Serum FGF23 Levels Research Articles

OR24-6 Liver-Specific Inhibition of Sialic Acid Biosynthesis Improves Systemic Glucose Homeostasis in Mice

Abstract Glycosylation is an important posttranslational modification that modulates protein expression and function. Sialic acid is the most abundant terminal monosaccharide of N-linked glycosylation in mammalian cells, and its biosynthesis is controlled by the rate-limited enzyme UDP-GlcNAc 2-epimerase/ManNac kinase (GNE). There is a positive association between the abundance of terminally sialylated plasma glycoproteins and the risk of type 2 diabetes (T2DM). The majority of glycosylated plasma proteins are liver-derived, and key hepatic receptors involved in glucose metabolism, such as the insulin receptor (IR) and glucagon receptor (GCGR), are terminally sialylated. Whether and how protein sialylation in the liver influences glucose homeostasis is unknown. To address this question we generated floxed GNE mice and at 4 weeks of age injected males with either AAV8 encoding a liver-specific targeted Cre recombinase or GFP, to yield mice lacking or normally expressing GNE in liver (GNELKO and GNELWT, respectively). Two weeks post AAV8 injection, GNELKO showed a >98% loss of GNE protein selectively in liver and drastic reductions in the sialylation of liver and plasma proteins detected by glycan-specific lectin-based analyses. Whereas body weights/body composition and plasma lipids were unaltered, GNELKO had lower fasting serum glucose and greater glucose tolerance and insulin sensitivity compared to GNELWT; serum insulin or glucose-stimulated insulin secretion were unchanged. In GNELKO mice hyperinsulinemic-euglycemic clamps displayed a loss of insulin suppression of hepatic glucose production, hepatic IRa and IRb subunit expression and Akt and GSK phosphorylation were decreased, and liver glycogen content was lowered >85%. However, there was also evidence of markedly impaired GCGR function in GNELKO mice, with serum glucagon levels raised 18-fold and attenuation of hepatic cAMP production, CREB phosphorylation and gluconeogenesis in response to glucagon. Regarding extrahepatic mechanisms, GNELKO mice displayed enhanced peripheral glucose disposal, and this was associated with increased IRb, Akt and GSK phosphorylation in skeletal muscle, and with serum FGF21 levels elevated by 406%. In additional studies, when invoked following 12 weeks of high fat diet feeding, liver GNE silencing caused dramatic improvements in glucose tolerance and insulin sensitivity. To evaluate the relevance of these findings to humans, liver GNE transcript levels were queried in a publicly available cohort, and they were higher in T2DM patients compared to non-diabetic controls in two independent cohorts (n= 54 and n=9 for Cohort I and n=4 and n=4 for Cohort II, respectively). Collectively these observations reveal that protein sialylation in the liver has dramatic impact on both insulin and glucagon action in the liver, and on peripheral glucose disposal. Further interrogation of the modulation of glucose control mechanisms by protein sialylation may lead to novel approaches to combatting glucose intolerance in T2DM and other conditions. Presentation: Monday, June 13, 2022 12:15 p.m. - 12:30 p.m.

LBSUN132 Adipocyte-specific Ablation Of Fgf23 Attenuates Diet-induced Obesity In Female Mice

Abstract Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that regulates phosphate homeostasis and vitamin D metabolism. In addition to its central role in mineral balance, recent findings suggested that FGF23 is associated with chronic metabolic conditions including cardiovascular disease, diabetes mellitus, and obesity. Circulating FGF23 levels are elevated in obese individuals, and they are correlated with body fat mass and abdominal obesity. Moreover, consumption of high fat diet (HFD) increases serum FGF23 levels. However, the actions of FGF23 in adipocytes and its role in lipid metabolism have not been demonstrated. To understand the role of FGF23 in adipocytes, particularly in obesity, we generated adipocyte-specific Fgf23 null mice using Cre recombinase under the control of the mouse adiponectin (Adipoq) promoter. Both male and female control (Fgf23flox/flox) and knockout (KO, AdipoqCreFgf23flox/flox) mice were fed either HFD (60%kcal fat) or normal fat diet (NFD) at 8 weeks of age for 24 weeks. Body weight measurements were taken every week and percentage of body fat was determined after longitudinally during 24 weeks of diet interventation using in vivo by an EchoMRI scannermicroCT. Serum, adipose tissue, and liver were collected upon sacrifice. After 24 weeks of HFD, male control and KO mice had comparable gain in body weight (BW) and body fat percentage. However, female KO mice had significantly lower body weight and percentage of body fat. Moreover, serum total cholesterol levels were reduced in female KO mice. Triglyceride (TG) content in the liver was significantly reduced in female KO mice, and it corresponded with downregulation of lipid droplet protein Perilipin and fatty acid transporter CD36 mRNA expression in the liver. Transcript levels of hepatic PPARγ, which is positively correlated with fat accumulation in obesity, were also suppressed in female KO mice compared to controls. Obesity is associated with low-grade chronic inflammation, and we found that hepatic mRNA expression of the inflammatory cytokine TNFα was diminished in female KO mice, suggesting that adipocytic Fgf23 modulates lipid accumulation and inflammation. In summary, our results demonstrate for the first time that adipocyte-specific ablation of Fgf23 alleviates attenuates diet-induced obesity and regulates lipid metabolism in a sex-specific manner. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Serum Intact and Total Fibroblast Growth Factor 23 Levels and Iron-related Parameters in Hemodialysis Patients

