Determination of the relationship between plasma leptin levels and physical activity among children in rural Tanzania

神经性厌食症(AN)患者严格限制他们的食物摄入，但仍显示出物理PA水平的增加。这些患者，就像一般营养不良的人一样，其特点是体内脂肪比例低于正常水平。因此，在血浆中只能检测到低浓度的饱腹感激素瘦素，这种激素主要由脂肪细胞分泌。在发展中国家，特别是在农村地区，贫穷和营养状况差是相当普遍的。来自这些国家(如肯尼亚、莫桑比克或哥伦比亚)的单项研究表明，营养不良/体重不足的贫困儿童比营养较好的儿童更活跃。基于我们以前对AN患者和半饥饿大鼠模型的研究，我们假设低水平的瘦素会触发PA的增加，这可能代表了饥饿开始时的一种觅食行为。由于低于正常水平的瘦素水平在发达国家的儿童中并不常见，我们求助于发展中国家的儿童来验证这一假设。这项研究的目的是确定200名坦桑尼亚农村9至12岁儿童的血浆瘦素水平(来自毛细血管血)和PA(加速度计)之间的关系。与我们在患者和半饥饿大鼠中的研究结果类似，我们假设，在其他方面健康但营养不良、脂肪质量显著减少和低血浆症的儿童比营养较好的未成年人有更高的PA。除了低血浆瘦素浓度是PA增加的驱动力外，还将评估环境因素，包括环境温度、父母的社会经济地位、父母健康、食物不安全以及上学或完成家务的步行距离。这项研究将有助于(1)解释发展中国家人口中PA的个体间差异，(2)理解适应食物供应减少的机制，以及(3)首次解释生物学对所谓的体力活动转变的贡献(在从发展中国家向新兴工业化国家转变的范围内，营养状况改善伴随PA减少)。我们将与Akwilina Mwanri博士合作，他的研究兴趣除其他外包括坦桑尼亚的身体活动和粮食安全。

Patients with anorexia nervosa (AN) severely restrict their food intake and nevertheless show increased levels of physical PA. These patients, just like undernourished individuals in general, are characterized by a subnormal percentage of body fat. Hence, only a low concentration of the satiety hormone leptin, which is primarily secreted by adipocytes, can be detected in plasma. In developing countries, especially in rural parts, poverty and a poor nutritional status are quite common. Single studies from these countries (e.g. Kenya, Mozambique or Colombia) have revealed that poor undernourished/underweight children are physically more active than the better nourished. Based on our previous studies of AN patients and the semi-starvation rat model we hypothesize that low leptin levels trigger increased PA which might represent a foraging behavior upon initiation of starvation. Because subnormal leptin levels are uncommon in children of developed countries we resort to children of developing countries to test this hypothesis. The aim of the study is to determine the relationship between plasma leptin levels (from capillary blood) and PA (accelerometry) in 200 9- to 12-year old children from rural Tanzania. Analogous to our findings in AN patients and semi-starved rats, we assume that otherwise healthy albeit undernourished children with a significantly decreased fat mass and hypoleptinemia have a higher PA than better nourished minors. Apart from low plasma leptin concentrations as a driving force for increased PA, environmental factors including the ambient temperature, socio-economic status of parents, parental health, food insecurity, and walking distances to school or to fulfill household chores will be assessed. The study will be helpful (1) to explain inter-individual variance of PA in populations of developing countries, (2) to understand the mechanisms of adaptation to a reduced food supply, and (3) to explain for the first time a biological contribution to the so-called physical activity transition (improved nutritional situation accompanied by reduced PA within the scope of the transition from a developing country to a newly industrializing country). We will cooperate with Dr. Akwilina Mwanri whose research interests are among others physical activity and food security in Tanzania.