Phytosterols can impair vitamin D intestinal absorption in vitro and in mice

Dietary cholesterol increases body levels of oral administered vitamin D3 in mice

Vitamin D and cholesterol share the same intestinal transporters. Thus, it was hypothesized that dietary cholesterol adversely affects vitamin D uptake. The current studies investigated the influence of cholesterol on the availability of oral vitamin D. First, 42 wild-type mice received a diet with 25 µg/kg labelled vitamin D3 (vitamin D3-d3), supplemented with either 0% (control), 0.2%, 0.4%, 0.6%, 0.8%, 1.0% or 2.0% cholesterol for four weeks to investigate vitamin D uptake. In a second study, 10 wild-type mice received diets containing 0% (control) or 1% cholesterol over four weeks to determine cholesterol-induced changes in bile acids. Finally, we investigated the impact of cholesterol versus bile acids on vitamin D uptake in Caco-2 cells. Surprisingly, dietary cholesterol intake was associated with 40% higher serum levels of vitamin D3-d3 and 2.3-fold higher vitamin D3-d3 concentrations in the liver compared to controls. The second study showed that cholesterol intake resulted in higher concentrations of faecal bile acids (control: 3.55 ± 1.71 mg/g dry matter; 1% dietary cholesterol: 8.95 ± 3.69 mg/g dry matter; P < 0.05) and changes in the bile acid profile with lower contents of muricholic acids (P < 0.1) and higher contents of taurodeoxycholic acid (P < 0.01) compared to controls. In-vitro analyses revealed that taurocholic acid (P < 0.001) but not cholesterol increased the cellular uptake of vitamin D by Caco-2 cells. To conclude, dietary cholesterol seems to improve the bioavailability of oral vitamin D by stimulating the release of bile acids and increasing the hydrophobicity of bile.

Pharmacokinetics of vitamin dosage forms: A complete overview

Vitamins are crucial for sustaining life because they play an essential role in numerous physiological processes. Vitamin deficiencies can lead to a wide range of severe health issues. In this context, there is a need to administer vitamin supplements through appropriate routes, such as the oral route, to ensure effective treatment. Therefore, understanding the pharmacokinetics of vitamins provides critical insights into absorption, distribution, and metabolism, all of which are essential for achieving the desired pharmacological response. In this review paper, we present information on vitamin deficiencies and emphasize the significance of understanding vitamin pharmacokinetics for improved clinical research. The pharmacokinetics of several vitamins face various challenges, and thus, this work briefly outlines the current issues and their potential solutions. We also discuss the feasibility of enhanced nanocarrier-based pharmaceutical formulations for delivering vitamins. Recent studies have shown a preference for nanoformulations, which can address major limitations such as stability, solubility, absorption, and toxicity. Ultimately, the pharmacokinetics of pharmaceutical dosage forms containing vitamins can impede the treatment of diseases and disorders related to vitamin deficiency.

Microalgae-derived sterols do not reduce the bioavailability of oral vitamin D3 in mice

Microalgae have drawn increasing attention as sustainable food sources, also because of their lipid-lowering phytosterols. As phytosterols are also discussed critically regarding their effect on the availability of fat-soluble vitamins, this study aimed to investigate microalgae-derived phytosterols and their effect on vitamin D status. GC-MS analysis showed large variations in the phytosterol profiles of microalgal species. The most frequent sterols were β-sitosterol and stigmasterol. To investigate their effects on vitamin D status, 40 mice were randomized to four groups and fed a vitamin D3-adequate (25 μg/kg) Western-style diet with 0% phytosterols (control) or 1% ergosterol (a fungal sterol not typical for microalgae), β-sitosterol or stigmasterol for four weeks. Contrary to the hypothesis that phytosterols adversely affect vitamin D uptake, mice fed β-sitosterol had significantly higher concentrations of vitamin D3 in plasma (3.15-fold, p<0.01), liver (3.15-fold, p<0.05), and skin (4.12-fold, p<0.005) than the control group. Small increases in vitamin D3 in plasma and skin were also observed in mice fed stigmasterol. In contrast, vitamin D3 levels in the ergosterol and control groups did not differ. The increased tissue levels of vitamin D3 in mice fed β-sitosterol and stigmasterol were not attributable to the observed reduction in liver triglycerides in these groups. The data rather suggest that changes in bile acid profiles were responsible for the beneficial effect of microalgae sterols on the bioavailability of vitamin D3. In conclusion, consumption of microalgae might not adversely affect vitamin D status.

Phytosterols Protect against Osteoporosis by Regulating Gut Microbiota

Osteoporosis is increasingly prevalent worldwide, representing a major health burden. However, there is a lack of nutritional strategies for osteoporotic therapy. Phytosterols, as natural bioactive compounds, have the potential to alleviate osteoporosis. In this study, a glucocorticoid-induced osteoporosis mouse model and treatment with low and high concentrations of phytosterols for 4 weeks were established. The results demonstrated that compared to the control group, low-concentration phytosterols (LP) (0.3 mg/mL) increased bone mass, improved trabecular microstructure, reduced serum levels of cross-linked C-telopeptide of type I collagen (CTX-1), and elevated serum levels of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). Conversely, high-concentration phytosterols (0.5 mg/mL) showed no effect. Additionally, we validated the effect of LP in ameliorating osteoporosis using an ovariectomized (OVX)-induced osteoporosis mouse model. Mechanistically, phytosterols altered the microbial composition to counteract glucocorticoid-induced gut microbiota disorder and improve the length and morphology of the small intestine. Particularly, based on selection strategy and correlation analysis, phytosterols increased the relative abundance of Ruminococcus and decreased the relative abundance of Bilophila, which were significantly associated with glucocorticoid-induced osteoporosis indications. Overall, these findings suggest that phytosterols regulate gut microbiota to increase bone mass, thereby exerting an antiosteoporotic effect.

