Father's sperm may pass on obesity to kids

Researchers found that sperm from normal weight and
obese men differed in how some genes were turned "on" or
"off". And the differences were seen in gene regions linked to
brain development and appetite control.
The Danish scientists said the findings may offer one
biological explanation for why heavy dads often have heavy
kids.
Active or dormant genes
"At a basic level, most people know that overweight parents
often have overweight kids," said Anthony Comuzzie, a
spokesman for the Obesity Society and a researcher at the
Texas Biomedical Research Institute, in San Antonio.
"That's not all genetics, of course, but a good part of it is,"
said Comuzzie, who was not involved in the new study.
However, he added, it may be more complicated than the set
of genes you inherit. The current study tackled "epigenetics",
chemical mechanisms that determine whether a gene is active
or dormant at certain times.
Research has shown that epigenetic patterns can be altered
through behaviour, including diet and exercise. And like genes,
epigenetic patterns can be inherited.
Scientists are just beginning to understand how it works, but
research in insects and rodents shows that parents' epigenetic
"marks" can affect the health of their offspring.
It all suggests that we inherit more than a "random mix of
genes from our ancestors", said lead researcher Romain
Barres, an associate professor at the University of
Copenhagen, in Denmark.
Appetite control
Instead, he said, people may also receive "a biological imprint
of their parent's behaviour and lifestyle".
For the study, published online in the journal Cell Metabolism ,
Barres and colleagues analysed sperm from 10 men who were
obese and 13 men with a normal weight. The investigators
found that the two groups showed different DNA methylation
patterns in their sperm including in gene regions linked to
appetite control.
Comuzzie explained it this way: "You can have two genes that
are structurally identical. But they will not function the same
way if they have different DNA methylation patterns."
To see whether obesity, per se, could be the reason for the
differences, the researchers next studied a group of severely
obese men undergoing weight-loss surgery. They found that
the drop in weight post-surgery caused a "dramatic" change in
DNA methylation in the men's sperm.
"That finding is really intriguing," Comuzzie said.
But a big unknown, he added, is what the epigenetic patterns
in sperm ultimately mean for a man's children.
"To what extent do these patterns get passed?" Comuzzie
said. "Does the pattern get 'reset' in the fertilised egg? We
don't know."
Pre-pregnancy behaviour
"We have not investigated the offspring of the men we
studied," Barres said.
But his team is now working with a fertility clinic to study
epigenetic differences in unused embryos, created with sperm
from men of various weights. (In Denmark, fertility clinics
must discard unused embryos after five years, and they can
be used for research.)
For now, Comuzzie said, the findings suggest that it's not only
women who need to be conscious of their lifestyle and health
going into pregnancy.
"Dad does matter, too," he said.
Barres agreed. "Our results might help change pre-pregnancy
behaviour for parents-to-be," he said.
- Health24