Caspase-1 as a Central Regulator of High Fat Diet-Induced Non-Alcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is associated with caspase activation. However, a role for pro-inflammatory caspases or inflammasomes has not been explored in diet-induced liver injury. Our aims were to examine the role of caspase-1 in high fat-induced NASH. C57BL/6 wild-type and caspase 1-knockout (Casp1(-/-)) mice were placed on a 12-week high fat diet. Wildtype mice on the high fat diet increased hepatic expression of pro-caspase-1 and IL-1 beta. Both wild-type and Casp1(-/-) mice on the high fat diet gained more weight than mice on a control diet. Hepatic steatosis and TG levels were increased in wildtype mice on high fat diet, but were attenuated in the absence of caspase-1. Plasma cholesterol and free fatty acids were elevated in wild-type, but not Casp1(-/-) mice, on high fat diet. ALT levels were elevated in both wild-type and Casp1(-/-) mice on high fat diet compared to control. Hepatic mRNA expression for genes associated with lipogenesis was lower in Casp1(-/-) mice on high fat diet compared to wild-type mice on high fat diet, while genes associated with fatty acid oxidation were not affected by diet or genotype. Hepatic Tnf alpha and Mcp-1 mRNA expression was increased in wild-type mice on high fat diet, but not in Casp1(-/-) mice on high fat diet. alpha SMA positive cells, Sirius red staining, and Col1 alpha 1 mRNA were increased in wildtype mice on high fat diet compared to control. Deficiency of caspase-1 prevented those increases. In summary, the absence of caspase-1 ameliorates the injurious effects of high fat diet-induced obesity on the liver. Specifically, mice deficient in caspase-1 are protected from high fat-induced hepatic steatosis, inflammation and early fibrogenesis. These data point to the inflammasome as an important therapeutic target for NASH.