Limit-feeding a high-energy diet to meet energy requirements in the dry period alters plasma metabolite concentrations but does not affect intake or milk production in early lactation

Limit-feeding dry cows a high-energy diet may enable adequate energy intake to be sustained as parturition approaches, thus reducing the extent of negative energy balance after parturition. Our objective was to evaluate the effect of dry period feeding strategy on plasma concentrations of hormones and metabolites that reflect energy status. Multiparous Holstein cows (n = 18) were dried off 45 d before expected parturition, paired by expected calving date, parity, and previous lactation milk yield, and randomly assigned to 1 of 2 dry-period diets formulated to meet nutrient requirements at ad libitum or limited intakes. All cows were fed the same diet for ad libitum intake after parturition. Prepartum dry matter intake (DMI) for limit-fed cows was 9.4 kg/d vs. 13.7 kg/d for cows fed ad libitum. During the dry period, limit-fed cows consumed enough feed to meet calculated energy requirements, and ad libitum-fed cows were in positive calculated net energy for lactation (NEL) balance (0.02 vs. 6.37 Mcal/d, respectively). After parturition, milk yield, milk protein concentration, DMI, body condition score, and body weight were not affected by the prepartum treatments. Cows limit fed during the dry period had a less-negative calculated energy balance during wk 1 postpartum. Milk fat concentration and yield were greater for the ad libitum treatment during wk 1 but were lower in wk 2 and 3 postpartum. Plasma insulin and glucose concentrations decreased after calving. Plasma insulin concentration was greater in ad libitum-fed cows on d -2 relative to calving, but did not differ by dietary treatment at other times. Plasma glucose concentrations were lower before and after parturition for cows limit-fed during the dry period. Plasma nonesterified fatty acid concentrations peaked after parturition on d 1 and 4 for the limit-fed and ad libitum treatments, respectively, and were greater for limit-fed cows on d -18, -9, -5, and -2. Plasma tumor necrosis factor-alpha concentrations did not differ by treatment in either the pre- or postpartum period, but tended to decrease after parturition. Apart from a reduction in body energy loss in the first week after calving, limit feeding a higher NEL diet during the dry period had little effect on intake and milk production during the first month of lactation.

Identification of a novel mammalian post-translational modification, phosphocholine, on placental secretory polypeptides

Placental neurokinin B appears to be post-translationally modified by phosphocholine (PC) attached to the aspartyl side chain at residue 4 of the mature peptide. Corticotrophin releasing factor (CRF) was found to be expressed by the rat placenta with the main secreted forms being phosphocholinated proCRF+/- one or two polysaccharide moieties. A combination of high-pressure liquid chromatography (HPLC) and two-site immunometric analysis suggested that PC was also attached to the placental precursors of adrenocorticotrophin, hemokinin, activin and follistatin. However, the fully processed forms of rat placental activin and CRF were free of PC. Formerly, the parasitic filarial nematodes have used PC as a post-translational modification, attached via the polysaccharicle moiety of certain secretory glycoproteins to attenuate the host immune system allowing parasite survival, but it is the PC group itself which endows the carrier with the biological activity. The fact that treatment of proCRF peptides with phospholipase C but not endoglycosidase destroyed PC immunoreactivity suggested a simpler mode of attachment of PC to placental peptides than that used by nematodes. Thus, it is possible that by analogy the placenta uses its secreted phosphocholinated hormones to modulate the mother's immune system and help protect the placenta from rejection.

Role of gamma-MSH peptides in the regulation of adrenal steroidogenesis

Alpha-, beta- and gamma-melanocyte stimulating hormones (MSHs) are peptides derived from the ACTH precursor, pro-opiomelanocortin. All three peptides have been highly conserved throughout evolution but their exact biological function in mammals is still largely obscure. In recent years, there has been a surge of interest in alpha-MSH and its role in the regulation of feeding. Gamma-MSH by contrast has been shown to be involved in the regulation of adrenal steroidogenesis and also has effects on the cardiovascular and renal systems. This review will provide an overview of the role that gamma-MSH peptides play in the regulation of adrenal steroidogenesis. (c) 2005 Elsevier Inc. All rights reserved.

