An improvement in parameters of glycemic control has been observed with Momordica charantia in patients with type 2 diabetes mellitus (T2DM). It is unknown whether this improvement is through a modification of insulin secretion, insulin sensitivity, or both. We hypothesized that M. charantia administration can improve insulin secretion and/or insulin sensitivity in patients with T2DM, without pharmacological treatment. The objective of the study was to evaluate the effect of M. charantia administration on insulin secretion and sensitivity. A randomized, double-blinded, placebo-controlled, clinical trial was carried out in 24 patients who received M. charantia (2000 mg/day) or placebo for 3 months. A 2-h oral glucose tolerance test (OGTT) was done before and after the intervention to calculate areas under the curve (AUC) of glucose and insulin, total insulin secretion (insulinogenic index), first phase of insulin secretion (Stumvoll index), and insulin sensitivity (Matsuda index). In the M. charantia group, there were significant decreases in weight, body mass index (BMI), fat percentage, waist circumference (WC), glycated hemoglobin A1c (A1C), 2-h glucose in OGTT, and AUC of glucose. A significant increase in insulin AUC (56,562 ± 36,078 vs. 65,256 ± 42,720 pmol/L/min, P = .043), in total insulin secretion (0.29 ± 0.18 vs. 0.41 ± 0.29, P = .028), and during the first phase of insulin secretion (557.8 ± 645.6 vs. 1135.7 ± 725.0, P = .043) was observed after M. charantia administration. Insulin sensitivity was not modified with any intervention. In conclusion, M. charantia administration reduced A1C, 2-h glucose, glucose AUC, weight, BMI, fat percentage, and WC, with an increment of insulin AUC, first phase and total insulin secretion.

Nutraceutic therapies such as berberine, bitter melon, Gymnema sylvestre, Irvingia gabonensis, resveratrol and ursolic acid have been shown to help control metabolic syndrome (MetS). The effect of berberine on glucose and lipid metabolism, hypertension, obesity and MetS has been evaluated in animal models and humans. Most clinical trials involving bitter melon have been conducted to evaluate its effect on glucose metabolism; nevertheless, some studies have reported favorable effects on lipids and blood pressure although there is little information about its effect on body weight. Gymnema sylvestre helps to decrease body weight and blood sugar levels; however, there is limited information on dyslipidemia and hypertension. Clinical trials of Irvingia gabonensis have shown important effects decreasing glucose and cholesterol concentrations as well decreasing body weight. Resveratrol acts through different mechanisms to decrease blood pressure, lipids, glucose and weight, showing its effects on the population with MetS. Finally, there is evidence of positive effects with ursolic acid in in vitro and in vivo studies on glucose and lipid metabolism and on body weight and visceral fat. Therefore, a review of the beneficial effects and limitations of the above-mentioned nutraceutic therapies is presented.

The aim of this study was to evaluate the effect of Irvingia gabonensis on metabolic syndrome (MetS), insulin sensitivity, and insulin secretion. A randomized, double-blind, placebo-controlled clinical trial was performed in 24 patients with MetS in accordance with the International Diabetes Federation criteria. Twelve patients received I. gabonensis (150 mg) twice a day during 90 days, and 12 patients received placebo. Glucose and insulin concentrations were measured during a 2-h oral glucose tolerance test. Also, lipid profile, creatinine, uric acid, and hepatic enzymes were determined. The area under the curve (AUC) of glucose and insulin, total insulin secretion, first phase of insulin secretion, and insulin sensitivity were calculated. Data were tested using non-parametric tests. The Ethics Committee approved the protocol. After I. gabonensis administration, significant decreases in waist circumference (WC) (94.0 ± 8.0 vs. 91.0 ± 8.2 cm, P < .01), glucose 90' (10.0 ± 2.5 vs. 8.6 ± 2.7 mmol/L, P < .05), glucose 120' (8.8 ± 2.4 vs. 7.6 ± 2.7 mmol/L, P < .05), triglycerides (2.5 ± 1.2 vs. 2.0 ± 1.1 mmol/L, P < .05), very low-density lipoproteins (VLDL) (0.5 ± 0.2 vs. 0.4 ± 0.2 mmol/L, P < .05), and AUC of glucose (694 ± 142 vs. 629 ± 172 mmol/L/min, P < .05) were found. Seven patients (58.3%) of the I. gabonensis group showed remission of MetS and two patients (16.7%) of the placebo group (P = .045). I. gabonensis lead to remission of MetS in 58.3% of the patients and significantly decreased WC, glucose 90', glucose 120', triglycerides, VLDL, and AUC of glucose.

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Type 2 diabetes mellitus (T2DM) is a complex disease that has become a major global health concern. Given the efficacy of antidiabetic drugs, pharmacological therapy is considered the first-line treatment of T2DM; however, due to their potential side effects and high costs, new and cost-effective treatments with minimal side effects are needed. Medicinal plants have been used for centuries as part of traditional medicine to treat T2DM. Among these, fenugreek, cinnamon, Curcuma longa, berberine, and Momordica charantia have demonstrated different degrees of hypoglycemic activity in clinical studies and animal models. Therefore, the aim of this review is to synthesize the mechanisms of action of five medicinal plants, as well as the experimental and clinical evidence of their hypoglycemic activity from the published literature.