Leptin and muscle hypertrophy

Training increases muscles receptors density
(obviously, dieting is not good)

Muscle hypertrophy and increased expression of leptin receptors in the musculus triceps brachii of the dominant arm
in professional tennis players

Eur J Appl Physiol (2010) 108:749–758

Hugo Olmedillas · Joaquin Sanchis-Moysi

In rodents, endurance training increases leptin
sensitivity in skeletal muscle; however, little is known
about the effects of exercise on the leptin signalling system
in human skeletal muscle. Thus, to determine whether
chronic muscle loading increases leptin receptor (OBR170)
protein expression, body composition dual-energy
X-ray absorptiometry was assessed in nine professional
male tennis players (24 § 4 years old) and muscle biopsies
were obtained from the dominant (DTB) and non-dominant
(NDTB) arm triceps brachii (TB), and also from the right
vastus lateralis (VL). In each biopsy, the protein content of
OB-R170, perilipin A, suppressor of cytokine signalling 3
(SOCS3), protein tyrosine phosphatase 1B (PTP1B) and
signal transducer and activator of transcription 3 (STAT3)
phosphorylation were determined by western blot. The
DTB had 15% greater lean mass (P < 0.05) and 62%
greater OB-R170 protein expression (P < 0.05) than the
NDTB. SOCS3 and PTP1B protein expression was similar
in both arms, while STAT3 phosphorylation was reduced in
the NDTB. OB-R170 protein content was also higher in
DTB than in VL (P < 0.05). In summary, this study shows
that the functional isoform of the leptin receptor is up-regulated
in the hypertrophied TB. The latter combined with the
fact that both SOCS3 and PTP1B protein expression were
unaltered is compatible with increased leptin sensitivity in
this muscle. Our findings are also consistent with a role of
leptin signalling in muscle hypertrophy in healthy humans.

Introduction

The ob/ob mouse, which does not produce leptin,
and the db/db mouse, which lacks functional leptin
receptors, have lower muscle mass than comparable wildtype
lean mice (Madiehe et al. 2002; Trostler et al. 1979).
Leptin administration to these mice promotes muscle
hypertrophy (Madiehe et al. 2002; Sainz et al. 2009).

Thus, muscle loading facilitates the expression of leptin
receptors when accompanied by muscle hypertrophy, at
least in muscles with a high proportion of type 2 fibres, as
in the TB (Sanchís-Moysi et al. 2009).

In summary, this study shows that TB hypertrophy is
accompanied by up-regulation of the functional isoform of
the leptin receptor. Given the cross-talk between IGF-I signalling
and leptin signalling, this finding is compatible with
a role for leptin signalling in muscle hypertrophy in healthy
humans. Since hypertrophy occurred predominantly in type
2 fibres in the loaded TB and in type 1 fibres in the VL, our
findings are consistent with a greater increase in OB-Rb
content in hypertrophied type 2 muscle fibres.

Source: michaelgundill.com

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