Early Life Nutrition, Developmental Plasticity, and Reproductive Ecology in Filipino Males

在美国国家科学基金会的支持下，克里斯·库泽博士和一个来自西北大学、北卡罗来纳大学教堂山分校和菲律宾宿雾市圣卡洛斯大学的国际团队将调查胎儿和婴儿的营养和生长是否会影响男性生殖生物学，这是在菲律宾参加一项长期健康研究的大约1000名年轻人中测量的。具体来说，他们将测试这样一种假设，即出生前（根据出生体重或母亲孕期营养状况）或出生后几个月（根据婴儿喂养方式或生长速度）营养不良会导致睾丸功能下降，包括睾丸激素和其他与男性生殖力相关的激素分泌减少。此外，该项目还将调查睾丸激素变化对健康的更广泛影响，比如肌肉、力量或血压的变化。这一系列问题的基本原理来自最近的一项研究，该研究表明，早期营养不良对老鼠和绵羊的这些特征有类似的长期影响。到目前为止，还没有在人类身上对这些关系进行大规模的测试。这项研究为探索这些关系提供了独特的条件，因为所有的参与者都是在他们的母亲怀孕时（1983年）首次参加研究的。随着年龄的增长，对每个人的出生尺寸、生长速度、营养和其他重要特征进行了定期监测，为他们的生活经历提供了丰富的记录。这些人现在已经22岁了，因此这项研究可以评估生命早期的营养和生长状况是否能预测几十年后成年后的生殖功能和健康状况。为了回答这项研究的具体假设，这些数据将通过访谈中测量的成人生活方式和饮食信息以及用于测量生殖激素的生物样本（血液和唾液）来增强。所有这些补充数据和标本都是最近使用为解决本研究的研究目标而设计的协议收集的，标本现在在西北大学冷冻储存。美国国家科学基金会的资金只需要支付分析这些样本中的激素的费用，这些样本将在西北大学人类学系的人类生物学研究实验室进行测量。这项研究承诺对一个具有相当理论和应用重要性的问题有重要的见解。与女性一样，跨文化研究也记录了男性生殖功能的大量人口差异。然而，与女性不同的是，这种生物变异在男性身上很难解释。这项研究将通过调查早期营养和生长的差异是否会影响男性生殖功能来解决这一矛盾。这个问题的答案也可能为人类适应的一种重要模式提供见解：在面临具有挑战性的营养环境时，减少“昂贵”特征（如繁殖和肌肉质量）的支出可能是一种必要的（如果不是理想的）反应。本研究更广泛的影响包括为有兴趣获得实验室研究经验的研究生和本科生提供培训机会。它还将加强美国和菲律宾的一个国际研究小组之间的合作关系，他们在了解男性生育能力的原因和后果方面有着共同的兴趣。

With NSF support, Dr. Chris Kuzawa and an international team based out of Northwestern University, the University of North Carolina, Chapel Hill, and the University of San Carlos, Cebu City (the Philippines), will investigate whether fetal and infant nutrition and growth influence male reproductive biology, as measured in roughly 1,000 young adults participating in a long-term study of health in the Philippines. Specifically, they will test the hypothesis that undernutrition prior to birth (as indicated by birth weight or maternal pregnancy nutrition) or during the months after birth (as indicated by mode of infant feeding or growth rate) will predict reduced testicular function, including lower production of testosterone and other hormones that are correlated with male fecundity. In addition, this project will also investigate the broader health effects of any changes in testosterone, such as reductions in muscle, strength or changes in blood pressure. The rationale for this series of questions comes from recent research showing similar long-term effects of early life undernutrition on these traits in rats and sheep. To date, no large scale test of these relationships have been conducted in humans.This study is uniquely equipped to explore these relationships, because all of the participants were first enrolled in the study when their mothers were pregnant with them (in 1983). Birth size, growth rate, nutrition and other important characteristics were monitored periodically as each person aged, providing a rich record of their life experiences. These individuals are now 22 years of age, allowing this study to evaluate if nutrition and growth measured early in life predict reproductive function and health measured several decades later in adulthood.To answer this study's specific hypotheses, these data will be augmented by adult information on lifestyle and diet measured in interviews, and biological specimens (blood and saliva) for the measurement of reproductive hormones. All of these supplemental data and specimens were recently collected using a protocol designed to address this study's research goals, and the specimens are now in freezer storage at Northwestern University. NSF funding will only be required to cover the costs of analyzing hormones in these samples, which will be measured in the Laboratory for Human Biology Research housed in the Department of Anthropology at Northwestern University.This study promises significant insights into an issue of considerable theoretical and applied importance. As is true for females, cross-cultural research has documented a great deal of population variation in male reproductive function. However, unlike in females, this biological variability has been difficult to explain in males. This study will address this paradox by investigating whether differences in early life nutrition and growth influence male reproduction function. The answer to this question may also provide insights into an important mode of human adaptation: reducing expenditure on "costly" traits, such as reproduction and muscle mass, might be a necessary (if less than ideal) response when faced with a challenging nutritional environment.The broader impacts of this study include training opportunities for both graduate and undergraduate students interested in gaining experience with laboratory research. It will also strengthen the collaborative ties between an international team of researchers based in the US and the Philippines, who share interests in understanding the causes and consequences of male fertility.