Increase of bile acid production by tacrolimus in the rat liver

Vancomycin relieves tacrolimus-induced hyperglycemia by eliminating gut bacterial beta-glucuronidase enzyme activity

Up to 40% of transplant recipients treated long-term with tacrolimus (TAC) develop post-transplant diabetes mellitus (PTDM). TAC is an important risk factor for PTDM, but is also essential for immunosuppression after transplantation. Long-term TAC treatment alters the gut microbiome, but the mechanisms of TAC-induced gut microbiota in the pathogenesis of PTDM are poorly characterized. Here, we showed that vancomycin, an inhibitor of bacterial beta-glucuronidase (GUS), prevents TAC-induced glucose disorder and insulin resistance in mice. Metagenomics shows that GUS-producing bacteria are predominant and flourish in the TAC-induced hyperglycemia mouse model, with upregulation of intestinal GUS activity. Targeted metabolomics analysis revealed that in the presence of high GUS activity, the hydrolysis of bile acid (BAs)-glucuronic conjugates is increased and most BAs are overproduced in the serum and liver, which, in turn, activates the ileal farnesoid X receptor (FXR) and suppresses GLP-1 secretion by L-cells. The GUS inhibitor vancomycin significantly eliminated GUS-producing bacteria and inhibited bacterial GUS activity and BAs levels, thereby enhancing L-cell GLP-1 secretion and preventing hyperglycemia. Our results propose a novel clinical strategy for inhibiting the bacterial GUS enzyme to prevent hyperglycemia without requiring withdrawal of TAC treatment. This strategy exerted its effect through the ileal bile acid-FXR-GLP-1 pathway.

Immunosuppressants and new onset gallstone disease in patients having undergone renal transplantation

BACKGROUND

There are very few reports describing the development of gallstone disease after renal transplantation (GSDART) in Asia. The aim of this population-based study was to explore the prevalence, predictive factors, and outcomes of newly developed GSDART. The relationship between immunosuppressant and GSDART was also explored.

PATIENTS AND METHODS

Renal transplantation (RT) recipients were identified from the National Health Insurance Research Database of Taiwan during January 1998-December 2012. In total, 2,630 adult patients, who had neither been diagnosed with gallstone disease (GSD) nor undergone cholecystectomy, were included in this study. These patients underwent follow-up till the diagnosis of GSDART was established. Risk factors and post-RT immunosuppressant treatments were investigated and analyzed using Cox regression analysis. The cumulative mortality in patients with and without GSDART was also evaluated.

RESULTS

The final dataset comprised 143 patients who developed GSDART and 2,487 patients who had not been diagnosed with GSDART during the follow-up period. The prevalence of GSDART was 5.4%. On performing univariate analysis, age (p=0.0276) and certain immunosuppressant administrations were identified as significant risk factors for GSDART. After adjusting for age, multivariable analysis showed that everolimus (adjusted hazard ratio 0.287, p=0.0013) was independently associated with the development of GSDART. The overall mortality rate (6.99%, p=0.0341) was significantly decreased in the GSDART group.

CONCLUSION

Increased age was the most consistent risk factor for GSD, and everolimus-based immunotherapy indicated a decreased incidence of GSDART in RT recipients. The long-term mortality rate was significantly decreased in patients with GSDART.

Small bowel obstruction due to an unconjugated ursodeoxycholic acid enterolith following living donor liver transplantation: Report of a case

We report an unusual case of small bowel obstruction due to an ursodeoxycholic acid (UDCA) enterolith that occurred 7 years after liver transplantation. A 70-year-old man had undergone multiple operations, including a living donor liver transplantation (LDLT) and hepaticojejunostomy. Four years after the LDLT, cholestasis developed, for which oral UDCA was administrated. Seven years after the LDLT, he was admitted to our hospital because of pneumonia; intestinal obstruction occurred following its resolution. A radiographic contrast study and computed tomographic scan indicated a movable mass as the cause of the ileus, suggesting a giant stone. We were unable to observe or remove the stone by double balloon enteroscopy owing to the presence of severe adhesion; thus, we surgically removed the mass. The patient's postoperative course was uneventful. He was discharged 20 days after the operation. An infrared spectrophotometric analysis revealed that the stone was a true enterolith, primarily composed of unconjugated UDCA. An ileus caused by a true enterolith is a rare clinical complication of LDLT. Nevertheless, it must be considered in the differential diagnosis of intestinal obstructions in liver transplant recipients with Roux-en-Y hepaticojejunostomies and/or bowel stasis.

Biliary diseases in heart transplanted patients: a comparison between cyclosporine A versus tacrolimus-based immunosuppression

A cyclosporine (CsA)-based immunosuppression is associated with an increased incidence of cholelithiasis after heart transplantation. It is not known if tacrolimus (Tac) has comparable biliary side effects in humans.

We evaluated the incidence of gallbladder sludge and cholelithiasis under Tac-based immunosuppression by ultrasound examinations in 31 cardiac transplants (25 male, 6 female, mean age: 59 ± 11 years). Data were compared to 57 patients (47 male, 10 female, mean age: 58 ± 11 years) who received CsA-based immunosuppression.

6 patients receiving Tac and 6 patients receiving CsA had already gallstones prior to transplantation so that finally 25 patients of the Tac group and 51 patients of the CsA group could be evaluated.

In the Tac group the incidence of biliary sludge was 4% (1 of 25), of gallstones 28% (7 of 25). In comparison, patients receiving CsA developed biliary sludge in also 4% (2 of 51) and gallstones in 25% (13 of 51). Nine of 42 males in the CsA group (21%) and eight of 20 males in the Tac group (40%) developed either gallstones or sludge (n.s). Six of nine females in the CsA group (67%), but none of five females in the Tac group (0%) developed either gallstones or sludge (p = 0.01).

In summary, the incidence of biliary disease in patients with Tac is comparable with CsA-based immunosuppression. We recommend regular sonographical examinations to detect biliary diseases as early as possible. In cases of clinically, laboratory and sonographical signs of cholecystitis cholecystectomy is indicated. It seems that towards lithogenicity female patients benefit more from a Tac-based treatment because the occurrence of gallstones is rare.