α-Klotho is a non-enzymatic molecular scaffold for FGF23 hormone signalling

NMR resonance assignment of a fibroblast growth factor 8 splicing isoform b

The splicing isoform b of human fibroblast growth factor 8 (FGF8b) is an important regulator of brain embryonic development. Here, we report the almost complete NMR chemical shift assignment of the backbone and aliphatic side chains of FGF8b. Obtained chemical shifts are in good agreement with the previously reported X-ray data, excluding the N-terminal gN helix, which apparently forms only in complex with the receptor. The reported data provide an NMR starting point for the investigation of FGF8b interaction with its receptors and with potential drugs or inhibitors.

Discovery of a Selective and Orally Bioavailable FGFR2 Degrader for Treating Gastric Cancer

Abnormal activation of fibroblast growth factor receptors (FGFRs) results in the development and progression of human cancers. FGFR2 is frequently amplified or mutated in cancers; therefore, it is an attractive target for tumor therapy. Despite the development of several pan-FGFR inhibitors, their long-term therapeutic efficacy is hindered by acquired mutations and low isoform selectivity. Herein, we report the discovery of an efficient and selective FGFR2 proteolysis-targeting chimeric molecule, LC-MB12, that incorporates an essential rigid linker. LC-MB12 preferentially internalizes and degrades membrane-bound FGFR2 among the four FGFR isoforms; this may promote greater clinical benefits. LC-MB12 exhibits superior potency in FGFR signaling suppression and anti-proliferative activity compared to the parental inhibitor. Furthermore, LC-MB12 is orally bioavailable and shows significant antitumor effects in FGFR2-dependent gastric cancer in vivo. Taken together, LC-MB12 is a candidate FGFR2 degrader for alternative FGFR2-targeting strategies and offers a promising starting point for drug development.

Pathophysiology and Clinical Impacts of Chronic Kidney Disease on Coronary Artery Calcification

The global prevalence of chronic kidney disease (CKD) has increased in recent years. Adverse cardiovascular events have become the main cause of life-threatening events in patients with CKD, and vascular calcification is a risk factor for cardiovascular disease. Vascular calcification, especially coronary artery calcification, is more prevalent, severe, rapidly progressive, and harmful in patients with CKD. Some features and risk factors are unique to vascular calcification in patients with CKD; the formation of vascular calcification is not only influenced by the phenotypic transformation of vascular smooth muscle cells, but also by electrolyte and endocrine dysfunction, uremic toxin accumulation, and other novel factors. The study on the mechanism of vascular calcification in patients with renal insufficiency can provide a basis and new target for the prevention and treatment of this disease. This review aims to illustrate the impact of CKD on vascular calcification and to discuss the recent research data on the pathogenesis and factors involved in vascular calcification, mainly focusing on coronary artery calcification, in patients with CKD.

Branched Multimeric Peptides as Affinity Reagents for the Detection of α-Klotho Protein

α-Klotho, an aging-related protein found in the kidney, parathyroid gland, and choroid plexus, acts as an essential co-receptor with the fibroblast growth factor 23 receptor complex to regulate serum phosphate and vitamin D levels. Decreased levels of α-Klotho are a hallmark of age-associated diseases. Detecting or labeling α-Klotho in biological milieu has long been a challenge, however, hampering the understanding of its role. Here, we developed branched peptides by single-shot parallel automated fast-flow synthesis that recognize α-Klotho with improved affinity relative to their monomeric versions. These peptides were further shown to selectively label Klotho for live imaging in kidney cells. Our results demonstrate that automated flow technology enables rapid synthesis of complex peptide architectures, showing promise for future detection of α-Klotho in physiological settings.

Pre-granulosa cell-derived FGF23 protects oocytes from premature apoptosis during primordial follicle formation by inhibiting p38 MAPK in mice

A large number of oocytes in the perinatal ovary in rodents get lost for unknown reasons. The granulosa cell-oocyte mutual communication is pivotal for directing formation of the primordial follicle, however little is known if paracrine factors participate in modulating programmed oocyte death perinatally. We report here that pre-granulosa cell-derived fibroblast growth factor 23 (FGF23) functioned in preventing oocyte apoptosis in the perinatal mouse ovary. Our results showed that FGF23 was exclusively expressed in pre-granulosa cells while fibroblast growth factor receptors (FGFRs) were specifically expressed in the oocytes in perinatal ovaries. FGFR1 was one of the representative receptors in mediating FGF23 signaling during the formation of the primordial follicle. In cultured ovaries, the number of alive oocytes declines significantly, accompanied by the activation of the p38 MAPK signaling pathway, under the condition of FGFR1 disruption by specific inhibitors of FGFR1 or silencing of Fgf23. As a result, oocyte apoptosis increased and eventually led to a decrease in the number of germ cells in perinatal ovaries following the treatments. In the perinatal mouse ovary, pre-granulosa cell-derived FGF23 binds to FGFR1 and activates at least, the p38 MAPK signaling pathway, thereby regulating the level of apoptosis during primordial follicle formation. This study re-emphasizes the importance of granulosa cell - oocyte mutual communication in modulating primordial follicle formation and supporting oocyte survival under physiological conditions.

Upstream and downstream regulators of Klotho expression in chronic kidney disease

Klotho is a critical protein that protects the kidney. Klotho is severely downregulated in chronic kidney disease (CKD), and its deficiency is implicated in the pathogenesis and progression of CKD. Conversely, an increase in Klotho levels results in improved kidney function and delays CKD progression, supporting the notion that modulating Klotho levels could represent a possible therapeutic strategy for CKD treatment. Nevertheless, the regulatory mechanisms responsible for the loss of Klotho remain elusive. Previous studies have demonstrated that oxidative stress, inflammation, and epigenetic modifications can modulate Klotho levels. These mechanisms result in a decrease in Klotho mRNA transcript levels and reduced translation, thus can be grouped together as upstream regulatory mechanisms. However, therapeutic strategies that aim to rescue Klotho levels by targeting these upstream mechanisms do not always result in increased Klotho, indicating the involvement of other regulatory mechanisms. Emerging evidence has shown that endoplasmic reticulum (ER) stress, the unfolded protein response, and ER-associated degradation also affect the modification, translocation, and degradation of Klotho, and thus are proposed to be downstream regulatory mechanisms. Here, we discuss the current understanding of upstream and downstream regulatory mechanisms of Klotho and examine potential therapeutic strategies to upregulate Klotho expression for CKD treatment.

Mineral Metabolism in Children: Interrelation between Vitamin D and FGF23

Fibroblast growth factor 23 (FGF23) was identified at the turn of the century as the long-sought circulating phosphatonin in human pathology. Since then, several clinical and experimental studies have investigated the metabolism of FGF23 and revealed its relevant pathogenic role in various diseases. Most of these studies have been performed in adult individuals. However, the mineral metabolism of the child is, to a large extent, different from that of the adult because, in addition to bone remodeling, the child undergoes a specific process of endochondral ossification responsible for adequate mineralization of long bones’ metaphysis and growth in height. Vitamin D metabolism is known to be deeply involved in these processes. FGF23 might have an influence on bones’ growth as well as on the high and age-dependent serum phosphate concentrations found in infancy and childhood. However, the interaction between FGF23 and vitamin D in children is largely unknown. Thus, this review focuses on the following aspects of FGF23 metabolism in the pediatric age: circulating concentrations’ reference values, as well as those of other major variables involved in mineral homeostasis, and the relationship with vitamin D metabolism in the neonatal period, in vitamin D deficiency, in chronic kidney disease (CKD) and in hypophosphatemic disorders.

mTORC1-induced bone marrow-derived mesenchymal stem cell exhaustion contributes to the bone abnormalities in klotho-deficient mice of premature aging

Stem cell exhaustion is a hallmark of aging. Klotho-deficient mice (kl/kl mice) is a murine model that mimics human aging with significant bone abnormalities. The aim of this study is using kl/kl mice to investigate the functional change of bone marrow-derived mesenchymal stem cells (BMSCs) and explore the underlying mechanism. We found klotho-deficiency leads to bone abnormalities. In addition, kl/kl BMSCs manifested hyper-active proliferation but functional declined both in vivo and in vitro. mTORC1 activity was higher in freshly isolated kl/kl BMSCs and autophagy in kl/kl BMSCs were significantly decreased, possibly through mTORC1 activation. Conditional medium containing soluble Klotho protein (sKL) rescued hyper-proliferation of kl/kl BMSCs by inhibiting mTORC1 activity and restoring autophagy. Finally, intraperitoneally injection of mTORC1 inhibitor rapamycin restored BMSC quiescence, ameliorated bone phenotype and increased lifespan of kl/kl mice in vivo. This research highlights a therapeutic strategy to maintain the homeostasis of adult stem cell pool for healthy bone aging.

