Dietary cocoa ameliorates obesity-related inflammation in high fat-fed mice

Abstract

Purpose: To investigate the effect of cocoa powder supplementation on obesity-related inflammation in high fat (HF)-fed obese mice.

Methods: Male C57BL/6J (n = 126) were fed with either low-fat (LF, 10 % kcal from fat) or HF (60 % kcal from fat) diet for 18 weeks. After 8 weeks, mice from HF group were randomized to HF diet or HF diet supplemented with 8 % cocoa powder (HF-HFC group) for 10 weeks. Blood and tissue samples were collected for biochemical analyses.

Results: Cocoa powder supplementation significantly reduced the rate of body weight gain (15.8 %) and increased fecal lipid content (55.2 %) compared to HF-fed control mice. Further, cocoa supplementation attenuated insulin resistance, as indicated by improved HOMA-IR, and reduced the severity of obesity-related fatty liver disease (decreased plasma alanine aminotransferase and liver triglyceride) compared to HF group. Cocoa supplementation also significantly decreased plasma levels of the pro-inflammatory mediators interleukin-6 (IL-6, 30.4 %), monocyte chemoattractant protein-1 (MCP-1, 25.2 %), and increased adiponectin (33.7 %) compared to HF-fed mice. Expression of pro-inflammatory genes (Il6, Il12b, Nos2, and Emr1) in the stromal vascular fraction (SVF) of the epididymal white adipose tissue (WAT) was significantly reduced (37-56 %) in the cocoa-supplemented mice.

Conclusions: Dietary supplementation with cocoa ameliorates obesity-related inflammation, insulin resistance, and fatty liver disease in HF-fed obese mice, principally through the down-regulation of pro-inflammatory gene expression in WAT. These effects appear to be mediated in part by a modulation of dietary fat absorption and inhibition of macrophage infiltration in WAT.

Fig. 1

Effect of cocoa supplementation on body weight, body fat mass, and organ weight. a Body weights were determined over the course of 18 weeks. b The rate of body weight gain was calculated after cocoa supplementation (week 9–18). c Visceral fat mass and d gross organ weights were determined at the end of the experiment. Data were pooled from two identical studies (Experiment 1 and Experiment 2). LF, n = 35; HF, n = 44; and HF-HFC, n = 47. Values are expressed as mean ± SEM. Body weights were compared by two-way ANOVA with Bonferroni’s posttest (an asterisk indicates P < 0.05 compared to HF group). Mice body weights in LF group were significantly lower than HF mice since week 1. All other parameters were compared by one-way ANOVA with Dunnett’s posttest (an asterisk indicates P < 0.05 compared to HF-fed controls)

Fig. 2

Effect of cocoa supplementation on the markers of ORFLD. a Plasma alanine aminotransferase (ALT) and b liver triglyceride levels were determined at the end of the experiment. Values are expressed as mean ± SEM. Plasma samples were taken from Experiment 1. LF, n = 12; HF, n = 23 and HF-HFC, n = 23. Lipid was extracted from liver samples from Experiment 2. LF, n = 23; HF, n = 21 and HF-HFC, n = 24. Means were compared to the HF-fed controls by one-way ANOVA with Dunnett’s posttest (an asterisk indicates P < 0.05)

Fig. 3

Effect of cocoa supplementation on systemic circulating levels of cytokines, chemokines, and adipokines. Plasma levels of a MCP-1, b IL-6, c TNF-α, and d adiponectin. Plasma samples were taken from Experiment 1. LF, n = 12; HF, n = 23; and HF-HFC, n = 23. Values are expressed as mean ± SEM. Means were compared to the HF-fed controls by one-way ANOVA with Dunnett’s posttest (an asterisk indicates P < 0.05)

Fig. 4

Effect of cocoa supplementation on the expression of pro-inflammatory genes in SVF of WAT. Expression of a Il6, b Il12b, c Nos2, and d Emr1 was determined at the end of the experiment using RNA isolated from the epididymal SVF from a set of representative mice from Experiment 2. LF, n = 10; HF, n = 18; and HF-HFC, n = 18. Values are expressed as mean ± SEM. Means were compared to the HF-fed controls by one-way ANOVA with Dunnett’s posttest (an asterisk indicates P < 0.05)