Investigation of plasma leptin level in patients with type 2 diabetes mellitus

Nội dung text: Investigation of plasma leptin level in patients with type 2 diabetes mellitus

1. Journal of military pharmaco-medicine N o7-2016 INVESTIGATION OF PLASMA LEPTIN LEVEL IN PATIENTS WITH TYPE 2 DIABETES MELLITUS Nguyen Van Hoan*; Nguyen Thanh Binh**; Doan Van De*; Nguyen Linh Toan*** SUMMARY Objectives: Adipose tissue-derived hormones are associated with metabolic disorders including type 2 diabetes mellitus (T2DM). This study investigated clinical parameters and the levels of leptin cytokine in patients with T2DM with or without overweight/obese. Materials and methods: Based on body mass index (BMI), 130 patients with T2DM were divided either as overweight/obese or non-overweight/non-obese subjects. 125 overweight/obese and non- overweight/non-obese individuals devoid of T2DM were included as healthy controls. The leptin levels were measured in the plasma samples in all study subjects by ELISA and clinical parameters. Results: The leptin levels were significantly lower in patients with T2DM compared to controls ([1202.75 pg/ml median vs. 1715.4 pg/ml], p = 0.05). The leptin levels were increased in overweight/obese T2DM patients and in overweight/obese healthy subjects compared to without overweight/obese T2DM patients and healthy induviduals (p < 0.05). The levels of leptin were significantly increased in female patients with T2DM and in T2DM patients with metabolic syndrome (MS) compared to those of male patients (p < 0.001) and T2DM patients with none-MS (p < 0.05). Conclusions: Leptin cytokine is associated with T2DM and may serve as a prognostic marker for overweight/obese-related T2DM. * Keywords: Type 2 diabetes mellitus; Overweight; Obesity; Leptin; Insulin. INTRODUCTION diabetes in the age group of 30 - 69 years is estimated to be 5.7% across Vietnam Type 2 diabetes mellitus is a chronic and 7% in urban areas [2]. metabolic disorder with an exponential T2DM constitutes up to 95% of all increase in developing countries . The diabetes and is characterized by chronic international diabetes federation (IDF) hyperglycaemia resulting from defects in reported 382 million diabetes cases in insulin secretion and/or insulin action and 2013 with a prediction of 592 million cases metabolic disorders of protein and lipids [3] . by 2035, and 80% of these cases are in The pathogenesis of T2DM consists of developing countries [1]. In Vietnam, the two major abnormalities including insulin number of patients with T2DM is growing resistance and dysfunction of insulin with an estimated 3.3 million diabetes cases production, which lead to the disability to reported for 2014. The prevalence of regulate blood glucose level [4]. * 103 Hospital * Nghean Endocrine Hospital *** Military Medical University Corresponding author: Nguyen Linh Toan (toannl@vmmu.edu.vn) 41
2. Journal of military pharmaco-medicine N o7-2016 The damage of pancreatic β cells to MATERIALS AND METHODS produce sufficient insulin and adiponectin 1. Patients and controls. as well as an increased production of One hundred thirty (n = 130) patients pro-inflammatory cytokines due to obesity with T2DM and one hundred twenty five are the major contributing factors for T2DM (n = 125) control individuals were included [3] . Insulin resistance appeared years before in the study. The patients were classified the clinical manifestation of T2DM and into two subgroups based on their BMI and is significantly associated with obesity, T2DM status. The first subgroup includes especially with abdominal and visceral the patients with both overweight/obese obesity with an abnormally increased (BMI ≥ 23) and T2DM (patients with waist-to-hip ratio (WHR), dyslipidemia, overweight T2DM, n = 57). The second hypertension and other metabolic disorders. subgroup includes patients with T2DM Therefore, obesity largely contributes to but without overweight (BMI < 23) (non- insulin resistance in patients with T2DM [5]. overweight T2DM, n = 73). The patients Adipose tissue is recently recognized were diagnosed for T2DM based on as an organ for metabolism of sexual the standard criteria reported by world steroids and production of adipsin that health organization (WHO) in 1998 and by significantly contributes to loss of body International Diabetes Federation (IDF) in weight [6]. Adipose tissue-derived proteins 2005. The anthropometric indicators such as regulate metabolic functionalities including height, weight, waist and hip circumference hormone activities [7]. Adipose tissue is were measured for all study participants. also known as an endocrine organ that can BMI and waist-hip ratio (WHR) were produce various peptides with bioactivities calculated based on their anthropometric indicators (table 1 ). namely adipokines. Increased adipose tissue due to obesity, especially deposition of All the individuals in the control group visceral fat, is associated with insulin were clinically examined and were considered resistance, increased blood glucose levels, healthy during