Molecular aspects of adipokine-bone interactions

Osteocalcin-expressing endothelial progenitor cells and serum osteocalcin forms are independent biomarkers of coronary atherosclerotic disease severity in male and female patients

PURPOSE

Osteocalcin (OC), an osteoblast-derived regulator of metabolic processes, and circulating early endothelial progenitor cells (EPC, CD34 - /CD133 + /KDR +) expressing OC (OC +) are potential candidates linking bone metabolism and the vasculature and might be involved in vascular atherosclerotic calcification. This study aimed at assessing the association of circulating levels of different OC forms and of EPCs count with disease severity in patients with documented coronary atherosclerosis (CAD).

METHODS

Patients (n = 59) undergoing coronary angiography were divided, according to stenosis severity, into (1) early coronary atherosclerosis (ECA) (n = 22), and (2) late coronary atherosclerosis (LCA) (n = 37). Total OC (TOC), carboxylated OC (cOC), undercarboxylated OC (unOC) were quantified by ELISA. EPC OC + count was assessed by flow cytometry.

RESULTS

EPC OC + counts showed significant differences between ECA and LCA groups. unOC and unOC/TOC ratio were inversely correlated with EPC OC + count. A significant decrease in TOC and unOC plasma levels was associated with higher cardiovascular risk factors (CVRFs) number. EPC OC + count was correlated with LDL-C, total cholesterol, and triglycerides, with a greater significance in the LCA group. No association between the different forms of circulating OC (TOC, ucOC, cOC) and severity of CAD was found.

CONCLUSION

This study showed a significant association between EPCs (CD34 - /CD133 + /KDR + /OC +), CAD severity and CVRFs, suggesting an active role for EPC OC + in the development of CAD. An inverse correlation between TOC, ucOC, and number of CVRFs was observed, suggesting that OC, regardless of its carboxylation status, may be developed as a further cardiovascular risk biomarker.

Space Flight-Promoted Insulin Resistance as a Possible Disruptor of Wound Healing

During space flight, especially when prolonged, exposure to microgravity results in a number of pathophysiological changes such as bone loss, muscle atrophy, cardiovascular and metabolic changes and impaired wound healing, among others. Interestingly, chronic low-grade inflammation and insulin resistance appear to be pivotal events linking many of them. Interestingly, real and experimental microgravity is also associated to altered wound repair, a process that is becoming increasingly important in view of prolonged space flights. The association of insulin resistance and wound healing impairment may be hypothesized from some dysmetabolic conditions, like the metabolic syndrome, type 2 diabetes mellitus and abdominal/visceral obesity, where derangement of glucose and lipid metabolism, greater low-grade inflammation, altered adipokine secretion and adipocyte dysfunction converge to produce systemic effects that also negatively involve wound healing. Indeed, wound healing impairment after traumatic events and surgery in space remains a relevant concern for space agencies. Further studies are required to clarify the molecular connection between insulin resistance and wound healing during space flight, addressing the ability of physical, endocrine/metabolic, and pharmacological countermeasures, as well as nutritional strategies to prevent long-term detrimental effects on tissue repair linked to insulin resistance. Based on these considerations, this paper discusses the pathophysiological links between microgravity-associated insulin resistance and impaired wound healing.

Insulin resistance and bone health in adolescents

Insulin resistance may be linked to bone health in young people. This study is the first on adolescents that jointly examined the association of bone health with insulin resistance and body composition. Our results revealed significant negative association between bone parameters and insulin resistance, even after adjustment for confounding factors.

PURPOSE

Previous studies are suggestive of the protective role of insulin on bone in adults. Whether this association exists in younger individuals is not clear, yet. This investigation aimed to evaluate the association between insulin resistance, bone parameters, and body composition amongst Iranian adolescents᾽ population.

METHODS

A cross-sectional study was conducted on 423 participants (224 girls and 199 boys) aged 9-19 years old. Insulin resistance was assessed, using a homeostatic model assessment of insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI). Bone mineral density (BMD), bone mineral content (BMC), total body fat mass (TBFM), and total body lean mass (TBLM) were measured, using dual energy X-ray absorptiometry (DXA), and bone mineral apparent density (BMAD) was calculated.

RESULTS

In multiple regression analyses adjusted for potential confounders, the HOMA-IR showed statistically significant negative association with most of the bone parameters (β = - 1.1 to - 0.002, P = 0.004 to 0.036). On the subject of QUICKI index, this relationship was detected only for lumbar spine (LS) parameters (β = 0.062 to 37.21, P = 0.0001 to 0.026) and femoral neck bone mineral content (FNBMC) (β = 1.297, P = 0.013).

CONCLUSION

Our results suggest that insulin resistance may be inversely and independently associated with the bone indices in younger individuals. Whether high insulin levels have detrimental effects on growing bone is still unclear and has to be answered.

LGR4 Gene Polymorphisms Are Associated With Bone and Obesity Phenotypes in Chinese Female Nuclear Families

OBJECTIVE

The current study was conducted to determine whether peak bone mineral density (BMD) and obesity phenotypes are associated with certain LGR4 gene polymorphisms found in Chinese nuclear families with female children.

METHODS

A total of 22 single nucleotide polymorphisms (SNPs) located in and around the LGR4 gene were identified in 1,300 subjects who were members of 390 Chinese nuclear families with female children. Then, BMD readings of the femoral neck, total hip, and lumbar spine as well as measurements of the total lean mass (TLM), total fat mass (TFM), and trunk fat mass were obtained via dual-energy X-ray absorptiometry. The quantitative transmission disequilibrium test was used to analyze the associations between specific SNPs and LGR4 haplotypes and peak BMD as well as between LGR4 haplotypes and TLM, percent lean mass, TFM, percent fat mass, trunk fat mass, and body mass index (BMI).

RESULTS

Here, rs7936621 was significantly associated with the BMD values for the total hip and lumbar spine, while rs10835171 and rs6484295 were associated with the trunk fat mass and BMI, respectively. Regarding the haplotypes, we found significant associations between GAA in block 2 and trunk fat mass and BMI, between AGCGT in block 3 and total hip BMD, between TGCTCC in block 5 and femoral neck BMD, and between TACTTC in block 5 and both lumbar spine and femoral neck BMD (all P-values < 0.05).

CONCLUSION

Genetic variations of the LGR4 gene are related to peak BMD, BMI, and trunk fat mass.

