Oral Administration of Propolis and Lysozyme Combination Improves Feline Oral Health and Modulates Systemic Inflammatory and Oxidative Responses

Abstract

Oral diseases are highly prevalent among domestic cats, with microbiota dysbiosis as a primary etiological factor. However, effective microbiota-targeted interventions remain limited. This study evaluated the efficacy of a dietary supplement combining propolis and lysozyme (PL) in mitigating feline oral health issues, based on a cohort of 24 cats divided equally into placebo, treatment, and healthy control groups (n = 8 per group). Supragingival microbiota were analyzed via 16S rRNA gene sequencing, alongside assessments of volatile sulfur compounds (VSCs), oral health indices, and systemic inflammatory, oxidative, and immune markers. After 28 days of intervention, cats receiving PL supplementation demonstrated significant improvements, including a 35.4% reduction in VSCs and notable decreases in debris (34.9%), plaque (51.2%), and gingival indices (61.0%). Systemically, MDA and TNF-α levels decreased, while SOD, T-AOC, and IL-4 increased. Microbiota analysis revealed suppression of Porphyromonas and Selenomonas and enrichment of Moraxella and Bergeyella. Reductions in VSCs, gingival index, and TNF-α were correlated with lower Porphyromonas abundance, while Moraxella and Luteimonas were positively associated with antioxidant status. Functional predictions indicated downregulation of virulence-related pathways and increased expression of glutathione reductase. These findings highlight PL's potential as a natural, microbiota-based intervention that improves feline oral health and modulates the oral-systemic axis, supporting its application in integrative oral care strategies.

Keywords: feline; inflammatory; lysozyme; oral health; oral microbiota; oxidative responses; propolis.

Figure 1

Changes in the VSCs’ profile after 28 days of intervention. (a) Longitudinal change in the overall VSC concentrations (ppb) in the placebo and treatment groups during the 28-day intervention, with a dashed line indicating the mean VSC level in healthy cats. (b) Individual VSC concentrations for each cat at baseline (0 days) and after 28 days of intervention. Healthy baseline values are shown as green reference points. (c) Percentage change in VSC concentration at the end of the experiment relative to the starting point for each cat in the placebo and treatment groups (* p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001).

Figure 2

Oral health scores and visual records of oral symptoms in cats throughout the experiment: (a) DI scores at 0, 14, and 28 days; (b) PI scores on days 0, 14, and 28; (c) CI scores at 0, 14, and 28 days; and (d) GI scores in 0, 14, and 28 days. Healthy control values are shown as baseline references (* p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001).

Figure 3

Analysis of immune responses, oxidative stress levels, and inflammatory markers in cat serum. (a) Analysis of immune responses in cat serum, showing changes in immunoglobulin levels (IgA, IgG, IgM) (* p < 0.05). (b) Analysis of oxidative stress levels in cat serum, showing changes in MDA, T-AOC, CAT, SOD, and GSH-PX (* p < 0.05). (c) Analysis of inflammatory markers in cat serum, showing changes in TNF-α, IFN-γ, IL-4, and IL-2 (* p < 0.05). IgA: immunoglobulin A; IgG: immunoglobulin G; IgM: immunoglobulin M; MDA: malondialdehyde; SOD: superoxide dismutase; T-AOC: total antioxidant capacity; TNF-α: tumor necrosis factor alpha; IFN-γ: interferon gamma; IL-4: interleukin-4; IL-2: interleukin-2.

Figure 4

Changes in diversity and species composition of the supragingival microbiome after 28 days of intervention. HC, healthy control. (a) Venn diagram showing the overlap of OTUs across the different groups. (b) Kruskal–Wallis H test comparing Shannon and Chao diversity indices between groups. (c) Microbiota composition at the phylum level for each group. (d) Microbiota composition at the genus level for each group.

Figure 5

Changes in the genus composition of the supragingival microbiome of cats during the 28 days of intervention: (a) PCoA of the three groups at the genus level on day 0; (b) PCoA of the three groups at the genus level on day 14; and (c) PCoA of the three groups at the genus level on day 28.

Figure 6

Effects of PL intervention on abundance changes in characteristic taxa at the genus level. (a) Taxonomic cladogram from LEfSe analysis showing differences in genus-level composition between the healthy control and treatment groups. (b) Taxonomic cladogram from LEfSe analysis showing differences in genus-level composition between the placebo and treatment groups after PL intervention. (c) Comparison of the relative abundance of 12 characteristic genera across the three groups (* p < 0.05, *** p < 0.001).

Figure 7

Analysis of the correlation between oral microbiome and oral, as well as overall health (* p < 0.05, ** p < 0.01, *** p < 0.001).

Figure 8

Tax4Fun-predicted functional differences between placebo and PL groups on day 28. (a) KEGG pathway differences, including reduced biofilm formation and LPS biosynthesis in the treatment group. (b) Predicted enzyme differences, with a higher abundance of redox and amino acid-related enzymes in the treatment group.