Thursday, February 14, 2013

Vitamin D in chronic liver disease

Vitamin D in chronic liver disease
  1. Caroline S. Stokes1,*,
  2. Dietrich A. Volmer2,
  3. Frank Grünhage1,
  4. Frank Lammert1
Article first published online: 12 FEB 2013
DOI: 10.1111/liv.12106

Liver International
Volume 33, Issue 3, pages 338–352, March 2013
Keywords:bioavailability;cholecalciferol;epimers;hepatic disease;hepatic osteodystrophy;25-hydroxyvitamin D;vitamin D metabolites


Chronic liver disease (CLD) and several related extrahepatic manifestations such as hepatic osteodystrophy are associated with deficiency of vitamin D, which has therefore been suggested as therapeutic target. Vitamin D undergoes hepatic 25-hydroxylation, rendering the liver critical to the metabolic activation of this vitamin. Vitamin D deficiency is highly prevalent in Chronic liver disease (CLD) patients, and vitamin D levels are inversely related to the severity of CLD. Declining levels of carrier proteins such as albumin and vitamin D-binding protein might also be critical in CLD. Intervention studies report improvements of CLD following supplementation, and benefits to health outcomes in particular with respect to hepatitis C virus infection have recently been documented.
Content:We discuss vitamin D sources, functions and metabolism with a focus on the inherent complications of analytical measurements, such as the interference of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D C-3 epimers. Global discrepancies in the definition of optimal serum 25-hydroxyvitamin D levels are covered, and the prevalence of vitamin D deficiency in CLD is reviewed. We also address the functional mechanisms underlying this deficiency, and refer to associations between genetic variation in vitamin D metabolism and CLD. Lastly, we consider the health implications of a vitamin D deficiency in CLD and consider therapeutic options.

Herein, we focus on the epidemiological and functional relationships between vitamin D deficiency and CLD, followed by a discussion of the potential implications for therapeutic interventions.

Chronic liver disease (CLD) is defined as the process of long-term progressive destruction and regeneration of the liver, and with advancing disease, hepatic fibrosis (scarring) and cirrhosis frequently occur [1]. Progression of CLD and deterioration of liver function are associated with various hepatic complications such as chronic liver failure, hepatocellular carcinoma (HCC) and infections. Hepatic osteodystrophy is an important extrahepatic manifestation of advanced liver disease mimicking features of classical osteoporosis with an increased risk for fractures [2]. Recently, the role of vitamin D in CLD has received much attention, given its inherent activation process by the liver and the high prevalence of vitamin D deficiency in this patient group [3]. Evidence is also beginning to unravel possible direct therapeutic benefits of vitamin D therapy. While clear evidence of an association between vitamin D and liver disease exists, it remains unknown whether vitamin D deficiency confers an enhanced risk to liver disease or whether liver disease causes vitamin D deficiency.

This review summarizes the role of vitamin D in Chronic liver disease CLD, highlighting important functional aspects of the vitamin D/ CLD relationship.

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