Endocrine changes and liver mRNA abundance of somatotropic axis and insulin system constituents during negative energy balance at different stages of lactation in dairy cows

The liver has an important role in metabolic regulation and control of the somatotropic axis to adapt successfully to physiological and environmental changes in dairy cows. The aim of this study was to investigate the adaptation to negative energy balance (NEB) at parturition and to a deliberately induced NEB by feed restriction at 100 days in milk. The hepatic gene expression and the endocrine system of the somatotropic axis and related parameters were compared between the early and late NEB period. Fifty multiparous cows were subjected to 3 periods (1=early lactation up to 12 wk postpartum, 2=feed restriction for 3 wk beginning at around 100 days in milk with a feed-restricted and a control group, and 3=subsequent realimentation period for the feed-restricted group for 8 wk). In period 1, plasma growth hormone reached a maximum in early lactation, whereas insulin-like growth factor-I (IGF-I), leptin, the thyroid hormones, insulin, and the revised quantitative insulin sensitivity check index increased gradually after a nadir in early lactation. Three days after parturition, hepatic mRNA abundance of growth hormone receptor 1A, IGF-I, IGF-I receptor and IGF-binding protein-3 (IGFBP-3) were decreased, whereas mRNA of IGFBP-1 and -2 and insulin receptor were upregulated as compared with wk 3 antepartum. During period 2, feed-restricted cows showed decreased plasma concentrations of IGF-I and leptin compared with those of control cows. The revised quantitative insulin sensitivity check index was lower for feed-restricted cows (period 2) than for control cows. Compared with the NEB in period 1, the changes due to the deliberately induced NEB (period 2) in hormones were less pronounced. At the end of the 3-wk feed restriction, the mRNA abundance of IGF-I, IGFBP-1, -2, -3, and insulin receptor was increased as compared with the control group. The different effects of energy deficiency at the 2 stages in lactation show that the endocrine regulation changes qualitatively and quantitatively during the course of lactation.

Hypoxia-induced gene activity in disused oxidative muscle

Hypoxia is an important modulator of the skeletal muscle's oxidative phenotype. However, little is known regarding the molecular circuitry underlying the muscular hypoxia response and the interaction of hypoxia with other stimuli of muscle oxidative capacity. We hypothesized that exposure of mice to severe hypoxia would promote the expression of genes involved in capillary morphogenesis and glucose over fatty acid metabolism in active or disused soleus muscle of mice. Specifically, we tested whether the hypoxic response depends on oxygen sensing via the alpha-subunit of hypoxia-inducible factor-1 (HIF-1 alpha). Spontaneously active wildtype and HIF-1 alpha heterozygous deficient adult female C57B1/6 mice were subjected to hypoxia (PiO2 70 mmHg). In addition, animals were subjected to hypoxia after 7 days of muscle disuse provoked by hindlimb suspension. Soleus muscles were rapidly isolated and analyzed for transcript level alterations with custom-designed AtlasTM cDNA expression arrays (BD Biosciences) and cluster analysis of differentially expressed mRNAs. Multiple mRNA elevations of factors involved in dissolution and stabilization of blood vessels, glycolysis, and mitochondrial respiration were evident after 24 hours of hypoxia in soleus muscle. In parallel transcripts of fat metabolism were reduced. A comparable hypoxia-induced expression pattern involving complex alterations of the IGF-I axis was observed in reloaded muscle after disuse. This hypoxia response in spontaneously active animals was blunted in the HIF-1 alpha heterozygous deficient mice demonstrating 35% lower HIF-1 alpha mRNA levels. Our molecular observations support the concept that severe hypoxia provides HIF-1-dependent signals for remodeling of existing blood vessels, a shift towards glycolytic metabolism and altered myogenic regulation in oxidative mouse muscle and which is amplified by enhanced muscle use. These findings further imply differential mitochondrial turnover and a negative role of HIF-1 alpha for control of fatty acid oxidation in skeletal muscle exposed to one day of severe hypoxia.

