Niacin's cholesterol-lowering mechanism proposed

06-Jun-2008

Related topics: Research

The cholesterol-lowering effects of niacin may be located in the liver, suggests new research that fills in the gaps in our understanding of the heart healthy benefits of the B vitamin.

The cell study indicates that niacin may reduce the removal of HDL 'good' cholesterol by about 35 per cent, according to findings published in the Journal of Lipid Research.

"Although niacin has been commonly used to increase plasma HDL levels, the mechanism(s) by which niacin exerts its action is not clearly understood," wrote the authors from the University of California, Irvine and the Atherosclerosis Research Center, VA Healthcare System in Long Beach.

The new study moves us closer to an answer, and 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.

High levels of cholesterol, particularly LDL cholesterol, has a long association with many diseases, particularly cardiovascular disease (CVD), the cause of almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year. Approaches revolve around reducing LDL levels and/or boosting HDL levels.

Study details

The researchers focused on a certain component in ATP synthase, the protein that makes the body's energy source ATP. A subunit of the protein known as the 'beta chain' can take up HDL, and therefore reduce the body's levels of 'good' cholesterol.

Using human cells, Moti Kashyap and colleagues found that this beta chain is the basis of niacin's effect. When human liver HepG2 cells were incubated with niacin a 27 percent reduction in the presence of beta chains on the cell surface was observed.

Moreover, a 35 per cent reduction in the uptake of HDL was recorded.

"In this report, we show, for the first time, that niacin decreases the surface expression of beta chain of ATP synthase in cultured HepG2 cells," wrote the authors.

In simple terms, the results indicate niacin hinders the liver from removing HDL from the blood, thus maintaining high plasma HDL levels.

Interestingly, the researchers did not document any affect on another major pathway known as "Reverse Cholesterol Transport", which allows for the removal of other cholesterol types.

"The findings add to our expanding knowledge about the mechanism of niacin action on its wide range of clinical effects including… anti-inflammatory, anti-thrombotic and flushing effects," concluded the researchers.

Vitamin B market

Despite the hurdle of rising costs, a strategic analysis of the European Vitamin B Market by Frost & Sullivan said the market was worth €415m (£280m) in 2005. This is anticipated to grow to €901m (£607m) by 2012, equivalent to a compound annual growth (CAGR) of 11.7 per cent for the sector.

Analysts at the firm said the growth of B-complex vitamins was being driven by a consumer interest towards self-medication.

The B vitamins act as coenzymes in numerous biochemical reactions in the body. They are essential for proper growth and maintenance of cells, tissue and organs.

Source: Journal of Lipid Research

June 2008, Volume 49, Pages 1195-1201

"Niacin inhibits surface expression of ATP synthase B-chain in HepG2 cells: implications for raising HDL."

Authors: L.-H. Zhang, V.S. Kamanna, M.C. Zhang, M.L. Kashyap