Preserved C-peptide secretion is associated with fewer low-glucose events and lower glucose variability on flash glucose monitoring in adults with type 1 diabetes

MRM-based LC-MS method for accurate C-peptide quantitation

Introduction

C-peptide secretion mirrors beta-cell function and has emerged as a valuable clinical biomarker for diabetes mellitus. C-peptide measurements can provide estimates of insulin secretory capacity, aiding in clinical decision-making and differentiation between diabetes types. Unfortunately, C-peptide assays are still not standardized, which may limit their practical clinical use. We have developed an MRM-based LC-MS method that demonstrated accuracy close to our reference method.

Objective

To develop and validate a mass spectrometry method for accurate quantitation of C-peptide.

Method

A serum sample was spiked with isotope-labeled C-peptide as a standard. The enrichment process involved protein precipitation with methanol, solid-phase extraction, and anion exchange for C-peptide enrichment followed by Glu-C digestion. The peptide LGGGPGAGSLQPLALE was quantitated using MRM in positive ion mode. The calibration process includes C-peptide CRM material to ensure a complete traceability chain for the measurement.

Results

The assay exhibited linearity across a wide range of C-peptide concentrations and a limit of quantitation of 0.058 nmol/L. The inter-day imprecision was less than 9.6 % CV, and the intra-day imprecision was less than 8.9 % CV. Spiking with bilirubin, triglycerides, and hemoglobin demonstrated no interference, except for triglycerides at very high levels. The method exhibited a strong correlation to the C-peptide reference method (r2 = 0.95).

Conclusion

The developed mass spectrometry method has demonstrated accurate results in C-peptide quantitation and can serve as a supplemental method to the existing C-peptide reference method. This ensures sustained stability over time and ultimately refines the existing reference system.

Plasma C-Peptide Levels and the Continuous Glucose Monitoring-Defined Coefficient of Variation in Risk Prediction for Hypoglycemia in Korean People with Diabetes Having Normal and Impaired Kidney Function

BACKGRUOUND

We aimed to investigate the predictive values of plasma C-peptide levels and the continuous glucose monitoring (CGM)-defined coefficient of variation (CV) in risk prediction for hypoglycemia in Korean people with diabetes with normal and impaired kidney function.

METHODS

We analyzed data from 1,185 participants diagnosed with type 1 and type 2 diabetes who underwent blinded professional CGM between January 2009 and May 2021 at outpatient clinics. We explored correlations among CGM-defined CV, plasma C-peptide levels, and time below range at <70 and 54 mg/dL across different kidney function categories.

RESULTS

In patients with chronic kidney disease (CKD) stages 1-2 (n=934), 89.3% who had a random plasma C-peptide level higher than 600 pmol/L exhibited a CV of ≤36%. Among those in CKD stage 3 (n=161) with a random plasma C-peptide level exceeding 600 pmol/L, 66.7% showed a CV of ≤36%. In stages 4-5 of CKD (n=90), the correlation between random C-peptide levels and CV was not significant (r=-0.05, P=0.640), including cases with a CV greater than 36% despite very high random plasma C-peptide levels. Random plasma C-peptide levels and CGM-assessed CV significantly predicted hypoglycemia in CKD stages 1-2 and 1-5, respectively.

CONCLUSION

The established C-peptide criteria in Western populations are applicable to Korean people with diabetes for hypoglycemic risk prediction, unless kidney function is impaired equivalent to CKD stage 3-5. The CGM-defined CV is informative for hypoglycemic risk prediction regardless of kidney function.

Association of detectable C-peptide levels with glycemic control and chronic complications in individuals with type 1 diabetes mellitus: A systematic review and meta-analysis

AIMS

Multiple studies have addressed the association between detectable levels of C-peptide and glycemic control, as well as the development of chronic complications of type 1 diabetes mellitus (T1DM), including both macrovascular and microvascular diseases. We aimed to summarize the available evidence on the clinical significance of detectable levels of C-peptide in T1DM.

METHOD

A systematic search was performed on online databases using the following key terms: T1DM, C-peptide, diabetes mellitus complications, and glycemic parameters. We pooled standardized mean difference (SMD) and odds ratios (OR).

RESULTS

Of the 1519 articles retrieved from the initial search, 38 (12 cohort and 26 cross-sectional studies) met our eligibility criteria. Individuals with T1DM in the detectable C-peptide group, compared with the undetectable C-peptide group, had lower mean HbA1c [pooled SMD (95 % confidence interval (95 % CI)): -0.08 (-0.13 to -0.02), I2 = 0 %, p.

VALUE

0.005] and daily insulin dose [-0.41 (-0.65 to -0.18), I2 = 83 %, p.value < 0.001]. They also showed lower odds for retinopathy [pooled crude OR (95 % CI): 0.53 (0.41 to 0.69), I2 = 65 %, p.value < 0.001] and nephropathy complications [0.62 (0.55 to 0.70), I2 = 19 %, p.value < 0.001]; however, the two groups were similar regarding neuropathy [0.92 (0.65 to 1.31), I2 = 0 %, p.

VALUE

0.31].

CONCLUSIONS

The available evidence suggests that individuals with T1DM in the detectable C-peptide group may experience better clinical outcomes.

Residual C-peptide secretion is associated with better CGM-metrics in adults with short-lasting type 1 diabetes

AIM

To investigate whether the risk of hypoglycemia is associated with residual β-cell function in adults with type 1 diabetes (T1D).

METHODS

This cross-sectional study included 61 subjects with T1D duration <15 years using continuous glucose monitoring (CGM). Random C-peptide levels were compared between participants with time below range (TBR) ≥3 % (n = 15) and TBR <3 % (n = 45). The associations of C-peptide levels with other CGM metrics and clinical characteristics of the study participants were also tested. Analyses were adjusted for disease duration.

RESULTS

Median [25th - 75th percentiles] C-peptide levels were generally low: 49.3 [15.7-152] pmol/L. Participants in the low-TBR group had significantly higher C-peptide levels compared to those in the high-TBR group (52.9 [19.5-176.3] vs. 21.0 [9.4-106.6] pmol/L, p = 0.036), independently from disease duration. Higher C-peptide levels were associated with better CGM-metrics (p < 0.05). A C-peptide threshold of 15.1 pmol/L was the best cut-off to distinguish people at high risk of hypoglycemia.

CONCLUSIONS

C-peptide microsecretion is associated with a low risk of hypoglycemia and improved CGM metrics. Therapeutic approaches aimed at preserving minimal C-peptide secretion could potentially enhance glycemic outcomes and reduce hypoglycemic risk in individual with T1D.

Unveiling the Therapeutic Potential of the Second-Generation Incretin Analogs Semaglutide and Tirzepatide in Type 1 Diabetes and Latent Autoimmune Diabetes in Adults

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease caused by the immune-mediated destruction of insulin-producing pancreatic beta cells, resulting in the lifelong need for exogenous insulin. Over the last few years, overweight and obesity have recently emerged as growing health issues also afflicting patients with T1D. In this context, the term "double diabetes" has been coined to indicate patients with T1D who have a family history of type 2 diabetes mellitus (T2D) and/or patients with T1D who are affected by insulin resistance and/or overweight/obesity and/or metabolic syndrome. At the same time, the use of second-generation incretin analogs semaglutide and tirzepatide has substantially increased on a global scale over the last few years, given the remarkable clinical benefits of these drugs (in terms of glucose control and weight loss) in patients with T2D and/or overweight/obesity. Although the glucagon-like peptide-1 (GLP-1) receptor agonists and the novel dual GIP (glucose-dependent insulinotropic polypeptide)/GLP-1 receptor agonist tirzepatide are currently not approved for the treatment of T1D, a growing body of evidence over the last few years has shown that these medications may serve as valid add-on treatments to insulin with substantial efficacy in improving glucose control, promoting weight loss, preserving residual beta-cell function and providing other beneficial metabolic effects in patients with T1D, double diabetes and latent autoimmune diabetes in adults (LADA). This manuscript aims to comprehensively review the currently available literature (mostly consisting of real-world studies) regarding the safety and therapeutic use (for different purposes) of semaglutide and tirzepatide in patients with T1D (at different stages of the disease), double diabetes and LADA.

