Chronobiology investigates biological rhythms and chronological regularities (periodical life processes). Circadian rhythms are of special interest. They fluctuate in physiological, biochemical, and behavioural processes over about 24 hours. The sleep-wake cycle, body core temperature, and levels of hormones like melatonin show circadian rhythmicity. These rhythms are generated by an endogenous timekeeping mechanism called circadian clock and adjusted to 24 hours by exogenous factors (e.g., dark-light cycle). Our research focuses on the analysis of changes in circadian rhythms with respect to human aging. The question is being addressed using an integrative approach investigating molecular genetic (clock genes), physiological, and hormonal aspects.

The term body composition describes the different compartments of the human body (fat mass, lean body mass, body cell mass, extracellular mass, extracellular and intracellular body water). The determination of these compartments gives insight into human growth processes, aging, disease and nutritional states. With respect to human aging, body cell mass and total body water have been analyzed using whole-body counting of potassium (40K) and isotope deuterium dilution technique, respectively. Based on these results, specific age-related equations have been developed for predicting body cell mass and total body water by multifrequency bioelectrical impedance analysis in elderly populations. Our actual research focuses on changes in muscle mass (body cell mass) and muscle function during aging as well as on associated sarcopenia (age-related decrease in muscle mass and strength). Further research methods will be evaluated and validated. This includes analysis of resting metabolism, specific hormones and non-biological risk factors for sarcopenia.

High altitude (> 3000 m) in the South American Andes is characterized by extreme environmental conditions, in particular cold, hypoxia, variation in temperature, high UV radiation and dry air. Nevertheless, populations are living there for centuries adapting themselves to these environmental conditions. Their reproductive rate and physical performance are increased at high altitude compared to lowland populations. Since hypoxia is the most limiting factor for human life at high altitude, we are analyzing genetic adaptations to hypoxia. For this, we are searching for changes in genes which are related to the oxygen supply of the human body. The project is performed in cooperation with the Universidad de Chile, Santiago, Chile.

Oxidative stress is one reason for natural human aging. Free radicals and reactive oxygen species (ROS) are causing damage by oxidation to proteins, lipids and DNA. They are generated as byproducts of cellular energy production and by environmental factors, e.g. ionizing radiation. Protective enzymatic and non-enzymatic antioxidant defence mechanisms reduce oxidative stress by degradating ROS. DNA repair enzymes repair DNA damages generated by ROS. In a pilot study in cooperation with the Institute of Pharmacy, University of Mainz, the relationship between natural human aging, oxidative stress, antioxidative enzymatic defence mechanisms as well as oxidative DNA damage (8-oxo-7,8-dihydro-2´-deoxyguanosin) have been analyzed. Future studies will include biochemical, hormonal and molecular genetical parameters.The objective of these studies is to characterize the relationship between oxidative stress and protective mechanisms in natural aging processes in order to develop methods for prevention of premature aging.

The investigations are performed in accordance with the declarations of Helsinki.