Asymptomatic gastric anisakiasis detected in gastric cancer screening: A case report.

Anisakiasis is a parasitic disease caused by Anisakis simplex and has become an emerging zoonosis as preferences for eating raw or undercooked seafood have become more common. Few case reports of asymptomatic anisakiasis have been published to date. A 79-year-old asymptomatic man underwent esophagogastroduodenoscopy (EGD) for gastric cancer screening. The gastroenterologist diagnosed superficial gastritis without any malignant lesions but found an Anisakis larva while reviewing EGD images. The physician performed a second EGD and removed the larva. The patient reported that he ate the flatfish sashimi for dinner on the day before the first EGD. This case indicates the existence of asymptomatic gastric anisakiasis, indicating that anisakiasis incidence may have previously been underestimated.

Demographic and geographical characteristics of pediatric patients presenting to a convenient clinic at a large railway station in a metropolitan area of Tokyo.

There is an increasing demand for medical provision systems that are friendly for working mothers with sick children in Japan. The aim of this cross-sectional, observational study was to analyze the demographic characteristics of pediatric patients presenting to a convenient care clinic, which was located in a large railway station and offered primary care with after-hours accessibility in a metropolitan area of Tokyo.We analyzed anonymous data for patients who had visited the pediatric department at a clinic between August 2013 and June 2016. Data regarding patients' sex, age, time of visit, waiting time, presence or absence of an appointment, diagnosis, and addresses were collected from electronic health and billing records.Overall, 8091 patients visited the department 45,388 times. The numbers of visits by patients who resided within 2, 5, and 10 miles of the clinic were 37,160 (84.6%), 42,336 (96.4%), and 43,399 (98.8%), respectively. No seasonal variation in the number of visits was observed. Male patients visited the clinic 23,742 times (52.3%) and the patients' median age was 3 years (interquartile range, 1-6). Most visits occurred on Mondays, and 5643 (15.2%) and 4790 (12.9%) patients visited the clinic when consultations began at 10 AM and 3 PM, respectively. Approximately 20% of weekday visits occurred after 6 PM, when other pediatricians' offices were typically closed. Children older than 7 years of age visited the clinic more frequently after 6 PM. The overall median waiting time was 650 seconds (interquartile range, 429-1020). The 3 most common diagnoses were upper respiratory tract infection (27,173), asthmatic bronchitis (23,744), and allergic rhinitis (10,556). The number of individuals who were referred to other medical institutions was 284 (0.6%).The majority of patients were children aged 1 to 4 years living near the clinic and 80% of visits were during the daytime. However, children older than 7 years of age visited the clinic more frequently after 6 PM. The convenience of the clinic contributed to the fulfillment of the medical needs of children with mild illnesses whose mothers were in full-time employment.

Bibliometric Study of Obstetrics Articles Published in the Journal of the American Medical Association, 1997-2016.

Introduction A recent increase in cases of advanced maternal age in the US has been partly associated with a higher incidence of pregnancy-related complications and infertility. However, little is known on how such social changes may have influenced obstetrics articles published in high-impact medical journals subscribed by diverse physicians. The objective of this study is to elucidate the presence and trend of obstetrics investigations in high-profile medical journals. Material and methods This bibliometric study retrospectively analyzed original articles published in the Journal of the American Medical Association (JAMA) from 1997 to 2016. Two reviewers extracted obstetrics articles from PubMed, assessed whether to include specific articles, and categorized them by subtopic. Main outcomes measure was the annual number of original investigations in obstetrics divided by that of original investigations from all fields during the study period, expressed as a trend. Results A total of 3486 original investigations were published during the study period. Regarding obstetrics, 1989 articles were originally extracted from PubMed; after a two-step review process, 199 (10.0%) obstetrics-related original investigations remained. Among them, 134 (67.4%) were classified as pregnancy-related abnormalities or complications (non-infection). The proportion of obstetrics articles decreased during the first 10 years but increased in the last 10 years. The highest figures in the first 10 and last 10 years were 8.5% in 1999 and 9.4% in 2014, respectively, whereas the lowest was 1.4% in 2008. The proportion articles on pregnancy-associated complications or abnormalities (non-infection) steadily increased during the study period, that of articles on infertility increased, and that of articles on human immunodeficiency virus (HIV) infection steadily decreased. Conclusions The observed trend may suggest a changing interest in obstetrics investigations among general physicians in the last 20 years. What is particularly notable is a heightened presence of research on pregnancy-related complications and infertility, which may reflect an increasing frequency in advanced maternal age in the US.

