The American cockroach (Periplaneta americana) is an urban pest with a precise chemosensory system that helps it achieve complex physiological behaviours, including locating food and mating. However, its chemosensory mechanisms have not been well studied. Here, we identified 71 putative odorant carrier protein genes in P. americana, including 57 new odorant-binding proteins (OBPs) and 11 chemosensory proteins (CSPs). To identify their physiological functions, we investigated their tissue expression patterns in antennae, mouthparts, legs, and the remainder of the body of both sexes, and determined that most of these genes were expressed in chemosensory organs. A phylogenetic tree showed that the putative pheromone-binding proteins of P. americana were in different clades from those of moths. Two genes, PameOBP24 and PameCSP7, were expressed equally in antennae of both sexes and highly expressed amongst the OBPs and CSPs. These genes were expressed in Escherichia coli and the resultant proteins were purified. The binding affinities of 74 common odorant compounds were tested with recombinant PameOBP24 and PameCSP7. Both proteins bound a variety of ligands. Our findings provide a foundation for future research into the chemosensory mechanisms of P. americana and help in identifying potential target genes for managing this pest.

CB1 (also known as CNR1), a main receptor for cannabinoids acting at PPARs, can enhance fat deposition. Carnitine palmitoyltransferase-1 (CPT1), an enzyme responsible for the transport of long-chain fatty acids for β-oxidation, is closely related to fat deposition. Whether CB1 can regulate intramuscular adipocytes lipid accumulation through regulation of CPT1 is unclear. Based on the investigation of tissue- and breed-specific CPT1A and CPT1B mRNA expression levels in Jinhua and Landrace pigs, we studied the effects of CB1 on lipid accumulation and CPT1B expression by treating porcine intramuscular adipocytes with CB1 antagonist Δ9-THC and antagonist SR141716. Results showed that muscle CPT1 mRNA was expressed at higher levels in the longissimus dorsi and subcutaneous fat. Liver CPT1A mRNA expression levels were higher in the pancreas, duodenum and liver. Compared with Landrace pigs, CPT1A and CPT1B in the longissimus dorsi of Jinhua pigs were significantly higher and positively correlated with intramuscular fat content. However, for subcutaneous fat, CPT1 levels were significantly lower and negatively correlated with body fat percentage. Δ9-THC significantly increased CB1 mRNA levels and lipid accumulation but decreased CPT1A and CPT1B mRNA levels. Conversely, SR141716 reduced CB1 mRNA levels but increased CPT1A and CPT1B mRNA levels, resulting in decreased lipid accumulation. The CPT1 antagonist etomoxir did not affect CB1 expression, suggesting that CB1 is likely upstream of CPT1A and CPT1B. Meanwhile, PPARA expression was greatly decreased when CPT1A and CPT1B were inhibited and enhanced when CPT1A and CPT1B were activated. Taken together, these data indicate that CB1 can affect intramuscular fat deposition by regulating both CPT1A and CPT1B mRNA expression, with the PPARA signal pathway likely playing a major role in this process.