Corn Silk -- A Natural Herb for Diabetes

Tiejun Tang

Diabetes is a very common disease. According to the WHO Global Report on Diabetes in 2014, there are 422 million adults suffering from diabetes. Most patients have to rely on chemical hypoglycaemic agents or even insulin injection for their whole life. Chemical drugs often cause many side effects after long term use, and the blood sugar levels are still not properly controlled in some cases. Good news for diabetes patient is that a Chinese herb has good effect on reducing blood sugar. It is a natural way to fight diabetes.

Corn silk (CS) is a commonly used Chinese herbal medicine. In Chinese it is called Yumixu. It was used to treat Xiao Ke (diabetes) for hundreds of years in China. It may be used alone or in combination with other herbs according to syndrome differentiation diagnosis. It also can be used as daily food therapy for diabetes patients. The hypoglycaemic mechanisms of CS have been investigated by many researchers around world.

The peroxisome proliferator-activated receptors play a pivotal role in metazoan lipid and glucose homeostasis. Synthetic activators of PPAR alpha (fibrates) and PPAR gamma (glitazones) are therefore widely used for treatment of dislipidemia and diabetes. Rau O (2006) reported CS showed a significant effect of PPAR gamma activator ^[1].  Non-enzymatic glycation and the accumulation of advanced glycation end products (AGEs) are associated with diabetes. Farsi DA (2008) reported that secondary metabolites from several plant species are known to inhibit non-enzymatic glycation and the formation of AGEs, including flavonoids found in CS. The results identify modern resistant and high phenolic maize inbreds as promising candidates for the development of natural AGE inhibitors for the prevention and treatment of diabetic complications^[2]. Guo J (2009) reported CS extract markedly reduced hyperglycaemia in alloxan-induced diabetic mice. The action of CS extract on glycaemic metabolism is through increasing insulin level as well as recovering the injured beta-cells. Their research results suggest that CS extract may be used as a hypoglycaemic food or medicine for hyperglycaemic people^[3]. Zhao W (2012) reported polysaccharides of CS have significant anti-diabetic effect on streptozotocin (STZ)-induced diabetic rats. The results demonstrated that daily treatment with 100-500 mg/kg body weight of CS extraction the diabetic rats could not only lead to a significant decrease on the animal's blood glucose level, but also reduce the serum lipid level including total cholesterol and total triglyceride ^[4]. Wen X (2015) reported Corn Silk Polysaccharide (CSP) D3 can inhibit the expression level of TGF-β1 of diabetic rat’s kidney and restrain macrophages in order to protect the kidneys of diabetic rats^[5]. Zhang Y (2015) reported flavonoids extracted from CS can significantly reduce the body weight loss, water consumption, and especially the blood glucose of diabetic mice. It can increase serum total superoxide dismutase (SOD) and high density lipoprotein cholesterol level (HDL-C), decrease total cholesterol, triacylglycerol, low density lipoprotein cholesterol (LDL-C) ^[6]. Sabiu S (2016) reported in vitro analysis of CS extract that the result showed it exhibited potent and moderate inhibitory potential against α-amylase and α-glucosidase, respectively^[7]. Cha JH (2016) reported CS extract improves levels of adipocytokine secretion and glucose homeostasis. It is also effective in decreasing the regulatory pool of hepatic cholesterol, in line with decreased blood and hepatic levels of cholesterol through modulation of mRNA expression levels of HMG-CoA reductase, acyltransferase (ACAT), and farnesoid X receptor (FXR)^[8]. Chang CC (2016) report, the ethyl acetate fraction of CS exhibits dual antioxidant and anti-glycation activities and protects insulin-secreting cells from glucotoxicity^[9]. Wang B (2017) reported CS has multiple beneficial effects, including hypotensive, anti-diabetic, and hypolipidemic properties. This suggests that CS could be used to treat or prevent metabolic syndrome^[10]. Pan Y (2017) aimed to investigate the physicochemical properties and antidiabetic effects of a polysaccharide obtained from corn silk (PCS2). The results showed that PCS2 was a heteropolysaccharide with the average molecular weight of 45.5kDa. PCS2 treatment significantly reduced the body weight loss, decreased blood glucose and serum insulin levels, and improved glucose intolerance. The levels of serum lipid profile were regulated and the levels of glycated serum protein, non-esterified fatty acid were decreased significantly. The activities of superoxide dismutase, glutathione peroxidase and catalase were notably improved. PCS2 also exerted cytoprotective action from histopathological observation. These results suggested that PCS2 could be a good candidate for functional food or medicine for diabetes treatment^[11].

The hypoglycaemic mechanism of CS is a multi-target approach. It not only reduces blood sugar but also balances the blood lipid, preventing and reducing complications of diabetes. This multi-target approach is different from western medicine treatment. The hypoglycaemic effect of CS is not as fast and strong as metformin, but it’s effects are more stable and much safer.  

Except CS many other Chinese herbs also have a good effect to reduce blood sugar. In my clinical practice I usually select few herbs to compose a formula for different individual patients.  For the early stages of Type 2 diabetes the use of herbal medicine can get the sugar level under control. For severe cases, when patients have to use western medicine, CS can be elected to enhance the effect of western medicine and reduce their side effect.

Reference:

1. Rau O, et al. Screening of herbal extracts for activation of the human peroxisome proliferator-activated receptor. Pharmazie. 2006; 61(11):952-6.
2. Farsi DA, et al. Inhibition of non-enzymatic glycation by silk extracts from a Mexican land race and modern inbred lines of maize (Zea mays).  Phytother Res. 2008; 22(1):108-12.
3. Guo J, et al. The effects of corn silk on glycaemic metabolism. Nutr Metab (Lond). 2009; 23(6):47.
4. Zhao W, et al. Comparison of anti-diabetic effects of polysaccharides from corn silk on normal and hyperglycemia rats.Int J Biol Macromol. 2012; 50(4):1133-7.
5. Wen X, et al. The Influence of Corn Silk Polysaccharide on Signal Pathway of TGF-β1 in Type 2 Diabetic Mellitus Rat. Open Biomed Eng J. 2015; 9: 204-8 
6. Zhang Y, et al. Anti-Diabetic, Anti-Oxidant and Anti-Hyperlipidemic Activities of Flavonoids from Corn Silk on STZ-Induced Diabetic Mice. Molecules. 2015; 21(1):E7.
7. Sabiu S, et al. Kinetics of α-amylase and α-glucosidase inhibitory potential of Zea mays Linnaeus (Poaceae), Stigma maydis aqueous extract: An in vitro assessment. J Ethnopharmacol. 2016; 183:1-8.
8. Cha JH, et al. Corn silk extract improves cholesterol metabolism in C57BL/6J mouse fed high-fat diets.Nutr Res Pract. 2016; 10(5): 501-506.
9. Chang CC, et al. The ethyl acetate fraction of corn silk exhibits dual antioxidant and anti-glycation activities and protects insulin-secreting cells from glucotoxicity. BMC Complement Altern Med. 2016; 16(1):432.
10. Wang B, et al. Beneficial Effects of Corn Silk on Metabolic Syndrome. Curr Pharm Des. 2017 Sep 26. doi: 10.2174/1381612823666170926152425. [Epub ahead of print] 
11. Pan Y,et al. Physicochemical properties and antidiabetic effects of a polysaccharide from corn silk in high-fat diet and streptozotocin-induced diabetic mice. Carbohydr Polym. 2017; 164: 370-378.