sampling. None of them had any chronic infectious diseases or lipid metabolic disorders, hypertension conditions such as hepatitis, liver cirrhosis, and inflammation [7]. The adipose tissue- obstructive pulmonary disease, gout and/or derived hormones such as adiponectin, any infection. The control group was also leptin, adipsin, and resistin have been further divided into two subgroups. The shown to be associated with metabolic first control subgroup include normal healthy disorders and are risk factors for T2DM individuals, (non-overweight control individuals, and cardiovascular diseases . This study n = 57), with fasting venous blood glucose aims to investigate the levels of leptin and test < 5.6 mmol/L, blood pressure < 130 their correlations with insulin resistance of mmHg and < 85 mmHg, ECG in normal overweight/obese and T2DM. limits, other tests in the normal range, 42
3. Journal of military pharmaco-medicine N o7-2016 BMI from 18.5 to 23. The second control insulin resistance index (QUICK-IR index). subgroup is healthy individuals with BMI In addition, the β-cell function (homeostatic ≥ 23 (overweight/obese control individuals, model assessment- HOMA-β) and the n = 68), fasting venous blood glucose test insulin secretion of β-cell were evaluated < 5.6 mmol/L, blood pressure < 130 mmHg, according to Matthews’ method. and < 85 mmHg, ECG in normal limits 3. Measurement of leptin levels. (table 1 ). The levels of leptin were measured in 2. Measurement of biochemical the respective plasma samples of the study parameters. participants by using a commercial ELISA The levels of lipid components including kit following the manufacturer’s instruction cholesterol (CT), triglycerides (TG), high- (Human leptin, Sigma, USA). density lipoprotein - cholesterol (HDL-C), * Statistical analysis: low-density lipoprotein - cholesterol (LDL-C) Clinical and demographic data were were measured by using automatic presented in median values with range for biochemical AVADIA 1800 (Siemens, USA). continuous variables. The student’s t-tests Fasting glucose levels were measured in or one-way ANOVA were used for comparing blood by measurement of the UV with mean of two or more groups, respectively. Hexokinase. Insulin levels were measured Chi-square or Fisher’s exact tests were by the Achitech i2000SR (Abbott, USA). used to compare categorical variables. Blood fasting glycosylated hemoglobin Kruskal-Wallis or Mann-Whitney U test was (HbA1c) levels were quantified by the ion- used to analyze the plasma levels of exchange method using high performance leptin in the patients with T2DM and in liquid chromatography (HPLC). Insulin controls wherever appropriate. All statistical resistance index was evaluated according analyses were performed using IBM to the homeostasis model assessment Statistics SPSS v.19 (IBM Corp, Armonk, insulin resistance index (HOMA-IR index) NY. the USA), and the level of significance and the quantitative insulin sensitivity check was set at a P value of less than 0.05. RESULTS 1. Demographic, clinical and biochemical characteristics of the study subjects. Table 1: Characteristics of patients with type 2 diabetes mellitus and controls. Type 2 diabetes mellitus Without type 2 diabetes mellitus p value (*) Non- Overweight/obese Non-overweight Characteristics Overweight/obese overweight p value individuals, individuals, p value T2DM, n = 73 T2DM, n = 57 n = 68 n = 57 Age (years) 57.82 ± 7.98 58.89 ± 6.99 NS 55.88 ± 8.54 57.84 ± 6.93 NS < 0.05 Gender (M/F) 46/27 32/25 NS 28/40 13/44 0.02 0.03 BMI 26.03 ± 2.24 21.24 ± 1.37 < 0.0001 24.99 ± 1.7 20.69 ± 1.63 < 0.0001 NS WHR 0.93 ± 0.04 0.92 ± 0.07 < 0.05 0.91 ± 0.08 0.88 ± 0.06 < 0.05 0.001 43
4. o Journal of military pharmaco-medicine N 7-2016 Fasting glucose 9.50 ± 3.07 8.63 ± 2.07 NS 5.19 ± 0.34 5.17 ± 0.35 NS (mmol/L) < 0.0001 Total Cholesterol 5.14 ± 0.99 5.17 ± 0.75 NS 5.13 ± 0.97 5.09 ± 1.02 NS (mmol/L) NS Triglyceride (mmol/L) 2.91 ± 2.65 2.22 ± 1.59 NS 2.08 ± 2.10 1.59 ± 1.13 NS < 0.05 HDL-C (mmol/L) 1.15 ± 0.25 1.27 ± 0.52 NS 1.31 ± 0.32 1.45 ± 0.37 NS NS LDL-C (mmol/L) 2.70 ± 0.82 2.93 ± 0.74 NS 2.95 ± 0.88 2.99 ± 1.06 NS NS HbA1c (%) 7.37 ± 1.23 7.24 ± 1.3 NS 5.63 ± 0.57 5.6 ± 0.28 NS NS Insulin (pmol/L) 10.64 ± 9.87 7.30 ± 4.30 < 0.001 7.33 ± 2.42 6.32 ± 2.94 NS < 0.0001 HOMA-RI 4.90 ± 6.15 2.82 ± 1.77 < 0.05 1.69 ± 0.58 1.46 ± 0.70 < 0.05 < 0.0001 QUICKI 0.81 ± 0.10 0.85 ± 0.08 < 0.01 0.92 ± 0.07 0.97 ± 0.10 < 0.01 < 0.0001 HOMA-β 38.80 ± 35.83 31.27 ± 20.78 > 0.05 92.12 ± 47.35 78.60 ± 38.79 > 0.05 < 0.0001 (*) Comparison between type 2 diabetes mellitus and non-diabetes mellitus. The mean age of the patients with T2DM was higher than control individuals (without T2DM) (p < 0.05), while there was no difference in mean age between the patients with overweight T2DM and non-overweight T2DM. The proportion of male patients with T2DM was higher than the control group (p = 0.03). The levels of fasting glucose, triglycerides were significantly higher in the patients with T2DM compared to control individuals (p < 0.05). The levels of insulin and homeostasis model assessment insulin resistance (HOMA-RI) were significantly higher in the patients with T2DM compared to control individuals (p < 0.001). In contrast, the levels of quantitative insulin sensitivity check index (QUICKI) and homeostatic model assessment β-cell function (HOMA-β) were significantly lower in the patients with T2DM compared to control individuals (p < 0.001). 2. Leptin levels in patients with type 2 diabetes mellitus and in controls. Figure 1: Leptin level in type 2 diabetes mellitus (T2D) patients and heathy controls (HC). (A) Leptin level was measured in the plasma of patients with T2DM and healthy controls and was compared between groups. (B) Leptin level in patients with overweight/obese 44