Dietary vitamin D intake and sun exposure are not associated with type 1 diabetic schoolchildren and adolescents: A first report in Algeria

BACKGROUND: A large number of children and adolescents worldwide suffer from physiological vitamin D (VD) deficiency, which has been associated with sun exposure and, consequently, the risk of developing various autoimmune diseases, including type 1 diabetes (T1D). However, the association of the disease with VD intake and sun exposure has yet to be explored. MATERIALS AND METHODS: We conducted a food frequency questionnaire and a 24-hour food recall survey, using “Ciqual table 2016” in 335 type 1 diabetic and age- and gender-matched healthy Algerian school children and adolescents from sunny Saharan and relatively less sunny Northern regions, aged between 5 and 19 years. RESULTS: Both dietary VD intake and VD levels were similar in T1D patients when comparing northern and southern regions (for both comparisons, p > 0.05). Neither sun exposure nor VD intake was associated with the disease (respectively, relative risk [RR] = 1.050, p = 0.680; RR = 1.082, p = 1.000. For Cochran and Mantel-Haenszel analysis; RR = 0.841, p = 0.862). VD intake showed a significant difference between diabetics and non-diabetics in the sunny region (p = 0.022). Additionally, significant differences were found between normal and T1D schoolboys (p = 0.038), and when comparing the two groups according to the dry areas (p = 0.016). Moreover, in contrast to circulating VD levels, which were lower in T1D patients than in healthy controls, those of VD intake were significantly higher (p < 0.05), especially in male patients and in those with balanced diet, low protein or carbohydrate consumption, specific food intolerances, and regular meals (p < 0.05), as well as in patients with a moderate or low consumption of cooked meals or steamed foods (p < 0.01). Conversely, VD intake was markedly lower in type 1 diabetics than in controls for dry and sunny areas, including the region of Adrar, as well as for consumption of low-fat foods and eggs (p < 0.05 for all comparisons). Nevertheless, the relative risk of sun exposure and dietary vitamin D intake according to the World Health Organization (WHO) standard did not show a significant association with T1D (common Mantel-Haenszel estimation, RR = 0.841, 95% CI 0.118–5.973, p > 0.05). CONCLUSIONS: T1D does not appear to be associated with VD intake and sun exposure in the Algerian Sahara region. Therefore, the consumption of VD in T1D patients in the Algerian Sahara would suspect that its association with the disease would be related to its synthesis alteration.

Dry Eye Disease: What Is the Role of Vitamin D?

Dry eye disease (DED) is a multifactorial condition resulting from reduced tear secretion from the lacrimal glands, increased tear water evaporation or the production of poor-quality tears. Such tear instability can lead to inflammation and damage of the ocular surface, as well as to abnormal nociception. Historically, tear substitutes and corticosteroids have been the bastion of DED therapy, but a substantial number of patients still suffer from residual symptoms even after being treated with traditional treatments. Aiming to find safe and effective alternative therapies, recent efforts have been focused on the role of vitamin D in the cellular physiology of the eye. Possibly because of its positive effect in modulating the immune and inflammatory responses, the systemic supplementation of vitamin D seems, indeed, to be an effective therapeutic strategy, especially, but not only, for patients affected by DED that does not respond to conventional treatments. In this context, this review focuses on the literature reporting on the pathogenesis and treatment of DED, with a special emphasis on the recent investigations reporting on the potential role of the systemic administration of vitamin D as a therapeutic approach in the management of such condition.

Fortification by design: A rational approach to designing vitamin D delivery systems for foods and beverages

Over the past few decades, vitamin D deficiency has been recognized as a serious global public health challenge. The World Health Organization has recommended fortification of foods with vitamin D, but this is often challenging because of its low water solubility, poor chemical stability, and low bioavailability. Studies have shown that these challenges can be overcome by encapsulating vitamin D within well-designed delivery systems containing nanoscale or microscale particles. The characteristics of these particles, such as their composition, size, structure, interfacial properties, and charge, can be controlled to attain desired functionality for specific applications. Recently, there has been great interest in the design, production, and application of vitamin-D loaded delivery systems. Many of the delivery systems reported in the literature are unsuitable for widespread application due to the complexity and high costs of the processing operations required to fabricate them, or because they are incompatible with food matrices. In this article, the concept of "fortification by design" is introduced, which involves a systematic approach to the design, production, and testing of colloidal delivery systems for the encapsulation and fortification of oil-soluble vitamins, using vitamin D as a model. Initially, the challenges associated with the incorporation of vitamin D into foods and beverages are reviewed. The fortification by design concept is then described, which involves several steps: (i) selection of appropriate vitamin D form; (ii) selection of appropriate food matrix; (iii) identification of appropriate delivery system; (iv) identification of appropriate production method; (vii) establishment of appropriate testing procedures; and (viii) system optimization.

Vitamin D: sources, physiological role, biokinetics, deficiency, therapeutic use, toxicity, and overview of analytical methods for detection of vitamin D and its metabolites

Vitamin D has a well-known role in the calcium homeostasis associated with the maintenance of healthy bones. It increases the efficiency of the intestinal absorption of dietary calcium, reduces calcium losses in urine, and mobilizes calcium stored in the skeleton. However, vitamin D receptors are present ubiquitously in the human body and indeed, vitamin D has a plethora of non-calcemic functions. In contrast to most vitamins, sufficient vitamin D can be synthesized in human skin. However, its production can be markedly decreased due to factors such as clothing, sunscreens, intentional avoidance of the direct sunlight, or the high latitude of the residence. Indeed, more than one billion people worldwide are vitamin D deficient, and the deficiency is frequently undiagnosed. The chronic deficiency is not only associated with rickets/osteomalacia/osteoporosis but it is also linked to a higher risk of hypertension, type 1 diabetes, multiple sclerosis, or cancer. Supplementation of vitamin D may be hence beneficial, but the intake of vitamin D should be under the supervision of health professionals because overdosing leads to intoxication with severe health consequences. For monitoring vitamin D, several analytical methods are employed, and their advantages and disadvantages are discussed in detail in this review.

