Growth hormone binding proteins in pig adipose tissue: number, size and effects of pGH treatment on pGH and bGH binding

The Impact of Feed Supplementations on Asian Buffaloes: A Review

Simple Summary

Apart from feeding with forages, dietary supplementation with concentrate and rumen bypass fat is one of the feeding strategies to enhance nutrient availability and improve buffalo performance and productivity. This review paper thoroughly discussed the utilization of concentrate and bypass fat as dietary supplementation in buffalo feeding, and discussed the effects on performance, fermentation characteristics and general health of buffaloes to give better insight about the potential and challenges of dietary supplementation in buffalo diet. Based on the literature studies, it can be summarized that supplementation of concentrate and bypass fat in buffaloes may overcome the nutritional problems and improve the growth performance, health status, rumen environment and carcass traits.

Abstract

With the increase in the global buffalo herd, the use of supplementation in the ruminant feeding has become an important area for many researchers who are looking for an isocaloric and isonitrogenous diet to improve production parameters. In order to improve the performance of the Asian water buffalo, the optimal balance of all nutrients, including energy and protein, are important as macronutrients. Dietary supplementation is one of the alternatives to enhance the essential nutrient content in the buffalo diet and to improve the rumen metabolism of the animal. Researchers have found that supplementation of concentrate and rumen bypass fat could change growth performance and carcass traits without causing any adverse effects on the buffalo growth. Some studies showed that dry matter intake, body condition score and some blood parameters and hormones related to growth responded positively to concentrate and rumen bypass fat supplementation. In addition, changes of feeding management by adding the supplement to the ruminant basal diet helped to increase the profit of the local farmers due to the increased performance and productivity of the animals. Nevertheless, the effects of dietary supplementation on the performance of ruminants are inconsistent. Thus, its long-term effects on the health and productivity of buffaloes still need to be further investigated.

Dietary Energy Levels Affect Growth Performance through Growth Hormone and Insulin-Like Growth Factor 1 in Yak (Bos grunniens)

The objective of this study was to investigate the effects of different dietary energy levels on serum concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1), as well as gene expression of their associated binding proteins and receptors in yak. Fifteen adult male yaks with BW of 276.1 ± 3.5 kg were allotted in three dietary groups and were fed with low (LE), medium (ME), and high energy (HE) level diet having different NEg of 5.5 MJ/kg, 6.2 MJ/kg, 6.9 MJ/kg, respectively. The effects of these treatments on ADG, BW, ADFI, and feed conversion ratio were significant (p < 0.05) throughout the experimental period. Serum GH concentration decreased (p < 0.05) with an increase in dietary energy level on d 30 and d 60. While IGF-1 concentration was higher (p < 0.05) in ME group, as compared to LE and HE groups on d 60. The expression level of growth hormone receptor (GHR) was decreased (p < 0.001) and IGF-1 was increased with the increase in the dietary energy level. The relative expression of insulin-like growth factor binding protein 3 (IGFBP-3) was higher (p < 0.001) in ME and HE groups, except the LE group. In conclusion, our findings provide a first insight into the combined effect of GH and IGF-1 in controlling the metabolism and productivity of yak. It also showed that medium energy level diet contributed to promote growth performance of yak during the cold season.

IGF-I gene polymorphism, but not its blood concentration, is associated with milk fat and protein in Holstein dairy cows

We estimated the allele and genotype frequencies of IGF-I/SnaBI gene polymorphism and the concentration of this protein in Holstein dairy cows. We also examined the association with milk yield (305-day milk yield) and milk components (fat and protein percentage, and 305-day milk protein and fat yield). Blood IGF-I levels were measured and genotyping was performed on 250 Holstein cows of four different herds. In the association studies, traits of interest were analyzed using the GLM procedure of SAS; means of the IGF-I level among genotypes were compared by the LSMeans test. The AB and AA genotypes were the most (0.583-0.661) and least (0.083-0.192) frequent in the herds, respectively; the frequency of the BB genotype ranged from 0.201 to 0.333. The frequency of the A allele ranged from 0.375 to 0.495, while the frequency of the B allele ranged from 0.504 to 0.625, being the dominant allele. The mean level of IGF-I was 107 +/- 22 ng/mL for all groups, without any significant correlation with the production traits. Association of IGF-I/SnaBI genotypes with percentage of fat and protein in the milk was relatively high (P < 0.1 and P < 0.05, respectively); the AB genotype was superior to AA and BB genotypes. We concluded that this marker should be considered for milk component selection in Holstein dairy cattle.