Detection of Insulin in Insulin-Deficient Islets of Patients with Type 1 Diabetes

Type 1 diabetes (T1D) is related to the autoimmune destruction of β-cells, leading to their almost complete absence in patients with longstanding T1D. However, endogenous insulin secretion persists in such patients as evidenced by the measurement of plasma C-peptide. Recently, a low level of insulin has been found in non-β islet cells of patients with longstanding T1D, indicating that other islet cell types may contribute to persistent insulin secretion. The present study aimed to test the ability of various antibodies to detect insulin in insulin-deficient islets of T1D patients. Pancreatic autopsies from two children with recent-onset T1D, two adults with longstanding T1D, and three control subjects were examined using double immunofluorescent labeling with antibodies to insulin, glucagon and somatostatin. Immunoreactivity to insulin in glucagon+ cells of insulin-deficient islets was revealed using polyclonal antibodies and monoclonal antibodies simultaneously recognizing insulin and proinsulin. Along with this, immunoreactivity to insulin was observed in the majority of glucagon+ cells of insulin-containing islets of control subjects and children with recent-onset T1D. These results suggest that islet α-cells may contain insulin and/or other insulin-like proteins (proinsulin, C-peptide). Future studies are needed to evaluate the role of α-cells in insulin secretion and diabetes pathogenesis.

Residual C-peptide is associated with new and persistent impaired awareness of hypoglycaemia in type 1 diabetes

AIMS

To describe the change in impaired awareness of hypoglycaemia (IAH) over time and to identify factors associated with this change in the Dutch Type 1 Diabetes biomarkers cohort (NCT04977635).

METHODS

A prospective cohort of type 1 diabetes patients, with C-peptide <300 pmol/L, who had completed the Clarke questionnaire, to determine IAH status, at baseline and after 2 years. Changes in awareness status were defined and compares as follows: unchanged normal awareness (NAH) versus unchanged IAH, new IAH versus reversal of IAH. Multivariate logistic regression models were fitted using forward and backward stepwise selection using a 0.10 P-value cut-off, and stepwise backward selection using AIC criteria.

RESULTS

A total of 431 out of 611 participants were included. The baseline prevalence of IAH was 17 % and 20 % after 2 years. The incidence proportion of new IAH and reversal of IAH were, 9.5 % and 31 %, respectively. For every 2.7-fold increase in C-peptide, the odds of IAH decrease by 58 %. A 1-unit increase in BMI over the 2-year follow-up period is associated with a 5.27-fold increase in the odds of reversing IAH.

CONCLUSIONS

Higher C-peptide levels are protective against new IAH, and an increase in BMI over time is associated with the reversal of IAH.

Metabolic impact of residual C-peptide secretion in type 1 diabetes mellitus

Objective

This study aimed to evaluate the association of detectable C-peptide levels with various continuous glucose monitoring (CGM) metrics and diabetes complications in patients with type 1 diabetes mellitus (T1DM).

Subjects and methods

Retrospective, descriptive study of 112 patients with T1DM undergoing intensive insulin therapy, categorized according to fasting C-peptide level into undetectable (<0.05 ng/mL) and detectable (≥0.05 ng/mL) groups.

Results

The patients' median age at diagnosis was 22 (12-34) years and the median T1DM duration was 18.5 (12-29) years. Patients with detectable versus undetectable C-peptide levels were older (27.5 [16.5-38.5] versus 17.5 [9.8-28.8] years, respectively, p = 0.002) and had shorter disease duration (14 [9-24] versus 20 [14-32] years, respectively, p = 0.004). After adjustment for covariates (sex, disease duration, body mass index, and use of continuous subcutaneous insulin infusion), detectable C-peptide level was associated with lower time above range (TAR; aβ -11.03, p = 0.002), glucose management indicator (GMI, aβ -0.55, p = 0.024), and average glucose (aβ -14.48, p = 0.045) and HbA1c (aβ -0.41, p = 0.035) levels. Patients with detectable versus those with undetectable C-peptide level had significantly higher time in range (TIR) before (β = 7.13, p = 0.044) and after (aβ = 11.42, p = 0.001) adjustments. Detectable C-peptide level was not associated with lower time below range (TBR), coefficient of variation (CV), or prevalence of chronic microvascular and macrovascular complications.

Conclusions

Persistent C-peptide secretion in patients with T1DM was associated with significantly better metabolic control reflected by different glucose metrics, namely, TIR, TAR, GMI, and HbA1c.

Autologous Pancreatic Islet Cell Transplantation Following Pancreatectomy for Pancreas Diseases Other Than Chronic Pancreatitis: A 15-y Study of the Milan Protocol

BACKGROUND

Pancreatogenic diabetes, a consequence of pancreatic tissue loss following pancreatectomy, poses a significant challenge for patients undergoing pancreatic surgery. Islet autotransplantation (IAT) offers a promising approach to prevent or alleviate pancreatogenic diabetes, but its application has been limited to individuals with painful chronic pancreatitis.

METHODS

This study presents a 15-y clinical experience with the Milan Protocol, which expands IAT after pancreatectomy to a broader spectrum of patients with malignant and nonmalignant pancreatic diseases. The analysis evaluates feasibility, efficacy, and safety of IAT. Modified Igls criteria validated through the arginine test and mixed meal tolerance tests were used to assess long-term metabolic outcomes.

RESULTS

Between November 2008 and June 2023, IAT procedures were performed on 114 of 147 candidates. IAT-related complications occurred in 19 of 114 patients (16.7%), with 5 being potentially serious. Patients exhibited sustained C-peptide secretion over the 10-y follow-up period, demonstrating a prevalence of optimal and good beta-cell function. Individuals who underwent partial pancreatectomy demonstrated superior metabolic outcomes, including sustained C-peptide secretion and a reduced risk of developing diabetes or insulin dependence compared with those who underwent total pancreatectomy. For patients who had total pancreatectomy, the quantity of infused islets and tissue volume were identified as critical factors influencing metabolic outcomes. An increased risk of recurrence or progression of baseline diseases was not observed in subjects with neoplasms.

CONCLUSIONS

These findings provide valuable insights into the benefits and applications of IAT as a therapeutic option for pancreatogenic diabetes after pancreatic surgery, expanding its potential beyond painful chronic pancreatitis.

Abnormal late postprandial glucagon response in type 1 diabetes is a function of differences in stimulated C-peptide concentrations

Background

The functional changes in alpha cells in patients with type 1 diabetes (T1D) with different residual beta cell functions remain poorly elucidated. The study aimed to investigate the relationship between glucagon secretion and C-peptide levels and to explore the relationship between glucagon response and glucose increment in respond to a secretagogue in a steamed bread meal tolerance test (BMTT) in T1D.

Methods

The study enrolled 43 adult patients with T1D and 24 healthy control subjects. Patients with T1D who underwent BMTT were divided into two groups based on peak C-peptide levels: C peptide low (CPL; C-peptide < 200 pmol/L; n=14) and high (CPH; C peptide ≥ 200 pmol/L; n=29). Plasma glucose, C-peptide, glucagon levels at 0, 30, 60, 120, and 180 min were measured. The glucagon response to the BMTT was defined by areas under the curve (AUC) as early (AUC0-30), late (AUC30-180), or total (AUC0-180) glucagon.

Results

Compared to healthy individuals, fasting plasma glucagon was lower and postprandial plasma glucagon level was increased in patients with T1D. Glucagon levels after BMTT between the CPL and CPH group showed significant group by time interaction. Peak glucagon and glucagon at 60-180 min, total and late glucagon response were higher in CPL than CPH group, while fasting glucagon and early glucagon response adjusted for glucose were comparable between CPL and CPH group. The higher late glucagon response and late glucagon response adjusted for glucose were associated with lower peak C-peptide in T1D. The higher late glucagon response and lower peak C-peptide were associated with the higher value of ▵glucose at 180 min.

Conclusion

Stimulated C-peptide levels affect the paradoxical increase in postprandial glucagon secretion in patients with T1D, especially late glucagon response. The exaggerated postprandial glucagon secretion further stimulates the elevation of postprandial glucose in patients with T1D.

A cross-sectional questionnaire study: Impaired awareness of hypoglycaemia remains prevalent in adults with type 1 diabetes and is associated with the risk of severe hypoglycaemia

OBJECTIVE

Impaired awareness of hypoglycaemia (IAH) is a risk factor for severe hypoglycaemia (SH) in type 1 diabetes (T1D). Much of the IAH prevalence data comes from older studies where participants did not have the benefit of the latest insulins and technologies. This study surveyed the prevalence of IAH and SH in a tertiary adult clinic population and investigated the associated factors.

METHODS

Adults (≥18 years) attending a tertiary T1D clinic completed a questionnaire, including a Gold and Clarke score. Background information was collected from health records.