Pleiotropic genomic variants at 17q21.31 associated with bone mineral density and body fat mass: a bivariate genome-wide association analysis

Osteoporosis and obesity are two severe complex diseases threatening public health worldwide. Both diseases are under strong genetic determinants as well as genetically correlated. Aiming to identify pleiotropic genes underlying obesity and osteoporosis, we performed a bivariate genome-wide association (GWA) meta-analysis of hip bone mineral density (BMD) and total body fat mass (TBFM) in 12,981 participants from seven samples, and followed by in silico replication in the UK biobank (UKB) cohort sample (N = 217,822). Combining the results from discovery meta-analysis and replication sample, we identified one novel locus, 17q21.31 (lead SNP rs12150327, NC_000017.11:g.44956910G > A, discovery bivariate P = 4.83 × 10^-9, replication P = 5.75 × 10^-5) at the genome-wide significance level (ɑ = 5.0 × 10^-8), which may have pleiotropic effects to both hip BMD and TBFM. Functional annotations highlighted several candidate genes, including KIF18B, C1QL1, and PRPF19 that may exert pleiotropic effects to the development of both body mass and bone mass. Our findings can improve our understanding of the etiology of osteoporosis and obesity, as well as shed light on potential new therapies.

High Body Mass Index and Triglycerides Help Protect against Osteoporosis in Patients with Type 2 Diabetes Mellitus

PURPOSE

This study was conducted to investigate whether high body mass index (BMI) and triglycerides (TGs) were protective factors for reducing osteoporosis (OP) in patients with type 2 diabetes mellitus (T2DM). Participants and Methods. Seventy-nine patients (aged 20 to 81) with T2DM were included in the study. Basic information and blood indicators were collected. Bone mineral density was used to diagnose OP. Participants were grouped according to BMI (normal weight vs. overweight/obese participants), TG (normal TG vs. hypertriglyceridemia), and OP (non-OP vs. OP), and differences were compared between groups. Regression analysis was used to explore whether BMI or TG were independent factors affecting OP.

RESULTS

The proportions of OP in the overweight/obese and hypertriglyceridemic groups were significantly lower than those in the normal weight (30.0% vs. 69.0%; P = 0.001) and normal TG (27.3% vs. 56.5%; P = 0.010) groups. In the OP group, the BMI (24.8 ± 3.4 vs. 26.6 ± 2.5 kg/m²; P = 0.009) was significantly lower than that in the non-OP group, and TG showed the same trend (1.30 (0.81) vs. 1.71 (1.1) mmol/L; P = 0.020). Logistic regression in the crude model showed that the odds ratios (ORs) of OP in the overweight/obese and hypertriglyceridemic groups were 0.193 (95% CI: 0.071, 0.520) and 0.315 (95% CI: 0.119, 0.830) compared with those of the normal weight and normal TG groups. After adjusting for sex and smoking, the ORs were 0.204 (95% CI: 0.074, 0.567) and 0.242 (95% CI: 0.082, 0.709) for the overweight/obese and hypertriglyceridemic groups, respectively. After adjusting for all confounding factors, the ORs for these groups were 0.248 (95% CI: 0.083, 0.746) and 0.299 (95% CI: 0.091, 0.989), respectively.

CONCLUSION

BMI and TG are independent protective factors against OP in patients with T2DM.

Chronic dietary supplementation with kynurenic acid, a neuroactive metabolite of tryptophan, decreased body weight without negative influence on densitometry and mandibular bone biomechanical endurance in young rats

Kynurenic acid (KYNA) is a neuroactive metabolite of tryptophan. KYNA naturally occurs in breast milk and its content increases with lactation, indicating the role of neonatal nutrition in general growth with long-term health effects. KYNA is also an antagonist of ionotropic glutamate receptors expressed in bone cells. The aim of this study was to establish the effects of chronic KYNA supplementation on bone homeostasis in young rats, using mandible as a model bone. Female and male newborn Wistar rats were divided into control and KYNA-administered groups until 60 days of age (25x10¹ mg/L or 25x10² mg/L in drinking water). Hemimandibles were subjected to densitometry, computed tomography analysis and mechanical testing. Rats supplemented with KYNA at both doses showed a decrease in body weight. There were no effects of KYNA administration and mandible histomorphometry. In males, a significant quadratic effect (P < 0.001) was observed in the densitometry of the hemimandible, where BMD increased in the group supplemented with 2.5x10¹ mg/L of KYNA. Analysis of mechanical tests data showed that when fracture forces were corrected for bone geometry and rats body weight the improvement of bone material properties was observed in male and female rats supplemented with lower dose of KYNA. This study showed that chronic supplementation with KYNA may limit weight gain in the young, without adversely affecting the development of the skeleton.

Lipid profiles as potential mediators linking body mass index to osteoporosis among Chinese adults: the Henan Rural Cohort Study

This study is to examine the relationship between body mass index (BMI) and osteoporosis in rural areas of China, and then explore whether this association was mediated by lipid profiles. Results showed that with the increasing of BMI, the risk of osteoporosis was reduced, and lipid profiles mediate this association.

INTRODUCTION

To examine the relationship between BMI and osteoporosis, and explore whether this association was mediated by lipid profiles.

METHODS

A total of 8272 participants (18-79 years) were enrolled from the Henan Rural Cohort Study. The bone mineral density of the calcaneus was measured using an ultrasonic bone density apparatus. Logistic regression and restricted cubic splines were used to evaluate the odds ratio (OR) and 95% confidence intervals (95% CI). Mediation analysis using bootstrap was performed to examine the contribution of lipid profiles to BMI-related osteoporosis.

RESULTS

The crude and age-standardized prevalence of osteoporosis were 15.93% and 11.77%, respectively. The mean BMIs were 24.12 kg/m² for participants with osteoporosis and 25.06 kg/m² for non-osteoporosis participants (P < 0.001). After adjusting for potential confounders, subjects with obesity had a lower OR of osteoporosis (0.493 [95% CI: 0.405-0.600], P_trend < 0.001) compared with normal-weight individuals. Mediation analysis showed that lipid profile partly mediated the relationship between BMI and osteoporosis with indirect effect OR (95% CI) of 0.985 (0.978-0.992), and the proportion explained of BMI was 15.48% for lipid profile.

CONCLUSION

With the increasing of BMI, the risk of osteoporosis was reduced in the Chinese adult population, and lipid profiles may be a potential mediator linking reduced risk of osteoporosis. Elucidating the underlying mechanisms will facilitate developing feasible preventive and therapeutic measures for osteoporosis. Chinese clinical trial register: ChiCTR-OOC-15006699.

Congenital lipodystrophy induces severe osteosclerosis

Berardinelli-Seip congenital generalized lipodystrophy is associated with increased bone mass suggesting that fat tissue regulates the skeleton. Because there is little mechanistic information regarding this issue, we generated "fat-free" (FF) mice completely lacking visible visceral, subcutaneous and brown fat. Due to robust osteoblastic activity, trabecular and cortical bone volume is markedly enhanced in these animals. FF mice, like Berardinelli-Seip patients, are diabetic but normalization of glucose tolerance and significant reduction in circulating insulin fails to alter their skeletal phenotype. Importantly, the skeletal phenotype of FF mice is completely rescued by transplantation of adipocyte precursors or white or brown fat depots, indicating that adipocyte derived products regulate bone mass. Confirming such is the case, transplantation of fat derived from adiponectin and leptin double knockout mice, unlike that obtained from their WT counterparts, fails to normalize FF bone. These observations suggest a paucity of leptin and adiponectin may contribute to the increased bone mass of Berardinelli-Seip patients.