A model-based estimation of inter-prefectural migration of physicians within Japan and associated factors: A 20-year retrospective study.

Despite an increase in the number of physicians in Japan, misdistribution of physicians within the 47 prefectures remains a major issue. Migration of physicians among prefectures might partly explain the misdistribution. However, geographical differences and the magnitude of physicians' migration are unclear. The aim of this study was to estimate the extent of migration of physicians among prefectures and explore possible factors associated with physicians' migration patterns.Using a publicly available government database from 1995 to 2014, a quantitative estimation of physicians' migration after graduation from a medical school was performed. The inflow and outflow of physicians were ostensibly calculated in each prefecture based on the differences between the number of newly licensed physicians and the actual number of practicing physicians after an adjustment for the number of deceased or retired physicians. Simple and multiple linear regression analyses were conducted to examine socio-demographic background factors.During the 20-year study period, the mean annual numbers of newly licensed physicians, deceased or retired physicians, and increase in practicing physicians in the whole country were 7416, 3382, and 4034, respectively. Among the 47 prefectures, the median annual number of newly licensed physicians to 100,000 population ratio (PPR) was 6.4 (range 1.5-16.5), the median annual adjusted number of newly licensed physicians was 61 (range, -18 to 845; the negative and positive values denote outflow and inflow, respectively), whereas the median annual number of migrating physicians was 13 (range, -171 to 241). The minimum and maximum migration ratios observed were -68% and 245%, respectively. In the final regression model of the 8 variables examined, only "newly licensed PPR" remained significantly associated with physician's migration ratios.A significant inequality in the proportion of the migration of physicians among prefectures in Japan was observed. The multivariate analyses suggest that the newly licensed PPRs, and not from-rural-to-urban migration, might be one of the keys to explaining the migration ratios of physicians. The differences and magnitude of physicians' migration should be factored into mitigate misdistribution of physicians.

Patients' demographics of a convenient clinic located in a large railway station in metropolitan Tokyo area.

Hidden barriers to visit a medical facility especially for young busy workers have been neglected in the aging society. The aim of this cross-sectional study is to analyze demographics of patients who had visited the first known convenient clinic located inside a railway station, which is adjusted to the lifestyle of working generations.We analyzed de-identified data of patients who had visited the department of internal medicine of a clinic, which is located inside a railway station building and offers primary care with after-hours accessibility in Tokyo, between August 2013 and June 2016. Data were collected on patients' sex, age, time of visit, waiting time, presence or absence of an appointment, diagnosis, and patients' addresses using the electronic health and billing records.Overall, 28,001 patients visited 87,126 times. Number of visits increased in winter season compared with the other seasons. Sixty-one percent were women and the median age of all patients was 38 years (range, 0-102). The number of visits on Mondays was the highest in a week and the most frequent visiting time was between 6 and 7 p.m. The number of visits of working generations (from 15 to 65 years old) and men increased after 6 p.m. and on weekends. The 3 most common diagnoses were upper respiratory tract infection (22,457), allergic rhinitis (20,916), and hypertension (4869). The number of individuals who were referred to other medical institutions was 1022 (1.2%). The median waiting time was 748 seconds (range, 2-5344). The number of visits from within 2-, 5-, and 10-mile radius from our clinic was 41,696 (50.6%), 63,190 (76.7%), and 75,015 (91.1%), respectively, and patients' addresses were mainly located along the railway network.The locational and temporal convenience of our clinic has attracted the unmet medical demands especially for young workers who have difficulty in visiting conventional medical institutions.

