Thoughts on Lactate
by Roberto
In the past, when I thought about lactate (or lactic acid), two things immediately came to mind: the many ways lactic acid bacteria (LAB) furnish us with delicious, fermented foods and the grueling "lactate threshold" training sessions in preparing for endurance athletic events. For the non-athletes among our STC readers, these sessions are done at high intensity to increase blood lactate to levels that signal exhaustion. Now I have a third concept to mull over when lactate comes to mind because I recently read a paper that suggests lactate may have a role in limiting autoimmune diseases, for example multiple sclerosis.
Fig. 1. Lactate threshold. Runner silhouettes, lactic acid. Design: Roberto Kolter
The paper is heavy on immunology and so I can only recommend it for those who are deeply steeped in the subject. I confess that I spent many hours reading background papers and it was certainly worth it. But remember, I have the luxury of lots of time for such endeavors. Here I'll distill what I feel are the paper's main messages. The investigators use an induced disease in mice (EAE) that in many ways resembles multiple sclerosis. By administering lactate to the mice, they observed an amelioration of the disease symptoms. Interestingly, they saw similar effects when they colonized the mice with an E. coli strain engineered to secrete lactate. This is important because what they discovered was that the lactate effects on intestinal immune cells led to reduced inflammation in the central nervous system. The gut-brain axis does not cease to amaze me.
As a microbiologist, I immediately asked myself why did the investigators use an engineered E. coli instead of lactic acid bacteria? The authors' arguments for this decision seem to center around issues of the rigor required for mechanistic studies. They say: "...the mechanism of action of unmanipulated probiotics is often unclear, which limits their utility for mechanistic studies." That is, the E. coli strain allowed them to pinpoint the effects they observed on lactate. OK. But that won't lead me switch from yogurt to eating their E. coli for prophylactic purposes. Chalk another plus for fermented foods!
As an athlete, I immediately dreamt of the possible prophylactic health benefits of lactate threshold training sessions. The riveting movie "100 Meters," came to mind. It's the true story of a young man afflicted with multiple sclerosis who manages to keep the disease at bay by training for long distance triathlons. Along the way, of course, he had to do lots of lactate threshold sessions. Could the higher lactate levels in his blood during those sessions have helped to slow down the disease progression? I wondered if there were population studies looking for the incidence of multiple sclerosis among athletes. I did not find much although exercise is broadly recommended as part of therapy and some indication of lower incidence correlating with increased physical activity. Nothing conclusive. Clearly, more research is needed. But the idea of periodic high lactate blood levels as prophylaxis for autoimmune disease does give me added incentive to continue those tough sessions.
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