Objective: Fibroblast growth factor (FGF)23 suppresses erythropoiesis and is implicated in iron metabolism. It was investigated whether high levels of FGF23 was associated with hepcidin levels of iron metabolism markers in hemodialysis patients. Methods: The serum hepcidin, erythroferrone, and intact-FGF23 or total-FGF23 level as well as iron-related parameters at pre-dialysis in 70 hemodialysis (HD) patients was measured and performed a regression analysis. Results: Each measurement for FGF23, including the intact-/total-FGF23 ratio, correlated strongly with both serum inorganic phosphate and calcium-phosphate product concentrations. Serum hepcidin levels showed a positive correlation with TSAT or serum ferritin concentration. In addition, a negative correlation was found between serum of hepcidin and erythroferrone levels, but no correlation was found between FGF23-related measurements and serum hepcidin levels. Both serum FGF23 levels and erythroferrone levels correlated with erythropoietin-stimulating agent treatment. Conclusion: It was strongly suggested that both serum phosphate concentrations and calcium-phosphate products were associated with FGF23 production in HD patients. As previously reported, the association between hepcidin and iron metabolism markers was reconfirmed, but a simple linear relationship between hepcidin and FGF23 was not observed even after adjusting FGF23. However, a significant negative correlation between erythroferrone and serum hepcidin levels was confirmed in HD patients.

Serum Klotho and FGF23 Levels in Patients with Schizophrenia.

The aim of this study is to compare the serum levels of Klotho and fibroblast growth factor 23 in patients with schizophrenia, in whom etiopathogenesis inflammation plays an important role, with those of healthy control subjects and to investigate a possible correlation between these levels. Forty male patients with schizophrenia and 40 healthy male control subjects who were followed up and/or treated at the High-Security Forensic Psychiatry Clinic participated in the study. Sociodemographic data form, the Positive and Negative Syndrome Scale, and the Clinical Global Impression Scale were collected from all subjects, and participants' fibroblast growth factor 23 and Klotho serum levels were measured by the enzyme-linked immunosorbent assay method. The serum levels of Klotho and fibroblast growth factor 23 were significantly higher in schizophrenia patients than in healthy controls (P = .048 and P = .010, respectively). A significant positive correlation was observed between serum levels of Klotho and fibroblast growth factor 23 in subjects (r = 0.816; P < .001). Our study is the first to show significantly higher combined serum levels of fibroblast growth factor 23 and Klotho in patients with schizophrenia. The Klotho/fibroblast growth factor 23 pathway may play a role in the pathogenesis of schizophrenia. The involvement of Klotho and fibroblast growth factor 23 in inflammatory processes has the potential to provide alternative approaches to elucidate the etiopathogenesis and treatment of schizophrenia.

Hepatic metabolite responses to 4-day complete fasting and subsequent refeeding in rats.

BackgroundFasting has been widely used to improve various metabolic diseases in humans. Adaptive fasting is necessary for metabolic adaptation during prolonged fasting, which could overcome the great advantages of short-term fasting. The liver is the main organ responsible for energy metabolism and metabolic homeostasis. To date, we lack literature that describes the physiologically relevant adaptations of the liver during prolonged fasting and refeeding. For that reason, this study aims to evaluate the response of the liver of Sprague-Dawley (SD) rats to prolonged fasting and refeeding.MethodsSixty-six male SD rats were divided into the fasting groups, which were fasted for 0, 4, 8, 12, 24, 48, 72, or 96 h, and the refeeding groups, which were refed for 1, 3, or 6 days after 96 h of fasting. Serum glucose, TG, FFA, β-hydroxybutyrate, insulin, glucagon, leptin, adiponectin and FGF21 levels were assessed. The glucose content, PEPCK activity, TG concentration and FFA content were measured in liver tissue, and the expression of genes involved in gluconeogenesis (PEPCK and G6Pase), ketogenesis (PPARα, CPT-1a and HMGCS2) and the protein expression of nutrient-sensing signaling molecules (AMPK, mTOR and SIRT1) were determined by RT-qPCR and western blotting, respectively.ResultsFasting significantly decreased the body weight, which was totally recovered to baseline after 3 days of refeeding. A 4-day fast triggered an energy metabolic substrate shift from glucose to ketones and caused serum hormone changes and changes in the protein expression levels of nutrient-sensing signaling molecules. Glycogenolysis served as the primary fuel source during the first 24 h of fasting, while gluconeogenesis supplied the most glucose thereafter. Serum FFA concentrations increased significantly with 48 h of fasting. Serum FFAs partly caused high serum β-hydroxybutyrate levels, which became an important energy source with the prolongation of the fasting duration. One day of refeeding quickly reversed the energy substrate switch. Nutrient-sensing signaling molecules (AMPK and SIRT1 but not mTOR signaling) were highly expressed at the beginning of fasting (in the first 4 h). Serum insulin and leptin decreased with fasting initiation, and serum glucagon increased, but adiponectin and FGF21 showed no significant changes. Herein, we depicted in detail the timing of the metabolic response and adaptation of the liver to a 4-day water-only fast and subsequent refeeding in rats, which provides helpful support for the design of safe prolonged and intermittent fasting regimens.

Perioperative variation in serum FGF-23 level and its correlation with MACCE risk in unprotected left main coronary artery disease patients receiving coronary artery bypassing grafting.