Dietary vitamin D intake and sun exposure are not associated with type 1 diabetic schoolchildren and adolescents: a first report in Algerian Sahara.. [DOI: 10.1101/2022.07.17.22276883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background

A great number of children and adolescents worldwide suffer from physiological Vitamin D (VD) deficiency, which has been associated to the sun exposure and, consequently, to the risk of the development of various autoimmune diseases, including type 1 diabetes (T1D). However, the association of the disease with VD intake and sun exposure have yet to be explored.

Materials and methods

We conducted a food frequency questionnaire and 24-hour recall food survey, using “Ciqual table 2016” in 335 type 1 diabetic and age- and gender-matched healthy Algerian school children and teenager pupils from sunny Saharan and relatively less sunny Northern regions, aged between 5 and 19 years old.

Results

Both dietary VD intake and VD levels were similar in T1D patients when comparing between North and South regions (for the two comparisons, p > 0.05). Neither sun exposure, nor VD intake was associated with the disease (respectively, relative risk [RR] = 1.050, p = 0.680; RR = 1.082, p = 1.000. For Cochran and Mantel-Haenszel analysis; RR = 0.841, p = 0.862). VD intake showed a significant difference between diabetics and non-diabetics in sunny region (p = 0.022). Additionally, significant differences were highlighted between normal and T1D schoolboys (p = 0.038), and when comparing the two groups according to the dry areas (p = 0.016). Moreover, in contrast with the levels of circulating VD, which is decreased in T1D patients than in healthy controls, those of VD intake was significantly higher (p < 0.05), especially in male patients and in those with balanced diet, poor protein or carbohydrate consumption, a particular food intolerance, and a regular meal (p < 0.05), as well as in patients with a moderate or low consumption of cooked meals or steamed food (p < 0.01). Conversely, VD intake was markedly lower in type 1 diabetics than in controls regarding dry sunny region, including Adrar area, as well as in low fatty foods and eggs consumption (p < 0.05 for all comparisons). Nevertheless, relative risk of sun exposure and dietary vitamin D intake according to the WHO standard showed no significant association with T1D (common Mantel-Haenszel estimation, RR = 0.841, 95% CI 0.118-5.973, p > 0.05).

Conclusions

T1D seems to be not associated with VD intake and sun exposure in the Algerian Sahara region. Therefore, the consumption of VD in T1D patients from the Algerian Sahara would suspect that its association with the disease would be related to its synthesis alteration.

Co-administration of vitamin D3 and Lacticaseibacillus paracasei DG increase 25-hydroxyvitamin D serum levels in mice

Purpose

Subclinical vitamin D (vitD) deficiency enhances the predisposition to a myriad of acute and chronic pathologies in many people worldwide. Due to the scarcity of vitD-rich foods, the consumption of supplements or fortified foods can be required to maintain healthy serum levels of 25-hydroxyvitamin D [25(OH)D], and the major circulating form of vitD that is commonly measured in serum to determine the vitD status. Since the vitD absorption seems to resemble that of lipids, improved emulsification in the gut could favor vitD permeation through the enterocyte membrane. Contextually, we hypothesized that a microorganism with cholecalciferol (vitD3)-solubilization properties may potentially result in enhanced serum vitD levels.

Methods and results

Six probiotic strains were screened for their ability to create a stable suspension of vitD3 in water: Lacticaseibacillus paracasei DG, L. paracasei LPC-S01, L. paracasei Shirota, L. rhamnosus GG, Limosilactobacillus reuteri DSM 17938, and Lactobacillus acidophilus LA5. The DG strain displayed the strongest vitD3 solubilization ability and, consequently, were used in an in vivo trial where a commercial preparation of vitD3 in refined olive oil was administered by gavage to CD-1 mice with or without the concurrent administration of L. paracasei DG. ELISA measurements showed that the DG strain significantly increased the serum levels of 25(OH) D when administered once a day for 1 week in association with the vitD3 supplement.

Conclusion

This preliminary pre-clinical study suggests that the combined administration of L. paracasei DG with an oil-based cholecalciferol supplement could contribute to the maintenance of the adequate 25(OH) D serum levels in people at risk of vitD deficiency.

The Complex ABCG5/ABCG8 Regulates Vitamin D Absorption Rate and Contributes to its Efflux from the Intestine

SCOPE

Most people are vitamin D insufficient around the world. Vitamin D intestinal absorption should thus be optimized. The role of the ATP-binging cassette G5/G8 (ABCG5/G8) heterodimer in vitamin D intestinal efflux is investigated.

METHODS AND RESULTS

Both cholecalciferol and 25-hydroxycholecalciferol apical effluxes are increased by ABCG5/G8 overexpression in human Griptite cells. Mice deficient in ABCG5/G8 at the intestinal level (I-Abcg5/g8^-/- mice) display an accumulation of cholecalciferol in plasma in females and in liver in males compared to control animals. I-Abcg5/g8^{- / -} mice display a delay in cholecalciferol postprandial response after gavage compared with controls. 25-Hydroxycholecalciferol transfer from plasma to lumen is observed in vivo in intestine-perfused mice, and the lack of intestinal ABCG5/G8 complex induces a decrease in this efflux, while vitamin D bile excretion remains unchanged.

