Alkaline Phosphatases: Biochemistry, Functions, and Measurement

Toward the point-of-care testing of alkaline phosphatase in human serum

This work addresses challenges of simple but reliable determination of enzyme alkaline phosphatase (ALP) in μL-sized serum samples. The single-tube assay and plate-based immunoassay were developed by using a commercial glucose test strip (GTS) to transduce analytical signal from the ALP + glucose-6-phosphate (G6P) reaction. The glucose released from G6P contributed to the flow of anodic charge Q20s through GTS. The interferences from serum matrix including those from native glucose were eliminated by devising a signal ΔQ20s = Q20s (total) - Q20s (matrix). The ΔQ20s was proportional to ALP activity within a linear range of 7.4-720 IU L-1 for assay (R2, 0.995) and 10-300 IU L-1 for immunoassay (R2, 0.983), which far exceeded a normal clinical range for ALP in adult human serum (30-150 IU L-1). Both methods required no auxiliary enzymes or labels, and were accurate (93-99 % signal recovery) and precise (RSD ≤10%). The assay was a simpler option because it required only one 20-min incubation step to determine ALP. The immunoassay involved three steps but it was still less laborious (by ∼70%) than a traditional enzyme-linked immunosorbent assay (ELISA) of ALP due to the substitution of ELISA detection antibody with GTS. The GTS-G6P-based methods bring ALP testing closer to the point-of-care locations, which is important considering the growing role of ALP as a prophylactic, therapeutic, and anti-inflammatory agent, and a marker of human diseases.

Insights into chlorantraniliprole exposure via activating cytochrome P450-mediated xenobiotic metabolism pathway in the Procambarus clarkii: Identification of P450 genes involved in detoxification

To investigate the impact of chlorantraniliprole on Procambarus clarkii, acute toxicity tests were performed. Results indicated that 96 h post-exposure to chlorantraniliprole (60 mg/L) led to the separation of the hepatopancreas basement membrane, causing cell swelling, rupture, and vacuolation. Moreover, acid phosphatase (ACP) and alkaline phosphatase (AKP) activities exhibited divergent trends across four concentrations of chlorantraniliprole (0, 30, 60, and 90 mg/L). Hydrogen peroxide (H2O2) and catalase (CAT) levels significantly increased, while total superoxide dismutase (T-SOD) and malonaldehyde (MDA) activities decreased, indicating oxidative stress in the hepatopancreas. A total of 276 differentially expressed genes (DEGs) were identified, with 204 up-regulated and 72 down-regulated. Out of these, 114 DEGs were successfully annotated and classified into 99 pathways, with a primary focus on the cytochrome P450-mediated xenobiotic metabolism pathway. The DEGs enriched in this pathway, along with transcriptome data, were validated using quantitative-polymerase chain reaction. This study enhances the transcriptome database of P. clarkii and provides fundamental insights into its immune defense and antioxidant mechanisms. Additionally, it lays a theoretical foundation for future research on disease prevention in P. clarkii within rice-shrimp culture systems.

Unraveling the role of BMI and blood markers in the relationship between plant-based diets and osteoporosis: A prospective cohort study

BACKGROUND

The potential adverse effects of plant-based diets on bone health have raised significant concern, while the prospective evidence is limited. This study aimed to evaluate the association between plant-based diet indexes and incident osteoporosis while exploring the underlying mechanisms involved in this relationship.

METHODS

The analysis included 202,063 UK Biobank participants conducted between 2006 and 2022. Plant-based diet indexes (hPDI and uPDI) were calculated using the 24-h dietary questionnaire. Cox proportional risk regression and mediation analysis were used to explore the associations of plant-based diet indexes with osteoporosis, estimating the contribution of BMI and blood markers.

