HNF4α contributes to hepatic CAR dysfunction in polymicrobial sepsis.

The constitutive androstane receptor (CAR), encoded by the gene, is a nuclear receptor mainly expressed in the liver, where it regulates (xenobiotic) drug and bile acid metabolism, bilirubin clearance and energy homeostasis. CAR has emerged as a promising therapeutic target for diabetes, fatty liver disease and alcoholic liver disease, but it has barely been investigated in the context of sepsis. Since alterations in drug metabolism have been observed in sepsis patients, who may also exhibit increased serum bilirubin and bile acid levels, we hypothesize that CAR function may be impaired during sepsis.

Unraveling mitochondrial pyruvate dysfunction to mitigate hyperlactatemia and lethality in sepsis.

Sepsis, killing 11 million people yearly, is associated with increased production of lactate-a metabolite mechanistically linked to mortality-complicating glucose administration in sepsis. To understand the mechanism behind hyperlactatemia, we applied the cecal ligation and puncture (CLP) model and studied all pyruvate processing routes in liver mitochondria during acute sepsis. Our data suggest that mitochondrial pyruvate-driven respiration is nearly nonexistent in sepsis, not due to insufficient pyruvate uptake or carboxylation, but due to a dysfunctional pyruvate dehydrogenase complex (PDC).

Balancing metabolism and regeneration in liver diseases through HNF4α targeting.

Transcription factor hepatocyte nuclear factor 4 alpha (HNF4α) is considered the master regulator of hepatocyte differentiation. During homeostasis, HNF4α maintains liver identity by supporting metabolism while inhibiting proliferation. It is downregulated in response to both acute and chronic insults; however, although this supports hepatic regeneration in mild acute settings, severe or chronic downregulation may further compromise liver function and lead to a lethal outcome.

A critical role for HNF4α in polymicrobial sepsis-associated metabolic reprogramming and death.

In sepsis, limited food intake and increased energy expenditure induce a starvation response, which is compromised by a quick decline in the expression of hepatic PPARα, a transcription factor essential in intracellular catabolism of free fatty acids. The mechanism upstream of this PPARα downregulation is unknown. We found that sepsis causes a progressive hepatic loss-of-function of HNF4α, which has a strong impact on the expression of several important nuclear receptors, including PPARα.

Hepatic Peroxisome Proliferator-Activated Receptor Alpha Dysfunction in Porcine Septic Shock.

Despite decades of research, sepsis remains one of the most urgent unmet medical needs. Mechanistic investigations into sepsis have mainly focused on targeting inflammatory pathways; however, recent data indicate that sepsis should also be seen as a metabolic disease. Targeting metabolic dysregulations that take place in sepsis might uncover novel therapeutic opportunities.