Gene expression in skeletal muscle of coronary artery disease patients after concentric and eccentric endurance training

Low-intensity concentric (CET) and eccentric (EET) endurance-type training induce specific structural adaptations in skeletal muscle. We evaluated to which extent steady-state adaptations in transcript levels are involved in the compensatory alterations of muscle mitochondria and myofibrils with CET versus EET at a matched metabolic exercise intensity of medicated, stable coronary patients (CAD). Biopsies were obtained from vastus lateralis muscle before and after 8 weeks of CET (n=6) or EET (n=6). Transcript levels for factors involved in mitochondrial biogenesis (PGC-1alpha, Tfam), mitochondrial function (COX-1, COX-4), control of contractile phenotype (MyHC I, IIa, IIx) as well as mechanical stress marker (IGF-I) were quantified using an reverse-transcriptase polymerase chain reaction approach. After 8 weeks of EET, a reduction of the COX-4 mRNA level by 41% and a tendency for a drop in Tfam transcript concentration (-33%, P=0.06) was noted. This down-regulation corresponded to a drop in total mitochondrial volume density. MyHC-IIa transcript levels were specifically decreased after EET, and MyHC-I mRNA showed a trend towards a reduction (P=0.08). Total fiber cross-sectional area was not altered. After CET and EET, the IGF-I mRNA level was significantly increased. The PGC-1alpha significantly correlated with Tfam, and both PGC-1alpha and Tfam significantly correlated with COX-1 and COX-4 mRNAs. Post-hoc analysis identified significant interactions between the concurrent medication and muscular transcript levels as well as fiber size. Our findings support the concept that specific transcriptional adaptations mediate the divergent mitochondrial response of muscle cells to endurance training under different load condition and indicate a mismatch of processes related to muscle hypertrophy in medicated CAD patients.

Effects of Delta12-prostaglandin J2 on bone regeneration and growth factor expression in rats

OBJECTIVES: Cyclopentenone prostaglandins have been shown to promote osteoblast differentiation in vitro. The aim of this study was to examine in a rat model the effects of local delivery of Delta(12)-prostaglandin J(2) (Delta(12)-PGJ(2)) on new bone formation and growth factor expression in (i) cortical defects and (ii) around titanium implants. MATERIAL AND METHODS: Standardized transcortical defects were prepared bilaterally in the femur of 28 male Wistar rats. Ten microliters of Delta(12)-PGJ(2) at 4 concentrations (10(-9), 10(-7), 10(-5) and 10(-3) mol/l) in a collagen vehicle were delivered inside a half-cylindrical titanium chamber fixed over the defect. Contralateral defects served as vehicle controls. Ten days after surgery, the amount of new bone formation in the cortical defect area was determined by histomorphometry and expression of platelet-derived growth factor (PDGF)-A and -B, insulin-like growth factor (IGF)-I/II, bone morphogenetic protein (BMP)-2 and -6 was examined by immunohistochemistry. In an additional six rats, 24 titanium implants were inserted into the femur. Five microliters of carboxymethylcellulose alone (control) or with Delta(12)-PGJ(2) (10(-5) and 10(-3) mol/l) were delivered into surgically prepared beds prior to implant installation. RESULTS: Delta(12)-PGJ(2) (10(-5) and 10(-3) mol/l) significantly enhanced new bone formation (33%, P<0.05) compared with control cortical defects. Delivery of Delta(12)-PGJ(2) at 10(-3) mol/l significantly increased PDGF-A and -B and BMP-2 and -6 protein expression (P<0.05) compared with control defects. No significant difference was found in IGF-I/II expression compared with controls. Administration of Delta(12)-PGJ(2) also significantly increased endosteal new bone formation around implants compared with controls. CONCLUSION: Local delivery of Delta(12)-PGJ(2) promoted new bone formation in the cortical defect area and around titanium implants. Enhanced expression of BMP-2 and -6 as well as PDGF-A and -B may be involved in Delta(12)-PGJ(2)-induced new bone formation.

Cyclooxygenase-2 inhibition selectively attenuates bone morphogenetic protein-6 synthesis and bone formation during guided tissue regeneration in a rat model

