Pregnancy stage and number of fetuses may influence maternal plasma leptin in ewes

Effects of poor maternal nutrition during gestation on ewe and offspring plasma concentrations of leptin and ghrelin

Poor maternal nutrition during gestation can negatively affect offspring growth, development, and health. Leptin and ghrelin, key hormones in energy homeostasis and appetite control, may mediate these changes. We hypothesized that restricted- and over-feeding during gestation would alter plasma concentrations of leptin and ghrelin in ewes and offspring. Pregnant ewes (n = 37) were fed 1 of 3 diets starting on d 30 ± 0.02 of gestation until necropsy at d 135 of gestation or parturition: restricted- [RES; 60% National Research Council (NRC) requirements for total digestible nutrients, n = 13], control- (CON; 100% NRC, n = 11), or over-fed (OVER; 140% NRC, n = 13). Blood samples were collected from pregnant ewes at days 20, 30, 44, 72, 100, 128, and 142 of gestation. Offspring blood samples were collected within 24 h after birth (n = 21 CON, 25 RES, 23 OVER). Plasma leptin and ghrelin concentrations were determined by RIA. Ewe data were analyzed using the MIXED procedure in SAS with ewe as the repeated subject. Offspring data were analyzed using the MIXED procedure. Correlations between BW and leptin and ghrelin concentrations were identified using PROC CORR. At d 100, RES (5.39 ± 2.58 ng/mL) had decreased leptin concentrations compared with OVER (14.97 ± 2.48 ng/mL; P = 0.008) and at d 128, RES (6.39 ± 2.50 ng/mL) also had decreased leptin concentrations compared with OVER (13.61 ± 2.47 ng/mL; P = 0.04). At d 142, RES (0.26 ± 0.04 ng/mL) had increased ghrelin concentrations compared with CON (0.15 ± 0.04 ng/mL; P = 0.04). Leptin and ghrelin concentrations were also altered between days of gestation within a dietary treatment. In CON ewes, plasma concentrations of leptin were increased at d 30 (19.28 ± 7.43 ng/mL) compared with d 44 (5.20 ± 3.10 ng/mL; P = 0.03), and the plasma concentrations of ghrelin at d 128 (0.20 ± 0.03 ng/mL) were increased compared with d 30 (0.16 ± 0.03 ng/mL; P = 0.01) and d 100 (0.17 ± 0.03 ng/mL; P = 0.04). Maternal diet did not alter plasma ghrelin or leptin concentrations in the offspring (P > 0.50). There were no strong, significant correlations between ewe BW and leptin (r < 0.33; P > 0.06) or ghrelin (r > -0.47; P > 0.001) concentrations or lamb BW and leptin or ghrelin concentrations (r > -0.32, P > 0.06). Maternal alterations in circulating leptin and ghrelin may program changes in energy balance that could result in increased adiposity in adult offspring. Alterations in energy homeostasis may be a mechanism behind the long-lasting changes in growth, body composition, development, and metabolism in the offspring of poorly nourished ewes.

Leptin and the Blood-Brain Barrier: Curiosities and Controversies

Leptin for over 25 years has been a central theme in the study of appetite, obesity, and starvation. As the major site of leptin production is peripheral, and the site of action of greatest interest is the hypothalamus, how leptin accesses the central nervous system (CNS) and crosses the blood-brain barrier (BBB) has been of great interest. We review here the ongoing research that addresses fundamental questions such as the sites of leptin resistances in obesity and other conditions, the causes of resistances and their relations to one another, the three barrier sites of entry into the CNS, why recent studies using suprapharmacological doses cannot address these questions but give insight into nonsaturable entry of leptin into the CNS, and how that might be useful in using leptin therapeutically. The current status of the controversy of whether the short form of the leptin receptor acts as the BBB leptin transporter and how obesity may transform leptin transport is reviewed. Review of these and other topics summarizes in a new appreciation of what leptin may have actually evolved to do and what physiological role leptin resistance may play. © 2021 American Physiological Society. Compr Physiol 11:1-19, 2021.

Validation of a handheld β-hydroxybutyrate acid meter to identify hyperketonaemia in ewes

Background

The end of pregnancy is the period with the highest risk of occurrences of ketosis and pregnancy toxemia due to fat mobilization and increasing non-esterified fatty acids in the liver which are converted in ketone bodies, mainly β-hydroxybutyrate acid (BHB). This ketone body may also become elevated in the bloodstream. The present study validates the use of a handheld meter for determining the blood concentration of BHB and ascertaining the predictive value and accuracy of BHB measurements in diagnosing hyperketonaemia in ewes.

