Normal bone density and trabecular bone score, but high serum sclerostin in congenital generalized lipodystrophy

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.

Sclerostin as a Genetic Determinant of Trabecular Bone Score in Postmenopausal Women: The Bushehr Elderly Health (BEH) Program

Background

Sclerostin, a protein encoded by the SOST gene, is an important genetic risk factor for osteoporosis in postmenopausal women. This study was conducted on the Iranian postmenopausal women, to investigate the association between this gene and the Trabecular Bone Score (TBS) as a novel index used for assessing osteoporosis.

Methods

The present study, conducted in 2024, was performed on 1071 women aged 60 years and older who participated in the Bushehr Elderly Health (BEH) program. The associations between seven independent Single Nucleotide Polymorphisms (SNPs) within the SOST gene and mean TBS of L1 to L4 were examined using the additive, dominant, and recessive models. Genetic risk scores (GRS) were calculated for each postmenopausal woman based on the coefficient regressions derived from the additive and dominant models. The relationship between the GRS quartiles and TBS was evaluated using a linear regression model.

Results

After adjusting for age and Body Mass Index (BMI), the associations between the rs2023794-C and TBS were significant in the additive (β = 0.03, P= 4.7×10-5, PFDR= 0.0003) and dominant (β = 0.032, P= 5×10-5, PFDR= 0.0003) models. The GRS derived from both additive and dominant models were related to TBS (P<0.05). For the additive model GRS, TBS showed an average increase of 0.022 score for the fourth quartile in comparison with the first quartile, adjusted for age, BMI, type 2 diabetes mellitus (T2DM), and smoking status (P=0.001).

Conclusion

SOST gene is associated with TBS and may have implications for personalized medicine. Targeting sclerostin through SOST could offer a therapeutic approach in managing osteoporosis in high-risk postmenopausal women.

Crosstalk between Lipid Metabolism and Bone Homeostasis: Exploring Intricate Signaling Relationships

Bone is a dynamic tissue reshaped by constant bone formation and bone resorption to maintain its function. The skeletal system accounts for approximately 70% of the total volume of the body, and continuous bone remodeling requires quantities of energy and material consumption. Adipose tissue is the main energy storehouse of the body and has a strong adaptive capacity to participate in the regulation of various physiological processes. Considering that obesity and metabolic syndrome have become major public health challenges, while osteoporosis and osteoporotic fractures have become other major health problems in the aging population, it would be interesting to explore these 2 diseases together. Currently, an increasing number of researchers are focusing on the interactions between multiple tissue systems, i.e., multiple organs and tissues that are functionally coordinated together and pathologically pathologically interact with each other in the body. However, there is lack of detailed reviews summarizing the effects of lipid metabolism on bone homeostasis and the interactions between adipose tissue and bone tissue. This review provides a detailed summary of recent advances in understanding how lipid molecules and adipose-derived hormones affect bone homeostasis, how bone tissue, as a metabolic organ, affects lipid metabolism, and how lipid metabolism is regulated by bone-derived cytokines.

Ectopic fat in muscle and poor glycemic control are negatively associated with trabecular bone score in type 2 diabetes

INTRODUCTION

Type 2 Diabetes (T2D) is associated with fractures, despite preserved Bone Mineral Density (BMD). This study aimed to evaluate the relationship between BMD and trabecular bone score (TBS) with the reallocation of fat within muscle in individuals with eutrophy, obesity, and T2D.

METHODS

The subjects were divided into three groups: eutrophic controls paired by age and sex with the T2D group (n = 23), controls diagnosed with obesity paired by age, sex, and body mass index with the T2D group (n = 27), and the T2D group (n = 29). BMD and body fat percentage were determined using dual-energy X-Ray absorptiometry. TBS was determined using TBS iNsight software. Intra and extramyocellular lipids in the soleus were measured using proton magnetic resonance spectroscopy.

