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Item 445 The effects of dietary fiber based on fermentability and viscosity on phosphorus absorption and the gut microbiome in chronic kidney disease-mineral and bone disorder(Cambridge University Press, 2023-04-24) Biruete, Annabel; Chen, Neal X.; Srinivasan, Shruthi; O'Neill, Kalisha; Nelson, David; Hill Gallant, Kathleen M.; Moe, Sharon M.; Medicine, School of MedicineOBJECTIVES/GOALS: To compare the effects of dietary fiber supplementation based on fermentability and viscosity on phosphorus fractional absorption and the gut microbiome in a rat model of chronic kidney disease-mineral and bone disorder (CKD-MBD). METHODS/STUDY POPULATION: 25-week-old Cy/+ male rats (CKD hereafter) will be randomly assigned to receive one of four fiber treatments (10% w/w each) based on fermentability and viscosity: 1) Cellulose (-fermentability, -viscosity), 2) inulin (+fermentability, -viscosity), 3) psyllium husk (-fermentability, +viscosity), or 4) pectin (+ fermentability, +viscosity). Diets will be formulated with a semipurified diet containing 0.7% phosphorus. Treatments will last for 10 weeks, and rats will be euthanized at 35 weeks of age, where animals have reached kidney failure. Intravenous and oral 33P will be used for intestinal phosphorus fractional absorption and cecal/fecal samples will be obtained at euthanasia for microbiome assessment using shotgun metagenomics. RESULTS/ANTICIPATED RESULTS: Our preliminary data show that fermentable dietary fiber (inulin) impacted phosphorus homeostasis by increasing the circulating levels of fibroblast growth factor-23 (a bone-derived hormone that increases phosphorus excretion in urine) and lowering circulating levels of phosphorus in the Cy/+ male rat model of progressive chronic kidney disease. We hypothesize that dietary fiber impacts phosphorus absorption in gut microbiome-dependent and independent mechanisms. For example, fermentable fiber enhances the production of short-chain fatty acids, lowering the intraluminal pH, and enhancing mineral solubility and absorption. Meanwhile, viscous fibers may encapsulate minerals limiting their absorption if these fibers are non-fermentable. DISCUSSION/SIGNIFICANCE: Hyperphosphatemia, or high circulating phosphorus, is a major factor in the pathogenesis of CKD-MBD. Treatment of hyperphosphatemia is focused on reducing intestinal absorption. However, available therapies vary in their efficacy and focus on phosphorus absorption in the small intestine, ignoring the possible impact of the large intestine.Item Acute High Dietary Phosphorus Following Low-Phosphorus Diet Acclimation Does Not Enhance Intestinal Fractional Phosphorus Absorption in Nephrectomized Male Rats(Wiley, 2022-11-16) Burstad, Kendal M.; Cladis, Dennis P.; Vorland, Colby J.; Wastney, Meryl E.; Biruete, Annabel; Dominguez, James M., II; O’Neill, Kalisha D.; Chen, Neal X.; Moe, Sharon M.; Hill Gallant, Kathleen M.; Medicine, School of MedicineDietary phosphorus restriction and phosphorus binders are commonly prescribed for patients with chronic kidney disease (CKD). However, occurrences of non-adherence to these interventions are common. As low-phosphorus (LP) diets have been consistently experimentally shown in vitro to increase intestinal phosphorus absorption efficiency, a bout of non-adherence to diet or binders may cause an unintended consequence of enhanced intestinal phosphorus absorption. Thus, we aimed to determine the effect of a single bout of high-phosphorus (HP) intake after acclimation to a LP diet. Male Sprague Dawley rats with 5/6 nephrectomy (n = 36) or sham operation (n = 36) were block-randomized to 1 of 3 diets: LP (0.1% P w/w), HP (1.2%), or LP followed by acute HP (LPHP 0.1% then 1.2%). Phosphorus absorption tests were conducted using 33P radioisotope administrated by oral gavage or intravenously (iv). Although the overall two-way ANCOVA model for intestinal fractional phosphorus absorption was non-significant, exploratory comparisons showed intestinal fractional phosphorus absorption efficiency tended to be higher in rats in the LP compared with HP or LPHP groups. Rats in the HP or LPHP groups had higher plasma phosphorus compared with rats in the LP group, but the LPHP group was not different from the HP group. Gene expression of the major intestinal phosphate