5.1. The First Level of Health-Promoting Strategies
Microbiome is crucial for the life of an individual, and comparably to other systems, it shows an interindividual variation, particularly in ALL cases. Today, the growing evidence suggests that these differences originate not in later stages of life cycle of an individual, but rather in the early periods. Such last constitute critical windows of rapid growth under a strong epigenetic remodeling, and, showing, thereby, high phenotypical dynamicity and plasticity during which an organism results predominantly susceptible to environmental conditions, harmfully impacting tissue, organ and system development and disease tendency later in life or after some years from the birth. A clear example are the ALL cases (widely quoted in [
51,
94]).
We, here, have reported, how HS is developmentally programmed, as other systems, and, thereby, in adulthood, or after some years at the birth, it results the representation of the developmental programming, and particularly the consequence of numerous developmental programming events. Among these, the endothelium (re) programming is first included, being the hub of the HS origin, homeostasis, and function, as well as of other human systems [
95,
96,
97,
98]. In turn, endothelium (re)programming influences HS and immune programming with the cooperation of hormonal and metabolic alterations (altered HPA axis and increased release of cortisol, but also of other crucial hormones). After, they induce epigenetic and microbial programming in progeny. The combination of all these programming conditions makes the progeny ‘s HS susceptible to assume long-term structural and functional alterations, that permanently modulate its functions, raise disease risk and velocity to get old. However, their prevention, as well as the prevention of consequent pathologies at long or short (i.e., ALL) onset, may be feasible, and consequently represent a certainty and not an illusion. Accordingly, evidence supports the positive effects of a healthful diet (i.e., Mediterranean) physical activity, low stress, non-usage of smoking, alcohol, and drugs during pregnancy [
99,
100,
101,
102,
103].
Here, we first suggest of recommending such strategies fat both parents who want to have kids, before and during pregnancy. McGowan and Matthews 2018 have supported such strategies, stressing the role of both parents and their lifestyle in developmental programming. Precisely, they affirm that parental danger (not only maternal, but also paternal), related to stress and/or to their changed clinical status related to be affected to eventual diseases (i.e., hypertension, type 2 diabetes) or to have an insalubrious lifestyle (linked to consumption of alcohol, use of drugs, diet, or to be smoker and sedentary), causes deep biological effects on both fetal development and subsequent functionality of HPA axis and specific systems. Furthermore, these effects show of being species-, gender-, and age-specific, and vary in function of timing and duration of exposure, as stressed by McGowan and Matthews (2018) [
75].
5.2. Some Therapeutic Approaches of Second Level
In addition to the first level of health-promoting strategies, we also recommend of utilizing some therapeutic approaches of second level to apply during prenatal and neonatal periods or in adult life. Among these, importance has been given to the pharmacological targets/targeting of pathways involved in the crosstalk of endothelium-HS, cellular/tissue reprogramming, use of miRNAs, and modulation of microbiota of both parents and new-borns through the innovative method of fecal microbiota transplantation (FMT) [
104]. Precisely, FMT is a promising treatment for diseases related to gut dysbiosis, as it can help to rebalance the composition and function of the gut microbiota by transferring fecal preparations from healthy donors. Each gram of human feces contains ≈1011 bacterial cells, 108-109 virus-like particles (most are bacteriophages), ≈107 colonocytes, ≈108 archaea, ≈106 fungi, protists, and metabolites, [
105]. The efficacy of the treatment can be explained by considering, for example, metabolites derived from the phylum
Firmicutes, particularly the SCFAs and secondary bile acids, which with their beneficial roles such as fortifying the intestinal barrier and alleviating inflammation, promoting host homeostasis [
106]. FMT can directly change the recipient’s GM for normalizing the composition and to provide a therapeutic benefit. FMT has initially been applied for the treatment of recurrent and refractory
Clostridium difficile infection, thanks to the decisive consensus of United States Food and Drug Administration, occurred in 2013. Today, its application is not only limited to gastrointestinal disorders, but to other diseases [
104]. Accordingly, a recent systematic review highlighted that FMT can be adopted for the treatment of 85 specific diseases in clinical settings globally from 2011 to 2021 [
107]. Furthermore, a study conducted at the University of Minnesota, enrolling patients suffering from acute myeloid leukemia and patients undergoing hematopoietic cell transplantation, experimented with microbiota transplantation. The subjects enrolled were fragile and could contract a high number of infections, also linked to alterations in the microbiota (dysbiosis) following the treatment. Although microbiota transplantation does not have a significant effect against infections, it can still normalize the composition of the microbiota, obtaining therapeutic benefits by improving the diversity of intestinal microorganisms, increasing the levels of some anaerobic commensal bacteria, and reducing the concentration of other species that could be the cause of some disorders [
108].
