What began with a stock tip at a Denver gym in April 2010 could lead to years in prison for a Colorado hedge fund manager.

Drew K. “Bo” Brownstein, 35, pleaded guilty to securities fraud Friday for his role in an insider-trading scheme.

The case showed how corporate secrets can get passed from person to person, spawning an expanding circle of illegal trades.

Brownstein’s trading on behalf of himself and others generated millions of dollars of illegal profits, according to the government. The Justice Department put the tally from certain of his trades at “nearly $2.5 million,” while the Securities and Exchange Commission said Brownstein’s trading generated “ill-gotten profits” of “approximately $5 million.”

Brownstein is the founder and chief executive of the hedge fund management firm Big 5 Asset Management.

On April 8, 2010, as the government tells it, he met his close friend Drew Peterson for a workout, and Peterson shared some sensitive information: It appeared that a company called Mariner Energy was about to be acquired.

Peterson, 35, had a pipeline to the Mariner boardroom. His father, Clayton Peterson, 66, a former managing director at the now-defunct accounting firm Arthur Andersen, was a Mariner director. The father had told the son about the impending deal and had him to buy Mariner stock for a family member, according to the government.

At the Denver gym, Drew Peterson told Brownstein to think about buying Mariner stock because the elder Peterson had been attending a lot of board meetings and it appeared that something important was about to happen, the government said in a court filing. The two friends speculated about who might be buying the company, the government said.

They both placed bets that the stock would rise, and they won those bets after the acquisition by Apache Corp. was announced. Then the government began investigating.

The Petersons were charged and pleaded guilty in August. Clayton Peterson was recently sentenced to two years of probation, three months of home confinement and a $400,000 fine.

The absence of a prison sentence “underscores that Clayton’s lapse in judgment was an aberration from his otherwise exemplary life,” his attorney, Steven R. Glaser, said in a statement.

Drew Peterson is awaiting sentencing.

Brownstein’s plea agreement suggests that he could be sentenced to between 37 and 46 months in prison. He also faces an SEC civil suit.

“This case is further evidence of the pervasive nature of insider trading by hedge funds, and a sobering reminder that such conduct is not limited to the immediate vicinity of Wall Street,” Sanjay Wadhwa, associate director of the SEC’s New York office, said in a statement.

Amid a broad federal crackdown, Brownstein became the 55th person charged in insider-trading cases in the Southern District of New York since August 2009 and the 51st to be convicted.