The progression from obesity to type 2 diabetes in Alstrom syndrome

Background: Alstrom syndrome (ALMS) is a rare autosomal recessive monogenic disease associated with obesity, hyperinsulinemia, and alterations of glucose metabolism that often lead to the development of type 2 diabetes at a young age. Objective: To study the relationship between weight and metabolism in a group of ALMS patients and matched controls. Research design and methods: Fifteen ALMS patients (eight males, seven females; aged 3-51) were compared in a cross-sectional study with an age-and weight-matched control population. Anthropometric parameters, fat mass, glucose and insulin secretion in basal and dynamic oral glucose tolerance test (OGTT) conditions were measured. Furthermore, anthropometric and body composition data were obtained from an international group of 27 ALMS patients (13 males, 14 females, age range: 4-29 yr). Results: In ALMS we observed an inverse correlation between age and standard deviation scores for height, weight, and body mass index. The OGTT glycemic curves of ALMS subjects were similar to those of age-matched controls, whereas insulin response was clearly greater. In ALMS individuals the insulin response showed a reduction with age. We documented pathologic values of the derived indices homeostasis model assessment of insulin resistance (HOMA-IR), insulin sensitivity index, HOMA% beta-cell and insulinogenic index in ALMS, but unlike the insulin-resistance indices, the beta-cell function indices showed a significant reduction with age. Conclusions: In ALMS the progression from the early onset obesity toward the impaired fasting glucose or impaired glucose tolerance and overt diabetes is mostly because of a progressive failure of beta-cell insulin secretion without any further worsening of insulin resistance with age, even in the presence of weight reduction.