medwireNews: Any amount of residual C-peptide is protective against some type 1 diabetes complications, show findings from a large, population-based study.
Researchers Paul McKeigue (University of Edinburgh, UK) and team found that residual C-peptide down to the lower limits of detectability protected people with type 1 diabetes against hypoglycemia and retinopathy.
By contrast, there was a threshold effect for insulin dose, glycated hemoglobin (HbA1c), and risk for diabetic ketoacidosis.
The analysis included over 5700 individuals with type 1 diabetes lasting an average of 20.9 years, who were followed up for 5.2 years, on average. The majority of people had C-peptide levels below 5 pmol/L, but more than 2000 had higher levels.
In total, 27% participants had experienced at least one hypoglycemic episode that required third-party assistance during the previous year. But the risk for having had such an event was significantly lower in those with C-peptide levels of at least 5 pmol/L versus lower levels, at a 27% reduction for people with levels from 5 to less than 30 pmol/L and around a 50% reduction for those with higher levels. There was a similar protective effect on hypoglycemia incidence, and both were independent of age at diabetes onset, diabetes duration, HbA1c level, and BMI.
“The size of this effect is enough to be clinically significant and does not differ much between those with relatively short duration and those with longer duration,” write the researchers in Diabetes Care.
There was a similar relationship between C-peptide and risk for retinopathy, with an inverse, approximately linear association seen, which continued down to the lower limit of C-peptide detectability.
By contrast, residual C-peptide had to be 200 pmol/L or higher to result in a lower insulin dose and HbA1c levels, and to be protective against diabetic ketoacidosis. C-peptide level was not associated with the risk for renal disease.
The effect on insulin dose was “modest,” notes the team, with C-peptide levels of 200 pmol/L or higher associated with a dose reduction of around 10%.
Accounting for insulin dose, people with this amount of residual C-peptide also had HbA1c levels that were 3.6 mmol/mol lower, on average, than those in a lower C-peptide category.
“These results support the contention that assessment of the clinical benefit of an intervention that preserves or restores C-peptide secretion should be based not on its effect on insulin dose requirements or glycemic control but on its effect on the rate of serious hypoglycemic events and the risk of retinopathy,” say McKeigue and team.
“Even if such interventions do not appreciably reduce insulin requirement, they may still profoundly improve quality of life for people with type 1 diabetes.”
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Diabetes Care 2020; doi:10.2337/dc20-0567