Active vitamin D possesses beneficial effects on the interaction between muscle and bone

Association between changes in body composition and progression of liver fibrosis in patients with type 2 diabetes mellitus

Aim

The correlation between type 2 diabetes mellitus (T2DM) and the occurrence of liver fibrosis is well-established. However, the longitudinal association between body composition and liver fibrosis progression in patients with T2DM remains incompletely explored.

Methods

Total of 390 patients with T2DM underwent body composition assessments, followed by a median duration of 2.13 years. The calculated parameters included body mass index (BMI), fat mass index (FMI), trunk fat mass index (TFMI), appendicular skeletal muscle mass index (ASMI), muscle/fat mass ratio (M/F) and appendicular skeletal muscle mass/trunk fat mass ratio (A/T). Liver fibrosis was evaluated through liver stiffness measurement (LSM). Patients were classified according to BMI and body composition, followed by a comprehensive investigation into the impact of body composition changes on liver fibrosis outcomes.

Results

Among 72 patients with incident advanced liver fibrosis at readmission, ΔBMI, ΔFMI and ΔTFMI increased, while ΔM/F and ΔA/T decreased. Individuals who kept obese had a dramatically elevated hazard of incident advanced liver fibrosis compared to those who kept non-obese, with an adjusted odds ratio of 3.464. When TFMI heightened, the hazard of incident advanced liver fibrosis was 3.601 times higher compared to the decreased group. Additionally, individuals in increased ASMI and A/T groups showed a slight advantage in preventing incident advanced liver fibrosis compared to the stable groups.

Conclusion

Stable obesity was associated with a greater hazard of liver fibrosis advancement, and an increase in TFMI may promote the progression of liver fibrosis. Maintaining a balanced muscle/fat ratio appeared to help prevent the progression.

Association between bone turnover markers, bone mineral density, and serum osteoglycine in middle-aged men with Type 2 Diabetes mellitus

BACKGROUND

Patients with Type 2 diabetes mellitus (T2DM) have decreased bone health. We aimed to investigate serum levels of bone turnover markers (BTMs) (markers of bone formation and bone resorption) and bone mineral density (BMD) at three sites (lumber, neck femur, and total femur) in middle-aged men with type 2 diabetes and to analyze the relationship between them. Also to evaluate serum osteoglycin as a novel marker and its relation to BTMs, BMD, and diabetic status.

METHODS

We recruited seventy-eight patients with T2DM and thirteen non-diabetic, male volunteers as a control group. BMD was measured using a DEXA scan. BTMs (carboxy-terminal crosslinking telopeptide of type 1 collagen [CTX] and procollagen type 1 N propeptide [P1NP]), osteoglycin, PTH, and vitamin D were estimated. Data was compared among subjects and statistical analysis was performed.

RESULTS

Most of the patients were having normal BMD with no significant difference between patients and the controls. BTMs and osteoglycin were significantly higher and vitamin D was significantly lower in the diabetic patients. Serum osteoglycin was positively correlated with DEXA Neck Femur (r = 0.233; p-value < 0.05).

CONCLUSION

Body mass index and Serum osteoglycin have a significant positive effect on BMD. Both markers of bone formation and bone resorption were increased indicating a state of increased bone turnover in T2DM.

miRNA-seq analysis of high glucose induced osteoblasts provides insight into the mechanism underlying diabetic osteoporosis

The present study aims to explore the etiology of Diabetic osteoporosis (DOP), a chronic complication associated with diabetes mellitus. Specifically, the research seeks to identify potential miRNA biomarkers of DOP and investigated role in regulating osteoblasts. To achieve this, an animal model of DOP was established through the administration of a high-sugar and high-fat diet, and then injection of streptozotocin. Bone microarchitecture and histopathology analysis were analyzed. Rat calvarial osteoblasts (ROBs) were stimulated with high glucose (HG). MiRNA profiles of the stimulated osteoblasts were compared to control osteoblasts using sequencing. Proliferation and mineralization abilities were assessed using MTT assay, alkaline phosphatase, and alizarin red staining. Expression levels of OGN, Runx2, and ALP were determined through qRT-PCR and Western blot. MiRNA-sequencing results revealed increased miRNA-702-5p levels. Luciferase reporter gene was utilized to study the correlation between miR-702-5p and OGN. High glucose impaired cell proliferation and mineralization in vitro by inhibiting OGN, Runx2, and ALP expressions. Interference with miR-702-5p decreased OGN, Runx2, and ALP levels, which were restored by OGN overexpression. Additionally, downregulation of OGN and Runx2 in DOP rat femurs was confirmed. Therefore, the miRNA-702-5p/OGN/Runx2 signaling axis may play a role in DOP, and could be diagnostic biomarker and therapeutic target for not only DOP but also other forms of osteoporosis.

Glycative stress inhibits hypertrophy and impairs cell membrane integrity in overloaded mouse skeletal muscle

BACKGROUND

Glycative stress, characterized by the formation and accumulation of advanced glycation end products (AGEs) associated with protein glycation reactions, has been implicated in inducing a decline of muscle function. Although the inverse correlation between glycative stress and muscle mass and strength has been demonstrated, the underlying molecular mechanisms are not fully understood. This study aimed to elucidate how glycative stress affects the skeletal muscle, particularly the adaptive muscle response to hypertrophic stimuli and its molecular mechanism.

METHODS

Male C57BL/6NCr mice were randomly divided into the following two groups: the bovine serum albumin (BSA)-treated and AGE-treated groups. Mice in the AGE-treated group were intraperitoneally administered AGEs (0.5 mg/g) once daily, whereas those in the BSA-treated group received an equal amount of BSA (0.5 mg/g) as the vehicle control. After 7 days of continuous administration, the right leg plantaris muscle of mice in each group underwent functional overload treatment by synergist ablation for 7 days to induce muscle hypertrophy. In in vitro studies, cultured C2C12 myocytes were treated with AGEs (1 mg/mL) to examine cell adhesion and cell membrane permeability.

RESULTS

Continuous AGE administration increased the levels of fluorescent AGEs, Nε-(carboxymethyl) lysine, and methylglyoxal-derived hydroimidazolone-1 in both plasma and skeletal muscle. Plantaris muscle weight, muscle fibre cross-sectional area, protein synthesis rate, and the number of myonuclei increased with functional overload in both groups; however, the increase was significantly reduced by AGE treatment. Some muscles of AGE-treated mice were destroyed by functional overload. Proteomic analysis was performed to explore the mechanisms of muscle hypertrophy suppression and myofibre destruction by AGEs. When principal component analysis was performed on 4659 data obtained by proteomic analysis, AGE treatment was observed to affect protein expression only in functionally overloaded muscles. Enrichment analysis of the 436 proteins extracted using the K-means method further identified a group of proteins involved in cell adhesion. Consistent with this finding, dystrophin-glycoprotein complex proteins and cell adhesion-related proteins were confirmed to increase with functional overload; however, this was attenuated by AGE treatment. Additionally, the treatment of C2C12 muscle cells with AGEs inhibited their ability to adhere and increased cell membrane permeability.

CONCLUSIONS

This study indicates that glycative stress may be a novel pathogenic factor in skeletal muscle dysfunctions by causing loss of membrane integrity and preventing muscle mass gain.

The Synergistic Effect of Zuogui Pill and Eldecalcitol on Improving Bone Mass and Osteogenesis in Type 2 Diabetic Osteoporosis

Background and Objectives: The incidence of diabetic osteoporosis, an important complication of diabetes mellitus, is increasing gradually. This study investigated the combined effect of the Zuogui pill (ZGP) and eldecalcitol (ED-71), a novel vitamin D analog, on type 2 diabetic osteoporosis (T2DOP) and explored their action mechanism. Materials and Methods: Blood glucose levels were routinely monitored in db/db mice while inducing T2DOP. We used hematoxylin and eosin staining, Masson staining, micro-computed tomography, and serum biochemical analysis to evaluate changes in the bone mass and blood calcium and phosphate levels of mice. Immunohistochemical staining was performed to assess the osteoblast and osteoclast statuses. The MC3T3-E1 cell line was cultured in vitro under a high glucose concentration and induced to undergo osteogenic differentiation. Quantitative real-time polymerase chain reaction, Western blot, immunofluorescence, ALP, and alizarin red staining were carried out to detect osteogenic differentiation and PI3K-AKT signaling pathway activity. Results: ZGP and ED-71 led to a dramatic decrease in blood glucose levels and an increase in bone mass in the db/db mice. The effect was strongest when both were used together. ZGP combined with ED-71 promoted osteoblast activity and inhibited osteoclast activity in the trabecular bone region. The in vitro results revealed that ZGP and ED-71 synergistically promoted osteogenic differentiation and activated the PI3K-AKT signaling pathway. The PI3K inhibitor LY294002 or AKT inhibitor ARQ092 altered the synergistic action of both on osteogenic differentiation. Conclusions: The combined use of ZGP and ED-71 reduced blood glucose levels in diabetic mice and promoted osteogenic differentiation through the PI3K-AKT signaling pathway, resulting in improved bone mass. Our study suggests that the abovementioned combination constitutes an effective treatment for T2DOP.

