Effect of active immunization against growth hormone releasing factor on concentrations of somatotropin and insulin-like growth factor I in lactating beef cows.
Moore. K L KL; Armstrong. J D JD; Harvey. R W RW; Campbell. R M RM; Heimer. E P EP
Key Findings
- Active immunization against GRF‑1‑29 reduced the frequency and magnitude of GH (somatotropin) pulses in lactating cows.
- Serum IGF‑1 concentrations were consistently lower in vaccinated cows compared to controls.
- Vaccinated cows did not increase GH in response to an opioid agonist (FK33‑824) or an arginine challenge, whereas control cows did.
- A lower dose and single booster still achieved some reduction in GH/IGF‑1, but response varied among individual cows.
Practical Outcomes
- For biohackers, the study shows that blocking GHRH can effectively lower GH and IGF‑1 levels, which some associate with longevity benefits. However, the method used (active immunization) is not practical for humans, and the data come from cows, not people. If lowering IGF‑1 is a goal, exploring GHRH antagonists or other pharmacologic blockers may be more feasible, but further human research is needed.
Summary
In dairy cows, vaccinating against the hormone‑releasing factor (GRF‑1‑29) dramatically cut the amount and spikes of growth hormone (GH) and the downstream hormone IGF‑1. The cows that got the vaccine showed almost no GH release after typical triggers, and their IGF‑1 stayed low throughout lactation.
Abstract
Two experiments were conducted to determine the effects of immunoneutralization of growth hormone-releasing factor [GRF(1-29)-NH2] on concentrations of somatotropin (ST) and insulin-like growth factor I (IGF-I) in lactating beef cows. In Experiment 1, multiparous Hereford cows were immunized against 2 mg GRF(1-29)-(Gly)4-Cys-NH2 conjugated to human serum albumin (GRFi, n = 3) or 2 mg human serum albumin (HSAi, n = 3) at 52 +/- 1 d prior to parturition. Boosters (1 mg) were administered on days 12, 40 and 114 postpartum (pp). Serum samples were collected at 15-min intervals for 5 hr on days 18, 46 and 120 pp, followed by administration (IV) of an opioid agonist (FK33-824; 10 micrograms/kg) and an antagonist (naloxone; .5 mg/kg) at hours 5 and 7, respectively. A GRF-analog ([desamino-Tyr1, D-Ala2, Ala15] GRF (1-29)-NH2; 3.5 micrograms/kg) and arginine (.5 g/kg) were administered at hour 10 on days 47 and 121, respectively. Percentage binding of [125I]GRF (1:100 dilution of serum) 28 d after primary immunization was greater in GRFi (14.3 +/- 4.9) than in HSAi (.7 +/- .3) cows. Binding increased to 29.3 +/- 6.5% after first booster in GRFi cows. Episodic release of ST was abolished by immunization against GRF; concentration and frequency of release of ST were lower (P less than .05) in GRFi than in HSAi cows on all days pp. Concentrations of IGF-I were lower in GRFi than in HSAi cows throughout lactation. Serum ST failed to increase following FK33-824 or arginine in GRFi; however, ST increased after both compounds in HSAi cows. Concentrations of ST following GRF-analog were greater (P less than .05) in HSAi than in GRFi cows. Experiment 2 was conducted to determine if a lower dose of antigen and a single booster would be sufficient to lower ST and IGF-I in lactating cows. Multiparous Hereford and Angus cows were assigned to GRFi (n = 6) or HSAi (n = 6). Primary (1.2 mg) and booster (.5 mg) immunizations were administered -14 and 8 d from calving, respectively. Cows were restricted to 60% of recommended intake of energy during lactation in order to elevate concentrations of ST. Serum samples were collected at 15-min intervals for 6 hr on days 26, 50, 73, 90 and 109 pp. Two of six GRFi cows had binding less than 10% (1:1,000 dilution of serum) and were omitted from further analyses.(ABSTRACT TRUNCATED AT 400 WORDS)
Study Information
pubmed
1992
10.1016/0739-7240(92)90026-t