RESULTS

189 people (56.1% female) with T1D (median [IQR] disease duration 19.3 [11.5, 29.1] years and age of 41.0 [29.0, 52.0] years) participated. 17.5% had IAH and 16.0% reported ≥1 episode of SH in the previous 12 months. Those with IAH were more likely to report SH (37.5% versus 11.7%, p = 0.001) a greater number of SH episodes per person (median [IQR] 0 [0,2] versus 0 [0,0] P<0.001) and be female (72.7% versus 52.6%, p = 0.036). Socio-economic deprivation was associated with IAH (p = 0.032) and SH (p = 0.005). Use of technology was the same between IAH vs aware groups, however, participants reporting SH were more likely to use multiple daily injections (p = 0.026). Higher detectable C-peptide concentrations were associated with a reduced risk of SH (p = 0.04).

CONCLUSION

Insulin pump and continuous glucose monitor use was comparable in IAH versus aware groups. Despite this, IAH remains a risk factor for SH and is prevalent in females and in older people. Socioeconomic deprivation was associated with IAH and SH, making this an important population to target for interventions.

Associations between time in range and insulin secretory capacity in Japanese patients with type 2 diabetes

Impaired insulin secretory capacity is associated with high glycemic variability in patients with type 2 diabetes (T2DM). However, there are no existing reports on the association between insulin secretory capacity and time in range (TIR). This retrospective study involved 330 T2DM admitted for diabetes education who underwent intermittently scanned continuous glucose monitoring (isCGM) and had their fasting serum C-peptide immunoreactivity (S-CPR) measured within 5 days of admission. The baseline characteristics were as follows: age, 60.2 years; glycated hemoglobin (HbA1c), 9.2%; S-CPR, 2.2 ng/mL; S-CPR index (S-CPR [ng/mL]/fasting plasma glucose [mg/dL] × 100), 1.6; and TIR, 60.3%. TIR correlated significantly with the S-CPR index, which was confirmed by multivariate analysis that included various factors such as HbA1c. Receiver operating characteristic (ROC) analysis showed that 1.88 was the optimal S-CPR index level to predict TIR ≥ 70%. In addition to HbA1c and biguanide use, the S-CPR index was a significant factor associated with TIR > 70%. S-CPR index values of ≥ 1.88 also correlated significantly with TIR > 70%. In conclusion, insulin secretory capacity is associated with TIR in Japanese T2DM, suggesting that the S-CPR index might be a potentially useful biomarker insulin secretory capacity, in association with TIR.Trial registration UMIN0000254333.

An in-silico modeling approach to separate exogenous and endogenous plasma insulin appearance, with application to inhaled insulin

The aim of this study was to develop a dynamic model-based approach to separately quantify the exogenous and endogenous contributions to total plasma insulin concentration and to apply it to assess the effects of inhaled-insulin administration on endogenous insulin secretion during a meal test. A three-step dynamic in-silico modeling approach was developed to estimate the two insulin contributions of total plasma insulin in a group of 21 healthy subjects who underwent two equivalent standardized meal tests on separate days, one of which preceded by inhalation of a Technosphere® Insulin dose (22U or 20U). In the 30-120 min test interval, the calculated endogenous insulin component showed a divergence in the time course between the test with and without inhaled insulin. Moreover, the supra-basal area-under-the-curve of endogenous insulin in the test with inhaled insulin was significantly lower than that in the test without (2.1 ± 1.7 × 104 pmol·min/L vs 4.2 ± 1.8 × 104 pmol·min/L, p < 0.01). The percentage of exogenous insulin reaching the plasma, relative to the inhaled dose, was 42 ± 21%. The proposed in-silico approach separates exogenous and endogenous insulin contributions to total plasma insulin, provides individual bioavailability estimates, and can be used to assess the effect of inhaled insulin on endogenous insulin secretion during a meal.

Preserved C-peptide is common and associated with higher time in range in Chinese type 1 diabetes

Objective

The aim of this study is to determine the residual C-peptide level and to explore the clinical significance of preserved C-peptide secretion in glycemic control in Chinese individuals with type 1 diabetes (T1D).

Research design and methods

A total of 534 participants with T1D were enrolled and divided into two groups, low-C-peptide group (fasting C-peptide ≤10 pmol/L) and preserved-C-peptide group (fasting C-peptide >10 pmol/L), and clinical factors were compared between the two groups. In 174 participants who were followed, factors associated with C-peptide loss were also identified by Cox regression. In addition, glucose metrics derived from intermittently scanned continuous glucose monitoring were compared between individuals with low C-peptide and those with preserved C-peptide in 178 participants.

Results

The lack of preserved C-peptide was associated with longer diabetes duration, glutamic acid decarboxylase autoantibody, and higher daily insulin doses, after adjustment {OR, 1.10 [interquartile range (IQR), 1.06-1.14]; OR, 0.46 (IQR, 0.27-0.77); OR, 1.04 (IQR, 1.02-1.06)}. In the longitudinal analysis, the percentages of individuals with preserved C-peptide were 71.4%, 56.8%, 71.7%, 62.5%, and 22.2% over 5 years of follow-up. Preserved C-peptide was also associated with higher time in range after adjustment of diabetes duration [62.4 (IQR, 47.3-76.6) vs. 50.3 (IQR, 36.2-63.0) %, adjusted P = 0.003].

Conclusions

Our results indicate that a high proportion of Chinese patients with T1D had preserved C-peptide secretion. Meanwhile, residual C-peptide was associated with favorable glycemic control, suggesting the importance of research on adjunctive therapy to maintain β-cell function in T1D.

Non-invasive imaging of functional pancreatic islet beta-cell mass in people with type 1 diabetes mellitus

AIMS

To investigate whether manganese-enhanced magnetic resonance imaging can assess functional pancreatic beta-cell mass in people with type 1 diabetes mellitus.

METHODS

In a prospective case-control study, 20 people with type 1 diabetes mellitus (10 with low (≥50 pmol/L) and 10 with very low (<50 pmol/L) C-peptide concentrations) and 15 healthy volunteers underwent manganese-enhanced magnetic resonance imaging of the pancreas following an oral glucose load. Scan-rescan reproducibility was performed in 10 participants.

RESULTS

Mean pancreatic manganese uptake was 31 ± 6 mL/100 g of tissue/min in healthy volunteers (median 32 [interquartile range 23-36] years, 6 women), falling to 23 ± 4 and 13 ± 5 mL/100 g of tissue/min (p ≤ 0.002 for both) in people with type1 diabetes mellitus (52 [44-61] years, 6 women) and low or very low plasma C-peptide concentrations respectively. Pancreatic manganese uptake correlated strongly with plasma C-peptide concentrations in people with type1 diabetes mellitus (r = 0.73, p < 0.001) but not in healthy volunteers (r = -0.054, p = 0.880). There were no statistically significant correlations between manganese uptake and age, body-mass index, or glycated haemoglobin. There was strong intra-observer (mean difference: 0.31 (limits of agreement -1.42 to 2.05) mL/100 g of tissue/min; intra-class correlation, ICC = 0.99), inter-observer (-1.23 (-5.74 to 3.27) mL/100 g of tissue/min; ICC = 0.85) and scan-rescan (-0.72 (-2.9 to 1.6) mL/100 g of tissue/min; ICC = 0.96) agreement for pancreatic manganese uptake.

CONCLUSIONS

Manganese-enhanced magnetic resonance imaging provides a potential reproducible non-invasive measure of functional beta-cell mass in people with type 1 diabetes mellitus. This holds major promise for investigating type 1 diabetes, monitoring disease progression and assessing novel immunomodulatory interventions.

Expert Recommendations for Using Time-in-Range and Other Continuous Glucose Monitoring Metrics to Achieve Patient-Centered Glycemic Control in People With Diabetes

New metrics for assessing glycemic control beyond HbA1c have recently emerged due to the increasing use of continuous glucose monitoring (CGM) in diabetes clinical practice. Among them, time in range (TIR) has appeared as a simple and intuitive metric that correlates inversely with HbA1c and has also been newly linked to the risk of long-term diabetes complications. The International Consensus on Time in Range established a series of target glucose ranges (TIR, time below range and time above range) and recommendations for time spent within these ranges for different diabetes populations. These parameters should be evaluated together with the ambulatory glucose profile (AGP). Using standardized visual reporting may help people with diabetes and healthcare professionals in the evaluation of glucose control in frequent clinical situations. The objective of the present review is to provide practical insights to quick interpretation of patient-centered metrics based on flash glucose monitoring data, as well as showing some visual examples of common clinical situations and giving practical recommendations for their management.

Islet cells in human type 1 diabetes: from recent advances to novel therapies - a symposium-based roadmap for future research

There is a growing understanding that the early phases of type 1 diabetes (T1D) are characterised by a deleterious dialogue between the pancreatic beta cells and the immune system. This, combined with the urgent need to better translate this growing knowledge into novel therapies, provided the background for the JDRF-DiabetesUK-INNODIA-nPOD symposium entitled 'Islet cells in human T1D: from recent advances to novel therapies', which took place in Stockholm, Sweden, in September 2022. We provide in this article an overview of the main themes addressed in the symposium, pointing to both promising conclusions and key unmet needs that remain to be addressed in order to achieve better approaches to prevent or reverse T1D.