TGIF governs a feed-forward network that empowers Wnt signaling to drive mammary tumorigenesis.

Many types of human cancers having hyperactivated Wnt signaling display no causative alterations in known effectors of this pathway. Here, we report a function of TGIF in Wnt signaling. TGIF associates with and diverts Axin1 and Axin2 from the ß-catenin destruction complex, therefore allowing ß-catenin accrual. Intriguingly, activation of Wnt signaling induces the expression of TGIF, which unveils a feed-forward loop that ensures effective integration of Wnt signaling. In triple-negative breast cancers (TNBC), elevated levels of TGIF correlate with high Wnt signaling and poor survival of patients. Moreover, genetic experiments revealed that Tgif1 ablation impeded mammary tumor development in MMTV-Wnt1 mice, further underscoring a requirement of TGIF for oncogenic Wnt signaling.

Calpain 1 inhibitor BDA-410 ameliorates α-klotho-deficiency phenotypes resembling human aging-related syndromes.

Taking good care of elderly is a major challenge of our society, and thus identification of potential drug targets to reduce age-associated disease burden is desirable. α-klotho(-/-) (α-kl) is a short-lived mouse model that displays multiple phenotypes resembling human aging-related syndromes. Such ageing phenotype of α-kl(-/-) mice is associated with activation of a proteolytic enzyme, Calpain-1. We hypothesized that uncontrolled activation of calpain-1 might be causing age-related phenotypes in α-kl-deficient mice. We found that daily administration of BDA-410, a calpain-1 inhibitor, strikingly ameliorated multiple aging-related phenotypes. Treated mice showed recovery of reproductive ability, increased body weight, reduced organ atrophy, and suppression of ectopic calcifications, bone mineral density reduction, pulmonary emphysema and senile atrophy of skin. We also observed ectopic expression of FGF23 in calcified arteries of α-kl(-/-) mice, which might account for the clinically observed association of increased FGF23 level with increased risk of cardiovascular mortality. These findings allow us to propose that modulation of calpain-1 activity is a potential therapeutic option for delaying age-associated organ pathology, particularly caused by the dysregulation of mineral ion homeostasis.

Identification of PHRF1 as a tumor suppressor that promotes the TGF-ß cytostatic program through selective release of TGIF-driven PML inactivation.

The homeodomain protein TGIF (TG-interacting factor) restricts TGF-ß/Smad cytostatic signaling by interfering with the nucleocytoplasmic transit of the tumor suppressor cPML. Here, we identify PHRF1 as a ubiquitin ligase that enforces TGIF decay by driving its ubiquitination at lysine 130. In so doing, PHRF1 ensures redistribution of cPML into the cytoplasm, where it associates with SARA and coordinates activation of Smad2 by the TGF-ß receptor. The PHRF1 gene resides within the tumor suppressor locus 11p15.5, which displays frequent loss in a wide variety of malignancies, including breast cancer. Remarkably, we found that the PHRF1 gene is deleted or silenced in a high proportion of human breast cancer samples and cancer cell lines. Reconstitution of PHRF1 into deficient cells impeded their propensity to form tumors in vivo, most likely because of the reemergence of TGF-ß responsiveness. These findings unveil a paradigm behind inactivation of the cPML tumor suppressor network in human malignancies.

Osteo-renal cross-talk and phosphate metabolism by the FGF23-Klotho system.

