A Case of Hypophosphatasia With Normal Alkaline Phosphatase Levels.

Background/Objective: Hypophosphatasia (HPP) is a rare disease associated with low serum alkaline phosphatase (ALP) activity. Here, we present a case of a patient with normal serum ALP levels diagnosed with HPP. Case Report: A 36-year-old woman presented with progressive fatigue, weakness, and joint pain. She had been evaluated in the past for genetic disorders due to these symptoms and was found to have a history of several total ALP levels within normal limits but elevated vitamin B6 levels. She also reported having loose teeth and "gray gums" during her childhood. Bone-specific ALP was tested for suspicion of HPP and returned at 4.4 µ/L (reference range, 5.3-19.5 µg/L), which prompted genetic testing. Genetic testing confirmed a positive pathogenetic variant of the ALPL gene, the c.542C>T (p.Ser181Leu) variant. She started asfotase alfa treatment to improve her symptoms. Discussion: HPP was diagnosed based on clinical suspicion supported by laboratory findings, which can cause it to be underdiagnosed or misdiagnosed. Current literature reports that a low total ALP level is the main biochemical marker of HPP and the only level needed to diagnose the disease. However, bone-specific ALP, a common marker used for bone turnover, has not been required to be tested. Conclusion: This case highlights a patient with normal total ALP, but low bone-specific ALP diagnosed with HPP confirmed by genetic testing. This case warrants future investigation into the diagnostic approach to HPP and the diagnostic utility between ALP and bone-specific ALP.

Serum alkaline phosphatase can be elevated in patients with hypophosphatasia due to liver disease.

BACKGROUND: Hypophosphatasia (HPP) is a rare inherited disorder caused by pathogenic loss-of-function variants in the ALPL gene, encoding the tissue-nonspecific isoenzym of alkaline phosphatase (ALP; TNSALP). Low serum ALP is the biochemical hallmark of HPP, but it is unknown whether ALP levels can increase due to concurring liver disease, which may lead to a missed diagnose of HPP. We present a patient with genetically confirmed HPP, who showed a transient increase of serum ALP levels due to alcohol-induced hepatitis. CLINICAL REPORT: A 71-year old man was seen at our Bone Center for surveillance of HPP. Serum ALP was always low (23 U/L; reference value: <115 U/L). During follow-up, his serum ALP increased (156 U/L, further rising to 204 U/L), with concomitantly elevated serum gamma-glutamyl transferase and transaminases, and a rise in bone specific ALP (18.7 µg/L; reference value: 5.7-32.9 µg/L). This was attributed to alcohol-induced hepatitis. After refraining from alcohol intake, both serum ALP and bone specific ALP levels returned to initial low levels (30 U/L and 4.3 µg/L respectively). CONCLUSIONS: We demonstrated the history of a 71-year old patient with HPP, presenting during routine follow-up with an elevated serum ALP level up to 204 U/L due to alcohol-induced hepatitis. This case illustrates that the diagnosis of HPP can potentially be missed when ALP levels are normal or elevated due to a concomitant liver disease.

Hypophosphatasia: from birth to adulthood.

Hypophosphatasia (HPP) is an inherited disease caused by a low activity of tissue-nonspecific alkaline phosphatase, a hydrolase that removes phosphate groups from many molecules. Decreased alkaline phosphatase activity leads to the accumulation of three main metabolites, i.e., pyridoxal 5´-phosphate (PLP), inorganic pyrophosphate (PPi), and phosphoethanolamine. Impairment in PLP dephosphorylation induces seizures, while PPi accumulation inhibits bone mineralization. Clinically, HPP has a wide spectrum of presentations, ranging from neonatal death to an apparent lack of symptoms. This disease is classified into six subtypes according to the age at onset of first signs or symptoms. The clinical manifestations of the disease include rickets-like bone changes, bone demineralization, fragility fractures, reduced muscular strength, chest deformity, pulmonary hypoplasia, nephrolithiasis, nephrocalcinosis, and chondrocalcinosis. Treatment of HPP consists of enzyme replacement therapy. Before this therapy was approved, treatment was palliative and associated with high morbidity and mortality. Asfotase alfa has changed the prognosis of the disease by reducing bone deformity and improving bone mineralization, lung function, and muscle weakness, among other benefits. In adults, teriparatide and anti-sclerostin antibody have been used off-label in selected cases, demonstrating benefit in accelerating fracture healing and in concomitant treatment of osteoporosis. This review summarizes the main aspects of HPP and identifies the particularities of the disease in adult patients.

