ALTERED DUODENAL MUCOSAL MITOCHONDRIAL GENE EXPRESSION IS ASSOCIATED WITH DELAYED GASTRIC EMPTYING IN DIABETIC GASTROENTEROPATHY [miRNA-Seq]
Introduction. Hindered by a limited understanding of the molecular mechanisms responsible for diabetic gastroenteropathy (DGE), patients are managed by symptom-based therapies.  We investigated the duodenal mucosal expression of protein-coding genes and miRNAs in DGE and related these abnormalities to clinical features. Methods. mRNA and micro RNA (miRNA) expression and ultrastructure of duodenal mucosal biopsies were investigated in 39 DGE patients and 21 healthy controls. Results were analyzed in the context of diabetic phenotype and gastric emptying. Results. There were 3175 differentially-expressed genes (FDR<0.05), especially mitochondrial genes, in DGE versus controls.  Several mitochondrial (mt) DNA-encoded genes (12 of 13 protein coding genes mainly involved in oxidative phosphorylation (OXPHOS), both rRNAs and 9 of 22 tRNAs) were downregulated; conversely, nuclear (n) DNA-encoded mitochondrial genes (eg, OXPHOS, TCA cycle) were upregulated in DGE.  Motif analysis uncovered binding sites for transcription factors NRF1, GABPA and YY1, which regulate mitochondrial biogenesis, in the promoters of differentially expressed genes.  Seventeen of 30 differentially expressed miRNAs in DGE targeted differentially expressed mitochondrial genes.  Mitochondrial density was also reduced and correlated with the expression of 9 mt-DNA OXPHOS genes in DGE.  Uncovered by a principal component (PC) analysis of OXPHOS genes, PC1 was significantly associated with neuropathy (P = 0.01) and with delayed gastric emptying (P < 0.05). Conclusion. In DGE, mtDNA- and nDNA-encoded mitochondrial genes are reduced and increased, respectively, associated with reduced mitochondrial density, neuropathy, and delayed gastric emptying, and correlated with cognate miRNA expression.  Together, these findings provide substantial evidence for clinically-relevant mitochondrial disturbances in DGE. Overall design: Comparison of gene expression by RNA sequencing in the duodenal mucosa of patients with DM and healthy controls