Variation in pituitary expression of mRNAs encoding the putative inhibin co-receptor (betaglycan) and type-I and type-II activin receptors during the chicken ovulatory cycle

Secretion of LH and FSH from the anterior pituitary is regulated primarily by hypothalamic GnRH and ovarian steroid hormones. More recent evidence indicates regulatory roles for certain members of the transforming growth factor beta (TGF beta) superfamily including inhibin and activin. The aim of this study was to identify expression of mRNAs encoding key receptors and ligands of the inhibin/activin system in the hen pituitary gland and to monitor their expression throughout the 24-25-h ovulatory cycle. Hens maintained on long days (16 h light/8 h dark) were killed 20, 12, 6 and 2 h before predicted ovulation of a midsequence egg (n = 8 per group). Anterior pituitary glands were removed, RNA extracted and cDNA synthesized. Plasma concentrations of LH, FSH, progesterone and inhibin A were measured. Real-time quantitative PCR was used to quantify pituitary expression of mRNAs encoding betaglycan, activin receptor (ActR) subtypes (type I, IIA), GnRH receptor (GnP,H-R), LH beta subunit, FSH beta subunit and GAPDH. Levels of mRNA for inhibin/activin beta A and beta B subunits, inhibin alpha subunit, follistatin and ActRIIB mRNA in pituitary were undetectable by quantitative PCR (< 2 amol/reaction). Significant changes in expression (P < 0.05) of ActRIIA and betaglycan mRNA were found, both peaking 6 h before ovulation just prior to the preovulatory LH surge and reaching a nadir 2 h before ovulation, just after the LH surge. There were no significant changes in expression of ActRI mRNA throughout the cycle although values were correlated with mRNA levels for both ActRIIA (r=0.77; P < 0.001) and betaglycan (r=0.45; P < 0.01). Expression of GnRH-R mRNA was lowest 20 h before ovulation and highest (P < 0.05) 6 h before ovulation; values were weakly correlated with betaglycan (r=0.33; P=0.06) and ActRIIA (r=0.34; P=0.06) mRNA levels. Expression of mRNAs encoding LH beta and FSH beta subunit were both lowest (P < 0.05) after the LH surge, 2 h before ovulation. These results are consistent with an endocrine, but not a local intrapituitary, role of inhibin-related proteins in modulating gonadotroph function during the ovulatory cycle of the hen, potentially through interaction with betaglycan and ActRIIA. In contrast to mammals, intrapituitary expression of inhibin/activin subunits and follistatin appears to be extremely low or absent in the domestic fowl.

Development of the mammalian urethra is controlled by Fgfr2-IIIb

Development of external genitalia in mammalian embryos requires tight coordination of a complex series of morphogenetic events involving outgrowth, proximodistal and dorsoventral patterning, and epithelial tubulogenesis. Hypospadias is a congenital defect of the external genitalia that results from failure of urethral tube closure. Although this is the second most common birth defect in humans, affecting one in every 250 children, the molecular mechanisms that regulate morphogenesis of the mammalian urethra are poorly understood. We report that mice lacking the IIIb isoform of fibroblast growth factor receptor 2 (Fgfr2) exhibit severe hypospadias. Urethral signaling regions, as indicated by Shh and Fgf8 expression, are established in Fgfr2-IIIb null mice; however, cell proliferation arrests prematurely and maturation of the urethral epithelium is disrupted. Fgfr2-IIIb(-/-) mutants fail to maintain the progenitor cell population required for uroepithelial renewal during tubular morphogenesis. In addition, we show that antagonism of the androgen receptor (AR) leads to loss of Fgfr2-IIIb and Fgf10 expression in the urethra, and an associated hypospadias phenotype, suggesting that these genes are downstream targets of AR during external genital development. Genitourinary defects resulting from disruption of AR activity, by either genetic or environmental factors, may therefore involve negative regulation of the Fgfr2 pathway. This represents the first example of how the developing genitourinary system integrates cues from systemically circulating steroid hormones with a locally expressed growth factor pathway.