Impact of Sarcopenia on Non-Alcoholic Fatty Liver Disease

With the increasing incidence of non-alcoholic fatty liver disease (NAFLD) and the aging of the population, sarcopenia is attracting attention as one of the pathological conditions involved in the development and progression of NAFLD. In NAFLD, sarcopenia is closely associated with insulin resistance and results from the atrophy of skeletal muscle, an insulin target organ. In addition, inflammatory cytokines that promote skeletal muscle protein breakdown, low adiponectin levels leading to decreased insulin sensitivity, and hyperleptinemia are also involved in NAFLD pathogenesis. The presence of sarcopenia is a prognostic factor and increases the risk of mortality in patients with cirrhosis and post-treatment liver cancer. Sarcopenia, the presence of which mainly occurs due to decreased muscle mass, combined with increased visceral fat, can lead to sarcopenia-associated obesity, which increases the risk of NASH, liver fibrosis, and cardiovascular disease. In order to treat sarcopenia, it is necessary to properly evaluate sarcopenia status. Patients with high BMI, as in sarcopenic obesity, may improve with caloric restriction. However, inadequate oral intake may lead to further loss of muscle mass. Aerobic and resistance exercise should also be used appropriately.

Interaction between sarcopenia and nonalcoholic fatty liver disease

Sarcopenia and nonalcoholic fatty liver disease (NAFLD) are common health problems related to aging. Despite the differences in their diagnostic methods, several cross-sectional and longitudinal studies have revealed the close link between sarcopenia and NAFLD. Sarcopenia and NAFLD are linked by several shared pathogenetic mechanisms, including insulin resistance, hormonal imbalance, systemic inflammation, myostatin and adiponectin dysregulation, nutritional deficiencies, and physical inactivity, thus implicating a bidirectional relationship between sarcopenia and NAFLD. However, there is not sufficient data to support a direct causal relationship between sarcopenia and NAFLD. Moreover, it is currently difficult to conclude whether sarcopenia is a risk factor for nonalcoholic steatohepatitis (NASH) or is a consequence of NASH. Therefore, this review intends to touch on the shared common mechanisms and the bidirectional relationship between sarcopenia and NAFLD.

ED-71 Prevents Glucocorticoid-Induced Osteoporosis by Regulating Osteoblast Differentiation via Notch and Wnt/β-Catenin Pathways

PURPOSE

Long-term glucocorticoid- usage can lead to glucocorticoid-induced osteoporosis (GIOP). The study focused on the preventative effects of a novel active vitamin D3 analog, eldecalcitol (ED-71), against GIOP and explored the underlying molecular mechanisms.

METHODS

Intraperitoneal injection of methylprednisolone (MPED) or dexamethasone (DEX) induced the GIOP model within C57BL/6 mice in vivo. Simultaneously, ED-71 was orally supplemented. Bone histological alterations, microstructure parameters, novel bone formation rates, and osteogenic factor changes were evaluated by hematoxylin-eosin (HE) staining, micro-computed tomography, calcein/tetracycline labeling, and immunohistochemical (IHC) staining. The osteogenic differentiation level and mineralization in pre-osteoblast MC3T3-E1 cells were evaluated in vitro using alkaline phosphatase (ALP) staining, alizarin red (AR) staining, quantitative polymerase chain reaction (qPCR), Western blotting, and immunofluorescence staining.

RESULTS

ED-71 partially prevented bone mass reduction and microstructure parameter alterations among GIOP-induced mice. Moreover, ED-71 also promoted new bone formation and osteoblast activity while inhibiting osteoclasts. In vitro, ED-71 promoted osteogenic differentiation and mineralization in DEX-treated MC3T3-E1 cells and boosted the levels of osteogenic-related factors. Additionally, GSK3-β and β-catenin expression levels were elevated after ED-71 was added to cells and were accompanied by reduced Notch expression. The Wnt signaling inhibitor XAV939 and Notch overexpression reversed the ED-71 promotional effects toward osteogenic differentiation and mineralization.

CONCLUSION

ED-71 prevented GIOP by enhancing osteogenic differentiation through Notch and Wnt/GSK-3β/β-catenin signaling. The results provide a novel translational direction for the clinical application of ED-71 against GIOP.

Renal failure suppresses muscle irisin expression, and irisin blunts cortical bone loss in mice

BACKGROUND

Chronic renal failure induces bone mineral disorders and sarcopenia. Skeletal muscle affects other tissues, including bone, by releasing myokines. However, the effects of chronic renal failure on the interactions between muscle and bone remain unclear.

METHODS

We investigated the effects of renal failure on bone, muscle, and myokines linking muscle to bone using a mouse 5/6 nephrectomy (Nx) model. Muscle mass and bone mineral density (BMD) were analysed by quantitative computed tomography 8 weeks after Nx.

RESULTS

Nephrectomy significantly reduced muscle mass in the whole body (12.1% reduction, P < 0.05), grip strength (10.1% reduction, P < 0.05), and cortical BMD at the femurs of mice (9.5% reduction, P < 0.01) 8 weeks after surgery, but did not affect trabecular BMD at the femurs. Among the myokines linking muscle to bone, Nx reduced the expression of irisin, a proteolytic product of fibronectin type III domain-containing 5 (Fndc5), in the gastrocnemius muscles of mice (38% reduction, P < 0.01). Nx increased myostatin mRNA levels in the gastrocnemius muscles of mice (54% increase, P < 0.01). In simple regression analyses, cortical BMD, but not trabecular BMD, at the femurs was positively related to Fndc5 mRNA levels in the gastrocnemius muscles of mice (r = 0.651, P < 0.05). The weekly administration of recombinant irisin to mice ameliorated the decrease in cortical BMD, but not muscle mass or grip strength, induced by Nx (6.2% reduction in mice with Nx vs. 3.3% reduction in mice with Nx and irisin treatment, P < 0.05).

CONCLUSIONS

The present results demonstrated that renal failure decreases the expression of irisin in the gastrocnemius muscles of mice. Irisin may contribute to cortical bone loss induced by renal failure in mice as a myokine linking muscle to bone.

Impact of Sarcopenia on the Severity of the Liver Damage in Patients With Non-alcoholic Fatty Liver Disease

An extensive body of the literature shows a strong interrelationship between the pathogenic pathways of non-alcoholic fatty liver disease (NAFLD) and sarcopenia through the muscle-liver-adipose tissue axis. NAFLD is one of the leading causes of chronic liver diseases (CLD) affecting more than one-quarter of the general population worldwide. The disease severity spectrum ranges from simple steatosis to non-alcoholic steatohepatitis (NASH), cirrhosis, and its complications: end-stage chronic liver disease and hepatocellular carcinoma. Sarcopenia, defined as a progressive loss of the skeletal muscle mass, reduces physical performances, is associated with metabolic dysfunction and, possibly, has a causative role in NAFLD pathogenesis. Muscle mass is a key determinant of the whole-body insulin-mediated glucose metabolism and impacts fatty liver oxidation and energy homeostasis. These mechanisms drive the accumulation of ectopic fat both in the liver (steatosis, fatty liver) and in the muscle (myosteatosis). Myosteatosis rather than the muscle mass per se, seems to be closely associated with the severity of the liver injury. Sarcopenic obesity is a recently described entity which associates both sarcopenia and obesity and may trigger worse clinical outcomes including hepatic fibrosis progression and musculoskeletal disabilities. Furthermore, the muscle-liver-adipose tissue axis has a pivotal role in changes of the body composition, resulting in a distinct clinical phenotype that enables the identification of the "sarcopenic NAFLD phenotype." This review aims to bring some light into the complex relationship between sarcopenia and NAFLD and critically discuss the key mechanisms linking NAFLD to sarcopenia, as well as some of the clinical consequences associated with the coexistence of these two entities: the impact of body composition phenotypes on muscle morphology, the concept of sarcopenic obesity, the relationship between sarcopenia and the severity of the liver damage and finally, the future directions and the existing gaps in the knowledge.

