Hepatic vitamin D 25-hydroxylase: inhibition by bile duct ligation or bile salts

Adaptive homeostasis of the vitamin D-vitamin D nuclear receptor axis in 8-methoxypsoralen-induced hepatotoxicity

8-methoxypsoralen (8-MOP) with ultraviolet A radiation therapy (PUVA) is the standard therapy for patients with psoriasis, despite the reported potential risks of 8-MOP-induced cholestatic liver injury in both humans and animals. Usually, patients with chronic cholestasis exhibit lower serum 25-hydroxy vitamin D (25(OH)D) levels. But those patients receiving PUVA for psoriasis showed an increase in serum 25(OH)D levels, probably highlighting that the vitamin D-vitamin D nuclear receptor (VD-VDR) axis play a protective role in 8-MOP-induced hepatotoxicity. The present study confirmed 8-MOP could increase serum 25(OH)D levels in conventional lighting and diet (CLD) and vitamin D deficient (VDD) Sprague-Dawley rats. Potential liver risks were also found in CLD and VDD rats after 8-MOP treatment. We proved that 8-MOP could be a potent ligand for VDR using molecular docking and luciferase report assay. Effect of 8-MOP on VDR subcellular distribution was determined using human liver cell line L02. We found 8-MOP could increase VDR protein expression in the nuclear and cytosol extracts and also total cell extracts in L02. siRNAs for VDR were used to determine the role of VDR in protecting 8-MOP-induced cholestasis and potential cellular mechanisms. The results showed 8-MOP could affect the CYP7A1, SHP and MRP3 expression via VDR, and such effects could be reversed by knockdown of VDR expression, suggesting a vital role of VDR involved in 8-MOP-regulated bile acid synthesis and transportation. In conclusion, these results revealed activation of VD-VDR axis may play a beneficial role in 8-MOP-mediated regulation of bile acid synthesis and transportation.

Can skin exposure to sunlight prevent liver inflammation?

Liver inflammation contributes towards the pathology of non-alcoholic fatty liver disease (NAFLD). Here we discuss how skin exposure to sunlight may suppress liver inflammation and the severity of NAFLD. Following exposure to sunlight-derived ultraviolet radiation (UVR), the skin releases anti-inflammatory mediators such as vitamin D and nitric oxide. Animal modeling studies suggest that exposure to UVR can prevent the development of NAFLD. Association studies also support a negative link between circulating 25-hydroxyvitamin D and NAFLD incidence or severity. Clinical trials are in their infancy and are yet to demonstrate a clear beneficial effect of vitamin D supplementation. There are a number of potentially interdependent mechanisms whereby vitamin D could dampen liver inflammation, by inhibiting hepatocyte apoptosis and liver fibrosis, modulating the gut microbiome and through altered production and transport of bile acids. While there has been a focus on vitamin D, other mediators induced by sun exposure, such as nitric oxide may also play important roles in curtailing liver inflammation.

Calcium plus vitamin D supplementation affects pregnancy outcomes in gestational diabetes: randomized, double-blind, placebo-controlled trial

OBJECTIVE

The present study was designed to assess the effects of Ca+vitamin D supplementation on pregnancy outcomes in women with gestational diabetes mellitus (GDM).

DESIGN

A randomized, double-blind, placebo-controlled trial was conducted among sixty women with GDM. Participants were divided into two groups to receive Ca+vitamin D supplements or placebo. Individuals in the Ca+vitamin D group (n 30) received 1000 mg Ca/d and two pearls containing 1250 µg (50 000 IU) of cholecalciferol (vitamin D(3)) during the intervention (one at study baseline and another at day 21 of the intervention); those in the placebo group (n 30) received two placebos of vitamin D at the mentioned times and placebos of Ca every day for 6 weeks. Pregnancy outcomes were determined.

SETTING

A urban community setting in Arak, Iran.

SUBJECTS

Sixty women with GDM and their newborns, living in Arak, Iran were enrolled.

RESULTS

Women treated with Ca+vitamin D had a significant decrease in caesarean section rate (23·3 % v. 63·3 %, P=0·002) and maternal hospitalization (0 v. 13·3 %, P=0·03) compared with those receiving placebo. In addition, newborns of GDM women randomized to Ca+vitamin D had no case of macrosomia, while the prevalence of macrosomia among those randomized to placebo was 13·3 % (P=0·03). Lower rates of hyperbilirubinaemia (20·0 % v. 56·7 %, P=0·03) and hospitalization (20·0 % v. 56·7 %, P=0·03) were also seen in the supplemented group of newborns than in the placebo group.