Although FMT appears to be a generally safe therapeutic method with few adverse effects, it is, however, necessary to monitor clinical efficacy and long-term adverse events [
104]. Consequently, it is imperative to fix regular follow-up for both identifying the periodicity and length of FMT treatment and monitoring the clinical efficacy and long-term adverse events. In addition, further studies are needed for developing personalized FMT treatments for everyone and his clinical conditions according to diverse features of hosts and diseases/conditions to treat, such as adverse HS programming, and leukemia.
Another strategy might be the use of serotherapeutic therapy, that includes three therapeutic approaches: (i) the treatment with molecules able to selectively kill senescent cells (SCs), that is, senolytics; (ii) the use of compounds having the capacity to reduce the proinflammatory program of SCs, or that modify the senescent phenotype, that is, senomorphics; and (iii) prevention of the accumulation of senescent cells [
109,
110,
111,
112]. All these measures may consent a) to reduce the effects of developmental adversity, b) to favor a well-matched HS development programming principally acting on endothelium, and 3) to delay/retard the onset of leukemia in children and adulthood. Furthermore, the development of other optional treatments is increasing. These last have the aim to recover the disturbed epigenetic profiles linked to altered programming. However, the detrimental epigenetic alterations are understood to be potentially reversible; therefore, they may likely be corrected by certain lifestyle factors such as diet, physical activity, etc., as well as by pharmacological interventions specifically targeted at epigenome [
13,
14,
15,
16]. If these therapeutic strategies will be established, then such an approach would provide a way to slow down the epigenetic clock and to modify the dynamics of epigenetic age during the life course and, thus, to slowing down and/or delaying age-related processes [
94,
117,
118]. The lack of specific biomarkers for monitoring developmental programming makes difficult to test and verify the biological effects of eventual interventions and treatments. The group of Goswami has suggested the telomere length as optimal biomarker for developmental programming [
119]. The epigenetic age indices such as DNA methylation-based biomarkers are also considered now as another promising option [
120]. These obstacles, as well as the need to identify the unknown longterm outcomes of the described interventions and therapeutic approaches, reflect several gaps and the need of performing further studies. Multidisciplinary investigations are particularly suggested, being everyone the result of the sophisticated interplay of environmental factors with its genome, trascriptome, proteome, metabolome, microbiome, epigenome, exposome, as evidenced in describing and discussing on HS programming. Further studies are hence imperative, in different types of patients and with different conditions and diseases [
104].
Diet plays a key role from the earliest days of life in human health in cell metabolism, regulation of the GM and immunological processes via epigenomic factors, as above mentioned, [
121]. Many studies have reported a correlation between habits such as smoking and drinking alcohol during pregnancy and increased risk of leukemia, but other dietary factors also have an important influence [
122,
123]. Intake of fruit and vegetables provides the necessary folic acid intake to avoid the risk of leukemia in children, and it has been reported that maternal fruit and vegetable consumption is inversely related to childhood ALL [
124]. In California, in accordance with this premise, a study has been conducted for evaluating the link between maternal diet quality prior to pregnancy, considering a diet quality index, and the risk of childhood ALL. On the other hand, maternal malnutrition and low micronutrient levels could cause elevated maternal cortisol concentrations, affecting the development of the fetal immune system, and interfering with normal immune cell proliferation and organogenesis [
125]. Studies have reported a correlation between diet and risk of ALL. It has been observed by some researchers that a diet that includes fish, seafood, beans, and beef correlates with a low risk of ALL [
126]. Instead, the risk of ALL may increases when mothers consume various foods such as sugars or syrups [
127]. Regarding the risk of ALL in children, there is a positive association between the risk of this disease with consumption of more coffee and/or caffeinated beverages [
128,
129].
Dietary habits can influence the diversity of the GM and dietary components can influence both the microbial population and its metabolic activity. The Mediterranean diet has been proposed and it includes foods such as vegetables mainly, fiber and omega-3 fatty acids and animal protein and saturated fats but in smaller quantities. Adherence to the Mediterranean diet leads to an increase in certain bacteria such as
Bifidobacteria, Lactobacilli, Prevotella,
Eubacteria,
Bacteroides, in contrast, a high-fat diet leads to an increase in
Bacteroides and
Enterobacteria and a decrease in
Bifidobacteria, Lactobacilli, Prevotella and
Eubacteria. Different studies affirm this diet-dependent change in the microbiota [
130].
In a study by De Filippis and colleagues, in 153 individuals habitually following omnivore, vegetarian or vegan diets, adherence to this diet has been observed and shown to be associated with increased levels of fiber-degrading SCFA (short chain fatty acids),
Prevotella and
Firmicutes [
131].