ObjectiveFibroblast growth factor-23 (FGF-23) mediates vascular endothelial injury, inflammatory infiltration, and atherosclerosis, which could reflect major adverse cardiac and cerebrovascular event (MACCE) risk in several cardiovascular diseases. This study aims to further investigate the perioperative change of FGF-23, as well as its association with clinical characteristics and MACCE risk in unprotected left main coronary artery disease (ULMCAD) patients receiving coronary artery bypass grafting (CABG).MethodsA total of 226 ULMCAD patients who underwent CABG were enrolled. Serum samples of the patients were collected on the day before CABG, the third day (D3) after CABG, and at discharge; then, the FGF-23 level was determined by enzyme-linked immunosorbent assay. The MACCE rate was recorded during a median follow-up of 25.5 (range: 2.0–46.0) months.ResultsThe median, interquartile range (IQR), and range of FGF-23 level in ULMCAD patients receiving CABG were 717.0, 582.5–869.8, and 407.0–1765.0 pg/ml, respectively. FGF-23 level was increased in patients with both previous heart failure (P = 0.046) and chronic renal failure (P = 0.009) compared to those without. FGF-23 level increased from before surgery [median (IQR): 712.5 (574.5–879.8) pg/ml] to D3 [median (IQR): 844.0 (666.0–1072.5) pg/ml], then declined at discharge [median (IQR): 764.5 (569.3–986.8) pg/ml] (P < 0.001). Meanwhile, the preoperative FGF-23 level (P = 0.028), but not the FGF-23 level at discharge (P = 0.067) was positively correlated with the cumulative MACCE rate. Multivariable Cox's analyses found that preoperative FGF-23 level could independently predict cumulative MACCE rate [P = 0.015, hazards ratio (HR) = 2.940].ConclusionPreoperative FGF-23 level predicts higher MACCE risk in ULMCAD patients undergoing CABG surgery.

P8.151: Serum Klotho and FGF-23 Levels and Their Variability Within Two Years After Kidney Transplantation

Purpose: Klotho is a protein produced in renal tubular cells with nephroprotective actions which acts as a co-receptor for phosphaturic factor FGF-23. The natural history of the production and expression of post-transplant klotho and FGF-23 is still unknown. Our aim is to know the evolution of these molecules during two years after kidney transplant (KT). Methods: Klotho and FGF-23 levels were determined in 42 patients at baseline, third, twelve and twenty-fourth month after kidney transplant (KT), measured by ELISA. The glomerular filtration rate (GFR) of the kidney graft was performed by indirect methods (formula:MDRa and CKD-EPI) at each study visit. Results: A total of 146 kidney transplant patients were included in the study and 42 patients have completed the follow-up. The clinical and demographic characteristics of donor and recipients are shown in Table 1. Klotho levels at the third month decreased significantly in both groups (basal 452,69±236,85 vs third month 408,83± 223,34;p=0.01) rising in month 12 (523.9±279.6), remaining at these values in the second year after KT (511.1±308.3), even higher than before KT. Similarly, when we analyzed the pre-transplant FGF23 in 56 patients, we observed a reduction trend at the third month, which was maintained until 24 months (baseline 783 vs 193.88 at third month, 158.32 at month 12 and 192.10 in month 24;p=0.066).Conclusions: We describe a decreasement in Klotho levels which increase after one year post KT, which could be justified by the “stunned” of the renal tubule after KT, caused by ischemia-reperfusion time, tubular necrosis, treatment with calcineurin inhibitors, which improves and rises to levels even higher than those prior to KT. More prospective studies are needed to confirm these hypotheses.

β-Hydroxybutyrate upregulates FGF21 expression through inhibition of histone deacetylases in hepatocytes.

Fibroblast growth factor 21 (FGF21) is secreted by hepatocytes as a peptide hormone to regulate glucose and lipid metabolism. FGF21 promotes hepatic ketogenesis and increases ketone body utilization in starvation. Histones are the target molecules of nutrients in regulating hepatic metabolic homeostasis. However, the effect of ketone bodies on FGF21 expression and the involvement of histones in it is not clear yet. The present study observed the effects of β-hydroxybutyrate (β-OHB), the main physiological ketone body, on FGF21 expression in human hepatoma HepG2 cells in vitro and in mice in vivo, and the role of histone deacetylases (HDACs) in β-OHB-regulated FGF21 expression was investigated. The results showed that β-OHB significantly upregulated FGF21 gene expression and increased FGF21 protein levels while it inhibited HDACs’ activity in HepG2 cells. HDACs’ inhibition by entinostat upregulated FGF21 expression and eliminated β-OHB-stimulated FGF21 expression in HepG2 cells. Intraperitoneal injections of β-OHB in mice resulted in the elevation of serum β-OHB and the inhibition of hepatic HDACs’ activity. Meanwhile, hepatic FGF21 expression and serum FGF21 levels were significantly increased in β-OHB-treated mice compared with the control. It is suggested that β-OHB upregulates FGF21 expression through inhibition of HDACs’ activity in hepatocytes.

FGF21 Is Released During Increased Lipogenesis State Following Rapid-Onset Radioiodine-Induced Hypothyroidism.