transporter, NaPi-2b, was lower in the jejunum of rats in the LPHP group compared with rats in the HP group but not different in the duodenum. These results demonstrate that an acute HP load after acclimation to a LP diet does not lead to enhanced intestinal fractional phosphorus absorption efficiency in 5/6 nephrectomized male rats. These data provide evidence against the notion that dietary phosphorus restriction or binder use adversely increases absorption efficiency after a single instance of dietary or binder non-adherence. However, other adverse consequences of fluctuating dietary phosphorus intake cannot be ruled out.Item Adverse effects of autoclaved diets on the progression of chronic kidney disease (CKD) and CKD-Mineral Bone Disorder in rats(Karger, 2020) Biruete, Annabel; Srinivasan, Shruthi; O’Neill, Kalisha D.; Vorland, Colby J.; Hill Gallant, Kathleen M.; Cai, Weijing; Uribarri, Jaime; Johnston, Nancy; Allen, Matthew R.; Chen, Neal X.; Moe, Sharon M.; Medicine, School of MedicineBackground: Autoclaving rodent diets is common in laboratory animals, but autoclaving increases the formation of dietary advanced glycation end-products (AGE). We studied the effect of autoclaved (AC) diet alone or in combination with a diet high in bioavailable phosphorus on biochemistries of chronic kidney disease-mineral and bone disorder (CKD-MBD), intestinal gene expression, and oxidative stress. Methods: Male CKD rats (Cy/+) and normal littermates were fed 1 of 3 diets: AC 0.7% phosphorus grain-based diet for 28 weeks (AC); AC diet for 17 weeks followed by non-autoclaved (Non-AC) 0.7% phosphorus casein diet until 28 weeks (AC + Casein); or Non-AC diet for 16 weeks followed by a Non-AC purified diet until 30 weeks (Non-AC + Casein). Results: AC diets contained ~3× higher AGEs and levels varied depending on the location within the autoclave. Rats fed the AC and AC + Casein diets had higher total AGEs and oxidative stress, irrespective of kidney function. Kidney function was more severely compromised in CKD rats fed AC or AC + Casein compared to Non-AC + Casein. There was a disease-by-diet interaction for plasma phosphorus, parathyroid hormone, and c-terminal fibroblast growth factor-23, driven by high values in the CKD rats fed the AC + Casein diet. Compared to Non-AC + Casein, AC and AC + Casein-fed groups had increased expression of receptor of AGEs and intestinal NADPH oxidase dual oxidase-2, independent of kidney function. Conclusions: Autoclaving rodent diets impacts the progression of CKD and CKD-MBD, highlighting the critical importance of standardizing diets in experiments.Item Adverse mandibular bone effects associated with kidney disease are only partially corrected with bisphosphonate and/or calcium treatment(Karger, 2013) Allen, Matthew R.; Chen, Neal X.; Gattone II, Vincent H.; Moe, Sharon M.; Anatomy & Cell Biology, School of MedicineBACKGROUND/AIMS: Patients with chronic kidney disease (CKD) have a high prevalence of periodontal disease that may predispose to tooth loss and inflammation. The goal of this study was to test the hypotheses that a genetic rat model of progressive CKD would exhibit altered oral bone properties and that treatment with either bisphosphonates or calcium could attenuate these adverse changes. METHODS: At 25 weeks of age, rats were treated with zoledronate (ZOL), calcium gluconate, or their combination for 5 or 10 weeks. Mandible bone properties were assessed using micro-computed tomography to determine bone volume (BV/TV) and cementum-enamel junction to alveolar crest distance (CEJ-AC). RESULTS: Untreated CKD animals had significantly lower BV/TV at both 30 (-5%) and 35 (-14%) weeks of age and higher CEJ-AC (+27 and 29%) compared to normal animals. CKD animals had a significantly higher parathyroid hormone (PTH) compared to normal animals, yet similar levels of C-reactive protein (CRP). ZOL treatment normalized BV/TV over the first 5 weeks but this benefit was lost by 10 weeks. Calcium treatment, alone or in combination with ZOL, was effective in normalizing BV/TV at both time points. Neither ZOL nor calcium was able to correct the higher CEJ-AC caused by CKD. Calcium, but not ZOL, significantly reduced serum PTH, while neither treatment affected CRP. CONCLUSIONS: (i) This progressive animal model of CKD shows a clear mandibular skeletal phenotype consistent with