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Low density lipoprotein binding and uptake by human and rat islet beta cells
A Y Grupping1, M Cnop, C F Van Schravendijk
1Department of Metabolism and Endocrinology, Vrije Universiteit Brussel, Belgium. agrup@mebo.vub.ac.be
Endocrinology
|October 10, 1997
Summary
Low density lipoproteins (LDL) bind to and are internalized by pancreatic beta cells in rats and humans. This interaction may influence beta cell function in diabetes.
Area of Science:
- Endocrinology
- Metabolic research
- Cell biology
Background:
- Lipoprotein metabolism abnormalities are frequent in diabetes.
- The impact of lipoprotein variations on pancreatic beta cell function remains unclear.
Purpose of the Study:
- To investigate specific interactions between low density lipoproteins (LDL) and pancreatic islet beta cells.
- To determine if LDL binding, uptake, and degradation occur in beta cells.
Main Methods:
- Utilized radioactively labeled LDL (125I-LDL) and fluorescently labeled LDL (DiI-LDL) as tracers.
- Assessed LDL binding affinity (K(d)) and receptor regulation in rat and human islet cells.
- Investigated LDL uptake and lysosomal degradation at 37°C.
Main Results:
- Rat islet beta cells possess high-affinity LDL binding sites (K(d) = 9 nM), also recognized by very low density lipoproteins.
- LDL binding is specific to beta cells and leads to receptor down-regulation.
- Islet beta cells internalize and degrade LDL, a process also observed in human islet cells.
- Human islet cells show lower LDL binding capacity but similar down-regulation sensitivity compared to rat cells.
Conclusions:
- Human and rat islet beta cells express LDL receptors capable of internalizing LDL.
- The LDL internalization pathway in beta cells warrants further investigation for its role in pancreatic beta cell (dys)regulation.