Effect of ovariectomy on the progression of chronic kidney disease-mineral bone disorder (CKD-MBD) in female Cy/+ rats

Musculoskeletal Health Worsened from Carnitine Supplementation and Not Impacted by a Novel Individualized Treadmill Training Protocol

INTRODUCTION

Chronic kidney disease (CKD) negatively affects musculoskeletal health, leading to reduced mobility, and quality of life. In healthy populations, carnitine supplementation and aerobic exercise have been reported to improve musculoskeletal health. However, there are inconclusive results regarding their effectiveness and safety in CKD. We hypothesized that carnitine supplementation and individualized treadmill exercise would improve musculoskeletal health in CKD.

METHODS

We used a spontaneously progressive CKD rat model (Cy/+ rat) (n = 11-12/gr): (1) Cy/+ (CKD-Ctrl), (2) CKD-carnitine (CKD-Carn), and (3) CKD-treadmill (CKD-TM). Carnitine (250 mg/kg) was injected daily for 10 weeks. Rats in the treadmill group ran 4 days/week on a 5° incline for 10 weeks progressing from 30 min/day for week one to 40 min/day for week two to 50 min/day for the remaining 8 weeks. At 32 weeks of age, we assessed overall cardiopulmonary fitness, muscle function, bone histology and architecture, and kidney function. Data were analyzed by one-way ANOVA with Tukey's multiple comparisons tests.

RESULTS

Moderate to severe CKD was confirmed by biochemistries for blood urea nitrogen (mean 43 ± 5 mg/dL CKD-Ctrl), phosphorus (mean 8 ± 1 mg/dL CKD-Ctrl), parathyroid hormone (PTH; mean 625 ± 185 pg/mL CKD-Ctrl), and serum creatinine (mean 1.1 ± 0.2 mg/mL CKD-Ctrl). Carnitine worsened phosphorous (mean 11 ± 3 mg/dL CKD-Carn; p < 0.0001), PTH (mean 1,738 ± 1,233 pg/mL CKD-Carn; p < 0.0001), creatinine (mean 1 ± 0.3 mg/dL CKD-Carn; p < 0.0001), cortical bone thickness (mean 0.5 ± 0.1 mm CKD-Ctrl, 0.4 ± 0.1 mm CKD-Carn; p < 0.05). Treadmill running significantly improves maximal aerobic capacity when compared to CKD-Ctrl (mean 14 ± 2 min CKD-TM, 10 ± 2 min CKD-Ctrl; p < 0.01).

CONCLUSION

Carnitine supplementation worsened CKD progression, mineral metabolism biochemistries, and cortical porosity and did not have an impact on physical function. Individualized treadmill running improved maximal aerobic capacity but did not have an impact on CKD progression or bone properties. Future studies should seek to better understand carnitine doses in conditions of compromised renal function to prevent toxicity which may result from elevated carnitine levels and to optimize exercise prescriptions for musculoskeletal health.

The Dietary Fiber Inulin Slows Progression of Chronic Kidney Disease-Mineral Bone Disorder (CKD-MBD) in a Rat Model of CKD

Chronic kidney disease (CKD)-mineral bone disorder (CKD-MBD) leads to fractures and cardiovascular disease. Observational studies suggest beneficial effects of dietary fiber on both bone and cardiovascular outcomes, but the effect of fiber on CKD-MBD is unknown. To determine the effect of fiber on CKD-MBD, we fed the Cy/+ rat with progressive CKD a casein-based diet of 0.7% phosphate with 10% inulin (fermentable fiber) or cellulose (non-fermentable fiber) from 22 weeks to either 30 or 32 weeks of age (~30% and ~15% of normal kidney function; CKD 4 and 5). We assessed CKD-MBD end points of biochemistry, bone quantity and quality, cardiovascular health, and cecal microbiota and serum gut-derived uremic toxins. Results were analyzed by two-way analysis of variance (ANOVA) to evaluate the main effects of CKD stage and inulin, and their interaction. The results showed that in CKD animals, inulin did not alter kidney function but reduced the increase from stage 4 to 5 in serum levels of phosphate and parathyroid hormone, but not fibroblast growth factor-23 (FGF23). Bone turnover and cortical bone parameters were similarly improved but mechanical properties were not altered. Inulin slowed progression of aorta and cardiac calcification, left ventricular mass index, and fibrosis. To understand the mechanism, we assessed intestinal microbiota and found changes in alpha and beta diversity and significant changes in several taxa with inulin, together with a reduction in circulating gut derived uremic toxins such as indoxyl sulfate and short-chain fatty acids. In conclusion, the addition of the fermentable fiber inulin to the diet of CKD rats led to a slowed progression of CKD-MBD without affecting kidney function, likely mediated by changes in the gut microbiota composition and lowered gut-derived uremic toxins. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Differences in hepatocellular iron metabolism underlie sexual dimorphism in hepatocyte ferroptosis

