Effect of milk fat globules on growth and metabolism in rats fed an unbalanced diet

We assessed the effects of supplementing milk fat globules (MFG) on the growth and development of the skeleton in rats fed a Western unbalanced diet (UBD). The UBD is high in sugar and fat, low in protein, fiber, and micronutrients, and negatively impacts health. The MFG—a complex structure secreted in milk—has a unique proteome and lipidome, and differs significantly from isolated dietary ingredients. Rats consuming the UBD exhibited growth retardation and disrupted bone structural and mechanical parameters; these were improved by supplementation with small MFG. The addition of small MFG increased the efficiency of protein utilization for growth, and improved trabecular and cortical bone parameters. Furthermore, consumption of UBD led to a decreased concentration of saturated fatty acids and increased levels of polyunsaturated fatty acids (PUFA), particularly omega-6 PUFA, in the serum, liver, and adipose tissue. The addition of small MFG restored PUFA concentration and the ratio of omega-6 to omega-3 PUFA in bone marrow and adipose tissue. Finally, large but not small MFG supplementation affected the cecal microbiome in rats. Overall, our results suggest that natural structure MFG supplementation can improve metabolism and bone development in rats fed an UBD, with the effects depending on MFG size, whereas the detrimental effects of an UBD on the microbiome were not mitigated by MFG supplementation. 3 week old Sprague-Dawley rats were fed for 6 weeks with a control diet, UBD or UBD+MFG. After the sacrifice, caecal stool samples were collected and used for 16S rRNA sequencing of the V4 region using 515F–806R primers.

本研究评估了添加乳脂肪球（milk fat globules, MFG）对喂食西式不平衡膳食（Western unbalanced diet, UBD）的大鼠骨骼生长发育的影响。该UBD高糖高脂，蛋白质、膳食纤维与微量营养素含量偏低，会对健康产生负面影响。乳脂肪球是乳汁分泌的复杂结构，拥有独特的蛋白质组（proteome）与脂质组（lipidome），与提纯的膳食成分存在显著差异。喂食UBD的大鼠出现生长迟缓，骨骼结构与力学参数紊乱；补充小型MFG可有效改善此类异常。补充小型MFG可提升生长所需的蛋白质利用效率，并改善小梁骨（trabecular bone）与皮质骨（cortical bone）的相关参数。此外，喂食UBD会使大鼠血清、肝脏与脂肪组织中的饱和脂肪酸浓度降低，多不饱和脂肪酸（polyunsaturated fatty acids, PUFA）水平升高，尤其是ω-6型多不饱和脂肪酸。补充小型MFG可恢复骨髓与脂肪组织中的PUFA浓度，以及ω-6与ω-3型PUFA的比值。此外，补充大型而非小型MFG会改变大鼠的盲肠微生物组（cecal microbiome）。综上，本研究结果表明，补充天然结构的MFG可改善喂食UBD大鼠的代谢水平与骨骼发育，且其作用效果取决于MFG的粒径大小；但UBD对微生物组的有害影响并未因MFG补充而得到缓解。选取3周龄的斯普拉格-道利大鼠（Sprague-Dawley rats），分别喂食对照膳食、UBD或UBD+MFG，喂养周期为6周。处死后收集盲肠粪便样本，采用515F–806R引物对V4区域进行16S核糖体RNA（16S rRNA）测序。