Molecular aspects of intestinal calcium absorption

Adaptations in Gastrointestinal Nutrient Absorption and its Determinants During Pregnancy in Monogastric Mammals: A Scoping Review

CONTEXT

Pregnancy increases nutrient demand, but how nutrient uptake and its determinants adapt to facilitate this is unclear.

OBJECTIVE

This review aimed to identify and characterize evidence and evidence gaps regarding changes in gastrointestinal nutrient absorption and its determinants during pregnancy in monogastric mammals.

DATA SOURCES

A scoping review of peer-reviewed sources was conducted across PubMed, Scopus, Web of Science, Embase, and ProQuest (theses and dissertations) databases.

DATA EXTRACTION

Data extracted included species, pregnancy stages and outcomes. Where sufficient data for a given outcome was available, relative values were summarized graphically or in tables, to allow comparison across pregnancy stages and/or small intestine regions. Searches identified 26 855 sources, of which only 159 were eligible. Mechanistic studies were largely restricted to rodents, and most compared non- and late-pregnant groups, with fewer studies including early- or mid-pregnant groups.

DATA ANALYSIS

During pregnancy, there is some evidence for greater capacity for glucose uptake but unchanged amino acid uptake, and good evidence for increased uptake of calcium, iron, and zinc, and slower gastrointestinal passage of nutrients. The available evidence indicates that acute glucose uptake, gastric emptying, and the activities of sucrase, maltase, and lactase do not change during pregnancy. Gaps in the knowledge include the effects of pregnancy on uptake of specific amino acids, lipids, and most minerals and vitamins.

CONCLUSION

The results indicate that the gastrointestinal tract adapts during pregnancy to facilitate increased nutrient absorption. Additional data is required in order to assess the underlying mechanisms for and impacts on the absorption of many nutrients, as well as to determine the timing of these adaptations.

Ovarian Aging: The Silent Catalyst of Age-Related Disorders in Female Body

Age-related diseases have emerged as a global concern as the population ages. Consequently, understanding the underlying causes of aging and exploring potential anti-aging interventions is imperative. In females, the ovaries serve as the principal organs responsible for ovulation and the production of female hormones. The aging ovaries are related to infertility, menopause, and associated menopausal syndromes, with menopause representing the culmination of ovarian aging. Current evidence indicates that ovarian aging may contribute to dysfunction across multiple organ systems, including, but not limited to, cognitive impairment, osteoporosis, and cardiovascular disease. Nevertheless, due to the widespread distribution of sex hormone receptors throughout the body, ovarian aging affects not only these specific organs but also influences a broader spectrum of age-related diseases in women. Despite this, the impact of ovarian aging on overall age-related diseases has been largely neglected. This review provides a thorough summary of the impact of ovarian aging on age-related diseases, encompassing the nervous, circulatory, locomotor, urinary, digestive, respiratory, and endocrine systems. Additionally, we have outlined prospective therapeutic approaches for addressing both ovarian aging and age-related diseases, with the aim of mitigating their impacts and preserving women's fertility, physical health, and psychological well-being.

Improving the diagnostic of absorptive hypercalciuria: a comparative analysis of calcium load tests at 2-hour and 4-hour intervals

Introduction

The calcium load test (CLT) was developed by Pak et al. in 1974 to better discriminate hypercalciuria. Absorptive hypercalciuria (AH) is defined by an increase of the difference between urinary calcium/creatinine ratio (ΔUCa/Cr) of more than 0.5 mmol/mmol with a 4-hour CLT. In clinical practice and more recent studies, CLT is a 2-hour test. We hypothesized that the 4 h timepoint is more efficient in AH diagnosis.

Methods

We report a single-centre retrospective study including all patients who underwent CLT because of hypercalciuria or hyperparathyroidism. After a 3-day low-calcium diet and a 12-hour fast, 24-hour urines were collected. Blood and urinary samples were done at arrival and after 2 h and 4 h of oral ingestion of 1 g of calcium. AH was diagnosed by ΔUCa/Cr between baseline and 2 h or 4 h of more than 0.05 mmol/mmol.

Results

We included 328 patients. Baseline UCa/Cr ratio was 0.3 ± 0.2 mmol/mmol and increased significantly after 2 h and 4 h (0.6 ± 0.3 and 0.8 ± 0.4 mmol/mmol, P < 0.001). ΔUCa/Cr was significantly different between baseline and 2 h or 4 h (0.2 ± 0.2 versus 0.5 ± 0.4, P < 0.001). AH was diagnosed in 35 (10.7%) patients after 2 h, 84 (25.6%) more were diagnosed at 4 h (P < 0.001).

Conclusions

The 4 h CLT improves the diagnosis of AH with more than 50% of AH diagnosed within 4 h of calcium ingestion. It seems that there are cases of AH of later diagnosis with a similar clinical and biological profile depending on enteral absorption.

Antioxidative Function of Zinc and Its Protection Against the Onset and Progression of Kidney Disease Due to Cadmium

Chronic kidney disease (CKD) is now the world's top seventh cause of death from a non-communicable disease, and its incidence is projected to increase further as its major risk factors, including obesity, diabetes, hypertension, and non-alcoholic fatty liver disease (NAFLD), continue to rise. Current evidence has linked the increased prevalence of CKD, diabetes, hypertension, and NAFLD to chronic exposure to the metal pollutant cadmium (Cd). Exposure to Cd is widespread because diet is the main exposure route for most people. Notably, however, the health risk of dietary Cd exposure is underappreciated, and the existing tolerable exposure guidelines for Cd do not afford health protection. New health-protective exposure guidelines are needed. From one's diet, Cd is absorbed by the intestinal epithelium from where it passes through the liver and accumulates within the kidney tubular epithelial cells. Here, it is bound to metallothionine (MT), and as it is gradually released, it induces tubular damage, tubulointerstitial inflammation and fibrosis, and nephron destruction. The present review provides an update on our knowledge of the exposure levels of Cd that are found to be associated with CKD, NAFLD, and mortality from cardiovascular disease. It discusses the co-existence of hypertension and CKD in people environmentally exposed to Cd. It highlights nuclear and mitochondrial targeting and zinc deficiency as the universal cytotoxic mechanisms of Cd. Special emphasis is placed on the novel antioxidative function of zinc involving de novo heme biosynthesis and the induced expression of heme oxygenase-1 (HO-1). Other exogenous biomolecules with promising anti-Cd toxicity are highlighted.

Long-term excessive salt consumption alters villous and crypt morphology and the protein expression of uroguanylin, TRPV6 and PMCA1b in the rat small intestine

Although long-term high dietary sodium consumption often aggravates hypertension and bone loss, sodium in the intestinal lumen has been known to promote absorption of nutrients and other ions, e.g., glucose and calcium. However, whether high-salt diet (HSD) altered mucosal morphology, villous cell turnover and calcium transporter expression remained elusive. Herein, rats were treated with HSD containing 8% wt/wt NaCl for up to 5 months. HSD rats exhibited a marked increase in sodium intake with high fecal and urinary sodium excretion, as compared to the control group treated with normal diet. Intestinal histomorphometry revealed increasing of crypt depth and villous height in 3- and 4-month HSD groups, respectively, consistent with larger mucosal-to-serosal amplification ratio that reflected an increased surface area for nutrient absorption. The signals of Ki-67-positive cells was enhanced in the crypts as visualized by multiphoton fluorescence microscopy, whereas the TUNEL-positive cells were decreased in the villi of HSD, suggesting greater crypt cell proliferation and a reduction of villous cell apoptosis. Confocal microscopy showed higher expression of TRPV6 protein in the villous tip of HSD, while PMCA1 expression was increased in villous tip and crypt areas. The percentage of cells with highly expressed uroguanylin-an endogenous intestinal natriuretic peptide-was significantly higher in HSD group. In conclusion, HSD profoundly changed the intestinal morphology and turnover of epithelial cell, increased the expression of calcium transporters and uroguanylin. Our findings reflect pathophysiological adaptations in the intestine, which might be another target organ for drug discovery against HSD-induced osteopathy in the future.