Novel polymorphisms of the growth hormone gene and their effect on growth traits in Chinese goats

The polymorphisms of the growth hormone (GH) gene were analyzed in 686 individuals from four goat populations, Three haplotypes (A, B and C) and three observed genotypes (AA, AB and AC) were detected at the P2 locus, and three haplotypes (E, F and G) and three observed genotypes (EE, EF and EG) were also detected at the P4 locus. In addition, five single nucleotide polymorphisms (SNPs)-A112G, C142T (Gly>Ser), C214T (P2 locus), C266A (Pro>His) and C214T (P4 locus, Arg>Trp), were identified by GH gene sequencing and PCR-SSCP analysis. The SNPs loci were in Hardy-Weinberg disequilibrium in three goat populations (P<0.05). Association of polymorphisms with growth traits was done in BG, F1 and F1 populations, which were shown to be associated with growth traits in three goat populations. The SNPs in the goat GH gene had significant effects on growth traits (P<0.05). suggesting that the GH gene is a strong candidate gene that affects growth traits in goat.

Physiology and pathophysiology of growth hormone-binding protein: methodological and clinical aspects

Circulating GH is partly bound to a high-affinity binding protein (GHBP), which in humans is derived from cleavage of the extracellular domain of the GH receptor. The precise biological function GHBP is unknown, although a regulation of GH bioactivity appears plausible. GHBP levels are determined by GH secretory status, body composition, age, and sex hormones, but the cause-effect relationships remain unclarified. In addition to the possible in vivo significance of GHBP, the interaction between GH and GHBP has methodological implications for both GH and GHBP assays. The present review concentrates on methodological aspects of GHBP measurements, GHBP levels in certain clinical conditions with a special emphasis on disturbances in the GH-IGF axis, and discusses the possible relationship between plasma GHBP and GH receptor status in peripheral tissues.

Effects of polymorphic microsatellites in the regulatory region of IGF1 and GHR on growth and carcass traits in beef cattle

Growth hormone (GH), insulin-like growth factors 1 and 2 (IGF1 and IGF2) and their associated binding proteins and transmembrane receptors (GHR, IGF1R and IGF2R) play an important role in the physiology of mammalian growth. The objectives of the present study were to estimate the allele and genotype frequencies of microsatellite markers located in the 5'-regulatory region of the IGF1 and GHR genes in beef cattle belonging to different genetic groups and to determine effects of these markers on growth and carcass traits in these animals under an intensive production system. For this purpose, genotyping was performed on 384 bulls including 79 Nellore, 30 Canchim (5/8 Charolais + 3/8 Zebu) and 275 crossbred animals originating from crosses of Simmental (1/2 Simmental, n = 30) and Angus (1/2 Angus, n = 245) sires with Nellore females. The effects of substituting L allele for S allele of GHR microsatellite across Nellore, Canchim and 1/2 Angus were significant for weight gain and body weight (P < 0.05). The IGF1 microsatellite allele substitutions of 229 for 225 within Nellore group and of 225 for 229 within 1/2 Angus were not significant for any of the traits.

