Equol Production and Increased Leukocyte Mitochondrial DNA in Postmenopausal Women

Juwon Ahn; Seungha Baek; Kijeong Kim; Hyowon Bang; Jaehong Ko; Jung-Ha Kim

doi:10.15384/kjhp.2015.15.3.108

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Ahn, Baek, Kim, Bang, Ko, and Kim: Equol Production and Increased Leukocyte Mitochondrial DNA in Postmenopausal Women

Original Article

Korean J Health Promot 2015;15(3):108-114.

Published online: 19 December 2015

DOI: https://doi.org/10.15384/kjhp.2015.15.3.108

Equol Production and Increased Leukocyte Mitochondrial DNA in Postmenopausal Women

Juwon Ahn¹, Seungha Baek¹, Kijeong Kim², Hyowon Bang³, Jaehong Ko³, Jung-Ha Kim¹

¹Department of Family Medicine, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Korea

²Department of Microbiology, Chung-Ang University College of Medicine, Seoul, Korea

³Department of Physiology, Chung-Ang University College of Medicine, Seoul, Korea

Corresponding author：Jung-Ha Kim, MD Department of Family Medicine, Chung-Ang University Hospital, Chung-Ang University College of Medicine, 102 Heukseok-ro, Dongjak-gu, Seoul 06973, Korea Tel: +82-1800-1114, Fax: +82-6264-8272 E-mail: girlpower219@cau.ac.kr

Received 9 March 2015 Accepted 11 July 2015

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

Equol, a metabolite of diadzein, is produced by some intestinal bacteria. Equol acts as an estrogen receptor agonist and has been reported to have several beneficial health effects. Leukocytes play an important role in the pathogenesis of autoimmune, metabolic, and cardiovascular diseases. Decreased leukocyte mitochondrial DNA (mtDNA) content, as an index of mitochondrial function, is associated with metabolic syndrome, bone mineral density, and aging. The possible association between equol production and leukocyte mitochondrial function has not been studied to date. Therefore, we investigated whether equol production is associated with leukocyte mtDNA copy number in postmenopausal women.

Methods

This observational cross-sectional study included 71 postmenopausal women. They completed a lifestyle questionnaire and medical history. In addition, a dietary assessment using a 24-hour recall method and food frequency questionnaire, anthropometric evaluation, and blood sampling were conducted. Serum equol concentration was measured in the fasting state. Leukocyte mtDNA copy number was measured by real-time polymerase chain reaction.

Results

Among older females, 33.8% were equol producers. The leukocyte mtDNA copy number was lower in non-equol producers versus equol producers. Furthermore, the leukocyte mtDNA copy number was positively associated with the serum equol concentration (r=0.42, P<0.01). Stepwise multiple regression analysis showed that equol production (β=47.864, P<0.01) was an independent factor associated with mtDNA copy number.

Conclusions

Equol production was associated with elevated mtDNA content in the peripheral blood of postmenopausal women. This finding suggests that the beneficial health effects of equol in postmenopausal women may be related to increased mitochondrial function.

Keywords: Equol, Leukocytes, DNA, Mitochondria, Postmenopause

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Figure 1.

Leukocyte mitochondrial DNA copy number among premenopausal women, postmenopausal equol producers, and postmenopausal non-equol producers. Premenopausal women: 262.21 (50.04); postmenopausal equol producers: 190.72 (29.19); and postmenopausal non-equol producers: 143.36 (26.58). P-values were calculated using ANCOVA for adjustment of age. ^aPremenopausal women; ^bPostmenopausal equol producer women; ^cPostmenopausal non-equol producer women.

Figure 2.

Association between leukocyte mitochondrial DNA copy number and serum equol concentrations. P-values were calculated by Pearson’s correlation.

Table 1.

