabolism of cementoblasts remains incompletely understood. First, immunohistochemistry staining and in vivo tracing with 18 F-fluorodeoxyglucose (18 F-FDG) revealed significantly higher glucose metabolism in cementum formation. To test the bioenergetic pathways of cementoblast differentiation, we compared the bioenergetic profiles of mineralized and unmineralized cementoblasts. As a result, we observed a significant increase in the consumption of glucose and production of lactate, coupled with the higher expression of glycolysis-related genes. However, the expression of oxidative phosphorylation-related genes was downregulated. The verified results were consistent with the RNA sequencing results. Likewise, targeted energy metabolomics shows that the levels of glycolytic metabolites were significantly higher in the mineralized cementoblasts. Seahorse assays identified an increase in glycolytic flux and reduced oxygen consumption during cementoblast mineralization. Apart from that, we also found that lactate dehydrogenase A (LDHA), a key glycolysis enzyme, positively regulates the mineralization of cementoblasts. In summary, cementoblasts mainly utilized glycolysis rather than oxidative phosphorylation during the mineralization process.

Plasma Levels of Branched Chain Amino Acids, Incident Hip Fractures, and Bone Mineral Density of the Hip and Spine

OBJECTIVE

Branched chain amino acids (BCAA) are building blocks for protein, an essential component of bone. However, the association of plasma levels of BCAA with fractures in populations outside of Hong Kong or with hip fractures in particular is not known. The purpose of these analyses was to determine the relationship of BCAA including valine, leucine, and isoleucine and total BCAA (SD of the sum of Z-scores for each BCAA) with incident hip fractures and bone mineral density (BMD) of the hip and lumbar spine in older African American and Caucasian men and women in the Cardiovascular Health Study.

DESIGN

Longitudinal analyses of association of plasma levels of BCAA with incident hip fractures and cross-sectional BMD of the hip and lumbar spine from the Cardiovascular Health Study.

SETTING

Community.

PARTICIPANTS

A total of 1850 men (38% of cohort) and women; mean age 73 years.

MAIN OUTCOME MEASURES

Incident hip fractures and cross-sectional BMD of the total hip, femoral neck, and lumbar spine.

RESULTS

In fully adjusted models, over 12 years of follow-up, we observed no significant association between incident hip fracture and plasma values of valine, leucine, isoleucine, or total BCAA per 1 SD higher of each BCAA. Plasma values of leucine but not valine, isoleucine, or total BCAA, were positively and significantly associated with BMD of the total hip (P = .03) and femoral neck (P = .02), but not the lumbar spine (P = .07).

CONCLUSIONS

Plasma levels of the BCAA leucine may be associated with higher BMD in older men and women. However, given the lack of significant association with hip fracture risk, further information is needed to determine whether BCAAs would be novel targets for osteoporosis therapies.

The Functional Roles of Methionine and Arginine in Intestinal and Bone Health of Poultry: Review

This review explores the roles of methionine and arginine in promoting the well-being of poultry, with a specific focus on their impacts on intestinal and bone health. The metabolic pathways of methionine and arginine are elucidated, highlighting their distinct routes within the avian system. Beyond their fundamental importance in protein synthesis, methionine and arginine also exert their functional roles through their antioxidant capacities, immunomodulating effects, and involvement in the synthesis of metabolically important molecules such as S-adenosylmethionine, nitric oxide, and polyamines. These multifaceted actions enable methionine and arginine to influence various aspects of intestinal health such as maintaining the integrity of the intestinal barrier, regulating immune responses, and even influencing the composition of the gut microbiota. Additionally, they could play a pivotal role in promoting bone development and regulating bone remodeling, ultimately fostering optimal bone health. In conclusion, this review provides a comprehensive understanding of the potential roles of methionine and arginine in intestinal and bone health in poultry, thereby contributing to advancing the nutrition, overall health, and productivity of poultry in a sustainable manner.

Microbial Secondary Metabolites via Fermentation Approaches for Dietary Supplementation Formulations

Food supplementation formulations refer to products that are designed to provide additional nutrients to the diet. Vitamins, dietary fibers, minerals and other functional compounds (such as antioxidants) are concentrated in dietary supplements. Specific amounts of dietary compounds are given to the body through food supplements, and these include as well so-called non-essential compounds such as secondary plant bioactive components or microbial natural products in addition to nutrients in the narrower sense. A significant social challenge represents how to moderately use the natural resources in light of the growing world population. In terms of economic production of (especially natural) bioactive molecules, ways of white biotechnology production with various microorganisms have recently been intensively explored. In the current review other relevant dietary supplements and natural substances (e.g., vitamins, amino acids, antioxidants) used in production of dietary supplements formulations and their microbial natural production via fermentative biotechnological approaches are briefly reviewed. Biotechnology plays a crucial role in optimizing fermentation conditions to maximize the yield and quality of the target compounds. Advantages of microbial production include the ability to use renewable feedstocks, high production yields, and the potential for cost-effective large-scale production. Additionally, it can be more environmentally friendly compared to chemical synthesis, as it reduces the reliance on petrochemicals and minimizes waste generation. Educating consumers about the benefits, safety, and production methods of microbial products in general is crucial. Providing clear and accurate information about the science behind microbial production can help address any concerns or misconceptions consumers may have.

Amino Acid Metabolism and Disease

The origin of life is still a matter of debate, and several hypotheses have been proposed to explain how the building blocks leading to the minimal cell were formed [...].

What Nutraceuticals Can Do for Duchenne Muscular Dystrophy: Lessons Learned from Amino Acid Supplementation in Mouse Models

Duchenne muscular dystrophy (DMD), the severest form of muscular dystrophy, is characterized by progressive muscle weakness with fatal outcomes most often before the fourth decade of life. Despite the recent addition of molecular treatments, DMD remains a disease without a cure, and the need persists for the development of supportive therapies aiming to help improve patients' quality of life. This review focuses on the therapeutical potential of amino acid and derivative supplements, summarizing results obtained in preclinical studies in murine disease models. Several promising compounds have emerged, with L-arginine, N-acetylcysteine, and taurine featuring among the most intensively investigated. Their beneficial effects include reduced inflammatory, oxidative, fibrotic, and necrotic damage to skeletal muscle tissues. Improvement of muscle strength and endurance have been reported; however, mild side effects have also surfaced. More explorative, placebo-controlled and long-term clinical trials would need to be conducted in order to identify amino acid formulae that are safe and of true benefit to DMD patients.

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 Metabolic Features of Osteoblasts: Implications for Multiple Myeloma (MM) Bone Disease

The study of osteoblast (OB) metabolism has recently received increased attention due to the considerable amount of energy used during the bone remodeling process. In addition to glucose, the main nutrient for the osteoblast lineages, recent data highlight the importance of amino acid and fatty acid metabolism in providing the fuel necessary for the proper functioning of OBs. Among the amino acids, it has been reported that OBs are largely dependent on glutamine (Gln) for their differentiation and activity. In this review, we describe the main metabolic pathways governing OBs' fate and functions, both in physiological and pathological malignant conditions. In particular, we focus on multiple myeloma (MM) bone disease, which is characterized by a severe imbalance in OB differentiation due to the presence of malignant plasma cells into the bone microenvironment. Here, we describe the most important metabolic alterations involved in the inhibition of OB formation and activity in MM patients.