Serum Concentrations of IGF-1 and Steroids in Growing Boars, Barrows and Gilts.

It is known that boars, barrows, and gilts grow at different rates and with varying defficiencies. Gilts generally eat less, grow slower, but are more efficient and have leaner carcasses than. One way in which growth may be regulated in pigs is through changes in circulating IGF-I and (or) IGF binding proteins (IGFBPs) Insulin-like growth factors-I has been shown to stimulate amino acid and lgucose uptake and increase protein synthesis, while IGFBPs can function to inhibit or protentiate the actions of IGFs. Estradiol has been demonstrated to regulate expression of the IGF system. Administration of estradiol increased serum concentrations of IGF-I and relative amounts of IGFBP-3 and -4 in the ewe. Boars produce more estradiol than gilts or barrows and also exhibit greater serum concentrations of IGF-1 and IGFB-3. Boars produce more testosterone than gilts or barrows, which may work in concert with stradiol to increase circulating levels of IGF-1 and IGFBP-3 similar to what is observed in implanted steers. The objectives of the current experiment were to determine 1) if serum concentrations of IGF-1, estradiol-17β, testosterone, and relative amounts of IGFBPs differ in growing boars, barrows, and gilts, and 2) if growht rate and cirulating levels of IGF-1 and relative amounts of serum IGFBPs were related to serum concentrations of estradiol and testosterone

Effects of Administration of Estradiol-17P on the Serum and Anterior Pituitary IGF System in Pigs

The anterior pituitary (AP) gland functions as a storage and releasing unit for several hormones; growth hormone (GH), gonadotrophins (luteinizing hormone and follicle stimulating hormone), prolactin, adrenocorticotropin hormone, and tyroid stimulating hormone. Luteinizing hormone (LH) functions to increase ovarian follicular growth and maturation and responds to increasing concentrations of estradiol-17β (E2) that occur at estrus to cause ovulation. Production and secretion of the protein, insulin-like grwoth factor-I (IGF-I), occurs primarily in the liver, in response to GH release from the anterior pituitary gland. Insulin-like growth factor-I increases glucose uptake, amino acid transport, and glycogen synthesis resulting in increased protein accretion Mitogenic effects of IGF-I can be manifested by increases in DNA, RNA, and protein. Furthermore, IGF-I stimulates differentiation at low levels usually preceding a mitogenic response. The biological effects of IGF-I are mediated by its interaction with the IGF type 1 receptor and modulated by IGF binding proteins (IGFBPs). Insulin-like grwoth factor-I, IGFBPs, and IGF receptors have been detected in the AP gland of several species and may exert regulatory effects at the hypthalmaic-hypophyseal level affecting gonadotrophins, and in turn, reproductive performance

Effects of High Protein/low Carbohydrate Swine Diets During the Final Finishing Phase on Pork Muscle Quality

Pork color and water-holding capacity defects (pale, soft and exudative, or PSE pork) are functions of muscle pH and cost of the U.S. pork industry $60 million per year (Morgan et al., 1994). Pork with a low ultimate hP (pH\u3c5.5) has a paler color and lower water-holding capacity. Lactic acid build-up is responsible for lowering pH from 7.0, at the time of death, to 5.2-6.0 at 24h postmortem. Postmortem glycolysis produces lactic acid and can only occur in the presence of the substrate glycogen. Therefore, more glycogen in the muscle at slaughter will result in more lactic acid build up and a lower ultimate pH, which will result in a paler color and a lower water-holding capacity (Ellis et al, 1997) Consumption of carbohydrates is the main source of glucose in the blood (Guyton and Hall, 1996). In human studies conducted by Snitker et al., (1997) eight adult males were given one of two isoenergetic diets: a high-carbohydrate diet (75% of energy as carbohydrate, 15% as protein, and 10% as fat), or a low-carbohydrate diet (10% of energy as carbohydrate, 15% as protein, and 75% as fat) for three days. After the three day dietary maniuplation, glycogen content in the vastus lateralis muscle was significatnly lower for the low-carbohydrate subjects; 296 vs 426 mmol glucose/kg dry muscle, respectively (P\u3c0.001) (Snitker et al., 1997). Therefore, this study was conducted to determine if feeding ultra-high protein/low carbohydrate swine diets during the final finishing phase could reduce muscle glycogen and thereby imporve pork muscle quality