Fracture incidence in relation to the pattern of use of hormone therapy in postmenopausal women

Context: Evidence is limited on the effects of different patterns of use of postmenopausal hormone therapy on fracture incidence and particularly on the effects of ceasing use. Objective: To investigate the effect of different patterns of hormone therapy use on fracture incidence. Design, Setting, and Participants: Prospective study of 138737 postmenopausal women aged 50 to 69 years recruited from the UK general population in 19961998 (the Million Women Study) and followed up for 1.9 to 3.9 years (average, 2.8 years) for fracture incidence. Main Outcome Measure: Adjusted relative risk (RR) for incident fracture (except fracture of the fingers, toes, and ribs) in hormone therapy users compared with never users at baseline. Results: A total of 5197 women (3.7%) reported 1 or more fractures, 79% resulting from falls. Current users of hormone therapy at baseline had a significantly reduced incidence of fracture (RR, 0.62; 95% confidence interval [CI], 0.58-0.66; P<.001). This protection was evident soon after hormone therapy began, and the RR decreased with increasing duration of use (P=.001). Among current users at baseline the RR of fracture did not vary significantly according to whether estrogen-only, estrogen-progestin, or other types of hormones were used (RR [95% CI], 0.64 [0.58-0.71], 0.58 [0.53-0.64], and 0.67 [0.56-0.80], respectively; P=19), nor did it vary significantly according to estrogen dose or estrogen or progestin constituents. The RR associated with current use of hormone therapy did not vary significantly according to 11 personal characteristics of study participants, including their age at menopause, body mass index, and physical activity. Past users of hormone therapy at baseline experienced no significant protection against fractures (RR, 1.07; 95% CI, 0.99-1.15); incidence rates returned to those of never-users within about a year of ceasing use. Conclusions: All types of hormone therapy studied confer substantial protection against fracture while they are used. This protection appears rapidly after use commences and wears off rapidly after use ceases. The older women are, the greater is their absolute reduction in fracture incidence while using hormone therapy.

Oocyte-mediated suppression of follicle-stimulating hormone- and insulin-like growth factor-induced secretion of steroids and inhibin-related proteins by bovine granulosa cells in vitro: Possible role of transforming growth factor alpha

The objective was to investigate the potential role of the oocyte in modulating proliferation and basal, FSH-induced and insulin-like growth factor (IGF)-induced secretion of inhibin A (inh A), activin A (act A), follistatin (FS), estradiol (E-2), and progesterone (P-4) by mural bovine granulosa cells. Cells from 4- to 6-mm follicles were cultured in serum-free medium containing insulin and androstenedione, and the effects of ovine FSH and IGF analogue (LR3-IGF-1) were tested alone and in the presence of denuded bovine oocytes (2, 8, or 20 per well). Medium was changed every 48 h, cultures were terminated after 144 h, and viable cell number was determined. Results are based on combined data from four independent cultures and are presented for the last time period only when responses were maximal. Both FSH and IGF increased (P < 0.001) secretion of inh A, act A, FS, E-2, and P-4 and raised cell number. In the absence of FSH or IGF, coculture with oocytes had no effect on any of the measured hormones, although cell number was increased up to 1.8-fold (P < 0.0001). Addition of oocytes to FSH-stimulated cells dose-dependently suppressed (P < 0.0001) inh A (6-fold maximum suppression), act A (5.5-fold), FS (3.6-fold), E-2 (4.6-fold), and P-4 (2.4-fold), with suppression increasing with FSH dose. Likewise, oocytes suppressed (P < 0.001) IGF-induced secretion of inh A, act A, FS, and E-2 (P < 0.05) but enhanced IGF-induced P-4 secretion (1.7-fold; P < 0.05). Given the similarity of these oocyte-mediated actions to those we observed previously following epidermal growth factor (EGF) treatment, we used immunocytochemistry to determine whether bovine oocytes express EGF or transforming growth factor (TGF) alpha. Intense staining with TGFalpha antibody (but not with EGF antibody) was detected in oocytes both before and after coculture. Experiments involving addition of TGFalpha to granulosa cells confirmed that the peptide mimicked the effects of oocytes on cell proliferation and on FSH- and IGF-induced hormone secretion. These experiments indicate that bovine oocytes secrete a factor(s) capable of modulating granulosa cell proliferation and responsiveness to FSH and IGF in terms of steroidogenesis and production of inhibin-related peptides, bovine oocytes express TGFalpha but not EGF, and TGFalpha is a prime candidate for mediating the actions of oocytes on bovine granulosa cells.

