Type 2 Diabetes Is Causally Associated With Reduced Serum Osteocalcin: A Genomewide Association and Mendelian Randomization Study

Causality of Genetically Determined Metabolites on Chronic Kidney Disease: A Two-Sample Mendelian Randomization Study In Silico

Introduction: Chronic kidney disease (CKD) is associated with metabolic disorders. However, the evidence for the causality of circulating metabolites to promote or prevent CKD is still lacking. Methods: The two-sample Mendelian randomization (MR) analysis was conducted to evaluate the latent causal relationship between the genetically proxied 486 blood metabolites and CKD. Genome-wide association study (GWAS) data for exposures were derived from 7824 European GWAS on metabolite levels, which have been extensively utilized in the medical field to elucidate the mechanisms underlying disease onset and progression. The random inverse variance weighted (IVW) is the primary analysis for causality analysis while MR-Egger and weighted median as complementary analyses. For the further identification of metabolites, reverse MR and linkage disequilibrium score regression were performed for further evaluation. The drug target for N-acetylornithine was subsequently supplemented into the analysis, with MR and colocalization analysis being utilized. Key metabolic pathways were identified via MetaboAnalyst 4.0 (https://www.metaboanalyst.ca/) online website. Results: N-acetylornithine was identified as a reliable metabolite that increases the susceptibility to estimated glomerular filtration rate (eGFR) decrease (β = 0.047; 95% confidence interval: -0.068 to -0.026; PIVW = 1.5E-5). The "glyoxylate and dicarboxylate metabolism" pathway showed significant relevance to CKD development (P = 6E-4), whereas the "glycine, serine, and threonine metabolism" pathway was also recognized as associated with CKD by general practitioners (P = 7E-4). Colocalization analysis revealed a robust genetic link between N-acetylornithine and both CKD and eGFR, with 85.1% and 99.4% colocalization rates, respectively. IVW-MR analysis substantiated these findings with a significant positive association for CKD (odds ratio = 1.43, P = 4.7E-5) and a negative correlation with eGFR (b = -0.04, P = 1.13E-31). Conclusions: MR was utilized to explore the potential causal links between 61 genetic serum metabolites and CKD. N-acetylornithine and NAT8 were further explored as a potential therapeutic target for CKD treatment.

Current knowledge of bone-derived factor osteocalcin: its role in the management and treatment of diabetes mellitus, osteoporosis, osteopetrosis and inflammatory joint diseases

Osteocalcin (OC) is the most abundant non-collagenous and osteoblast-secreted protein in bone. It consists of two forms such as carboxylated OC (cOC) and undercarboxylated OC (ucOC). While cOC promotes bone mineralization and increases bone strength, ucOC is regarded an endocrinologically active form that may have several functions in multiple end organs and tissues. Total OC (tOC) includes both of these forms (cOC and ucOC) and is considered a marker of bone turnover in clinical settings. Most of the data on OC is limited to preclinical studies and therefore may not accurately reflect the situation in clinical conditions. For the stated reason, the aim of this review was not only to summarize current knowledge of all forms of OC and characterize its role in diabetes mellitus, osteoporosis, osteopetrosis, inflammatory joint diseases, but also to provide new interpretations of its involvement in the management and treatment of aforementioned diseases. In this context, special emphasis was placed on available clinical trials. Significantly lower levels of tOC and ucOC could be associated with the risk of type 2 diabetes mellitus. On the contrary, tOC level does not seem to be a good indicator of high bone turnover status in postmenopausal osteoporosis, osteoarthritis and rheumatoid arthritis. The associations between several pharmacological drugs used to treat all disorders mentioned above and OC levels have also been provided. From this perspective, OC may serve as a medium through which certain medications can influence glucose metabolism, body weight, adiponectin secretion, and synovial inflammation.

