Sony, which is putting more money into internal start-ups, is seeing big profits from its holding in a little-known health-care company.

The Tokyo-based consumer electronics company has seen the value of its stake in M3 rise more than 50 per cent over the past year to about $4 billion, according to data compiled by Bloomberg. The 39 per cent holding has increased by more than $1 billion in the last 12 months.

M3 is a medical web portal founded in 2000 that is used by doctors in Japan, China, the US and other countries to find medical studies, look up drug information and network with each other. The company, also based in Tokyo, said earlier this year that it plans to increase its own investments in health-care start-ups in Japan and abroad.

M3 acquired assets from Sony in 2003 and went public in 2004. M3 shares have surged this year on rising sales and profits. The stock slipped 1 per cent on Thursday after gaining 4.5 per cent to an all-time high of 3,480 yen on Wednesday. Sony shares lost 1.4 per cent.

A spokeswoman for Sony declined to comment on the investment.