Reduced Insulin Clearance And Lower Insulin-degrading Enzyme Expression In The Liver Might Contribute To The Thrifty Phenotype Of Protein-restricted Mice.

Nutrient restriction during the early stages of life usually leads to alterations in glucose homeostasis, mainly insulin secretion and sensitivity, increasing the risk of metabolic disorders in adulthood. Despite growing evidence regarding the importance of insulin clearance during glucose homeostasis in health and disease, no information exists about this process in malnourished animals. Thus, in the present study, we aimed to determine the effect of a nutrient-restricted diet on insulin clearance using a model in which 30-d-old C57BL/6 mice were exposed to a protein-restricted diet for 14 weeks. After this period, we evaluated many metabolic variables and extracted pancreatic islet, liver, gastrocnemius muscle (GCK) and white adipose tissue samples from the control (normal-protein diet) and restricted (low-protein diet, LP) mice. Insulin concentrations were determined using RIA and protein expression and phosphorylation by Western blot analysis. The LP mice exhibited lower body weight, glycaemia, and insulinaemia, increased glucose tolerance and altered insulin dynamics after the glucose challenge. The improved glucose tolerance could partially be explained by an increase in insulin sensitivity through the phosphorylation of the insulin receptor/protein kinase B and AMP-activated protein kinase/acetyl-CoA carboxylase in the liver, whereas the changes in insulin dynamics could be attributed to reduced insulin secretion coupled with reduced insulin clearance and lower insulin-degrading enzyme (IDE) expression in the liver and GCK. In summary, protein-restricted mice not only produce and secrete less insulin, but also remove and degrade less insulin. This phenomenon has the double benefit of sparing insulin while prolonging and potentiating its effects, probably due to the lower expression of IDE in the liver, possibly with long-term consequences.

Assayentwicklung zur Analyse des proteolytischen Abbaus von Abetafibrillen 1-40, 3-40 und pE3-40

Alzheimer ist eine neurodegenerative Erkrankung deren molekulare Ursache, die Anhäufung von Amyloid-Plaques im Gehirn und die Bildung von Neurofibrillen in den Nervenzellen ist. Grund für diese molekularen Ursachen ist das Peptid Amylois beta, welches sich im Gehirn von Alzheimer Patienten anhäuft und zu Fibrillen aggregiert. In der Arbeit wurde untersucht, ob es Unterschiede bezüglich des proteolytischen Abbaus zwischen Abetafibrillen 1-40, 3-40 und pE3-40 gibt und ob die Fibrillen von unterschiedlichen Enzymen abgebaut werden können. Zudem wurden die Spaltprodukte, die bei diesem Abbau entstanden, miteinander verglichen und analysiert. Es wurde also untersucht, ob die Enzyme eine abbauende Wirkung auf aggregierte Aβ-Peptide haben und wie sich diese im Vergleich zu den gelösten Abeta-Peptiden verhalten. Die Untersuchungen fanden mit den Enzymen Neprilysin, Neprilysin 2, Insulysin, Matrix-Metalloproteinasen 2, 3, 9, 13, Plasmin, Plasma Kallikrein, Tissue Kallikrein und Meprin A statt und wurden Mittels MALDO-TOF analysiert.