Exploring blood metabolites and thyroid disorders: a bidirectional mendelian randomization study

Background

Human blood metabolites have demonstrated close associations with thyroid disorders in observational studies. However, it's essential to determine whether these correlations imply causation. Mendelian Randomization (MR) offers a promising approach to investigate these patterns.

Aims

The primary aim of our investigation is to establish causality between blood metabolites and three thyroid disorders: TC, GD, and HT.

Methods

We employed a two-sample bidirectional MR analysis approach to assess the relationships between 452 blood metabolites and the three aforementioned thyroid disorders. Causal links were estimated using the IVW method, with sensitivity analyses conducted via MR-Egger, Weighted Median, and MR-PRESSO. We assessed potential heterogeneity and pleiotropy using MR-Egger intercept and Cochran's Q statistic. Additionally, we conducted pathway analysis to identify potential metabolic pathways.

Results

We found 46 metabolites that showed suggestive associations with thyroid disease risk, especially Aspartate (ORIVW=7.41; 95%CI: 1.51-36.27; PIVW=0.013) and C-glycosyltryptophan (ORIVW=0.04; 95%CI: 0.00-0.29; PIVW=0.001) impacted TC, Kynurenine (ORIVW=2.69; 95%CI: 1.08-6.66; PIVW=0.032) and 4-androsten-3beta,17beta-diol disulfate 2 (ORIVW=0.78; 95%CI: 0.48-0.91; PIVW=0.024) significantly impacted GD, and Alpha-ketoglutarate (ORIVW=46.89; 95%CI: 4.65-473.28; PIVW=0.001) and X-14189-leucylalanine (ORIVW=0.31; 95%CI: 0.15-0.64 PIVW=0.001) significantly impacted HT. We also detected 23 metabolites influenced by TC and GD. Multiple metabolic pathways have been found to be involved in thyroid disease.

Conclusion

Our MR findings suggest that the identified metabolites and pathways can serve as biomarkers for clinical thyroid disorder screening and prevention, while also providing new insights for future mechanistic exploration and drug target selection.

Investigation of the causal relationship between osteocalcin and dementia: A Mendelian randomization study

Objective

Basic medical studies have reported an improved effect of osteocalcin on cognition. We explored the causal link between osteocalcin and dementia via the implementation of Mendelian randomization methodology.

Methods

Genome-wide association studies were employed to identify single nucleotide polymorphisms (SNPs) showing significant correlations with osteocalcin. Subsequently, A two-sample Mendelian randomization analysis was conducted utilizing the inverse-variance-weighted (IVW) technique to assess the causal relationship between osteocalcin and various types of dementia, including Alzheimer's disease (AD), Parkinson's disease (PD), Lewy body dementia (LBD), and vascular dementia (VD). This approach aimed to minimize potential sources of confounding bias and provide more robust results. Multivariable MR (MVMR) analysis was conducted to adjust for potential genetic pleiotropy.

Results

The study employed three SNPs, namely rs71631868, rs9271374, and rs116843408, as genetic tools to evaluate the causal association of osteocalcin with dementia. The IVW analysis indicated that osteocalcin may have a potential protective effect against AD with an odds ratio (OR) of 0.790 (95 % CI: 0.688-0.906; P < 0.001). However, no significant relationship was observed between osteocalcin and other types of dementia. Furthermore, the MVMR analysis indicated that the impact of osteocalcin on AD remained consistent even after adjusting for age-related macular degeneration and Type 2 diabetes with an OR of 0.856 (95 % CI: 0.744-0.985; P = 0.030).

Conclusions

Our findings provide important insights into the role of osteocalcin in the pathogenesis of AD. Future research is required to clarify the underlying mechanisms and their clinical applications.