RESULTS

We found the highest quintile for hPDI (HR = 1.16; 95% CI: 1.05 to 1.28) and uPDI (HR = 1.15; 95% CI: 1.05 to 1.26) were associated with an increased risk of osteoporosis. BMI was identified as an important mediator in the association between hPDI and osteoporosis, with mediation proportions of 46.17%. For blood markers, the mediating (suppressing) effects of C-reactive protein, alkaline phosphatase, and insulin-like growth factor-1 on the association between uPDI (hPDI) and osteoporosis were significant, ranging from 5.63%-16.87% (4.57%-6.22%).

CONCLUSION

Adherence to a plant-based diet is associated with a higher risk of osteoporosis, with BMI and blood markers potentially contributing to this relationship. Notably, even a healthy plant-based diet necessitates attention to weight management to mitigate its impact on bone loss. These findings emphasize the importance of personalized dietary recommendations and lifestyle interventions to decrease the risk of osteoporosis.

The age-related effects on orthodontic tooth movement and the surrounding periodontal environment

Orthodontic treatment in adults is often related to longer treatment time as well as higher periodontal risks compared to adolescents. The aim of this review is to explore the influence of age-related chages on orthodontic tooth movement (OTM) from macro and micro perspectives. Adults tend to show slower tooth movement speed compared to adolescence, especially during the early phase. Under orthodontic forces, the biological responses of the periodontal ligament (PDL) and alveolar bone is different between adult and adolescents. The adult PDL shows extended disorganization time, increased cell senescence, less cell signaling and a more inflammatory microenvironment than the adolescent PDL. In addition, the blood vessel surface area is reduced during the late movement phase, and fiber elasticity decreases. At the same time, adult alveolar bone shows a higher density, as well as a reduced osteoblast and osteoclast activation, under orthodontic forces. The local cytokine expression also differs between adults and adolescents. Side-effects, such as excessive root resorption, greater orthodontic pain, and reduced pulpal blood flow, also occur more frequently in adults than in adolescents.

Latent metabolic bone disease, skeletal dysplasia and other conditions related to low bone formation among 38 patients with subtrochanteric femoral fractures: a retrospective observational study

Subtrochanteric femoral fracture is rare and intractable due to the possible association with low bone formation. Retrospective analysis of 38 patients with subtrochanteric femoral fractures revealed that four patients suffered from disorders related to low bone formation and there were specific treatments for two of them.

PURPOSE

The main aim of this study was to detect latent metabolic bone diseases and skeletal dysplasia associated with low bone formation among patients with morphologic atypical femoral fracture (AFF). A second aim was to evaluate the frequency of recognized risk factors, such as antiresorptive agents, glucocorticoids, and age.

METHODS

Clinical information was retrospectively analyzed among 38 Japanese patients who were admitted to the Department of Orthopedic Surgery and Spinal Surgery and the Division of Emergency and Critical Care Medicine at the University of Tokyo Hospital with diagnoses of subtrochanteric fractures between February 2012 and March 2022.

RESULTS

Among 38 patients (including 30 females), 21 patients were aged 75 and over. Ten patients had past oral glucocorticoid use, and 18 had past antiresorptive agent use. Two patients were diagnosed with hypophosphatemic osteomalacia after the development of fractures. One patient was suspected to be a carrier of a loss-of-function variant of alkaline phosphatase, biomineralization associated (ALPL), and one other patient had previously been genetically diagnosed with pycnodysostosis. Among four patients with a diagnosis or suspicion of these metabolic bone diseases and skeletal dysplasia, four had past clinical fractures, two had past subtrochanteric femoral fractures, and two had subtrochanteric femoral fractures on both sides.

CONCLUSION

If clinicians encounter patients with morphologic AFF, latent diseases related to low bone formation should be carefully differentiated because appropriate treatment may prevent delayed union and recurrent fractures. Additionally, it may be desirable to exclude these bone diseases in advance before initiating long-term use of antiresorptive agents in osteoporotic patients by screening with serum alkaline phosphatase levels to reduce the risk of morphologic AFF.

