The results of one of the experiments conducted by the group clarified the mechanism by which a low-calorie diet can prevent the death of neurons in the brain associated with diseases such as Alzheimer’s, Parkinson’s, epilepsy, and acute cerebrovascular accident. In one of the experiments, the authors divided mice into two groups and calculated the average number of calories that the control group mice would consume without food restrictions. The animals in the experimental group were fed a diet that was 40% lower in calories than the calculated value. After 14 weeks, animals in both groups were injected with a compound that causes seizures, nerve tissue damage, and neuron death. As a result, seizures developed only in animals in the control group, which were not restricted in their calorie intake. To study the changes occurring at the cellular level, the researchers isolated organelles from the brain cells of mice in both groups and placed them in a nutrient medium. When calcium ions were added to this medium, they were more actively absorbed by the mitochondria of the animals in the experimental group. The fundamental role of mitochondria in the cell is to produce energy. The results of an earlier study showed that under conditions of a low-calorie diet, mitochondria activate the process of calcium ion absorption when their concentration is pathologically elevated. Insulin The results of a series of experiments on cultures of insulin-producing beta cells of the islets of Langerhans in the pancreas showed that a low-calorie diet improves the response of the cells of this organ to an increase in blood glucose concentration. The culture medium of these cells was supplemented with blood serum from mice fed different diets. When blood serum from animals consuming a reduced number of calories was added to the medium, the beta cells produced insulin normally: in small amounts at low glucose concentrations and in large amounts at high concentrations. This did not happen when serum from obese animals, which had developed as a result of consuming large amounts of calories, was added to the medium. The results of the experiment indicated the existence of some factor circulating in the blood that modifies the functions of beta cells. The researchers again hypothesised that this phenomenon is related to mitochondria, since insulin secretion depends on the availability of ATP (adenosine triphosphate, an energy-carrying molecule) in the cell. When measuring oxygen consumption in two cell cultures, it was found that this value was higher for cells whose culture medium contained serum from animals on a low-calorie diet. Since cellular respiration (oxygen consumption) is a key condition for the release of insulin by beta cells in conditions of elevated glucose levels, this observation indicated an increase in ATP production when serum from animals on a low-calorie diet was added to the medium. Other experiments also demonstrated that the mitochondria of cells, to whose culture medium the blood serum of animals on a low-calorie diet was added, exchanged material with each other more actively, which increased their efficiency. Healthy ageing Professor Kowaltski emphasises that understanding the mechanisms underlying the maintenance of normal metabolism is essential for the prevention and treatment of metabolic diseases such as obesity. It is well known that obesity is one of the prognostic factors for pathological ageing. People with obesity are much more likely to develop age-related diseases, including neurodegenerative diseases such as Alzheimer’s disease, proliferative diseases such as cancer, metabolic diseases such as type 2 diabetes and hyperlipidaemia, as well as heart failure and acute cerebrovascular accident. Preventing obesity will help prevent the development of all these diseases. However, even constant warnings about the exceptional importance of a balanced diet and physical activity have no effect on this global epidemic. Therefore, understanding the mechanisms by which obesity increases the risk of developing all of the above diseases will provide us with more tools for their prevention.