[pronut-hiv] Study finds evidence linking fat loss to the activity of the nervous system

["ProNut-HIV" <pronut-hiv@healthnet.org>]

Aidsmap
Study finds evidence linking fat loss to the activity of the nervous
system

A small Dutch study has shown that HIV-positive patients with fat loss
as a side-effect of HIV treatment have high levels of the
neurotransmitter noradrenaline in their fat tissue. The investigators
believe that this could be evidence of a link between lipoatrophy and
alterations in the activity of the nervous system. The study's
findings were presented in the 21st March edition of AIDS. 

In late 2003, the same group of doctors published an article in the
journal The Lancet describing their hypothesis that antiretrovirals
could cause body fat redistribution through their action on the
unconscious 'autonomic' nervous system. 

They argued that lipoatrophy could be caused by overactivity of the
'sympathetic' component of the autonomic nervous system in fat
deposits under the skin. Backing up their hypothesis with observations
from animal and human studies, they proposed that this could lead to a
breakdown of the fat tissue under the skin, leaving other types of fat
intact. 

Now, the doctors have measured the activity of the sympathetic nervous
system and levels of its main signalling chemical noradrenaline in the
fat and muscle of seven HIV-positive patients with body fat
redistribution. They compared these measurements to those from seven
HIV-negative control patients and seven HIV-positive patients who have
never taken anti-HIV drugs. 

Noradrenaline levels tended to be higher in the muscle and the fat of
the patients with lipoatrophy than in the HIV-negative patients.
However, when the investigators calculated ratios of noradrenaline
levels in the fat to those in the muscle, they found a significantly
higher ratio in the patients with lipoatrophy (p < 0.05). 

In contrast, the HIV-positive patients without lipoatrophy had similar
levels of noradrenaline to the HIV-negative control patients. However,
the investigators did not give the ratio of noradrenaline levels for
this group of patients. 

"The interstitial concentration of noradrenaline in subcutaneous fat
relative to that in skeletal muscle tended to be higher in
HIV-associated adipose redistribution syndrome (HARS) patients," the
doctors conclude. This is "consistent with an increased noradrenaline
content in subcutaneous fat, compared with the other groups." 

The investigators did not see any differences in the overall whole-body
activity of the sympathetic nervous system, as measured by noradrenaline
levels in the blood or by examining the blood pressure and heart rate of
the patients. 

They did find that the activity of the sympathetic nerves leading to
the leg muscles was lower in the patients with lipoatrophy than the
other two groups (p < 0.05). However, the doctors did not measure the
activity of nerves targeting the fat tissue. 

Although their observations fall short of proving that local
alterations in the activity of the sympathetic nervous system are
responsible for the loss of fat from under the skin, they provide some
evidence to support their original hypothesis. However, more research is
needed to examine whether changes in the activity of nerves targeting
the fat tissue occur in patients with lipoatrophy, and whether these
changes can be linked to the effects of anti-HIV drugs in the brain. 

"In the context of an unchanged global sympathetic activity,
HIV-infected patients with HARS appear to have increased noradrenaline
concentrations at the level of skeletal muscle and subcutaneous fat
tissue, which may be consistent with the hypothesis that regional
changes in autonomic activity contribute to the selective loss of
peripheral fat as observed in HARS," the investigators conclude. 

"These findings suggest that disturbances in local sympathetic
nervous system activity play a role in this remarkable syndrome, but
this requires further investigation." 

Reference 

van Gurp PJ et al. Sympathetic nervous system function in
HIV-associated adipose redistribution syndrome. AIDS 20: 773-775, 2006.