The complex pathophysiology of bone fragility in obesity and type 2 diabetes mellitus: therapeutic targets to promote osteogenesis

Fractures associated with Type2 diabetes (T2DM) are major public health concerns in an increasingly obese and aging population. Patients with obesity or T2DM have normal or better than normal bone mineral density but at an increased risk for fractures. Hence it is crucial to understand the pathophysiology and mechanism of how T2DM and obesity result in altered bone physiology leading to increased fracture risk. Although enhanced osteoclast mediated bone resorption has been reported for these patients, the most notable observation among patients with T2DM is the reduction in bone formation from mostly dysfunction in osteoblast differentiation and survival. Studies have shown that obesity and T2DM are associated with increased adipogenesis which is most likely at the expense of reduced osteogenesis and myogenesis considering that adipocytes, osteoblasts, and myoblasts originate from the same progenitor cells. Furthermore, emerging data point to an inter-relationship between bone and metabolic homeostasis suggesting that these physiologic processes could be under the control of common regulatory pathways. Thus, this review aims to explore the complex mechanisms involved in lineage differentiation and their effect on bone pathophysiology in patients with obesity and T2DM along with an examination of potential novel pharmacological targets or a re-evaluation of existing drugs to improve bone homeostasis.

The effect of type 2 diabetes mellitus on the prognosis of osteoporotic vertebral compression fracture with osteoporotic fracture classification after vertebroplasty

BACKGROUND

To analyze the clinical and radiological effects of type 2 diabetes mellitus on the prognosis of osteoporotic vertebral compression fracture after percutaneous vertebroplasty, and explore the prognostic value of osteoporotic fracture classification.

METHODS

Osteoporotic vertebral compression fracture patients who received vertebroplasty from January 1, 2016 to June 30, 2021 were divided into type 2 diabetes mellitus group and control group in this retrospective cohort study. Visual analogue scale, Oswestry Disability Index, bone cement leakage, new compression fracture, anterior, middle, and posterior portion heights of vertebral body and local Cobb angle on X-ray before surgery, 2 days after surgery, 6 months, and 12 months after surgery were recorded, and the osteoporotic fracture classification was performed. P < 0.05 was set as statistical significance.

RESULTS

A total of 261 vertebral bodies were included, containing 68 in the type 2 diabetes mellitus group and 193 in the control group. There were no differences in baseline characteristics between the two groups. At 6 months after vertebroplasty, the local Cobb angle of the type 2 diabetes mellitus group was 8.29 ± 4.90° greater than that of the control group 6.05 ± 5.18° (P = 0.002). At 12 months, compared with pre-operation, the anterior portion height recovered 8.13 ± 12.90%, which was less than 12.51 ± 14.92% of the control group (P = 0.032), and 19.07 ± 16.47% of the middle portion height recovery was less than the control group's 24.63 ± 17.67% (P = 0.024). Compared with the control group, osteoporotic fracture 2 vertebral bodies of the type 2 diabetes mellitus group at 12 months postoperatively in middle portion height (14.82 ± 14.71% vs 24.78 ± 18.16%, P = 0.023) and local Cobb angle (5.65 ± 4.06° vs 3.26 ± 4.86°, P = 0.043) restored significantly worse. Besides, osteoporotic fracture 3 with type 2 diabetes mellitus restored worse in anterior portion height (5.40 ± 11.02% vs 13.57 ± 12.79%, P = 0.008), middle portion height (11.22 ± 15.53% vs 17.84 ± 12.36%, P = 0.041) and local Cobb angle (10.85 ± 3.79 vs 7.97 ± 3.83°, P = 0.002) at 12 months postoperatively. There was no difference in radiological outcomes of osteoporotic fracture 4 between the two groups.

CONCLUSIONS

The degree of fractured vertebral compression, the recovery of the height and angle obtained immediately after surgery and the clinical symptoms in type 2 diabetes mellitus patients were not different from those in the control. However, vertebral body morphology of type 2 diabetes mellitus patients was worse since the sixth month after surgery. Osteoporotic fracture classification has a good prognostic reference value for both the control and the type 2 diabetes mellitus population.