Methods

A total of 19, non-pregnant, crossbred ewes were subjected to 2 h of intravenous infusion of a saturated BHB solution. Over 6 h of evaluation, 247 blood samples were obtained in 13 sampling moments. The BHB concentration was measured by an enzymatic colorimetric method in an automated biochemical analyzer (gold-standard) and by a handheld meter using an electrochemical enzyme technique.

Results

There was a high correlation between both methods (r = 0.98; P < 0.001). Considering the blood BHB concentrations range 0.8–1.6 mmol/L for moderate ketosis the handheld meter presented sensitivity and specificity of 0.98 and 0.81, respectively. For severe ketosis (BHB ≥ 1.6 mmol/L) sensitivity and specificity were 0.99 and 0.75, respectively. Thus, the handheld device can be useful for diagnoses of cases of mild or severe pregnancy toxemia at field conditions.

Use Of Hormonal and Ultrasonographic Examinations to Determine the Fetal Number in Bulgarian Local Goats

The purpose of the present study was to determine the fetal number in goats by using hormonal and ultrasonographic examinations. The experiments were conducted with 106 clinically healthy Bulgarian local goats, 1.5 to 7 years of age, weighing 35-52 kg. Hormonal examinations were performed on 24 goats. Serum progesterone concentrations were measured during a 7 days interval, between 21-63 day of pregnancy, and during a 14 days interval until the 133rd day of pregnancy. Ultrasound examinations were performed on 82 goats with a multi-frequency linear transducer (5.0-12.0 MHz). All animals were studied once during an interval of 7 days transrectally (21-28 day, 29-35 day, 36-42 day) and transabdominally (43-49 day, 50-56 day, 57-63 day), respectively. The accuracy of determining the number of singleton and multiple pregnancies by hormonal analysis were 51%, 58%, 69% and 47%, 52%, 62%, respectively. The accuracy of ultrasonography to determine the number of fetuses is highest in singletons 76.18%, followed by twins 72.56% and the lowest in triplets and more fetuses 21.43%. Highest accuracy, sensitivity and positive predictive diagnosis were established in the period 43-49 day of pregnancy (P<0.05). The obtained results show that the most appropriate period is between 42 and 49 day of pregnancy for determination of the fetal number in Bulgarian local goats using ultrasonography.

Phenomenon of leptin resistance in seasonal animals: the failure of leptin action in the brain

The core of the leptin resistance hypothesis promulgated several years ago to explain obesity as a result of environmental causes consists of 2 tenets: the extinction of leptin-induced intracellular signaling downstream of leptin binding to the long form of the neuronal receptor LTRb in the hypothalamus and the impedance to leptin entry imposed at the blood-brain barrier (BBB). A recent comprehensive investigation concluded that a central leptin insufficiency associated with obesity can be attributed to a decreased efficiency of BBB leptin transport and not to leptin insensitivity within the hypothalamus. Interestingly, anorectic leptin's effects are counteracted in some individuals by a natural resistance associated with hyperleptinemia, which is related to changes in hypothalamic sensitivity to leptin (eg, due to malnutrition, obesity, or seasonal variations due to day-length-dependent reproduction changes). In sheep, it has been observed that the hypothalamus is resistant to leptin in some periods, which is related to the adaptation of these animals to annual changes in energy supply and demand. However, a broad range of ambiguities exists regarding the implications that the intracellular signaling of signal transducer and activator of transcription-2/suppressor of cytokine signaling 3 (STAT2/SOCS3) imparts central leptin resistance. Furthermore, several plausible alternative possibilities have been proposed, such as compensatory functional and anatomic reorganizations in the appetite regulating network, rearrangements in the afferent hormonal feedback signaling involved in weight homeostasis, and modifications in leptin transport to the hypothalamus across the BBB. Taken together, these observations suggest that the contention that impaired intracellular signaling downstream of leptin entry into the appetite regulating network expedites environmentally induced obesity remains unsubstantiated and requires further evidence. Furthermore, pregnancy decreases hypothalamic sensitivity to leptin (or other unknown mechanisms), and lactation can also alter the appetite-suppressing central activity of leptin. The objective of this review was to offer an approach to understanding (1) how information regarding nutritional status is transmitted to and interpreted within the hypothalamus in animals, with special attention on seasonally breeding animals and (2) whether central leptin resistance and/or leptin insufficiency in the hypothalamus favors the development of obesity.