A transcriptome-wide association study to detect novel genes for volumetric bone mineral density

Transcriptome-wide association studies (TWAS) systematically investigate the association of genetically predicted gene expression with disease risk, providing an effective approach to identify novel susceptibility genes. Osteoporosis is the most common metabolic bone disease, associated with reduced bone mineral density (BMD) and increased risk of osteoporotic fractures, whereas genetic factors explain approximately 70% of the variance in phenotypes associated with bone. BMD is commonly assessed using dual-energy X-ray absorptiometry (DXA) to obtain measurements (g/cm2) of areal BMD. However, quantitative computed tomography (QCT) measured 3D volumetric BMD (vBMD) (g/cm3) has important advantages compared with DXA since it can evaluate cortical and trabecular microstructural features of bone quality, which can be used to directly predict fracture risk. Here, we performed the first TWAS for volumetric BMD (vBMD) by integrating genome-wide association studies (GWAS) data from two independent cohorts, namely the Framingham Heart Study (FHS, n = 3298) and the Osteoporotic Fractures in Men (MrOS, n = 4641), with tissue-specific gene expression data from the Genotype-Tissue Expression (GTEx) project. We first used stratified linkage disequilibrium (LD) score regression approach to identify 12 vBMD-relevant tissues, for which vBMD heritability is enriched in tissue-specific genes of the given tissue. Focusing on these tissues, we subsequently leveraged GTEx expression reference panels to predict tissue-specific gene expression levels based on the genotype data from FHS and MrOS. The associations between predicted gene expression levels and vBMD variation were then tested by MultiXcan, an innovative TWAS method that integrates information available across multiple tissues. We identified 70 significant genes associated with vBMD, including some previously identified osteoporosis-related genes such as LYRM2 and NME8, as well as some novel loci such as DNAAF2 and SPAG16. Our findings provide novel insights into the pathophysiological mechanisms of osteoporosis and highlight several novel vBMD-associated genes that warrant further investigation.

Elevated serum pentosidine is independently associated with the high prevalence of sarcopenia in Chinese middle-aged and elderly men with type 2 diabetes mellitus

AIMS/INTRODUCTION

Sarcopenia has recently been recognized as another complication associated with diabetes, but its early screening still lacks clinical markers. Here, we aimed to investigate the relationship between serum levels of pentosidine, which is an advanced glycation end-product, and sarcopenia in Chinese middle-aged and elderly men with type 2 diabetes mellitus and evaluate whether pentosidine could be used as a kind of screening maker.

MATERIALS AND METHODS

A total of 182 male type 2 diabetes mellitus patients aged ≥50 years were selected in the cross-sectional study for whole-body dual-energy X-ray measurement and calculating the appendicular skeletal muscle mass index. At the same time, handgrip strength and gait speed were assessed. According to the updated consensus on Asian sarcopenia in 2019, the patients were divided into the sarcopenia group (n = 83) and non-sarcopenia group (n = 99). Serum pentosidine levels in the two groups were detected using enzyme-linked immunosorbent assay.

RESULTS

Serum pentosidine was significantly higher in the sarcopenia group (191.27 pmol/mL) than in the non-sarcopenia group (34.93 pmol/mL). Serum pentosidine was negatively correlated with appendicular skeletal muscle mass index and handgrip strength (r = -0.30 and -0.25, respectively; P < 0.05), but not gait speed. The prevalence of sarcopenia increased as the quartile of serum pentosidine increased (P < 0.05). The association between pentosidine and the prevalence of sarcopenia was still significant after additional adjustments (odds ratio 1.01, P < 0.05).

CONCLUSIONS

Pentosidine is an independent risk factor for sarcopenia in Chinese middle-aged and elderly men with type 2 diabetes mellitus. The detection of serum pentosidine levels in clinics might be helpful for the monitoring of type 2 diabetes mellitus complicated with sarcopenia.

Evaluation of myostatin as a possible regulator and marker of skeletal muscle-cortical bone interaction in adults

INTRODUCTION

Bone mass was recently reported to be related to skeletal muscle mass in humans, and a decrease in cortical bone is a risk factor for osteoporosis. Because circulating myostatin is a factor that primarily controls muscle metabolism, this study examined the role of myostatin in bone mass-skeletal muscle mass interactions.

METHODS

The subjects were 375 middle-aged community residents with no history of osteoporosis or sarcopenia who participated in a health check-up. Cortical bone thickness and cancellous bone density were measured by ultrasonic bone densitometry in a health check-up survey. The subjects were divided into those with low cortical bone thickness (LCT) or low cancellous bone density (LBD) and those with normal values (NCT/NBD). Bone metabolism markers (TRACP-5b, etc.), skeletal muscle mass, serum myostatin levels, and lifestyle were then compared between the groups.

RESULTS

The percentage of diabetic participants, TRACP-5b, and myostatin levels were significantly higher, and the frequency of physical activity, skeletal muscle mass, grip strength, and leg strength were significantly lower in the LCT group than in the NCT group. The odds ratio (OR) of high myostatin levels in the LCT group compared with the NCT group was significant (OR 2.17) even after adjusting for related factors. Between the low cancellous bone density (LBD) and normal cancellous bone density (NBD) groups, significant differences were observed in the same items as between the LCT and NCT groups, but no significant differences were observed in skeletal muscle mass and blood myostatin levels. The myostatin level was significantly negatively correlated with cortical bone thickness and skeletal muscle mass.

CONCLUSIONS

A decrease in cortical bone thickness was associated with a decrease in skeletal muscle mass accompanied by an increase in the blood myostatin level. Blood myostatin may regulate the bone-skeletal muscle relationship and serve as a surrogate marker of bone metabolism, potentially linking muscle mass to bone structure.

Urinary pentosidine level is associated with grip strength and gait speed in community-dwelling adults: a cross-sectional study

Background

Muscle and bone interactions might be associated with osteoporosis and sarcopenia. Urinary pentosidine and serum 25-hydroxyvitamin D (25(OH)D) might affect muscle and bone interactions. It is unclear whether these biomarkers are affected by age and sex or play a role in muscle and physical functions. We aimed to investigate the association between urinary pentosidine and serum 25(OH)D levels with muscle mass, muscle strength, and physical performance in community-dwelling adults.

Methods

Two-hundred and fifty-four middle-aged and elderly adults were enrolled. There was no significant difference in age between 97 men (75.0 ± 8.9 years) and 157 women (73.6 ± 8.1 years). The skeletal muscle mass index (SMI), grip strength, and gait speed were assessed. The urinary pentosidine level was measured. We evaluated the association of urinary pentosidine and serum 25(OH)D levels with age and sex (student’s t-test) and correlations between biomarker and each variable (Pearson’s correlation coefficients). Multiple regression analysis was performed with grip strength and gait speed as dependent variables and with age, height, weight, body mass index (BMI), speed of sound (SOS), SMI, glycated hemoglobin (HbA1c), estimated glomerular filtration rate (eGFR), 25(OH)D, and pentosidine as independent variables using the stepwise method.

Results

The urinary pentosidine level was negatively correlated with grip strength, gait speed, eGFR, and insulin-like growth factor-1 (IGF-1) in men and with SOS, grip strength, and gait speed in women. The serum 25(OH)D level was positively correlated with IGF-1 in women and grip strength in men. Grip strength was associated with age, height, and pentosidine in men and height and pentosidine in women. Gait speed was associated with age, BMI, and pentosidine in men and age, height, and pentosidine in women.

Conclusion

Urinary pentosidine levels are significantly associated with grip strength and gait speed and may serve as a biomarker of muscle and bone interactions.

Vitamin D Supplementation and Impact on Skeletal Muscle Function in Cell and Animal Models and an Aging Population: What Do We Know So Far?