OBJECTIVES: Bone formation during guided tissue regeneration is a tightly regulated process involving cells, extracellular matrix and growth factors. The aims of this study were (i) to examine the expression of cyclooxygenase-2 (COX-2) during bone regeneration and (ii) the effects of selective COX-2 inhibition on osseous regeneration and growth factor expression in the rodent femur model. MATERIAL AND METHODS: A standardized transcortical defect of 5 x 1.5 mm was prepared in the femur of 12 male rats and a closed half-cylindrical titanium chamber was placed over the defect. The expression of COX-2 and of platelet-derived growth factor-B (PDGF-B), bone morphogenetic protein-6 (BMP-6) and insulin-like growth factor-I/II (IGF-I/II) was analyzed at Days 3, 7, 21 and 28 semiquantitatively by reverse transcriptase-polymerase chain reaction and immunohistochemistry. The effects of COX-2 inhibition by intraperitoneal injection of NS-398 (3 mg/kg/day) were analyzed in five additional animals sacrificed at Day 14. RESULTS: Histomorphometry revealed that new bone formation occurred in the cortical defect area as well as in the supracortical region, i.e. region within the chamber by Day 7 and increased through Day 28. Immunohistochemical evidence of COX-2 and PDGF-B levels were observed early (i.e. Day 3) and decreased rapidly by Day 7. BMP-6 expression was maximal at Day 3 and slowly declined by Day 28. In contrast, IGF-I/II expression gradually increased during the 28-day period. Systemic administration NS-398 caused a statistically significant reduction (P<0.05) in new bone formation (25-30%) and was associated with a statistically significant reduction in BMP-6 protein and mRNA expression (50% and 65% at P<0.05 and P<0.01, respectively). PDGF-B mRNA or protein expression was not affected by NS-398 treatment. CONCLUSION: COX-2 inhibition resulted in reduced BMP-6 expression and impaired osseous regeneration suggesting an important role for COX-2-induced signaling in BMP synthesis and new bone formation.

GH mutant (R77C) in a pedigree presenting with the delay of growth and pubertal development: structural analysis of the mutant and evaluation of the biological activity

A heterozygous missense mutation in the GH-1 gene converting codon 77 from arginine (R) to cysteine (C), which was previously reported to have some GH antagonistic effect, was identified in a Syrian family. The index patient, a boy, was referred for assessment of his short stature (-2.5 SDS) at the age of 6 years. His mother and grandfather were also carrying the same mutation, but did not differ in adult height from the other unaffected family members. Hormonal examination in all affected subjects revealed increased basal GH, low IGF-I concentrations, and subnormal IGF-I response in generation test leading to the diagnosis of partial GH insensitivity. However, GH receptor gene (GHR) sequencing demonstrated no abnormalities. As other family members carrying the GH-R77C form showed similar alterations at the hormonal level, but presented with normal final height, no GH therapy was given to the boy, but he was followed through his pubertal development which was delayed. At the age of 20 years he reached his final height, which was normal within his parental target height. Functional characterization of the GH-R77C, assessed through activation of Jak2/Stat5 pathway, revealed no differences in the bioactivity between wild-type-GH (wt-GH) and GH-R77C. Detailed structural analysis indicated that the structure of GH-R77C, in terms of disulfide bond formation, is almost identical to that of the wt-GH despite the introduced mutation (Cys77). Previous studies from our group demonstrated a reduced capability of GH-R77C to induce GHR/GH-binding protein (GHBP) gene transcription rate when compared with wt-GH. Therefore, reduced GHR/GHBP expression might well be the possible cause for the partial GH insensitivity found in our patients. In addition, this group of patients deserve further attention because they could represent a distinct clinical entity underlining that an altered GH peptide may also have a direct impact on GHR/GHBP gene expression causing partial GH insensitivity. This might be responsible for the delay of growth and pubertal development. Finally, we clearly demonstrate that GH-R77C is not invariably associated with short stature, but that great care needs to be taken in ascribing growth failure to various heterozygous mutations affecting the GH-IGF axis and that careful functional studies are mandatory.

Catch-up growth in autosomal dominant isolated growth hormone deficiency (IGHD type II)

OBJECTIVE: Data on the GH-induced catch-up growth of severely GH-deficient children affected by monogenetic defects are missing. PATIENTS: Catch-up growth of 21 prepubertal children (6 females, 15 males) affected with IGHD type II was analyzed in a retrospective chart review. At start of therapy, mean age was 6.2 years (range, 1.6-15.0), mean height SDS was -4.7 (-7.6 to -2.2), mean IGF-I SDS was -6.2 (-10.1 to -2.2). GH was substituted using a mean dose of 30.5microg/kg*d. RESULTS: Catch-up growth was characterized by a mean height gain of +0.92, +0.82, and +0.61 SDS after 1, 2, and 3 years of GH therapy, respectively. Mean height velocities were 10.7, 9.2 and 7.7cm/year during the first three years. Mean duration of complete catch-up growth was 6 years (3-9). Mean height SDS reached was -0.97 (-2.3 to +1.1), which was within the range of the estimated target height of -0.60 SDS (-1.20 to -0.15). The younger and shorter the children were at start of therapy the better they grew during the first year independent of the dose. Mean bone age was delayed at start by 2.1 years and progressed by 2.5 years during the first two years of therapy. Incomplete catch-up growth was caused by late initiation or irregular administration of GH in four cases. CONCLUSIONS: Our data suggest that GH-treated children with severe IGHD show a sustained catch-up growth over 6 years (mean) and reach their target height range. This response to GH is considered to be characteristic for young children with severe growth retardation due to IGHD.

