Taxifolin and cilostazol for cognitive function in patients with mild cognitive impairment or mild dementia: a retrospective exploratory analysis

Abstract

Background: We previously reported that each taxifolin (TAX) and cilostazol (CSZ) have neuroprotective pleiotropic effects that target amyloid β, and that TAX is clinically associated with cognitive improvement. Thus, TAX and CSZ combination therapy could amplify cognitive improvement.

Methods and Results: In this retrospective longitudinal study, we collected data from 29 patients diagnosed with mild cognitive impairment and mild dementia who received TAX (300 mg/day) and regularly underwent the Montreal Cognitive Assessment (MoCA) or Mini-Mental State Examination (MMSE) and Alzheimer’s Disease Assessment Scale–Cognitive Subscale 13 (ADAS-Cog). The total MMSE scores were converted to the total MoCA score based on the established calculation method. The total MoCA and ADAS-Cog score changes were compared between the nontreatment (pre-TAX) period (180 ± 100 days) and the following treatment (on-TAX) period (180 ± 100 days) in patients taking CSZ (TAX/CSZ group, n = 6) and those not taking CSZ (TAX group, n = 23). Increase in the mean total MoCA scores was significantly greater during the on-TAX period than the non-TAX period in the TAX group (0.96 vs. –1.30, p = 0.016) and in the TAX/CSZ group (1.83 vs. –1.83, p = 0.011). Furthermore, the increase during the on-TAX period tended to be greater in the TAX/CSZ group than in the TAX group (1.83 vs. 0.96, p = 0.21). However, the changes in mean total ADAS-Cog score were comparable between the on-TAX and the non-TAX periods in the TAX group (p = 0.21) and the TAX/CSZ group (p = 0.44).

Conclusion: TAX and CSZ combination therapy could serve as a novel strategy for maintaining brain health during aging.

 Introduction

Disease-modifying drugs for early Alzheimer’s disease (AD), including the monoclonal anti-β amyloid (Aβ) antibodies lecanemab¹⁾ and donanemab²⁾, have been approved in several countries, including Japan, the United States, China, and Great Britain. However, these novel treatments slow the progression of cognitive deterioration rather than improve cognitive function^1,2). One of the leading reasons for this is that age-related or late-life dementia is generally characterized by neurodegeneration induced by the accumulation of amyloid plaques and neurofibrillary tangles as well as by several overlapping features, including vascular risk factors (e.g., hypertension, diabetes mellitus, and obesity), stroke, inflammation, and apolipoprotein E (APOE) genotypes³⁾. Only a small percentage of people older than 80 years indeed have “pure AD” or “pure vascular dementia”³⁾. Thus, to overcome limits in therapeutic efficacy, pleiotropic approaches may be required to achieve cognitive improvement or prevent cognitive deterioration.

Taxifolin (TAX), also called dihydroquercetin, is a natural bioactive flavonoid⁴⁾. TAX has attracted increased attention as a potential treatment for diabetes mellitus⁵⁾ and cardiovascular diseases⁶⁾ through its various positive effects, including anti-inflammatory, antioxidant, antiapoptotic, and mitochondrial protective effects⁷⁾. Specifically, in vitro and in vivo studies of brain diseases in which Aβ is overexpressed have shown that TAX inhibits aggregation of Aβ₄₀ and Aβ₄₂ and formation of oligomers⁸⁾, stimulates brain lymphangiogenesis⁹⁾, and suppresses inflammation and oxidative tissue damage in the hippocampus and cortex, thereby alleviating the accumulation of triggering receptors expressed on myeloid cell 2–expressing cells and reducing glutamate levels⁹⁾. Furthermore, in the clinical setting, we found that the long-term oral administration of TAX was significantly associated with cognitive improvement in patients with early AD and did not show any adverse events¹⁰⁾.

Cilostazol (CSZ) is a phosphodiesterase III inhibitor that has been approved for treating intermittent claudication and for the secondary prevention of noncardioembolic ischemic stroke or transient ischemic attack. In our in vivo experimental studies, we found that CSZ was notably associated with Aβ clearance through intramural periarterial drainage, ameliorating Aβ deposition¹¹⁾. Such effects may explain the fourfold increase in the serum levels of the Aβ-albumin complex after 6 months of treatment with CSZ compared with the placebo in our clinical trial, the COMCID study¹²⁾. In addition, by inhibiting glycogen synthase kinase 3β, CSZ may alleviate Aβ production and suppress tau phosphorylation^13,14). Thus, in this exploratory study, we investigated whether combination therapy of TAX with CSZ (TAX/CSZ) could serve as a pleiotropic approach to achieve cognitive improvement or prevent cognitive deterioration more effectively than TAX monotherapy.

