A synbiotic nanoemulsion modulates metabolic dysfunction and organ functioning in high-fat diet-induced obese mice

High-fat diet (HFD)-induced obesity is associated with metabolic disturbance and structural changes in the intestine, liver, kidney, and adipose tissue. This study evaluated the effects of a co-formulated nanoemulsion containing silk fibroin (a proposed prebiotic) and Lactobacillus rhamnosus (a probiotic), referred to here as a synbiotic nanoemulsion, in HFD-induced obese mice. A synbiotic nanoemulsion was prepared using a high-energy method and characterized by UV-visible spectroscopy and FTIR analysis. Forty-eight male mice were randomly divided into eight groups (n = 6) and fed different diet for 16 weeks. Body weight was recorded weekly, following biochemical, histological, and histomorphometric analysis. Compared with the normal diet group (31.82 ± 1.18 g), HFD-fed mice showed a significant increase in body weight (48.7 ± 0.07 g) and severe dyslipidemia, evidenced by elevated total cholesterol (222-276.5 mg/dL), triglycerides (195-289.5 mg/dL), and low-density lipoprotein (104.8-140 mg/dL), with reduced high-density lipoprotein levels (9-23 mg/dL). Synbiotic supplementation significantly reduced blood urea nitrogen (8-10 mg/dL), serum creatinine (0.55-1.0 mg/dL), alanine aminotransferase (28-39 U/L), and aspartate aminotransferase (129-141 U/L). Furthermore, systemic inflammation was also reduced reflected by lowered TNF-α, IL-6, and IL-1β, alongside increased IL-10 levels as compared to HFD group. Histological and histomorphometric analysis showed improved organ architecture in the synbiotic-treated group, with several measurements close to those of the normal diet group. In this HFD mouse model, the fibroin-L. rhamnosus nanoemulsion was associated with lower body weight, improved lipid profile, liver, kidney, and inflammatory markers, and improved tissue morphology. These findings support further study of the formulation. The design does not allow conclusions about synergy, nanoemulsion-specific delivery effects or mechanisms.