Differential toxicity profile of secreted and processed α-Klotho expression over mineral metabolism and bone microstructure

The aging-protective gene α-Klotho (KL) produces two main transcripts. The full-length mRNA generates a transmembrane protein that after proteolytic ectodomain shedding can be detected in serum as processed Klotho (p-KL), and a shorter transcript which codes for a putatively secreted protein (s-KL). Both isoforms exhibit potent pleiotropic beneficial properties, although previous reports showed negative side effects on mineral homeostasis after increasing p-KL concentration exogenously. Here, we expressed independently both isoforms using gene transfer vectors, to assess s-KL effects on mineral metabolism. While mice treated with p-KL presented altered expression of several kidney ion channels, as well as altered levels of P_i and Ca²⁺ in blood, s-KL treated mice had levels comparable to Null-treated control mice. Besides, bone gene expression of Fgf23 showed a fourfold increase after p-KL treatment, effects not observed with the s-KL isoform. Similarly, bone microstructure parameters of p-KL-treated mice were significantly worse than in control animals, while this was not observed for s-KL, which showed an unexpected increase in trabecular thickness and cortical mineral density. As a conclusion, s-KL (but not p-KL) is a safe therapeutic strategy to exploit KL anti-aging protective effects, presenting no apparent negative effects over mineral metabolism and bone microstructure.

Fibroblast growth factor 5 (FGF5) and its missense mutant FGF5-H174 underlying trichomegaly: a molecular dynamics simulation investigation

The missense mutation Y174H of FGF5 (FGF5-H174) had been associated with trichomegaly, characterized by abnormally long and pigmented eyelashes. The amino acid tyrosine (Tyr/Y) at position 174 is conserved across many species, proposedly holding important characteristics for the functions of FGF5. Microsecond molecular dynamics simulations along with protein-protein docking and residue interacting network analysis were employed to investigate the structural dynamics and binding mode of both wild-type (FGF5-WT) and its mutated counterpart (FGF5-H174). It was found that the mutation decreased number of hydrogen bonds within the protein, sheet secondary structure, interaction of residue 174 with other residues, and number of salt-bridges. On the other hand, the mutation increased solvent accessible surface area, number of hydrogen bonds between the protein and solvent, coil secondary structure, protein C-alpha backbone root mean square deviation, protein residue root mean square fluctuations, as well as occupied conformational space. In addition, protein-protein docking integrated with molecular dynamics simulations and molecular mechanics - Poisson-Boltzmann surface area (MM/PBSA) binding energy calculation demonstrated that the mutated variant possessed stronger binding affinity towards fibroblast growth factor receptor 1 (FGFR1). However, residue interaction network analysis demonstrated that the binding mode of the FGFR1-FGF5-H174 complex was drastically different from that of the FGFR1-FGF5-WT complex. In conclusion, the missense mutation conferred more instability within itself and stronger binding affinity towards FGFR1 with distinctively altered binding mode or residue connectivity. These findings might help explain the decreased pharmacological activity of FGF5-H174 towards FGFR1, underlying trichomegaly.Communicated by Ramaswamy H. Sarma.

One half-century of advances in the evaluation and management of disorders of bone and mineral metabolism in children and adolescents

The past 50 years of research in pediatric bone and mineral metabolism have led to remarkable progress in the identification and characterization of disorders that affect the developing skeleton. Progress has been facilitated through advances in both technology and biology and this paper provides a brief description of some but not all of the key findings, including identification of the calcium sensing receptor and the polypeptides parathyroid hormone and parathyroid hormone-related protein as well as their shared receptor and signal generating pathways; the elucidation of vitamin D metabolism and actions; discovery of fibroblast growth factor 23 (FGF23), the sodium-phosphate co-transporters and the other components that regulate phosphate metabolism. Moreover, the past half-century of research has led to the delineation of the molecular bases for genetic forms of hypoparathyroidism, pseudohypoparathyroidism, and primary hyperparathyroidism as well as the determination of the genetic causes of osteogenesis imperfecta, osteopetrosis, hypophosphatasia, and other disorders of mineral/bone homeostasis. During the next decade we expect that many of these fundamental discoveries will lead to the development of innovative treatments that will improve the lives of children with these disorders.

Association between anemia and serum Klotho in middle-aged and older adults

BACKGROUND

The role of Klotho as a multifunctional protein in anemia is unclear. This study aimed to determine the association between anemia and serum Klotho concentrations in middle-aged and elderly populations.

METHODS

In this cross-sectional study, we used data collected from the National Health and Nutrition Examination Survey (NHANES) 2007-2016. A total of 13,357 individuals who received serum Klotho measurements, biochemical tests, and demographic surveys were analyzed. Multivariate linear regression models adjusting for covariates were used to investigate the associations between anemia and serum Klotho.

RESULTS

Multivariable regression showed that serum Klotho correlates positively with hemoglobin and red blood cells and inversely with red cell distribution width. After adjusting for all covariates, compared with Q4, there was a significantly increased risk of anemia in serum Klotho quartiles 1 to 2 (OR=1.54, 95% CI:1.21-1.95, P=0.002; OR=1.30, 95% CI:1.02-1.64, P=0.042,respectively). Segmented regression showed that for every 100 pg/mL increase in serum Klotho <9.746 pg/mL, the risk of anemia was reduced by 10.9%, and this reduction was significant (P<0.001). Furthermore, stratified analyses yielded a stronger association between reduced anemia and high levels of Klotho in men and those with diabetes (P< 0.05 for interaction). However, this association was not found to be significantly altered by chronic kidney disease.

CONCLUSIONS

In summary, we indicated that low serum Klotho is associated with an increased likelihood of anemia using a nationally representative sample of middle-aged and older adults.

Heparin is essential for optimal cell signaling by FGF21 and for regulation of βKlotho cellular stability

While important insights were gained about how FGF21 and other endocrine fibroblast growth factors (FGFs) bind to Klotho proteins, the exact mechanism of Klotho/FGF receptor assembly that drives receptor dimerization and activation has not been elucidated. The prevailing dogma is that Klotho proteins substitute for the loss of heparan sulfate proteoglycan (HSPG) binding to endocrine FGFs by high-affinity binding of endocrine FGF molecules to Klotho receptors. To explore a potential role of HSPG in FGF21 signaling, we have analyzed the dynamic properties of FGF21-induced FGF21-βKlotho-FGFR1c complexes on the surface of living wild-type (WT) or HSPG-deficient Chinese hamster ovary (CHO) cells by employing quantitative single-molecule fluorescence imaging analyses. Moreover, detailed analyses of FGF21 and FGF1 stimulation of cellular signaling pathways activated in WT or in HSPG-deficient CHO cells are also analyzed and compared. These experiments demonstrate that heparin is required for the formation of FGF21-βKlotho-FGFR1c complexes on the cell membrane and that binding of heparin or HSPG to FGFR1c is essential for optimal FGF21 stimulation of FGFR1c activation, mitogen-activated protein kinase responses, and intracellular Ca²⁺ release. It is also shown that FGF1 binding stimulates assembly of βKlotho and FGFR1c on cell membranes, resulting in endocytosis and degradation of βKlotho. We conclude that heparin or HSPG is essential for FGF21 signaling and for regulation of βKlotho cellular stability by acting as a coligand of FGFR1c.

FGF23 Actions in CKD-MBD and other Organs During CKD

Fibroblast growth factor 23 (FGF23) is a new endocrine product discovered in the past decade. In addition to being related to bone diseases, it has also been found to be related to kidney metabolism and parathyroid metabolism, especially as a biomarker and a key factor to be used in kidney diseases. FGF23 is upregulated as early as the second and third stages of chronic kidney disease (CKD) in response to relative phosphorus overload. The early rise of FGF23 has a protective effect on the body and is essential for maintaining phosphate balance. However, with the decline in renal function, eGFR (estimated glomerular filtration rate) declines, and the phosphorus excretion effect caused by FGF23 is weakened. It eventually leads to a variety of complications, such as bone disease (Chronic Kidney Disease-Mineral and Bone Metabolism Disorder), vascular calcification (VC), and more. Monoclonal antibodies against FGF23 are currently used to treat genetic diseases with increased FGF23. CKD is also a state of increased FGF23. This article reviews the current role of FGF23 in CKD and discusses the crosstalk between various organs under CKD conditions and FGF23. Studying the effect of hyperphosphatemia on different organs of CKD is important. The prospect of FGF23 for therapy is also discussed.