RESULTS

TBS was lower in the T2D group than in the other two groups. Glycated hemoglobin (A1c) was negatively associated with TBS. Body fat percentage was negatively associated with TBS and Total Hip (TH) BMD. TH BMD was positively associated with intramuscular lipids. A trend of negative association was observed between intramuscular lipids and TBS.

CONCLUSION

This study showed for the first time that the reallocation of lipids within muscle has a negative association with TBS. Moreover, these results are consistent with previous studies showing a negative association between a parameter related to insulin resistance (intramuscular lipids) and TBS.

Heterogeneity and high prevalence of bone manifestations, and bone mineral density in congenital generalized lipodystrophy subtypes 1 and 2

Introduction

Congenital Generalized Lipodystrophy (CGL) is a rare autosomal recessive disease caused by mutations in genes responsible for the formation and development of adipocytes. Bone abnormalities are described. However, there is a scarcity of data.

Objective

To describe bone characteristics in a large CGL1 and 2 case series.

Methods

Cross-sectional study that assessed bone radiological features of CGL patients of a reference hospital in Fortaleza (CE), Brazil. Patients underwent clinical and bone mineral metabolism evaluation, radiographs of the axial and appendicular skeleton and bone mineral density (BMD) assessment by DEXA (dual energy X-ray absorptiometry).

Results

Nineteen patients were included, fourteen were CGL1 and 5, CGL2. Median age was 20 years (8-42) and 58% were women. Median BMI and percentage of body fat were, respectively, 21 Kg/m² (16-24), and 10.5% (7.6-15). The median leptin concentration was 1 ng/mL (0.1-3.3). Diabetes mellitus and dyslipidemia were present in 79% and 63% of patients, respectively. Median calcium and phosphate were normal in almost all patients (95%). Median parathyroid hormone and 25-OH-vitamin D were 23 pg/mL (7-75) and 28 ng/mL (18-43). Osteolytic lesions, osteosclerosis and pseudo-osteopoikylosis, were present in 74%, 42% and 32% of patients, respectively. Lytic lesions were found predominantly in the extremities of long bones, bilaterally and symmetrically, spine was spared. Osteosclerosis was present in axial and appendicular skeleton. Pseudo-osteopoikilosis was found symmetrically in epiphyses of femur and humerus, in addition to the pelvis. BMD Z-score greater than +2.5 SD was observed in 13 patients (68.4%). BMD was higher in CGL1 compared to CGL2 in lumbar spine and total body in adults. No associations were found between high BMD and HOMA-IR (p=0.686), DM (p=0.750), osteosclerosis (p=0.127) or pseudo-osteopoikilosis (p=0.342), and, between pain and bone lesions. Fractures were found in 3 patients.

Conclusion

Bone manifestations are prevalent, heterogeneous, and silent in CGL1 and CGL2. Osteolytic lesions are the most common, followed by osteosclerosis and pseudo-osteopoikilosis. Bone mass is high in most cases. There was no pain complaint related to bone lesions. Thus, systematic assessment of bone manifestations in CGL is essential. Studies are needed to better understand its pathogenesis and clinical consequences.

Refining Evaluation of Bone Mass and Adipose Distribution in Dunnigan Syndrome

Familial partial lipodystrophies (FPLD) are rare diseases characterized by selective loss of subcutaneous adipose tissue at different sites. This cross-sectional observational study aimed to estimate adipose tissue in the bone marrow (BMAT), intra (IMCL) and extra-myocyte lipids (EMCL), and define the bone phenotype in the context of FPLD2/Dunnigan syndrome (DS). The subjects comprised 23 controls (C) and 18 DS patients, matched by age, weight and height. Blood samples, dual-energy X-ray absorptiometry for bone mineral density (BMD) and trabecular bone score (TBS) and 1H-spectroscopy using magnetic resonance to estimate BMAT in the lumbar spine, IMCL, EMCL and osteoclastogenesis were assessed. The prevalence of diabetes mellitus was 78% in DS patients. Glucose, HbA1c, triglycerides, insulin and HOMA-IR levels were elevated in DS, whereas HDLc, 25(OH)D, PTH and osteocalcin levels were reduced. BMD was similar between groups at all sites, except 1/3 radius, which was lower in DS group. TBS was reduced in DS. DS presented increased osteoclastogenesis and elevated BMAT, with greater saturation levels and higher IMCL than the C group. HOMA-IR and EMCL were negatively associated with TBS; osteocalcin and EMCL were correlated negatively with BMD. This study contributes to refining the estimation of adipose tissue in DS by showing increased adiposity in the lumbar spine and muscle tissue. DXA detected lower TBS and BMD in the 1/3 radius, suggesting impairment in bone quality and that bone mass is mainly affected in the cortical bone.

