Decreased Insulin Binding in Cultured Lymphocytes from Two Patients with Extreme Insulin Resistance*

Abstract

[125I]Insulin binding has been studied in two patients with extreme insulin resistance using cultured B-lymphocytes transformed with Epstein-Barr virus. A cell line from a female infant with leprechaunism had insulin binding which was decreased 90% below the lower limit of normal. Lymphocytes from a young woman with type A extreme insulin resistance (associated with acanthosis nigricans and virilization) had insulin binding which was 80% depressed. In both cases, the defect in binding resulted from a decrease in the number of receptors per cell. The remaining receptors had normal properties, including a normal affinity for insulin and a normal specificity for insulin analogs. Insulin binding in cultured lymphocytes from these two insulin-resistant patients was also inhibited normally by antibodies to the insulin receptor. Immunological assays using anti-receptor antibodies confirmed the conclusion that the number of receptors was decreased. Affinity labeling of the leprechaun insulin receptor with [125I]insulin demonstrated the existence of an alpha-subunit with apparently normal molecular weight (130,000 daltons). However, the number of receptor molecules per cell appeared reduced.

Pancreatic A and B cell hyperfunction in the mendenhall syndrome

“…Furthermore, the low levels of IgG insulin antibodies make it unlikely that the resistance was caused by insulin antibodies. Further studies recently carried out by Taylor et al [23] in this patient have also established abnormally low levels of insulin binding to cultured lymphocytes and to cultured skin fibroblasts, with a concomitant decrease in the affinity of t25I-insulin binding to the latter cell system. All these findings are in agreement with the observations of Podskalny and Kahn [19,20] in cultured fibroblasts from patients suffering from other syndromes of extreme insulin resistance.…”

Functional properties of a heterozygous mutation (Arg1174 → Gln) in the tyrosine kinase domain of the insulin receptor from a Type A insulin resistant patient

“…The insulin receptor number of patient cells was lower than the mean value of normal control subjects, but it was still within the normal range. The observed high degree of variability of insulin receptor numbers on EBV-transformed cells of normal subjects has already previously been documented [17,40]. The finding of Autophosphorylation and substrate phosphorylation studies of partially purified insulin receptors were performed as described in section 2.3.…”

“…Transformed lymphocyte culture. EBV-transformed lymphocyte cell lines were established from peripheral blood lymphocytes from the patient and 6 normal subjects as described elsewhere [17]. The incubation of freshly isolated lymphocytes with conditioned medium of marmoset B9518-cells was performed in the presence of 600 ng/ml Cyclosporin A.…”

“…Insulin binding. ~zsI-insulin binding to transformed lymphocytes was performed at RT for 2 h as previously described [17]. Insulin binding to lectin purified insulin receptors was measured as described before [18].…”

Insulin Resistance in a Boy with Congenital Generalized Lipodystrophy

“…Insulin binding was performed on circulating erythrocytes, monolayer cultures of skin fibroblasts, and EBV-transformed lymphocytes according to the methods of Gambhir et al (14), Baldwin et al (15) and Taylor et al (13), respectively.…”