Males show higher incidence and severity than females in hepatic injury and many liver diseases, but the mechanisms are not well understood. Ferroptosis, an iron-mediated lipid peroxidation-dependent death, plays an important role in the pathogenesis of liver diseases. We determined whether hepatocyte ferroptosis displays gender difference, accounting for sexual dimorphism in liver diseases. Compared to female hepatocytes, male hepatocytes were much more vulnerable to ferroptosis by iron and pharmacological inducers including RSL3 and iFSP1. Male but not female hepatocytes exhibited significant increases in mitochondrial Fe2+ and mitochondrial ROS (mtROS) contents. Female hepatocytes showed a lower expression of iron importer transferrin receptor 1 (TfR1) and mitochondrial iron importer mitoferrin 1 (Mfrn1), but a higher expression of iron storage protein ferritin heavy chain 1 (FTH1). It is well known that TfR1 expression is positively correlated with ferroptosis. Herein, we showed that silencing FTH1 enhanced while knockdown of Mfrn1 decreased ferroptosis in HepG2 cells. Removing female hormones by ovariectomy (OVX) did not dampen but rather enhanced hepatocyte resistance to ferroptosis. Mechanistically, OVX potentiated the decrease in TfR1 and increase in FTH1 expression. OVX also increased FSP1 expression in ERK-dependent manner. Elevation in FSP1 suppressed mitochondrial Fe2+ accumulation and mtROS production, constituting a novel mechanism of FSP1-mediated inhibition of ferroptosis. In conclusion, differences in hepatocellular iron handling between male and female account, at least in part, for sexual dimorphism in induced ferroptosis of the hepatocytes.

Assessing cortical bone porosity with MRI in an animal model of chronic kidney disease

Chronic kidney disease (CKD) is characterized by secondary hyperparathyroidism and an increased risk of hip fractures predominantly related to cortical porosity. Unfortunately, bone mineral density measurements and high-resolution peripheral computed tomography (HR-pQCT) imaging have shortcomings that limit their utility in these patients. Ultrashort echo time magnetic resonance imaging (UTE-MRI) has the potential to overcome these limitations by providing an alternative assessment of cortical porosity. The goal of the current study was to determine if UTE-MRI could detect changes in porosity in an established rat model of CKD. Cy/+ rats (n = 11), an established animal model of CKD-MBD, and their normal littermates (n = 12) were imaged using microcomputed tomography (microCT) and UTE-MRI at 30 and 35 weeks of age (which approximates late-stage kidney disease in humans). Images were obtained at the distal tibia and the proximal femur. Cortical porosity was assessed using the percent porosity (Pore%) calculated from microCT imaging and the porosity index (PI) calculated from UTE-MRI. Correlations between Pore% and PI were also calculated. Cy/+ rats had higher Pore% than normal rats at both skeletal sites at 35 weeks (tibia = 7.13 % +/- 5.59 % vs. 0.51 % +/- 0.09 %, femur = 19.99 % +/- 7.72 % vs. 2.72 % +/- 0.32 %). They also had greater PI at the distal tibia at 30 weeks of age (0.47 +/- 0.06 vs. 0.40 +/- 0.08). However, Pore% and PI were only correlated in the proximal femur at 35 weeks of age (ρ = 0.929, Spearman). These microCT results are consistent with prior studies in this animal model utilizing microCT imaging. The UTE-MRI results were inconsistent, resulting in variable correlations with microCT imaging, which may be related to suboptimal bound and pore water discrimination at higher magnetic field strengths. Nevertheless, UTE-MRI may still provide an additional clinical tool to assess fracture risk without using ionizing radiation in CKD patients.

The Dietary Fermentable Fiber Inulin Alters the Intestinal Microbiome and Improves Chronic Kidney Disease Mineral-Bone Disorder in a Rat Model of CKD

Background

Dietary fiber is important for a healthy diet, but intake is low in CKD patients and the impact this has on the manifestations of CKD-Mineral Bone Disorder (MBD) is unknown.