Relationships between sclerostin and morphometric vertebral fractures, bone mineral density, and bone microarchitecture in postmenopausal women

Higher sclerostin levels in postmenopausal women are associated with improved bone microarchitecture, areal and volumetric bone mineral density, and bone strength. However, the serum sclerostin level had no independent associations with the prevalence of morphometric vertebral fractures in this population after multivariable adjustment.

PURPOSE

We aim to investigate the associations between serum sclerostin levels and morphometric vertebral fractures (VFs) prevalence, bone mineral density (BMD), and bone microarchitecture in postmenopausal women.

METHODS

A total of 274 community-dwelling postmenopausal women were randomized enrolled. We collected general information and measured the serum sclerostin level. Morphometric VFs were assessed on the lateral thoracic and lumbar spine X-rays. Areal BMD and calculated trabecular bone score (TBS) were detected by dual-energy X-ray absorptiometry, and volumetric BMD and bone microarchitecture data were acquired from high-resolution peripheral quantitative computed tomography.

RESULTS

The prevalence of morphometric VFs was 18.6% in the cohort, and it was significantly higher in the lowest quartile of the sclerostin group than that in the highest quartile of the sclerostin group (27.9% vs. 11.8%, p<0.05). But the serum sclerostin had no independent association with the prevalence of morphometric VFs after adjusting by age, body mass index, BMD at the lumbar vertebrae 1-4, and fragility fracture history after 50 years old (odds ratio: 0.995, 95% confidence interval: 0.987-1.003, p=0.239). The serum sclerostin level positively correlated with the areal, volumetric BMDs, and TBS. It also had significant positive associations with Tb.BV/TV, Tb.N, Tb.Th, and Ct.Th, and negative associations with Tb.Sp and Tb.1/N.SD.

CONCLUSION

Chinese postmenopausal women with higher serum sclerostin levels had a lower prevalence of morphometric VFs, higher BMDs, and better bone microarchitecture. Nevertheless, the serum sclerostin level had no independent association with the prevalence of morphometric VFs.

Bone, fat, and muscle interactions in health and disease

Energy metabolism is a point of integration among the various organs and tissues of the human body, not only in terms of consumption of energy substrates but also because it concentrates a wide interconnected network controlled by endocrine factors. Thus, not only do tissues consume substrates, but they also participate in modulating energy metabolism. Soft mesenchymal tissues, in particular, play a key role in this process. The recognition that high energy consumption is involved in bone remodeling has been accompanied by evidence showing that osteoblasts and osteocytes produce factors that influence, for example, insulin sensitivity and appetite. Additionally, there are significant interactions between muscle, adipose, and bone tissues to control mutual tissue trophism. Not by chance, trophic and functional changes in these tissues go hand in hand from the beginning of an individual's development until aging. Likewise, metabolic and nutritional diseases deeply affect the musculoskeletal system and adipose tissue. The present narrative review highlights the importance of the interaction of the mesenchymal tissues for bone development and maintenance and the impact on bone from diseases marked by functional and trophic disorders of adipose and muscle tissues.