Uncarboxylated Osteocalcin Decreases SCD1 by Activating AMPK to Alleviate Hepatocyte Lipid Accumulation

Uncarboxylated osteocalcin (GluOC), a small-molecule protein specifically synthesized and secreted by osteoblasts, is important in the regulation of energy metabolism. In our previous study, GluOC was shown to be effective in ameliorating dyslipidemia and hepatic steatosis in KKAy mice. However, the underlying mechanism of GluOC action on hepatocytes has not been well validated. In this study, oleic acid/palmitic acid (OA/PA)-induced HepG2 and NCTC 1469 cells were used as non-alcoholic fatty liver disease (NAFLD) cell models, and triacylglycerol (TG) levels were measured by oil red O staining, Nile Red staining, and ELISA. The fatty acid synthesis-related protein expression was detected by real-time quantitative polymerase chain reaction, Western blotting, and immunofluorescence. The results show that GluOC reduced triglyceride levels, and decreased the expression of sterol regulatory element-binding protein-1c (SREBP-1c) and stearyl-coenzyme A desaturase 1 (SCD1). si-SCD1 mimicked the lipid accumulation-reducing effect of GluOC, while overexpression of SCD1 attenuated the effect of GluOC. In addition, GluOC activated AMP-activated protein kinase (AMPK) phosphorylation to affect lipid metabolism in hepatocytes. Overall, the results of this study suggest that GluOC decreases SCD1 by activating AMPK to alleviate hepatocyte lipid accumulation, which provides a new target for improving NAFLD in further research.

Causal linkage of tobacco smoking with ageing: Mendelian randomization analysis towards telomere attrition and sarcopenia

BACKGROUND

Ageing traits and frailty are important health issues in modern medicine. Evidence supporting the causal effects of tobacco smoking on various ageing traits is required.

METHODS

This study performed Mendelian randomization (MR) analysis instrumenting 377 genetic variants associated with being an ever-smoker at a genome-wide significance level to test the causal estimates from tobacco smoking. The outcome data were obtained from 337 138 white British ancestry participants from the UK Biobank. Leucocyte telomere length, appendicular lean mass index, subjective walking pace, handgrip strength, and wristband accelerometry-determined physical activity degree were collected as ageing-related outcomes. Summary-level MR analysis was performed using the inverse variance-weighted method and pleiotropy-robust MR methods, including weighted median and MR-Egger. Observational association between the outcome traits and phenotypically being an ever-smoker was also investigated.

RESULTS

Summary-level MR analysis indicated that a higher genetic predisposition for tobacco smoking was significantly associated with shorter leucocyte telomere length (twofold increase in prevalence of smoking towards standardized Z-score, -0.041 [-0.054, -0.028]), lower appendicular lean mass index (-0.007 [-0.010, -0.005]), slower walking pace (ordinal category, -0.047 [-0.054, -0.033]) and lower time spent on moderate-to-vigorous physical activity (hours per week, -0.39 [-0.56, -0.23]). The causal estimates were non-significant towards handgrip strength phenotype (kg, 0.074 [-0.055, 0.204]). Pleiotropy-robust MR results generally supported the main causal estimates. The observational findings also showed significant association between being an ever-smoker and the ageing traits.

CONCLUSIONS

Genetically predicted and observational tobacco smoking status are significantly associated with poor ageing phenotypes. Healthcare providers may continue to reduce tobacco use, which may be helpful in reducing the burden of ageing and frailty.

Twelve Loci Associated With Bone Density in Middle-aged and Elderly Chinese: The Shanghai Changfeng Study

CONTEXT

Previous genome-wide association studies (GWASs) of bone mineral density (BMD) were mainly conducted in Europeans.

OBJECTIVE

To explore genetic variants that affect BMD and sex differences in a Chinese population.