BackgroundFGF21 pharmacological treatment reverses fatty liver and lowers serum triglyceride concentration but FGF21 serum level is increased in hepatic steatosis. FGF21 secretion is induced by thyroid hormones in vitro.PurposeTo determine the influence of thyroid hormones and metabolic changes secondary to thyroid dysfunction on FGF21 secretion in humans.Materials and MethodsThis was a case-control study. 82 hyperthyroid and 15 hypothyroid patients were recruited together with 25 healthy controls. Of those with hyperthyroidism, 56 received radioiodine treatment and 42 of them achieved hypothyroidism and then euthyroidism within one year following therapy. Radioiodine-induced hypothyroidism developed abruptly within a six week interval between clinic visits. FGF21 serum levels were determined with an ELISA method.ResultsSerum FGF21 levels did not differ in hyper- and hypothyroid patients in comparison to controls [median 103.25 (interquartile range, 60.90-189.48) and 86.10 (54.05-251.02) vs 85.20 (58.00-116.80) pg/mL P=0.200 and 0.503, respectively]. In hyperthyroid patients treated with radioiodine, serum FGF21 levels increased significantly in rapid-onset hypothyroidism in comparison to the hyperthyroid and euthyroid phase [median 160.55 (interquartile range, 92.48 - 259.35) vs 119.55 (67.78-192.32) and 104.43 (55.93-231.93) pg/mL, P=0.034 and 0.033, respectively]. The rising serum FGF21 level correlated positively with serum triglycerides (Spearman coefficient rs=0.36, P=0.017) and inversely with serum SHBG (rs=-0.41, P=0.007), but did not correlate with thyroid hormone levels.ConclusionsThere was a transient increase in FGF21 serum level during rapid-onset hypothyroidism following radioiodine treatment. There was no association between FGF21 serum level and thyroid hormones. In radioiodine-induced hypothyroidism, the rising serum FGF21 concentration correlated positively with rising serum triglycerides and negatively with falling SHBG, reflecting increased hepatic lipogenesis.

The impact of apical periodontitis, non-surgical root canal retreatment and periapical surgery on serum inflammatory biomarkers.

AimThe aim of the study was to measure serum levels of molecular markers of inflammation in patients undergoing non‐surgical root canal retreatment (Re‐RCT) and periapical surgery (PS) for the treatment of apical periodontitis and to establish if such levels are influenced by the size of apical radiolucencies at baseline and by the treatment outcome.MethodologyA total of 115 participants were recruited (n = 50 Controls, n = 35 Re‐RCT, n = 30 PS). Preoperative periapical radiographs and cone beam CT (CBCT) scans of teeth were taken. Blood was collected from treatment groups at baseline, 3‐, 6‐, and 12‐month post‐treatment and from controls at baseline and 12 months. Serum levels of IL‐1β, IL‐6, IL‐8, TNF‐α, Pentraxin 3, ICAM‐1, VCAM‐1, hs‐CRP, FGF‐23, MMP‐2, MMP‐8, MMP‐9, C3 and ADMA were analysed using multiplex immunoassay and enzyme‐linked immunosorbent assay. Different time points within the same group were compared using Wilcoxon signed‐rank test, and differences between groups were analysed using the Mann–Whitney test. Non‐linear association between different factors was assessed using Spearman's correlation.ResultsPreoperative serum levels of FGF‐23, IL‐1β, hs‐CRP and ADMA were significantly higher in the diseased groups compared with controls (p < .001; p = .008; p < .001; p = .013, respectively). The preoperative size of the radiolucency was associated with increased levels of FGF‐23, IL‐1β and IL‐6. At 3‐months following treatment, IL‐1β, IL‐8, hs‐CRP, C3, MMP‐2 and MMP‐9 levels increased compared with baseline in treatment groups. IL‐1β and IL‐8 further increased at 6 months, whereas FGF‐23, hs‐CRP, C3, MMP2 and MMP‐9 decreased. One‐year post‐treatment, FGF‐23, pentraxin‐3 and ADMA were significantly reduced below baseline levels. At the 1‐year review, CBCT revealed that 25.9% of treated cases completely healed, while 63% were healing, and 11.1% failed. Treatment outcome was found to be influenced by preoperative levels of ADMA and IL‐8 levels at 6 months.ConclusionsBoth symptomatic and asymptomatic apical periodontitis (AP) can contribute to increased levels of molecular markers of inflammation. A further transient inflammatory markers rise after root canal retreatment and apical surgery were demonstrated. Successful endodontic treatment and periapical surgery result in a long‐term reduction in inflammatory marker levels.

Evaluation of IL17A, FGF21 and CXC12 in Post-menopause Iraqi Sample with Osteoporosis and Osteopenia

Osteoporosis (OP) is a systemic skeletal disorder that is characterized by reduced bone mass and micro-architectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. The most frequent osteoporotic fractures are fractures of the hip, wrist, and spine. The exact causes of OP are still unknown; several factors contribute to the disorder. Subjects and Methods: This study consists of patient groups, this group (Group A) was composed of 80 postmenopausal women with OP and osteopenia and the patient group was subdivided into two group; First group (GroupA1) was composed of 50 postmenopausal women with OP and the second group (Group A2) composed of (30) Postmenopausal Women with osteopenia. In addition, to control group (20), 5 mL of venous blood sample were collected from each patient and healthy control in the population study, and the blood sample was transferred to a clean gel tube, left at room temperature for at least 30 minutes for clotting, then centrifuged for 5–10 minutes at 3000 rpm. Then, separated and divided into aliquots to obtain the serum, then its kept frozen at -20°C until analysis. The obtained serum was used to measure IL17A, FGF21, CXC12, calcium, and alkaline Phosphatase (ALP). Measurement of IL17A, FGF21 and CXC12 levels were performed by ELISA. The total calcium and serum ALK were measured by spectrophotometric-based method. Results: Serum levels of IL17A, FGF21 and CXC12 are significantly increased in Group A and subgroup (A1 and A2). Serum levels of total calcium and ALP are non-significant in Group A and sub group patients. Significant negative correlation between serum levels of IL17A and T score, FGF21 and T score, CXC12 and T score, IL 17A and Z score, IL17A and Calcium. Conclusions: Serum levels of IL17A, FGF21 and CXC12 is significantly increased in Group A and subgroup patients. Serum levels of total calcium and ALP are non-significant in Group A and sub group patients. Significant negative correlation exists between serum levels of IL17A and T score, FGF21 and T score, CXC12 and T score in Groups A and A1.

