The role of leptin in regulating bone metabolism

Novel estrogen receptor-α gene inactivating missense variant in a woman: Therapeutic challenge and long-term follow-up data

BACKGROUND

Rare mutations of the ESR1 gene, encoding the estrogen receptor alpha (ERα), have been shown to cause estrogen resistance in humans. Phenotypic features include impaired maturation of epiphyseal cartilage, osteoporosis, and infertility. Clinical phenotype is not well described and the available data reflect inconsistency. To date, there are no effective therapeutic options.

METHOD

This retrospective study provides a detailed description of bone and metabolic phenotype and 8-year follow-up data of a female with a novel p.Met543Thr missense variant in the homozygous state, localized in the ligand-binding domain.

RESULTS

The patient, first seen at the age of 21.3 years, presented with a tall stature (+2.2 SD), a delayed bone age (13 years). She had no breast development, normal axillary and pubic pilosity and bilateral axillary acanthosis nigricans. The metabolic phenotype included insulin resistance, decreased insulin sensitivity and increased leptinemia. The patient presented a continuous linear growth (height + 3SD at the age of 28.6 years). She had a severe osteoporosis of the lumbar spine (Z-score -3.9) and osteopenia of the femoral neck (Z-score -1.8). Osteoporosis worsened (Z-score -5.6 at the lumbar spine; Z-score -4.4 at the femoral neck) despite successive treatments with ethinyl-estradiol and tamoxifen (selective estrogen modulator). Markers of bone turnover were increased and unresponsive to treatment. Treatment with ethinyl-estradiol improved insulin sensitivity, lowered leptinemia, increased some estrogen-regulated liver proteins and the E2/T ratio.

CONCLUSION

This report brings new insights to the estrogen resistance syndrome and improves our understanding of the skeletal and tissue specific roles of ERα in humans.

Concentration and genetic regulation of sex hormone binding globulin and fracture risk in older women

OBJECTIVE

This study aimed to examine the association between concentrations of sex hormone binding globulin (SHBG) and fracture risk in community-dwelling older women and explore whether this was explained by the genetic regulation of SHBG.

METHODS

This prospective cohort study examined 4871 women aged ≥70 years who were not taking medications influencing SHBG concentrations. A genome-wide association study was undertaken to identify single nucleotide polymorphisms (SNPs) associated with SHBG concentrations. Incident fracture was confirmed by medical imaging and adjudicated by expert review committee.

RESULTS

The median age of participants was 74.0 years. Over 3.9 (standard deviation 1.4) years of follow-up, 484 participants had an incident fracture. There was a linear trend for a positive association between SHBG concentrations and fracture risk (p = 0.001), with the highest SHBG quartile associated with a significantly greater fracture risk compared with the lowest quartile (hazard ratio 1.54, 95% confidence interval 1.16-2.04, p = 0.003), adjusting for age, body mass index, alcohol consumption, smoking, diabetes, impaired renal function, treatment allocation, medications affecting bone and high-density lipoprotein cholesterol. Two independent SNPs were associated with SHBG concentrations, rs10822163 and rs727428, but neither was associated with fracture risk.

CONCLUSION

SHBG concentrations were positively associated with a greater fracture risk in community-dwelling women aged ≥70 years, which was not explained by genetic variants associated with SHBG regulation.

Leptin Levels and Bone Mineral Density: A Friend or a Foe for Bone Loss? A Systematic Review of the Association Between Leptin Levels and Low Bone Mineral Density

The introduction of CFTR modulators in the clinics has improved body mass index in cystic fibrosis (CF) individuals. Leptin is a major regulator of appetite and energy expenditure but is also involved in bone metabolism. Whether circulating leptin levels are associated with low bone mineral density (BMD) and fracture risk in CF remains unknown. Therefore, the present study aims to analyze and integrate the current evidence linking leptin and bone loss in CF. As no scientific evidence was found, we focused on secondary dysregulations of bone loss in CF that may be linked to pathologies that are similar to the various dysregulations and multisystemic manifestations in CF. Studies published from 2001 to 2022 were identified through the PubMed, Scopus, and Web of Science databases, and screening was performed following the PRISMA guidelines. The included studies were assessed using a quality checklist. From the 774 records identified, 28 studies met the inclusion criteria. Although no evidence has been found directly related to bone loss in CF individuals, some studies revealed a positive association between leptin levels and BMD, while others found an inverse association. Current evidence suggests that for circulating leptin levels to be a predictive biomarker of bone health, further research will be needed to reveal the direct and indirect mechanisms behind leptin and bone loss and to understand whether changes in leptin levels correlate with changes in BMD. Of note, studies with CF people would be of high importance to understand the role of leptin in CF-related bone disease.

The "Burden" of Childhood Obesity on Bone Health: A Look at Prevention and Treatment

Childhood obesity represents a multifaceted challenge to bone health, influenced by a combination of endocrine, metabolic, and mechanical factors. Excess body fat correlates with an increase in bone mineral density (BMD) yet paradoxically elevates fracture risk due to compromised bone quality and increased mechanical loading on atypical sites. Additionally, subjects with syndromic obesity, as well as individuals with atypical nutritional patterns, including those with eating disorders, show bone fragility through unique genetic and hormonal dysregulations. Emerging evidence underscores the adverse effects of new pharmacological treatments for severe obesity on bone health. Novel drugs, such as glucagon-like peptide-1 (GLP-1) receptor agonists, and bariatric surgery demonstrate potential in achieving weight loss, though limited evidence is available regarding their short- and long-term impacts on skeletal health. This review provides a comprehensive analysis of the mechanisms underlying the impact of childhood obesity on bone health. It critically appraises evidence from in vitro studies, animal models, and clinical research in children with exogenous obesity, syndromic obesity, and eating disorders. It also explores the effects of emerging pharmacological and surgical treatments for severe obesity on skeletal integrity, highlights prevention strategies, and identifies research gaps.

Deep learning and genome-wide association meta-analyses of bone marrow adiposity in the UK Biobank

Bone marrow adipose tissue is a distinct adipose subtype comprising more than 10% of fat mass in healthy humans. However, the functions and pathophysiological correlates of this tissue are unclear, and its genetic determinants remain unknown. Here, we use deep learning to measure bone marrow adiposity in the femoral head, total hip, femoral diaphysis, and spine from MRI scans of approximately 47,000 UK Biobank participants, including over 41,000 white and over 6300 non-white participants. We then establish the heritability and genome-wide significant associations for bone marrow adiposity at each site. Our meta-GWAS in the white population finds 67, 147, 134, and 174 independent significant single nucleotide polymorphisms, which map to 54, 90, 43, and 100 genes for the femoral head, total hip, femoral diaphysis, and spine, respectively. Transcriptome-wide association studies, colocalization analyses, and sex-stratified meta-GWASes in the white participants further resolve functional and sex-specific genes associated with bone marrow adiposity at each site. Finally, we perform a multi-ancestry meta-GWAS to identify genes associated with bone marrow adiposity across the different bone regions and across ancestry groups. Our findings provide insights into BMAT formation and function and provide a basis to study the impact of BMAT on human health and disease.

Adipokine dysregulation as an underlying pathology for diffuse ectopic ossification of spinal posterior longitudinal ligament in patients with obesity

BACKGROUND CONTEXT

Growing evidence suggests that obesity is implicated in the progression of heterotopic ossification of the posterior longitudinal ligament of the spine (OPLL), a major cause of myelopathy in Asians. However, it remains unclear whether dysregulation of adipokine production due to fat accumulation contributes to OPLL progression.

PURPOSE

To determine whether adipose-derived biochemical signals are associated with OPLL development or severity.

STUDY DESIGN/SETTING

A nationwide, multicenter, case-control study.

PATIENT SAMPLE

Patients with symptomatic thoracic OPLL (T-OPLL) who received treatment between June 2017 and March 2021 and 111 controls without OPLL.

OUTCOME MEASURES

OPLL severity index based on whole-spine computed tomography.

METHODS

Serum concentrations of adipokines, including leptin (Lep), tumor necrosis factor α (TNFα), and adiponectin (Adpn), as well as the Adpn/Lep ratio-an indicator of adipokine production dysregulation-were compared between the multiple-region OPLL and the single-region OPLL groups. Regression analysis was performed to examine the correlation between adipokine concentrations and OPLL severity index, which was calculated using whole-spine computed tomography images of 77 patients with T-OPLL within 3 years of onset. Using propensity score matching, the adipokine profiles of 59 patients with T-OPLL were compared with those of 59 non-OPLL controls.

RESULTS

Patients with multiple-region OPLL exhibited a higher body mass index (BMI), lower serum Adpn/Lep ratio, and higher serum concentration of osteocalcin (OCN) than those with single-region OPLL. The OPLL severity index exhibited a weak positive correlation with BMI and serum Lep levels and a weak negative correlation with the Adpn/Lep ratio. Serum TNFα and OCN concentrations were significantly higher in patients with T-OPLL than in controls with similar age, sex, and BMI.

CONCLUSIONS

Patients with diffuse OPLL over the entire spine are often metabolically obese with low Adpn/Lep ratios. In patients with OPLL, TNFα and OCN serum concentrations were essentially elevated regardless of obesity, suggesting a potential association with OPLL development. Considering the absence of therapeutic drugs for OPLL, the findings presented herein offer valuable insights that can aid in identifying therapeutic targets and formulating strategies to impede its progression.

