Date of Award
Doctor of Philosophy (PhD)
Biotechnology Science and Engineering
Joseph D. Ng
Shawn E. Levy
Luis Rogelio Cruz-Vera
Diabetes--Research., Nucleotide sequence., Islands of Langerhans.
Type 1 Diabetes is chronic disease where immune moderated destruction of insulin producing β cells disrupts normal glucose homeostasis in the body. Recent findings show that few β cells remain in the pancreatic islets decades after disease onset challenging the previous understanding that β cells are completely destroyed. Overcoming the limited availability of T1D tissues, we studied functional and molecular features of pancreatic islets from individuals with T1D and investigated the nature of the remaining β cells. We found that remnant β cells have normal insulin secretory function and normally express key transcription factor that regulates β cell function. On the other hand, glucagon producing α cells, in normal physiology, counters insulin action and assist in producing glucose from liver when glucose levels fall too low. However, in T1D patients, counterregulatory response of glucagon is abnormal and exogenous insulin treatment can sometimes induce hypoglycemic shock (low glucose). We found that remaining α cells in pancreatic islets of T1D individuals had impaired glucagon secretion and expression of key transcription factor important for normal α cell function were compromised. We propose a model for disrupted α cell function based on our inspection of altered expression of genes in T1D α cells that furthers our understanding of susceptibility to hypoglycemia in T1D. We further advanced the molecular characterization of pancreatic islets from normal individuals through single cell resolution. Islets are highly multicellular where various cell types collectively contribute to proper islet function. Efforts to purify each cell type and investigate their transcriptional features has been challenging from flow cytometry approach due lack of cell type specific markers and traditional single cell RNA-sequencing approach has been low throughput compromising sensitivity. We applied a high throughput approach on single cell RNA-sequencing to profile ~40,075 single cells from pancreatic islets of healthy individuals. We obtained pure populations of all pancreatic cell types based on transcriptional similarity and further identified transcriptional heterogeneity in β and α cells highlighting their intrinsic properties of subpopulation and cellular states. With this approach and findings about α and β cells subpopulations, we can further investigate their changes at various age and diabetic state.
Shrestha, Shristi, "Comprehensive functional and transcriptional analysis of human pancreatic islets from controls and individuals with Type 1 diabetes (T1D)" (2018). Dissertations. 147.