Has the mechanism by which the endocrine placenta scavenges the mother whilst sparing the foetus been unmasked?

The endocrine placenta has a dilemma; it shares the foetal circulation and yet it needs to secrete active peptide hormones into the maternal circulation to control her metabolism to meet the demands of the growing foetus. Simultaneously, it needs to allow the endocrine systems of the foetus to develop independently. This article will describe how peptide hormones are processed from inactive intermediates and will propose a hypothesis of how the placenta has revised this process to protect the foetus from the potentially damaging affects of these products.

Identification of stimulatory and inhibitory inputs to the hypothalamic-pituitary-adrenal axis during hypoglycaemia or transport in ewes

This study used the novel approach of statistical modelling to investigate the control of hypothalamic-pituitary-adrenal (HPA) axis and quantify temporal relationships between hormones. Two experimental paradigms were chosen, insulin-induced hypoglycaemia and 2 h transport, to assess differences in control between noncognitive and cognitive stimuli. Vasopressin and corticotropin-releasing hormone (CRH) were measured in hypophysial portal plasma, and adrenocorticotropin hormone (ACTH) and cortisol in jugular plasma of conscious sheep, and deconvolution analysis was used to calculate secretory rates, before modelling. During hypoglycaemia, the relationship between plasma glucose and vasopressin or CRH was best described by log(10) transforming variables (i.e. a positive power-curve relationship). A negative-feedback relationship with log(10) cortisol concentration 2 h previously was detected. Analysis of the 'transport' stimulus suggested that the strength of the perceived stimulus decreased over time after accounting for cortisol facilitation and negative-feedback. The time course of vasopressin and CRH responses to each stimulus were different However, at the pituitary level, the data suggested that log(10) ACTH secretion rate was related to log(10) vasopressin and CRH concentrations with very similar regression coefficients and an identical ratio of actions (2.3 : 1) for both stimuli. Similar magnitude negative-feedback effects of log(10) cortisol at -110 min (hypoglycaemia) or -40 min (transport) were detected, and both models contained a stimulatory relationship with cortisol at 0 min (facilitation). At adrenal gland level, cortisol secretory rates were related to simultaneously measured untransformed ACTH concentration but the regression coefficient for the hypoglycaemia model was 2.5-fold greater than for transport. No individual sustained maximum cortisol secretion for longer than 20 min during hypoglycaemia and 40 min during transport. These unique models demonstrate that corticosteroid negative-feedback is a significant control mechanism at both the pituitary and hypothalamus. The amplitude of HPA response may be related to stimulus intensity and corticosteroid negative-feedback, while duration depended on feedback alone.

The effect of impaired thyroid function during development on the mechanical properties of avian bone

Thyroid hormones show fluctuating levels during the post-hatching development of birds. In this paper we report the results of the first mechanical tests to quantify the effect of hypothyroidism, during post-natal development, on the skeletal properties of a precocial bird, the barnacle goose, as determined by microhardness testing. The effect of hypothyroidism is tissue-specific; bone from the femora of birds is not significantly affected by induced hypothyroidism, however, there is a strong positive relationship between the levels of circulating thyroid hormones and the mechanical properties of bone from humeri. In the barnacle goose the development of the wing skeleton and musculature depends on an increase in circulating thyroid hormones and our analysis shows that, in its absence, the mechanical competence of the bone mineral itself is reduced in addition to the decreased bone length and muscle development previously reported in the literature. (C) 2004 Wiley-Liss, Inc.

