Can fumonisin exposure impair liver insulin signaling and promote fatty liver physiology?

Research indicates that fumonisin exposure, particularly Fumonisin B1 (FB1), initiates a cascade of hepatic metabolic dysfunction through the disruption of sphingolipid metabolism and the induction of cellular stress.

Mechanistic pathways of hepatotoxicity

The primary mechanism of fumonisin toxicity is the potent inhibition of ceramide synthase. This inhibition leads to an accumulation of sphinganine and sphingosine, which directly promotes the generation of reactive oxygen species (ROS) and the depletion of antioxidants like glutathione (GSH). This oxidative milieu activates the NF-κB pathway, triggering the release of pro-inflammatory cytokines such as TNF-α and IL-6. These molecular shifts cause significant lipid peroxidation (measured by increased malondialdehyde) and structural damage to hepatocytes.

Impact on insulin signaling

There is robust evidence that the resulting oxidative stress and inflammation impair hepatic insulin signaling. Increased levels of ROS and TNF-α activate stress-sensitive kinases, including JNK and IKKβ. These kinases perform inhibitory serine phosphorylation on Insulin Receptor Substrate 1 (IRS-1), effectively blocking the downstream PI3K/Akt pathway. This disruption prevents the liver from properly regulating glucose production and lipid metabolism, a hallmark of hepatic insulin resistance.

Progression to fatty liver physiology

The combination of impaired insulin signaling and sphingolipid imbalance alters lipid handling within the liver. Studies in animal models have demonstrated that FB1 exposure leads to the accumulation of hepatic lipid droplets and shifts in fatty acid profiles, such as reduced polyunsaturated fatty acids (PUFAs). While the severity of clinical steatosis may depend on the dose and duration of exposure, the mechanistic link between toxin-induced oxidative stress, mitochondrial dysfunction, and impaired fatty acid oxidation strongly supports the promotion of a fatty liver physiology similar to non-alcoholic fatty liver disease (NAFLD).

Bottom line

Fumonisins promote fatty liver physiology by inhibiting ceramide synthase, which triggers oxidative stress and inflammation. These processes activate stress kinases that disrupt hepatic insulin signaling via IRS-1 inhibition, leading to altered lipid metabolism and steatosis.