Bone characteristics of autosomal dominant hypophosphatemic rickets patients

OBJECTIVE

Autosomal dominant hypophosphatemic rickets (ADHR) is a rare disease caused by activating mutations in fibroblast growth factor 23 (FGF23) gene. With FGF23 activation, ADHR is a good model to explore the effects of FGF23 on skeletal development and mineralization. However, the bone microarchitecture of ADHR patients is poorly investigated. This study aims to illustrate the bone properties of ADHR patients and clarify the effect of FGF23 on load bearing and non-load bearing bone.

METHODS

Bone microarchitectures of 11 ADHR subjects and sex- and age-matched healthy controls were analyzed by HR-pQCT. The effect of FGF23 mutations on load bearing and non-load bearing bone was explored by comparison of bone microarchitecture in distal radius and distal tibia. The BMD, bone microarchitecture and bone strength were compared between 7 ADHR patients and 7 age- and sex-matched XLH patients.

RESULTS

Among 11 subjects with FGF23 mutations, 10 patients presented with obvious symptoms, five of which had received 1-3 years of iron supplement, neutral phosphate, and calcitriol treatments. The symptomatic patients presented with low bone density and fractures in X rays, with decreased Z score of aBMD (L1-L4: -1.3 ± 1.4, femoral neck: -2.1 ± 1.8, total hip: -1.85 ± 1.6). Compared with controls, HR-pQCT analysis of 5 untreated ADHR patients showed increased total area (+61.6 %, p = 0.03) and cortical perimeter (+17.2 %, p = 0.03) in distal radius. No significant differences were found in other parameters in distal radius. In distal tibia, the patients presented obvious defects in cancellous bone, with decreased trabecular vBMD (-62.9 %, p = 0.003), trabecular BV/TV (-48.7 %, p = 0.003) and trabecular number (-42.2 %, p = 0.001). The trabecular separation (+113.3 %, p = 0.007) and trabecular network inhomogeneity (+226.7 %, p = 0.001) were accordingly increased. In addition to another 5 treated patients, the bone microarchitecture changes revealed similar pattern, but the increase of total area and cortical perimeter in distal radius was no longer statistically significant. The non-symptomatic ADHR patient demonstrated slightly decreased total vBMD, trabecular vBMD and trabecular BV/TV in distal tibia. The changing pattern of bone geometry and microarchitecture of ADHR patients were similar to XLH patients but showed less deficit and stronger bone strength.

CONCLUSION

ADHR patients presented increased total area and cortical perimeter in distal radius, and obvious defect in cancellous bone in distal tibia. FGF23 have impairment effect on trabecular bone especially in weight bearing site.

Updates in the chronic kidney disease-mineral bone disorder show the role of osteocytic proteins, a potential mechanism of the bone-Vascular paradox, a therapeutic target, and a biomarker

The chronic kidney disease-mineral bone disorder (CKD-MBD) is a complex multi-component syndrome occurring during kidney disease and its progression. Here, we update progress in the components of the syndrome, and synthesize recent investigations, which suggest a potential mechanism of the bone-vascular paradox. The discovery that calcified arteries in chronic kidney disease inhibit bone remodeling lead to the identification of factors produced by the vasculature that inhibit the skeleton, thus providing a potential explanation for the bone-vascular paradox. Among the factors produced by calcifying arteries, sclerostin secretion is especially enlightening. Sclerostin is a potent inhibitor of bone remodeling and an osteocyte specific protein. Its production by the vasculature in chronic kidney disease identifies the key role of vascular cell osteoblastic/osteocytic transdifferentiation in vascular calcification and renal osteodystrophy. Subsequent studies showing that inhibition of sclerostin activity by a monoclonal antibody improved bone remodeling as expected, but stimulated vascular calcification, demonstrate that vascular sclerostin functions to brake the Wnt stimulation of the calcification milieu. Thus, the target of therapy in the chronic kidney disease-mineral bone disorder is not inhibition of sclerostin function, which would intensify vascular calcification. Rather, decreasing sclerostin production by decreasing the vascular osteoblastic/osteocytic transdifferentiation is the goal. This might decrease vascular calcification, decrease vascular stiffness, decrease cardiac hypertrophy, decrease sclerostin production, reduce serum sclerostin and improve skeletal remodeling. Thus, the therapeutic target of the chronic kidney disease-mineral bone disorder may be vascular osteoblastic transdifferentiation, and sclerostin levels may be a useful biomarker for the diagnosis of the chronic kidney disease-mineral bone disorder and the progress of its therapy.

Heating-mediated purification of active FGF21 and structure-based design of its variant with enhanced potency

Fibroblast growth factor 21 (FGF21) has pharmaceutical potential against obesity-related metabolic disorders, including non-alcoholic fatty liver disease. Since thermal stability is a desirable factor for therapeutic proteins, we investigated the thermal behavior of human FGF21. FGF21 remained soluble after heating; thus, we examined its temperature-induced structural changes using circular dichroism (CD). FGF21 showed inter-convertible temperature-specific CD spectra. The CD spectrum at 100 °C returned to that at 20 °C when the heated FGF21 solution was cooled. Through loop swapping, the connecting loop between β10 and β12 in FGF21 was revealed to be associated with the unique thermal behavior of FGF21. According to surface plasmon resonance (SPR) experiments, in vitro cell-based assays, and model high-fat diet (HFD)-induced obesity studies, heated FGF21 maintained biological activities that were comparable to those of non-heated and commercial FGF21s. Based on sequence comparison and structural analysis, five point-mutations were introduced into FGF21. Compared with the wild type, the heated FGF21 variant displayed improved therapeutic potential in terms of body weight loss, the levels of hepatic triglycerides and lipids, and the degree of vacuolization of liver in HFD-fed mice.

Association between Serum Soluble α-Klotho and Urinary Albumin Excretion in Middle-Aged and Older US Adults: NHANES 2007-2016

(1) Background: Preclinical and clinical studies on the anti-aging effect of α-Klotho are emerging. Urinary albumin excretion (UAE) is a well-known biomarker of kidney injury and generalized damage in the cardiovascular system. However, the potential relationship between α-Klotho and UAE is limited and controversial. This study aimed to quantify this relationship in the general middle-aged and elderly population from the National Health and Nutrition Survey (NHANES) 2007-2016. (2) Methods: Serum α-Klotho was measured by enzyme-linked immunosorbent assay. UAE was assessed by the albumin-to-creatinine ratio (ACR). After adjusting for several confounding variables, the relationship between α-Klotho and ACR was analyzed by weighted multivariable logistic regression, subgroup analysis, and interaction tests. A generalized additive model (GAM) with smooth functions using the two-piecewise linear regression model was used to examine the potential nonlinear relationship between α-Klotho and ACR. (3) Results: Among 13,584 participants aged 40-79 years, we observed an independent and significant negative correlation between α-Klotho and ACR (β = -12.22; 95% CI, -23.91, -0.53, p = 0.0448) by multivariable logistic regression analysis, especially in those with age ≥ 60 years, pulse pressure (PP) ≥ 60 mmHg, hypertension or diabetes. We further discovered the nonlinear relationship between α-Klotho and ACR by GAM, revealing the first negative and then positive correlations with an inflection point of 9.91 pg/mL between α-Klotho and ACR. (4) Conclusions: A dose-response relationship between α-Klotho and ACR was demonstrated, and the negative correlation therein indicated that α-Klotho has potential as a serum marker and prophylactic or therapeutic agent despite its metabolic and effective mechanisms needing to be further explored.

