Pitavastatin attenuates hypercholesterolemia-induced decline in serotonin transporter availability

Abstract

Introduction: Hypercholesterolemia is associated with increased inflammation and impaired serotonin neurotransmission, potentially contributing to depressive symptoms. However, the role of statins, particularly pitavastatin, in modulating serotonin transporter (SERT) function within this context remains underexplored. This study aimed to investigate whether pitavastatin counteracts the neurobiological effects of hypercholesterolemia.

Methods: Low-density lipoprotein receptor knockout (LDLR^-/-) mice on a C57BL/6 background were assigned to three groups: a control group fed a standard chow diet, a group fed a high-fat diet (HFD), and a third group fed a high-fat diet supplemented with pitavastatin (HFD + Pita). We evaluated the effects of HFD with or without pitavastatin on lipid profiles, inflammatory markers, and SERT availability using small-animal positron emission tomography (PET) scans with the radioligand 4-[¹⁸F]-ADAM over a 20-week period.

Results: Pitavastatin treatment in HFD-fed mice significantly reduced both total cholesterol and LDL cholesterol levels in HFD-fed mice compared to those on HFD alone. Elevated inflammatory markers such as IL-1α, MCP-1/CCL2, and TNF-α in HFD mice were notably decreased in the HFD + Pita group. PET scans showed reduced SERT availability in the brains of HFD mice; however, pitavastatin improved this in brain regions associated with mood regulation, suggesting enhanced serotonin neurotransmission. Additionally, the sucrose preference test showed a trend towards increased preference in the HFD + Pita group compared to the HFD group, indicating a potential reduction in depressive-like behavior.

Conclusion: Our findings demonstrate that pitavastatin not only lowers cholesterol and reduces inflammation but also enhances SERT availability, suggesting a potential role in alleviating depressive symptoms associated with hypercholesterolemia. These results highlight the multifaceted benefits of pitavastatin, extending beyond its lipid-lowering effects to potentially improving mood regulation and neurotransmitter function.

Keywords: 4-[18F]-ADAM; Depression; Hypercholesterolemia; Pitavastatin; Positron emission tomography; Serotonin transporter (SERT).

Fig. 1

Schematic of the study design. All mice started on a standard chow diet after weaning. Mice were randomly divided into 3 groups at 8 weeks of age. Group 1 continued on the chow diet (CD). Group 2 switched to a high-fat diet (HFD). Group 3 switched to a HFD and began pitavastatin treatment at week 12. The 4-[¹⁸F]-ADAM micro-PET imaging was performed for all groups at weeks 12 and 20. After PET imaging at weeks 20, mice were sacrificed, and blood samples were collected for lipid profiles and analyses of inflammatory cytokines or chemokines. A separate batch of mice, following the same treatment protocol, underwent behavioral tests (not involving PET imaging)

Fig. 2

Serum lipid profiles of mice at 20 weeks of age. Data are presented as mean ± SD. Statistical analyses were performed using one-way ANOVA followed by Tukey’s test for post-hoc comparisons. Abbreviation: CD, chow diet; HFD, high-fat diet; TG, triglycerides; HDL-C, high-density lipoprotein cholesterol; TCHO, total cholesterol; LDL-C, low-density lipoprotein cholesterol; GPT, alanine aminotransferase; GOT, aspartate aminotransferase. Each group consisted of n = 5 mice. Statistical significance is indicated by ***p < 0.005 compared with the CD group; ###p < 0.005 compared with the HFD group

Fig. 3

Plasma levels of cytokine and chemokine in LDLR.^−/− mice at week 20. Plasma samples were analyzed using Merck Multiplex Assays for cytokines and chemokines analyses, including: (A) IL-1α; (B) IL-5; (C) IL-6; (D) IL-15; (E) MCP-1/CCL2; (F) MIP-1α/CCL3; (G) RANTES/CCL5; (H) Eotaxin/CCL11; (I) KC/CXCL1; (J) MIP-2/CXCL2; (K) MIG/CXCL9; (L) IP-10/CXCL10; (M) TNF-α; (N) G-CSF. Data are presented as mean ± SD. Statistical analyses were performed using one-way ANOVA followed by Tukey’s test for post-hoc comparisons. Statistical significance is indicated by *p < 0.05, **p < 0.01, and ***p < 0.005 compared with the CD group; #p < 0.05, and ###p < 0.005 compared with the HFD group. Abbreviation: CD, chow diet; HFD, high-fat diet; IL, interleukin; MCP, monocyte chemoattractant protein; CCL, CC chemokine ligand; MIP, macrophage inflammatory protein; RANTES, regulated on activation, normal T-cell expressed and secreted; KC, keratinocyte-derived chemokine; CXCL, CXC chemokine ligand; MIG, monokine induced by interferon-γ; IP, interferon-γ-induced protein; TNF-α, tumor necrosis factor α; G-CSF, granulocyte colony-stimulating factor (n = 4 in each group)

Fig. 4

PET imaging of 4-[¹⁸F]-ADAM in mouse brain regions at weeks 12 and 20. The representative PET images display the uptake of 4-[¹⁸F]-ADAM in various brain regions at two time points, weeks 12 and 20. These images are superimposed with MRI images to provide an anatomical reference, delineating the regions of interest (shown on the far left). The standardized uptake ratio (SUVr) is used to quantify the PET signal intensity relative to a reference region, the cerebellum

Fig. 5

Standardized uptake ratios (SUVr) of 4-[¹⁸F]-ADAM in mouse brain regions at weeks 12 and 20. The figure dysplays a series of plots that graphically represent the SUVr of 4-[¹⁸F]-ADAM in various brain regions of mice at two time points, weeks 12 and 20. Lines represent the different groups: CD (chow diet, n = 6, depicted in black), HFD (high-fat diet, n = 5, depicted in red), and HFD + Pita (high-fat diet with pitavastatin, n = 5, depicted in blue). Statistical differences were analyzed by repeated measures ANOVA. Statistical significance between the groups is marked with symbols: asterisks (*) indicating significance compared to the CD group (*p < 0.05, **p < 0.01) and a hash (#) indicating significance compared to the HFD group (#p < 0.05)

Fig. 6

Comparison of sucrose preference and tail-suspension tests among groups. Data of the sucrose preference test and the tail-suspension test are presented as mean ± SD for the CD (chow diet, n = 5), HFD (high-fat diet, n = 9), and HFD + Pita (high-fat diet with pitavastatin, n = 7) groups. Statistical significance is denoted by ***p < 0.005