Henry Advances in Food and Nutrition Research

1. Auflage 2014
ISBN: 978-0-12-800368-8
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 71, 248 Seiten

Reihe: Advances in Food and Nutrition Research

Advances in Food and Nutrition Research recognizes the integral relationship between the food and nutritional sciences and brings together outstanding and comprehensive reviews that highlight this relationship. Contributions detail scientific developments in the broad areas of food science and nutrition and are intended to provide those in academia and industry with the latest information on emerging research in these constantly evolving sciences. - The latest important information for food scientists and nutritionists - Peer-reviewed articles by a panel of respected scientists - The go-to series since 1948

Autoren/Hrsg.

Henry, Jeya

Leseproben

Chapter Two Micronutrient Status in Type 2 Diabetes
A Review
Bhupinder Kaur 1; Jeyakumar Henry    Clinical Nutrition Research Centre, Singapore Institute for Clinical Sciences, Singapore, Singapore
1 Corresponding author: email address: [e-mail] Abstract
Type 2 diabetes is characterized by significant losses of important micronutrients due to metabolic basis of the disease and its complications. Evidence of changes in trace mineral and vitamin metabolism as a consequence of type 2 diabetes is reviewed in this chapter. This review is not a meta-analysis but an overview of the micronutrient status, metabolic needs, and potential micronutrient requirements in type 2 diabetics. This chapter will not concentrate on vitamin D and type 2 diabetes as this is a topic that has been extensively reviewed before. The less well-known micronutrients notably zinc, magnesium, chromium, copper, manganese, iron, selenium, vanadium, B-group vitamins, and certain antioxidants are assessed. While some evidence is available to demonstrate the positive influence of micronutrient supplementation on glycemic control, much remains to be investigated. Additional research is necessary to characterize better biomarkers of micronutrient status and requirements in type 2 diabetics. The optimal level of micronutrient supplementation to achieve glucose homeostasis in type 2 diabetics remains a challenge. Keywords Micronutrient Type 2 diabetes Glycemic control Supplementation 1 Introduction
Diabetes mellitus is one of the leading chronic diseases in the world with the number of diabetics and prediabetics increasing rapidly due to population growth, aging, urbanization, increasing prevalence of obesity, and physical inactivity (Wild, Roglic, Green, Sicree, & King, 2004). Type 2 diabetes is the most common form accounting for approximately 90% of all diabetes cases. The hallmark features in the pathogenesis of type 2 diabetes are insulin resistance and inability of the pancreas to produce sufficient quantities of insulin to maintain normoglycemia. There is also depletion of the cellular antioxidant defence system secondary to increased oxidative stress resulting from hyperglycemia and hyperinsulinemia. Type 2 diabetes is characterized by an increased risk for the development of macrovascular disease and microvascular complications (retinopathy, neuropathy, and nephropathy). Nutritional management of type 2 diabetes mellitus has concentrated on macronutrient intakes. But evidence has shown that micronutrient intake is important in promoting optimum health for diabetic patients especially when they are essential cofactors in glucose metabolic pathways, pancreatic ß-cell function, and in the insulin signaling cascade (Bhanot, Thompson, & McNeill, 1994). Alterations in micronutrient status in diabetes mellitus have been well established in human and animal trials (Mooradian & Morley, 1987; Rossetti, Giaccari, Klein-Robbenhaar, & Vogel, 1990). Lower plasma concentrations and higher urinary excretion of certain micronutrients have been reported in type 2 diabetics compared to healthy controls (Ma et al., 1995; Nadler et al., 1992). Some of these changes in micronutrient levels in the body appear to have a negative impact on glucose homeostasis and insulin sensitivity in type 2 diabetics and sometimes leading to complications of the disease. Therefore, a significant volume of research has looked at the effects of micronutrient supplementation on markers of glycemic control to quantify the magnitude of response to supplementation. Many of these studies seem to conclusively show a link between micronutrients and glucose homeostasis. Type 2 diabetes is a multifactorial metabolic disorder characterized by chronic hyperglycemia due to relative or absolute lack of endogenous insulin (Sena, Bento, Pereira, & Seica, 2010). Type 2 diabetes patients have elevated fasting and postprandial plasma glucose levels. Defects in insulin action and secretion result in high blood glucose concentrations due to the ß-cells’ inability to remove glucose from the bloodstream. Diabetes mellitus is characterized by