Nowadays, obesity has reached epidemic proportions globally. It can lead to several chronic diseases, including insulin resistance/type 2 diabetes mellitus. Feeding behaviour is regulated in the... Show moreNowadays, obesity has reached epidemic proportions globally. It can lead to several chronic diseases, including insulin resistance/type 2 diabetes mellitus. Feeding behaviour is regulated in the hypothalamus of the brain by two opposing pathways: NPY/AgRP neurons vs. POMC/CART neurons. In addition, there are numerous peripheral signals, deriving from stomach, gut, pancreas and adipose tissue, that act on the hypothalamus and thereby contribute to the regulation of food intake. The aim of the studies we have performed, was to investigate the effects of some of these neuropeptides and peripheral signals that affect these neuropeptides, on insulin action. Our experiments showed, that NPY can cause insulin resistance, specifically in the liver. The POMC pathway can improve insulin-mediated glucose disposal and does not affect hepatic insulin sensitivity. Therefore, both pathways are not completely opposing each other’s effects, but seem to have a different tissue-specific effect. Experiments with gut hormones like PYY and ghrelin showed that these hormones affect insulin sensitivity as well. Also leptin, and specifically leptin signalling in the brain, was found to be important for insulin sensitivity. In conclusion, this work showed that neuropeptides/hormones that are involved in the regulation of food intake also affect insulin sensitivity. Show less
The scope of the current thesis is to obtain insight in immunological aspects of transplantation and diabetes. This thesis underscores the current concept of collaboration between the innate and... Show moreThe scope of the current thesis is to obtain insight in immunological aspects of transplantation and diabetes. This thesis underscores the current concept of collaboration between the innate and adaptive immune system by showing close interactions between both immune systems. Mannose binding lectin as a major recognition molecule of the lectin pathway and as a key protein of the immune system was studied in relation to its functional characteristics. Appreciating the Jekyll-and-Hyde character of MBL and the fact that MBL serum levels and functionality are under strict genetic control, MBL was studied under distinct pathological conditions. Chapter 2 describes molecular and biological aspects of mannose binding lectin and the interaction of MBL with the adaptive immune system. Chapter 3 focuses on the involvement of MBL in autoimmunity, by studying juvenile type 1 diabetic patients at disease onset. Chapter 4 addresses the role of the liver in production of serum MBL and evaluates the effect of MBL variant alleles on the susceptibility to infection after liver transplantation. Chapter 5 focuses on the effect of the adaptive immune system on islet transplantation, a novel treatment of type 1 diabetes. Show less