Regulation of development and metabolism of adipose tissue by growth hormone and the insulin-like growth factor system

White adipose tissue plays a key role in the regulation of the energy balance of vertebrates. This tissue is also now recognized to secrete a variety of factors such as leptin, which is thought to be involved in the modulation of adipose mass. Unlike other tissues, adipose tissue mass has considerable capacity to expand. The review deals primarily on the regulation of development and metabolism of adipose tissue by growth hormone (GH) and the insulin-like growth factor (IGF) system, with a special focus on the pig. The anti-insulin effects of GH are well-documented in pigs as in other species. In vitro exposure of adipose precursor cells to GH leads to a decrease in differentiation of those cells in pigs, in contrast to data obtained in murine cell lines. In vivo treatment and prolonged in vitro incubation of adipose tissue or isolated adipocytes with GH result in a decrease in glucose transport and lipogenesis, especially at the level of the fatty acid synthase gene, resulting in a reduction of the lipid content and adipose tissue mass. The mechanism by which GH antagonizes insulin stimulation of lipogenesis is still unresolved, as it is not mediated by protein kinase A, protein kinase C and Janus kinase-2 at the signaling level, or upstream stimulatory factor 1 or sterol regulatory element binding protein-1 at the transcriptional level. GH is apparently the main regulator of IGF-I mRNA expression in adipose tissue, however, the effects of IGF-I on this tissue are rather unclear.

Role of the somatotropic axis in the mammalian metabolism

The metabolism in mammalian is regulated by multiple levels of hormone action, with complex feedback and control mechanisms. The somatotropic axis, essentially consisting of growth hormone (GH), insulin-like growth factors (IGF-I and -II), their associated carrier proteins, and receptors, plays a key role in the control of the regulation of metabolism and physiological process. Among this axis, other hormones like insulin, leptine, glucocorticoids or thyroid hormones are involved in this mechanism by modulating GH and/or IGF-I synthesis and availability. This review summarizes the complexity of the regulation of the metabolism by the somatotropic axis using different examples such as special nutritional situations or growth promoters administration.

GH and IGF-I binding in adipose tissue, liver, and skeletal muscle in response to milk intake level in piglets

Two experiments were undertaken to get a better understanding of the regulation of the GH/IGF-I axis by nutritional status in suckling piglets. In experiment 1, 18 newborn unsuckled piglets were bottle-fed low (L), intermediate (I), or high (H) levels of sow colostrum and milk from birth to 7 days of age. L and H levels corresponded to maintenance requirement and ad libitum intake, respectively. Plasma IGF-I and 43-39 kDa IGFBP levels decreased (P<0.05) with the reduction of milk intake. Specific binding of (125)I-bGH in liver decreased (P<0.01) with decreasing milk intake. It did not differ (P>0.1) between the groups in skeletal muscle. Specific binding of (125)I-IGF-I increased (P<0.05) with decreasing milk intake in skeletal muscle but did not differ (P>0.1) between the three groups in liver. In experiment 2, variation in milk intake was induced by litter size manipulation. In the 24 h following birth, the litter sizes of six litters were normalized to 6 (L6) or 12 piglets (L12). Animals were killed at 21 days of age. Plasma IGF-I concentrations (P<0.001) and 43-39 kDa IGFBP levels (P<0.05) were lower in L12 than in L6. Specific binding of (125)I-bGH in adipose tissue, liver, and skeletal muscle did not differ (P>0.1) between the two groups. Specific binding of (125)I-IGF-I in liver was lower (P<0.001) in L12 than in L6, whereas it did not differ (P>0.05) between groups in other tissues. In conclusion, the present report shows that undernutrition consistently decreases plasma IGF-I and 43-39 kDa IGFBP levels but produces variable responses at the GH and IGF-I binding levels in piglets.