Effects of Infantile Hypophosphatasia on Human Dental Tissue.

Hypophosphatasia (HPP) is an inherited, systemic disorder, caused by loss-of-function variants of the ALPL gene encoding the enzyme tissue non-specific alkaline phosphatase (TNSALP). HPP is characterized by low serum TNSALP concentrations associated with defective bone mineralization and increased fracture risk. Dental manifestations have been reported as the exclusive feature (odontohypophosphatasia) and in combination with skeletal complications. Enzyme replacement therapy (asfotase alfa) has been shown to improve respiratory insufficiency and skeletal complications in HPP patients, while its effects on dental status have been understudied to date. In this study, quantitative backscattered electron imaging (qBEI) and histological analysis were performed on teeth from two patients with infantile HPP before and during asfotase alfa treatment and compared to matched healthy control teeth. qBEI and histological methods revealed varying mineralization patterns in cementum and dentin with lower mineralization in HPP. Furthermore, a significantly higher repair cementum thickness was observed in HPP compared to control teeth. Comparison before and during treatment showed minor improvements in mineralization and histological parameters in the patient when normalized to matched control teeth. HPP induces heterogeneous effects on mineralization and morphology of the dental status. Short treatment with asfotase alfa slightly affects mineralization in cementum and dentin. Despite HPP being a rare disease, its mild form occurs at higher prevalence. This study is of high clinical relevance as it expands our knowledge of HPP and dental involvement. Furthermore, it contributes to the understanding of dental tissue treatment, which has hardly been studied so far.

Hypophosphatasia: from birth to adulthood

ABSTRACT Hypophosphatasia (HPP) is an inherited disease caused by a low activity of tissue-nonspecific alkaline phosphatase, a hydrolase that removes phosphate groups from many molecules. Decreased alkaline phosphatase activity leads to the accumulation of three main metabolites, i.e., pyridoxal 5'-phosphate (PLP), inorganic pyrophosphate (PPi), and phosphoethanolamine. Impairment in PLP dephosphorylation induces seizures, while PPi accumulation inhibits bone mineralization. Clinically, HPP has a wide spectrum of presentations, ranging from neonatal death to an apparent lack of symptoms. This disease is classified into six subtypes according to the age at onset of first signs or symptoms. The clinical manifestations of the disease include rickets-like bone changes, bone demineralization, fragility fractures, reduced muscular strength, chest deformity, pulmonary hypoplasia, nephrolithiasis, nephrocalcinosis, and chondrocalcinosis. Treatment of HPP consists of enzyme replacement therapy. Before this therapy was approved, treatment was palliative and associated with high morbidity and mortality. Asfotase alfa has changed the prognosis of the disease by reducing bone deformity and improving bone mineralization, lung function, and muscle weakness, among other benefits. In adults, teriparatide and anti-sclerostin antibody have been used off-label in selected cases, demonstrating benefit in accelerating fracture healing and in concomitant treatment of osteoporosis. This review summarizes the main aspects of HPP and identifies the particularities of the disease in adult patients.

Dental manifestation and management of hypophosphatasia.

