Diabetes Mellitus (DM) is a group of metabolic diseases that affects over 422 million individuals worldwide, with this number on the rise. It is one of the leading contributing factors to deaths worldwide, causing 1.5 million deaths in 2016. A significant correlating factor contributing to the onset of Type 2 DM (T2DM) is being inactive, overweight, and obese (BMI 30 kg/m2)The aim of this thesis is to widen the understanding of the effects of the diet and its relationship in the onset of T2DM, focusing on the ability for the overconsumption of fatty acids to cause lipotoxicity in multiple organ types (kidney, liver and brain). Furthermore, this work explores the role of the incretin hormone GLP-1, and its ability to protect against fatty acid-inducedlipotoxicity, comparing native GLP-1 (7-36) and incretin mimetic, liraglutide. The saturated fatty acid palmitate has been shown previously to induce lipotoxicity and insulin resistance in pancreatic, cardiovascular and skeletal muscle models, where monounsaturated fats are able to diminish these lipotoxic effects. Whilst these provide a good insight into the effects of fatty acid-induced toxicity, fatty acid consumption involves a plethora of different fatty acids. Therefore, the work in this thesis sets out to establish the effect of palmitate, oleate, stearate and all three fats in combination (POS) and their effect on HEK293T, HepG2 and SH-SY5Y cell lines. Literature has also proposed a differential response present in low oxygen concentrations, and therefore this project also looked at this effect in hypoxia (2% oxygen). The results from this thesis show that fatty acids caused a decrease in cell growth in all three cell lines under both normoxic and hypoxic conditions, where the extent of damage differed amongst oxygen availability and cell line in all cell lines. Incretin hormones are secreted in the gut in response to the consumption of oral glucose, and due to their insulinotropic effects, are marketed for the indication of T2DM. However, since their initial marketing, they are now approved for the indication of obesity. They have been shown to hold therapeutic effects against diabetic complications and cardiac disease progression. The results of this thesis show that incretin hormone treatment increases cell growth in kidney and brain cell lines under normoxic and hypoxic conditions, where hypoxic conditions diminish this effect. In the HepG2 cell line, due to the lack of presence of the GLP-1 receptor, no protection or cell growth was seen. Literature has focused on the progression of cells to a more physiologically relevant in vivogenotype using 3D cell culture. In 3D spheroids, formed using ultra low adhesion plates, fatty Page | iiiacids caused a decrease in cell growth however to a lesser extent than that seen in 2D cultured cells. Incretin hormone treatments still offered protection against fatty acid-induced toxicity. Interestingly, the incretin hormones were also able to reduce lipotoxicity in the 3D HepG2 model, showing the potential progression of cell gene expression from traditional 2D methodologies and 3D culture. In conclusion, the results presented in this thesis show that fatty acids offer a differential extent of lipotoxicity in 2D kidney, liver and brain cells, where this lipotoxic effect is reduced in 3D counterparts. Incretin hormone presence can protect against lipotoxicity by increasing cell growth in cell lines where the GLP-1 receptor or GIP receptor is present. Between 2D and 3D cells, the expression of receptors may change, therefore allowing for more physiologically relevant models for pharmacological testing in vitro
The Multi-Organ Protective Effects Of The Incretin Hormones
Judge, A. (Author). May 2024
Student thesis: Doctoral Thesis › Doctor of Philosophy