After chalking up another quarter of better-than-expected profits, UnitedHealth Group officials on Tuesday described the potential for growth through a new venture fund the company is using to invest in innovative health care startups.

Minnetonka-based UnitedHealth first described the venture fund to investors in November and announced in March that Larry Renfro, the chief executive of the company's Optum division, would lead the effort.

During a conference call Tuesday to discuss first-quarter results, Renfro said the venture fund will invest in a variety of emerging health care technologies including digital care, consumer care and health analytics with artificial intelligence, big data and machine learning.

"A tremendous effort will go into ventures," Renfro said. "We hope to accelerate early-stage, open-market innovations across the breadth of the health care services marketplace, with up to $600 million in newly committed funds."

UnitedHealth Group, which is the nation's largest health insurer, posted first-quarter financial results Tuesday that beat analyst estimates for earnings and revenue. The company boosted financial guidance for the year and saw its stock close Tuesday up more than 3.5 percent.

Optum, which is the company's fast-growing division for health care services, saw operating earnings grow at a faster rate than the legacy health insurance business. The new investment fund is called Optum Ventures.

In November, UnitedHealth listed among the venture fund's first four investments a startup called Mindstrong Health, which uses machine learning and artificial intelligence to analyze a patient's smartphone interactions. The goal is "to help diagnose and treat neuropsychiatric and neurodegenerative disorders such as depression, schizophrenia and post-traumatic stress disorder," UnitedHealth Group said in a news release.

UnitedHealth in November also highlighted startups that were developing cloud-based computing platforms for analytics that could be used by health care professionals or life-science companies. A startup called Buoy Health was developing a digital health assistant to help patients better understand symptoms and get advice on where to go for care and what to do.

On Tuesday, UnitedHealth Group didn't discuss specific investments, but Chief Executive David Wichmann said investments in venture-based enterprises will be key to growth over the next five to 10 years.

"We see a growing number of smaller, well-suited organizations that we are partnering with to really open-source innovation into UnitedHealth Group," Wichmann said.

Renfro said it will be "business as usual" until he's replaced as Optum CEO this summer by Andrew Witty, the former chief executive at pharmaceutical giant GlaxoSmithKline. Renfro said of the venture fund: "We're off and running in terms of putting programs together."

In his first public comments since the executive transition at Optum was announced in March, Wichmann told investors that Witty would bring to Optum "strong global health care insights."

"He also has a very balanced social conscience as well as a growth and financial return orientation," Wichmann said. "And, of course, the knowledge that he has around pharmacy is extremely helpful at this critical time in health care broadly."

Optum is one of the nation's largest pharmaceutical benefits managers (PBM). Insurers and employers hire the unit, called OptumRx, to manage the pharmacy portion of health plans. Optum also sells IT services and provides health care directly to patients via urgent care, surgery centers and clinics.

During the first quarter, UnitedHealth Group posted $2.84 billion in earnings, up 31 percent compared with last year, on revenue of $55.2 billion. Earnings per share of $3.04 beat the $2.91 expected by analysts surveyed by Thomson Reuters.

U.S. membership in the company's UnitedHealthcare health insurance products grew only slightly in the first quarter as gains in Medicare and Medicaid health plan coverage offset a decline in commercial coverage purchased by employer groups.

The health insurance business added about 2 million members in South America with the acquisition of Empresas Banmedica, a large health insurance and hospital company in Chile, Colombia and Peru that is meant to supplement UnitedHealth Group's large health care business in Brazil.

"Optum is serving more consumers and clients than ever before," Wichmann said. "UnitedHealthcare continued to deliver distinctive growth, serving 2.2 million more people in the first quarter."

For the year, UnitedHealth Group now expects adjusted net earnings of $12.40 and $12.65 per share, up from previous guidance of $12.30 to $12.60 per share.

UnitedHealth Group now employs about 285,000 people worldwide including 18,000 in Minnesota. Shares of UnitedHealth Group closed Tuesday at $238.54, up $8.22 for the day, or about 3.6 percent.