Published online 2016 Aug 10
Fonyuy E. Wirngo, Max N. Lambert, and Per B. Jeppesen
Abstract
The tremendous rise in the economic burden of type 2 diabetes (T2D) has prompted a search for alternative and less expensive medicines. Dandelion offers a compelling profile of bioactive components with potential anti-diabetic properties. The Taraxacum genus from the Asteraceae family is found in the temperate zone of the Northern hemisphere. It is available in several areas around the world. In many countries, it is used as food and in some countries as therapeutics for the control and treatment of T2D. The anti-diabetic properties of dandelion are attributed to bioactive chemical components; these include chicoric acid, taraxasterol (TS), chlorogenic acid, and sesquiterpene lactones. Studies have outlined the useful pharmacological profile of dandelion for the treatment of an array of diseases, although little attention has been paid to the effects of its bioactive components on T2D to date. This review recapitulates previous work on dandelion and its potential for the treatment and prevention of T2D, highlighting its anti-diabetic properties, the structures of its chemical components, and their potential mechanisms of action in T2D. Although initial research appears promising, data on the cellular impact of dandelion are limited, necessitating further work on clonal β-cell lines (INS-1E), α-cell lines, and human skeletal cell lines for better identification of the active components that could be of use in the control and treatment of T2D. In fact, extensive in-vitro, in-vivo, and clinical research is required to investigate further the pharmacological, physiological, and biochemical mechanisms underlying the effects of dandelion-derived compounds on T2D.
Keywords: type 2 diabetes, dandelion, dandelion, chicory acid, taraxasterol, sesquiterpene
Abbreviations: ADP – adenosine diphosphate; AFLD – alcoholic fatty liver disease; AMPK – adenosine monophosphate-activated protein kinase; ATP – adenosine triphosphate; cAMP – cyclic adenosine monophosphate; CGA – chlorogenic acid; CoA – coenzyme A; CRA – chicory acid; DAG – diacylglycerol; DBD – DNA-binding domain; DNA – deoxyribonucleic acid; DPPH – 2,2-diphenyl-1-picrylhydrazyl; Dw – dry weight; FOS – fructose oligosaccharide; G6P – glucose-6-phosphate; GDP – guanosine 5′-diphosphate; GLP-1 – glucagon-like peptide 1; GLUT2 – glucose transporter 2; GLUT4 – muscle glucose transporter protein 4; GPCR – G protein-coupled receptor; GTP – guanosine triphosphate; HNB – 2-hydroxy-5-nitrobenzenaledehyde; HPLC – high-pressure liquid chromatography; IC50 – half maximal inhibitory concentration; IDF – International Diabetes Federation; IDX-1 – islet duodenum homeobox 1; IL-1α – interleukin 1 alpha; INS-1E – rat insulinoma clonal beta-cell line; IR – insulin receptor; IRS-1 – insulin receptor substrate 1; Km – Michaelis constant; IP3 – inositol triphosphate; IRS-1 – insulin receptor substrate 1; LBD – ligand-binding domain; LC-DAD – liquid chromatography with (photo) diode array detection; LPS – lipopolysaccharide; MAPK – mitogen-activated protein kinase; NADH – nicotinamide adenine dinucleotide; NAFLD – non-alcoholic fatty liver disease; NF-κb – nuclear factor kappa B; NO – nitric oxide; PI3K – phosphatidylinositol 3 kinase; PKA – protein kinase A; PKC – protein kinase C; PPAR-γ – peroxisome proliferator-activated receptor gamma; ROS – reactive oxygen species; RxR – retinoid X receptor; SEL – sesquiterpene lactones; SUR1 – sulphonylurea receptor 1; T2D – type 2 diabetes; TAG – triacylglycerol; TNF-α – tumor necrosis factor; TO – Taraxacum officinale; TS – taraxasterol; UPLC-MS/MS – ultra-performance liquid chromatography – tandem mass spectrometry; UV/VIS – ultraviolet visible; WHO – World Health Organization
1. Introduction
Societies in both developed and developing countries are engulfed by the metabolic disorder of type 2 diabetes (T2D). The world is facing a huge clinical and economic burden due to the enormous increase in diabetes incidence. It is estimated that approximately 382 million people in the world have T2D today, and by 2035, this number is expected to rise by more than 200 million if preventive measures are not established [1]. A WHO survey indicated that 70-80% of the world’s population is relying on non-conventional medicines, primarily because of a lack of availability of and economic barriers to conventional medicine. In the past, plant-derived therapeutics have been widely disregarded as a possible cost-effective means to treat diabetes; hence evidence-based documentation of efficacy is commonly unavailable. In spite of this deficit, it is well known that plant-derived therapeutics provide promising sources of alternative treatment measures, which can even lead to improved efficacy and reduced side effects in comparison to existing conventional medicines [2]. Therefore, there has been increasing interest in food, nutraceuticals, and medicinal products from plants and other natural sources that retain beneficial health properties in developed countries [3].
According to statistics from the International Diabetes Federation (IDF), 80% of people with T2D live in countries characterized by low and middle income. Even more alarmingly, it is estimated that 175 million people with diabetes still go undiagnosed [4]. In poorer regions, treatment of diabetes is very expensive, which makes medical treatment unattainable, resulting in poor healthcare and the use of alternative medicine [5]. Traditional medicine involving the use of bioactive plants has demonstrated potential to alleviate diabetic symptoms, enable recovery, and improve health [6]. Diabetes treatment has been attempted with different plants and poly-herbal formulations, with anti-diabetic activities originating from their bioactive components [7]. About 80% of people worldwide use traditional medicine, while approximately 75% of modern pharmaceuticals are derived from plants [8]. Medicinal plants include a wide variety of anti-diabetic components; frequently their discovery arises from ethnomedical knowledge [9, 10].
The metabolic syndrome, characterized by obesity, hypertension, cardiovascular abnormalities, coronary artery disease, and dyslipidemias, is a core feature of T2D. This non-communicable disease is a metabolic disorder that involves alterations in carbohydrate, lipid, and protein metabolism, as well as pancreas function [7, 11]. T2D is a chronic multifactorial disease, resulting from defects in insulin and glucagon secretion and action, which may cause a progressive increase in plasma glucose levels and a disruption of biological mechanisms in liver, endocrine pancreas, skeletal muscle, adipose tissue, central nervous system, and gut, causing the dysregulation of glucose homeostasis, which plays a key role in the development of T2D [12]. T2D is a common endocrine disorder leading to increased water and food consumption, lipid formation, hyperglycemia, and elevated insulin production, which reinforces existing insulin resistance and contributes to pancreatic failure [13–15]. Insensitivity to insulin leads to dysregulation of muscles, fat, and liver cells due to inadequate transportation of glucose and abnormal storage of lipids [16, 17]. Eventually, chronic diabetes can cause blindness and renal failure, and is a major risk factor for cardiovascular diseases and stroke. In severe cases, it may result in lower limb amputations [13].
The aim of this review is to evaluate the properties of a promising herbal candidate, dandelion, and to explore its diverse biological activities relevant to T2D, with a particular focus on the most current literature regarding the effects of its bioactive components on insulin function and glucose homeostasis.