Insulin sensitivity during late gestation in ewes affected by pregnancy toxemia and in ewes with high and low susceptibility to this disorder.

BACKGROUND: Insulin resistance during late gestation might act as 1 etiologic factor causing pregnancy toxemia in ewes. OBJECTIVE: Evaluation of pancreatic insulin secretion and peripheral insulin sensitivity in ewes with differing susceptibility to pregnancy toxemia and in ketotic ewes. ANIMALS: Pregnant ewes suffering from (PT, n = 5) and ewes with high (HR, n = 7) and low risk (LR, n = 5) of being affected by pregnancy toxemia. METHODS: In a case-control study, the pancreatic insulin release and the peripheral insulin sensitivity were assessed by means of the intravenous glucose tolerance test with subsequent measurement of the plasma concentrations of glucose, insulin, nonesterified fatty acids (NEFA), and ß-hydroxybutyrate (ß-HB). The ewes were tested during late pregnancy within 5 and 15 days antepartum. RESULTS: The insulin secretion after glucose administration was significantly lower in the HR and PT than in the LR ewes. The baseline rate of lipolysis was significantly increased in the HR ewes, but the NEFA clearance was similar in both risk groups, albeit delayed in the PT ewes. The baseline ß-HB concentration was significantly higher in the PT than in the HR and LR ewes. In the HR and in the PT ewes, the plasma ß-HB concentrations did not decrease after glucose administration. CONCLUSION AND CLINICAL IMPORTANCE: There is reduced pancreatic first-phase insulin response and impaired insulin-dependent inhibition of the ketone body formation during late pregnancy in the HR and PT ewes. This insulin resistance might represent 1 causative factor in the pathogenesis of ovine pregnancy toxemia.

Pancreatic insulin release and peripheral insulin sensitivity in German black headed mutton and Finish Landrace ewes: evaluation of the role of insulin resistance in the susceptibility to ovine pregnancy toxemia.

German black headed mutton (GBM) ewes are recognized as being highly susceptible to ovine pregnancy toxemia (OPT). The present trial was performed to evaluate whether a breed-dependent gestational diabetes mellitus-like insulin resistance during late pregnancy might be responsible for the high incidence of OPT in the GBM breed. Modified frequently sampled intravenous glucose tolerance tests (300 mg glucose and 0.03 IU insulin per kg of BW) were performed during mid and late pregnancy, the periparturient, and the dry period in polytocous 3.5-yr-old GBM and Finnish Landrace (FL) ewes fed according to their requirements. The corresponding blood samples were analyzed for plasma concentrations of glucose, insulin, nonesterified fatty acids (NEFAs) and ß-hydroxybutyrate (ß-HB). In addition, the baseline plasma cortisol concentrations were determined during late pregnancy. The BW gain during pregnancy and the rearing success did not differ between the GBM and FL ewes. In both breeds, late pregnancy was associated with decreased basal plasma glucose concentrations and enhanced glucose disposal, as well as elevated baseline ß-HB values. Only in the GBM ewes did the plasma NEFA concentrations increase significantly during advancing pregnancy. Moreover, significantly higher baseline plasma NEFA concentrations as well as lower (P < 0.05) basal plasma glucose values were recorded during late pregnancy in the GBM than in the FL ewes. The first-phase insulin secretion, the peripheral insulin sensitivity, and the baseline plasma cortisol values did not differ between both breeds during late pregnancy. It is concluded that increased lipolysis during late pregnancy is a characteristic of the GBM breed. Moreover, elevated plasma NEFA concentrations may contribute to impaired pancreatic insulin response and peripheral insulin resistance in GBM ewes and thus promote OPT.

Post-glucose load changes of plasma key metabolite and insulin concentrations during pregnancy and lactation in ewes with different susceptibility to pregnancy toxaemia.

