J Korean Diabetes Assoc.  2006 Jan;30(1):39-46.

A Study on Insulin action using fibroblast of leprechaunism patients

• Koh SW
• Oh YJ
• Chang MK
• Bae YS
• Jin DK

Abstract

BACKGROUND: Leprechaunism, which is caused by insulin receptor defect, is clinically characterized by hyperinsulinemia, stunted growth, dysmorphic somatic abnormalities, lipodystrophy and early death around 2-3 years of age.
METHODS
In this study we describe 2 cases of Korean leprechaunism patients. In addition, the disturbed insulin induced effects such as glucose uptake, insulin binding assay, thymidine uptake and PDGF stimulated phosphorylation change were investigated using the fibroblasts from 1 Korean patient and those from 4 foreign leprechaunism patients.
RESULTS
The morphologic study of fibroblasts derived from patient suggests that the fibroblasts of patient are less differentiated than the fibroblasts of control. Moreover, insulin induced pathways as well as PDGF stimulated phosphorylation change were disturbed in the fibroblasts of the patient.
CONCLUSION
Our results suggest that the signal transduction in the fibroblasts of leprechaunism is reduced not only by insulin stimuli but also by other growth factors like PDGF.

Keyword

Leprechaunism; insulin receptor defects; insulin signal transduction

MeSH Terms

Donohue Syndrome*
Fibroblasts*
Glucose
Humans
Hyperinsulinism
Insulin*
Intercellular Signaling Peptides and Proteins
Lipodystrophy
Phosphorylation
Receptor, Insulin
Signal Transduction
Thymidine
Glucose
Insulin
Intercellular Signaling Peptides and Proteins
Receptor, Insulin
Thymidine

Figure

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  Fig. 1 Reported mutations in the insulin receptor gene in patients with leprechaunism.

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  Fig. 2 Phase contrast microscopy of cultured fibroblasts, a) from a normal control and b) from a patient with leprechaunism.

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  Fig. 3 Stimulation of glucose uptake by insulin in normal controls and patients fibroblasts. Glucose uptake was measured as described in the Materials Method. Data are represented mean (± S.D. Significant differences in insulin-stimulated glucose uptake were not noted between all leprechaunism patient fibroblasts (Normal: P < 0.05, Patient: P < 0.001). Statistical comparisons between the means were made with t-test.

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  Fig. 4 Insulin stimulation of thymidine incorporation in the fibroblasts derived from patients and normal control. Cells were growth-arrested by incubating the cells in serum-free DMEM for 48 h. The cells were incubated with increasing concentrations of insulin. After 16 h of incubation, cells were labeled with 0.5 µCi/ml of [3H]thymidine for another 4h. The radioactivity was counted using a scintillation counter. Data are expressed as mean ± SEM. Statistical comparisons between the means were made with Mann-Whitney test.

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  Fig. 5 Receptor binding assay. a, c) Binding of 125I-IGF-1; b, d) binding of 125I-insulin. In receptor binding assay, the cell extracts were incubated with increasing concentrations (a, 0-10000ng/ml, c, 0-5000ng/ml) of 125I-IGF-I and 125I-insulin (b, 0-10000ng/ml, d, 0-5000ng/ml). Data are represented mean ± S.D. Statistical comparisons between the means were made with Mann-Whitney test.

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  Fig. 6 Reduced tyrosine phosphorylation by PDGF in the fibroblast cells from leprechaunism patients. The cells were seeded in 6-well plates and serum starved for 16 hours before receiving 50 ng/ml PDGF for the 10min. Fibroblast cell lysates were immunoblotted with anti-phosphotyrosine.

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