Insights into the physiology of C-peptide

Copper Deficiency Associated with Glycemic Control in Individuals with Type 2 Diabetes Mellitus

Adequate copper (Cu) status has been associated with improved glycemic control, partly because of its role in reducing oxidative stress through superoxide dismutase (SOD) activity. Thus, the aim was to investigate the relationship between plasma Cu concentration and markers associated with glycemic control in individuals with type 2 diabetes mellitus (T2DM). This observational and cross-sectional study was conducted in individuals with T2DM of both sexes, aged between 19 and 59 years. Plasma Cu levels were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). Fasting glucose and insulin concentrations, C-peptide levels, SOD activity, and glycated hemoglobin (%HbA1c) were measured. Homeostatic model assessments (HOMA%B, HOMA%S, and HOMA-IR) were also performed. Additionally, %body fat and waist circumference were measured, and body mass index was calculated. Participants were categorized based on their plasma Cu concentrations (< 70 µg/dL and ≥ 70 µg/dL). The associations between variables were analyzed using chi-squared or Fisher's test and binary logistic regression models. Statistical significance was set at P < 0.05. Of the 97 participants (74.2% women), 85.5% had Cu deficiency. Cu-deficient individuals showed elevated C-peptide concentrations and HOMA%B values compared to those with adequate Cu levels (2.8 ng/mL vs. 1.8 ng/mL, P = 0.011; and 71.4 vs. 31.0, P = 0.003), respectively. Cu deficiency was associated with insulin resistance (P = 0.044) and decreased likelihood of exceeding the target serum glucose level (OR = 0.147, P = 0.013). However, no significant association was found between SOD activity and plasma Cu concentration. Consequently, Cu deficiency was linked to improved glycemic control, although it was not associated with the other markers.

Future clinical prospects of C-peptide testing in the early diagnosis of gestational diabetes

Gestational diabetes is typically diagnosed in the late second or third trimester of pregnancy. It is one of the most common metabolic disorders among expectant mothers, with potential serious short- and long-term complications for both maternal and offspring health. C-peptide is secreted from pancreatic beta-cells into circulation in equimolar amounts with insulin. It is a useful biomarker to estimate the beta-cell function because it undergoes negligible hepatic clearance and consequently it has a longer half-life compared to insulin. Pregnancy induces increased insulin resistance due to physiological changes in hormonal and metabolic homeostasis. Inadequate compensation by islet beta-cells results in hyperglycemia. The standard oral glucose tolerance test at 24-28 wk of gestation sets the diagnosis. Accumulated evidence from prospective studies indicates a link between early pregnancy C-peptide levels and the risk of subsequent gestational diabetes. Elevated C-peptide levels and surrogate glycemic indices at the beginning of pregnancy could prompt appropriate strategies for secondary prevention.

Effect of Serum C-Peptide Levels on the Development of Contrast-Induced Nephropathy in Diabetic Patients Undergoing Coronary Angiography

Contrast-induced nephropathy (CIN) is an important cause of morbidity and mortality, in patients with diabetes who undergo coronary angiography (CAG). It is known that serum C-peptide has renoprotective effects in diabetic nephropathy. Patients with diabetes (n = 552) who underwent CAG in our center between January 2020 and December 2021 were included, retrospectively. The patients were divided into 2 groups: not-developing CIN (group 1) and developing CIN (group 2). CIN developed in 128 (23.1%) of the patients with diabetes who underwent CAG. C-peptide, albumin, hemoglobin, hematocrit, initial creatinine, ejection fraction (EF), were significantly lower in the group that developed CIN compared with the group that did not (P < .05, for all). In correlation analysis, creatinine increase rate (ΔCr) was negatively correlated with C-peptide, hematocrit, and ejection fraction (r = -.241, P < .001; r = -.135, P < .001; r = -.194, P = .001; respectively). In logistic regression analysis, C-peptide level (Odds Ratio: .404, 95% Confidence Interval: .286-.571, P < .001) was an independent predictor of CIN. In the present study, C-peptide level was an independent predictor of CIN in patients with diabetes. This study suggests that low levels of C-peptide are associated with a greater risk of CIN.