 Methods

 Study design

We conducted this single-center retrospective longitudinal study at the National Cerebral and Cardiovascular Center (NCVC). The Ethics Review Committee of the NCVC approved the study (approval No. R24045), which was conducted in accordance with the standards of the Declaration of Helsinki. We used opt-out consent, which meant that participants were included in the study unless they expressed their decision to be excluded. We surveyed the electronic medical charts of outpatients, obtained from June 2020 to November 2021, to identify patients who met the following criteria as a primary analysis: (1) patients who underwent the Montreal Cognitive Assessment (MoCA) or Mini-Mental State Examination (MMSE) and the Alzheimer’s Disease Assessment Scale–Cognitive Subscale 13 (ADAS-Cog) at visit 1 and the MoCA and ADAS-Cog at visits 2 and 3 with an interval of 180 ± 100 days (Fig. 1A); (2) patients diagnosed with mild cognitive impairment (MCI) or mild dementia by dementia specialists certified by the Japan Society for Dementia Research (Y.H. and M.I.); (3) patients with a history of spontaneous purchase and oral intake of TAX 300 mg/day (Taxifolin Tablet, Towa Pharmaceutical, Japan) after visit 2; and (4) those who provided consent for NCVC Biobank to genotype APOE4. We converted the total MMSE score to that of the MoCA based on the established calculation¹⁵⁾. The patients voluntarily purchased TAX after a clinical research coordinator provided the following information to the patients and/or their families for more than 30 minutes, independent of the attending physicians: TAX ameliorated cognitive impairment in a study of dementia in Aβ-overexpressing mice⁸⁾, although it is unclear whether TAX is effective in patients with MCI or mild dementia. Taxifolin Tablet manufactured by Towa Pharmaceutical Co., Ltd. are commercially available. Thus, the study design consisted of two periods: the pre-taxifolin (pre-TAX) period between visits 1 and 2 and the on-taxifolin (on-TAX) period between visits 2 and 3 (Fig. 1A). Two well-trained clinical psychologists (C.K. and M.Y.) scored the MoCA and ADAS-Cog. Hypertension, dyslipidemia, and diabetes mellitus were defined based on the patient’s diagnosis history of the administration of oral antihypertensive, antihyperlipidemic, or antidiabetic drug therapy (or insulin) prescribed by the attending physician, respectively. We also surveyed antidementia drugs, including cholinesterase inhibitors (donepezil, rivastigmine, and galantamine) and memantine, which may influence cognitive function, in the enrolled patients. We excluded patients whose dosage of antidementia drugs was changed during this study. We compared the longitudinal changes in the total MoCA and ADAS-Cog scores between the pre-TAX and on-TAX periods in patients who regularly did not take CSZ (TAX group) and those who took CSZ daily (TAX/CLZ group). The primary outcome was whether the combination therapy of TAX with CSZ was associated with further cognitive improvement as compared with TAX monotherapy.

Fig. 1  Flowchart of the study: the primary analysis (A) and sensitivity analysis (B)

Abbreviations: ADAS-Cog, Alzheimer’s Disease Assessment Scale–Cognitive Subscale 13; MMSE, Mini-Mental State Examination; MoCA, Montreal Cognitive Assessment; TAX, taxifolin.

For a sensitivity analysis, we identified patients from the medical records from June 2020 to November 2021 who regularly underwent MoCA and ADAS-Cog at visits 1, 2, and 3 with an interval of 180 ± 100 days; spontaneously purchased and took TAX 300 mg/day after visit 2; and provided informed consent for the NCVC Biobank to genotype APOE4 (Fig. 1B).

