Elsevier

Journal of Ethnopharmacology

Volume 231, 1 March 2019, Pages 311-324
Journal of Ethnopharmacology

Review
Momordica charantia L. lowers elevated glycaemia in type 2 diabetes mellitus patients: Systematic review and meta-analysis

https://doi.org/10.1016/j.jep.2018.10.033Get rights and content

Abstract

Ethnopharmacological relevance

Momordica charantia Linnaeus (Cucurbitaceae) has been extensively used traditionally as food and herbal medicine for type 2 diabetes mellitus in Asia, Brazil, and east Africa. In vitro and in vivo studies suggest its glycemic control potential; however, clinical studies produced conflicting results.

Aim of the study

To evaluate the efficacy of M. charantia preparations in lowering elevated plasma glucose level in prediabetes and type 2 diabetes mellitus patients.

Methods

Electronic search of the Cochrane library, PubMed®, CINAHL, and SCOPUS databases was done from 1st January 1960–30th April 2018 without language restriction. Two independent reviewers extracted data and assessed risk of bias of articles. Revman var. 5.3 software was used for data synthesis in meta-analysis. Heterogeneity was assessed using Chi-square and I2 tests. Treatment effect was estimated using mean difference at follow up in outcome measures between M. charantia preparations and placebo or oral hypoglycemic agents control group. The protocol of this study has a registration number PROSPERO CRD42018083653.

Results

Ten studies of type 2 diabetes mellitus (n = 1045) were included in the meta-analysis. They had 4–16 weeks follow up and overall moderate to high risk of bias. Compared to placebo, M. charantia monoherbal formulation significantly reduces FPG, PPG and HBA1c with mean difference of − 0.72 mmol/L, (95% CI: −1.33, −0.12), I2 = 14%, − 1.43 mmol/L, (95% CI: −2.18, −0.67), I2 = 0, − 0.26%, (95% CI: -0.49, −0.03), I2 = 0 respectively. M. charantia also lowered FPG in prediabetes (mean difference −0.31 mmol/L, n = 52); the evidence was downgraded to low quality because the study had unclear risk of bias and inadequate sample size. No serious adverse effects were reported.

Conclusion

M. charantia adjunct preparations improved glycemic control in T2DM patients. However, this conclusion is based on low to very low quality evidences for the primary outcomes and sparse data for several safety outcomes, thus, warrant further research. Particularly needed are the researches that focus on standardizing M. charantia formulation and determine its efficacy and safety in clinical trials with adequate sample size, designed with random sequence generation, allocation concealment of intervention and blinding of both research personnel and participants.

Introduction

Diabetes mellitus is a group of metabolic disorders characterized by elevated blood glucose level. Type 2 diabetes mellitus (T2DM) is the most common form of diabetes mellitus, accounting for over 90% of all diabetes cases (IDF, 2017, , 2016). It is commonly seen in older adults, but increasingly seen in children, adolescents and younger adults due to rising level of obesity, physical inactivity and poor quality diet.

Diabetes mellitus has been recognized as an important cause of morbidity and permanent disability in adults which overwhelms social and economic welfare of all nations irrespective of their level of economy. The international diabetes federation (IDF)’s diabetes atlas estimates that, about 425 million adults aged 20–79 years were living with diabetes in 2017 globally, and projected to increase to 629 million in 2045 with developing nations disproportionately burdened (IDF, 2017). The increase in diabetes mellitus is predominantly linked to rapid increasing urbanization, population ageing, obesity, ethnicity, family history of diabetes (WHO, 2016), and history of gestation diabetes (Bellamy et al., 2009). Other modifiable factors contributing to the increase include physical inactivity (Whiting et al., 2011), poor quality diet, and prediabetes (Ley et al., 2014).

Treatment of T2DM involves the use of oral hypoglycemic agents (OHAs) singly or combined in order to achieve controlled hyperglycemia (Ghadge and Kuvalekar, 2016, Simo and Hernandez, 2002). The sustained reduction in hyperglycemia reduces the risk of microvascular diseases among T2DM (Gaster and Hirsch, 1998). However, the OHAs are; expensive (Justin-Temu et al., 2009, Smith-Spangler et al., 2012); have adverse effects such as severe hypoglycemia, lactic acidosis, idiosyncratic liver cell injury, permanent neurological deficit, digestive discomfort, headache, dizziness, and even death (Abhishank Singh, 2017, Okayasu et al., 2012); and increasingly associated with failure rate (Alhadramy, 2016, Banerjee et al., 2002). In light of the above, herb based therapies have become alternative to mainstream western medical treatment because herbs are known to have few adverse effects and readily accessible to majority of patients (Naja et al., 2015, , 2002).