Methods

The Cy/+ rat with progressive CKD was fed a casein-based diet of 0.7% phosphate with 10% inulin (fermentable fiber) or cellulose (non-fermentable fiber) from 22 weeks to either 30 or 32 weeks of age (~30 and ~15 % of normal kidney function). We assessed CKD-MBD, cecal microbiota, and serum gut-derived uremic toxins. Two-way ANOVA was used to evaluate the effect of age and inulin diet, and their interaction.

Results

In CKD animals, dietary inulin led to changes in microbiota alpha and beta diversity at 30 and 32 weeks, with higher relative abundance of several taxa, including Bifidobacterium and Bacteroides , and lower Lactobacillus . Inulin reduced serum levels of gut-derived uremic toxins, phosphate, and parathyroid hormone, but not fibroblast growth factor-23. Dietary inulin decreased aorta and cardiac calcification and reduced left ventricular mass index and cardiac fibrosis. Bone turnover and cortical bone parameters were improved with inulin; however, bone mechanical properties were not altered.

Conclusions

The addition of the fermentable fiber inulin to the diet of CKD rats led to changes in the gut microbiota composition, lowered gut-derived uremic toxins, and improved most parameters of CKD-MBD. Future studies should assess this fiber as an additive therapy to other pharmacologic and diet interventions in CKD.

Significance Statement

Dietary fiber has well established beneficial health effects. However, the impact of fermentable dietary fiber on the intestinal microbiome and CKD-MBD is poorly understood. We used an animal model of progressive CKD and demonstrated that the addition of 10% of the fermentable fiber inulin to the diet altered the intestinal microbiota and lowered circulating gut-derived uremic toxins, phosphorus, and parathyroid hormone. These changes were associated with improved cortical bone parameters, lower vascular calcification, and reduced cardiac hypertrophy, fibrosis and calcification. Taken together, dietary fermentable fiber may be a novel additive intervention to traditional therapies of CKD-MBD.

Cortical porosity occurs at varying degrees throughout the skeleton in rats with chronic kidney disease

Cortical porosity develops in chronic kidney disease (CKD) and increases with progressing disease. Cortical porosity is likely a prominent contributor to skeletal fragility/fracture. The degree to which cortical porosity occurs throughout the skeleton is not fully known. In this study, we assessed cortical bone porosity via micro-computed tomography at multiple skeletal sites in rats with progressive chronic kidney disease. We hypothesized that cortical porosity would occur in long bones throughout the body, but to a lesser degree in flat bones and irregular bones. Porosity was measured, using micro-CT, at 17 different skeletal sites in 6 male rats with CKD. Varying degrees of porosity were seen throughout the skeleton with higher porosity in flat and irregular bone (i.e. parietal bone, mandible) vs. long bones (p = 0.01) and in non-weightbearing bones vs. weightbearing bones (p = 0.01). Porosity was also higher in proximal sites vs. distal sites in long bones (p < 0.01 in all comparisons). There was large heterogeneity in porosity within skeletal sites across rats and within the same rat across skeletal sites. Correlations showed cortical porosity of the proximal tibia was positively associated with porosity at the other sites with the strongest correlation to the parietal bone and the weakest to the ulna. Overall, our data demonstrates varying and significant cortical bone porosity across the skeleton of animals with chronic kidney disease. These data point to careful selection of skeletal sites to assess porosity in pre-clinical studies and the potential for fractures at multiple skeletal sites in patients with CKD.

Effects of ferric citrate and intravenous iron sucrose on markers of mineral, bone, and iron homeostasis in a rat model of CKD-MBD

BACKGROUND

Anemia and chronic kidney disease-mineral and bone disorder (CKD-MBD) are common and begin early in CKD. Limited studies have concurrently compared the effects of ferric citrate (FC) versus intravenous (IV) iron on CKD-MBD and iron homeostasis in moderate CKD.

METHODS

We tested the effects of 10 weeks of 2% FC versus IV iron sucrose in rats with moderate CKD (Cy/+ male rat) and untreated normal (NL) littermates. Outcomes included a comprehensive assessment of CKD-MBD, iron homeostasis and oxidative stress.

RESULTS

CKD rats had azotemia, elevated phosphorus, parathyroid hormone and fibroblast growth factor-23 (FGF23). Compared with untreated CKD rats, treatment with FC led to lower plasma phosphorus, intact FGF23 and a trend (P = 0.07) toward lower C-terminal FGF23. FC and IV iron equally reduced aorta and heart calcifications to levels similar to NL animals. Compared with NL animals, CKD animals had higher bone turnover, lower trabecular volume and no difference in mineralization; these were unaffected by either iron treatment. Rats treated with IV iron had cortical and bone mechanical properties similar to NL animals. FC increased the transferrin saturation rate compared with untreated CKD and NL rats. Neither iron treatment increased oxidative stress above that of untreated CKD.

