Direct suppression of human islet dedifferentiation, progenitor genes, but not epithelial to mesenchymal transition by liraglutide

Abstract

β-cell dedifferentiation has been accounted as one of the major mechanisms for β-cell failure; thus, is a cause to diabetes. We study direct impacts of liraglutide treatment on ex vivo human dedifferentiated islets, and its effects on genes important in endocrine function, progenitor states, and epithelial mesenchymal transition (EMT). Human islets from non-diabetic donors, were purified and incubated until day 1 and day 4, and were determined insulin contents, numbers of insulin (INS + ) and glucagon (GCG + ) cells. The islets from day 3 to day 7 were treated with diabetic drugs, the long acting GLP-1 receptor agonist, liraglutide. As observed in pancreatic islets of type 2 diabetic patients, ex vivo dedifferentiated islets showed more than 50% reduced insulin contents while number of glucagon increased from 10% to about 20%. β-cell specific genes: PDX1 , MAFA , as well as β-cell functional markers: GLUT1 and SUR1, were significantly depleted more than 40%. Notably, we found increased levels of glucagon regulator, ARX and pre-glucagon transcripts, and remarkably upregulated progenitor expressions: NEUROG3 and ALDH1A identified as β-cell dysfunction markers in diabetic models. Hyperglucagonemia was often observed in type 2 patients that could lead to over production of gluconeogenesis by the liver. Liraglutide treatments resulted in decreased number of GCG + cells, increased numbers of GLP-1 positive cells but did not alter elevated levels of EMT marker genes: ACTA2, CDH-2, SNAIL2, and VIM . These effects of liraglutide were blunted when FOXO1 transcripts were depleted. This work illustrates that ex vivo human isolated islets can be used as a tool to study different aspects of β-cell dedifferentiation. Our novel finding suggests a role of GLP-1 pathway in beta-cell maintenance in FOXO1-dependent manner. Importantly, dedifferentiated islets ex vivo is a useful model that can be utilized to verify the actions of potential drugs to diabetic β-cell failure.

The Plasticity of Pancreatic β-Cells

“…In pancreatic islet cultures from non-diabetic patients, β-cell dedifferentiation progresses over time, and their insulin content decreases by 50% in about one week. When this happens, the expression of mature β-cell markers (Pdx-1 and MafA) is decreased, and the expression of endocrine progenitor cell markers (Ngn3 and Aldh1a) is increased [ 48 ]. The addition of GLP-1 to human islets suppressed the expression of these dedifferentiation markers, and knockdown of FoxO1 diminished these effects, suggesting that FoxO1 may be involved in the GLP-1-induced suppression of pancreatic β-cell dedifferentiation [ 48 ].…”

Global proteomics reveals insulin abundance as a marker of human islet homeostasis alterations

“…Nevertheless, among the intrinsic factors, the observed decrease in other islet hormones and neuroendocrine marker CHGA abundance advances a scenario in which the decreased insulin abundance in the islets of the LOW insulin group is part of a more general phenomenon of dedifferentiation. During dedifferentiation, islet cells reduce or even lose the expression of key markers 32,33 leading to their metabolic reconfiguration and ultimately, | 11 of 15 MATHISEN et al in the case of beta-cells, defective insulin secretion. 34 In our pilot study, we identified both the loss of key markers and changes affecting metabolic signature of the islets, including the inhibition of insulin secretion pathway.…”

“…Islet cell dedifferentiation is a known pathological phenomenon in the development of diabetes, in mice 35,36 as well as in humans, especially in the context of T2D. [37][38][39] Moreover, it is known to affect islets in culture 33,40 in a time-dependent fashion. As all islet samples analyzed were cultured for the same amount of time, the observed dedifferentiation event must have a different trigger.…”