Lessons and Gaps in the Prediction and Prevention of Type 1 Diabetes

Type 1 diabetes (T1D) is a serious chronic autoimmune condition. Even though the root cause of T1D development has yet to be determined, enough is known about the natural history of T1D pathogenesis to allow study of interventions that may delay or even prevent the onset of hyperglycemia and clinical T1D. Primary prevention aims to prevent the onset of beta cell autoimmunity in asymptomatic people at high genetic risk for T1D. Secondary prevention strategies aim to preserve functional beta cells once autoimmunity is present, and tertiary prevention aims to initiate and extend partial remission of beta cell destruction after the clinical onset of T1D. The approval of teplizumab in the United States to delay the onset of clinical T1D marks an impressive milestone in diabetes care. This treatment opens the door to a paradigm shift in T1D care. People with T1D risk need to be identified early by measuring T1D related islet autoantibodies. Identifying people with T1D before they have symptoms will facilitate better understanding of pre-symptomatic T1D progression and T1D prevention strategies that may be effective.

Importance of beta cell mass for glycaemic control in people with type 1 diabetes

AIMS/HYPOTHESIS

The role of beta cell mass in the balance of glucose control and hypoglycaemic burden in people with type 1 diabetes is unclear. We applied positron emission tomography (PET) imaging with radiolabelled exendin to compare beta cell mass among people with type 1 diabetes and either low glucose variability (LGV) or high glucose variability (HGV).

METHODS

All participants with either LGV (n=9) or HGV (n=7) underwent a mixed-meal tolerance test to determine beta cell function and wore a blinded continuous glucose monitor for a week. After an i.v. injection with [68Ga]Ga-NODAGA-exendin-4, PET images were acquired for the quantification of pancreatic uptake of radiolabelled exendin. The mean standardised uptake value (SUVmean) of the pancreas was used to determine the amount of beta cell mass.

RESULTS

Participants with LGV had lower HbA1c (46.0 mmol/mol [44.5-52.5] [6.4% (6.3-7)] vs 80 mmol/mol [69.0-110] [9.5% (8.5-12.2)], p=0.001) and higher time in range (TIR) (75.6% [73.5-90.3] vs 38.7% [25.1-48.5], p=0.002) than those with HGV. The SUVmean of the pancreas was higher for the LGV than for the HGV group (5.1 [3.6-5.6] vs 2.9 [2.1-3.4], p=0.008). The AUCC-peptide:AUCglucose ratio was numerically, but not statistically, higher in the LGV compared with the HGV group (2.7×10-2 [6.2×10-4-5.3×10-2] vs 9.3×10-4 [4.7×10-4-5.2×10-3], p=0.21). SUVmean correlated with the AUCC-peptide:AUCglucose ratio (Pearson r=0.64, p=0.01), as well as with the TIR (r=0.64, p=0.01) and the SD of interstitial glucose levels (r=-0.66, p=0.007).

CONCLUSION/INTERPRETATION

Our data show higher beta cell mass in people with type 1 diabetes and LGV than in those with HGV, independent of beta cell function.

Study protocol: a randomised controlled proof-of-concept real-world study - does maximising time in range using hybrid closed loop insulin delivery and a low carbohydrate diet restore the glucagon response to hypoglycaemia in adults with type 1 diabetes?

INTRODUCTION

People with type 1 diabetes (T1D) develop an impaired glucagon response to hypoglycaemia within 5 years of diagnosis, increasing their risk of severe hypoglycaemia. It is not known whether eliminating hypoglycaemia and hyperglycaemia allows recovery of this glucagon response. Hybrid closed loop (HCL) technologies improve glycaemic time in range (TIR). However, post-prandial glycaemic excursions are still evident. Consuming a low carbohydrate diet (LCD) may minimise these excursions.

METHODS AND ANALYSIS

This feasibility study will assess if maximising TIR (glucose ≥3.9 mmol/L≤10 mmol/L) using HCL systems plus an LCD (defined here as <130 g carbohydrate/day) for >8 months, restores the glucagon response to insulin-induced hypoglycaemia. Adults (n=24) with T1D (C-peptide <200 pmol/L), naïve to continuous glucose monitoring (CGM) and HCL systems, will be recruited and randomised to: group 1 (non-HCL) to continue their standard diabetes care with intermittent blinded CGM; or group 2 (HCL-LCD) to use the HCL system and follow a LCD. Baseline data on diet and glycaemia will be collected from all participants. The HCL-LCD group will then enter a 2-week run-in to acclimatise to their devices. Throughout, the HCL-LCD group will have their glucose closely monitored and adjusted aiming for glycaemic TIR >70%. Participants will have their glucagon response to hypoglycaemia measured at the beginning and 8 months later at the study end using a stepped hyperinsulinaemic hypoglycaemic clamp, in combination with the stable isotopes 6,6-²H₂-glucose (D2-glucose) and 1,1,2,3,3-²H₅-glycerol (D5-glycerol) to assess glucose and glycerol kinetics. The impact of hypoglycaemia on symptoms and cognitive function will be assessed during each clamp study. The primary outcome is the difference in the glucagon response to hypoglycaemia between and within groups at baseline versus study end.

ETHICS AND DISSEMINATION

Ethical (20/SS/0117)/institutional review board (2021/0001) approval has been obtained. The study will be disseminated by peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

NCT04614168.

Preserved C-peptide secretion is associated with higher time in range (TIR) on intermittently scanned continuous glucose monitoring in Chinese adults with type 1 diabetes

Objective

To explore the relationship between C-peptide secretion and time in range (TIR) in adult patients with type 1 diabetes.

Methods

From December 2018 to December 2020, 76 type 1 diabetes participants were enrolled from the Department of Endocrinology and Metabolism of Peking University People's Hospital. All participants wore intermittently scanned continuous glucose monitoring (isCGM), and insulin dosage was adjusted according to standardized clinical procedures. Subjects were divided into low C-peptide group (<10 pmol/L) and preserved C-peptide group (10-200 pmol/L) based on fasting serum C-peptide levels. Differences of TIR, metrics related to glucose variability and hypoglycemic events were compared.

Results

A total of 94,846 isCGM values obtained from 39 male and 37 female participants were analyzed. Individuals with preserved C-peptide secretion had shorter diabetes duration (2.0 (0.5, 10.0) vs 10.0 (3.0, 18.3) years, P = 0.002). TIR was higher in the individuals with preserved C-peptide than those with decreased C-peptide (67.1% (54.2, 75.8) vs 45.5% (33.9, 56.1), P < 0.001), and time above range was significantly lower in those with preserved C-peptide (28.0% (15.6, 42.4) vs 49.4% (39.1, 64.2), P < 0.001). Preserved C-peptide was associated with lower glucose variability, as defined by s.d. (3.0 mmol/L (2.6, 3.4) vs 3.8 mmol/L (3.2, 4.3), P < 0.001) and interquartile range (4.3 mmol/L (3.1, 4.8) vs 5.3 mmol/L (4.5, 6.3), P < 0.001). Metrics related to hypoglycemia were not different between the two groups.

Conclusion

Preserved C-peptide secretion was associated with higher TIR and lower glucose variability in Chinese type 1 diabetes adults.

Precision medicine in type 1 diabetes

First envisioned by early diabetes clinicians, a person-centred approach to care was an aspirational goal that aimed to match insulin therapy to each individual's unique requirements. In the 100 years since the discovery of insulin, this goal has evolved to include personalised approaches to type 1 diabetes diagnosis, treatment, prevention and prediction. These advances have been facilitated by the recognition of type 1 diabetes as an autoimmune disease and by advances in our understanding of diabetes pathophysiology, genetics and natural history, which have occurred in parallel with advancements in insulin delivery, glucose monitoring and tools for self-management. In this review, we discuss how these personalised approaches have improved diabetes care and how improved understanding of pathogenesis and human biology might inform precision medicine in the future.

