J Lipid Research 2011 Apr;52(4):771-81. Epub 2010 Dec
Cheng, Y; Duan, RD; Hansen, GH; Koentgen, F; Niels-Christiansen, LL; Nilsson, A; Ohlsson, L; Zhang, Y
Gastroenterology and Nutrition Laboratory, Biomedical Center B11, Lund University, S-221 84 Lund, Sweden.
Alkaline sphingomyelinase (alk-SMase) hydrolyses sphingomyelin (SM) to ceramide in the gut. To evaluate the physiological importance of the enzyme, we generated alk-SMase knockout (KO) mice by the Cre-recombinase-Locus of X-over P1(Cre-LoxP) system and studied SM digestion. Both wild-type (WT) and KO mice were fed H-palmitic acid labeled SM together with milk SM by gavage. The lipids in intestinal content, intestinal tissues, serum, and liver were analyzed by TLC. In KO mice, nondigested H-SM in the intestinal content increased by 6-fold and the formation of H-ceramide decreased markedly, resulting in 98% reduction of H-ceramide/ H-SM ratio 1 h after gavage. The absorbed H-palmitic acid portion was decreased by 95%. After 3 h, a small increase in H-ceramide was identified in distal intestine in KO mice. In feces, H-SM was increased by 243% and ceramide decreased by 74% in the KO mice. The KO mice also showed significantly decreased radioactivity in liver and serum. Furthermore, alkaline phosphatase activity in the mucosa was reduced by 50% and histological comparison of two female littermates preliminarily suggested mucosal hypertrophy in KO mice. This study provides definite proof for crucial roles of alk-SMase in SM digestion and points to possible roles in regulating mucosal growth and alkaline phosphatase function.
The team at Ozgene has over two decades of experience creating customised knockout and knock-in mice for pivotal medical research globally. Over 400 scientific publications are based on research using Ozgene mice.