Consuming probiotics protects against cadmium exposure from rice consumption while promotes gut health: An assessment based on a mouse model

Cadmium (Cd) in rice constitutes a global health risk. It is crucial to develop strategies that not only reduce the bioavailability of Cd in rice but also confer additional health benefits. One potential approach involves the consumption of probiotics, which can bind Cd in the intestines and enhance gut health. The effects of consuming Akkermansia muciniphila, Bifidobacterium pseudolongum, and Psychrobacter sp. on the bioavailability of Cd in rice and gut health were evaluated using in vivo mouse bioassays and in vitro Cd immobilization assays. In mice fed Cd-contaminated rice without dietary calcium (Ca) and iron (Fe) supplementation (i.e., under conditions of mineral deficiency), the intake of these probiotics insignificantly reduced Cd accumulation in the kidneys and livers, although it did promote Cd excretion via feces. This outcome was primarily due to the competition for Ca and Fe between the probiotics and the host, which led to increased intestinal expression of Ca and Fe transporters under mineral-deficient conditions, thereby mitigating the probiotics' ability to reduce Cd bioavailability. Conversely, in mice fed Cd-contaminated rice with adequate dietary Ca and Fe (i.e., under conditions of mineral adequacy), probiotic intake significantly decreased Cd concentrations in the kidneys by 60.0 %-72.0 % compared to the control group exposed to Cd. Additionally, probiotic consumption fostered the growth of beneficial gut bacteria and strengthened intestinal tight junctions, reducing the inflammatory response in the intestines. These findings suggest that combining probiotics with sufficient Ca and Fe intake can effectively reduce dietary Cd exposure and enhance gut health.

Glycated walnut meal peptide‑calcium chelates (COS-MMGGED-Ca): Preparation, characterization, and calcium absorption-promoting

This study isolated a novel peptide MMGGED with strong calcium-binding capacity from defatted walnut meal and synthesized a novel peptide‑calcium chelate COS-MMGGED-Ca with high stability via glycation. Structural characterization and computer simulation identified binding sites, while in vitro digestion stability and calcium transport experiments explored the chelate's properties. Results showed that after glycation, COS-MMGGED bound Ca2+ with 88.75 ± 1.75 %, mainly via aspartic and glutamic acids. COS-MMGGED-Ca released Ca2+ steadily (60.27 %), with thermal denaturation temperature increased by 18 °C and 37 °C compared to MMGGED-Ca, indicating good processing performance. Furthermore, COS-MMGGED significantly enhanced Ca2+ transport across Caco-2 monolayers, 1.13-fold and 1.62-fold higher than CaCl2 and MMGGED, respectively, at 240 h. These findings prove glycation enhances structural properties, stability, calcium loading, and transport of peptide‑calcium chelates, providing a scientific basis for developing novel efficient calcium supplements and high-value utilization of walnut meal.

Preparation, characterization, stability and replenishing calcium ability of Moringa oleifera leaf peptide-calcium chelates

Calcium deficiency has garnered significant attention as a global public health issue. A new generation of calcium supplements, peptide-calcium chelates, is expected to increase in market value. In this study, we produced MORP (MW < 1 kDa) from Moringa oleifera leaf protein via enzymatic hydrolysis for chelation with Ca2+ to produce MORP-Ca. SEM, EDS, FTIR and FS characterized the structure of MORP-Ca. The results indicate alterations in both the appearance and internal structure of MORP following calcium chelation. The functional groups of N-H, C-H, C-N, -C = O, -COO-, C-O, and -OH in MORP are involved in chelating Ca2+ to form MORP-Ca. In addition, MORP-Ca exhibits poor stability in the stomach; however, it demonstrates high stability in the intestine and under various temperature conditions. The results of the cellular experiments demonstrated that MORP-Ca is an effective promoter of calcium transport and absorption. MORP-Ca effectively increased bone mineral density and improved bone formation in animal studies. In addition, MORP-Ca supplementation improved the gut microbiota imbalance in rats fed a calcium-deficient diet, resulting in an increase in Firmicutes and a decrease in Actinobacteria. Thus, there is a connection between altered gastrointestinal flora and calcium absorption. LC-MS/MS and molecular docking analyses identified ARNEGRDL, RELIIGDR, YTPDYETK, YYTPDYETK, and IKFEFPAVDTL as key peptide sequences for the calcium-supplementing role of MORP (MW < 1 kDa). These results establish a theoretical foundation for the use of MORP-Ca as a calcium supplement or functional food.

Effects of Magnesium Forms on the Magnesium Balance and Jejunal Transporters in Healthy Rats

Magnesium (Mg) is a mineral necessary for many biological activities in mammals. Here, we compared the effect of two Mg compounds [Mg picolinate (MgPic) to Mg oxide (MgO)] on Mg bioavailability and intestinal Mg and calcium transporter protein levels. Three groups of 21 male Wistar-Albino rats were randomly allocated and fed a standard diet (control) or a 500 mg/kg Mg-supplemented (MgPic or MgO) diet for 8 weeks. The serum and liver Mg levels, Mg absorptivity, and retentivity were augmented in the MgPic group compared with the MgO group (P<0.05). Only MgPic supplementation elevated the expression of the genes encoding CLDN2, CLDN15, CNNM4, NCX1, PMCA1b, NCX2, and Calbindin-D9k in the jejunum by 1.59, 1.58, 1.70, 1.82, 2.02, 2.03, and 2.31 fold, respectively (P<0.05). Compared to the MgO-fed rats, MgPic rats had higher expression of the genes encoding NCX1, NCX2, PMCA1b, and Calbindin-D9k in the jejunum by 1.43, 1.72, 1.54, and 1.69 fold, respectively (P<0.01). These results suggest that MgPic increases Mg absorptivity and retentivity more than Mg bioavailability. In addition, MgPic can improve the paracellular and transcellular cationic mineral transport process. Thus, Mg deficiency disorders might be alleviated by MgPic more effectively than MgO.

LPL-RH suppresses bone loss in ovariectomised rat models

BACKGROUND

Evidence has revealed that oestrogen deprivation-induced osteolysis is microbiota-dependent and can be treated by probiotics. However, the underlying mechanism require further investigation. This study aims to provide additional evidence supporting the use of probiotics as an adjuvant treatment and to explore the pathophysiology of oestrogen-deprived osteolysis.

METHODS

Forty-five SD rats were randomly divided into five groups (n = 9). Rats from four groups were ovariectomised and treated with NS, calcium, probiotics, or calcium + probiotics, while one group underwent a sham operation and was treated with NS. The osteometabolic effects were evaluated, and the mechanistic role of the probiotic supplement was explored.

RESULTS

Intragastric administration of Bifidobacterium animalis subsp. lactis LPL-RH (LPL-RH) markedly suppressed osteoclastic activation and bone calcium loss by downregulating TRAP enzymatic activity, the OPG/RANKL ratio, and the downstream signalling pathway RANKL/TRAF6/NF-κB/NFATc1/TRAP in ovariectomised SD rats. LPL-RH also reduced CD4+IL-17 A+ TH17 cells in the bone marrow, the pro-osteoclastogenic cytokine IL-17 A, pro-inflammatory molecules (LPS), and its binding protein (LBP) in the blood. LPL-RH restored intestinal ZO-1, occludin, claudin 2, claudin 12, and claudin 15, which improved ileal histopathology, reduced ileal oxidative stress, and attenuated the LPS-responsive TLR4/MyD88/NF-κB pathway. Furthermore, 16 S rRNA sequencing revealed that LPL-RH altered the faecal microbiome by reducing the relative abundance of S24-7 at the family level and promoting Prevotella and Bacteroides at the genus level.

CONCLUSION

Collectively, LPL-RH suppressed osteoclastogenesis and osteolysis by modulating type 17 immunity and gut microbiome.

