TLR2 and metabolic disease: Indeed, gut microbiota also influences host metabolism through bacterial derivatives such as microRNA, extracellular vesicles, and membrane proteins.47,48 For example, gut microbial DNA-containing extracellular vesicles (mEVs) are delivered to the metabolic tissues in obesity, and the leakage of mEVs contributes to the development of obesity-associated inflammation and metabolic diseases.49 Unfortunately, we did not reveal how L. R activates TLR2/4/MyD88/NF-κB signaling, but the potential of L. R as a probiotic in regulating melatonin production is worthy of further exploration.