C-peptide determination in the diagnosis of type of diabetes and its management: A clinical perspective

Impaired beta-cell function is a recognized cornerstone of diabetes pathophysiology. Estimates of insulin secretory capacity are useful to inform clinical practice, helping to classify types of diabetes, complication risk stratification and to guide treatment decisions. Because C-peptide secretion mirrors beta-cell function, it has emerged as a valuable clinical biomarker, mainly in autoimmune diabetes and especially in adult-onset diabetes. Nonetheless, the lack of robust evidence about the clinical utility of C-peptide measurement in type 2 diabetes, where insulin resistance is a major confounder, limits its use in such cases. Furthermore, problems remain in the standardization of the assay for C-peptide, raising concerns about comparability of measurements between different laboratories. To approach the heterogeneity and complexity of diabetes, reliable, simple and inexpensive clinical markers are required that can inform clinicians about probable pathophysiology and disease progression, and so enable personalization of management and therapy. This review summarizes the current evidence base about the potential value of C-peptide in the management of the two most prevalent forms of diabetes (type 2 diabetes and autoimmune diabetes) to address how its measurement may assist daily clinical practice and to highlight current limitations and areas of uncertainties to be covered by future research.

Analysis of detrended fluctuation function derived from continuous glucose monitoring may assist in distinguishing latent autoimmune diabetes in adults from T2DM

BACKGROUND

We aimed to explore the performance of detrended fluctuation function (DFF) in distinguishing patients with latent autoimmune diabetes in adults (LADA) from type 2 diabetes mellitus (T2DM) with glucose data derived from continuous glucose monitoring.

METHODS

In total, 71 LADA and 152 T2DM patients were enrolled. Correlations between glucose parameters including time in range (TIR), mean glucose, standard deviation (SD), mean amplitude of glucose excursions (MAGE), coefficient of variation (CV), DFF and fasting and 2-hour postprandial C-peptide (FCP, 2hCP) were analyzed and compared. Receiver operating characteristics curve (ROC) analysis and 10-fold cross-validation were employed to explore and validate the performance of DFF in diabetes classification respectively.

RESULTS

Patients with LADA had a higher mean glucose, lower TIR, greater SD, MAGE and CV than those of T2DM (P<0.001). DFF achieved the strongest correlation with FCP (r = -0.705, P<0.001) as compared with TIR (r = 0.485, P<0.001), mean glucose (r = -0.337, P<0.001), SD (r = -0.645, P<0.001), MAGE (r = -0.663, P<0.001) and CV (r = -0.639, P<0.001). ROC analysis showed that DFF yielded the greatest area under the curve (AUC) of 0.862 (sensitivity: 71.2%, specificity: 84.9%) in differentiating LADA from T2DM as compared with TIR, mean glucose, SD, MAGE and CV (AUC: 0.722, 0.650, 0.800, 0.820 and 0.807, sensitivity: 71.8%, 47.9%, 63.6%, 72.7% and 78.8%, specificity: 67.8%, 83.6%, 80.9%, 80.3% and 72.4%, respectively). The kappa test indicated a good consistency between DFF and the actual diagnosis (kappa = 0.551, P<0.001). Ten-fold cross-validation showed a stable performance of DFF with a mean AUC of 0.863 (sensitivity: 78.8%, specificity: 77.8%) in 10 training sets and a mean AUC of 0.866 (sensitivity: 80.9%, specificity: 84.1%) in 10 test sets.

CONCLUSIONS

A more violent glucose fluctuation pattern was marked in patients with LADA than T2DM. We first proposed the possible role of DFF in distinguishing patients with LADA from T2DM in our study population, which may assist in diabetes classification.

Factors associated with high glucose variability in patients with type 1 diabetes

BACKGROUND: High glucose variability (GV) is recognized as a risk factor for vascular diabetic complications and hypoglycemia. Factors affecting GV in patients with diabetes needed to be clarified.

AIM: To determine the factors associated with high GV in adult patients with type 1 diabetes.

MATERIALS AND METHODS: We conducted a single center cross-sectional observational study. In-patients with type 1 diabetes aged 18 to 65 years on basal bolus insulin therapy were included. Day-time and nocturnal Coefficient of Variation (CV), Mean Amplitude of Glycemic Excursions (MAGE), Mean Absolute Glucose (MAG) were calculated from continuous glucose monitoring data. The values of CV, MAGE, MAG within the upper quartile were considered high.

RESULTS: The study included 400 individuals, including 111 on continuous subcutaneous insulin infusion (CSII). Patients with high GV had lower fasting and postprandial C-peptide levels and higher insulin doses. According to ROC analysis, daily insulin dose >0.69 U/kg and estimated glomerular filtration rate (eGFR) ≥90.5 ml/min×1.73 m2 were associated with high nocturnal CV values. Dose of basal insulin >0.292 U/kg and bolus insulin >0.325 U/day were associated with nocturnal MAGE. Body mass index (BMI) ≤23.2 kg/m2, waist circumference ≤80.5 cm, daily insulin dose ≥0.69 U/kg, HbA1c ≥8.3%, eGFR ≥89.5 ml/ min×1.73m2 increased risk of high MAG at night. High day-time CV values were associated with daily insulin dose ≥0.675 U/kg and daily dose of BI ≥0.286 U/kg. The risk of high MAGE was increased with HbA1c ≥8.24% and basal insulin dose ≥0.286 U/kg. BMI ≤23.2 kg/m2, waist circumference ≤80.5 cm, daily insulin dose ≥0.69 U/kg, daily dose of bolus and basal insulin ≥0.325 and ≥0.29 U/kg respectively, and HbA1c ≥8.33% were the risk factors for high day-time MAG. Patients on CSII had lower MAGE (p<0.001) and MAG (p=0.008) compared to those on multiple daily injections.

CONCLUSION: In type 1 diabetes, high GV is associated with undetectable residual insulin secretion, normal or reduced body weight, preserved kidney function, supraphysiological doses of insulin, and non-target HbA1c. Patients on CSII have a lower GV than those on multiple daily injections. 

Continuous glucose monitoring to assess glucose variability in type 3c diabetes

AIM

The effectiveness of continuous glucose monitoring (CGM) in maintaining glycaemic control in type 1 diabetes mellitus and type 2 diabetes mellitus has been well demonstrated. However, the degree of glycaemic variability (GV) in people with type 3c diabetes mellitus has not been fully explored using CGM. This study aims to evaluate GV in type 3c diabetes mellitus participants and compare it to type 1 diabetes mellitus and type 2 diabetes mellitus.

METHODS

Participants were grouped according to type of diabetes. GV, defined as percentage coefficient of variation (%CV), and other glycaemic indices were obtained using CGM (FreeStyle Libre, Abbott, Australia) from 82 participants across all three cohorts over a 14-day period. Comparison of baseline characteristics and GV were performed across all groups. Correlation of GV with C-peptide values, and whether pancreatic supplementation had an effect on GV were also assessed in the type 3c diabetes mellitus cohort.

RESULTS

GV of type 3c diabetes mellitus participants was within the recommended target of less than %CV 36% (p = 0.004). Type 3c diabetes mellitus participants had the lowest GV among the three groups (p = 0.001). There was a trend for lower C-peptide levels to be associated with higher GV in type 3c diabetes mellitus participants (p = 0.22). Pancreatic enzyme supplementation in type 3c diabetes mellitus participants did not have an effect on GV (p = 0.664).

CONCLUSIONS

Although type 3c diabetes mellitus participants were the least variable, they had the highest mean glucose levels and estimated HbA_1c , which suggests that the concept of 'brittle' diabetes in type 3c diabetes mellitus is not supported by the results of CGM in this study and may be leading to poorer glycaemic control.

Capturing the real-world benefit of residual β-cell function during clinically important time-periods in established Type 1 diabetes

AIMS

Many individuals with type 1 diabetes retain residual β-cell function, with increased endogenous insulin secretion associated with reduced hyperglycaemia, hypoglycaemia and glycaemic variability. However, it is unknown when these improvements occur during the day. Dysglycaemia is common in overnight and postprandial periods and associated with diabetes complications. Therefore, this study aimed to determine the influence of residual β-cell function upon nocturnal and postprandial glycaemic control in established type 1 diabetes.

METHODS

Under free-living conditions, 66 participants wore a blinded continuous glucose monitor (CGM), kept a food diary, and completed a stimulated urine C-peptide creatinine (UCPCR) test. Nocturnal, and postprandial CGM outcomes (participant means and discrete event analysis) were compared between UCPCR groups: undetectable (Cpep_und ), low (Cpep_low : 0.001-0.19 nmol/mmol) and high (Cpep_high : ≥0.2 nmol/mmol).