Abstract 5140: Evaluation of multiple serological biomarkers for treatment response in HCC patients

Abstract Background: Although there have been some scientific advances in the diagnosis and treatment of hepatocellular carcinoma (HCC), there still remains challenges due to late presentation, therapeutic resistance, and recurrence. Because not all patients respond to therapeutic treatments, it is urgently needed to more precisely identify the patients who fail to achieve complete response and only have a partial response or no response to treatments. No biomarker(s) or assay(s) are currently available to predict the treatment response in HCC patients. Aim: To evaluate serological biomarkers in BCLC Stage B &amp; C HCC patients undergoing treatment(s) including trans-arterial doxorubicin-eluting beads (DEB), trans-arterial radioembolization (Y-90 beads), and targeted molecular therapy (sorafenib). Methods: Fifty newly diagnosed primary HCC patients without any treatment were recruited between January 2014 and December 2018. Patients received, DEB, Y-90 beads, and Nexavar throughout their treatment course. The serum samples were collated before treatment (Pre-tx) and post treatment (Post-tx) at month 3, month 6 and month 9. A U-PLEX assay (Meso Scale Diagnostics) was performed to detect multiple serological biomarkers in serum, including growth factors (FGF19, HGF, insulin and FGF21) and inflammatory cytokines (IFN-γ, IL-17, IL-6, and TNF-α). The U-PLEX data were further validated by enzyme-linked immunosorbent assay. All patients were followed 3-5 years for survival with or without further surgical operations including tumor resection/ablation and orthotopic liver transplantation. Results: Based on the treatment outcome, patients were divided into 3 groups: a. overall survival (OS) &amp;lt; 1 year was defined as poor response; b. progression-free survival 3-5 years was defined as moderate response; and c. OS &amp;gt; 5 years was defined as good response. In the patients with moderate response and good response, the serum levels of FGF21 showed an increasing trend, with significant increases Post-tx at month 3, month 6 and month 9 (p &amp;lt; 0.05 vs Pre-tx). The serum levels of IFN-γ also showed an increasing trend, with significant increases at Post-tx-month 9 (p &amp;lt; 0.05 vs Pre-tx). In the patients with poor response, the serum levels of HGF and IL-6 were increased Post-tx, with statistically significance at Post-tx-month 6 (p &amp;lt; 0.05 vs Pre-tx). Increased serum levels of IL-17, TNF-α, FGF19, and insulin were found in the patients with poor response but no statistically significance reached (p &amp;gt; 0.05 versus Pre-tx). Conclusion: 1) Combination of growth factors and cytokines are applicable to find serological biomarkers in cancer patients for treatment response; 2) FGF21 and IFN-γ for good response and HGF and IL-6 for poor response may be used as biomarkers to monitor the HCC patients with adjuvant treatment(s); 3) Further study is needed to recruit more patients to correlate the serological biomarkers with their clinical outcome. Citation Format: Yan Li. Evaluation of multiple serological biomarkers for treatment response in HCC patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5140.

High phosphate intake induces bone loss in nephrectomized thalassemic mice.

Although patients with either β-thalassemia or chronic kidney disease (CKD) clinically correlate with severe osteoporosis, the mechanism by which CKD exposed to high phosphate affects bone turnover has not been characterized in β-thalassemia. We aimed to determine the effects of renal insufficiency on high phosphate intake induced changes in bone metabolism after 5/6th nephrectomy in hemizygous β-globin knockout (BKO) mice. Male BKO mice manifested severe anemia and osteopenia. Nephrectomy induced renal fibrosis and reduced renal function as assessed by increased serum urea nitrogen levels. Moreover, nephrectomy increased bone turnover leading to bone loss in wild type (WT) but not BKO mice. In nephrectomized BKO, PBS in drinking water induced hyperphosphatemia, and hypercalcemia along with osteopenia in both cancellous and cortical bone. Histomorphometric analysis confirmed reduced cancellous bone volume due to decreased bone formation rate, osteoblast number and osteoclast number. The mRNA levels for Alpl, Sp7, Kl, Tnfsf11, and Tnfsf11/Tnfrsf11b were decreased in nephrectomized BKO mice drinking PBS. Interestingly, Fgf23, a bone-derived hormone produced by osteocytes and osteoblasts in response to hyperphosphatemia, were remarkably increased in nephrectomized BKO mice following PBS intake. Serum FGF23 and erythropoietin levels were markedly elevated in BKO mice. Nephrectomy decreased serum erythropoietin but not FGF23 levels. Hyperphosphatemia in BKO mice increased serum erythropoietin, FGF23, and PTH levels, nominating these factors as candidate mediators of bone loss in thalassemic mice with CKD during phosphate retention.

