Insects and Lentil as Sustainable Protein Sources: Effects on Gut Microbiota, Lipid Metabolism, and Antioxidant Activity

Background/Objectives: The purpose of this study was to evaluate the nutrient compo-sition of selected arthropods (insects and crustaceans) and lentil, and to investigate their effects as dietary protein sources on gut microbiota, host metabolism, and associated metabolites. Methods: A total of 63 male Wistar rats were randomly assigned to eight experimental groups and fed diets adjusted to 20% protein from different sources: control (C), cricket (CR), acocil (AC), chinicuil (CHI), beef (B), picanha (P), egg (E), and lentil (L). Diets were administered for 45 days. At the end of the intervention, serum was collected to assess biochemical parameters and microbiota-derived metabolites, liver samples were obtained for histological analysis, and feces were collected for intestinal microbiota pro-filing. Results: Nutritional analysis revealed that L, CR, AC, and CHI contained signif-icantly lower concentrations of choline, carnitine, and phosphatidylcholine—precursors of trimethylamine-N-oxide—than animal-derived sources (E, B, P). CHI was enriched in oleic acid, CR in linolenic acid, and L in linoleic acid, while L also displayed significantly lower cholesterol levels than E. CR, AC, and CHI had the highest chitin contents, followed by L. Consumption of CR or L significantly reduced fat mass, improved glucose sensi-tivity, and lowered hepatic cholesterol and triglycerides compared with E. CHI enhanced hepatic fatty acid β-oxidation. Gut microbiota analysis showed comparable α-diversity after CR, AC, L, and B diets, while high-fat sources (CHI, P, E) reduced diversity. CR increased Faecalibacterium prausnitzii, associated with antioxidant activity, whereas L promoted Bifidobacterium bifidum, inversely related to liver lipids. Both CR and L reduced circulating LPS and glucose AUC. Conclusions: These findings suggest that CR and L represent sustainable and health-promoting protein sources.