Melatonin decreases IRF-3 protein expression in the gastrocnemius muscle, reduces IL-1β and LPS plasma concentrations, and improves the lipid profile in rats with apical periodontitis fed on a high-fat diet

To evaluate the effects of melatonin (MEL) on the expression of toll-like receptor-4 (TLR4); myeloid differentiation primary response protein-88 (MyD88); TIR-domain-containing adapter-inducing interferon-beta (TRIF); IFN regulatory-factor-3 (IRF-3); nuclear factor kappa-B (NF-kappa B); plasma concentrations of interleukin-1 beta (IL-1 beta) and lipopolysaccharide (LPS); and lipid profile of rats with apical periodontitis (AP) fed on a high-fat diet (HFD). Eighty 60-day-old rats were divided into eight groups: control, AP, HFD, HFDAP, CNMEL, APMEL, HFDMEL and HFDAPMEL. HFD groups were fed on a HFD for 107 days. On day 7, experimental AP was induced in the AP groups, and after 70 days, MEL (5 mg/kg) was administered to the MEL groups for 30 days. Plasma concentrations of LPS and IL-1 beta were analyzed using enzyme-linked immunosorbent assay, and the lipid profile was analyzed using biochemical tests. The expression of proteins involved in the TLR4 pathway (TLR4, MyD88, TRIF, IRF-3 and NF-kappa B) in the gastrocnemius muscle (GM) was evaluated using western blotting and qRT-PCR. Treatment with MEL decreased IRF-3 protein expression in GM and IL-1 beta plasma concentration in the APMEL and HFDMEL groups. Reduction in LPS plasma concentration was reported only in the HFDMEL group. Additionally, a decrease in LDL and an increase in HDL were observed in the HFDMEL and HFDAPMEL groups. Treatment with MEL exhibited anti-inflammatory and anti-hyperlipidemic effects attributed to HFD and AP by reducing the plasma concentrations of IL-1 beta and LPS in addition to reducing IRF-3 protein expression in the GM, which is associated with the production of inflammatory cytokines.

Automated summary

This study evaluated the effects of melatonin (MEL) on the expression of TLR4, MyD88, TRIF, IRF-3, NF-kappa B, IL-1 beta and LPS, as well as the lipid profile in rats with apical periodontitis (AP) fed on a high-fat diet (HFD). MEL treatment reduced IRF-3 protein expression in the gastrocnemius muscle (GM) and IL-1 beta plasma concentration in the APMEL and HFDMEL groups. LPS plasma concentration decreased only in the HFDMEL group. Additionally, LDL decreased and HDL increased in the HFDMEL and HFDAPMEL groups. Treatment with MEL exhibited anti-inflammatory and anti-hyperlipidemic effects.