periodontitis, (ii) the periodontitis is not associated with systemic inflammation as measured by CRP, and (iii) reducing PTH has positive effects on the mandible phenotype.Item Adverse mandibular bone effects associated with kidney disease are only partially corrected with bisphosphonate and/or calcium treatment(Published article can be found at: http://www.karger.com/Article/FullText/356335 doi: 10.1159/000356335, 2013-10) Allen, Matthew R.; Chen, Neal X.; Gattone II, Vincent H.; Moe, Sharon M.Background/Aims: Patients with chronic kidney disease (CKD) have high prevalence of periodontal disease that may predispose to tooth loss and inflammation. The goal of this study was to test the hypotheses that a genetic rat model of progressive CKD would exhibit altered oral bone properties and that treatment with either bisphosphonates or calcium could attenuate these adverse changes. Methods: At 25 weeks of age, rats were treated with zoledronate, calcium gluconate, or their combination for 5 or 10 weeks. Mandible bone properties were assessed using micro-computed tomography to determine bone volume (BV/TV) and cementenamel junction to alveolar crest distance (CEJ-AC). Results: Untreated CKD animals had significantly lower BV/TV at both 30 (-5%) and 35 (-14%) weeks of age and higher CEJ-AC (+27 and 29%) compared to normal animals. CKD animals had significantly higher PTH compared to normal animals yet similar levels of C-reactive protein. Zoledronate-treatment normalized BV/TV over the first 5 weeks but this benefit was lost by 10 weeks. Calcium treatment, alone or in combination with zoledronate, was effective in normalizing BV/TV at both time points. Neither zoledronate nor calcium was able to correct the higher CEJ-AC caused by CKD. Calcium, but not zoledronate, significantly reduced serum parathyroid hormone (PTH) while neither treatment affected C-reactive protein. Conclusions: 1) this progressive animal model of chronic kidney disease shows a clear mandibular skeletal phenotype consistent with periodontitis, 2) the periodontitis is not associated with systemic inflammation as measured by C-reactive protein, and 3) reducing PTH has positive effects on the mandible phenotype.Item Age and sex effects on FGF23-mediated response to mild phosphate challenge(Elsevier, 2021) Tippen, Samantha P.; Noonan, Megan L.; Ni, Pu; Metzger, Corinne E.; Swallow, Elizabeth A.; Sacks, Spencer A.; Chen, Neal X.; Thompson, William R.; Prideaux, Matthew; Atkins, Gerald J.; Moe, Sharon M.; Allen, Matthew R.; White, Kenneth E.; Medical and Molecular Genetics, School of MedicineBackground: During aging, there is a normal and mild loss in kidney function that leads to abnormalities of the kidney-bone metabolic axis. In the setting of increased phosphorus intake, hyperphosphatemia can occur despite increased concentrations of the phosphaturic hormone FGF23. This is likely from decreased expression of the FGF23 co-receptor Klotho (KL) with age; however, the roles of age and sex in the homeostatic responses to mild phosphate challenges remain unclear. Methods: Male and female 16-week and 78-week mice were placed on either normal grain-based chow or casein (higher bioavailable phosphate) diets for 8 weeks. Gene expression, serum biochemistries, micro-computed tomography, and skeletal mechanics were used to assess the impact of mild phosphate challenge on multiple organ systems. Cell culture of differentiated osteoblast/osteocytes was used to test mechanisms driving key outcomes. Results: Aging female mice responded to phosphate challenge by significantly elevating serum intact FGF23 (iFGF23) versus control diet; males did not show this response. Male mice, regardless of age, exhibited higher kidney KL mRNA with similar phosphate levels across both sexes. However, males and females had similar blood phosphate, calcium, and creatinine levels irrespective of age, suggesting that female mice upregulated FGF23 to maintain blood phosphorus, and compromised renal function could not explain the increased serum iFGF23. The 17β-estradiol levels were not different between groups, and in vivo bone steroid receptor (estrogen receptor 1 [Esr1], estrogen receptor 2 [Esr2], androgen receptor [Ar]) expression was not different by age, sex, or diet. Trabecular bone volume was higher in males but decreased with both age and phosphate challenge