Transcriptomic Analysis of Glycosylation and Neuroregulatory Pathways in Rodent Models in Response to Psychedelic Molecules

The potential for psychedelic molecules in impacting cognitive flexibility has long been supported and acknowledged across scientific reports. In the current study, an approach leveraging knowledge-based gene-set information analysis has been adopted to explore the potential impact of psychedelic molecules on both glycosylation, (a post-translational modifications (PTM)) and on neuro-regulatory pathways. Though limitations and restrictions rise from the scarcity of publicly available 'omics' data, targeted analysis enabled us to identify a number of key glycogenes (Hexb, Hs6st2, Col9a2, B3gat2, Mgat5, Bgn) involved the structural organization of extracellular matrix and neuroprotective factors (Kl, Pomc, Oxt, Gal, Avp, Cartpt) which play vital roles in neuron protection, development as well as synaptic stability. In response to psychedelic molecules, we found that these genes and associated pathways are transcriptional altered in rodent models. The approach used indicates the potential to exploit existing datasets for hypothesis generation and testing for the molecular processes which play a role in the physiological response to psychedelic molecule effects. These reported findings, which focused on alterations in glycogenes and neuro-regulatory factors may provide a novel range of biomarkers to track the beneficial, as well as potential toxicological effects of psychedelic molecules.

The impact of SGLT2 inhibitors on αKlotho in renal MDCK and HK-2 cells

αKlotho is a transmembrane protein predominantly expressed in the kidney serving as a co-receptor for phosphate homeostasis-regulating hormone FGF23 and has an extracellular domain that can be cleaved off and is a hormone. αKlotho deficiency results in accelerated aging and early onset of aging-associated diseases while its overexpression strongly expands the lifespan of mice. Moreover, αKlotho exerts health-beneficial anti-inflammatory, anti-neoplastic, anti-fibrotic, and anti-oxidant effects. Higher αKlotho levels are associated with better outcomes in renal and cardiovascular diseases. SGLT2 inhibitors are novel drugs in the treatment of diabetes by inhibiting renal glucose transport and have additional nephro- and cardioprotective effects. We explored whether SGLT2 inhibitors affect αKlotho gene expression and protein secretion. Experiments were performed in renal MDCK and HK-2 cells, and αKlotho transcripts were determined by qRT-PCR and Klotho protein by ELISA. SGLT2 inhibitors canagliflozin, sotagliflozin, and dapagliflozin enhanced whereas empagliflozin reduced αKlotho gene expression in MDCK cells. By the same token, canagliflozin, sotagliflozin, dapagliflozin, but not empagliflozin down-regulated p65 subunit of pro-inflammatory NFκB. In HK-2 cells, all SGLT2 inhibitors reduced αKlotho transcripts. Canagliflozin and sotagliflozin, however, increased Klotho protein concentration in the cell culture supernatant, an effect paralleled by up-regulation of ADAM17. Taken together, our investigations demonstrate complex effects of different SGLT2 inhibitors on αKlotho gene expression and protein secretion in renal MDCK and HK-2 cells.

VEGFR2 insufficiency enhances phosphotoxicity and undermines Klotho's protection against peritubular capillary rarefaction and kidney fibrosis

Vascular endothelial growth factor (VEGF) and its cognate receptor (VEGFR2) system are crucial for cell functions associated with angiogenesis and vasculogenesis. Klotho contributes to vascular health maintenance in the kidney and other organs in mammals, but it is unknown whether renoprotection by Klotho is dependent on VEGF/VEGFR2 signaling. We used heterozygous VEGFR2-haploinsufficient (VEGFR2+/-) mice resulting from heterozygous knockin of green fluorescent protein in the locus of fetal liver kinase 1 encoding VEGFR2 to test the interplay of Klotho, phosphate, and VEGFR2 in kidney function, the vasculature, and fibrosis. VEGFR2+/- mice displayed downregulated VEGF/VEGFR2 signaling in the kidney, lower density of peritubular capillaries, and accelerated kidney fibrosis, all of which were also found in the homozygous Klotho hypomorphic mice. High dietary phosphate induced higher plasma phosphate, greater peritubular capillary rarefaction, and more kidney fibrosis in VEGFR2+/- mice compared with wild-type mice. Genetic overexpression of Klotho significantly attenuated the elevated plasma phosphate, kidney dysfunction, peritubular capillary rarefaction, and kidney fibrosis induced by a high-phosphate diet in wild-type mice but only modestly ameliorated these changes in the VEGFR2+/- background. In cultured endothelial cells, VEGFR2 inhibition reduced free VEGFR2 but enhanced its costaining of an endothelial marker (CD31) and exacerbated phosphotoxicity. Klotho protein maintained VEGFR2 expression and attenuated high phosphate-induced cell injury, which was reduced by VEGFR2 inhibition. In conclusion, normal VEGFR2 function is required for vascular integrity and for Klotho to exert vascular protective and antifibrotic actions in the kidney partially through the regulation of VEGFR2 function.NEW & NOTEWORTHY This research paper studied the interplay of vascular endothelial growth factor receptor type 2 (VEGFR2), high dietary phosphate, and Klotho, an antiaging protein, in peritubular structure and kidney fibrosis. Klotho protein was shown to maintain VEGFR2 expression in the kidney and reduce high phosphate-induced cell injury. However, Klotho cytoprotection was attenuated by VEGFR2 inhibition. Thus, normal VEGFR2 function is required for vascular integrity and Klotho to exert vascular protective and antifibrotic actions in the kidney.

Quantification of Calciprotein Particles (CPPs) in Serum/Plasma Samples Using a Fluorescent Bisphosphonate

Calciprotein particles (CPPs) are mineral-protein complexes containing solid-phase calcium-phosphate and the serum protein fetuin-A. CPPs are dispersed in the blood as colloids. Previous clinical studies revealed that circulating levels of CPPs were correlated with inflammation and vascular calcification/stiffness in patients with chronic kidney disease (CKD). Measurement of blood CPP levels is challenging because CPPs are unstable and change their physical and chemical properties spontaneously over time in vitro. Several different methods have been developed for quantification of blood CPP levels with different advantages and limitations. We have developed a simple and sensitive assay using a fluorescent probe that bound to calcium-phosphate crystals. This assay may be useful as a clinical test to evaluate the cardiovascular risk and prognosis in CKD patients.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

FGF23 AND ALTERED MINERAL HOMEOSTASIS IN KIDNEY DISEASE AND FOLLOWING INTRAVENOUS IRON

Fibroblast growth factor 23 (FGF23) is an endocrine hormone that stimulates renal phosphate excretion and suppresses circulating concentrations of 1,25-dihydroxyvitamin D (1,25D). These effects of FGF23 are most evident in rare diseases that are characterized by FGF23-mediated hypophosphatemic rickets-osteomalacia. More commonly, elevated FGF23 is a ubiquitous, early consequence of chronic kidney disease (CKD) in which it helps to maintain normal serum phosphate levels but causes secondary hyperparathyroidism by suppressing 1,25D, and directly promotes cardiovascular disease and death. Elevated FGF23 is also a common complication of intravenous administration of ferric carboxymaltose (FCM), which is widely used to treat iron deficiency anemia. Among patients with normal kidney function who receive FCM, the resulting increase in FGF23 and subsequent FGF23-mediated reduction of 1,25D and secondary hyperparathyroidism promote hypophosphatemia that can be symptomatic, severe, and associated with musculoskeletal complications. Ongoing research is needed to design novel therapeutic approaches to mitigate FGF23-related illnesses.

Research progress of fibroblast growth factor in nervous system diseases

Fibroblast growth factors (FGF) are a group of structurally related polypeptides which constitute an elaborate signaling system with their receptors. Evidence accumulated in the years suggests that the FGF family plays a key role in the repair of central nervous system injury. The main protective mechanisms include activating the expression of PI3K-Akt, peroxisome proliferator-activated receptor (PPARγ) and other signals; inhibiting NF-κB-mediated inflammatory response, oxidative stress and apoptosis; regulating neuronal differentiation and neuronal excitability as well as participating in protection of neurovascular units and nerve function repair. This paper comprehensively summarizes the latest research progress in FGF signaling related to diseases of the central nervous system such as cerebral infarction, cerebral hemorrhage, traumatic brain injury, Alzheimer's disease, Parkinson's disease, epilepsy and depression, aiming to provide scientific basis and reference for the development of innovative FGF drugs for the prevention and treatment of neurological diseases.

