Browsing by Subject "calcium"

The contact site between the endoplasmic reticulum and mitochondria, also known as the mitochondria endoplasmic reticulum contact sites (MERCS), have a crucial role in maintaining the homeostasis within the cell. Across the MERCS multiple functions, such as regulation of calcium (Ca2+) homeostasis, lipid metabolism, ER stress, mitochondrial quality control (MQC) and regulation of unfolded protein response (UPR) take place. These processes have been shown to be implicated in numerous different neurodegenerative diseases, such as Parkinson’s disease. Parkinson’s disease is the second most common neurodegenerative disease that at the moment has no cure. The main obstacle in developing a neuroprotective treatment for the disease is the limited understanding of the key molecular events leading to neurodegeneration. One of the things in Parkinson’s disease that has eluded scientists for years is the selective death of the dopaminergic (DA) neurons in substantia nigra pars compacta. One hypothesis that could explain the selective death is the Ca2+ hypothesis, looking at the Ca2+ vulnerability of SNpc DA neurons as a plausible cause leading to the selective cell death. This project focused looking at the protein level and morphological changes of the ER and MERCS in stressed neurons, hypothesizing these as possible sites that contribute to the neuron vulnerability, as they are known to be the key modulators of the intracellular Ca2+ homeostasis. This study looked closer at two MERC proteins, GRP75 and BAP31, and one ER protein, SERCA2, to see how they are affected in stressed dopamine-like neurons. Firstly, the in vitro model was established by differentiating SH-SY5Y neuroblastoma cells to dopamine-like neurons expressing tyrosine hydroxylase. Three different molecular compounds were tested as possible stressors affecting the Ca2+ homeostasis within the neurons, and we concluded that thapsigargin, a commonly used stressor to model PD like pathology, leads to the highest measurable ER Ca2+ depletion. Lastly, we quantitatively and qualitatively analyzed the effect of 24-hour treatment with each stressor on the differentiated SH-SY5Y neurons. Thapsigargin treatment lead to an increased level of GRP75 and SERCA2. A slight increase in BAP31 was also detected after thapsigargin treatment, but no apparent changes of the ER morphology were detected. The results, together with previous research, show GRP75 to be a possible contributor to the pathology of the disease, but further research is needed to see if it could be a possible target for treatment.

Oat β-glucan is a non-starch polysaccharide, and it is well-known that oat β-glucan provides physiological functionalities, such as reducing glycemic response. It is proposed that the reduction of glycemic response is due to the elevation of digesta’s viscosity in the intestinal tract, which is attributed to the viscosity generated by β-glucan. An increase in viscosity of digesta is assumed to hinder starch digestion, thus reducing glucose absorption. However, it is not known whether viscous β-glucan or β-glucan gel causes such physiological responses. Thus, the aim of this Master’s thesis was to study the effects of viscous β-glucan on in vitro starch digestion. The in vitro starch digestibility method was adjusted to suit the viscous β-glucan. The hypothesis was that sample containing oat β-glucan would hinder starch hydrolysis compared to the sample without oat β-glucan. Viscosity and viscoelasticity of wheat starch were analyzed to ensure that the concentration of the wheat starch used was appropriate for the study. The viscosities of oat β-glucan solutions at different concentrations were also measured. The in vitro starch digestibility result was evaluated by measuring the concentration of starch hydrolysis product. Viscosity and viscoelasticity tests of wheat starch showed that 4% wheat starch was suitable in the starch digestibility study. The viscosities of various concentrations of oat β-glucan exhibited pseudoplastic flow behavior. In vitro starch digestibility showed that oat β-glucan slowed down the starch hydrolysis. Calcium contained in oat β-glucan was found to enhance the activity of α-amylase, resulting in a higher concentration of the starch hydrolysis product. 2160 µg/g Ca2+ was added to all samples in order to compensate for different Ca2+ concentrations in each sample. The maximum Ca2+ concentration that 1 U α-amylase could utilize was 98 µg/g Ca2+. The results of this study confirmed that the viscous oat β-glucan hindered the starch digestibility compared to the sample without oat β-glucan and calcium ions played a role in starch digestibility.