Determinants of Low Bone Turnover in Type 2 Diabetes-the Role of PTH

Serum Pentosidine in Relation to Obesity in Patients with Type 2 Diabetes and Healthy Controls

Pentosidine (PEN), a surrogate marker of advanced glycation end-product formation, reflects increased non-enzymatic cross-linking in bone collagen, which is thought to be an important determinant of bone fragility in type 2 diabetes mellitus (T2DM). We aimed to investigate serum concentrations of PEN in patients with T2DM and controls without T2DM and to examine its relationship with bone parameters and metabolic state such as glycaemic control, insulin resistance and body weight. In a cross-sectional study-design, data from postmenopausal women and men with T2DM (n = 110) and controls without T2DM (n = 111) were evaluated. Serum PEN was measured using an ELISA-based assay (CSB-E09415h, Cusabio). In addition, biochemical markers of glucose metabolism and bone turnover markers were measured. Bone mineral density (BMD) was assessed by dual-energy X-ray absorptiometry. After adjustment for age, gender and body mass index (BMI), serum PEN was significantly higher in patients with T2DM compared to controls (p = 0.02) and most prominently in women with T2DM (p = 0.09). We found a strong association of serum PEN concentrations with BMI in the entire study population (R = 0.43, p < 0.001) as well as in patients with T2DM (R = 0.28, p < 0.01). While bone turnover markers were significantly decreased, and BMD increased in patients with T2DM, only weak or no associations were observed between these skeletal surrogate markers and serum PEN. We conclude that serum PEN is strongly associated with BMI with highest levels in obese women with T2DM. Adjustment for patient's weight is needed when evaluating serum PEN levels in patients with T2DM.Clinical Trial Information: NCT02551315.

Role of Anabolic Anti-Osteoporosis Therapy in Diabetes Subjects

Diabetes mellitus (DM) is a metabolic disorder that leads to the destruction of various tissues including bones. The pathogenesis of osteoporosis (OP) varies in DM due to many specific factors. DM increases the risk of fracture as well as post-fracture mortality. It is because of this fact that OP treatment should not be neglected in patients with DM. OP therapy comprises anabolic as well as anti-resorptive agents. Primary OP as observed in post-menopausal women is associated with high bone turnover, whereas OP in DM is a disease of low bone turnover. Therefore, anabolic agents seem to be quite promising in cases of OP in DM. Although the anti-fracture efficacy of these drugs is proven beyond any doubt in the general population without DM, evidence in persons with DM is limited. Among the anabolic agents, teriparatide has the most evidence in favor of its efficacy and safety in persons with DM. Studies evaluating other anabolic agents such as abaloparatide and romosozumab in diabetic osteopathy are scarce in the literature. Future studies specifically in both type 1 and type 2 DM populations are needed to evaluate the effects of osteoanabolic agents.

Understanding the impact of diabetes on bone health: A clinical review

Diabetic bone disease, a form of secondary osteoporosis, is characterized by weakened bones and an increased risk of fractures, especially in patients with type 2 diabetes (T2D). This review explores the key mechanisms driving this condition, including hyperglycemia, insulin resistance, advanced glycation end products (AGEs), and proinflammatory cytokines, all of which disturb normal bone turnover by disrupting the functions of osteoblasts and osteoclasts. We examine the roles of bone turnover and mineralization, as well as how microvascular complications affect bone microarchitecture. Additionally, the influence of gut hormones, such as GLP-1 and GIP, and gut microbiota, particularly species like Akkermansia muciniphila, on the gut-bone axis is discussed, as these factors play a role in regulating bone density and structure. While T2D patients may show normal or even elevated bone mineral density (BMD), the underlying quality of bone is often compromised, leading to increased fragility. This review integrates current knowledge on the molecular, hormonal, and microbial interactions contributing to diabetic bone disease. By highlighting these pathways, we aim to offer insights into potential therapeutic strategies and inform future research aimed at improving the diagnosis, treatment, and overall management of this condition.

Bone mass, microarchitecture and turnover among young Indian women with non-alcoholic fatty liver disease

PURPOSE

To evaluate comprehensive bone health among young Indian women, including bone mass, microarchitecture, and turnover, in relation to their non-alcoholic fatty liver disease (NAFLD) status.

