PSAT1 and obesity due to melanocortin 4 receptor deficiency: Lactobacillus rhamnosus hsryfm 1301 fermented milk inhibited transcription of Psat1 and Phgdh by increasing the levels of L-Threonine, L-Serine and glyceric acid, which, in turn, regulated the amino acid metabolic pathways and alleviated onset and development of obesity.