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Tissue-nonspecific alkaline phosphatase (TNAP) is one of four isozymes, which include germ cell, placental and intestinal alkaline phosphatases. The TNAP isozyme has 3 isoforms (liver, bone and kidney) which differ by tissue expression and glycosylation pattern. Despite a long history of investigation, the exact function of TNAP in many tissues is largely unknown. Only the bone isoform has been well characterised during mineralization where the enzyme hydrolyses pyrophosphate to inorganic phosphate, which combines with calcium to form hydroxyapatite crystals deposited as new bone. The inorganic phosphate also increases gene expression of proteins that support tissue mineralization. Recent studies have shown that TNAP is expressed in preadipocytes from several species, and that inhibition of TNAP activity causes attenuation of intracellular lipid accumulation in these and other lipid-storing cells. The mechanism by which TNAP stimulates lipid accumulation is not known; however, proteins that are important for controlling phosphate levels in bone are also expressed in adipocytes. This review examines the evidence that inorganic phosphate generated by TNAP promotes transcription that enhances the expression of the regulators of lipid storage and consequently, that TNAP has a major function of lipid metabolism., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Introduction: Studies have shown that systemic levels of branched-chain amino acids (BCAAs) and aromatic amino acids (AAAs) are elevated in cardiometabolic diseases (CMDs) in populations resident in high income countries. However, little is known about the association of BCAAs and AAAs with metabolic syndrome and its components in Asian Indian (AI) and Black African (BA) populations., Objective: The aim of this study was to describe the association of BCAAs and AAAs with the metabolic syndrome, its individual components and insulin resistance in AI and BA populations., Methods: Serum samples collected from AI (n = 349) and BA (n = 369) subjects were used to measure levels of BCAAs and AAAs by ultra-pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Anthropometric, demographic and cardiometabolic variables were measured in all subjects., Results: The sum of BCAAs and AAAs was higher in AIs compared to BAs. The BCAAs and AAAs were positively associated with insulin resistance, metabolic syndrome and its individual components. This was particularly the case for AI subjects, in unadjusted regression models. However, these associations were non-significant after adjusting for co-variates, particularly visceral adipose tissue (VAT). Triglyceride levels were significantly associated with valine and leucine levels in BAs even after adjustment for co-variates. Lastly, we found that fasting circulatory BCAA and AAA levels are strongly correlated with VAT in both populations., Conclusion: This study identified specific associations of serum valine and leucine levels with triglycerides in BAs. The association of amino acids with CMDs was observed in AIs, but was found to be the result of confounding by VAT. Further studies are required to determine whether BCAAs and AAAs are aetiological factors in CMDs and how VAT modulates their serum levels.

Background: The increasing prevalence of obesity in sub-Saharan African women is not well understood, and black South African women in the region are particularly vulnerable. This study aimed to examine whether the relationship of socioeconomic status (SES) with changes in body mass index (BMI) and waist circumference (WC) is mediated by physical activity in ageing African women., Methods: In a longitudinal analysis of the 518 caregivers associated with the Birth to Twenty Plus study, the role of SES associated with 10-year changes in BMI and WC was tested using structural equation modelling (SEM). The degree of mediation of moderate-vigorous physical activity (MVPA) and sitting time in this association was also assessed., Results: The prevalence of obesity increased significantly from baseline to follow-up ( p  < 0.0001). In the SEM models, baseline SES had a direct positive effect on changes in BMI (β, 95% CI, 0.02 (0.005 to 0.04), and a direct negative effect on changes in MVPA (β, 95% CI, - 3.81 (- 6.92 to - 0.70). Baseline MVPA had a direct negative effect (β, 95% CI, - 0.002 (- 0.003 to - 0.0003) and indirect positive effect via change in MVPA (β, 95% CI, 0.01 (0.0001 to 0.001) on change in WC., Conclusions: Our study demonstrates the role and interaction of sociodemographic and behavioural predictors of obesity, and suggests a multifaceted approach to management of the crisis in communities of ageing urban African women., Competing Interests: Ethical approval was granted by the University of the Witwatersrand (Ethics certificate number: M110627) and all participants provided written consent.The authors declare that they have no competing interests.Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Purpose: Parathyroid hormone (PTH) has been shown to correlate positively with fat mass, however there are no studies that have investigated whether this association is a result of, or is modified by, body fat distribution. The aim of this study was to investigate the association of PTH with several body composition indices, namely visceral (VAT) and subcutaneous adiposity (SCAT) as well as with lean mass and with serum leptin, which has been reported to increase PTH., Methods: This was a cross-sectional study in which PTH was measured by chemiluminescent assay; body fat and lean mass by dual-energy X-ray absorptiometry (DXA) and abdominal fat by ultrasonography in 714 healthy adults aged 18-65 years. Serum leptin was measured by ELISA., Results: In a multivariate linear regression model that included height, age, gender, ethnicity, serum 25 hydroxyvitamin D, leptin levels, calcium, magnesium and phosphate concentrations, glomerular filtration rate, smoking status, and calcium and vitamin D supplementation as independent variables and PTH as the dependent variable, VAT (β = 0.094, p = 0.035) correlated significantly with PTH levels but SCAT (β = -0.045, p = 0.386) and body fat mass (β = 0.098, p = 0.126) did not. Leptin did not correlate with PTH (β = 0.013, p = 0.832) in this regression model., Conclusions: Plasma PTH is significantly associated with VAT in healthy adults. In view of the association of PTH with increased cardiovascular mortality, it is important to investigate this association further.

The number of mature osteoblasts and marrow adipocytes in bone is influenced by the differentiation of the common mesenchymal progenitor cell towards one phenotype and away from the other. Consequently, factors which promote adipogenesis not only lead to fatty marrow but also inhibit osteoblastogenesis, resulting in decreased osteoblast numbers, diminished bone formation and, potentially, inadequate bone mass and osteoporosis. In addition to osteoblast and bone adipocyte numbers being influenced by this skewing of progenitor cell differentiation towards one phenotype, mature osteoblasts and adipocytes secrete factors which may evoke changes in the cell fate and function of each other. This review examines the endogenous factors, such as PPAR-γ2, Wnt, IGF-1, GH, FGF-2, oestrogen, the GP130 signalling cytokines, vitamin D and glucocorticoids, which regulate the selection between osteoblastogenesis and adipogenesis and the interrelationship between fat and bone. The role of adipokines on bone, such as adiponectin and leptin, as well as adipose-derived oestrogen, is reviewed and the role of bone as an energy regulating endocrine organ is discussed.