Phosphate is widely distributed in the body and an adequate balance is required for maintaining essential cellular and organ functions. Dysregulation of phosphate balance, either in the form of hypophosphatemia or hyperphosphatemia can induce disorders ranging from rickets/osteomalacia to cardiovascular calcification. A physiologic phosphate balance is delicately maintained by multiorgan cross-talks among the intestine, kidney, and bone. Sodium-dependent phosphate (Na/Pi) cotransporters present in the intestine and kidney play a major role in phosphate absorption and reabsorption, according to the body's demand. Some of the calcium regulating factors, including parathyroid hormone and vitamin D can influence the activities of Na/Pi cotransporters, and thereby can affect phosphate balance. In addition, molecular analysis of the unexplained hypophosphatemic diseases, including autosomal-dominant hypophosphatemic rickets and tumor-induced osteomalacia has led to the identification of fibroblast growth factor 23 (FGF23). Subsequent studies have documented that bone-derived FGF23 and kidney-derived klotho can form an endocrine network to control urinary phosphate excretion. Studies have also documented negative effect of FGF23/klotho system on vitamin D metabolism and Na/Pi cotransporter activities. This article will summarize how the FGF23/klotho system might influence systemic phosphate metabolism, and consequences of its abnormal regulation will be briefly described.

Can salivary phosphate levels be an early biomarker to monitor the evolvement of obesity?

Phosphate is an essential nutrient required for important biological reactions that maintain the normal homoeostatic control of the cell. The adverse effects of phosphate metabolism in obesity have not been studied in detail, chiefly because such an association is thought to be uncommon. However, in some animal models of obesity, serum phosphate levels were noted to be higher than the nonobese controls. For example, leptin-deficient (ob/ob) mice become severely obese and have high serum phosphate levels. In this study, we analyzed the phosphate content in saliva collected from children (n = 77; 10.5 ± 1.8) to evaluate association with body mass index; there is a significant increase of salivary phosphate content in obese compared to normal-weight children (ANOVA p < 0.001). The correlation coefficient (r) between BMI and phosphate was 0.33 (p = 0.0032). Our results suggest that the human salivary phosphate level may be an early biomarker of the genesis of obesity in children. The diagnostic importance lies in the fact that the salivary phosphate level could provide a noninvasive predictive marker in the development of obesity. Further studies will be required to understand the underlying mechanism of increased salivary phosphate accumulation in obese and overweight children. Nevertheless, its occurrence without systemic changes could be of diagnostic value, particularly in monitoring evolvement of obesity.

Conversion of a paracrine fibroblast growth factor into an endocrine fibroblast growth factor.

FGFs 19, 21, and 23 are hormones that regulate in a Klotho co-receptor-dependent fashion major metabolic processes such as glucose and lipid metabolism (FGF21) and phosphate and vitamin D homeostasis (FGF23). The role of heparan sulfate glycosaminoglycan in the formation of the cell surface signaling complex of endocrine FGFs has remained unclear. Here we show that heparan sulfate is not a component of the signal transduction unit of FGF19 and FGF23. In support of our model, we convert a paracrine FGF into an endocrine ligand by diminishing heparan sulfate-binding affinity of the paracrine FGF and substituting its C-terminal tail for that of an endocrine FGF containing the Klotho co-receptor-binding site to home the ligand into the target tissue. In addition to serving as a proof of concept, the ligand conversion provides a novel strategy for engineering endocrine FGF-like molecules for the treatment of metabolic disorders, including global epidemics such as type 2 diabetes and obesity.

Klotho coreceptors inhibit signaling by paracrine fibroblast growth factor 8 subfamily ligands.

It has been recently established that Klotho coreceptors associate with fibroblast growth factor (FGF) receptor tyrosine kinases (FGFRs) to enable signaling by endocrine-acting FGFs. However, the molecular interactions leading to FGF-FGFR-Klotho ternary complex formation remain incompletely understood. Here, we show that in contrast to αKlotho, ßKlotho binds its cognate endocrine FGF ligand (FGF19 or FGF21) and FGFR independently through two distinct binding sites. FGF19 and FGF21 use their respective C-terminal tails to bind to a common binding site on ßKlotho. Importantly, we also show that Klotho coreceptors engage a conserved hydrophobic groove in the immunoglobulin-like domain III (D3) of the "c" splice isoform of FGFR. Intriguingly, this hydrophobic groove is also used by ligands of the paracrine-acting FGF8 subfamily for receptor binding. Based on this binding site overlap, we conclude that while Klotho coreceptors enhance binding affinity of FGFR for endocrine FGFs, they actively suppress binding of FGF8 subfamily ligands to FGFR.