The HbA1c/C-Peptide Ratio is Associated With the No-Reflow Phenomenon in Patients With ST-Elevation Myocardial Infarction

Currently, the gold standard treatment for ST-elevation myocardial infarction (STEMI) is primary percutaneous coronary intervention (pPCI), but even after successful pPCI, a perfusion disorder in the epicardial coronary arteries, termed no-reflow phenomenon (NR), can develop, resulting in short- and long-term adverse events. The present study assessed the relationship between NR and HbA1c/C-peptide ratio (HCR) in 1834 consecutive patients who underwent pPCI due to STEMI. Participants were divided into two groups according to NR status and the demographic, clinical and periprocedural characteristics of the groups were compared. NR developed in 352 (19.1%) of the patients in the study. While C-peptide levels were significantly lower in the NR group, HbA1c and HCR were significantly higher (P < .001, for all). In multivariable analysis, C-peptide, HbA1c, and HCR, were determined as independent predictors for NR (P < .05, for all). In Receiver Operating Characteristic (ROC) analysis, HCR predicted the NR with 80% specificity and 77% sensitivity. In STEMI patients, combining HbA1c and C-peptide in a single fraction has a predictive value for NR independent of diabetes. This ratio may contribute to risk stratification of STEMI patients.

Comparison of customized vacuum sealing drainage and vacuum sealing drainage in the treatment of diabetic foot ulcers: a retrospective analysis

BACKGROUND

The prevalence of diabetic foot ulcers, a common, more serious chronic diabetes-related complication, is increasing. Vacuum sealing drainage (VSD) constitutes an effective adjunctive treatment for diabetic foot ulcers. Factors, such as poor glycemic control, ischemia, and infection prolong wound healing time, and VSD products are expensive and unaffordable for many patients.

OBJECTIVE

To compare the use of customized VSD and customized VSD in the treatment of diabetic foot ulcer.

METHOD

This retrospective study included 83 patients with diabetic foot ulcers in customized VSD (n = 44) and VSD (n = 39) groups. Baseline data, efficacy after 14 days, total treatment efficiency, final outcome (28 days after treatment, healing rate), average treatment cost, and hospitalization (days) of the two groups were compared. Factors affecting wound healing were analyzed.

RESULTS

No significant intergroup differences in the baseline data were detected (VSD vs. customized VAD, p > 0.05). Treatment efficacy was higher in the customized VSD group than in the VSD group after 14 days (p < 0.05), although total treatment efficiency in both groups reached 100%. The final outcome in the customized VSD group was better (vs. VSD group, p < 0.05), and the wound healing rate was higher than in the VSD group (66.7% vs. 33.3%). The mean treatment cost and hospital days were greater in the VSD group (vs. customized VSD group; p < 0.05). Factors affecting wound healing include age, Wagner classification, HDL-C, and fasting C-peptide. Younger age, low Wagner classification grade, low HDL-C level, and high fasting C-peptide contribute to higher healing rate, CONCLUSION: Efficacy and final outcome of customized VSD were better than that of VSD; the customized VSD device is simple and convenient to operate, and enables cost-effective treatment.

Molecular Mechanisms for the Vicious Cycle between Insulin Resistance and the Inflammatory Response in Obesity

