Although exercise helps to reduce weight, protects from cardiovascular disease and improves diabetes, there has been no real understanding of why exercise has these effects. A scientific study, led by Robert Gerszten at the Massachusetts General Hospital, Boston, MA, shows for the first time how exercise improves blood sugar and activates beneficial metabolic pathways.
The goal was to analyze a large number of blood metabolites before, during, and after exercise. Previous studies have focused primarily on metabolites closely related to muscle function, while this study looked at a much broader spectrum of metabolites. The research subjects were outpatients from Massachusetts General Hospital, who had been recommended for exercise and amateur runners taking part in the Boston Marathon. The outpatients exercised by walking on a treadmill or rode a stationary bicycle. Blood samples were taken before exercise, at the peak of exercise, usually 10 minutes after starting, and at 60 minutes after finishing exercising. Blood samples were collected from the Boston Marathon runners before the marathon and again after they reached the finish line. Using liquid chromatography-mass spectrometry, the researchers were able to analyze a huge number of metabolites, made possible by advances in technology.
More than 20 metabolites changed during exercise. Unlike parameters such as pulse and blood pressure, which return to normal after one hour, many exercise induced metabolites were still present. One metabolite, niacinamide, which enhances insulin release and improves blood sugar control, increased by 79 percent after exercise. In leaner and more fit individuals, the increase in niacinamide was twice that of people with an above average body mass. Changes in other metabolites also suggested that the more fit an individual is, the more easily fats are broken down. The concentration of an indicator of oxidative stress, allantoin, also fell after acute exercise in all subjects, but to a greater extent in fit individuals. In contrast, lactic acid, a product of muscle activity, was identical in fit and unfit people after exercise.
Because this study gives a “snapshot” or “fingerprint” of what happens during exercise, the results can be used to track and improve exercise regimens. The relevant metabolites can also be used to monitor the effectiveness of exercise on diabetes and heart disease. Also, looking at the metabolic “fingerprint” of exercise can be used to determine which nutrients become deficient during exercise and these can be added to drinks or foods for exercising individuals. This study looked at more than 200 metabolites, but there still may be other important metabolic changes that were not analyzed in this study and wait to be discovered.
Lewis, G.D. et al. Metabolic Signatures of Exercise in Human Plasma. Sci. Transl. Med. (2010) 2, 33ra37