Mechanistic Determinants of Dietary Polyphenol Bioactivity in Bone

摘要 含有姜黄素的姜黄素膳食补充剂(DS)的销量呈指数级增长，目前最畅销 在美国，植物DS与姜黄DS使用量的显著增加有关， 美国人用于治疗慢性肌肉骨骼疾病，如类风湿性关节炎(30% 流行率)。然而，从科学上讲，很难调和骨骼保护作用的活体证据。 姜黄素在人类和啮齿动物体内的药代动力学数据显示几乎检测不到循环水平 姜黄素摄入后的苷元姜黄素，由于其在肠道和肝脏快速结合而形成 姜黄素葡萄糖醛酸苷，一种主要的循环代谢物，被证明在很大程度上是不活跃的。我们实验室最近的工作 揭示了这一过程，展示了姜黄素的高活性酶去卷曲 在骨内形成生物活性苷元，其浓度与体外抑制所需的浓度相似 骨吸收破骨细胞形成，是包括骨质疏松症在内的所有主要骨骼疾病中骨丢失的关键驱动因素。 由于葡萄糖醛酸化是许多保护骨骼的饮食多酚的共同代谢命运，因此主要的 该项目的目标是确定骨保护多酚的生物活性是否类似地依赖于 葡萄糖醛酸苷酶(GUSB)，姜黄素和其他骨骼中葡萄糖醛酸类化合物的去结合所需的酶 骨骼中具有保护性的饮食多酚，如槲皮素。这个问题具有重大的临床意义，因为 在人类群体中，GUSB的表达具有很高的变异性。实验将利用绝经后的模型 骨质丢失(去卵巢[OVX]小鼠)，GUSB活动和/或加工缺陷小鼠，以及 添加FDA批准的GUSB酶评估骨保存对GUSB的依赖性 在去卵巢小鼠中对姜黄素或槲皮素治疗的反应。对……的相对重要性的调查 细胞外(例如分泌)与细胞内GUSB介导的饮食多酚葡萄糖醛酸苷的去共轭作用， 在评估人类相关的酶表型和替代疗法时，一个关键问题也将是 地址。鉴于最近有关姜黄膳食补充剂相关肝毒性的临床报道， 姜黄素治疗的小鼠的GUSB表型对肝功能的影响将是次要结果。我们的协作 调查小组已做好准备来解决这些研究问题。此处获得的概念验证数据将 发挥影响力，挑战我们对酶的理解并支持有关酶作用的新研究 饮食多酚对维持骨骼健康的表型反应，并开辟新的途径 促进美国老龄化人口健康的个性化方法。

ABSTRACT An exponential increase in sales of curcumin-containing turmeric dietary supplements (DS), now the top selling botanical DS in the United States, has been associated with a marked increase in turmeric DS usage by Americans for the treatment of chronic musculoskeletal conditions, such as rheumatoid arthritis (30% prevalence). Scientifically, however, it has been difficult to reconcile in vivo evidence of bone protective effects of curcumin in humans and rodents with pharmacokinetic data demonstrating barely detectable circulating levels of aglycone curcumin following curcumin ingestion, due to its rapid conjugation by intestine and liver to form curcumin glucuronide, a major circulating metabolite shown to be largely inactive. Recent work by our laboratory has shed light on this process, demonstrating high activity levels of enzymatic deconjugation of curcumin glucuronide within bone to form bioactive aglycone in concentrations similar to those required in vitro to inhibit bone-resorbing osteoclast formation, a key driver of bone loss in all major bone diseases, including osteoporosis. Because glucuronidation is a common metabolic fate for many bone-protective dietary polyphenols, the primary goal of this project is to determine whether bone-protective polyphenol bioactivity is similarly dependent on ß- glucuronidase (GUSB), the enzyme required for the deconjugation of glucuronides of curcumin and other bone protective dietary polyphenols, such as quercetin, within bone. This question has great clinical relevance since GUSB expression is highly variable in human populations. Experiments will utilize a model of post-menopausal bone loss (ovariectomized [OVX] mice), mice with defects in GUSB activity and/or processing, and supplementation with a FDA-approved GUSB enzyme to assess the GUSB-dependence of bone preservation in OVX mice in response to curcumin or quercetin treatment. An investigation of the relative importance of extracellular (e.g. secreted) vs. intracellular GUSB-mediated deconjugation of dietary polyphenol glucuronides, a key question when assessing relevant enzyme phenotypes and replacement therapies in humans, will also be addressed. Given recent clinical reports of turmeric dietary supplement-associated hepatotoxicity, effects of GUSB phenotypes on liver function in curcumin-treated mice will be a secondary outcome. Our collaborative investigative team is well poised to address these research questions. Proof of concept data obtained here will be impactful, challenging our understanding and supporting new research regarding the role of enzyme phenotypes in maintaining bone health in response to dietary polyphenols, and opening new avenues for personalized approaches to promote the healthspan of our aging US population.