Inhibition of stearoyl-CoA desaturase-1 in differentiating 3T3-L1 preadipocytes upregulates elongase 6 and downregulates genes affecting triacylglycerol synthesis.

BACKGROUND: Stearoyl-CoA desaturase-1 (SCD1) is rate limiting for the conversion of saturated fatty acids palmitate (16:0) and stearate (18:0) to monounsaturated fatty acids palmitoleate (16:1n7) and oleate (18:1n9), respectively. Given that reduced SCD1 activity is associated with improved insulin sensitivity and decreased body weight, there is considerable interest to elucidate the role of this enzyme in adipocytes. During adipogenesis, SCD1 levels increase concomitantly with the accumulation of triacylglycerol (TG); however, the extent to which reduced SCD1 activity can influence TG synthesis and metabolic pathways in differentiating adipocytes remains relatively unexplored. OBJECTIVE: The aim of this work was to delineate how reduced SCD1 activity affects gene expression, protein content and cellular fatty acids in differentiating murine preadipocytes. METHODS: 3T3-L1 preadipocytes were treated with an SCD1 inhibitor (10 nM) throughout differentiation. After 7 days, global gene expression, protein content and fatty acid profiles were examined using microarrays, western blotting and gas chromatography, respectively. RESULTS: SCD1 inhibition increased the abundance of 16:0 and 18:0 (45% and 194%, respectively) and decreased 16:1n7 and 18:1n7 (61% and 35%, respectively) in differentiated preadipocytes. Interestingly, 18:1n9 levels increased by 61%. The augmented 18:0 suggested a possible increase in elongase activity. Elongase 6 (Elovl6) gene expression was increased 2.8-fold (P = 0.04); however, changes were not detected for ELOVL6 protein content. Microarray analysis revealed that genes affecting TG synthesis were downregulated with SCD1 inhibition, which coincided with a 33% decrease in cellular TG content. CONCLUSION: These results provide new mechanistic insight into the role of SCD1 as a regulator of fatty acid profiles and TG synthesis in adipocytes, and reinforce that modulating SCD1 activity may help reduce the risk of obesity-related complications.

Pandemic influenza A(H1N1)v viruses currently circulating in New Zealand are sensitive to oseltamivir.

New Zealand, like other southern hemisphere countries with a temperate climate, has been in the winter period with seasonal influenza activity. New Zealand has also experienced a dramatic increase in the number of cases of pandemic influenza A(H1N1)v virus. Early reports from the northern hemisphere at the beginning of the pandemic showed that the virus was sensitive to the antiviral drug oseltamivir. In this study we report that pandemic influenza A(H1N1)v viruses currently circulating in New Zealand are sensitive to oseltamivir, but seasonal influenza A(H1N1) viruses - the co-circulating predominant seasonal strain, is resistant to oseltamivir.

Evaluation of ELISA for detection of antibodies to CAEV in milk.

Milk was found to be a suitable alternative specimen for the serological diagnosis of caprine arthritis-encephalitis virus (CAEV) using the ELISA. The relative sensitivity and specificity of testing individual milk samples as compared to individual sera was 96.4 and 97.3% respectively. The overall agreement between the testing of milk and sera was 96.9% and the correlation coefficient between testing sera and milk, 0.94%. The testing of bulk milk could be used to predict approximately the prevalence of CAEV infection in a dairy goat flock. It was estimated that a prevalence of about 1.6% to 7.5% could be detected in the ELISA when bulk milk samples from two infected goat flocks were tested. Either chilled milk samples or milk samples treated with merthiolate were found to be suitable for testing.

Polymerase chain reaction amplification of latent Aujeszky's disease virus in dexamethasone treated pigs.

A polymerase chain reaction (PCR) amplification assay was developed for the detection of Aujeszky's disease virus (ADV) DNA in cell cultures and clinical samples. Pigs vaccinated with commercial ADV vaccines and challenged with a field isolate of ADV were immunosuppressed by dexamethasone treatment. Nasal swabs collected from the pigs at various times post-immunosuppression showed that ADV was excreted for at least four to six days starting from day 8 or day 10 following dexamethasone treatment, by virus isolation and/or PCR. However, PCR only detected latent ADV in the trigeminal ganglia, mandibular lymph node, spleen and tonsils, but not in the brain stem, pons and olfactory lobe of two pigs following dexamethasone treatment, whereas tissue explanation and cocultivation failed to demonstrate the presence of the virus.

A comparison of the efficacy of two commercial Aujeszky's disease vaccines with glycoprotein-I deletion in pigs.

Two commercial Aujeszky's disease vaccines, a modified killed vaccine and a sub-unit vaccine, both carrying a deletion of glycoprotein-I, were evaluated in pigs. Each vaccine was administered to two groups of four pigs, twice at 4-week intervals, with two pigs held as unvaccinated controls. All pigs were challenged with a New Zealand field isolate of Aujeszky's disease virus 3 weeks after the second vaccination. The results indicate that the sub-unit vaccine was able to protect pigs against clinical Aujeszky's disease much better than the pigs vaccinated with the modified killed vaccine when challenged with a virulent virus. However, the amount and the duration of virulent virus excretion following challenge was greater with the sub-unit vaccine than the modified killed vaccine. Pigs vaccinated with the sub-unit vaccine were shown to be latently infected following challenge. Latent infection was demonstrated by excretion of Aujeszky's disease virus from the nasal cavity after dexamethasone treatment and seroconversion of a sentinel in contact pigs to Aujeszky's disease virus.

gIII antibody responses in pigs following vaccination and challenge to Aujeszky's disease.

Serological responses to a genetically engineered Aujeszky's disease "marker" vaccine (dl gIII + dl tk) were monitored using a blocking-ELISA (B-ELISA), a serum neutralisation test (SNT) and an indirect ELISA (I-ELISA). The B-ELISA is capable of differentiating pigs vaccinated with the above vaccine from natural infection. The SNT and the I-ELISA indicated that the pigs responded to vaccination and challenge. All three tests showed that the controls and the in-contact pigs always reacted negative for antibodies. The B-ELISA was able to detect pigs challenged with a field isolate 24 days post-challenge. These pigs remained positive until 110 days post-challenge when last tested. These findings indicate that the B-ELISA could be used successfully with this vaccine in a control eradication programme. This trial also shows that the vaccine virus did not spread to the in-contact pigs and also the vaccinated and challenged pigs did not transmit the disease to other susceptible pigs when they were introduced 14 days after challenge.