Caveolin-1 Secreted from Adipose Tissues and Adipocytes Functions as an Adipogenesis Enhancer.

Chang CC， Chen CY， Wen HC， Huang CY， Hung MS， Lu HC， Chen WL， Chang CH

Abstract

OBJECTIVE:
Caveolin-1 (Cav-1) is expressed abundantly in adipose tissue and involved in many physiological processes. While Cav-1 has been reported to be secreted in pancreatic acinar cells and LNCaP prostate cancer cells， its secretion from adipose tissue awaits investigation.

METHODS:
Cav-1 secretion from 3T3-L1 adipocytes and fat tissues from normal chow diet- and high-fat diet (HFD)-fed mice was measured. Functions and uptake of secreted Cav-1 proteins were assessed by adding Cav-1 back to preadipocytes and LNCaP cells.

RESULTS:
Cav-1 secretion was evident in adipose tissues and were substantially promoted in HFD-fed mice. Cav-1 was detectable in the conditioned media of 3T3-L1 adipocytes but not preadipocytes. Hypertrophied adipocytes induced by glucose and fatty acids secreted more Cav-1， suggesting that hypertrophied adipocytes were responsible for enhanced Cav-1 secretion in obese mice. Secreted Cav-1 was taken up by preadipocytes and LNCaP cells. 3T3-L1 preadipocytes overexpressing Cav-1 were better differentiated， suggesting that secreted Cav-1 may promote adipogenesis. Hypertrophied 3T3-L1 adipocytes enhanced ERK1/2 activation， and the attenuation of ERK1/2 activity by PD98059 inhibited Cav-1 secretion.

CONCLUSIONS:
Cav-1 is actively secreted from adipocytes as a putative adipogenesis enhancer. Hypertrophied adipocytes secrete Cav-1 via ERK1/2-dependent mechanisms to promote adipogenesis， thus establishing a vicious cycle.

Obesity 2017;25(11):1932-40
https://www.ncbi.nlm.nih.gov/pubmed/28944626