Genetic induction of phosphate toxicity significantly reduces the survival of hypercholesterolemic obese mice.

OBJECTIVE: The adverse effects of metabolic disorders in obesity have been extensively studied; however, the pathologic effects of hyperphosphatemia or phosphate toxicity in obesity have not been studied in similar depth and detail, chiefly because such an association is thought to be uncommon. Studies have established that the incidence of obesity-associated nephropathy is increasing. Because hyperphosphatemia is a major consequence of renal impairment, this study determines the in vivo effects of hyperphosphatemia in obesity. METHODS AND RESULTS: We genetically induced hyperphosphatemia in leptin-deficient obese (ob/ob) mice by generating ob/ob and klotho double knockout [ob/ob-klotho(-/-)] mice. As a control, we made ob/ob mice with hypophosphatemia by generating ob/ob and 1-alpha hydroxylase double knockout [ob/ob-1α(OH)ase(-/-)] mice. Compared to the wild-type mice, all three obese background mice, namely ob/ob, ob/ob-klotho(-/-), and ob/ob-1α(OH)ase(-/-) mice developed hypercholesterolemia. In addition, the hyperphosphatemic, ob/ob-klotho(-/-) genetic background induced generalized tissue atrophy and widespread soft-tissue and vascular calcifications, which led to a shorter lifespan; no such changes were observed in the hypophosphatemic, ob/ob-1α(OH)ase(-/-) mice. Significantly, in contrast to the reduced survival of the ob/ob-klotho(-/-) mice, lowering serum phosphate levels in ob/ob-1α(OH)ase(-/-) mice showed no such compromised survival, despite both mice being hypercholesterolemic. CONCLUSION: These genetic manipulation studies suggest phosphate toxicity is an important risk factor in obesity that can adversely affect survival.

Dietary and genetic evidence for enhancing glucose metabolism and reducing obesity by inhibiting klotho functions.

Klotho is a multifunctional protein involved in numerous biological functions, ranging from mineral ion metabolism to signaling activities. Recent studies have identified klotho as a target gene for peroxisome proliferator-activated receptor-γ (PPAR-γ), a master regulator of adipocyte differentiation, and an adipogenesis-promoting factor. In a similar line of observation, eliminating klotho function from mice resulted in the generation of lean mice with almost no detectable fat tissue. In contrast to the klotho-knockout mice (11.7±0.3 g at 9 wk), leptin-deficient (ob/ob) mice are severely obese (49.3±0.6 g at 9 wk), due to excessive fat accumulation. To study the in vivo role of klotho in obesity, we have generated and characterized ob/ob mice lacking klotho activity [ob/ob-klotho double-knockout (DKO) mice]. The ob/ob mice started to get bigger from 3 wk onward and gained almost 2 times more weight than their wild-type (WT) counterparts (WT vs. ob/ob: 34.8±1.3 vs. 65.5±1.2 g at 21 wk). The generated ob/ob-klotho DKO mice were not only viable throughout their adulthood but also showed markedly reduced fat tissue accumulation compared to their ob/ob littermates. The ob/ob-klotho DKO mice had significantly (P<0.01) less retroperitoneal, mesenteric, and epididymal fat accumulation, compared to their ob/ob counterparts. Similarly, the fatty liver that was consistently observed in the ob/ob mice was eliminated in the ob/ob-klotho DKO mice. Such structural improvement in the liver was also evident from markedly reduced fasting blood glucose levels in ob/ob-klotho DKO mice, compared to their ob/ob counterparts (ob/ob vs. ob/ob-klotho DKO: 266 ± 36 vs. 65±2 mg/dl). Finally, to study whether the absence of klotho can induce resistance to high-fat-diet-induced obesity, we provided a high-fat (60%) diet to klotho-knockout mice and compared them with normal-fat (20%) diet-fed klotho-knockout mice. No significant difference in body weight was detected in klotho-knockout mice fed either the normal-fat diet or high-fat diet, while WT mice fed the high-fat diet gradually gained body weight, compared to the normal-fat-diet-fed counterparts. The results of our dietary and genetic manipulation studies provide in vivo evidence for a role of klotho in obesity and offer a novel target to manipulate obesity and associated complications.