Adiponectin Deficiency Triggers Bone Loss by Up-Regulation of Osteoclastogenesis and Down-Regulation of Osteoblastogenesis

Osteoporosis and bone disorders related to the metabolic syndrome are often associated with adipokines secreted by adipocytes in bone. Adiponectin, a type of adipokine, is a regulator of immune responses and metabolic processes, but its role in bone biology remains uncertain. We investigated the role of adiponectin in bone metabolism using adiponectin-deficient mice in vivo and in vitro. Adiponectin-deficient mice exhibited reduced bone mass and increased adiposity. Adiponectin-deficient calvarial cells were prone to differentiate into adipocytes rather than osteoblasts. Although bone marrow macrophages (BMMs) from adiponectin-deficient mice had low osteoclastogenic potential as osteoclast precursors with increasing interferon regulatory factor 5 expression, under co-culture conditions of calvarial cells and BMMs, the enhanced receptor activator of nuclear factor κB ligand/osteoprotegerin (RANKL/OPG) ratio of adiponectin-deficient mesenchymal progenitor cells facilitated osteoclast differentiation. In addition, increased RANKL/OPG ratio was observed in the bone marrow extracellular fluid of adiponectin-deficient mice compared to that of wild-type mice. Notably, recombinant adiponectin treatment enhanced RANKL-induced osteoclast differentiation from BMMs but up-regulated OPG production in recombinant adiponectin-exposed calvarial cells, which inhibited osteoclast differentiation. Taken together, these results suggest that adiponectin plays an inhibitory role in bone metabolism through cross talk between precursor cells of both osteoclasts and osteoblasts by regulating RANKL/OPG ratio in the bone marrow microenvironment.

Epicardial Fat Thickness and Bone Mineral Content: The Healthy Twin Study in Korea

Background

The conventional concept of positive association between general obesity and bone health was challenged in recent studies reporting the different effects of specific fat deposition on bone health. In the present study, we investigated the association between epicardial fat and bone health.

Methods

We measured echocardiographic epicardial fat thickness (EFT) and bone mineral content (BMC) in a twin-family cohort of Koreans (n = 1,198; 525 men, 460 pre- and 213 post-menopausal women). A total 121 pairs of monozygotic twin (MZ) and 404 pairs of dizygotic twin and sibling pairs (DZ/Sib) were included.

Results

EFT was positively associated with BMC in total, as well as in three subgroups (β = 0.107, 0.076, and 0.058 for men, pre-, and post-menopausal women, respectively). The positive association between EFT and BMC remained for DZ/Sib difference analysis, but was absent for MZ comparisons. The positive association between BMI and BMC was consistent for DZ/Sib and MZ difference analysis. After adjusting for the effect of general obesity via BMI, the association between BMC and EFT was statistically non-significant (β = 0.020, 0.000, and −0.009 for men, pre-, and post-menopausal women, respectively).

Conclusion

Our findings do not support epicardial fat’s beneficial effects on bone health, whereas general adiposity has an osteotropic effect. The association between EFT and BMC is through common genetic component factors.

Identification of Novel Potentially Pleiotropic Variants Associated With Osteoporosis and Obesity Using the cFDR Method

CONTEXT

Genome-wide association studies (GWASs) have been successful in identifying loci associated with osteoporosis and obesity. However, the findings explain only a small fraction of the total genetic variance.

OBJECTIVE

The aim of this study was to identify novel pleiotropic genes important in osteoporosis and obesity.

DESIGN AND SETTING

A pleiotropic conditional false discovery rate method was applied to three independent GWAS summary statistics of femoral neck bone mineral density, body mass index, and waist-to-hip ratio. Next, differential expression analysis was performed for the potentially pleiotropic genes, and weighted genes coexpression network analysis (WGCNA) was conducted to identify functional connections between the suggested pleiotropic genes and known osteoporosis/obesity genes using transcriptomic expression data sets in osteoporosis/obesity-related cells.

RESULTS

We identified seven potentially pleiotropic loci-rs3759579 (MARK3), rs2178950 (TRPS1), rs1473 (PUM1), rs9825174 (XXYLT1), rs2047937 (ZNF423), rs17277372 (DNM3), and rs335170 (PRDM6)-associated with osteoporosis and obesity. Of these loci, the PUM1 gene was differentially expressed in osteoporosis-related cells (B lymphocytes) and obesity-related cells (adipocytes). WGCNA showed that PUM1 positively interacted with several known osteoporosis genes (AKAP11, JAG1, and SPTBN1). ZNF423 was the highly connected intramodular hub gene and interconnected with 21 known osteoporosis-related genes, including JAG1, EN1, and FAM3C.

CONCLUSIONS

Our study identified seven potentially pleiotropic genes associated with osteoporosis and obesity. The findings may provide new insights into a potential genetic determination and codetermination mechanism of osteoporosis and obesity.

Physical activity and hypocaloric diet recovers osteoblasts homeostasis in women affected by abdominal obesity

Obesity is a multifactorial disease linked to metabolic chronic disorders such as diabetes, and hypertension. Also, it has recently been associated with skeletal alterations and low bone mineral density. We previously demonstrated that exposure of osteoblasts to sera of sedentary subjects affected by obesity alters cell homeostasis in vitro, leading to disruption of intracellular differentiation pathways and cellular activity. Thus, the purpose of the present study has been to evaluate whether sera of sedentary obese women, subjected to physical activity and hypocaloric diet, could recover osteoblast homeostasis in vitro as compared to the sera of same patients before intervention protocol. To this aim, obese women were evaluated at time 0 and after 4, 6, and 12 months of individualized prescribed physical activity and hypocaloric diet. Dual-energy-X-ray absorptiometry measurements were performed at each time point, as well as blood was collected at the same points. Cells were incubated with sera of subjects before and after physical activity as described: obese at baseline and after for 4, 6, and 12 months of physical activity and nutritional protocol intervention. Osteoblasts exposed to sera of patients, who displayed increased lean and decreased fat mass (from 55.5 ± 6.5 to 57.1 ± 5.6% p ≤ 0.05; from 44.5 ± 1.1 to 40.9 ± 2.6% p ≤ 0.01 respectively), showed a time-dependent increase of Wnt/β-catenin signaling, versus cells exposed to sera of obese patients before intervention protocol, suggesting recovery of osteoblast homeostasis upon improvement of body composition. An increase in β-catenin nuclear accumulation and nuclear translocation was also observed, accompanied by an increase in Adiponectin receptor 1 protein expression, suggesting positive effect on cell differentiation program. Furthermore, a decrease in sclerostin amount and an increase of type 1 procollagen amino-terminal-propeptide were depicted as compared to baseline, proportionally to the time of physical activity, suggesting a recovery of bone remodeling modulation and an increase of osteoblast activity induced by improvement of body composition. In conclusion, our results show for the first time that sera of obese sedentary women who increased lean mass and decreased fat mass, by physical activity and hypocaloric diet, rescue osteoblasts differentiation and activity likely due to a reactivation of Wnt/β-catenin-pathway, suggesting that a correct life style can improve skeletal metabolic alteration induced by obesity.

