Mukesh Ambani, who runs India's most-valued business empire Reliance Industries [Get Quote] group, also saw the highest fluctuation of about $35 billion in his net worth over the past year, even as he trailed his estranged brother Anil as the world's second-biggest wealth creator.

Mukesh, however, managed to maintain a slender lead of $1 billion over Anil in terms of net worth, as per a Forbes billionaire list released on Thursday. The magazine has ranked Mukesh as world's fifth richest with a net worth of $43 billion, followed by Anil with $42 billion.

According to the magazine, Anil emerged as the biggest gainer in the world with his wealth soaring by $23.8 billion, followed by $22.9 billion gained by Mukesh.

In Forbes' 2007 list, Mukesh's net worth stood at $20.1 billion, as against Anil Ambani's $18.2 billion. Mukesh and Anil were ranked at 14th and 18^th positions, respectively, on the previous year's list.

"Stocks fluctuate, as they say. Some of the world's 1,125 billionaires have lost serious money in the recent correction. On the other hand, quite a few have watched their fortunes wax and wane in the past year," the magazine said.

According to Forbes, Mukesh's peak net worth was at $55 billion in past one year to February 11, on which date the net worth of all the billionaires were calculated for the latest list. His wealth peaked early this year and was at the lowest level in February-March period 2007.

NRI steel tycoon Lakshmi Mittal saw his net worth peaking at $55 billion, as against $32 billion in previous year's list and $45 billion in the latest list.

Among other prominent billionaires to have seen a major fluctuation in net worth, US-based casino and hotel baron Sheldon Adelson of Las Vegas Sands saw a peak worth of $38.5 billion, as against a final figure of $26 billion and 2007 figure of $26.5 billion.

Microsoft's Bill Gates' wealth peaked at $65 billion, before he slipped to the world's third richest man this year with $58 billion. He was the world's richest with $56 billion in the 2007 list.

Besides, Google's Sergey Brin saw a peak net worth of $25.5 billion. His current net worth stands at $18.7 billion, whereas the same was at $16.6 billion in 2007.

"Hong Kong's Li Ka-shing was worth $23 billion last year, jumped to $32 billion on January 4, 2008, then dipped to $26.5 billion on February 11, our valuation day," Forbes said.

Besides, after her father transferred his stock to her, "Yang Huiyan, the largest shareholder in Chinese property developer Country Garden, became Asia's richest woman in April, when the company debuted on the Hong Kong stock exchange. Back then, she was worth $8.8 billion. Yang topped out at $17.3 billion in September and is now down to $7.4 billion," it noted.