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* Topix hits lowest since Sept 2017
* Nidec soars after posting record H1 profit
* Sumco nosedives after Credit Suisse cuts rating on oversupply
* Komatsu falls on Caterpillar's Wall St selloff
By Ayai Tomisawa
TOKYO, Oct 24 (Reuters) - Japan's Nikkei edged lower on Wednesday morning in choppy trade with investor sentiment still fragile after the recent heavy selling in global shares though focus was now shifting to corporate earnings.
The Nikkei share average opened a tad higher but turned negative in midmorning trade, falling 0.3 percent to 21,951.27. It dropped 2.7 percent on Tuesday, hit by a pullback in global equities.
The broader Topix fell 0.5 percent to 1,642.71, after hitting as low as 1,641.69, a level not seen since Sept. 2017.
Subaru Corp stumbled 7 percent to hit a more than four-year low after the automaker nearly halved its operating profit forecast for the April-September period due to higher quality-related costs. The increase in costs follows a vehicle recall after the company failed to adhere to proper inspection steps last year.
Elsewhere, Nidec Corp soared as much as 5.7 percent after the company posted a record April-Sept operating profit and raised its annual dividend projections.
"Global investors' sentiment is still weak so we may see volatile trade for a while. We need to continue monitoring how Chinese shares move," said Norihiro Fujito, a chief investment strategist at Mitsubishi UFJ Morgan Stanley Securities.
Wednesday's losers included silicon products maker Sumco Corp, which nosedived 10 percent to 1,397 yen after Credit Suisse slashed its stock rating to "neutral" from "outperform" and cut its target price to 1,385 yen from 3,530 yen, citing an oversupply from greater-than-expected capacity expansion.
Construction equipment maker Komatsu tumbled 4.6 percent to a level not seen since June 2017 after Caterpillar Inc dived 7.6 percent after it did not raise its annual profit forecast again.
Domestic-demand sensitive stocks outperformed. Retail, food and utility stocks attracted buying, with Fast Retailing gaining 2.3 percent and Isetan Mitsukoshi soaring 2.5 percent, Kikkoman Corp surging 3.1 percent and Tokyo Gas advancing 1.9 percent. (Editing by Sam Holmes)