Infant Growth, Milk Composition, and Maternal Energetics in a High Altitude Environment

在人类历史的大部分时间里，母乳一直是婴儿营养的主要来源。最近的研究表明，母乳是一种极其复杂的液体，含有丰富的常量营养素、免疫因子和激素成分，所有这些都可以喂给婴儿。同样，母乳的变化也令人难以置信，不同社会和生活环境的女性会产生不同数量的这些成分。尽管有越来越多的研究，但关于牛奶在不同生态环境下如何以及为什么会发生变化，以及这些差异如何影响婴儿的健康和生长，还有很多事情需要了解。这项研究对生活在尼泊尔努布里山谷高海拔环境中的一个种群进行了详细的观察，以调查在相当大的生态压力下母乳如何参与婴儿生长的调节。该项目将为本科生和研究生的研究和培训提供机会，并促进研究地点的区域卫生和科学教育。了解生态压力如海拔和冷应激如何影响母乳成分，进而影响婴儿的代谢和生理发育，可能对了解工业化和快速工业化人群中超重和代谢功能障碍的危险因素至关重要。考虑到母乳在婴儿期的主要作用，母乳本身是一个关键的选择时期，很可能存在相当大的自然选择对母乳成分的影响。在牛奶中发现的生长因子和代谢激素与线性生长、体重增加、无脂肪量和年龄大小有显著关联，这使得牛奶中产生的激素和细胞因子可能是婴儿身体组成发育规划的候选者。然而，这些关联从未在生态压力大的种群中进行过调查，在这些种群中，环境选择对婴儿表型可能很严重。该项目将调查喜马拉雅山（尼泊尔）努布里山谷9个村庄115对母婴的生态、母亲生理、乳汁成分和婴儿生长发育之间的关系。这里的人口是藏族人，根据家族历史记录，至少有700人从青藏高原移民到这里。村庄的海拔高度在海拔7500 - 13100英尺之间。母乳样本、代谢测试和身体热扫描将在婴儿生命的第一年的四个时间点收集。母亲和孩子的热成像是一项创新，它将显示身体脂肪模式的差异。此外，对母亲的访谈和母亲和孩子的人体测量数据（身高、体重、身体组成）将从出生开始收集，之后每隔两个月收集一次。由此产生的数据将提供迄今为止收集到的海拔和季节相关的生长差异、乳汁激素和母亲出生后第一年生殖状况的最完整的图景。

For the vast majority of human history, breast milk has been the primary source of nutrients during infancy. Recent research has shown human milk to be a tremendously complex fluid containing a wealth of macronutrients, immune factors and hormonal components, all of which get fed to the baby. Similarly, mothers' milk is incredibly variable, with women in different societies and living situations producing different amounts of many of these components. Despite a growing body of research, there is still much left to understand about how and why milk varies in different ecological circumstances and how these differences may affect the health and growth of infants. This study takes a detailed look at a population which lives in the high altitude environment of the Nubri Valley, Nepal, to investigate how breast milk may be involved in the regulation of infant growth under considerable ecological stress. The project will provide opportunities for undergraduate and graduate student research and training, and facilitate regional health and science education at the study location. Understanding how ecological pressures such as altitude and cold stress influence human milk composition and in turn, infant metabolism and physiological development, may be crucial in understanding the risk factors for overweight and metabolic dysfunction in industrialized and rapidly industrializing populations.It is likely that there has been considerable natural selection on human milk composition given the primary role human milk has during infancy, itself a critical period of selection. Growth factors and metabolic hormones found in milk show significant associations with linear growth, weight gain, fat free mass, and size for age, making milk born hormones and cytokines likely candidates for developmental programming of infant body composition. However, these associations have never been investigated in an ecologically stressed population where environmental selection on infant phenotypes may be severe. This project will investigate associations between ecology, maternal physiology, milk composition, and infant growth and development in 115 mother-infant pairs from nine villages in the Nubri Valley of the Himalayas (Nepal). The population is ethnically Tibetan, with family histories recording occupation in the valley for at least 700 hundreds following immigration from the Tibetan plateau. Villages range in altitude from 7,500-13,100 feet above sea level. Milk samples, metabolic tests, and thermal body scans will be collected at four time points over the first year of infant life. The thermal imaging of mother and child is an innovation which will show differences in body fat patterning. Additionally, interviews of the mothers and anthropometric measurements (height, weight, body composition) of both mother and child will be collected beginning at birth and at two month intervals afterward. The resulting data will provide the most complete picture ever collected of altitude- and seasonality-associated differences in growth, milk hormones, and maternal reproductive condition across the first year of life.