Mechanical signals protect stem cell lineage selection, preserving the bone and muscle phenotypes in obesity

The incidence of obesity is rapidly rising, increasing morbidity and mortality rates worldwide. Associated comorbidities include type 2 diabetes, heart disease, fatty liver disease, and cancer. The impact of excess fat on musculoskeletal health is still unclear, although it is associated with increased fracture risk and a decline in muscular function. The complexity of obesity makes understanding the etiology of bone and muscle abnormalities difficult. Exercise is an effective and commonly prescribed nonpharmacological treatment option, but it can be difficult or unsafe for the frail, elderly, and morbidly obese. Exercise alternatives, such as low-intensity vibration (LIV), have potential for improving musculoskeletal health, particularly in conditions with excess fat. LIV has been shown to influence bone marrow mesenchymal stem cell differentiation toward higher-order tissues (i.e., bone) and away from fat. While the exact mechanisms are not fully understood, recent studies utilizing LIV both at the bench and in the clinic have demonstrated some efficacy. Here, we discuss the current literature investigating the effects of obesity on bone, muscle, and bone marrow and how exercise and LIV can be used as effective treatments for combating the negative effects in the presence of excess fat.

Fat, Sugar, and Bone Health: A Complex Relationship

With people aging, osteoporosis is expected to increase notably. Nutritional status is a relatively easily-modified risk factor, associated with many chronic diseases, and is involved in obesity, diabetes, and coronary heart disease (CHD), along with osteoporosis. Nutrients, such as fats, sugars, and proteins, play a primary function in bone metabolism and maintaining bone health. In Western nations, diets are generally high in saturated fats, however, currently, the nutritional patterns dominating in China continue to be high in carbohydrates from starch, cereals, and sugars. Moreover, high fat or high sugar (fructose, glucose, or sucrose) impart a significant impact on bone structural integrity. Due to diet being modifiable, demonstrating the effects of nutrition on bone health can provide an approach for osteoporosis prevention. Most researchers have reported that a high-fat diet consumption is associated with bone mineral density (BMD) and, as bone strength diminishes, adverse microstructure changes occur in the cancellous bone compartment, which is involved with lipid metabolism modulation disorder and the alteration of the bone marrow environment, along with an increased inflammatory environment. Some studies, however, demonstrated that a high-fat diet contributes to achieving peak bone mass, along with microstructure, at a younger age. Contrary to these results, others have shown that a high-fructose diet consumption leads to stronger bones with a superior microarchitecture than those with the intake of a high-glucose diet and, at the same time, research indicated that a high-fat diet usually deteriorates cancellous bone parameters, and that the incorporation of fructose into a high-fat diet did not aggravate bone mass loss. High-fat/high-sucrose diets have shown both beneficial and detrimental influences on bone metabolism. Combined, these studies showed that nutrition exerts different effects on bone health. Thus, a better understanding of the regulation between dietary nutrition and bone health might provide a basis for the development of strategies to improve bone health by modifying nutritional components.

Association of ADIPOQ, leptin, LEPR, and resistin polymorphisms with obesity parameters in Hammam Sousse Sahloul Heart Study

BACKGROUND

Adipose tissue is an important endocrine organ that secretes a number of adipokines, such as adiponectin (ADIPOQ), leptin (LEP), leptin receptor (LEPR), and resistin (RETN) which may be implicated in obesity. Some adipokines' polymorphisms of genes might influence their concentrations and/or activities. Our aim was to study the relationship between seven SNPs in ADIPOQ (+45T<G (rs2241766); +276G<T (rs1501299); -4255C<T (rs822393); -395G<T (rs17366568)), LEP (2548G<A (rs7799039)), LEPR (223Q<R (rs1137101)), and RETN (-420C<G (rs1862513)) and obesity in Hammam Sousse Sahloul Heart Study (HSHS).

METHODS

The study, carried out between February and June 2009, is mainly focused on 1121 respondents in HSHS which is a population-based epidemiological study of type "community-based" on cardiovascular risk. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Serum lipids and anthropometric parameters were measured. Statistic analysis was performed on SPSSv19.

RESULTS

The polymorphisms of ADIPOQ 4522C<T and 276G<T, LEP 2548G<A, and RETN 420C<G seem to contribute to obesity. In fact, adjusted odds ratios (ORs) of obesity associated with mutated genotypes of each polymorphism were respectively OR=1.38, P=.037; OR=0.608, P<.001; OR=2.23, P=.034; and OR=2.18, P<.001. The 276G<T, 4522C<T, and 420C<G were associated with increased BMI (P=.010, P=.028, and P<.001). A significant association was found between the 276G<T; 4522C<T, LEP 2548G<A and 420C<G, and the waist circumference and hip measurements.

CONCLUSION

ADIPOQ, LEP, and RETN gene polymorphisms were associated with obesity parameters in HSHS population.

Obesity is a concern for bone health with aging

Accumulating evidence supports a complex relationship between adiposity and osteoporosis in overweight/obese individuals, with local interactions and endocrine regulation by adipose tissue on bone metabolism and fracture risk in elderly populations. This review was conducted to summarize existing evidence to test the hypothesis that obesity is a risk factor for bone health in aging individuals. Mechanisms by which obesity adversely affects bone health are believed to be multiple, such as an alteration of bone-regulating hormones, inflammation, oxidative stress, the endocannabinoid system, that affect bone cell metabolism are discussed. In addition, evidence on the effect of fat mass and distribution on bone mass and quality is reviewed together with findings relating energy and fat intake with bone health. In summary, studies indicate that the positive effects of body weight on bone mineral density cannot counteract the detrimental effects of obesity on bone quality. However, the exact mechanism underlying bone deterioration in the obese is not clear yet and further research is required to elucidate the effect of adipose depots on bone and fracture risk in the obese population.

Do metabolic syndrome and its components have an impact on bone mineral density in adolescents?

