Comparison of Duodenal Biopsies and Organoids From Healthy Horses With and Without Insulin Resistance

Abstract: Background– Equine metabolic syndrome (EMS), characterized by insulin resistance (IR), may be associated with altered enterocyte glucose absorption or incretin expression (GI hormones). Intestinal organoids are utilized for understanding epithelial biology and disease in human medicine. Organoids may be used to investigate intestine-specific contributions to EMS. However, the alteration of relevant cellular markers in equine organoid culture has not been explored.Objective– To compare duodenal organoids and biopsies from healthy horses with and without IR. Animals– 12 healthy adult NC State- or client-owned horses (age: 3-22 years, 6 mares/6 geldings). All horses were maintained on pasture and biopsied during April-July.Methods- After fasting, an Oral Sugar Test (OST; 0.45 ml/kg Karo syrup) was performed. Horses were categorized as IR based on [insulin] at 60 or 90 minutes post-OST. Gastroscopy was performed to obtain duodenal biopsies, which were used for qRT-PCR, immunofluorescence, or duodenal organoid culture. After 5-7 days growth, organoids were used for qRT-PCR or immunofluorescence. Gene expression for representative enterocyte genes was compared between tissue and organoids. Results– 5/12 (41%) horses were characterized as IR. IR horses trended towards increased SGLT1 expression in biopsies (Figure 1). Organoid culture caused downregulation of several genes (GIP, GCG, SGLT1, MUC2, LGR5) and upregulation of OLFM4 and LYZ (Figure 1,2). There was no change in CHGA expression. Conclusions and clinical importance– Duodenal organoids have altered gene expression compared to biopsies and this should be considered when studying intestinal disease in vitro. Increased duodenal SGLT1 expression may be associated with EMS independent of diet.