The findings linking CYP3A4 and CYP3A5 to the response to atorvastatin are not entirely consistent [3, 7,8,9,10,11,12, 14,15,16,17,18]. Some studies have associated polymorphisms of these enzymes with positive clinical consequences after atorvastatin therapy, and other studies have associated them with negative therapeutic outcomes [3, 7,8,9,10,11,12, 14,15,16,17,18]. These dissimilar responses are significantly apparent among different populations [45,46,47]. The observed variation in results may be attributed to the influence of ethnic diversity on the response to medications [48]. It is imperative to consider ethnic diversity when interpreting and implementing pharmacogenomic findings in clinical practice [48]. In this context, the impacts of genetic variations in CYP3A4 (rs2740574 C/T) and CYP3A5*3 (rs776746 T/C) on the response to atorvastatin treatment have not been previously studied among Egyptians [7]. Accordingly, this study investigated the effects of these genetic polymorphisms on atorvastatin therapy among the Egyptian population. This research revealed significant associations between genetic variations in CYP3A4 (rs2740574 C/T)/CYP3A5*3 (rs776746 T/C) and the response to atorvastatin therapy.

Allele frequencies of the SNPs among the study Egyptian participants

Both alleles C and T of the variant rs2740574 in the CYP3A4 gene have yet to be examined in the Egyptian population (Arab population). This study revealed a high frequency of the CYP3A4*1B variant allele (T) in Egyptian participants, similar to previous findings in the Jordanian population [49].

Similarly, the findings indicate a high frequency of the CYP3A5*3 variant allele (C) among Egyptian study subjects, which is consistent with previous reports from research involving Egyptian volunteers [50]. Additionally, the homozygous mutant genotype of the CYP3A5*3 variant is prevalent, and the frequency of this variant is predominant among 76 Egyptian kidney transplant patients [51].

Therefore, the allelic frequencies of the CYP3A4*1B and CYP3A5*3 variant alleles were widespread among the Egyptian study subjects.

Effect of genetic polymorphisms on atorvastatin effectivenessThe CYP3A4*1B (rs2740574 C/T) genetic variant

The results of this study revealed that the change in the serum TG concentration after atorvastatin therapy was affected by the CYP3A4*1B variant. The decrease in the serum TG percentage was more remarkable in the carriers of the variant allele (T) of CYP3A4*1B ((C/T) and (T/T) individuals) than in the carriers of the homozygous wild-type genotype (C/C). Hence, this relationship is considered to be close and comparable to that reported in research on 142 hypercholesterolemic Chilean patients [3]. This Chilean study attributed the substantial improvement in lipid and lipoprotein profiles after four weeks of atorvastatin treatment to the CYP3A4*1B (rs2740574) SNP, which reduces the activity of CYP3A4 and enhances the efficacy of atorvastatin [3].

The CYP3A5*3 (rs776746 T/C) genetic variant

Serum TG reduction after atorvastatin therapy was affected by the CYP3A5*3 (rs776746 T/C) variant. This significant reduction was greater in the homozygous mutant genotype (C/C) carriers than in the C/T genotype carriers. Our findings were congruent with those of a study in Greek patients, revealing an apparent improvement in the lipid panel in carriers of the variant allele CYP3A5*3 [52]. Furthermore, a study in European Caucasians concluded that the CYP3A5*3 SNP enhanced the response to atorvastatin therapy (P value < 0.05) [9, 10, 14]. Conversely, in a different population, research demonstrated that the CYP3A5*3 (rs776746) SNP did not influence the response to atorvastatin in Chilean subjects [3].

From this perspective, the CYP3A5*3 (rs776746 T/C) variant increased the response to atorvastatin in Egyptians.

Effect of genetic polymorphisms on the safety of atorvastatinThe CYP3A4*1B (rs2740574 C/T) genetic variantCYP3A4*1B and serum TB

Carriers of the homozygous mutant (T/T) genotype of the variant CYP3A4*1B (rs2740574 C/T) had greater baseline TB than (C/T) genotype carriers did. Elevated serum TB levels are associated with reduced CYP3A enzymatic activity (P < 0.05) [30]. Thus, the greater elevation in baseline TB levels in (T/T) carriers than in (C/T) carriers revealed a more significant reduction in enzymatic activity in the case of the (T/T) genotype than in the (C/T) genotype.

