Mysql nested query slower than two distinct query

gistfile1.sql

SELECT `topics`.* FROM `topics` WHERE `topics`.`id` IN (
	SELECT DISTINCT `topic_comments`.`topic_id` FROM `topic_comments` WHERE  (created_at > '2011-11-08 04:56:58') ORDER BY `topic_comments`.`created_at` DESC)
LIMIT 10 OFFSET 0;


SELECT DISTINCT `topic_comments`.`topic_id` FROM `topic_comments` WHERE (created_at > '2011-11-08 04:56:58') ORDER BY `topic_comments`.`created_at` DESC;

select topics.* from topics where topics.id in (45756,45334,44759,44799,44769,44697,43755,43445,43591,43754,42620,42643,42683,41333,42277,41678,41868,41610,41530,525,41336,41066,41067,41068,40596,40800,40575,40264,40292,40038,39744,39348,40082,39859,39702,40039,39532,38440,38658,8346,38218,37760,33297,37123,37353,37002,37089,36948,36870,36617,36727,16621,25468,25465,16972,8741,9604,17498,14175,14898,26513,26143,26058,10957,8799,35054,36728,36430,36393,36395,35816,7642,36278,36279,36097,24377,33299,35087,35053,32413,34660,34489,34510,33823,34077,33873,33557,32656,32600,33123,30970,32880,32924,116,29133,32274,32409,32104,32148,30946,31798,30962,31158,30969,30676,30677,30811,30538,30409,30408,30122,30189,18523,29667,29711,29714,29654,29666,29053,27083,28637,24776,28351,27796,27801,27559,27438,27393,26985,27267,26320,26939,25940,26465,25978,25620,1,24602,11490,25041,23421,24018,24704) LIMIT 10 OFFSET 0