The effect of GH and IGF-I on preadipocytes from Large White and Meishan pigs in primary culture

Proliferation and differentiation of preadipocytes from 7-day-old Large White (LW) and Meishan (MS) pigs were studied in primary culture. The effects of porcine GH (pGH) and IGF-I as well as the expression of GH (GHR) and IGF-I (IGF-IR) receptors mRNA were examined. Preadipocytes were exposed to serum-supplemented and serum-free medium to determine proliferation and differentiation, respectively. Proliferation was higher in MS than in LW pigs. Treatment with pGH (2 nM) or IGF-I (10 nM) resulted in a similar decrease in proliferation in LW and MS pigs. Parameters assessing differentiation and the effects of pGH and IGF-I on differentiation did not differ between the two breeds. The percentage of differentiating cells and LPL and ME activities were markedly reduced by pGH. IGF-I did not reduce differentiation significantly. Both GHR and IGF-IR mRNA were expressed in adipose tissue, adipocytes, preadipocytes, and 6-day-cultured cells from LW and MS pigs. The similar action of pGH and IGF-I on preadipocyte proliferation and differentiation, associated with the similar expression of GHR and IGF-IR mRNA in LW and MS pigs, suggests that the GH/IGF-I axis is not impaired in MS pigs. The difference in preadipocyte proliferation observed between LW and MS pigs could account for their adiposity difference.

Leptin expression in porcine adipose tissue is not increased by endotoxin but is reduced by growth hormone

The physiologic response to infection includes reductions in tissue concentrations of anabolic growth factors as a means of reducing growth and conserving nutrients for immunologic processes. This repartitioning of nutrients is accompanied by anorexia, which has been linked to increased leptin expression. Furthermore, leptin and growth hormone (GH) concentrations are inversely related, with leptin being required for normal GH release. The objective of this study was to determine if pretreatment with GH would influence endotoxin-induced changes in leptin expression or attenuate endotoxin-induced reductions in serum insulin-like growth factor-1 (IGF-1) and IGF-1 expression in liver and longissimus muscle. In experiment 1, 40 pigs were assigned to four treatments (n = 10 per treatment) arranged as a 2x2 factorial with GH (s.c. injection, 2 mg 1 h before challenge and 2 mg 2 h after challenge) and endotoxin (single i.m. injection, 25 microg/kg body weight) as main effect variables. Pretreatment with GH resulted in a marked increase (p<0.001) in serum GH within 1 h that was sustained throughout the study. Endotoxin challenge reduced (p<0.003) serum IGF-1 independent of GH (GH x endotoxin, p>0.682), and reduced (p<0.05) IGF-1 expression in longissimus muscle but not liver. Leptin mRNA abundance was reduced 56% (p<0.005) by GH but was not affected by endotoxin (p>0.81). In experiment 2, 36 pigs (n = 12 per treatment) were either allowed ad libitum feed consumption with no injection or deprived of feed and injected twice with either saline or endotoxin 24 h apart. Feed deprivation reduced leptin expression (p<0.05). However, endotoxin did not change leptin expression but markedly increased (p<0.05) serum haptoglobin. These data indicate that changes in IGF-1 status in endotoxin-challenged pigs are independent of serum GH and that leptin expression is not increased by endotoxin challenge in the pig. These data also indicate a regulatory linkage between GH and leptin in vivo.

Expression of a functional porcine growth hormone receptor cDNA in mouse L cells

Porcine (p) growth hormone receptor (GHR) complementary DNA (cDNA) has been cloned and the primary amino acid structure was deduced from the nucleotide sequence. A comparison of pGHR to other GHRs revealed an approximately 70% similarity in amino acid sequence (Cioffi et al., 1990). Hybridization of this receptor cDNA to RNA samples isolated from various porcine tissues revealed a single RNA band of 4.2 kb. The full-length pGHR cDNA was subcloned into an eukaryotic expression vector, transcription of which was directed by the mouse metallothionein-I transcriptional regulatory sequence. Stable mouse L cell lines which express the pGHR cDNA were established. Approximately 80% of the cell lines were found to possess pGHR mRNA (approximately 2 kb) which corresponds to the length of the cloned pGHR cDNA. Binding studies showed that the stable cell lines were capable of specifically binding 125I-labeled pGH with a dissociation constant (Kd) of approximately 1.0 nM. The apparent molecular mass of the receptor, as determined by cross-linking studies, was found to be 118 kDa. Also, the receptor-ligand complex could be internalized. These results suggest that an active form of pGHR had been cloned and stably expressed in mouse L cells.