MON-184 Disrupted ACTH-Cortisol Temporal Coupling in Healthy Men After an Overnight Fast, and the Modulatory Role of Orally Ingested Macronutrients

While long term fasting is reported to augment the corticotropic function, effect of short term (overnight) fasting on ACTH-cortisol coordinated release pattern and potential effect(s) of nutrient intake is not fully defined. Eleven healthy men (age: 33-70 yrs, BMI 20.4-31.5 kg-m2) were studied after overnight fast on 4 separate days, involving oral ingestion of 300 ml of either water, dextrose, protein, or lipid solutions. Test meals were isocaloric (400 kcal). Sessions were 6.5 h long, starting at 0800-0900 hrs. Blood was collected at 10-min intervals for ACTH (pg per mL), and cortisol (µg per dL) measurements. Linear regression, cross-correlation, deconvolution, and ApEn were used for data analyses. ACTH and cortisol concentration time series during short-term fast (water day) were found not to be chronologically coupled per linear regression (r2= 0.0014, P=0.82), and cross-correlation (r= - 0.156, lag=150 min) statistics. Oral intake of the 3 macronutrients improved the temporal relationship between ACTH and cortisol concentrations, verified by linear regression (r2:P- dextrose 0.54:0.0001, protein 0.65: 0.0001, lipid 0.42:0.0001), and cross-correlation (r:lag in min- dextrose 0.8:10, protein 0.77:10, lipid 0.78:20). Oral ingestion of either macronutrient did not significantly alter mean ACTH and cortisol concentrations and their respective secretion pattern (total, pulsatile, basal) over the period of 6.5 hr. However compared to the control (water) session, dextrose ingestion evoked less frequent and larger ACTH secretory bursts, and more regular ACTH and cortisol secretory patterns. In this study, we have observed lack of concordance between ACTH and cortisol after overnight fasting, which is restored with oral intake of macronutrients. This effect appears to be uniform among the 3 macronutrients, except for less frequent and lager ACTH bursts and more regular ACTH and cortisol release events after dextrose intake. These findings and the specific role of nutrients being direct or via physiologic nutrient-induced hormonal adaptation warrants future investigation.