METHODS

This cross-sectional study (May 2018-November 2019) recruited women with a history of gestational diabetes mellitus (GDM) and normoglycemia in their index pregnancy, who were at least 6 months postpartum. All participants underwent abdominal ultrasonography for determination of NAFLD status (grades 2 and 3: severe NAFLD) and transient elastography (FibroScan) for hepatic fibrosis (LSM >6 kPa). Bone mass was assessed by DXA, bone microarchitecture with trabecular bone score {TBS} (low TBS ≤ 1.310) and bone turnover with markers of bone formation (osteocalcin and P1NP), and resorption (CTX).

RESULTS

Bone mineral density (BMD) at femoral neck (p = 0.026) and total hip (p = 0.007) was significantly higher among women with NAFLD (n = 170) compared to those without (n = 124). There was no significant difference in bone turnover markers between the two groups. The presence of NAFLD [adjusted OR: 1.82 (1.07, 3.11)] was associated with low TBS, with a greater strength of association among women with severe NAFLD [adjusted OR: 2.97 (1.12, 7.88)]. However, these associations were attenuated and no longer significant after additionally adjusting for BMI. Women with NAFLD and hepatic fibrosis manifested significantly higher BMD at lumbar spine, femoral neck, and total hip (p < 0.001 for all) and significantly lower bone turnover markers (osteocalcin, p = 0.009 and CTX, p = 0.029), however, the association with low TBS was not observed.

CONCLUSION

Among young Indian women, NAFLD is associated with increased bone mass and impaired bone microarchitecture, and hepatic fibrosis with increased bone mass and reduced bone turnover.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Short- and long-term exposure to high glucose induces unique transcriptional changes in osteoblasts in vitro

Bone is increasingly recognized as a target for diabetic complications. In order to evaluate the direct effects of high glucose on bone, we investigated the global transcriptional changes induced by hyperglycemia in osteoblasts in vitro. Rat bone marrow-derived mesenchymal stromal cells were differentiated into osteoblasts for 10 days, and prior to analysis, they were exposed to hyperglycemia (25 mM) for the short-term (1 or 3 days) or long-term (10 days). Genes and pathways regulated by hyperglycemia were identified using mRNA sequencing and verified with qPCR. Genes upregulated by 1-day hyperglycemia were, for example, related to extracellular matrix organization, collagen synthesis and bone formation. This stimulatory effect was attenuated by 3 days. Long-term exposure impaired osteoblast viability, and downregulated, for example, extracellular matrix organization and lysosomal pathways, and increased intracellular oxidative stress. Interestingly, transcriptional changes by different exposure times were mostly unique and only 89 common genes responding to glucose were identified. In conclusion, short-term hyperglycemia had a stimulatory effect on osteoblasts and bone formation, whereas long-term hyperglycemia had a negative effect on intracellular redox balance, osteoblast viability and function.

Parathyroid Hormone is Negatively Correlated with Glycated Hemoglobin in Newly Diagnosed Type 2 Diabetic Patients

Objective

The growing evidence shows that parathyroid hormone (PTH) may affect glucose metabolism. However, the relationship between them is still controversial among diabetic patients. The current study aimed to investigate the relationship between PTH and glucose metabolism in the patients with newly diagnosed type 2 diabetes (T2D).

Methods

A total of 532 participants, including 387 patients with newly diagnosed T2D and 145 healthy controls, were recruited in the present study. PTH and metabolic parameters were measured in all participants.

Results

The PTH levels were significantly lower in the newly diagnosed T2D patients compared with the control group (35.10 (25.90, 47.20) vs. 47.15 (35.83, 58.65) pg/ml, P < 0.001). The T2D patients with a higher glycated hemoglobin (HbA1c) tertile had lower PTH levels than the patients with a lower HbA1c tertile (32.90 (24.85, 41.40) vs. 37.50 (26.10, 54.55) pg/ml, P < 0.001). Spearman correlation analysis showed that PTH was positively correlated with the body mass index (BMI), fasting insulin (FINS), homeostasis model assessment of β-cell function (HOMA-β), and homeostasis model assessment of insulin resistance (HOMA-IR) and negatively correlated with HbA1c, blood calcium (Ca), blood phosphorus (P), and 25-hydroxyvitamin D3 (25-OH-D3). Multiple linear regression analysis demonstrated that PTH was significantly associated with HbA1c (β = -1.475, P=0.003) and HOMA-β (β = 0.090, P=0.001) after adjusting for age, sex, BMI, season, 25-OH-D3, Ca, and P.