Aging is associated with impairment in skeletal muscle mass and contractile function, predisposing to fat mass gain, insulin resistance and diabetes. The impact of Vitamin D (VitD) supplementation on skeletal muscle mass and function in older adults is still controversial. The aim of this review was to summarize data from randomized clinical trials, animal dietary intervention and cell studies in order to clarify current knowledge on the effects of VitD on skeletal muscle as reported for these three types of experiments. A structured research of the literature in Medline via PubMed was conducted and a total of 43 articles were analysed (cells n = 18, animals n = 13 and humans n = 13). The results as described by these key studies demonstrate, overall, at cell and animal levels, that VitD treatments had positive effects on the development of muscle fibres in cells in culture, skeletal muscle force and hypertrophy. Vitamin D supplementation appears to regulate not only lipid and mitochondrial muscle metabolism but also to have a direct effect on glucose metabolism and insulin driven signalling. However, considering the human perspective, results revealed a predominance of null effects of the vitamin on muscle in the ageing population, but experimental design may have influenced the study outcome in humans. Well-designed long duration double-blinded trials, standardised VitD dosing regimen, larger sample sized studies and standardised measurements may be helpful tools to accurately determine results and compare to those observed in cells and animal dietary intervention models.

Associations of Circulating Osteoglycin With Bone Parameters and Metabolic Markers in Patients With Diabetes

Objective

Circulating osteoglycin may facilitate the crosstalk between bone and pancreas to empower adaptation of bone mass to whole body energy balance. We aimed to examine whether osteoglycin is associated with bone and metabolic parameters and if osteoglycin levels differ between patients with type 1 and 2 diabetes (T1D and T2D).

Design and methods

A cross-sectional study of 190 patients with diabetes mellitus and stable hemoglobin A1c (HbA1c) (97 T1D and 93 T2D) was conducted. S-osteoglycin was analyzed by ELISA. Unpaired t-tests were performed to test differences between patients with T1D and T2D and linear regression analyses were performed to investigate associations between osteoglycin, glycemic markers, bone turnover markers and characteristics.

Results

S-osteoglycin did not differ between patients with T1D and T2D (p=0.10). No associations were present between osteoglycin and age, gender, microvascular complications, HbA1c, or plasma glucose in T1D or T2D patients (p>0.05 for all). S-osteoglycin was not associated with levels of bone turnover markers (C-terminal cross-linked telopeptide of type-I collagen (CTX), P-procollagen type 1 amino terminal propeptide (P1NP), P-osteocalcin (OC), P-sclerostin, S-osteoprotegerin (OPG) or S-Receptor Activator of Nuclear factor Kappa beta Ligand (RANKL)) in neither T1D or T2D patients (p>0.05 for all).

Conclusion

Osteoglycin levels were similar in T1D and T2D patients. Osteoglycin did not correlate with glucose, HbA1c or any other biochemical marker of bone turnover. Thus, we did not find evidence supporting the existence of an osteoglycin-bone-pancreas axis.

Clinical Trial Registration

ClinicalTrials.gov, identifier NCT01870557.

Pleiotropic actions of Vitamin D in composite musculoskeletal trauma

Composite tissue injuries are the result of high energy impacts caused by motor vehicle accidents, gunshot wounds or blasts. These are highly traumatic injuries characterized by wide-spread, penetrating wounds affecting the entire musculoskeletal system, and are generally defined by frank volumetric muscle loss with concomitant segmental bone defects. At the tissue level, the breadth of damage to multiple tissue systems, and potential for infection from penetration, have been shown to lead to an exaggerated, often chronic inflammatory response with subsequent dysregulation of normal musculoskeletal healing mechanisms. Aside from the direct effects of inflammation on myogenesis and osteogenesis, frank muscle loss has been shown to directly impair fracture union and ultimately contribute to failed wound regeneration. Care for these injuries requires extensive surgical intervention and acute care strategies. However, often these interventions do not adequately mitigate inflammation or promote proper musculoskeletal injury repair and force amputation of the limb. Therefore, identification of factors that can promote tissue regeneration and mitigate inflammation could be key to restoring wound healing after composite tissue injury. One such factor that may directly affect both inflammation and tissue regeneration in response to these multi-tissue injuries may be Vitamin D. Beyond traditional roles, the pleiotropic and localized actions of Vitamin D are increasingly being recognized in most aspects of wound healing in complex tissue injuries - e.g., regulation of inflammation, myogenesis, fracture callus mineralization and remodeling. Conversely, pre-existing Vitamin D deficiency leads to musculoskeletal dysfunction, increased fracture risk or fracture non-unions, decreased strength/function and reduced capacity to heal wounds through increased inflammation. This Vitamin D deficient state requires acute supplementation in order to quickly restore circulating levels to an optimal level, thereby facilitating a robust wound healing response. Herein, the purpose of this review is to address the roles and critical functions of Vitamin D throughout the wound healing process. Findings from this review suggest that careful monitoring and/or supplementation of Vitamin D may be critical for wound regeneration in composite tissue injuries.

Risk factors predicting osteosarcopenia in postmenopausal women with osteoporosis: A retrospective study

There is growing interest in “osteosarcopenia” as the coexistence of osteoporosis and sarcopenia exacerbates negative outcomes. However, limited information is available regarding the risk factors of osteosarcopenia development in patients with osteoporosis. Therefore, we retrospectively reviewed 276 consecutive patients with postmenopausal osteoporosis who regularly visited Showa University Hospital. Patients were eligible for the study if they were ≥65 years of age and underwent dual-energy X-ray absorptiometry, blood sampling, and physical performance assessment. Patients were divided into the osteosarcopenia and osteoporosis alone groups according to the diagnostic criteria of the Asian Working Group for Sarcopenia. Of the 276 patients with osteoporosis, 54 patients (19.6%) had osteosarcopenia. Patients in the osteosarcopenia group had a greater risk of frailty than did those in the osteoporosis alone group (odds ratio 2.33; 95% confidence interval, 1.13–4.80, P = 0.028). Low body mass index seemed to be the strongest factor related to the development of osteosarcopenia, and none of the patients in the osteosarcopenia group were obese (BMI ≥27.5 kg/m²). Multiple logistic analyses revealed that patients aged 65–74 years who had comorbidities such as kidney dysfunction and high levels of HbA1c were at risk of developing osteosarcopenia. Thus, we strongly recommend the assessment of the key components of the diagnosis of osteosarcopenia in an osteoporosis clinic for patients with low body mass index. Furthermore, appropriate assessments, including comorbidities, will help in identifying patients at greater risk of developing osteosarcopenia.

Vitamin D protects against immobilization-induced muscle atrophy via neural crest-derived cells in mice

Vitamin D deficiency is a recognized risk factor for sarcopenia development, but mechanisms underlying this outcome are unclear. Here, we show that low vitamin D status worsens immobilization-induced muscle atrophy in mice. Mice globally lacking vitamin D receptor (VDR) exhibited more severe muscle atrophy following limb immobilization than controls. Moreover, immobilization-induced muscle atrophy was worse in neural crest-specific than in skeletal muscle-specific VDR-deficient mice. Tnfα expression was significantly higher in immobilized muscle of VDR-deficient relative to control mice, and was significantly elevated in neural crest-specific but not muscle-specific VDR-deficient mice. Furthermore, muscle atrophy induced by limb immobilization in low vitamin D mice was significantly inhibited in Tnfα-deficient mice. We conclude that vitamin D antagonizes immobilization-induced muscle atrophy via VDR expressed in neural crest-derived cells.

Bone Mass Loss and Sarcopenia in Ecuadorian Patients

OBJECTIVE

To study the association between osteoporosis and sarcopenia and determine the prevalence of osteosarcopenia in patients who attended a rheumatology center in Ecuador.

METHODS

A cross-sectional study was conducted in a population of patients who had a densitometric study. The diagnosis of sarcopenia was determined by the DXA standard gold test, screening, and conventional methods (bioimpedance, anthropometric measurements, SARC-F, muscle function, and gait test).

RESULTS

A total of 92 patients were studied. The median age was 66 ± 10, 90% females. Using the criteria of SMI, 65% had sarcopenia of which 9% had only sarcopenia and 56% had osteosarcopenia; 22% had only osteopenia/osteoporosis; and 13% none of these conditions. The prevalence of sarcopenia according to handgrip strength was 60%, gait speed 45%, and SARC-F score 40%. The prevalence of osteosarcopenia according to handgrip strength was 51%, gait speed 34%, and SARC-F score 32%. Osteoporosis was associated with a higher prevalence of sarcopenia using the criteria of SMI since 40% had sarcopenia in the normal DXA group, 64% in the osteopenia group, and 76% in the osteoporosis group (p=0.017). Of the women, 69% had sarcopenia compared to 33% of the men (p=0.034). The BMI was lower in the group with sarcopenia (25.1 ± 4.1 kg/m2) compared to the group without sarcopenia (29.4 ± 4.1 kg/m2, p < 0.001). Patients with osteosarcopenia and sarcopenia had lower BMI, handgrip strength, ASM, SMI, and total-body skeletal muscle mass than those with osteopenia/osteoporosis or normal patients.

