C-peptide measurement in the differentiation of Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetes mellitus

Abstract

To determine whether individual subjects with Type 1 (insulin-dependent) diabetes or Type 2 (non-insulin-dependent) diabetes, who are treated with insulin, could be reliably distinguished, C-peptide concentrations and urinary C-peptide excretion were measured in 10 Caucasoids and 10 Pima Indians. All the subjects had developed diabetes before 21 years of age and were receiving insulin treatment. Fasting C-peptide concentrations were significantly higher in the Pima Indians (0.73 +/- 0.17 versus 0.02 +/- 0.01 nmol/l in Caucasoids; p less than 0.001), but there were slight overlaps in individual values. Urinary C-peptide excretion, an index of 24-h-insulin excretion, was also higher in the Pima Indian group (27.6 +/- 1.85 versus 0.72 +/- 0.18 pmol/min in Caucasoids; p less than 0.001) and there was no overlap in the individual values between the groups. The Pima Indians with early onset diabetes have been previously shown to have Type 2 diabetes, and the Caucasoids with an early onset are most likely to have Type 1 diabetes. These results suggest that distinction between these two major types of diabetes can be made effectively by using C-peptide measurements provided that overt renal disease is absent. This differentiation between insulin-treated patients will be useful for a variety of research applications and possibly in making clinical management decisions.

Increasing prevalence of Type II diabetes in American Indian children

“…Differentiating Type II diabetes from Type I diabetes in children can be a diagnostic challenge [20]. Even when it occurs at a young age, diabetes in Pimas is not associated with high titres of islet cell antibodies [5], insulin and C-peptide concentrations are not subnormal [8], and exogenous insulin is not required to prevent ketosis [6,7]. For our patients, the clinical features suggest Type II rather than Type I diabetes and include family history of Type II diabetes, lack of symptoms at diagnosis, presence of obesity and low frequency of insulin treatment.…”

Type 2 diabetes in children and adolescents: literature review

“…Katzeff e colaboradores, analisando o peptídeo C de dois grupos de crianças, entre os índios Pima com DM2 e caucasóides com DM1, verificaram que a determinação urinária ou plasmática do peptídeo C foi suficiente para discriminar os dois grupos 44 . Os baixos valores encontrados nas crianças caucasianas refletem a insulinopenia típica do DM1, enquanto que o diabetes dos índios Pima, mesmo quando iniciado em idade precoce, não é insulinopênico 44 .…”

“…Os baixos valores encontrados nas crianças caucasianas refletem a insulinopenia típica do DM1, enquanto que o diabetes dos índios Pima, mesmo quando iniciado em idade precoce, não é insulinopênico 44 . Assim, valores do peptídeo C no jejum maiores que 0,6 ng/ml (0,2 nmol/l) ou após sobrecarga com Sustacal ® oral maiores que 1,5 ng/ml (0,6 nmol/L) demonstram reservas de insulina significativas 45 .…”

Comparison of the Effect of Plasma Glucose Concentrations on Microvascular Disease Between Pima Indian Youths and Adults

“…Characterized by a strong genetic predisposition but without linkage or association to known maturity-onset diabetes of the young (MODY) loci, as well as lack of an insulin requirement for survival and absence of islet-cell antibodies, diabetes in the Pima Indian is entirely type 2 (12)(13)(14)(15)(16). In addition, GAD65Ab is not increased in Pima children diagnosed with diabetes (17).…”