Characteristics of the study subjects (n=71)^a

	Equol producer (n=24)	Non-equol producer (n=47)
Age, y	71.6±4.4	69.9±3.7
Body mass index, kg/m²	25.62.8	24.73.2
Waist-hip ratio	0.9±0.1	0.9±0.1
Total body fat, %	35.6±6.2	34.5±7.0
Total body lean mass, kg	21.0±2.6	19.6±2.3
Systolic blood pressure, mmHg	127.6±11.9	129.4±11.7
Diastolic blood pressure, mmHg	72.3±9.4	74.8±9.2
Fasting glucose, mg/dL	101.4±18.2	102.8±16.0
Fasting insulin, μIU/mL	6.9±3.0	6.7±2.9
HOMA-IR	1.7±0.8	1.7±0.8
Total cholesterol, mg/dL	199.2±41.2	202.5±46.3
Triglyceride, mg/dL^b	106.5 (64.0-131.0)	127 (81-127)
HDL-cholesterol, mg/dL	51.9±10.5	51.1±9.8
LDL-cholesterol, mg/dL	121.1±34.5	123.5±37.4
Estimated GFR, mL/min	97.5±19.7	93.8±17.4
Leukocyte, /μL	5,662.8±1,410.8	5,862.5±1,473.0
Hs-CRP, mg/mL^b	0.6 (0.3-1.3)	0.8 (0.4-2.6)
TSH, μIU/mL	1.9±1.1	2.2±1.1
25-OH vitamin D, ng/mL	12.5±5.2	12.2±6.1
Total energy intake, kcal/d	1,488.9±283.4	1,587.7±314.8
Protein intake, % kcal	15.9±2.0	16.0±2.7
Isoflavone intake, mg/d^b	38.3 (13.9-59.5)	25.5 (13.4-41.0)
Current smoker	1 (4.2)	0
Alcohol consumption^c	4 (16.7)	6 (12.8)
Regular exercise	12 (50.0)	20 (42.6)
Medication
Hypertension	10 (41.7)	20 (42.6)
Diabetes	3 (12.5)	7 (14.9)
Dyslipidemia	4 (16.7)	8 (17.0)

Abbreviations: HOMA-IR, homeostasis model assessment of insulin resistance; HDL, high-density lipoprotein; LDL, low-density lipoprotein; GFR, glomerular filtration rate; Hs-CRP, high-sensitivity C-reactive protein; TSH, thyroid-stimulating hormone; 25-OH vitamin D, 25-hydroxyvitamin D.

^a Values are presented as mean±SD unless otherwise indicated.

^b Median (interquartile range, IQR).

^c Defined as consumption of 72 g or more of alcohol per week.

Table 2.

Correlation between leukocyte mitochondrial DNA copy number and variables^a

Variables	r	P^b
Age	-0.20	0.040
Body mass index	-0.12	0.240
Waist hip ratio	-0.20	0.050
Total body fat	0.01	0.930
Total lean body mass	0.16	0.110
Systolic blood pressure	-0.26	0.005
Diastolic blood pressure	-0.10	0.320
Fasting glucose	-0.17	0.070
Fasting insulin	-0.01	0.910
HOMA-IR	-0.06	0.550
Total cholesterol	-0.06	0.540
Triglyceride^c	-0.15	0.120
HDL-cholesterol	0.03	0.780
LDL-cholesterol	-0.04	0.650
Estimated GFR	0.20	0.040
Leukocyte	-0.14	0.160
Hs-CRP^c	-0.22	0.030
TSH	-0.13	0.120
25-OH vitamin D	0.17	0.090
Total energy intake	-0.05	0.610
Protein intake	0.08	0.460
Isoflavone intake^c	0.17	0.150

^a Mitochondrial DNA copy number has been analyzed after log-transformation.

^b Calculated by Pearson’s correlation analysis.

^c Median (interquartile range, IQR).

Table 3.

Stepwise multiple linear regression analysis to identify independent clinical variables associated with leukocyte mitochondrial DNA copy number

Variables	β	Standard error	F-value	P
Equol production	47.864	10.446	42.83	0.002
Age	-1.141	0.364	6.15	0.020
Total lean body mass	4.483	1.577	7.25	0.010

All variables remaining in the model are significant at the 0.15 level. No other variables met the 0.15 significance level for entry into the model; R² for telomere length was 0.81; Variables included in the stepwise model were body mass index; waist-hip ratio; total body fat; systolic blood pressure; estimated GFR; fasting glucose; hs-CRP; 25-OH vitamin D; alcohol consumption; regular exercise; and use of anti- hypertensive, anti-diabetic, and lipid lowering agents.

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