Exercise during pregnancy confers metabolic protection to children and, in addition, these benefits last beyond childhood. In fact, studies in animals have shown that the mother's exercise when pregnant protects the children from deterioration in the glucose metabolism associated with age and prevents the increase in adipose tissue and cardiovascular disorders (1,2). Since genetic factors do not intervene in the metabolic benefits transmitted to their children of mothers who exercise (3), the question then is, what factors intervene in the transfer of these mothers' benefits to children? 

One of these mechanisms has recently been described in a beautiful and impressive article published in the journal Nature Metabolism (4) in which it is shown as a component of breast milk seems to be one of the molecules involved. The researchers at first studied in a crossed model in rodents how it influences that young mothers' youngs They feed on milk from sedentary mothers (ENTR-SED). The results showed that when they raised them, at 52 weeks, those who had raised with mothers who had exercised during pregnancy (Sed-onnt) weighed less, had a lower percentage of fat, better glucose tolerance, less insulin on an empty stomach and a better cardiac function (measured as an ejection fraction) if compared to those of the Ent-SED group (Figure 1). Therefore, the offspring of sedentary mothers who were raised with the milk of mothers who exercised during pregnancy had a better metabolic and cardiac health. These findings indicate that the intrauterine environment of exercised mothers does not seem to be crucial in exercise induced metabolic protection, which supports the hypothesis that the factors are probably present in breast milk.

With the aim of verifying if this is so, the researchers analyzed the composition of breast milk in order to find common elements between mice and humans. The search focused on complex sugars, the oligosaccharides of human milk (HMO), which are present in a concentration of 5 to 15% in humans and rodents, while on the cow length (the basis of the majority of the majority of children's formulas) represent less than 0.5% (5). Because one of these oligosaccharides, the 3'Sialilactosea (3′sl), is the predominant sialilated olisosaccharide of the human lady (90-95% of the HMO content) and is also one of the two oligosaccharides of the lecha. Mice, the researchers focused on it. To determine if the maternal physical activity correlated with the concentration of 3:SL in human milk, physical activity and daily steps were recorded during pregnancy of 139 women and correlated with the HMO levels. The results showed that the 3′SL content in the milk of these women was positively correlated with high levels of physical activity and the number of steps, and negatively with the body mass index (Figure 2). That is, the more these women moved, the higher their 3′sl levels in the maternal chair.

To determine if the increase of 3′SL is one of the key mechanisms in improving the metabolic and cardiac phenotype in the offspring of trained mothers, the researchers used genetically modified mice to lack 3′sl in the maternal milk and saw that the Breastfeeding did not grant benefits to the offspring. On the other hand, the young of mothers who lacked 3′sl but were fed by mothers who did have this oligosaccharide, had metabolic protection (lower body weight and fat mass, and greater glucose tolerance). Therefore, the presence of 3′sl in the maternal chair seems to be a key element to have a healthy metabolic profile.

In a last part of the study, and in order to prove the therapeutic potential of this oligosaccharide, the researchers supplemented mice that descended from sedentary mothers with a dose of 3′sl that mimics the amount received from the breast milk of exercised mothers. Surprisingly, and as happened with the mice that had been breastfed with trained mothers, the supplemented offspring weighed less and had a lower percentage of body fat, greater tolerance to glucose and lower insulin on an empty stomach in their old age (52 weeks) that the group that was not supplemented. In addition, the ventricular mass and the ejection fraction of the offspring was increased in the group that was supplemented, which gives this molecule a potential cardioprotective effect.

On the other hand, a fact to take into account in this study is that, as has been seen in other investigations (6.7), the metabolic benefits transmitted by maternal exercise were significantly more pronounced in the male offspring, while The female offspring experienced very modest benefits. In relation to this, researchers do not give any justification that explains it, confirming the need to continue investigating. 

Although there are still mechanisms to elucidate, these results show a therapeutic potential of the breast milk of trained mothers, demonstrating that exercise is necessary during pregnancy so that children can have better cardiovascular and metabolic health. Presumably the translation will be aimed at creating products that imitate the effects of the exercise, either enriching drinks or formulating new drugs. Meanwhile, the most sensible and sure thing is to go to the original treatment, since as much as you try to add a single decontextualized molecule of the thousands of molecular waterfalls that produces the exercise of synchronized form, the results are surely not the same. If you want to transmit the effects of exercise during pregnancy, there is no simpler way to achieve it: train. 

References:

1. Carter LG, Qi NR, from Cabo R, Perason KJ. Maternal Exercise Improvs Insulin Sensitivity in Mature Rat Offspring. MED SCI SPORT EXER. 2013; 45 (5). 

2. Harris je, Baer la, Stanford Ki. Maternal Exercise Improves The Metabolic Health of Adult offspring. Trends Endocrinol Metab. 2018 Mar 1; 29 (3): 164–77. 

3. Moreira JBN, Wisløff U. Post-Excise Breast Milk: The New Polypill? Nat Metab. 2020

4. Harris je, Pincikard Km, Wright Kr, Baer La, Arts PJ, Abay E, et al. Exercise-Induced 3′-Sialyllactose in Breast Milk is a Critical Medator to Improve Metabolic Health and Cardiac Function in Mouse offspring. Nat Metab. 2020

5. Bode L. Human Milk Oligosaccharides: Every Baby Needs to Sugar Mama. Glycobiology. 2012 Apr 18; 22 (9): 1147–62.

6. Stanford Ki, Lee My, Getchell Km, So K, Hirshman MF, Goodyear LJ. Exercise Before and During Pregnancy Prevents The Deleterioous Effects of Maternal High-Fat Feeding On Metabolic Health of Male Offspring. Diabetes. 2015 Feb 1; 64 (2): 427 LP - 433.

7. Stanford Ki, Rasmussen M, Baer la, Lehnig Ac, Rowland la, White JD, et al. Paternal Exercise Improves Glucose Metabolism in adult offspring. Diabetes . 2018 Dec 1; 67 (12): 2530 LP - 2540.