The L-type calcium channel CaV1.3: A potential target for cancer therapy

Cancer remains a prominent cause to life expectancy, and targeted cancer therapy stands as a pivotal approach in contemporary therapy. Calcium (Ca2+) signalling plays a multifaceted role in cancer progression, such as proliferation, invasion and distant metastasis. Otherwise, it also exerts an important influence on the efficacy of clinical treatment, including cancer therapy resistance. In this review we discuss the role of the L-type calcium channel CaV1.3 (calcium voltage-gated channel subunit alpha1 D) in different types of cancers, highlighting its potential as a therapeutic target for certain cancer types. The development of selective blockers of the CaV1.3 channel has been of great interest and is expected to be a new option for the treatment of cancers such as prostate cancer and endometrial cancer. We present the pharmacological properties of CaV1.3 and the current status of selective blocker development, and analyse the challenges and possible directions for breakthroughs in the development of tailored medicines.

The complex relationship between vitamin D and kidney stones: balance, risks, and prevention strategies

The association between vitamin D and kidney stones is characterized by a remarkable multi-dimensional complexity involving numerous physiological and metabolic pathways. Vitamin D is pivotal in maintaining calcium-phosphorus metabolic homeostasis and bone health. However, fluctuations in its intake, whether excessive or insufficient, May potentially increase the risk of kidney stones. Vitamin D exerts its influence on kidney stone formation indirectly by increasing the efficiency of intestinal calcium absorption and regulating renal calcium excretion. Moreover, there is a robust correlation between various states of vitamin D, particularly its active form, 1,25-dihydroxyvitamin D, and the development of numerous kidney stones. This finding underscores the necessity of individualized medical treatment in vitamin D supplementation and kidney stone prevention. When developing treatment strategies, it is essential to consider the patient's genetic background, lifestyle, environmental factors, and overall health. To prevent the formation of kidney stones, it is recommended that patients adopt a comprehensive approach, which May include measures such as moderate sun exposure, dietary modification, moderate exercise, and weight management. These preventive measures are designed to maintain healthy calcium and phosphorus metabolism and reduce kidney stone formation risk. Future studies should aim to elucidate the detailed mechanisms of vitamin D metabolism, individual differences, and the role of genes in this process. Furthermore, the role of lifestyle interventions in preventing kidney stones requires greater attention. Moreover, the implementation of large-scale, long-term prospective studies and randomized controlled trials will facilitate the assessment of the actual effects of diverse vitamin D supplementation strategies, thereby providing a robust scientific foundation for advancing more precise prevention strategies and clinical guidelines.

Plasma Biochemistry, Intestinal Health, and Transcriptome Analysis Reveal Why Laying Hens Produce Translucent Eggs

Producing translucent eggs has been found to reduce the quality and safety of the eggs, as well as the demand from consumers. However, the intestinal function and the molecular mechanism for the production of translucent eggs remain uncertain. A total of 120 eggs from 276-day-old Jining Bairi were divided into two groups based on eggshell translucence: the translucent egg group (group T) and the normal group (group C). Group T exhibited thicker eggshells and a lower egg yolk color. Subsequently, we divided the chickens into translucent and normal groups based on their egg quality. We then assessed the plasma biochemical index, intestinal morphology and structure, enzyme activity, and antioxidant capacity of the hens producing translucent eggs compared to those producing normal eggs. The results showed that the ratio of duodenal villus length to crypt depth, succinate dehydrogenase (SDH) activity, chymotrypsin, total ATPase (T-ATPase), alkaline phosphatase (AKP), and glutathione peroxidase (GSH-Px) activities were decreased in the hens produced translucent eggs (p < 0.05), but malondialdehyde (MDA) content was increased (p < 0.05); jejunal lipase activity, Na+K+-ATPase activity, total antioxidant capacity (T-AOC), and GSH-Px activities were decreased (p < 0.05) in group T; ileal amylase and Ca2+Mg2+-ATPase activities were also decreased (p < 0.05) in group T. In addition, we identified a total of 471 differentially expressed genes (DEGs) in duodenal tissue, with 327 up-regulated genes and 144 down-regulated genes (|log2FC| ≥ 1 and p < 0.05). Enrichment analysis showed that the up-regulated genes, such as GSTT1, GSTO2, and GSTA3, were mostly enriched in metabolism of xenobiotics by cytochrome P450, drug metabolism-cytochrome P450, and oxidative phosphorylation pathways. The results of our study indicate that plasma lipid metabolism disorder, decreased intestinal antioxidant capacity, and altered intestinal metabolism capabilities may influence the formation of translucent eggs.

Identification of calcium chelating peptides from peanut protein hydrolysate and absorption activity of peptide-calcium complex

BACKGROUND

Peanut peptides have good chelating ability with metal ions. However, there are few studies on the chelation mechanism of peanut peptides with calcium and absorption properties of peptide-calcium complex.

RESULTS

Peptides with high calcium chelating rate were isolated and purified from peanut protein hydrolysate (PPH), and the chelation rate of component F21 was higher (81.4 ± 0.8%). Six peptides were identified from component F21 by liquid chromatography-tandem mass spectrometry, and the frequency of acidic amino acids and arginine in the amino acid sequence was higher in all six peptides. Peanut peptide-calcium complex (PPH21-Ca) was prepared by selecting component F21 (PPH21). Ultraviolet analysis indicated that the chelate reaction occurred between peanut peptide and calcium ions. Fourier transform infrared analysis showed that the chelating sites were carboxyl and amino groups on the amino acid residues of peptides. Scanning electron microscopy revealed that the surface of peanut peptide had a smooth block structure, but the surface of the complex had a granular morphology. Caco-2 cell model tests revealed that the bioavailability of PPH21-Ca was 58.4 ± 0.5%, which was significantly higher than that of inorganic calcium at 37.0 ± 0.4%.

CONCLUSION

Peanut peptides can chelate calcium ions by carboxyl and amino groups, and the peptide-calcium complex had higher bioavailability. This study provides a theoretical basis for the development of new calcium supplement products that are absorbed easily. © 2024 Society of Chemical Industry.

Digested casein phosphopeptides impact intestinal calcium transport in vitro

Calcium is the most abundant mineral in the human body and is involved in critical physiological and cellular processes. It is essential for the development, maintenance, and integrity of bone tissue throughout life. Identifying new natural food-grade chelating agents to improve calcium uptake is of increasing interest. Casein phosphopeptides (CPPs), highly phosphorylated peptides obtained after enzymatic hydrolysis of caseins, represent promising calcium-chelating candidates. The aim of this study was to investigate, using cell culture models, the ability of a digested milk matrix enriched in CPPs to regulate calcium transport through the intestinal barrier and elucidate the involved mechanisms. To this end, a CPP-preparation underwent in vitro static digestion and was subsequently incubated with an intestinal barrier model to monitor calcium uptake and transport. Our results demonstrated that the digested CPP preparation enhanced the trans-epithelial calcium transport via paracellular pathways and that CPPs, identified by peptidomics, crossed the intestinal barrier in the same time.

Interaction and competition for intestinal absorption by zinc, iron, copper, and manganese at the intestinal mucus layer

Trace elements such as zinc, manganese, copper, or iron are essential for a wide range of physiological functions. It is therefore crucial to ensure an adequate supply of these elements to the body. Many previous investigations have dealt with the role of transport proteins, in particular their selectivity for, and competition between, different ions. Another so far less well investigated major factor influencing the absorption of trace elements seems to be the intestinal mucus layer. This gel-like substance covers the entire gastrointestinal tract and its physiochemical properties can be mainly assigned to the glycoproteins it contains, so-called mucins. Interaction with mucins has already been demonstrated for some metals. However, knowledge about the impact on the respective bioavailability and competition between those metals is still sketchy. This review therefore aims to summarize the findings and knowledge gaps about potential effects regarding the interaction between gastrointestinal mucins and the trace elements iron, zinc, manganese, and copper. Mucins play an indispensable role in the absorption of these trace elements in the neutral to slightly alkaline environment of the intestine, by keeping them in a soluble form that can be absorbed by enterocytes. Furthermore, the studies so far indicate that the competition between these trace elements for uptake already starts at the intestinal mucus layer, yet further research is required to completely understand this interaction.

