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Coupling mechanisms of insulin secretion - roles of mitochondrial metabolism and cAMP.

Krus, Ulrika LU (2006)
Abstract
Type 2 diabetes is a disease that increases tremendously in the western world. It is characterized by insulin resistance and defects in insulin secretion. Insulin resistance is tightly linked to obesity, and usually precedes the onset of type 2 diabetes. When insulin resistance develops, the pancreatic beta-cells compensate by in¬creasing their secretion of insulin, causing hyperinsulinemia. This state may not be a major risk factor per se; in fact, many people develop severe insulin resistance and hyperinsulinemia without ever acquiring diabetes. However, beta-cells in some individuals, perhaps genetically predisposed, are unable to increase their secretion sufficiently to meet the new requirements. This leads to hyperglycemia, the main... (More)
Type 2 diabetes is a disease that increases tremendously in the western world. It is characterized by insulin resistance and defects in insulin secretion. Insulin resistance is tightly linked to obesity, and usually precedes the onset of type 2 diabetes. When insulin resistance develops, the pancreatic beta-cells compensate by in¬creasing their secretion of insulin, causing hyperinsulinemia. This state may not be a major risk factor per se; in fact, many people develop severe insulin resistance and hyperinsulinemia without ever acquiring diabetes. However, beta-cells in some individuals, perhaps genetically predisposed, are unable to increase their secretion sufficiently to meet the new requirements. This leads to hyperglycemia, the main hallmark of diabetes. To be able to treat diabetes, the defects in the beta-cells causing impaired insulin secretion must be elucidated.



The aim of this thesis was to investigate the mechanisms of insulin secretion, and especially what couples glucose stimulation of the beta-cell to insulin secretion.



We have found that anaplerosis via pyruvate carboxylase is essential for both phases of glucose-stimulated insulin secretion, presumably via generation of an increased ATP/ADP ratio. Further, we discovered that expression of PDK1 is upregulated in INS-1 832/13 cells cultured at high concentrations of glucose, and that knock-down of PDK1 enhances insulin secretion. Both these findings prove that mitochondrial metabolism is important for insulin secretion, and points to the involvement of pyruvate cycling. We have also showed that PKA signaling is stimulated by glucose, and that inhibition of PKA decreases glucose-stimulated insulin secretion in INS-1 832/13 cells. (Less)
Abstract (Swedish)
Popular Abstract in Swedish

Typ 2 diabetes är en sjukdom som ökar lavinartat i västvärlden. Dess främsta kännetecken är insulinresistens och defekter i insulinsekretion. Insulinresistens är kopplat till fetma, och framträder ofta långt innan man utvecklar typ 2 diabetes. När man blir insulinresistent kompenseras detta av att betacellerna i de langerhanska öarna i bukspottskörteln producerar mer insulin, vilket leder till hyperinsulinemi. Detta tillstånd behöver inte utgöra en riskfaktor i sig själv, många utvecklar allvarlig insulinresistens och hyperinsulinemi utan att någonsin få typ 2 diabetes. Emellertid har vissa personer betaceller som inte klarar av att öka produktionen av insulin tillräckligt mycket för att... (More)
Popular Abstract in Swedish

Typ 2 diabetes är en sjukdom som ökar lavinartat i västvärlden. Dess främsta kännetecken är insulinresistens och defekter i insulinsekretion. Insulinresistens är kopplat till fetma, och framträder ofta långt innan man utvecklar typ 2 diabetes. När man blir insulinresistent kompenseras detta av att betacellerna i de langerhanska öarna i bukspottskörteln producerar mer insulin, vilket leder till hyperinsulinemi. Detta tillstånd behöver inte utgöra en riskfaktor i sig själv, många utvecklar allvarlig insulinresistens och hyperinsulinemi utan att någonsin få typ 2 diabetes. Emellertid har vissa personer betaceller som inte klarar av att öka produktionen av insulin tillräckligt mycket för att kompensera för insulinresistensen, något som kan orsakas av genetiska faktorer. Detta leder till hyperglykemi, vilket är definitionen på diabetes. För att kunna behandla diabetes måste man klarlägga vilka defekter i betacellerna som orsakar den försämrade insulinutsöndringen.



