Diabetes & Metabolic Syndrome: Clinical Research & Reviews 13 (2019) 3099e3104 Contents lists available at ScienceDirect Diabetes & Metabolic Syndrome: Clinical Research & Reviews journal homepage: www.elsevier.com/locate/dsx C-peptide concentrations in patients with type 2 diabetes treated with insulin * Mehmet Uzunlulu a, Aytekin Oguz a, Müzeyyen Arslan Bahadir b, Ayse Naciye Erbakan c, , Mirac Vural Keskinler b, Banu Alpaslan Mesci a a Istanbul Medeniyet University, Goztepe€ Training and Research Hospital, Istanbul, Turkey b Goztepe€ Training and Research Hospital, Istanbul, Turkey c Nisa Hospital, Istanbul, Turkey article info abstract Article history: Aims: To determine beta cell reserves of patients with type 2 diabetes who are treated with insulin by Received 25 July 2019 using fasting C-peptide concentrations and to investigate the clinical features related to C-peptide Received in revised form concentrations. 14 November 2019 Materials and methods: Patients with type 2 diabetes, who were using insulin as monotherapy or in Accepted 15 November 2019 combination therapy, were divided into three groups; those with an insufficient beta cell reserve (C- peptide: <0.5 ng/mL), borderline reserve (C-peptide: 0.5e2 ng/mL) and sufficient reserve (C-peptide:> Keywords: 2 ng/mL). Type 2 diabetes ± C-peptide Results: In the 249 patients (mean age, 61.77 9.34 years; 40.6% male), the mean duration of diabetes ± Beta-cell reserve was 13.9 8.43 years. The mean HbA1c concentrations, fasting glucose and C-peptide concentrations Insulin use were 8.88 ± 1.87%, 184.29 ± 77.88 mg/dL and 1.95 ± 1.37 ng/mL, respectively. Fifty-seven percent of patients (n ¼ 142) had a borderline beta cell reserve and 37% (n ¼ 92) had high C-peptide concentrations. Only 6% of patients (n ¼ 15) had an insufficient beta cell reserve. C-peptide levels were positively correlated with waist circumference (r: 0.282; p ¼ 0.001), hip circumference (r: 0.251; p ¼ 0.001), body mass index (r: 0.279; p ¼ 0.001), fasting glucose concentrations (r: 0.309; p ¼ 0.001) and triglyceride concentrations (r: 0.358; p ¼ 0.001). Conclusion: In this study, almost all patients with type 2 diabetes using insulin were found to have sufficient or borderline beta cell reserves and insulin resistance-related parameters were prominent in those with adequate beta cell reserve. Clinical trials no: NCT04005261 © 2019 Diabetes India. Published by Elsevier Ltd. All rights reserved. 1. Introduction medications [3]. It has been suggested that C-peptide concentra- tions correlate with microvascular and macrovascular complica- C-peptide is secreted in equimolar amounts with insulin from tions in both type 1 and type 2 diabetes and can be a reliable pancreatic beta cells and is reported to be a more useful laboratory indicator for predicting future insulin needs [4e6]. In patients with parameter than insulin in evaluating endogenous insulin reserve type 2 diabetes, initiation of insulin therapy is indicated in several [1,2]. C-peptide measurement can be used in the differential diag- conditions such as severe insulin resistance, acute metabolic de- nosis of type 1 and type 2 diabetes, for the identification of patients compensations, surgery, pregnancy, and progression of diabetic with maturity-onset diabetes of the young (MODY) or latent complications, and also when glycemic control cannot be achieved autoimmune diabetes of adults (LADA); for the detection of abso- with effective lifestyle regulation and non-insulin antidiabetic lute insulin deficiency; and in planning timely changes of treatment medications [7,8]. At that point, a low C-peptide level is considered in patients with diabetes using either insulin and other diabetic to be a reliable parameter in the decision to start insulin therapy except in extreme hyperglycemic conditions. In our “National Diabetes Consensus Group Diabetes Diagnosis and Treatment” guideline, it is recommended that glycated he- * Corresponding author. E-mail address: [email protected] (A.N. Erbakan). moglobin (HbA1c), as well as C-peptide concentrations, should be https://doi.org/10.1016/j.dsx.2019.11.010 1871-4021/© 2019 Diabetes India. Published by Elsevier Ltd. All rights reserved. 