[What is the value of determining immunoreactive GHRH in acromegaly?]

Acromegaly is usually due to autonomous, excessive secretion of growth hormone from a pituitary adenoma. One would expect growth hormone-releasing factor (GHRH) in these patients to be suppressed. In the available literature referring to acromegaly, immunoreactive GHRH levels were determined in 259 acromegalic patients. When growth hormone was measured simultaneously, no correlation was found between serum growth hormone and plasma GHRH concentrations, irrespective of whether the acromegalic patients were treated or not. A possible explanation for this finding might be the lack of a feedback regulation between plasma growth hormone and GHRH. Also, since growth hormone is secreted in a pulsatile fashion the interpretation of single growth hormone values can be difficult. IGF I, which correlates well with mean growth hormone production, may therefore represent a more valuable criterion for the assessment of activity and GHRH plasma levels in acromegalics. However, no study has yet been performed to elucidate the relationship between GHRH and IGF I in acromegaly. To examine this relationship we measured the concentration of plasma GHRH and IGF I in 18 treated patients with acromegaly (age range 32-64 years median 50.5 years; median follow-up 6.5 years, range 3 months to 33 years). All immunoreactive GHRH levels were within the limits described as normal in the literature (mean +/- SD 22.89 +/- 2.72 pg/ml, range 19-28 pg/ml). The IGFI level was 396.78 +/- 224.26 ng/ml (mean +/- SD, range 71-876 ng/ml; reference ranges, age group 25-39 years: 114-492 ng/ml; 40-54 years: 90-360 ng/ml; > 55 years: 71-290 ng/ml). We found no correlation between IGF I and GHRH concentrations (r = 0.17). We therefore conclude that measuring plasma GHRH is not useful in the evaluation of the activity or therapy of acromegaly but may be helpful in its differential diagnosis since a massive elevation of GHRH is typically associated with the ectopic GHRH syndrome, a rare cause of acromegaly.

Effect of GH on human skeletal muscle lipid metabolism in GH deficiency

Adult-onset growth hormone (GH) deficiency (GHD) is associated with insulin resistance and decreased exercise capacity. Intramyocellular lipids (IMCL) depend on training status, diet, and insulin sensitivity. Using magnetic resonance spectroscopy, we studied IMCL content following physical activity (IMCL-depleted) and high-fat diet (IMCL-repleted) in 15 patients with GHD before and after 4 mo of GH replacement therapy (GHRT) and in 11 healthy control subjects. Measurements of insulin resistance and exercise capacity were performed and skeletal muscle biopsies were carried out to assess expression of mRNA of key enzymes involved in skeletal muscle lipid metabolism by real-time PCR and ultrastructure by electron microscopy. Compared with control subjects, patients with GHD showed significantly higher difference between IMCL-depleted and IMCL-repleted. GHRT resulted in an increase in skeletal muscle mRNA expression of IGF-I, hormone-sensitive lipase, and a tendency for an increase in fatty acid binding protein-3. Electron microscopy examination did not reveal significant differences after GHRT. In conclusion, variation of IMCL may be increased in patients with GHD compared with healthy control subjects. Qualitative changes within the skeletal muscle (i.e., an increase in free fatty acids availability from systemic and/or local sources) may contribute to the increase in insulin resistance and possibly to the improvement of exercise capacity after GHRT. The upregulation of IGF-I mRNA suggests a paracrine/autocrine role of IGF-I on skeletal muscle.