excessive thirst, increased hunger, poor wound healing, and increased fluid losses due to excessive urine production (WHO, 2011). Patients with diabetes mellitus may also experience excessive sweating during attacks of hypoglycemia (Leung, Chan, & Choi, 1999). These symptoms where fluid losses occur could result in fluid deficit averaging 6 l or more in diabetic adults (Chiasson et al., 2003; Ennis, 1994; Kitabchi et al., 2001). Significant fluid losses from the body contribute to increased nutrient losses in diabetics. Diabetes mellitus can also affect protein metabolism which in turn is highly influenced by the presence of insulin (Tessari et al., 2011). Insulin is a key regulator of the response to nutrient intake in achieving net protein retention. Defects in the regulation of insulin by protein metabolism in type 2 diabetes may lead to changes in body tissue composition, metabolic rates, individual amino acid metabolic steps, and nutrient status. Altered protein metabolism and increased fluid losses in diabetes result in elevated excretion of micronutrients in the urine and reduced plasma micronutrient levels (Fig. 2.1). Figure 2.1Diagrammatic representation of the concept of micronutrient status in type 2 diabetics. With the homeostasis of micronutrients being disrupted due to diabetes, there is an increased metabolic demand for them. A growing body of interest has looked at the beneficial role of micronutrients in glycemic control in type 2 diabetics. In this review, the current status of knowledge on the micronutrients status in type 2 diabetics is characterized and the effect of micronutrient supplementation on glycemic control in diabetics is summarized. 2 Evidence-Based Review
2.1 Micronutrient metabolism in diabetes mellitus
Micronutrients are required in small quantities for specific functions in the body. They enhance insulin action through activating insulin receptor sites, serve as cofactors or components for enzyme systems involved in glucose metabolism, increase insulin sensitivity, and act antioxidants to prevent tissue oxidation (O'Connell, 2001). Chronic hyperglycemia causes significant alterations in the status of micronutrients in the body (Mooradian, Failla, Hoogwerf, Maryniuk, & Wylie-Rosett, 1994). The disturbance in micronutrient status and increased oxidative stress in diabetes mellitus may contribute to insulin resistance and the development of diabetic complications (Vincent, Russell, Low, & Feldman, 2004). The progression of diabetes mellitus may also lead to perturbation in micronutrient metabolism and status (Friederich, Hansell, & Palm, 2009). Several studies have reported an association between diabetes mellitus and alterations in the metabolism of several micronutrients. 2.1.1 Zinc Zinc (Zn) is an essential micronutrient required for proper growth and maintenance of biological systems in the body. Zinc is found in most tissues of the human body, predominant in the pancreas. This micronutrient is important for over 300 enzymatic reactions (Meunier et al., 2005) and is part of more than 2000 Zn-dependent transcription factors and other protein domains such as zinc metaloenzymes (Song, Wang, Li, & Cai, 2005). Zinc levels in pancreatic islet cells are tightly regulated. Dysregulation of Zn metabolism affects the synthesis, storage, and secretion of insulin and therefore glycemic control (Howell, Young, & Lacy, 1969; Kelleher, McCormick, Velasquez, & Lopez, 2011; Kinlaw, Levine, Morley, Silvis, & McClain, 1983). Zinc homeostasis is partly controlled by metallothioneins, which are small proteins found primarily found in the liver, kidneys, intestinal mucosa, and pancreas. Metahllothioneins help protect cells and tissues from free radicals that cause oxidative stress and facilitate metal exchange with Zn metalloenzymes thereby playing a vital role in gluconeogenesis and lipogenesis (Thirumoorthy, Manisenthil Kumar, Shyam Sundar, Panayappan, & Chatterjee, 2007; Vardatsikos, Pandey, & Srivastava, 2013). Findings from early published studies on the homeostasis of Zn in diabetes have been equivocal. Hyperzincuria was accompanied by large decreases in plasma Zn levels but the level of Zn in muscle tissue and erythrocytes remained unaltered in humans (Pidduck, Wren, & Evans, 1970; Sjogren, Floren, & Nilsson, 1988). In contrast, type 2 diabetic mouse models showed reduced Zn concentrations in the pancreas and increased urinary excretion of Zn (Begin-Heick, Dalpe-Scott, Rowe, & Heick, 1985; Lau and Failla, 1984). Several human studies confirmed that diabetes had an effect on disrupting Zn homeostasis. A defect in Zn homeostasis in type 2 diabetes human subjects was reported by several researchers. Urinary Zn excretion was higher in type 2 diabetics compared to controls (El-Yazigi & Legayada, 1996; Jansen, Karges, & Rink, 2009; Kazi et al., 2008; Kinlaw et al., 1983; Niewoehner, Allen, Boosalis, Levine, & Morley, 1986; Walter et al., 1991). According to Kazi and colleagues, the...