Hypophosphatasia is an inherited metabolic disorder characterized by defective mineralization of bones and teeth with a wide variety of manifestations, ranging from stillbirth to dental symptoms alone. Recently, the prognosis of severe hypophosphatasia patients has been greatly improved by the introduction of enzyme replacement therapy. The typical dental manifestation is early exfoliation of primary teeth due to disturbed cementum formation, so dentures are recommended to ensure that important oral functions are acquired. Some studies have shown that enzyme replacement therapy improves dental mineralization, resulting in the stabilization of periodontal tissues and better growth of tooth roots. A nationwide Japanese survey revealed the common genetic and dental manifestations of patients with mild hypophosphatasia, which markedly differ from those of the severe forms. There may be many undiagnosed mild patients, so dentists should contribute to the early diagnosis by screening possible cases based on the typical finding of early exfoliation of primary teeth. Early diagnosis is important for patients to receive early intervention in both medical and dental fields. The establishment of fundamental dental therapy to solve the dental problems is still underway and is eagerly anticipated.

ALPL Genotypes in Patients With Atypical Femur Fractures or Other Biochemical and Clinical Signs of Hypophosphatasia.

CONTEXT: Hypophosphatasia (HPP) is a rare metabolic disorder caused by deficiency of alkaline phosphatase (ALP) enzyme activity, leading to defective mineralization, due to pathogenic variants of the ALPL gene, encoding the tissue nonspecific alkaline phosphatase (TNSALP) enzyme. Inheritance can be autosomal recessive or autosomal dominant. An abnormal ALPL genetic test enables accurate diagnosis, avoiding the administration of contraindicated antiresorptive drugs that, in patients with HPP, substantially increase the risk of atypical femur fractures (AFFs) and worsen the fracture healing process that is usually already compromised in these patients. OBJECTIVE: Performing ALPL genetic testing to identify rare variants in suspected adult patients with HPP. Comparing frequencies of ALPL common variants in individuals with biochemical and/or clinical signs suggestive of adult HPP and non-HPP controls, and among different clinical subgroups of patients with a clinical suspicion of adult HPP. METHODS: Patients with suspected adult HPP were retrospectively selected for the genetic testing of the ALPL gene. Patients included were from 3 main European Bone Units (Florence, Naples, and Geneva); 106 patients with biochemical and/or clinical signs suggestive of a mild form of HPP were included. RESULTS: Genetic testing led to the identification of a heterozygote rare variant in 2.8% of cases who were initially referred as suspected osteoporosis. The analysis of frequencies of ALPL common variants showed a high prevalence (30.8%) of homozygosity in subjects who developed an AFF, in association with normal serum total ALP activity. CONCLUSION: The results suggest homozygosity of common ALPL variants as a possible genetic mark of risk for these fractures.

Case Report: Variations in the ALPL Gene in Chinese Patients With Hypophosphatasia.

Background: Hypophosphatasia (HPP) is an autosomal genetic disorder characterized biochemically by abnormal of bone parameters and serum alkaline phosphatase (ALP) activity as well as clinically by deficiency of teeth and bone mineralization. The clinical presentation is a continuum ranging from a prenatal lethal form with no skeletal mineralization to a mild form with late adult onset presenting with non-pathognomonic symptoms. ALP deficiency is the key to the pathogenesis of abnormal metabolism and skeletal system damage in HPP patients. Methods: We investigated five patients with skeletal dysplasia in the clinic. Whole-exome sequencing was performed in order to aid diagnosis of the patients. Results: Eight variants in the ALPL gene in the five unrelated Chinese patients (PA-1: c.649_650insC and c.707A > G; PA2: c.98C > T and c.707A > G; PA3: c.407G > A and c.650delTinsCTAA; PA4: c.1247G > T (homozygous); PA5: c.406C > T and c.1178A > G; NM_000478.5) were found. These variations caused two types of HPP: perinatal HPP and Odonto HPP. All cases reported in this study were autosomal recessive. Among the variants, c.1247G > T/p.Gly416Val (PA-4); c.1178A > G/p.Asn393Ser (PA-5) and c.707A > G/p.Tyr236Cys (PA-1, PA-2) have never been reported before. Conclusion: Clinical phenotypes of perinatal HPP (PA-1,PA-2,PA-3 and PA-4) include skeletal dysplasia, shorter long bones, bowing of long bones, tetraphocomelia, abnormal posturing and abnormal bone ossification. Odonto HPP (PA-5) only presents as dental abnormality with severe dental caries and decreased ALP activity. Our study extends the pool of ALPL variants in different populations.

