Affinity chromatography on heparin sepharose was used to identify 2 lipolytic enzymes in heparinized plasma from horses. One enzyme was typical of hepatic triglyceride lipase (HTGL), because it was resistant to inactivation by high concentrations of NaCl, and it did not require the addition of serum for activity. The other enzyme was identified as lipoprotein lipase (LPL), because of its inactivation at NaCl concentrations in excess of 0.2M, and its dependency on addition of serum as a source of apolipoprotein C-II activator. The enzymes were purified by 347- (HTGL) and 442- (LPL) fold, with yields of 54 and 58%, respectively. The partially purified enzymes were used to design incubation conditions that gave optimal activities for each enzyme in vitro. A selective assay was then developed for direct measurement of LPL and HTGL activities in heparinized plasma from horses. Analysis of HTGL took advantage of the almost complete inactivition of LPL when serum cofactor was excluded from the assay at the NaCl concentration that gave optimal HTGL activity. Prior incubation of heparinized plasma with sodium dodecyl sulfate to inhibit HTGL was necessary for measurement of LPL, because HTGL retained 67% of its activity at the NaCl concentration required for optimal LPL activity. Activity of each enzyme was measured in heparinized plasma from 12 Shetland ponies. The mean activity +/- SD for LPL was 3.22 +/- 1.04 micromoles of fatty acids/ml of heparinized plasma/h (micromoles of FA/ml/h). The mean activity for HTGL was 4.9 +/- 1.56 micromoles of FA/ml/h. The performance of the assay was assessed by replicate analysis of pools of each enzyme with high and low activities. The intra-assay coefficient of variation ranged between 3.4 and 8.7% (n = 10), and the interassay coefficient of variation ranged between 5.2 and 10.7% (n = 7) for the same pools analyzed over 7 weeks.

OBJECTIVE To evaluate the effects of withholding food on the results for measurements of serum concentrations of cobalamin, folate, canine pancreatic lipase immunoreactivity (cPLI), and canine trypsin-like immunoreactivity (cTLI) in healthy dogs. ANIMALS 11 healthy employee- or student-owned dogs. PROCEDURES Food was withheld from the dogs for 12 hours, baseline blood samples were collected, then dogs were fed. Postprandial blood samples collected 1, 2, 4, and 8 hours later were assessed. A mixed-effects ANOVA model with fasting duration (time) as a fixed factor and dog as a random effect was fit for each analyte variable. Additionally, a mixed-effects ANOVA model controlling for the variable of time was fit to assess whether lipemia affected serum concentrations of the analytes. RESULTS The median serum cobalamin concentration was lower at 4 hours (428 ng/L) and 8 hours (429 ng/L) postprandially, compared with baseline (479 ng/L), but this difference was not clinically meaningful. Although there were no substantial differences in serum concentrations of folate, cPLI, or cTLI, postprandial changes in serum concentrations of cTLI or folate could potentially affect diagnoses in some dogs. CONCLUSIONS AND CLINICAL RELEVANCE Although results indicated that feedings rarely resulted in clinically important differences in the median serum concentrations of cobalamin, folate, cPLI, or cTLI in healthy dogs, given the further processing required for lipemic samples, withholding food for at least 8 hours is an appropriate recommendation when measuring these analytes. Similar research is needed in dogs with gastrointestinal disease to determine whether the withholding of food is necessary when measuring these analytes in affected dogs.

The objective of this study was to examine the effects of immunosuppressive prednisolone therapy on pancreatic tissue and the concentration of serum canine pancreatic lipase immunoreactivity (cPLI) in healthy dogs. Six healthy beagle dogs were subcutaneously administered an immunosuppressive dose of prednisolone [4 mg/kg body weight (BW)] once daily for either 2 or 3 weeks. Serum cPLI concentration was measured before and after treatment. Ultrasonographic examination of the pancreas and laparoscopic biopsy and histopathological examination of the right pancreatic lobe and the liver were also conducted before and after treatment. The expression of pancreatic lipase messenger ribonucleic acid (mRNA) in the pancreas and liver was examined by polymerase chain reaction (PCR). Although the serum cPLI concentration was significantly higher on day 14 and on the day of the second laparoscopy than before treatment, it was classified as normal (≤ 200 μg/L) in 5 dogs and as abnormal (≥ 400 μg/L) in only 1 dog. None of the 6 dogs showed clinical signs of pancreatitis during the study period. After treatment, ultrasonographic examination of the pancreas showed no changes except for a hypoechoic pancreas in 1 dog. Histopathological examination of the right pancreatic lobe in all dogs showed no evidence of pancreatitis after treatment. Pancreatic lipase mRNA expression was detected in the pancreas, but not in the liver, before and after treatment. The administration of 4 mg/kg BW per day of prednisolone for 2 or 3 weeks increased the serum cPLI concentration without clinical signs of pancreatitis, although an abnormal cPLI concentration (≥ 400 μg/L) was observed in only 1 dog. No ultrasonographic or histological evidence of pancreatitis was observed in any of the dogs.

