14 | New Scientist | 27 July 2019
DementiaA HIGH profile scientific journal is
investigating a study it published
that suggests global warming is
largely down to natural solar cycles.
The study was published online
on 24 June by Scientific Reports,
an open access journal run by
Nature Research. The authors say
that Earth’s 1°C temperature rise
over the past two centuries could
largely be explained by changes inthe distance between Earth and
the sun as the sun orbits our solar
system’s centre of mass, called
the barycentre.
Ken Rice at the University of
Edinburgh, UK, criticised the paper
for an “elementary” mistake about
celestial mechanics. “It’s well
known that the sun moves around
the barycentre of the solar system
due to the influence of the other
solar system bodies, mainly Jupiter,”
he says. “This does not mean, as
the paper is claiming, that this then
leads to changes in the distance
between the sun and the Earth.”Rice is urging the journal
to withdraw the paper.
“The sun-Earth distance does
not vary with the motion of the
sun-Earth system around the
barycentre of the sun-Jupiter
system, nor the sun-galactic
centre system or any other purely
mathematical reference point,” says
Gavin Schmidt of the NASA Goddard
Institute for Space Studies. He saysthe journal must retract the paper
if it wants to retain any credibility.
Lead author Valentina Zharkova
of Northumbria University, UK,
defended the study. “The close
links between oscillations of solar
baseline magnetic field, solar
irradiance and temperature are
established in our paper without any
involvement of solar inertial motion.”
A Scientific Reports spokesperson
told New Scientist that it is aware of
concerns raised over the paper, and
that it has begun an “established
process” to investigate the paper. ❚ENCOURAGING results have
been announced from a small
trial of a new kind of treatment
for Alzheimer’s disease, which
targets gum disease bacteria.
Trial participants showed
improvements in the levels of
certain molecules in their blood
and spinal fluid, says Cortexyme,
the US firm developing the
therapy. However, the company
hasn’t yet shown that the
treatment can reduce the severity
of dementia.
“It isn’t enough to get excited
about, but it’s enough to say this
hypothesis is interesting,” says
Carol Routledge of the charity
Alzheimer’s Research UK.
The new approach is at odds
with decades of thinking about
Alzheimer’s. It was believed that
the condition is caused by a
build-up of toxic plaques in the
brain made of a protein called
amyloid. But numerous therapies
that block amyloid failed to halt
progression of the disease in trials.
Many researchers now think the
protein may be a side effect of
Alzheimer’s, not the root cause.
Cortexyme believes Alzheimer’s
may be due to bacteria calledPorphyromonas gingivalis – better
known for causing gum disease –
somehow getting into the brain
and sparking inflammation.
The microbe and its toxins have
been found at somewhat higher
levels in the brains of people
with Alzheimer’s, and can trigger
amyloid build-up if put into
the brains of mice.
Cortexyme has developed an
oral medicine called COR388 that
can block the activity of the toxins
released by the bacteria. Last year,
the firm carried out short trials inhealthy volunteers and nine
people with mild to moderate
Alzheimer’s disease, six of whom
got twice-daily capsules, while
the rest got a placebo version.
After four weeks, there were
small improvements in two kinds
of tests for dementia severity
for those who got the medicine,
but these were too small to be
classed as statistically significant.Cortexyme says that is because the
trial was designed as a safety test
and was too small to show efficacy.
Yet there were falls in a marker
of inflammation in the blood,
the firm told the Alzheimer’s
Association International
Conference in Los Angeles last
week. There was also a drop in
fragments of a protein called
ApoE in people’s spinal fluid.
This protein is damaged by the
bacterial toxin, and people
who make a particular genetic
variant of it are more likely to
develop Alzheimer’s.
The drop in both molecules
suggests the medicine is working
as intended, says Mike Detke of
Cortexyme. “It’s very promising.”
Routledge says we shouldn’t
assume changes in blood or spinal
fluid substances will translate into
reduced dementia symptoms, as
similar ones have given false hope
in past trials of other approaches.
“We definitely need some more
data before we can understand
the consequences of having this
bacteria in the brain,” she says.
Cortexyme has now begun a
year-long trial in 570 people with
Alzheimer’s disease. ❚“ The sun moves,
but this doesn’t change
the distance between
the sun and Earth”Climate science
Could these pink bacteria
below cause Alzheimer’s
by harming brain cells?Clare WilsonCORT
EX
YMENews Gum disease and Alzheimer’s
Your questions answered
newscientist.com/alzheimers-gum-disease
Experimental Alzheimer’s drug
Treatment targeting gum disease bacteria shows early promise
Controversial
climate study under
investigationAdam Vaughan