CONCLUSIONS

Ca+vitamin D supplementation for 6 weeks among pregnant women with GDM led to decreased caesarean section rate and maternal hospitalization, and decreased macrosomia, hyperbilirubinaemia and hospitalization in newborns.

Melatonin attenuates oxidative stress, liver damage and hepatocyte apoptosis after bile-duct ligation in rats

The goal of this study was to evaluate the possible protective effects of melatonin against cholestatic oxidative stress, liver damage and hepatocyte apoptosis in the common rats with bile duct ligation (BDL). A total of 24 male Wistar albino rats were divided into three groups: control, BDL and BDL + received melatonin; each group contains eight animals. Melatonin-treated BDL rats received daily melatonin 100 mg/kg/day via intraperitoneal injection. The application of BDL clearly increased the malondialdehyde (MDA) levels and decreased the superoxide dismutase (SOD) and glutathione (GSH) activities. Melatonin treatment significantly decreased the elevated tissue MDA levels and increased the reduced SOD and GSH enzyme levels in the tissues. The changes demonstrate that the bile duct proliferation and fibrosis in expanded portal tracts include the extension of proliferated bile ducts into lobules, mononuclear cells and neutrophil infiltration into the widened portal areas as observed in the BDL group. The data indicate that melatonin attenuates BDL-induced cholestatic liver injury, bile duct proliferation and fibrosis. The α-smooth muscle actin (α-SMA) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells in the BDL were observed to be reduced with the melatonin treatment. These results suggest that administration of melatonin is a potentially beneficial agent to reduce liver damage in BDL by decreasing oxidative stress.

Glycine ameliorates liver injury and vitamin D deficiency induced by bile duct ligation

BACKGROUND

Patients with chronic liver disease had lower serum concentrations 25-hydroxyvitamin D (25OHD). Glycine, a nonessential amino acid, exerts anti-inflammatory, cytoprotective, and immunomodulatory properties. This study aimed to establish a tandem mass spectrometry assay to measure 25OHD in guinea pigs serum and to investigate the effects of glycine against the liver damage induced by bile duct ligation (BDL).

METHODS

BDL was performed on male guinea pigs. Glycine, alanine, serine or tyrosine was given by intraperitoneal injection. The animals were sacrificed and examined at 7 and 14 days after BDL. Serum concentrations of total bilirubin and aminotransferase were measured. Serum concentrations of 25OHD2 and 25OHD3 were measured by API 5000 mass spectrometer. In addition, oxidative stress was assessed by serum ischemia-modified albumin (IMA) and hepatic malondialdehyde (MDA), and apoptosis by hepatic caspase 3 activities.

RESULTS

Serum 25OHD concentrations were decreased around 50% in the BDL group at days 7 and 14 post ligation, compared to sham (mean 65.3 ng/ml, p<0.005). Glycine but not other amino acid treatment blunted the reduced serum 25OHD (52.6 ng/ml, p<0.05) resulting from BDL. The concentrations of 25OHD were negatively associated with concentrations of IMA (r=-0.305, p<0.05) and caspase 3 (r=-0.562, p<0.0001). At day-14 post ligation, glycine treatment also ameliorated liver damage indicated by serum AST (p<0.005), ALT (p<0.05) and hepatic caspase 3 activities (p<0.05) and oxidative stress.

CONCLUSION

Our results indicate that glycine may protect against BDL-induced liver injury through attenuation of oxidative stress, apoptosis and the vitamin D deficiency.

Effects of sphingosylphosphorylcholine against cholestatic oxidative stress and liver damage in the common bile duct ligated rats

