ACTH and α-MSH inhibit leptin expression and secretion in 3T3-L1 adipocytes: Model for a central-peripheral melanocortin-leptin pathway

Dennis Norman, Andrea M. Isidori, Vanni Frajese, Massimiliano Caprio, Shern L. Chew, Ashley B. Grossman, Adrian J. Clark, G. Michael Besser, Andrea Fabbri

Research output: Contribution to journalArticlepeer-review

Abstract

Leptin is the 167 amino-acid protein product of the Lep (obese) gene that is released predominantly from adipose tissue and circulates at levels related to the amount of fat. Leptin expression is hormonally regulated: insulin and glucocorticoids are stimulators, while inhibitors include β-adrenergic agonists and testosterone. Recently, adenylate cyclase-coupled melanocortin receptors have been identified in murine adipose tissue, the 3T3-L1 adipocyte cell line, and in human fat tissue. These studies prompted us to evaluate the effects of pro-opiomelanocortin (POMC)-derived peptides on leptin production and expression in 3T3-L1 adipocytes in culture. 3T3-L1 pre-adipocytes differentiated by the insulin/indomethacin (I/I) method produced leptin at levels that were two times higher than those obtained in cells differentiated by the more traditional insulin/dexamethasone/isobutylmethylxanthine (I/D/M) method. By RT-PCR studies, 3T3-L1 cells expressed both the melanocortin 2 receptors (MC2-R) and melanocortin 5 receptors (MC5-R) isoforms of the melanocortin receptor at an early stage of differentiation. When I/I differentiated 3T3-L1 adipocytes were incubated with different concentrations of dibutyryl cAMP (db-cAMP) or POMC-derived peptides (ACTH and α-MSH), ACTH and α-MSH stimulated cAMP production after 30 min (2-fold increase) associated with a dose-dependent inhibition of leptin secretion (ACTH≫α-MSH; IC50=3.2±0.4 SE and 36±5 nM, respectively), maximal after 3 h of incubation (30% inhibition). In addition, 100 nM ACTH and α-MSH induced a 60% reduction in leptin expression by RT-PCR. Incubation of cells with 0.5 mM db-cAMP led to a more prominent inhibition of leptin expression and secretion (up to 80% at 1 and 24 h, respectively). The ACTH and α-MSH inhibitory effects on leptin secretion were mediated by activation of the MC2-R and MC5-R and were reversed by the MC-R antagonists ACTH11-24 and ACTH7-38. In summary, we have shown that POMC-peptides are potent inhibitors of leptin expression and production in 3T3-L1 adipocytes. The finding of ACTH/α-MSH receptor-induced inhibition of leptin production and expression in adipocytes support the possibility that there is a control mechanism for modulation of adipose tissue function via a melanocortin-leptin axis.

Original languageEnglish
Pages (from-to)99-109
Number of pages11
JournalMolecular and Cellular Endocrinology
Volume200
Issue number1-2
DOIs
Publication statusPublished - Feb 28 2003

Keywords

  • α-MSH
  • ACTH
  • Leptin
  • Melanocortin receptors

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

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