in both sexes. Cortical porosity increased with age in males but not females. In vitro studies demonstrated that 17β-estradiol treatment upregulated FGF23 and Esr2 mRNAs in a dose-dependent manner. Conclusions: Our study demonstrates that aging female mice upregulate FGF23 to a greater degree during a mild phosphate challenge to maintain blood phosphorus versus young female and young/old male mice, potentially due to direct estradiol effects on osteocytes. Thus, the control of phosphate intake during aging could have modifiable outcomes for FGF23-related phenotypes.Item Anti-Sclerostin Antibody Treatment in a Rat Model of Progressive Renal Osteodystrophy(2014-11-18) Moe, Sharon M.; Chen, Neal X.; Newman, Christopher L.; Organ, Jason M.; Kneissel, Michaela; Kramer, Ina; Gattone II, Vincent H.; Allen, Matthew R.Chronic Kidney Disease (CKD) is associated with abnormalities in bone quantity and quality leading to increased fractures. Recent studies suggest abnormalities of Wnt signaling in animal models of CKD and elevated sclerostin levels in patients with CKD. The goal of this study was to evaluate the effectiveness of anti-sclerostin antibody treatment in an animal model of progressive CKD with low and high parathyroid hormone (PTH) levels. Cy/+ male rats (CKD) were treated without or with calcium in the drinking water at 25 weeks of age to stratify the animals into high PTH and low PTH groups, respectively, by 30 weeks. Animals were then treated with anti-sclerostin antibody at 100 mg/kg IV weekly for 5 doses, a single 20 ug/kg subcutaneous dose of zoledronic acid, or no treatment and sacrificed at 35 weeks. As a positive control, the efficacy of anti-sclerostin antibody treatment was also evaluated in normal littermates. The results demonstrated that the CKD animals with high PTH had lower calcium, higher phosphorus, and lower FGF23 compared to the CKD animals with low PTH. Treatment with anti-sclerostin Ab had no effect on any of the biochemistries, while zoledronic acid lowered dkk-1 levels. The anti-sclerostin antibody increased trabecular BV/TV., trabecular mineralization surface, in animals with low, but not high, PTH. Neither anti-sclerostin antibody nor zoledronic acid improved biomechanical properties in the animals. Cortical porosity was severe in high PTH animals and unaffected by either treatment. In contrast, in normal animals treated with anti-sclerostin antibody, there was an improvement in bone volume, cortical geometry, and biomechanical properties. In summary, this is the first study to test the efficacy of anti-sclerostin Ab treatment on animals with advanced CKD. We found efficacy in improving bone properties only when the PTH levels were low.Item Calcitriol suppression of parathyroid hormone fails to improve skeletal properties in an animal model of chronic kidney disease(Karger, 2016) Newman, Christopher L.; Tian, Nannan; Hammond, Max A.; Wallace, Joseph M.; Brown, Drew M.; Chen, Neal X.; Moe, Sharon M.; Allen, Matthew R.; Department of Anatomy & Cell Biology, IU School of MedicineBACKGROUND: Chronic kidney disease (CKD) leads to complex metabolic changes and an increased risk of fracture. Currently, calcitriol is the standard of care as it effectively suppresses parathyroid hormone (PTH) levels in CKD patients. While calcitriol and its analogs improve BMD and reduce fractures in the general population, the extension of these benefits to patients with advanced kidney disease is unclear. Here, the impact of calcitriol on the skeleton was examined in the setting of reduction in PTH. METHODS: Male Cy/+ rats, a PKD-like CKD model, were treated with either vehicle or calcitriol for 5 weeks. Their normal littermates served as controls. Animals were assessed for changes in mineral metabolism and skeletal parameters (microCT, histology, whole bone mechanics and bone quality). RESULTS: PTH levels were significantly higher (12-fold) in animals with CKD compared to normal controls. CKD animals also exhibited negative changes in bone structural and mechanical properties. Calcitriol treatment resulted in a 60% suppression of PTH levels in animals with CKD. Despite these changes, it had no impact on bone volume (cortical or cancellous), bone turnover, osteoclast number or whole bone mechanical properties. CONCLUSIONS: These data indicate that while calcitriol effectively lowered PTH