CONCLUSION

Overall, it is showed for the first time that the ABCG5/G8 heterodimer regulates the kinetics of absorption of dietary vitamin D by contributing to its efflux back to the lumen, and that it also participates in vitamin D transintestinal efflux.

Oral Intake of Lumisterol Affects the Metabolism of Vitamin D

SCOPE

The treatment of food with ultraviolet-B (UV-B) light to increase the vitamin D content is accompanied by the formation of photoisomers, such as lumisterol2 . The physiological impact of photoisomers is largely unknown.

METHODS AND RESULTS

Three groups of C57Bl/6 mice are fed diets containing 50 µg kg-1 deuterated vitamin D3 with 0, 50 (moderate-dose) or 2000 µg kg-1 (high-dose) lumisterol2 for four weeks. Considerable quantities of lumisterol2 and vitamin D2 are found in the plasma and tissues of mice fed with 2000 µg kg-1 lumisterol2 but not in those fed 0 or 50 µg kg-1 lumisterol2 . Mice fed with 2000 µg kg-1 lumisterol2 showed strongly reduced deuterated 25-hydroxyvitamin D3 (-50%) and calcitriol (-80%) levels in plasma, accompanied by downregulated mRNA abundance of cytochrom P450 (Cyp)27b1 and upregulated Cyp24a1 in the kidneys. Increased tissue levels of vitamin D2 were also seen in mice in a second study that are kept on a diet with 0.2% UV-B exposed yeast versus those fed 0.2% untreated yeast containing iso-amounts of vitamin D2 .

CONCLUSION

High doses of lumisterol2 can enter the body, induce the formation of vitamin D2 , reduce the levels of 25(OH)D3 and calcitriol and strongly impact the expression of genes involved in the degradation and synthesis of bioactive vitamin D.

Mechanisms of absorption of vitamin D3 delivered in protein nanoparticles in the absence and presence of fat

Novel protein-based nanovehicles offer alternatives to fat for delivery of lipophilic bioactives (nutraceuticals and drugs), yet they raise important questions regarding the bioavailability and absorption mechanism of the bioactive without fat. To provide answers, we chose vitamin D₃ (VD₃) as a model lipophilic-nutraceutical, re-assembled casein-micelles (rCM) as model protein-based nanovehicles, and non-fat yoghurt as a model food. We prepared three yoghurt formulations: 3% fat with VD₃ dissolved in milk-fat, non-fat and 3% fat, both latter enriched with VD₃ within rCM. Following in vitro digestion, VD₃ retention and bioaccessibility were high (∼90% and ∼70%, respectively) in all formulations. VD₃ uptake by Caco-2 cells was three-fold higher (p < 0.005) in the non-fat yoghurt enriched with VD₃ in rCM compared with enriched fat-containing yoghurts. SR-BI, CD36 and NPC1L1 transporters were involved in VD₃ absorption irrespective of the composition. Thus, our findings demonstrate that protein nanovehicles may improve VD₃ bioavailability, without altering its absorption mechanism compared to that from fat.

Combining a liquid-liquid extraction with successive air assisted liquid-liquid microextraction for the analysis of phytosterols present in animal based butter and oil samples

In this study, an elevated temperature liquid-liquid extraction combined method with successive air-assisted liquid-liquid microextraction has been proposed for the extraction of four phytosterols in cow milk butter and animal oil samples prior to gas chromatography-flame ionization detector. The method is started by combining a few grams of the melted butter or oil samples with ethanol. The mixture is vortexed and placed into a water-bath adjusted at 50 ⁰C. After a few minutes, the mixture is allowed to cool at room temperature. In this step, the butter or oil is become stiff and ethanol is collected on top of the sample. The separated ethanol phase is collected and mixed with deionized water to obtain a homogenous solution. After that, a few microliters of ethyl methyl ammonium chloride: pivalic acid deep eutectic solvent is added into the solution and the mixture was pulled into a glass test tube and pushed back to the tube for five times. After centrifugation, whole of the collected phase at the bottom of tube was withdrawn and transferred into a microtube and contacted with sodium hydroxide solution. The mixture is withdrawn and released to the tube 2 times to remove the extracted fatty acids. The validation data verified that high enrichment factors (385-450) and extraction recoveries (77-90%), low limits of quantification (2.6-5.2 ng g^-1) and detection (0.73-1.5 ng g^-1), and satisfactory relative standard deviations (≤ 9.3%) can be obtained with this method. At last, the developed method was successfully used for the analysis of phytosterols in various butter and oil samples marketed in Tabriz, Iran.

In vitro solubilization of fat-soluble vitamins in structurally defined mixed intestinal assemblies

The structures of fed state intestinal assemblies containing bile components, dietary fat, and fat-soluble vitamins are not well known, although they are involved in lipid transport. In this study, several methods were used to investigate structural transitions upon various dietary lipids or various fat-soluble vitamins incorporation in bile intestinal assemblies. In particular, DLS and turbidimetry were used to study transition points as a function of component concentration, and cryo-TEM and SAXS were used to resolve assembly structures at microscopic and supramolecular scales, respectively. Results showed that increasing the concentration of dietary lipids in bile assembly induced a transition from core-shell micelles to unilamellar vesicles (except with caprylate lipids, always yielding micelles). In these specific assemblies, increasing the concentration of a fat-soluble vitamin either induced a systematic structural transition, defining a solubilization capacity (α-tocopherol or phylloquinone), or induced a structural transition only in micelles (retinol), or did not induce any structural transition up to very high concentrations (cholecalciferol). Using SAXS data, ideal molecular organizations are proposed for assemblies in the absence or presence of α-tocopherol.

