Garcinia cambogia Extract Increased Hepatic Levels of Lipolysis-Stimulated Lipoprotein Receptor and Lipids in Mice on Normal Diet

Abstract

Garcinia cambogia extract (GCE) is a popular weight-loss supplement that also lowers plasma triglyceride (TG) levels. We hypothesized that GCE-mediated inhibition of ATP citrate lyase and thereby hepatic TG production could lead to compensatory mechanisms, including increased hepatic TG uptake via lipoprotein receptors. GCE (20 mg/day) administered 40 days orally to female C57BL/6Rj mice on a standard chow diet led to a decrease in both plasma fasting and post-prandial TG-rich lipoprotein levels, but with no significant change in body weight gain. Lipolysis stimulated lipoprotein receptor (LSR) protein levels, but not those of LDL-receptor, were increased as compared to controls. Mouse Hepa1-6 cells treated with the GCE active ingredient, hydroxycitrate, also led to increased LSR protein levels. Hepatic total cholesterol, TG, and muscle TG contents were higher in GCE-treated animals as compared to controls, whereas adipose TG levels were unchanged. LSR and LDL-receptor protein levels were correlated with liver total cholesterol, but only LDL-receptor was associated with liver TG. These results show that GCE treatment in mice on a standard chow diet led to significantly increased liver and muscle lipids, with no significant change in adipose tissue TG levels, which should be considered in the long-term use of GCE.

Keywords: Garcinia cambogia; lipid homeostasis; lipoprotein receptors; liver; mice; triglycerides.

Figure 1

Effect of GCE on body mass in C57BL/6J mice. Ten-week-old female C57BL/6J mice received 300 µL of 50% (v/v) corn oil emulsion in physiological saline containing 20 mg GCE (■, GCE, n = 10); control mice received only the corn oil emulsion (CTRL, ☐, n = 10), as described in Materials and Methods. Body mass was monitored at the indicated times; changes in body mass compared to Day 1 are shown as mean ± SEM. Statistical analyses were performed using a 2-way ANOVA (# p < 0.05 as compared to day 1 CTRL; * p < 0.05 or ** p < 0.01, as compared to Day 1 GCE).

Figure 2

Effect of GCE treatment on daily food intake per body mass and feed efficiency. Daily food intake and body mass were measured at the indicated days in CTRL (CTRL, ☐, and n = 10) and GCE (GCE, ■, and n = 10) groups treated as described in Figure 1. Results are the means ± SEM of the ratio of daily food intake (kcal) per body mass (A) and feed efficiency (body weight gain from Day 1 per daily caloric intake). (B) Statistical analyses were performed using 2-way ANOVA (* p < 0.05, ** p < 0.01, or *** p < 0.001 comparing CTRL and GCE groups; # p < 0.05, ## p < 0.01, and ### p < 0.001, compared to Day 8 of the same group; and § p < 0.05 and §§ p < 0.01, compared to Day 15 of the same group).

Figure 3

Effect of GCE on plasma lipid and glucose levels and lipoprotein profiles in C57BL/6J mice. C57BL/6J mice were treated with GCE as described in Figure 1 (GCE, n = 10, and ■; CTRL, n = 10, and ☐). On day 30 of treatment, blood samples from CTRL and GCE groups were taken between 8:00 AM and 9:00 AM, representing the post-prandial period, and after a 3 h fasting period (3 h fasting), from which plasma was isolated and plasma triglycerides (TG) (A), total cholesterol (TC) (B), and glucose (C) levels were determined. Results are shown as means ± SEM; all p-values were calculated from Student’s t-test. (D) On day 40 of treatment, mice were anesthetized, and blood samples were obtained via cardiac puncture. Plasma was isolated and pooled from 3 mice from each group, from which a lipoprotein profile was obtained using gel filtration chromatography as described in Materials and Methods. Fractions were analyzed for TG (top panel) and TC (bottom panel) content. The elution of TG-rich lipoproteins, including VLDL and chylomicrons, LDL, and HDL, is indicated with arrows.

Figure 4

Effect of GCE on hepatic protein levels of lipoprotein receptors and enzymes involved in TG metabolism. C57BL/6J mice were treated with GCE as described in Figure 1. On day 40 of treatment, mice were sacrificed, and livers were excised. Liver membranes and non-membrane fractions were prepared. Proteins from each fraction were separated on SDS-PAGE, followed by immunoblots to detect (A) LSR and (B) LDL-R in the total membrane fractions, (C) lipoprotein lipase (LpL), (D) ACL, and (E) FAS in the non-membrane fractions prepared from livers of CTRL (☐) and GCE (■) groups. For LSR and LDL-R, the leptin receptor (Ob-R) was used as internal control as its protein levels did not significantly change between each group of animals. For LpL, ACL, and FAS, β-tubulin was used as the internal control. Representative immunoblots are shown (top panels), as well as results of densitometric analyses (bottom panels) as means ± SEM (n = 5–8 per group); p-values are shown in the figure and were calculated using Student’s t-test.

Figure 5

Correlation matrix comparing plasma and tissue lipid parameters with liver proteins from both CTRL and GCE groups. Correlations between different parameters are shown as heatmap, ranging from +1.0 (blue) to −1.0 (red) (PP, post-prandial; AT, adipose tissue; and SM, skeletal muscle).

Figure 6

Effect of HCA or the lactone form of HCA (HCA-lactone) on LSR and ACL protein levels in Hepa1-6 cells. Hepa1-6 cells at 80–90% confluency were incubated with the indicated concentrations of (A) HCA or (B) HCA-lactone for 18 h at 37 °C, followed by cell lysis to extract total proteins. Immunoblots were performed on the cell protein extracts to detect LSR or ACL, as described in Methods and Materials. Densitometric analyses were performed using β-tubulin as the loading control. Results are shown as means ± SEM (n = 3). Statistical analyses were performed using Student’s t-test; p values are shown in the figure.