Effects of long-term dietary administration of estrogen receptor-beta agonist diarylpropionitrile on ovariectomized female ICR (CD-1) mice

Abstract

Diarylpropionitrile (DPN) is an estrogen receptor-β-specific agonist that has been linked to neuroprotection, preserving cognitive function with age, the suppression of anxiety-like behaviors, inhibition of cancer growth, and other positive properties. We hypothesized that DPN may have pro-longevity properties. DPN was administered via feed at a dose corresponding to approximately 3 mg/kg/day to ovariectomized female mice beginning at 7 months of age. Mice were followed for the duration of their lifespans while monitoring body mass, aspects of behavior, learning, memory, and frailty. DPN-treated mice gained more body mass over the first 2 years of age (17 months of the study). A test of voluntary running behavior at 24 months of age behavior revealed no deficits in DPN-treated mice, which were as likely as control mice to engage in extended bouts of wheel running, and did so at higher average speeds. DPN administration had anxiolytic-like effects when measured using an elevated plus maze at 9 months of age. A mouse frailty index was used to assess age-related changes. The correlation between age and frailty differed between control and DPN-treated mice. Overall, dietary DPN administration had some beneficial effects on the aging phenotype of ovariectomized female mice with few significant detrimental effects.

Keywords: Aging; Anxiety; Diarylpropionitrile; Estrogen receptor beta; Frailty; Lifespan.

Fig. 1

Increased food consumption and body mass in DPN-treated mice. a Average daily food consumption over the first 2 years of the study (corresponding to mouse ages 7–31 months). Regression lines for control (solid) and DPN-treated (dashed) are shown. b Average daily food consumption of control (open bars) and DPN-treated (filled bars) mice over the course of the study. c Average body mass of control (open bars) and DPN-treated (filled bars) mice calculated over 20-week periods. Where shown, error bars represent SEM. * = p < 0.05 (Student’s t test)

Fig. 2

Long-term DPN treatment affects running wheel behavior at 24 months of age. Purposeful running behavior, defined as events involving wheel rotations of > 30, was evaluated in single wheel activity chambers over a 23.5-h period. a No differences between control and DPN-treated mice were observed for aggregate number of revolutions. b DPN-treated mice ran with greater average velocity. Error bars represent SEM. * = p < 0.05 (Student’s t test). n = 15 (control) and 17 (DPN). Only mice that were considered healthy at the time of testing were included

Fig. 3

Long-term DPN treatment has subtle anxiolytic effects in mice. The potential anxiolytic effect of continuous dietary administration of DPN was evaluated using a single elevated plus maze trial (a, b; 9-month-old mice in the study for 2 months) and serial open field tests (c–e; mice aged 9–20 months in the study for 2–13 months). a No difference in zone time between control and DPN-treated mice. b Increased zone entries in DPN-treated mice. c–e No difference in c total distance traveled in central and peripheral zones, d average velocity in each zone, or e permanence time in the central zone between control and DPN-treated mice at each time point. n = 23–26. Error bars represent SEM. * = p < 0.05 (Student’s t test) for individual comparisons. Note that p = 0.08 (ANOVA) for the main effect of DPN treatment on permanence time in central zone

Fig. 4

Long-term DPN treatment benefits spatial learning and memory at 28 months of age. Spatial learning and memory were tested using a Barnes maze. DPN-treated mice a spent more time in the target quadrant and b took less time to locate and investigate the escape hole than controls. n = 7 (control) and 14 (DPN). Open bars = control; filled bars = DPN-treated. Error bars represent SEM. * = p < 0.05 (t test)

Fig. 5

Long-term DPN treatment affects mouse frailty index. Relationship between age and average calculated frailty index differed in control (open symbols, dashed line) and DPN-treated (filled symbols, solid line) mice. Equations and goodness of fit of linear regression lines are shown

Fig. 6

Survivorship curves for control and DPN-treated mice. Twenty-four control mice (open symbols, dotted line) and 26 DPN-treated mice (filled symbols, solid line) were included in the study