Functional effects of vitamin D: From nutrient to immunomodulator

Vitamin D can be obtained from the endogenous synthesis in the epidermis by exposure to UVB light, and from foods and supplements in the form of ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃). The main metabolite used to measure vitamin D serum status is calcidiol [25(OH)D]. However, its active metabolite calcitriol [1α,25(OH)₂D] performs pleiotropic effects in the cardiovascular, neurological, and adipose tissue as well as immune cells. Calcitriol exerts its effects through genomic mechanisms modulated by the nuclear vitamin D receptor (VDR)/retinoid X receptor (RXR) complex, to bind to vitamin D response elements (VDRE) in target genes of several cells such as activated T and B lymphocytes, neutrophils, macrophages, and dendritic cells; besides of its genomic mechanisms, VDR performs novel non-genomic mechanisms that involve its membrane expression and soluble form; highlighting that vitamin D could be an immunomodulatory nutrient that plays a key role during physiological and pathological events. Therefore, the aim of this comprehensive literature review was to describe the most relevant findings of vitamin D dietary sources, absorption, synthesis, metabolism, and factors that influence its serum status, signaling pathways, and biological effects of this immunonutrient in the health and disease.

Absorbability of Astaxanthin Was Much Lower in Obese Mice Than in Normal Mice

Astaxanthin has been favored as a health food supplement by obese consumers. However, no detailed descriptions are available concerning the absorption of astaxanthin in obese individuals. In this study, we conducted acute and chronic feeding experiments in C57BL/6J mice to study the differences in astaxanthin absorption in normal and obese bodies. The obesity condition greatly decreased astaxanthin concentration in the blood and liver, its accumulation in tissues and organs, and the bioaccessibility. This may be related to the excessive intake of sucrose, fatty acids, and cholesterol, the increased gastrointestinal motility, and the disorder of gut microbiota in the obese body. Overall, our study showed that the obese body had a far less oral absorbability of astaxanthin than a normal body, and we suggest that the recommended or approved doses of astaxanthin can be properly increased for the obese body in the hope that astaxanthin will play a more active role in obese individuals.

Vitamin D Status of Mice Deficient in Scavenger Receptor Class B Type 1, Cluster Determinant 36 and ATP-Binding Cassette Proteins G5/G8

Classical lipid transporters are suggested to modulate cellular vitamin D uptake. This study investigated the vitamin D levels in serum and tissues of mice deficient in SR-B1 (Srb1^-/-), CD36 (Cd36^-/-) and ABC-G5/G8 (Abcg5/g8^-/-) and compared them with corresponding wild-type (WT) mice. All mice received triple-deuterated vitamin D₃ (vitamin D₃-d₃) for six weeks. All knockout mice vs. WT mice showed specific alterations in their vitamin D concentrations. Srb1^-/- mice had higher levels of vitamin D₃-d₃ in the serum, adipose tissue, kidney and heart, whereas liver levels of vitamin D₃-d₃ remained unaffected. Additionally, Srb1^-/- mice had lower levels of deuterated 25-hydroxyvitamin D₃ (25(OH)D₃-d₃) in the serum, liver and kidney compared to WT mice. In contrast, Cd36^-/- and WT mice did not differ in the serum and tissue levels of vitamin D₃-d₃, but Cd36^-/- vs. WT mice were characterized by lower levels of 25(OH)D₃-d₃ in the serum, liver and kidney. Finally, Abcg5/g8^-/- mice tended to have higher levels of vitamin D₃-d₃ in the serum and liver. Major alterations in Abcg5/g8^-/- mice were notably higher levels of 25(OH)D₃-d₃ in the serum and kidney, accompanied by a higher hepatic mRNA abundance of Cyp27a1 hydroxylase. To conclude, the current data emphasize the significant role of lipid transporters in the uptake, tissue distribution and activation of vitamin D.

Vitamin D microencapsulation and fortification: Trends and technologies

Today, as per the latest medical reports available, majority of the population throughout globe is facing vitamin D (Vit D) deficiency. Even in sub-tropical countries like India and many others Vit D deficiency is highly prevalent despite the exuberant available sunshine (a major source of Vit D) throughtout the year. The reason could be attributed to an array of factors including socioeconomical, cultural and religious. Further, other than the sunlight, there are very limited sources of Vit D to fulfil the recommended dietary allowance of Vit D (RDA: 400-800 IU per day). A large proportion of Vit D is lost during food processing and storage due to environmental stress conditions such as temperature, pH, salt, oxygen and light. Vita D, an important micronutrient, is essentially required for the prevention of disorders such as neurodegenerative diseases, cardiovascular diseases, cancer etc. in addition to its traditional role in bone metabolism. Therefore, in order to meet the daily requirements of Vit D for human body, WHO has recognized fortification as the most efficient and safest method to address malnutrition. But there are innumerable chellenges involved during food fortification using Vit D as fortificants such as homogeneity into the food matrix, physico-chemical/photochemical degradation, loss during processing and storage, interactions with other components of food matrix resulting into change in taste, texture and appearance thus affecting acceptability, palatability and marketability. Fortification of Vit D into food products especially the ones which have an aqueous portion, is not simple for food technologist. Recent advances in nanotechnology offer various microencapsulation techniques such as liposome, solid-lipid particles, nanostructured lipid carriers, emulsion, spray drying etc. which have been used to design efficient nanomaterials with desired functionality and have great potential for fortification of fortificants like Vit D. The present review is an undate on Vit D, in light of its fortification level, RDA, factors affecting its bioavailability and various microencapsulation techniques adopted to develop Vit D-nanomaterials and their fate in food fortification.

Intestinal absorption of vitamin D: a systematic review

Context

Vitamin D is frequently prescribed as a supplement, yet its absorption remains poorly understood.

Objective

This systematic review was performed to evaluate data on mechanisms involved in the intestinal absorption of vitamin D.

Data Sources

PubMed, Embase, and Cochrane Library databases were searched.