Hypophosphatasia: A Unique Disorder of Bone Mineralization.

Hypophosphatasia (HPP) is a rare genetic disease characterized by a decrease in the activity of tissue non-specific alkaline phosphatase (TNSALP). TNSALP is encoded by the ALPL gene, which is abundantly expressed in the skeleton, liver, kidney, and developing teeth. HPP exhibits high clinical variability largely due to the high allelic heterogeneity of the ALPL gene. HPP is characterized by multisystemic complications, although the most common clinical manifestations are those that occur in the skeleton, muscles, and teeth. These complications are mainly due to the accumulation of inorganic pyrophosphate (PPi) and pyridoxal-5'-phosphate (PLP). It has been observed that the prevalence of mild forms of the disease is more than 40 times the prevalence of severe forms. Patients with HPP present at least one mutation in the ALPL gene. However, it is known that there are other causes that lead to decreased alkaline phosphatase (ALP) levels without mutations in the ALPL gene. Although the phenotype can be correlated with the genotype in HPP, the prediction of the phenotype from the genotype cannot be made with complete certainty. The availability of a specific enzyme replacement therapy for HPP undoubtedly represents an advance in therapeutic strategy, especially in severe forms of the disease in pediatric patients.

Genotype-Phenotype Associations in 72 Adults with Suspected ALPL-Associated Hypophosphatasia.

Hypophosphatasia (HPP) is a rare inborn error of metabolism due to a decreased activity of tissue nonspecific alkaline phosphatase (TNSALP). As the onset and severity of HPP are heterogenous, it can be challenging to determine the pathogenicity of detected rare ALPL variants in symptomatic patients. We aimed to characterize patients with rare ALPL variants to propose which patients can be diagnosed with adult HPP. We included 72 patients with (1) clinical symptoms of adult HPP or positive family history and (2) low TNSALP activity and/or high pyridoxal 5'-phosphate (PLP) levels, who underwent ALPL gene sequencing. The patients were analyzed and divided into three groups depending on ALPL variant pathogenicity according to the classification of the American College of Medical Genetics and Genomics (ACMG). Reported pathogenic (n = 34 patients), rare (n = 17) and common (n = 21) ALPL variants only were found. Muscular complaints were the most frequent symptoms (> 80%), followed by bone affection (> 50%). Tooth involvement was significantly more common in patients with pathogenic or rare ALPL variants. Seven rare variants could be classified as likely pathogenic (ACMG class 4) of which five have not yet been described. Inconclusive genetic findings and less specific symptoms make diagnosis difficult in cases where adult HPP is not obvious. As not every pathogenic or rare ALPL variant leads to a manifestation of HPP, only patients with bone complications and at least one additional complication concerning teeth, muscle, central nervous and mental system, repeated low TNSALP activity and high PLP levels should be diagnosed as adult HPP if rare ALPL gene variants of ACMG class 4 or higher support the diagnosis.

Intrafamilial phenotypic distinction of hypophosphatasia with identical tissue nonspecific alkaline phosphatase gene mutation: a family report.

Hypophosphatasia (HPP) is caused by mutations in the tissue nonspecific alkaline phosphatase (TNSALP) gene in an autosomal recessive or dominant manner and characterized by defective mineralization of bone and low serum ALP levels. In this report, we present a family with HPP mother (case 1) and HPP child (case 2) who have identical TNSALP gene mutation (c.1015G>A p.Gly339Arg heterozygous mutation) but distinct clinical phenotypes. Whereas case 1 appeared to be asymptomatic despite extremely low levels of serum ALP, case 2 had several HPP-related symptoms, such as tooth loss, fractures, short stature, with slightly decreased ALP levels. Upon the diagnosis of HPP, case 1 discontinued denosumab, which was used to treat her rheumatoid arthritis, concerning the risk of atypical femoral fractures. The clinical course of this family was suggestive in a genotype-phenotype imbalance in HPP, the underdiagnosis of HPP in adults, and the risk of atypical femoral fractures using bone resorption inhibitors.

