Oleuropein supplementation increases resting skeletal muscle fractional PDH activity but does not influence whole-body metabolism: A randomized, double-blind, placebo-controlled trial in healthy, older males.

Background The polyphenol oleuropein activates mitochondrial calcium import, which increases pyruvate dehydrogenase (PDH) activity. Preclinically, this increase in PDH activity following oleuropein supplementation resulted in improved mitochondrial bioenergetics and fatigue resistance.Objective This study aimed to examine the effects of acute and chronic oleuropein supplementation on muscle energy metabolism, whole-body substrate metabolism, strength, and fatigue resistance in older males.Methods In a randomized, double-blind, placebo-controlled trial, 40 healthy older males (60±5y) received either placebo (PLA) or 100mg oleuropein from olive leaf extract (OLE) supplementation daily for 36 days. On day 1 and 36, muscle and blood samples were collected, and indirect calorimetry was performed, before and up to 120min following supplement intake. Leg strength and fatigue were measured before and after 29 days of supplementation. Results were analyzed using ANCOVA or robust ANCOVA.Results OLE ingestion on day 1 and 36 increased plasma oleuropein metabolites (P<0.001). On day 1, no differences were observed in muscle PDH activity, mitochondrial respiration, or whole-body substrate metabolism 120min after acute OLE ingestion. RNA sequencing revealed upregulation of oxidative phosphorylation gene pathways (FDR<0.05), while PDH-Ser293-phosphorylation was higher after acute OLE vs PLA ingestion (P=0.015). Following chronic supplementation, fractional PDH activity was ∼25% greater in OLE vs PLA (49±14 vs 38±10%; P=0.016) with no differences in absolute PDH activity and PDH-Ser293-phosphorylation between groups. Mitochondrial respiration and protein content, whole-body substrate metabolism, leg strength and fatigue resistance, were not different between OLE vs PLA. Plasma LDL cholesterol was lower after chronic OLE vs PLA (P=0.043) with no differences in other blood metabolic markers.Conclusions Chronic OLE supplementation resulted in higher skeletal muscle fractional PDH activity in healthy, older males, which may impact resting energy metabolism. Acute or chronic oleuropein supplementation do not modulate skeletal muscle mitochondrial respiration, muscle strength, muscle fatigue, or whole-body substrate metabolism.Clinical Trial Registration Https://clinicaltrials.gov/study/NCT05217433. Registry: https://clinicaltrials.gov/study/NCT05217433.