Leptin signalling altered in infantile nephropathic cystinosis-related bone disorder

BACKGROUND

The CTNS gene mutation causes infantile nephropathic cystinosis (INC). Patients with INC develop Fanconi syndrome and chronic kidney disease (CKD) with significant bone deformations. C57BL/6 Ctns-/- mice are an animal model for studying INC. Hyperleptinaemia results from the kidney's inability to eliminate the hormone leptin in CKD. Ctns-/- mice have elevated serum leptin concentrations. Leptin regulates bone metabolism through its receptor that signals further via the hypothalamic melanocortin 4 receptor (MC4R). Leptin signalling may affect bone health in Ctns-/- mice.

METHODS

We first defined the time course of bone abnormalities in Ctns-/- mice between 1 and 12 months of age. We used both genetic and pharmacological approaches to investigate leptin signalling in Ctns-/- mice. We generated Ctns-/-Mc4r-/- double knockout mice. Bone phenotype of Ctns-/-Mc4r-/- mice, Ctns-/- mice and wild type (WT) mice at 1, 4, and 9 months of age were compared. We then treated 12-month-old Ctns-/- mice and WT mice with a pegylated leptin receptor antagonist (PLA) (7 mg/kg/day, IP), a MC4R antagonist agouti-related peptide (AgRP) (2 nmol, intracranial infusion on days 0, 3, 6, 9, 12, 15, 18, 21, 24, and 27), or vehicle (normal saline), respectively, for 28 days. Whole-body (BMC/BMD, bone area) and femoral bone phenotype (BMC/BMD, bone area, length and failure load) of mice were measured by DXA and femoral shaft biochemical test. We also measured lean mass content by EchoMRI and muscle function (grip strength and rotarod activity) in mice. Femur protein content of JAK2 and STAT3 was measured by ELISA kits, respectively.

RESULTS

Bone defects are present in Ctns-/- mice throughout its first year of life. The deletion of the Mc4r gene attenuated bone disorder in Ctns-/- mice. Femoral BMD, bone area, length, and strength (failure load) were significantly increased in 9-month-old Ctns-/-Mc4r-/- mice than in age-matched Ctns-/- mice. PLA and AgRP treatment significantly increased femoral bone density (BMC/BMD) and mechanical strength in 12-month-old Ctns-/- mice. We adopted the pair-feeding approach for this study to show that the protective effects of PLA or AgRP on bone phenotype are independent of their potent orexigenic effect. Furthermore, an increase in lean mass and in vivo muscle function (grip strength and rotarod activity) are associated with improvements in bone phenotype (femoral BMC/BMD and mechanical strength) in Ctns-/- mice, suggesting a muscle-bone interplay. Decreased femur protein content of JAK2 and STAT3 was evident in Ctns-/- mice. PLA or AgRP treatment attenuated femur STAT3 content in Ctns-/- mice.

CONCLUSIONS

Our findings suggest a significant role for dysregulated leptin signalling in INC-related bone disorder, either directly or potentially involving a muscle-bone interplay. Leptin signalling blockade may represent a novel approach to treating bone disease as well as muscle wasting in INC.

Evidence from clinical studies of leptin: current and future clinical applications in humans

Leptin has been established as the prototype adipose tissue secreted hormone and as a major regulator of several human physiology functions. Here, we are primarily reviewing the findings from studies in humans involving leptin administration. We are describing the metabolic, endocrine and immunologic effects of leptin replacement in conditions of leptin deficiency, such as short-term fasting in healthy individuals, relative energy deficiency in sports (REDS), congenital leptin deficiency (CLD), generalized (GL) and partial lipodystrophy (PL), HIV-associated lipodystrophy (HIV-L) and of leptin treatment in conditions of leptin excess (common obesity, type 2 diabetes, steatotic liver disease). We are comparing the results with the findings from preclinical models and present the main conclusions regarding the role of leptin in human physiology, pathophysiology and therapeutics. We conclude that, in conditions of energy deficiency, leptin substitution effectively reduces body weight and fat mass through reduction of appetite, it improves hypertriglyceridemia, insulin resistance and hepatic steatosis (especially in GL and PL), it restores neuroendocrine function (especially the gonadotropic axis), it regulates adaptive immune system cell populations and it improves bone health. On the contrary, leptin treatment in conditions of leptin excess, such as common obesity and type 2 diabetes, does not improve any metabolic abnormalities. Strategies to overcome leptin tolerance/resistance in obesity and type 2 diabetes have provided promising results in animal studies, which should though be tested in humans in randomized clinical trials.

The impact of weight loss on fat-free mass, muscle, bone and hematopoiesis health: Implications for emerging pharmacotherapies aiming at fat reduction and lean mass preservation

Similar to bariatric surgery, incretin receptor agonists have revolutionized the treatment of obesity, achieving up to 15-25 % weight loss in many patients, i.e., at a rate approaching that achieved with bariatric surgery. However, over 25 % of total weight lost from both surgery and pharmacotherapy typically comes from fat-free mass, including skeletal muscle mass, which is often overlooked and can impair metabolic health and increase the risk of subsequent sarcopenic obesity. Loss of muscle and bone as well as anemia can compromise physical function, metabolic rate, and overall health, especially in older adults. The myostatin-activin-follistatin-inhibin system, originally implicated in reproductive function and subsequently muscle regulation, appears to be crucial for muscle and bone maintenance during weight loss. Activins and myostatin promote muscle degradation, while follistatins inhibit their activity in states of negative energy balance, thereby preserving lean mass. Novel compounds in the pipeline, such as Bimagrumab, Trevogrumab, and Garetosmab-which inhibit activin and myostatin signaling-have demonstrated promise in preventing muscle loss while promoting fat loss. Either alone or combined with incretin receptor agonists, these medications may enhance fat loss while preserving or even increasing muscle and bone mass, offering a potential solution for improving body composition and metabolic health during significant weight loss. Since this dual therapeutic approach could help address the challenges of muscle and bone loss during weight loss, well-designed studies are needed to optimize these strategies and assess long-term benefits. For the time being, considerations like advanced age and prefrailty may affect the choice of suitable candidates in clinical practice for current and emerging anti-obesity medications due to the associated risk of sarcopenia.

Leptin physiology and pathophysiology in energy homeostasis, immune function, neuroendocrine regulation and bone health

Since its discovery and over the past thirty years, extensive research has significantly expanded our understanding of leptin and its diverse roles in human physiology, pathophysiology and therapeutics. A prototypical adipokine initially identified for its critical function in appetite regulation and energy homeostasis, leptin has been revealed to also exert profound effects on the hypothalamic-pituitary-gonadal, thyroid, adrenal and growth hormone axis, differentially between animals and humans, as well as in regulating immune function. Beyond these roles, leptin plays a pivotal role in significantly affecting bone health by promoting bone formation and regulating bone metabolism both directly and indirectly through its neuroendocrine actions. The diverse actions of leptin are particularly notable in leptin-deficient animal models and in conditions characterized by low circulating leptin levels, such as lipodystrophies and relative energy deficiency. Conversely, the effectiveness of leptin is attenuated in leptin-sufficient states, such as obesity and other high-adiposity conditions associated with hyperleptinemia and leptin tolerance. This review attempts to consolidate 30 years of leptin research with an emphasis on its physiology and pathophysiology in humans, including its promising therapeutic potential. We discuss preclinical and human studies describing the pathophysiology of energy deficiency across organ systems and the significant role of leptin in regulating neuroendocrine, immune, reproductive and bone health. We finally present past proof of concept clinical trials of leptin administration in leptin-deficient subjects that have demonstrated positive neuroendocrine, reproductive, and bone health outcomes, setting the stage for future phase IIb and III randomized clinical trials in these conditions.

Postnatal surge of adipose-secreted leptin is a robust predictor of fat mass trajectory in mice

The transient postnatal increase in circulating leptin levels, known as leptin surge, may increase later susceptibility to diet-induced obesity in rodents. However, the source of leptin during the surge needs to be better characterized, and the long-term effects of leptin are contradictory. Characterization of the interaction of leptin with the genetic background, sex, and other factors is required. Here, we focused on the impact of circulating leptin levels and several related variables, measured in 2- and 4-wk-old i) obesity-prone C57BL/6 (B6) and ii) obesity-resistant A/J mice. In total, 264 mice of both sexes were used. Posttranscriptionally controlled leptin secretion from subcutaneous white adipose tissue, the largest adipose tissue depot in mice pups, was the primary determinant of plasma leptin levels. When the animals were randomly assigned standard chow or high-fat diet (HFD) between 12 and 24 wk of age, the obesogenic effect of HFD feeding was observed in B6 but not A/J mice. Only leptin levels at 2 wk, i.e., close to the maximum in the postnatal leptin surge, correlated with both body weight (BW) trajectory throughout the life and adiposity of the 24-wk-old mice. Leptin surge explained 13 and 7% of the variance in BW and adiposity of B6 mice, and 9 and 35% of the variance in these parameters in A/J mice, with a minor role of sex. Our results prove the positive correlation between the leptin surge and adiposity in adulthood, reflecting the fundamental biological role of leptin. This role could be compromised in subjects with obesity.NEW & NOTEWORTHY The postnatal surge in circulating leptin levels in mice reflects particularly posttranscriptionally controlled release of this hormone from subcutaneous white adipose tissue. Leptinemia in 2-wk-old pups predicts both body weight and adiposity in adult mice fed a high-fat diet. The extent of these effects depends on genetically determined differences in propensity to obesity between C57BL/6 and A/J mice. The leptin effect on adiposity is compromised in the obesity-prone C57BL/6 mice.