Conclusion

PTH was negatively correlated with HbA1c in the newly diagnosed T2D patients. Our results suggested that the PTH level within the reference range is related to islet β-cell function and hyperglycemia.

La osteocalcina se asocia con la densidad mineral ósea y los polimorfismos del gen VDR en la diabetes tipo 1 y 2

Objetivos

El metabolismo óseo se encuentra alterado en la diabetes mellitus (DM). El objetivo de este estudio es evaluar la relación entre los marcadores de remodelado óseo (MRO), los polimorfismos en el gen receptor de la vitamina D (VDR) y la densidad mineral ósea (DMO) en la DM tipo 1 (T1D) y tipo 2 (T2D).

Métodos

Se incluyó a 165 pacientes (53 T1D y 112 T2D). La DMO se midió mediante absorciometría de rayos X de energía dual (DEXA). Se realizó un análisis de la osteocalcina (OC) en plasma, beta-CrossLaps (β-CTX), propéptido aminoterminal del procolágeno tipo 1 (P1NP) y los polimorfismos en el gen VDR.

Resultados

Se incluyó a 53 pacientes con T1D (41 años (31–48)) y 112 con T2D (60 años [51–66]). No se observaron diferencias estadísticamente significativas en relación a la DMO. Los pacientes con T1D presentaron niveles superiores de OC (p<0,001) y P1NP (p<0,001). Las áreas bajo la curva para la predicción de patología ósea para la OC fueron 0,732 (p=0,038) en T1D y 0,697 (p=0,007) en T2D. Se observó una relación estadísticamente significativa entre el alelo A de BsmI (p=0,03), el alelo A de ApaI (p=0,04) y el alelo C de Taql (p=0,046) y una menor DMO. Así mismo, se encontró una correlación significativa entre los niveles elevados de OC y el alelo G de BsmI (p=0,044), el alelo C de ApaI (p=0,011), el alelo T de Taql (p=0,006) y el alelo C de FokI (p=0,004).

Conclusiones

El elevado valor predictivo negativo del punto de corte de la OC indica que la OC podría ser útil a la hora de descartar el riesgo de pérdida ósea, lo que permitiría diseñar un tratamiento personalizado para prevenir dicha patología.

Osteocalcin associates with bone mineral density and VDR gene polymorphisms in type 1 and type 2 diabetes

Objectives

Bone metabolism is impaired in diabetes mellitus (DM). Our objective is to evaluate the association of bone turnover markers (BTM) and vitamin D receptor (VDR) gene polymorphisms with bone mineral density (BMD) in DM type 1 (T1D) and DM type 2 (T2D).

Methods

A total of 165 patients (53 T1D and 112 T2D) were enrolled. BMD was measured by dual-energy X-ray absorptiometry (DEXA). Plasma osteocalcin (OC), beta-CrossLaps (β-CTX) and N-amino terminal propeptide of type I collagen (P1NP) and VDR gene polymorphisms were evaluated.

Results

Participants were 53 T1D (41 years [31-48]) and 112 T2D (60 years [51-66]). BMD were not statistically different between the groups. OC (p<0.001) and P1NP levels (p<0.001) were higher in patients with T1D. The areas under the curve for the prediction of bone pathology were 0.732 (p=0.038) for OC in T1D and 0.697 (p=0.007) in T2D. A significant association was found between lower lumbar BMD and the A allele of BsmI (p=0.03), the A allele of ApaI (p=0.04) and the allele C of the Taql (p=0.046). Also, a significant correlation was found with higher OC levels and the G allele of BsmI (p=0.044), C allele of ApaI (p=0.011), T allele of Taql (p=0.006) and with C allele of FokI (p=0.004).

Conclusions

The high negative predictive value of the cut-off point for OC suggests that could be useful in excluding the risk suffering bone loss, allowing offering a personalized clinical approach to prevent this pathology.

Effects of metformin on bone mineral density and bone turnover markers: a systematic review and meta-analysis

OBJECTIVES

Metformin is associated with osteoblastogenesis and osteoclastogenesis. This study aims to investigate the impacts of metformin therapy on bone mineral density (BMD) and bone turnover markers.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

METHODS

Searches were carried out in PubMed, EMBASE, Web of science, Cochrane library, ClinicalTrials.gov from database inception to 26 September 2022. Two review authors assessed trial eligibility in accordance with established inclusion criteria. The risk of bias was assessed using the Cochrane Risk of Bias tool (RoB V.2.0). Data analysis was conducted with Stata Statistical Software V.16.0 and Review Manager Software V.5.3.