Bone Mineral Density in Congenital Generalized Lipodystrophy: The Role of Bone Marrow Tissue, Adipokines, and Insulin Resistance

Congenital Generalized Lipodystrophy (CGL) is a rare syndrome characterized by the almost total absence of subcutaneous adipose tissue due to the inability of storing lipid in adipocytes. Patients present generalized lack of subcutaneous fat and normal to low weight. They evolve with severe metabolic disorders, non-alcoholic fatty liver disease, early cardiac abnormalities, and infectious complications. Although low body weight is a known risk factor for osteoporosis, it has been reported that type 1 and 2 CGL have a tendency of high bone mineral density (BMD). In this review, we discuss the role of bone marrow tissue, adipokines, and insulin resistance in the setting of the normal to high BMD of CGL patients. Data bases from Pubmed and LILACS were searched, and 113 articles published until 10 April 2021 were obtained. Of these, 76 were excluded for not covering the review topic. A manual search for additional literature was performed using the bibliographies of the studies located. The elucidation of the mechanisms responsible for the increase in BMD in this unique model of insulin resistance may contribute to the understanding of the interrelationships between bone, muscle, and adipose tissue in a pathophysiological and therapeutic perspective.

Exercise Increases Bone in SEIPIN Deficient Lipodystrophy, Despite Low Marrow Adiposity

Exercise, typically beneficial for skeletal health, has not yet been studied in lipodystrophy, a condition characterized by paucity of white adipose tissue, with eventual diabetes, and steatosis. We applied a mouse model of global deficiency of Bscl2 (SEIPIN), required for lipid droplet formation. Male twelve-week-old B6 knockouts (KO) and wild type (WT) littermates were assigned six-weeks of voluntary, running exercise (E) versus non-exercise (N=5-8). KO weighed 14% less than WT (p=0.01) and exhibited an absence of epididymal adipose tissue; KO liver Plin1 via qPCR was 9-fold that of WT (p=0.04), consistent with steatosis. Bone marrow adipose tissue (BMAT), unlike white adipose, was measurable, although 40.5% lower in KO vs WT (p=0.0003) via 9.4T MRI/advanced image analysis. SEIPIN ablation's most notable effect marrow adiposity was in the proximal femoral diaphysis (-56% KO vs WT, p=0.005), with relative preservation in KO-distal-femur. Bone via μCT was preserved in SEIPIN KO, though some quality parameters were attenuated. Running distance, speed, and time were comparable in KO and WT. Exercise reduced weight (-24% WT-E vs WT p<0.001) but not in KO. Notably, exercise increased trabecular BV/TV in both (+31%, KO-E vs KO, p=0.004; +14%, WT-E vs WT, p=0.006). The presence and distribution of BMAT in SEIPIN KO, though lower than WT, is unexpected and points to a uniqueness of this depot. That trabecular bone increases were achievable in both KO and WT, despite a difference in BMAT quantity/distribution, points to potential metabolic flexibility during exercise-induced skeletal anabolism.

Prevalence and causes of elevated bone mass

INTRODUCTION

Reports of elevated bone mass (EBM) on routine DXA scanning are not infrequent. However, epidemiological studies of EBM are few in number and definition thresholds variable. The purpose of this study was to assess the prevalence and causes of EBM in the general population referred to a single university hospital - catering for a population of 4 million inhabitants - for DXA scanning.

MATERIAL AND METHODS

DXA databases were initially searched for individuals with a bone mineral density (BMD) Z-score ≥+4 at any site in the lumbar spine or hip from April 1st, 2008 to April 30st, 2018. Two Hologic scanners were available at the Lille University Hospital (France). Prevalence of EBM was evaluated, as were causes associated with EBM.