Interaction of Vitamin D with Peptide Hormones with Emphasis on Parathyroid Hormone, FGF23, and the Renin-Angiotensin-Aldosterone System

The seminal discoveries that parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) are major endocrine regulators of vitamin D metabolism led to a significant improvement in our understanding of the pivotal roles of peptide hormones and small proteohormones in the crosstalk between different organs, regulating vitamin D metabolism. The interaction of vitamin D, FGF23 and PTH in the kidney is essential for maintaining mineral homeostasis. The proteohormone FGF23 is mainly secreted from osteoblasts and osteoclasts in the bone. FGF23 acts on proximal renal tubules to decrease production of the active form of vitamin D (1,25(OH)₂D) by downregulating transcription of 1α-hydroxylase (CYP27B1), and by activating transcription of the key enzyme responsible for vitamin D degradation, 24-hydroxylase (CYP24A1). Conversely, the peptide hormone PTH stimulates 1,25(OH)₂D renal production by upregulating the expression of 1α-hydroxylase and downregulating that of 24-hydroxylase. The circulating concentration of 1,25(OH)₂D is a positive regulator of FGF23 secretion in the bone, and a negative regulator of PTH secretion from the parathyroid gland, forming feedback loops between kidney and bone, and between kidney and parathyroid gland, respectively. In recent years, it has become clear that vitamin D signaling has important functions beyond mineral metabolism. Observation of seasonal variations in blood pressure and the subsequent identification of vitamin D receptor (VDR) and 1α-hydroxylase in non-renal tissues such as cardiomyocytes, endothelial and smooth muscle cells, suggested that vitamin D may play a role in maintaining cardiovascular health. Indeed, observational studies in humans have found an association between vitamin D deficiency and hypertension, left ventricular hypertrophy and heart failure, and experimental studies provided strong evidence for a role of vitamin D signaling in the regulation of cardiovascular function. One of the proposed mechanisms of action of vitamin D is that it functions as a negative regulator of the renin-angiotensin-aldosterone system (RAAS). This finding established a novel link between vitamin D and RAAS that was unexplored until then. During recent years, major progress has been made towards a more complete understanding of the mechanisms by which FGF23, PTH, and RAAS regulate vitamin D metabolism, especially at the genomic level. However, there are still major gaps in our knowledge that need to be filled by future research. The purpose of this review is to highlight our current understanding of the molecular mechanisms underlying the interaction between vitamin D, FGF23, PTH, and RAAS, and to discuss the role of these mechanisms in physiology and pathophysiology.

Meclozine ameliorates bone mineralization and growth plate structure in a mouse model of X‑linked hypophosphatemia

X-linked hypophosphatemic rickets (XLH) is characterized by hypo-mineralization of the bone due to hypophosphatemia. XLH is caused by abnormally high levels of fibroblast growth factor 23, which trigger renal phosphate wasting. Activated fibroblast growth factor receptor 3 (FGFR3) signaling is considered to be involved in XLH pathology. Our previous study revealed that meclozine attenuated FGFR3 signaling and promoted longitudinal bone growth in an achondroplasia mouse model. The present study aimed to examine whether meclozine affected the bone phenotype in a mouse model of XLH [X-linked hypophosphatemic (Hyp) mice]. Meclozine was administered orally to 7-day-old Hyp mice for 10 days, after which the mice were subjected to blood sampling and histological analyses of the first coccygeal vertebra, femur and tibia. Villanueva Goldner staining was used to assess bone mineralization, hematoxylin and eosin staining was used to determine the growth plate structure and tartrate-resistant acid phosphatase staining was used to measure osteoclast activity. The osteoid volume/bone volume of cortical bone was lower in meclozine-treated Hyp mice compared with untreated Hyp mice. Meclozine treatment improved the abnormally thick hypertrophic zone of the growth plate and ameliorated the downregulation of osteoclast surface/bone surface in Hyp mice. However, meclozine had only a marginal effect on mineralization in the trabecular bone and on calcium and phosphate plasma levels. A 10-day-tratment with meclozine partially ameliorated bone mineralization in Hyp mice; hence, meclozine could alleviate XLH symptoms.

Biofabrication of Human Skin with Its Appendages

Much effort has been made to generate human skin organ in the laboratory. Yet, the current models are limited due to the lack of many critical biological and structural features of the skin. Importantly, these in vitro models lack appendages and fail to recapitulate the whole human skin construction. Thus, engineering a human skin with the capacity to generate all components, including appendages, is a major challenge. This review intends to provide an update on the recent efforts underway to regenerate appendage-bearing skin organs based on scaffold-free and scaffold-based bioengineering approaches. Although the mouse skin equivalents containing hair follicles, sebaceous glands, and sweat glands have been established in vitro, there has been limited success in humans. A combination of biofabricated matrices and cell aggregates, such as organoids, can pave the way for generating skin substitutes with human-like biological, structural, and physical features. Accordingly, the formation of human skin organoids and reconstruction of vascularized skin equipped with immune cells prompt calls for more scientific research. The generation of appendage-bearing skin substitutes can be applied in practice for wound healing, hair restoration, and scar treatment.

FGFR redundancy limits the efficacy of FGFR4-selective inhibitors in hepatocellular carcinoma

The fibroblast growth factor 19 (FGF19)–FGF receptor 4 (FGFR4)–coreceptor klotho β (KLB) signaling axis has been implicated as a therapeutic target in 20 to 30% of hepatocellular carcinomas. However, patient responses to FGFR4-selective inhibitors were unsatisfactory in recent clinical trials. In this study, we reveal the redundancy of FGFR3 and FGFR4 as mechanisms of de novo resistance to FGFR4-selective inhibitors, supporting the clinical evaluation of pan-FGFR inhibitors for treating FGF19-positive hepatocellular carcinoma.

Aberrant fibroblast growth factor 19 (FGF19) signaling mediated by its receptor, FGF receptor 4 (FGFR4), and coreceptor, klotho β (KLB), is a driver of hepatocellular carcinoma (HCC). Several potent FGFR4-selective inhibitors have been developed but have exhibited limited efficacy in HCC clinical trials. Here, by using HCC cell line models from the Cancer Cell Line Encyclopedia (CCLE) and the Liver Cancer Model Repository (LIMORE), we show that selective FGFR4 inactivation was not sufficient to inhibit cancer cell proliferation and tumor growth in FGF19-positive HCC. Moreover, genetic inactivation of KLB in these HCC cells resulted in a fitness defect more severe than that resulting from inactivation of FGFR4. By a combination of biochemical and genetic approaches, we found that KLB associated with FGFR3 and FGFR4 to mediate the prosurvival functions of FGF19. KLB mutants defective in interacting with FGFR3 or FGFR4 could not support the growth or survival of HCC cells. Genome-wide CRISPR loss-of-function screening revealed that FGFR3 restricted the activity of FGFR4-selective inhibitors in inducing cell death; the pan-FGFR inhibitor erdafitinib displayed superior potency than FGFR4-selective inhibitors in suppressing the growth and survival of FGF19-positive HCC cells. Among FGF19-positive HCC cases from The Cancer Genome Atlas (TCGA), FGFR3 is prevalently coexpressed with FGFR4 and KLB, suggesting that FGFR redundancy may be a common mechanism underlying the de novo resistance to FGFR4 inhibitors. Our study provides a rationale for clinical testing of pan-FGFR inhibitors as a treatment strategy for FGF19-positive HCC.

Isoform-specific inhibition of FGFR signaling achieved by a de-novo-designed mini-protein

Cellular signaling by fibroblast growth factor receptors (FGFRs) is a highly regulated process mediated by specific interactions between distinct subsets of fibroblast growth factor (FGF) ligands and two FGFR isoforms generated by alternative splicing: an epithelial b- and mesenchymal c-isoforms. Here, we investigate the properties of a mini-protein, mb7, developed by an in silico design strategy to bind to the ligand-binding region of FGFR2. We describe structural, biophysical, and cellular analyses demonstrating that mb7 binds with high affinity to the c-isoforms of FGFR, resulting in inhibition of cellular signaling induced by a subset of FGFs that preferentially activate c-isoforms of FGFR. Notably, as mb7 blocks interaction between FGFR with Klotho proteins, it functions as an antagonist of the metabolic hormones FGF19 and FGF21, providing mechanistic insights and strategies for the development of therapeutics for diseases driven by aberrantly activated FGFRs.

Park et al. show that a de-novo-designed mini-protein, mb7, can specifically recognize c-isoforms of FGFRs. By masking the regions of FGFR that are critical for the FGFR activation, mb7 can potently inhibit cellular signaling by a subset of FGFs that preferentially activate FGFR c-isoform signaling.

