Amongst many key functions, the liver plays a critical part in lipid metabolism. Non alcoholic liver disease or fatty liver relates to abnormally elevated lipid storage in this organ, in the absence of excess alcohol intake. This disease has recently become a major public health issue.

PPARs (for “Peroxisome Proliferator-Activated Receptors”) are nuclear receptors expressed in many organs (liver, adipose tissues, kidney, muscles…). Stimulated by binding to lipids (fatty acids and their derivatives), a number of drugs and endocrine disruptors (food contaminants), they regulate the expression of a subset of target genes.

In order to investigate the role of PPARα in liver lipid accumulation, a group of scientists from INRA and LKCMedicine has developed a mouse model lacking the receptor, specifically in the liver.

The lack of PPARα in hepatocytes promotes Non Alcoholic Fatty Liver Disease

This original model allows scientists to determine that the absence of the receptor in hepatocytes disrupt fatty acid breakdown and leads to lipid deposition in the liver in response to fasting or to diets enriched in dietary fat. Moreover, animals lacking the receptor spontaneously developed the disease in aging without being overweight and diabetic. This work reveals that the receptor PPARα controls the specific expression pattern of the hormone FGF21 over the day. FGF21 is known for its impacts on health, including growth, fertility, metabolism, and longevity.

The circadian PPARα activity is sensitive to adipocyte lipolysis and gut microbiota

The results published in Gut further our knowledge about the autonomous activities of the receptor in hepatocytes and provide evidence that PPARα is required for the dialog between the liver and the white adipose tissues. Moreover, another recent publication from the same groups (Scientific reports) establishes that PPARα is sensitive to signals derived from the microbiota, the bacterial community hosted in the gut. More broadly, the gut microbiota regulates circadian liver activities such as the production of metabolites and hormones, including FGF21.

Altogether, these works further define the role of PPARα in hepatocytes as an integrator of multiple signals required for normal liver function. They open new perspectives of our understanding of the receptor, its influence during the perinatal period, its role in Type 2 diabetes, its tissue-specific activities and its interaction with other members of the PPAR family.

For INRA, this is very important since PPARs are critical nutritional (dietary lipids) and xenobiotic (food contaminants) sensors. The use of PPAR ligands as drugs for metabolic diseases is highly relevant to the current research at LKCMedicine.