Monday, January 9, 2017

Is there an association between vitamin D and liver fibrosis in patients with chronic hepatitis C?

Arq. Gastroenterol. vol.54 no.1 São Paulo Jan./Mar. 2017
Original Article
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Is there an association between vitamin D and liver fibrosis in patients with chronic hepatitis C?
Kalinca da Silva OLIVEIRA1, Caroline BUSS1,2 and Cristiane Valle TOVO1,3

Vitamin D is known for its immunomodulatory, anti-inflammatory and antifibrotic properties, which are quite relevant in the pathogenesis and treatment of many causes of chronic liver disease.

This study aimed to evaluate the association between serum vitamin D levels and the histopathological findings in patients with chronic hepatitis C virus infection.

Cross-sectional study composed of patients with chronic hepatitis C. All patients underwent vitamin D 25 dosage and anthropometric data analysis. Liver biopsy was performed in a maximum 36-month period before inclusion in the study.

Of the 74 patients included in the study, 45 (60.8%) were women, mean age was 57.03±9.24 years, and 63 (85.1%) were white. No association was observed between the serum levels of vitamin D and inflammatory activity (P=0.699) nor with the degree of liver fibrosis (P=0.269).

In this study, no association was observed between vitamin D and inflammatory activity, as well as the degree of liver fibrosis, in patients with chronic hepatitis C.

Discussion Only
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No association between the vitamin D serum levels and the different degrees of inflammatory activity or liver fibrosis was found in this study. Some studies examined the relationship between the vitamin D serum level and the progression of the disease in patients with chronic hepatitis C5,10,12, but this is a controversial issue.

It has been suggested that HCV reduces the production of 7-dehydrocholesterol, the precursor of endogenous vitamin D. Most patients presented low vitamin D levels, suggesting that HCV depresses serum levels and changes the lipid metabolism6.

Vitamin D deficiency is closely related to the severity of some chronic liver disease1,2,7,17,23. Vitamin D anti-inflammatory and modulating properties could impact on disease progression especially on HCV chronic liver disease12. Some authors observed that vitamin D might have an impact on other outcomes and in the response to the treatment of patients with chronic hepatitis C 8,18,21,26.

In the present study, 9 (12.2%) patients presented was observed deficiency. Similar results have been shown in the literature9 in the population with HCV, although some reports present a high index of vitamin D deficiency/insufficiency.

A recent study9 showed an inverse relationship between vitamin D levels and viral load, liver fibrosis and treatment outcomes, supporting the hypothesis that the improvement of vitamin D status may have considerable potential to amend the host defense against HCV infection and response to therapy.

An independent association between low vitamin D serum level and higher degree of inflammatory activity has been suggested 4,13. A probable explanation for the association between lower vitamin D levels and lower inflammatory activity in the liver would be the decrease of 25-hydroxylase activity, promoting decrease in vitamin D hydroxylation activity and, hence, lower serum levels13. However, this association was not observed in this study, corroborating Petta et al.'s findings 20, putting in question this potential mechanism.

Some studies show that vitamin D serum levels are inversely related to liver fibrosis, showing a relationship between the anti-inflammatory effects10,14,20. Thus, vitamin D deficiency could contribute to a more advanced liver fibrosis and the use of supplementation should have an antifibrotic effect on HCV carriers5. On the other hand, Kitson et al.13) and Bitetto et al.4 did not find association between vitamin D serum levels and the degree of liver fibrosis in their studies, in which the contribuiting factors were not clear, with chances of being racial, genetic or methodological differences used in vitamin D analysis.

It should be questioned if vitamin D deficiency increases with age and the patients included in the present study should be quite young to assess this relationship. Vitamin D concentration was evaluated in individuals in the city of São Paulo belonging to different age groups15. A total of 591 individuals were included. The authors hypothesized that there would be cyclic patterns for the vitamin D and the UV radiation values that repeat every 12 months. They concluded that there was seasonal variation in the vitamin D concentration for all the groups studied; however, the amplitude of the variation was higher for the groups of young and physically active people, possibly due to the higher level of sunlight exposure for these groups. The lowest vitamin D concentration was detected in the spring. In the present study, however, this variable was analyzed and there was no association between age and vitamin D level when we considered the cutoffs for sunny countries established by Holick et al.11.

The fact that this study does not present data on the potential confounders that may influence vitamin D serum levels (sunlight exposure, use of medications or osteoporosis prevalence) can be considered as a limiting factor, although all patients collected the blood in the same season of the year.

Some authors reported that some drugs used for diabetes, for reducing cholesterol or diuretics may interfere lowering serum levels of vitamin D 24. This may be an interesting observation, however, this was not evaluated in the present study.

In conclusion, there was no association between vitamin D serum levels and inflammatory activity or the degree of liver fibrosis in the patients with chronic HCV infection.

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