Potential pathological role of single nucleotide polymorphism (c.787T>C) in alkaline phosphatase (ALPL) for the phenotypes of hypophosphatasia.

Hypophosphatasia (HPP; OMIM 241510, 241500, and 146300) is an inherited metabolic disease characterized by defects of bone and tooth mineralization, which is caused by loss-of-function mutations in the ALPL gene encoding tissue non-specific alkaline phosphatase (TNSALP). In the last three decades, several studies have focused on the genotype-phenotype correlation in hypophosphatasia (HPP). In particular, functional tests based on in vitro analysis for the residual enzymatic activities of mutations have revealed a clear but imperfect genotype-phenotype correlation, suggesting that multiple potential factors modulate the phenotype. One of the missense variants identified in the tissue non-specific alkaline phosphatase (ALPL) gene, c.787T>C, has been considered as a benign polymorphism in HPP; however, its pathogenicity and role in disease manifestation remain controversial. We here report our recent experience of three unrelated families harboring the c.787T>C variant, suggesting clinical implications regarding the controversial pathogenicity of c.787T>C. First, despite the lack of obvious clinical phenotypes, homozygous c.787T>C would decrease the serum level of ALP activity. Second, c.787T>C might deteriorate phenotypes of a patient harboring another ALPL variant, especially one that has thus far presumed to be benign, e.g., the c.1144G>A variant. These cases contribute to the recent advances in understanding HPP to facilitate clinical recognition of more subtle phenotypes, further providing insights into the pathogenesis of HPP.

Biological stenciling of mineralization in the skeleton: Local enzymatic removal of inhibitors in the extracellular matrix.

Biomineralization is remarkably diverse and provides myriad functions across many organismal systems. Biomineralization processes typically produce hardened, hierarchically organized structures usually having nanostructured mineral assemblies that are formed through inorganic-organic (usually protein) interactions. Calcium­carbonate biomineral predominates in structures of small invertebrate organisms abundant in marine environments, particularly in shells (remarkably it is also found in the inner ear otoconia of vertebrates), whereas calcium-phosphate biomineral predominates in the skeletons and dentitions of both marine and terrestrial vertebrates, including humans. Reconciliation of the interplay between organic moieties and inorganic crystals in bones and teeth is a cornerstone of biomineralization research. Key molecular determinants of skeletal and dental mineralization have been identified in health and disease, and in pathologic ectopic calcification, ranging from small molecules such as pyrophosphate, to small membrane-bounded matrix vesicles shed from cells, and to noncollagenous extracellular matrix proteins such as osteopontin and their derived bioactive peptides. Beyond partly knowing the regulatory role of the direct actions of inhibitors on vertebrate mineralization, more recently the importance of their enzymatic removal from the extracellular matrix has become increasingly understood. Great progress has been made in deciphering the relationship between mineralization inhibitors and the enzymes that degrade them, and how adverse changes in this physiologic pathway (such as gene mutations causing disease) result in mineralization defects. Two examples of this are rare skeletal diseases having osteomalacia/odontomalacia (soft bones and teeth) - namely hypophosphatasia (HPP) and X-linked hypophosphatemia (XLH) - where inactivating mutations occur in the gene for the enzymes tissue-nonspecific alkaline phosphatase (TNAP, TNSALP, ALPL) and phosphate-regulating endopeptidase homolog X-linked (PHEX), respectively. Here, we review and provide a concept for how existing and new information now comes together to describe the dual nature of regulation of mineralization - through systemic mineral ion homeostasis involving circulating factors, coupled with molecular determinants operating at the local level in the extracellular matrix. For the local mineralization events in the extracellular matrix, we present a focused concept in skeletal mineralization biology called the Stenciling Principle - a principle (building upon seminal work by Neuman and Fleisch) describing how the action of enzymes to remove tissue-resident inhibitors defines with precision the location and progression of mineralization.

