Table 2.

Summary of included studies referring to the influence of statins in gut microbiome composition (Outcome 2)

Study details (Author, year, country)	Sample Characteristics (n)	Treatment ‐Drug ‐dose/day ‐via of admin. ‐duration	Study design	Sequencing method	Results		Author's conclusion
					Taxonomy	Diversity
Human studies
Khan et al, 2018, Saudi Arabia 37	Men and women (42), with hypercholesterolemia	Atorvastatin, 20 mg, Oral, n/a	»the 42 subjects enrolled were divided into three groups: *HP (n = 15) statin‐naive *At‐HP (n = 27) treated with atorvastatin for the last 2 y *HS (n = 19) as the control group »Fecal samples collected at the evaluation point.	Amplification by PCR of the V3‐V4 regions of 16S rRNA gene.	Phylum »HP group: higher proportions of Proteobacteria »At‐HP: increased proportions of Firmicutes Family » HP group: increased proportions of Enterobacteriaceae and Prevotellaceae »At‐HP group: higher proportions of Ruminococcaceae and Verrucomicrobiaceae	Alpha diversity »HS group: was the most diverse, followed by HP group, being the At‐HP the less diverse from the three groups. Beta diversity »HP group: presented a separate cluster, with the other two groups, HS and At‐HP, exhibiting similar taxa.	Although less diverse, the treated group was able to shift the bacterial composition towards a more anti‐inflammatory GM environment.
Animal studies
Khan et al, 2018, Saudi Arabia 40	Wistar rats, pathogen‐free (42)	Atorvastatin, 5, 10, 15 e 20 mg Kg‐1 BW, Oral, 4 wk	»Random division in two groups: *NCD (n = 12) and HFD (n = 30) for 5 wk »NCD group was further divided into two groups: *NCD control (n = 6) and NCD‐T (n = 6) with atorvastatin »HFD was also divided into five groups: *HFD control (n = 6), HFD‐T 5mg/Kg/d; HFD‐T 10mg/Kg/d, HFD‐T 15mg/Kg/d, or HFD‐T 20 mg/Kg/d, for 4 weeks »Blood LDLc, HDLc and Tc were measured at wk 0 and 4 »Cecal samples collected at wk 4.	Amplification by PCR of the V3‐V4 regions of 16S rRNA gene	All groups were dominated by the phyla Firmicutes, Bacteroidetes and Proteobacteria. Atorvastatin promoted significantly the relative abundance of Proteobacteria and reduced the abundance of Firmicutes.	Alpha diversity Statin‐treated HFD groups presented higher GM diversity. Beta diversity Statin‐treated HFD groups clustered together, showing very little differences between them; in addition, their composition tends to be closer to the NCD group. The untreated HFD group presented a more distinct diversity.	A more careful analysis should be taken, regarding GM modifying effects, when prescribing a cholesterol lowering drug, as there might be implications for host health.
Caparrós‐Martín et al, 2017, Australia 41	Female C57BL/6J wild‐type mice (30‐36)	Atorvastatin, 10 mg Kg−1 BW, or Pravastatin 10 mg Kg−1 BW, Oral, 12 wk	»Random division in two groups: *NCD and HFD »Then each group was divided into three minor groups: *one remained as a control with no intervention, other was given ATV, another PV, for 12 wk »mice were weighed, and blood collected, weekly »at the end of treatment blood and fecal samples were collected	Amplification by PCR of the V3‐V4 regions of 16S rRNA gene	Predominant phyla in the NCD control group were Firmicutes and Bacteroidetes. Statin treatment triggered a large enrichment within the phylum Bacteroidetes and a marked reduction in the abundance of the phylum Firmicutes.	Alpha diversity Statin‐treated NCD groups showed a lower diversity than the NCD, with greater difference after ATV treatment. Beta diversity the three groups (NCD, ATV treated NCD and PV treated NCD) presented distinctive GM patterns. No significant differences were spotted between HFD, ATV treated HFD and PV treated HFD, regarding alpha and beta diversities.	It is possible, through distinct metabolic pathways, that statin therapy could be a driving force for some GM alterations.
Ryan et al, 2017, Ireland 42	Male ApoEtm1Unc/J mice (35)	Atorvastatin, 1‐5 mg Kg‐1 BW, Oral, 24 wk	»Random division into three groups of interest: *NCD (n = 7) *HFD (n = 14) *HFD_At (n = 14) was given atorvastatin 1‐5 mg/Kg BW	Amplification by PCR of the V3‐V4 regions of 16S rRNA gene	HFD_At treated group displayed an increase in Ruminococcus relative abundance (of ~ 50%) and revealed a significant decrease in Verrucomicrobia levels.	HFD_At had reduced diversity for phylogenetic whole tree.	Statin had not a major impact in GM composition and was not the most important intervention seeking a better cardiovascular and metabolic health.
Nolan et al, 2017, Ireland 43	Female C57BL/6J mice (20)	Rosuvastatin, 9,3 mg Kg−1 BW, Oral, 4 wk	»Mice were fed an HFD for 2 wk prior to statin intake »a group of 10 mice was given sterile water with dissolved RSV 9,3 mg kg‐1 BW/d »other group of 10 mice were only administered untreated sterile water, for 4 wk. »blood, cecal and fecal samples at wk 4.	Amplification by PCR of the V4‐V5 regions of 16S rRNA gene	In both groups, Firmicutes and Bacteroidetes were dominant.	Alpha diversity Significant lower diversity in the RSV treated group in comparison with the untreated group. No significant differences between groups, in fecal samples analysis. Beta diversity Distinct clustering between groups was noted in GM of cecal samples, conversely to the fecal samples.	RSV altered the GM in mice, but it is uncertain how statins influence the GM or if alterations are secondary to host responses.
Catry et al, 2015, Belgium 44	Male C57BL/6J mice (29‐32)	Simvastatin, 0,1% w/w or Ezetimibe 0,021% w/w, Oral, 1 wk	»Mice were divided in four groups: *one was offered a control diet (DT); *another was offered the same diet supplemented with SV 0.1% w/w; *other the same diet with EZT 0.021% w/w; *and the last one with the same diet and a combination of SV and EZT. »Experiment last one week. »blood and fecal samples at wk 1.	Amplification by PCR of the V3‐V4 regions of 16S rRNA gene	Bacteroides‐Prevotella spp. and Roseburia spp., measured in the caecal content did not differ between groups. Also, Bifidobacteria level was not modified by the statin treatment	Abundance of the total bacteria measured in cecal content was not affected by any treatment.	EZT alone affected GM composition in favor of Lactobacillus spp..

Abbreviations: At‐HP, atorvastatin‐treated hypercholesterolemic patients; ATV, Atorvastatin; HFD, High Fat Diet; HFD‐At, High Fat Diet + Atorvastatin; HFD‐T, High Fat Diet treated patient; HP, hypercholesterolemic patients; HS, healthy subjects; n/a, nonavailable; NCD, Normal Chow Diet; NCD‐T, Normal Chow Diet‐treated patient; PV, Pravastatin; RSV, Rosuvastatin; w/w, weight for weight.