Comparative aspects of the apparent Michaelis constant for neutral amino acid transport in several animal tissues

Effects of L-isoleucine and L-valine on hot flushes and serum homocysteine: a randomized controlled trial

OBJECTIVE

To investigate whether L-isoleucine was effective in the treatment of hot flushes and whether L-isoleucine, L-valine, or the combination of both amino acids reduced fasting serum homocysteine.

METHODS

After a 1-week baseline period, 100 postmenopausal women experiencing at least five moderate-severe hot flushes per day were randomized with equal probability to one of four groups (phase 1/phase 2): placebo/L-valine, placebo/L-valine and L-isoleucine, L-isoleucine/L-valine, and L-isoleucine/L-valine and L-isoleucine. Phase 1 was 12 weeks long, and phase 2 was 10 weeks long. Patients took five capsules by mouth, twice a day throughout the study, with each capsule containing 500 mg of compound. Data were obtained from daily hot flush diaries, fasting blood work, and several questionnaires. The primary outcome variable was the percent change in hot flush composite score from baseline to week 12.

RESULTS

In phase 1 of the study, there were no significant differences between the L-isoleucine and placebo groups for any of the outcome measures. At week 12, there was a mean 13.9% decrease in hot flush composite score compared with baseline in the L-isoleucine group and a mean 25% decrease in the placebo group (P=.28). In phase 2 of the study, there was no significant change in fasting serum homocysteine levels associated with any of the amino acid therapies.

CONCLUSION

L-isoleucine therapy appears to be ineffective in the treatment of hot flushes in postmenopausal women. L-isoleucine and L-valine, either alone or in combination, appear to have no effect on fasting serum homocysteine levels. CLINCIAL TRIAL REGISTRATION: ClinicalTrials.gov, (www.clinicaltrials.gov), NCT00081952.

LEVEL OF EVIDENCE

I.