Loss of Compliance in Small Arteries, but Not in Conduit Arteries, After 6 Weeks Exposure to High Fat Diet

Cell-To-Cell Communication in the Resistance Vasculature

The arterial vasculature can be divided into large conduit arteries, intermediate contractile arteries, resistance arteries, arterioles, and capillaries. Resistance arteries and arterioles primarily function to control systemic blood pressure. The resistance arteries are composed of a layer of endothelial cells oriented parallel to the direction of blood flow, which are separated by a matrix layer termed the internal elastic lamina from several layers of smooth muscle cells oriented perpendicular to the direction of blood flow. Cells within the vessel walls communicate in a homocellular and heterocellular fashion to govern luminal diameter, arterial resistance, and blood pressure. At rest, potassium currents govern the basal state of endothelial and smooth muscle cells. Multiple stimuli can elicit rises in intracellular calcium levels in either endothelial cells or smooth muscle cells, sourced from intracellular stores such as the endoplasmic reticulum or the extracellular space. In general, activation of endothelial cells results in the production of a vasodilatory signal, usually in the form of nitric oxide or endothelial-derived hyperpolarization. Conversely, activation of smooth muscle cells results in a vasoconstriction response through smooth muscle cell contraction. © 2022 American Physiological Society. Compr Physiol 12: 1-35, 2022.

Biomechanical Properties of Mouse Carotid Arteries With Diet-Induced Metabolic Syndrome and Aging

Metabolic syndrome increases the risk of cardiovascular diseases. Arteries gradually stiffen with aging; however, it can be worsened by the presence of conditions associated with metabolic syndrome. In this study, we investigated the combined effects of diet-induced metabolic syndrome and aging on the biomechanical properties of mouse common carotid arteries (CCA). Male mice at 2 months of age were fed a normal or a high fat and high sucrose (HFHS) diet for 2 (young group), 8 (adult group) and 18-20 (old group) months. CCAs were excised and subjected to in vitro biaxial inflation-extension tests and the Cauchy stress-stretch relationships were determined in both the circumferential and longitudinal directions. The elastic energy storage of CCAs was obtained using a four-fiber family constitutive model, while the material stiffness in the circumferential and longitudinal directions was computed. Our study showed that aging is a dominant factor affecting arterial remodeling in the adult and old mice, to a similar extent, with stiffening manifested with a significantly reduced capability of energy storage by ∼50% (p < 0.05) and decreases in material stiffness and stress (p < 0.05), regardless of diet. On the other hand, high fat high sucrose diet resulted in an accelerated arterial remodeling in the young group at pre-diabetic stage by affecting the circumferential material stiffness and stress (p < 0.05), which was eventually overshadowed by aging progression. These findings have important implications on the effects of metabolic syndrome on elastic arteries in the younger populations.

Emblica officinalis (Amla) Ameliorates High-Fat Diet Induced Alteration of Cardiovascular Pathophysiology

BACKGROUND

Dietary high fat possibly causes oxidative stress. Also, it alters the pathophysiology of metabolically active myocardial tissues and vascular architecture. Emblica officinalis contains a potential antioxidant that counteracts oxidative stress and possibly maintains vascular integrity.

OBJECTIVES

To assess the effect of ethanolic extract of Emblica officinalis (EEO) on High Fat Diet (HFD) induced changes in vascular chemistry and histopathology of the cardiovascular system in male albino rats.

MATERIALS AND METHODS

Ethanolic extract of Emblica officinalis (EEO) was prepared and phytochemical analysis was done. Rats were divided into four groups, having six rats in each group as follows: group 1- Control (20% fat); group 2 (20% fat+ EEO 100 mg/kg/b w); group 3 (30% fat) and group 4 (30% fat + EEO 100 mg/kg/b w). Dietary and EEO supplementation was continued for 21 days. Gravimetric and oxidative stress markers like MDA, NO, antioxidants like Vitamin C and E, and molecular marker (NOS₃) were evaluated. Histopathological analysis was done on the myocardium and elastic artery along with measurement of coronary arterial wall thickness and lumen diameter. One way ANOVA was done for analysis of data.

RESULTS

High fat diet showed a significant increase in MDA, decrease of NO with unaltered NOS₃ protein in rats fed with high fat diet, which indicate possible alteration of vascular pathophysiology. Supplementation of EEO showed an ameliorating effect on high fat diet induced oxidative stress. These results were further corroborated with findings of a histopathological study on the myocardium, elastic artery and coronary arterial architecture.

CONCLUSION

Ethanolic extract of Emblica officinalis (EEO) indicates its cardioprotective efficacy against rats fed with high fat diet.

Arterial Stiffening in Western Diet-Fed Mice Is Associated with Increased Vascular Elastin, Transforming Growth Factor-β, and Plasma Neuraminidase

Consumption of excess fat and carbohydrate (Western diet, WD) is associated with alterations in the structural characteristics of blood vessels. This vascular remodeling contributes to the development of cardiovascular disease, particularly as it affects conduit and resistance arteries. Vascular remodeling is often associated with changes in the elastin-rich internal elastic lamina (IEL) and the activation of transforming growth factor (TGF)-β. In addition, obesity and type II diabetes have been associated with increased serum neuraminidase, an enzyme known to increase TGF-β cellular output. Therefore, we hypothesized that WD-feeding would induce structural modifications to the IEL of mesenteric resistance arteries in mice, and that these changes would be associated with increased levels of circulating neuraminidase and the up-regulation of elastin and TGF-β in the arterial wall. To test this hypothesis, a WD, high in fat and sugar, was used to induce obesity in mice, and the effect of this diet on the structure of mesenteric resistance arteries was investigated. 4-week old, Post-weaning mice were fed either a normal diet (ND) or WD for 16 weeks. Mechanically, arteries from WD-fed mice were stiffer and less distensible, with marginally increased wall stress for a given strain, and a significantly increased Young's modulus of elasticity. Structurally, the wall cross-sectional area and the number of fenestrae found in the internal elastic lamina (IEL) of mesenteric arteries from mice fed a WD were significantly smaller than those of arteries from the ND-fed mice. There was also a significant increase in the volume of elastin, but not collagen in arteries from the WD cohort. Plasma levels of neuraminidase and the amount of TGF-β in mesenteric arteries were elevated in mice fed a WD, while ex vivo, cultured vascular smooth muscle cells exposed to neuraminidase secreted greater amounts of tropoelastin and TGF-β than those exposed to vehicle. These data suggest that consumption of a diet high in fat and sugar causes stiffening of the vascular wall in resistance arteries through a process that may involve increased neuraminidase and TGF-β activity, elevated production of elastin, and a reduction in the size and number of fenestrae in the arterial IEL.