The comprehensive anabolic effects of insulin throughout the body, in addition to the control of glycemia, include ensuring lipid homeostasis and anti-inflammatory modulation, especially in adipose tissue (AT). The prevalence of obesity, defined as a body mass index (BMI) ≥ 30 kg/m², has been increasing worldwide on a pandemic scale with accompanying syndemic health problems, including glucose intolerance, insulin resistance (IR), and diabetes. Impaired tissue sensitivity to insulin or IR paradoxically leads to diseases with an inflammatory component despite hyperinsulinemia. Therefore, an excess of visceral AT in obesity initiates chronic low-grade inflammatory conditions that interfere with insulin signaling via insulin receptors (INSRs). Moreover, in response to IR, hyperglycemia itself stimulates a primarily defensive inflammatory response associated with the subsequent release of numerous inflammatory cytokines and a real threat of organ function deterioration. In this review, all components of this vicious cycle are characterized with particular emphasis on the interplay between insulin signaling and both the innate and adaptive immune responses related to obesity. Increased visceral AT accumulation in obesity should be considered the main environmental factor responsible for the disruption in the epigenetic regulatory mechanisms in the immune system, resulting in autoimmunity and inflammation.

Valproate-Induced Metabolic Syndrome

Valproic acid (VPA) and its salts (sodium calcium magnesium and orotic) are psychotropic drugs that are widely used in neurology and psychiatry. The long-term use of VPA increases the risk of developing adverse drug reactions (ADRs), among which metabolic syndrome (MetS) plays a special role. MetS belongs to a cluster of metabolic conditions such as abdominal obesity, high blood pressure, high blood glucose, high serum triglycerides, and low serum high-density lipoprotein. Valproate-induced MetS (VPA-MetS) is a common ADR that needs an updated multidisciplinary approach to its prevention and diagnosis. In this review, we consider the results of studies of blood (serum and plasma) and the urinary biomarkers of VPA-MetS. These metabolic biomarkers may provide the key to the development of a new multidisciplinary personalized strategy for the prevention and diagnosis of VPA-MetS in patients with neurological diseases, psychiatric disorders, and addiction diseases.

The average 30-minute post-prandial C-peptide predicted diabetic retinopathy progress: a retro-prospective study

BACKGROUND

The conclusion between Connecting peptide (C-peptide) and diabetic chronic complication was controversial. The purpose of this study is to explore the possible association between average C-peptide with diabetic retinopathy (DR) progression in Chinese patients with type 2 diabetes.

METHODS

This is a retro-prospective study. 622 patients with type 2 diabetes were included. DR was evaluated using non-mydriatic fundus photography and DR progression was defined as any deterioration of either eye. Fasting and postprandial c-peptide levels were assayed at baseline and follow-up period. Differences between continuous variables were compared using the Mann-Whitney U test; and categorical variables were analyzed by the chi-square test. Correlation between parameters and 30-minute postprandial C-peptide were determined by Spearman correlation test. The relationship between C-peptide and DR progression was evaluated by multivariable binary logistic regression. Two-tailed P-values < 0.05 were regarded as statistically significant.

RESULTS

DR was present in 162 (26.0%) patients at baseline, and 26.4% of patients were found progression of DR at follow-up. Patients with progression of DR had lower average levels of 30-minute postprandial C-peptide (2.01 ng/ml vs. 2.6 ng/ml, p = 0.015) and 120-minute postprandial C-peptide (3.17 ng/ml vs. 3.92 ng/ml, p < 0.029), as well as average increment of 30-minute (0.41 ng/ml vs. 0.64 ng/ml, p = 0.015) and 120-minute postprandial C-peptide (1.48 ng/ml vs. 1.93 ng/ml, p < 0.017), than those without DR aggravation. Multivariate logistic regression analysis determined that 30-minute postprandial C-peptide and its increment were related to reduced odds ratios for DR progression (odds ratios [OR] = 0.83 and 0.74, respectively).

CONCLUSION

Our results suggest that the Average 30-minute post-prandial C-peptide and increment were negatively correlated with DR progression, which further demonstrates the importance to preserve β-cell residual function in the prevention for DR progression.

TRIAL REGISTRATION

Not applicable.

A General Strategy to Install Amidine Functional Groups Along the Peptide Backbone

Amidines are a structural surrogate for peptide bonds, yet have received considerably little attention in peptides due to limitations in existing methods to access them. The synthetic strategy developed in this study represents the first robust and general procedure for the introduction of amidines into the peptide backbone. We exploit and further develop the utility and efficiency of thioimidate protecting groups as a means to side-step reactivity that ultimately renders existing methods unsuitable for the installation of amidines along the main-chain of peptides. This work is significant because it describes a generally applicable path to access unexplored peptide designs and architectures for new therapeutics made possible by the unique properties of amidines.

