EVIDENCE OF APOPTOSIS IN PARVOCELLULAR NUCLEI OF HYPOTHALAMUS IN DIABETES MELLITUS
Keywords:hypothalamus, arcuate nucleus, ventromedial nucleus, neuron, neuroendocrine cell, streptozotocin-induced diabetes mellitus
Diabetes mellitus (DM) causes great socio-economic damage, which is determined by medical expenses and expenditure on social security to patients due to invalidity and loss of labour capacity. Researchers are studying the role of hypothalamic neuropeptides and their involvement in the regulation of pancreatic islet function. In view of the above, the aim of our study was to establish the features of morphofunctional changes in the arcuate nucleus (AN) and ventromedial nucleus (VN) of the hypothalamus in streptozotocin-induced diabetes mellitus (SIDM).
Histological, immunohistochemical, electron-microscopic, biochemical and statistical research methods were used.
Polymorphic changes were noted in AN and VN at early stages of development of SIDM (on the 14th day). In AN, the area of neurons and their nuclei became larger, the numerical density of dark functionally more active neurons increased, and dinuclear light neuroendocrine cells (NC) appeared. In light and dark NCs of AN, there was a significant increase in the bulk density of neurosecretory granules – by 2-4 times compared with the control, in VN – by 1.2-2 times.
Such morphofunctional changes in parvocellular nuclei of the hypothalamus and the increase in the bulk density of neurosecretory granules in their NCs indicate boosted synthesis of neurohormones which directly affect the adenohypophysis and improving functional activity of NCs in AN and VN.
On the 70th day of SIDM in AN and VN of the hypothalamus, there was a decrease in the numerical density of neurons due to light NC and increase in the numerical density of vacuolated, dark pycnomorphic and apoptotic neurons. The apoptotic index in the studied nuclei of the hypothalamus increased by 2-4 times compared with the control. The area of the profile field of NC increased and the area of nuclei decreased, which led to the reduced nuclear-cytoplasmic index and indicated a decrease in their functional activity and was confirmed by a decrease in the bulk density of neurosecretory granules in NC by 1.9-2.1 times in AN and by 2.7-4.7 times in VN. At the ultrastructural level, pronounced destructive processes such as vacuolar dystrophy, development of satelliteosis and neuronophagia were observed in light NCs.
Thus, prolonged hyperglycemia in SIDM in parvocellular nuclei of the hypothalamus causes neuronal death to a lesser extent due to apoptosis, and to a greater extentdue due to hydropic dystrophy and colliquative necrosis, especially in the long term of the experiment (on the 70th day), and leads to the development of diabetic neuroendocrinopathy.
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