The Effects of Ketogenic Supplements on Protein Expression and Autophagy in The Drosophila melanogaster Feeding Third Instar Larval Fat Body



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The ketogenic diet is a low carbohydrate, high fat diet that is thought to be beneficial to health. Due to the low intake of carbohydrates in the ketogenic diet, the main energy fuel, glucose is depleted, and insulin levels drastically decrease. The body enters a catabolic state in which gluconeogenesis and ketogenesis occur. When the glucose level cannot be compensated by gluconeogenesis, ketogenesis provides the body with an alternative fuel -- ketone bodies, the most abundant ketone body is β-hydroxybutyrate (BHB). An elevated level of ketone bodies in the blood and urine is referred to as ketosis. Autophagy is a natural degradative process that cleans out damaged and dysfunctional organelles in order to recycle and generate healthy cells. This process maintains proper homeostasis under normal physiological conditions, and is associated with anti-aging effects. Autophagy is activated under stress conditions, such as energy deprivation, glucose depletion, fasting, starvation, intense exercise (Ravanan et al, 2017). The autophagosome is a key structure in autophagy, and Atg8 proteins are involved in autophagosome formation. The presence of Atg8 proteins such as Atg8a is widely used for detecting autophagic activity. A high ratio of lipidated atg8a (atg8a-II) and non-lipided atg8a (atg8a-I) indicates an intense level of autophagy. The ketogenic diet mimics the effects of fasting, and numerous studies have shown that fasting and endogenously induced ketosis induces autophagy by meeting the prerequisites of calorie restriction, glucose deficiency and glycogen depletion (Alirezaei et al, 2010; Hansen et al, 2008; Chung et al, 2019). Exogenous ketogenic supplement, like ketogenic diet, elevated blood ketone bodies, resulting in a similar but not at all identical ketosis (Poff et al, 2020). Various adverse effects are observed in people who eat on a ketogenic diet, for example hypoglycemia, nausea, vomiting, fatigue, constipation, and irregular menstrual cycles. The use of nutritional supplements is suggested to safely enter into nutritional ketosis and easier to administrate (Bostock et al, 2020). Little is known about the underlying mechanisms by which ketogenic supplements induce ketosis and ketogenesis without carbohydrate restriction. There is not enough evidence on whether ketogenic supplement induces autophagy. Therefore, in this study, I am testing the hypothesis that ketogenic supplements, beta-hydroxybutyrate, like the ketogenic diet or fasting, will increase autophagic activity in the fat cells of the fruit fly, Drosophila melanogaster. I hypothesize that beta-hydroxybutyrate induces the expression of autophagy-inducing proteins (Atg8a), and the beta-hydroxybutyrate diet group will exhibit a higher ratio of atg8a-II to atg8a-I than the control group. My findings indicate that BHB increases the ratio of Atg8a-II to Atg8a-I in the fat body, indicating an increased autophagy activity and thus supporting my hypothesis.



autophagy, ketogenic supplement, Drosophila melanogaster, biochemistry