Joslowski, Gesa: The relevance of dietary insulin demand and dietary protein intake during adolescence for the development of body composition and the adult GH-IGF axis. - Bonn, 2014. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{Gesa Joslowski}},
title = {The relevance of dietary insulin demand and dietary protein intake during adolescence for the development of body composition and the adult GH-IGF axis},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2014,
month = may,

note = {Obese children are likely to stay obese, resulting comorbidities may emerge already in childhood and tend to persist until adulthood. So-called critical periods for overweight development are early life, the time around the adiposity rebound, and puberty. The growth hormone insulin-like growth factor (GH-IGF) axis plays an important role during growth. It remains to be clarified whether it can be programmed by protein intake during growth. The first aim of this thesis was to examine the associations between dietary insulin demand during adolescence and its relevance for both adult body composition among healthy individuals and weight loss among obese adolescents with clinical features of insulin resistance. Under the second aim, prospective relations between dietary protein intake during different potentially critical, developmental periods and body composition as well as the GH-IGF axis in adulthood were investigated. Data came from two studies conducted in Germany and Australia; an ongoing, open cohort study, the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study and a randomised controlled trial, the Researching Effective Strategies to Improve Insulin Sensitivity in Children and Teenagers (RESIST) study, respectively.
Study I revealed that among 262 DONALD participants, a higher pubertal dietary insulin demand was associated with higher body fat percentage in young adulthood. In Study II, a higher dietary insulin demand was related to less weight loss expressed as BMI as percentage of the 95th percentile (BMI %95 centile) among 91 RESIST participants. Inclusion of total energy intake in the model explained the observed associations between dietary insulin demand and change in BMI %95 centile. Study III, including 262 DONALD participants, indicated that a higher pubertal animal protein intake was independently associated with higher adult fat-free mass index (FFMI), but not fat mass index (FMI), in women. Among men, a higher pubertal animal protein intake was related to higher FFMI and lower FMI only after adjusting FFMI for FMI levels in young adulthood and vice versa. Plant protein intake was not associated with adult body composition among either sex. Study IV, also based on data from the DONALD study (n=213 and n=201, respectively), showed that a habitually higher animal protein intake during puberty was related to higher levels of adult IGF-I, IGFBP-3, and lower IGFBP-2, but not to IGFBP-1 among women. In turn, animal protein intake in early life (n=130) was inversely related to IGF-I levels in younger adulthood among males only. However, no association was observed between animal protein intake around adiposity rebound (n=179) and IGF-I in younger adulthood. No relations were observed between plant protein intakes in all three periods and adult GH-IGF axis.
In conclusion, results indicate that a lower dietary insulin demand and a higher dietary protein intake may be favourably related to adult body composition. Among women, a higher pubertal animal protein intake may induce an up-regulation of the GH-IGF axis which persists until adulthood. By contrast, inverse associations between higher animal protein intakes in early life and IGF-I concentrations among men support the idea that habitually higher animal protein intakes in this period may trigger an early programming of the GH-IGF axis. Although these findings need to be confirmed in other populations, a reduction of dietary insulin demand and a moderate increase in dietary protein intake may have beneficial effects in the prevention of obesity. Moreover, it needs to be identified which mechanisms lie behind observed associations between dietary animal protein intake and the GH-IGF axis so as to determine to what extent they reflect physiological adaptations or whether these associations indicate higher or lower risks of future diseases.},

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