Atorvastatin significantly elevated TB levels after the four-week treatment in both C/T and T/T carriers. The findings of this study are consistent with research reporting an association between atorvastatin therapy and increased TB levels (p < 0.001) [53]. In this context, after the atorvastatin-induced increase in serum TB, there was no evidence of a difference between the increases in serum TB levels in both C/T and T/T genotype subjects. Furthermore, the statistical arithmetic mean values of posttreatment TB levels in both the C/T and T/T genotypes were approximately equal. However, the baseline serum TB concentration was greater in the C/T genotype group than in the T/T genotype group. Consequently, the posttreatment increase in the serum TB percentage was greater in the (C/T) genotype carriers than in the (T/T) carriers.

In light of this, atorvastatin therapy significantly elevated serum TB levels in carriers of the variant T allele of CYP3A4*1B (rs2740574).

CYP3A4*1B and serum CK

(C/C) Genotype and serum CK: With respect to the (C/C) genotype of the CYP3A4*1B (rs2740574 C/T) variant, the pretreatment serum CK level was greater than that of the other genotypes. This elevation was attributed to one of the two (C/C) genotype carriers, a 38-year-old male with a body mass index (BMI) of 31 kg/m2 (class I obesity). This subject participated in a long-distance running race for weight loss before being recruited for this study. This (C/C) carrier has not returned to this strenuous physical exercise since he entered the research. Accordingly, this patient’s pretreatment serum CK level was elevated (237 U/L) because of physical activity. This high level elevated the mean value of the baseline serum CK in the (C/C) genotype carriers more than in the other genotypes.

Furthermore, both the postatorvastatin treatment change and percentage change in the serum CK levels in both the C/T and T/T genotypes were greater than those in the C/C genotype. This significant difference was due to the cessation of strenuous exercise in the case of the (C/C) genotype carrier. This interpretation is consistent with a study that revealed a significant increase in serum CK levels after long-distance running (P value < 0.001) [54].

CYP3A4*1B genotypes/atorvastatin dose and serum CK: The CYP3A4*1B (rs2740574 C/T) variant is linked to decreased enzymatic activity, which increases the chance of elevating the plasma level of atorvastatin [3]. Similarly, in the literature, a high plasma concentration of atorvastatin was linked to increased serum CK [55]. However, in the present study, the atorvastatin concentration did not appear to be associated with the seemingly high changes in serum CK in the case of the C/T and T/T genotypes. Regarding the (T/T) genotype, the atorvastatin concentration was more than twice as high as the concentration in the case of the (C/T) genotype. Conversely, there was no evidence of a difference between these two genotypes in either the change in or the percentage change in the serum CK concentration. These findings are consistent with a study that reported no association between CYP3A4*1B genotypes and high serum CK levels (P value > 0.05) [17]. In addition, in this study, the participants adhered to atorvastatin 40 mg. Nonetheless, atorvastatin at this dose was not high enough to be linked to the apparent serum CK level in the case of the C/T and T/T genotypes. This finding was consistent with research reporting a significant increase in posttreatment serum CK levels with increasing atorvastatin dose (80 mg) (P value < 0.05) [55].

Therefore, there was no evidence of a relationship between CK elevation and the CYP3A4*1B genotype or atorvastatin at a dose of 40 mg.

The CYP3A5*3 (rs776746 T/C) genetic variant

In this study, the homozygous mutant genotype (C/C) carriers of the CYP3A5*3 (rs776746 T/C) variant presented higher baseline liver enzymes and TB levels than did the T/C genotype carriers. Previous research has shown that carriers of the (C/C) genotype are CYP3A5 nonexpressors [14, 56]. In this context, a study reported that high ALT and TB levels were associated with decreased CYP3A enzymatic activity (P < 0.05) [30]. The increased elevation in the baseline liver enzymes and TB values in the C/C carriers subsequently resulted in a more significant reduction in enzymatic activity.

