Demographic Characteristics
The study was performed between June 2018 and April 2019 including recruitment and follow-up visits. Demographic data are shown in Table S1 in the electronic supplementary material. Ten subjects were Caucasian and 14 were Latino. Average age was similar between men and women (p = 0.204). Men had greater weight and height than women (p < 0.001); however, the BMI values did not differ significantly (p = 0.798).
Genotype Frequencies
The genotype frequencies of the analysed genes are shown in Table S2. HTR2C rs3813929 and rs518147, ABCB1 rs4728709 and COMT rs13306278 were not in Hardy–Weinberg equilibrium (p ≤ 0.05). The rest of the polymorphisms were in Hardy–Weinberg equilibrium (p ≥ 0.05).
Genotype frequencies of ABCB1 C1236T, G2677T/A, 10276036 and rs4148737 and HTR2C rs518147 polymorphisms were significantly different between men and women (Table S2).
Pharmacokinetic Analysis
Mean and standard deviation (SD) of ARI, DARI and OLA pharmacokinetic parameters are shown in Table 1. Women had lower DARI/ARI ratio than men (p = 0.046). The remaining pharmacokinetic parameters were not statistically different between the two sexes. Associations between pharmacokinetic parameters and polymorphisms were reported previously [20].
Table 1 Pharmacokinetic parameters of aripiprazole, dehydroaripiprazole and olanzapine after administration of five multiple doses Prolactin Concentrations and Their Relationship with Pharmacogenetics
OLA caused a significant elevation in prolactin levels (p < 0.001, ηp2 = 0.474) (Fig. 1; men and women are shown separately because of the known differences of prolactin levels between the two sexes). Men had lower prolactin levels than women; however, the extent of the increment did not differ between them. Additionally, a significant interaction was found between OLA Cmax and prolactin levels (p = 0.006, ηp2 = 0.168). Moreover, DRD3 Gly carriers had significantly higher prolactin concentrations than volunteers with the Ser/Ser genotype (p = 0.036, ηp2 = 0.121).
Compared to OLA, ARI did not elevate prolactin levels. On the contrary, a tendency for decrease was observed but it did not reach significance (p = 0.052) (Fig. 1). Additionally, CYP3A poor metabolizers (PMs) had higher prolactin concentrations during ARI treatment compared to intermediate metabolizers (IMs) and extensive metabolizers (EMs) (p = 0.001, ηp2 = 0.226). ABCB1 rs10280101 A/A, rs12720067 C/C and rs11983225 T/T subjects had significantly higher prolactin concentrations compared to C, T and C allele carriers (p = 0.037, ηp2 = 0.123). However, when analysing ABCB1 haplotypes, this association could not be detected.
The same genetic associations were found in men and women. Prolactin levels were significantly higher during OLA treatment compared to ARI (p < 0.0001, ηp2 = 0.356). Prolactin levels were outside of the recommended range (men, 2–18 ng/mL; women, 3–30 ng/mL) during OLA treatment in 9 (75%) men and 9 (75%) women [27].
Glucose Metabolism and Its Relationship with Pharmacogenetics
C-peptide concentrations were significantly higher after completing ARI treatment compared to its initial levels (p = 0.030, ηp2 = 0.205) (Table 2). Additionally, the increase of C-peptide levels was greater in COMT rs4680 G/G subjects and rs13306278 T carriers compared to A carriers and C/C homozygotes, respectively (p = 0.010, ηp2 = 0.289; p < 0.001, ηp2 = 0.535, respectively). This association could not be detected when analysing the COMT phenotype. Moreover, although the insulin levels only tended to increase after ARI administration (p = 0.073), BDNF rs6265 C/C subjects had greater increment compared to the other genotypes (p = 0.040, ηp2 = 0.237). Likewise, DARI AUClast was indirectly proportional to the changes in insulin levels (p = 0.045, ηp2 = 0.228).
Table 2 C-peptide, insulin, haemoglobin A1c and glucose levels during aripiprazole and olanzapine multiple dose treatment After completing OLA treatment, the 1 and 2 h glucose levels after performing GTT were higher compared to the measurements on the first day (p = 0.007, ηp2 = 0.213) (Table 2). In addition, these changes were dependent on the UGT1A1 rs887829 genotype: C/C homozygote subjects had significantly higher glucose concentrations in GTT both after 1 h and 2 h than the T allele carriers (p = 0.014, ηp2 = 0.186). Moreover, this polymorphism was additionally related to a higher increase in glucose levels in C/C subjects compared to the T allele carriers (p = 0.013, ηp2 = 0.258). Additionally, the insulin levels of CYP3A PMs incremented more compared to EMs and IMs (p = 0.029, ηp2 = 0.217). Moreover, OLA administration increased the C-peptide/insulin ratio (p = 0.044, ηp2 = 0.196).
Glucose levels in the first day’s GTT test were higher in OLA-treated subjects compared to ARI-treated subjects (p = 0.011, ηp2 = 0.131); however, ARI showed the same tendency. The increment in glucose levels after GTT and the increment of C-peptide levels did not differ between ARI and OLA (Table 2). No changes were detected in HbA1c.
No differences were found between men and women, nor in C-peptide, insulin, glucose and GTT levels, and nor in the genetic associations. No levels were outside of the normal range.
