Expression of the cannabinoid system in muscle: effects of a high-fat diet and CB1 receptor blockade.

The ECS (endocannabinoid system) plays an important role in the onset of obesity and metabolic disorders, implicating central and peripheral mechanisms predominantly via CB1 (cannabinoid type 1) receptors. CB1 receptor antagonist/inverse agonist treatment improves cardiometabolic risk factors and insulin resistance. However, the relative contribution of peripheral organs to the net beneficial metabolic effects remains unclear. In the present study, we have identified the presence of the endocannabinoid signalling machinery in skeletal muscle and also investigated the impact of an HFD (high-fat diet) on lipid-metabolism-related genes and endocannabinoid-related proteins. Finally, we tested whether administration of the CB1 inverse agonist AM251 restored the alterations induced by the HFD. Rats were fed on either an STD (standard/low-fat diet) or an HFD for 10 weeks and then treated with AM251 (3 mg/kg of body weight per day) for 14 days. The accumulated caloric intake was progressively higher in rats fed on the HFD than the STD, resulting in a divergence in body weight gain. AM251 treatment reduced accumulated food/caloric intake and body weight gain, being more marked in rats fed on the HFD. CB2 (cannabinoid type 2) receptor and PPARα (peroxisome-proliferator-activated receptor α) gene expression was decreased in HFD-fed rats, whereas MAGL (monoglyceride lipase) gene expression was up-regulated. These data suggest an altered endocannabinoid signalling as a result of the HFD. AM251 treatment reduced CB2 receptor, PPARγ and AdipoR1 (adiponectin receptor 1) gene expression in STD-fed rats, but only partially normalized the CB2 receptor in HFD-fed rats. Protein levels corroborated gene expression results, but also showed a decrease in DAGL (diacylglycerol) ß and DAGLα after AM251 treatment in STD- and HFD-fed rats respectively. In conclusion, the results of the present study indicate a diet-sensitive ECS in skeletal muscle, suggesting that blockade of CB1 receptors could work towards restoration of the metabolic adaption imposed by diet.

Genetic diversity and comparative analysis of gene expression between Heterorhabditis bacteriophora Az29 and Az36 isolates: uncovering candidate genes involved in insect pathogenicity.

Entomopathogenic nematode Heterorhabditis bacteriophora Az29 and Az36 isolates with different virulence against Popillia unipuncta and soil survival time were isolated from the Azorean archipelago (Portugal) and used for the study. RAPD analysis revealed a very low-level of genetic diversity (GD(axenic Az36 isolate)(axenic Az29 isolate)=0.2338±0.0541) between axenic Az29 and Az36 isolates, and a relative low-level of diversity (GD(Az36 isolate)(Az29 isolate)=0.3366±0.0471) between Az29 and Az36 isolates. To unravel the molecular differences, a suppressive subtractive hybridization library was constructed from the parasitic stage. Assembling 150 high quality ESTs produced 70 singletons and 17 contigs. BLAST analysis revealed that 48 ESTs showed significant similarity to known protein and 39 ESTs had no significant hits in the database, perhaps representing novel genes. Functional annotation revealed some of these genes to be involved in metabolism, cellular process and signaling, information storage and processing, stress response and host-parasite interactions. Genes with a role in the parasitism process were identified including lectin, metalloprotease, enolase, chitinase, surface-associated antigen, and as well as genes (aquaporin, Hsp70A, Hsp10 and Hsp20) essential for stresses tolerance. The work described here provides the molecular data necessary for investigating the fundamental molecular aspects of host-parasite interactions. Future investigations should be focused on determining the molecular mechanism of those genes in entomopathogenic nematode life cycle.

The complete mitochondrial genome of the entomopathogenic nematode Steinernema carpocapsae: insights into nematode mitochondrial DNA evolution and phylogeny.

We determined the complete sequence of the mitochondrial DNA of the entomopathogenic nematode Steinernema carpocapsae and analyzed its structure and composition as well as the secondary structures predicted for its tRNAs and rRNAs. Almost the complete genome has been amplified in one fragment with long PCR and sequenced using a shotgun strategy. The 13,925-bp genome contains genes for 2 rRNAs, 22 tRNAs, and 12 proteins and lacks an ORF encoding ATPase subunit 8. Four initiation codons were inferred, TTT, TTA, ATA, and ATT, most of the genes ended with TAA or TAG, and only two had a T as an incomplete stop codon. All predicted tRNAs showed the nonconventional secondary structure typical of Secernentea. Although we were able to fold the sequences of trnN, trnD, and trnC into more conventional cloverleaf structures after adding adjacent nucleotides, northern blot experiments showed that the nonstandard tRNAs are actually expressed. Phylogenetic and comparative analyses showed that the mitochondrial genome of S. carpocapsae is more closely related to the genomes of A. suum and C. elegans than to that of Strongyloides stercoralis. This finding does not support the phylogeny based on nuclear small subunit ribosomal DNA sequences previously published. This discrepancy may result from differential reproductive strategies and/or differential selective pressure acting on nuclear and mitochondrial genes. The distinctive characteristics observed among mitochondrial genomes of Secernentea may have arisen to counteract the deleterious effects of Muller's ratchet, which is probably enhanced by the reproductive strategies and selective pressures referred to above.