The Presence of Growth Hormone Secretagogue Receptor (ghrelin receptor) in Metabolic Tissues of Beef Cattle with Differences in Composition of Gain

Beef steers (n = 72) of similar age, weight (651 ± 3.1 lb), and genetic (Angus crossbred) background were used to determine the effects of growing diet composition (high‐forage vs. high‐concentrate) on the abundance of growth hormone secretagogue receptor (GHS‐R or ghrelin receptor) in metabolically important tissues of beef cattle. At trial initiation (d 0), 8 steers were harvested for initial carcass composition. The remaining 64 steers were allotted, by weight, to pen and treatment was assigned randomly. Treatments were 1) a high‐forage diet fed during the growing period (116 d) followed by a high‐concentrate diet during the finishing period (117‐209 d; GRW‐FNSH) or 2) a high‐concentrate diet fed for the duration of the trial (0‐209 d; FNSH‐FNSH). Steers were allowed ad libitum consumption regardless of dietary treatment. Eight steers per treatment were harvested on d 88, 116, 165, and 209. Immediately following harvest, liver, muscle (sternomandibularis), and subcutaneous adipose tissue samples were collected from each steer and immersed in liquid nitrogen. Longissimus dorsi samples were collected following a 48 h chill to establish a preliminary analysis of GHS‐R abundance within an economically important muscle tissue. Protein separation and quantification was determined using SDSPAGE and Western blotting techniques. Protein abundance was detected using the LI‐COR® system and standardized to β‐Actin. Protein abundance data were analyzed statistically using the GLM procedure of SAS comparing diet, harvest date, and their interaction. Protein abundance of GHS‐R in longissimus dorsi tissue fluctuated relative to serial harvest date (P \u3c 0.001), and was highest on d 88 in both treatment groups. The FNSH‐FNSH steers had increased abundance of GHS‐R in longissimus dorsi on d 88 and 116 compared with the GRW‐FNSH steers. A dietary treatment by serial harvest day interaction (P \u3c 0.05) occurred for protein abundance of GHS‐R in subcutaneous adipose tissue. Abundance of GHS‐R in subcutaneous adipose tissue of the GRW‐FNSH was greatest on d 88, whereas abundance for the FNSHFNSH treatment was greatest at the end of the finishing period (d 209). An interaction of dietary treatment and serial harvest day resulted (P \u3c 0.05) for GHS‐R abundance in liver tissue. The GRW‐FNSH steers had increased liver GHS‐R abundance following realimentation compared with the FNSH‐FNSH steers which were on a continuous plane of nutrition. Protein abundance for liver GHS‐R in both dietary treatments increased quadraticly (P \u3c 0.001) throughout the feeding period. The GHS‐R was not detected in sternomandibularis tissue. Overall liver GHS‐R abundance increased in both dietary treatments following realimentation which is inconsistent with our hypothesis. Increased GHS‐R abundance in various tissues of beef cattle while ghrelin concentrations are high and excess fat deposition is occurring warrants further investigation

URB602 inhibits monoacylglycerol lipase and selectively blocks 2-arachidonoylglycerol degradation in intact brain slices.

The N-aryl carbamate URB602 (biphenyl-3-ylcarbamic acid cyclohexyl ester) is an inhibitor of monoacylglycerol lipase (MGL), a serine hydrolase involved in the biological deactivation of the endocannabinoid 2-arachidonoyl-snglycerol (2-AG). Here, we investigated the mechanism by which URB602 inhibits purified recombinant rat MGL by using a combination of biochemical and structure-activity relationship (SAR) approaches. We found that URB602 weakly inhibits recombinant MGL (IC50 = 223 ± 63 microM) through a rapid and noncompetitive mechanism. Dialysis experiments and SAR analyses suggest that URB602 acts through a partially reversible mechanism rather than by irreversible carbamoylation of MGL. Finally, URB602 (100 microM) elevates 2-AG levels in hippocampal slice cultures without affecting levels of other endocannabinoid-related substances. Thus, URB602 may provide a useful tool by which to investigate the physiological roles of 2-AG and explore the potential interest of MGL as a therapeutic target