Is the combined use of insulin resistance indices, including adipokines, more reliable in metabolic syndrome?

Turkish Journal of Medical Sciences http://journals.tubitak.gov.tr/medical/ Research Article Turk J Med Sci (2014) 44: 1021-1028 © TÜBİTAK doi:10.3906/sag-1310-90 Is the combined use of insulin resistance indices, including adipokines, more reliable in metabolic syndrome? 1, 1 2 1 Birgül KURAL *, Orhan DEĞER , Cihangir EREM , Fulya BALABAN YÜCESAN , 3 4 Rezzan ALİYAZICIOĞLU , Yaşam BARLAK 1 Department of Medical Biochemistry, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey 2 Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey 3 Faculty of Pharmacy, Karadeniz Technical University, Trabzon, Turkey 4 School of Health Sciences, Gümüşhane University, Gümüşhane, Turkey Received: 24.10.2013 Accepted: 23.01.2014 Published Online: 24.10.2014 Printed: 21.11.2014 Background/aim: To determine the levels of adipokines (leptin, adiponectin, resistin, and visfatin) and the indices of insulin sensitivity/ resistance, and to examine the relationship among them in patients with metabolic syndrome (MetS). Materials and methods: The study groups included 45 subjects with MetS (31 women/14 men), and 45 sex- and age-matched non-MetS healthy volunteers (31 women/14 men). The levels of adipokines were determined by enzyme-linked immunosorbent assay. Results: The levels of leptin and visfatin were significantly higher in the MetS than in the non-MetS subjects (P < 0.01). There was no difference in adiponectin levels in subjects with and without MetS (P = 0.052). Similarly, resistin did not show any statistically significant difference. A statistically significant positive correlation of leptin with insulin levels was observed, while negative correlations of visfatin levels with age, and resistin levels with the ratio of adiponectin to leptin, were found in the MetS (P < 0.05). The combination of adipokines, insulin resistance-sensitivity parameters, and MetS criteria parameters gave more significant differences than a single parameter. Conclusion: Since the parameters mentioned above might affect, interact with, and/or interfere with each other, the combinations of these parameters might give more reliable results to evaluate the insulin resistance/sensitivity in MetS patients. Key words: Adiponectin, insulin resistance, metabolic syndrome, leptin, resistin, visfatin 1. Introduction Metabolic syndrome (MetS) is a clustering of cardiovascular risk factors associated with insulin resistance, central adiposity, hyperglycemia, hypertension, hypertriglyceridemia, and low high-density lipoprotein cholesterol (HDL-C) levels (1,2). Adipokines are secreted by adipose tissue and influence a variety of physiological processes such as food intake control, energy homeostasis, insulin sensitivity, angiogenesis, blood pressure regulation, and blood coagulation (3). They play significant roles in the pathogenesis of obesity, MetS, and chronic inflammatory and autoimmune diseases (4). Leptin is one adipokine that contributes to the regulation of body weight, modulation of insulin sensitivity, metabolism, and reproductive function (5). In addition, it affects * Correspondence: thermogenesis, hematopoiesis, angiogenesis, and immune homeostasis (6). Another adipokine, adiponectin, produced exclusively by adipocytes of white adipose tissue, plays a significant role in the regulation of insulin sensitivity and has antiatherosclerotic and antiinflammatory properties (3). Resistin is another adipokine that may be involved in sensing the nutritional status—its mRNA level decreases during fasting and increases after food consumption. It is associated with a variety of disorders: obesity, diabetes, atherosclerosis, endothelial dysfunction, thrombosis, angiogenesis, inflammation, and smooth muscle cell dysfunction (4,7). The adipokine visfatin shows insulinlike properties, inhibits glucose release by liver cells, and promotes the storage of triglycerides in preadipocytes (8). It plays roles in immunity, metabolism, aging and 1021 KURAL et al. / Turk J Med Sci inflammation, and stress response, and it participates in cardio-cerebrovascular diseases (9). The current study had the following goals: 1) to determine the levels of leptin, resistin, adiponectin, and visfatin; 2) to investigate whether the ratios of the adipokines and of the MetS criteria give more reliable results; 3) to determine the insulin resistance and sensitivity indices; and 4) to examine the relationships among all the parameters (single and combined parameters) in MetS. This is a complicated study of adipokines, adipokine ratios, criteria ratios, and insulin resistance indices, leading to the suggestion of novel criteria. 2. Materials and methods 2.1. Study population The study was carried out in the Departments of Medical Biochemistry and Internal Medicine of the Faculty of Medicine, Karadeniz Technical University. All participants gave informed consent and the study protocol was approved by the Local Ethics Board of the Faculty of Medicine (No. 2006/25). The subjects were considered to have MetS if they had any 3 or more of the following criteria [according to the National Cholesterol Education Program (NCEP)/Adult Treatment Panel (ATP) III]: 1) abdominal obesity: waist circumference (WC) of >102 cm in men and >88 cm in women; 2) hypertriglyceridemia: serum triglyceride (TG) level of ≥150 mg/dL (1.69 mmol/L) and 3) low HDL-C of <40 mg/dL (1.04 mmol/L) in men and <50 mg/dL (1.29 mmol/L) in women; 4) high blood pressure: systolic blood pressure (SBP) of ≥130 mmHg and/or diastolic blood pressure (DBP) of ≥85 mmHg or receiving treatment for hypertension; and 5) high fasting blood glucose: serum glucose level of ≥110 mg/dL (6.1 mmol/L) or receiving treatment for diabetes (10). WC was measured 2 times at the narrowest horizontal point between the costal margin and the iliac crests at the end of normal expiration to the nearest 0.1 cm. Measurements of SBP and DBP were made 3 times in sitting position after 15 min of rest and their mean was calculated. Before measuring the blood pressures, participants were advised to avoid caffeinated beverages and exercise for at least 30 min (11,12). The study group included 45 patients with MetS (14 men/31 women) and 45 sex- and age-matched non-MetS healthy volunteers (14 men/31 women) who did not meet any MetS criteria. The patient group met the criteria in the following ratios: abdominal obesity 44/45 (97.7%), hypertriglyceridemia 43/45 (95.6%), low HDL-C 40/45 (88.9%), hypertension 33/45 (73.3%), and high fasting 1022 glucose 17/45 (37.8%). Nine of the MetS subjects met 5 criteria and the rest met 4 criteria. MetS patients with high glucose level (MetS-HGL) (n = 17, 5 men and 12 women) formed another group of interest in this study. 2.2. Determination of the biochemical parameters Blood samples were collected in the morning after 10–12 h of fasting and the sera were separated following cl (...truncated)