The importance of growth hormone in the regulation of erythropoiesis, red cell mass, and plasma volume in adults with growth hormone deficiency

Total body water (TBW) is reduced in adult GH deficiency (GHD) largely due to a reduction of extracellular water. It is unknown whether total blood volume (TBV) contributes to the reduced extracellular water in GHD. GH and insulin-like growth factor I (IGF-I) have been demonstrated to stimulate erythropoiesis in vitro, in animal models, and in growing children. Whether GH has a regulatory effect on red cell mass (RCM) in adults is not known. We analyzed body composition by bioelectrical impedance and used standard radionuclide dilution methods to measure RCM and plasma volume (PV) along with measuring full blood count, ferritin, vitamin B12, red cell folate, IGF-I, IGF-binding protein-3, and erythropoietin in 13 adult patients with GHD as part of a 3-month, double blind, placebo-controlled trial of GH (0.036 U/kg.day). TBW and lean body mass significantly increased by 2.5 +/- 0.53 kg (mean +/- SEM; P < 0.004) and 3.4 +/- 0.73 kg (P < 0.004), respectively, and fat mass significantly decreased by 2.4 +/- 0.32 kg (P < 0.001) in the GH-treated group. The baseline RCM of all patients with GHD was lower than the predicted normal values (1635 +/- 108 vs. 1850 +/- 104 mL; P < 0.002). GH significantly increased RCM, PV, and TBV by 183 +/- 43 (P < 0.006), 350 +/- 117 (P < 0.03), and 515 +/- 109 (P < 0.004) mL, respectively. The red cell count increased by 0.36 +/- 0.116 x 10(12)/L (P < 0.03) with a decrease in ferritin levels by 39.1 +/- 4.84 micrograms/L (P < 0.001) after GH treatment. Serum IGF-I and IGF-binding protein-3 concentrations increased by 3.0 +/- 0.43 (P < 0.001) and 1.3 +/- 0.15 (P < 0.001) SD, respectively, but the erythropoietin concentration was unchanged after GH treatment. No significant changes in body composition or blood volume were recorded in the placebo group. Significant positive correlations could be established between changes in TBW and TBV, lean body mass and TBV (r = 0.78; P < 0.04 and r = 0.77; P < 0.04, respectively), and a significant negative correlation existed between changes in fat mass and changes in TBV in the GH-treated group (r = -0.95; P < 0.02). We conclude that 1) erythropoiesis is impaired in GHD; 2) GH stimulates erythropoiesis in adult GHD; and 3) GH increases PV and TBV, which may contribute to the increased exercise performance seen in these patients.

Effect of regular physical training on age-associated alteration of body composition in men

Body composition changes with increasing age in men, in that lean body mass decreases whereas fat mass increases. Whether this altered body composition is related to decreasing physical activity or to the known age-associated decrease in growth hormone secretion is uncertain. To address this question, three groups of healthy men (n = 14 in each group), matched for weight, height and body mass index, were investigated using dual-energy X-ray absorptiometry, indirect calorimetry and estimate of daily growth hormone secretion [i.e. plasma insulin-like growth factor I (IGF-I-) levels]. Group 1 comprised young untrained subjects aged 31.0 +/- 2.1 years (mean +/- SEM) taking no regular physical exercise; group 2 consisted of old untrained men aged 68.6 +/- 1.2 years; and group 3 consisted of healthy old men aged 67.4 +/- 1.2 years undergoing regular physical training for more than 10 years with a training distance of at least 30 km per week. Subjects in group 3 had for the past three years taken part in the 'Grand Prix of Berne', a 16.5-km race run at a speed of 4.7 +/- 0.6 min km-1 (most recent race). Fat mass was more than 4 kg higher in old untrained men (P < 0.01, ANOVA) than in the other groups (young untrained men, 12.0 +/- 0.9 kg; old untrained men, 16.1 +/- 1.0 kg; old trained men, 11.0 +/- 0.8 kg), whereas body fat distribution (i.e. the ratio of upper to lower body fat mass) was similar between the three groups. The lean mass of old untrained men was more than 3.5 kg lower (P < 0.02, ANOVA) than in the other two groups (young untrained men, 56.4 +/- 1.0 kg; old untrained men, 52.4 +/- 1.0 kg; old trained men, 56.0 +/- 1.0 kg), mostly because of a loss of skeletal muscle mass in the arms and legs (young untrained men, 24.0 +/- 0.5 kg; old untrained men 20.8 +/- 0.5 kg; old trained men, 23.6 +/- 0.7 kg; P < 0.01, ANOVA). Resting metabolic rate per kilogram lean mass decreased with increasing age independently of physical activity (r = -0.42, P < 0.005). Fuel metabolism was determined by indirect calorimetry at rest. Protein oxidation was similar in the three groups. Old untrained men had higher (P < 0.001) carbohydrate oxidation (young untrained men, 13.2 +/- 1.0 kcal kg-1 lean mass; old untrained men, 15.2 +/- 1.3 kcal Kg-1; old trained men, 7.8 +/- 0.8 kcal kg-1), but lower (P < 0.05, ANOVA) fat oxidation (young untrained men, 10.1 +/- 1.2 kcal kg-1 lean mass; old untrained men, 6.5 +/- 1.0 kcal kg-1; old trained men, 13.7 +/- 1.0 kcal kg-1) than the other two groups. Mean plasma IGF-I level in old trained men was higher than in old untrained men (P < 0.05), but was still lower than that observed in young untrained men (P < 0.005) (young untrained men, 236 +/- 24 ng mL-1; old untrained men, 119 +/- 13 ng mL-1; old trained men, 166 +/- 14 ng mL-1). In summary, regular physical training in older men seems to prevent the changes in body composition and fuel metabolism normally associated with ageing. Whether regular physical training in formerly untrained old subjects would result in similar changes awaits further study.