 APOE genotyping

The APOE gene was genotyped using a fully automated gene analysis system (GTS-7000; Shimadzu Corporation, Kyoto, Japan). GTS-7000 directly detected single-nucleotide polymorphisms (SNPs) in 1 μL of whole-blood samples using polymerase chain reaction¹⁶⁾. We examined two SNPs, rs429358 and rs7412, which determine the APOE ε allele. APOE4 was determined using rs429358-C and rs7412-C¹⁷⁾. The primer sequences for rs429358 and rs7412 were 5'-CAAGGAGCTGCAGGCGG-3' (forward), 5'-CAGCTCCTCGGTGCTCTG-3' (reverse), and 5'-CGCAAGCTGCGTAAGCG-3' (forward) and 5'-CGCGGATGGCGCTGAG-3' (reverse), respectively. The probe sets were 5'-GGACGTGTGCGGCCG-3' for rs429358-T, 5'-GGACGTGCGCGGCCG-3' for rs429358-C, 5'-CTGCAGAAGCGCCTGGC-3' for rs7412-C, and 5'-CTGCAGAAGTGCCTGGC-3' for rs7412-T.

 Statistical analysis

Data on patient characteristics are summarized as mean ± standard deviation (SD) for continuous variables and as frequencies and percentages for categorical variables. We assessed differences in the categorical variables using the chi-square test and differences in continuous variables using the Student’s t test. We calculated temporal cognitive changes by subtracting the total scores of the MoCA and ADAS-Cog between the pre-TAX and on-TAX periods using the paired t test. All reported p values were one-sided, and p values <0.05 were considered statistically significant. We performed all analyses using SPSS software (IBM, Armonk, NY, USA) and GraphPad PRISM (GraphPad Software, Boston, MA, USA).

 Results

 Baseline characteristics of the patients

This study included 29 patients with a history of three cognitive tests and TAX intake during the on-TAX period. Among the 29 patients, 23 did not take CSZ (TAX group) and 6 took CSZ daily (TAX/CSZ group). The mean age (78.4 vs. 77.0 years; p = 0.58) and the proportion of male patients (9 [39.1%] vs. 3 [50.0%]; p = 0.63) were comparable between the two groups. The numbers of APOE4 carriers were 5 (22.7%) and 3 (50.0%), respectively (p = 0.93). At visit 1, the baseline mean total MoCA scores were 20.2 and 19.0 (p = 0.51). Moreover, the baseline mean total ADAS-Cog scores at visit 1 were 24.8 and 25.6 (p = 0.82). Hence, these patients presented with MCI or mild dementia. The mean lengths of the observational periods were 173.3 days and 200.7 days in the pre-TAX period (p = 0.31) and 180.1 days and 177.3 days in the on-TAX period (p = 0.80) for the TAX and TAX/CSZ groups, respectively (Table 1).

Table 1 Baseline characteristics of the patients

	TAX group	TAX/CSZ group	p value
Number	23	6	—
Age [years]	78.4 ± 5.8	77.0 ± 4.4	0.58
Male	9 (39.1)	3 (50.0)	0.63
APOE4	5 (21.7)	3 (50.0)	0.31
Hypertension	19 (82.6)	3 (50.0)	0.10
Diabetes mellitus	3 (13.0)	1 (16.7)	0.82
Dyslipidemia	17 (73.9)	4 (66.7)	0.72
Antihypertensive drug use	19 (82.6)	3 (50.0)	0.10
Statin use	15 (65.2)	3 (50.0)	0.49
Antidiabetic drug use	3 (13.0)	0 (0.0)	0.35
Antidementia drug use	7 (30.4)	0 (0.0)	0.12
Hemoglobin A1c [%]	6.1 ± 0.7	6.0 ± 0.5	0.75
Triglyceride [mg/dL]	130.1 ± 77.1	77.2 ± 27.5	0.11
LDL-C [mg/dL]	97.8 ± 27.1	100.1 ± 32.0	0.86
HDL-C [mg/dL]	64.2 ± 15.6	62.8 ± 13.4	0.86
Total MoCA score at visit 1*	20.2 ± 3.8	19.0 ± 5.0	0.51
Total ADAS-Cog score at visit 1	24.8 ± 7.0	25.6 ± 7.8	0.82
Observational period (pre-TAX period) [days]	173.3 ± 60.1	200.7 ± 38.0	0.31
Observational period (on-TAX period) [days]	180.1 ± 23.9	177.3 ± 25.3	0.80

Data are presented as the mean ± SD or number (%).

* The mean total MoCA score was calculated from the total MoCA score (TAX group, n = 13; TAX/CSZ group, n = 3) and the converted MoCA score from the total score of the Mini-Mental State Examination using an established conversion calculation (TAX group, n = 10; TAX/CSZ group, n = 3).

Abbreviations: ADAS-Cog, Alzheimer’s Disease Assessment Scale–Cognitive Subscale 13; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; MoCA, Montreal Cognitive Assessment; TAX, taxifolin.