CONCLUSIONS

Oral FC improved phosphorus homeostasis, some iron-related parameters and the production and cleavage of FGF23. The intermittent effect of low-dose IV iron sucrose on cardiovascular calcification and bone should be further explored in moderate-advanced CKD.

Exosomes Derived from BM-MSCs Mitigate the Development of Chronic Kidney Damage Post-Menopause via Interfering with Fibrosis and Apoptosis

The rate of chronic kidney disease (CKD) is increasing globally, and it is caused by continuous damage to kidney tissue. With time the renal damage becomes irreversible, leading to CKD development. In females, post-menopause lack of estrogen supply has been described as a risk factor for CKD development, and studies targeting post-menopause CKD are scarce. In the present study, we used exosomes isolated from bone marrow mesenchymal stem/stromal cells (BM-MSCs) to test their therapeutic potential against the development of CKD. At first, the menopause model was achieved by surgical bilateral ovariectomy in female albino rats. After that, 100 µg of exosomes was given to ovariectomized rats, and the study continued for 2 months. Changes in urine volume, urine protein content, kidney function biochemical parameters (creatinine and BUN), kidney antioxidant parameters (SOD, GPx and CAT), histological changes, immunohistochemical levels of caspase 3, and the gene expression of NGAL (related to kidney damage), TGFβ1 and αSMA (related to fibrosis and EMT), and caspase 3 (related to apoptosis) were studied. After the ovariectomy, the occurrence of CKD was confirmed in the rats by the drastic reduction of serum estrogen and progesterone levels, reduced urine output, increased urinary protein excretion, elevated serum creatinine and BUN, reduced GPx SOD, and CAT in kidney tissue, degenerative and fibrotic lesions in the histopathological examination, higher immunohistochemical expression of caspase 3 and increased expression of all studied genes. After exosomes administration, the entire chronic inflammatory picture in the kidney was corrected, and a near-normal kidney structure and function were attained. This study shows for the first time that BM-MSCs exosomes are potent for reducing apoptosis and fibrosis levels and, thus, can reduce the chronic damage of the kidneys in females that are in their menopause period. Therefore, MSCs-derived exosomes should be considered a valuable therapy for preserving postmenopausal kidney structure and function and, subsequently, could improve the quality of females’ life during menopause.

Non-Additive Effects of Combined NOX1/4 Inhibition and Calcimimetic Treatment on a Rat Model of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD)

Chronic kidney disease-mineral and bone disorder (CKD-MBD) increases cardiovascular calcification and skeletal fragility in part by increasing systemic oxidative stress and disrupting mineral homeostasis through secondary hyperparathyroidism. We hypothesized that treatments to reduce reactive oxygen species formation and reduce parathyroid hormone (PTH) levels would have additive beneficial effects to prevent cardiovascular calcification and deleterious bone architecture and mechanics before end-stage kidney disease. To test this hypothesis, we treated a naturally progressive model of CKD-MBD, the Cy/+ rat, beginning early in CKD with the NADPH oxidase (NOX1/4) inhibitor GKT-137831 (GKT), the preclinical analogue of the calcimimetic etelcalcetide, KP-2326 (KP), and their combination. The results demonstrated that CKD animals had elevated blood urea nitrogen, PTH, fibroblast growth factor 23 (FGF23), and phosphorus. Treatment with KP reduced PTH levels compared with CKD animals, whereas GKT treatment increased C-terminal FGF23 levels without altering intact FGF23. GKT treatment alone reduced aortic calcification and NOX4 expression but did not alter the oxidative stress marker 8-OHdG in the serum or aorta. KP treatment reduced aortic 8-OHdG and inhibited the ability for GKT to reduce aortic calcification. Treatments did not alter heart calcification or left ventricular mass. In the skeleton, CKD animals had reduced trabecular bone volume fraction and trabecular number with increased trabecular spacing that were not improved with either treatment. The cortical bone was not altered by CKD or by treatments at this early stage of CKD. These results suggest that GKT reduces aortic calcification while KP reduces aortic oxidative stress and reduces PTH, but the combination was not additive. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Effects of Ovariectomy and Exercise Training on Mineral Status in a High-Fat Diet-Induced Obesity Rat Model

