Plasma Immunoreactive C-peptide Research Articles

Biochemical changes in rhesus monkey during the first days after streptozotocin administration are indicative of selective β cell destruction

Hormonal and glycemic changes in 22 rhesus monkeys were characterized during the first days after treatment with streptozotocin (STZ) (45 to 55 mg/kg, administered intravenously [IV]. Almost half ( 10 22 ) of the monkeys developed insulin-dependent diabetes mellitus (STZ-IDDM) within five days following injection. Four of the remaining monkeys did not become insulin dependent for at least 6 months after STZ treatment, during which time they were considered non-insulin-dependent, and eight monkeys never required exogenous insulin. In the STZ-IDDM group, plasma immunoreactive c-peptide (IRC-P) levels fell by three hours after STZ from a mean ± SEM of 252 ± 82 to 101 ± 45 pg/mL, as glucose and immunoreactive glucagon (IRG) levels increased from 65 ± 3 and 120 ± 37, respectively, to 336 ± 43 mg/dL and 234 ± 52 pg/mL, respectively. Between six and 30 hours after treatment, IRC-P increased to a peak of 1,561 ± 360 pg/mL before falling permanently to <60 pg/mL by 66 hours. During this period, glucose and IRG responded in a reciprocal fashion by falling and then increasing to levels above 300 mg/dL and 300 pl/mL, respectively, by 66 hours. In the non-insulin-dependent diabetes mellitus (STZ-NIDDM) group, no clear reciprocal relationship between IRC-P and glucose and IRG was obtained. In nine additional monkeys subjected to total pancreatectomy (Px), IRC-P and IRG levels fell immediately and permanently by >90% and 75%, respectively. Levels of immunoreactive somatostatin increased steadily over the initial 96 hours following STZ, but did so in both STZ-IDDM and Px monkey groups. Plasma lipid hydroperoxide levels measured in two monkeys that developed STZ-IDDM were unchanged during the first 96 hours after STZ administration. In conclusion, the glycemic and hormonal pattern observed with STZ-IDDM rhesus monkeys during the first days following treatment is indicative of selective pancreatic β-cell destruction resulting from a direct action of STZ.

Factors influencing residual pancreatic beta cell function in recently diagnosed Type 1 diabetic children.

. Children with type 1 diabetes mellitus usually show partial recovery of pancreatic β cell function after initial stabilization. This partial remission may favourably influence the diabetic state. This study aimed to investigate factors that may influence β cell recovery. Studies were made on 26 newly diagnosed diabetic children. Residual β cell function was estimated by plasma immunoreactive C-peptide (CPR) values in the fasting state and after meal stimulus. Some residual function was detected in all diabetics studied. C-peptide secreted in response to a meal varied between 0.03–0.415 pmol/ml (0.182 ± 0.144 pmol/ml, mean ± SD). Statistical analysis of variables hypothesised to relate to β cell function showed significant positive correlations between ΔCPRmax. and age, admission pH, duration of preceding symptoms, and duration of treatment. Significant negative correlations were obtained between ΔCPRmax. and fasting glucose and insulin dosage at resuscitation. No significant correlations were observed between fasting CPR and the parameters mentioned. Multiple regression analysis reinforced the relationship between ΔCPRmax. and age at onset, fasting glucose and admission pH. It is concluded that β cell responsiveness is related to these factors at initial presentation and to quality of control as indicated by fasting blood glucose levels

Degradation and Secretion of Insulin in Hepatic Cirrhosis

To clarify the mechanism of hyperinsulinism of hepatic cirrhosis, plasma insulin and C-peptide levels before and after oral glucose loads were measured in 34 patients with cirrhosis, 15 patients with chronic hepatitis, and 25 normal subjects. While plasma immunoreactive insulin (IRI) levels during oral glucose tolerance testing (OGTT) were significantly increased in cirrhotics, plasma immunoreactive C-peptide (CPR) levels were elevated slightly. The C-peptide to insulin ratio throughout OGTT was significantly smaller in cirrhotics than in normal subjects (P less than 0.01). A decreased hepatic insulin degradation rate has been suggested to one of the main causes of hyperinsulinism in hepatic cirrhosis. The ratio of the difference between basal and 30-min CPR values and basal and 30-min OGTT blood glucose values [delta CPR: delta BS(30)'] as well as the delta IRI: delta BS(30') ratio was significantly decreased in cirrhotics (P less than 0.01). These results indicate that insulin secretion in response to a glycemic stimulus is reduced in cirrhotics. Both the ratios of the sums of six IRS and CPR values of OGTT (sigma CPR: sigma IRI) and delta CPR: delta BS(30') and sigma CPR: sigma BS(30') were found in inverse relationship with indocyanine green retention rate in cirrhotics.