Syftet med den här avhandlingen var att undersöka mekanismer för insulinutsöndring, och speciellt att utröna vad som kopplar glukosstimulering av betacellen till insulinutsöndring. Vi har upptäckt att anapleros via pyruvatkarboxylas är nödvändigt för både första och andra fasen i glukosstimulerad insulinfrisättning, och att det förmodligen sker genom en ökning av ATP/ADP ration. Vidare har vi funnit att uttrycket av PDK1 är uppreglerat i INS-1 832/13 celler som odlats i höga glukoskoncentrationer, och att hämning av PDK1 förbättrar insulinutsöndringen. Båda dessa upptäckter visar att mitokondriell metabolism är viktigt för insulinutsöndring, och tyder på att olika kretslopp för pyruvat är inblandat. Vi har också visat att PKA-signalering stimuleras av glukos, och att inhibering av PKA leder till försämrad insulinsekretion i INS-1 832/13 celler. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • professor Wollheim, Claes, University of Geneva, Switzerland
organization
publishing date
type
Thesis
publication status
published
subject
keywords
secreting systems, Endocrinology, pyruvate dehydrogenase kinase, beta-cells, pyruvate carboxylase, diabetology, Endokrinologi, sekretion, diabetologi, diabetes
pages
88 pages
publisher
Experimental Medical Science, Lund University
defense location
Segerfalkssalen, Wallenberg neurocentrum, Sölvegatan 17
defense date
2006-12-15 09:15:00
ISBN
91-85559-67-9
language
English
LU publication?
yes
additional info
id
c40b33e0-70fc-4786-b332-806527fe6c85 (old id 547657)
date added to LUP
2016-04-01 16:00:20
date last changed
2018-11-21 20:38:03
@phdthesis{c40b33e0-70fc-4786-b332-806527fe6c85,
  abstract     = {Type 2 diabetes is a disease that increases tremendously in the western world. It is characterized by insulin resistance and defects in insulin secretion. Insulin resistance is tightly linked to obesity, and usually precedes the onset of type 2 diabetes. When insulin resistance develops, the pancreatic beta-cells compensate by in¬creasing their secretion of insulin, causing hyperinsulinemia. This state may not be a major risk factor per se; in fact, many people develop severe insulin resistance and hyperinsulinemia without ever acquiring diabetes. However, beta-cells in some individuals, perhaps genetically predisposed, are unable to increase their secretion sufficiently to meet the new requirements. This leads to hyperglycemia, the main hallmark of diabetes. To be able to treat diabetes, the defects in the beta-cells causing impaired insulin secretion must be elucidated.<br/><br>
<br/><br>
The aim of this thesis was to investigate the mechanisms of insulin secretion, and especially what couples glucose stimulation of the beta-cell to insulin secretion.<br/><br>
<br/><br>
We have found that anaplerosis via pyruvate carboxylase is essential for both phases of glucose-stimulated insulin secretion, presumably via generation of an increased ATP/ADP ratio. Further, we discovered that expression of PDK1 is upregulated in INS-1 832/13 cells cultured at high concentrations of glucose, and that knock-down of PDK1 enhances insulin secretion. Both these findings prove that mitochondrial metabolism is important for insulin secretion, and points to the involvement of pyruvate cycling. We have also showed that PKA signaling is stimulated by glucose, and that inhibition of PKA decreases glucose-stimulated insulin secretion in INS-1 832/13 cells.},
  author       = {Krus, Ulrika},
  isbn         = {91-85559-67-9},
  language     = {eng},
  publisher    = {Experimental Medical Science, Lund University},
  school       = {Lund University},
  title        = {Coupling mechanisms of insulin secretion - roles of mitochondrial metabolism and cAMP.},
  url          = {https://lup.lub.lu.se/search/ws/files/4540800/547659.pdf},
  year         = {2006},
}