Osteoporosis is a growing public health issue for an aging society. Previous studies have found both beneficial and detrimental effects of obesity on bone health. The purpose of this study was to investigate the impact of estrogen deficiency and physical activity on bone and blood concentrations of macrominerals (Ca, P, and Mg) and microminerals (Zn, Se, Cu, and Fe) in a high-fat diet-induced obesity rat model. Forty-eight female Wistar rats were divided into six groups: sham-operated and ovariectomized rats that received a standard diet (SD), high-fat diet (HFD), or HFD accompanied by physical exercise. The effect of ovariectomy on bone minerals varied with diet. Ovariectomy significantly decreased femoral Ca and Mg in sedentary rats receiving a SD; femoral Se, Cu, Zn, and Fe in sedentary rats on HFD; and plasma Fe in both sedentary rats on SD and exercising rats on HFD. The interaction of ovariectomy and diet had the strongest impact on Mg and Se concentrations in femur. In ovariectomized rats, HFD showed to have a protective effect on bone mineralization (femoral Ca and Mg), and a negative one on antioxidant microminerals (femoral Se, Cu, and Zn). Physical activity reduced the decline of Se, Cu, Zn, and Fe in the femur of ovariectomized rats on HFD. In the current state of knowledge, it is difficult to suggest if decreased femoral levels of antioxidant microminerals may contribute to the pathophysiology of osteoporosis in obese individuals or just reflect the mineral status in the body.

Chios Mastic Gum Consumption Has a Protective Effect on Ovariectomy-Induced Bone Loss in Rats

The purpose of this study was to examine the potential effect of Chios Mastic Gum (CMG) consumption on bone mineral density (BMD) and strength of ovariectomized rats. CMG is a known resin used from ancient times for its beneficial biological properties. Thirty mature female Wistar rats were randomized into three equal groups: sham-operated (control), ovariectomized (OVX), and ovariectomized and administered CMG per os (OVX+CMG). BMD of the total tibia, proximal tibia, and the 6th lumbar vertebra were measured at baseline and at 3 and 6 months post ovariectomy. Bone strength was assessed with three-point-bending (3pb) of the right femur. At 3 and 6 months, BMD values of the OVX+CMG group were significantly higher for the anatomical cites evaluated than those of the OVX group. Femoral thickness assessed via 3pb had intermediate values in the treated group compared to the other groups. Cytology of vaginal smears and uterine weight of the OVX+CMG group were consistent with estrogen depletion. Gastrocnemius muscle and intraperitoneal fat ratios to body weight (BW) of the OVX+CMG group did not significantly differ from the control group. Daily consumption CMG had a protective effect on BMD of the total and proximal tibia and the 6th lumbar vertebra of the rats, without causing undesirable effects on the vaginal epithelium and uterus. The 3pb results also demonstrated a favorable effect on the thickness of rat femurs. In addition, CMG was beneficial for both the muscular system and the intraperitoneal fat/BW ratio of the rats.

Adenine-induced chronic kidney disease induces a similar skeletal phenotype in male and female C57BL/6 mice with more severe deficits in cortical bone properties of male mice

Chronic kidney disease (CKD) causes bone loss, particularly in cortical bone, through formation of cortical pores which lead to skeletal fragility. Animal models of CKD have shown variability in the skeletal response to CKD between males and females suggesting sex may play a role in this variation. Our aim was to compare the impact of adenine-induced CKD on cortical parameters in skeletally mature male and female C57Bl/6 mice. After 10-weeks of adenine-induced CKD, both male and female adenine mice had high serum parathyroid hormone (PTH), high bone turnover, and cortical porosity compared to non-CKD controls. Both sexes had lower cortical thickness, but only male mice had lower cortical bone area. CKD imparted greater deficits in mechanical properties of male mice compared to female mice. These data demonstrate that both male and female mice develop high PTH/high bone turnover in response to adenine-induced CKD and that cortical bone phenotypes are slightly more severe in males, particularly in mechanical properties deficits.

