Extract Enriched in Flavan-3-ols and Mainly Procyanidin Dimers Improves Metabolic Alterations in a Mouse Model of Obesity-Related Disorders Partially via Estrogen Receptor Alpha

Abstract

Red wine polyphenol extracts improve cardiovascular and metabolic disorders linked to obesity. Their vascular protection is mediated by the activation of the alpha isoform of the estrogen receptor (ERα). In the present study, we explored the effects of a grape seed extract (GSE) enriched in the flavan-3-ols procyanidin dimers on obesity-related cardiovascular and metabolic disorders; with a particular interest in the role/contribution of ERα. Ovariectomized wild type or ERα knockout (KO) mice were fed with standard or western diet, supplemented or not with GSE, for 12 weeks. Their body weight was monitored throughout the study, and an echocardiography was performed at the end of the treatment. Blood and tissues were collected for biochemical and functional analysis, including nitric oxide and oxidative stress measurement. Vascular reactivity and liver mitochondrial complexes activity were also analyzed. In western diet-fed mice, GSE reduced adiposity, plasma triglycerides, and oxidative stress in the heart, liver, adipose and skeletal tissues; but did not improve the vascular dysfunction. In western diet-fed mice, ERα deletion prevented or reduced the beneficial effects of GSE on plasma triglycerides and visceral adiposity. ERα deletion also prevented/reduced the anti-oxidant effect of GSE in the liver, but did not affect its capacity to reduce oxidative stress in the heart and adipose tissue. In conclusion, dietary supplementation of GSE attenuated features of metabolic syndrome partially through ERα-dependent mechanisms. This report highlights the therapeutic potential of polyphenols, and especially extract enriched in procyanidin dimers, against the metabolic disorders associated with excessive energy intake.

Keywords: estrogen receptor α; grape seed extract; metabolic disorders; obesity; vascular disorders.

FIGURE 1

The evolution of body weight gain (A,B) of estrogen receptor alpha (ERα) wild type (WT) (A) and knockout (KO) (B) mice receiving standard diet, western diet, or standard diet and western diet containing grap seed extract (GSE) at the concentration of 150 mg/kg during 12 weeks. The body weight was recorded twice a week. The data are expressed as the mean ± SEM. Statistical analyses were performed by a linear mixed model and post hoc analyses followed by Sidak correction, ^∗∗∗P < 0.001.

FIGURE 2

Circulating levels of triglycerides (A), total cholesterol (B), ratio between LDL- and HDL-cholesterol (C), and glucose (D) were evaluated in fasting plasma of ERα WT and KO mice receiving standard diet, western diet, or standard diet and western diet containing GSE at the concentration of 150 mg/kg during 12 weeks. Blood was collected by cardiac puncture at sacrifice. The data are expressed as the mean ± SEM. Statistical analyses were performed by one-way ANOVA and and post hoc analyses followed by Sidak correction, ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001.

FIGURE 3

Concentration-response curves to Ach (A,B) and 5-HT (C,D) in aortic rings from ERα WT (A,C) and KO (B,D) mice receiving standard diet, western diet, or standard diet and western diet containing GSE at the concentration of 150 mg/kg during 12 weeks. The data are expressed as the mean ± SEM. Statistical analyses were performed by a linear mixed model and post hoc analyses followed by Sidak correction, ^∗P < 0.05.

FIGURE 4

Measurement of enzymatic activities of mitochondrial cytrate synthase (CS) (A) and respiratory chain complexes (I, II, and IV) (B–D) in liver from ERα WT and KO mice receiving standard diet, western diet, or standard diet and western diet containing GSE at the concentration of 150 mg/kg for 12 weeks. The data are expressed as the mean ± SEM. Statistical analyses were performed by one-way ANOVA and post hoc analyses followed by Sidak correction ^∗P < 0.05, ^∗∗P < 0.01.

FIGURE 5

Measurement of in situ nitric oxide (NO^⋅) production by electron paramagnetic resonance (EPR) in aorta (A), heart (B), visceral (C), and subcutaneous (D) adipose tissues, liver (E), and skeletal muscle (F) from ERα WT and KO mice receiving standard diet, western diet, or standard diet and western diet containing GSE at the concentration of 150 mg/kg during 12 weeks. The data were expressed as the mean ± SEM. Statistical analyses were performed by one-way ANOVA and post hoc analyses followed by Sidak correction, ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001.

FIGURE 6

Measurement of in situ ROS production by EPR in aorta (A,B), heart (C), visceral (D), and subcutaneous (E) adipose tissues, liver (F), and skeletal muscle (G) from ERα WT and KO mice receiving standard diet, western diet, or standard diet and western diet containing GSE at the concentration of 150 mg/kg during 12 weeks. The data were expressed as the mean ± SEM. Statistical analyses were performed by one-way ANOVA and post hoc analyses followed by Sidak correction, ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001.

FIGURE 7

In western diet-fed mice, dietary supplementation with GSE reduced circulating triglycerides, liver oxidative stress and adiposity, and increased hepatic complex II activity via an ERα-dependent mechanism. However, in skeletal muscle, heart and adipose tissue, GSE supplementation decreased ROS production independently to ERα. Hence, the effects triggered by GSE attenuate most features of metabolic dysfunctions partially via ERα.