Klaus Völker

Apoptosis or programmed cell death is a process of fundamental importance for regulation of the immune response. Several reasons suggest that apoptosis is involved in exercise-induced alterations of the immune system such as postexercise lymphocytopenia. Healthy volunteers performed two treadmill exercise tests; the first was performed at 80% maximal oxygen uptake until exhaustion (exhaustive exercise) and the second 2 wk later at 60% maximal oxygen uptake with the identical running time (moderate exercise). Blood samples were taken before, immediately after, and 1 h after the test. Lymphocytes were analyzed for apoptotic and necrotic cells by using FITC-labeled annexin V-antibodies and nuclear propidium iodide uptake, respectively. In addition, apoptotic/necrotic cells were measured after a 24-h incubation of lymphocytes in the presence of camptothecin or phytohemagglutinin. Finally, plasma membrane expression of CD95-receptor and CD95-receptor ligand was investigated. Immediately after the exhaustive exercise, the percentage of apoptotic cells increased significantly, whereas it remained unchanged after the moderate exercise. Similar results were obtained after 24-h incubation of lymphocytes in medium alone or in the presence of camptothecin, but not with phytohemagglutinin. We found an upregulation of CD95-receptor expression after both exercise tests. However, only after exhaustive exercise a characteristic shift in CD95 expression profile toward cells with a high receptor density was observed. Expression of the CD95-receptor ligand remained unchanged after both exhaustive and moderate exercise. These results suggest that apoptosis may contribute to the regulation of the immune response after exhaustive exercise. Whether this mechanism can be regarded either as beneficial, i.e., deletion of autoreactive cells, or harmful, i.e., suppression of the immune response, awaits further investigations.

The incidence of insulin resistance and metabolic syndrome correlates with the availability of magnesium (Mg). We studied the effect of oral Mg supplementation on insulin sensitivity and other characteristics of the metabolic syndrome in normomagnesemic, overweight, insulin resistant, non-diabetic subjects. Subjects were tested for eligibility using oral glucose tolerance test (OGTT) and subsequently randomized to receive either Mg-aspartate-hydrochloride (n = 27) or placebo (n = 25) for 6 months. As trial endpoints, several indices of insulin sensitivity, plasma glucose, serum insulin, blood pressure and lipid profile were determined. Mg supplementation resulted in a significant improvement of fasting plasma glucose and some insulin sensitivity indices (ISIs) compared to placebo. Blood pressure and lipid profile did not show significant changes. The results provide significant evidence that oral Mg supplementation improves insulin sensitivity even in normomagnesemic, overweight, non-diabetic subjects emphasizing the need for an early optimization of Mg status to prevent insulin resistance and subsequently type 2 diabetes.