Treating obesity is one of the
largest challenges to modern society, and both scientific and unscientific
methods for losing weight are often mentioned in mainstream media. One
unconventional scientific finding that has gained attention recently is the
suggestion that sildenafil (the key ingredient in Viagra) could be useful to
treat obesity in humans. In this article we take a critical approach to the
study behind these findings.
The study, which was published in
Federation of American Societies for
Experimental Biology, was an animal study that used both mice and mice
cells to investigate what effect a signalling messenger called cGMP would have
on fat tissue. It is important to note that the study was not exclusively
related to the effect of sildenafil on fat tissue, and other experiments within
this publication considered alternative aspects of cGMP on the fat cells. With
regards to the sildenafil experiments it was hypothesised that if sildenafil could
effectively block an enzyme known to break down cGMP, then the increased levels
of cGMP could be considered to contribute to potential changes in the fat
cells.
Overall, the sildenafil
experiment lasted seven days. During this period the mice were split into two
groups, with one group being given 12mg/kg sildenafil and the other group being
given a placebo containing 0.9% salt. These treatments were administered on a
daily basis. Once the treatments were finished, the researchers compared
changes in weight and body composition before and after the treatment between
the groups. In addition to that the researchers also looked at tissue samples
taken from the mice’s abdominal region. The key findings indicated that the
weight and body composition was not affected in either group. However, the
observation of the samples of abdominal cells suggested that, for the mice in
the sildenafil group, the white fat cells had changed to have some features of
brown adipose tissue (known for their ability to generate heat from fat). Based
on this, the researchers argued that sildenafil could contribute to “browning”
of white fat cells, which could be useful for considering obesity treatments.
Although this study outlined an
intriguing hypothesis for the underlying mechanism of browning, it is clear
that the many limitations of the study demonstrated that the findings are too
small and too recent to warrant the conclusions. The fact that the findings
cannot be extrapolated to humans at this stage is obvious given that this was
an animal study that had a very short duration. Similarly, several factors such
as whether all the mice were obese, ages of the mice and levels of stress
tolerance that could have contributed to different reactions between the groups
were not specified, thus making it challenging to rule out alternative
explanations.
What stood out the most for us
when reading the article was the absence of two distinctions in particular. The
first one was the researchers’ failure to make a distinction between browning
cells and brown cells when discussing their results, thus making it difficult
to know whether their ability to create heat from fat comes from an identical
process and is comparable to other studies of brown cells. Consequently, this
omission led to the study’s main strength of explaining an underlying
relationship between sildenafil and fat cells becoming subject to more
questions than answers. The second distinction was the fact that the
researchers gave the mice very high doses of sildenafil, which were much higher
than the current doses prescribed for erectile dysfunction treatment in humans.
This, of course, made us wonder for whom they were designing this treatment and
where the value of the finding lies.
If high doses are likely to be
considered unsuitable for humans, then they are even more unlikely to be a
prescribed by most clinicians. While the findings in this study can raise hope,
it is important to know that they are far from being established facts in the
scientific community and even further from being considered safe and reliable
treatments in the clinical community.