alpha-Lactalbumin hydrolysate stimulates glucagon-like peptide-2 secretion and small intestinal growth in suckling rats.
We investigated whether bovine milk constituents influenced glucagon-like peptide (GLP)-2 secretion and intestinal growth in suckling rats. Male Sprague-Dawley rats (14 d old) received i.g. infusions of a milk protein fraction, a lactose solution, or the cream fraction of milk. The serum concentration of GLP-2, but not GLP-1, markedly increased in rats administered milk protein compared with those given the lactose solution or the cream fraction from 60 to 120 min after administration. In another experiment, both casein (CN) and whey protein isolate stimulated GLP-2 secretion at 120 min after administration, but soy protein and ovalbumin did not. Stimulation of GLP-2 secretion by several milk proteins was similar, including alpha-CN, alpha-lactalbumin (alpha-La), and beta-lactoglobulin, in a separate experiment. A hydrolysate of alpha-La obtained by incubation with protease A extracted from Aspergillus oryzae (LaHPA) caused almost twice the GLP-2 release due to intact alpha-La and other alpha-La hydrolysates. Free amino acid concentrations and molecular size distributions did not differ among alpha-La hydrolysates, including LaHPA. In rat pups reared with milk formulae containing alpha-La or LaHPA, LaHPA significantly promoted small intestinal elongation and increased the number of crypt epithelial cells compared with a formula containing intact alpha-La. LaHPA administration also increased the maltase:lactase activity ratio, a marker of maturation of the intestinal mucosa. In conclusion, milk proteins stimulate GLP-2 secretion and contribute to growth and maturation of the small intestine in suckling rats.
Izumi
Hirohisa
H
Nutritional Science Laboratory, Morinaga Milk Industry Co., Ltd., Zama, Kanagawa 228-8583, Japan. h-izumi@morinagamilk.co.jp
Ishizuka
Satoshi
S
Inafune
Ayako
A
Hira
Tohru
T
Ozawa
Kazuhiro
K
Shimizu
Takashi
T
Takase
Mitsunori
M
Hara
Hiroshi
H
D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D002417:Cattle; D052216:Glucagon-Like Peptide 1 / Q000097:blood / Q000378:metabolism; D053767:Glucagon-Like Peptide 2 / Q000097:blood / Q000187:drug effects / Q000378:metabolism*; D006868:Hydrolysis; D007421:Intestine, Small / Q000187:drug effects / Q000254:growth & development*; D007768:Lactalbumin / Q000494:pharmacology*; D007785:Lactose / Q000494:pharmacology; D008297:Male; D008892:Milk; D008894:Milk Proteins / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D053767:Glucagon-Like Peptide 2; D008894:Milk Proteins; D052216:Glucagon-Like Peptide 1; D007768:Lactalbumin; D007785:Lactose