Tissue non-specific alkaline phosphatase activity and mineralization capacity of bi-allelic mutations from severe perinatal and asymptomatic hypophosphatasia phenotypes: Results from an in vitro mutagenesis model.

BACKGROUND: Hypophosphatasia (HPP) is an inherited metabolic bone disease characterized by reduced mineralization due to mutations in the tissue non-specific alkaline phosphatase (ALPL) gene. HPP is clinically variable with extensive allelic heterogeneity in the ALPL gene. We report the findings of in vitro functional studies following site-directed mutagenesis in bi-allelic mutations causing extreme clinical phenotypes; severe perinatal and asymptomatic HPP. AIMS: Elucidate genotype-phenotype correlation using in vitro functional studies and 3 dimensional (3D) ALP modelling. METHODS: Clinical, biochemical and radiological features were recorded in two children with extreme HPP phenotypes: Subject 1 (S1): Perinatal HPP with compound heterozygous mutations (c.110T>C; c.532T>C); Subject 2 (S2): asymptomatic with homozygous missense mutation (c.715G>T). Plasmids created for mutants 1 c.110T>C (L37P), 2 c.532T>C (Y178H) and 3 c.715G>T (D239Y) using in vitro mutagenesis were transfected into human osteosarcoma (U2OS) cells and compared to wildtype (WT) and mock cDNA. ALP activity was measured using enzyme kinetics with p-nitrophenylphosphate. Mineral deposition was evaluated photometrically with Alizarin Red S staining after culture with mineralization medium. Western blot analysis was performed to identify the mature type protein expression (80 kDa). Mutations were located on a 3D ALP model. Co-transfection was performed to identify dominant negative effect of the mutants. RESULTS: Phenotype: S1, had typical perinatal HPP phenotype at birth; extremely under-mineralized bones and pulmonary hypoplasia. S2, diagnosed incidentally by laboratory tests at 4 years, had normal growth, development, dentition and radiology. All S2's siblings (3 homozygous, 1 heterozygous) were asymptomatic. All subjects had typical biochemical features of HPP (low ALP, high serum pyridoxal-5'-phosphate), except the heterozygous sibling (normal ALP). Functional assay: Mutants 1 and 2 demonstrated negligible ALP activity and mineralization was 7.9% and 9.3% of WT, respectively. Mutant 3 demonstrated about 50% ALP activity and 15.5% mineralization of WT. On Western blot analysis, mutants 1 and 2 were detected as faint bands indicating reduced expression and mutant 3 was expressed as mature form protein with 50% of WT expression. Mutant 1 was located near the Glycosylphosphatidylinositol anchor, 2 at the core structure of the ALP protein and 3 at the periphery of the protein structure. Co-transfection did not reveal a dominant negative effect in any of the mutants. CONCLUSION: Our findings expand the current knowledge of functional effect of individual mutations and the importance of their location in the ALP structure.

Liver-type of tissue non-specific alkaline phosphatase is induced during mouse bone and tooth cell differentiation.