Alveolar Epithelial Type 2 Cell Dysfunction in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible pulmonary interstitial disease that seriously affects the patient's quality of life and lifespan. The pathogenesis of IPF has not been clarified, and its treatment is limited to pirfenidone and nintedanib, which only delays the decline of lung function. Alveolar epithelial type 2 (AT2) cells are indispensable in the regeneration and lung surfactant secretion of alveolar epithelial cells. Studies have shown that AT2 cell dysfunction initiates the occurrence and progression of IPF. This review expounds on the AT2 cell dysfunction in IPF, involving senescence, apoptosis, endoplasmic reticulum stress, mitochondrial damage, metabolic reprogramming, and the transitional state of AT2 cells. This article also briefly summarizes potential treatments targeting AT2 cell dysfunction.

Strategies to lower fibroblast growth factor 23 bioactivity

Fibroblast growth factor 23 (FGF23) is a circulating hormone derived from the bone whose release is controlled by many factors and exerts a multitude of systemic actions. There are congenital and acquired disorders of increased and decreased FGF23 levels. In chronic kidney disease (CKD), elevations of FGF23 levels can be 1000-fold above the upper physiological limit. It is still debated whether this high FGF23 in CKD is a biomarker or causally related to morbidity and mortality. Data from human association studies support pathogenicity, while experimental data are less robust. Knowledge of the biology and pathobiology of FGF23 has generated a plethora of means to reduce FGF23 bioactivity at many levels that will be useful for therapeutic translations. This article summarizes these approaches and addresses several critical questions that still need to be answered.

KL-FGF23-VD Axis in Improving Late-Onset Alzheimer's Disease by Modulating IKK/NF-κB Signal Pathway

Materials and Methods

LOAD rats and Aβ microglia were constructed by using Aβ 1-40 and IBO mixture. The effect of KL-FGF23-VD axis on LOAD was investigated by transfecting overexpressing and interfering with KL gene adenovirus, and IKK-16 was added to Aβ microglia to explore the effect of KL-FGF23-VD axis on regulation of IKK/NF-κB signaling pathway.

Results

The results showed that, in KL-OE group, FGF23 was decreased in the hippocampus of LOAD rats compared with control and KL-si, and the trend was opposite in the KL-si group. The KL-FGF23-VD axis can alleviate inflammatory response, reduce the deposition of Aβ, and inhibit activation of the NF-κB pathway and neuron apoptosis in brain tissue of LOAD rats. In Aβ microglia, the expression of KL-FGF23-VD axis was consistent with animal experiments. The KL-FGF23-VD axis can inhibit the expression of Aβ microglia inflammatory factors and the activation of microglia and NF-κB pathway. Meanwhile, IKK expression was decreased in KL-OE group compared with KL-si and Control. In the IKK-16 addition group, the ability of KL-FGF23-VD axis to inhibit the activation of microglia and NF-κB pathway was enhanced.

Conclusions

These findings suggest a potential role of the KL-FGF23-VD axis in AD treatment by regulating the IKK/NF-κB pathway.

Prediction of the structural interface between fibroblast growth factor23 and Burosumab using alanine scanning and molecular docking

Burosumab, an FGF23 targeting monoclonal antibody, was approved by the FDA in 2018 for use in children and adults with X-linked hypophosphatemia (or XLH). While several clinical studies have demonstrated the long-term safety and efficacy of Burosumab, the molecular basis of FGF23-Burosumab interaction which underpins its mechanism of action remains unknown. In this study, we employed molecular docking combined with alanine scanning of epitope and paratope to predict a model of FGF23-Burosumab interaction. Then, we used the model to understand the species-species cross-reactivity of Burosumab and to reverse engineer mouse FGF23 with 'back to human' mutations to bind Burosumab. Finally, we redesigned the CDRs with two mutations to engineer an affinity enhanced variant of the antibody. Our study provides insights into the FGF23-Burosumab interaction and demonstrates that alanine-scanning coupled with molecular docking can be used to optimize antibody candidates (e.g., structure-guided affinity maturation) for therapeutic use.

The role of α-klotho in human cancer: molecular and clinical aspects

Klotho is a well-established longevity hormone. Its most prominent function is the regulation of phosphate homeostasis. However, klotho possesses multiple pleiotropic activities, including inhibition of major signaling pathways, reducing oxidative stress and suppressing inflammation. These activities are tightly associated with cancer, and klotho was discovered as a universal tumor suppressor. We review here novel molecular aspects of klotho activity in cancer, focusing on its structure-function relationships and clinical aspects regarding its expression, blood levels, clinical risk, and prognostic value in the clinical setting. In addition, the potential benefit of klotho treatment combined with chemotherapy, biological therapy, or immunotherapy, are discussed. Finally, as klotho was shown in preclinical models to inhibit cancer development and growth, we discuss various approaches to developing klotho-based therapies.

Phosphate Metabolic Inhibition Contributes to Irradiation-Induced Myelosuppression through Dampening Hematopoietic Stem Cell Survival

Myelosuppression is a common and intractable side effect of cancer therapies including radiotherapy and chemotherapy, while the underlying mechanism remains incompletely understood. Here, using a mouse model of radiotherapy-induced myelosuppression, we show that inorganic phosphate (Pi) metabolism is acutely inhibited in hematopoietic stem cells (HSCs) during irradiation-induced myelosuppression, and closely correlated with the severity and prognosis of myelosuppression. Mechanistically, the acute Pi metabolic inhibition in HSCs results from extrinsic Pi loss in the bone marrow niche and the intrinsic transcriptional suppression of soluble carrier family 20 member 1 (SLC20A1)-mediated Pi uptake by p53. Meanwhile, Pi metabolic inhibition blunts irradiation-induced Akt hyperactivation in HSCs, thereby weakening its ability to counteract p53-mediated Pi metabolic inhibition and the apoptosis of HSCs and consequently contributing to myelosuppression progression. Conversely, the modulation of the Pi metabolism in HSCs via a high Pi diet or renal Klotho deficiency protects against irradiation-induced myelosuppression. These findings reveal that Pi metabolism and HSC survival are causally linked by the Akt/p53–SLC20A1 axis during myelosuppression and provide valuable insights into the pathogenesis and management of myelosuppression.

Association of aging-related genes with prognosis and immune infiltration in pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PAAD) is one of the deadliest malignancies. Aging is described as the degeneration of physiological function, which is complexly correlated with cancer. It is significant to explore the influences of aging-related genes (ARGs) on PAAD. Based on The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) datasets, we used univariate Cox regression analysis and acquired eight differentially expressed ARGs with prognostic values. Two molecular subtypes were identified based on these ARGs to depict PAAD patients’ overall survival (OS) and immune microenvironments preliminarily. Cluster 1 had a poor OS as well as a worse immune microenvironment. Through least absolute shrinkage and selection operator (LASSO) regression analysis, we constructed a seven-ARG risk signature based on the TCGA dataset and verified it in Gene Expression Omnibus (GEO) and International Cancer Genome Consortium (ICGC) to predict the prognoses, immune microenvironments, signal pathways, tumor mutations, and drug sensitivity of PAAD patients. The high-risk group possessed an unfavorable OS compared with that of the low-risk group. We also verified the independence and clinical availability of the risk signature by Cox regression analyses and the establishment of a nomogram, respectively. The higher risk score was associated with several clinical factors such as higher grade and advanced tumor stage as well as lower immunoscore and cluster 1. The negative associations of risk scores with immune, stroma, and estimate scores proved the terrible immune microenvironment in the high-risk group. Relationships between risk score and immune checkpoint gene expression as well as signal pathways provided several therapeutic targets. PAAD patients in the low-risk group possessed lower tumor mutations as well as a higher susceptibility to axitinib and vorinostat. The high-risk group bore a higher TMB and cisplatin and dasatinib may be better options. We used immunohistochemistry and qPCR to confirm the expression of key ARGs with their influences on OS. In conclusion, we identified two ARG-mediated molecular subtypes and a novel seven-ARG risk signature to predict prognoses, immune microenvironments, signal pathways, tumor mutations, and drug sensitivity of PAAD patients.