Dietary and genetic evidence for phosphate toxicity accelerating mammalian aging.

Identifying factors that accelerate the aging process can provide important therapeutic targets for slowing down this process. Misregulation of phosphate homeostasis has been noted in various skeletal, cardiac, and renal diseases, but the exact role of phosphate toxicity in mammalian aging is not clearly defined. Phosphate is widely distributed in the body and is involved in cell signaling, energy metabolism, nucleic acid synthesis, and the maintenance of acid-base balance by urinary buffering. In this study, we used an in vivo genetic approach to determine the role of phosphate toxicity in mammalian aging. Klotho-knockout mice (klotho(-/-)) have a short life span and show numerous physical, biochemical, and morphological features consistent with premature aging, including kyphosis, uncoordinated movement, hypogonadism, infertility, severe skeletal muscle wasting, emphysema, and osteopenia, as well as generalized atrophy of the skin, intestine, thymus, and spleen. Molecular and biochemical analyses suggest that increased renal activity of sodium-phosphate cotransporters (NaPi2a) leads to severe hyperphosphatemia in klotho(-/-) mice. Genetically reducing serum phosphate levels in klotho(-/-) mice by generating a NaPi2a and klotho double-knockout (NaPi2a(-/-)/klotho(-/-)) strain resulted in amelioration of premature aging-like features. The NaPi2a(-/-)/klotho(-/-) double-knockout mice regained reproductive ability, recovered their body weight, reduced their organ atrophy, and suppressed ectopic calcifications, with the resulting effect being prolonged survival. More important, when hyperphosphatemia was induced in NaPi2a(-/-)/klotho(-/-) mice by feeding with a high-phosphate diet, premature aging-like features reappeared, clearly suggesting that phosphate toxicity is the main cause of premature aging in klotho(-/-) mice. The results of our dietary and genetic manipulation studies provide in vivo evidence for phosphate toxicity accelerating the aging process and suggest a novel role for phosphate in mammalian aging.

In vivo genetic evidence for suppressing vascular and soft-tissue calcification through the reduction of serum phosphate levels, even in the presence of high serum calcium and 1,25-dihydroxyvitamin d levels.

BACKGROUND: Klotho-knockout mice (klotho(-/-)) have increased renal expression of sodium/phosphate cotransporters (NaPi2a), associated with severe hyperphosphatemia. Such serum biochemical changes in klotho(-/-) mice lead to extensive soft-tissue anomalies and vascular calcification. To determine the significance of increased renal expression of the NaPi2a protein and concomitant hyperphosphatemia and vascular calcification in klotho(-/-) mice, we generated klotho and NaPi2a double-knockout (klotho(-/-)/NaPi2a(-/-)) mice. METHODS AND RESULTS: Genetic inactivation of NaPi2a activity from klotho(-/-) mice reversed the severe hyperphosphatemia to mild hypophosphatemia or normophosphatemia. Importantly, despite significantly higher serum calcium and 1,25-dihydroxyvitamin D levels in klotho(-/-)/NaPi2a(-/-) mice, the vascular and soft-tissue calcifications were reduced. Extensive soft-tissue anomalies and cardiovascular calcification were consistently noted in klotho(-/-) mice by 6 weeks of age; however, these vascular and soft-tissue abnormalities were absent even in 12-week-old double-knockout mice. Klotho(-/-)/NaPi2a(-/-) mice also regained body weight and did not develop the generalized tissue atrophy often noted in klotho(-/-) single-knockout mice. CONCLUSIONS: Our in vivo genetic manipulation studies have provided compelling evidence for a pathological role of increased NaPi2a activities in regulating abnormal mineral ion metabolism and soft-tissue anomalies in klotho(-/-) mice. Notably, our results suggest that serum phosphate levels are the important in vivo determinant of calcification and that lowering serum phosphate levels can reduce or eliminate soft-tissue and vascular calcification, even in presence of extremely high serum calcium and 1,25-dihydroxyvitamin D levels. These in vivo observations have significant clinical importance and therapeutic implications for patients with chronic kidney disease with cardiovascular calcification.