Microbiome and physical activity

Regular physical activity promotes health benefits and contributes to develop the individual biological potential. Chronical physical activity performed at moderate and high-intensity is the intensity more favorable to produce health development in athletes and improve the gut microbiota balance. The athletic microbiome is characterized by increased microbial diversity and abundance as well as greater phenotypic versatility. In addition, physical activity and microbiota composition have bidirectional effects, with regular physical activity improving microbial composition and microbial composition enhancing physical performance. The improvement of physical performance by a healthy microbiota is related to different phenotypes: i) efficient metabolic development, ii) improved regulation of intestinal permeability, iii) favourable modulation of local and systemic inflammatory and efficient immune responses, iv) efective regulation of systemic pH and, v) protection against acute stressful events such as environmental exposure to altitude or heat. The type of sport, both intensity or volume characteristics promote microbiota specialisation. Individual assessment of the state of the gut microbiota can be an effective biomarker for monitoring health in the medium to long term. The relationship between the microbiota and the rest of the body is bidirectional and symbiotic, with a full connection between the systemic functions of the nervous, musculoskeletal, endocrine, metabolic, acid-base and immune systems. In addition, circadian rhythms, including regular physical activity, directly influence the adaptive response of the microbiota. In conclusion, regular stimuli of moderate- and high-intensity physical activity promote greater diversity, abundance, resilience and versatility of the gut microbiota. This effect is highly beneficial for human health when healthy lifestyle habits including nutrition, hydration, rest, chronoregulation and physical activity.

The potential benefits and mechanisms of protein nutritional intervention on bone health improvement

Osteoporosis commonly occurs in the older people and severe patients, with the main reason of the imbalance of bone metabolism (the rate of bone resorption exceeding the rate of bone formation), resulting in a decrease in bone mineral density and destruction of bone microstructure and further leading to the increased risk of fragility fracture. Recent studies indicate that protein nutritional support is beneficial for attenuating osteoporosis and improving bone health. This review summarized the classical mechanisms of protein intervention for alleviating osteoporosis on both suppressing bone resorption and regulating bone formation related pathways (promoting osteoblasts generation and proliferation, enhancing calcium absorption, and increasing collagen and mineral deposition), as well as the potential novel mechanisms via activating autophagy of osteoblasts, altering bone related miRNA profiles, regulating muscle-bone axis, and modulating gut microbiota abundance. Protein nutritional intervention is expected to provide novel approaches for the prevention and adjuvant therapy of osteoporosis.

Mineral supplementation for very preterm infants fed fortified human milk

OBJECTIVES

The safety and feasibility of human milk fortification with bovine colostrum (BC) were investigated in very preterm infants (FortiColos trial, NCT03537365). The BC product contained lower calcium, phosphate, and iron levels compared to the conventional fortifier (CF). We tested whether fortification with BC plus extra phosphate was sufficient to support the infants' mineral status assessed by blood biochemistry.

METHODS

In a randomised controlled trial (FortiColos, NCT03537365), mineral status was compared after fortification with BC versus CF. Blood calcium, phosphate, and haemoglobin were determined before and up to 3 weeks after the start of fortification (at the mean age of 8-9 days). The maximum supplemental doses of calcium, phosphate, and iron given were retrieved from patient medical records. Results were adjusted for gestational age, birth weight, and enteral nutrition with the mother's own milk and/or donor human milk.

RESULTS

Blood values of calcium, phosphate, and haemoglobin were similar between groups. Infants in both groups required supplementation with calcium and phosphate, but infants fed BC required higher maximum doses of phosphate and calcium (p < 0.05) to maintain acceptable blood values. Regardless of fortification groups, the most immature (<29 weeks of gestation) and small for gestational age infants showed a higher risk for requiring additional phosphate (odds ratio [OR]: 3.9, p < 0.001; OR: 2.14, p = 0.07, respectively).

CONCLUSIONS

The use of BC as a fortifier for human milk requires additional phosphate and calcium relative to a CF. Regardless of the fortification product, the most immature and small infants require additional mineral supplementation.

Modulation of Adverse Health Effects of Environmental Cadmium Exposure by Zinc and Its Transporters

Zinc (Zn) is the second most abundant metal in the human body and is essential for the function of 10% of all proteins. As metals cannot be synthesized or degraded, they must be assimilated from the diet by specialized transport proteins, which unfortunately also provide an entry route for the toxic metal pollutant cadmium (Cd). The intestinal absorption of Zn depends on the composition of food that is consumed, firstly the amount of Zn itself and then the quantity of other food constituents such as phytate, protein, and calcium (Ca). In cells, Zn is involved in the regulation of intermediary metabolism, gene expression, cell growth, differentiation, apoptosis, and antioxidant defense mechanisms. The cellular influx, efflux, subcellular compartmentalization, and trafficking of Zn are coordinated by transporter proteins, solute-linked carriers 30A and 39A (SLC30A and SLC39A), known as the ZnT and Zrt/Irt-like protein (ZIP). Because of its chemical similarity with Zn and Ca, Cd disrupts the physiological functions of both. The concurrent induction of a Zn efflux transporter ZnT1 (SLC30A1) and metallothionein by Cd disrupts the homeostasis and reduces the bioavailability of Zn. The present review highlights the increased mortality and the severity of various diseases among Cd-exposed persons and the roles of Zn and other transport proteins in the manifestation of Cd cytotoxicity. Special emphasis is given to Zn intake levels that may lower the risk of vision loss and bone fracture associated with Cd exposure. The difficult challenge of determining a permissible intake level of Cd is discussed in relation to the recommended dietary Zn intake levels.

Characterization and Mechanism of a Novel Rice Protein Peptide (AHVGMSGEEPE) Calcium Chelate in Enhancing Calcium Absorption in Caco-2 Cells

Rice protein peptides (RPP) are a potentially valuable source of high-quality calcium chelating properties. However, there is a lack of information regarding the calcium-absorption-promoting effect of RPP and its underlying mechanism. The present study adopted molecular docking methodologies to analyze the 10 most potent peptide segments from RPP. Results revealed that the peptide AHVGMSGEEPE (AHV) displayed optimal calcium binding properties (calcium-chelating capacity 55.69 ± 0.66 mg/g). Quantum chemistry analysis revealed that the AHV peptide effectively binds and forms stable complexes with calcium via the carbonyl oxygen atoms in valine at position 3 and the carbonyl of the C-terminal carboxyl group of glutamate at position 11. The spectral analysis results indicated that AHV may bind to calcium through carboxyl oxygen atoms, resulting in a transition from a smooth surface block-like structure to a dense granular structure. Furthermore, this study demonstrated that the 4 mmol/L AHV-Ca chelate (61.75 ± 13.23 μg/well) significantly increases calcium absorption compared to 1 mM CaCl2 (28.57 ± 8.59 μg/well) in the Caco-2 cell monolayer. In terms of mechanisms, the novel peptide-calcium chelate AHV-Ca derived from RPP exerts a cell-level effect by upregulating the expression of TRPV6 calcium-ion-channel-related genes and proteins (TRPV6 and Calbindin-D9k). This study provides a theoretical basis for developing functional foods with the AHV peptide as ingredients to improve calcium absorption.

Fermented foods and gastrointestinal health: underlying mechanisms

Although fermentation probably originally developed as a means of preserving food substrates, many fermented foods (FFs), and components therein, are thought to have a beneficial effect on various aspects of human health, and gastrointestinal health in particular. It is important that any such perceived benefits are underpinned by rigorous scientific research to understand the associated mechanisms of action. Here, we review in vitro, ex vivo and in vivo studies that have provided insights into the ways in which the specific food components, including FF microorganisms and a variety of bioactives, can contribute to health-promoting activities. More specifically, we draw on representative examples of FFs to discuss the mechanisms through which functional components are produced or enriched during fermentation (such as bioactive peptides and exopolysaccharides), potentially toxic or harmful compounds (such as phytic acid, mycotoxins and lactose) are removed from the food substrate, and how the introduction of fermentation-associated live or dead microorganisms, or components thereof, to the gut can convey health benefits. These studies, combined with a deeper understanding of the microbial composition of a wider variety of modern and traditional FFs, can facilitate the future optimization of FFs, and associated microorganisms, to retain and maximize beneficial effects in the gut.

