Dietary supplementation with vitamin D stimulates intestinal epithelial cell turnover after massive small bowel resection in rats

Interactions between Intestinal Homeostasis and NAD+ Biology in Regulating Incretin Production and Postprandial Glucose Metabolism

The intestine has garnered attention as a target organ for developing new therapies for impaired glucose tolerance. The intestine, which produces incretin hormones, is the central regulator of glucose metabolism. Glucagon-like peptide-1 (GLP-1) production, which determines postprandial glucose levels, is regulated by intestinal homeostasis. Nicotinamide phosphoribosyltransferase (NAMPT)-mediated nicotinamide adenine dinucleotide (NAD⁺) biosynthesis in major metabolic organs such as the liver, adipose tissue, and skeletal muscle plays a crucial role in obesity- and aging-associated organ derangements. Furthermore, NAMPT-mediated NAD⁺ biosynthesis in the intestines and its upstream and downstream mediators, adenosine monophosphate-activated protein kinase (AMPK) and NAD⁺-dependent deacetylase sirtuins (SIRTs), respectively, are critical for intestinal homeostasis, including gut microbiota composition and bile acid metabolism, and GLP-1 production. Thus, boosting the intestinal AMPK-NAMPT-NAD⁺-SIRT pathway to improve intestinal homeostasis, GLP-1 production, and postprandial glucose metabolism has gained significant attention as a novel strategy to improve impaired glucose tolerance. Herein, we aimed to review in detail the regulatory mechanisms and importance of intestinal NAMPT-mediated NAD⁺ biosynthesis in regulating intestinal homeostasis and GLP-1 secretion in obesity and aging. Furthermore, dietary and molecular factors regulating intestinal NAMPT-mediated NAD⁺ biosynthesis were critically explored to facilitate the development of new therapeutic strategies for postprandial glucose dysregulation.

Mummy Induces Apoptosis Through Inhibiting of Epithelial-Mesenchymal Transition (EMT) in Human Breast Cancer Cells

Background:

Mummy (Iranian pure shilajit) is a remedy with possessing anti-inflammatory, antioxidant and anticancer activities. This study aimed to examine mummy effects on epithelial-mesenchymal transition (EMT) and invasiveness of MCF-7 and MDA-MB-231 breast cancer (BC) cell lines with underlying its mechanism.

Materials and Methods:

The dose-dependent inhibitory effect of the mummy on cell proliferation in vitro was determined using the MTT assay. Flow cytometry and 4’,6-diamidino-2-phenylindole dihydrochloride staining were respectively used for quantitative and qualitative analysis of cellular apoptosis, and gene expression analysis was conducted using real-time PCR.

Results:

MDA-MB-231 showed more sensitivity than the MCF-7 cell line to the anticancer activity of mummy, while mummy did not exhibit significant cell cytotoxicity against human normal cells (MCF-10A). The gene expression profile demonstrated a significant decrease in TGF-β1, TGF-βR1, TWIST1, NOTCH1, CTNNB1, SRC along with an increase in E-cadherin mRNA levels in mummy treated cells compared to the untreated control group (P≤0.05).

Conclusion:

Mummy triggers inhibition of EMT and metastasis in breast cancer cells mainly through the downregulation of TGFβ1 activity, and more studies required to find its specific anticancer activity with details.

Nutritional and pharmacological strategy in children with short bowel syndrome

Short bowel syndrome in neonates is a severe and life-threatening disease after a major loss of small bowel with or without large bowel. Intestinal adaptation, by which the organism tries to restore digestive and absorptive capacities, is entirely dependent on stimulation of the active enterocytes by enteral nutrition. This review summarizes recent knowledge about the pathophysiologic consequences after the loss of different intestinal parts and outlines the options for enteral nutrition and pharmacological therapies to support the adaptation process.

