88 Diabetes Care Volume 37, January 2014 Alicja Budek Mark,1 Malene Consumption of a Diet Low Wibe Poulsen,1 Stine Andersen,1 Jeanette Marker Andersen,1,2 Monika Judyta Bak,1,3 in Advanced Glycation End Products Christian Ritz,1 Jens Juul Holst,4 John Nielsen,2 Barbora de Courten,3,5,6 for4WeeksImprovesInsulin Lars Ove Dragsted,1 and Susanne Sensitivity in Overweight Women Gjedsted Bugel¨ 1 CLIN CARE/EDUCATION/NUTRITION/PSYCHOSOCIAL OBJECTIVE High-heat cooking of food induces the formation of advanced glycation end products (AGEs), which are thought to impair glucose metabolism in type 2 di- abetic patients. High intake of fructose might additionally affect endogenous formation of AGEs. This parallel intervention study investigated whether the ad- dition of fructose or cooking methods influencing the AGE content of food affect insulin sensitivity in overweight individuals. 1Department of Nutrition, Exercise and Sports, RESEARCH DESIGN AND METHODS Faculty of Science, University of Copenhagen, Seventy-four overweight women were randomized to follow either a high- or low- Copenhagen, Denmark 2Department of Drug Design and Pharmacology, AGE diet for 4 weeks, together with consumption of either fructose or glucose Faculty of Health and Medical Sciences, drinks. Glucose and insulin concentrationsdafter fasting and 2 h after an oral University of Copenhagen, Copenhagen, glucose tolerance testdwere measured before and after the intervention. Ho- Denmark 3 meostasis model assessment of insulin resistance (HOMA-IR) and insulin sensi- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of tivity index were calculated. Dietary and urinary AGE concentrations were Copenhagen, Copenhagen, Denmark measured (liquid chromatography tandem mass spectrometry) to estimate AGE 4Novo Nordisk Foundation Center for Basic intake and excretion. Metabolic Research, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, RESULTS University of Copenhagen, Copenhagen, Denmark When adjusted for changes in anthropometric measures during the intervention, 5Baker IDI Heart and Diabetes Institute, the low-AGE diet decreased urinary AGEs, fasting insulin concentrations, and Melbourne, Australia HOMA-IR, compared with the high-AGE diet. Addition of fructose did not affect 6Steno Diabetes Center, Copenhagen, any outcomes. Denmark Corresponding author: Susanne Gjedsted Bugel,¨ CONCLUSIONS [email protected]. Diets with high AGE content may increase the development of insulin resistance. Received 10 April 2013 and accepted 13 August 2013. AGEs can be reduced by modulation of cooking methods but is unaffected by Clinical trial reg. no. NCT01617304, clinicaltrials. moderate fructose intake. gov. – Diabetes Care 2014;37:88 95 | DOI: 10.2337/dc13-0842 This article contains Supplementary Data online at http://care.diabetesjournals.org/lookup/ suppl/doi:10.2337/dc13-0842/-/DC1. Consumption of highly processed foods has increased over the past 20 years (1), A.B.M. and M.W.P. contributed equally to this which has probably resulted in an increased exposure to advanced glycation end work. products (AGEs). AGEs are formed from the Maillard reaction, a process that is © 2014 by the American Diabetes Association. important for the formation of aroma, flavor, and the color of foods (2). Cooking See http://creativecommons.org/licenses/by- temperature is a critical factor; high-heat cooking, such as baking, roasting, frying, nc-nd/3.0/ for details. care.diabetesjournals.org Mark and Associates 89 and grilling, is a potent promoter of We compared the effects on insulin and a significance level of 0.05. The advanced glycation (3). High levels of sensitivity of cooking methods targeted study was conducted according to the AGEs are therefore found in many at inducing or reducing AGE formation Declaration of Helsinki, and the protocol common foods, such as bakery (high- and low-AGE diets, respectively) was approved by The Danish Research products, cooked meat, and roasted together with fructose or glucose Ethics Committee and registered at coffee (3,4). Extracts of dietary AGEs supplements in a two-factorial design, clinicaltrials.gov (NCT01617304). Not all have been shown to induce oxidative 4-week parallel dietary intervention in the originally planned analyses were stress and inflammation in vitro (5), and overweight women. The primary end performed because of economic dietary AGEs are therefore believed to point was HOMA-IR. Secondary end constraints. be inflammatory pro-oxidants in vivo points include the plasma variables (6). There is accumulating evidence glucose, insulin, glucagon-like peptide-1 Study Design from animal studies indicating that a (GLP-1), and lipid profile, insulin This was a two-factorial, parallel, dietary diet high in AGEs, produced