Acute ketone monoester ingestion increases monocyte lysine β-hydroxybutyrylation and plasma β-hydroxybutyrate amino acid conjugates in humans.

Acute ketone monoester ingestion significantly increased blood BHB concentration, peaking at 2 hours post-consumption.

• 13 healthy adults (7 females, 6 males; age 28 ± 7 yr) consumed 0.750 g/kg body mass KME [(R)-3-hydroxybutyl (R)-3-hydroxybutyrate]
• Blood BHB concentration significantly increased after KME consumption (P < 0.0001)
• Peak BHB concentration at 2 h was 5.0 ± 0.8 mmol/L
• Blood samples were collected before and 2 hours after consumption, coinciding with peak plasma BHB concentration

Monocyte lysine β-hydroxybutyrylation (Kbhb) was significantly increased approximately 70% after KME consumption.

• Monocytes (CD14+) were isolated by negative immunomagnetic selection
• Kbhb was assessed by immunoblotting
• Compared with baseline, monocyte Kbhb was significantly increased after 2 h (~70% increase; P = 0.004)
• This study provides the first in vivo evidence that exogenous ketone supplementation elevates lysine Kbhb in monocytes of healthy humans

Plasma BHB-amino acid conjugates were significantly increased at 2 hours after KME ingestion.

• BHB-amino acid conjugates were quantified by mass spectrometry
• BHB-phenylalanine, BHB-leucine, BHB-valine, and BHB-methionine were all increased at 2 h (P < 0.0001)
• These BHB-amino acid conjugates were recently discovered circulating molecules hypothesized to have functional physiological consequences

Changes in capillary blood BHB and BHB-amino acid conjugate concentrations were positively correlated, suggesting a dose-dependent relationship.

• Correlation coefficient r ≥ 0.58 for changes in capillary blood BHB and BHB-amino acid concentrations
• Statistical significance: P ≤ 0.046
• The positive correlation was observed across all measured BHB-amino acid conjugates (BHB-phenylalanine, -leucine, -valine, and -methionine)

Endogenous ketosis during fasting is known to induce Kbhb of lysine residues on proteins in human immune cells and increase circulating BHB amino acid conjugates.

• Prior to this study, it was unknown whether similar modifications occur with acute consumption of an exogenous ketone monoester supplement
• Both Kbhb and BHB-amino acid conjugates are hypothesized to have functional physiological consequences
• KME supplementation robustly increases circulating BHB