Decreased GLUT4 expression, impaired insulin receptor (IR), IRS-1, and pp60/IRS-3 tyrosine phosphorylation are characteristics of adipocytes from insulin-resistant animal models and obese NIDDM humans. However, the sequence of events leading to the development of insulin signaling defects and the significance of decreased GLUT4 expression in causing adipocyte insulin resistance are unknown. The present study used male heterozygous GLUT4 knockout mice (GLUT4(+/-)) as a novel model of diabetes to study the development of insulin signaling defects in adipocytes with the progression of whole body insulin resistance and diabetes. Male GLUT4(+/-) mice with normal fed glycemia and insulinemia (N/N), normal fed glycemia and hyperinsulinemia (N/H), and fed hyperglycemia with hyperinsulinemia (H/H) exist at all ages. The expression of GLUT4 protein and the maximal insulin-stimulated glucose transport was 50% decreased in adipocytes from all three groups. Insulin signaling was normal in N/N adipose cells. From 35 to 70% reductions in insulin-stimulated tyrosine phosphorylation of IR, IRS-1, and pp60/IRS-3 were noted with no changes in the cellular content of IR, IRS-1, and p85 in N/H adipocytes. Insulin-stimulated protein tyrosine phosphorylation was further decreased to 12-23% in H/H adipose cells accompanied by 42% decreased IR and 80% increased p85 expression. Insulin-stimulated, IRS-1-associated PI3 kinase activity was decreased by 20% in N/H and 68% reduced in H/H GLUT4(+/-) adipocytes. However, total insulin-stimulated PI3 kinase activity was normal in H/H GLUT4(+/-) adipocytes. Taken together, these results strongly suggest that hyperinsulinemia triggers a reduction of IR tyrosine kinase activity that is further exacerbated by the appearance of hyperglycemia. However, the insulin signaling cascade has sufficient plasticity to accommodate significant changes in specific components without further reducing glucose uptake. Furthermore, the data indicate that the cellular content of GLUT4 is the rate-limiting factor in mediating maximal insulin-stimulated glucose uptake in GLUT4(+/-) adipocytes.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1096/fasebj.14.9.1117 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
ISG15 increases the apoptosis of β cells in type 1 diabetes.
Cell Signal
January 2025
Department of Endocrinology, The Third Xiangya Hospital, Central South University, 410007 Changsha, Hunan, China. Electronic address:
Type 1 diabetes (T1D) is an autoimmune disease characterized by hyperglycemia caused by the destruction of insulin-producing β cells. Viral infection is an important environmental factor which is associated with the islet autoimmunity in genetically susceptible individuals. Loss of β-cells and triggering of insulitis following viral infection could result from several non-exclusive mechanisms.
View Article and Find Full Text PDFSodium arsenite induces islets β-cells apoptosis and dysfunction via SET-Rac1-mediated cytoskeleton disturbance.
Ecotoxicol Environ Saf
January 2025
Department of Occupational and Environmental Health, School of Public Health, Dalian Medical University, No. 9 West Section Lvshun South Road, Dalian 116044, China; Global Health Research Center, Dalian Medical University, No. 9 West Section Lvshun South Road, Dalian 116044, China. Electronic address:
Sodium arsenite (NaAsO), the most common form of inorganic arsenic prevalent in the environment, has been closely linked to islet β-cell dysfunction, a critical pathological hallmark of type 2 diabetes (T2D). Even though apoptosis plays a pivotal role in arsenic-induced islet β-cell dysfunction, the explicit underlying mechanisms remain elusive. Here, we have identified that the SET-Rac1 signaling pathway is instrumental in the apoptosis and dysfunction of islet β-cells induced by NaAsO.
View Article and Find Full Text PDFWhile most pregnancies are affected by nausea and vomiting, hyperemesis gravidarum (HG) is at the severe end of the clinical spectrum and is associated with dehydration, undernutrition, and adverse maternal, fetal, and child outcomes. Herein we performed a multi-ancestry genome-wide association study (GWAS) of severe nausea and vomiting of pregnancy of 10,974 cases and 461,461 controls across European, Asian, African, and Latino ancestries. We identified ten significantly associated loci, of which six were novel ( , , , , , and and confirmed previous genome-wide significant associations with risk genes , , , and .
View Article and Find Full Text PDFDiabetes is associated with the dysfunction of glucagon-producing pancreatic islet α-cells, although the underlying mechanisms regulating glucagon secretion and α-cell dysfunction remain unclear. While insulin secretion from pancreatic β-cells has long been known to be partly controlled by intracellular phospholipid signaling, very little is known about the role of phospholipids in glucagon secretion. Here we show that TMEM55A, a lipid phosphatase that dephosphorylates phosphatidylinositol-4,5-bisphosphate (PIP2) to phosphatidylinositol-5-phosphate (PI5P), regulates α-cell exocytosis and glucagon secretion.
View Article and Find Full Text PDFUnlabelled: All eukaryotes utilize regulated secretion to release molecular signals packaged in secretory granules for local and remote signaling. An anion shunt conductance was first suggested in secretory granules of bovine chromaffin cells nearly five decades ago. Biochemical identity of this conductance remains undefined.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!