Propionate promotes vitamin D receptor expression via yes-associated protein in rats with short bowel syndrome

Vitamin D deficiency and refractory osteoporosis are common complications in patients with short bowel syndrome (SBS). The symptom of bone loss is not effectively alleviated, even after the oral administration of vitamin D in SBS patients who had been weaned off parenteral nutrition. In this study, we aimed to investigate the effect of propionate on the expression of the vitamin D receptor (VDR) in the small intestine of rats with SBS. Firstly, IEC-6 (intestinal epithelioid cell line No. 6) cells were incubated in vitro with 1 mM sodium propionate for 24 h. This resulted in a significant increase in the expression of VDR and yes-associated protein (YAP) compared with that in the control group. Transfection of IEC-6 cells with YAP siRNA significantly down-regulated the expression of VDR. By contrast, after incubating IEC-6 cells with lysophosphatidic acid, an agonist of YAP, upregulation of VDR and YAP was observed. Next, we investigated whether this effect occurs in vivo. Five-week-old male Sprague-Dawley rats underwent 80% small bowel resection to establish an SBS model. Rats treated with 1% w/v sodium propionate had high levels of VDR and YAP expression in the intestine and intestinal adaptation was clearly observed compared to the control group. However, these effects were blocked by intraperitoneal injection of verteporfin. Thus, this study showed that propionate promoted VDR expression in the intestine via the activity of YAP, both in vitro and in vivo. Moreover, propionate was shown to play an active role in postoperative intestinal adaptation in SBS rats.

The Effect of Serum Vitamin D on Serum ALT Levels in Healthy Individuals

BACKGROUND

Several studies have examined the relationship between vitamin D (VD) and liver disease but none have explored this relationship in adults with normal liver enzymes. Our aim was to explore an independent association of VD with alanine aminotransferase (ALT) in a large sample of the US adults with liver enzymes in normal range (≤39 U/L).

METHODS

We used the continuous National Health and Nutrition Examination Survey from 2001 to 2006. We excluded individuals with serum ALT>39 U/L. We built linear regression models to estimate unadjusted and adjusted (age, sex, race, diabetes, hypertension, alcohol use, smoking, and body mass index) effect sizes, taking into account the complex probability survey design.

RESULTS

Of the 12,155 participants, 6635 (54.6%) were women, mean±SD age was 49.9±19.4 years, VD was 21.9±9.2 ng/mL, and ALT was 20.9±6.9 U/L. In unadjusted analysis, VD was significantly associated with serum ALT (0.02 U/L/ng/mL of VD, P=0.007). After adjustment for confounders, VD remained statistically significantly associated with serum ALT levels (0.04 U/L, P<0.001). Similarly, individuals in the highest quartile of VD had significantly higher serum levels of ALT than those in the lowest quartile (unadjusted difference=0.98 U/L, P<0.001; adjusted difference=1.21 U/L, P<0.001).

CONCLUSIONS

We found a positive association between VD and ALT after excluding individuals with suspected active liver injury (ALT>39 U/L). The underlying mechanisms for this association are not known and needs further study.

Calcium and 1,25-dihydroxyvitamin D3 modulate genes of immune and inflammatory pathways in the human colon: a human crossover trial

BACKGROUND

A high dietary calcium intake with adequate vitamin D status has been linked to lower colorectal cancer risk, but the mechanisms of these effects are poorly understood.

OBJECTIVE

The objective of this study was to elucidate the effects of a Western-style diet (WD) and supplemental calcium and/or 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on the colorectal mucosa.

DESIGN

We conducted 2 crossover trials to define molecular pathways in the human colorectum altered by 1) a 4-wk WD supplemented with and without 2 g calcium carbonate/d and 2) a 4-wk WD supplemented with 1,25(OH)2D3 (0.5 μg/d) with or without 2 g calcium carbonate/d. The primary study endpoint was genome-wide gene expression in biopsy specimens of the rectosigmoid colonic mucosa. Serum and urinary calcium concentrations were also measured.

