Plasma metabolites indicate energy metabolism disruption during the preclinical phase of bovine spongiform encephalopathy infection

Normal ranges and temporal variation in plasma concentrations of L-lactate and free amino acids in adult sheep

To determine baseline variation in blood plasma concentrations of free amino acids and l-lactate, samples were collected at a single time point from nine flocks of different breeds of ewes at a common physiological stage and monthly from one flock of crossbred mule ewes over a 12 month period. Significant differences were detected between time points in the concentrations of all plasma metabolites. With few exceptions prion protein genotype had no significant effect on the plasma metabolite concentrations measured.

Changes in plasma metabolites and muscle glycogen are correlated to bovine spongiform encephalopathy in infected dairy cattle

During the clinical phase of bovine spongiform encephalopathy (BSE), a significant decrease was observed in the ratio of muscle glycogen to plasma L-lactic acid concentrations in BSE infected field case and experimentally infected dairy cattle compared with healthy control cattle (P<0.001), this being due to changes in the concentration of both metabolites in the BSE infected cattle compared with the control group. Furthermore, the concentration of plasma alanine was significantly increased (P<0.05) in the infected animals. No significant difference was detected between these two groups in the ratio of hepatic glycogen to plasma lactate. We infer that BSE infected cattle exhibit signs of altered energy metabolism and when applied in conjunction with changes in other metabolite biomarkers these changes may be useful for discriminating BSE infected cattle from healthy cattle or those suffering with other disorders or diseases.

Sequential pressurized liquid extraction to determine brain-originating fatty acids in meat products as markers in bovine spongiform encephalopathy risk assessment studies

A new approach using sequential pressurized liquid extraction described recently [J. Poerschmann, R. Carlson, J. Chromatogr. A, 1127 (2006) 18-25] was applied to determine lipid markers originating from central nervous system (CNS) tissue of cows in heat-processed sausages. These studies are very important in quality control as well as risk assessment studies in the face of the bovine spongiform encephalopathy (BSE) crisis. Diagnostic CNS lipid markers, which should not be present in meat products without CNS addition, were recognized on complete transesterification as polar 2-hydroxy-fatty acids (2OH-24:0, 2OH-24:1, 2OH-22:0, 2OH-18:0, shorthand designation) as well as odd-numbered non-branched fatty acids beyond C(22). An array of other fatty acids including lignoceric acid (24:0), nervonic acid (24:1), arachidonic acid (20:4), and polyunsaturated nC(22)-surrogates are strongly related to CNS lipids, but occur as traces in meat products without CNS addition as well, thus reducing their value as diagnostic markers. Samples including meat products without CNS addition, meat with 3% CNS addition, as well as pure CNS homogenates, were subjected to sequential PLE (pressurized liquid extraction) consisting of two steps: n-hexane/acetone 9:1 (v/v) extraction at 50 degrees C to remove neutral lipids, followed by chloroform/methanol 1:4 (v/v) extraction at 110 degrees C to isolate polar CNS lipids (two 10 min PLE cycles each). To enhance the fractionation efficiency, cyanopropyl modified silica as well as chemically not modified silica sorbent was used at the outlet of the PLE cartridge to retard polar lipids in the first extraction step. This method proved superior to widely distributed exhaustive lipid extraction followed by solid-phase extraction (SPE) using silica regarding lipid recoveries and clear-cut boundaries between lipid classes. Methodological studies showed that the alcoholysis using trimethylchlorosilane/methanol (1:9, v/v) is an excellent method for the complete transesterification of lipids and quantitative formation of methyl esters.

Scrapie infection alters the distribution of plasma metabolites in diseased Cheviot sheep indicating a change in energy metabolism

Nuclear magnetic resonance (NMR) spectroscopy has been used to profile the metabolic status of plasma from; sheep showing clinical signs of scrapie, those known to be infected with scrapie but yet to show clinical signs, and control animals. The NMR measurements have shown that energy metabolism in scrapie infected animals is altered before the onset of clinical symptoms. These metabolic changes may provide the foundation for a pre-clinical diagnostic test for scrapie in sheep.