Identification of the toxic threshold of 3-hydroxybutyrate-sodium supplementation in septic mice

Abstract

Background In septic mice, supplementing parenteral nutrition with 150 mg/day 3-hydroxybutyrate-sodium-salt (3HB-Na) has previously shown to prevent muscle weakness without obvious toxicity. The main objective of this study was to identify the toxic threshold of 3HB-Na supplementation in septic mice, prior to translation of this promising intervention to human use. Methods In a centrally-catheterized, antibiotic-treated, fluid-resuscitated, parenterally fed mouse model of prolonged sepsis, we compared with placebo the effects of stepwise escalating doses starting from 150 mg/day 3HB-Na on illness severity and mortality (n = 103). For 5-day survivors, also the impact on ex-vivo-measured muscle force, blood electrolytes, and markers of vital organ inflammation/damage was documented. Results By doubling the reference dose of 150 mg/day to 300 mg/day 3HB-Na, illness severity scores doubled (p = 0.004) and mortality increased from 30.4 to 87.5 % (p = 0.002). De-escalating this dose to 225 mg still increased mortality (p ≤ 0.03) and reducing the dose to 180 mg/day still increased illness severity (p ≤ 0.04). Doses of 180 mg/day and higher caused more pronounced metabolic alkalosis and hypernatremia (p ≤ 0.04) and increased markers of kidney damage (p ≤ 0.05). Doses of 225 mg/day 3HB-Na and higher caused dehydration of brain and lungs (p ≤ 0.05) and increased markers of hippocampal neuronal damage and inflammation (p ≤ 0.02). Among survivors, 150 mg/day and 180 mg/day increased muscle force compared with placebo (p ≤ 0.05) up to healthy control levels (p ≥ 0.3). Conclusions This study indicates that 150 mg/day 3HB-Na supplementation prevented sepsis-induced muscle weakness in mice. However, this dose appeared maximally effective though close to the toxic threshold, possibly in part explained by excessive Na+ intake with 3HB-Na. Although lower doses were not tested and thus might still hold therapeutic potential, the current results point towards a low toxic threshold for the clinical use of ketone salts in human critically ill patients. Whether 3HB-esters are equally effective and less toxic should be investigated.

Efficacy and safety of ketone ester infusion to prevent muscle weakness in a mouse model of sepsis-induced critical illness

“…The racemic mixture of 3HHB reached a maximal effect on muscle force at 40 mmol/kg/day, the same dose at which 3HB-Na reached its maximal effect 10 . However, as one molecule of 3HHB can be metabolized to two molecules of 3HB, this difference in efficacy might point to an incomplete metabolism of 3HHB.…”

“…In these previous studies, the ketone body was administered as daily subcutaneous bolus injections of a racemic mixture of d , l -3-hydroxybutyrate sodium salt (3HB-Na). However, an escalating dose-finding study revealed that the effective dose of 40 mmol/kg/day of 3HB-Na was close to the toxic threshold 10 . Indeed, augmenting the daily dose with 20% or more increased severity of illness, markers of vital organ damage and mortality, in part explained by excessive Na + intake.…”

“…These tissue specific differences in uptake and metabolization indicate that both enantiomers might have other beneficial effects 17 , 19 . In our previous experiments performed in septic mice, a racemic mixture of the 3HB salt was used and found effective to prevent muscle weakness 8 , 10 . A racemic 3HB mixture has also been investigated in humans suffering from congenital metabolic disorders and with the aim to improve cognition 21 , 22 .…”

Recurrent metabolic alkalosis following ketone body treatment of adult mitochondrial trifunctional protein deficiency: A case report

“…KEs induced mild acidosis shortly after administration and did not significantly affect blood pH in the long term 23,26 . Attributing the alkalizing effect of KSs to its cation load is further substantiated by KS toxicology studies in mice, which found a quick intracellular uptake of βHB from the circulation, whereas the accompanying Na + remained 27 . This cation load may limit the tolerability of KSs, since dosages needed to treat adults with FAODs are relatively high.…”

“… 23 , 26 Attributing the alkalizing effect of KSs to its cation load is further substantiated by KS toxicology studies in mice, which found a quick intracellular uptake of βHB from the circulation, whereas the accompanying Na + remained. 27 This cation load may limit the tolerability of KSs, since dosages needed to treat adults with FAODs are relatively high. Although previous studies have shown therapeutic benefits of KS supplementation in pediatric patients, alternative forms of βHB without a salt load (e.g., KEs) might be more suitable to adults.…”