Vitamin D, Calbindin, and calcium signaling: Unraveling the Alzheimer's connection

Calcium is a ubiquitous second messenger that is indispensable in regulating neurotransmission and memory formation. A precise intracellular calcium level is achieved through the concerted action of calcium channels, and calcium exerts its effect by binding to an array of calcium-binding proteins, including calmodulin (CAM), calcium-calmodulin complex-dependent protein kinase-II (CAMK-II), calbindin (CAL), and calcineurin (CAN). Calbindin orchestrates a plethora of signaling events that regulate synaptic transmission and depolarizing signals. Vitamin D, an endogenous fat-soluble metabolite, is synthesized in the skin upon exposure to ultraviolet B radiation. It modulates calcium signaling by increasing the expression of the calcium-sensing receptor (CaSR), stimulating phospholipase C activity, and regulating the expression of calcium channels such as TRPV6. Vitamin D also modulates the activity of calcium-binding proteins, including CAM and calbindin, and increases their expression. Calbindin, a high-affinity calcium-binding protein, is involved in calcium buffering and transport in neurons. It has been shown to inhibit apoptosis and caspase-3 activity stimulated by presenilin 1 and 2 in AD. Whereas CAM, another calcium-binding protein, is implicated in regulating neurotransmitter release and memory formation by phosphorylating CAN, CAMK-II, and other calcium-regulated proteins. CAMK-II and CAN regulate actin-induced spine shape changes, which are further modulated by CAM. Low levels of both calbindin and vitamin D are attributed to the pathology of Alzheimer's disease. Further research on vitamin D via calbindin-CAMK-II signaling may provide newer insights, revealing novel therapeutic targets and strategies for treatment.

Vitamin D3 mediated peptides-calcium chelate self-assembly: Fabrication, stability and improvement on cellular calcium transport

A self-assembled peptides-calcium-Vitamin D3 ternary delivery system (CSPH-Ca-VD3) was prepared to investigate the promotion of cellular calcium transport. The constructed CSPH-Ca-VD3 nanocomplex exhibited a spherical structure with a size of 135.2 ± 10.2 nm. Based on the thermodynamic calculation of fluorescent spectra, hydrophobic interaction was shown as the major driving force for this nanocomplex structure. CSPH-Ca-VD3 nanocomplex possessed excellent stability during simulated gastrointestinal digestion, contributing to the prevention of acid degradation of VD3 and the enhancement of calcium solubility. Furthermore, the calcium transport efficiency in the form of CSPH-Ca-VD3 (4 mg/mL) across a Caco-2 cells monolayer was significantly increased 2.3-fold compared to that of free Ca2+, mainly attributed to the upregulation in the presence of CSPH-Ca-VD3 of TRPV6, calbindin D9k and PMCA1b expression in Caco-2 cells. The present study provided a basis for developing a novel delivery system of peptides-calcium chelate with the dual effects of VD3 protection and calcium uptake promotion.

Structural characterization and calcium absorption-promoting effect of sucrose-calcium chelate in Caco-2 monolayer cells and mice

Sucrose emerges as a chelating agent to form a stable sucrose-metal-ion chelate that can potentially improve metal-ion absorption. This study aimed to analyze the structure of sucrose-calcium chelate and its potential to promote calcium absorption in both Caco-2 monolayer cells and mice. The characterization results showed that calcium ions mainly chelated with hydroxyl groups in sucrose to produce sucrose-calcium chelate, altering the crystal structure of sucrose (forming polymer particles) and improving its thermal stability. Sucrose-calcium chelate dose dependently increased the amount of calcium uptake, retention, and transport in the Caco-2 monolayer cell model. Compared to CaCl2 , there was a significant improvement in the proportion of absorbed calcium utilized for transport but not retention (93.13 ± 1.75% vs. 67.67 ± 7.55%). Further treatment of calcium channel inhibitors demonstrated the active transport of sucrose-calcium chelate through Cav1.3. Cellular thermal shift assay and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays indicated that the ability of sucrose-calcium chelate to promote calcium transport was attributed to its superior ability to bind with PMCA1b, a calcium transporter located on the basement membrane, and stimulate its gene expression compared to CaCl2 . Pharmacokinetic analysis of mice confirmed the calcium absorption-promoting effect of sucrose-calcium chelate, as evident by the higher serum calcium level (44.12 ± 1.90 mg/L vs. 37.42 ± 1.88 mmol/L) and intestinal PMCA1b gene expression than CaCl2 . These findings offer a new understanding of how sucrose-calcium chelate enhances intestinal calcium absorption and could be used as an ingredient in functional foods to treat calcium deficiency. PRACTICAL APPLICATION: The development of high-quality calcium supplements is crucial for addressing the various adverse symptoms associated with calcium deficiency. This study aimed to prepare a sucrose-calcium chelate and analyze its structure, as well as its potential to enhance calcium absorption in Caco-2 monolayer cells and mice. The results demonstrated that the sucrose-calcium chelate effectively promoted calcium absorption. Notably, its ability to enhance calcium transport was linked to its strong binding with PMCA1b, a calcium transporter located on the basement membrane, and its capacity to stimulate PMCA1b gene expression. These findings contribute to a deeper understanding of how the sucrose-calcium chelate enhances intestinal calcium absorption and suggest its potential use as an ingredient in functional foods for treating calcium deficiency.

PMAIP1, a novel diagnostic and potential therapeutic biomarker in osteoporosis

BACKGROUND

Osteoporosis is a common endocrine metabolic bone disease, which may lead to severe consequences. However, the unknown molecular mechanism of osteoporosis, the observable side effects of present treatments and the inability to fundamentally improve bone metabolism seriously restrict the impact of prevention and treatment. The study aims to identify potential biomarkers from osteoclast progenitors, specifically peripheral blood monocytes on predicting the osteoporotic phenotype.

METHODS

Datasets were obtained from Gene Expression Omnibus (GEO). Based on the differentially expressed genes (DEGs) and GSEA results, GO and KEGG analyses were performed using the DAVID database and Metascape database. PPI network, TF network, drug-gene interaction network, and ceRNA network were established to determine the hub genes. Its osteogenesis, migration, and proliferation abilities in bone marrow mesenchymal stem cells (BMSCs) were validated through RT-qPCR, WB, ALP staining, VK staining, wound healing assay, transwell assay, and CCK-8 assay.

RESULTS

A total of 63 significant DEGs were screened. Functional and pathway enrichment analysis discovered that the functions of the significant DEGs (SDEGs) are mainly related to immunity and metal ions. A comprehensive evaluation of all the network analyses, PMAIP1 was defined as osteoporosis's core gene. This conclusion was further confirmed in clinical cohort data. A series of experiments demonstrated that the PMAIP1 gene can promote the osteogenesis, migration and proliferation of BMSC cells.

CONCLUSIONS

All of these outcomes showed a new theoretical basis for further research in the treatment of osteoporosis, and PMAIP1 was identified as a potential biomarker for osteoporosis diagnosis and treatment.

The Effects of Acid on Calcium and Phosphate Metabolism

A variety of changes in mineral metabolism aiming to restore acid-base balance occur in acid loading and metabolic acidosis. Phosphate plays a key role in defense against metabolic acidosis, both as an intracellular and extracellular buffer, as well as in the renal excretion of excess acid in the form of urinary titratable acid. The skeleton acts as an extracellular buffer in states of metabolic acidosis, as the bone matrix demineralizes, leading to bone apatite dissolution and the release of phosphate, calcium, carbonate, and citrate into the circulation. The renal handling of calcium, phosphate and citrate is also affected, with resultant hypercalciuria, hyperphosphaturia and hypocitraturia.

