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Niacin's role in maintaining good
cholesterol
A research team has uncovered the likely
target of niacin (vitamin B3) in the liver,
which should provide a clearer picture of
how this vitamin helps maintain adequate HDL-cholesterol
levels in the blood and thus lower the risk
of heart disease.
While niacin can increase plasma HDL levels,
the mechanism of how it works has been
mysterious, although it's believed that
niacin does not actually increase HDL
production.
Recent work had uncovered that a component
of ATP synthase (the protein that makes ATP)
is present on the surface of liver cells,
and this subunit known as the 'beta chain'
can take up HDL.
Now, Moti Kashyap and colleagues found that
this beta chain is the basis of niacin's
effect. They added niacin to samples of
human liver cells and found that treatment
reduced the presence of Beta chain on the
cell surface by ~27%, and as a result HDL
uptake was reduced by ~35%. In comparison,
nicotinamide, a related molecule with no
clinical benefit, had far weaker effects.
These results indicate niacin hinders the
liver from removing HDL from the blood, thus
maintaining high plasma HDL levels.
Importantly, niacin does not affect another
major pathway known as "Reverse Cholesterol
Transport." Therefore, it maintains HDL
levels while still allowing the removal of
other cholesterol types, explaining why
niacin is especially beneficial.
The work also identifies a new drug target,
as no other drug in currently known to raise
HDL by inhibiting the surface expression of
the beta chain of ATP synthase.
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