Influence of N- and/or P-restriction on bone metabolism in young goats

Ruminants can recycle nitrogen (N) and phosphorus (P), which are essential for vital body processes. Reduced N- and P-intake in ruminants is desirable for economic and ecologic reasons. Simultaneous modulation of mineral homoeostasis and bone metabolism occurs in young goats. This study aimed to investigate potential effects of dietary N- and/or P-restriction on molecular changes in bone metabolism. The twenty-eight young male goats were fed a control diet, an N-reduced diet, a P-reduced diet or a combined N- and P-reduced diet for 6-8 weeks. The N-restricted goats had lower plasma Ca concentration and higher plasma osteocalcin (OC) and CrossLaps concentrations. The P-restricted goats had reduced plasma inorganic phosphate (Pi) concentrations and increased plasma Ca concentrations. Due to the initiation of a signalling pathway that inhibits the fibroblast growth factor 23 (FGF23) expression, this was lower with P-restriction. Consequently, lower Pi concentrations were the main factor influencing the reduction in FGF23. The changes in mineral homoeostasis associated with P-restriction led to a reduction in OC, bone mineral content and mineral density. Simultaneously, bone resorption potentially increased with P-restriction as indicated by an increased receptor activator of NF-κB ligand/osteoprotegerin (OPG) ratio and an increase in OPG mRNA expression. Additionally, the increased mRNA expression of the calcitonin receptor during P-restriction points to a higher number of osteoclasts. This study demonstrates an impairment of bone remodelling processes in young goats by N- or P-restriction. With P-restriction, bone mineralisation rate was potentially reduced and bone quality impaired, while with N-restriction, bone remodelling increased.

A microbiome-directed therapeutic food for children recovering from severe acute malnutrition

Globally, severe acute malnutrition (SAM), defined as a weight-for-length z-score more than three SDs below a reference mean (WLZ < -3), affects 14 million children under 5 years of age. Complete anthropometric recovery after standard, short-term interventions is rare, with children often left with moderate acute malnutrition (MAM; WLZ -2 to -3). We conducted a randomized controlled trial (RCT) involving 12- to 18-month-old Bangladeshi children from urban and rural sites, who, after initial hospital-based treatment for SAM, received a 3-month intervention with a microbiome-directed complementary food (MDCF-2) or a calorically more dense, standard ready-to-use supplementary food (RUSF). The rate of WLZ improvement was significantly greater in MDCF-2-treated children (P = 8.73 × 10-3), similar to our previous RCT of Bangladeshi children with MAM without antecedent SAM (P = 0.032). A correlated meta-analysis of plasma levels of 4520 proteins in both RCTs revealed 215 positively associated with WLZ (largely representing musculoskeletal and central nervous system development) and 44 negatively associated (primarily related to immune activation). Moreover, the positively associated proteins were significantly enriched by MDCF-2 (q = 1.1 × 10-6). Characterizing the abundances of 754 bacterial metagenome-assembled genomes in serially collected fecal samples disclosed the effects of acute rehabilitation for SAM on the microbiome and how, during treatment for MAM, specific strains of Prevotella copri function at the intersection between MDCF-2 glycan metabolism and anthropometric recovery. These results provide a rationale for further testing the generalizability of MDCF efficacy and for identifying biomarkers to define treatment responses.

The association between myasthenia gravis and risk of fracture: a systematic review and meta-analysis

Patients with myasthenia gravis (MG), because of their muscle weakness and exposure to corticosteroids treatment, are generally considered to be at increased risk for osteoporosis or fracture. However, clinical evidence of this issue is lacking. In this review, we systematically searched databases, including Cochrane Library, PubMed, Embase, and Airiti library from inception to the end of November 2023 for cohort studies that compared participants with MG and participants without MG for incidence of osteoporosis or fracture. We used the Newcastle-Ottawa Scale for quality assessment. In total, we included 3 studies with 34,865 participants. The pooled meta-analysis using the random effect model demonstrated no significant difference in risk of fracture in the MG group (odds ratio = 1.52; 95% confidence interval = 0.74 to 3.12; I2 = 93%; between-study variance [τ2] = 0.32) compared with that for the non-MG group. Due to limited studies, we could not perform a quantitative analysis for risk of osteoporosis. In conclusion, we found no robust evidence to support the proposition that patients with MG are at higher risk for fracture than general comparators. The explanations and underlying mechanisms of this finding remain unclear, we therefore conclude that additional studies are warranted.

Relative Energy Deficiency in Sport (REDs): Endocrine Manifestations, Pathophysiology and Treatments

Research on lean, energy-deficient athletic and military cohorts has broadened the concept of the Female Athlete Triad into the Relative Energy Deficiency in Sport (REDs) syndrome. REDs represents a spectrum of abnormalities induced by low energy availability (LEA), which serves as the underlying cause of all symptoms described within the REDs concept, affecting exercising populations of either biological sex. Both short- and long-term LEA, in conjunction with other moderating factors, may produce a multitude of maladaptive changes that impair various physiological systems and adversely affect health, well-being, and sport performance. Consequently, the comprehensive definition of REDs encompasses a broad spectrum of physiological sequelae and adverse clinical outcomes related to LEA, such as neuroendocrine, bone, immune, and hematological effects, ultimately resulting in compromised health and performance. In this review, we discuss the pathophysiology of REDs and associated disorders. We briefly examine current treatment recommendations for REDs, primarily focusing on nonpharmacological, behavioral, and lifestyle modifications that target its underlying cause-energy deficit. We also discuss treatment approaches aimed at managing symptoms, such as menstrual dysfunction and bone stress injuries, and explore potential novel treatments that target the underlying physiology, emphasizing the roles of leptin and the activin-follistatin-inhibin axis, the roles of which remain to be fully elucidated, in the pathophysiology and management of REDs. In the near future, novel therapies leveraging our emerging understanding of molecules and physiological axes underlying energy availability or lack thereof may restore LEA-related abnormalities, thus preventing and/or treating REDs-related health complications, such as stress fractures, and improving performance.

Association Between Osteoporosis and Adiposity Index Reveals Nonlinearity Among Postmenopausal Women and Linearity Among Men Aged over 50 Years

PURPOSE

Previous research shows conflicting views on the relationship between obesity and osteoporosis, partly due to variations in obesity classification and the nonlinear nature of these relationships. This study investigated the association between adiposity indices and osteoporosis, diagnosed using dual-energy X-ray absorptiometry (DXA), employing nonlinear models and offering optimal thresholds to prevent further bone mineral density decline.

METHODS

In 2019, a prospective study enrolled males over 50 years and postmenopausal women. Anthropometric measurements, blood biochemistry, and osteoporosis measured by DXA were collected. Associations between adiposity indices and osteoporosis were analyzed using a generalized additive model and segmented regression model.

RESULTS

The study included 872 women and 1321 men. Indices such as abdominal volume index (AVI), visceral adiposity index (VAI), waist circumference (WC), hip circumference, body mass index (BMI), waist-to-hip ratio, and waist-to-height ratio (WHtR) were inversely associated with osteoporosis. In women, the relationship between the risk of osteoporosis and the adiposity indices was U-shaped, with thresholds of WC = 94 cm, AVI = 17.67 cm2, BMI = 25.74 kg/m2, VAI = 4.29, and WHtR = 0.61, considering changes in bone mineral density. Conversely, men exhibited a linear patterns for the inverse association.

CONCLUSION

The impact of obesity and adiposity on osteoporosis varies significantly between women and men. In postmenopausal women, the relationship is nonlinear (U-shaped), with both very low and very high adiposity linked to higher osteoporosis risk. In men over 50, the relationship is linear, with higher adiposity associated with lower osteoporosis risk. The study suggests that maintaining specific levels of adiposity could help prevent osteoporosis in postmenopausal women.

Nutrient and Hormonal Effects on Long Bone Growth in Healthy and Obese Children: A Literature Review

Longitudinal bone growth is mediated through several mechanisms including macro- and micronutrients, and endocrine and paracrine hormones. These mechanisms can be affected by childhood obesity as excess adiposity may affect signaling pathways, place undue stress on the body, and affect normal physiology. This review describes the physiology of the epiphyseal growth plate, its regulation under healthy weight and obesity parameters, and bone pathology following obesity. A literature review was performed utilizing PubMed, PMC, NIH, and the Cochrane Database of Systematic Reviews pertinent to hormonal and nutritional effects on bone development, child obesity, and pathologic bone development related to weight. The review indicates a complex network of nutrients, hormones, and multi-system interactions mediates long bone growth. As growth of long bones occurs during childhood and the pubertal growth spurt, pediatric bones require adequate levels of minerals, vitamins, amino acids, and a base caloric supply for energy. Recommendations should focus on a nutrient-dense dietary approach rather than restrictive caloric diets to maintain optimal health. In conclusion, childhood obesity has profound multifaceted effects on the developing musculoskeletal system, ultimately causing poor nutritional status during development. Weight loss, under medical supervision, with proper nutritional guidelines, can help counteract the ill effects of childhood obesity.