Insight into the potential of bone turnover biomarkers: integration in the management of osteoporosis and chronic kidney disease-associated osteoporosis

PURPOSE OF REVIEW

Disturbances in mineral and bone metabolism occurring in osteoporosis and chronic kidney disease-associated osteoporosis place patients at high risk of fracture making these conditions a major public health concern. Due to the limited use of bone histomorphometry in clinical practice, the gold standard for assessing bone turnover, extensive efforts have been made to identify bone turnover markers (BTMs) as noninvasive surrogates. Since the identification of certain commonly used markers several decades ago, considerable experience has been acquired regarding their clinical utility in such bone disorders.

RECENT FINDINGS

Mounting evidence suggested that BTMs represent a simple, low-risk, rapid and convenient way to obtain data on the skeletal health and that they may be useful in guiding therapeutic choices and monitoring the response to treatment.

SUMMARY

BTMs could provide clinicians with useful information, independent from, and often complementary to bone mineral density (BMD) measurements. They have proven valuable for monitoring the effectiveness of osteoporosis therapy, as well as promising for discriminating low and high turnover states. Improved performance is observed when BTMs are combined, which may be useful for selecting treatments for chronic kidney disease-bone mineral disorders (CKD-MBD).

Benign transient hyperphosphatasemia in the pediatric population: a single center cohort study

OBJECTIVES

Alkaline phosphatase (ALP) can be increased in a benign condition known as benign-transient hyperphosphatasemia (BTH). We aimed to evaluate the demographic, and clinical characteristics of infants and children with BTH.

METHODS

In our retrospective study, infants and children diagnosed with BTH between September 2019 and September 2023 were included.

RESULTS

Of 249 children with elevated ALP levels, 95 (38.1 %) had BTH. The mean age at diagnosis of children with BTH was 2.4 ± 1.3 years (min 0.6 - max 6.2 years). ALP mean value was 2,587 ± 1252 U/L (min 972 - max 5757 U/L). ALP value was an average 7.4 ± 3.6 times higher than the corresponding upper limit of normal. The second measurement was made after an average of 13.2 ± 6 days, and a statistically significant difference was detected compared to the first value, with a decrease of 61 ± 23 % in the ALP value (p<0.001). ALP value returned to normal in an average of 44 ± 29.2 days. Elevated ALP was detected during infection in 49 (51.6 %) children. When the sample was divided into those under 2 years of age and aged 2 and over, no statistical difference was observed in ALP levels in the time it took for ALP levels to return to the normal range (p=0.480).

CONCLUSIONS

BTH should be kept in mind if high serum ALP is detected in children without clinical or laboratory suspicion of bone or liver disease. In the follow up detecting a significant decrease trend compared to the first value may be guiding for BTH.

Investigating the Interplay of Toxic Metals and Essential Elements in Liver Disease

Liver diseases, including non-alcoholic fatty liver disease (NAFLD), are a growing global health issue. Environmental exposure to toxic metals can harm the liver, increasing the risk of NAFLD. Essential elements are vital for liver health, but imbalances or deficiencies can contribute to the development of NAFLD. Therefore, understanding the interplay between toxic metals and essential elements in liver disease is important. This study aims to assess the individual and combined effects of toxic metals (lead(Pb), cadmium (Cd), mercury (Hg)), and essential elements (manganese and selenium) on the risk of liver disease. Methods: We assessed the individual and combined effects of Pb, Cd, Hg, manganese (Mn), and selenium (Se) on liver disease risk using data from the National Health and Nutrition Examination Survey between 2017 and 2018. We performed descriptive statistics and linear regression analysis and then utilized Bayesian Kernel Machine Regression (BKMR) techniques such as univariate, bivariate, and overall effect analysis. BKMR enabled the assessment of non-linear exposure-response functions and interactions between metals and essential elements. Posterior Inclusion Probabilities (PIPs) were calculated to determine the importance of each metal and essential element in contributing to liver disease. Regarding our study results, the regression analysis of liver injury biomarkers ALT, AST, ALP, GGT, total bilirubin, and the FLI-an indicator of NAFLD-with toxic metals and essential elements, adjusting for covariates such as age, sex, BMI, alcohol consumption, ethnicity, income, and smoking status, demonstrated the differential effects of these contaminants on the markers of interest. Our BKMR analysis provided further insights. For instance, the PIP results underscored Pb's consistent importance in contributing to liver disease (PIP = 1.000), followed by Hg (PIP = 0.9512), Cd (PIP = 0.5796), Se (PIP = 0.5572), and Mn (PIP = 0.4248). Our univariate analysis showed a positive trend with Pb, while other exposures were relatively flat. Our analysis of the single-variable effects of toxic metals and essential elements on NAFLD also revealed that Pb significantly affected the risk of NAFLD. Our bivariate analysis found a positive (toxic) trend when Pb was combined with other metals and essential elements. For the overall exposure effect of exposure to all the contaminants together, the estimated risk of NAFLD showed a steady increase from the 60th to the 75th percentile. In conclusion, our study indicates that Pb exposure, when combined with other toxic metals and essential elements, plays a significant role in bringing about adverse liver disease outcomes.

