Exogenous ketosis elevates circulating erythropoietin and stimulates muscular angiogenesis during endurance training overload.

De novo capillarization is a primary muscular adaptation to endurance exercise training and is crucial to improve performance. Excess training load, however, impedes such beneficial adaptations, yet we recently demonstrated that such downregulation may be counteracted by ketone ester ingestion (KE) post-exercise. Therefore, we investigated whether KE could increase pro-angiogenic factors and thereby stimulate muscular angiogenesis during a three-week endurance training-overload period involving 10 training sessions/week in healthy, male volunteers. Subjects received either 25g of a ketone ester (KE, n = 9) or a control drink (CON, n = 9) immediately after each training session and before sleep. In KE, but not in CON, the training intervention increased number of capillary contacts and capillary-to-fiber perimeter exchange index by 44% and 42%, respectively. Furthermore, KE also substantially increased VEGF and eNOS expression both at the protein and mRNA level. Serum erythropoietin concentration was concomitantly increased by 26%. Conversely, in CON the training intervention increased only the protein content of eNOS. These data indicate that intermittent exogenous ketosis during endurance overload training stimulates muscular angiogenesis. This likely resulted from a direct stimulation of muscle angiogenesis, which may be at least partly due to stimulation of erythropoietin secretion and elevated VEGF activity, and/or an inhibition of the suppressive effect of overload training on the normal angiogenic response to training. This study provides novel evidence to support the potential of exogenous ketosis to benefit endurance training-induced muscular adaptation. KEY POINTS SUMMARY: Increased capillarization is a primary muscular adaptation to endurance exercise training. However, excess training load may impede such response. We previously observed that intermittent exogenous ketosis by postexercise and pre-sleep ketone ester ingestion (KE) counteracted physiological dysregulations induced by endurance overload training. Therefore, we investigated whether KE could increase pro-angiogenic factors thereby stimulating muscular angiogenesis during a three-week endurance training-overload period. We show that the overload training period in the presence, but not in the absence of KE, markedly increased muscle capillarization (+40%). This increase was accompanied by higher circulating erythropoietin concentration and stimulation of the pro-angiogenic factors VEGF and eNOS in skeletal muscle. Collectively, our data indicate that intermittent exogenous ketosis may evolve as a potent nutritional strategy to facilitate recovery from strenuous endurance exercise, thereby stimulating beneficial muscular adaptations. Abstract figure legend: Eighteen healthy, fit male volunteers were subjected to a 3 week endurance training-overload program. Subjects received either 25g of a ketone ester drink or an isocaloric placebo immediately after each training session and before sleep. The training intervention increased skeletal muscle capillarization in the ketone ester group, but not in the placebo group. The angiogenic response in the ketone ester group was accompanied by an increase in circulating erythropoietin (EPO) concentrations, and stimulation of pro-angiogenic factors in skeletal muscle. These findings indicate that intermittent ketone ester supplementation stimulates beneficial muscular adaptations during strenuous endurance exercise training. This article is protected by copyright. All rights reserved.