Endocrine Abstracts

Background: Chronic hypercortisolism is known to alter the circadian rhythm and to impair protein metabolism. Altered amino acid (AA) and biogenic amine (BA) levels were found in basal blood in patients with hypercortisolism. However, poor information is available on the physiologic circadian fluctuation of these molecules. Furthermore, the potential derangement caused by hypercortisolism was never investigated.

Aim: To characterize diurnal levels and fluctuations of AA and BA in convenient dried blood spots (DBS) from finger-prick in healthy subjects (HS) and in patients affected by autonomous cortisol secretion (ACS) or Cushing syndrome (CS).

Methods: HS (38.0±15.5 y; n=9), ACS (64.8±8.4 y; n=6) and CS (53.4±8.0 y; n=5) patients underwent a 7-days standardized isocaloric Mediterranean diet. On the 7th day, subjects collected DBS at 7 time-points: 30 min before and 2 h after breakfast, lunch and dinner, and at bedtime. 21 AA and 21 BA were measured in DBS by LC-MS/MS.

Results: Compared to HS, ACS patients had lower His (P=0.026), while CS patients had lower Asn (P=0.030) and higher spermidine (P=0.003). CS also had higher spermine (P=0.028) and t4-OH-Pro (P=0.032) compared to ACS patients. A daily rhythm was detected in HS for 11 AA (Met, Leu, Ile, Arg, Cit, Glu, His, Pro, Trp, Val; P:0.001-0.037) and Met-SO (P:0.010), mostly with levels higher at awakening and bedtime, and lower in the morning (positive quadratic trend). Of these, some maintained their rhythm also in ACS (Ile, Leu, Trp, Val, Met-SO; P:0.043); however, only Leu maintained a similar rhythm in CS patients (P:0.006). Fluctuation of other compounds were found in ACS (Gly, His, Lys, Orn, Phe, Ser, Thr, t4-OH-Pro; P:<0.001-0.006) and in CS (asymmetric-dimethylarginine (ADMA), creatinine, spermine; P:0.003-0.018) with variable trends. AUCs of Arg (R:0.632, P:0.037), spermidine (R:0.743, P:0.009), spermine (R:0.729, P:0.011) and taurine (R:0.788, P:0.004) were directly correlated with post-dexamethasone test cortisol. AUCs of ADMA (R: -0.513, P:0.030) and Orn (R:-0.573, P:0.013) were negatively associated with fat free mass.

Conclusions: A panel of AA displayed a physiologic diurnal fluctuation consistent with day/night protein anabolic/catabolic processes. Daily fluctuations were revealed in ACS for a different panel of AA, and were almost all lost in CS. ACS and CS also showed disease specific fluctuations in some BA. Finally, ACS showed a deranged histidine metabolism, whereas CS showed an enhanced polyamine pathway.