Mora-Gutierrez Adela, Farrell Harold M, Attaie Rahmat, McWhinney Velva J, Wang Changzheng
Cooperative Agricultural Research Center, Prairie View AandM University, Prairie View, TX 77446, USA.
J Dairy Res. 2007 Aug;74(3):356-66. doi: 10.1017/S0022029907002725. Epub 2007 Jul 26.
Bovine and caprine milks have a similar overall gross composition, but vary considerably in the ratios of their casein components. These differences cause significant changes in the ability of caseins to bind and stabilize calcium (Ca). It might be expected that these in vitro variations, which are thought to be due to differences in casein phosphopeptides (CPP) content, could lead to in vivo differences in the digestion and absorption of Ca. To test this hypothesis three milks with different casein ratios [bovine (B), caprine high in alphas1-casein (CH) and caprine low in alphas1-casein (CL)] were compared with regard to Ca absorption and deposition in growing male rats. For comparison, each milk was Ca-fortified (BCa-milk, CHCa-milk, and CLCa-milk) and CPP, prepared by enzymatic hydrolysis from the respective caseins (extrinsic CPP), were added to both native and Ca-milks. The effects of added CPP (extrinsic) could then be compared with intrinsic CPP released from the gastrointestinal digestion of caseins. Total gastric Ca was sampled at 15, 30 and 60 min after ingestion. No differences were found among the native milks with or without CPP, but the Ca from all Ca-milks (regardless of casein type) appeared to clear the stomach more rapidly and this was enhanced by the extrinsic CPP. The total intestinal Ca was not different among the native milks+/-CPP, however, it rose more rapidly with Ca fortification, and was higher at 30 min for all CPP-Ca-milks. At 60 min the total intestinal Ca level fell for the CPP-Ca-milks while all others continued to rise. These observations suggest that the CPP in Ca-milks enhance gastric clearance and uptake from the intestine. Ca availability from BCa-milk, CHCa-milk, and CLCa-milk with and without CPP was estimated by both plasma and femur uptake of 45Ca. Ca availability was enhanced at 5 h in the plasma in each case by added CPP. In all cases CPP stimulated Ca availability in the femur, but the CL-CPP was higher (P<0.05) than that of either CH-CPP or B-CPP (extrinsic CPP). Based on the results of this study we can conclude that the addition of CPP will have beneficial effect on the absorption of Ca in growing rats from CaCO3 added to bovine and caprine milks.
牛乳和羊乳的总体粗略成分相似，但酪蛋白成分的比例差异很大。这些差异导致酪蛋白结合和稳定钙（Ca）的能力发生显著变化。可以预期，这些体外差异（被认为是由于酪蛋白磷酸肽（CPP）含量不同所致）可能会导致体内钙消化和吸收的差异。为了验证这一假设，比较了三种酪蛋白比例不同的牛奶[牛乳（B）、αs1-酪蛋白含量高的羊乳（CH）和αs1-酪蛋白含量低的羊乳（CL）]对生长中的雄性大鼠钙吸收和沉积的影响。作为对照，每种牛奶都进行了钙强化（BCa-牛奶、CHCa-牛奶和CLCa-牛奶），并将通过各自酪蛋白酶解制备的CPP（外源性CPP）添加到天然牛奶和钙强化牛奶中。然后可以将添加CPP（外源性）的效果与酪蛋白在胃肠道消化过程中释放的内源性CPP的效果进行比较。在摄入后15、30和60分钟采集胃内总钙。添加或未添加CPP的天然牛奶之间未发现差异，但所有钙强化牛奶（无论酪蛋白类型如何）中的钙似乎更快地排空胃，并且外源性CPP增强了这种作用。天然牛奶±CPP之间的肠道总钙没有差异，然而，钙强化后其上升更快，并且在30分钟时所有添加CPP的钙强化牛奶中的肠道总钙更高。在60分钟时，添加CPP的钙强化牛奶的肠道总钙水平下降，而其他所有牛奶的总钙水平继续上升。这些观察结果表明，钙强化牛奶中的CPP可增强胃排空和肠道吸收。通过45Ca在血浆和股骨中的摄取来估计添加或未添加CPP的BCa-牛奶、CHCa-牛奶和CLCa-牛奶中钙的可利用性。在每种情况下，添加CPP后血浆中5小时时钙的可利用性均增强。在所有情况下，CPP均刺激股骨中钙的可利用性，但CL-CPP高于CH-CPP或B-CPP（外源性CPP）（P<0.05）。基于本研究结果，我们可以得出结论，添加CPP对生长大鼠从添加到牛乳和羊乳中的碳酸钙中吸收钙具有有益作用。
