  Citation: Ochoci ´ nska, A.; Wysocka-Mincewicz, M.; Groszek, A.; Rybak, A.; Konopka, E.; Bierla, J.B.; Trojanowska, I.; Szalecki, M.; Cukrowska, B. Could I-FABP Be an Early Marker of Celiac Disease in Children with Type 1 Diabetes? Retrospective Study from the Tertiary Reference Centre. Nutrients 2022, 14, 414. https://doi.org/10.3390/ nu14030414 Academic Editor: Francesca Ferretti Received: 16 December 2021 Accepted: 16 January 2022 Published: 18 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). nutrients Article Could I-FABP Be an Early Marker of Celiac Disease in Children with Type 1 Diabetes? Retrospective Study from the Tertiary Reference Centre Agnieszka Ochoci ´ nska 1, * , Marta Wysocka-Mincewicz 2 , Artur Groszek 2 , Anna Rybak 3 , Ewa Konopka 4 , Joanna Beata Bierla 4 , Ilona Trojanowska 4 , Mieczyslaw Szalecki 2,5 and Bo ˙ zena Cukrowska 4 1 Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children’s Memorial Health Institute, Aleja Dzieci Polskich 20, 04-730 Warsaw, Poland 2 Department of Endocrinology and Diabetology, The Children’s Memorial Health Institute, Aleja Dzieci Polskich 20, 04-730 Warsaw, Poland; m.wysocka@ipczd.pl (M.W.-M.); a.groszek@ipczd.pl (A.G.); m.szalecki@ipczd.pl (M.S.) 3 Department of Gastroenterology, Great Ormond Street Hospital NHS Trust, Great Ormond Street, London WC1N 3JH, UK; anna.rybak@gosh.nhs.uk 4 Department of Pathomorphology, The Children’s Memorial Health Institute, Aleja Dzieci Polskich 20, 04-730 Warsaw, Poland; e.konopka@ipczd.pl (E.K.); j.bierla@ipczd.pl (J.B.B.); i.trojanowska@ipczd.pl (I.T.); b.cukrowska@ipczd.pl (B.C.) 5 Collegium Medicum, Jan Kochanowski University, Aleja IX Wieków Kielce 19A, 25-317 Kielce, Poland * Correspondence: a.ochocinska@ipczd.pl; Tel.:+48-22-815-73-01 Abstract: Patients with type 1 diabetes (T1D) are at higher risk of celiac disease (CD). Recently, intestinal fatty acid binding protein (I-FABP) has been shown to be a serological biomarker of impaired intestinal barrier in CD. Thus, the aim of this study was to verify whether I-FABP could be an early marker of CD in pediatric T1D patients. I-FABP was measured in sera of patients with T1D (n = 156), active CD (n = 38), T1D with active CD (T1D-CD, n= 51), and age-matched healthy children (n = 55). Additionally, I-FABP was determined in T1D patients with negative CD serology at least one year before CD diagnosis (T1D-CD-1, n = 22), in CD patients on a gluten-free diet (CD-GFD, n = 36), and T1D-CD patients on GFD (T1D-CD-GFD, n = 39). Sera were tested using immunoenzymatic assay. Significantly increased levels of I-FABP were found in the T1D, active CD, and T1D-CD groups (1153 ± 665, 1104 ± 916, and 1208 ± 878, respectively) in comparison to healthy with controls (485 ± 416, p < 0.05). GFD induced a significant decrease in I-FABP levels in CD and T1D-CD groups (510 ± 492 and 548 ± 439, respectively). Interestingly, in T1D-CD-1 and T1D, I-FABP levels were comparable (833 ± 369 vs. 1153 ± 665), and significantly increased in relation to healthy controls and T1D-CD values on GFD. The results indicate that the epithelial barrier is disrupted in T1D patients independently of CD development; therefore, I-FABP cannot serve as an early marker of CD in T1D patients. Although GFD can improve epithelial recovery, the question remains as to whether GFD could exert beneficial effects on the intestinal barrier in early stages of T1D. Keywords: type 1 diabetes; celiac disease; biomarker; intestinal fatty acid binding protein; impaired epithelial barrier; I-FABP; gluten-free diet; intestinal barrier 1. Introduction Type 1 diabetes (T1D) is a multifactorial and complex autoimmune disease. Its comor- bidity with other autoimmune diseases, including celiac disease (CD), is well established. The co-diagnosis of CD affects from 2 to 16% of diabetic patients worldwide [1]. According to the latest Polish reports, the frequency of CD among T1D patients is now much higher than ten years ago (8.3% vs. 5.7%) and higher in girls (13.9%) than boys (4.9%), which is in line with previous reports by Cerutti et al. about the higher risk of having both diseases for girls than for boys [2,3]. Nutrients 2022, 14, 414. https://doi.org/10.3390/nu14030414 https://www.mdpi.com/journal/nutrients