Arkansas Children's Nutrition Center (J.-R.C., O.P.L, M.L.B., T.M.B., M.J.J.R.), Little Rock, Arkansas 72202; and Department of Pediatrics (J.-R.C., O.P.L, M.L.B., T.M.B., M.J.J.R.), University of Arkansas for Medical Sciences, Little Rock, Arkansas 72202.
Endocrinology. 2015 Feb;156(2):475-87. doi: 10.1210/en.2014-1427. Epub 2014 Dec 9.
Chronic consumption by experimental animals of a typical Western diet high in saturated fats and cholesterol during postnatal life has been demonstrated to impair skeletal development. However, the underlying mechanism by which high-fat, energy-dense diets affect bone-forming cell phenotypes is poorly understood. Here, we show that male weanling rats fed a diet containing 45% fat and 0.5% cholesterol made with casein (HF-Cas) for 6 weeks displayed lower bone mineral density and strength compared with those of AIN-93G-fed dietary controls. Substitution of casein with soy protein isolate (SPI) in the high-fat diet (HF-SPI) prevented these effects. The bone-sparing effects of SPI were associated with prevention of HF-Cas-induced osteoblast senescence pathways through suppression of the p53/p21 signaling pathways. HF-Cas-fed rats had increased caveolin-1 and down-regulated Sirt1, leading to activations of peroxisome proliferator-activated receptor γ (PPARγ) and p53/p21, whereas rats fed HF-SPI suppressed caveolin-1 and activated Sirt1 to deacetylate PPARγ and p53 in bone. Treatment of osteoblastic cells with nonesterified free fatty acid (NEFA) increased cell senescence signaling pathways. Isoflavones significantly blocked activations of senescence-associated β-galactosidase and PPARγ/p53/p21 by NEFA. Finally, replicative senescent osteoblastic cells and bone marrow mesenchymal ST2 cells exhibited behavior similar to that of cells treated with NEFA and in vivo bone cells in rats fed the HF-Cas diet. These results suggest that (1) high concentrations of NEFA occurring with HF intake are mediators of osteoblast cell senescence leading to impairment of bone development and acquisition and (2) the molecular mechanisms underlying the SPI-protective effects involve isoflavone-induced inhibition of osteoblastic cell senescence to prevent HF-induced bone impairments.
在生命后期，实验动物长期慢性摄入富含饱和脂肪和胆固醇的典型西式饮食会损害骨骼发育。然而，高脂肪、高能量饮食影响成骨细胞表型的潜在机制仍知之甚少。在这里，我们发现，6 周内喂食含有 45%脂肪和 0.5%胆固醇的酪蛋白（HF-Cas）饮食的雄性断奶大鼠的骨矿物质密度和骨强度均低于AIN-93G 饮食对照组。在高脂肪饮食中用大豆蛋白分离物（SPI）替代酪蛋白（HF-SPI）可预防这些影响。SPI 的骨保护作用与通过抑制 p53/p21 信号通路预防 HF-Cas 诱导的成骨细胞衰老途径有关。HF-Cas 喂养的大鼠 caveolin-1 增加，Sirt1 下调，导致过氧化物酶体增殖物激活受体 γ（PPARγ）和 p53/p21 的激活，而 HF-SPI 喂养的大鼠则抑制 caveolin-1 并激活 Sirt1，使 PPARγ 和 p53 在骨中去乙酰化。用非酯化游离脂肪酸（NEFA）处理成骨细胞会增加细胞衰老信号通路。异黄酮显著阻断了 NEFA 对衰老相关β-半乳糖苷酶和 PPARγ/p53/p21 的激活。最后，复制衰老的成骨细胞和骨髓间充质 ST2 细胞表现出类似于用 NEFA 处理的细胞和用 HF-Cas 饮食喂养的大鼠体内骨细胞的行为。这些结果表明：（1）HF 摄入时发生的高浓度 NEFA 是成骨细胞衰老的介质，导致骨发育和获得受损；（2）SPI 保护作用的分子机制涉及异黄酮诱导的成骨细胞衰老抑制，以防止 HF 引起的骨损伤。