The goal of this study was to evaluate the possible protective effects of sphingosylphosphorylcholine (SPC) against cholestatic oxidative stress and liver damage in the common bile duct ligated rats. Fifty-six animals were included in each of the following 7 groups: control, SPC control, phosphate-buffered solution control, sham operated, bile duct ligation (BDL), BDL plus phosphate-buffered solution, and BDL plus SPC. Sphingosylphosphorylcholine was administered 14 days at a daily dose of 2 microm/mL intraperitoneally. The severity of cholestasis and hepatic injury was determined by changes in the plasma enzyme activities of aspartate aminotransferase, alanine aminotransferase, gama glutamin transferase, and levels of total bilirubin and direct bilirubin. Malondialdehyde, nitric oxide, and superoxide dismutase were determined to evaluate the oxidative status in the liver tissue. Myeloperoxidase activity and levels of tissue hydroxyproline were determined to assess neutrophil activation and collagen accumulation, respectively. Treatment with SPC markedly reduced serum transaminase activities as compared to BDL rats. Sphingosylphosphorylcholine also inhibited the increase in liver malondialdehyde; nitric oxide levels significantly and also attenuated the depletion of superoxide dismutase in the liver after BDL. Similarly, the increase in tissue myeloperoxidase activity and hydroxyproline owing to BDL was also attenuated by the SPC treatment. These data were supported by histopathologic findings. The alpha-smooth muscle actin-positive cells in the BDL were observed to be reduced with the SPC treatment. In conclusion, these findings suggested that SPC can attenuate hepatic damage in extrahepatic cholestasis by prevention of oxidative stress, and inflammatory process. All these findings suggest that SPC may be a promising new therapeutic agent for cholestatic liver injury.

Vitamin D and parathyroid hormone in outpatients with noncholestatic chronic liver disease

BACKGROUND & AIMS

The liver plays a central role in vitamin D metabolism. Our aim was to determine the prevalence and type of vitamin D-parathyroid hormone (PTH) disturbance in ambulatory patients with noncholestatic chronic liver disease (CLD) and its relationship with disease severity and liver function.

METHODS

We studied 100 consecutive outpatients (63 men, 37 women; mean age, 49.0 +/- 12.1 [SD] y) with noncholestatic CLD caused by alcohol (n = 40), hepatitis C (n = 38), hepatitis B (n = 12), autoimmune hepatitis (n = 4), hemochromatosis (n = 4), and nonalcoholic steatohepatitis (n = 2); 51 patients had cirrhosis. Serum concentrations of 25-hydroxyvitamin D (25[OH]D), PTH, calcium, phosphate, magnesium, creatinine, and liver function tests were determined.

RESULTS

Serum 25(OH)D levels were inadequate in 91 patients: vitamin D deficiency (<50 nmol/L) was found in 68 patients and vitamin D insufficiency (50-80 nmol/L) was found in 23 patients. Secondary hyperparathyroidism (serum PTH, >6.8 pmol/L) was present in 16 patients. The prevalence of vitamin D deficiency was significantly higher in cirrhotic vs noncirrhotic patients (86.3% vs 49.0%; P = .0001). In Child-Pugh class C patients, 25(OH)D levels were significantly lower than in class A patients (22.7 +/- 10.0 nmol/L vs 45.8 +/- 16.8 nmol/L; P < .001). Serum 25(OH)D independently correlated with international normalized ratio (negatively; P = .018) and serum albumin (positively; P = .007). Serum 25(OH)D levels of less than 25 nmol/L predicted coagulopathy, hyperbilirubinemia, hypoalbuminemia, increased alkaline phosphatase, and anemia and thrombocytopenia.

CONCLUSIONS

Vitamin D inadequacy is common in noncholestatic CLD and correlates with disease severity, but secondary hyperparathyroidism is relatively infrequent. Management of CLD should include assessment of vitamin D status in all patients and replacement when necessary.

Fractures in biliary atresia misinterpreted as child abuse

Bone fractures in children without a history of injury are highly suspicious for child abuse. Biliary atresia is a disorder associated with metabolic bone disease, and there are numerous reports of osteopenia, rickets, and/or fractures in this population. We report 3 cases of children with biliary atresia who had bony fractures as well as osteopenia whose caretakers were investigated for child abuse. Pediatricians should be aware of an increased incidence of fractures and overall prevalence of bone disease in this population.

Bone mineral metabolism and histomorphometry in rats with cholestatic liver disease

BACKGROUND

The etiology of osteopenia in cholestatic liver disease is uncertain. An animal model is needed in order to study the efficacy of therapeutic agents.

AIMS

In order to characterise the bone disease in rats with cholestatic liver disease.

METHODS

Four-month old male Sprague-Dawley bile duct-ligated (BDL) and sham-operated (SO) rats were studied. Twenty-eight days after surgery serum osteocalcin, a bone-formation marker, urinary deoxypyridinoline (DPD) cross-links, a resorption marker, and 25-hydroxyvitamin D3 were determined. Static and dynamic (tetracycline-based) histomorphometric analysis was performed on femurs and tibiae.