In recent years, there has been growing concern about the occurrence of metabolic syndrome (MetS) at an early age and its effects on bone mass in adolescents. Adolescence is considered a critical period for bone mass gain. Impaired bone acquisition during this phase can lead to “suboptimal” peak bone mass and increase the risk of osteopenia/osteoporosis and fractures in old age. The objective of this review was to perform a critical analysis of articles that specifically focus on this age group, evaluating the influence of MetS and its components on bone mineral density in adolescents. A possible relationship between this syndrome and bone mass has been demonstrated, but the number of studies addressing this topic in adolescents is small. Despite the scarcity of evidence, the results of those studies show that Metabolic Syndrome is negatively correlated with bone mass and also that some components of MetS are negatively correlated with bone mineral density in adolescents. However, the associations between MetS and bone mass development need to be further explored in the age group corresponding to adolescence. Further good-quality studies are necessary to complement the understanding of this relationship.

Diabetes and Obesity as Independent Risk Factors for Osteoporosis: Updated Results from the ROIS/EMEROS Registry in a Population of Five Thousand Post-Menopausal Women Living in a Region Characterized by Heavy Environmental Pressure

Objectives: We aimed to analyze bone mineralization and the effect of different risk factors for osteoporosis in postmenopausal women. Methods: We found 4909 postmenopausal subjects within ≥10,000 records from the ROIS/EMEROS (Ionian and Salento Osteoporosis Registry/Euro Mediterranean Registry of Osteoporosis) registry, a population study carried out in an area characterized by heavy environmental pressure between Brindisi and Taranto from 2009 to 2016. All subjects were assessed via phalangeal quantitative ultrasound (QUS) to evaluate their bone mineralization (assessed via amplitude dependent speed of sound (AD-SoS)) and the association between demineralization and the presence of other conditions or risk factors. Results: Mean age was 64 ± 9.5 years and mean body mass index (BMI) was 28.7 ± 3.5 kg/m². Pearson correlation analyses revealed a negative association between bone mineralization (AD-SoS) and BMI (p < 0.001). By using multivariate logistic regression analysis, we observed significant values of odds ratios (ORs) of osteoporosis (adjusted for age, physical activity, and the use of drugs known to increase the risk of fractures) in subjects with diabetes and obesity: 1.39 (confidence interval (CI): 1.05-1.83) and 1.46 (CI: 1.20-1.78), respectively. A statistically significant linear trend of higher ORs of osteoporosis was found for increasing values of BMI. Conclusions: Our study confirmed the high impact of obesity and type 1 and type 2 diabetes on osteoporosis.

Association between omentin-1, adiponectin and bone health under consideration of osteoprotegerin as possible mediator

PURPOSE

Several studies implicated a crosstalk between bone and fat in the pathogenesis of osteoporosis. Few studies indicated an association between adiponectin and omentin-1 on the bone remodeling process and bone mineral density, and suggested osteoprotegerin (OPG) as a mediator of this relationship. However, only limited evidence on this relationship is available in humans. Therefore, this study aimed to investigate the association between omentin-1, adiponectin and broadband ultrasound attenuation (BUA) in peri-/premenopausal and postmenopausal women, and to assess the role of OPG as a possible mediator.

METHODS

Data from the German population-based EPIC-Potsdam cohort comprising 637 women were analyzed. Multivariable-adjusted ANCOVA including age, BMI, waist circumference, smoking status, education, physical activity, adiponectin or omentin-1 and hormone use was used to investigate potential relationships between the adipokines and BUA levels. A mediation analysis assessed the mediating effect of OPG on the association of BUA and omentin-1 levels.

RESULTS

Peri-/premenopausal women had higher BUA levels (112.5 ± 10.1 dB/MHz), compared to postmenopausal women (106.3 ± 10.0 dB/MHz). In peri-/premenopausal women neither adiponectin nor omentin-1 was significantly associated with BUA. In postmenopausal women, adiponectin was not associated with BUA, but 10 % increase in the omentin-1 concentration was significantly associated with 0.44 dB/MHz lower BUA levels (p = 0.01). Omentin-1 was positively associated with OPG (p = 0.02); however, OPG was not significantly related to BUA (p = 0.62).

CONCLUSION

Our study provides evidence for an inverse association between circulating omentin-1 and BUA levels in postmenopausal women. However, the present findings do not support a mediating effect of OPG in the adipose tissue-bone pathway.

The obesity of bone

During the last decades, obesity and osteoporosis have become important global health problems, and the belief that obesity is protective against osteoporosis has recently come into question. In fact, some recent epidemiologic and clinical studies have shown that a high level of fat mass might be a risk factor for osteoporosis and fragility fractures. Several potential mechanisms have been proposed to explain the complex relationship between adipose tissue and bone. Indeed, adipose tissue secretes various molecules, named adipokines, which are thought to have effects on metabolic, skeletal and cardiovascular systems. Moreover, fat tissue is one of the major sources of aromatase, an enzyme that synthesizes estrogens from androgen precursors, hormones that play a pivotal role in the maintenance of skeletal homeostasis, protecting against osteoporosis. Moreover, bone cells express several specific hormone receptors and recent observations have shown that bone-derived factors, such as osteocalcin and osteopontin, affect body weight control and glucose homeostasis. Thus, the skeleton is considered an endocrine target organ and an endocrine organ itself, likely influencing other organs as well. Finally, adipocytes and osteoblasts originate from a common progenitor, a pluripotential mesenchymal stem cell, which has an equal propensity for differentiation into adipocytes or osteoblasts (or other lines) under the influence of several cell-derived transcription factors. This review will highlight recent insights into the relationship between fat and bone, evaluating both potential positive and negative influences between adipose and bone tissue. It will also focus on the hypothesis that osteoporosis might be considered the obesity of bone.

Bone health as a function of adipokines and vitamin D pattern in elderly patients

BACKGROUND

Adiponectin, leptin, and resistin are involved in bone metabolism, but the evidence regarding their effects is not conclusive. We analyzed the relationship between these adipokines, vitamin D, and bone health using a cluster analysis approach.

METHODS

We used cross-sectional data coming from the InCHIANTI study, in which bone density and area were estimated using computed tomography. The sample size was 690 (women, 57.5%; mean age, 75.2 years; range, 65-102). Five clusters were generated on the basis of gender, age, adipokines, and vitamin D concentrations. The clusters were characterized, respectively, by higher resistin and older age (hR-O, n=134), higher vitamin D and younger age (hD-Y, n=152), higher adiponectin (hA, n=65), and higher leptin (hL, n=52). The last cluster had intermediate values of all the constituting variables (I, n=287). The clusters were compared with respect to bone parameters and clinical characteristics.

RESULTS

Cluster hR-O had the lowest total and cortical bone density. Cluster hD-Y had the lowest adiponectin (9.29 g/mL) and leptin (7.9 ng/mL) serum concentrations, the highest prevalence of men (71.1%), and total/cortical bone density and area. No statistically significant difference across clusters was observed for age- and sex-standardized measures of bone mineral density and bone area, but leptin was associated with these parameters in a linear model adjusted for age, gender, vitamin D, resistin, and leptin.

CONCLUSIONS

In an elderly population, age and sex almost completely explain the variability in bone status across cluster characterized by different levels of circulating adipokines and vitamin D. The role of leptin, however, seems worthy of consideration.

