Urinary C-peptide analysis in an intervention study: experience from the DEFEND-2 otelixizumab trial

Effect of Immunotherapy on C-peptide Levels in Patients With Type I Diabetes Mellitus: A Systematic Review of Randomized Controlled Trials

Type 1 diabetes mellitus is an autoimmune condition characterized by insulin deficiency resulting from loss of function of beta cells in the pancreas, leading to hyperglycemia and associated long-term systemic complications and even death. Immunotherapy demonstrates beta cell function-preserving potential; however, its impact on C-peptide levels, a definitive biomarker of beta cell function, and endogenous insulin secretion remain unclear. A systematic review of various immunotherapeutic interventions is hence needed for a comprehensive assessment of their effectiveness as well as identifying research gaps and influencing future research and clinical decisions. An extensive literature search was done in PubMed, Scopus, and Cochrane Library databases using precise keywords and filters to identify relevant studies. Three independent reviewers assessed eligibility according to predetermined eligibility criteria, and data was extracted. The Cochrane risk of bias assessment tool (RoB 2.0) was used to evaluate the quality and validity of the included studies. A senior reviewer resolved discrepancies and differences of opinion between independent reviewers. A total of 11 studies were included, with 1464 study participants. Both Phase II and III trials were included. Within the included studies, four studies assessed the anti-CD3 monoclonal antibody otelixizumab as an intervention. Another anti-CD3 monoclonal antibody, teplizumab, was assessed as an intervention in four studies, whereas two studies assessed the anti-CD20 antibody rituximab and one study assessed abatacept as its interventional drug. Otelixizumab demonstrated benefits at higher doses but was associated with adverse effects like Ebstein-Barr virus reactivation and cytomegalovirus infection, while at lower doses it failed to show a significant difference in C-peptide levels or glycosylated hemoglobin (HbA1c). Teplizumab, on the other hand, showed promise in reducing C-peptide loss and exogenous insulin requirements and was associated with adverse events such as rash, lymphopenia, urinary tract infection, and cytokine release syndrome. However, these reactions were only associated with therapy initiation, and they subsided on their own. Rituximab improved C-peptide responses, and abatacept therapy demonstrated reduced loss of C-peptide, improved C-peptide levels, and lowered HbA1c. Teplizumab, rituximab, otelixizumab, and abatacept show potential for preserving beta cell function by reducing C-peptide loss in patients with type I diabetes mellitus. However, careful monitoring of adverse reactions, particularly viral infections and cytokine release syndrome, is necessary for the safe implementation of these therapies.

Approaches to Measuring Beta Cell Reserve and Defining Partial Clinical Remission in Paediatric Type 1 Diabetes

CONTEXT

Type 1 diabetes (T1D) results from the autoimmune T-cell mediated destruction of pancreatic beta cells leading to insufficient insulin secretion. At the time of diagnosis of T1D, there is residual beta cell function that declines over the subsequent months to years. Recent interventions have been approved to preserve beta cell function in evolving T1D.

OBJECTIVE

The aim of this review is to summarise the approaches used to assess residual beta cell function in evolving T1D, and to highlight potential future directions.

METHODS

Studies including subjects aged 0 to 18 years were included in this review. The following search terms were used; "(type 1 diabetes) and (partial remission)" and "(type 1 diabetes) and (honeymoon)". References of included studies were reviewed to determine if additional relevant studies were eligible.

RESULTS

There are numerous approaches to quantifying beta cell reserve in evolving T1D. These include c-peptide measurement after a mixed meal or glucagon stimuli, fasting c-peptide, the urinary c-peptide/creatinine ratio, insulin dose-adjusted haemoglobin A1c, and other clinical models to estimate beta cell function. Other biomarkers may have a role, including the proinsulin/c-peptide ratio, cytokines, and microRNA. Studies using thresholds to determine if residual beta cell function is present often differ in values used to define remission.

CONCLUSIONS

As interventions are approved to preserve beta cell function, it will become increasingly necessary to quantify residual beta cell function in research and clinical contexts. In this report, we have highlighted the strengths and limitations of the current approaches.

Surrogate markers and predictors of endogenous insulin secretion in children and adolescents with type 1 diabetes

BACKGROUND

No studies have examined endogenous insulin secretion in pediatric patients with type 1 diabetes in China using the gold-standard mixed-meal tolerance test. Because the latter is labor-intensive, we examined simpler surrogate markers of endogenous insulin secretion in Chinese youth, as previously reported for a European population.

METHODS

Participants were 57 children and adolescents with type 1 diabetes aged 4.4-16.8 years (56% females). We performed 120-minute mixed-meal tolerance tests with serum C-peptide (CP) measurements every 30 minutes. Severe insulin deficiency (SID) was defined as CP peak < 0.2 nmol/L. Urine CP and creatinine levels were measured at 0 and 120 minutes.

RESULTS

Twenty-five (44%) patients had SID. Fasting CP levels missed one case (96% sensitivity) with no false positives (100% specificity). While the 120-minute urine CP/creatinine had 100% sensitivity, it yielded markedly lower specificity (63%). Every 1-year increase in diabetes duration and 1-year decrease in age at diagnosis were associated with 37% (P < 0.001) and 20% (P = 0.005) reductions in serum CP area-under-the-curve, respectively. Thus, 86% of children aged < 5 years had SID compared to none among patients aged ≥ 11 years.

CONCLUSIONS

Simple fasting CP measurements could be used to detect most SID cases in Chinese youth with type 1 diabetes. Fasting CP is a far more reliable measure of endogenous insulin secretion than the more commonly used insulin dose. Therefore, it could more precisely determine insulin secretory capacity to target those who could benefit, if treatments to preserve residual insulin secretion are developed.

Stimulated urine C-peptide creatinine ratio vs serum C-peptide level for monitoring of β-cell function in the first year after diagnosis of Type 1 diabetes

AIMS

To determine if urine C-peptide/creatinine ratio is a useful tool for monitoring β-cell function in new-onset Type 1 diabetes.

METHODS

Data were obtained from a prospective immunomodulation study in people with Type 1 diabetes ≤ 3 months from diagnosis, with a standard mixed-meal tolerance test and measurement of urine C-peptide/creatinine ratio carried out at 0, 3, 6, 9 and 12 months. The change in the insulin-dose-adjusted HbA_1c level was also correlated with the change in serum/urine C-peptide level during the 12-month follow-up period.

RESULTS

A significant reduction in urine C-peptide/creatinine ratio, measured after a mixed-meal, was reached at 9 months (-45.4%), whilst the reduction in stimulated serum C-peptide level reached significance after 3 months (-54.7%) in placebo-treated participants. Neither change in stimulated serum C-peptide nor change in urine C-peptide level correlated with each other, and nor did change in insulin-dose-adjusted HbA_1c level in the first 6 months, but all measures correlated significantly in the second half of the 12-month follow-up period.

CONCLUSION

Mixed-meal-stimulated urine C-peptide/creatinine ratio was similar to, although less sensitive than, stimulated serum C-peptide level in monitoring β-cell function during the first year after diagnosis. Because the former is significantly less invasive, it warrants inclusion in further studies in Type 1 diabetes and may represent an attractive alternative outcome measure in cohort studies and in children.