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Bestimmung der Beziehung zwischen Plasma-Leptinkonzentration und körperlicher Aktivität ländlich lebender tansanischer Kinder

Fachliche Zuordnung Biologische Psychiatrie
Public Health, Gesundheitsbezogene Versorgungsforschung, Sozial- und Arbeitsmedizin
Förderung Förderung von 2018 bis 2020
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 391378309
 
Erstellungsjahr 2021

Zusammenfassung der Projektergebnisse

Rodent and human studies e.g. in patients with anorexia nervosa in high-income countries have shown that low leptin levels as a result from starvation trigger high physical activity (PA). Leptin is mainly synthesized in adipocytes. Thus, low leptin levels can also be expected in children living in low- and middle-income countries (LMIC), especially in rural parts, where poverty and a poor nutritional status are quite common. In Sub-Saharan African countries processes such as urbanization and increasing socioeconomic status could result in improved nutritional status over time resulting in increments of leptin levels. In parallel, these alterations are known to be associated with a transition to decreased physical activity in these countries; the term physical transition has been coined to describe this decrease from an originally high to a lower activity level. Accordingly, we examined the hypothesis that low leptin levels are associated with high PA in lean children of LMICs. If correct, increments in circulating leptin upon transition from a rural to an urban lifestyle in LMIC may represent an endocrine link related to the PA transition. The study was conducted in three wards of Chamwino District, i.e. Dabalo, Itiso, and Haneti, located in Dodoma Region, United Republic of Tanzania. Within each ward, two primary schools participated in this study. Four of these schools were only reachable via dirt roads, whereas two schools in Haneti were located at a main tarmac road. This distinction was used to later examine associations between different infrastructural settings and PA among the study population, with the schools in Haneti considered to have better infrastructure (as a proximal indicator of development). Since previous studies showed the largest variance in PA in children with low BMI6, we focused on children with apparently low body weight for sample recruitment. The final sample consisted of 223 children (9 to 12 years of age). Seven-day PA was assessed with accelerometers (ActiGraph GT3X) with moderate-to-vigorous PA (MVPA) and total accelerometer counts per day indicating total physical activity as outcome variables. Leptin was determined using enzyme linked immunosorbent assay (ELISA) tests from dried blood spots from capillary blood drops. Anthropometric assessments were conducted and food insecurity and sociodemographic data were gathered using semi-structured interviews. The statistical analysis of the relationship between leptin levels (exposition variable) and PA parameters (outcome variables) was conducted using linear regression models considering significant covariates. As expected, this sample of school children in rural Tanzania had low leptin serum concentrations (median: 0.91 ng/mL, P25: 0.55, P75: 1.69), body mass index z-scores (median: -1.35, P25: -1.93, P75: -0.82), and height-for-age-z-scores (median: -1.16, P25: -1.96, P75: -0.61). Overall, 37% of children were undernourished, i.e. either too thin according to BMI z-score (< -2 z-scores) or stunted according to heightfor-age z-score (< -2 z-scores) or both. In contrast, PA levels of this sample were high with a median MVPA time of 119 min/day. According to univariate analyses using Spearman-Rho, correlations between leptin concentrations and parameters of PA increased with intensity levels of the latter from light PA (rs =.148, p=.05), over moderate activity (rs =-.242, p=.01), towards vigorous activity (rs =-.401, p=.01). Linear regression confirmed a negative association between leptin levels and MVPA (beta: -18.1; 95%CI: -29.7;- 6.5; p=0.002) and total accelerometer counts (beta: -90,256; 95%CI: -154,146;-26,365; p=0.006). Children residing in areas with better infrastructure had lower MVPA levels (p<0.001) and tended to have higher leptin levels (p=0.062) than children residing in areas only reachable via dirt roads. In conclusion, our cross-sectional field study is the first that supports the hypothesis of low leptin levels as a potential endocrine trigger of high PA in lean children of a LMIC. We observed early signs of a PA transition towards a less active lifestyle in a subgroup residing in areas with better infrastructure that concomitantly tended to have higher leptin concentrations. Although our study sample was not representative for that area, nutritional deficits in these regions and their effect on PA should be further addressed, preferably in longitudinal settings to support causality. We hypothesize that improvements of nutrition status could result in increases of the currently low leptin levels and, considering our current results, be related to a reduced level of discretionary PA in the respective children.

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