A dynamic network of estrogen receptors in murine lymphocytes: fine-tuning the immune response

The actual level of circulating estrogen (17β-estradiol, E2) has a serious impact on regulation of diverse immune cell functions, where their classical cytoplasmic receptors, ERα and ERβ, act as nuclear transcriptional regulators of multiple target genes. There is growing evidence, however, for rapid, "non-nuclear" regulatory effects of E2 on lymphocytes. Such effects are likely mediated by putative membrane-associated receptor(s) (mER), but the mechanistic details and the involved signaling pathways still remained largely unknown because of their complexity. Here, we show that in lymphocytes, mERs can signalize themselves, and upon ligation, they are able to coordinate translocation of other E2Rs to the PM. Our data firmly imply existence of a complex, dynamic network of at least seven ER forms in murine lymphocytes: cytoplasmic and membrane-linked forms of ERα, ERβ, or GPR30 and a mER that can receive extracellular E2 signals. The latter mERs are likely palmitoylated, as they are enriched in lipid-raft microdomains, and their E2 binding is also cholesterol dependent. The data also support that ligation of mERs can induce rapid regulatory signals to lymphocytes and then internalize and let the E2 liberate in lysosomes. In addition, they can dynamically control the cell-surface linkage of other cytoplasmic ERs. As demonstrated by the differential effects of mER or cytoplasmic ER ligation on the proliferation of activated T and B lymphocytes, such a dynamic E2R network can be considered as a tool to manage accommodation/fine-tuning of lymphocytes to rapidly changing hormone levels.

Effect of pregnancy and foetal number on diameter of corpus luteum, maternal progesterone concentration and oxidant/antioxidant balance in ewes

The aim of this study was to determine the changes in diameter of corpus luteum (CL), maternal progesterone (P) concentration, lipid peroxidation and non-enzymatic antioxidant levels along with enzymatic antioxidant activities in pregnant ewes bearing single and twin foetuses. The ewes were selected from healthy animals that were brought to the abattoir for slaughtering. The ewes were divided into three groups: Group 1 (non-pregnant, non-oestrous, n = 30), Group 2 (pregnant bearing a single foetus, n = 30) and Group 3 (pregnant bearing twin foetuses, n = 12) after they were slaughtered. Pregnant ewes were in the first half of the pregnancy. The diameter of CL and P concentration of pregnant ewes bearing a single foetus or twin foetuses were found higher than that found in non-pregnant ewes. Similarly, the P concentration of pregnant ewes bearing twin foetuses was higher than that found in pregnant ewes bearing a single foetus. Malondialdehyde (MDA) level in pregnant ewes bearing twin foetuses was higher than that found in both non-pregnant and pregnant ewes bearing a single foetus. The serum glutathione (GSH) level and glutathione-peroxidase (GSH-Px) activity of pregnant ewes bearing twin foetuses were found lower than that found in non-pregnant ewes. Additionally, the GSH-Px activity of pregnant ewes bearing twin foetuses was found lower than that found in pregnant ewes bearing a single foetus. No significant difference was found between pregnant ewes bearing female and male foetus with respect to diameter of CL, P concentration and oxidative stress parameters. There were significant positive correlations between foetal number (0, 1, 2) and diameter of CL, P concentration, MDA level, and between P concentration and diameter of CL, MDA level. However, significant negative correlations were found between foetal number (0, 1, 2) and GSH level, GSH-Px activity, and between P concentration and GSH-Px activity. In conclusion, the diameter of CL enlarges, P production increases and oxidant/antioxidant balance impairs because of the gestation stress in ewes during pregnancy.

Effect of prepartum energetic supplementation on productive and reproductive characteristics, and metabolic and hormonal profiles in dairy cows under grazing conditions

The effect of cracked corn grain supplementation (3.5 kg/day) during 3 weeks before the expected calving date on milk production and composition, body condition score (BCS), metabolic and hormonal profiles and length of postpartum anoestrus was evaluated in multiparous Holstein dairy cows under grazing conditions (Energy supplemented group, n = 10; Control group, n = 10). Body condition score was weekly recorded during the peripartum period, from days -21 to +35 (parturition = day 0). Non-esterified fatty acids, beta-hydroxybutyrate, cholesterol, urea, insulin, insulin-like growth factor I (IGF-I), leptin, thyroxine (T(4)) and 3,3''5-triiodothyroinine (T(3)) were weekly determined in plasma from days -21 to +35. The reinitiation of ovarian cyclicity was twice weekly determined by ovarian ultrasonography and confirmed by plasma progesterone concentrations. Cows fed energy concentrate prepartum had higher BCS during the prepartum and postpartum and produced more milk. Non-esterified fatty acids plasma concentrations were significantly higher in the energy group, while cholesterol was higher in the control group. Treated cows had higher levels of plasma insulin, IGF-I and leptin pre-calving. IGF-I, leptin and T(4) were diminished during the early postpartum period in both groups. Insulin levels were also diminished in the control group, but levels remained high in the energy-supplemented group. Treated cows ovulated sooner after parturition than controls. We conclude that Energetic supplementation prepartum in cows under grazing conditions increased milk production and reduced the reinitiation of ovarian activity, consistent with a better EB (BCS), higher prepartum levels of IGF-I, leptin and insulin, and higher insulin levels during early postpartum.