METHODS

A total of 5428 middle-aged and elderly Chinese were included. Dual-energy X-ray absorptiometry was used to measure BMD at the lumbar spine, and total and specific sites of the hip. A mixed linear model was used to analyze the associations between BMD and autosomal genetic variants, adjusting for age, age squared, sex, and menopausal women (model 1); model 2 was further adjusted for height and weight. A GWAS of osteoporosis in the Biobank Japan (BBJ) project was used for replication. GWAMA software was used to detect the statistical significance of sex differences of estimated effects. Gene annotation and pathway enrichment analysis were performed.

RESULTS

Women lost BMD at earlier ages and faster than men. The 2 models identified a total of 12 loci that were associated with BMD at any site. Single nucleotide polymorphisms rs72354346, rs2024219, rs1463093, rs10037512, and rs5880932 were successfully replicated in the BBJ. Variations of rs79262027 G>A (VKORC1L1) and rs4795209 A>G (DDX52) were associated with BMD only in men, and rs1239055408 G>GA (KCNJ2) was associated with BMD only in women. Gene enrichment analysis showed that BMD in a Chinese elderly population was mainly related to ossification, bone resorption, sex hormones, and kidney physiology.

CONCLUSION

The present GWAS identified 12 loci that were significantly associated with BMD at any site in a Chinese population, and 3 of them showed sex differences in their effects.

Genetic Determinants of 25-Hydroxyvitamin D Concentrations and Their Relevance to Public Health

Twin studies suggest a considerable genetic contribution to the variability in 25-hydroxyvitamin D (25(OH)D) concentrations, reporting heritability estimates up to 80% in some studies. While genome-wide association studies (GWAS) suggest notably lower rates (13−16%), they have identified many independent variants that associate with serum 25(OH)D concentrations. These discoveries have provided some novel insight into the metabolic pathway, and in this review we outline findings from GWAS studies to date with a particular focus on 35 variants which have provided replicating evidence for an association with 25(OH)D across independent large-scale analyses. Some of the 25(OH)D associating variants are linked directly to the vitamin D metabolic pathway, while others may reflect differences in storage capacity, lipid metabolism, and pathways reflecting skin properties. By constructing a genetic score including these 25(OH)D associated variants we show that genetic differences in 25(OH)D concentrations persist across the seasons, and the odds of having low concentrations (<50 nmol/L) are about halved for individuals in the highest 20% of vitamin D genetic score compared to the lowest quintile, an impact which may have notable influences on retaining adequate levels. We also discuss recent studies on personalized approaches to vitamin D supplementation and show how Mendelian randomization studies can help inform public health strategies to reduce adverse health impacts of vitamin D deficiency.

Causality of genetically determined metabolites on anxiety disorders: a two-sample Mendelian randomization study

BACKGROUND

Although anxiety disorders are one of the most prevalent mental disorders, their underlying biological mechanisms have not yet been fully elucidated. In recent years, genetically determined metabolites (GDMs) have been used to reveal the biological mechanisms of mental disorders. However, this strategy has not been applied to anxiety disorders. Herein, we explored the causality of GDMs on anxiety disorders through Mendelian randomization study, with the overarching goal of unraveling the biological mechanisms.

METHODS

A two-sample Mendelian randomization (MR) analysis was implemented to assess the causality of GDMs on anxiety disorders. A genome-wide association study (GWAS) of 486 metabolites was used as the exposure, whereas four different GWAS datasets of anxiety disorders were the outcomes. Notably, all datasets were acquired from publicly available databases. A genetic instrumental variable (IV) was used to explore the causality between the metabolite and anxiety disorders for each metabolite. The MR Steiger filtering method was implemented to examine the causality between metabolites and anxiety disorders. The standard inverse variance weighted (IVW) method was first used for the causality analysis, followed by three additional MR methods (the MR-Egger, weighted median, and MR-PRESSO (pleiotropy residual sum and outlier) methods) for sensitivity analyses in MR analysis. MR-Egger intercept, and Cochran's Q statistical analysis were used to evaluate possible heterogeneity and pleiotropy. Bonferroni correction was used to determine the causative association features (P < 1.03 × 10^-4). Furthermore, metabolic pathways analysis was performed using the web-based MetaboAnalyst 5.0 software. All statistical analysis were performed in R software. The STROBE-MR checklist for the reporting of MR studies was used in this study.