5. Journal of military pharmaco-medicine N o7-2016 (OV/O) T2DM and those with-without overweight/obese (WOV/O) T2DM and in OV/O and WOV/O control individuals. P values were calculated by using Mann-Whitney U test. The leptin levels were significantly lower in the patients with T2DM [median: 1202.75 pg/ml] compared to the controls [median: 1715.4 pg/ml] (p = 0.05) ( figure 1A ). Among the patients with T2DM, the leptin levels were significantly lower in the T2DM patients with WOV/O compared to those with OV/O T2DM (p < 0.05). Among the control group, the leptin levels were significantly increased in the overweight/obese individuals compared to the WOV/O individuals (p < 0.05) ( figure 1B ). Figure 2: Leptin level in male and female patients with T2DM, in the T2DM patients with and without MS and in overweight/obese levels of subjects. The levels of leptin were significantly increased in female patients with T2DM and in T2DM patients with MS compared to those of male patients (p < 0.001) and T2DM patients with none-MS (p < 0.05) ( figure 2A and 2B ). The levels of leptin were significantly increased associated to BMI of subjects (p < 0.001) (figure 2C ). 45
6. Journal of military pharmaco-medicine N o7-2016 DISCUSSION Recently studies shown that low leptin levels were also associated with the Leptin, a hormone secreted by adipocytes pathogenesis of many other diseases in quantities which mainly reflect fat mass such as lipid metabolic disorders and and serves as an important signal of body obesity . The leptin level was significant energy stores. Leptin deficiency in mice correlated to T2DM clinical parameters and/or in humans is associated with including insulin (r = 0.23, p < 0.05) and neuroendocrine and metabolic abnormalities, HOMA-β (r = 0.216, p < 0.05) and inversity including insulin resistance and diabetes. correlated to QUICKI (r = -0.366, p < 0.0001). All these abnormalities are corrected by However, our data show that the leptin exogenous leptin administration, suggesting levels are not correlated with numerous that leptin plays a role in glucose homeo- clinical parameters such as triglycerides, stasis and possibly in the pathogenesis of cholesterol, HDL-C and LDL-C (data not other obesity-related metabolic complications shown). Those observations indicate that [4]. adiponectin levels involve in the development Previous studies have shown that plasma of T2DM. Therefore, based on the levels leptin levels are closely associated with of leptin, an adipose-derive cytokine could adiposity [8], and its level correlated with be useful for diagnosis of insulin resistance. increased MS components [9]. Plasma leptin However, more studies are required to level in diabetes is still controversial; propose a new index and verify the one recent study does not observe any diagnostic accuracy in clinical practice significant difference between diabetic and and to establish a cut-off value and reference non-diabetic subjects, others reported range of insulin sensitivity for specific significant lower level in type 1 diabetic populations [11]. subjects and type 2 diabetics with similar CONCLUSON adiposity [10]. In line with other studies, our results revealed that leptin levels were Our study demonstrated that the levels significantly increased in OV/O patients of leptin are significantly modulated during with T2DM and in OV/O healthy individuals the development of overweight/obese and compared to patients with WOV/O T2DM T2DM. The leptin levels were significantly and healthy individuals, respectively associated to BMI, genders and MS and (figure 1 ). In addition, our investigations with clinical parameters of obesity and revealed that leptin levels were increased T2DM. Leptin may possibly modulate the in female T2DM patients and in T2MS pathogenesis of overweight and T2DM. patients with MS. The increasing leptin Acknowledgements levels were associated with BMI of We thank all the study subjects for subjects ( figure 2 ). These results indicate their participation. This research is funded that increased leptin may potentially respond by Vietnam National Foundation for Science to the development of overweight/obese and and Technology Development (NAFOSTED) T2DM and metabolic disorders. under grant number 106-YS.02-2014.36. 46
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