Insulin resistance during late gestation may act as a predisposing factor of ovine pregnancy toxaemia (OPT). To evaluate the insulin action on energy metabolism in ewes with different susceptibilities to OPT, intravenous glucose tolerance tests (1 mmol glucose/kg body weight) were performed in 5.6 ± 0.7 year old, slightly underfed German Blackheaded Mutton ewes [high-risk (HR) ewes] and 2.5 year old, overnourished Finnish Landrace ewes [low-risk (LR) ewes] during mid and late pregnancy, during early lactation and during the dry period. Plasma samples were analysed for glucose, insulin, non-esterified fatty acids (NEFA) and ß-hydroxybutyrate (ß-HB). The glucose elimination rate and the glucose-stimulated first-phase insulin secretion were significantly (p < 0.05) lower in the HR, in relation to the LR group combining the data of all gestational stages. The basal rate of lipolysis was significantly increased in the HR ewes during late pregnancy, but the NEFA clearance after the glucose load was similar in both groups during all reproductive stages. Plasma ß-HB concentrations decreased only in the LR ewes after the glucose load during late pregnancy. Results indicate an insulin resistance in the HR ewes regarding the glucose utilization and the ketone body formation during late pregnancy. The insulin resistance in the HR ewes may represent one predisposing factor responsible for the susceptibility to OPT. Further scientific work is necessary to elucidate whether this insulin resistance was due to breed, age or nutritional state.

Distribution patterns of the glucose transporters GLUT4 and GLUT1 in skeletal muscles of rats (Rattus norvegicus), pigs (Sus scrofa), cows (Bos taurus), adult goats, goat kids (Capra hircus), and camels (Camelus dromedarius).

Earlier studies demonstrated that forestomach herbivores are less insulin sensitive than monogastric omnivores. The present study was carried out to determine if different distribution patterns of the glucose transporters GLUT1 and GLUT4 may contribute to these different insulin sensitivities. Western blotting was used to measure GLUT1 and GLUT4 protein contents in oxidative (masseter, diaphragm) and glycolytic (longissimus lumborum, semitendinosus) skeletal muscle membranes of monogastric omnivores (rats and pigs), and of forestomach herbivores (cows, adult goats, goat kids, and camels). Muscles were characterized biochemically. Comparing red and white muscles, the isocitrate dehydrogenase (ICDH) activity was 1.5-15-times higher in oxidative muscles of all species, whereas lactate dehydrogenase (LDH) activity was 1.4-4.4-times higher in glycolytic muscles except in adult goats. GLUT4 levels were 1.5-6.3-times higher in oxidative muscles. GLUT1 levels were 2.2-8.3-times higher in glycolytic muscles in forestomach herbivores but not in monogastric animals. We conclude that GLUT1 may be the predominant glucose transporter in glycolytic muscles of ruminating animals. The GLUT1 distribution patterns were identical in adult and pre-ruminant goats, indicating that GLUT1 expression among these muscles is determined genetically. The high blood glucose levels of camels cited in literature may be due to an "NIDDM-like" impaired GLUT4 activity in skeletal muscle.

Assessment of the antioxidative potential of dietary supplementation with α-tocopherol in low-nitrite salami-type sausages.

The objective of this study was to determine the effects of dietary α-tocopherol supplementation to pigs on the lipid stability of nitrite-reduced salami-type sausages (custom-produced for this study). Fourteen crossbred pigs were divided into two equal groups. The control group (CG) was fed a basal diet containing 34ppm α-tocopherol, and the experimental group (EG), a diet supplemented with 364ppm α-tocopherol, both for 35 days. After slaughter, salami-type sausages were produced with the addition of different nitrite levels in the curing salt (100, 50, 25 and 0ppm), ripened for four weeks, sliced, and packaged under a protective atmosphere (80 parts N(2) to 20 parts CO(2)). The packed products were stored for eight weeks under simulation of the usual conditions in self-service shelves with permanent lighting (9°C, 200 lux). The sausages were regularly assessed for their oxidative status (thiobarbituric acid-reactive substances, fatty acid pattern) and the amount of α-tocopherol, and by sensory evaluation. In the EG sausages, α-tocopherol concentrations were twice as high and TBARS were lower than in the CG sausages. The α-tocopherol in EG prevented the loss of unsaturated fatty acids during storage. Sausages of EG containing 100ppm nitrite had the longest sensory stability. However, the biochemical parameters did not indicate that nitrite had any effect on the antioxidative potential of the sausages.