CONCLUSION

65% of the studied population had sarcopenia. It is clear that the prevalence of sarcopenia is higher in patients with greater loss of bone mass. Identifying pathways that affect both bone and muscle could facilitate the development of treatments that simultaneously improve osteoporosis and sarcopenia.

Impact of intracellular toxic advanced glycation end-products (TAGE) on murine myoblast cell death

BACKGROUND

Sarcopenia is a progressive condition that is characterized by decreases in skeletal muscle mass and function. Although sarcopenia is associated with lifestyle-related diseases (LSRD), the mechanisms underlying cell death in myoblasts, which differentiate to myotubes, remain unclear. We previously designated glyceraldehyde (an intermediate of glucose/fructose metabolism)-derived advanced glycation end-products (AGEs) as toxic AGEs (TAGE) because of their cytotoxicity and involvement in LSRD, and hypothesized that TAGE contribute to cell death in myoblasts.

METHODS

C2C12 cells, which are murine myoblasts, were treated with 0, 0.5, 1, 1.5, and 2 mM glyceraldehyde for 24 h. Cell viability and intracellular TAGE were then assessed using 5-[2,4,-bis(sodioxysulfonyl)phenyl]-3-(2-methoxy-4-nitrophenyl)-2-(4-nitrophenyl)-2H-tetrazole-3-ium (WST-8) and slot blot assays. Cells were pretreated with 8 mM aminoguanidine, an inhibitor of AGE production, for 2 h, followed by 0, 1.5, and 2 mM glyceraldehyde for 24 h. Cell viability and intracellular TAGE levels were then assessed. Serum TAGE levels in STAM mice, in which there were four stages (no steatosis, simple steatosis, steatohepatitis, and fibrosis), were measured using a competitive enzyme-linked immunosorbent assay. Results were expressed as TAGE units (U) per milliliter of serum, with 1 U corresponding to 1.0 μg of glyceraldehyde-derived AGE-bovine serum albumin (BSA) (TAGE-BSA). The viability of cells treated with 20, 50, and 100 μg/mL non-glycated BSA and TAGE-BSA for 24 h was assessed using the WST-8 assay.

RESULTS

In C2C12 cells treated with 1.5 and 2 mM glyceraldehyde, cell viability decreased to 47.7% (p = 0.0021) and 5.0% (p = 0.0001) and intracellular TAGE levels increased to 6.0 and 15.9 μg/mg protein, respectively. Changes in cell viability and TAGE production were completely inhibited by 8 mM aminoguanidine. Serum TAGE levels at the steatohepatitis and fibrosis stages were 10.51 ± 1.16 and 10.44 ± 0.95 U/mL, respectively, and were higher than those at the no steatosis stage (7.27 ± 0.18 U/mL). Cell death was not induced by 20 or 50 μg/mL TAGE-BSA. The viabilities of C2C12 cells treated with 100 μg/mL non-glycated BSA and TAGE-BSA were 105.0% (p = 0.2890) and 85.3% (p = 0.0217), respectively.

CONCLUSION

Intracellular TAGE strongly induced cell death in C2C12 cells and may also induce myoblast cell death in LSRD model mice.

Osteoglycin and Bone-a Systematic Review

PURPOSE OF REVIEW

Bone turnover is a regulated process. Osteoglycin is suggested to have an important impact on bone function but may also affect cardiovascular and metabolic functions. This review investigates the action of osteoglycin in bone as well as its potential endocrine effects.

RECENT FINDINGS

Osteoglycin is expressed by several tissues including bone and muscle. Some studies suggest that osteoglycin increases osteoblast differentiation whereas others suggest that osteoglycin decreases osteoblast differentiation. Thus, findings on the influence of osteoglycin in bone are conflicting. A recent study found increased bone mass in osteoglycin deficient mice. Another study reported that osteoglycin is a marker of low bone mineral density and vertebral fractures in women with type 2 diabetes. Furthermore, clinical studies link osteoglycin to insulin resistance and cardiovascular disease. Osteoglycin may be a novel marker of a muscle, pancreatic, and bone axis. However, current evidence is limited and further research investigating osteoglycin in both a pre-clinical and a clinical setting is needed.

Relationship among urinary advanced glycation-end products, skeletal muscle mass and physical performance in community-dwelling older adults

AIM

Advanced glycation end-products are important factors in muscle function and physical performance among older adults. However, the association between sarcopenia and urinary carboxymethyl-lysine (uCML) levels remains unclear. The present study aimed to investigate the relationship among uCML levels, skeletal muscle mass, physical performance and sarcopenia among community-dwelling older adults.

METHODS

This work was a community-based cross-sectional study. The participants were recruited from the Taichung Community Health Study-Elderly and were followed up until 2017. A total of 104 participants underwent dual-energy X-ray absorptiometry examination, physical performance tests and measurement of uCML levels. After the natural log transformation of the uCML levels, Pearson's correlation coefficient and a general linear model were used for statistical analysis.

RESULTS

The mean uCML levels of older men and women were 1.34 μg/mg and 1.63 μg/mg creatinine, respectively. After multivariate adjustment, grip strength among older women significantly decreased as uCML levels increased. Participants with uCML levels and Timed Up and Go test values higher than the median had a 13.76-fold risk of acquiring sarcopenia compared with those whose corresponding variables were lower than the median after adjusting for age, sex, body fat percentage, and serum creatinine and blood urea nitrogen levels.

CONCLUSIONS

uCML levels were negatively associated with grip strength among older women. The joint association of uCML and Timed Up and Go test values was correlated with the risk of acquiring sarcopenia among older adults. This finding suggests that uCML levels can be used as a biomarker for screening sarcopenia and as a strategy for treating sarcopenia. Geriatr Gerontol Int 2019; 19: 1017-1022.

Insulin-Like Growth Factor-I Protects Against the Detrimental Effects of Advanced Glycation End Products and High Glucose in Myoblastic C2C12 Cells

Previous studies suggested that advanced glycation end products (AGEs) and insulin-like growth factor-I (IGF-I) are involved in the mechanism of diabetes-induced sarcopenia. In this study, we examined effects of treatments with AGEs and/or IGF-I for 24 h on myogenic differentiation and apoptosis in mouse myoblastic C2C12 cells. Real-time PCR and Western blot were performed to investigate mRNA and protein expressions, and apoptosis was examined by using a DNA fragment detection ELISA kit. AGE3 significantly decreased mRNA and protein expressions of MyoD and Myogenin, whereas IGF-I significantly increased them and attenuated the effects of AGE3. AGEs significantly decreased endogenous IGF-I mRNA expression and suppressed IGF-I-induced Akt activation. High glucose (22 mM) significantly increased mRNA expression of Rage, a receptor for AGEs, while IGF-I significantly decreased it. DNA fragment ELISA showed that AGE2 and AGE3 significantly increased apoptosis of C2C12 cells, whereas IGF-I significantly suppressed the AGE2- and AGE3-induced apoptosis. In contrast, high glucose enhanced AGE3-induced apoptosis. IGF-I significantly attenuated the effects of high glucose plus AGE3 on the mRNA and protein expressions of MyoD and Myogenin as well as the apoptosis. These findings indicate that AGEs inhibit myogenic differentiation and increase apoptosis in C2C12 cells, and that high glucose increases RAGE and enhances the AGE3-induced apoptosis, suggesting that AGEs and high glucose might contribute to the reduction of muscle mass and function. Moreover, IGF-I attenuated the detrimental effects of AGEs and high glucose in myoblastic cells; thus, IGF-I-Akt signal could be a therapeutic target of DM-induced sarcopenia.

Age-Related Decrease in Skeletal Muscle Mass Is an Independent Risk Factor for Incident Nonalcoholic Fatty Liver Disease: A 10-Year Retrospective Cohort Study

Background/Aims

Sarcopenia has emerged as an important risk factor for nonalcoholic fatty liver disease (NAFLD). Although aging is the main cause of sarcopenia, the longitudinal association between age-related body composition changes and NAFLD development has not been fully investigated. Thus, we evaluated whether age-related increased fat mass or decreased muscle mass is an independent risk factor for incident NAFLD.

Methods

We conducted a retrospective cohort study involving 4,398 initially NAFLD-free subjects who underwent routine health examinations during 2004 to 2005 and returned for a follow-up during 2014 to 2015. Their body composition was measured by bioelectrical impedance analysis, and fatty liver was diagnosed by abdominal ultrasonography.