Abdominal Fat and Sarcopenia in Women Significantly Alter Osteoblasts Homeostasis In Vitro by a WNT/ β -Catenin Dependent Mechanism

Obesity and sarcopenia have been associated with mineral metabolism derangement and low bone mineral density (BMD). We investigated whether imbalance of serum factors in obese or obese sarcopenic patients could affect bone cell activity in vitro. To evaluate and characterize potential cellular and molecular changes of human osteoblasts, cells were exposed to sera of four groups of patients: (1) affected by obesity with normal BMD (O), (2) affected by obesity with low BMD (OO), (3) affected by obesity and sarcopenia (OS), and (4) affected by obesity, sarcopenia, and low BMD (OOS) as compared to subjects with normal body weight and normal BMD (CTL). Patients were previously investigated and characterized for body composition, biochemical and bone turnover markers. Then, sera of different groups of patients were used to incubate human osteoblasts and evaluate potential alterations in cell homeostasis. Exposure to OO, OS, and OOS sera significantly reduced alkaline phosphatase, osteopontin, and BMP4 expression compared to cells exposed to O and CTL, indicating a detrimental effect on osteoblast differentiation. Interestingly, sera of all groups of patients induced intracellular alteration in Wnt/ β -catenin molecular pathway, as demonstrated by the significant alteration of specific target genes expression and by altered β -catenin cellular compartmentalization and GSK3 β phosphorylation. In conclusion our results show for the first time that sera of obese subjects with low bone mineral density and sarcopenia significantly alter osteoblasts homeostasis in vitro, indicating potential detrimental effects of trunk fat on bone formation and skeletal homeostasis.

Cytokines and Hormones That Contribute to the Positive Association between Fat and Bone

The positive association between body weight and bone density has been established in numerous laboratory and clinical studies. Apart from the direct effect of soft tissue mass on bone through skeletal loading, a number of cytokines and hormones contribute to the positive association between adipose and bone tissue, acting either locally in sites where cells of the two tissues are adjacent to each other or systemically through the circulation. The current review describes the effects of such local and systemic factors on bone physiology. One class of factors are the adipocyte-secreted peptides (adipokines), which affect bone turnover through a combination of direct effects in bone cells and indirect mechanisms mediated by the central nervous system. Another source of hormones that contribute to the coupling between fat and bone tissue are beta cells of the pancreas. Insulin, amylin, and preptin are co-secreted from pancreatic beta cells in response to increased glucose levels after feeding, and are also found in high circulating levels in obesity. A number of peptide hormones secreted from the gastrointestinal tract in response to feeding affect both fat and bone cells and thus can also act as mediators of the association between the two tissues. The current review focuses on results of laboratory studies investigating possible mechanism involved in the positive association between fat mass and bone mass.

CER1 gene variations associated with bone mineral density, bone markers, and early menopause in postmenopausal women

Background

Osteoporosis has a multifactorial pathogenesis characterized by a combination of low bone mass and increased fragility. In our study, we focused on the effects of polymorphisms in CER1 and DKK1 genes, recently reported as important susceptibility genes for osteoporosis, on bone mineral density (BMD) and bone markers in osteoporotic women. Our objective was to evaluate the effect of CER1 and DKK1 variations in 607 postmenopausal women. The entire DKK1 gene sequence and five selected CER1 SNPs were amplified and resequenced to assess whether there is a correlation between these genes and BMD, early menopause, and bone turnover markers in osteoporotic patients.

Results

Osteoporotic women seem to suffer menopause 2 years earlier than the control group. The entire DKK1 gene sequence analysis revealed six variations. There was no correlation between the six DKK1 variations and osteoporosis, in contrast to the five common CER1 variations that were significantly associated with BMD. Additionally, osteoporotic patients with rs3747532 and rs7022304 CER1 variations had significantly higher serum levels of parathyroid hormone and calcitonin and lower serum levels of osteocalcin and IGF-1.

Conclusions

No significant association between the studied DKK1 variations and osteoporosis was found, while CER1 variations seem to play a significant role in the determination of osteoporosis and a potential predictive role, combined with bone markers, in postmenopausal osteoporotic women.

Adipokines and C-reactive protein in relation to bone mineralization in pediatric nonalcoholic fatty liver disease

AIM: To investigate bone mineral density (BMD) in obese children with and without nonalcoholic fatty liver disease (NAFLD); and the association between BMD and serum adipokines, and high-sensitivity C-reactive protein (HSCRP).

METHODS: A case-control study was performed. Cases were 44 obese children with NAFLD. The diagnosis of NAFLD was based on magnetic resonance imaging (MRI) with high hepatic fat fraction (≥ 5%). Other causes of chronic liver disease were ruled out. Controls were selected from obese children with normal levels of aminotransferases, and without MRI evidence of fatty liver as well as of other causes of chronic liver diseases. Controls were matched (1- to 1-basis) with the cases on age, gender, pubertal stage and as closely as possible on body mass index-SD score. All participants underwent clinical examination, laboratory tests, and whole body (WB) and lumbar spine (LS) BMD by dual energy X-ray absorptiometry. BMD Z-scores were calculated using race and gender specific LMS curves.

RESULTS: Obese children with NAFLD had a significantly lower LS BMD Z-score than those without NAFLD [mean, 0.55 (95%CI: 0.23-0.86) vs 1.29 (95%CI: 0.95-1.63); P < 0.01]. WB BMD Z-score was also decreased in obese children with NAFLD compared to obese children with no NAFLD, though borderline significance was observed [1.55 (95%CI: 1.23-1.87) vs 1.95 (95%CI: 1.67-2.10); P = 0.06]. Children with NAFLD had significantly higher HSCRP, lower adiponectin, but similar leptin levels. Thirty five of the 44 children with MRI-diagnosed NAFLD underwent liver biopsy. Among the children with biopsy-proven NAFLD, 20 (57%) had nonalcoholic steatohepatitis (NASH), while 15 (43%) no NASH. Compared to children without NASH, those with NASH had a significantly lower LS BMD Z-score [mean, 0.27 (95%CI: -0.17-0.71) vs 0.75 (95%CI: 0.13-1.39); P < 0.05] as well as a significantly lower WB BMD Z-score [1.38 (95%CI: 0.89-1.17) vs 1.93 (95%CI: 1.32-2.36); P < 0.05]. In multiple regression analysis, NASH (standardized β coefficient, -0.272; P < 0.01) and HSCRP (standardized β coefficient, -0.192; P < 0.05) were significantly and independently associated with LS BMD Z-score. Similar results were obtained when NAFLD (instead of NASH) was included in the model. WB BMD Z-scores were significantly and independently associated with NASH (standardized β coefficient, -0.248; P < 0.05) and fat mass (standardized β coefficient, -0.224; P < 0.05).