Variation in hepatic regulation of metabolism during the dry period and in early lactation in dairy cows

The purpose of this study was to investigate variations in hepatic regulation of metabolism during the dry period, after parturition, and in early lactation in dairy cows. For this evaluation, cows were divided into 2 groups based on the plasma concentration of beta-hydroxybutyric acid (BHBA) in wk 4 postpartum (PP; group HB, BHBA >0.75 mmol/L; group LB, BHBA <0.75 mmol/L, respectively). Liver biopsies were obtained from 28 cows at drying off (mean 59 +/- 8 d antepartum), on d 1, and in wk 4 and 14 PP. Blood samples were collected every 2 wk during this entire period. Liver samples were analyzed for mRNA abundance of genes related to carbohydrate metabolism (pyruvate carboxylase, PC; phosphoenolpyruvate carboxykinase, PEPCK; citrate synthase, CS), fatty acid biosynthesis (ATP citrate lyase, ACLY) and oxidation (acyl-CoA synthetase long-chain, ACSL; carnitine palmitoyltransferase 1A, CPT 1A; carnitine palmitoyltransferase 2, CPT 2; acyl-coenzyme A dehydrogenase very long chain, ACADVL), cholesterol biosynthesis (3-hydroxy-3-methylglutaryl-coenzyme A synthase 1, HMGCS1), ketogenesis (3-hydroxy-3-methylglutaryl-coenzyme A synthase 2, HMGCS2), and of genes encoding the transcription factors peroxisome proliferator-activated receptor alpha (PPARalpha), peroxisome proliferator-activated receptor gamma (PPARgamma), and sterol regulatory element binding factor 1 (SREBF1). Blood plasma was assayed for concentrations of glucose, BHBA, nonesterified fatty acids, cholesterol, triglycerides, insulin, insulin-like growth factor-I, and thyroid hormones. In both groups, plasma parameters followed a pattern usually observed in dairy cows. However, changes were moderate and the energy balance in cows turned positive in wk 7 PP for both groups. Additionally, the energy balance and milk yield were similar for both groups after parturition onwards. Significant group effects were found at drying off, when plasma concentrations of triglycerides were higher in LB than in HB, and in wk 4 PP, when plasma concentrations of glucose and IGF-I were lower in HB than in LB. Similarly, moderate changes in mRNA expression of hepatic genes between the different time points were observed, although HB cows showed more adaptive performance than LB cows based on changes in mRNA expression of PEPCKc, PEPCKm, CS, CPT 1A, CPT 2, and PPARalpha. Part of the variation measured in this study was explained by parity. Significant Spearman rank correlation coefficients between the variables were not similar at each time point and were not similar between the groups at each time point, suggesting that metabolic regulation differs between cows. In conclusion, metabolic regulation in dairy cows is a dynamic system, and differs obviously between cows at different metabolic stages related to parturition.

Heterozygous GHR gene mutation in a child with idiopathic short stature.