The bidirectional association of C-peptide with cardiovascular risk in nondiabetic adults and patients with newly diagnosed type 2 diabetes mellitus: a retrospective cohort study

Background

Recent literature reported the biological role of C-peptide, but this role is still controversial and unclear. The primary aim of this study was to investigate associations between C-peptide and cardiovascular biomarkers as well as events.

Methods

A total of 55636 participants who had a health examination from 2017 to 2021 were included. Of them, 6727 participants visited the hospital at least twice. Cardiovascular biomarkers like high-sensitivity C-reactive protein (hs-CRP) and high-sensitivity cardiac troponin T (hs-cTnT) were measured and their relationships with fasting C-peptide were evaluated for all participants. Cardiovascular events were obtained during the last visit and their associations with C-peptide were evaluated for those participants who visited the hospital at least twice.

Results

Among the included participants, 11.1% had a previous type 2 diabetes mellitus (T2DM). In the participants without previous T2DM, the relationships between fasting C-peptide and hs-CRP and hs-cTnT were negative if the value of fasting C-peptide was < 1.4 ng/mL and positive if the value was ≥ 1.4 ng/mL. These relationships remained significant after adjusting for hemoglobin A1c, insulin resistance index, and its interaction with C-peptide, even if the participants were stratified by glucose metabolism status or levels of insulin resistance index. Hazard ratios of cardiovascular events were first decreased and then increased with the increasing of baseline C-peptide levels, though these associations became unsignificant using the multivariate Cox regression model. Unlike the participants without previous T2DM, the associations of C-peptide with cardiovascular biomarkers and events were not significant in the patients with previous T2DM.

Conclusions

The associations of C-peptide with cardiovascular biomarkers and events were different between the participants without previous T2DM and those with previous T2DM. The effect of C-peptide on cardiovascular risk may be bidirectional, play a benefit role at a low level, and play a harmful role at a high level in the nondiabetic adults and the patients with newly diagnosed T2DM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01636-z.

Biomarkers of Glucose Metabolism Alterations and the Onset of Metabolic Syndrome in Survivors of Childhood Acute Lymphoblastic Leukemia

Owing to advances in treatment modalities and supportive care, overall survival rates have reached up to 90% among children with acute lymphoblastic leukemia (ALL). However, due to the underlying illness and therapy, they are at a greater risk of developing lifestyle diseases. Hence, special attention is paid to early detection of the components of metabolic syndrome (MetS). This study aimed at investigating the association of plasma levels of nine diabetes markers with being overweight and components of MetS in ALL survivors. The study included 56 subjects with mean age of 12.36 ± 5.15 years. The commercially available Bio-Plex Pro Human Diabetes 10-Plex Panel kit was used to evaluate levels of diabetes biomarkers. ALL survivors presented statistically higher concentrations of GIP (p = 0.026), glucagon (p = 0.001), leptin (p = 0.022), and PAI-1 (p = 0.047), whereas the concentration of ghrelin was lower (p < 0.001) compared to the control group. Moreover, subjects within normal BMI range showed higher GIP (p = 0.005) and lower ghrelin concentration (p < 0.001) compared to healthy peers. At least one risk factor of MetS was present in 58.9% of participants, who showed significantly higher levels of C-peptide (p = 0.028), leptin (p = 0.003), and PAI-1 (p = 0.034) than survivors who did not meet any MetS criteria. In conclusion, ALL survivors are at greater risk of disturbances in carbohydrate metabolism. Understanding the pathogenesis and applicability of diabetes markers is crucial for developing strategies to prevent metabolic syndrome in ALL survivors.

