Antimicrobial peptides (AMP) are essential components of innate immunity with a broad
range of antimicrobial activities against bacteria, viruses, and fungi. The aim of this study was to
investigate AMP expression in the upper gastrointestinal tract in normal and pathological metabolic
states in humans. Furthermore, we examined the correlation between vitamin D levels and AMP
expression in the same cohort. Serum concentrations of 25-hydroxyvitamin D3 were measured, and
mRNA expression of β-defensins HBD-1, -2, -3, -4, α-defensins HD-5 and -6 and cathelicidin in the
upper gastrointestinal tract epithelia were determined by quantitative RT-PCR in 31 individuals
(10 with type 2 diabetes, 10 with insulin resistance, and 11 healthy controls). The majority of the cohort
showed low vitamin D concentrations, which were negatively correlated with mRNA expression
levels of HBD-3 in corpus mucosa. HBD-1 and HBD-3 mRNA were expressed in corpus mucosa, with
the former significantly decreased in patients with diabetes. Hence, we conclude that type 2 diabetes
is associated with reduced AMP expression in the upper gastrointestinal tract, which might contribute
towards epithelial barrier dysfunction and increased bacterial translocation in these patients