 TAX and CSZ combination therapy was significantly associated with an improvement in the total MoCA score change

We compared the total MoCA and ADAS-Cog score changes between the pre-TAX and on-TAX periods in the TAX and TAX/CSZ groups, respectively. With regard to the total MoCA score, the TAX group showed that the mean total score change during the on-TAX period was significantly greater than that during the pre-TAX period (pre-TAX period: –1.30 ± 3.24 vs. on-TAX period: 0.96 ± 2.29, p = 0.016) (Fig. 2A). Furthermore, the TAX/CSZ group showed that the mean total score change during the on-TAX period was significantly greater than that during the pre-TAX period (–1.83 ± 1.33 vs. 1.83 ± 2.40, p = 0.011) (Fig. 2B). In contrast, the ADAS-Cog score changes did not differ between the pre-TAX and on-TAX periods in the TAX (–0.14 ± 3.27 vs. 0.92 ± 4.12, p = 0.21) and TAX/CSZ (0.65 ± 1.52 vs. 0.99 ± 5.64, p = 0.44) groups (Figs. 2C, D). During the on-TAX period, the mean total MoCA score change tended to be greater in the TAX/CSZ group than in the TAX group (TAX: 0.96 ± 2.29 vs. TAX/CSZ: 1.83 ± 2.40, p = 0.21) (Fig. 3).

Fig. 2  Temporal cognitive changes in the total scores of the MoCA and ADAS-Cog between the pre-TAX and on-TAX periods in the TAX and combination therapy of TAX/CSZ groups

Bar graphs showing the total MoCA score changes (A, TAX group; B, TAX/CSZ group) and the total ADAS-Cog score changes (C, TAX group; D, TAX/CSZ group). Blue bars indicate total score changes during the pre-TAX period and red bars during the on-TAX period.

Abbreviations: ADAS-Cog, Alzheimer’s Disease Assessment Scale–Cognitive Subscale 13; CSZ, Cilostazol; MoCA, Montreal Cognitive Assessment; TAX, taxifolin.

Fig. 3  Comparison of temporal cognitive changes in the total scores of the MoCA during the on-TAX period between the TAX and combination therapy (CT) of TAX/CSZ groups

Abbreviations: CSZ, cilostazol; MoCA, Montreal Cognitive Assessment; TAX, taxifolin.

Additionally, we compared the total MoCA changes between the pre-TAX and on-TAX periods in the TAX and TAX/CSZ groups according to APOE4 carriage. APOE4 noncarriers exhibited a significantly greater mean total score change during the on-TAX period than during the pre-TAX period (TAX group: –1.56 ± 3.57 vs. 1.06 ± 2.36, p = 0.050; TAX/CSZ group: –1.33 ± 1.16 vs. 3.33 ± 1.16, p = 0.020), whereas we did not observe significant changes in APOE4 carriers (TAX group: –0.40 ± 1.52 vs. 0.60 ± 2.19, p = 0.33; TAX/CSZ group: –2.33 ± 1.53 vs. 0.33 ± 2.52, p = 0.35).

 TAX and CSZ combination therapy remained significantly associated with improvement in total MoCA score change in the sensitivity analysis

The sensitivity analysis included 16 patients, consisting of 13 in the TAX group and 3 in the TAX/CSZ group. The mean age (77.5 vs. 77.7 years; p = 0.97) and the proportion of male patients (4 [30.8%] vs. 2 [75.0%]; p = 0.25) were comparable between the two groups. The numbers of APOE4 carriers were 4 (30.8%) in the TAX group and 1 (33.3%) in the TAX/CSZ group (p = 0.93). At visit 1, the baseline mean total MoCA scores were 21.4 and 19.0 (p = 0.25), whereas the baseline mean total ADAS-Cog scores at visit 1 were 22.7 and 25.8 (p = 0.49). The length of the mean observational periods were 157.5 days and 210.0 days in the pre-TAX period (p = 0.19) and 182.5 days and 191.3 days in the on-TAX period (p = 0.66) for the TAX and TAX/CSZ groups, respectively (Table 2).

