Modulation of atherosclerosis by probiotic bacteria VSL#3 and LGG in ApoE-/- mice

Abstract

Atherosclerosis is the major cause of cardiovascular diseases, which constitute the top ten leading causes of death worldwide. Atherosclerotic plaque development initiates from the inflamed endothelium under an atherogenic environment – chronic low grade inflammation, hypercholesterolemia, endotoxemia, etc. The principal cause of such inflammation has yet to be defined – with growing evidence that microbial stimulants like lipopolysaccharide (LPS) and peptidoglycan (PGN), which can activate toll-like receptors (TLRs) and nuclear factor-kappaB (NFκB) signaling might be the plausible origins. The gastrointestinal tract is suggested to be the major site for absorption and translocation of such stimulants, where gut microbiota have been associated with systemic inflammation and is essential in generating atherogenic substances. Since probiotics have the potential to induce systemic anti-inflammatory effects and fortify gut barrier to reduce bacterial translocation, evaluation of whether probiotics can help reduce atherogenesis was done by feeding the disease model, ApoE-/- mice with high fat diet alone, with telmisartan (1 or 5 mg/kg/day, positive controls) or with probiotics VSL#3 (2.8 x 1011 CFU/day) and/or Lactobacillus rhamnosus strain GG (LGG) (1x108 CFU/day), or the combination of which for 12 weeks. All treatments reduced lesion size significantly; with some treatments reduced plasma endotoxin, cholesterol and various proinflammatory biomarkers. The gut microbiota assessed with PCR-amplified 16S rRNA gene sequences using 454 pyrosequencing and thereafter correlation studies revealed that at least 20 bacterial families that were significantly altered by high fat diet in apolipoprotein E knockout (ApoE-/-)mice correlated with atherosclerotic plaque size and related biomarkers including cholesterol, adipocyte fatty acidbinding protein (A-FABP), etc. Probiotics showed potential in improving atherogenic environment by immunomodulation and induction or inhibition of growth of bacteria correlated with the atherosclerotic plaque and biomarkers. The atherosclerotic condition was also improved by telmisartan, which correlated with the altered gut microbiota. The newly identified atherosclerosis-related gut bacteria will require further exploration into their properties and mechanisms, which will eventually lead to the potential of developing probiotics for the treatment or prevention of atherosclerosis, and thus may be used as an affordable and non-invasive alternative that brings health benefits worldwide.