Phosphorylation modification of bovine bone collagen peptide enhanced its effect on mineralization of MC3T3-E1 cells via improving calcium-binding capacity

This study aimed to investigate the effect of phosphorylation modification of collagen peptide on its calcium-binding capacity and pro-mineralization activity. In this study, collagen peptide (Leu-Thr-Phe, LTF) and phosphorylated LTF (P-LTF) were synthesized and further chelated with calcium ions. The results showed that phosphorylation of LTF significantly enhanced its calcium-binding capacity. Spectra analysis revealed that the calcium-binding sites of P-LTF were mainly carbonyl, carboxyl, and phosphate groups. Molecular docking further demonstrated that the phosphate group introduced by phosphorylation enhanced the calcium-binding capacity of LTF by ionic bonds and coordination bonds. The stability analysis results suggested that intestinal fluid could repair the peptide-calcium complex destroyed by gastric fluid. The cell experiment displayed that P-LTF-Ca significantly improved the mineralization activity of MC3T3-E1 cells, and the order of effective influence was P-LTF-Ca > LTF-Ca > P-LTF > LTF. This study provided the theoretical basis for the potential application of phosphorylation modification in improving bone health.

Casein phosphopeptide calcium chelation: preparation optimization, in vitro gastrointestinal simulated digestion, and peptide fragment exploration

BACKGROUND

Calcium is important in the formation of bones and teeth, cell metabolism, and other physiological activities. In this work, casein phosphopeptide-calcium chelate (CPP-Ca) was synthesized and the optimal process parameters for the chelation reaction were obtained. The bioavailability of calcium in CPP-Ca was investigated by in vitro gastrointestinal simulated digestion. The existence of phytic acid and oxalic acid in the digestion system was evaluated to clarify the calcium holding ability of casein phosphopeptide (CPP). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify oligopeptides from CPP-Ca.

RESULTS

The optimal process parameters for the chelation reaction were: peptide concentration 7.76 mgmL-1 , pH 8.54, and reaction temperature 43.3 °C. The digestion in vitro results indicated that the calcium release rate of CPP-Ca in the stomach for 2 h reached 85%, and about 50% of the ionized calcium was re-chelated with CPP in the intestine. Phytic acid and oxalic acid could lead to a sharp decrease in soluble calcium but around 50% of the calcium was still retained in the form of chelates in the presence of CPP. The LC-MS/MS identified 19 casein-derived oligopeptides after digestion, and calcium modifications were found on eight peptides derived from β-casein and αs2 -casein.

CONCLUSIONS

This study clarified the excellent calcium holding capacity of CPP in the presence of phytic acid and oxalic acid. Liquid chromatography-tandem mass spectrometry also revealed peptide changes, and identified peptides that chelate with calcium. These findings provided significant insights that could be relevant to the further utilization and product development of peptide-calcium chelate in the food industry. © 2023 Society of Chemical Industry.

Is Kidney Stone Associated with Thyroid Disease? The United States National Health and Nutrition Examination Survey 2007-2018

BACKGROUND

Kidney stones and thyroid disease are two common diseases in the general population, with multiple common risk factors. The associations between kidney stones and thyroid disease are unclear.

AIM

This study aims to assess the association between 'once had a thyroid disease' and the odds of kidney stones.

METHODS

Adult participants from the National Health and Nutrition Examination Survey (NHANES) 2007-2018 with reliable kidney stone and thyroid disease data were included. Adjusting for age, gender, race, education level, and marital status, diabetes, hypertension, gout, angina pectoris, stroke, and asthma, logistic regression was used to examine the relationship between kidney stones and thyroid illness.

RESULTS

Using stratified analysis, the association between thyroid illness and kidney stones was investigated further. Among the participants, 4.9% had kidney stones, and 10.1% had thyroid disease. Kidney stone was associated with thyroid disease (OR=1.441, (95% CI:1.294-1.604), p <0.01), which remained significant (OR=1.166, (95% CI:1.041-1.305), p <0.01) after adjustments with age, gender, race, education level and marital status, diabetes, hypertension, gout, angina pectoris, stroke, and asthma. Stratified by blood lead, blood cadmium, and blood urea nitrogen levels in the human body, the odds of kidney stones still increased with once having a previous thyroid disease.

CONCLUSIONS

In this large nationally representative survey over 10 years, kidney stone was strongly associated with thyroid disease. In this cross-sectional study, we explored the association between thyroid disease and kidney stones, which may help clinicians intervene in them early.

Pectin Modulates Calcium Absorption in Polarized Caco-2 Cells via a Pathway Distinct from Vitamin D Stimulation

Pectin, a type of soluble fiber, promotes morphological changes in the small intestinal villi. Although its physiological significance is unknown, we hypothesized that changes in villus morphology enhance the efficiency of nutrient absorption in the small intestine and investigated the effect of pectin derived from persimmon on calcium absorption using polarized Caco-2 cells. In polarized Caco-2 cells, pectin altered the mRNA expression levels of substances involved in calcium absorption and the regulation of intracellular calcium concentration and significantly reduced calcium absorption. Although this was comparable to the results of absorption and permeability associated with the addition of active vitamin D, the simultaneous action of pectin and active vitamin D did not show any additive effects. Furthermore, as active vitamin D significantly increases the activity of intestinal alkaline phosphatase (ALP), which is known to be involved in the regulation of intestinal absorption of calcium and lipids, we also investigated the effect of pectin on intestinal ALP activity. As a result, it was found that, unlike the effect of active vitamin D, pectin significantly reduced intestinal ALP activity. These results suggest that pectin stimulates polarized Caco-2 cells through a mechanism distinct from the regulation of calcium absorption by vitamin D, modulating total calcium absorption from the elongated villi through morphological changes in the small intestine by suppressing it at the cellular level.

Disorders of Calcium and Magnesium

This review will discuss the importance and homeostasis of calcium and magnesium in the human body, as well as the implications and treatment of disordered calcium and magnesium. With calcium and magnesium often considered to be the "forgotten cations" in medicine, it is our hope that this review will lead providers to evaluate for and effectively manage these electrolyte disorders in the emergency department.

Expert consensus on multidisciplinary approach to the diagnosis and treatment of primary hyperparathyroidism in pregnancy in China

Primary hyperparathyroidism in pregnancy is a rare disease that can have detrimental effects on both maternal and fetal/neonatal outcomes. The physiological changes that occur during pregnancy can complicate the diagnosis, imaging examinations, and treatment of this disorder. To enhance our understanding and management of primary hyperparathyroidism in pregnancy, experts from various fields, including endocrinology, obstetrics, surgery, ultrasonography, nuclear medicine, pediatrics, nephrology, and general practice in China, collaborated to develop a consensus addressing the critical aspects of the diagnosis and treatment of primary hyperparathyroidism in pregnancy with a multidisciplinary team approach. This consensus provides valuable guidance for healthcare professionals in managing this condition, ultimately improving outcomes for both mothers and their babies.

Vitamins as regulators of calcium-containing kidney stones - new perspectives on the role of the gut microbiome

Calcium-based kidney stone disease is a highly prevalent and morbid condition, with an often complicated and multifactorial aetiology. An abundance of research on the role of specific vitamins (B6, C and D) in stone formation exists, but no consensus has been reached on how these vitamins influence stone disease. As a consequence of emerging research on the role of the gut microbiota in urolithiasis, previous notions on the contribution of these vitamins to urolithiasis are being reconsidered in the field, and investigation into previously overlooked vitamins (A, E and K) was expanded. Understanding how the microbiota influences host vitamin regulation could help to determine the role of vitamins in stone disease.

