Abstract 11575: The Effects of Tlr4 Deletion on Aortic Stiffness and Gut Microbiota Composition in High Fat Diet-Fed Mice

Abstract

Introduction: We have previously shown that alterations to the gut microbiota are an important mediator of diet-induced cardiometabolic dysfunction. One potential mechanism by which these microbial alterations may affect cardiometabolic function is via lipopolysaccharide (LPS), a component of gram-negative bacteria that can enter circulation following dysbiosis-related intestinal permeability. Once in circulation, LPS binds to toll-like receptor 4 (TLR4) in various tissues and induces a robust inflammatory response. TLR4 null mice are partially protected from obesity-related metabolic dysfunction, but it’s unclear if this mutation offers protection from vascular dysfunction. Methods: 24 male mice lacking the TLR4 receptor (KO) and 24 C57BL/6 wild type male mice (WT) were fed either a control diet (CON) containing 4% fat or a high fat diet containing 60% fat (HFD) for 6 months, yielding the following four experimental group: WT+CON; WT+HFD; KO+CON; KO+HFD. After 6 months, mice underwent measurement arterial stiffness (via pulse wave velocity), and glucose tolerance (via ip glucose tolerance test). The gut microbiota was analyzed by 16S gene sequencing. Results: Mice fed a high fat diet increased body weight, although the magnitude of weight gain was attenuated in KO+HFD vs WT+HFD (p<0.05). Oral administration of FITC-dextran was used to determine intestinal permeability, HFD fed mice exhibited an increase intestinal permeability, compared to their respective control groups (p<0.05). Circulating LPS binding protein was increased in both HFD groups compared to WT. Aortic pulse wave velocity was increased in WT+HFD but not KO+HFD. Glucose tolerance was higher in WT+CON compared to the other three experimental groups. Microbiota shifts occurred between groups, and surprisingly, genotype was the main driver of these shifts, followed by diet (explaining 27% and 22% respectively). Conclusions: These data indicate that deletion of TLR4 in male mice partially protects from arterial stiffness. These data support the supposition that LPS signaling downstream of gut dysbiosis may be an important factor in diet-induced vascular dysfunction.