Here we go! Part 3 of this review paper written by Inigo San-Millan. This post will explore some of the bioenergetics of mitochondria.
Mitochondria burn (oxidize) energy from macronutrients through oxidative phosphorylation that occurs in the Krebs cycle. Mitochondria oxidize all major substrates derived from macronutrients.
Mitochondria oxidizes pyruvate from carbohydrates, fatty acids derived from fat, amino acids derived from protein (rare), and ketone bodies under stress and fasting conditions.
Take home message – Lactate is the obligatory byproduct of glycolysis. Lactate is a very important fuel for mitochondria and could even be the fuel preferred by most cells. The other byproducts are CO2, H2O, and ATP.
Neat note: Skeletal muscle is the largest organ in the body; also, the largest contributor to aerobic capacity through mitochondrial respiration. Hence, skeletal muscle mitochondrial function is crucial for whole-body metabolic function and health.
Quick bonus note from Andy Galpin’s Perform episode on lactate. The three primary functions of lactate are:
- The primary energy source of mitochondrial respiration
- The primary precursor of gluconeogenesis
- Signaling molecule – hormone. Lactohormone as quoted by San-Millan
Another cool note from Dr. Galpin’s lecture. The net result of all metabolism is ATP, H2O, and CO2. Galpin continues with stating that the evidence is not only clear, but it is beyond reproach, fuel through your muscle is never limited by oxygen. Lactate is not created because you are out of oxygen. The end product of pyruvate metabolism is always lactate. 10-50:1 lactate to pyruvate concentrations. Lactate is quickly made out pyruvate and that ratio can go up a magnitude during exercise.
Furthermore, transporters specific to pyruvate and lactate get you into mitochondria. MCT is the abbreviation for this transport. These MCT transports exist in my organelles in your body.
Lactate is the preferred fuel source for the heart over glucose. Also, for the brain’s astrocytes. They prefer lactate over glucose. Lactate is predigested carbohydrate. It is a lovely fuel source.
- San-Millán I. The Key Role of Mitochondrial Function in Health and Disease. Antioxidants (Basel). 2023;12(4):782. Published 2023 Mar 23. doi:10.3390/antiox12040782