The effects and predictive value of calcium and magnesium concentrations on nutritional improvement, inflammatory response and diagnosis in patients with Crohn's disease

BACKGROUND

Crohn's disease (CD) is a progressive inflammatory disease of the gastrointestinal tract associated with malnutrition, high levels of inflammation and calcium and magnesium deficiencies. However, the relationships between these symptoms are poorly defined.

METHOD

Seventy-six adult CD patients who had not yet started treatment and 83 healthy volunteers were recruited. The dietary intakes, serum calcium and magnesium levels, nutritional indicators and biochemical markers of disease activity were measured.

RESULTS

Most participants had inadequate magnesium and calcium intake. The serum magnesium and calcium levels, as well as nutritional and inflammatory indicators, differed significantly between CD patients and controls, especially in the active phase. Serum levels of magnesium and calcium correlated with both nutritional status and inflammation. The cut-off values for CD development were 0.835 mmol/L (magnesium) and 2.315 mmol/L (calcium), whereas those for the active phase were 0.785 and 2.28 mmol/L, respectively.

CONCLUSION

Adequate intake of magnesium and calcium may both improve the nutritional status of CD patients and reduce inflammation, benefiting disease relief. As both magnesium and calcium reflect CD status, they may be useful markers for CD diagnosis and disease activity.

Ion channels and transporters regulate nutrient absorption in health and disease

Ion channels and transporters are ubiquitously expressed on cell membrane, which involve in a plethora of physiological process such as contraction, neurotransmission, secretion and so on. Ion channels and transporters is of great importance to maintaining membrane potential homeostasis, which is essential to absorption of nutrients in gastrointestinal tract. Most of nutrients are electrogenic and require ion channels and transporters to absorb. This review summarizes the latest research on the role of ion channels and transporters in regulating nutrient uptake such as K+ channels, Ca2+ channels and ion exchangers. Revealing the mechanism of ion channels and transporters associated with nutrient uptake will be helpful to provide new methods to diagnosis and find potential targets for diseases like diabetes, inflammatory bowel diseases, etc. Even though some of study still remain ambiguous and in early stage, we believe that ion channels and transporters will be novel therapeutic targets in the future.

Transcriptome wide analyses reveal intraspecific diversity in thermal stress responses of a dominant habitat-forming species

The impact of climate change on biodiversity has stimulated the need to understand environmental stress responses, particularly for ecosystem engineers whose responses to climate affect large numbers of associated organisms. Distinct species differ substantially in their resilience to thermal stress but there are also within-species variations in thermal tolerance for which the molecular mechanisms underpinning such variation remain largely unclear. Intertidal mussels are well-known for their role as ecosystem engineers. First, we exposed two genetic lineages of the intertidal mussel Perna perna to heat stress treatments in air and water. Next, we ran a high throughput RNA sequencing experiment to identify differences in gene expression between the thermally resilient eastern lineage and the thermally sensitive western lineage. We highlight different thermal tolerances that concord with their distributional ranges. Critically, we also identified lineage-specific patterns of gene expression under heat stress and revealed intraspecific differences in the underlying transcriptional pathways in response to warmer temperatures that are potentially linked to the within-species differences in thermal tolerance. Beyond the species, we show how unravelling within-species variability in mechanistic responses to heat stress promotes a better understanding of global evolutionary trajectories of the species as a whole in response to changing climate.

Calcifediol: a review of its pharmacological characteristics and clinical use in correcting vitamin D deficiency

BACKGROUND

In addition to the role of vitamin D in bone mineralization, calcium and phosphate homeostasis, and skeletal health, evidence suggests an association between vitamin D deficiency and a wide range of chronic conditions. This is of clinical concern given the substantial global prevalence of vitamin D deficiency. Vitamin D deficiency has traditionally been treated with vitamin D₃ (cholecalciferol) or vitamin D₂ (ergocalciferol). Calcifediol (25-hydroxyvitamin D₃) has recently become available more widely.

METHODS

By means of targeted literature searches of PubMed, this narrative review overviews the physiological functions and metabolic pathways of vitamin D, examines the differences between calcifediol and vitamin D₃, and highlights clinical trials conducted with calcifediol in patients with bone disease or other conditions.

RESULTS

For supplemental use in the healthy population, calcifediol can be used at doses of up to 10 µg per day for children ≥ 11 years and adults and up to 5 µg/day in children 3-10 years. For therapeutic use of calcifediol under medical supervision, the dose, frequency and duration of treatment is determined according to serum 25(OH)D concentrations, condition, type of patient and comorbidities. Calcifediol differs pharmacokinetically from vitamin D₃ in several ways. It is independent of hepatic 25-hydroxylation and thus is one step closer in the metabolic pathway to active vitamin D. At comparable doses to vitamin D₃, calcifediol achieves target serum 25(OH)D concentrations more rapidly and in contrast to vitamin D₃, it has a predictable and linear dose-response curve irrespective of baseline serum 25(OH)D concentrations. The intestinal absorption of calcifediol is relatively preserved in patients with fat malabsorption and it is more hydrophilic than vitamin D₃ and thus is less prone to sequestration in adipose tissue.

CONCLUSION

Calcifediol is suitable for use in all patients with vitamin D deficiency and may be preferable to vitamin D₃ for patients with obesity, liver disease, malabsorption and those who require a rapid increase in 25(OH)D concentrations.

New insight into scale inhibition during tea brewing: Ca2+/Mg2+ complexing and alkalinity consumption

Scale not only affects the taste and color of water, but also increases the risks of osteoporosis and cardiovascular diseases associated with drinking it. As a popular beverage, tea is rich many substances that have considerable potential for scale inhibition, including protein, tea polyphenols and organic acids. In this study, the effect of tea brewing on scale formation was explored. It was found that the proteins, catechins and organic acids in tea leaves could be released when the green tea was brewed in water with sufficient hardness and alkalinity. The tea-released protein was able to provide carboxyl groups to chelate with calcium ions (Ca²⁺), preventing the Ca²⁺ from reacting with the carbonate ions (CO₃^2-). The B rings of catechins were another important structure in the complexation of Ca²⁺ and magnesium ions (Mg²⁺). The carboxyl and hydroxyl groups on the organic acids was able to form five-membered chelating rings with Ca²⁺ and Mg²⁺, resulting in a significant decrease in Ca²⁺ from 100.0 to 60.0 mg/L. Additionally, the hydrogen ions (H⁺) provided by the organic acids consumed and decreased the alkalinity of the water from 250.0 to 131.4 mg/L, leading to a remarkable reduction in pH from 8.93 to 7.73. It further prevented the bicarbonate (HCO₃^-) from producing CO₃^2- when the water was heated. The reaction of the tea constituents with the hardness and alkalinity inhibited the formation of scale, leading to a significant decrease in turbidity from 10.6 to 1.4 NTU. Overall, this study provides information to help build towards an understanding of the scale inhibition properties of tea and the prospects of tea for anti-scaling in industrial applications.

Calcium bioaccessibility increased during gastrointestinal digestion of α-lactalbumin and β-lactoglobulin

Calcium bioaccessibility depends on the amount of soluble calcium under intestinal digestion. The changes in calcium during in vitro static digestion of α-lactalbumin and β-lactoglobulin in presence of calcium chloride (0 mM, 20 mM and 50 mM) were followed by combining electrochemical determination of free calcium with the determination of soluble calcium by inductively coupled plasma optical emission spectroscopy. α-Lactalbumin and, more evident, β-lactoglobulin were found to increase calcium bioaccessibility with increasing intestinal digestion time by around 5% and 10%, respectively, due to the complex binding of calcium to peptides formed from protein hydrolysis by gastrointestinal enzymes. In vitro digested samples of β-lactoglobulin in presence of CaCl₂ had nearly twice as much complex bound calcium as α-lactalbumin samples. The calcium bioaccessibility decreased significantly with the increasing concentration of added calcium chloride, although the amount of calcium chloride had little effect on the extension of digestion of α-lactalbumin and β-lactoglobulin. Simulated digestion fluids were found to have a negative effect on calcium bioaccessibility, especially the presence of hydrogen phosphate, and the amount of precipitated calcium increased significantly with increasing amount of added calcium chloride. Based on analysis and visualization by sequences of the peptides formed during digestion of α-lactalbumin and β-lactoglobulin, it was observed that peptides containing aspartic acid and glutamic acid acting as calcium chelators, may prevent precipitation of calcium in the intestines and increase calcium bioaccessibility. These results provide knowledge for the design of new dairy based functional foods to prevent calcium deficiency.

