The function of MT-RNR1 (mitochondrially encoded 12S rRNA, Ensembl gene identifier ENSG00000211459) is as follows. Regulates insulin sensitivity and metabolic homeostasis (PubMed:25738459, PubMed:33468709). Inhibits the folate cycle, thereby reducing de novo purine biosynthesis which leads to the accumulation of the de novo purine synthesis intermediate 5-aminoimidazole-4- carboxamide (AICAR) and the activation of the metabolic regulator 5'- AMP-activated protein kinase (AMPK) (PubMed:25738459). Protects against age-dependent and diet-induced insulin resistance as well as diet- induced obesity (PubMed:25738459). In response to metabolic stress, translocates to the nucleus where it binds to antioxidant response elements (ARE) present in the promoter regions of a number of genes and plays a role in regulating nuclear gene expression in an NFE2L2- dependent manner and increasing cellular resistance to metabolic stress (PubMed:29983246). Increases mitochondrial respiration and levels of CPT1A and cytokines IL1B, IL6, IL8, IL10 and TNF in senescent cells (PubMed:29886458). Increases activity of the serine/threonine protein kinase complex mTORC2 and reduces activity of the PTEN phosphatase, thus promoting phosphorylation of AKT (PubMed:33554779). This promotes AKT-mediated phosphorylation of transcription factor FOXO1 which reduces FOXO1 activity, leading to reduced levels of MSTN and promotion of skeletal muscle growth (PubMed:33554779). Promotes osteogenic differentiation of bone marrow mesenchymal stem cells via the TGFB/SMAD pathway (PubMed:30468456). Promotes osteoblast proliferation and osteoblast synthesis of type I collagens COL1A1 and COL1A2 via the TGFB/SMAD pathway (PubMed:31081069). {ECO:0000269|PubMed:25738459, ECO:0000269|PubMed:29886458, ECO:0000269|PubMed:29983246, ECO:0000269|PubMed:30468456, ECO:0000269|PubMed:31081069, ECO:0000269|PubMed:33468709, ECO:0000269|PubMed:33554779}.