Insect Meal as Alternative Protein Source Exerts Pronounced Lipid-Lowering Effects in Hyperlipidemic Obese Zucker Rats

BACKGROUND: Specific dietary proteins exert strong health-related effects compared with casein. OBJECTIVE: Herein, the hypothesis was tested using screening and conventional biochemical and molecular biological techniques that protein-rich insect meal compared with casein influences metabolic health in hyperlipidemic rats. METHODS: A 4-wk feeding trial with male, 8-wk-old homozygous obese Zucker rats (n = 36) and male, 8-wk-old heterozygous lean Zucker rats (n = 12) was performed. Obese rats were randomly divided into 3 obese groups (OC, OI50, and OI100) of 12 rats each and lean rats served as a lean control group (LC). LC and OC were fed a control diet with 20% casein as protein source, whereas in OI50 and OI100 50% and 100% of the casein, respectively, was replaced isonitrogenously by insect meal from Tenebrio molitor L. All data were analyzed by 1-factor ANOVA, except transcriptomic data which were analyzed by groupwise comparisons with the OC group. RESULTS: Transcript profiling revealed a coordinated inhibition by -17% to -521% and -37% to -859% of genes involved in fatty acid, triacylglycerol (TG), and cholesterol biosynthesis in the livers of OI100 and OI50, respectively, compared with OC (P < 0.05). Enzyme activities of fatty acid synthase, glucose-6 phosphate dehydrogenase, and 3-hydroxy-3-methylglutaryl-coenzyme-A reductase in the liver were 100-150% greater in OC compared with LC, but reduced by 50-60% in OI100 compared with OC (P < 0.05), to the same level as in LC. Liver and plasma concentrations of TG and cholesterol were 250-1000%, 30-800%, and 40-600% higher in OC, OI50, and OI100, respectively, than in LC (P < 0.05), but 40-60% and 20-60% lower in OI100 and OI50, respectively, than in group OC (P < 0.05). Plasma and liver concentrations of homocysteine were 20-30% lower in group OI100 than in group OC (P < 0.05). CONCLUSION: Insect meal exerts pronounced lipid-lowering effects in hyperlipidemic rats and, thus, might be useful for hyperlipidemic individuals.