RESULTS

At the lumbar spine, 18,229 bone density tests were performed in women and 10,209 in men. At the hip, 17,390 tests were performed in women and 9857 in men. The total number of patients who had at least one bone density test was 14,745, of which 64.2% were female. Of these 14,745 patients, 211 had a Z-score ≥+4 at any site, i.e. a prevalence of 1.43% [1.25%-1.64%]. The DXA scans and medical records of 92 men and 119 women with elevated BMD were reviewed to assess causes. An artefactual cause was found in 164 patients (75%) with EBM (mostly degenerative disease of the spine), and an acquired cause of focal EBM was found in only 2 patients, both of whom had sclerotic bone metastases from prostate cancer. An acquired cause of generalized EBM was found in 32 patients (15%), the vast majority of whom had renal osteodystrophy (n = 11), followed by hematological disorders (n = 9; e.g. myeloproliferative syndromes and mastocytosis) and diffuse bone metastases from solid cancer (n = 5). Of the remaining causes, rare hereditary diseases (e.g. osteopetrosis…) and unexplained EBM were found in 10 and 6 cases respectively.

CONCLUSION

The prevalence of EBM (Z-score ≥+4 at any site) was 1.43% [1.25%-1.64%]. In nearly all instances (97.1%) the explanation for EBM could be found in the medical record and through conventional investigations. This study suggests that the main cause of EBM is degenerative disease of the spine. Further studies are needed to differentiate artefactual EBM from hereditary or acquired EBM, and to investigate unexplained EBM. Genetic testing may prove useful in elucidating rare unknown causes.

Genotype-phenotype correlations of Berardinelli-Seip congenital lipodystrophy and novel candidate genes prediction

BACKGROUND

Berardinelli-Seip congenital lipodystrophy (BSCL) is a heterogeneous autosomal recessive disorder characterized by an almost total lack of adipose tissue in the body. Mutations in the AGPAT2, BSCL2, CAV1 and PTRF genes define I-IV subtype of BSLC respectively and clinical data indicate that new causative genes remain to be discovered. Here, we retrieved 341 cases from 60 BSCL-related studies worldwide and aimed to explore genotype-phenotype correlations based on mutations of AGPAT2 and BSCL2 genes from 251 cases. We also inferred new candidate genes for BSCL through protein-protein interaction and phenotype-similarity.

RESULTS

Analysis results show that BSCL type II with earlier age of onset of diabetes mellitus, higher risk to suffer from premature death and mental retardation, is a more severe disorder than BSCL type I, but BSCL type I patients are more likely to have bone cysts. In BSCL type I, females are at higher risk of developing diabetes mellitus and acanthosis nigricans than males, while in BSCL type II, males suffer from diabetes mellitus earlier than females. In addition, some significant correlations among BSCL-related phenotypes were identified. New candidate genes prediction through protein-protein interaction and phenotype-similarity was conducted and we found that CAV3, EBP, SNAP29, HK1, CHRM3, OBSL1 and DNAJC13 genes could be the pathogenic factors for BSCL. Particularly, CAV3 and EBP could be high-priority candidate genes contributing to pathogenesis of BSCL.

CONCLUSIONS

Our study largely enhances the current knowledge of phenotypic and genotypic heterogeneity of BSCL and promotes the more comprehensive understanding of pathogenic mechanisms for BSCL.

Assessment of Sclerostin and Interleukin 6 Levels and Selected Anthropometric Parameters in Patients Receiving Hemodialysis Replacement Therapy-Pilot Study

Background and Objectives: Chronic kidney disease (CKD) is an important public health problem associated with, e.g., progressive renal insufficiency, bone mineral disorders, and increased inflammatory marker levels. The objective of this study was to compare selected biochemical parameters and to evaluate potential correlations between selected anthropometric parameters and levels of sclerostin and interleukin 6 (IL-6) in blood plasma. Materials and Methods: The study group consisted of 34 patients aged 59.8 ± 9.8 years, receiving hemodialysis therapy. The control group consisted of 31 individuals aged 55.4 ± 9.37 years, presenting with GFR (glomerular filtration rate) of more than 60 mL/min/1.73 m2. Selected anthropometric and biochemical parameters were assessed at baseline, as well as 3 and 6 months into the study. Statistical analyses were performed using the Statistica 2014 software package (StatSoft, Inc.Tulsa, OK, USA). Analyses included descriptive statistics, intergroup comparisons using the Mann-Whitney U-test or the Kruskal-Wallis test, and Spearman's correlation analysis. The significance level was set at p ≤ 0.005. Results: At all measurement time points, i.e., at baseline, at month 3, and at month 6, the IL-6 levels in the study group were significantly higher than those in the control group. No correlations were observed in the study group between SCL or IL-6 levels and anthropometric parameters such as body weight, body mass index (BMI), or waist circumference. Conclusions: Patients receiving hemodialysis replacement therapy present with significantly higher levels of IL-6 in their blood. Anthropometric parameters (body weight, BMI, and waist circumference) have no impact on sclerostin and IL-6 levels in patients undergoing hemodialysis therapy. The results obtained are satisfactory, and the research will be continued.

