Previous studies have shown that α-mangostin (α-MG) suppresses intracellular fat accumulation and stimulation of lipolysis in in vitro systems. Together with the relatively high distribution of α-MG in liver and fat, these observations made it possible to propose a plausible hypothesis that an α-MG supplement may regulate hepatic steatosis and obesity. An α-MG supplement (50 mg/kg) reduced the body weight gain (13.8%) and epidymal and retroperitoneal fat mass accumulation (15.0 and 11.3%, respectively), as well as the biochemical serum profiles such as cholesterol [TC (26.9%), LDL-C (39.1%), and HDL-C (15.3%)], glucose (30.2%), triglyceride (29.7%), and fatty acid (30.3%) levels in high-fat fed mice compared with the high-fat diet-treated group, indicating that α-MG may regulate lipid metabolism. In addition, an α-MG supplement up-regulated hepatic AMPK, SirT1, and PPARγ levels compared with the high-fat diet states, suggesting that α-MG regulates hepatic steatosis and obesity through the SirT1-AMPK and PPARγ pathways in high-fat diet-induced obese mice.

This study investigated the effects of mangosteen on metabolic syndromes in high-fat (HF) diet-fed mice and the underlying mechanisms related to adipogenesis. Mangosteen-supplemented mice gained significantly less body weight, compared with the HF group. The levels were markedly elevated in HF mice for serum glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, glucose, triglyceride, total cholesterol, low-density lipoprotein (LDL) cholesterol, and free fatty acid; whereas these levels were significantly lower in the 200 mg/kg of the mangosteen extract-treated group. The mangosteen extract did not modify high-density lipoprotein (HDL)-cholesterol, however, LDL-cholesterol was lower and HDL/LDL ratio was higher (9.4 vs. 3.7 in HF group). Furthermore, 200 mg/kg of mangosteen treatment activated the hepatic AMP-activated protein kinase and Sirtuin 1 in an in vivo system. Thus, the results of this study suggest that mangosteen extract exerts antiobesity effects by regulating energy metabolism and hepatic lipid homeostasis.

1. The metformin and Scutellariae radix extract (SB) combination has been previously reported to enhance anti-diabetic activity. Considering that organic cation transporters (OCTs) and multi-drug and toxin extrusion proteins (MATEs) in the liver and kidney are determinant factors on hepatic distribution and renal clearance of metformin, the effects of SB on OCT or MATE-mediated systemic exposure of metformin as well as on glucose tolerance and hypoglycemia were examined. 2. Although SB inhibited metformin uptake through human transporters OCT1 and MATE1 in vitro, the systemic exposures of metformin in vivo rats were not altered after metformin treatment with and without SB due to unchanged renal excretion of metformin. 3. However, 28-day metformin treatment with SB decreased the mRNA level of hepatic MATE1 in rats, resulting in reduced biliary excretion of metformin and thereby higher concentration of metformin in the liver. In addition, in rats with 28-day metformin treatment with SB, glucose tolerance and plasma lactate level were enhanced, while hypoglycemia was not detected. 4. Thus in rats, intervention of SB on transporter-mediated metformin transportation partially improves glucose tolerance without hypoglycemia and increases hepatic distribution of metformin. Also the further investigations in humans are required to clarify the relevance of these findings to the clinical significance.

Metformin as an oral glucose-lowering drug is used to treat type 2 diabetic mellitus. Considering the relatively high incidence of cardiovascular complications and other metabolic diseases in diabetic mellitus patients, a combination of metformin plus herbal supplements is a preferrable way to improve the therapeutic outcomes of metformin. Ginseng berry, the fruit of Panax ginseng Meyer, has investigated as a candidate in metformin combination mainly due to its anti-hyperglycemic, anti-hyperlipidemic, anti-obesity, anti-hepatic steatosis and anti-inflammatory effects. Moreover, the pharmacokinetic interaction of metformin via OCTs and MATEs leads to changes in the efficacy and/or toxicity of metformin. Thus, we assessed how ginseng berry extract (GB) affects metformin pharmacokinetics in mice, specially focusing on the effect of the treatment period (i.e., 1-day and 28-day) of GB on metformin pharmacokinetics. In 1-day and 28-day co-treatment of metformin and GB, GB did not affect renal excretion as a main elimination route of metformin and GB therefore did not change the systemic exposure of metformin. Interestingly, 28-day co-treatment of GB increased metformin concentration in the livers (i.e., 37.3, 59.3% and 60.9% increases versus 1-day metformin, 1-day metformin plus GB and 28-day metformin groups, respectively). This was probably due to the increased metformin uptake via OCT1 and decreased metformin biliary excretion via MATE1 in the livers. These results suggest that co-treatment of GB for 28 days (i.e., long-term combined treatment of GB) enhanced metformin concentration in the liver as a pharmacological target tissue of metformin. However, GB showed a negligible impact on the systemic exposure of metformin in relation to its toxicity (i.e., renal and plasma concentrations of metformin).

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