RESULTS

In MR analysis, 85 significant causative relationship GDMs were identified. Among them, 11 metabolites were overlapped in the four different datasets of anxiety disorders. Bonferroni correction showing1-linoleoylglycerophosphoethanolamine (OR_{fixed-effect IVW} = 1.04; 95% CI 1.021-1.06; P_{fixed-effect IVW} = 4.3 × 10^-5) was the most reliable causal metabolite. Our results were robust even without a single SNP because of a "leave-one-out" analysis. The MR-Egger intercept test indicated that genetic pleiotropy had no effect on the results (intercept = - 0.0013, SE = 0.0006, P = 0.06). No heterogeneity was detected by Cochran's Q test (MR-Egger. Q = 7.68, P = 0.742; IVW. Q = 12.12, P = 0.436). A directionality test conducted by MR Steiger confirmed our estimation of potential causal direction (P < 0.001). In addition, two significant pathways, the "primary bile acid biosynthesis" pathway (P = 0.008) and the "valine, leucine, and isoleucine biosynthesis" pathway (P = 0.03), were identified through metabolic pathway analysis.

CONCLUSION

This study provides new insights into the causal effects of GDMs on anxiety disorders by integrating genomics and metabolomics. The metabolites that drive anxiety disorders may be suited to serve as biomarkers and also will help to unravel the biological mechanisms of anxiety disorders.

Musculoskeletal Biomarkers Response to Exercise in Older Adults

Exercise is an essential component of any good health style, being particularly important for older adults to counteract the effects of aging, including sarcopenia and osteoporosis, which can result in lower fall probability. Exercise programs for older adults are especially designed for that population. A rigorous evaluation of those programs is necessary to assure most benefit is achieved. Serum biomarkers of proteins intrinsic to musculoskeletal homeostasis could contribute objectively to the assessment of the benefits of exercise. In this work, in addition to the usual physical fitness and balance tests, ELISA assays quantified the serum levels of six proteins and one polysaccharide important for the homeostasis of muscle (troponin T and alpha-actinin), tendon/ligament (tenomodulin), cartilage (cartilage oligomeric matrix protein and hyaluronan) and bone (osteocalcin and sclerostin), before and after 8 weeks of an exercise program tailored to older adults, Stay Strong Stay Healthy, offered at a Community Center and at an Independent Senior Living facility. Statistical significance was determined by non-parametric tests (Wilcoxon Signed Ranks and Mann-Whitney U). Physical fitness and balance improved as expected along with a significant decrease in sclerostin, pointing to less inhibition of bone deposition. However, when considering each type of dwelling separately, older adults always saw a significant decrease of the isoform of troponin T associated with fast-twitch muscles, suggesting that daily levels of physical activity may also have a role in the benefit of older adults from exercise.

Decreased Serum Osteocalcin is an Independent Risk Factor for Metabolic Dysfunction-Associated Fatty Liver Disease in Type 2 Diabetes

PURPOSE

The association between serum osteocalcin (OCN) levels and metabolic dysfunction-associated fatty liver disease (MAFLD) is still controversial. Moreover, few studies have explored their relationship in type 2 diabetes mellitus (T2DM) patients so far. The present study aimed to investigate the association of serum OCN levels with MAFLD in Chinese T2DM patients.

METHODS

This cross-sectional, real-world study included 1889 Chinese T2DM inpatients. MAFLD was diagnosed by abdominal ultrasonography. Participants were divided into four groups according to serum OCN quartiles, among which the clinical characteristics were compared. The association of serum OCN levels with the presence of MAFLD was also analyzed in subjects.

