The term "oxidative stress" was first coined by Helmut Sies in 1985. This process develops in tissues and organs when the rate of formation of highly reactive compounds, such as reactive oxygen species (ROS), nitrogen, sulphur, and halogens, prevails over the ability of endogenous antioxidant systems to neutralise them. Normally, reactive compounds are produced during metabolic processes in low concentrations. A large number of works have been devoted to the study of this phenomenon. To date, the relationship between the development of oxidative stress and the pathogenesis of metabolic syndrome, atherosclerosis, cardiovascular diseases, neurodegenerative diseases, diabetes, infertility, kidney diseases, digestive system and liver diseases has been shown. However, despite the accumulated pool of data, the specific mechanisms of disease development remain poorly understood. In this regard, the development of models of socially significant human diseases is an urgent direction of modern biomedical research. Transgenic mice and rats, as well as the bony fish Danio rerio (zebrafish) act as model objects. Although mice and rats seem to be more suitable objects for studying human diseases due to their belonging to mammals, in recent years, works have appeared demonstrating the imperfection of rodent-based models. At the same time, the creation of mouse and rat models is labour-intensive, time-consuming, and expensive. Recently, the creation of human disease models based on Danio rerio has been quite actively developed. Zebrafish has a fairly high degree of genetic similarity to humans, as well as several advantages compared to mammals: a large number of offspring that can be derived from the same parents at the same time, allowing rapid recruitment of a homogeneous experimental group for research and experimental effects; rapid development, which ensures faster production of transgenic individuals compared to mice and rats; transparency of tissues for a long time, which facilitates the lifetime observation of cells and organs. One of the new and actively developing methods of model generation is chemogenetic tools. The present study will specifically implement a chemogenetic approach using D-amino acid oxidase (DAAO, DAO), an enzyme that converts D-amino acids into alpha-keto acids. DAAO takes two electrons from the amino acid and transfers them to molecular oxygen, resulting in the formation of hydrogen peroxide. This tool allows controlled induction of oxidative stress and has already been shown to be effective for modelling neurodegenerative processes and cardiac pathologies in mice and rats. We will use this technique to investigate the role of hydrogen peroxide in the initiation and development of processes leading to pancreatic cell damage and, consequently, diabetes. We will also initiate the development of oxidative stress in brain neurons during critical periods of nervous system development and investigate the links between early exposure and the appearance of neurodegenerative manifestations in the Danio rerio model. The resulting models will be characterised in detail using next-generation genetically encoded fluorescent sensors developed in our laboratory that visualise the developing oxidative stress induced by hydrogen peroxide (HyPer7), active forms of halogens (Hypocrates) - participants in inflammatory immune responses, as well as a sensor detecting long-chain acyl-CoA - key intermediates of fatty acid metabolism that act as regulatory molecules, influencing the expression of some genes, enzymes, and ion channels, which will be optimised for in vivo applications. The new models of brain and pancreas diseases in D.rerio developed by us within the framework of this project can be used in the future not only to study the molecular basis of pathologies but also to search for and test new drugs aimed at the therapy of these pathologies.