RESULTS

Greater β-cell function was associated with incremental improvements in glycaemia. Cpep_high spent significantly greater time in normoglycaemia than Cpep_und overnight (76 ± 20% vs. 58 ± 20%, p = 0.005) and 0-300 mins postprandially (68 ± 22% vs. 51 ± 22%, p = 0.045), while also having reducing nocturnal variability (SD 1.12 ± 0.41 vs. 1.52 ± 0.43 mmol/L, p = 0.010). Analysis of individual events, controlling for diabetes duration, BMI, basal insulin, use of a continuous or flash glucose monitor and (for postprandial) meal type, carbohydrate and bolus insulin intake, replicated the group findings, additionally demonstrating Cpep_und had increased hyperglycaemia versus Cpep_low overnight and increased postprandial hypoglycaemic events compared with Cpep_high . For all participants, breakfast had a significantly higher incremental area under the curve than lunch and dinner.

CONCLUSIONS

Residual β-cell function is associated with improved nocturnal and postprandial glycaemic control. These data may be of clinical importance for identifying specific periods and individuals where further glycaemic management strategies would be beneficial.

Impact of flash glucose monitoring on glycemic control varies with the age and residual β-cell function of patients with type 1 diabetes mellitus

AIMS/INTRODUCTION

We aimed to explore the clinical factors associated with glycemic variability (GV) assessed with flash glucose monitoring (FGM), and investigate the impact of FGM on glycemic control among Chinese type 1 diabetes mellitus patients in a real-life clinical setting.

MATERIALS AND METHODS

A total of 171 patients were included. GV was assessed from FGM data. A total of 110 patients wore FGM continuously for 6 months (longitudinal cohort). Hemoglobin A1c (HbA1c), fasting and 2-h postprandial C-peptide, and glucose profiles were collected. Changes in HbA1c and glycemic parameters were assessed during a 6-month FGM period.

RESULTS

Individuals with high residual C-peptide (HRCP; 2-h postprandial C-peptide >200 pmol/L) had less GV than patients with low residual C-peptide ( 2-h postprandial C-peptide ≤200 pmol/L; P < 0.001). In the longitudinal cohort (n = 110), HbA1c and mean glucose decreased, time in range (TIR) increased during the follow-up period (P < 0.05). The 110 patients were further divided into age and residual C-peptide subgroups: (i) HbA1c and mean glucose were reduced significantly only in the subgroup aged ≤14 years during the follow-up period, whereas time below range also increased in this subgroup at 3 months (P = 0.047); and (ii) HbA1c improved in the HRCP subgroup at 3 and 6 months (P < 0.05). The mean glucose decreased and TIR improved significantly in the low residual C-peptide subgroup; however, TIR was still lower and time below range was higher than those of the HRCP subgroup at all time points (P < 0.05).

CONCLUSIONS

HRCP was associated with less GV. FGM wearing significantly reduced HbA1c, especially in pediatric patients and those with HRCP. Additionally, the mean glucose and TIR were also found to improve.

Type 1 Diabetes Patients With Different Residual Beta-Cell Function but Similar Age, HBA1c, and Cardiorespiratory Fitness Have Differing Exercise-Induced Angiogenic Cell Mobilisation

BACKGROUND

Many individuals with type 1 diabetes retain residual beta-cell function. Sustained endogenous insulin and C-peptide secretion is associated with reduced diabetes related complications, but underlying mechanisms remain unclear. Lower circulating numbers of endothelial and hematopoietic progenitor cells (EPCs and HPCs), and the inability to increase the count of these cells in response to exercise, are also associated with increased diabetes complications and cardiovascular disease. It is unknown whether residual beta-cell function influences HPCs and EPCs. Thus, this study examined the influence of residual beta-cell function in type 1 diabetes upon exercise-induced changes in haematopoietic (HPCs) and endothelial progenitor cells (EPCs).

METHODS

Participants with undetectable stimulated C-peptide (n=11; Cpep_und), 10 high C-peptide (Cpep_high; >200 pmol/L), and 11 non-diabetes controls took part in this observational exercise study, completing 45 minutes of intensive walking at 60% V˙O2peak . Clinically significant HPCs (CD34⁺) and EPCs (CD34⁺VEGFR2⁺) phenotypes for predicting future adverse cardiovascular outcomes, and subsequent cell surface expression of chemokine receptor 4 (CXCR4) and 7 (CXCR7), were enumerated at rest and immediately post-exercise by flow cytometry.

RESULTS

Exercise increased HPCs and EPCs phenotypes similarly in the Cpep_high and control groups (+34-121% across phenotypes, p<0.04); but Cpep_und group did not significantly increase from rest, even after controlling for diabetes duration. Strikingly, the post-exercise Cpep_und counts were still lower than Cpep_high at rest.

CONCLUSIONS

Residual beta-cell function is associated with an intact exercise-induced HPCs and EPCs mobilisation. As key characteristics (age, fitness, HbA1c) were similar between groups, the mechanisms underpinning the absent mobilisation within those with negative C-peptide, and the vascular implications, require further investigation.

Residual C-peptide secretion and hypoglycemia awareness in people with type 1 diabetes

INTRODUCTION

This study aimed to assess the association between fasting serum C-peptide levels and the presence of impaired awareness of hypoglycemia (IAH) in people with type 1 diabetes.

RESEARCH DESIGN AND METHODS

We performed a cross-sectional study among 509 individuals with type 1 diabetes (diabetes duration 5-65 years). Extensive clinical data and fasting serum C-peptide concentrations were collected and related to the presence or absence of IAH, which was evaluated using the validated Dutch version of the Clarke questionnaire. A multivariable logistic regression model was constructed to investigate the association of C-peptide and other clinical variables with IAH.

RESULTS

In 129 (25%) individuals, residual C-peptide secretion was detected, while 75 (15%) individuals reported IAH. The median (IQR) C-peptide concentration among all participants was 0.0 (0.0-3.9) pmol/L. The prevalence of severe hypoglycemia was lower in people with demonstrable C-peptide versus those with absent C-peptide (30% vs 41%, p=0.025). Individuals with IAH were older, had longer diabetes duration, more frequently had macrovascular and microvascular complications, and more often used antihypertensive drugs, antiplatelet agents and cholesterol-lowering medication. There was a strong association between IAH and having a severe hypoglycemia in the preceding year. In multivariable regression analysis, residual C-peptide, either continuously or dichotomous, was associated with lower prevalence of IAH (p=0.040-0.042), while age at diabetes onset (p=0.001), presence of microvascular complications (p=0.003) and body mass index (BMI) (p=0.003) were also independently associated with the presence of IAH.

CONCLUSIONS

Higher BMI, the presence of microvascular complications and higher age at diabetes onset were independent risk factors for IAH in people with type 1 diabetes, while residual C-peptide secretion was associated with lower risk of this complication.

β-Cell failure in diabetes: Common susceptibility and mechanisms shared between type 1 and type 2 diabetes

Diabetes mellitus is etiologically classified into type 1, type 2 and other types of diabetes. Despite distinct etiologies and pathogenesis of these subtypes, many studies have suggested the presence of shared susceptibilities and underlying mechanisms in β-cell failure among different types of diabetes. Understanding these susceptibilities and mechanisms can help in the development of therapeutic strategies regardless of the diabetes subtype. In this review, we discuss recent evidence indicating the shared genetic susceptibilities and common molecular mechanisms between type 1, type 2 and other types of diabetes, and highlight the future prospects as well.

Glucagon as a Therapeutic Approach to Severe Hypoglycemia: After 100 Years, Is It Still the Antidote of Insulin?

Hypoglycemia represents a dark and tormented side of diabetes mellitus therapy. Patients treated with insulin or drug inducing hypoglycemia, consider hypoglycemia as a harmful element, which leads to their resistance and lack of acceptance of the pathology and relative therapies. Severe hypoglycemia, in itself, is a risk for patients and relatives. The possibility to have novel strategies and scientific knowledge concerning hypoglycemia could represent an enormous benefit. Novel available glucagon formulations, even now, allow clinicians to deal with hypoglycemia differently with respect to past years. Novel scientific evidence leads to advances concerning physiopathological mechanisms that regulated glycemic homeostasis. In this review, we will try to show some of the important aspects of this field.

Glucose Variability: How Does It Work?

A growing body of evidence points to the role of glucose variability (GV) in the development of the microvascular and macrovascular complications of diabetes. In this review, we summarize data on GV-induced biochemical, cellular and molecular events involved in the pathogenesis of diabetic complications. Current data indicate that the deteriorating effect of GV on target organs can be realized through oxidative stress, glycation, chronic low-grade inflammation, endothelial dysfunction, platelet activation, impaired angiogenesis and renal fibrosis. The effects of GV on oxidative stress, inflammation, endothelial dysfunction and hypercoagulability could be aggravated by hypoglycemia, associated with high GV. Oscillating hyperglycemia contributes to beta cell dysfunction, which leads to a further increase in GV and completes the vicious circle. In cells, the GV-induced cytotoxic effect includes mitochondrial dysfunction, endoplasmic reticulum stress and disturbances in autophagic flux, which are accompanied by reduced viability, activation of apoptosis and abnormalities in cell proliferation. These effects are realized through the up- and down-regulation of a large number of genes and the activity of signaling pathways such as PI3K/Akt, NF-κB, MAPK (ERK), JNK and TGF-β/Smad. Epigenetic modifications mediate the postponed effects of glucose fluctuations. The multiple deteriorative effects of GV provide further support for considering it as a therapeutic target in diabetes.

