Targeted disruption of the beta 3-adrenergic receptor gene

J Biol Chem. 1995 Dec 8;270(49):29483-92. doi: 10.1074/jbc.270.49.29483.

Abstract

beta 3-Adrenergic receptors (beta 3-ARs) are expressed predominantly in white and brown adipose tissue, and beta 3-selective agonists are potential anti-obesity drugs. However, the role of beta 3-ARs in normal physiology is unknown. To address this issue, homologous recombination was used to generate mice that lack beta 3-ARs. This was accomplished by direct injection of a DNA-targeting construct into mouse zygotes. Twenty-three transgenic mice were generated, of which two had targeted disruption of the beta 3-AR gene. Mice that were homozygous for the disrupted allele had undetectable levels of intact beta 3-AR mRNA, as assessed by RNase protection assay and Northern blotting, and lacked functional beta 3-ARs, as demonstrated by complete loss of beta 3-agonist (CL 316,243)-induced stimulation of adenylate cyclase activity and lipolysis. beta 3-AR-deficient mice had modestly increased fat stores (females more than males), indicating that beta 3-ARs play a role in regulating energy balance. Importantly, beta 1 but not beta 2-AR mRNA levels up-regulated in white and brown adipose tissue of beta 3-AR-deficient mice (brown more than white), strongly implying that beta 3-ARs mediate physiologically relevant signaling under normal conditions and that "cross-talk" exists between beta 3-ARs and beta 1-AR gene expression. Finally, acute treatment of normal mice with CL 316,243 increased serum levels of free fatty acids (FFAs) (3.2-fold) and insulin (140-fold), increased energy expenditure (2-fold), and reduced food intake (by 45%). These effects were completely absent in beta 3-AR-deficient mice, proving that the actions of CL are mediated exclusively by beta 3-ARs. beta 3-AR-deficient mice should be useful as a means to a better understanding of the physiology and pharmacology of beta 3-ARs.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenylyl Cyclases / metabolism
  • Adipose Tissue / chemistry
  • Animals
  • Fatty Acids, Nonesterified / blood
  • Female
  • Gene Targeting*
  • Lipolysis
  • Male
  • Mice
  • Phenotype
  • RNA, Messenger / analysis
  • Receptors, Adrenergic, beta / drug effects
  • Receptors, Adrenergic, beta / genetics*
  • Receptors, Adrenergic, beta-1 / genetics
  • Receptors, Adrenergic, beta-2 / genetics
  • Receptors, Adrenergic, beta-3

Substances

  • Fatty Acids, Nonesterified
  • RNA, Messenger
  • Receptors, Adrenergic, beta
  • Receptors, Adrenergic, beta-1
  • Receptors, Adrenergic, beta-2
  • Receptors, Adrenergic, beta-3
  • Adenylyl Cyclases