Columbus-based insurer Aflac reported on Tuesday a 77 percent gain in net income in the second quarter, though investment troubles in Europe continue to weigh on the company's results.

Aflac said its revenue grew 16 percent to $5.9 billion, reflecting a beneficial yen-to-dollar exchange rate and strong sales of life insurance in Japan, Aflac's largest market.

Investments in Europe have hurt the company, however, with net after-tax realized investment losses of $272 million. That was an improvement over the second quarter a year ago when Aflac reported $453 million of such losses.

Aflac said it earned $483 million, or $1.03 per share in second quarter 2012, compared to. $274 million, or 58 cents per share a year ago.

Aflac said it expects earnings for the year of $6.45 to $6.52 per share, which was lowered a bit, reflecting lower investment yields.