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

神经性厌食症（AN）患者严重限制他们的食物摄入量，但表现出增加的物理PA水平。这些患者，就像一般营养不良的人一样，其特点是身体脂肪的比例低于正常水平。因此，在血浆中只能检测到低浓度的饱腹激素瘦素，瘦素主要由脂肪细胞分泌。在发展中国家，特别是在农村地区，贫困和营养不良状况相当普遍。对这些国家（例如肯尼亚、莫桑比克或哥伦比亚）进行的单项研究表明，营养不良/体重不足的贫困儿童比营养较好的儿童更活跃。基于我们先前对AN患者和半饥饿大鼠模型的研究，我们假设低瘦素水平触发PA增加，这可能代表饥饿开始时的觅食行为。由于发达国家儿童的瘦素水平低于正常水平是罕见的，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血浆瘦素水平（从毛细血管血）和PA（加速度计）在200 9至12岁的儿童从坦桑尼亚农村之间的关系。类似于我们在AN患者和半饥饿大鼠中的发现，我们假设，尽管营养不良，但脂肪量显著减少和低肽血症的健康儿童的PA高于营养良好的未成年人。除了低血浆瘦素浓度作为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、粮食不安全以及上学或完成家务的步行距离。本研究将有助于（1）解释发展中国家人口中PA的个体间差异，（2）了解对食物供应减少的适应机制，第一次解释了所谓的体力活动转变的生物学贡献（在从发展中国家向新兴工业化国家过渡的范围内，营养状况得到改善，同时PA减少）。我们将与Akwilina Mwanri博士合作，他的研究兴趣是坦桑尼亚的体育活动和粮食安全。

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.