Abstract Several monogenic defects have been reported to be associated with idiopathic short stature. Focusing on growth hormone receptor (GHR)-gene alterations, the heterozygosity of the same gene defect may be associated with a range of growth deficits. We found a heterozygous mutation (V144I) within exon 6 of the GHR gene in a patient with a low level of insulin-like growth factor I (IGF-I), normal level of GH, and severe short stature. Despite the lack of statistical difference, an overall tendency for reduced wt-GH-induction of GHR activation and Jak/Stat signalling in cells transiently expressing GHR-V144I alone or co-expressing wt-GHR compared to cells expressing only wt-GHR was found when GH doses were increased. Our results suggest that, although GHR sequence variants are responsible for some functional alterations commonly observed in children with idiopathic short stature, these changes may not explain all the height deficits observed in these subjects.

Radiometrical, hormonal and biological correlates of skeletal growth in the female rat from birth to senescence

OBJECTIVE We investigated the skeletal growth profile of female rats from birth to senescence (100weeks) on the basis of sequential radiometrical, hormonal and biochemical parameters. DESIGN Weaning rats entered the study which was divided into two sections: a) sequential measurements of vertebral and tibial growths and bone mineral density (BMD), estimation of mineral content of the entire skeleton (BMC) and chemical analysis of vertebral Ca; and b) determination of basal and pulsatile growth hormone (rGH), insulin-like growth hormone (IGF-I), estradiol (E2), parathyroid hormone (PTH), osteocalcin (OC) and urinary d-pyridinoline (dp) throughout the experimental period. RESULTS Vertebral and tibial growths ceased at week 25 whereas BMD and BMC as well as total vertebral Ca exhibited a peak bone mass at week 40. rGH pulsatile profiles were significantly higher in younger animals coinciding with the period of active growth and IGF-I peaked at 7weeks, slowly declining thereafter and stabilizing after week 60. OC and dp closely paralleled IGF-I coinciding with the period of enhanced skeletal growth, remaining thereafter in the low range indicative of reduced bone turnover. E2 increased during reproductive life but the lower values subsequently recorded were still in the physiological range, strongly suggesting a protective role of this steroid on bone remodeling. PTH followed a similar profile to E2, but the significance of this after completion of growth remains unclear. CONCLUSIONS Mechanisms governing skeletal growth in the female rat appear similar to those in humans. Bone progression and attainment of peak bone mass are under simultaneous control of rGH, IGF-I and calciotropic hormones and are modulated by E2. This steroid seems to protect the skeleton from resorption before senescence whereas the role of PTH in this context remains uncertain.

Comparison of hepatic adaptation in extreme metabolic phenotypes observed in early lactation dairy cows on-farm

The aim was to study the variation in metabolic responses in early-lactating dairy cows (n = 232) on-farm that were pre-selected for a high milk fat content (>45 g/l) and a high fat/protein ratio in milk (>1.5) in their previous lactation. Blood was assayed for concentrations of metabolites and hormones. Liver was measured for mRNA abundance of 25 candidate genes encoding enzymes and receptors involved in gluconeogenesis (6), fatty acid β-oxidation (6), fatty acid and triglyceride synthesis (5), cholesterol synthesis (4), ketogenesis (2) and the urea cycle (2). Two groups of cows were formed based on the plasma concentrations of glucose, non-esterified fatty acids (NEFA) and β-hydroxybutyric acid (BHBA) (GRP+, high metabolic load; glucose <3.0 mm, NEFA >300 μm and BHBA >1.0 mm, n = 30; GRP-, low metabolic load; glucose >3.0 mm, NEFA <300 μm and BHBA <1.0 mm, n = 30). No differences were found between GRP+ and GRP- for the milk yield at 3 weeks post-partum, but milk fat content was higher (p < 0.01) for GRP+ than for GRP-. In week 8 post-partum, milk yield was higher in GRP+ in relation to GRP- (37.5 vs. 32.5 kg/d; p < 0.01). GRP+ in relation to GRP- had higher (p < 0.001) NEFA and BHBA and lower glucose, insulin, IGF-I, T3 , T4 concentrations (p < 0.01). The mRNA abundance of genes related to gluconeogenesis, fatty acid β-oxidation, fatty acid and triglyceride synthesis, cholesterol synthesis and the urea cycle was different in GRP+ compared to GRP- (p < 0.05), although gene transcripts related to ketogenesis were similar between GRP+ and GRP-. In conclusion, high metabolic load post-partum in dairy cows on-farm corresponds to differences in the liver in relation to dairy cows with low metabolic load, even though all cows were pre-selected for a high milk fat content and fat/protein ratio in milk in their previous lactation.