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Evidence for a functional beta 3-adrenoceptor in man
F Lönnqvist1, S Krief, A D Strosberg
1Department of Medicine, Huddinge University Hospital, Karolinska Institute, Stockholm, Sweden.
British Journal of Pharmacology
|November 1, 1993
Summary
Human fat cells possess a unique beta 3-adrenoceptor, distinct from beta 1 and beta 2 types. This receptor, identified through lipolytic action and mRNA analysis, plays a role in fat cell function.
Area of Science:
- Pharmacology
- Endocrinology
- Molecular Biology
Background:
- Human white fat cells express beta 1- and beta 2-adrenoceptors.
- The existence and function of beta 3-adrenoceptors in humans remain under investigation.
Purpose of the Study:
- To investigate the presence and characteristics of a functional beta 3-adrenoceptor in human white omental and subcutaneous fat cells.
- To determine the pharmacological profile of this atypical adrenoceptor.
Main Methods:
- Studied the lipolytic response of isolated human white fat cells to various selective and non-selective adrenoceptor agents.
- Utilized Schild analysis to determine antagonist pA2 values.
- Investigated beta 3-adrenoceptor mRNA expression using polymerase chain reaction (PCR).
Main Results:
- A non-selective beta 1/beta 2-adrenoceptor antagonist, CGP 12177, demonstrated lipolytic activity in both omental and subcutaneous fat cells.
- Selective beta 1 (CGP 20712A) and beta 2 (ICI 118,551) antagonists showed limited effect on CGP 12177-induced lipolysis.
- pA2 values indicated that CGP 12177's lipolytic effect was poorly antagonized by selective beta 1 and beta 2 blockers.
- Beta 3-adrenoceptor mRNA was detected in human white adipocytes.
Conclusions:
- Human white fat cells possess an atypical adrenoceptor, in addition to beta 1 and beta 2 subtypes.
- This atypical receptor is selectively stimulated by CGP 12177 and is poorly blocked by selective beta 1/beta 2 antagonists.
- Pharmacological and molecular data suggest this atypical receptor is the human beta 3-adrenoceptor subtype.