Kinetics of myo-inositol loading in women of reproductive age

Myo-inositol plays a key role in an important intracellular signalling pathway. A deranged myo-inositol metabolism has been associated with neural tube defects. A myo-inositol loading test was performed to investigate the kinetics in healthy women of reproductive age.

Five healthy non-obese females [mean age (standard deviation: SD) 22.8 (2.2) years] were recruited at the University Medical Center Nijmegen. Blood samples were drawn fasting and at 20, 40, 60, 90, 180 and 270 min after ingestion of 100 mg/kg body weight of myo-inositol. Urine samples were collected before myo-inositol loading and at 180 and 270 min post-loading. Samples were analysed for serum myo-, epi- and scyllo-inositol and glucose concentrations by gas chromatography. Plasma insulin concentrations were determined by radio-immunoassay. Random intercept models were fitted to evaluate the data.

The estimated myo-inositol and scyllo-inositol concentrations both reached maximum values at 180 min post-loading, respectively: mean (SD) 101.5 (9.2) micro mol/L and 1.09 (0.11) micro mol/L. The estimated plasma insulin and serum glucose concentrations decreased slightly but significantly during the experiment: P < 0.0001 and P < 0.05, respectively. At 180 and 270 min post-loading, urinary myo-inositol concentrations were increased and urinary glucose concentrations were unchanged.

Myo-inositol enters the bloodstream quickly after oral ingestion and a small amount of myo-inositol is converted to scyllo-inositol. The synthesis of glucose from myo-inositol could not be detected by serum measurements. These data can be used in further research into the association between myo-inositol and neural tube defects.