Study Selection

The following studies were included: experimental laboratory studies of vitamin D absorption through the enterocyte brush-border membrane; absorption tests that used radiolabeled vitamin D; and clinical trials in adults that investigated a single dose of cholecalciferol or ergocalciferol and reported at least 2 measurements of serum cholecalciferol, ergocalciferol, or 25-hydroxyvitamin D.

Data Extraction

From 2069 articles identified, 46 met the inclusion criteria.

Results

Different methods were employed to evaluate vitamin D absorption. Recent research suggests that vitamin D absorption is not an exclusive simple diffusion process. Vitamin D was better absorbed when it was consumed with fat-containing meals, but absorption also occurred without fat or oily vehicles. Factors that modified cholesterol absorption also altered vitamin D absorption.

Conclusion

Vitamin D is probably absorbed through passive diffusion and a mechanism involving membrane carriers, especially cholesterol transporters, although data remain scarce. Some data suggest that fat, when consumed concomitantly with vitamin D, improves vitamin D absorption.

Comparison of the bioavailability and intestinal absorption sites of phytoene, phytofluene, lycopene and β-carotene

The mechanisms of main tomato carotenes (phytoene, phytofluene, lycopene and β-carotene) intestinal absorption are still only partly understood. We thus compared carotene bioavailability in mice after gavage with carotene-rich oil-in-water emulsions. We also determined each carotene absorption profile along the duodenal-ileal axis of the intestine to identify their respective absorption sites and compared these profiles with the gene expression sites of their identified transporters, i.e. SR-BI and CD36. Our data show that phytofluene presented a significantly higher bioavailability compared to lycopene and β-carotene (areas under the curve of 0.76 ± 0.09 vs. 0.30 ± 0.05, 0.09 ± 0.05 and 0.08 ± 0.01 μmol/L·h for phytofluene, phytoene, lycopene and β-carotene, respectively). β-Carotene was mostly converted in the proximal and median intestine. Phytoene and phytofluene accumulation tended to be more important in the distal intestine, which did not correlate with the proximal expression of both Scarb1 and CD36. Overall, these results highlight the high bioavailability of phytofluene.

Modification of the sterol profile in milk through feeding

The fortification of milk with phytosterols is an increasingly common practice to enhance the sterol profile and offer consumers potential health benefits. This study investigated whether cattle feed can influence the profile of phytosterols and cholesterol in the milk produced as an alternative to direct fortification of milk. Five experiments were performed using feeds commonly used by Australian dairy farmers and selected formulated rumen-protected feeds. Statistical significances were observed for some individual plant sterols and cholesterol in milk under these differing feeding regimens compared with the respective controls. In the case of the phytosterols, where the daily recommended consumption is typically 2 g per day, the total phytosterols were <0.12 mg/100 mL of milk. An experiment using a rumen-protected feed with high phytosterol levels suggested a decreased transfer of cholesterol to the milk by as much as 20%, although further work is required to confirm these preliminary results. Overall, the study suggests that different feeding practices have minimal effect on the resulting sterol profile of the milk.

Factors influencing the absorption of vitamin D in GIT: an overview

Vitamin D refers to a group of secosteroid compounds and recognized as the antirachitic vitamin, as it counters rickets, mineral desorption from fully-grown bones (Osteodistrophy), bone, joint disorders, and fragility of bones. On one hand, there is scarcity of vitamin D rich food while on other hand a number of factors negotiate its absorption efficiency in human gastrointestinal tract (GIT). These factors include variations in the physiochemical state of the vitamin D (molecular forms, potency and their physiological linkages), the complexity of food matrix (the amount and type of fatty acids, dietary fibers and presence/absence of vitamin D enhancer and inhibitor), and its interaction of other fat soluble compounds with vitamin D as well as the host-associated factors (age, disease, surgery, obesity, genetic variation etc.). It is hypothesized that the bioavailability of vitamin D in GIT is compromised if there changes within these factors. Present article is intended to review the contribution of these factors anticipated to be influencing vitamin D absorption in GIT.

Impact of Lipid Components and Emulsifiers on Plant Sterols Bioaccessibility from Milk-Based Fruit Beverages

Sterol bioaccessibility (BA) of three plant sterol (PS)-enriched milk-based fruit beverages (MFb) with different fat contents (1.1-2.4%), lipid sources (animal or vegetable), and without or with emulsifiers (whey proteins enriched with milk fat globule membrane (MFGM) or soy lecithin) was evaluated after simulated gastrointestinal digestion. The BA of total PS followed the order 31.4% (MFbM containing milk fat and whey proteins enriched with MFGM) = 28.2% (MFbO containing extra virgin olive oil and soy lecithin) > 8.7% (MFb without fat addition). Total and individual PS content in the bioaccessible fractions followed the order MFbM > MFbO > MFb. Consequently, formulation with MFGM is proposed in beverages of this kind to ensure optimum bioavailability of PS. Our results suggest that the BA of PS is influenced by the type and quantity of fat and the emulsifier type involved.

