* Alcoa beats expectations but cautions of slowdown
* Yum Brands defies China sluggish growth, raises outlook
* Futures off: Dow 37 pts, S&P 0.5 pt, Nasdaq 3.5 pts
NEW YORK, Oct 10 (Reuters) - U.S. stock index futures edged lower on Wednesday after Alcoa kicked off earnings season by warning of a slight slowdown in some markets, highlighting concerns about sluggish global growth, even as its quarterly results beat expectations.
* Stronger demand for aluminum products from airplane and automobile producers helped Alcoa Inc's third-quarter profit beat analysts expectations, but it scaled back its global aluminum consumption outlook for 2012, citing the slowdown in China. Alcoa shares lost 1.4 percent to $9 in light premarket trade.
* China's slowdown is expected to rein in corporate earnings in the third quarter and dent profit forecasts as the world's second-largest economy feels the effect of the debt crisis in the euro zone, a key trading partner of the Asian nation.
* Earlier in the week, the World Bank cut its growth forecast for East Asia on concerns China's slowdown could last longer than expected.
* Analysts forecast third-quarter earnings of Wall Street's S&P 500 companies would fall 2.3 percent from the year-ago quarter, according to Thomson Reuters data, which would be the first drop in U.S. quarterly earnings in three years.
* According to data through Tuesday, 94 companies in the benchmark S&P index have issued negative outlooks, compared with 22 positive pre-announcements, for a ratio of 4.3, the weakest showing since the third quarter of 2001.
* Going against general declines was Yum Brands Inc, which gained 2.1 percent to $67.42 in premarket trading. The KFC parent company had raised its full-year outlook after sales in China held up, despite that nation's cooling economy.
* S&P 500 futures shed 0.5 point and were slightly below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 37 points, and Nasdaq 100 futures lost 3.5 points.
* U.S. engine maker Cummins Inc lowered its 2012 forecast for a second time this year, citing delays in customer spending due to a weakening global economy, and said it would cut up to 1500 jobs.
* Chevron Corp, the second-largest U.S. oil company, warned that third-quarter profits would be "substantially lower" than in the previous quarter as a hurricane and maintenance curbed its oil and gas output and a fire hit its refining arm.
* Earnings from warehouse chain Costco Wholesale Corp were a bright spot; the company reported a 27 percent jump in fourth quarter profit, on higher sales and membership fees.
* Coming on the heels of a 2013 profit forecast that was cut last month, FedEx Corp said it plans to slash costs at its underperforming express air freight and services divisions, with profit improvements of $1.7 billion planned at those operations over the next four years.
* Economic data expected Wednesday include wholesale inventories for August at 10:00 a.m. (1400 GMT) and the Federal Reserve's Beige Book of economic conditions at 2:00 p.m. (1800 GMT).
* European shares were lower for a third straight session, hurt by expectations of weak corporate results that may weigh on equity markets into next month.
* Asian shares fell, with Japanese stocks sliding 2 percent to a two-month low, on concerns that the corporate results season will reveal weaker earnings in the face of flagging global economic growth.