Measurement of Peak C-Peptide at Diagnosis Informs Glycemic Control but not Hypoglycemia in Adults With Type 1 Diabetes

Context

High-residual C-peptide in longer-duration type 1 diabetes (T1D) is associated with fewer hypoglycemic events and reduced glycemic variability. Little is known about the impact of C-peptide close to diagnosis.

Objective

Using continuous glucose monitoring (CGM) data from a study of newly diagnosed adults with T1D, we aimed to explore if variation in C-peptide close to diagnosis influenced glycemic variability and risk of hypoglycemia.

Methods

We studied newly diagnosed adults with T1D who wore a Dexcom G4 CGM for 7 days as part of the Exercise in Type 1 Diabetes (EXTOD) study. We examined the relationship between peak stimulated C-peptide and glycemic metrics of variability and hypoglycemia for 36 CGM traces from 23 participants.

Results

For every 100 pmol/L-increase in peak C-peptide, the percentage of time spent in the range 3.9 to 10 mmol/L increased by 2.4% (95% CI, 0.5-4.3), P = .01) with a reduction in time spent at level 1 hyperglycemia (> 10 mmol/L) and level 2 hyperglycemia (> 13.9 mmol/L) by 2.6% (95% CI, –4.9 to –0.4, P = .02) and 1.3% (95% CI, –2.7 to –0.006, P = .04), respectively. Glucose levels were on average lower by 0.19 mmol/L (95% CI, –0.4 to 0.02, P = .06) and SD reduced by 0.14 (95% CI, –0.3 to –0.02, P = .02). Hypoglycemia was not common in this group and no association was observed between time spent in hypoglycemia (P = .97) or hypoglycemic risk (P = .72). There was no association between peak C-peptide and insulin dose–adjusted glycated hemoglobin A_1c (P = .45).

Conclusion

C-peptide is associated with time spent in the normal glucose range and with less hyperglycemia, but not risk of hypoglycemia in newly diagnosed people with T1D.

Impact of routine clinic measurement of serum C-peptide in people with a clinician-diagnosis of type 1 diabetes

AIMS/HYPOTHESIS

The aim of this study was to determine the impact of the routine use of serum C-peptide in an out-patient clinic setting on individuals with a clinician-diagnosis of type 1 diabetes.

METHODS

In this single-centre study, individuals with type 1 diabetes of at least 3 years duration were offered random serum C-peptide testing at routine clinic review. A C-peptide ≥200 pmol/L prompted further evaluation of the individual using a diagnostic algorithm that included measurement of islet cell antibodies and genetic testing. Where appropriate, a trial of anti-diabetic co-therapies was considered.

RESULTS

Serum C-peptide testing was performed in 859 individuals (90% of the eligible cohort), of whom 114 (13.2%) had C-peptide ≥200 pmol/L. The cause of diabetes was reclassified in 58 individuals (6.8% of the tested cohort). The majority of reclassifications were to type 2 diabetes (44 individuals; 5.1%), with a smaller proportion of monogenic diabetes (14 individuals; 1.6%). Overall, 13 individuals (1.5%) successfully discontinued insulin, while a further 16 individuals (1.9%) had improved glycaemic control following the addition of co-therapies. The estimated total cost of the testing programme was £23,262 (~€26,053), that is, £27 (~€30) per individual tested. In current terms, the cost of prior insulin therapy in the individuals with monogenic diabetes who successfully stopped insulin was approximately £57,000 (~€64,000).

CONCLUSIONS/INTERPRETATION

Serum C-peptide testing can easily be incorporated into an out-patient clinic setting and could be a cost-effective intervention. C-peptide testing should be strongly considered in individuals with a clinician-diagnosis of type 1 diabetes of at least 3 years duration.

C-peptide enhances glucagon secretion in response to hyperinsulinemia under euglycemic and hypoglycemic conditions

Several studies have associated the presence of residual insulin secretion capability (also referred to as being C-peptide positive) with lower risk of insulin-induced hypoglycemia in patients with type 1 diabetes (T1D), although the reason is unclear. We tested the hypothesis that C-peptide infusion would enhance glucagon secretion in response to hyperinsulinemia during euglycemic and hypoglycemic conditions in dogs (5 male/4 female). After a 2-hour basal period, an intravenous (IV) infusion of insulin was started, and dextrose was infused to maintain euglycemia for 2 hours. At the same time, an IV infusion of either saline (SAL) or C-peptide (CPEP) was started. After this euglycemic period, the insulin and SAL/CPEP infusions were continued for another 2 hours, but the glucose was allowed to fall to approximately 50 mg/dL. In response to euglycemic-hyperinsulinemia, glucagon secretion decreased in SAL but remained unchanged from the basal period in CPEP condition. During hypoglycemia, glucagon secretion in CPEP was 2 times higher than SAL, and this increased net hepatic glucose output and reduced the amount of exogenous glucose required to maintain glycemia. These data suggest that the presence of C-peptide during IV insulin infusion can preserve glucagon secretion during euglycemia and enhance it during hypoglycemia, which could explain why T1D patients with residual insulin secretion are less susceptible to hypoglycemia.

A Bittersweet Response to Infection in Diabetes; Targeting Neutrophils to Modify Inflammation and Improve Host Immunity

Chronic and recurrent infections occur commonly in both type 1 and type 2 diabetes (T1D, T2D) and increase patient morbidity and mortality. Neutrophils are professional phagocytes of the innate immune system that are critical in pathogen handling. Neutrophil responses to infection are dysregulated in diabetes, predominantly mediated by persistent hyperglycaemia; the chief biochemical abnormality in T1D and T2D. Therapeutically enhancing host immunity in diabetes to improve infection resolution is an expanding area of research. Individuals with diabetes are also at an increased risk of severe coronavirus disease 2019 (COVID-19), highlighting the need for re-invigorated and urgent focus on this field. The aim of this review is to explore the breadth of previous literature investigating neutrophil function in both T1D and T2D, in order to understand the complex neutrophil phenotype present in this disease and also to focus on the development of new therapies to improve aberrant neutrophil function in diabetes. Existing literature illustrates a dual neutrophil dysfunction in diabetes. Key pathogen handling mechanisms of neutrophil recruitment, chemotaxis, phagocytosis and intracellular reactive oxygen species (ROS) production are decreased in diabetes, weakening the immune response to infection. However, pro-inflammatory neutrophil pathways, mainly neutrophil extracellular trap (NET) formation, extracellular ROS generation and pro-inflammatory cytokine generation, are significantly upregulated, causing damage to the host and perpetuating inflammation. Reducing these proinflammatory outputs therapeutically is emerging as a credible strategy to improve infection resolution in diabetes, and also more recently COVID-19. Future research needs to drive forward the exploration of novel treatments to improve infection resolution in T1D and T2D to improve patient morbidity and mortality.

Combination of vitamin D and dipeptidyl peptidase-4 inhibitors (VIDPP-4i) as an immunomodulation therapy for autoimmune diabetes

Type 1 diabetes (T1D) and latent autoimmune diabetes in adults (LADA) represent the most common types of autoimmune diabetes and are characterized by different age of onset, degrees of immune-mediated destruction of pancreatic beta cells and rates of disease progression towards insulin dependence. Several immunotherapies aimed to counteract autoimmune responses against beta cells and preserve beta-cell function are currently being investigated, particularly in T1D. Preliminary findings suggest a potential role of combination therapy with vitamin D and dipeptidyl peptidase-4 (DPP-4) inhibitors (VIDPP-4i) in preserving beta-cell function in autoimmune diabetes. This manuscript aims to provide a comprehensive overview of the immunomodulatory properties of vitamin D and DPP-4 inhibitors, as well as the rationale for investigation of their combined use as an immunomodulation therapy for autoimmune diabetes.

Time in Range as a Research Outcome Measure

Time in range (TIR) is gaining ground as an outcome measure in type 1 diabetes trials. However, inclusion of TIR raises several issues for trial design. In this article, the authors begin by defining TIR and describing the current international consensus around TIR targets. They then expand on evidence for the validity of TIR as a primary clinical trial outcome before concluding with some practical, ethical, and logistical implications.

