Nitrate-containing beetroot enhances myocyte metabolism and mitochondrial content

Beetroot (甜菜 tián cài) juice consumption is of current interest for improving aerobic performance by acting as a vasodilator and possibly through alterations in skeletal muscle metabolism and physiology. This work explored the effects of a commercially available beetroot supplement on metabolism, gene expression, and mitochondrial content in cultured myocytes. C2C12 myocytes were treated with various concentrations of the beetroot supplement for various durations. Glycolytic metabolism and oxidative metabolism were quantified via measurement of extracellular acidification and oxygen consumption, respectively. Metabolic gene expression was measured using quantitative reverse transcription–polymerase chain reaction, and mitochondrial content was assessed with flow cytometry and confocal microscopy. Cells treated with beetroot exhibited significantly increased oxidative metabolism, concurrently with elevated metabolic gene expression including peroxisome proliferator-activated receptor gamma coactivator-1 alpha, nuclear respiratory factor 1, mitochondrial transcription factor A, and glucose transporter 4, leading to increased mitochondrial biogenesis. Our data show that treatment with a beetroot supplement increases basal oxidative metabolism. Our observations are also among the first to demonstrate that beetroot extract is an inducer of metabolic gene expression and mitochondrial biogenesis. These observations support the need for further investigation into the therapeutic and pharmacological effects of nitrate-containing supplements for health and athletic benefits.

Graphical abstractEffects of beet root supplement on myocyte metabolism. Treatment of myocytes with beetroot increases AMPK and PGC-1α expression, leading to heightened mitochondrial content and oxidative metabolism. Note. Dark bold arrow indicates increased substrate oxidation; light arrow indicates decreased substrate oxidation; short dashed line indicates glucose uptake; long dashed arrow indicates glucose metabolism. AMPK = 5′ adenosine monophosphate-activated protein kinase; G = glucose; GLUT4 = glucose transporter 4; La = lactate; NRF-1 = nuclear respiratory factor 1; P = pyruvate; PGC-1α = peroxisome proliferator-activated receptor γ coactivator 1α.Figure optionsDownload full-size imageDownload as PowerPoint slide