The effect of 48-hour fasting on taurine status in healthy adult dogs

Low circulating taurine concentrations may be a risk factor for dilated cardiomyopathy (DCM) in dogs. Circulating taurine is typically measured in the clinic 4-5 h after feeding, largely because the impact of later sampling is not known. The objective of this study was to measure taurine in the blood during a 48-h fast in 12 healthy adult Labrador Retrievers to refine sampling methodology for determination of taurine status. Plasma and whole blood (WB) taurine concentrations did not fall to levels indicative of clinical deficiency throughout fasting; WB was the more reliable indicator of taurine status. This study shows that blood samples can be taken for assessment of taurine status any time up to 48 h after ingestion of a meal in healthy adult dogs.

Overexpression of serine acetlytransferase produced large increases in O-acetylserine and free cysteine in developing seeds of a grain legume

There have been many attempts to increase concentrations of the nutritionally essential sulphur amino acids by modifying their biosynthetic pathway in leaves of transgenic plants. This report describes the first modification of cysteine biosynthesis in developing seeds; those of the grain legume, narrow leaf lupin (Lupinus angustifolius, L.). Expression in developing lupin embryos of a serine acetyltransferase (SAT) from Arabidopsis thaliana (AtSAT1 or AtSerat 2;1) was associated with increases of up to 5-fold in the concentrations of O-acetylserine (OAS), the immediate product of SAT, and up to 26-fold in free cysteine, resulting in some of the highest in vivo concentrations of these metabolites yet reported. Despite the dramatic changes in free cysteine in developing embryos of SAT overexpressers, concentrations of free methionine in developing embryos, and the total cysteine and methionine concentrations in mature seeds were not significantly altered. Pooled F(2) seeds segregating for the SAT transgene and for a transgene encoding a methionine- and cysteine-rich sunflower seed storage protein also had increased OAS and free cysteine, but not free methionine, during development, and no increase in mature seed total sulphur amino acids compared with controls lacking SAT overexpression. The data support the view that the cysteine biosynthetic pathway is active in developing seeds, and indicate that SAT activity limits cysteine biosynthesis, but that cysteine supply is not limiting for methionine biosynthesis or for storage protein synthesis in maturing lupin embryos in conditions of adequate sulphur nutrition. OAS and free methionine, but not free cysteine, were implicated as signalling metabolites controlling expression of a gene for a cysteine-rich seed storage protein.