A Belgian team of scientists presented in the journal “Gut” the newly discovered bacterium Dysosmobacter welbionis, which exerts astonishing influence on body weight, fat metabolism and the tendency to diabetes mellitus – in mice.
Current Western culture – this must probably still be pointed out in view of various tendencies that put things into perspective, such as plus-size models – is full of preconceptions about obese people. This prejudice goes back to antiquity, when the ideal of "mens sana in corpore sano", a healthy mind in a healthy body, was formulated by Plato. What is meant by "corpore sano", at least today, is invariably a healthy-looking, a slim and trained body. In our culture, a not so slim, not so trained body is frequently associated with a lack of mental goal orientation. This is the only way we can understand the famous plea of Shakespeare's coup-prone Julius Caesar: "Let me have men about me that are fat" - because he believes big people to be less aggressive, less envious of leadership and less intent on murder.
This prejudice expresses at least two unsubstantiated assumptions. On the one hand, the assumption that body image and mental characteristics correlate with each other. On the other hand, that our body image can be controlled or determined by our will. Both are false. The doctrine of physiognomy should have been shelved at the latest since the end of National Socialism in Germany. There are narrow limits to how much the will can influence the appearance of the body – and perhaps even narrower than is already known, as is suggested by this study on mice.
It is worth countering a disrespectful sniff with the fact that D. welbionis is a common component of the human gut microbiome, that has yet to be scientifically described. Studies on large, scientifically documented collections of human stool samples have shown that D. welbionis is a natural component of the gut flora of almost 70% of all (healthy) people included in the collection. What's more, there is an inverse correlation between the number of D. welbionis in the intestinal flora and the BMI, the plasma glucose level on an empty stomach and HbA1c in overweight people. Furthermore, D. welbionis does not settle permanently in mice even when given a high daily dose of live germs.
The researchers specifically investigated the strain J115T of D. welbionis. This showed that administering 1 x 109 live germs per day to mice on a high-fat diet (HFD) prevented the development of diet-induced obesity and significantly reduced mesenteric and subcutaneous fat reserves in already overweight mice.
The intestinal microbiome of the mice was not altered following the administration of D. welbionis J115T. A slight modification of the intestinal morphology of treated mice was indeed observed, but without any influence on absorption. There was also no evidence of inflammation as a result of the germs, which could have explained the effects of D. welbionis J115T administration.
In the mice on HFD, D. welbionis J115T reduced the increase in adipose tissue and improved glucose tolerance. The diameter of the mice's adipocytes decreased, as did the inflammation level in the fat tissue. In the animals' brown fat tissue, the number of mitochondria went up, which was ultimately reflected in a 0.25 °C increase in temperature in the animals, as was to be expected with an increased activation of the fat reserves.
The scientists around Tiphaine Le Roy from the Université Catholique de Louvain in Brussels consider their results in the mouse experiments to support the observed correlations between D. welbionis J115T and obesity and diabetes parameters in humans. In their opinion, the study indicates a direct influence of D. welbionis J115T on the metabolism, as no changes in the microbiome of the animals were observed as a result of administering D. welbionis J115T.
The mechanism by which D. welbionis J115T triggers these effects in animals and humans is still unknown. Butyrate, which is produced by the bacterium, could be a potential mediator. Yet, no elevated butyrate levels could be detected either in the plasma or in the intestines of the animals.
Overall, the data indicated a possible positive effect of D. welbionis J115T on diet-induced obesity and diabetes. Therefore, the researchers recognise D. welbionis J115T as a bacterium with potential therapeutic use. The study thus raises two questions. The concrete and practical one is to what extent will the effects of administering D. welbionis J115T also occur in humans?
Second, the socio-medical question touches on how overweight people are treated both in the medical profession and in society in general. If the discovery of a bacterium that was unknown only a few months ago suggests the possibility of new therapies to treat obesity and its consequences, then what are we to make of the often blaming demands on overweight people to reduce their calorie intake and increase their physical activity to lose weight?
Shouldn't the fact that there are glaring gaps in our knowledge about the relationship between food intake and the nutritional effects caused by the microbiome in the organism lead to more restraint in our attitude towards overweight people? The truth seems to be that science still knows far too little about the origins of obesity to even be able to address prejudiced and discriminatory aspects such as "weakness of will". The mechanistic and highly simplified assumption of a purely physical relationship between energy intake and its consequences in the organism is wrong, as this study demonstrates. There is great doubt whether fat murderers would have let Caesar slip away. And accordingly, physicians should exercise restraint when the next obese patient comes to see them.
Source:
Le Roy T, et al. Dysosmobacter welbionis is a newly isolated human commensal bacterium preventing diet-induced obesity and metabolic disorders in mice. Gut 2022; 71: 534–543.