Loss of hepatic miR-33 improves metabolic homeostasis and liver function without altering body weight or atherosclerosis

miR-33 is an intronic miRNA within the gene encoding the SREBP2 transcription factor. Like its host gene, miR-33 has been shown to be an important regulator of lipid metabolism. Inhibition of miR-33 has been shown to promote cholesterol efflux in macrophages by targeting the cholesterol transporter ABCA1, thus reducing atherosclerotic plaque burden. Inhibition of miR-33 has also been shown to improve HDL biogenesis in the liver and increase circulating HDL-C levels in both rodents and non-human primates. However, evaluating the extent to which these changes in HDL metabolism contribute to atherogenesis has been hindered by the obesity and metabolic dysfunction observed in whole body miR-33 knockout mice. To determine the impact of hepatic miR-33 deficiency on obesity, metabolic function and atherosclerosis, we have generated a conditional knockout mouse model that lacks miR-33 only in the liver. Characterization of this model demonstrates that loss of miR-33 in the liver does not lead to increased body weight or adiposity. Hepatic miR-33 deficiency actually improves regulation of glucose homeostasis and impedes the development of fibrosis and inflammation. We further demonstrate that hepatic miR-33 deficiency increases circulating HDL-C levels and reverse cholesterol transport capacity in mice fed a chow diet, but these changes are not sufficient to reduce atherosclerotic plaque size under hyperlipidemic conditions. By elucidating the role of miR-33 in the liver, and the impact of hepatic miR-33 deficiency on obesity and atherosclerosis, this work will help inform ongoing efforts to develop novel targeted therapies against cardio-metabolic diseases. Hepatic mRNA profiles from control and liver specific miR-33 knockout mice on standard diet or high fat diet