Biomarkers and Biochemical Indicators to Evaluate Bone Metabolism in Preterm Neonates

The purpose of the present study was to evaluate the concentrations of some bone turnover markers in preterm neonates with uncomplicated clinical course in the first month of life. Samples from 13 preterm neonates were collected at three different times: at birth (T0) from umbilical cord blood (UCB); and at 15 (T1) and 30 (T2) days of life from peripheral blood (PB). The concentrations of calcium (Ca), phosphate (P), total alkaline phosphatase (ALP), Collagen Type 1 Amino-terminal Propeptide (PINP), osteocalcin (OC), Collagen Type 1 Carboxyl-Terminal Telopeptide (CTX) and Leptin were assessed. A statistically significant difference for ALP concentration at birth versus T1 and T2 was found. An evident increase in the median concentrations of CTX, OC and PINP from T0 to T2 were observed. A significant difference was also found for Leptin concentration at T0 compared to T1. In preterm infants, in the absence of acute or chronic medical conditions and without risk factors for metabolic bone disease (MBD) of prematurity, there is a significant increase in bone turnover markers during the first month of life. The knowledge of the variations in these markers in the first weeks of life, integrated by the variations in the biochemical indicators of bone metabolism, could help in recognizing any conditions at risk of developing bone diseases.

Analysis of the relationship between shorter sleep duration and wrist fractures: based on NHANES

BACKGROUND

Wrist fracture is one of the common limb fractures. Its incidence rate increases with age and osteoporosis. Nowadays, Sleep health is increasingly valued, but the relationship between wrist fractures and sleep time is not yet clear.

METHODS

Data in this study were collected and screened from the NHANES from 2005 to 2010 and 2013 to 2014. The variables were extracted from interviews and compared between the wrist fractures and the sleep duration. The data was analyzed by weighted multivariate logistic regression.

RESULTS

After excluding individuals who were not eligible and had invalid data, we finally identified 1835 participants for inclusion in this study. We found a negative association between the sleep duration and the fractured of the wrist (OR = 1.027,95% CI (1.027, 1.028), P < 0.00001).

CONCLUSION

This study demons that the association between the sleep duration and the fractures of the wrist is significant. Our findings provide a better understanding of the relationship between sleep duration and wrist fractures. This study may help us reducing the incidence of wrist fractures in the population based on healthy sleep management in the future, and improve the quality of life of middle-aged and elderly patients. Provide evidence for clinical patients to manage healthy sleep.

Obesity, diabetes and risk of bone fragility: How BMAT behavior is affected by metabolic disturbances and its influence on bone health

PURPOSE

Osteoporosis is a metabolic bone disease characterized by decreased bone strength and mass, which predisposes patients to fractures and is associated with high morbidity and mortality. Like osteoporosis, obesity and diabetes are systemic metabolic diseases associated with modifiable risk factors and lifestyle, and their prevalence is increasing. They are related to decreased quality of life, functional loss and increased mortality, generating high costs for health systems and representing a worldwide public health problem. Growing evidence reinforces the role of bone marrow adipose tissue (BMAT) as an influential factor in the bone microenvironment and systemic metabolism. Given the impact of obesity and diabetes on metabolism and their possible effect on the bone microenvironment, changes in BMAT behavior may explain the risk of developing osteoporosis in the presence of these comorbidities.

METHODS

This study reviewed the scientific literature on the behavior of BMAT in pathological metabolic conditions, such as obesity and diabetes, and its potential involvement in the pathogenesis of bone fragility.

RESULTS

Published data strongly suggest a relationship between increased BMAT adiposity and the risk of bone fragility in the context of obesity and diabetes.

CONCLUSION

By secreting a broad range of factors, BMAT modulates the bone microenvironment and metabolism, ultimately affecting skeletal health. A better understanding of the relationship between BMAT expansion and metabolic disturbances observed in diabetic and obese patients will help to identify regulatory pathways and new targets for the treatment of bone-related diseases, with BMAT as a potential therapeutic target.

Gut-Derived Peptide Hormone Analogues and Potential Treatment of Bone Disorders in Obesity and Diabetes Mellitus

Obesity and diabetes mellitus are prevalent metabolic disorders that have a detrimental impact on overall health. In this regard, there is now a clear link between these metabolic disorders and compromised bone health. Interestingly, both obesity and diabetes lead to elevated risk of bone fracture which is independent of effects on bone mineral density (BMD). In this regard, gastrointestinal (GIT)-derived peptide hormones and their related long-acting analogues, some of which are already clinically approved for diabetes and/or obesity, also seem to possess positive effects on bone remodelling and microarchitecture to reduce bone fracture risk. Specifically, the incretin peptides, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), as well as glucagon-like peptide-2 (GLP-2), exert key direct and/or indirect benefits on bone metabolism. This review aims to provide an initial appraisal of the relationship between obesity, diabetes and bone, with a focus on the positive impact of these GIT-derived peptide hormones for bone health in obesity/diabetes. Brief discussion of related peptides such as parathyroid hormone, leptin, calcitonin and growth hormone is also included. Taken together, drugs engineered to promote GIP, GLP-1 and GLP-2 receptor signalling may have potential to offer therapeutic promise for improving bone health in obesity and diabetes.

Adipokines in atopic dermatitis: the link between obesity and atopic dermatitis

Atopic dermatitis (AD) is a chronic skin condition with intense pruritus, eczema, and dry skin. The recurrent intense pruritus and numerous complications in patients with AD can profoundly affect their quality of life. Obesity is one of its comorbidities that has been confirmed to be the hazard factor of AD and also worsen its severity. Nevertheless, the specific mechanisms that explain the connection between obesity and AD remain incompletely recognized. Recent studies have built hopes on various adipokines to explain this connection. Adipokines, which are disturbed by an obese state, may lead to immune system imbalances in people with AD and promote the development of the disease. This review focuses on the abnormal expression patterns of adipokines in patients with AD and their potential regulatory molecular mechanisms associated with AD. The connection between AD and obesity is elucidated through the involvement of adipokines. This conduces to the in-depth exploration of AD pathogenesis and provides a new perspective to develop therapeutic targets.

Crosstalk Between the Neuroendocrine System and Bone Homeostasis

The homeostasis of bone microenvironment is the foundation of bone health and comprises 2 concerted events: bone formation by osteoblasts and bone resorption by osteoclasts. In the early 21st century, leptin, an adipocytes-derived hormone, was found to affect bone homeostasis through hypothalamic relay and the sympathetic nervous system, involving neurotransmitters like serotonin and norepinephrine. This discovery has provided a new perspective regarding the synergistic effects of endocrine and nervous systems on skeletal homeostasis. Since then, more studies have been conducted, gradually uncovering the complex neuroendocrine regulation underlying bone homeostasis. Intriguingly, bone is also considered as an endocrine organ that can produce regulatory factors that in turn exert effects on neuroendocrine activities. After decades of exploration into bone regulation mechanisms, separate bioactive factors have been extensively investigated, whereas few studies have systematically shown a global view of bone homeostasis regulation. Therefore, we summarized the previously studied regulatory patterns from the nervous system and endocrine system to bone. This review will provide readers with a panoramic view of the intimate relationship between the neuroendocrine system and bone, compensating for the current understanding of the regulation patterns of bone homeostasis, and probably developing new therapeutic strategies for its related disorders.

Interrogating Causal Effects of Body Composition and Puberty-Related Risk Factors on Adolescent Idiopathic Scoliosis: A Two-Sample Mendelian Randomization Study

Adolescent idiopathic scoliosis (AIS) is the most common form of pediatric musculoskeletal disorder. Observational studies have pointed to several risk factors for AIS, but almost no evidence exists to support their causal association with AIS. Here, we applied Mendelian randomization (MR), known to limit bias from confounding and reverse causation, to investigate causal associations between body composition and puberty-related exposures and AIS risk in Europeans and Asians. For our two-sample MR studies, we used single nucleotide polymorphisms (SNPs) associated with body mass index (BMI), waist-hip ratio, lean mass, childhood obesity, bone mineral density (BMD), 25-hydroxyvitamin D (25OHD), age at menarche, and pubertal growth in large European genome-wide association studies (GWAS), and with adult osteoporosis risk and age of menarche in Biobank Japan. We extracted estimates of the aforementioned SNPs on AIS risk from the European or Asian subsets of the largest multiancestry AIS GWAS (N = 7956 cases/88,459 controls). The results of our inverse variance-weighted (IVW) MR estimates suggest no causal association between the aforementioned risk factors and risk of AIS. Pleiotropy-sensitive MR methods yielded similar results. However, restricting our analysis to European females with AIS, we observed a causal association between estimated BMD and the risk of AIS (IVW odds ratio for AIS = 0.1, 95% confidence interval 0.01 to 0.7, p = 0.02 per SD increase in estimated BMD), but this association was no longer significant after adjusting for BMI, body fat mass, and 25OHD and remained significant after adjusting for age at menarche in multivariable MR. In conclusion, we demonstrated a protective causal effect of BMD on AIS risk in females of European ancestry, but this effect was modified by BMI, body fat mass, and 25OHD levels. Future MR studies using larger AIS GWAS are needed to investigate small effects of the aforementioned exposures on AIS. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Reduction of leptin levels during acute exercise is dependent on fasting but not on caloric restriction during chronic exercise: A systematic review and meta-analysis

BACKGROUND

The importance of leptin in controlling body mass has recently gained more attention. Its levels are directly associated with the amount of fat mass, but not necessarily dependent on it. Exercise has great potential in reducing leptin levels, however the response of exercise to this cytokine is still not well understood.

