Excerpt
The worldwide obesity pandemic has driven to the research of its responsible environmental factors. Gut microbiota is attracting growing interest between environmental factors, as alterations in its composition and in energy storage capacity seem to play a key role in the pathogenesis of obesity and its comorbidities (such as insulin resistance, diabetes, and cardiovascular disease). Compared with lean, obese individuals show, indeed, changes in the relative abundance of the two dominant bacterial divisions in human gut: about 50 % reduction in Bacteroidetes species and a proportional increase in Firmicutes [
1]. These modifications promote adiposity, systemic inflammation, and insulin resistance, influence metabolic processes in peripheral organs, such as the control of satiety in the brain, the release of hormones from the gut, and the synthesis, storage, and metabolism of lipids in the adipose tissue, liver, and muscle [
2] and, above all, induce a metabolic profile impairment of gut microbiota, showing an increased capacity for functional host genes to harvest energy from diet in animal models [
1]. However, no significant evidence of this metabolic capacity has been identified for humans [
3], probably, according to us, for the incapacity to obtain an exact monitoring of energy balance in humans compared to mouse models. Recently, study findings have reported that antibiotics exposure, used effectively for over half a century to treat bacterial infections in humans and animals, strongly affects microbial intestinal composition and metabolism [
4], bringing long-term physiological changes. Interestingly, chronic exposure to low-residue antibiotics from food and environment and to high-dose for childhood infections promotes obesity [
5]. Assumption of antibiotics during the first 6 months of life, but no later in infancy, indeed, has been recognized, besides delivery mode and pre-pregnancy maternal body mass index (BMI), as related to a significant increase in body mass, [
4]. A small increase in BMI has been observed, indeed, in a large international cross-sectional survey, after exposure to antibiotics during the first 12 months of life only in boys aged 5–8 years [
6]. On the basis of these findings, more randomized controlled trials are needed to assess whether an appropriate reconsideration of antibiotic prescription in childhood is required in clinical practice to prevent adult metabolic alterations, also in line with the modern urgency to discontinue the risk of a “post-antibiotic era.” The effect strictly depends on antibiotic type (Gram-positive or Gram-negative) and on its route of administration (intravenous or orally administered). Compared to amoxicillin, an antibiotic treating more effectively Gram-negative infections, indeed, intravenous vancomycin, more effective against Gram-positive bacteria, has been demonstrated efficacious in the development of adult obesity [
7] as well as, when orally administered in subjects with metabolic syndrome, in the modulation of intestinal microbiota diversity, bile acid metabolism, and peripheral insulin sensitivity [
8]. Interestingly, the evaluation of the initial gut microbiota composition could represent a predictive parameter to identify individuals susceptible to gain weight under vancomycin treatment [
9]. In our opinion, this finding could be a useful tool to furnish and aware information to patients about the risk and, as a consequence, to target treatment choices and personalize therapy. Overall, as a consequence of its innate resilience to perturbations, gut microbiota could furnish novel insights into the management of obesity and clinical treatments. In our opinion, probiotic treatments represent the most promising approach to target microbiota and to reverse the alterations linked to obesity phenotype [
3]. However, the identification of the bacterial species and the antibiotics, in a defined route of administration, specifically responsible of transition from a healthy gut status to an obese one, together with the determination of the individual gut composition is still needed to improve obese phenotype and to predict personal response to therapy. …