CONCLUSION: This study reveals that NAFLD is associated with low BMD in obese children, and that systemic, low-grade inflammation may accelerate loss of bone mass in patients with NAFLD.

Deficiency of adiponectin protects against ovariectomy-induced osteoporosis in mice

Adipokine adiponectin (APN) has been recently reported to play a role in regulating bone mineral density (BMD). To explore the mechanism by which APN affects BMD, we investigated BMD and biomechanical strength properties of the femur and vertebra in sham-operated (Sham) and ovariectomized (OVX) APN knockout (KO) mice as compared to their operated wild-type (WT) littermates. The results show that APN deficiency has no effect on BMD but induces increased ALP activity and osteoclast cell number. While OVX indeed leads to significant bone loss in both femora and vertebras of WT mice with comparable osteogenic activity and a significant increase in osteoclast cell number when compared to that of sham control. However, no differences in BMD, ALP activity and osteoclast cell number were found between Sham and OVX mice deficient for APN. Further studies using bone marrow derived mesenchymal stem cells (MSCs) demonstrate an enhanced osteogenic differentiation and extracellular matrix calcification in APN KO mice. The possible mechanism for APN deletion induced acceleration of osteogenesis could involve increased proliferation of MSCs and higher expression of Runx2 and Osterix genes. These findings indicate that APN deficiency can protect against OVX-induced osteoporosis in mice, suggesting a potential role of APN in regulating the balance of bone formation and bone resorption, especially in the development of post-menopausal osteoporosis.

Does excess weight interfere with bone mass accumulation during adolescence?

Obesity and osteoporosis are important global health problems characterized by increasing prevalence with high impact on morbidity and mortality. The objective of this review was to determine whether excess weight during adolescence interferes with bone mass accumulation. If bone mineral gain can be optimized during puberty, adults are less likely to suffer from the devastating complications of osteoporosis. The increased fracture risk in obese children has also been attributed to a lower bone mass for weight compared to non-obese children. Thus, adiposity present in this age group may not result in the protection of bone mass, in contrast to what has been observed in adults. However, studies involving adolescents have reported both protective and detrimental effects of obesity on bone. The results and mechanisms of these interactions are controversial and have not been fully elucidated, a fact highlighting the extreme relevance of this topic and the need to monitor intervening and interactive variables.

Altered gene expression involved in insulin signaling pathway in type II diabetic osteoporosis rats model

It is well established that both estrogen loss and type II diabetes mellitus (DMII) can impair bone metabolism, but whether estrogen loss exacerbates the effects of DMII is unclear. Therefore, we determined if ovariectomy (OVX) of rats on a long-term high-fat/sugar diet and injection of a low dose of streptozotocin (DMII) decreased bone mineral density (BMD) more than OVX or DMII alone. Bone insulin signaling is known to support bone metabolism; therefore, we also tested the hypothesis that OVX DMII rats (DOVX) would exhibit greater reductions in the expression of proteins important in insulin signaling, including IRS-1, IRS-2, and IGF-1. As hypothesized, BMD and plasma estrogen levels were decreased more in DOVX rats than in rats following OVX (NOVX) or DMII (DS) alone. IGF-1 expression was decreased in the liver, kidney, skeletal muscle, and bone of DOVX, DS, and NOVX rats; however, the decrease was larger and occurred sooner in DOVX rats. While IRS-1 and IRS-2 decreased in most groups in all tissues examined, the expression patterns differed in both a group- and tissue-dependent fashion. In conclusion, these data demonstrate that estrogen loss and DMII induced by a high-fat/sugar diet interact to produce osteoporosis and support the hypothesis that the bone loss may be mediated at least in part by concurrent decreases in the insulin signaling proteins in bone.

Lower circulating preptin levels in male patients with osteoporosis are correlated with bone mineral density and bone formation

Background

Serum preptin levels among subjects with different bone mineral densities (BMD) were measured and investigated to determine the correlation between BMD and bone-metabolic markers.

Methods

Approximately 52 elderly male patients with osteoporosis, 50 elderly men with osteopaenia, and 31 age-matched normal bone mass controls participated in the study. The serum preptin levels and bone metabolic markers were measured by enzyme-linked immunosorbent assay. The relationships between preptin levels, BMD, and metabolic parameters were also assessed.

Results

The serum preptin level was the lowest in the osteoporosis group and positively correlated with BMD. All the bone formation markers in the osteoporosis and osteopaenia groups were significantly reduced compared with those in the normal group. Serum preptin level was positively correlated with all the bone formation markers, whereas no correlation was observed with the bone resorption marker TRACP-5b.

Conclusions

Serum preptin levels are decreased in osteoporosis and osteopaenia patients and positively correlated with BMD. Therefore, preptin is involved in the pathogenesis of osteoporosis, probably through bone formation rather than bone resorption.

Resistin polymorphisms show associations with obesity, but not with bone parameters in men: results from the Odense Androgen Study

Resistin is an obesity-related adipokine which has also been implicated in bone metabolism. Therefore, we designed a study to investigate the possible role of resistin gene variation in both obesity and bone mineral density. We included 1,155 individuals from the Odense Androgen Study (663 young subjects and 492 older subjects), a population-based, prospective, observational study on the inter-relationship between endocrine status, body composition, muscle function, and bone metabolism in men, in an association study with resistin (RETN) polymorphisms. Three RETN variants (rs1862513, rs3745367 and rs3745369) were genotyped with TaqMan Pre-Designed Genotyping assays. Linear regression was performed to investigate the possible association of these variants with several obesity- and bone-related parameters. After genotyping 1,155 Danish men, 663 young subjects and 492 older subjects, we found that rs3745367 was associated with several obesity-related measures in both the young and elderly cohort. Rs3745369 was only associated with obesity-phenotypes in the elderly cohort. When studying the combined cohorts, we could confirm the associations of rs3745367 with several obesity-related parameters. We were unable to identify any association between RETN polymorphisms and bone-related measurements. Together, these results illustrate resistin's role in the development of obesity. Rs3745367 gives the most consistent results in the current study and these should be confirmed in other populations. Research into its possible functional effect might also be required. A role for RETN variants in determining bone mineral density seems unlikely from our results.

Examining the link between bariatric surgery, bone loss, and osteoporosis: a review of bone density studies

As the popularity of bariatric surgery to treat morbid obesity has risen, so has a concern of increased skeletal fragility secondary to accelerated bone loss following bariatric procedures. We reviewed cross-sectional and prospective literature reporting bone density outcomes following bariatric surgical treatment for morbid obesity. Prospective research provides evidence of hip and lumbar spine areal bone mineral density (aBMD) reductions primarily in women despite calcium and vitamin D supplementation. Femoral neck aBMD declines of 9-11% and lumbar spine aBMD reductions up to 8% were observed at the first post-operative year following malabsorptive procedures. Mean T- and Z-scores up to 25 years following surgery remained within normal and healthy ranges. Of those studies reporting development of osteoporosis following gastric bypass, one woman became osteoporotic after 1 year. Despite observed bone loss in the hip region post-surgery, data do not conclusively support increased incidence of osteoporosis or increased fracture risk in post-bariatric patients. However, given the limitations of dual energy X-ray absorptiometry technology in this population and the relative lack of long-term prospective studies that include control populations, further research is needed to provide conclusive evidence regarding fracture outcomes in this population.

