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The study aimed to test the hypothesis that monomethyl branched-chain fatty acids (BCFAs) and a lipid extract of Conidiobolus heterosporus (CHLE), rich in monomethyl BCFAs, are able to activate the nuclear transcription factor peroxisome proliferator-activated receptor alpha (PPARalpha). Rat Fao cells were incubated with the monomethyl BCFAs 12-methyltridecanoic acid (MTriA), 12-methyltetradecanoic acid (MTA), isopalmitic acid (IPA) and 14-methylhexadecanoic acid (MHD), and the direct activation of PPARalpha was evaluated by reporter gene assay using a PPARalpha responsive reporter gene. Furthermore, Fao cells were incubated with different concentrations of the CHLE and PPARalpha activation was also evaluated by using the reporter gene assay, and by determining the mRNA concentrations of selected PPARalpha target genes by real-time RT-PCR. The reporter gene assay revealed that IPA and the CHLE, but not MTriA, MHD and MTA, activate the PPARalpha responsive reporter gene. CHLE dose-dependently increased mRNA concentrations of the PPARalpha target genes acyl-CoA oxidase (ACOX1), cytochrome P450 4A1 (CYP4A1), carnitine palmitoyltransferase 1A (CPT1A) and solute carrier family 22 (organic cation/carnitine transporter), member 5 (SLC22A5). In conclusion, the monomethyl BCFA IPA is a potent PPARalpha activator. CHLE activates PPARalpha-dependent gene expression in Fao cells, an effect that is possibly mediated by IPA.

The hypothesis tested was that dietary inclusion of insect meal (IM) causes an alteration in the cecal microbiota composition and its fermentation activity of growing pigs. Five-week-old male crossbred pigs were randomly assigned to three groups of 10 pigs each, and fed isonitrogenous diets either without (CON) or with 5% IM (IM5) or 10% IM (IM10) from Tenebrio molitor larvae for four weeks. The relative abundance of the phylum Bacteroidetes was lower in group IM10 than in group CON (p < 0.05), whereas the relative abundance of Firmicutes and the Firmicutes:Bacteroidetes-ratio tended to be higher in groups IM10 and IM5 than in group CON (p < 0.1). The relative abundance of the Proteobacteria tended to be higher in group IM10 than in groups CON and IM5 (p < 0.1). The concentrations of the total short-chain fatty acids in the cecal digesta did not differ between the three groups, but the concentrations of the branched-chain fatty acids in the cecal digesta were higher in group IM5 and IM10 than in group CON (p < 0.05). The present study shows for the first time that the replacement of soybean meal by Tenebrio molitor larvae meal causes a shift of the cecal microbial community and its fermentation activity in growing pigs.