**6. Discussions**

In the present study, as we observed strong correlations between the levels of inflammation expressed by PCT, CRP, and the severity of cytolytic syndrome, comparable results were also reported by other researches, related to various causes of liver pathologies. Thus, the correlation of PCT and transaminases levels were noted in patients suffering from various forms of acute liver failure, where authors observed that PCT identified not the potential bacterial infections but the severity of the liver cell injury [30]. Another study published in 2019 reported that the levels of serum CRP and serum PCT were positively correlated with transaminases levels and alkaline phosphatase as well, in patients with acute pancreatitis and associated liver injury [31].

As far as we know, at the moment, there are not so many studies addressing the relationship between NAFLD/NASH, procalcitonin, and gut dysbiosis. One case control study that included 50 patients with NAFLD proven by histology did not reveal significant increase of PCT when compared with healthy controls. However, CRP was considered useful in the diagnosis of NAFLD being significant augmented in patients by comparing to controls, but was not capable to discriminate between NASH and simple steatosis [32]. An important relationship between inflammation and NAFLD

### *Nonalcoholic Fatty Liver Disease, Procalcitonin, and Gut Microbiota: Players in the Same Team DOI: http://dx.doi.org/10.5772/intechopen.110134*

was observed by others, as we also noted in the present study. One cross-sectional study that included 55 patients over 30 years old, diagnosed with NAFLD, demonstrated a relationship between fatty liver and CRP levels, bringing additional proof regarding the role of inflammation in NAFLD. Of the proinflammatory cytokines, it seems that tumor necrosis factor-alpha (TNF-alpha) may play a pivotal role in liver inflammation. Also, proinflammatory cytokines and several interleukins (ILs) as well as LPS could trigger reactive oxygen species (ROS). As a consequence, the augmentation of the hepatocyte damage will develop, accompanied by activation of Kupffer cells and further increase of expression of TNF-α and IL-6 that will increase the levels of local and systemic proinflammatory cytokines [33]. A recent review starting from the known phenomenon of persistent inflammation in NAFLD discussed the relationship between continuing subclinical inflammation in NAFLD and the risk for developing hepatocellular carcinoma [34].

According to the Pearson's parametric correlation analysis, the present paper revealed that the levels of PCT correlated strong with certain characteristics of the bioindicators of the intestinal microbiota, namely, the Shannon-Wiener index of alpha biodiversity and the F/B ratio. We have not found in the literature similar studies that analyze this relationship, PCT-gut DB in patients with NAFLD. Regarding this particular relationship between PCT and DB, recently, literature studies have been especially focused on the DB-PCT relationship mostly in COVID-19-infected patients. Thus, in patients suffering from COVID-19 infection and associated hyperinflammatory reaction with augmentation of CRP ≥ 10 mg/dl, PCT ≥ 5 ng/ml, and WBC ≥ 15 G/l, alterations of the gut microbiota finger print were reported, with modification characterized by increase of *Parabacteroides* sp. and *Lachnoclostridium* sp., and reduction of *Blautia* sp., *Faecalibacterium* sp., and *Ruminococcus* sp. [35]. Other studies reported that the so-called triad in patients infected by COVID-19, expressed by the dysbiosis of the gut microbiota, augmented immune response, and high inflammatory state could make the difference between patients, regarding the way they can cope, either being resilient or being fragile and developing the "cytokine storm" with its consecutive severe outcome [36]. Understanding the changes in the intestinal microbiome in COVID-infected patients that could associate a particular host response could explain the unfavorable evolution of those with severe inflammation and increase of CRP and PCT, as well as the persistence of some symptoms as a consequence of remnant dysbiosis [37]. If situations that result in more or less expressed inflammatory syndrome, in which it was demonstrated the increase of the level of CRP and PCT, that were associated with some specific changes in the intestinal microbiota, we could hypothesize that the dysbiosis associated with NAFLD would generate an inflammation and would result in the growth of inflammatory proteins of the acute phase, such as CRP and PCT.

As others and we previously reported, several alterations of the gut microbiome were observed in the present study regarding dysbiotic patients with NAFLD [38, 39]. These modifications were characterized by the decrease of biodiversity of the F/B ratio and of *Akkermansia muciniphila* sp*.* and by the increase of the LPS (+) bacteria. Modifications of the enterotypes of the microbiota in patients with NAFLD and associated dysbiosis were also seen; thus, *Bacteroides* sp. and *Prevotella* sp. were the dominant enterotypes (enterotypes I and II) in three-fourth of patients, only onefourth expressing *Ruminococcus* sp. (enterotype III) [40, 41].

Many studies advocated the anti-inflammatory role of statins, but only recently researchers have reported a relationship between statins and gut microbiome. We also observed that patients with NAFLD, obesity, and associated metabolic issues exhibited alterations of gut microbiota and were less treated with statins for their dyslipidemia. Recent studies reported that patients with obesity presented gut dysbiosis that was negatively associated with statin treatment. Thus, patients displayed alterations of gut microbiota with modifications of the enterotypes of study participants [42]. Others also hypothesize the possibility of statins to even modulate the gut microbiome [43, 44].

Results of the present study showed that patients with NAFLD and dysbiosis with increase of LPS positive bacteria and decrease of *Akkermansia* sp. were less treated with biguanides, by comparing with those without dysbiosis. Alteration of gut microbiota and antidiabetic drugs especially biguanides is a subject to recent debates. Researchers reported that metformin could associate an increase of small chain fatty acid (SCFA)-producing bacteria and may favor some species such as *Proteobacteria phylum*, *Allobaculum Lactobacillus* genera, and *Verrucomicrobia phylum.* The mucindegrading bacteria are also abundant, such as *Akkermansia* sp. It was also observed that metformin increases *Escherichia* sp. and decreases *Intestinibacter* sp. in human gut microbiota and some species such as *Bifidobacterium adolescentis* were negatively correlated with HbA1c. From this point of view, the lowering effect of the glucose level can also be mediated by the microbiome modifications induced by metformin [45].
