A diet high in fat and sugar triggered immune system abnormalities — including reduced levels of natural killer T (NKT) cells — in the livers of mice, says a study led by Johns Hopkins University in Baltimore.
The study authors said these diet-related changes may contribute to obesity-related liver disease. The findings appear in the October issue of the journal Hepatology.
Natural killer T (NKT) cells in the liver regulate production of cytokines, which are cell proteins.
The study found that the mice on the high-fat diet gained much more weight than mice fed a normal diet. The mice on the high-fat diet also developed fatty livers and had increased production of IL-12, a cytokine that reduces NKT cell viability, and had increased NKT cell death.
The high-fat diet also promoted production of pro-inflammatory cytokines. When the researchers induced liver injury in the mice, they found that those on the high-fat diet experienced more liver inflammation and damage than mice on the normal diet.
The findings show that high-fat diets are associated with a chronic inflammatory state in the liver, which promotes chronic liver disease, the study authors said. They said this may be the result of diet-induced depletion of NKT cells that normally balance production of pro- and anti-inflammatory cytokines.
“Further evaluation of other mouse strains, different age groups and genders will be necessary to clarify if any of these factors modulate susceptibility to diet-related changes in hepatic NKT cells,” the authors said. “Nevertheless, our findings are important because they clearly demonstrate significant dietary effects on ‘classic’ NKT cells and cytokine production by other liver mononuclear cells.”