The effect of growth hormone-releasing peptide-2 (KP102) administration on plasma insulin-like growth factor (IGF)-1 and IGF-binding proteins in Holstein steers on different planes of nutrition.
Lee. H G HG; Vega. R A RA; Phung. L T LT; Matsunaga. N N; Kuwayama. H H; Hidari. H H
Key Findings
- GHRP‑2 caused an immediate rise in plasma growth hormone in both high‑intake (HI) and low‑intake (LI) steers.
- IGF‑1 levels increased only in the HI group, peaking around Day 2 and returning to baseline by Day 4.
- IGFBP‑3 (38‑43 kDa) and IGFBP‑4 (24 kDa) rose with GHRP‑2 treatment, but again only in the HI steers; IGFBP‑2 decreased in HI steers.
- Nutritional status (caloric intake) modulated the IGF‑1 and IGFBP response to GHRP‑2.
Practical Outcomes
- For self‑experimenters, the study suggests that the IGF‑1‑boosting effects of GHRP‑2 are much stronger when you’re in a caloric surplus or high‑protein diet. Using GHRP‑2 while fasting or on a low‑calorie diet may still raise growth hormone but likely won’t increase IGF‑1. Therefore, if the goal is to elevate IGF‑1 for muscle growth or recovery, pair GHRP‑2 with adequate nutrition rather than using it alone.
Summary
In young Holstein steers, giving the peptide GHRP‑2 (KP102) raised growth hormone and, only when the animals were fed a high amount of food, also boosted IGF‑1 and certain IGF‑binding proteins. When the steers ate less, the peptide still raised growth hormone but did not increase IGF‑1 or the binding proteins.
Abstract
This study was conducted to investigate the nutrition-dependent changes in insulin-like growth factor (IGF)-1 and IGF-binding proteins (IGFBPs) with growth hormone releasing peptide-2 (D-Ala-D-betaNal-Ala-Trp-D-Phe-Lys-NH(2); GHRP-2 or KP102) treatment in growing Holstein steers. Eight 13 month-old Holstein steers were grouped on two levels of feed intake (high intake (HI); 2.43% body weight or low intake (LI); 1.22%) and each group was daily injected with KP102 (12.5 microg/kg body weight/day) or saline solution into the jugular vein during 6-day period. The concentration of plasma GH showed an increase after an i.v. bolus injection of KP102 on Day 1 and Day 6 in both the LI and HI groups. Plasma IGF-1 began to increase 10 hr following an i.v. bolus injection of KP102, but this was only observed in the HI group (P < 0.05). Also, the plasma IGF-1 in the HI group with daily injections was significantly greater than the LI group from Day 1 of KP102 administration (P < 0.05). It reached maximum values of 125.1 +/- 7.6 ng/ml after Day 2, and returned to pre-injection levels after Day 4, however, no change in plasma IGF-1 was observed in LI with administration of KP102. During 6 days of treatment, plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 were significantly higher in KP102 treated steers but only in the HI group (P < 0.05). Plasma 34 kDa IGFBP-2 decreased in the HI group and did not show any change following an injection of KP102. In conclusion, the effect of stimulated endogenous GH with KP102 administration increased plasma IGF-1, 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 levels in the HI group of growing Holstein steers, but not in the LI one. Thus, we strongly believe that the plasma IGF-1 and IGFBPs response to KP102 treatment is modulated by the nutritional status of growing Holstein steers and the increased plasma IGF-1 concentration with KP102 treatment may be regulated by plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 in Holstein steers.
Study Information
pubmed
2000
10.1016/s0739-7240(00)00051-5