Marrow Adipocytes: Origin, Structure, and Function

The skeleton harbors an array of lineage cells that have an essential role in whole body homeostasis. Adipocytes start the colonization of marrow space early in postnatal life, expanding progressively and influencing other components of the bone marrow through paracrine signaling. In this unique, closed, and hypoxic environment close to the endosteal surface and adjacent to the microvascular space the marrow adipocyte can store or provide energy, secrete adipokines, and target neighboring bone cells. Adipocyte progenitors can also migrate from the bone marrow to populate white adipose tissue, a process that accelerates during weight gain. The marrow adipocyte also has an endocrine role in whole body homeostasis through its varied secretome that targets distant adipose depots, skeletal muscle, and the nervous system. Further insights into the biology of this unique and versatile cell will undoubtedly lead to novel therapeutic approaches to metabolic and age-related disorders such as osteoporosis and diabetes mellitus.

Phenotypic and Genetic Characteristics of Lipodystrophy: Pathophysiology, Metabolic Abnormalities, and Comorbidities

PURPOSE OF REVIEW

This article focuses on recent progress in understanding the genetics of lipodystrophy syndromes, the pathophysiology of severe metabolic abnormalities caused by these syndromes, and causes of severe morbidity and a possible signal of increased mortality associated with lipodystrophy. An updated classification scheme is also presented.

RECENT FINDINGS

Lipodystrophy encompasses a group of heterogeneous rare diseases characterized by generalized or partial lack of adipose tissue and associated metabolic abnormalities including altered lipid metabolism and insulin resistance. Recent advances in the field have led to the discovery of new genes associated with lipodystrophy and have also improved our understanding of adipose biology, including differentiation, lipid droplet assembly, and metabolism. Several registries have documented the natural history of the disease and the serious comorbidities that patients with lipodystrophy face. There is also evolving evidence for increased mortality rates associated with lipodystrophy. Lipodystrophy syndromes represent a challenging cluster of diseases that lead to severe insulin resistance, a myriad of metabolic abnormalities, and serious morbidity. The understanding of these syndromes is evolving in parallel with the identification of novel disease-causing mechanisms.

Nurses' knowledge about Berardinelli-Seip Congenital Lipodystrophy

Berardinelli-Seip Congenital Lipodystrophy (BSCL) is a rare autosomal recessive disease characterized by the almost complete absence of adipose tissue. Due to a strong founder effect that resulted in a higher prevalence of BSCL in Rio Grande do Norte (RN), a state in northeastern Brazil, it has been essential that health professionals develop knowledge about this disease. Nurses are often the first point of contact with patients during health care assistance. The purpose of this study was to investigate the knowledge of these professionals about BSCL in two main hospitals in RN state. A questionnaire was applied to 199 nurses working in the Hospital Regional Mariano Coelho—HRMC (Regional Hospital Mariano Coelho), in Currais Novos–RN, and in the Hospital Universitário Onofre Lopes—HUOL (University Hospital Onofre Lopes), in Natal–RN. This study showed that most nursing professionals do not know about the disease, although they have already received patients with BSCL in those hospitals. The nurses from HRMC and HUOL lacked knowledge of BSCL and the healthcare of these patients requires immediate improvement. Significant efforts are required to close the gap between current and needed practice patterns.