Research Article Dietary Hyaluronic Acid Migrates into the Skin of Rats Mariko Oe, 1 Koichi Mitsugi, 2 Wataru Odanaka, 1 Hideto Yoshida, 1 Ryosuke Matsuoka, 1 Satoshi Seino, 1 Tomoyuki Kanemitsu, 1 and Yasunobu Masuda 1 1 R&D Division, Kewpie Corporation, 2-5-7 Sengawa Kewport, Sengawa, Chofu, Tokyo 182-0002, Japan 2 ADME & Tox. Research Institute, Sekisui Medical Co., Ltd., 2117 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1182, Japan Correspondence should be addressed to Ryosuke Matsuoka; ryosuke matsuoka@kewpie.co.jp Received 8 May 2014; Revised 31 July 2014; Accepted 31 July 2014; Published 14 October 2014 Academic Editor: Enzo Berardesca Copyright © 2014 Mariko Oe et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Hyaluronic acid is a constituent of the skin and helps to maintain hydration. Te oral intake of hyaluronic acid increases water in the horny layer as demonstrated by human trials, but in vivo kinetics has not been shown. Tis study confrmed the absorption, migration, and excretion of 14 C-labeled hyaluronic acid ( 14 C-hyaluronic acid). 14 C-hyaluronic acid was orally or intravenously administered to male SD rats aged 7 to 8 weeks. Plasma radioactivity afer oral administration showed the highest level 8 hours afer administration, and orally administered 14 C-hyaluronic acid was found in the blood. Approximately 90% of 14 C-hyaluronic acid was absorbed from the digestive tract and used as an energy source or a structural constituent of tissues based on tests of the urine, feces, expired air, and cadaver up to 168 hours (one week) afer administration. Te autoradiographic results suggested that radioactivity was distributed systematically and then reduced over time. Te radioactivity was higher in the skin than in the blood at 24 and 96 hours afer administration. Te results show the possibility that orally administered hyaluronic acid migrated into the skin. No excessive accumulation was observed and more than 90% of the hyaluronic acid was excreted in expired air or urine. 1. Introduction Hyaluronic acid is a high molecular mass linear polysac- charide composed of D-glucuronic acid and N-acetyl-D- glucosamine [1]. Hyaluronic acid is well known and was frst isolated and identifed from cattle eyes by Meyer and Palmer in 1934 [2]. Hyaluronic acid is synthesized by all animals and in some microbes, existing in all connective tissues of the body, including the skin, joint fuid, blood vessels, serum, brain, cartilage, heart valves, and umbilical cord. Te total volume of hyaluronic acid in the body is about 15 g for an adult weighing 70 kg, replacing one third of the hyaluronic acid afer degradation and synthesis everyday [3]. Hyaluronic acid is used in medicines, cosmetics, and foods and is a material receiving attention worldwide. Mixed into supplements, confectioneries, beverages, and processed foods, hyaluronic acid is approved as health food material for new resource foods in China, food additives and health function food in Korea, and as a food additive in Japan. Hyaluronic acid is marketed as a supplement in the USA, Canada, Italy, and Belgium. Safety tests of hyaluronic acid included repeated dose oral toxicity tests [4], chronic toxicity tests [5], acute toxicity tests [6–8], subacute toxicity tests [9–11], reproductive and developmental toxicity studies [12–18], antigenicity tests [19, 20], mutagenicity tests [21–23], and micronucleus assays [24, 25]. Safety was confrmed; hence, hyaluronic acid is a food ingredient that can be ingested with confdence. Hyaluronic acid supplements are used to treat joint pain in Europe and America, whereas it is known as a moisturizer for the skin in addition to treating joint pain in Japan. Te oral intake of hyaluronic acid is reported to increase water in the horny layer as demonstrated in human trials [26–28]. On the other hand, further study is required whether orally administered high-molecular hyaluronic acid is taken up into the body and exerts efects. Starch, a high molecular polysaccharide, is degraded into disaccharides by saliva and pancreatic juice and further Hindawi Publishing Corporation e Scientific World Journal Volume 2014, Article ID 378024, 8 pages http://dx.doi.org/10.1155/2014/378024