BACKGROUND AND OBJECTIVE: Tissue non-specific alkaline phosphatase (TNSALP) contains two types-bone- and liver-type-which are produced from the same gene due to differences in splicing. These two differ in their promoter, but the amino acid sequences of the mature proteins are identical. In this study, we examined the relationship between the two types of TNSALP expression and osteoblast differentiation. DESIGN: Gene expression of the two types of TNSALP was observed by reverse transcription-polymerase chain reaction. MC3T3-NM4 was sub-cloned from an established mouse osteoblastic cell line in which osteoblast characters do not appear without dexamethasone. The C2C12 mouse myoblastic cell line, which can be induced to osteoblasts with bone morphogenic protein 2, and organ-cultured tooth germs were also used in this work. RESULTS: The gene expression of liver-type TNSALP was observed in only MC3T3-NM4 activated by dexamethasone. For C2C12, the gene expression of bone-type TNSALP was observed even in non-induced conditions where myotubes were formed, whereas the liver-type TNSALP mRNA was only expressed when C2C12 differentiated into osteoblasts by bone morphogenic protein 2. Furthermore, in the organ-cultured tooth germs, the liver-type TNSALP mRNA was expressed according to differentiation of tooth germs. CONCLUSION: These results suggest that the liver-type TNSALP mRNA is induced according to differentiation of bone and tooth.

Consumption of non-digestible oligosaccharides elevates colonic alkaline phosphatase activity by up-regulating the expression of IAP-I, with increased mucins and microbial fermentation in rats fed a high-fat diet.

We have recently reported that soluble dietary fibre, glucomannan, increased colonic alkaline phosphatase (ALP) activity and the gene expression without affecting the small-intestinal activity and that colonic ALP was correlated with gut mucins (index of intestinal barrier function). We speculated that dietary fermentable carbohydrates including oligosaccharides commonly elevate colonic ALP and gene expression as well as increase mucin secretion and microbial fermentation. To test this hypothesis, male Sprague-Dawley rats were fed a diet containing 30 % lard with or without 4 % fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), raffinose (RAF) and lactulose (LAC), which are non-digestible oligosaccharides or isomalto-oligosaccharides (IMOS; some digestible oligosaccharides) for 2 weeks. Colon ALP activity, the gene expression and gut luminal variables including mucins, organic acids and microbiota were measured. Colonic ALP was significantly elevated in the FOS, RAF and LAC groups, and a similar trend was observed in the GOS group. Colonic expression of intestinal alkaline phosphatase (IAP -I), an ALP gene, was significantly elevated in the FOS, GOS and RAF groups and tended to be increased in the LAC group. Dietary FOS, GOS, RAF and LAC significantly elevated faecal mucins, caecal n-butyrate and faecal ratio of Bifidobacterium spp. Dietary IMOS had no effect on colonic ALP, mucins, organic acids and microbiota. Colon ALP was correlated with mucins, caecal n-butyrate and faecal Bifidobacterium spp. This study demonstrated that non-digestible and fermentable oligosaccharides commonly elevate colonic ALP activity and the expression of IAP-I, with increasing mucins and microbial fermentation, which might be important for protection of gut epithelial homoeostasis.

Neurological symptoms in Hypophosphatasia.

Hypophosphatasia (HPP) typically manifests with fractures, tooth loss, and muscle pain. Although mental health diagnoses and neurological symptoms have not been previously well documented in HPP, they occur commonly. The recognition of non-traditional symptoms may improve patient satisfaction, preempt costly evaluation and misdiagnosis, and lead to further treatment options. INTRODUCTION: Hypophosphatasia (HPP) is an inborn error of metabolism due to deficiency of tissue non-specific alkaline phosphatase (TNSALP). It is traditionally characterized by rickets in children and osteomalacia in adults, along with fractures, tooth loss, and muscle pain. Neurological symptoms and mental health diagnoses have not been widely reported, and we therefore report their prevalence in a cohort of patients with HPP. METHODS: A retrospective chart review was performed on a series of 82 HPP patients. Patient charts were reviewed to identify the possible presence and onset of 13 common neurological symptoms. RESULTS: Median age was 36 years (2 to 79). Seventeen had adult onset HPP (> 18 years) and 65 had pediatric onset HPP (< 18 years). Median time from symptom onset to HPP diagnosis was 8 years (0 to 67). Seventy-four percent had a family history of bone disease, while 17% had a family history of neurologic disease. Bone problems occurred in 89%, dental problems in 77%, and muscle problems in 66%. Fatigue occurred in 66%, headache in 61%, sleep disturbance in 51%, gait change in 44%, vertigo in 43%, depression in 39%, anxiety in 35%, neuropathy in 35%, and hearing loss in 33%. CONCLUSIONS: The extra-skeletal manifestations of HPP, specifically neurological symptoms, have not been previously well documented. However, mental health diagnoses and neurological symptoms such as headache and sleep disturbance occur commonly in patients with HPP. The recognition of non-traditional symptoms in HPP may improve patient satisfaction, preempt costly evaluation and misdiagnosis, and may lead to further treatment options.