Subnormal Serum Liver Enzyme Levels: A Review of Pathophysiology and Clinical Significance

Subnormal levels of liver enzymes, below the lower limit of normal on local laboratory reports, can be useful diagnostically. For instance, subnormal levels of aminotransferases can be observed in vitamin B6 deficiency and chronic kidney disease. Subnormal alkaline phosphatase levels may indicate the presence of hypophosphatasia, Wilson's disease, deficiencies of divalent ions, or malnutrition. Subnormal levels of gamma glutamyl transferase may be seen in cases of acute intrahepatic cholestasis, the use of certain medications, and in bone disease. Finally, subnormal levels of 5'-nucleotidase have been reported in lead poisoning and nonspherocytic hemolytic anemia. The aim of this review is to bring attention to the fact that subnormal levels of these enzymes should not be ignored as they may indicate pathological conditions and provide a means of early diagnosis.

Injectable and Self-Curing Single-Component Hydrogel for Stem Cell Encapsulation and In Vivo Bone Regeneration

An ideal hydrogel for stem cell therapy would be injectable and efficiently promote stem cell proliferation and differentiation in body. Herein, an injectable, single-component hydrogel with hyaluronic acid (HA) modified with phenylboronic acid (PBA) and spermidine (SM) is introduced. The resulting HAps (HA-PBA-SM) hydrogel is based on the reversible crosslinking between the diol and the ionized PBA, which is stabilized by the SM. It has a shear-thinning property, enabling its injection through a syringe to form a stable hydrogel inside the body. In addition, HAps hydrogel undergoes a post-injection "self-curing," which stiffens the hydrogel over time. This property allows the HAps hydrogel to meet the physical requirements for stem cell therapy in rigid tissues, such as bone, while maintaining injectability. The hydrogel enabled favorable proliferation of human mesenchymal stem cells (hMSCs) and promoted their differentiation and mineralization. After the injection of hMSCs-containing HAps into a rat femoral defect model, efficient osteogenic differentiation of hMSCs and bone regeneration is observed. The study demonstrates that simple cationic modification of PBA-based hydrogel enabled efficient gelation with shear-thinning and self-curing properties, and it would be highly useful for stem cell therapy and in vivo bone regeneration.

Factors Associated with Increased Intraocular Pressure in Type 2 Diabetes Patients

BACKGROUND

Over one-third of patients living with diabetes will develop ocular disease during their lifetime. The present study analyzes the association between metabolic and anthropometric markers, associated comorbidities, and intraocular pressure (IOP) in patients with type 2 diabetes mellitus (DM).

METHODS

The retrospective study included 87 adult patients with type 2 DM who underwent routine eye examinations and blood/urine tests.