RESULTS

A total of 15 studies with 3394 participants were identified for the present meta-analysis. Our pooled results indicated that metformin had no statistically significant effects on BMD at lumbar spine (SMD=-0.05, 95% CI=-0.19 to 0.09, p=0.47, participants=810; studies=7), at femoral (MD=-0.01 g/cm2, 95% CI=-0.04 to 0.01 g/cm2, p=0.25, participants=601; studies=3) and at hip (MD=0.01 g/cm2, 95% CI=-0.02 to 0.03 g/cm2, p=0.56, participants=634; studies=4). Metformin did not lead to significant change in osteocalcin, osteoprotegerin and bone alkaline phosphatase. Metformin induced decreases in N-terminal propeptide of type I procollagen (MD=-6.09 µg/L, 95% CI=-9.38 to -2.81 µg/L, p=0.0003, participants=2316; studies=7) and C-terminal telopeptide of type I collagen (MD=-55.80 ng/L, 95% CI=-97.33 to -14.26 ng/L, p=0.008, participants=2325; studies=7).

CONCLUSION

This meta-analysis indicated that metformin had no significant effect on BMD. Metformin decreased some bone turnover markers as N-terminal propeptide of type I procollagen and C-terminal telopeptide of type I collagen. But the outcomes should be interpreted with caution due to several limitations.

Relative comparison of chronic kidney disease-mineral and bone disorder rat models

Objective: The aim of this study is to establish a suitable animal model of chronic kidney disease-mineral and bone disorder (CKD-MBD) by comparing CKD-MBD rat models induced by 5/6 Nx, AN, and UUO, accompanied by a low-calcium and high-phosphorus diet. Methods: Sprague‒Dawley rats were randomly divided into four groups: control group, 5/6 nephrectomy (5/6 Nx) group, Adriamycin nephropathy (AN) group, and unilateral ureteral obstruction (UUO) group. Serum biochemical indices were measured to evaluate renal function, mineral and bone metabolism, the severity of CKD-MBD, and the status of bone transformation. Hematoxylin-eosin staining (HE) and Masson's trichrome (Masson) staining were used for histopathological analysis of the kidney. Goldner's trichrome (Goldner) and tartrate-resistant acid phosphatase (TRAP) staining were utilized to observe bone mineralization and osteoclasts in the femur, respectively. Micro-CT images were applied to study the structure of the femur. The expression levels of osterix and cathepsin K in the femur were measured by immunohistochemistry (IHC) to confirm the status of bone transformation. Results: The levels of serum creatinine (Scr) and blood urea nitrogen (BUN) in the 5/6 Nx and AN group rats were significantly higher than those in the control rats, and this change was accompanied by marked changes in the levels of calcium (Ca), phosphate (Pi), intact parathyroid hormone (i-PTH), fibroblast growth factor 23 (FGF23), osteocalcin (OC), and cross-linked C-telopeptide of type 1 collagen (CTX-1); UUO group rats exhibited slight and inconsistent variations in the levels of Scr, BUN, Ca, Pi, i-PTH, FGF23, OC, and CTX-1 in serum. Histopathological analysis of the kidney showed that the UUO group rats suffered serious fibrosis and 5/6 Nx group rats exhibited severe focal calcification. Histopathological analysis of the femur showed that the AN group rats had minimal bone mineralization and that the 5/6 Nx group rats had overactive osteoclasts. Micro-CT revealed that the AN model had the most severe bone destruction and that the 5/6 Nx model had the least severe bone loss among the three models. The expression of cathepsin K in the femur was significantly increased in all models, while the expression of osterix in the femur was only significantly increased in the 5/6 Nx model. Conclusion: 5/6 Nx, AN, and UUO accompanied by a low-calcium and high-phosphorus diet successfully induced CKD-MBD in rats. The 5/6 N_X model presented the progression of high-turnover bone disease, with consistency between biochemical indices in serum and histomorphometric analysis of the femur, and the AN and UUO models developed a severe deterioration in bone quantity and severe bone resorption; however, the changes in biochemical indices were subtle in the UUO model, and liver injury was obvious in the AN model.