RESULTS

All BDL rats developed biliary cirrhosis. Bile duct-ligated rats had lower bone mass, reflected in statistically significantly 13.5% lower femoral dry-weight, 16% lower femoral ash-weight, 42.7% lower tibial cancellous bone area and 19% lower trabecular thickness, compared with SO rats. Bile duct-ligated rats exhibited decreased bone formation manifested by statistically significantly 70% lower tetracycline double-labelling, 40% lower mineralising surface, 51% lower bone-formation rate and 47% lower osteocalcin compared with SO rats. Deoxypyridinoline levels were 20% lower in BDL rats. Bile duct-ligated rats had 52% lower serum 25-hydroxyvitamin D3 level, but no significant increase in cortical osteoid area.

CONCLUSIONS

Bile duct-ligated rats develop osteopenia characterised by low bone-formation rate, and can be used for studying therapeutic agents for patients with cholestatic liver disease displaying similar bone changes.

Hepatic osteodystrophy: the influence of liver disease and portal hypertension on cytokine activation

Chronic liver disease is frequently complicated by bone disease. The mechanisms leading to bone-loss are unknown but are probably not related to abnormal vitamin D metabolism. The effects of portal hypertension and porto-systemic shunting on bone-loss have not been studied. It is postulated that liver disease, or the complications of liver disease (portal hypertension or porto-systemic shunting), might be responsible for the activation of cytokines. It is further postulated that these cytokines might be the final common pathway leading to bone-loss in both parenchymal and cholestatic liver disorders by modifying osteoblast or osteoclast function.

TIMP expression in toxic and cholestatic liver injury in rat

BACKGROUND/AIMS

Hepatic fibrosis is a dynamic pathological process with a net accumulation of extracellular matrix proteins. Recent evidence suggests that besides their increased synthesis, inhibition of matrix degradation plays a significant role. ECM degradation occurs via metalloproteinases which are inhibited in situ by specific tissue inhibitors of metalloproteinases (TIMPs). The aim of our studies was to determine the expression of TIMPs during toxic liver injury and cholestatic liver injury leading to fibrosis.

METHODS

We examined the expression of TIMP-1, -2 and -3 in two different rat models for liver injury (intraperitoneal CCl4 injection and bile duct ligation) by Northern blot analysis and in situ hybridization. For comparison, the mRNA expression of the acute phase protein haptoglobin was measured.

RESULTS

TIMP-1 was increased during the early phase of toxic liver injury and in cholestasis. Its expression occurred predominantly in areas of inflammation, in hepatocytes, and in mesenchymal and endothelial cells. There was a slight upregulation of TIMP-2 expression during cholestasis. TIMP-3 was not detected at all.

CONCLUSIONS

Our results emphasize an involvement of TIMP-1 in matrix homeostasis, indicating its possible participation in liver fibrosis.

Severe cholestasis leads to vitamin D depletion without perturbing its C-25 hydroxylation in the dog

The role of the liver as a contributory factor in the vitamin D deficiency of cholestatic liver disease has been studied in vivo in dogs with chronic bile duct ligation, whereas controls underwent diversion of the bile flow through the urinary bladder via a choledococystostomy anastomosis. The hepatic extraction of vitamin D3 was evaluated by the multiple indicator dilution technique, and the formation of 25-hydroxyvitamin D3 was assessed by directly sampling the hepatic effluent for up to 150 min after vitamin D3 administration. The serum and hemodynamic data indicate that dogs with chronic bile duct ligation had severe cholestasis and hepatocellular injury; histologically, macronodular cirrhosis was present. Dogs with choledococystostomy anastomosis had normal livers and normal liver function. The data indicate that the absence of normal bile flow into the intestinal lumen led to a progressive depletion of vitamin D reserve in both animals with choledococystostomy anastomosis and those with chronic bile duct ligation. However, neither the hepatic fractional extraction of vitamin D3, its hepatic clearance nor its transformation into 25-hydroxyvitamin D3 was significantly changed by chronic bile duct ligation. The results of the present studies indicate that the hepatic handling of vitamin D3 including its C-25 hydroxylation, is well preserved in the presence of severe cholestasis. They also suggest that the state of vitamin D depletion which often accompanies chronic cholestatic liver disease can largely be accounted for by factors such as secondary malabsorption of the vitamin due to the absence of adequate amounts of bile salts in the intestinal lumen, or by other factors which seem independent of the hepatic metabolism of vitamin D.