Clinical value and expression of Homer 1, homocysteine, S-adenosyl-l-homocysteine, fibroblast growth factors 23 in coronary heart disease

BackgroundThis study aimed to explore clinical value and expression of Homer 1, S-adenosyl-l-homocysteine (SAH), homocysteine (Hcy), fibroblast growth factors (FGF) 23 in coronary heart disease (CHD).MethodsFrom March 2020 to April 2021, a total of 137 patients with CHD and 138 healthy subjects who came to our hospital for physical examination and had no cardiovascular disease were retrospectively enrolled, and they were assigned to the CHD group and the control group, respectively. Patients in the CHD group were divided into stable angina pectoris (SAP) group (n = 48), unstable angina pectoris (UAP) group (n = 46), and acute myocardial infarction (AMI) group (n = 43) according to clinical characteristics for subgroup analysis. The degree of coronary artery stenosis was assessed by Gensini score, which is a reliable assessment tool for the severity of coronary artery disease. The levels of Homer 1, SAH, Hcy, and FGF 23 were tested and compared. Spearman correlation analysis was used to analyze the correlation between serum Homer1, SAH, Hcy, FGF23 levels and Gensini score, and multivariate unconditional Logistic regression was used to analyze the risk factors of coronary heart disease.ResultsDemographic characteristics of each group were comparable (P > 0.05). The body mass index (BMI), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and glucose levels of the SAP group, UAP group and AMI group were significantly higher than those of the control group, and the number of patients with smoking, alcohol consumption, hypertension, and diabetes history was significantly more than that of the control group, respectively (P < 0.05). The level of high-density lipoprotein cholesterol (HDL-C) of each subgroup was significantly lower than the control group (P < 0.05). The above indicators showed no significant difference among three subgroups (P > 0.05). Serum SAH, Hcy, Homer1 and FGF23 levels in each subgroup were significantly higher than those in control group (P < 0.05). And above indicators in SAP group and UAP group were significantly lower than those in AMI group (P < 0.05), and the levels of above indicators in SAP group were significantly lower than those in UAP group (P < 0.05). The results of Spearman correlation analysis showed that serum Homer1, FGF23, SAH, Hcy levels were positively correlated with Gensini score (r = 0.376, 0.623, 0.291, 0.372, all P < 0.01). Multivariate logistic regression analysis showed that smoking, hypertension, diabetes, alcohol consumption, obesity, HDL-C, FGF23, SAH, Hcy, Homer 1 were independent risk factors for coronary heart disease.ConclusionThe levels of FGF23, SAH, Hcy, and Homer1 tend to increase in patients with CHD compared with normal population, and the more severe the disease, the higher the levels, which has certain reference value for the clinical diagnosis of CHD and the evaluation and monitoring of the disease.

FGF21-FGFR4 signaling in cardiac myocytes promotes concentric cardiac hypertrophy in mouse models of diabetes.

Fibroblast growth factor (FGF) 21, a hormone that increases insulin sensitivity, has shown promise as a therapeutic agent to improve metabolic dysregulation. Here we report that FGF21 directly targets cardiac myocytes by binding β-klotho and FGF receptor (FGFR) 4. In combination with high glucose, FGF21 induces cardiac myocyte growth in width mediated by extracellular signal-regulated kinase 1/2 (ERK1/2) signaling. While short-term FGF21 elevation can be cardio-protective, we find that in type 2 diabetes (T2D) in mice, where serum FGF21 levels are elevated, FGFR4 activation induces concentric cardiac hypertrophy. As T2D patients are at risk for heart failure with preserved ejection fraction (HFpEF), we propose that induction of concentric hypertrophy by elevated FGF21-FGFR4 signaling may constitute a novel mechanism promoting T2D-associated HFpEF such that FGFR4 blockade might serve as a cardio-protective therapy in T2D. In addition, potential adverse cardiac effects of FGF21 mimetics currently in clinical trials should be investigated.

MO037: Burosumab in adult patients with X-linked hyphophosphatemic rickets: an Italian Experience

Abstract BACKGROUND AND AIMS X-linked hypophosphoremic rickets (XLH) is a rare disease caused by mutations in the PHEX gene leading to an increase in the serum levels of FGF23, which inhibits the tubular reabsorption of phosphates and the production of 1,25(OH)2D. These alterations cause hypophosphatemia, rickets, bone deformities, growth retardation and muscle activity impairment. METHOD Burosumab (B) is a monoclonal antibody against FGF23, used for the treatment of XLH. In Italy B can be employed in adults only as compassionate use. In 2020, we treated four adult XLH patients with B (1 mg/kg sc every 4 weeks) for 24 weeks. These patients, V.M. (M, 32 years), S.T. (F, 47), E.R. (M, 46) and S.M. (F, 20) had legs deformities, musculoskeletal pain and severe disability. RESULTS In all patients, phosphorus levels were normalized by B 2 weeks after the B injection, but its levels decreased during the following 28 days; the effect of B on serum phosphate declined during the 24-week follow-up. Plasma values of 1,25(OH)2D and CTX (C-terminal telopeptide of type I collagen) increased after burosumab, but their increase was less marked after the first two injections. In contrast, PTH and bALP values did not change during B therapy. Scores of BPI test, chair test and walking test confirmed an improvement in the fatigue resistance and physical performance. Other tests showed the improvement of self-reported well-being and quality of life in all patients. These effects were not observed in adult patients on conventional therapy with phosphate salts and active vitamin D. CONCLUSION Therefore, markers of physical conditions and life quality may be more indicative for the necessity of burosumab treatment than serum phosphate, which may not be a significant marker to initiate burosumab treatment in adult patients. Burosumab treatment of XLH patients is well-tolerated and leads to prolonged beneficial effects on general conditions of patients although the inconstant improvement of serum phosphate.

