In Gaucher disease (GD), the deficiency of glucocerebrosidase causes lysosomal accumulation of glucosylceramide (GlcCer), which is partly converted by acid ceramidase to glucosylsphingosine (GlcSph... Show moreIn Gaucher disease (GD), the deficiency of glucocerebrosidase causes lysosomal accumulation of glucosylceramide (GlcCer), which is partly converted by acid ceramidase to glucosylsphingosine (GlcSph) in the lysosome. Chronically elevated blood and tissue GlcSph is thought to contribute to symptoms in GD patients as well as to increased risk for Parkinson's disease. On the other hand, formation of GlcSph may be beneficial since the water soluble sphingoid base is excreted via urine and bile. To study the role of excessive GlcSph formation during glucocerebrosidase deficiency, we studied zebrafish that have two orthologs of acid ceramidase, Asah1a and Asah1b. Only the latter is involved in the formation of GlcSph in glucocerebrosidase-deficient zebrafish as revealed by knockouts of Asah1a or Asah1b with glucocerebrosidase deficiency (either pharmacologically induced or genetic). Comparison of zebrafish with excessive GlcSph (gba1-/- fish) and without GlcSph (gba1-/-:asah1b-/- fish) allowed us to study the consequences of chronic high levels of GlcSph. Prevention of excessive GlcSph in gba1-/-:asah1b-/- fish did not restrict storage cells, GlcCer accumulation, or neuroinflammation. However, GD fish lacking excessive GlcSph show an ameliorated course of disease reflected by significantly increased lifespan, delayed locomotor abnormality, and delayed development of an abnormal curved back posture. The loss of tyrosine hydroxylase 1 (th1) mRNA, a marker of dopaminergic neurons, is slowed down in brain of GD fish lacking excessive GlcSph. In conclusion, in the zebrafish GD model, excess GlcSph has little impact on (neuro)inflammation or the presence of GlcCer-laden macrophages but rather seems harmful to th1-positive dopaminergic neurons. Show less
Barrier function is the natural role of the skin. The lipid matrix present in the outermost layer of the skin, the stratum corneum is important for this function. Barrier impairment and altered... Show moreBarrier function is the natural role of the skin. The lipid matrix present in the outermost layer of the skin, the stratum corneum is important for this function. Barrier impairment and altered lipid composition are observed in several inflammatory skin diseases including atopic dermatitis and psoriasis. However, the relationship between the lipid properties and barrier function is not comprehended.In this project, a lipid model was prepared from synthetic lipids that closely resemble the stratum corneum lipid composition and organization. Subsequently, diseased skin models were developed to mimic various abnormalities in lipid composition observed in atopic dermatitis patients’ skin. Biophysical methods were used to monitor the changes in lipid organization in these models. Diffusion studies and trans-epidermal water loss measurements were performed to monitor the barrier function. This allowed the determination of the changes in lipid properties that were most instrumental in reducing the lipid barrier.This thesis further describes the use of simple skin lipid model membranes incorporating fewer components to provide a detailed insight into the relationship between lipid composition, lipid organization, and the skin barrier. The information gained in this project offers the opportunity to develop a new generation of formulations to treat these patients. Show less
Sphingolipids are important membrane compounds with a variety of functions. In mammalian cells, different enzymes are involved in the metabolism of sphingolipids, but interruption of this... Show moreSphingolipids are important membrane compounds with a variety of functions. In mammalian cells, different enzymes are involved in the metabolism of sphingolipids, but interruption of this metabolism process leads to different diseases. To study the functions of sphingolipids and there related diseases, analogues of sphingolipids are needed. This thesis focuses on such sphingolipids analogues, and specifically on the design and synthesis of stable isotope encoded sphingolipids. Show less
Wisse, P.; Gold, H.; Mirzaian, M.; Guimaraes Da Lomba Ferraz, M.J.; Lutteke, G.; Berg, R.J.B.H.N. van den; ... ; Overkleeft, H.S. 2015
The metabolic syndrome is an increasing problem in our Western society. Many of the features of the metabolic syndrome, like obesity, insulin resistance, dyslipidemia, and hepatic steatosis are... Show moreThe metabolic syndrome is an increasing problem in our Western society. Many of the features of the metabolic syndrome, like obesity, insulin resistance, dyslipidemia, and hepatic steatosis are established risk factors for cardiovascular disease. Growing evidence supports the important role of body free fatty acid handling and/or body distribution of triglycerides in the pathogenesis of the metabolic syndrome-associated problems. We used several different approaches to study the development of obesity, insulin resistance, dyslipidemia, and liver steatosis. In chapter 2 we found that absence of apoC3, a natural LPL inhibitor, enhances FA uptake from plasma triglycerides in adipose tissue leading to increased susceptibility to diet-induced obesity, followed by more severe development of insulin resistance. Therefore, we have shown that regulation of body distribution of triglycerides, in a LPL-dependent process, plays an important role in obesity development. In chapter 3 we found that acute inhibition of the β-oxidation of FA indeed increases hepatic lipid content, but neither stimulates hepatic VLDL secretion nor reduces insulin sensitivity. In chapter 4 we showed that the combination of proteomics with relevant physiological parameters in a sensitive animal model, is a powerful tool, which will aid in identifying workingmechanisms of various dietary FA. In chapter 5 we found that sphingolipids protect the liver from fat and cholesterol-induced steatosis. Since sphingolipids are nutritional compounds present in several daily foods, such as milk and meat, addition of sphingolipids to the diet may decrease traditional cardiovascular risk factors, such as plasma cholesterol and triglycerides. Show less