Suppression of rat hepatic vitamin D-25-hydroxylase by cholecalciferol, but not by 25-hydroxy- or 1,25-dihydroxymetabolites

Hepatic vitamin D-25-hydroxylase activity is greater in vitamin D-depleted than replete animals. We investigated whether vitamin D itself or a metabolite of vitamin D was responsible for modulating the activity of vitamin D-25-hydroxylase. Accordingly, we repleted vitamin D-depleted rats with subcutaneous injections of 2600, 520, and 130 pmoles of cholecalciferol (D3), 25-hydroxycholecalciferol (25(OH)D3), and 1,25-dihydroxycholecalciferol (1,25(OH)2D3), respectively, for up to 3 weeks. Repletion resulted in accelerated weight gain and in increased activity of gut mucosal alkaline phosphatase. Using an improved assay to measure vitamin D-25-hydroxylase activity in liver homogenates, we found 78% reduction (P less than 0.001) in the D3-repleted group, maximal by 1 week, in contrast to no change in those groups treated with D3 metabolites. D3, 25(OH)D3, and D3-esters remaining in livers at the time of assay were estimated in a parallel experiment using [3H]D3-repleted rats. Residual D3 accounted for only a 9% dilution of substrate in the assay. 25(OH)D3 was present in the liver at concentrations two orders of magnitude lower than the amount required to inhibit vitamin D-25-hydroxylase activity in vitro. D3 esters had no inhibitory effect in vitro at 250-fold excess of that found in the repleted rat liver. Vitamin D appears to modulate its D-25-hydroxylase activity in biological systems by a mechanism other than feedback inhibition by 25(OH)D3, 1,25(OH)2D3, or D3-esters.

Vitamin D and mineral metabolism in intrahepatic cholestasis of pregnancy

Serum concentrations of 25(OH)D, 24,25(OH)2D, 1,25(OH)2D, total protein, calcium, phosphorus, magnesium and alkaline phosphatase were measured in patients with intrahepatic cholestasis of pregnancy and in control subjects at the third trimester of pregnancy and at delivery. 25(OH)D levels of 40.5 +/- 21.5 nmol/l in the patient group were initially significantly (P less than 0.01) higher than the value of 26.3 +/- 9.5 nmol/l in the control group and decreased significantly (P less than 0.01) to 26.0 +/- 16.3 nmol/l at delivery. The levels of active 1,25(OH)2D and inactive 24,25(OH)2D did not alter in either group. Also the concentrations of calcium, phosphorus and magnesium remained unchanged in both groups. No significant differences in fetal vitamin D metabolites were observed between patients and controls, and the other analysed fetal parameters were similar in both groups. Cholestyramine and/or phenobarbital treatment had no influence on vitamin D metabolites. Since levels of 1,25(OH)2D and mineral parameters remained normal and a change in 25(OH)D concentrations was only transient, the clinical role of 25(OH)D variations cannot be substantial.

Vitamin D metabolism and osteomalacia in cystic fibrosis

A 25-yr-old black man with cystic fibrosis and cirrhosis developed symptoms of osteomalacia and hypocalcemia, hypophosphatemia, secondary hyperparathyroidism, and low circulating 25-hydroxyvitamin D (25-OHD). Serum 1,25-dihydroxyvitamin D (1,25-[OH]2D) was within the normal range. Iliac crest bone biopsy confirmed the diagnosis of osteomalacia. Oral administration of 50,000 IU of vitamin D2 failed to relieve symptoms or raise serum 25-OHD levels to normal. Intramuscular vitamin D2, 10,000 IU every 8-12 week, improved symptoms, raised serum 25-OHD to normal, and increased circulating 1,25-[OH]2D to values five times normal. Over the next 10 mo circulating 1,25-[OH]2D remained elevated despite normalization of serum calcium, phosphorus, and parathyroid hormone. Repeat bone biopsy 1 yr after parenteral vitamin D showed healing of the osteomalacia. Malabsorption of vitamin D appears secondary to profound steatorrhea due to pancreatic insufficiency and secondary biliary cirrhosis. Although extensive hepatocellular disease was present, hepatic conversion of vitamin D to 25-OHD was intact. Both high and low circulating 1,25-[OH]2D levels during active osteomalacia have been reported; initially, the level was in the normal range and higher values in this patient occurred with repletion of 25-OHD substrate. This study shows that symptomatic osteomalacia may be a major manifestation of cystic fibrosis in those patients surviving into adulthood. Measurements of serum 25-OHD in cystic fibrosis patients may identify those who should receive supplemental vitamin D.