The Effects of High Salt and Western Diets on Microcirculatory and Glycocalyx Properties in Genetically Heterogeneous Young Mice

Abstract

A prominent feature of cardiovascular disease is microcirculatory dysfunction, characterized by low capillary density and a deteriorated glycocalyx. In most industrialized societies, individuals consume a high salt diet in combination with a western diet, characterized by excess consumption of fat and sugar. Therefore, we sought to determine the effects of high salt and/or western diet in genetically heterogeneous young mice. At 3 mo old, male and female UM‐HET3 mice were randomized into 1 of 4 dietary interventions for 12 weeks: 1. Normal chow diet (NC) (fat 13.5% kcal fat, N=19) 2. NC diet with 4% salt (NC4%) (13.0% kcal fat, N=19) 3. Western diet (WD) (39.1% kcal fat, N=19) 4. WD with 4% salt (WD4%) (40.4% kcal fat, N=18) Microvascular density and glycocalyx barrier function were evaluated in 4‐25 µm diameter microvessel segments in the mesenteric microcirculation using an intravital microscope equipped with an automated capture and analysis system. After 12 weeks of dietary intervention, WD and WD4% had ~32‐42% greater body mass and ~13‐16% greater blood glucose level than NC and NC4% (P<0.05 for all). Microvascular density at each microvessel segment diameter is presented in Figure 1A. Total microvascular density summed across 4‐25 µm microvessel segment diameters was lower in NC4% compared to NC, WD, and WD4% (Figure 1B; P<0.05). Total microvascular density in WD4% was also lower than NC (P<0.05). After separating microvessels into capillaries (4‐6 µm diameter) and large microvessels (10‐25 µm diameter), capillary density was lower in NC4% compared to NC, WD, and WD4% (Figure 1C; P<0.05). Capillary density was higher in WD compared to NC (P<0.05). Large microvessel density was lower in NC4% and WD4% compared to NC (Figure 1D; P<0.05). Perfused boundary region (PBR), a marker of glycocalyx barrier function, at each microvessel segment diameter is presented in Figure 2A. PBR averaged across 4‐25 µm microvessel segment diameters was similar between NC and NC4%, as well as between WD and WD4% (Figure 2B; P>0.05). Surprisingly, PBR was lower in WD and WD4% compared to NC and NC4% (P<0.05), indicating augmented glycocalyx barrier function in WD and WD4%. Capillary PBR was also lower in WD and WD4% and trending toward lower in NC (P=0.07) compared to NC4% (Figure 2C; P<0.05). Large microvessel PBR was lower in WD and WD4% compared to NC and NC4% (Figure 2D; P<0.05). There were strong, inverse relationships between PBR and body mass (Figure 2E; r=‐0.60, P<0.05) and blood glucose (Figure 2F; r=‐0.47, P<0.05). In summary, NC4% decreased microvascular density and glycocalyx barrier function. Although WD increased body mass and blood glucose, it appeared to augment capillary density and glycocalyx barrier function. Interestingly, the combination of high salt, western diet in WD4% resulted in lower total microvascular density that was similar to NC4%, as well as an elevation in body mass, blood glucose, capillary density, and glycocalyx barrier function that was similar to WD. These data indicate that there are distinct microcirculatory adaptations to high salt and western diets that appear to superimpose when these diets are combined in genetically heterogeneous male and female mice.