Profits at JPMorgan Chase (JPM) surged in the second quarter due partly to a one-time accounting boost, but another drop in a key source of lending revenue demonstrated the challenges facing even the biggest US bank.

Net income of $18 billion was up 25% from the same period a year ago thanks largely to an exchange of shares in credit card giant Visa (V) that provided roughly $8 billion in gains. Excluding those gains, JPMorgan earned $13.1 billion in the quarter.

But there were also new signs of how even JPMorgan is struggling to maintain its outsized performance during an extended stretch of high interest rates, elevated deposit costs and weak loan demand.

A key measure of lending profit known as net interest income fell for the second consecutive sequential quarter, by 1%.

JPMorgan's stock fell slightly in pre-market trading.

JPMorgan, however, is holding to its full-year net interest income forecast of $91 billion, excluding trading revenue.

That would amount to a 2% increase from the net interest income it raked in last year.

JPMorgan CEO Jamie Dimon said "while market valuations and credit spreads seem to reflect a rather benign economic outlook, we continue to be vigilant about potential tail risks," referencing geopolitical tensions and a persistent inflationary forces.

"Inflation and interest rates may stay higher than the market expects," he said.

The result from JPMorgan kicked off another earnings season for the US banking industry as lenders set out to prove that they are staying resilient in the face of uncertainty about the US economy, the path of monetary policy and the unknown outcome of this fall’s presidential election.

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