Identification of Small-Molecule Inhibitors of Fibroblast Growth Factor 23 Signaling via In Silico Hot Spot Prediction and Molecular Docking to α-Klotho

Fibroblast growth factor 23 (FGF23) is a therapeutic target for treating hereditary and acquired hypophosphatemic disorders, such as X-linked hypophosphatemic (XLH) rickets and tumor-induced osteomalacia (TIO), respectively. FGF23-induced hypophosphatemia is mediated by signaling through a ternary complex formed by FGF23, the FGF receptor (FGFR), and α-Klotho. Currently, disorders of excess FGF23 are treated with an FGF23-blocking antibody, burosumab. Small-molecule drugs that disrupt protein/protein interactions necessary for the ternary complex formation offer an alternative to disrupting FGF23 signaling. In this study, the FGF23:α-Klotho interface was targeted to identify small-molecule protein/protein interaction inhibitors since it was computationally predicted to have a large fraction of hot spots and two druggable residues on α-Klotho. We further identified Tyr433 on the KL1 domain of α-Klotho as a promising hot spot and α-Klotho as an appropriate drug-binding target at this interface. Subsequently, we performed in silico docking of ∼5.5 million compounds from the ZINC database to the interface region of α-Klotho from the ternary crystal structure. Following docking, 24 and 20 compounds were in the final list based on the lowest binding free energies to α-Klotho and the largest number of contacts with Tyr433, respectively. Five compounds were assessed experimentally by their FGF23-mediated extracellular signal-regulated kinase (ERK) activities in vitro, and two of these reduced activities significantly. Both these compounds were predicted to have favorable binding affinities to α-Klotho but not have a large number of contacts with the hot spot Tyr433. ZINC12409120 was found experimentally to disrupt FGF23:α-Klotho interaction to reduce FGF23-mediated ERK activities by 70% and have a half maximal inhibitory concentration (IC₅₀) of 5.0 ± 0.23 μM. Molecular dynamics (MD) simulations of the ZINC12409120:α-Klotho complex starting from in silico docking poses reveal that the ligand exhibits contacts with residues on the KL1 domain, the KL1-KL2 linker, and the KL2 domain of α-Klotho simultaneously, thereby possibly disrupting the regular function of α-Klotho and impeding FGF23:α-Klotho interaction. ZINC12409120 is a candidate for lead optimization.

Effects of a Topical Anti-aging Formulation on Skin Aging Biomarkers

OBJECTIVE

Following previous clinical trials, an antiaging product (Restorative Skin complex [RSC]; Alastin Skin Care Carlsbad, a Galderma company), was investigated for its effects on Klotho gene regulation, telomere length, and histological biopsy changes to provide a comprehensive picture of the mechanism and efficacy of its anti-aging effect.

METHODS

Neonatal human fibroblasts were used for telomere length studies to examine the effect of the full RSC formulation and the amino acid components Tripeptide-1 and Hexapeptide-12 (TriHex™) on these cellular aging mechanisms. In addition, RNA sequencing was conducted using human keratinocytes specifically investigating Klotho and related genes. This was supplemented by a clinical study using biopsy samples.

RESULTS

TriHex™ significantly upregulated the Klotho gene and related FGF23, FGFR1 and FOXO3B anti-aging genes. Significant telomere shortening reduction over control was demonstrated with the RSC formulation at four weeks and with TriHex™ at six weeks for all percentiles tested. Previous clinical studies demonstrated that the use of the antiaging regimen for 12 weeks produced a statistically significant improvement in scores for all evaluated parameters. Restaining of previous biopsy blocks from the clinical trial revealed positive ECM changes, stimulation of collagen, fibrillin, CD44 and elastin.

LIMITATIONS

The study was limited by a relatively small numbers of patients in the clinical trial and the non-competitive nature of the trial.

CONCLUSION

RSC anti-aging formulation and its TriHex™ components demonstrated significant reduction in telomere shortening, upregulation of Klotho and FOXO3 genes and biopsy validation of anti-aging efficacy. This new science supplements previous trials that demonstrated clinical efficacy of the formulation.

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, with soluble 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.

Heparin, klotho, and FGF23: the 3-beat waltz of the discordant heart

Excess fibroblast growth factor (FGF) 23 signaling in patients with chronic kidney disease induces left ventricular hypertrophy. In this issue, Yanucil et al. investigated the interaction of soluble klotho and heparin with FGF23 and FGF receptor isoforms. They concluded that heparin promotes the FGF23-FGF receptor isoform 4 interaction and FGF23 pathogenic effects, supporting an important role of heparin in the pathogenesis of FGF23-mediated left ventricular hypertrophy in chronic kidney disease.

Activation of RAAS Signaling Contributes to Hypertension in Aged Hyp Mice

High circulating levels of fibroblast growth factor-23 (FGF23) are associated with left ventricular hypertrophy as well as increased morbidity and mortality in patients suffering from chronic kidney disease. However, the mechanisms underlying this association are controversial. Here, we aimed to further characterize the cardiovascular sequelae of long term endogenous FGF23 hypersecretion using 14-month-old male Hyp mice as a model of FGF23 excess. Hyp mice were characterized by a ~10-fold increase in circulating intact FGF23, hypophosphatemia, increased serum aldosterone, but normal kidney function, relative to wildtype (WT) controls. Cardiovascular phenotyping did not reveal any evidence of left ventricular hypertrophy or functional impairment in 14-month-old Hyp mice. Fractional shortening, ejection fraction, molecular markers of hypertrophy (Anp, Bnp), and intracardiac markers of contractility and diastolic function were all unchanged in these animals. However, intraarterial catheterization revealed an increase in systolic, diastolic, and mean arterial pressure of ~12 mm Hg in aged Hyp mice relative to WT controls. Hypertension in Hyp mice was associated with increased peripheral vascular resistance. To test the hypothesis that a stimulation of the renin–angiotensin–aldosterone system (RAAS) contributes to hypertension in aged Hyp mice, we administered the angiotensin receptor blocker losartan (30 mg/kg twice daily) or the mineralocorticoid receptor antagonist canrenone (30 mg/kg once daily) to aged Hyp and WT mice over 5 days. Both drugs had minor effects on blood pressure in WT mice, but reduced blood pressure and peripheral vascular resistance in Hyp mice, suggesting that a stimulation of the RAAS contributes to hypertension in aged Hyp mice.

Pathobiology of the Klotho Antiaging Protein and Therapeutic Considerations

The α-Klotho protein (henceforth denoted Klotho) has antiaging properties, as first observed in mice homozygous for a hypomorphic Klotho gene (kl/kl). These mice have a shortened lifespan, stunted growth, renal disease, hyperphosphatemia, hypercalcemia, vascular calcification, cardiac hypertrophy, hypertension, pulmonary disease, cognitive impairment, multi-organ atrophy and fibrosis. Overexpression of Klotho has opposite effects, extending lifespan. In humans, Klotho levels decline with age, chronic kidney disease, diabetes, Alzheimer’s disease and other conditions. Low Klotho levels correlate with an increase in the death rate from all causes. Klotho acts either as an obligate coreceptor for fibroblast growth factor 23 (FGF23), or as a soluble pleiotropic endocrine hormone (s-Klotho). It is mainly produced in the kidneys, but also in the brain, pancreas and other tissues. On renal tubular-cell membranes, it associates with FGF receptors to bind FGF23. Produced in bones, FGF23 regulates renal excretion of phosphate (phosphaturic effect) and vitamin D metabolism. Lack of Klotho or FGF23 results in hyperphosphatemia and hypervitaminosis D. With age, human renal function often deteriorates, lowering Klotho levels. This appears to promote age-related pathology. Remarkably, Klotho inhibits four pathways that have been linked to aging in various ways: Transforming growth factor β (TGF-β), insulin-like growth factor 1 (IGF-1), Wnt and NF-κB. These can induce cellular senescence, apoptosis, inflammation, immune dysfunction, fibrosis and neoplasia. Furthermore, Klotho increases cell-protective antioxidant enzymes through Nrf2 and FoxO. In accord, preclinical Klotho therapy ameliorated renal, cardiovascular, diabetes-related and neurodegenerative diseases, as well as cancer. s-Klotho protein injection was effective, but requires further investigation. Several drugs enhance circulating Klotho levels, and some cross the blood-brain barrier to potentially act in the brain. In clinical trials, increased Klotho was noted with renin-angiotensin system inhibitors (losartan, valsartan), a statin (fluvastatin), mTOR inhibitors (rapamycin, everolimus), vitamin D and pentoxifylline. In preclinical work, antidiabetic drugs (metformin, GLP-1-based, GABA, PPAR-γ agonists) also enhanced Klotho. Several traditional medicines and/or nutraceuticals increased Klotho in rodents, including astaxanthin, curcumin, ginseng, ligustilide and resveratrol. Notably, exercise and sport activity increased Klotho. This review addresses molecular, physiological and therapeutic aspects of Klotho.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Novel Thermosensitive Hydrogel Promotes Spinal Cord Repair by Regulating Mitochondrial Function