Alkaline Phosphatase Controls Lineage Switching of Mesenchymal Stem Cells by Regulating the LRP6/GSK3ß Complex in Hypophosphatasia.

Lineage differentiation of bone marrow mesenchymal stem cells (BMMSCs) is the key to bone-fat reciprocity in bone marrow. To date, the regulators of BMMSC lineage switching have all been identified to be transcription factors, and researchers have not determined whether other genes control this process. This study aims to reveal a previously unknown role of tissue-nonspecific alkaline phosphatase (TNSALP) in controlling BMMSC lineage selection. Methods: We compared the characteristics of cultured BMMSCs from patients with hypophosphatasia (HPP), which is caused by mutations in the liver/bone/kidney alkaline phosphatase (ALPL) gene, and an ALPL knockout (ko) mouse model. We performed ALPL downregulation and overexpression experiments to investigate the regulatory role of ALPL in BMMSC lineage switching. Using the PathScan array, coimmunoprecipitation experiments and pathway-guided small molecule treatments, we explored the possible mechanism underlying the regulatory effects of ALPL on cell differentiation and evaluated its therapeutic effect on ALPL ko mice. Results: BMMSCs from both patients with HPP and ALPL ko mice exhibited defective lineage differentiation, including a decrease in osteogenic differentiation and a parallel increase in adipogenic differentiation. Mechanistically, TNSALP directly interacted with LRP6 and regulated the phosphorylation of GSK3ß, subsequently resulting in lineage switching of BMMSCs. Re-phosphorylation of GSK3ß induced by LiCl treatment restored differentiation of BMMSCs and attenuated skeletal deformities in Alpl+/- mice. Conclusion: Based on our findings, TNSALP acts as a signal regulator to control lineage switching of BMMSCs by regulating the LRP6/GSK3ß cascade.

Four novel mutations in the ALPL gene in Chinese patients with odonto, childhood, and adult hypophosphatasia.

Hypophosphatasia (HPP) is a rare inherited disorder characterized by defective bone and/or dental mineralization, and decreased serum alkaline phosphatase (ALP) activity. ALPL, the only gene related with HPP, encodes tissue non-specific ALP (TNSALP). Few studies were carried out in ALPL gene mutations in the Chinese population with HPP. The purpose of the present study is to elucidate the clinical and genetic characteristics of HPP in five unrelated Chinese families and two sporadic patients. Ten clinically diagnosed HPP patients from five unrelated Chinese families and two sporadic patients and fifty healthy controls were genetically investigated. All 12 exons and exon-intron boundaries of the ALPL gene were amplified by PCR and directly sequenced. The laboratory and radiological investigations were conducted simultaneously in these HPP ten patients. A 3D model of the TNSALP was used to predict the dominant negative effect of identified missense mutations. Three odonto, three childhood, and four adult types of HPP were clinically diagnosed. Ten mutations were identified in five unrelated Chinese families and two sporadic patients, including eight missense mutations and two frameshift mutations. Of which, four were novel: one frameshift mutation (p.R138Pfsx45); three missense mutations (p.C201R, p.V459A, p.C497S). No identical mutations and any other new ALPL mutations were found in unrelated 50 healthy controls. Our study demonstrated that the ALPL gene mutations are responsible for HPP in these Chinese families. These findings will be useful for clinicians to improve understanding of this heritable bone disorder.