Results

At the 10-year follow-up, 591 out of 4,398 participants (13.4%) had developed NAFLD. In men and women, both increased fat mass and decreased appendicular skeletal muscle mass (ASM) with aging were significantly associated with incident NAFLD after adjustment. A subgroup analysis according to the baseline obesity status showed that increased fat mass was significantly associated with incident NAFLD in obese and nonobese subjects. However, decreased ASM was significantly associated with incident NAFLD in nonobese but not in obese subjects. According to ΔASM tertiles (decrease of ASM), the odds ratios for incident NAFLD in nonobese subjects were 1.38 (95% confidence interval [CI], 1.04 to 1.84) for the second tertile and 1.81 (95% CI, 1.34 to 2.45) for the third tertile after adjustment (p=0.001).

Conclusions

A progressive increase in fat mass and a loss of ASM with aging were significantly associated with incident NAFLD. This association was more prominent in nonobese subjects.

Low skeletal muscle mass is associated with the risk of all-cause mortality in patients with type 2 diabetes mellitus

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) have an increased risk of muscle mass reduction. However, the association between muscle mass and mortality in T2DM remains unknown.

METHODS

This was a historical cohort study with the endpoint of all-cause mortality. This study included 163 Japanese men and 141 postmenopausal women with T2DM whose body compositions were evaluated using dual-energy X-ray absorptiometry. Low muscle mass was defined as a skeletal muscle mass index (SMI) of <7.0 kg/m² for men and <5.4 kg/m² for women.

RESULTS

During the 6-year follow-up period, 32 men and 14 women died. In a Cox regression analysis adjusted for age, T2DM duration, glycated hemoglobin, serum creatinine, fasting C-peptide, body mass index, and lean body mass were associated with the risk of mortality in men [hazard ratio (HR) = 1.81, 95% confidence interval (CI) = 1.00-3.28 per standard deviation (SD) decrease, p = 0.049] and women (HR = 4.53, 95% CI = 1.14-17.96 per SD decrease, p = 0.032). Neither fat mass nor bone mineral content was associated with mortality. Low SMI was associated with increased mortality in women (HR = 5.97, 95% CI = 1.04-34.37, p = 0.045), while the association between low SMI and mortality was marginal in men (HR = 2.38, 95% CI = 0.92-6.14, p = 0.074).

CONCLUSIONS

Low muscle mass was independently associated with all-cause mortality in patients with T2DM. The preservation of skeletal muscle mass is important to protect patients with T2DM from increased mortality risk.

Higher Serum Uric Acid is a Risk Factor of Reduced Muscle Mass in Men with Type 2 Diabetes Mellitus

OBJECTIVE

Sarcopenia has been recognized as a diabetic complication, and hyperuricemia is often accompanied by type 2 diabetes mellitus (T2DM). However, it is unknown whether serum uric acid (UA) levels are associated with reduced muscle mass in T2DM.

METHODS

We conducted a cross-sectional study to investigate the association of serum UA with muscle mass in 401 subjects with T2DM (209 men and 192 postmenopausal women). The relative skeletal muscle mass index (RSMI) was evaluated using whole-body dual-energy x-ray absorptiometry.

RESULTS

Multiple regression analyses adjusted for body weight, age, serum creatinine, hemoglobin A1c (HbA1c), and duration of T2DM showed that serum UA was negatively associated with RSMI in all subjects and men with T2DM (β=-0.13, p=0.001 and β=-0.17, p=0.003, respectively). Moreover, logistic regression analyses adjusted for these confounding factors showed that a higher serum UA level was significantly associated with low RSMI in men with T2DM [odds ratio (OR)=1.94, 95% confidence interval (CI)=1.10-3.45 per SD increase, p=0.023]. In addition, higher serum UA levels were significantly associated with low RSMI after additional adjustment for age, duration of T2DM, HbA1c level, serum creatinine level, and sex in all subjects with T2DM [OR=1.80, 95% CI=1.20-2.72 per SD increase, p=0.005].

CONCLUSIONS

The present study showed for the first time that higher serum UA is an independent risk factor of reduced muscle mass in men with T2DM.

Effects of activated vitamin D, alfacalcidol, and low-intensity aerobic exercise on osteopenia and muscle atrophy in type 2 diabetes mellitus model rats

Diabetes mellitus causes secondary osteoporosis and muscle atrophy. The ability of alfacalcidol (ALF) and exercise (Exe) to inhibit osteoporosis and muscle atrophy in type 2 diabetes mellitus (T2DM) model rats was examined. Twenty-week-old Otsuka Long-Evans Tokushima Fatty rats were randomized to ALF (orally 0.1 μg/kg/day), Exe (treadmill exercise at 10 m/min, 60 min/day, 5 days/week), Comb (ALF and Exe), and Cont (T2DM control treated with vehicle and no exercise) groups (n = 8–10 per group). Sedentary Long-Evans Tokushima Otsuka rats were used as a non-hyperphagic control. After treatment for 2 or 6 weeks, blood glucose (BG) levels, cross-sectional area (CSA) of tibialis anterior muscle fibers, femoral bone mineral density (BMD), and relative quantities of muscle anabolic markers (Pax7, MyoD, and myogenin) and catabolic markers (Atrogin-1, MuRF1, and REDD1) of the soleus muscle assessed by real-time polymerase chain reaction assays were measured. Exe and Comb treatments for 6 weeks decreased BG levels compared with those of the Cont group. ALF, Exe, and Comb treatments for 2 and 6 weeks recovered the CSA compared with that of the Cont group. ALF and Comb treatments for 6 weeks increased femoral BMDs compared with those of the Cont group. After 2 weeks of treatment, Comb treatment increased MyoD expression and decreased MuRF1 expression. ALF or Exe monotherapy significantly decreased Atrogin-1 or MuRF1 expression after 2 weeks of treatment, respectively. After 6 weeks of treatment, ALF and Comb treatments decreased Atrogin-1 and REDD1. These results demonstrate that a combination of ALF and Exe improved CSA from the early phase of treatment by stimulating skeletal muscle differentiation and suppressing muscle catabolic genes. Improvements in BG, BMD, and CSA were observed as long-term effects of the combination therapy. Continued suppression of muscle catabolic genes was observed as a background to these effects.

Diabetes Mellitus-induced Bone Fragility

Accumulating evidence has shown that the risk of osteoporotic fractures is increased in patients with diabetes mellitus (DM). Thus, DM-induced bone fragility has been recently recognized as a diabetic complication. Because the fracture risk is independent of the reduction in bone mineral density, deterioration of the bone quality may be the main cause of bone fragility. Although its mechanism remains poorly understood, accumulated collagen cross-links of advanced glycation end-products (AGEs) and dysfunctions of osteoblast and osteocyte may be involved. Previous studies have suggested that various diabetes-related factors, such as chronic hyperglycemia, insulin, insulin-like growth factor-I, AGEs, and homocysteine, are associated with the risk of bone fragility caused by impaired bone formation and bone remodeling. Furthermore, several anti-diabetic drugs are known to affect bone metabolism and fracture risk. We herein review the association between DM and fracture risk as well as the mechanism of DM-induced bone fragility based on recent evidence.

Role of plasminogen activator inhibitor-1 in glucocorticoid-induced muscle change in mice

We recently revealed that plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor, is involved in diabetes, osteoporosis and muscle wasting induced by glucocorticoid (GC) treatment in mice. In the present study, we investigated the detailed mechanisms by which GC induces muscle wasting through PAI-1 in vivo and in vitro. PAI-1 deficiency suppressed the mRNA levels of atrogin1 and muscle RING-Finger Protein 1 (MuRF1), ubiquitin ligases leading to muscle degradation, elevated by GC treatment in the gastrocnemius muscle of mice. In vitro study revealed that active PAI-1 treatment augmented the increase in atrogin1 mRNA levels enhanced by dexamethasone (Dex) in mouse myoblastic C2C12 cells. Moreover, a reduction in endogenous PAI-1 level by siRNA suppressed the mRNA levels of atrogin1 and MuRF1 enhanced by Dex in C2C12 cells. In contrast, a reduction in endogenous PAI-1 levels and active PAI-1 did not affect the phosphorylations of Akt and p70S6 kinase nor myogenic differentiation with or without Dex in C2C12 cells. In addition, PAI-1 deficiency blunted IGF-1 mRNA levels decreased by GC treatment in the gastrocnemius muscle of mice, although neither active PAI-1 nor a reduction in endogenous PAI-1 levels affected the levels of IGF-1 mRNA in C2C12 cells in the presence of Dex. In conclusion, our data suggest that paracrine PAI-1 is involved in GC-induced muscle wasting through the enhancement of muscle degradation in mice.

