Promotion of longitudinal bone growth by the intake of oat and green onion root water extracts in weaning rats through stimulating growth hormone secretion and elevating gut microbiota related to nervous system-related pathway

[Display omitted] •The intake of oat and green onion water extracts stimulated long bone growth in weaning male rats.•Oat and green onion components decreased the binding energy with GDF5 and IGF-1R using in silico analysis.•Its mixture intake elevated tibia and femur length by promoting growth plate proliferation.•The leg length increment was linked to increased growth hormone(GH) secretion potentially promoting the GH-IGF1R axis.•It was also dose-dependently related to the α-diversity of gut microbiota and metagenome function. We determined whether oral oat and green onion water extracts (GOO) supplementation could stimulate longitudinal bone growth in weaning rats. Fistuloside A, B, and C in the green onions and 26-desglucoavenacoside A and B and avenacoside A in the oats lowered the binding energy of growth differentiation factor-5 (GDF5) and insulin-like growth factor-1 receptor (IGF1R). After a 4-week treatment, serum growth hormone (GH) and osteoprotegerin concentrations in the High-GOO group (500 mg/kg body weight) were similar to those of the Positive-control. The femur and tibia lengths promoting the proliferative and hypertrophic zones of the growth plate in the High-GOO were also similar to Positive-control. Along with increasing serum propionate and butyrate concentrations, cecal bacteria in the High-GOO were higher in virus infection, steroid and sesquiterpenoid biosynthesis, and nervous system-related pathways than the Control in the metagenome function. It suggested that gut bacteria potentially enhanced bone growth by improving immunity and neurological activity. In conclusion, GOO increased leg length by enhancing the proliferation of the growth plate as much as GH treatment by preventing gut dysbiosis.