Date Published: April 23, 2019
Publisher: Public Library of Science
Author(s): Nalinee Poolsup, Naeti Suksomboon, Putu Dian Marani Kurnianta, Kulchalee Deawjaroen, Stephen L. Atkin.
Studies have demonstrated inconsistent effects of curcumin on glycemic outcomes and lipid parameters in patients with prediabetes and type 2 diabetes mellitus (T2DM). This study aimed to assess the effect of curcumin on glycemic control and lipid profile in prediabetes and T2DM.
A systematic search of randomized controlled trials (RCTs) was conducted from inception to June 2018 in electronic sources including AMED, ANZCTR, BioMed Central, CENTRAL, CINAHL, ClinicalTrials.gov, Expanded Academic Index, Google Scholar, ISRCTN, LILACS, MEDLINE, NCCIH, Science Direct, Scopus, Web of Science, and WHO ICTRP. Hand search was also performed. Of the total 486 records, four trials (N = 508) and eight trials (N = 646) were eligible for the meta-analysis of individuals with prediabetes and T2DM, respectively. Curcumin significantly reduced glycosylated hemoglobin (HbA1c) in prediabetics (MD: -0.9%, 95% CI: -1.7 to -0.1%, p = 0.03). Furthermore, T2DM subjects gained favorable reduction in both HbA1c (MD: -0.5%, 95% CI: -1.0 to -0.0%, p = 0.04) and fasting plasma glucose (MD: -11.7 mg/dL, 95% CI: -22.1 to -1.3 mg/dL, p = 0.03). Tendency of lipid profile improvement was also observed.
Our findings may encourage curcumin supplementation based on its meaningful effect on glycemic control and positive trend on lipid outcomes in prediabetes and T2DM.
Diabetes is a metabolic disease presenting with elevated blood glucose level. This disease accounted for not only 1.5 million deaths in 2012, but also an extra 2.2 million deaths for its attribution to cardiovascular disease and other diseases. Accordingly, diabetes has become a worldwide burden especially in less developed countries . Furthermore, the global prevalence of diabetes has been predicted to keep increasing to 13.5% of the total world population in 2040 . Among the growing number of people with diabetes, type 2 diabetes mellitus (T2DM) is the most prevalent. In order to manage with the worldwide issues of diabetes, effective prevention and management are entirely required.
We conducted a systematic review and meta-analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines .
The proposed mechanisms of curcumin antidiabetic effects were demonstrated through a whole picture of insulin resistance inhibition and some highlighted mechanisms. Curcumin improves insulin sensitivity by affecting three processes. Firstly, curcumin ameliorates glucose homeostasis by triggering glucokinase activity in the liver. Secondly, it induces lipid metabolism by raising lipoprotein lipase activity to reduce triglyceride. Thirdly, curcumin affects insulin pathway independently by inducing glucose transporter-4 (GLUT4) expression to increase peripheral glucose uptake. . Additionally, curcumin attenuates tumor necrosis factor-alpha, plasma free fatty acid, and thiobarbituric acid reactive substances level as well as the activity of sorbitol dehydrogenase . Interestingly, antihyperglycemic effect of curcumin and its analogues might be compared to the approved antidiabetic agent namely thiazolidinedione group. Curcumin activating PPAR-γ appears to offer good combination effect which improves insulin secretion, lipid metabolism, and free fatty acid receptor expression [8, 9]. Thus, all of these mechanisms may reflect glucose and lipid lowering effects in human.