Application of urine C-peptide creatinine ratio in type 2 diabetic patients with different levels of renal function

OBJECTIVE

This study aims to investigate the effect of single urine C peptide/creatinine (UCPCR) in assessing the islet β Cell function of type 2 diabetes mellitus (T2DM) patients with different renal function.

METHODS

A total of 85 T2DM patients were recruited in this study, all the patients were assigned to one group with estimated glomerular filtration rate (eGFR)≤60 ml·min^-1·1.73 m^-2 and another group complicated with eGFR>60 ml·min^-1·1.73 m^-2. Serum creatinine, urine creatinine, serum fasting C-peptide (FCP), fasting blood glucose (FBG), glycosylated hemoglobin (HbA1C) and 24-hour urinary C-peptide (24hUCP) were measured. The modified homeostasis model assessment-islet β cell function [HOMA-islet (CP-DM)], the modified homeostasis model assessment-insulin resistance [HOMA-IR(CP)] and UCPCR were calculated.

RESULTS

When compared with group eGFR ≤60 ml·min^-1·1.73 m^-2, the levels of UCPCR, FCP, the modified HOMA-IR(CP) and HOMA-islet (CP-DM) were promoted and the concentrations of HbA1C, FPG, creatinine were decreased in the patients of eGFR>60 ml·min^-1·1.73 m^-2 (P<0.05); FCP was uncorrelated with 24hUCP while associated with UCPCR in the patients of eGFR ≤ 60 ml·min^-1·1.73 m^-2; UCPCR was positively correlated with FCP and HOMA-IR(CP) in the T2DM patients with different levels of renal function; the cut-off (UCPCR ≤ 1.13 nmol/g) had 88.37% sensitivity and 95.24% specificity [95% confidence interval (CI):0.919-0.997] for identifying severe insulin deficiency in T2DM patients[area under the curve (AUC) 0.978].

CONCLUSION

UCPCR can be used to evaluate islets β Cell function in T2DM patients with different renal function status.

The Impact of C-Peptide and Diabetes Mellitus on Coronary Ectasia and Effect of Coronary Ectasia and C-Peptide on Long-Term Outcomes: A Retrospective Cohort Study

BACKGROUND

Coronary artery ectasia (CAE) is an entity frequently associated with atherosclerotic coronary artery disease (CAD) in clinical practice. Although it has common risk factors with atherosclerotic CAD in its development, the pathophysiology of CAE is not fully known and it is not seen in every CAD suggesting that different determinants may play a pivotal role in the development of CAD. This study aimed to reveal the impact of C-peptide and diabetes mellitus (DM) on CAE and the effect of C-peptide and coronary ectasia on long-term outcomes in patients who underwent coronary angiography.

METHODS

A total of 6611 patients who underwent coronary angiography were followed up retrospectively, and their major adverse cardiovascular event (MACE) status of an average of sixty months was recorded. According to their angiographic features, the patients were divided into two groups those with and without CAE. MACE development was accepted as the primary endpoint.

RESULTS

A total of 552 patients had CAE and MACE developed in 573 patients. Patients with CAE and higher C-peptide levels (Q4 + Q3) showed higher rates of MACE as compared to those without CAE and lower C-peptide levels (Q1 + Q2) (20.8% vs 7.6%; 70.1% vs 29.1%; p < 0.001, for both of them). In multivariate regression analysis, high C-peptide levels were determined as an independent risk factor for CAE (OR 2.417; 95% CI 2.212-2.641; p < 0.001). The Kaplan-Meier cumulative survival curves showed that the risks for MACE increased as the C-peptide levels increased. The Cox regression analysis for 5-years MACE related to the plasma C-peptide levels and presence of CAE, C-peptide, and CAE were found to be independent predictors of MACE (HR = 1.255, 95% CI: 1.164-1.336, p < 0.001 and HR = 1.012, 95% CI: 1.002-1.023, p=0.026, respectively).

CONCLUSION

Our study revealed that a high C-peptide level is an independent risk factor for CAE and that CAE and C-peptide are independent predictors for the development of MACE.