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Eighty percent of people with long-standing type 1 diabetes appear to be insulin “microsecretors,” meaning that they continue to produce perceptible amounts of insulin for years after diagnosis, according to new research published in Diabetes Care.
Recent data have contradicted the notion that type 1 diabetes leads to absolute insulin deficiency, with C-peptide assays showing that 43% to 74% of patients with long-standing type 1 diabetes are microsecretors of endogenous insulin, Richard A. Oram, BMBCh, BA(hons), MRCP, of the University of Exeter Medical School in the United Kingdom, and colleagues wrote.
These studies, however, were small and did not use representative samples. The researchers therefore set out to conduct a large, non-selected, population-based study of patients with type 1 diabetes.
In this study, the researchers assessed 924 patients from primary and secondary care at two centers in the U.K. They evaluated C-peptide levels using a home post-meal urine C-peptide-to-creatinine-ratio (UCPCR).
All patients had a clinical diagnosis of type 1 diabetes, were diagnosed before age 30 years and had the disease for longer than 5 years. Median age at diagnosis was 11 years and median duration of disease was 19 years.
Of all 924 patients, 740 (80%) had detectable endogenous C-peptide levels (UCPCR, >0.001 nmol/mmol), according to the data.
The majority of patients (52%) had historically very low undetectable levels, with UCPCR ranging from 0.001 nmol/mmol to 0.03 nmol/mmol. Twenty percent, however had a UCPCR ranging from 0.03 nmol/mmol to 0.2 nmol/mmol, and some (8%) had a UCPCR >0.2 nmol/mmol.
The researchers also observed decreases in absolute UCPCR levels with duration of disease.
In multivariate modeling, age at diagnosis and duration of disease were identified as independent predictors of C-peptide level.
“These findings provide strong evidence that complete beta-cell loss does not develop in most people with [type 1 diabetes], and that they will continue to secrete low levels of insulin for decades after receiving a diagnosis,” the researchers wrote.
“While the majority of patients are insulin microsecretors, some maintain clinically relevant endogenous insulin secretion for many years after the diagnosis of diabetes. Understanding this may lead to a better understanding of pathogenesis in [type 1 diabetes] and open new possibilities for treatment.”