The Common Mechanisms of Sarcopenia and NAFLD

Current studies have shown that sarcopenia and nonalcoholic fatty liver disease (NAFLD) have similar pathophysiological profiles. The cooccurrence of sarcopenia and NAFLD has been observed in elderly patients. The actions of these conditions are linked, and their treatments are similar. Therefore, studies should be conducted on NAFLD-sarcopenia rather than on NAFLD or sarcopenia.

Vitamin D, a modulator of musculoskeletal health in chronic kidney disease

The spectrum of activity of vitamin D goes beyond calcium and bone homeostasis, and growing evidence suggests that vitamin D contributes to maintain musculoskeletal health in healthy subjects as well as in patients with chronic kidney disease (CKD), who display the combination of bone metabolism disorder, muscle wasting, and weakness. Here, we review how vitamin D represents a pathway in which bone and muscle may interact. In vitro studies have confirmed that the vitamin D receptor is present on muscle, describing the mechanisms whereby vitamin D directly affects skeletal muscle. These include genomic and non-genomic (rapid) effects, regulating cellular differentiation and proliferation. Observational studies have shown that circulating 25-hydroxyvitamin D levels correlate with the clinical symptoms and muscle morphological changes observed in CKD patients. Vitamin D deficiency has been linked to low bone formation rate and bone mineral density, with an increased risk of skeletal fractures. The impact of low vitamin D status on skeletal muscle may also affect muscle metabolic pathways, including its sensitivity to insulin. Although some interventional studies have shown that vitamin D may improve physical performance and protect against the development of histological and radiological signs of hyperparathyroidism, evidence is still insufficient to draw definitive conclusions.

Association of serum vitamin D with osteosarcopenic obesity: Korea National Health and Nutrition Examination Survey 2008-2010

BACKGROUND

Serum vitamin D levels have been reported to be associated with individual components of body composition. However, the relationship between serum vitamin D and combined indices of adverse body composition is largely unknown. This cross-sectional study examined the association between serum vitamin D and osteosarcopenic obesity in a nationally representative sample of middle-aged and older adults.

METHODS

We analysed the Korea National Health and Nutrition Examination Surveys (IV and V) conducted in 2008-2010, consisting of 5908 (2485 men, 3423 women) aged ≥ 50 years. Serum vitamin D levels were determined by radioimmunoassay, and body composition was evaluated by dual-energy x-ray absorptiometry. The association between serum vitamin D levels and the number of abnormalities in body composition, including osteosarcopenic obesity, a low bone and muscle mass with concurrent high fat mass, was analysed by multinomial logistic regression adjusting for covariates.

RESULTS

In men, after controlling for covariates, higher vitamin D levels were associated with a significantly reduced likelihood of the number of phenotypes of adverse body composition (P for trend < 0.05). Those in the highest tertile group of serum vitamin D levels, compared with those in the lowest tertile, were less likely to have adverse body composition, numbering one (odds ratio [OR] = 0.67, 95% confidence interval [CI]: 0.49, 0.92), two (OR = 0.49, 95% CI: 0.33, 0.73), and three (osteosarcopenic obesity; OR = 0.42, 95% CI: 0.26, 0.67). In women, those in the highest tertile group of serum vitamin D levels, compared with those in the lowest tertile, were less likely to have osteosarcopenic obesity (OR = 0.55, 95% CI: 0.33, 0.93). Vitamin D deficiency (<20 ng/mL) in men was significantly associated with an increased likelihood of a higher number of adverse body composition, especially for osteosarcopenic obesity (OR = 2.08, 95% CI: 1.42, 3.03). Vitamin D deficient women, compared with those having normal levels of serum vitamin D, were also more likely to demonstrate osteosarcopenic obesity (OR = 1.99, 95% CI: 1.30, 3.05).

CONCLUSIONS

A high serum vitamin D level in mid- and late-life was associated with reduced odds of multiple adverse body composition, especially osteosarcopenic obesity, suggesting potential health benefits of maintaining adequate levels of vitamin D.

Association of osteoglycin and FAM5C with bone turnover markers, bone mineral density, and vertebral fractures in postmenopausal women with type 2 diabetes mellitus

OBJECTIVE

Accumulating evidence suggests a reciprocal relationship between muscle and bone. Previous in vitro studies showed that the muscle-derived factors, osteoglycin (OGN) and family with sequence similarity 5, member C (FAM5C), regulate osteoblastic differentiation. However, there are no reports investigating the association between circulating OGN and FAM5C and bone metabolism in humans.

DESIGN

We conducted a cross-sectional study and investigated the association of serum OGN and FAM5C levels and muscle mass examined by whole-body dual-energy x-ray absorptiometry with bone mineral density (BMD), bone turnover markers, and the presence of vertebral fractures (VFs) in 156 postmenopausal women with type 2 diabetes mellitus (T2DM).

RESULTS

Multiple regression analysis adjusted for age, duration of T2DM, body mass index, serum creatinine, and log(hemoglobin A1c) showed that log(OGN) was negatively associated with BMD at the femoral neck (β=-0.17, p=0.014). Serum OGN levels were higher in subjects with VFs than in those without VFs [mean±standard deviation (SD): 100.2±84.7 vs. 74.4±31.7pg/mL, p=0.013]. Moreover, logistic regression analysis adjusted for the confounding factors described above showed that the serum OGN level was positively associated with the presence of VFs (odds ratio=1.84, 95% confidence interval=1.03-3.29 per SD increase, p=0.039). In contrast, neither the serum FAM5C level nor muscle mass indices were associated with bone turnover markers and the presence of VFs.

CONCLUSIONS

The present study showed for the first time that higher serum OGN levels were associated with decreased BMD and increased risk of vertebral fractures in postmenopausal women with T2DM.

Reduced muscle mass and accumulation of visceral fat are independently associated with increased arterial stiffness in postmenopausal women with type 2 diabetes mellitus

BACKGROUND

Several studies showed that sarcopenia and visceral obesity are associated with arterial stiffness. Thus, their coexistence may be a crucial risk factor of arteriosclerosis. However, little is known about the cross relationships among muscle mass, visceral fat mass, and arterial stiffness in type 2 diabetes mellitus (T2DM).

METHODS

We recruited 97 postmenopausal women with T2DM and examine the association of muscle mass and visceral fat mass with brachial-ankle pulse wave velocity (baPWV). Relative skeletal muscle mass index (RSMI) and %trunk fat were evaluated by whole body dual-energy X-ray absorptiometry. Subcutaneous and visceral fat areas were measured by computed tomography.

RESULTS

Multiple regression analyses adjusted for age, duration of T2DM, systolic blood pressure, body mass index, HbA1c, serum creatinine, low-density lipoprotein-cholesterol, uric acid, and the usage of anti-hypertensive drug showed that RSMI was negatively associated with baPWV (β=-0.40, p=0.027), while %trunk fat and visceral fat area were positively associated with it (β=0.29, p=0.004 and β=0.51, p=0.001, respectively). Moreover, after additional adjustment for RSMI, %trunk fat and visceral fat area were positively associated with baPWV (β=0.26, p=0.010 and β=0.46, p=0.003, respectively) although the association between RSMI and baPWV became marginal after additional adjustment for %trunk fat or visceral fat area (β=-0.30, p=0.146 and β=-0.30, p=0.085, respectively).

CONCLUSIONS

Reduced muscle mass and increased visceral fat are independently associated with increased arterial stiffness in postmenopausal women with T2DM.

Effects of myokines on bone

The links between muscle and bone have been recently examined because of the increasing number of patients with osteoporosis and sarcopenia. Myokines are skeletal muscle-derived humoral cytokines and growth factors, which exert physiological and pathological functions in various distant organs, including the regulation of glucose, energy and bone metabolism. Myostatin is a crucial myokine, the expression of which is mainly limited to muscle tissues. The inhibition of myostatin signaling increases bone remodeling, bone mass and muscle mass, and it may provide a target for the treatment of both sarcopenia and osteoporosis. As myostatin is involved in osteoclast formation and bone destruction in rheumatoid arthritis, myostatin may be a target myokine for the treatment of accelerated bone resorption and joint destruction in rheumatoid arthritis. Numerous other myokines, including transforming growth factor-β, follistatin, insulin-like growth factor-I, fibroblast growth factor-2, osteoglycin, FAM5C, irisin, interleukin (IL)-6, leukemia inhibitory factor, IL-7, IL-15, monocyte chemoattractant protein-1, ciliary neurotrophic factor, osteonectin and matrix metalloproteinase 2, also affect bone cells in various manners. However, the effects of myokines on bone metabolism are largely unknown. Further research is expected to clarify the interaction between muscle and bone, which may lead to greater diagnosis and the development of the treatment for muscle and bone disorders, such as osteoporosis and sarcopenia.

