The Correlation Between Anemia of Chronic Diseases, Hepcidin and Vitamin D in IBD Patients

Crohn's disease (CD) and ulcerative colitis (UC) are chronic gastrointestinal diseases characterized by relapsing and remitting inflammation of the intestines . Anemia may often complicate the course of inflammatory bowel disease (IBD) . A recent systematic review showed that anemia is common and may affect roughly 17% of patients with IBD .

The cause of anemia in IBD is multifactorial. The most common cause for anemia in IBD patients is iron deficiency anemia (IDA) secondary to increased blood loss from inflamed gastrointestinal mucosa and impaired absorption of iron. The anemia can be macrocytic due to impaired absorption of other nutrients including folate and cobalamin. Other causes are anemia due to medication (such as sulfasalazine) and anemia of chronic disease (ACD) .

ACD is characterized by normochromic, normocytic or mildly microcytic erythrocytes, low or normal serum iron and total iron-binding capacity, normal or increased iron stores reflected by elevated ferritin levels, low transferrin levels, and an inappropriately low reticulocyte response relative to the degree of anemia. ACD is unresponsive to treatment with iron, vitamin B12 or folic acid.

In the chronically ill patients, it has been described that the mechanism underlying anemia involves hepcidin.

Hepcidin, a β-defensin-like antimicrobial peptide, is part of the innate immune system and thus constitutes the first-line defense against infections. In vivo and in vitro studies have demonstrated that hepcidin is active against Gram-positive and Gram-negative bacteria as well as yeasts . In addition to its antimicrobial activity, it acts as an iron regulatory hormone. Increased hepcidin synthesis inhibits iron flow into plasma from macrophages that have taken up and degraded senescent erythrocytes as well as their hemoglobin, and also from small intestinal epithelial cells involved in the absorption of dietary iron . This iron release from cytoplasmic stores is prevented by binding of hepcidin to the iron exporter protein ferroportin. Ferroportin is internalized and degraded upon hepcidin activity.