Inactivation of klotho function induces hyperphosphatemia even in presence of high serum fibroblast growth factor 23 levels in a genetically engineered hypophosphatemic (Hyp) mouse model.

Hyp mice possess a mutation that inactivates the phosphate-regulating gene, which is homologous to the endopeptidases of the X-chromosome (PHEX). The mutation is associated with severe hypophosphatemia due to excessive urinary phosphate wasting. Such urinary phosphate wasting in Hyp mice is associated with an increased serum accumulation of fibroblast growth factor (FGF) 23. We wanted to determine the biological significance of increased serum FGF23 levels and concomitant hypophosphatemia in Hyp mice and to evaluate whether FGF23 activity could be modified by manipulating klotho (a cofactor of FGF23 signaling). We generated Hyp and klotho double-mutant mice (Hyp/klotho(-/-)). Severe hypophosphatemia of Hyp mice was reversed to hyperphosphatemia in Hyp/klotho(-/-) double mutants, despite the fact that the double mutants showed significantly increased serum levels of FGF23. Hyperphosphatemia in Hyp/klotho(-/-) mice was associated with increased renal expression of sodium/phosphate cotransporter 2a (NaPi2a) protein. Exogenous injection of bioactive parathyroid hormone 1-34 down-regulated renal expression of NaPi2a and consequently reduced serum levels of phosphate in Hyp/klotho(-/-) mice. Moreover, in contrast to the Hyp mice, the Hyp/klotho(-/-) mice showed significantly higher serum levels of 1,25-dihydroxyvitamin D and developed extensive calcification in soft tissues and vascular walls. Furthermore, compared with the Hyp mice, Hyp/klotho(-/-) mice were smaller in size, showed features of generalized tissue atrophy, and generally died by 15-20 wk of age. Our in vivo studies provide genetic evidence for a pathological role of increased FGF23 activities in regulating abnormal phosphate homeostasis in Hyp mice. Moreover, these results suggest that even when serum levels of FGF23 are significantly high, in the absence of klotho, FGF23 is unable to regulate systemic phosphate homeostasis. Our in vivo observations have significant clinical implications in diseases associated with increased FGF23 activity and suggest that the functions of FGF23 can be therapeutically modulated by manipulating the effects of klotho.

Reversal of mineral ion homeostasis and soft-tissue calcification of klotho knockout mice by deletion of vitamin D 1alpha-hydroxylase.

Changes in the expression of klotho, a beta-glucuronidase, contribute to the development of features that resemble those of premature aging, as well as chronic renal failure. Klotho knockout mice have increased expression of the sodium/phosphate cotransporter (NaPi2a) and 1alpha-hydroxylase in their kidneys, along with increased serum levels of phosphate and 1,25-dihydroxyvitamin D. These changes are associated with widespread soft-tissue calcifications, generalized tissue atrophy, and a shorter lifespan in the knockout mice. To determine the role of the increased vitamin D activities in klotho knockout animals, we generated klotho and 1alpha-hydroxylase double-knockout mice. These double mutants regained body weight and developed hypophosphatemia with a complete elimination of the soft-tissue and vascular calcifications that were routinely found in klotho knockout mice. The markedly increased serum fibroblast growth factor 23 and the abnormally low serum parathyroid hormone levels, typical of klotho knockout mice, were significantly reversed in the double-knockout animals. These in vivo studies suggest that vitamin D has a pathologic role in regulating abnormal mineral ion metabolism and soft-tissue anomalies of klotho-deficient mice.