High-Dose Spermidine Supplementation Does Not Increase Spermidine Levels in Blood Plasma and Saliva of Healthy Adults: A Randomized Placebo-Controlled Pharmacokinetic and Metabolomic Study

Abstract

(1) Background: Spermidine is a biogenic polyamine that plays a crucial role in mammalian metabolism. As spermidine levels decline with age, spermidine supplementation is suggested to prevent or delay age-related diseases. However, valid pharmacokinetic data regarding spermidine remains lacking. Therefore, for the first time, the present study investigated the pharmacokinetics of oral spermidine supplementation. (2) Methods: This study was designed as a randomized, placebo-controlled, triple-blinded, two-armed crossover trial with two 5-day intervention phases separated by a washout phase of 9 days. In 12 healthy volunteers, 15 mg/d of spermidine was administered orally, and blood and saliva samples were taken. Spermidine, spermine, and putrescine were quantified by liquid chromatography-mass spectrometry (LC-MS/MS). The plasma metabolome was investigated using nuclear magnetic resonance (NMR) metabolomics. (3) Results: Compared with a placebo, spermidine supplementation significantly increased spermine levels in the plasma, but it did not affect spermidine or putrescine levels. No effect on salivary polyamine concentrations was observed. (4) Conclusions: This study's results suggest that dietary spermidine is presystemically converted into spermine, which then enters systemic circulation. Presumably, the in vitro and clinical effects of spermidine are at least in part attributable to its metabolite, spermine. It is rather unlikely that spermidine supplements with doses <15 mg/d exert any short-term effects.

Keywords: COVID-19; SARS-CoV-2; autophagy; putrescine; spermidine; spermine.

Figure 1

Study design.

Figure 2

A modified flow chart of the randomization phases according to CONSORT 2010 [43].

Figure 3

Detailed sequences of the two study phases. Depending on the randomization, the placebo was used first in intervention phase 1, followed by verum supplementation in phase 2, or vice versa. Five capsules: intake of five capsules of placebo or verum with the first bite of the meal; samples: blood and saliva samples were taken; breakfast: standard breakfast; breakfast at home: self-selected, non-standardized breakfast at home; lunch: standard lunch; snack: standard snack; dinner: standard dinner; dinner at home: self-selected, non-standardized dinner at home; 100 mL of water: intake of 100 mL of water immediately after taking the sample at the respective time. After lunch, water intake was provided ad libitum. Colored days/times mark study-related activities at the study center. Days/times with study-related activities at home or without any study-related activities are not colored.

Figure 4

Concentrations (mean ± SD, n = 12) of spermidine (left) and spermine (right) in plasma with time point t = 0 h corresponding to first intake of respective allocated treatment and respective baseline concentration obtained immediately before intake (A) at first measurement day of verum or placebo treatment, respectively (which can be day 1 or day 15 due to randomization), 0–8 h after first administration of verum or placebo; (B) first samples of days 1, 5, 15, and 19 and days 2, 3, 4, 16, 17, and 18 (all fasted matutinal samples of each intervention phase); (C) day 5 and day 19 (last measurement day of each intervention phase which can be verum or placebo due to randomization), 96–104 h after multiple administration of verum or placebo.

Figure 5

Spermine concentration in plasma measured for 0–104 h was determined by AUC_0-tlast after placebo and verum interventions.

Figure 6

Salivary concentrations (mean ± SD, n = 12) of spermidine (left) and spermine (right); (A) day 1 and day 15 (first measurement day of each intervention phase), 0–8 h after first administration of verum or placebo; (B) first sample days 1, 5, 15, and 19 and days 2, 3, 4, 16, 17, and 18 (all fasted matutinal samples of each intervention phase); (C) day 5 and day 19 (last measurement day of each intervention phase), 96–104 h after multiple administration of verum or placebo.

Figure 7

Correlation of saliva and plasma concentrations of spermidine (A) and spermine (B) for the verum intervention over all time points. Data were analyzed using Spearman’s rank correlation coefficient.

Figure 8

Correlation of saliva and plasma concentrations of spermidine (A) and spermine (B) for the placebo intervention over all time points; data were analyzed using Spearman’s rank correlation coefficient.