The Beneficial Effect of Boswellic Acid on Bone Metabolism and Possible Mechanisms of Action in Experimental Osteoporosis

Estrogen is instrumental in the pathological process of osteoporosis because a deficiency of this hormone increases the release of bone-resorbing cytokines. Acetyl-11-keto-β-boswellic acid (AKBA), a constituent from Boswellia serrata, has an anti-inflammatory effect by inhibiting tumor necrosis factor-α (TNF-α) expression, which leads to a decline in receptor activator of nuclear factor-kappa B (NF-κB) ligand, and consequently, a reduction in osteoclast activity. Hence, AKBA may be beneficial against bone loss during osteoporosis. Therefore, the current study intended to evaluate the beneficial effects of AKBA in ovariectomy-induced osteoporosis and to investigate its mechanism of action. Sham-operation or ovariectomy female Sprague Dawley rats were used for evaluating the antiosteoporotic effect of AKBA in this study. AKBA (35 mg/kg, p.o.) and estradiol (0.05 mg/kg, i.m.) were administered for 42 days. At the end of the experiment, body and uterus weights, serum and urine calcium and phosphorus, serum alkaline phosphatase, and urinary creatinine levels, besides serum levels of NF-κB and TNF-α were determined. Weight, length, thickness, hardness, calcium content, as well as the bone mineral density of femur bone and lumbar vertebra were measured. A histopathological examination was also carried out. AKBA ameliorated all tested parameters and restored a normal histological structure. Thus, AKBA showed good antiosteoporotic activity, which may be mediated through its suppression of the NF-κB-induced TNF-α signaling pathway.

Effect of Advanced Glycation End-Products (AGE) Lowering Drug ALT-711 on Biochemical, Vascular, and Bone Parameters in a Rat Model of CKD-MBD

Chronic kidney disease-mineral bone disorder (CKD-MBD) is a systemic disorder that affects blood measures of bone and mineral homeostasis, vascular calcification, and bone. We hypothesized that the accumulation of advanced glycation end-products (AGEs) in CKD may be responsible for the vascular and bone pathologies via alteration of collagen. We treated a naturally occurring model of CKD-MBD, the Cy/+ rat, with a normal and high dose of the AGE crosslink breaker alagebrium (ALT-711), or with calcium in the drinking water to mimic calcium phosphate binders for 10 weeks. These animals were compared to normal (NL) untreated animals. The results showed that CKD animals, compared to normal animals, had elevated blood urea nitrogen (BUN), PTH, FGF23 and phosphorus. Treatment with ALT-711 had no effect on kidney function or PTH, but 3 mg/kg lowered FGF23 whereas calcium lowered PTH. Vascular calcification of the aorta assessed biochemically was increased in CKD animals compared to NL, and decreased by the normal, but not high dose of ALT-711, with parallel decreases in left ventricular hypertrophy. ALT-711 (3 mg/kg) did not alter aorta AGE content, but reduced aorta expression of receptor for advanced glycation end products (RAGE) and NADPH oxidase 2 (NOX2), suggesting effects related to decreased oxidative stress at the cellular level. The elevated total bone AGE was decreased by 3 mg/kg ALT-711 and both bone AGE and cortical porosity were decreased by calcium treatment, but only calcium improved bone properties. In summary, treatment of CKD-MBD with an AGE breaker ALT-711, decreased FGF23, reduced aorta calcification, and reduced total bone AGE without improvement of bone mechanics. These results suggest little effect of ALT-711 on collagen, but potential cellular effects. The data also highlights the need to better measure specific types of AGE proteins at the tissue level in order to fully elucidate the impact of AGEs on CKD-MBD. © 2019 American Society for Bone and Mineral Research.

Biomechanical and tomographic differences in the microarchitecture and strength of trabecular and cortical bone in the early stage of male osteoporosis

Osteoporosis is a continuous process of loss of bone tissue. Compared to women, osteoporosis in men is associated with greater morbidity and mortality. In this study, we conducted tomographic and biomechanical evaluations of trabecular and cortical bone in the early stage of male osteoporosis. Male Wistar rats were subjected to orchiectomy and sham operation. Four weeks after being castrated, decreased levels of testosterone in plasma were found and resulted in concurrent bone loss. Separately, the orchiectomy led to significant tomographic alterations in the trabecular bone number, trabecular separation, and trabecular pattern factor. Data of a mechanistic compression test further showed that the orchiectomy diminished the maximum loading force, displacement at maximum load, energy at maximum load, and ultimate stress. Interestingly, orchiectomy-triggered changes in the maximum loading force and tomographic parameters were highly correlated. In contrast, tomographic and biomechanical analyses showed that 4 weeks after rats were orchiectomized, the thickness, area, maximum loading force, bone stiffness, energy at maximum load, and ultimate stress of the cortical bone were not changed. Taken together, this study showed specific differences in the microarchitecture and strength of trabecular bone in the early stage of male osteoporosis.