Investors have upped their interest in actively managed bond ETFs, pouring record capital into them in January as some paid up in hopes of stronger returns.

Vanguard Group (VOO), one of the world's largest ETF issuers, announced it is reducing fees on 168 mutual funds and ETF-related share classes, potentially saving investors over $350 million this year.

Asset manager Vanguard said on Monday it was lowering the cost of investing across its fund lineup in its largest cut ever and estimated that this would translate into savings of more than $350 million for its investors this year.