OBJECTIVE

The objective of the review was to analyze the effects of physical exercise on plasma leptin concentration, either acutely (post-exercise/training session) and/or after a training period (short- or long-term), as well as to investigate the existence of possible moderating variables.

METHODS

The studies included in this systematic review were published between 2005 and May 2023. Only peer-reviewed studies, available in English, performed with humans that evaluated the effects of any form of exercise on leptin levels were included. The search was conducted on May 03, 2023, in Embase (Elsevier), MEDLINE via PubMed®, and Web of Science (Core collection). The risk of bias in the included trials was assessed by the Physiotherapy Evidence Database tool, considering 11 questions regarding the methodology of each study with 10 questions being scored. The data (n, mean, and standard deviation) were extracted from included studies to perform random effects meta-analyses using standardized mean difference between the pre- and post-intervention effects.

RESULTS

Twenty-five studies (acute effect: 262 subjects; short- and long-term effect: 377 subjects) were included in this systematic review and meta-analysis. Short- and long-term physical exercise and caloric restriction plus exercise reduce plasma leptin levels, presenting statistically significant differences (p<0.001); as well as acute effect (p = 0.035), however the latter result was influenced by the pre-exercise meal as shown in the subgroup analysis. In this meta-analysis the effect of moderating factors on leptin reduction, not addressed by past reviews, is verified, such as the relationship with caloric restriction, exercise intensity and pre-exercise meal on acute responses.

CONCLUSION

Both acute and chronic exercise reduce leptin levels, yet the acute effect is dependent on the pre-exercise meal. In addition to having a long-term reduction in leptin levels, the minimum amount of weekly exercise to have a significant reduction in plasma leptin is 180 minutes of moderate-intensity exercise and 120 minutes of high-intensity exercise.

Milestones in the journey towards addressing obesity; Past trials and triumphs, recent breakthroughs, and an exciting future in the era of emerging effective medical therapies and integration of effective medical therapies with metabolic surgery

The 21st century is characterized by an increasing incidence and prevalence of obesity and the burden of its associated comorbidities, especially cardiometabolic diseases, which are reaching pandemic proportions. In the late '90s, the "black box" of adipose tissue and energy homeostasis was opened with the discovery of leptin, transforming the adipose tissue from an "inert fat-storage organ" to the largest human endocrine organ and creating the basis on which more intensified research efforts to elucidate the pathogenesis of obesity and develop novel treatments were based upon. Even though leptin was eventually not proven to be the "standalone magic bullet" for the treatment of common/polygenic obesity, it has been successful in the treatment of monogenic obesity syndromes. Additionally, it shifted the paradigm of treating obesity from a condition due to "lack of willpower" to a disease due to distinct underlying biological mechanisms for which specific pharmacotherapies would be needed in addition to lifestyle modification. Subsequently, the melanocortin pathway proved to be an equally valuable pathway for the pharmacotherapy of obesity. Melanocortin receptor agonists have recently been approved for treating certain types of syndromic obesity. Other molecules- such as incretins, implicated in energy and glucose homeostasis- are secreted by the gastrointestinal tract. Glucagon-like peptide 1 (GLP-1) is the most prominent one, with GLP-1 analogs approved for common/polygenic obesity. Unimolecular combinations with other incretins, e.g., GLP-1 with gastric inhibitory polypeptide and/or glucagon, are expected to be approved soon as more effective pharmacotherapies for obesity and its comorbidities. Unimolecular combinations with other compounds and small molecules activating the receptors of these molecules are currently under investigation as promising future pharmacotherapies. Moreover, metabolic and bariatric surgery has also demonstrated impressive results, especially in the case of morbid obesity. Consequently, this broadening therapeutic armamentarium calls for a well-thought-after and well-coordinated multidisciplinary approach, for instance, through cardiometabolic expertise centers, that would ideally address effectively and cost-effectively obesity and its comorbidities, providing tangible benefits to large segments of the population.

Longbie capsules reduce bone loss in the subchondral bone of rats with comorbid osteoporosis and osteoarthritis by regulating metabolite alterations

Background and objective

With the development of global population aging, comorbidity (≥2 diseases) is a common health problem among elderly people. Osteoarthritis (OA) and osteoporosis (OP) are common in elderly individuals. There is a lack of drug therapy for OA and OP comorbidities. The purpose of this study was to explore the efficacy and mechanism of Longbie capsule (LBJN), which contains various plant herbs, in treating OA and OP comorbidities (OA + OP) in rats using metabolomics techniques.

Methods

We created an OA + OP rat model through bilateral oophorectomy combined with meniscus instability surgery. Thirty SD rats were randomly divided into five groups (six in each group), namely, the sham group, OA group, OA + OP group, LBJN low-dose group (0.625 g/kg, OA + OP+LB-L group) and LBJN high-dose group (1.25 g/kg, OA + OP+LB-H group). After 8 weeks of intervention, we used micro-CT to detect bone microstructure status, ELISA to measure bone metabolism indicators, and UPLC-MS technology for metabolomics analysis. Finally, the screened differentially expressed metabolites were subjected to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and functional enrichment analysis.

Results

The micro-CT results showed that LBJN significantly improved the bone mineral density (BMD) and bone quality of subchondral bone in OA + OP rats, and LBJN regulated the expression of bone alkaline phosphatase (BALP), osteoprotegerin (OPG), and tartrate-resistant acid phosphatase (TRACP) in serum to maintain bone metabolism balance. Metabolomics analysis showed that the metabolic trajectory of OA + OP rats after intervention in the OA + OP+LB-H group showed significant changes, and 107 potential biomarkers could be identified. Among them, 50 metabolites were upregulated (such as zeranol) and 57 were downregulated (such as vanillactic acid). The KEGG functional enrichment results indicated that the differentially expressed metabolites are mainly involved in amino acid metabolism, lipid metabolism, and carbohydrate metabolism. The KEGG pathway enrichment results indicated that LBJN may exert therapeutic effects on OA + OP rats by regulating the cAMP signaling pathway, and the FoxO signaling pathway.

Conclusion

LBJN can maintain bone metabolism balance by regulating serum lipid metabolism, amino acid metabolism, carbohydrate metabolism, and estrogen, thereby reducing bone loss in subchondral bone, which may be a potential mechanism through which LBJN treats OA + OP.

Bone Involvement in Rheumatoid Arthritis and Spondyloartritis: An Updated Review

Several rheumatologic diseases are primarily distinguished by their involvement of bone tissue, which not only serves as a mere target of the condition but often plays a pivotal role in its pathogenesis. This scenario is particularly prominent in chronic inflammatory arthritis such as rheumatoid arthritis (RA) and spondyloarthritis (SpA). Given the immunological and systemic nature of these diseases, in this review, we report an overview of the pathogenic mechanisms underlying specific bone involvement, focusing on the complex interactions that occur between bone tissue's own cells and the molecular and cellular actors of the immune system, a recent and fascinating field of interest defined as osteoimmunology. Specifically, we comprehensively elaborate on the distinct pathogenic mechanisms of bone erosion seen in both rheumatoid arthritis and spondyloarthritis, as well as the characteristic process of aberrant bone formation observed in spondyloarthritis. Lastly, chronic inflammatory arthritis leads to systemic bone involvement, resulting in systemic bone loss and consequent osteoporosis, along with increased skeletal fragility.

Understanding the Consequences of Fatty Bone and Fatty Muscle: How the Osteosarcopenic Adiposity Phenotype Uncovers the Deterioration of Body Composition

Adiposity is central to aging and several chronic diseases. Adiposity encompasses not just the excess adipose tissue but also body fat redistribution, fat infiltration, hypertrophy of adipocytes, and the shifting of mesenchymal stem cell commitment to adipogenesis. Bone marrow adipose tissue expansion, inflammatory adipokines, and adipocyte-derived extracellular vesicles are central to the development of osteopenic adiposity. Adipose tissue infiltration and local adipogenesis within the muscle are critical in developing sarcopenic adiposity and subsequent poorer functional outcomes. Ultimately, osteosarcopenic adiposity syndrome is the result of all the processes noted above: fat infiltration and adipocyte expansion and redistribution within the bone, muscle, and adipose tissues, resulting in bone loss, muscle mass/strength loss, deteriorated adipose tissue, and subsequent functional decline. Increased fat tissue, typically referred to as obesity and expressed by body mass index (the latter often used inadequately), is now occurring in younger age groups, suggesting people will live longer with the negative effects of adiposity. This review discusses the role of adiposity in the deterioration of bone and muscle, as well as adipose tissue itself. It reveals how considering and including adiposity in the definition and diagnosis of osteopenic adiposity, sarcopenic adiposity, and osteosarcopenic adiposity will help in better understanding the pathophysiology of each and accelerate possible therapies and prevention approaches for both relatively healthy individuals or those with chronic disease.