Vitamin D bioavailability: state of the art

There has been renewed interest in vitamin D since numerous recent studies have suggested that besides its well-established roles in bone metabolism and immunity, vitamin D status is inversely associated with the incidence of several diseases, e.g., cancers, cardio-vascular diseases, and neurodegenerative diseases. Surprisingly, there is very little data on factors that affect absorption of this fat-soluble vitamin, although it is acknowledged that dietary vitamin D could help to fight against the subdeficient vitamin D status that is common in several populations. This review describes the state of the art concerning the fate of vitamin D in the human upper gastrointestinal tract and on the factors assumed to affect its absorption efficiency. The main conclusions are: (i) ergocalciferol (vitamin D2), the form mostly used in supplements and fortified foods, is apparently absorbed with similar efficiency to cholecalciferol (vitamin D3, the main dietary form), (ii) 25-hydroxyvitamin D (25OHD), the metabolite produced in the liver, and which can be found in foods, is better absorbed than the nonhydroxy vitamin D forms cholecalciferol and ergocalciferol, (iii) the amount of fat with which vitamin D is ingested does not seem to significantly modify the bioavailability of vitamin D3, (iv) the food matrix has apparently little effect on vitamin D bioavailability, (v) sucrose polyesters (Olestra) and tetrahydrolipstatin (orlistat) probably diminish vitamin D absorption, and (vi) there is apparently no effect of aging on vitamin D absorption efficiency. We also find that there is insufficient, or even no data on the following factors suspected of affecting vitamin D bioavailability: (i) effect of type and amount of dietary fiber, (ii) effect of vitamin D status, and (iii) effect of genetic variation in proteins involved in its intestinal absorption. In conclusion, further studies are needed to improve our knowledge of factors affecting vitamin D absorption efficiency. Clinical studies with labeled vitamin D, e.g., deuterated or (13)C, are needed to accurately and definitively assess the effect of various factors on its bioavailability.

Intestinal absorption of vitamin D: from the meal to the enterocyte

Vitamin D plays key roles in bone, infectious, inflammatory and metabolic diseases. As most people get inadequate sun exposure for sufficient vitamin D status, they need adequate intake of dietary vitamin D. Many studies see optimizing vitamin D status as a public health priority. It is thus vital to gain deeper insight into vitamin D intestinal absorption. It was long assumed that vitamin D intestinal absorption is a passive process, but new data from our laboratory showed that it is actually far more complex than previously thought. This review describes the fate of vitamin D in the human upper gastrointestinal lumen during digestion and focuses on the proteins involved in the intestinal membrane and cellular transport of vitamin D across the enterocyte. Although recent data significantly improve our understanding of vitamin D intestinal absorption, further studies are still needed to increase our knowledge of the molecular mechanisms underlying this phenomenon.

Impact of a cholesterol membrane transporter's inhibition on vitamin D absorption: A double-blind randomized placebo-controlled study

Oral supplements are important to prevent and treat vitamin D deficiency. Despite the growing number of prescriptions, vitamin D's absorptive mechanisms are not clearly elucidated. By evaluating the effect of ezetimibe on vitamin D absorption, we aim to determine if the cholesterol transporter Niemann-Pick C1-Like 1 transporter contributes to it. This randomized, double-blind, placebo-controlled trial (ClinicalTrials.govNCT02234544) was developed in a South Brazilian University Hospital. Fifty-one medical students were randomized to ezetimibe 10mg/day or placebo for 5 days. On the fifth and 19th days, blood samples for 25-hydroxycholecalciferol (25OHD), parathyroid hormone (PTH), calcium, and albumin were collected. After the first blood sample collection, all participants received a single oral 50,000 IU cholecalciferol dose during a 15 g-fat meal. Serum 25OHD levels were measured by the immunoassay Diasorin Liaison®. Measurements were compared in a general linear model adjusted for multiple comparisons by the Bonferroni test. Before cholecalciferol administration, 25OHD was <30 ng/mL and <20 ng/mL, respectively, in all and in 82.3% of the participants. Fourteen days after a single 50,000 IU oral dose of cholecalciferol, mean (SD) changes in serum 25OHD were similar in both groups, after adjustment to BMI and 25OHD levels before cholecalciferol administration (p=0.26): 8.7 (3.7) ng/mL in the ezetimibe group, versus 10.0 (3.8) ng/mL in the placebo group. Mean serum 25OHD, PTH, calcium and albumin levels remained similar in both groups. We conclude that ezetimibe had no effect on the mean change in serum 25OHD after a single oral dose of cholecalciferol, in these healthy and young adults.

Micellar lipid composition affects micelle interaction with class B scavenger receptor extracellular loops

Scavenger receptors (SRs) like cluster determinant 36 (CD36) and SR class B type I (SR-BI) play a debated role in lipid transport across the intestinal brush border membrane. We used surface plasmon resonance to analyze real-time interactions between the extracellular protein loops and various ligands ranging from single lipid molecules to mixed micelles. Micelles mimicking physiological structures were necessary for optimal binding to both the extracellular loop of CD36 (lCD36) and the extracellular loop of SR-BI (lSR-BI). Cholesterol, phospholipid, and fatty acid micellar content significantly modulated micelle binding to and dissociation from the transporters. In particular, high phospholipid micellar concentrations inhibited micelle binding to both receptors (-53.8 and -74.4% binding at 0.32 mM compared with 0.04 mM for lCD36 and lSR-BI, respectively, P < 0.05). The presence of fatty acids was crucial for micelle interactions with both proteins (94.4 and 81.3% binding with oleic acid for lCD36 and lSR-BI, respectively, P < 0.05) and fatty acid type substitution within the micelles was the component that most impacted micelle binding to the transporters. These effects were partly due to subsequent modifications in micellar size and surface electric charge, and could be correlated to micellar vitamin D uptake by Caco-2 cells. Our findings show for the first time that micellar lipid composition and micellar properties are key factors governing micelle interactions with SRs.

Fat-soluble vitamin intestinal absorption: absorption sites in the intestine and interactions for absorption

The interactions occurring at the intestinal level between the fat-soluble vitamins A, D, E and K (FSVs) are poorly documented. We first determined each FSV absorption profile along the duodenal-colonic axis of mouse intestine to clarify their respective absorption sites. We then investigated the interactions between FSVs during their uptake by Caco-2 cells. Our data show that vitamin A was mostly absorbed in the mouse proximal intestine, while vitamin D was absorbed in the median intestine, and vitamin E and K in the distal intestine. Significant competitive interactions for uptake were then elucidated among vitamin D, E and K, supporting the hypothesis of common absorption pathways. Vitamin A also significantly decreased the uptake of the other FSVs but, conversely, its uptake was not impaired by vitamins D and K and even promoted by vitamin E. These results should be taken into account, especially for supplement formulation, to optimise FSV absorption.