Weight and Lipid Metabolism and Their Relationship with Pharmacogenetics
During ARI treatment, volunteers’ weight decreased significantly (p < 0.0001, ηp2 = 0.301). On the contrary, a tendency for weight gain was observed during OLA treatment, but it did not reach significance (p = 0.120) (Fig. 2). Additionally, a significant difference was found when comparing weight changes between ARI and OLA treatment (p < 0.001, ηp2 = 0.301). Moreover, HTR2C rs1414334 C/C subjects gained significantly more weight compared to T carriers (p = 0.002; ηp2 = 0.196).
Triglyceride levels linearly decreased as a result of ARI and OLA administration (p = 0.009, ηp2 = 0.177; p = 0.047, ηp2 = 0.125, respectively) (Fig. 2). No significant difference was found in the extent of this decrease between ARI and OLA (p = 0.593). Additionally, ARI Cmax, DARI Cmax and ARI + DARI Cmax were inversely proportional to triglyceride levels (p = 0.003, ηp2 = 0.203; p < 0.001, ηp2 = 0.327; p < 0.001, ηp2 = 0.258, respectively). Moreover, CYP3A PMs had a significantly greater decrease in triglyceride levels during ARI treatment compared to the other phenotypes (p < 0.001, ηp2 = 0.296). Furthermore, APOC3 rs4520 C/C homozygotes had a lesser decrease in triglyceride concentrations after OLA administration than T allele carriers (p = 0.018, ηp2 = 0.162).
Likewise, total cholesterol levels diminished significantly during ARI and OLA treatment (p = 0.002, ηp2 = 0.250; p = 0.004, ηp2 = 0.209, respectively) (Fig. 2). No significant difference was found between ARI and OLA in the extent of this reduction (p = 0.241). Moreover, HTR2A rs6314 C/C subjects had higher cholesterol concentrations during ARI treatment compared to T allele carriers (p = 0.037, ηp2 = 0.141).
No differences were found between men and women in terms of changes of weight and triglyceride and cholesterol levels. No levels were outside of the normal range.
Hepatic Performance
GOT, GPT, GGT, ALP and albumin levels significantly decreased during ARI treatment (p = 0.001, ηp2 = 0.249; p = 0.004, ηp2 = 0.209; p = 0.001, ηp2 = 0.224; p < 0.001, ηp2 = 0.312; p < 0.001, ηp2 = 0.307, respectively) (Table S3). Additionally, GGT levels were inversely proportional to DARI and ARI + DARI Cmax (p = 0.050, ηp2 = 0.116; p = 0.043, ηp2 = 0.121). Likewise, ALP levels were dependent on ARI and ARI + DARI Cmax (p = 0.042, ηp2 = 0.121; p = 0.048, ηp2 = 0.117).
OLA treatment produced a decline in GGT, bilirubin, ALP and albumin levels (p < 0.001, ηp2 = 0.281; p = 0.045, ηp2 = 0.123; p = 0.007, ηp2 = 0.215; p = 0.004, ηp2 = 0.285, respectively). All GOT, GPT, GGT, bilirubin and ALP levels normalized after discontinuing ARI or OLA treatment (Table S3).
No differences were found between men and women in GOT, GPT, GGT, ALP, bilirubin and albumin levels. Additionally, the changes in albumin levels differed between ARI and OLA treatment (p = 0.009, ηp2 = 0.183). The changes in the rest of the parameters were not dependent on the treatment (ARI versus OLA). No levels were outside of the normal range.
Haematological Parameters
Platelet count significantly decreased during ARI treatment (p < 0.001, ηp2 = 0.361). Additionally, the prothrombin time increased and the prothrombin index decreased over time (p < 0.001, ηp2 = 0.360; p < 0.001, ηp2 = 0.410, respectively) (Table S4).
On the contrary, the leucocyte and platelet count decreased during OLA treatment (p = 0.004, ηp2 = 0.217; p = 0.007, ηp2 = 0.199, respectively). Similarly to ARI, the prothrombin index decreased over time (p = 0.006, ηp2 = 0.237) (Table S4).
No differences were found between men and women in leucocyte, platelet, haemoglobin, red blood cell and haematocrit count, and prothrombin time and index. No levels were outside of the normal range.
Thyroid Function
Free T4 levels significantly increased after ARI treatment (p = 0.035, ηp2 = 0.180). On the contrary, after OLA treatment, decreased levels were observed. However, this association did not reach significance (p = 0.230). Neither ARI nor OLA had a significant effect on TSH levels (Fig. 3). Nonetheless, a significant difference was found between ARI and OLA treatment in both free T4 and TSH levels (p = 0.010, ηp2 = 0.267; p = 0.022, ηp2 = 0.216). No differences were found between men and women in free T4 and TSH levels. No levels were outside of the normal range.
Renal Function
Uric acid levels significantly decreased during ARI and OLA treatment (p < 0.001, ηp2 = 0.324; p = 0.045, ηp2 = 0.116) (Table S5). No differences were found between men and women in urea, creatinine and uric acid levels. Additionally, the changes in their levels were not dependent on the treatment (ARI versus OLA). The uric acid levels were not outside of the normal range.
A summary of the effects of ARI and OLA on all metabolic parameters is shown in Table 3.
Table 3 Effects of aripiprazole and olanzapine on all measured metabolic parameters