Cold stress, protein, brown adipose tissue, and human skeletal phenotype

生物人类学家感兴趣的是了解现代人如何随着时间的推移适应广泛的环境，包括不同的气候。这个项目的目标是了解一种特殊的脂肪，称为棕色脂肪组织或棕色脂肪，如何帮助人类在寒冷中保暖，以及饮食、运动和棕色脂肪的组合如何影响适应不同气候的人的骨骼生长方式。今天活着的人的骨骼不如我们祖先的骨骼强壮。这一趋势可能部分是由于运动量减少造成的，但研究人员想知道温度(比如住在取暖的房子里)和/或饮食的变化是否也起到了作用。这项研究将促进一名女科学家和两名女研究生的职业生涯，其中一名是非裔美国人。研究人员将向高中生介绍有关骨骼健康的研讨会，介绍饮食、温度和运动如何影响骨骼健康，并与密歇根大学自然历史博物馆一起开发实践骨骼测量活动。这项建议测试一种名为TEMPS(热量、能量、机械负荷、蛋白质和骨骼)的新模型，以整合温度、饮食和运动对骨骼表型的影响。这项研究将专注于一种名为棕色脂肪组织的脂肪如何帮助发育强壮的骨骼。棕色脂肪燃烧能量产生热量，棕色脂肪较多的人往往骨骼更强壮，尽管原因尚不清楚。这项研究将检验这样一种假设，即食用高脂肪/高蛋白饮食通过为非颤抖的产热提供脂肪酸和蛋白质，使人类祖先更容易进入寒冷气候，而且这种饮食与寒冷应激和锻炼相结合，有助于寒冷适应人群的骨骼强度。研究人员将使用在老鼠身上进行的对照实验和在人类骨骼上进行的比较研究来测试他们的模型。他们将研究在凉爽、标准或温暖的温度下饲养并喂养标准或高蛋白饮食的幼鼠的骨骼生长。一些老鼠还会有笼轮来锻炼。研究人员将收集老鼠的数据，包括食物摄入量、身体质量、棕色脂肪质量、骨密度、骨大小和形状以及骨强度。这些数据将与博物馆中冷适应和热适应人类骨骼的微型计算机断层扫描数据进行比较，看看它们是否显示出类似的模式。研究结果将表明，寒冷暴露、高蛋白饮食和运动是否会使骨骼变得更强壮，并找到新的方法来最大化年轻人的骨量，以减少晚年的骨质疏松症。这些数据还将提高我们对人类和尼安德特人等适应较冷或较暖气候的原始人骨骼发育的理解。

Biological anthropologists are interested in understanding how modern human populations have adapted over time to a wide range of environments, including different climates. The goal of this project is to understand how a specific kind of fat, called brown adipose tissue or brown fat, helps humans keep warm in the cold, and how the combination of diet, exercise, and brown fat affects the way the skeleton grows in people who are adapted to different climates. The bones of people alive today are less strong than the bones of our ancestors. This trend is probably partly the result of decreased exercise, but the researchers want to understand whether changes in temperature (such as living in heated homes) and/or diet also contribute. This research will advance the career of a female scientist and two female graduate students, one of whom is African American. The investigators will present workshops on bone health to high school students about how diet, temperature, and exercise affect bone health and develop a hands-on bone measurement activity with the University of Michigan Museum of Natural History.This proposal tests a new model called TEMPS (Thermogenesis, Energy, Mechanical loading, Protein, and the Skeleton) to integrate the effects of temperature, diet, and exercise on skeletal phenotype. The research will focus on how a type of fat called brown adipose tissue, or brown fat, helps develop strong bones. Brown fat burns energy to produce heat, and individuals with more brown fat also tend to have stronger bones, although it is not clear why. The study will test the hypothesis that eating a high fat/high protein diet made it easier for human ancestors to move into cold climates by providing fatty acids and protein for non-shivering thermogenesis, and that this diet, combined with cold stress and exercise, contributed to bone strength in cold-adapted populations. The researchers will use a combination of controlled experiments in mice and comparative studies in human skeletons to test their model. They will study skeletal growth in young mice raised at cool, standard, or warm temperatures and fed either standard or high-protein diets. Some mice will also have cage wheels for exercise. The researchers will collect data from mice including food intake, body mass, brown fat mass, bone mineral density, bone size and shape, and bone strength. These data will be compared to microcomputed tomography data from museum skeletons of cold- and heat-adapted humans, to see if they show similar patterns. The results will show whether cold exposure, high protein diet, and exercise make bones stronger, and identify new ways to maximize bone mass in young people, in order to reduce osteoporosis later in life. The data will also improve our understanding of skeletal development in hominins such as humans and Neanderthals that are adapted to colder or warmer climates.