Dietary propolis transiently delays autoimmune diabetes onset and modulates immune responses in NOD mice

Propolis is a honey bee-derived resinous substance used in traditional medicine across many cultures to treat inflammatory and immune-related ailments. Its documented anti-inflammatory and immunomodulatory actions suggest potential value in autoimmune disease, yet its effects in type 1 diabetes (T1D) have not been examined.

To investigate whether dietary propolis modulates immune responses and alters the progression of autoimmune diabetes in non-obese diabetic (NOD) mice.

Female NOD mice (n = 66) received standard chow or chow supplemented with 1.8% or 3.6% (w/w) raw Danish propolis from 4 to 30 weeks of age. Diabetes incidence was monitored longitudinally. At 14 weeks, pancreatic insulitis, T cell subsets in pancreatic lymph nodes and spleen, serum cytokines, and gut microbiota composition were assessed.

Propolis delayed diabetes onset, significantly reducing incidence at 17 weeks, although cumulative incidence converged by 30 weeks. High-dose propolis reduced pancreatic immune infiltration and decreased CD4⁺ T helper cells in pancreatic lymph nodes, with a non-significant trend toward increased splenic T cell counts. Serum IL-10 and IFN-γ were elevated, while IL-4 was reduced. Akkermansia muciniphila abundance was increased.

Dietary propolis delayed autoimmune diabetes onset in NOD mice, although cumulative incidence converged by the end of the study, and was associated with changes in immune parameters and gut microbiota composition. These findings support further investigation of propolis as a candidate for modulating disease progression in autoimmune T1D, though the underlying mechanisms remain to be established.