The effect of GCE on body weight
This study shows that high-fat diet induces obesity in male rats, and the administration of low dose GCE resulted in weight loss in these obese rats. The chlorogenic acid content in GCE has been shown to have an anti-obesity effect [7, 8, 12]. Previously, a study in mice given high-fat diet and GCE at 100-200 mg/kg BW showed that GCE supplementation decreased body weight gain [13]. The observed anti-obesity effect may work by suppressing lipogenesis and stimulating lipolysis [13].
Our results are in line with previous findings in mice that showed chlorogenic acid affects obesity by lowering body fat accumulation through adipogenesis regulation [14]. Chlorogenic acid increases lipid metabolism in HFD-induced obese rats [8, 12]. GCE significantly reduced visceral fat accumulation, improved insulin resistance [9], and, when combined with energy-restricted diet, may lead to a significant reduction in body mass index, fat mass, and waist-hip ratio [15].
The effect of GCE on lipid profile
Antioxidant-rich foods known to lower serum cholesterol, LDL, and triglyceride levels. In this study, we found that low dose GCE administration lowers total serum cholesterol, triglycerides, and LDL-cholecsterol levels. GCE contains CGA, a potent antioxidant compound. It has been shown that CGA increases lipid metabolism, decreases triglyceride, and total cholesterol levels, possibly by its effect on fatty acid oxidation [16]. CGA in green coffee is an active compound capable of increasing metabolism rate [16], increasing fatty acid oxidation [8, 16], and decreasing hepatic triglyceride [7]. Apart from the CGA, the polyphenols in coffee also had a property in lowering visceral fat accumulation [18]. Unfortunately, we did not perform abdominal dissection to quantify visceral fat in this study.
In the current study, we found that the GCE has a negative effect on serum HDL levels. Serum HDL was lower in groups receiving 40 mg/kg BW/day dose. In contrast, those receiving lower dose (10 and 20 mg/kg BW/day) showed higher HDL levels despite not being statistically significant. This result is in line with a previous study were 28 days of chlorogenic acid intake lowered HDL level in male rats through regulation of hepatic PPARα expression [16, 19]. These results might be explained by the possibility that CGA works specifically through the pro-atherogenic pathway of cholesterol metabolism. A clinical study in obese women aged 20-45 years showed that green coffee extract combined with calorie-restricted diet affected lipid metabolism through significant change in serum total cholesterol, LDL, and free fatty acid [15].
The effect of GCE on TNF-α
Our result showed that GCE decreased serum TNF-α statistically significantly in the group receiving 40 mg/kg BW/day dose. We showed that the effect on TNF-α is dose-dependent; however, the normal level of TNF-α (10-100 pg/ml) could not be attained with the given doses. A higher dose or more prolonged intake of GCE may result in a further decrease of TNF-α. It has been shown that CGA, the powerful antioxidant in GCE, attenuates serum levels of TNF-α in liver inflammation model [20]. CGA may downregulate the activation of NF-kB, which leads to a lower level of ROS that inhibits the production of the pro-inflammatory cytokine, like TNF-α [21].