Expression of phosphate and calcium transporters and their regulators in parotid glands of mice

The concentration of inorganic phosphate (Pi) in plasma is under hormonal control, with deviations from normal values promptly corrected to avoid hyper- or hypophosphatemia. Major regulators include parathyroid hormone (PTH), fibroblast growth factor 23 (FGF-23), and active vitamin D₃ (calcitriol). This control is achieved by mechanisms largely dependent on regulating intestinal absorption and renal excretion, whose combined actions stabilise plasma Pi levels at around 1-2 mM. Instead, Pi concentrations up to 13 and 40 mM have been measured in saliva from humans and ruminants, respectively, suggesting that salivary glands have the capacity to concentrate Pi. Here we analysed the transcriptome of parotid glands, ileum, and kidneys of mice, to investigate their potential differences regarding the expression of genes responsible for epithelial transport of Pi as well as their known regulators. Given that Pi and Ca²⁺ homeostasis are tightly connected, the expression of genes involved in Ca²⁺ homeostasis was also included. In addition, we studied the effect of vitamin D₃ treatment on the expression of Pi and Ca²⁺ regulating genes in the three major salivary glands. We found that parotid glands are equipped preferentially with Slc20 rather than with Slc34 Na⁺/Pi cotransporters, are suited to transport Ca²⁺ through the transcellular and paracellular route and are potential targets for PTH and vitamin D₃ regulation.

Vitamin D in Neurological Diseases

Vitamin D may have multiple effects on the nervous system and its deficiency can represent a possible risk factor for the development of many neurological diseases. Recent studies are also trying to clarify the different effects of vitamin D supplementation over the course of progressive neurological diseases. In this narrative review, we summarise vitamin D chemistry, metabolism, mechanisms of action, and the recommended daily intake. The role of vitamin D on gene transcription and the immune response is also reviewed. Finally, we discuss the scientific evidence that links low 25-hydroxyvitamin D concentrations to the onset and progression of severe neurological diseases, such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, migraine, diabetic neuropathy and amyotrophic lateral sclerosis. Completed and ongoing clinical trials on vitamin D supplementation in neurological diseases are listed.

Effects of Dietary Phosphorus Levels on Growth Performance, Phosphorus Utilization and Intestinal Calcium and Phosphorus Transport-Related Genes Expression of Juvenile Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

A 60-day feeding trial was performed to assess the effects of dietary phosphorus levels on growth performance, body composition, phosphorus utilization, plasma physiological parameters and intestinal Ca and P transport-related gene expression of juvenile Chinese soft-shelled turtle (P. sinensis). Four diets containing available P at graded levels of 0.88%, 1.00%, 1.18% and 1.63% (termed as D0.88, D1.00, D1.18 and D1.63, respectively) were formulated and each diet was fed to turtles (5.39 ± 0.02 g) in sextuplicate. The turtles were randomly distributed to 24 tanks with 8 turtles per tank. The results indicated that final body weight, specific growth rate, feed conversion ratio and protein efficiency ratio performed best in turtles fed 1.00% available P diet. The crude lipids of the whole body exhibited a decreasing trend with the dietary available P, whereas the calcium and phosphorus of the whole body and bone phosphorus showed an opposite tendency. The apparent digestibility coefficient of phosphorus declined with the dietary available P. Turtles fed 1.00% available phosphorus had the highest phosphorus retention ratio compared with other treatments. Simultaneously they had significantly lower phosphorus loss than turtles fed D1.18 and D1.63 and had no differences in this respect from turtles fed a low-phosphorus diet. It was noteworthy that the lowest plasma calcium concentrations, and alkaline phosphatase activities in plasma and liver, were discovered in turtles fed the diet containing 1.63% available phosphorus. In addition, the high-phosphorus diet resulted in significantly down-regulated expression of intestinal phosphorus and calcium transport-related key genes. In conclusion, the available phosphorus requirement of juvenile P. sinensis was determined at 1.041% (total phosphorus was 1.80%) based on quadratic regression of weight gain rate, and excessive dietary phosphorus stunted turtle growth possibly via inhibiting intestinal calcium absorption.

The role of melatonin in the development of postmenopausal osteoporosis

Melatonin is an important endogenous hormone that modulates homeostasis in the microenvironment. Recent studies have indicated that serum melatonin levels are closely associated with the occurrence and development of osteoporosis in postmenopausal women. Exogenous melatonin could also improve bone mass and increase skeletal strength. To determine the underlying mechanisms of melatonin in the prevention and treatment of postmenopausal osteoporosis, we performed this review to analyze the role of melatonin in bone metabolism according to its physiological functions. Serum melatonin is related to bone mass, the measurement of which is a potential method for the diagnosis of osteoporosis. Melatonin has a direct effect on bone remodeling by promoting osteogenesis and suppressing osteoclastogenesis. Melatonin also regulates the biological rhythm of bone tissue, which benefits its osteogenic effect. Additionally, melatonin participates in the modulation of the bone microenvironment. Melatonin attenuates the damage induced by oxidative stress and inflammation on osteoblasts and prevents osteolysis from reactive oxygen species and inflammatory factors. As an alternative drug for osteoporosis, melatonin can improve the gut ecology, remodel microbiota composition, regulate substance absorption and maintain metabolic balance, all of which are beneficial to the health of bone structure. In conclusion, our review systematically demonstrates the effects of melatonin on bone metabolism. Based on the evidence in this review, melatonin will play a more important role in the diagnosis, prevention and treatment of postmenopausal osteoporosis.

The Formation, Structural Characteristics, Absorption Pathways and Bioavailability of Calcium–Peptide Chelates

Calcium is one of the most important mineral elements in the human body and is closely related to the maintenance of human health. To prevent calcium deficiency, various calcium supplements have been developed, but their application tends to be limited by low calcium content and highly irritating effects on the stomach, among other side effects. Recently, calcium–peptide chelates, which have excellent stability and are easily absorbed, have received attention as an alternative emerging calcium supplement. Calcium-binding peptides (CaBP) are usually obtained via the hydrolysis of animal or plant proteins, and calcium-binding capacity (CaBC) can be further improved through chromatographic purification techniques. In calcium ions, the phosphate group, carboxylic group and nitrogen atom in the peptide are the main binding sites, and the four modes of combination are the unidentate mode, bidentate mode, bridging mode and α mode. The stability and safety of calcium–peptide chelates are discussed in this paper, the intestinal absorption pathways of calcium elements and peptides are described, and the bioavailability of calcium–peptide chelates, both in vitro and in vivo, is also introduced. This review of the research status of calcium–peptide chelates aims to provide a reasonable theoretical basis for their application as calcium supplementation products.

A comprehensive review on preparation, structure-activities relationship, and calcium bioavailability of casein phosphopeptides

Calcium is one of the important elements for human health. Calcium deficiencies can lead to numerous diseases. Calcium chelating peptides have shown potential application in the management of calcium deficiencies. Casein phosphopeptides (CPP) are phosphoseryl-containing fragments of casein by enzymatic hydrolysis or fermentation during manufacture of milk products as well as during intestinal digestion. An increasing number of CPP with the ability to facilitate and enhance the bioavailability of calcium are being discovered and identified. In this review, 249 reported CPP derived from four types of bovine casein (αs1, αs2, β and κ) were collected, and the amino acid sequence and phosphoserine group information were sorted out. This review outlines the current enzyme hydrolysis, detection methods, purification, structure-activity relationship and mechanism of intestinal calcium absorption in vitro and in vivo as well as application of CPP.