During interval training and high-reps strength training, the muscles release large amounts of lactic acid into the blood stream. The lactic acid may well protect cells against aggressive molecules, and it helps cells to function better and delays processes of aging. Researchers at the University of Tokyo drew this conclusion from experiments they did with mice.
The researchers gave mice 1 g sodium lactate per kg bodyweight, administering it into their small intestine. Three hours later they looked to see whether the genes in the animals’ calf muscles had started to work differently. The figure below shows that the lactic acid had already disappeared from the bloodstream.
The researchers discovered that the lactic acid had made the gene Pgc-1-alpha work harder. The protein synthesised by this gene plays a key role in the production of mitochondria. These are the cells’ power generators, which convert nutrients from food into energy.
The Mt1 and Mt2 genes code for the enzymes metallothionein-1 and -2, which play a role in protecting cells against aggressive compounds.
Scientists hope that substances that induce cells to synthesise more mitochondria also boost fat burning and can delay aging processes. Recent studies have shown that aging is partly the result of a cellular energy crisis â€“ aging leads to a reduction in the number of mitochondria in the cells, and as a result the remaining mitochondria function less well. The consequence is that the cells start to function less well as a result of the energy shortage.
Good, the Japanese only describe the effect of lactic acid on the muscles in their article. But they do write that they suspect that lactic acid, normally produced by the muscles during intensive exercise, is also active in other parts of the body.
“Our results suggest that lactate, which is well known to be increased during exercise, also acts as a signal for upregulating genes related to mitochondrial function,” the researchers conclude.
“We previous study reported that treadmill running increased mRNA levels of PGC-1-alpha and PDK4 in the liver, and similar adaptations were observed with lactate injection [J Neurochem. 2013 Oct;127(1):91-100.] Furthermore, lactate injection increased the UCP1 mRNA level and induced browning of the white adipose tissue. [Diabetes. 2014 Oct;63(10):3253-65.]”
“Although the skeletal muscle is the primary site of lactate production, the effects of lactate may not be limited to the skeletal muscle.”
Lactate administration increases mRNA expression of PGC-1α and UCP3 in mouse skeletal muscle
To examine the potential role of lactate as a signalling molecule in skeletal muscle, we performed global gene expression analysis of the mouse gastrocnemius muscle, 3 h after lactate administration using the Affymetrix GeneChip system (Affymetrix, Santa Clara, Calif., USA). Among the top 15 genes with the largest fold change, increased expression of Ppargc1a, Pdk4, and Ucp3 was confirmed using real-time quantitative polymerase chain reaction. Our findings suggest that lactate serves as a signal for upregulating genes related to mitochondrial function.