Table 2 Baseline characteristics of the patients in the sensitivity analysis

	TAX group	TAX/CSZ group	p value
Number	13	3	—
Age [years]	77.5 ± 5.7	77.7 ± 4.2	0.97
Male	4 (30.8)	2 (66.7)	0.25
APOE4	4 (30.8)	1 (33.3)	0.93
Hypertension	9 (69.2)	1 (33.3)	0.25
Diabetes mellitus	1 (7.7)	0 (0.0)	0.62
Dyslipidemia	11 (84.6)	2 (66.7)	0.47
Antihypertensive drug use	9 (69.2)	1 (33.3)	0.25
Statin use	10 (76.9)	1 (33.3)	0.14
Antidiabetic drug use	1 (7.7)	0 (0.0)	0.62
Antidementia drug use	4 (30.8)	0 (0.0)	0.27
Hemoglobin A1c [%]	6.0 ± 0.4	5.9 ± 0.4	0.67
Triglyceride [mg/dL]	107.2 ± 62.6	88.3 ± 26.8	0.63
LDL-C [mg/dL]	94.7 ± 28.6	112.0 ± 44.1	0.40
HDL-C [mg/dL]	63.3 ± 15.6	58.0 ± 4.0	0.33
Total MoCA score at visit 1	21.4 ± 3.0	19.0 ± 3.6	0.25
Total ADAS-Cog score at visit 1	22.7 ± 6.4	25.8 ± 7.9	0.49
Observational period (pre-TAX period) [days]	157.5 ± 60.0	210.0 ± 55.6	0.19
Observational period (On-TAX period) [days]	182.5 ± 31.4	191.3 ± 28.3	0.66

Data are presented as the mean ± SD or number (%).

Abbreviations: ADAS-Cog, Alzheimer’s Disease Assessment Scale–Cognitive Subscale 13; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; MoCA, Montreal Cognitive Assessment; TAX, taxifolin.

In the TAX group, there was a tendency for a larger increase in the mean total MoCA score during the on-TAX period than during the pre-TAX period (–1.15 ± 2.76 vs. 0.77 ± 2.20, p = 0.072). Of note, the increase in the mean total MoCA score was significantly greater in the TAX/CSZ group during the on-TAX period than during the pre-TAX period (–1.00 ± 1.00 vs. 2.00 ± 2.00, p = 0.048) (Figs. 4A, B). However, there was no difference in the mean total ADAS-Cog score changes between the pre-TAX and on-TAX periods in either the TAX group (–0.73 ± 3.14 vs. 2.02 ± 3.79, p = 0.068) or TAX/CSZ group (–0.34 ± 0.67 vs. –0.52 ± 1.54, p = 0.45) (Figs. 4C, D).

Fig. 4  Temporal cognitive changes in the total scores of the MoCA and ADAS-Cog between the pre-TAX and on-TAX periods in the TAX and combination therapy of TAX/CSZ groups in the sensitivity analysis

Bar graphs showing the total MoCA score changes (A, TAX group; B, TAX/CSZ group) and the total ADAS-Cog score changes (C, TAX group; D, TAX/CSZ group). Blue bars indicate total score changes during the pre-TAX period and red bars during the on-TAX period.

Abbreviations: ADAS-Cog, Alzheimer’s Disease Assessment Scale–Cognitive Subscale 13; CSZ, cilostazol; MoCA, Montreal Cognitive Assessment; TAX, taxifolin.

 Discussion

This study revealed that the combination therapy of TAX with CSZ was associated with a greater improvement in cognitive function compared with TAX monotherapy. Thus, in patients with MCI or mild dementia, the addition of CSZ to TAX could contribute to further cognitive improvement.

Mixed vascular and neurodegenerative dementia, which often coexist with AD, has emerged as the leading cause of age-related cognitive impairment¹⁸⁾. In addition, according to the dynamic polygon hypothesis, age-related cognitive impairment or late-life dementia is considered to be a more complex disease: a set of pathological processes for cognitive impairment involves risk factors that affect the size of the cortex and hippocampus, such as tauopathy, inflammation, synucleinopathy, amyloid aggregation, and strokes, and environmental exposures that could affect cognitive function, including years of education, exercise, leisure activities, or body weight³⁾. Thus, to counteract cognitive deterioration, these risk and protective factors must be controlled, although plaques and tangles are two components among a larger set of factors that modulate synaptic density and the size of the cortex and hippocampus³⁾.

