Effects of frequency of treatment with recombinant equine somatotropin on selected biological responses in geldings.
Thatcher. C E CE; Thompson. D L DL
Key Findings
- Both daily and every‑other‑day eST increased glucose, insulin, NEFA and lowered plasma urea nitrogen in geldings.
- IGF‑I levels rose higher and earlier with daily injections compared to every‑other‑day dosing.
- Increasing injection frequency (twice or four times daily) produced proportionally larger IGF‑I and insulin spikes, while urea nitrogen reductions were unchanged.
Practical Outcomes
- If you experiment with growth‑hormone‑releasing peptides, dosing more than once a day may amplify IGF‑1 and insulin responses, but the optimal schedule depends on which biomarker you care about. The study is in horses, so human effects are uncertain and any protocol should be tested carefully on an individual basis.
Summary
In horses, giving recombinant growth hormone (eST) either every day or every other day raised blood sugar, insulin, and fatty acids while lowering waste nitrogen, but daily shots boosted IGF‑1 faster. Giving the hormone more than once a day (twice or four times) made IGF‑1 and insulin rise even more, though the waste nitrogen drop was the same no matter how often it was injected.
Abstract
Two experiments compared the efficacies of different treatment frequencies for recombinant equine somatotropin (eST). In Experiment 1, five geldings received daily injections of eST at 20 microg/kg of body weight, and five received every-other-day injections at 40 microg/kg of body weight, for a total of 30 days. Plasma glucose (P=0.0001), insulin (P=0.0135), and non-esterified fatty acid (NEFA, P=0.0001) concentrations increased, and plasma urea nitrogen (PUN) concentrations decreased (P=0.0001), in both groups, and only minor differences (P<0.05) occurred between the two groups. Insulin-like growth factor-I (IGF-I) concentrations increased (P=0.0001) in both groups over time, and were higher (P<0.05) after day 2 in geldings treated daily. Endogenous somatotropin (ST) response to secretagogue was inhibited (P<0.05) in geldings receiving daily injections relative to those receiving every-other-day injections. In Experiment 2, 16 geldings were allotted to four groups of four. A control group received daily saline injections, and the other three groups received eST at 20 microg/kg of body weight daily as a single injection, two injections (every 12h), or four injections (every 6h), for a total of 14 days. Plasma IGF-I and insulin concentrations increased (P<0.05) in all groups receiving eST, with the responses being proportional to injection frequency. In contrast, PUN concentrations decreased (P<0.05) in all groups equally. In conclusion, the efficacy of daily versus every-other-day injections of eST depends upon the response to be measured, and for IGF-I concentrations, the every-other-day regimen was not acceptable. Injection frequencies greater than once daily were more efficacious for IGF-I and insulin concentrations, but not for PUN concentrations. Thus, the optimum injection regimen for any new application for eST cannot simply be inferred from other biological responses, and will need to be determined empirically.
Study Information
pubmed
2002
10.1016/s0739-7240(02)00120-0