C-peptide reserve in insulin-dependent diabetes

Abstract

Residual beta cell secretory capacity was assessed in short term (2 months to 2 years) and long term (5 to 8 years) insulin-dependent diabetics by measurement of serum C-peptide immunoreactivity during three provocative tests: glucose, tolbutamide, and glucagon. Minimal C-peptide secretion could be detected in only one out of seven long term diabetics by the stimulatory tests. All seven short-term diabetics responded to at least one provocative test of beta cell reserve, although these responses were blunted. The greatest C-peptide responses occurred after glucagon administration (mean increase 0.62 pmol/ml) in short-term responders. Patients who responded to one test did not necessarily respond to another stimulus. There was no correlation between basal C-peptide levels and the ability to provoke further C-peptide secretion by any of the three tests. C-peptide responses did not correlate with % Haemoglobin A1c, mean fasting blood glucose levels, or mean blood glucose concentrations during an oral glucose tolerance test. The data indicate that stimulation tests are only useful in assessing endogenous beta cell reserve in patients with diabetes of less than 5 years duration. In diabetics of longer duration there is little insulin reserve above basal levels.

Residual β-Cell Function in Children With IDDM: Reproducibility of Testing and Factors Influencing Insulin Secretory Reserve

“…Frequency of insulin injections (1 vs. 2 times/day) did not differ in the C-peptide-positive versus -negative subjects. DISCUSSION D espite extensive investigation of residual (3-cell function in IDDM, the reproducibility of the Cpeptide response to the same stimulus has not been reported previously; only the response to different stimuli has been reported (5,9,14). There are reports of patients responding differently to various stimuli.…”

“…There are reports of a significant correlation between basal and stimulated C-peptide levels in response to glucagon and glucose (10,11). However, Mirel et al (5) found no correlation of basal concentrations and the peak attained in response to glucose, tolbutamide, or glucagon.…”

“…An increase in C-peptide concentrations has been found from several days to weeks after the diagnosis of diabetes (1,2). Studies indicate that during the first 2 yr of disease, many patients have some residual (3-cell function, whereas by 6-8 yr, only traces of C-peptide are detectable (3)(4)(5). Accurate measurement of C-peptide may be valuable in assessing children with IDDM because even minimal residual P-cell function appears to be important in achieving more physiologic glucose homeostasis (3,6).…”

“…The reproducibility of Cpeptide concentrations obtained in response to the same stimulus has not been evaluated, only the responses to different stimuli (5,9). The effect of exogenous insulin on C-peptide levels has also not been assessed.…”

Reduction of C-peptide secretion in noninsulin-dependent diabetic patients with long duration of insulin treatment.

“…Based on a study of Vol.30 in the patients who had diabetes for less than 5 years Grajwer et al, 1977;Ludvigsson and Heding, 1976;Hendrikson et al;. A similar correlation was found between short term (2 months to 2 years) and long term (5 to 8 years) insulin-dependent diabetic patients (Mirel et al, 1980). However, most of the above data dealt with patients with insulin-dependent diabetes mellitus (IDDM) who received insulin injections almost from the time of onset.…”