Particles in grilled meats may trigger liver disease, mouse study finds
But probiotics may help ease damage from long-term exposure
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Long-term exposure to particles produced from cooking grilled meat can trigger liver damage and cholestasis — slowing or stalling of the digestive fluid bile as it flows out of the liver — by altering the activity of gut bacteria, according to a new study done in mice.
Still, treatment with probiotics — live microorganisms found in yogurt, fermented foods, and dietary supplements that promote health — helped ease this type of liver damage in the animals, the data showed. Probiotics are also thought to improve gut health in humans.
“This study provides substantial evidence for the comprehensive assessment, control, and intervention regarding the [liver toxicity] of foodborne CQDs [carbon quantum dots],” the tiny molecular structures at issue, the researchers wrote.
Still, further studies are needed to verify the findings and understand the implications for human health, the team noted.
The study, “Exposure to Grilled Lamb-Borne Carbon Quantum Dots Induces Intrahepatic Cholestasis by Activating the Intestinal Microbial-Derived Lipopolysaccharide-TLR4 Pathway,” was published in the journal Small.
Carbon quantum dots, known more simply as CQDs, are structures composed of carbon atoms. These molecules often form when food is cooked, and have been identified in many heat-processed foods, from beer and caramel to bread and grilled meat.
“The long-term and frequent consumption of thermally processed foods leads to the accumulation of foodborne CQDs in the human body, posing unknown and potential hazards,” the researchers wrote.
Investigating the effects of long-term exposure in mice
Cell-based research suggests that CQDs are nontoxic at low concentrations but can cause cell death at high levels.
“However, the current … assessment of chronic exposure risk to foodborne CQDs [in living organisms] is exceedingly limited,” the team wrote.
To learn more, scientists in China investigated the impact of long-term exposure to grilled lamb-derived CQDs on the liver function of mice.
The team isolated CQDs from grilled lamb and conducted experiments in which mice were fed either a control diet or a diet supplemented with these meat-derived CQDs for nine weeks, or about two months.
The results showed that, although overall food and water intake were similar, mice given the CQDs had reduced body weight, and in particular, reduced liver size. This was accompanied by significantly increased levels of liver damage markers in the blood, and significantly lower levels of antioxidant molecules in the liver, indicating a state of oxidative stress, a type of cellular damage.
Livers of mice fed grilled lamb-derived CQDs also showed significantly higher levels of pro-inflammatory molecules compared with those from control mice.
“These findings suggest that exposure to CQDs caused liver damage in mice,” the researchers wrote.
More work needed to judge impact on human health
One of the liver’s most important jobs is to produce bile, a substance that’s used in digestion to help break down primarily fats and fat-soluble vitamins. Bile is transported from the liver to the intestines through a series of tubes called bile ducts.
The researchers found that in mice fed CQDs, bile flow within the liver was stalled — a condition known as intrahepatic cholestasis. That significantly increased levels of bile acids, which are the digestive fluid’s main component, in the liver.
Further analyses indicated that CQD exposure altered the levels of several liver proteins that are key regulators of bile production. Specifically, data indicated that the CQD group had significantly lower levels of molecules that activate the farnesoid X receptor (FXR), which suppresses bile production, and of proteins that help move bile out of the liver.
This ultimately led to bile buildup in the liver and intrahepatic cholestasis.
The team also found that CQD exposure increased the abundance of certain bacteria living in the mice’s gut that produce a powerfully proinflammatory molecule called lipopolysaccharide (LPS). At the same time, the walls of the intestines became more permeable.
Based on their findings, the researchers proposed that CQDs increase the amount of inflammatory bacterial molecules released from the intestines toward the liver, ultimately leading to cholestasis and liver damage.
“Long-term exposure to CQDs from grilled lamb disrupts the structure and composition of the gut [bacteria] in mice, resulting in an increase in LPS derived from intestinal [bacteria] and damage to the intestinal barrier,” the scientists wrote. This triggers inflammation, “culminating in increased [bile production] and reduced excretion, [which] ultimately leads to intrahepatic cholestasis.”
Probiotic supplementation for regulating intestinal microecology has emerged as a core strategy for managing the safety risk caused by emerging food hazards.
Based on their data, the team postulated that treatments aimed at reducing inflammation and dysregulation of gut bacteria could help reduce liver damage in CQD-fed mice.
“Probiotic supplementation for regulating intestinal microecology has emerged as a core strategy for managing the safety risk caused by emerging food hazards,” the researchers wrote.
In line with this, they found that treating CQD-exposed mice with a probiotic (Lactiplantibacillus plantarum) alleviated cholestasis and normalized bile production.
The team emphasized, however, that more work is needed to evaluate the impacts of CQDs on human health and the potential benefits of probiotics, writing that “further research is warranted to investigate the interactions between harmful substances that tend to accumulate in the intestine and probiotics, ensuring the efficacy of probiotic actions.”