Vitamin D deficiency aggravates diabetes-induced muscle wasting in female mice

We recently reported that vitamin D deficiency aggravates diabetic bone loss in mice. Although vitamin D affects both muscle and bone, the role of the vitamin D state in diabetic muscle loss and muscle-bone relationships remains unclear. In the present study, we examined the effects of vitamin D deficiency on muscle mass, muscle differentiation and muscle-derived humoral factors linking muscle to bone in diabetic female mice. Diabetes was induced in mice by streptozotocin (STZ) injection after feeding with a normal or vitamin D-deficient diet for 6 weeks. Quantitative computed tomography analysis showed that tibial muscle mass was significantly decreased in diabetic mice compared with control mice 4 weeks after induction of diabetes. Vitamin D deficiency accelerated muscle loss in diabetic mice. Vitamin D deficiency augmented the decreases in Pax7 mRNA levels and the increases in muscle RING-Finger Protein-1 and atrogin-1 mRNA levels induced by diabetes in the gastrocnemius muscle of mice. Moreover, vitamin D deficiency decreased the mRNA levels of insulin-like growth factor-1, fibroblast growth factor-2 and osteoglycin in muscle of diabetic mice. In conclusion, we demonstrated that vitamin D deficiency aggravates muscle loss induced by diabetes in female mice. Vitamin D may exert significant effects on the maintenance of the musculoskeletal system partly through the muscle-bone relationships in diabetic state.

The diverse functions of osteoglycin: a deceitful dwarf, or a master regulator of disease?

Small leucine-rich proteoglycans are emerging as important regulatory proteins within the extracellular matrix, where they exert both structural and nonstructural functions and hence are modulators of numerous biological processes, such as inflammation, fibrosis, and cell proliferation. One proteoglycan in particular, osteoglycin (OGN), also known as mimecan, shows great structural and functional diversity in normal physiology and in disease states, therefore making it a very interesting candidate for the development of novel therapeutic strategies. Unfortunately, the literature on OGN is confusing, as it has different names, and different transcript and protein variants have been identified. This review will give a clear overview of the different structures and functions of OGN that have been identified to date, portray its central role in pathophysiology, and highlight the importance of posttranslational processing, such as glycosylation, for the diversity of its functions.-Deckx, S., Heymans, S., Papageorgiou, A.-P. The diverse functions of osteoglycin: a deceitful dwarf, or a master regulator of disease?

Effects of eldecalcitol on bone and skeletal muscles in glucocorticoid-treated rats

Glucocorticoids cause secondary osteoporosis and myopathy, characterized by type II muscle fiber atrophy. We examined whether a new vitamin D3 analogue, eldecalcitol, could inhibit glucocorticoid-induced osteopenia or myopathy in rats, and also determined the effects of prednisolone (PSL) and/or eldecalcitol on muscle-related gene expression. Six-month-old female Wistar rats were randomized into four groups: PSL group (10 mg/kg PSL); E group (0.05 µg/kg eldecalcitol); PSL + E group; and control group. PSL, eldecalcitol, and vehicles were administered daily for 2 or 4 weeks. Right calf muscle strength, muscle fatigue, cross-sectional areas (CSAs) of left tibialis anterior muscle fibers, and bone mineral density (BMD) were measured following administration. Pax7, MyoD, and myogenin mRNA levels in gastrocnemius muscles were also determined. Muscle strength was significantly higher in the PSL + E group than in the PSL group (p < 0.05) after 4 weeks, but not after 2 weeks. No significant difference in muscle fatigue was seen between groups at 2 or 4 weeks. CSAs of type II muscle fibers were significantly larger in the E group and the PSL + E group than in the PSL group at 4 weeks (p = 0.0093, p = 0.0443, respectively). Eldecalcitol treatment for 4 weeks maintained the same BMD as the PSL + E group. After 2 weeks, but not 4 weeks, eldecalcitol treatment significantly increased Pax7 and myogenin mRNA expression in gastrocnemius muscle, and PSL also stimulated myogenin expression. Eldecalcitol appears to increase muscle volume and to protect against femur BMD loss in PSL-administered rats, and it may also stimulate myoblast differentiation into early myotubes.

Evidence for Vitamin D Receptor Expression and Direct Effects of 1α,25(OH)2D3 in Human Skeletal Muscle Precursor Cells

Presence of the vitamin D receptor and direct effects of vitamin D on the proliferation and differentiation of muscle precursor cells have been demonstrated in animal models. However, the effects and mechanisms of vitamin D actions in human skeletal muscle, and the presence of the vitamin D receptor in human adult skeletal muscle, remain to be established. Here, we investigated the role of vitamin D in human muscle cells at various stages of differentiation. We demonstrate that the components of the vitamin D-endocrine system are readily detected in human muscle precursor cells but are low to nondetectable in adult skeletal muscle and that human muscle cells lack the ability to convert the inactive vitamin D-metabolite 25-hydroxy-vitamin D3 to the active 1α,25-dihydroxy-vitamin D3 (1α,25(OH)2D3). In addition, we show that 1α,25(OH)2D3 inhibits myoblast proliferation and differentiation by altering the expression of cell cycle regulators and myogenic regulatory factors, with associated changes in forkhead box O3 and Notch signaling pathways. The present data add novel information regarding the direct effects of vitamin D in human skeletal muscle and provide functional and mechanistic insight to the regulation of myoblast cell fate decisions by 1α,25(OH)2D3.

Osteoporosis and sarcopenia: two diseases or one?

PURPOSE OF REVIEW

This article reviews recently published evidence for common pathways explaining bone and muscle wasting in normal ageing and pathological conditions.

RECENT FINDINGS

Numerous studies support the concept of a bone-muscle unit, where constant cross-talking between the two tissues takes place, involving molecules released by the skeletal muscle secretome, which affects bone, and osteokines secreted by the osteoblasts and osteocytes, which, in turn, impact muscle cells.

SUMMARY

New chemical entities aiming at concomitantly treating osteoporosis and sarcopenia could be developed by targeting pathways that centrally regulate bone and muscle or emerging pathways that facilitate the communication between the two tissues.

Bone muscle interactions and vitamin D

Beyond the established roles of vitamin D in bone and mineral homeostasis, we are becoming increasingly aware of its diverse effects in skeletal muscle. Subjects with severe vitamin D deficiency or mutations of the vitamin D receptor develop generalized atrophy of muscle and bone, suggesting coordinated effects of vitamin D in musculoskeletal physiology. At a mechanistic level, vitamin D exerts wide-ranging effects in muscle and bone calcium handling, differentiation and development. Vitamin D also modulates muscle and bone-derived hormones, facilitating cross-talk between these tissues. In this review, we discuss emerging evidence that vitamin D regulates bone and muscle in a direct, integrated fashion, positioning the vitamin D pathway as a potential therapeutic target for musculoskeletal diseases. This article is part of a Special Issue entitled "Muscle Bone Interactions".

Cachexia and sarcopenia: mechanisms and potential targets for intervention

Cachexia is a multi-organ syndrome associated with cancer and other chronic diseases, characterized by body weight loss, muscle and adipose tissue wasting and inflammation, being often associated with anorexia. Skeletal muscle tissue represents more than 40% of body weight and seems to be one of the main tissues involved in the wasting that occurs during cachexia. Sarcopenia is a degenerative loss of skeletal muscle mass, quality, and strength associated with healthy ageing. The molecular mechanisms behind cachexia and sarcopenia share some common trends. Muscle wasting is the result of a combination of an imbalance between synthetic and degradative protein pathways together with increased myocyte apoptosis and decreased regenerative capacity. Oxidative pathways are also altered in skeletal muscle during muscle wasting and this seems to be a consequence of mitochondrial abnormalities that include altered morphology and function, decreased ATP synthesis and uncoupling. The aim of the present review is to analyse common molecular pathways between cachexia and sarcopenia in order to put forward potential targets for intervention.