In subjects eating the Mediterranean diet, the
Prevotella-Bacteroides ratio was higher, indicating that a diet rich in natural fibre and resistant starch has a positive effect on the bacterial composition of human subjects [
132] A study conducted by Garcia’s group has focused on the eating habits of healthy subjects to test the variability of the microbiota adhering to the Mediterranean diet. What is observed following a questionnaire to which the volunteer subjects are submitted is that adherence to the Mediterranean diet allows a decrease in the
Firmicutes-Bacteroidetes ratio and greater presence of
Bacteroidetes was associated with lower animal protein intake. High consumption of animal protein, saturated fats, and sugars affected gut microbiota diversity [
133]. To confirm the observations of the above studies a preclinical study conducted on mice by Nagpal et al. analyzed the gut microbiome after adhering to either the typical Western diet or the Mediterranean diet [
134] They found that the microbiome of the study participants consuming the typical Western diet was significantly more diverse than the microbiome of the participants consuming the typical Mediterranean diet. They found that the microbiota of study participants consuming the Mediterranean diet was significantly more diverse than the microbiota of participants consuming the Western diet, characterized by in lard, beef tallow, butter, eggs, cholesterol, casein, lactoalbumin, dextrin, high-fructose corn syrup and sucrose. They also had a higher abundance of
Lactobacillus,
Clostridium,
Faecalibacterium and
Oscillospira and a lower abundance of
Ruminococcus and
Coprococcus [
134]
Another study states that the diet can alter the composition of the microbiota very rapidly, in less than a week, as shown by 31 in his study in which the consumption of particular types of foods is attested to that produces predictable changes in existing host bacterial genera. This influences host immune and metabolic parameters, with broad implications for human health [130]. Microbes in the distal intestine, where they are abundant, contribute to host health through the biosynthesis of essential vitamins and amino acids and the generation of important metabolic byproducts from food components not digested by the small intestine [
135].
Several studies have been able to comprehensively investigate the impact of diet component on gut microbial composition. The effects of dietary protein on the gut microbiota were first described in 1977.
Protein consumption is positively correlated with overall microbial diversity [136]. The consumption of whey and pea protein extract results in the increase of Bifdobacterium and intestinal Lactobacillus, while whey also reduces the pathogens Bacteroides fragilis and Clostridium perfringens [137]. Pea protein also has been associated with increased levels of intestinal SCFAs, which are considered anti-inflammatory and important for maintaining the mucosal barrier [138]. In contrast, consumption of animal protein causes an increase in the number of bile-tolerant anaerobes, such as Bacteroides, Alistipes, and Bilophila [136]. One study found that subjects on a high-protein/low-carbohydrate diet carbohydrate had a reduced presence of Roseburia and Eubacterium rectale in the gut microbiota and lower butyrate in the feces [139]. In their study, De Filippo et al.similarly observed lower fecal SCFAs in Italian subjects who consumed a protein-rich diet [140].
Adherence to the Mediterranean diet has also been shown to have positive effects on health, with a reduction in inflammatory molecules and thus a protective role against oncological diseases.
Regarding the panel of inflammation-related markers, a study was conducted examining the effects of the Mediterranean diet on the inflammatory profile. 612 non-fragile or pre-fragile subjects in five European countries (UK, France, Netherlands, Italy and Poland) were analysed before and after a 12-month Mediterranean diet intervention. A negative correlation in the inflammatory markers CRP, IL-17 and IL-2 with positive levels of the anti-inflammatory cytokine IL-10 was observed following adherence to the diet. This confirms how diet and in particular adherence to the Mediterranean diet can positively influence health by reducing the risk of chronic inflammatory [
141].
In addition to their effects on the composition of the microbiota, prebiotics also produce significant changes in metabolic and immune markers.
Several different studies have observed reductions in the proinflammatory cytokine IL-6, associated with the intake of non-digestible carbohydrates present in whole grains [
142].
West et al. noted an increase in plasma levels of the anti-inflammatory cytokine IL-10 with consumption of high-amylose corn starch butyrate [
143].
Therefore, prebiotics are thought to have a beneficial effect on the immune and metabolic function of the gut, and this is believed to be due to increased production of SCFAs and strengthening of gastrointestinal tract-associated lymphoid tissue (GALT) resulting from fibre fermentation [
144].
New evidence has reported that specific nutrients exert different actions on metabolic outcomes, depending on individual microbial patterns subject to specific individuals or conditions, suggesting the important role of personalized human nutritional treatment [145].
Another recent therapy is based on the use of butyrate-producing bacteria, which as previously mentioned has a protective role against ALL disease. These strains, such as those of
Clostridium butyricum and
Butyricicoccus pullicaecorum are thought to be specific next-generation niche probiotics and have good bile tolerance, viability, and metabolism and can be genetically manipulated to increase their ability to produce butyrate [
146,
147]. For example, heterologous genes required for butyrate production from butyrate from acetyl-CoA can be introduced by inactivating the gene that codes for conversion of acetyl-CoA to acetate and the gene encoding aldehyde/alcohol dehydrogenase for ethanol production or simply disrupt a CoA transferase gene, which could be an alternative pathway for acetate production. In addition, to obtain higher levels of butyrate and thus greater abundance of butyrate producers in the gut, co-culture can be carried out to obtain an interactive microbial population composed of more than microbes.