Serum TB levels were significantly increased after four weeks of atorvastatin treatment in both the T/C and C/C groups. Our results were concordant with research that revealed a link between atorvastatin therapy and elevated TB levels (p < 0.001) [53]. However, after the significant atorvastatin-induced increase in serum TB, there was no evidence of a difference between the increases in serum TB levels in both T/C and C/C genotype carriers.

Accordingly, atorvastatin therapy significantly elevated serum TB levels regardless of the genotype of CYP3A5*3 (rs776746 T/C).

Atorvastatin plasma level

Notably, atorvastatin levels (ng/ml) were greater in homozygous mutant genotype (T/T) carriers than in carriers of other genotypes. This increase could be attributed to the reduction in CYP3A4 metabolic activity caused by the CYP3A4*1B variant [3]. In light of this, the genotype (T/T) of the CYP3A4*1B (rs2740574 C/T) variant was associated with high atorvastatin plasma levels (ng/ml).

The carriers of the C/C genotype had prominently greater atorvastatin levels (ng/ml) than did those of the T/C genotype. This finding confirmed reports from the literature that subjects with the (C/C) genotype are nonexpressers of the metabolic enzyme CYP3A5 [14, 56]. Accordingly, the genotype (C/C) of the CYP3A5*3 (rs776746 T/C) SNP was linked to elevated plasma atorvastatin levels (ng/ml).

ROC curves

This study revealed that plasma atorvastatin levels had a substantial predictive effect on homozygous mutant genotypes (T/T) and (C/C) in carriers of the SNPs CYP3A4*1B (rs2740574 C/T) and CYP3A5*3 (rs776746 T/C). The probabilities of atorvastatin plasma levels correctly detecting the (T/T) and (C/C) genotypes of CYP3A4*1B and CYP3A5*3 were good and excellent, respectively. This apparent predictive performance may be attributed to the significant relationships between these genotypes (dependent binary variables) and plasma atorvastatin concentrations (predictor variables), as elucidated in this study by another predictive statistical analysis (logistic regression). Predicting these genotypes could be helpful in the case of barriers and challenges for the clinical application of genotyping. To our knowledge, no research has reported such a predictive statistical analysis.

Within this context, predicting the genetic polymorphisms of CYP3A4*1B and CYP3A5*3 has crucial clinical consequences. For instance, these polymorphisms influence the pharmacokinetics of statins [7, 10, 57]. Furthermore, both the CYP3A4*1B and CYP3A5*3 genotypes are vital for adjusting the dose of the immunosuppressant tacrolimus in the maintenance therapy stage after kidney transplantation [58, 59]. In addition, regarding CML, the response to the targeted cancer drug imatinib is associated with the CYP3A5*3 genotypes [60].

From this perspective, predicting CYP3A4*1B and CYP3A5*3 homozygous mutant genotypes with high sensitivity and specificity could help confront challenges in implementing genotyping. In addition, this prediction could have critical clinical significance if personalized medicine is applied.

Atorvastatin pharmacokinetics

Atorvastatin clinical pharmacokinetics were evaluated in Egyptians who carried both genotypes (T/T) and (C/C) of the SNPs CYP3A4*1B (rs2740574 C/T) and CYP3A5*3 (rs776746 T/C), respectively. Both genetic variants decreased the metabolic activities of both CYP3A4 [3] and CYP3A5 [14, 56]. Therefore, the pharmacokinetics of atorvastatin were significantly affected. The findings of this study were compared with the pharmacokinetics of atorvastatin in various populations (Table 8).

Comparison with the Arab population (Egyptians and Jordanians)

Atorvastatin pharmacokinetics were investigated in healthy Egyptian volunteers (without both genetic polymorphisms) [61]. This research revealed that the elimination half-life (t½) of atorvastatin significantly increased to more than double that of healthy Egyptians (P < 0.001). Moreover, the clearance (CL) in this study was significantly lower than that in Egyptian volunteers (P < 0.05) [61]. Furthermore, compared with healthy Arabian‒Asian Jordanian subjects, patients with CYP3A4*1B and CYP3A5*3 genetic polymorphisms had significantly reduced atorvastatin CL (P < 0.05) [62].