RESULTS

Changes in urinary calcium accurately reflected calcium consumption. The WD induced modest upregulation of genes involved in inflammatory pathways, including interferon signaling, and calcium supplementation reversed these toward baseline. In contrast, supplementation of the WD with 1,25(OH)2D3 induced striking upregulation of genes involved in inflammation, immune response, extracellular matrix, and cell adhesion. Calcium supplementation largely abrogated these changes.

CONCLUSIONS

Supplementing 1,25(OH)2D3 to a WD markedly upregulated genes in immune response and inflammation pathways, which were largely reversed by calcium supplementation. This study provides clinical trial evidence of global gene expression changes occurring in the human colorectum in response to calcium and 1,25(OH)2D3 intervention. One action of 1,25(OH)2D3 is to upregulate adaptive immunity. Calcium appears to modulate this effect, pointing to its biological interaction in the mucosa. This trial was registered at clinicaltrials.gov as NCT00298545 Trial protocol is available at http://clinicalstudies.rucares.org (protocol numbers PHO475 and PHO554).

Influence of vitamin D3 on ultramicrostructural changes of hepatic tissue in rats with experimental hepatic injury

AIM: To investigate the effect of vitamin D₃ (VitD₃) on the ultramicrostructural changes of hepatic tissue in Balb/c mice with CCl₄ induced acute liver injury.

METHODS: Twenty-five Balb/c mice were randomly and equally divided into five groups: a control group, a vehicle group, and high-, medium- and low-dose VitD₃ groups. Mice in the three VitD₃ groups were intraperitoneally injected daily with VitD₃ 15.0, 7.5, and 1.0 μg/kg, respectively. Mice in the control group and vehicle group were daily intraperitoneally injected with 0.9% NaCl. After 2 wk of treatment, the vehicle group and treatment groups were intraperitoneally injected with 0.1% CCl₄ in olive (0.2 mL/2 d) for 7 d. Meanwhile, the control group was given equal volume of 0.9% NaCl. At the end of administration of CCl₄ solution, eye blood and liver tissue samples were taken from all the mice. Alanine aminotransferase (ALT) and aspartate transaminase (AST) were detected routinely, and pathological changes in liver tissues were detected by HE staining. The ultramicrostructural changes of hepatic tissue were observed with an electron microscope.

RESULTS: The levels of liver index, ALT, and AST were significantly lower in the high- and medium-dose VitD₃ groups than in the vehicle group (high-dose group: P = 0.0000, 0.0000, 0.0002; medium-dose group: P = 0.0019, 0.0005, 0.0012). Compared with the control group, the levels of liver index, ALT, and AST were significantly higher in the vehicle group (P = 0.0000 for all). The improvement of histological changes in the treatment groups was significantly superior to that in the control group.

CONCLUSION: VitD₃ has a significant protective effect on hepatic ultramicrostructural damage in mice with experimental hepatic injury.

Relationship between vitamin D and nonalcoholic fatty liver disease

Vitamin D is an important secosteroid hormone with pleiotropic effects, including regulation of cell proliferation, differentiation, apoptosis, and immunomodulation. Recently certain evidence has indicated that insufficiency of vitamin D or vitamin D deficiency is related to nonalcoholic fatty liver disease (NAFLD). Subjects with NAFLD have lower serum vitamin D levels than controls, and low vitamin D levels are closely associated with histologic severity of steatosis, necrosis, inflammation and fibrosis in NAFLD. Vitamin D-deficient diet aggravated high fat diet-induced hepatic inflammation in NAFLD models, while vitamin D supplementation improved hepatic histopathology. Vitamin D may act as a regulator in NAFLD through activating VDR and controlling various genes. Modulating hepatic stellate cells is an important mechanism underlying the antifibrotic effect of vitamin D in NAFLD. Vitamin D is a potential drug for treatment for NAFLD, and further prospective RCT studies are required to acquire sufficient evidence.