Soy isoflavones increase preprandial peptide YY (PYY), but have no effect on ghrelin and body weight in healthy postmenopausal women

Background: Soy isoflavones show structural and functional similarities to estradiol. Available data indicate that estradiol and estradiol-like components may interact with gut "satiety hormones" such as peptide YY (PYY) and ghrelin, and thus influence body weight. In a randomized, double-blind, placebo-controlled, cross-over trial with 34 healthy postmenopausal women (59 ± 6 years, BMI: 24.7 ± 2.8 kg/m2), isoflavone-enriched cereal bars (50 mg isoflavones/day; genistein to daidzein ratio 2:1) or non-isoflavone-enriched control bars were consumed for 8 weeks (wash-out period: 8-weeks). Seventeen of the subjects were classified as equol producers. Plasma concentrations of ghrelin and PYY, as well as energy intake and body weight were measured at baseline and after four and eight weeks of each intervention arm. Results: Body weight increased in both treatment periods (isoflavone: 0.40 ± 0.94 kg, P < 0.001; placebo: 0.66 ± 0.87 kg, P = 0.018), with no significant difference between treatments. No significant differences in energy intake were observed (P = 0.634). PYY significantly increased during isoflavone treatment (51 ± 2 pmol/L vs. 55 ± 2 pmol/L), but not during placebo (52 ± 3 pmol/L vs. 50 ± 2 pmol/L), (P = 0.010 for treatment differences, independent of equol production). Baseline plasma ghrelin was significantly lower in equol producers (110 ± 16 pmol/L) than in equol non-producers (162 ± 17 pmol/L; P = 0.025). Conclusion: Soy isoflavone supplementation for eight weeks did not significantly reduce energy intake or body weight, even though plasma PYY increased during isoflavone treatment. Ghrelin remained unaffected by isoflavone treatment. A larger and more rigorous appetite experiment might detect smaller differences in energy intake after isoflavone consumption. However, the results of the present study do not indicate that increased PYY has a major role in the regulation of body weight, at least in healthy postmenopausal women.

Dietary vitamin E modulates differential gene expression in the rat hippocampus: potential implications for its neuroprotective properties

A wide range of cell culture, animal and human epidemiological studies are suggestive of a role of vitamin E (VE) in brain function and in the prevention of neurodegeneration. However, the underlying molecular mechanisms remain largely unknown. In the current investigation Affymetrix gene chip technology was utilised to establish the impact of chronic VE deficiency on hippocampal genes expression. Male albino rats were fed either a VE deficient or standard diet (60 mg/kg feed) for a period of 9 months. Rats were sacrificed, the hippocampus removed and genes expression established in individual animals. VE deficiency showed to have a strong impact on genes expression in the hippocampus. An important number of genes found to be regulated by VE was associated with hormones and hormone metabolism, nerve growth factor, apoptosis, dopaminergic neurotransmission, and clearance of amyloid-beta and advanced glycated endproducts. In particular, VE strongly affected the expression of an array of genes encoding for proteins directly or indirectly involved in the clearance of amyloid beta, changes which are consistent with a protective effect of VE on Alzheimer's disease progression.

Physiological mechanisms mediating aspartame-induced satiety

Aspartame has been previously shown to increase satiety. This study aimed to investigate a possible role for the satiety hormones cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) in this effect. The effects of the constituents of aspartame, phenylalanine and aspartic acid, were also examined. Six subjects consumed an encapsulated preload consisting of either 400 mg aspartame, 176 mg aspartic acid + 224 mg phenylalanine, or 400 mg corn flour (control), with 1.5 g paracetamol dissolved in 450 ml water to measure gastric emptying. A 1983-kJ liquid meal was consumed 60 min later. Plasma CCK, GLP-1, glucose-dependent insulinotropic polypeptide (GIP), glucose, and insulin were measured over 0-120 min. Gastric emptying was measured from 0 to 60 min. Plasma GLP-1 concentrations decreased following the liquid meal (60-120 min) after both the aspartame and amino acids preloads (control, 2096.9 pmol/l min; aspartame, 536.6 pmol/l min; amino acids, 861.8 pmol/l min; incremental area under the curve [AUC] 60-120 min, P<.05). Desire to cat was reduced from 60 to 120 min following the amino acids preload (control, -337.1 mm min; aspartame, -505.4 mm min; amino acids, -1497.1 mm min; incremental AUC 60-120 min, P<.05). However, gastric emptying rates, plasma CCK, GIP, insulin, and glucose concentrations were unaffected. There was a correlation between the increase in plasma phenylalanine and decrease in desire to eat after the liquid meal following the constituent amino acids (r = -.9774, P=.004). In conclusion, it is unlikely that aspartame increases satiety via CCK- or GLP-1-mediated mechanisms, but small changes in circulating phenylalanine concentrations may influence appetite. (C) 2003 Elsevier Science Inc. All rights reserved.

