Hepatic glycosphingolipid deficiency and liver function in mice

Area of Science:

• Biochemistry
• Metabolic Diseases
• Hepatology

Background:

• Recent studies suggest glycosphingolipids (GSLs) involvement in obesity-induced insulin resistance.
• Inhibition of GSL biosynthesis has shown potential in ameliorating insulin resistance and liver steatosis in obese mice.
• Pharmacological GSL depletion using Ugcg inhibitors has been employed, but potential off-target effects exist.

Purpose of the Study:

• To investigate the specific role of GSLs in hepatocytes using a genetic deletion approach.
• To determine if selective GSL deletion in hepatocytes impacts glucose, sterol, or lipoprotein metabolism.
• To assess the effect of hepatocyte-specific GSL deficiency on high-fat diet-induced liver steatosis.

Main Methods:

• Utilized a Cre/loxP system under the albumin promoter for selective GSL deletion in hepatocytes.
• Generated genetically modified mice with inhibited GSL biosynthesis specifically in liver cells.
• Assessed bile excretion, bile salt content, cholesterol levels, and lipoprotein concentrations.
• Evaluated glucose and insulin tolerance and liver steatosis after a high-fat diet.

Main Results:

• Selective GSL deletion in hepatocytes did not alter bile excretion quantity or bile salt content.
• Cholesterol concentrations in liver, bile, feces, and plasma remained unaffected.
• Lipoprotein levels in plasma were similar between mutant and control mice.
• No improvement in glucose tolerance or prevention of liver steatosis was observed in GSL-deficient mice on a high-fat diet.

Conclusions:

• Hepatocyte GSLs are not essential for sterol, glucose, or lipoprotein metabolism.
• GSL deficiency in hepatocytes does not protect against high-fat diet-induced liver steatosis.
• The effects of Ugcg inhibitors may be independent of GSLs in hepatocytes or mediated by other cell types.