MICRORNA-483 PROTECTS PANCREATIC ΒETA-CELLS BY TARGETING ALDH1A3

Author

Zhihong Wang, Michigan Technological University

Date of Award

2022

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Biological Sciences (PhD)

Administrative Home Department

Department of Biological Sciences

Advisor 1

Xiaoqing Tang

Committee Member 1

Ebenezer Tumban

Committee Member 2

Xiaohu Tang

Committee Member 3

Qinghui Chen

Abstract

Type 2 diabetes is a metabolic disorder that causes hyperglycemia in patients. Pancreatic β-cell dysfunction is central to the development and progression of type 2 diabetes. New evidence indicated that altered β-cell identity due to β-cell dedifferentiation is believed to be a new mechanism for β-cell dysfunction and loss during the development of T2D. However, the precise mechanisms involved in β-cell dedifferentiation are still under investigation. MicroRNAs (miRNA) are a group of small non-coding RNAs known to negatively regulate target gene expression in response to metabolic changes in pancreatic islets. Dysregulation of miRNAs has been associated with pancreatic islet dysfunction in type 2 diabetes. Our previous studies have shown that miR-483 expression is much higher in β-cells than α-cells. Elevated miR-483 is also observed in the islets of prediabetic db/db mice, indicating that miR-483 plays important function in β-cells.

In chapter 1 of this dissertation, we generated a βcell specific knockout mouse model of miR-483 in order to explore the physiological function of miR-483. We found that loss of miR-483 induced hyperglycemia and glucose intolerance through reduction of insulin secretion in miR-483 knockout mice (miR483-/-) fed high-fat-diet (HFD). miR-483 deficiency also induced alteration in blood lipid profile with increased low-density lipoproteins (LDL) and decreased high-density lipoprotein (HDL). RNA sequencing analysis of isolated islets indicated that miR-483 inactivation significantly increased multiple pathways involved in metabolic pathway and mitochondria function.

In chapter 2 of this dissertation, we validated that aldehyde dehydrogenase family 1, subfamily A3 (Aldh1a3) was a direct target of miR-483. ALDH1A3 is a recognized biomarker of β-cell dedifferentiation. miR-483 deficiency significantly increased ALDH1A3 expression in the islets of HFD-fed miR483-/- mice, whereas overexpression of miR-483 repressed ALDH1A3 expression. These data suggest that miR-483 is critical in protecting β-cell function by preventing β-cell dedifferentiation.

In chapter 3 of this dissertation, we further investigated the identity of dedifferentiated β-cells in miR483-/- mice. When mice fed HFD or injected with streptozotocin (STZ), a drug widely used to induce diabetes, a higher percentage of ALDH1A3-positive cells was colocalized with glucagon in miR483-/- mice compared to the control mice. Increased glucagon contents were further confirmed in miR483-/- islets and miR483-deleted MIN6 cells when treated with STZ. In addition, miR-483 inactivation significantly increases multiple enzymes involved in adaptive oxidative stress response including gamma-glutamyl transferase (GGT1). In summary, our data indicated that miR-483 is important for maintaining β-cell identity, and miR-483 deficiency induces oxidation stress and β-cell dedifferentiation.

Recommended Citation

Wang, Zhihong, "MICRORNA-483 PROTECTS PANCREATIC ΒETA-CELLS BY TARGETING ALDH1A3", Campus Access Dissertation, Michigan Technological University, 2022.

https://doi.org/10.37099/mtu.dc.etdr/1442