Application of a multicomponent model of convectional reaction-diffusion to description of glucose gradients in a neurovascular unit

Abstract

A supply of glucose to a nervous tissue is fulfilled by a cerebrovascular network, and further diffusion is known to occur at both an arteriolar and a microvascular level. Despite a direct relation, a blood flow dynamic and reaction-diffusion of metabolites are usually considered separately in the mathematical models. In the present study they are coupled in a multiphysical approach which allows to evaluate the effects of capillary blood flow changes on near-vessels nutrient concentration gradients evidently. Cerebral blood flow (CBF) was described by the non-steady-state Navier-Stokes equations for a non-Newtonian fluid whose constitutive law is given by the Carreau model. A three-level organization of blood–brain barrier (BBB) is modelled by the flux dysconnectivity functions including densities and kinetic properties of glucose transporters. The velocity of a fluid flow in brain extracellular space (ECS) was estimated using Darcy’s law. The equations of reaction-diffusion with convection based on a generated flow field for continues and porous media were used to describe spatial-time gradients of glucose in the capillary lumen and brain parenchyma of a neurovascular unit (NVU), respectively. Changes in CBF were directly simulated using smoothing step-like functions altering the difference of intracapillary pressure in time. The changes of CBF cover both the decrease (on 70%) and the increase (on 50%) in a capillary flow velocity. Analyzing the dynamics of glucose gradients, it was shown that a rapid decrease of a capillary blood flow yields an enhanced level of glucose in a near-capillary nervous tissue if the contacts between astrocytes end-feet are not tight. Under the increased CBF velocities the amplitude of glucose concentration gradients is always enhanced. The introduced approach can be used for estimation of blood flow changes influence not only on glucose but also on other nutrients concentration gradients and for the modelling of distributions of their concentrations near blood vessels in other tissues as well.

A spatial classification applied to convectional reaction-diffusion boundary problems basing on a geometrical polymorphism of biological objects

“…Therefore, to avoid this risk, one needs to consider right processes with right localization. In particular, for H/H I.2.2 models of glucose distribution in a neurovascular unit it was shown that the geometry of inner flux dysconnectivity barrier essentially determines the reply of the system on changes of cerebral blood flow in the capillary [10,11]. The same effect of geometrical polymorphism appears in other system corresponding to H/H I.2.1.…”

Molecular Mechanisms Underlying Therapeutic Action of Vitamin B6

“…При этом процесс синтеза PLP является АТР-зависимым, что, в свою очередь, требует энергетических затрат и активации митохондриального окислительного фосфорилирования в нейронах и астроцитах. Увеличение содержания PLP, активирующее глициндегидрогеназу, которая является частью системы расщепления глицина, что приведет к его снижению в плазме и спинномозговой жидкости и, возможно, повлияет на микроциркуляцию [37] и снабжение нервной ткани ключевыми метаболитами, в частности глюкозой [38,39].…”

Molecular Mechanisms Defining Application of Glycine and Zinc Combinationin Correction of Stress and Anxiety Main Manifestations

“…Примечательно, что глицин оказывает прямое действие на дилатацию артериол Том 10, Выпуск 5, 2022 [50,51], что является важнейшим аспектом общего воздействия данной аминокислоты на состояние ЦНС [52]. Воздействие на систему кровотока в микрососудах и капиллярах приводит к теоретически обоснованному [53][54][55] и экспериментально подтвержденному увеличению содержания глюкозы в тканях [56].…”