alpha-tocopherol affects androgen metabolism in male rat

The Alpha-Tocopherol Beta-Carotene Cancer Prevention Study has provided the first evidence implicating vitamin E in hormone synthesis. The effect of vitamin E on stereoidogenesis in testes and adrenal glands was assessed in growing rats using Affymetrix gene-chip technology. Dietary supplementation of rats with vitamin E (60 mg/kg feed) for a period of 429 days caused a significant repression of genes encoding for proteins centrally involved in the uptake (low-density lipoprotein receptor) and de novo synthesis (for example, 7-dehydrocholesterol reductase, 3-hydroxy-3-methylglutaryl coenzyme A synthase, 3-hydroxy-3-methylglutaryl-coenzyme A reductase, isopentenyl-diphosphate delta-isomerase, and farnesyl pyrophosphate synthetase) of cholesterol, the precursor of all steroid hormones. The present investigation indicates that dietary vitamin E may induce changes in stereoidogenesis by affecting cholesterol homeostasis.

Variation in pituitary expression of mRNAs encoding the putative inhibin co-receptor (betaglycan) and type-I and type-II activin receptors during the chicken ovulatory cycle

Secretion of LH and FSH from the anterior pituitary is regulated primarily by hypothalamic GnRH and ovarian steroid hormones. More recent evidence indicates regulatory roles for certain members of the transforming growth factor beta (TGF beta) superfamily including inhibin and activin. The aim of this study was to identify expression of mRNAs encoding key receptors and ligands of the inhibin/activin system in the hen pituitary gland and to monitor their expression throughout the 24-25-h ovulatory cycle. Hens maintained on long days (16 h light/8 h dark) were killed 20, 12, 6 and 2 h before predicted ovulation of a midsequence egg (n = 8 per group). Anterior pituitary glands were removed, RNA extracted and cDNA synthesized. Plasma concentrations of LH, FSH, progesterone and inhibin A were measured. Real-time quantitative PCR was used to quantify pituitary expression of mRNAs encoding betaglycan, activin receptor (ActR) subtypes (type I, IIA), GnRH receptor (GnP,H-R), LH beta subunit, FSH beta subunit and GAPDH. Levels of mRNA for inhibin/activin beta A and beta B subunits, inhibin alpha subunit, follistatin and ActRIIB mRNA in pituitary were undetectable by quantitative PCR (< 2 amol/reaction). Significant changes in expression (P < 0.05) of ActRIIA and betaglycan mRNA were found, both peaking 6 h before ovulation just prior to the preovulatory LH surge and reaching a nadir 2 h before ovulation, just after the LH surge. There were no significant changes in expression of ActRI mRNA throughout the cycle although values were correlated with mRNA levels for both ActRIIA (r=0.77; P < 0.001) and betaglycan (r=0.45; P < 0.01). Expression of GnRH-R mRNA was lowest 20 h before ovulation and highest (P < 0.05) 6 h before ovulation; values were weakly correlated with betaglycan (r=0.33; P=0.06) and ActRIIA (r=0.34; P=0.06) mRNA levels. Expression of mRNAs encoding LH beta and FSH beta subunit were both lowest (P < 0.05) after the LH surge, 2 h before ovulation. These results are consistent with an endocrine, but not a local intrapituitary, role of inhibin-related proteins in modulating gonadotroph function during the ovulatory cycle of the hen, potentially through interaction with betaglycan and ActRIIA. In contrast to mammals, intrapituitary expression of inhibin/activin subunits and follistatin appears to be extremely low or absent in the domestic fowl.