WASHINGTON, April 30 (Reuters) - The U.S. high-yield bond and leveraged loan markets saw mixed performances in April, according to a JPMorgan report, as companies continued to struggle through high interest rates and inflation.

The S&P 500 High Yield Corporate Bond Index showed a 0.71% loss in April, the weakest performance for high-yield bonds since October 2023, according to the Tuesday report.

Still, the index is showing a 0.90% gain so far in 2024. Year-to-date new issuance has greatly outpaced 2023 at $112.9 billion compared with $58.9 billion this time last year, boosted by aerospace supplier Boeing's $10 billion unsecured note sale on Monday.

The S&P Global Leveraged Loan Index gained 0.61% in April, due to little new issuance and elevated interest rates. Regardless, CCC-rated loans show a loss for the first time since November 2023.

The institutional loan market has seen a $76 billion contraction since June 2022, according to JPMorgan, its first contraction in a decade. It was driven by a collapse in net new issuance, an increase in bond-for-loan takeouts, outflows from retail investors, and continued growth of the private credit market, the report said.

Highly leveraged borrowers have continued to struggle through elevated interest rates and stubborn inflation. The dollar volume of corporate debt that has defaulted rose sharply in the first quarter, according to the latest Moody's Ratings default monitor, to $33 billion from $19 billion in the fourth quarter of 2023.

Markets will closely watch remarks by Federal Reserve Chairman Jerome Powell at Wednesday's press conference at the close of the Fed's two-day policy meeting, when the central bank is expected to hold rates steady.

(Reporting by Matt Tracy in Washington; Editing by Leslie Adler)