We previously reported that the long-term oral intake of TAX was associated with significant preservation of cognitive function as assessed by MoCA in patients with MCI or mild dementia¹⁰⁾. In vivo and in vitro studies have shown that TAX pleiotropically targets Aβ aggregation, production, and glycation; neuroinflammation; and brain lymphangiogenic effects. Previously, we administered TAX to vasculotropic Aβ–overexpressing mice^8,9). TAX prevents the formation of toxic Aβ oligomers from monomers⁸⁾, inhibits Aβ production via the suppression of the ApoE-extracellular signal-regulated kinase 1/2-amyloid precursor protein axis, and elevates the expression levels of lymphangiogenic factors, lymphatic vessel endothelial hyaluronic acid receptor 1, and vascular endothelial growth factor–D, potentially facilitating the intramural periarterial drainage system, which is responsible for waste clearance from the brain⁹⁾.

CSZ, a phosphodiesterase III inhibitor, may contribute to cognitive preservation or improvement through mechanisms other than those of TAX. In our previous preclinical study, we found that CSZ restored vascular reactivity and hemodynamic reserve, promoted intramural periarterial drainage of Aβ, reduced degenerative changes of the vascular walls with Aβ deposits, and prevented cognitive performance decline in vasculotropic Aβ–overexpressing mice because phosphodiesterase IIIA expression in the microvessels, predominantly in the smooth muscle cell layers, was markedly upregulated in patients with AD and cerebral amyloid angiopathy¹¹⁾. Thus, TAX and CSZ may exert the complementary effects shown above, and TAX and CSZ in addition to AD immunotherapy might be promising for the preservation of cognitive function.

This study demonstrated that TAX monotherapy and combination therapy of TAX and CSZ were associated with improvement in only the total MoCA score, not the total ADAS-Cog score. In our previous clinical study, we found that long-term TAX intake was significantly associated with improvement in visuospatial/executive function and verbal fluency on the MoCA, whereas it was not associated with memory on the MoCA or ADAS-Cog subscale scores¹⁰⁾. The ADAS-Cog primarily covers the memory domain (40/85 points). Furthermore, our experimental study showed that administration of cilostazol improved executive function in the Y-maze test in vasculotropic Aβ–overexpressing mice¹¹⁾. Thus, treatment with TAX/CSZ may primarily contribute to the improvement of executive function rather than memory.

It is well known that APOE4 is a major genetic risk factor for AD. The age at AD onset is decreased by approximately 8 years and 15 years in APOE4 heterozygotes and homozygotes, repectively¹⁹⁾. APOE4 promotes Aβ accumulation and aggregation²⁰⁾, inflammation²¹⁾, and reactive oxidative stress^22,23) in the brain. These detrimental effects may abolish the anti-Aβ, -inflammation, and -reactive oxidative stress effects of TAX monotherapy and combination therapy of TAX/CSZ. Accordingly, cognitive improvement during the on-TAX period was attenuated in APOE4 carriers in this study.

Our retrospective study had several limitations. First, we compared the temporal cognitive changes between the pre-TAX and subsequent on-TAX periods in the same subjects. In the pre-TAX period, the subjects received regular health advice only but not placebo or control drugs; therefore, the observed positive effect of TAX with CSZ on cognitive preservation might have resulted from a placebo effect. However, we observed an improvement in only the total MoCA scores, although not in ADAS-Cog scores, which suggests that the effects of TAX intake added on CSZ are specific to the cognitive domain but not solely explained by a general placebo effect on cognition. Second, this study’s sample size was small due to its exploratory nature; comprehensive testing with a larger sample size and a randomized controlled trial using placebo are warranted in the future.

In conclusion, cognitive improvement can be facilitated via the oral intake of TAX with CSZ, which has pleiotropic neuroprotective effects in patients with MCI or mild dementia. Because current monoclonal anti-Aβ antibodies do not improve cognitive function, the development of preventive therapy that targets multiple factors is eagerly awaited. Our results highlight the need for a randomized controlled study with placebo to analyze the effects of the combination therapy of TAX and CSZ on the preservation of cognitive function in patients with early-stage cognitive impairment.

 Funding

The study was funded by Nature Holding Col. Ltd. (Y.H.). The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.

 Disclosures

Masafumi Ihara is the Editor-in-Chief of this journal but was not involved in the peer-review process nor had access to any information regarding its peer review. Satoshi Saito and Masafumi Ihara have a patent for the combination therapy of cilostazol and taxifolin (WO2017199755A1). Yorito Hattori has no conflict of interest to report.

Acknowledgments

We thank the NCVC Biobank for providing the data. We thank Ms. Natsuki Hanada for technical assistance in genotyping APOE4, Ms. Chikage Kakuta and Ms. Miho Yamauchi for cognitive testing, and Ms. Akino Ohta for secretarial assistance.

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