While pancreatitis is now recognized as a common ailment in cats, the diagnosis remains challenging due to discordant results and suboptimal sensitivity of ultrasound and specific feline pancreatic lipase (Spec fPL) assay. Pancreatitis also shares similar clinical features with pancreatic carcinoma, a rare but aggressive disease with a grave prognosis. The objective of this pilot study was to compare the plasma proteomes of normal healthy cats (n = 6), cats with pancreatitis (n = 6), and cats with pancreatic carcinoma (n = 6) in order to identify potential new biomarkers of feline pancreatic disease. After plasma protein separation by 2-dimensional gel electrophoresis, protein spots were detected by Coomassie Brilliant Blue G-250 staining and identified by mass spectrometry. Alpha-1-acid glycoprotein (AGP), apolipoprotein-A1 (Apo-A1), and apolipoprotein-A1 precursor (Pre Apo-A1) appeared to be differentially expressed, which suggests the presence of a systemic acute-phase response and alteration of lipid metabolism in cats with pancreatic disease. Future studies involving greater case numbers are needed in order to assess the utility of these proteins as potential biomarkers. More sensitive proteomic techniques may also be helpful in detecting significant but low-abundance proteins.

Recently, a radioimmunoassay (RIA) for measurement of canine pancreatic lipase immunoreactivity (cPLI) in serum was developed and validated. However, RIAs require frequent use of radioactive materials. Therefore, the goal of this project was to develop and validate an enzyme-linked immunosorbent assay (ELISA) for cPLI. After purifying cPL, we developed and purified antiserum against cPL in rabbits. The purified antibody was bound to microtitre plates and used to capture antigen. A portion of the purified antibody was biotinylated and used to identify the captured antigen. Streptavidin labelled with horseradish peroxidase and a horseradish peroxidase substrate were used for detection. The assay was validated by determination of sensitivity, working range, linearity, accuracy, precision, and reproducibility. The reference interval for serum cPLI was determined by the central 95th percentile in 74 clinically healthy dogs: 2.2 to 102.1 μg/L. The sensitivity and the upper limit of the working range were 0.1 and 999.2 μg/L, respectively. The ratios of observed to expected values for dilutional parallelism for 6 serum samples ranged from 0.0 to 148.8%; the ratios for spiking recovery for 4 serum samples ranged from 90.4 to 112.6%, assuming 55% recovery of the cPL. Coefficients of variation for intra- and interassay variability for 6 different serum samples were 2.4, 3.4, 4.1, 5.8, 7.4, and 10.0% and 5.9, 7.7, 11.6, 13.9, 23.5, and 46.2%, respectively. We conclude that the ELISA described here is sufficiently sensitive, linear, accurate, precise, and reproducible for clinical application. Evaluation of its clinical usefulness for the diagnosis of exocrine pancreatic disorders in dogs is under way.

Methods available for measurement of plasma lipoprotein-cholesterol concentrations and activities of lipoprotein lipase, hepatic lipase, lecithin:cholesterol acyl transferase (LCAT), and cholesteryl ester transfer protein were adapted for use in cats. A combined ultracentrifugation/precipitation procedure was used to isolate very low-density lipoproteins (VLDL), then to separate low-density lipoproteins (LDL) from high-density lipoproteins (HDL). The reagent used, 92 mM heparin-manganese chloride, provided complete precipitation of LDL with only trace and insignificant contamination by HDL. Efforts to selectively measure lipoprotein lipase activity in plasma, collected after IV injection of heparin, by inhibiting hepatic lipase with sodium dodecyl sulfate were unsuccessful, and the activity of this enzyme was calculated as the difference between total and hepatic lipase activities. The latter was measured in the presence of high salt concentration to inhibit lipoprotein lipase. Cholesterol esterifying activity was identified in feline plasma and was typical of LCAT, in that it was dependent on apolipoprotein A-I as a cofactor. The intra-assay and interassay coefficients of variation for measurement of lipoprotein lipase, hepatic lipase, and LCAT activities were 18.4, 4.6, and 7.2%, and 20.4, 10.7, and 5.3%, respectively. Appreciable cholesteryl ester transfer protein activity was not detected in either undiluted or diluted plasma. These methods were subsequently used to investigate the effects of pregnancy and lactation on lipoprotein metabolism in a group of 10 queens. Plasma concentrations of cholesterol and triglycerides were unaltered during pregnancy, but the concentrations of VLDL-cholesterol increased and those of HDL-cholesterol decreased. During lactation, the concentrations of cholesterol and triglycerides decreased owing to reductions in VLDL-cholesterol and LDL-cholesterol concentrations and continued suppression of HDL-cholesterol. These changes were associated with alterations in the activities of lipoprotein lipase, which increased after parturition, and hepatic lipase, which increased during pregnancy and lactation, that may help explain their metabolic origins. The activity of LCAT remained unchanged.