Obesity is characterized by an expanded adipose tissue mass, and reversing
obesity reduces the risk of
insulin resistance and
cardiovascular disease.
Ciliary neurotrophic factor (
CNTF) reverses
obesity by promoting the preferential loss of white adipose tissue. We evaluated the cellular and molecular mechanisms by which
CNTF regulates adiposity. Obese mice fed a high-fat diet were treated with saline or recombinant
CNTF for 10 d, and adipose tissue was removed for analysis. Another group fed a high-fat diet was pair fed to
CNTF mice. In separate experiments, 3T3-L1 adipocytes were treated with
CNTF to examine metabolic responses and signaling.
CNTF reduced adipose mass that resulted from reductions in adipocyte area and
triglyceride content.
CNTF treatment did not affect lipolysis but resulted in decreases in fat esterification and lipogenesis and enhanced
fatty acid oxidation. The enhanced fat oxidation was associated with the expression of
peroxisome proliferator-activated receptor coactivator-1alpha (PGC1alpha) and
nuclear respiratory factor 1 and increases in oxidative phosphorylation subunits and mitochondrial biogenesis as determined by electron microscopy. Studies in cultured adipocytes revealed that
CNTF activates
p38 MAPK and
AMP-activated protein kinase. Inhibiting p38 activation prevented the
CNTF-induced increase in PGC1alpha but not
AMP-activated protein kinase activation. Diminished food intake with pair feeding induced similar decreases in fat mass, but this was related to increased expression of
uncoupling protein 1. We conclude that
CNTF reprograms adipose tissue to promote mitochondrial biogenesis, enhancing oxidative capacity and reducing lipogenic capacity, thereby resulting in
triglyceride loss.