The progression from obesity to type 2 diabetes in Alström syndrome

Abstract

Background: Alström 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%β-cell and insulinogenic index in ALMS, but unlike the insulin-resistance indices, the β-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 β-cell insulin secretion without any further worsening of insulin resistance with age, even in the presence of weight reduction.

Figure 1. Glucose and insulin responses during OGTT according to age groups in ALMS and controls

(a) glucose response < 7 y, (b) insulin response < 7 y, (c) glucose response 7-18 y, (d) insulin response 7-18 y, (e) glucose response > 18 y, (f) insulin response > 18 y. Alström subjects are indicated by white circles and white bars, control subjects by black circles and black bars. AUC, area under curves. *P < 0,05; **P < 0.01

Figure 2. Comparison of HOMA-IR, HOMA% β-cell, Insulin Sensitivity Index and Insulinogenic Index in ALMS patients and controls

Alström subjects are indicated by white bars, control subjects by black bars. Values of HOMA-IR (a), HOMA-βcell (b), Insulin Sensitivity Index (c) and Insulin ogenic Index (d) are reported as median ±SEM. * P< 0,05); ** P< 0,01

Figure 3. Hepatic and lipid profile in ALMS patients

Hepatic (a) and lipid (b) profile in ALMS patients considered by three different classes of age: <7 y (white bars), 7-18 y (dashed bars), > 18 y (black bars). Values are expressed as mean ± SEM. The dotted lines (a) indicate the upper limit of normal values of patients < 7 y, the dashed lines (a, b) indicate the upper limit for normal values of patients > 7 y. AST, aspartate aminotransferase; ALT, alanine aminotransferase; gGT, gamma glutamyl transpeptidase; TOT-C, total cholesterol; HDL-C, high density lipoprotein-cholesterol; TG, triglycerides; LDL-C, low density lipoprotein-cholesterol.