by heating sensitivity index (Si0,120), weight, BMI, intervention study consisting of two foods in the diet, contributes to waist circumference, waist-to-hip ratio, open-labeled arms (comparing high- increased insulin levels, insulin skin autofluorescence (AF), and urinary AGE and low-AGE diets) combined with resistance (IR), and type 2 diabetes (7,8). excretion of AGEs. two double-blinded arms (comparing Furthermore, a recent study found that fructose and glucose). The study was methylglyoxal derivatives induced IR, RESEARCH DESIGN AND METHODS performed at the Department of impaired insulin signaling, and induced Volunteers Nutrition, Exercise and Sports, proinflammatory phenotypes in A total of 74 overweight women aged University of Copenhagen, between successive generations of mice (9), 20–50 years were recruited from March and June 2012. The volunteers which further implicate dietary AGEs in Copenhagen, Denmark. The inclusion were randomized to follow either a the etiology of type 2 diabetes. criteria were as follows: BMI between high-AGE or a low-AGE diet with 2 Associations between plasma 25 and 40 kg/m and waist supplements of either fructose or concentrations of AGEs and markers of circumference .88 cm. The exclusion glucose. Blood sampling, IR have been reported in humans criteria were as follows: weight changes anthropometric measurements, oral (3,7,8,10). Beneficial effects of an AGE- .3 kg within the last 2 months, physical glucose tolerance test (OGTT), and AF restricted diet on glucose metabolism activity .8 h/week (self-reported), measurements were performed at have been demonstrated in type 2 current smoking, use of dietary baseline and after 4 weeks of diabetes patients, but markers of IR did supplements or medications, known intervention. Halfway through the not improve in a control group of medical condition, vegetarianism, intervention, telephone calls were made healthy individuals randomized to the pregnancy or breast feeding, surgery to to increase compliance. The volunteers same diet (11). In another study, treat obesity, postmenstrual conditions, were asked to restrain from rigorous homeostasis model assessment (HOMA) blood donation within the last 3 physical activity and alcohol of IR was increased after a high-heat– months, and hypersensitivity to para- consumption for 48 h before all treated diet, compared with a low-heat– aminobenzoic acid (PABA). All who measurements, and were required to treated diet (12), but the change in responded to the advertisements were fast (except for 500 mL water) from 8:00 HOMA-IR was not adjusted for changes prescreened by telephone interview. Of P.M. on the day prior to each blood in anthropometric measurements or these, 218 subjects were regarded as sampling day. additional differences between the being eligible and were invited to attend diets. an information meeting. Written Dietary Intervention informed consent was obtained from The volunteers received oral and AGEs are formed endogenously, 117 volunteers. Of these, two written instructions on how to comply particularly in diabetes, as the result of volunteers were excluded because of a with either high-AGE or low-AGE diets. increased carbonyl stress (13). A nonfasting capillary blood glucose Both diets resembled habitual Danish possible effect of fructose on concentration of .8.9 mmol/L and BMI food intake and were similar in nutrient endogenous AGE formation has not .40 kg/m2. Sixteen volunteers quality, but differed in cooking been investigated, although fructose is withdrew their consent before the methods. The instructions included an important reactant for several of the beginning of the study for personal thorough guidance on cooking AGE precursors (14). We speculated reasons. A total of 99 volunteers started methods, a food choice list, and that a high intake of fructose may the dietary intervention. One volunteer predefined recipes for mandatory exacerbate endogenous AGE formation was excluded because of poor meals. The high-AGE group was due to mitochondrial overload, because compliance, and 24 volunteers dropped instructed to fry, bake, roast, or grill hepatic fructose uptake is not strictly out for personal reasons. Seventy-four their foods; to consume toasted bread regulated in the same way as glucose women completed the study. A sample with a crust; and to choose foods with a (15) and may thus potentially lead to an size of 88 was estimated to be sufficient high content of AGEs based on the food increased formation by the glycolytic to detect a 30% change in the difference choice list. The low-AGE group was pathway of reactive trioses, known to be in HOMA-IR from baseline (SD , 0.6) instructed to boil or steam their food, to AGE precursors. in a parallel design