Connotation of serum levels of vitamin D3 and LL-37 with urinary tract infection in type 2 diabetic patients

<h2>Abstract</h2><h3>Problem considered</h3> Type 2 diabetes mellitus (T2DM) is characterized by inappropriacy of innate immunity leading to higher rates of urinary tract infection (UTI), an important risk factor for urinary tract complications. 25-hydroxy vitamin D may donate, via the production of the antimicrobial peptide cathelicidin (LL-37), to epithelial host defense against colonization of uro-pathogens. This study aimed to assess serum levels of vitamin D₃ and LL-37 in T2DM patients with and without UTI and to measure the association of these two parameters with metabolic profile and microbial distribution pattern. <h3>Methods</h3> Patients' characteristics were documented and included patients' age, sex, duration of being diagnosed with T2DM, concurrent treatments, other diseases, body mass index, and smoking status. Blood sample was collected from each enrolled patient for metabolic profiling, serum vitamin D_3, and LL-37 measurement. Urine sample was collected for urinalysis and patients were grouped accordingly into with-UTI (group A) and without-UTI (group B) groups. <h3>Results</h3> One hundred and twelve T2DM patients (aged 51.1±5.8 years) were enrolled; 50 patients with UTI and 62 without. Serum levels of vitamin D₃ were found to be significantly lower in patients with UTI (17.9 ± 4.8 ng/mL) than in patients without UTI (25.2 ± 5.7 ng/mL) (p < 0.01). In accordance, LL-37 levels were significantly reduced in group A members (27.5 ± 6.9 ng/mL) when compared to group B members (35.5 ± 8.6 ng/mL) (p-value < 0.01). <i>E. coli</i> was the most common isolated uro-pathogen (40%) followed by <i>P. aeruginosa</i> and <i>S. aureus</i> (14% each), <i>Enterobacter</i> (10%), <i>Klebsiella</i> spp (8%) and <i>Proteus</i> spp (4%). No significant difference in serum LL-37 levels was encountered between the three types of microbial isolates (p-value < 0.05). A strong positive correlation was reported between LL-37 and vitamin D₃ levels in patients without UTI ( <i>r</i>_s: 0.9855, p-value: <0.01). A weak, though non-significant, correlation was observed between LL-37 and vitamin D₃ in patients with UTI (<i>r</i>_s: 0.25283, p-value: > 0.05). <h3>Conclusion</h3> Findings suggest that diminished serum levels of vitamin D₃ and LL-37 could have clinical implications and could act as a potential immunological indicator for the tendency to develop UTI in diabetic patients.