Noggin is novel inducer of mesenchymal stem cell adipogenesis: implications for bone health and obesity

Noggin is a glycosylated-secreted protein known so far for its inhibitory effects on bone morphogenetic protein (BMP) signaling by sequestering the BMP ligand. We report here for the first time a novel mechanism by which noggin directly induces adipogenesis of mesenchymal stem cells independently of major human adipogenic signals through C/EBPδ, C/EBPα and peroxisome proliferator-activated receptor-γ. Evaluation of a possible mechanism for noggin-induced adipogenesis of mesenchymal stem cells identified the role of Pax-1 in mediating such differentiation. The relevance of elevated noggin levels in obesity was confirmed in a preclinical, immunocompetent mouse model of spontaneous obesity and in human patients with higher body mass index. These data clearly provide a novel role for noggin in inducing adipogenesis and possibly obesity and further indicates the potential of noggin as a therapeutic target to control obesity.

Correlation of circulating omentin-1 with bone mineral density in multiple sclerosis: the crosstalk between bone and adipose tissue

Background

Patients with multiple sclerosis (MS) are at increased risk of osteoporosis and fractures. Adipose tissue-derived adipokines may play important roles in the osteoimmunology of MS. In order to determine whether omentin-1 and vaspin may be related to bone health in MS patients, we compared circulating levels of these recently identified adipokines, between MS patients and healthy controls.

Methods

A total of 35 ambulatory MS patients with relapsing-remitting courses were compared with 38 age- and sex-matched healthy controls. Bone mineral density (BMD) was determined for the lumbar spine (L2–L4) and the proximal femur using dual-energy x-ray absorptiometry. Circulating omentin-1, vaspin, osteocalcin, osteopontin, osteoprotegerin, the receptor activator of nuclear factor-κB ligand, matrix metalloproteinase 9, C-reactive protein and 25-hydroxy vitamin D levels were evaluated by highly specific enzyme-linked immunosorbent assay methods.

Results

There was no significant difference between the two groups regarding bone-related cytokines, adipocytokines, and the BMD measurements of patients with MS and the healthy controls. However, in multiple regression analysis, serum omentin-1 levels were positively correlated with BMD at the femoral neck (β = 0.49, p = 0.016), total hip (β = 0.42, p = 0.035), osteopontin (β = 0.42, p = 0.030) and osteocalcin (β = 0.53, p = 0.004) in MS patients. No correlations were found between vaspin, biochemical, and BMD measures in both groups.

Conclusions

Elevated omentin-1 serum levels are correlated with BMD at the femoral neck and the serum levels of osteocalcin and osteopontin in MS patients. Therefore, there is crosstalk between adipose tissue and bone in MS.

Effects of increased hypothalamic leptin gene expression on ovariectomy-induced bone loss in rats

Estrogen deficiency results in accelerated bone turnover with a net increase in bone resorption. Subcutaneous administration of leptin attenuates bone loss in ovariectomized (ovx) rats by reducing bone resorption. However, in addition to its direct beneficial effects, leptin has been reported to have indirect (central nervous system-mediated) antiosteogenic effects on bone, which may limit the efficacy of elevated serum leptin to prevent estrogen deficiency-associated bone loss. The present study evaluated the long-term effects of increased hypothalamic leptin transgene expression, using recombinant adeno-associated virus-leptin (rAAV-Lep) gene therapy, on bone mass, architecture, and cellular endpoints in sexually mature ovx Sprague-Dawley rats. Ovx rats were implanted with cannulae in the 3rd ventricle of the hypothalamus and injected with either rAAV-Lep or rAAV-GFP (control vector encoding green fluorescent protein) and maintained for 10 weeks. Additional controls consisted of ovary-intact rats and ovx rats pair-fed to rAAV-Lep rats. Lumbar vertebrae were analyzed by micro-computed tomography and tibiae by histomorphometry. Cancellous bone volume was lower and osteoclast perimeter, osteoblast perimeter, and bone marrow adipocyte density were greater in ovx rats compared to ovary-intact controls. In contrast, differences among ovx groups were not detected for any endpoint evaluated. In conclusion, whereas estrogen deficiency resulted in marked cancellous osteopenia, increased bone turnover and marrow adiposity, increasing hypothalamic leptin transgene expression in ovx rats had neither detrimental nor beneficial effects on bone mass, architecture, or cellular endpoints. These findings demonstrate that the antiresorptive effects of subcutaneous leptin administration in ovx rats are mediated through leptin targets in the periphery.

Is obesity in women protective against osteoporosis?

The belief that obesity is protective against osteoporosis has recently come into question. The latest epidemiologic and clinical studies have shown that a high level of fat mass might be a risk factor for osteoporosis and fragility fractures. Further, increasing evidence seems to indicate that different components of the metabolic syndrome, ie, hypertension, increased triglycerides, reduced high-density lipoprotein cholesterol, are also potential risk factors for the development of low bone mineral density and osteoporosis. This review considers both the older and more recent data in the literature in order to evaluate further the relationship between fat tissue and bone tissue.

Hormone-sensitive lipase-knockout mice maintain high bone density during aging

We tested the hypothesis that the actions of hormone-sensitive lipase (HSL) affect the microenvironment of the bone marrow and that removal of HSL function by gene deletion maintains high bone mass in aging mice. We compared littermate control wild-type (WT) and HSL(-/-) mice during aging for changes in serum biochemical values, trabecular bone density using micro-computed tomography, bone histomorphometry, and characteristics of primary bone marrow cells and preosteoblasts. There is a regulated expression of HSL and genes involved in lipid metabolism in the bone marrow during aging. HSL(-/-) mice have increased serum levels of insulin and osteocalcin with decreased leptin levels. Compared with the marked adipocyte infiltration in WT bone marrow (65% by area) at 14 mo, HSL(-/-) mice have fewer (16%, P<0.05) and smaller adipocytes in bone marrow. While peak bone density is similar, HSL(-/-) mice maintain a higher bone density (bone volume/total volume 6.1%) with age than WT mice (2.6%, P<0.05). Primary osteoblasts from HSL(-/-) mice show increased growth rates and higher osteogenic potential, manifested by increased expression of Runx2 (3.5-fold, P<0.05) and osteocalcin (4-fold, P<0.05). The absence of HSL directs cells within the bone marrow toward osteoblast differentiation and favors the maintenance of bone density with aging.