Interoceptive regulation of skeletal tissue homeostasis and repair

Recent studies have determined that the nervous system can sense and respond to signals from skeletal tissue, a process known as skeletal interoception, which is crucial for maintaining bone homeostasis. The hypothalamus, located in the central nervous system (CNS), plays a key role in processing interoceptive signals and regulating bone homeostasis through the autonomic nervous system, neuropeptide release, and neuroendocrine mechanisms. These mechanisms control the differentiation of mesenchymal stem cells into osteoblasts (OBs), the activation of osteoclasts (OCs), and the functional activities of bone cells. Sensory nerves extensively innervate skeletal tissues, facilitating the transmission of interoceptive signals to the CNS. This review provides a comprehensive overview of current research on the generation and coordination of skeletal interoceptive signals by the CNS to maintain bone homeostasis and their potential role in pathological conditions. The findings expand our understanding of intersystem communication in bone biology and may have implications for developing novel therapeutic strategies for bone diseases.

The multiple regulatory effects of white adipose tissue on bone homeostasis

White adipose tissue (WAT) is not only an energy storage reservoir that is critical in energy homeostasis but is also a highly metabolically active endocrine organ. WAT can secrete a variety of adipocytokines, including leptin (LEP), adiponectin (APN), resistin, visfatin, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and osteopontin (OPN). It can also synthesize and secrete exosomes, which enhance intercellular communication and participate in various physiological processes in the body. It can also synthesize and secrete exosomes to enhance intercellular communication and participate in a variety of physiological processes in the body. The skeleton is an important organ for protecting internal organs. It forms the scaffolding of the body and gives the body its basic form. It drives muscle contraction to produce movement under the regulation of the nervous system. It is also an important hematopoietic organ; and it is regulated by the cytokines secreted by WAT. As research related to the release of adipocytokines from WAT to affect the skeleton continues to progress, an inextricable link between bone lipid regulation has been identified. In this paper, we review the literature to summarize the structure, function and metabolism of WAT, elaborate the specific molecular mechanisms by which WAT-secreted hormones, cytokines and exosomes regulate skeletal cells, provide a theoretical basis for the in-depth study of WAT cross-organ regulation of bone, and provide new ideas for finding new adipose-secreted targeting factors for the treatment of skeletal diseases.

Bones and Hormones: Interaction between Hormones of the Hypothalamus, Pituitary, Adipose Tissue and Bone

The bony skeleton, as a structural foundation for the human body, is essential in providing mechanical function and movement. The human skeleton is a highly specialized and dynamic organ that undergoes continuous remodeling as it adapts to the demands of its environment. Advances in research over the last decade have shone light on the various hormones that influence this process, modulating the metabolism and structural integrity of bone. More recently, novel and non-traditional functions of hypothalamic, pituitary, and adipose hormones and their effects on bone homeostasis have been proposed. This review highlights recent work on physiological bone remodeling and discusses our knowledge, as it currently stands, on the systemic interplay of factors regulating this interaction. In this review, we provide a summary of the literature on the relationship between bone physiology and hormones including kisspeptin, neuropeptide Y, follicle-stimulating hormone (FSH), prolactin (PRL), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), growth hormone (GH), leptin, and adiponectin. The discovery and understanding of this new functionality unveils an entirely new layer of physiologic circuitry.

High prevalence and risk factors for osteoporosis in 1839 patients with systemic sclerosis: a systematic review and meta-analysis

OBJECTIVES

Osteoporosis is prevalent in patients with systemic sclerosis (SSc). Updated evidence is required to complement the previous systematic review on this topic to provide best practices. This systematic review and meta-analysis aimed to quantitatively synthesize data from studies concerning the prevalence and risk factors for osteoporosis among patients with SSc.

METHODS

We searched PubMed, EMBASE, Web of Science, and ScienceDirect databases for potential studies published from inception to May 31, 2022. Eligibility screening, data extraction, and quality assessment of the retrieved articles were conducted independently by two reviewers. Then meta-analyses were performed to determine osteoporosis prevalence and risk factors in patients with SSc. Meta-regression analysis was conducted to explore the sources of heterogeneity.

RESULTS

The pooled prevalence of osteoporosis in patients with SSc was 27% (95% CI, 24-31), with moderate heterogeneity (I² = 61.6%). Meta-regression revealed no significant difference among all variables. And the presence of SSc increased the likelihood of having osteoporosis (OR = 3.05, 95% CI, 2.32-4.01) compared to controls. These significant risk factors for osteoporosis in SSc patients were age > 50 years (OR = 2.94, 95% CI, 1.52-5.68), menopause (OR = 3.90; 95% CI, 1.94-7.84), aging (MD = 8.40; 95% CI,6.10-10.71) and longer disease duration (MD = 4.78; 95% CI,1.83-7.73). However, female (OR = 1.45; 95% CI, 0.75-2.77), pulmonary arterial hypertension (OR = 0.50; 95% CI, 0.17-1.54), and diffuse cutaneous SSc (OR = 1.05; 95% CI, 0.75-1.48) were not significant risk factors for osteoporosis in SSc patients.

CONCLUSIONS

Osteoporosis was highly prevalent in patients with SSc, and the prevalence seemed to be high and similar in many countries. The age > 50 years, menopause, aging, and longer disease duration were identified as risk factors for osteoporosis in patients with SSc.

SUCNR1 signaling in adipocytes controls energy metabolism by modulating circadian clock and leptin expression

Adipose tissue modulates energy homeostasis by secreting leptin, but little is known about the factors governing leptin production. We show that succinate, long perceived as a mediator of immune response and lipolysis, controls leptin expression via its receptor SUCNR1. Adipocyte-specific deletion of Sucnr1 influences metabolic health according to nutritional status. Adipocyte Sucnr1 deficiency impairs leptin response to feeding, whereas oral succinate mimics nutrient-related leptin dynamics via SUCNR1. SUCNR1 activation controls leptin expression via the circadian clock in an AMPK/JNK-C/EBPα-dependent manner. Although the anti-lipolytic role of SUCNR1 prevails in obesity, its function as a regulator of leptin signaling contributes to the metabolically favorable phenotype in adipocyte-specific Sucnr1 knockout mice under standard dietary conditions. Obesity-associated hyperleptinemia in humans is linked to SUCNR1 overexpression in adipocytes, which emerges as the major predictor of adipose tissue leptin expression. Our study establishes the succinate/SUCNR1 axis as a metabolite-sensing pathway mediating nutrient-related leptin dynamics to control whole-body homeostasis.

Body composition assessment in adult females with anorexia nervosa and bulimia nervosa - a cross-sectional study comparing dual-energy X-ray absorptiometry scan and isotopic dilution of deuterium

BACKGROUND

Eating disorders (EDs) compromise individuals' nutritional status, affecting among other organs and systems, bone health.

OBJECTIVE

This study aimed to assess and compare bone mineral density (BMD) from dual-energy x-ray absorptiometry (DXA) scan and deuterium (D₂O) dilution of adult females with anorexia nervosa (AN) and bulimia nervosa (BN).

METHODS

This was a cross-sectional study with 53 female participants (18-49 years) with a diagnosis of AN (N = 25) or BN (N = 28). DXA scan was performed to assess BMD, fat mass, and fat-free mass, and D₂O dilution was used to assess total body water (TBW), fat mass, and fat-free mass. Interviews/questionnaires were used to assess symptoms, illness trajectory, and physical activity. T-test, Chi-squared test, Pearson's linear correlation, linear regressions, and Bland-Altman analyses were performed, with a significance level of 5%.

RESULTS

TBW below the recommended level for adult females (≥ 45%) was more frequent in BN (60%) compared with AN (21%; P = 0.013). FMI (soft tissue only) (t-test P = 0.06), and FFMI (t-test P = 0.08) agreed between DXA scan and D₂O dilution. Only FFMI did not show systematic bias of proportion (β:-0.2, P = 0.177). The diagnosis of BN, binge-eating episodes, and physical activity in AN were associated with the differences in the methods' results. FMI was positively associated with BMD in AN, and both FMI and FFMI were positively associated with BMD in BN.

CONCLUSION

In adult females with EDs, DXA scan and D₂O dilution achieved agreement for FMI and FFMI. Changes in fat mass and fat-free mass are important in understanding the mechanisms behind bone loss in EDs. Protocols for body composition assessment in EDs can help to minimize the effect of the ED diagnosis, ED behaviors (i.e., excessive exercise and purging behaviors) and weight on the accuracy of measurements.

Associations of Three-Dimensional Anthropometric Body Surface Scanning Measurements and Coronary Artery Disease

Background and Objectives: The relationship between three-dimensional (3D) scanning-derived body surface measurements and biomarkers in patients with coronary artery disease (CAD) were assessed. Methods and Methods: The recruitment of 98 patients with CAD confirmed by cardiac catheterization and 98 non-CAD patients were performed between March 2016 and December 2017. A health questionnaire on basic information, life style variables, and past medical and family history was completed. 3D body surface measurements and biomarkers were obtained. Differences between the two groups were assessed and multivariable analysis performed. Results: It was found that chest width (odds ratio [OR] 0.761, 95% confidence interval [CI] = 0.586-0.987, p = 0.0399), right arm length (OR 0.743, 95% CI = 0.632-0.875, p = 0.0004), waist circumference (OR 1.119, 95% CI = 1.035-1.21, p = 0.0048), leptin (OR 1.443, 95% CI = 1.184-1.76, p = 0.0003), adiponectin (OR 0.978, 95% CI = 0.963-0.994, p = 0.006), and interleukin 6 (OR 1.181, 95% CI = 1.021-1.366, p = 0.0254) were significantly associated with CAD. The combination of biomarker scores and body measurement scores had the greatest area under the curve and best association with CAD (area under the curve of 0.8049 and 95% CI = 0.7440-0.8657). Conclusions: Our study suggests that 3D derived body surface measurements in combination with leptin, adiponectin, and interleukin 6 levels may direct us to those at risk of CAD, allowing a non-invasive approach to identifying high-risk patients.