RESULTS

After controlling for sex, age, and diabetes duration, the prevalence of MAFLD significantly decreased across the serum OCN quartiles (55.3%, 52.0%, 48.6%, and 42.1% for the first, second, third, and fourth quartiles, respectively, P < 0.001 for trend). A fully adjusted multiple logistic regression analysis showed that serum OCN levels were independently and negatively associated with the presence of MAFLD in T2DM patients (odds ratio, 0.832; 95% confidence interval, 0.719-0.962; P = 0.013). Furthermore, there were significant decreases in HOMA-IR (P = 0.001 for trend) and C-reactive protein (P < 0.001 for trend) levels across the serum OCN quartiles after controlling for sex, age, and diabetes duration.

CONCLUSION

Serum OCN levels were independently and negatively associated with the presence of MAFLD in Chinese T2DM patients, partially due to the improvement of insulin resistance and inflammation mediated by OCN. Serum OCN may be used as a biomarker to assess the risk of MAFLD in T2DM patients.

The Emerging Role of Bone-Derived Hormones in Diabetes Mellitus and Diabetic Kidney Disease

Diabetic kidney disease (DKD) causes the greatest proportion of end-stage renal disease (ESRD)-related mortality and has become a high concern in patients with diabetes mellitus (DM). Bone is considered an endocrine organ, playing an emerging role in regulating glucose and energy metabolism. Accumulating research has proven that bone-derived hormones are involved in glucose metabolism and the pathogenesis of DM complications, especially DKD. Furthermore, these hormones are considered to be promising predictors and prospective treatment targets for DM and DKD. In this review, we focused on bone-derived hormones, including fibroblast growth factor 23, osteocalcin, sclerostin, and lipocalin 2, and summarized their role in regulating glucose metabolism and DKD.

Novel Insight into the Relationship Between Muscle-Fat and Bone in Type 2 Diabetes Ranging from Normal Weight to Obesity

OBJECTIVE

Decreased bone mineral density (BMD) is a common complication in individuals with type 2 diabetes mellitus (T2DM). Body weight, mainly consisting of muscle and fat, is the main determinant of BMD and fracture risks but does not accurately describe nutritional status. Most studies suggest that skeletal muscle mass (SMM) promotes BMD, while body fat mass (BFM) decreases BMD. However, the combined effect of SMM and BFM on BMD is elusive. Thus, the study aims to explore the combined effect of fat and muscle by the ratio index SMM/BFM on BMD in T2DM.

METHODS

BFM and SMM were measured by the bioelectrical impedance analysis (BIA) method among 593 T2DM individuals ranging from normal weight and obesity. BMD was analyzed by DXA. Novel non-linear generalized additive models (GAMs) were used as the statistical analysis method.

RESULTS

The results demonstrated that BMD T score/Z score of both femur and lumbar vertebrae were significantly higher and waist-hip ratio (WHR) was significantly lower in the high SMM/BFM group of both normal weight and overweight groups in T2DM individuals. Hence, SMM/BFM might be a good factor indicating BMD in different weight ranges. Additionally, the relationship between muscle fat and BMD was not linear. Notably, this correlation was not influenced by hyperglycemia in T2DM since different analytic models adjusted with the age, gender, BMI and HbA1c were adopted in this study. Furthermore, the impact of trunk fat (central, visceral fat most) and non-trunk fat (peripheral, the sum of subcutaneous limb fat most) on BMD was inconsistent. BMD presented unlimited reduction with trunk BFM increasing, while sustaining minimal diminishment with non-trunk BFM accumulation.

CONCLUSION

Our study provided a novel viewpoint relationship between muscle-fat and bone, and SMM/BFM might be a potential biomarker for bone health and clinical treatments of diabetes and related metabolic syndromes.

