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Functional GIP receptors are present on adipocytes
R G Yip1, M O Boylan, T J Kieffer
1Section of Gastroenterology, Boston Medical Center and Boston University School of Medicine, MA 02118, USA.
Endocrinology
|September 2, 1998
Summary
Glucose-dependent insulinotropic polypeptide (GIP) receptors are present and functional in fat cells. These GIP receptors are upregulated during adipocyte differentiation, impacting lipid metabolism and glucose homeostasis.
Area of Science:
- Endocrinology
- Metabolic Research
- Adipocyte Biology
Background:
- Glucose-dependent insulinotropic polypeptide (GIP) plays a role in glucose homeostasis and lipid metabolism.
- GIP influences lipoprotein lipase, fat incorporation, and chylomicron clearance.
- GIP receptors were not previously identified in fat cells, despite observed effects.
Purpose of the Study:
- To identify and characterize GIP receptors in isolated adipocytes and the 3T3-L1 fat cell line.
- To confirm the presence and functionality of GIP receptors in adipose tissue.
Main Methods:
- RNAse protection analysis to detect GIP receptor transcripts.
- Western blot analysis using GIP receptor antiserum.
- [125I] GIP binding assays.
- Intracellular cAMP accumulation assays.
Main Results:
- GIP receptor transcripts were found in rat adipocytes.
- GIP receptors were detected in rat fat and differentiated 3T3-L1 cells via Western blot.
- Specific GIP binding sites were identified in differentiated 3T3-L1 cells.
- GIP increased cAMP accumulation in rat fat cells and differentiated 3T3-L1 cells, indicating functional receptors.
Conclusions:
- GIP receptors are present in fat cells.
- GIP receptor expression is upregulated during 3T3-L1 cell differentiation into adipocytes.
- The identified GIP receptors are functional, mediating cAMP signaling pathways in adipose tissue.