MO736: The Role of Uremic Retention Solutes in the MIA Syndrome in Haemodialysis Subjects

Abstract BACKGROUND AND AIMS In end-stage renal disease (ESRD), the high morbidity and mortality risk for cardiovascular disease (CVD) is not easily explained only on the basis of traditional factors. Among non-traditional ones, malnutrition, inflammation and atherosclerosis/calcification have been described as the ‘MIA syndrome’. METHOD In this study, we evaluated the association between the variation in serum levels of 27 uremic retention solutes plus 6 indexes related to the MIA syndrome processes in dialysis patients. Uremic retention solute levels were detected by the ELISA or using an ultra-performance liquid chromatography—tandem mass spectrometry method. The pro-calcifying, pro-apoptotic and pro-necrotic effects of uremic serum were evaluated in an in vitro model of high-Pi induced calcification in vascular smooth muscle cells (VSMC). RESULTS As expected, we found reciprocal correlations between serum albumin, total cholesterol and phosphate, linking a better nutritional status with higher phosphate levels (r = 0.37, r = 0.40, r = 0.54, respectively; P &amp;lt; 0.05). The relationship between malnutrition and inflammation is highlighted by the negative correlation of serum cholesterol levels with serum alpha-1 acid glycoprotein and IL-6 levels (r = –0.56, r = –0.39, respectively; P &amp;lt; 0.05). These results suggest that the increase in inflammatory mediators is probably higher in malnourished patients, and a better nutritional state seems to correlate with lower inflammatory marker levels. Moreover, we found a significant direct correlation between alpha-1 acid glycoprotein and IL-6 with a correlation coefficient of 0.54 and P &amp;lt; 0.01, indicating that both these uremic toxins might participate in the maintenance of the inflammation. The relation between inflammation and atherosclerosis/calcification is supported by the correlations between IL-6 variations that significantly correlate with both PTX3 and VEGF (r = 0.36 and r = 0.81; P &amp;lt; 0.05) and with VSMC in vitro high-Pi induced calcification (r = 0.66; P &amp;lt; 0.01). Thus, IL-6, a regulator of acute phase protein synthesis, seems to be related to CVD markers (PTX3 and VEGF) and in vitro calcification, two robust indexes of increased cardiovascular risk. In addition, the Kyn/Try ratio directly correlates with serum FGF23 levels with a correlation coefficient r of 0.60 and P &amp;lt; 0.01. Regarding atherosclerosis/calcification, we found that PTX3, TMAO, IS, myoglobin and FGF23 correlate with each other in several combinations, reflecting the elevated cardiovascular risk present in ESRD. PTX3 shows a trend towards a direct correlation with TMAO (r = 0.37 and P &amp;lt; 0.05), and IS shows a trend towards a direct correlation both with TMAO, FGF23 and myoglobin (r = 0.46, r = 0.45 and r = 0.42; P &amp;lt; 0.05). Moreover, IS and TMAO correlate also with two processes strictly related to VSMC calcification, such as apoptosis and necrosis (IS: apoptosis r = 0.69 and necrosis r = 0.47; P &amp;lt; 0.05; TMAO: apoptosis r = 0.42 and necrosis r = 0.40 with P &amp;lt; 0.05). Finally, VEGF shows a robust correlation with in vitro calcification (r = 0.74; P &amp;lt; 0.01). CONCLUSION Among all the correlations found between uremic toxin variations in dialysis patients, IL-6 seems to have a central role correlating with malnutrition and several CV markers together with vascular calcification (VC). This might be explained by the characteristics of IL-6 being contemporary an inflammatory and a CVD marker in ESRD. On the other hand, IS has a potential role in VC, suggesting a central role of the uremic milieu in MIA syndrome development. Therefore, there is an urgent need to find a more efficient dialysis treatment to improve the clearance of uremic retention solutes in order to try to ameliorate CV outcomes in ESRD patients.

Soluble α-klotho and heparin modulate the pathologic cardiac actions of fibroblast growth factor 23 in chronic kidney disease