in rats with CKD, it did little to prevent the negative effects of secondary hyperparathyroidism on the skeleton.Item A comparison of calcium to zoledronic acid for improvement of cortical bone in an animal model of CKD(Wiley, 2014-04) Moe, Sharon M.; Chen, Neal X.; Newman, Christopher L.; Gattone II, Vincent H.; Organ, Jason M.; Chen, Xianming; Allen, Matthew R.; Department of Medicine, IU School of MedicinePatients with chronic kidney disease (CKD) have increased risk of fractures, yet the optimal treatment is unknown. In secondary analyses of large randomized trials, bisphosphonates have been shown to improve bone mineral density and reduce fractures. However, bisphosphonates are currently not recommended in patients with advanced kidney disease due to concern about oversuppressing bone remodeling, which may increase the risk of developing arterial calcification. In the present study we used a naturally occurring rat model of CKD with secondary hyperparathyroidism, the Cy/+ rat, and compared the efficacy of treatment with zoledronic acid, calcium given in water to simulate a phosphate binder, and the combination of calcium and zoledronic acid. Animals were treated beginning at 25 weeks of age (approximately 30% of normal renal function) and followed for 10 weeks. The results demonstrate that both zoledronic acid and calcium improved bone volume by micro-computed tomography (µCT) and both equally suppressed the mineral apposition rate, bone formation rate, and mineralizing surface of trabecular bone. In contrast, only calcium treatment with or without zoledronic acid improved cortical porosity and cortical biomechanical properties (ultimate load and stiffness) and lowered parathyroid hormone (PTH). However, only calcium treatment led to the adverse effects of increased arterial calcification and fibroblast growth factor 23 (FGF23). These results suggest zoledronic acid may improve trabecular bone volume in CKD in the presence of secondary hyperparathyroidism, but does not benefit extraskeletal calcification or cortical biomechanical properties. Calcium effectively reduces PTH and benefits both cortical and trabecular bone yet increases the degree of extra skeletal calcification.Item A comparison of calcium to zoledronic acid for improvement of cortical bone in an animal model of CKD(Published article can be found at: http://onlinelibrary.wiley.com/doi/10.1002/jbmr.2089/abstract doi: 10.1002/jbmr.2089, 2013-09-03) Moe, Sharon M.; Chen, Neal X.; Newman, Christopher L.; Gattone II, Vincent H.; Organ, Jason M.; Chen, Xianming; Allen, Matthew R.Patients with chronic kidney disease (CKD) have increased risk of fractures, yet the optimal treatment is unknown. In secondary analyses of large randomized trials, bisphosphonates have been shown to improve bone mineral density and reduce fractures. However, bisphosphonates are currently not recommended in patients with advanced kidney disease due to concern about over-suppressing bone remodeling, which may increase the risk of developing arterial calcification. In the present study we used a naturally occurring rat model of CKD with secondary hyperparathyroidism, the Cy/+ rat, and compared the efficacy of treatment with zoledronic acid, calcium given in water to simulate a phosphate binder, and the combination of calcium and zoledronic acid. Animals were treated beginning at 25 weeks of age (approximately 30% of normal renal function) and followed for ten weeks. The results demonstrate that both zoledronic acid and calcium improved bone volume by microCT and both equally suppressed mineral apposition rate, bone formation rate, and mineralizing surface of trabecular bone. In contrast, only calcium treatment with or without zoledronic acid improved cortical porosity and cortical biomechanical properties (ultimate load and stiffness) and lowered parathyroid hormone (PTH). However, only calcium treatment led to the adverse effects of increased arterial calcification and fibroblast growth factor 23 (FGF23). These results suggest zoledronic acid may improve trabecular bone volume in CKD in the presence of secondary hyperparathyroidism, but does not benefit extraskeletal calcification or cortical biomechanical properties. Calcium effectively reduces PTH and benefits both cortical and trabecular bone yet increases the degree of extra skeletal calcification.