Identification of miR-185 as a regulator of de novo cholesterol biosynthesis and low density lipoprotein uptake.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
overexpressing microRNA (miR)-185 | decrease | SREBP-2 expression and protein level | HepG2 cells | - | repressed | #1 |
miR-185-directed inhibition | decrease | SREBP-2-dependent gene expression, LDL uptake, and HMG-CoA reductase activity | HepG2 cells | - | caused decreased | #2 |
SREBP-1c | neutral | miR-185 expression | HepG2 cells | - | tightly regulated | #3 |
high-fat diet | increase | miR-185 expression levels | mice | - | elevated | #4 |
high-fat diet | increase | total cholesterol level | mice | - | increase | #5 |
high-fat diet | decrease | SREBP-2 expression and protein | mice | - | decrease | #6 |
- | increase | serum miR-185 expression | individuals with high cholesterol | 5-fold | had a 5-fold increase | #7 |
Dysregulation of cholesterol homeostasis is associated with various metabolic diseases, including atherosclerosis and type 2 diabetes. The sterol response element binding protein (SREBP)-2 transcription factor induces the expression of genes involved in de novo cholesterol biosynthesis and low density lipoprotein (LDL) uptake, thus it plays a crucial role in maintaining cholesterol homeostasis. Here, we found that overexpressing microRNA (miR)-185 in HepG2 cells repressed SREBP-2 expression and protein level. miR-185-directed inhibition caused decreased SREBP-2-dependent gene expression, LDL uptake, and HMG-CoA reductase activity. In addition, we found that miR-185 expression was tightly regulated by SREBP-1c, through its binding to a single sterol response element in the miR-185 promoter. Moreover, we found that miR-185 expression levels were elevated in mice fed a high-fat diet, and this increase correlated with an increase in total cholesterol level and a decrease in SREBP-2 expression and protein. Finally, we found that individuals with high cholesterol had a 5-fold increase in serum miR-185 expression compared with control individuals. Thus, miR-185 controls cholesterol homeostasis through regulating SREBP-2 expression and activity. In turn, SREBP-1c regulates miR-185 expression through a complex cholesterol-responsive feedback loop. Thus, a novel axis regulating cholesterol homeostasis exists that exploits miR-185-dependent regulation of SREBP-2 and requires SREBP-1c for function.