3100 M. Uzunlulu et al. / Diabetes & Metabolic Syndrome: Clinical Research & Reviews 13 (2019) 3099e3104 considered in the planning of type 2 diabetes treatment [9]. When, evaluate the relationship between fasting C-peptide and clinical in daily practice, C-peptide concentrations are observed to be features. normal or high in patients with type 2 diabetes who use insulin, it causes confusion about the treatment decision and raises the 2.2. Anthropometric measurements question as to whether the patients’ insulin use is necessary. The aim of this study was to investigate c-peptide concentra- Body weight, waist circumference, and height were measured tions in patients with type 2 diabetic using insulin as a mono- by the same physician using standard measuring instruments. therapy or as part of combination therapy, and to examine the Waist circumference was measured while the patient was standing, clinical features associated with predetermined C-peptide at the narrowest part of the waist with a slight expiration on the concentrations. midpoint between the lowest rib and the iliac crest, as defined by the World Health Organization. Hip circumference was measured at 2. Material and methods the level of the widest circumference over the greater trochanters. Body mass index (BMI) was calculated as weight (in kilograms) This prospective, observational clinical study was conducted on divided by height (in square meters). Blood pressure was obtained consecutive patients with type 2 diabetes aged 18 years or older using an appropriate mercury sphygmomanometer (based on who presented to the Diabetes Outpatient Clinics of Istanbul Korotkoff Phase I and Phase V sounds) on both arms with the pa- Medeniyet University Goztepe Training and Research Hospital be- tient in a comfortable sitting position after at least a 10-min rest. tween November 1st, 2018, and February 1st, 2019. Informed The second measurement was performed on the arm with a higher consent was obtained from all subjects included in the study. The value. Two measurements were taken at least 3 min apart and trial protocol was approved by the hospital ethics committee averaged to provide the values for systolic and diastolic pressure. (October 24, 2018; 2018/0396) and conducted in accordance with the Declaration of Helsinki. 2.3. Analytical measurements Sample size: Assuming a ¼ 0.05 and 80% power, 249 subjects were included in the study using the simple random sampling Fasting glucose concentrations were determined using the method. hexokinase method. Serum creatinine was assayed using the ki- Inclusion criteria: Patients with type 2 diabetes who had been netic Jaffe method. For alanine transaminase (ALT) concentrations, treated with insulin as a monotherapy or as a component of com- an enzymatic (without P-50-P, NADH) method was used. Fasting bination therapy for at least 3 months. plasma total cholesterol, HDL and LDL cholesterol and triglyceride Exclusion criteria: Diagnosis of other types of diabetes, end- concentrations were determined using enzymatic methods (Abbott stage renal failure, history of renal transplantation, diabetic acute Architect c16000 and c8000, Abbott). A Tosoh HLC-723 G8 (Tosoh metabolic decompensation, decompensated heart failure, G8) (Tosoh, Japan) (variant-mode) ion exchange high-performance advanced liver disease, pregnancy, acute or chronic pancreatitis, liquid chromatography (HPLC) system was used for HbA1c mea- pancreatic carcinoma, acute infections, use of medications that surements. The C-peptide was measured using a chem- might affect glucose regulation (e.g. corticosteroids). iluminescence microparticle immunoassay in the Abbott Architect Primary endpoint: Determination of C-peptide concentrations I2000 (Abbott Laboratories, Abbott Park, IL, USA) autoanalyzer. in patients with type 2 diabetes using insulin to evaluate pancreatic Glomerular filtration rate (GFR) was calculated using the beta cell reserve and compare clinical characteristics for C-peptide Chronic Kidney Disease Epidemiology Collaboration equation concentrations. (CKD-EPI) formula [10], and the presence of proteinuria was Secondary endpoint: Assessing the correlation between fasting determined using the protein/creatinine ratio in spot urine. C-peptide concentrations and the clinical features of patients with type 2 diabetes treated with insulin. 2.4. Statistical methods 2.1. Study design Statistical analysis was performed using the Number Cruncher Statistical System NCSS (Number Cruncher Statistical System) Duration of diabetes, demographic characteristics, comorbid- NCSS) version 2007 software (Kaysville, Utah, USA). The normal ities, treatment characteristics, and duration of medication use distribution of quantitative data was tested by using the were recorded for participants who met the inclusion criteria. The Kolmogorov-Smirnov and Shapiro-Wilk tests and graphical evalu- patients’ diabetes type, their medications, the dose of their medi- ations. For groups with normal distribution, one-way analysis of cations, and the regularity of use was further investigated using the variance (ANOVA) was used for multiple groups and the Bonferroni hospital prescription system and the National Medula electronic test was used to compare two groups of independent samples. For prescription system (//medeczane.sgk.gov.tr/doktor/login.jsp). groups