β-lactoglobulin as a vector for β-carotene food fortification

Food fortification is a strategy to overcome vitamin A deficiency in developing countries. Our aim was to investigate the involvement of the bovine milk protein β-lactoglobulin (β-Lg), a potential retinoid carrier, in vitamin A absorption. In vivo experiments were conducted by force-feeding mice with retinol or β-carotene associated with either β-Lg or oil-in-water emulsion, with subsequent determination of both vitamin A intestinal mucosa and plasma contents. Caco-2 cells were then used to investigate the mechanisms of vitamin A uptake when delivered by either β-Lg or mixed micelles. We showed that β-Lg was as efficient as emulsion to promote β-carotene, but not retinol, absorption in mice. Similar results were obtained in vitro. Interestingly, an inhibitor of the Scavenger Receptor Class B Type I significantly decreased the uptake of micellar β-carotene but not that of β-carotene bound to β-Lg. Overall, we showed that β-Lg would be a good vector for β-carotene food fortification.

Plant sterol and stanol intake in Finland: a comparison between users and nonusers of plant sterol- and plant stanol-enriched foods

BACKGROUND/ OBJECTIVES: We evaluated plant sterol and stanol (PS) intakes from natural sources and enriched foods in the Finnish population-based national FINDIET 2007 Survey. In addition, we compared the users and nonusers of PS-enriched foods in terms of their characteristics and dietary intake.

SUBJECTS/METHODS

This was a cross-sectional population-based study on 958 men and 1080 women aged 25-74. Users and nonusers of PS-enriched products were compared with respect to sex, age, education, region, cholesterol-lowering medication and cholesterol-lowering diet. Intakes of PS, energy, energy nutrients, fat composition, cholesterol and dietary fibre were calculated on the basis of a 48-h dietary recall. The distribution of PS intake was assessed for the users of enriched products.

RESULTS

PS-enriched foods were used by 9.5% of all subjects. The usage increased significantly with age (P<0.001) and level of education (P=0.01). The usage of enriched products was more common among those following a cholesterol-lowering medication or diet (P<0.001 for both). Among users, the mean intake of PS was 2.2 g/d for men and 1.6 g/d for women, and among nonusers it was 363 mg/d for men and 286 mg/d for women. The majority of users received less than 2 g/d of PS from enrichment, but 20% of users obtained more than 3 g of PS per day.

CONCLUSIONS

The intake of PS can reach several grams in a subgroup of subjects consuming PS-enriched foods. The manufacturers' recommendations on PS-enriched food consumption are not consistently followed, and customer guidance needs to be improved.

Regulation of cholesterol homeostasis

Hypercholesterolemia is an important risk factor for cardiovascular disease. It is caused by a disturbed balance between cholesterol secretion into the blood versus uptake. The pathways involved are regulated via a complex interplay of enzymes, transport proteins, transcription factors and non-coding RNA's. The last two decades insight into underlying mechanisms has increased vastly but there are still a lot of unknowns, particularly regarding intracellular cholesterol transport. After decades of concentration on the liver, in recent years the intestine has come into focus as an important control point in cholesterol homeostasis. This review will discuss current knowledge of cholesterol physiology, with emphasis on cholesterol absorption, cholesterol synthesis and fecal excretion, and new (possible) therapeutic options for hypercholesterolemia.

Application of in vitro bioaccessibility and bioavailability methods for calcium, carotenoids, folate, iron, magnesium, polyphenols, zinc, and vitamins B(6), B(12), D, and E

A review of in vitro bioaccessibility and bioavailability methods for polyphenols and selected nutrients is presented. The review focuses on in vitro solubility, dialyzability, the dynamic gastrointestinal model (TIM)™, and Caco-2 cell models, the latter primarily for uptake and transport, and a discussion of how these methods have been applied to generate data for a range of nutrients, carotenoids, and polyphenols. Recommendations are given regarding which methods are most justified for answering bioaccessibility or bioavailability related questions for specific nutrients. The need for more validation studies in which in vivo results are compared to in vitro results is also discussed.

Effects of physicochemical properties of carotenoids on their bioaccessibility, intestinal cell uptake, and blood and tissue concentrations

SCOPE

Carotenoid bioavailability is affected by numerous factors. Our aim was to assess the involvement of known carotenoid physicochemical properties (e.g., hydrophobicity, van der Waals volume,…) on the transport of the main dietary carotenoids (β-carotene, lycopene, lutein, and astaxanthin, from their food matrix to their main storage tissues.

METHODS AND RESULTS

We used four complementary models: synthetic mixed micelles, an in vitro digestion procedure, Caco-2 cell monolayers, and a gavage experiment in rats. The efficiency with which pure carotenoids were incorporated into synthetic mixed micelles was related to their melting points (r = 0.99, p = 0.015). The efficiency with which pure carotenoids were transferred from dietary triglycerides into mixed micelles was related to carotenoid hydrophobicity (r = -1, p = 0.005). There was no relationship between the carotenoid physicochemical properties studied and their uptake efficiency by Caco-2. The postprandial plasma carotenoid response to carotenoid gavage was related to carotenoid hydrophobicity (r = -0.99, p = 0.006). Carotenoid adipose tissue response was not related to the carotenoid physicochemical properties studied.

CONCLUSION

Thus, carotenoid hydrophobicity is important for bioaccessibility and postprandial blood response of carotenoids. In contrast, the carotenoid physicochemical properties studied are apparently not strong determinants of carotenoid uptake by enterocytes and adipose tissue.