MOSCOW — When a new government-backed investment fund opened five years ago, Moscow wanted to send a simple message: Russia was ready to take the politics out of business.

Authorities signed up a high-powered board of international advisers to oversee its activities, a group that included American private equity executives like David Bonderman of TPG and Stephen A. Schwarzman of the Blackstone Group. In a video on the fund’s site, Mr. Bonderman emphasized that the investments in Russia would be “transparent and make commercial decisions, not political decisions.”

After the United States and Europe slapped Russia with sanctions over the Ukraine conflict, many board members distanced themselves. And recently, the fund has faced an uncomfortable spotlight over a big investment to a politically connected company. Late last year, the Russian Direct Investment Fund made a $1.75 billion loan to Sibur, a giant petrochemical company with close ties to the Kremlin.

Such concerns have long clouded the investment landscape, that politics play a heavy hand in business. And they have only intensified with the current economic malaise, as the government struggles to deal with weak oil prices and Western sanctions.