The repair of spinal cord injury (SCI) is still a tough clinical challenge and needs innovative therapies. Mitochondrial function is significantly compromised after SCI and has emerged as an important factor causing neuronal apoptosis and hindering functional recovery. In this study, umbilical cord mesenchymal stem cells (UCMSC), which are promising seed cells for nerve regeneration, and basic fibroblast growth factor (bFGF) that have been demonstrated to have a variety of effects on neural regeneration were jointly immobilized in extracellular matrix (ECM) and heparin-poloxamer (HP) to create a polymer bioactive system that brings more hope and possibility for the treatment of SCI. Our results in vitro and in vivo showed that the UCMSC-bFGF-ECM-HP thermosensitive hydrogel has good therapeutic effects, mainly in reducing apoptosis and improving the mitochondrial function. It showed promising utility for the functional recovery of impaired mitochondrial function by promoting mitochondrial fusion, reducing pathological mitochondrial fragmentation, increasing mitochondrial energy supply, and improving the metabolism of MDA, LDH, and ROS. In addition, we uncovered a distinct molecular mechanism underlying the protective effects associated with activating p21-activated kinase 1 (PAK1) and mitochondrial sirtuin 4 (SIRT4) by the UCMSC-bFGF-ECM-HP hydrogel. The expansion of new insights into the molecular relationships between PAK1 and SIRT4, which links the mitochondrial function in SCI, can lay the foundation for future applications and help to provide promising interventions of stem-cell-based biological scaffold therapies and potential therapeutic targets for the clinical formulation of SCI treatment strategies.

Dietary vitamin D3 deprivation suppresses fibroblast growth factor 23 signals by reducing serum phosphorus levels in laying hens

The present study was carried out to evaluate the effect of dietary supplemental vitamin D₃ on fibroblast growth factor 23 (FGF23) signals as well as phosphorus homeostasis and metabolism in laying hens. Fourteen 40-week-old Hy-Line Brown layers were randomly assigned into 2 treatments: 1) vitamin D₃ restriction group (n = 7) fed 0 IU/kg vitamin D₃ diet, and 2) regular vitamin D₃ group (n = 7) fed 1,600 IU/kg vitamin D₃ diet. The study lasted for 21 d. Serum parameters, phosphorus and calcium excretion status, and tissue expressions of type II sodium-phosphate co-transporters (NPt2), FGF23 signals and vitamin D₃ metabolic regulators were determined. Hens fed the vitamin D₃ restricted diet had decreased serum phosphorus levels (by 31.3%, P = 0.028) when compared to those fed regular vitamin D₃ diet. In response to the decreased serum phosphorus, the vitamin D₃ restricted laying hens exhibited: 1) suppressed kidney expressions of 25-hydroxyvitamin D 1-α-hydroxylase (CYP27B1, by 52.8%, P = 0.036) and 1,25-dihydroxyvitamin D 24-hydroxylase (CYP24A1, by 99.4%, P = 0.032); 2) suppressed serum levels of FGF23 (by 14.6%, P = 0.048) and increased serum alkaline phosphatase level (by 414.1%, P = 0.012); 3) decreased calvaria mRNA expressions of fibroblast growth factor receptors (FGFR1, by 85.2%, P = 0.003, FGFR2, by 89.4%, P = 0.014, FGFR3, by 88.8%, P = 0.017, FGFR4, by 89.6%, P = 0.030); 4) decreased kidney mRNA expressions of FGFR1 (by 65.5%, P = 0.021), FGFR4 (by 66.0%, P = 0.050) and KLOTHO (by 68.8%, P = 0.038); 5) decreased kidney protein expression of type 2a sodium-phosphorus co-transporters (by 54.3%, P = 0.039); and 6) increased percent excreta calcium (by 26.9%, P = 0.002). In conclusion, the deprivation of dietary vitamin D₃ decreased FGF23 signals in laying hens by reducing serum FGF23 level and suppressing calvaria and kidney mRNA expressions of FGF23 receptors.

Ongoing Clinical Trials in Aging-Related Tissue Fibrosis and New Findings Related to AhR Pathways

Fibrosis is a pathological manifestation of wound healing that replaces dead/damaged tissue with collagen-rich scar tissue to maintain homeostasis, and complications from fibrosis contribute to nearly half of all deaths in the industrialized world. Ageing is closely associated with a progressive decline in organ function, and the prevalence of tissue fibrosis dramatically increases with age. Despite the heavy clinical and economic burden of organ fibrosis as the population ages, to date, there is a paucity of therapeutic strategies that are specifically designed to slow fibrosis. Aryl hydrocarbon receptor (AhR) is an environment-sensing transcription factor that exacerbates aging phenotypes in different tissues that has been brought back into the spotlight again with economic development since AhR could interact with persistent organic pollutants derived from incomplete waste combustion. In addition, gut microbiota dysbiosis plays a pivotal role in the pathogenesis of numerous diseases, and microbiota-associated tryptophan metabolites are dedicated contributors to fibrogenesis by acting as AhR ligands. Therefore, a better understanding of the effects of tryptophan metabolites on fibrosis modulation through AhR may facilitate the exploitation of new therapeutic avenues for patients with organ fibrosis. In this review, we primarily focus on how tryptophan-derived metabolites are involved in renal fibrosis, idiopathic pulmonary fibrosis, hepatic fibrosis and cardiac fibrosis. Moreover, a series of ongoing clinical trials are highlighted.

Molecular Basis of Bile Acid-FXR-FGF15/19 Signaling Axis

Bile acids (BAs) are a group of amphiphilic molecules consisting of a rigid steroid core attached to a hydroxyl group with a varying number, position, and orientation, and a hydrophilic side chain. While BAs act as detergents to solubilize lipophilic nutrients in the small intestine during digestion and absorption, they also act as hormones. Farnesoid X receptor (FXR) is a nuclear receptor that forms a heterodimer with retinoid X receptor α (RXRα), is activated by BAs in the enterohepatic circulation reabsorbed via transporters in the ileum and the colon, and plays a critical role in regulating gene expression involved in cholesterol, BA, and lipid metabolism in the liver. The FXR/RXRα heterodimer also exists in the distal ileum and regulates production of fibroblast growth factor (FGF) 15/FGF19, a hormone traveling via the enterohepatic circulation that activates hepatic FGF receptor 4 (FGFR4)-β-klotho receptor complex and regulates gene expression involved in cholesterol, BA, and lipid metabolism, as well as those regulating cell proliferation. Agonists for FXR and analogs for FGF15/19 are currently recognized as a promising therapeutic target for metabolic syndrome and cholestatic diseases.

Antibiotic-producing Micrococcales govern the microbiome that inhabits the fur of two- and three-toed sloths

Sloths have a dense coat on which insects, algae, and fungi coexist in a symbiotic relationship. This complex ecosystem requires different levels of control, however, most of these mechanisms remain unknown. We investigated the bacterial communities inhabiting the hair of two- (Choloepus Hoffmani) and three-toed (Bradypus variegatus) sloths and evaluated their potential for producing antibiotic molecules capable of exerting control over the hair microbiota. The analysis of 16S rRNA amplicon sequence variants (ASVs) revealed that the communities in both host species are dominated by Actinobacteriota and Firmicutes. The most abundant genera were Brevibacterium, Kocuria/Rothia, Staphylococcus, Rubrobacter, Nesterenkonia, and Janibacter. Furthermore, we isolated nine strains of Brevibacterium and Rothia capable of producing substances that inhibited the growth of common mammalian pathogens. The analysis of the biosynthetic gene clusters (BCGs) of these nine isolates suggests that the pathogen-inhibitory activity could be mediated by the presence of siderophores, terpenes, beta-lactones, Type III polyketide synthases (T3PKS), ribosomally synthesized, and post-translationally modified peptides (RiPPs), non-alpha poly-amino acids (NAPAA) like e-Polylysin, ectoine or nonribosomal peptides (NRPs). Our data suggest that Micrococcales that inhabit sloth hair could have a role in controlling microbial populations in that habitat, improving our understanding of this highly complex ecosystem. This article is protected by copyright. All rights reserved.