Fibroblast growth factor (FGF) 23 is a phosphate-regulating hormone that is elevated in patients with chronic kidney disease and associated with cardiovascular mortality. Experimental studies showed that elevated FGF23 levels induce cardiac hypertrophy by targeting cardiac myocytes via FGF receptor isoform 4 (FGFR4). A recent structural analysis revealed that the complex of FGF23 and FGFR1, the physiologic FGF23 receptor in the kidney, includes soluble α-klotho (klotho) and heparin, which both act as co-factors for FGF23/FGFR1 signaling. Here, we investigated whether soluble klotho, a circulating protein with cardio-protective properties, and heparin, a factor that is routinely infused into patients with kidney failure during the hemodialysis procedure, regulate FGF23/FGFR4 signaling and effects in cardiac myocytes. We developed a plate-based binding assay to quantify affinities of specific FGF23/FGFR interactions and found that soluble klotho and heparin mediate FGF23 binding to distinct FGFR isoforms. Heparin specifically mediated FGF23 binding to FGFR4 and increased FGF23 stimulatory effects on hypertrophic growth and contractility in isolated cardiac myocytes. When repetitively injected into two different mouse models with elevated serum FGF23 levels, heparin aggravated cardiac hypertrophy. We also developed a novel procedure for the synthesis and purification of recombinant soluble klotho, which showed anti-hypertrophic effects in FGF23-treated cardiac myocytes. Thus, soluble klotho and heparin act as independent FGF23 co-receptors with opposite effects on the pathologic actions of FGF23, withsoluble klotho reducing and heparin increasing FGF23-induced cardiac hypertrophy. Hence, whether heparin injections during hemodialysis in patients with extremely high serum FGF23 levels contribute to their high rates of cardiovascular events and mortality remains to be studied.

429 Elevated Phosphate Levels Induce Lung Inflammation and Exacerbate Pulmonary Fibrosis

OBJECTIVES/GOALS: Using a cell culture model, we will determine the effects of phosphate on primary lung cell cultures and use our results to delineate a pathway through which these changes are carried out. Using animal models, we will determine the effects of phosphate on inflammatory and fibrotic lung injury, both in the presence and absence of CKD. METHODS/STUDY POPULATION: For our in vitro experiments, human lung fibroblasts were treated with concentrations of 1 to 5 mM sodium phosphate and FGFR inhibitors. Expression levels of interleukin (IL)-1beta, IL-6, and IL-8 were analyzed by qPCR and secretion of these cytokines was measured by ELISA. Phosphorylation of PLCy and ERK was measured by western blot. Using an in vivo approach, we placed C57Bl/6 mice on a high phosphate (3%) diet to elevate serum phosphate levels in the absence of kidney injury and administered bleomycin via oropharyngeal aspiration to generate an acute inflammatory response. Serum FGF23 levels were measured by ELISA and serum analysis for phosphate and renal function were obtained. Furthermore, expression of FGF23 pathway and inflammatory markers were analyzed in murine lung tissue using qPCR and western blotting. RESULTS/ANTICIPATED RESULTS: Augmented phosphate concentrations led to increased cytokine expression and secretion from human lung fibroblasts as well as a concomitant increase in PLCy and ERK phosphorylation. Inhibition of FGFR1 reversed the effects of phosphate on the inflammatory cytokines and PLCy/ERK phosphorylation. Serum FGF23 levels were significantly upregulated in mice on a high phosphate diet and further increased in mice subjected to a high phosphate diet with exposure to bleomycin. Both serum phosphate and creatinine levels were significantly elevated as well. Additionally, high phosphate and bleomycin increased local FGF23 expression in murine lung tissue, when compared to controls or each stimulus alone. DISCUSSION/SIGNIFICANCE: Phosphate has a significant impact on inflammation and fibrosis in the lung, indicating that the existence of pulmo-renal crosstalk exaggerates pulmonary injury and that there are biological pathways that may be targeted therapeutically to mediate these effects. These results could have a substantial impact on the quality of life for CKD patients.

Regulation of Calcium Homeostasis in Acute Kidney Injury: A Prospective Observational Study.

BackgroundMaintaining homeostasis is an integral part of all physiological processes both in health and disease including critically ill patients and may impact clinical outcomes. The present study was designed to assess prevalence of serum calcium, phosphate, vitamin-D3, FGF-23, and PTH levels abnormalities in AKI.Patients and methodsSingle-center, prospective, observational study in a tertiary care hospital. Patients meeting KDIGO criteria for AKI were included. Paired blood samples were drawn from eligible patients—first sample within 24 hours of AKI diagnosis and second after 5 days or at time of hospital discharge, whichever was earlier for measuring serum calcium (albumin corrected), phosphate, PTH, 25(OH)Vit-D, and FGF-23 levels. Clinical outcomes analyzed included survival status, utilization of RRT, and hospital stay.ResultsOf the 50 patients with AKI, about three-fourths were males. Mean age of the participants was 57.32 ± 11.47 years. Around half of patients had hypocalcemia and four-fifths had low serum phosphate. Nearly 82% had low 25(OH)Vit-D and 52% cases had high PTH level. Patients who underwent RRT had numerically higher but not significant serum calcium and PTH levels. FGF-23 levels (pg/mL) were significantly higher in patients on RRT (81.70 ± 17.30 vs non-RRT, 72.43 ± 20.27, p = 0.049), nonsurvivors (87.96 ± 18.82 vs survivors 57.11 ± 15.19, p = 0.045), and those hospitalized for time of stay above median (109.67 ± 26.97 vs below median 70.27 ± 20.43, p = 0.046). Among all the bone and mineral parameters analyzed high FGF23 levels were consistently linked with poor clinical outcomes in AKI.ConclusionThe present study found high prevalence of calcium and phosphate disorders in AKI with dysregulated phosphate homeostasis as evidenced from elevated FGF-23 levels linked with morbidity and mortality in AKI.How to cite this articleSingh NP, Panwar V, Aggarwal NP, Chhabra SK, Gupta AK, Ganguli A. Regulation of Calcium Homeostasis in Acute Kidney Injury: A Prospective Observational Study. Indian J Crit Care Med 2022;26(3):302–306.