The relationship between adipokine levels and bone mass-A systematic review

INTRODUCTION

Adipose tissue is the source of a broad array of signalling molecules (adipokines), which mediate interorgan communication and regulate metabolic homeostasis. Alterations in adipokine levels have been causally implicated in various metabolic disorders, including changes in bone mass. Osteoporosis is the commonest progressive metabolic bone disease, characterized by elevated risk of fragility fractures as a result of a reduced bone mass and microarchitectural deterioration. The effects of different adipokines on bone mass have been studied in an attempt to identify novel modulators of bone mass or diagnostic biomarkers of osteoporosis.

METHODS

In this review, we sought to aggregate and assess evidence from independent studies that quantify specific adipokines and their effect on bone mineral density (BMD).

RESULTS

A literature search identified 57 articles that explored associations between different adipokines and BMD. Adiponectin and leptin were the most frequently studied adipokines, with most studies demonstrating that adiponectin levels are associated with decreased BMD at the lumbar spine and femoral neck. Conversely, leptin levels are associated with increased BMD at these sites. However, extensive heterogeneity with regards to sample size, characteristics of study subjects, ethnicity, as well as direction and magnitude of effect at specific skeletal anatomical sites was identified. The broad degree of conflicting findings reported in this study can be attributed several factors. These include differences in study design and ascertainment criteria, the analytic challenges of quantifying specific adipokines and their isoforms, pre-analytical variables (in particular patient preparation) and confounding effects of co-existing disease.

CONCLUSIONS

This review highlights the biological relevance of adipokines in bone metabolism and reinforces the need for longitudinal research to elucidate the causal relationship of adipokines on bone mass.

Cellular and Molecular Mechanisms Associating Obesity to Bone Loss

Obesity is an alarming disease that favors the upset of other illnesses and enhances mortality. It is spreading fast worldwide may affect more than 1 billion people by 2030. The imbalance between excessive food ingestion and less energy expenditure leads to pathological adipose tissue expansion, characterized by increased production of proinflammatory mediators with harmful interferences in the whole organism. Bone tissue is one of those target tissues in obesity. Bone is a mineralized connective tissue that is constantly renewed to maintain its mechanical properties. Osteoblasts are responsible for extracellular matrix synthesis, while osteoclasts resorb damaged bone, and the osteocytes have a regulatory role in this process, releasing growth factors and other proteins. A balanced activity among these actors is necessary for healthy bone remodeling. In obesity, several mechanisms may trigger incorrect remodeling, increasing bone resorption to the detriment of bone formation rates. Thus, excessive weight gain may represent higher bone fragility and fracture risk. This review highlights recent insights on the central mechanisms related to obesity-associated abnormal bone. Publications from the last ten years have shown that the main molecular mechanisms associated with obesity and bone loss involve: proinflammatory adipokines and osteokines production, oxidative stress, non-coding RNA interference, insulin resistance, and changes in gut microbiota. The data collection unveils new targets for prevention and putative therapeutic tools against unbalancing bone metabolism during obesity.

Contributors to impaired bone health in type 2 diabetes

Type 2 diabetes (T2D) is associated with numerous complications, including increased risk of fragility fractures, despite seemingly protective factors [e.g., normal bone mineral density and increased body mass index(BMI)]. However, fracture risk in T2D is underestimated by current fracture risk calculators. Importantly, post-fracture mortality is worse in T2D following any fracture, highlighting the importance of identifying high-risk patients that may benefit from targeted management. Several diabetes-related factors are associated with increased fracture risk, including exogenous insulin therapy, vascular complications, and poor glycaemic control, although detailed comprehensive studies to identify the independent contributions of these factors are lacking. The underlying pathophysiological mechanisms are complex and multifactorial, with different factors contributing during the course of T2D disease. These include obesity, hyperinsulinaemia, hyperglycaemia, accumulation of advanced glycation end products, and vascular supply affecting bone-cell function and survival and bone-matrix composition. This review summarises the current understanding of the contributors to impaired bone health in T2D, and proposes an updated approach to managing these patients.

Leptin's Immune Action: A Review Beyond Satiety

The adipose tissue is an endocrine organ that secretes adipokines such as leptin, which is one of the most important hormones for controlling satiety, metabolism, and energy homeostasis. This hormone acts in the regulation of innate and adaptive immune responses since immune cells have leptin receptors from which this hormone initiates its biological action. These receptors have been identified in hematopoietic stem cells in the bone marrow and mature immune cells, inducing signaling pathways mediated by JAK/STAT, PI3K, and ERK 1/2. It is known that the bone marrow also contains leptin-producing adipocytes, which are crucial for regulating hematopoiesis through largely unknown mechanisms. Therefore, we have reviewed the roles of leptin inside and outside the bone marrow, going beyond its action in the control of satiety.

Leptin ameliorates Aβ1-42-induced Alzheimer's disease by suppressing inflammation via activating p-Akt signaling pathway

Background

Alzheimer's disease (AD) is characterized by progressive neuronal loss, cognitive disorder, and memory decline. Leptin has been reported to have a neuroprotective effect on neurodegenerative diseases.

Objective

Our aim was to investigate whether intraperitoneal injection of leptin has a neuroprotective effect and to explore its underlying mechanisms in the AD mouse model.

Methods

Aβ1-42 was injected into male C57BL/6J mice to construct an AD mouse model, and leptin was injected intraperitoneally to cure AD. The Morris water maze test was used to investigate spatial learning ability. Neuronal loss was tested by tyrosine hydroxylase expression in the hippocampus, and terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling assay was applied to detect neuronal apoptosis. Pro-inflammatory cytokine levels were monitored by RT-PCR and western blotting was selected to explore which signaling pathway leptin acted on.

Results

Leptin ameliorated spatial learning impairment, restored neuronal loss and apoptosis, and inhibited pro-inflammatory cytokine expression by activating the p-Akt signaling pathway in Aβ1-42-induced AD mice.

Conclusion

Leptin ameliorates Aβ1-42-induced AD by suppressing inflammation via activating the p-Akt signaling pathway.

Depletion of Zinc Causes Osteoblast Apoptosis with Elevation of Leptin Secretion and Phosphorylation of JAK2/STAT3

Zinc (Zn) has been reported to mediate leptin secretion, and thus leptin can be an important candidate molecule linking Zn with bone formation. The present study investigated whether zinc deficiency induces leptin secretion by activating a JAK2/STAT3 signaling pathway and leads to osteoblastic apoptosis. MC3T3-E1 cells were incubated for 24 h in normal osteogenic differentiation medium (OSM) or OSM treated with either 1 μM (Low Zn) or 15 μM (High Zn) of ZnCl₂ containing 5 μM TPEN (Zn chelator). Our results demonstrated that low Zn stimulated extracellular leptin secretion and increased mRNA and protein expression of leptin in osteoblastic MC3T3-E1 cells. The OB-Rb (long isoform of leptin receptor) expressions were also elevated in osteoblasts under depletion of Zn. Leptin-signaling proteins, JAK2 and p-JAK2 in the cytosol of low Zn osteoblast conveyed leptin signaling, which ultimately induced higher p-STAT3 expression in the nucleus. Apoptotic effects of JAK2/STAT3 pathway were shown by increased caspase-3 in low Zn osteoblasts as well as apoptotic morphological features observed by TEM. Together, these data suggest that low Zn modulates leptin secretion by activating JAK2/STAT3 signaling pathway and induces apoptosis of osteoblastic MC3T3-E1 cells.

Obesity and Risk for Lymphoma: Possible Role of Leptin

Obesity, which is considered a pandemic due to its high prevalence, is a risk factor for many types of cancers, including lymphoma, through a variety of mechanisms by promoting an inflammatory state. Specifically, over the last few decades, obesity has been suggested not only to increase the risk of lymphoma but also to be associated with poor clinical outcomes and worse responses to different treatments for those diseases. Within the extensive range of proinflammatory mediators that adipose tissue releases, leptin has been demonstrated to be a key adipokine due to its pleotropic effects in many physiological systems and diseases. In this sense, different studies have analyzed leptin levels and leptin/leptin receptor expressions as a probable bridge between obesity and lymphomas. Since both obesity and lymphomas are prevalent pathophysiological conditions worldwide and their incidences have increased over the last few years, here we review the possible role of leptin as a promising proinflammatory mediator promoting lymphomas.

Insulin and body mass index decrease serum soluble leptin receptor levels in humans

PURPOSE

Test how serum soluble leptin receptor (sOb-R) is influenced by glucose, insulin, body fat, body mass index (BMI), food intake and physical activity.

METHODS

We performed an epidemiological triangulation combining cross-sectional, interventional and Mendelian randomization study designs. In five independent clinical studies (n = 24-823), sOb-R was quantified in serum or plasma by commercial ELISA kits using monoclonal antibodies. We performed mixed models regression and two-sample Mendelian randomization.

