Glucose-6-phosphatase (G6PC) plays an important role in glucose homeostasis because it catalyzes the final steps of gluconeogenesis and glycogenolysis. Maternal malnutrition during pregnancy affects G6PC activity, yet it is unknown whether epigenetic regulations of the G6PC gene are also affected. In this study, we fed primiparous, purebred Meishan sows either standard-protein (SP; 12% crude protein) or low-protein (LP; 6% crude protein) diets throughout gestation and analyzed hepatic G6PC expression in both male and female newborn piglets. The epigenetic regulation of G6PC, including DNA methylation, histone modifications, and micro RNA (miRNA), was determined to reveal potential mechanisms. Male, but not female, LP piglets had a significantly lower serum glucose concentration and greater hepatic G6PC mRNA expression and enzyme activity. Also, in LP males, glucocorticoid receptor binding to the G6PC promoter was lower compared with SP males, which was accompanied by hypomethylation of the G6PC promoter. Modifications in histones also were gender dependent; LP males had less histone H3 and histone H3 lysine 9 trimethylation and more histone H3 acetylation and histone H3 lysine 4 trimethylation on the G6PC promoter compared with the SP males, whereas LP females had more H3 and greater H3 methylation compared with their SP counterparts. Moreover, two miRNA, ssc-miR-339-5p and ssc-miR-532-3p, targeting the G6PC 3' untranslated region were significantly upregulated by the LP diet only in females. These results suggest that a maternal LP diet during pregnancy causes hepatic activation of G6PC gene expression in male piglets, which possibly contributes to adult-onset hyperglycemia.

In a series of experiments on female miniature pigs, the pattern of plasma LH and progesterone levels during the oestrous cycle, late pregnancy and lactation and after ovariectomy were characterized, and the effect of pentobarbitone treatment was tested. The preovulatory surge of LH occurred in seven out of eight animals between 00.00 and 12.0 h on day 0 of the oestrous cycle (day 1 of standing heat). Plasma progesterone strated to decline 8 days before oestrus and reached its lowest value 5 days before the preovulatory LH peak. Increases in progesteron concentration were already noticeable 48 h after the LH surge. During late pregnancy, parturition and lactation, plasma LH was low and showed only minor fluctuations, while plasma progesterone declined 4 to 5 days before parturition. Both hormones remained at low levels throughout lactation. Three weeks before parturition increases in LH were always followed by an increase in progesterone. This dependency was greatly diminished immediately before delivery. Four to 12 days after weaning the animals came into oestrus which was followed by an increase in LH and later an increase in progesterone concentrations. Ovariectomy during dioestrus resulted in a steady increase in plasma LH levels of 35-39 days. Ovariectomy caused abortion if performed on day 100 of pregnancy. It was followed by a rapid increase of plasma LH concentration. Normal parturition (around day 115) and lactation took place when animals were spayed on day 112 of pregnancy. In this case, plasma LH levels remained even lower than before ovariectomy as long as lactation was maintained. Immediately after weaning a rapid increase in the normal postovariectomy pattern of LH secretion was observed. Pentobarbitone anaesthesia (30-35 mg/kg body wt, initial dose), during pro-oestrusoestrus, for less than 5 h had no effect on the preovulatory LH increase. However, pentobarbitone anaesthesia for more than 6 h inhibitied the LH peak and ovulation if the animal was under deep anaesthesia before 24.00 h on the day before oestrus. Pentobarbitone treatment of ovariectomized pigs resulted in a clear decrease in LH levels 40 min after a single i.v. dose.

No abstract

Reliable physiological markers for performance evaluation in sport horses are missing. To determine the diagnostic value of plasma ACTH and cortisol measurements in the warmblood horse, 10 initially 3-yr-old geldings of the Hannovarian breed were either exposed to a training schedule or served as controls. During experimental Phase 1, horses were group-housed, and half of the horses were trained for 20 wk on a high-speed treadmill. During Phase 2, groups were switched and one group was trained for 10 wk as during Phase 1, whereas the control group was confined to boxes. During Phase 3 horses were initially schooled for riding. Thereafter, all horses were regularly schooled for dressage and jumping, and half of the horses received an additional endurance training for 24 wk. During all phases horses were exposed at regular intervals to various standardized treadmill exercise tests. During and after the tests frequent blood samples were taken from an indwelling jugular catheter for determination of ACTH and cortisol. Treadmill exercise increased both hormones. Maximum ACTH concentrations were recorded at the end of exercise, and maximum cortisol levels were recorded 20 to 30 min later. Except for one test there were no differences in ACTH levels between trained horses and controls. There was no significant effect of training on the cortisol response (net increase) to treadmill exercise in any of the tests during Phase 1. During Phase 2 higher cortisol responses were recorded in controls than in trained horses (P < .05) after 10 wk of training (controls confined to boxes). During Phase 3 plasma cortisol responses were also higher in controls than in trained horses (P < .05 after 6, 18, and 24, P < or = .07 after 12 wk of training) when the inclination of the treadmill was 5%, but not at 3%. There was no overlap in net cortisol responses at 30 min between trained and untrained horses. An ACTH application after 24 wk of training resulted in higher cortisol responses in controls than in trained horses (P < or = .05), without any overlap between the groups at 30 min after ACTH. Plasma cortisol responses to either treadmill exercise or ACTH injection may be a reliable physiological marker for performance evaluation. Prerequisites are sufficient differences in training status and sufficient intensity of exercise test conditions.

Leptin is a key mediator of signals regulating food intake and energy expenditure and exerts potent immunomodulatory effects. We investigated the mechanisms mediating the action of leptin on GH secretion from peripheral blood mononuclear cells (PBMCs). Using immunofluorescence microscopy, we demonstrated a polarized expression pattern of leptin receptor protein on the surface of mononuclear cells and constitutive expression of GH in PBMCs. Leptin exhibited a dose-dependent stimulatory effect on GH secretion by PBMCs and also up-regulated the GH receptor gene expression. We did not observe any additive effects of leptin on GH secretion upon activation of cells with the plant mitogen phytohemagglutinin, unlike leptin, phytohemagglutinin exerted no effect on GH receptor mRNA expression. Leptin led to a nitric oxide (NO) synthase (NOS)-specific, dose-dependent increase in NO production from PBMCs because leptin-induced NO release was blocked by the addition of the NOS inhibitor Nomega-Nitro-l-arginine methyl ester and protein kinase C (PKC) inhibitor calphostin C. This leptin-induced GH secretion was dependent on both PKC and NO activation because the addition of PKC and NOS inhibitors inhibited leptin-induced GH production. Although the addition of sodium nitroprusside, a spontaneous liberator of NO, stimulated GH release from PBMCs, leptin had no additive or synergistic effect on sodium nitroprusside-induced GH production. Together, these findings demonstrate a unique action of leptin on immune cells via its ability to stimulate the GH production by blood mononuclear cells via PKC- and NO-dependent pathways. These data also support a probable role for local immune-derived GH in mediating some of the pleiotropic actions of leptin.