Momordica charantia Linnaeus. (Family; Cucurbitaceae) has been widely used and extensively studied herb for its glycemic control effect in T2DM (Ooi et al., 2012, Yin et al., 2014). It is a tropical and subtropical vine, commonly found in Brazil, Asia, and some parts of east Africa including Tanzania (Garau et al., 2003, Krawinkel and Keding, 2006). Since ancient times, M. charantia has been used as a nutritional food and a medicinal herb for T2DM. Although efficacy and safety of M. charantia has been studied in randomized and non-randomized controlled clinical trials, results are still contradictory. This uncertain situation continues to put doubt on safety and efficacy of M. charantia for treatment of T2DM patients, challenging the recommendation of this alternative therapy for T2DM (Efird et al., 2014). The inconsistent and contradictory findings called for urgent need to review and synthesize data from studies that evaluated M. charantia preparation in prediabetes and T2DM. Therefore, this study systematically reviewed and synthesized evidences on the safety and efficacy of M. charantia preparations in lowering elevated plasma glucose in prediabetes and T2DM patients. The results of this study provided objective evaluation of clinical efficacy and safety of M. charantia for clinical decision making and set up directions for future research with regards to M. charantia and T2DM.

Section snippets

Study design

This is a systematic review based on manual and electronic databases search of literatures. The systematic review and meta-analysis was designed according to the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines (Moher et al., 2009). The study was conducted according to the registered protocol number PROSPERO CRD42018083653 (Peter et al., 2018).

Search strategy

A three-step search strategy was adopted. Initially PubMed®, SCOPUS, CINAHL and the cochrane library were searched

Results of the search

A total of 130 articles were identified through electronic and manual searching. After removal of duplicates and screened the articles based on the titles and abstracts, 27 articles remained. The 27 full-texts were examined for eligibility. Fourteen articles were further excluded because eight of them did not have outcome of interest (Ahamad et al., 2014, Akhtar, 1982, Inayat-ur-Rahman et al., 2009, Leatherdale et al., 1981, Salam et al., 2015, Tsai et al., 2012, Yadav et al., 2014; Welihinda

Effect of interventions on prediabetes

Only one RCT (n = 44) investigated glycemic control of powder of unripe whole fruit of M. charantia on prediabetes (Krawinkel et al., 2018). The RCT was a cross over trial that reported overall changes of FPG and HbA1c% variables as outcome indicators for glycemic control. With regard to the FPG; there was moderate quality evidence that, administration of M. charantia preparation reduced elevated FPG (Mean difference −0.31 mmol/L, n = 44). The HbA1c level increased (Mean difference 0.05%,

Summary of main findings

Our findings suggest that M. charantia monoherbal and polyherbal preparations taken orally at a dose of 2–6 g/day for at least four weeks significantly reduces elevated FPG level, PPG and HbA1c among adult T2DM patients. M. charantia monoherbal also reduces elevated FPG in prediabetes, indicating that M. charantia preparations could be used as adjunct therapy for glycemic control and thus could reduce risk for microvascular complications in T2DM patients.

It is possible that, the observed

Conclusions

M. charantia unripe fruits, seeds or fruit pulp preparations taken orally at a dose of 2–6 g/day for at least 4 weeks lowered elevated FPG, PPG and HbA1c level in type 2 diabetes mellitus. However, this conclusion should be considered in light of unclear to high risk of bias of included studies and low to very low level of certainty of evidence in all primary outcomes. Therefore, further research is needed in the aspect of standardizing M. charantia formulation and conduct high quality clinical

Acknowledgements

This work is part of PhD training of ELP; authors express their gratitude to World Bank through PHARMBIOTRAC-Africa Centre of Excellence (ACE II), Mbarara University of Science and Technology for funding the PhD training.

Competing interests

The authors have no competing interests.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author Contribution

Emanuel L. Peter conceived and drafted earlier version of the manuscript and a guarantor of a review. FMK, SD and AM revised the draft of manuscript. DS, PBN, CUT, PEO mentored, revised and edited the manuscript. All authors read and approved the final manuscript.

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