Comparison to the Caucasian populationAmerican subjects

This study showed a significantly greater AUC and t½ (approximately doubled) than did the studies of Kacey Anderson et al. (P < 0.05) and B. K. Birmingham (P < 0.05), which involved American Caucasian subjects [35, 63]. In addition, this study demonstrated significantly less apparent oral clearance (CL/F) (P < 0.05) than the other two studies did [35, 63]. The atorvastatin CL was approximately less than half of what was reported in Kacey Anderson et al.’s research (P < 0.001) and B. K. Birmingham’s research (P < 0.05) [35, 63]. Moreover, the atorvastatin CL/F and CL were significantly lower than those reported in the study by N. Rao et al., which recruited American subjects (P values < 0.05 and < 0.001, respectively) [64].

Finnish subjects

Compared with healthy Finnish Caucasians, the genetic variations in CYP3A4*1B and CYP3A5*3 increased both the AUC (almost doubled) (P < 0.05) and t½ (P < 0.05) [65]. Furthermore, this study revealed a lower CL/F (decrease to half) (P < 0.001) and CL (less than half) (P < 0.001) than those reported in studies of Finnish subjects [65].

German subjects

Compared with research on German Caucasians, this study revealed greater t½ value (P < 0.05) [66]. In addition, the CL/F was lower than that in German subjects (P values < 0.05) [66]. The CL of atorvastatin was also reduced by half (P values < 0.001) [66].

Swedish subjects

In contrast with Swedish Caucasian subjects, this study revealed a greater (nearly doubled) AUC (P < 0.05) [67]. In addition, both CL/F and CL were significantly reduced. Atorvastatin CL/F decreased to half (P < 0.05), and CL decreased to less than half (P < 0.05) of what was observed in Swedes [67].

Comparison with the Asian populationChinese and Japanese subjects

The genetic polymorphisms CYP3A4*1B and CYP3A5*3 elevated t½ (P < 0.05) in the participants in this study, which was greater than that in healthy Chinese and Japanese subjects [35]. Moreover, this study revealed fewer CLs (P < 0.05) than those reported for Chinese and Japanese volunteers [35].

Korean subjects

The findings revealed higher t½ values (more than doubled) than those reported in research involving healthy Korean Asian subjects (P < 0.05) [68]. On the other hand, there was no evidence of a difference regarding the CL corrected for the arithmetic mean of the reported body weights (P = 0.054) [68]. However, regarding the CL corrected for weights ≤ 63.2 kg in the Korean subjects, the patients in this study had significantly lower CLs (P < 0.05) [68].

Pakistani subjects

Compared with M. Sohail et al., the participants in this study had greater AUCs (P < 0.05) and t½ values (more than doubled) (P < 0.05) [69]. Furthermore, the CL/F of patients treated with atorvastatin was significantly lower than that of Pakistani volunteers (P < 0.05) [69].

Genetic polymorphisms and patients' medical histories

The CYP3A4*1B SNP has been associated with an increased risk of obesity [24,25,26]. However, this study revealed no evidence of a difference in BMI (kg/m2) among the three genotype carriers of the CYP3A4*1B variant. Similarly, the CYP3A5*3 variant has been linked to an increased likelihood of developing hypertension and increased levels of serum TG [28, 29]. Conversely, the study revealed that there was no evidence indicating a difference between individuals carrying the homozygous mutant genotype (C/C) and those carrying the heterozygous genotype (C/T) of the CYP3A5*3 SNP regarding systolic blood pressure, diastolic blood pressure or baseline serum TG levels.

Potential confounding factorsConcomitant medications

While recruiting participants, we ensured that all their concurrent medications would not interact with atorvastatin treatment or affect the analysis or the study objectives. In the same context, none of the study subjects had used lipid-lowering agents for at least one month before this research. This period was defined based on the literature, which suggests restarting a statin after at least two weeks of washout [70]. Additionally, washout periods (at least two weeks) before changing statin treatment regimens are sufficient to render statin-tolerant subjects [71]. In addition, subjects who were treated with insulin therapy were excluded from the study because insulin treatment significantly affects lipid profiles [72].

Comorbidities

All the participants were candidates for high-intensity statin treatment and did not suffer any comorbidities that may affect the analysis, such as uncontrolled hypothyroidism, which negatively impacts the lipid profile [