Log-linear relationship between endogenous insulin secretion and glycemic variability in patients with type 2 diabetes on continuous glucose monitoring

The contribution of endogenous insulin secretion to glycemic variability (GV) may differ between patients with impaired insulin secretion and those with preserved secretion. Our objective was to determine the linearity of the relationship between fasting C-peptide (CPR) as a marker of endogenous insulin secretion and GV in type 2 diabetes (T2DM), regardless of the type of antidiabetic treatment. We conducted a prospective observational study using continuous glucose monitoring obtained from 284 Japanese outpatients with T2DM with various HbA1c values and antidiabetic treatment. We constructed a prediction curve of base-line CPR versus coefficient of variation (CV) and identified the clinical factors associated with CV using multiple regression analysis. Fasting CPR showed a significant negative log-linear relationship with CV (P < 0.0001), and the latter being strikingly high in the low-CPR group. The multiple regression analysis showed that low CPR was an independent predictor of high CV (P < 0.0001). The significant correlations were sustained in both patients with/without insulin treatment. The contribution of endogenous insulin secretion to GV depends on the extent of insulin secretion impairment. Fasting CPR may represent a useful indicator of GV instability in T2DM.

1921-2021: From insulin discovery to islet transplantation in type 1 diabetes

One century after the discovery of insulin, the French Health regulations have just authorized the reimbursement for islet transplantation. Intraportal islet allotransplantation from a pancreatic donor is indicated in patients with type 1 diabetes (T1D) complicated with lability or hypoglycemia unawareness, or in case of a functioning kidney graft; islet auto-transplantation may be indicated after pancreatic surgery.Compared with insulin even administered in closed-loop pumps, the specificity of islet allotransplantation is the restoration of C-peptide secretion. Long-term insulin-independence is observed when the engrafted islet mass is sufficient, at the cost of immunosuppression. Fewer low-glucose events and less glucose variability, are observed even with minimal functional islet graft, after islet transplantation as at onset of T1D, when a residual C-peptide secretion is maintained, an objective currently approached with less aggressive immuno-modulating therapies than in the past. Therefore, restoration or preservation of endogen insulin secretion is an important goal, allowing to maintain a long-term glucose balance with more than 70% of time in range 3.9-10mmol/L and less than 3% of time <3.9mmol/L, thus reducing the occurrence of diabetic complications. In the clinical setting, - the preservation of C-peptide at early stage of T1D, - the use of technological ressources (multi-injections, sensors, insulin pump, closed-loop systems) at later stages, - and islet transplantation when hypoglycemia awareness becomes impaired are complementary for a personalized care all along the life of T1D patients.

Residual β-cell function after 10 years of autoimmune type 1 diabetes: prevalence, possible determinants, and implications for metabolism

Background

Type 1 diabetes (T1D) has long been considered a progressive autoimmune disease resulting in the failure of pancreatic β-cell function and absolute endogenous insulin deficiency. However, several studies have demonstrated patients with T1D have detectable C-peptide levels long after diagnosis, which has remarkable clinical significance. Since this issue has not been systematically explored in non-Caucasian populations, we aimed to identify the prevalence of residual β-cell function and its related clinical features in Chinese long-term T1D patients.

Methods

We enrolled 109 patients with T1D for ≥10 years and administered a mixed-meal tolerance test (MMTT). Fasting and postprandial C-peptide (FCP/PCP) levels were measured to evaluate the insulin secretion function of β-cells. Patients whose FCP and PCP levels were both below the lower detection limit (16.7 pmol/L) were grouped as ‘β-cell function depleted’, while others were thought to have ‘residual β-cell function’. Demographic data, metabolic status, and diabetic complications were compared between patients with or without residual β-cell function.

Results

38.5% of subjects retained residual β-cell function, and among those, 33.3% responded to MMTT by a two-fold or greater rise of their FCP levels. Clinical features associated with residual β-cell function were older age of diagnosis [27.5 (interquartile range:11.5–37.0) vs. 17.0 (interquartile range: 8.0–30.0) years, P=0.037], lower HbA1c (64.6±20.3 vs. 72.4±18.5 mmol/mol, P=0.026), and reduced rate of hypoglycemia (23.8% vs. 52.2%, P=0.003). Age of diagnosis was positively correlated with detectable FCP level (r=0.393, P=0.020). Individuals diagnosed after 30 years of age tended to retain residual β-cell function (OR =3.016, P=0.044). We found no association between residual β-cell function and chronic diabetic complications.

Conclusions

Residual β-cell function can be found in nearly 40% of long-term patients with T1D in China and is associated with older age at diagnosis and better glucose control. The relationship between residual β-cell function and chronic diabetic complications remains to be explored.

Socioeconomic deprivation, technology use, C-peptide, smoking and other predictors of glycaemic control in adults with type 1 diabetes

AIMS

Intensive glycaemic control is associated with substantial health benefits in people with type 1 diabetes. We sought to examine clinical and demographic factors associated with meeting glycaemic targets in type 1 diabetes.

METHODS

We conducted a cross-sectional analysis of 4594 individuals with type 1 diabetes. The primary outcome of the study was assessing factors associated with meeting HbA_1c targets. Secondary endpoints included factors associated with continuous subcutaneous insulin infusion (CSII) use and persistent C-peptide secretion.

RESULTS

Socioeconomic deprivation was strongly associated with a lower likelihood of achieving an HbA_1c <58 mmol/mol (7.5%) (20% in the most deprived quintile vs. 40% in the least deprived, p < 0.001). In multivariate analysis, absence of smoking history (OR 3.06, p < 0.001), flash monitoring (OR 1.49, p < 0.001), CSII (1.43, p = 0.022) and longer diabetes duration (OR 1.02 per year, p = 0.004) were independently associated with achieving HbA_1c <58 mmol/mol (7.5%), whereas increasing age (OR 0.99 per year, p = 0.004) and C-peptide <50 pM (OR 0.58, p < 0.001) were associated with a lower likelihood of meeting this target. Low C-peptide (<50 pM) was less likely in men (OR 0.55, p < 0.001) and never smokers (0.44, p < 0.001) in multivariate analysis.

CONCLUSIONS

Lower levels of deprivation, non-smoking, higher C-peptide, technology use, lower BMI and male gender were all associated with a higher likelihood of meeting HbA_1c targets. Access to proven diabetes treatments is lower in the most deprived individuals. Urgent efforts are required to provide treatments which are effective across the socioeconomic gradient.

Relationship of continuous glucose monitoring-related metrics with HbA1c and residual β-cell function in Japanese patients with type 1 diabetes

The targets for continuous glucose monitoring (CGM)-derived metrics were recently set; however, studies on CGM data over a long period with stable glycemic control are limited. We analyzed 194,279 CGM values obtained from 19 adult Japanese patients with type 1 diabetes. CGM data obtained during stable glycemic control over four months were analyzed. CGM-related metrics of different durations "within 120, 90, 60, 30, and 7 days" were calculated from baseline. Time in range (TIR; glucose 70-180 mg/dL), time above range (TAR; glucose ≥ 181 mg/dL), and average glucose levels, but not time below range (TBR; glucose ≤ 69 mg/dL), strongly correlated with glycated hemoglobin (HbA1c) values (P < 0.0001). TBR correlated with glucose coefficient of variation (CV) (P < 0.01). Fasting serum C-peptide levels negatively correlated with glucose CV (P < 0.01). HbA1c of approximately 7% corresponded to TIR of 74% and TAR of 20%. The shorter the CGM period, the weaker was the relationship between HbA1c and CGM-related metrics. TIR, TAR, and average glucose levels accurately reflected HbA1c values in Japanese patients with type 1 diabetes with stable glycemic control. Glucose CV and TBR complemented the limitation of HbA1c to detect glucose variability and hypoglycemia. Stable glycemic control with minimal hypoglycemia depended on residual β-cell function.

A little help from residual β cells has long-lasting clinical benefits

Following type 1 diabetes (T1D) diagnosis, declining C-peptide levels reflect deteriorating β cell function. However, the precise C-peptide levels that indicate protection from severe hypoglycemia remain unknown. In this issue of the JCI, Gubitosi-Klug et al. studied participants from the landmark and ongoing Diabetes Control and Complications Trial (DCCT) and the Epidemiology of Diabetes Interventions and Complications (EDIC) study that had long-standing (about 35 years) T1D. The authors correlated severe hypoglycemia and other disease outcomes with residual C-peptide levels. While C-peptide secretion failed to associate with hemoglobin A1c (HbA1c) or microvascular complications, C-peptide levels greater than 0.03 nmol/L were linked with fewer episodes of severe hypoglycemia. These findings suggest that efforts to preserve finite β cell function early in T1D can have meaningful, long-standing health benefits for patients.