101 Increased intake of polyunsaturated fatty acids, particularly n-6 polyunsaturated fatty acids, and animal protein parallel the increased incidence of CD in Japan.115 Similarly increased intake of dairy products and meat correlated with an increased UC incidence in a separate study.29
A more recent case-control Japanese study showed that a higher consumption of sweets, sweeteners, fats, fatty acids and oils were associated with an increased risk of CD and UC.116 Other factors with possible links to IBD such as breast feeding, altered hygiene, vaccinations, use of antibiotics and gastrointestinal infections have not been studied in Asian countries. Genetics. Differences in the IBD susceptibility genes between Asia and the West have recently undergone systematic review and meta-analysis.117 Nucleotide oligomerization domain (NOD)-2 variants associated with CD patients in the West have not been CHIR-99021 in vitro identified in CD in the Han Chinese,118–120 Japanese,121,122 Korean,123 Indian124 and Malaysian125 populations. New NOD2 mutations were, however, associated with CD in Malaysians (JW1 mutation), Han Chinese and Indian patients (P268S).125 The autophagy-related protein16-liked 1(ATG16L1) mutation also demonstrates global variation, with linkage MK 2206 to CD in the West not in Korea and Japan.126,127 Interleukin (IL)-23R mutation has been associated with CD in South Koreans;127 a single IL-23R nucleotide polymorphism, Gly149Arg,
was protective of CD in Han Chinese.128 In Asian
populations tumor necrosis factor (TNF)-SF15 polymorphisms were associated with CD with a high odds ratio,121,129,130 while TNF-308 polymorphisms were associated with UC.131–134 In summary, genetic mutations of IBD in Asians differ from Caucasians. Asian patients with IBD have different susceptibility genes to their Caucasian counterparts and have different mutations of the same genes to Caucasians. Novel genes identified in Asian IBD patients provide an opportunity 6-phosphogluconolactonase to explore new disease-associated mechanisms in this population of rising incidence. Extent and severity of disease. In studies from the West, disease extent for UC has traditionally been divided into proctitis (30–60%), left sided colitis (16–40%) and extensive colitis (18–35%).90,135,136 In most hospital-based studies from Asia, the extent of disease in UC is similar to that of the West; proctitis ranged from 9% to 50% and extensive colitis from 20% to 48%13,26,29,30,35,55,56,70,73,80,81,84,137–139 (Table 3). However a recent study from Sri Lanka documented extensive colitis in only 8.5% of patients at diagnosis,79 while a study from Thailand of 45 UC patients reported extensive colitis in 62.3%, although it is not clear if this was at the time of diagnosis.140 A study from Japan52 compared adult to pediatric disease and found a higher rate of extensive colitis in pediatric cases, mimicking a previous Western study.