The Effects Of Lactobacillus Rhamnosus GG And Its Supernatant On Intermittent Hypoxia Induced Cardiomyopathy In Obese Mice

Background:Obstructive sleep apnea(OSA)is a common disease characterized by recurrent upper airway obstruction during sleep.Intermittent hypoxia(IH)is the main pathogenic component of OSA and is closely associated with increased cardiovascular morbidity and mortality.The majority of patients with OSA are obese,thus effective treatment of OSA can significantly reduce mortality in obese populations.There is increasing evidence indicating that IH plays an important role in the pathological damage of various organs caused by OSA.Our previous research has confirmed that IH damages myocardial function in mice mainly through oxidative stress and inflammatory response.The intestine is colonized by a considerable community of microorganisms that cohabits within the host and plays a critical role in maintaining host homeostasis.Recently,accumulating evidence has revealed that the gut microbial ecology plays a pivotal role in the occurrence and development of cardiovascular disease(CVD).The effects of imbalances in microbe-host interactions on homeostasis can lead to the progression of CVD.Alterations in the composition of gut flora and disruptions in gut microbial metabolism are implicated in the pathogenesis of CVD.Exposure to IH may alter the gut ecology including the microbiome and metabolites,leading to gut microbial disorder.The multiple correlations between altered gut microbial imbalance and CVD susceptibility have highlighted the gut microbiota as a potential novel target for the treatment of CVD.The probiotics refers to live microorganisms that have been shown to confer health benefits with administration of adequate amounts,which has attractted widespread attention for its related therapies.It has been demonstrated that protective effects of Lactobacillus rhamnosus GG(LGG)and Lactobacillus rhamnosus GG cell-free supernatant(LGGs)against acute alcohol-induced hepatic steatosis and injury.However,it remains unknown whether LGG and LGGs have a protective effect on the heart tissue of obese mice exposed to IH and its underlying mechanism.Aim:Oral supplementation of IH-exposed obese mice with LGG and LGGs to clarify whether LGG and LGGs can prevent the development of IH-induced cardiomyopathy,and reveal what is the potential mechanism of LGG and LGGs interact with the myocardium of obese mice exposed to IH,and eventually provide basis for the application of probiotics to regulate the gut microbiota as a novel treatment of CVD.Methods:Six-week-old C57BL/6J male mice were randomly assigned to four groups.All mice were fed a high fat high fructose diet(HFHFD)for 15 weeks.The four groups of mice were treated separately during the whole process:(1)HFHFD group;(2)HFHFD+IH group:The mice were exposed to IH for 12 weeks from the fourth week of the whole process;(3)HFHFD+IH+LGG group:In addition to above-mentioned HFHFD and IH treatment,mice were treated with oral administration of LGG(10~9CFU bacteria/day)over the entire experiment for 15 weeks;(4)HFHFD+IH+LGGs group:In addition to above-mentioned HFHFD and IH treatment,mice were treated with oral administration of LGGs(dose equivalent to 10~9 CFU bacteria/day)over the entire experiment for 15 weeks.After 15 weeks of treatment,non-invasive cardiac ultrasound was performed to detect changes of the myocardial structure and function of these mice.Then,the mice were anesthetized and sacrificed to collect their heart tissues for recording the heart weight.Extract proteins and mRNA from heart tissues to detect expression of myocardial hypertrophy,fibrosis,inflammatory response and oxidative stress related molecules by Western blot and real-time quantitative polymerase chain reaction(RT-qPCR).Perform pathological staining and immunofluorescence staining of cardiac tissue sections to observe changes of morphology and specific molecular expression changes.Results:Obese mice exposed to IH exhibited myocardial remodeling and cardiac dysfunction,accompanied by increased levels of myocardial inflammation and oxidative stress.Oral supplementation with LGG or LGGs could prevent the above functional or pathological changes in myocardium of IH-exposed obese mice,LGG and LGGs could also up-regulate the expression of Nrf2 and its downstream antioxidant genes in mice heart.However,there was no significant difference in the degree of protection of myocardium between LGG and LGGs.Conclusions:IH damaged the myocardium of obese mice,leading to abnormal myocardial structure and function,while LGG and LGGs had protective effects on myocardium of obese mice exposed to IH,and this protective effect was associated with up-regulation of nuclear factor erythroid 2-related factor 2(Nrf2)-mediated antioxidant pathways.These results suggested that supplementation with probiotics or probiotic secreted bioactive molecules might be an effective method to reduce cardiovascular risk,and gut microbiota may represent a promising therapeutic target against cardiovascular complications in obese patients with OSA.