RESULTS

67.9% of the patients had an IOP > 14.5 mmHg and only 41.3% had an HbA1c < 7%. In a multivariate regression analysis, the mean IOP was associated with diabetes duration in subjects with a disease duration < 15 years and an HbA1c < 7% (adjusted R2 = 0.29, p = 0.008). Also, patients with shorter diabetes duration and optimal glucose control had a lower mean IOP than patients with a higher HbA1c (mean IOP 15.1 mmHG vs. 18.9 mmHg, p = 0.04). The patient's age, anthropometric or metabolic markers, associated comorbidities like hypertension (HTN) or retinal angiosclerosis, and diabetes therapies were not associated with IOP in this study.

CONCLUSION

Diabetes progression is directly associated with increased IOP. Avoiding clinical inertia and optimizing glycemic control could prevent or delay the increase of IOP. Routine eye examination should include measuring IOP, not only diabetic retinopathy screening.

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.

A Ratiometric Fluorescence Biosensor for Detection of Alkaline Phosphatase Via an Advanced Chemometric Model

In this paper, a ratiometric fluorescence biosensor was introduced for alkaline phosphatase (ALP) detection based on 2-aminopurine (2-Amp) and thioflavin T (ThT)-G-quadruplex system. We designed a special DNA (5'-AGGGTTAGGGTTAGGGTTAGGGAAA/i2-Amp/AAAA-PO4-3', AP) modified with a phosphate moiety at the 3'-end, G-quadruplex at the 5'-end, and a fluorophore (2-Amp) in the middle. In the absence of ALP, the G-rich AP strand could be prone to fold into G-quadruplex structures in the presence of K+. Then, ThT combined with G-quandruplex, resulting in the enhancement of fluorescence emission peak at 485 nm. However, ALP-mediated hydrolysis of the 3'-phosphoryl end promoted the cleavage of AP by the exonuclease I (Exo I), releasing 2-Amp which displayed a strong fluorescence emission peak at 365 nm. Moreover, the quantitative fluorescence model (QFM) was derived for the analysis of the fluorescence measurements obtained by the proposed ratiometric fluorescent biosensor. With the aid of the advanced model, the proposed ratiometric fluorescent biosensor possessed satisfactory results for the detection of ALP in the human serum samples, with accuracy comparable to that of the reference method-the commercial ALP assay kit. Under the optimized experimental conditions, this method exhibited good selectivity and higher sensitivity, and the detection limit was found to be as low as 0.017 U/L. Therefore, it is reasonable to expect that the method had a great potential to detect ALP quantitatively in clinical diagnosis.

Zinc and vitamin D deficiency and supplementation in hypophosphatasia patients - A retrospective study

Hypophosphatasia (HPP) is characterized by severe skeletal symptoms including mineralization defects, insufficiency fractures, and delayed facture healing or non-unions. HPP is caused by mutations of the tissue non-specific alkaline phosphatase (TNSALP). Zinc is a cofactor of TNSALP and vitamin D an important regulator of bone matrix mineralization. Data from this retrospective study indicates that deficiencies in zinc or vitamin D occur in HPP patients with a similar frequency as in the general population. While guidelines for repletion of these micronutrients have been established for the general population, the transferability of the efficacy and safety of these regiments to HPP patients still needed to be determined. We filtered for variant classification (ACMG 3-5, non-benign) and data completeness from a total cohort of 263 HPP patients. 73.5 % of this sub-cohort were vitamin D deficient while 27.2 % were zinc deficient. We retrospectively evaluated the effect of supplementation according to general guidelines in 10 patients with zinc-deficiency and 38 patients with vitamin d-deficiency. The treatments significantly raised serum zinc or vitamin D levels respectively. All other assessed disease markers (alkaline phosphatase, pyrodoxal-5-phosphate) or bone turnover markers (phosphate, calcium, parathyroid hormone, bone specific alkaline phosphatase, creatinine, desoxypyridinoline) remained unchanged. These results highlight that general guidelines for zinc and vitamin D repletion can be successfully applied to HPP patients in order to prevent deficiency symptoms without exacerbating the disease burden or causing adverse effects due to changes in bone and calcium homeostasis.