Osteocalcin and the Physiology of Danger

Bone biology has long been driven by the question as to what molecules affect cell differentiation or the functions of bone. Exploring this issue has been an extraordinarily powerful way to improve our knowledge of bone development and physiology. More recently, a second question has emerged: does bone have other functions besides making bone? Addressing this conundrum revealed that the bone-derived hormone osteocalcin affects a surprisingly large number of organs and physiological processes, including acute stress response. This review will focus on this emerging aspect of bone biology taking osteocalcin as a case study and will show how classical and endocrine functions of bone help to define a new functional identity for this tissue.

Embryonic osteocalcin signalling determines lifelong adrenal steroidogenesis and homeostasis in the mouse

Through their ability to regulate gene expression in most organs, glucocorticoid hormones influence numerous physiological processes and therefore are key regulators of organismal homeostasis. In bone, glucocorticoid hormones inhibit the expression of the hormone Osteocalcin for poorly understood reasons. Here we show that in a classical endocrine feedback loop, osteocalcin in return enhances the biosynthesis of glucocorticoid but also mineralocorticoid hormones (adrenal steroidogenesis) in rodents and primates. Conversely, inactivating osteocalcin signalling in adrenal glands significantly impairs adrenal growth and steroidogenesis in mice. Embryo-made osteocalcin is necessary for normal Sf1 expression in foetal adrenal cells and adrenal cell steroidogenic differentiation, it therefore determines the number of steroidogenic cells present in adrenal glands of adult animals. Embryonic not postnatal osteocalcin also governs adrenal growth, adrenal steroidogenesis, blood pressure, electrolyte equilibrium and the rise of circulating corticosterone during the acute stress response in adult offspring. This osteocalcin-dependent regulation of adrenal development and steroidogenesis occurs even in the absence of a functional of hypothalamus-pituitary-adrenal axis; this explains why osteocalcin administration during pregnancy promotes adrenal growth and steroidogenesis and improves survival of adrenocorticotropic hormone signalling-deficient animals. This study reveals that a bone-derived, embryonic hormone influences lifelong adrenal functions and organismal homeostasis in the mouse.

Causal effects of atrial fibrillation on brain white and gray matter volume: a Mendelian randomization study

BACKGROUND

Atrial fibrillation (AF) and brain volume loss are prevalent in older individuals. We aimed to assess the causal effect of atrial fibrillation on brain volume phenotypes by Mendelian randomization (MR) analysis.

METHODS

The genetic instrument for AF was constructed from a previous genome-wide association study (GWAS) meta-analysis (15,993 AF patients and 113,719 controls of European ancestry). The outcome summary statistics for head-size-normalized white or gray matter volume measured by magnetic resonance imaging were provided by a previous GWAS of 33,224 white British participants in the UK Biobank. Two-sample MR by the inverse variance-weighted method was performed, supported by pleiotropy-robust MR sensitivity analysis. The causal estimates for the effect of AF on ischemic stroke were also investigated in a dataset that included the findings from the MEGASTROKE study (34,217 stroke patients and 406,111 controls of European ancestry). The direct effects of AF on brain volume phenotypes adjusted for the mediating effect of ischemic stroke were studied by multivariable MR.

RESULTS

A higher genetic predisposition for AF was significantly associated with lower grey matter volume [beta -0.040, standard error (SE) 0.017, P=0.017], supported by pleiotropy-robust MR sensitivity analysis. Significant causal estimates were identified for the effect of AF on ischemic stroke (beta 0.188, SE 0.026, P=1.03E-12). The total effect of AF on lower brain grey matter volume was attenuated by adjusting for the effect of ischemic stroke (direct effects, beta -0.022, SE 0.033, P=0.528), suggesting that ischemic stroke is a mediator of the identified causal pathway. The causal estimates were nonsignificant for effects on brain white matter volume as an outcome.

CONCLUSIONS

This study identified that genetic predisposition for AF is significantly associated with lower gray matter volume but not white matter volume. The results indicated that the identified total effect of AF on gray matter volume may be mediated by ischemic stroke.