RESULTS

In pooled, cross-sectional data, levelling on study, sOb-R associated inversely with body mass index (BMI) (beta [95% CI] -0.19 [-0.21 to -0.17]), body fat (-0.12 [-0.14 to -0.10) and fasting C-peptide (-2.04 [-2.46 to -1.62]). sOb-R decreased in response to acute hyperinsulinaemia during euglycaemic glucose clamp in two independent clinical studies (-0.5 [-0.7 to -0.4] and -0.5 [-0.6 to -0.3]), and immediately increased in response to intensive exercise (0.18 [0.04 to 0.31]) and food intake (0.20 [0.06 to 0.34]). In two-sample Mendelian randomization, higher fasting insulin and higher BMI were causally linked to lower sOb-R levels (inverse variance weighted, -1.72 [-2.86 to -0.58], and -0.20 [-0.36 to -0.04], respectively). The relationship between hyperglycaemia and sOb-R were inconsistent in cross-sectional studies, non-significant in intervention studies, and two-sample Mendelian randomization suggested no causal effect of fasting glucose on sOb-R.

MAIN CONCLUSION

Both BMI and insulin causally decreased serum sOb-R levels. Conversely, intensive exercise and food intake acutely increased sOb-R. Our results suggest that sOb-R is involved in short-term regulation of leptin signalling, either directly or indirectly, and that hyperinsulinaemia may reduce leptin signalling.

Renal osteodystrophy: A historical review of its origins and conceptual evolution

Long considered an inert supporting framework, bone studies went neglected until the 17th century when they began as descriptive microscopic studies of structure which over time progressed into that of chemistry and physiology. It was in the mid-19th century that studies evolved into an inquisitive discipline which matured into the experimental investigation of bone in health and disease in the 20th century, and ultimately that of molecular studies now deciphering the genetic language of bone biology. These fundamental studies were catalyzed by increasing clinical interest in bone disease. The first bone disease to be identified was rickets in 1645. Its subsequent connection to albuminuric patients reported in 1883 later became renal osteodystrophy in 1942, launching studies that elucidated the functions of vitamin D and parathyroid hormone and their role in the altered calcium and phosphate metabolism of the disease. Studies in osteoporosis and renal osteodystrophy have driven most recent progress benefitting from technological advances in imaging and the precision of evaluating bone turnover, mineralization, and volume. This review exposes the progress of bone biology from a passive support structure to a dynamically regulated organ with vital homeostatic functions whose understanding has undergone more revisions and paradigm shifts than that of any other organ.

Differential impact of body mass index and leptin on baseline and longitudinal positron emission tomography measurements of the cerebral metabolic rate for glucose in amnestic mild cognitive impairment

Introduction

Several studies have suggested that greater adiposity in older adults is associated with a lower risk of Alzheimer's disease (AD) related cognitive decline, some investigators have postulated that this association may be due to the protective effects of the adipose tissue-derived hormone leptin. In this study we sought to demonstrate that higher body mass indices (BMIs) are associated with greater baseline FDG PET measurements of the regional cerebral metabolic rate for glucose (rCMRgl), a marker of local neuronal activity, slower rCMRgl declines in research participants with amnestic mild cognitive impairment (aMCI). We then sought to clarify the extent to which those relationships are attributable to cerebrospinal fluid (CSF) or plasma leptin concentrations.

Materials and methods

We used baseline PET images from 716 73 ± 8 years-old aMCI participants from the AD Neuroimaging Initiative (ADNI) of whom 453 had follow up images (≥6 months; mean follow up time 3.3 years). For the leptin analyses, we used baseline CSF samples from 81 of the participants and plasma samples from 212 of the participants.

Results

As predicted, higher baseline BMI was associated with greater baseline CMRgl measurements and slower declines within brain regions preferentially affected by AD. In contrast and independently of BMI, CSF, and plasma leptin concentrations were mainly related to less baseline CMRgl within mesocorticolimbic brain regions implicated in energy homeostasis.

Discussion

While higher BMIs are associated with greater baseline CMRgl and slower declines in persons with aMCI, these associations appear not to be primarily attributable to leptin concentrations.

Associations between bone mineral density, body composition and amenorrhoea in females with eating disorders: a systematic review and meta-analysis

BACKGROUND

Lower bone mineral density (BMD) increases the risk of osteoporosis in individuals with eating disorders (EDs), particularly women with anorexia nervosa (AN), making them susceptible to pain and fractures throughout adulthood. In AN, low weight, hypothalamic amenorrhoea, and longer illness duration are established risk factors for low BMD, and in people with other EDs a history of AN seems to be an important risk factor for low BMD.

PURPOSE

To conduct a systematic review and meta-analysis of BMD in individuals with EDs, including AN, bulimia nervosa (BN), binge-eating disorder (BED) and other specified feeding or eating disorders (OSFED) compared to healthy controls (HC).

METHODS

Following PRISMA guidelines, electronic databases were reviewed and supplemented with a literature search until 2/2022 of publications measuring BMD (dual-energy X-ray absorptiometry or dual photon absorptiometry) in females with any current ED diagnosis and a HC group. Primary outcomes were spine, hip, femur and total body BMD. Explanatory variables were fat mass, lean mass and ED clinical characteristics (age, illness duration, body mass index (BMI), amenorrhoea occurrence and duration, and oral contraceptives use).

RESULTS

Forty-three studies were identified (N = 4163 women, mean age 23.4 years, min: 14.0, max: 37.4). No study with individuals with BED met the inclusion criteria. BMD in individuals with AN (total body, spine, hip, and femur), with BN (total body and spine) and with OSFED (spine) was lower than in HC. Meta-regression analyses of women with any ED (AN, BN or OSFED) (N = 2058) showed low BMI, low fat mass, low lean mass and being amenorrhoeic significantly associated with lower total body and spine BMD. In AN, only low fat mass was significantly associated with low total body BMD.

CONCLUSION

Predictors of low BMD were low BMI, low fat mass, low lean mass and amenorrhoea, but not age or illness duration. In people with EDs, body composition measurement and menstrual status, in addition to BMI, are likely to provide a more accurate assessment of individual risk to low BMD and osteoporosis.

Normal bone mineral density and bone microarchitecture in adult males with high and low risk of exercise addiction

Exercise addiction describes a pattern of excessive and obsessive exercise and is associated with hypoleptinemia and low testosterone that may have adverse skeletal effects. We used a validated questionnaire to identify males with high and low risk of exercise addiction. In a cross-sectional design, males (aged 21–49 years) with high (n = 20, exercise addictive) and low risk (n = 20, exercise controls) of exercise addiction had examinations of bone mass, bone microarchitecture, and estimated bone strength performed using dual-energy x-ray absorptiometry of the hip and spine and high-resolution peripheral quantitative computed tomography of the distal radius and tibia. Findings were compared between the groups and to a population-based sample of healthy men aged 20–80 years (n = 236). We found similar hip and spine bone mineral density in exercise addictive and controls. Cortical and trabecular bone microarchitecture and estimated bone strength in radius and tibia did not differ significantly between the groups. Multiple regression analyses adjusting for age, body weight, free testosterone, and hours of weekly training did not alter findings. Also, bone indices from both groups were within 95% prediction bands derived from the population-based sample for the vast majority of indices. Neither group had no associations between circulating leptin or free testosterone and bone outcomes. In conclusion, in a study on younger males, we found no associations between high risk of exercise addiction and various indices of bone mass and bone quality indicative of altered skeletal health.

Amnion and chorion matrix maintain hMSC osteogenic response and enhance immunomodulatory and angiogenic potential in a mineralized collagen scaffold

Craniomaxillofacial (CMF) bone injuries present a major surgical challenge and cannot heal naturally due to their large size and complex topography. We are developing a mineralized collagen scaffold that mimics extracellular matrix (ECM) features of bone. These scaffolds induce in vitro human mesenchymal stem cell (hMSC) osteogenic differentiation and in vivo bone formation without the need for exogenous osteogenic supplements. Here, we seek to enhance pro-regenerative potential via inclusion of placental-derived products in the scaffold architecture. The amnion and chorion membranes are distinct components of the placenta that each have displayed anti-inflammatory, immunomodulatory, and osteogenic properties. While potentially a powerful modification to our mineralized collagen scaffolds, the route of inclusion (matrix-immobilized or soluble) is not well understood. Here we compare the effect of introducing amnion and chorion membrane matrix versus soluble extracts derived from these membranes into the collagen scaffolds on scaffold biophysical features and resultant hMSC osteogenic activity. While inclusion of amnion and chorion matrix into the scaffold microarchitecture during fabrication does not influence their porosity, it does influence compression properties. Incorporating soluble extracts from the amnion membrane into the scaffold post-fabrication induces the highest levels of hMSC metabolic activity and equivalent mineral deposition and elution of the osteoclast inhibitor osteoprotegerin (OPG) compared to the conventional mineralized collagen scaffolds. Mineralized collagen-amnion composite scaffolds elicited enhanced early stage osteogenic gene expression (BGLAP, BMP2), increased immunomodulatory gene expression (CCL2, HGF, and MCSF) and increased angiogenic gene expression (ANGPT1, VEGFA) in hMSCs. Mineralized collagen-chorion composite scaffolds promoted immunomodulatory gene expression in hMSCs (CCL2, HGF, and IL6) while unaffecting osteogenic gene expression. Together, these findings suggest that mineralized collagen scaffolds modified using matrix derived from amnion and chorion membranes represent a promising environment conducive to craniomaxillofacial bone repair.