RESUMO
OBJECTIVES: Dyslipidemia is a risk factor for post- transplant diabetes mellitus, especially in patients who are taking tacrolimus. Although lipotoxicity of dyslipidemia leads to ß-cell failure, the handling of lipids by ß cells is a mystery in molecular endocrinology. Likewise, lipid droplet homeostasis is appreciated as a key component of lipid metabolism in cells like hepatocytes, but its role in ß cells remains to be elucidated. MATERIALS AND METHODS: To evaluate the morphologic changes in ß cells with special focus on lipid droplets, we evaluated electron micrographs under metabolic stress conditions of glucotoxicity, lipotoxicity, and glucolipotoxicity in isolated rat insulinoma INS-1E ß cells. Cells were treated with palmitic acid (0.5 mM), glucose (33 mM), or both for 16 hours, after which morphologic changes were observed with an electron microscope. RESULTS: Many lipid droplets were observed in the cytoplasm of healthy ß cells in the control group (no treatment). Lipid droplets were also visible in the cytosol, and the cytoplasm was rich in organelles and insulin vesicles under high glucose stimulation. However, after treatment with palmitic acid, almost no lipid droplets were observed. Endocrine vesicles were also depleted, with severe morphologic disruption of other organelles. Under glucolipotoxic conditions, ß cells showed a decreased number of lipid droplets and insulin vesicles compared with controls. CONCLUSIONS: Lipid droplet dynamics seemed important in the homeostasis of ß-cell metabolism. In this preliminary study, healthy ß cells appeared rich in lipid droplets under normal conditions. However, lipotoxicity depleted and glucolipotoxicity decreased the number of lipid droplets in ß cells. Because dyslipidemia causing lipotoxicity is one of the most frequent metabolic problems in transplant patients and increases risk of posttransplant diabetes mellitus, understanding the mystery of lipid droplets in ß cells and the pathophysiology of diabetes in transplant patients is important, especially for those taking tacrolimus.
RESUMO
BACKGROUND: Mitochondrial uncoupling proteins (UCP) 1, 2 and 3 are members of the anion carrier protein family located in the inner mitochondrial membrane. There are various controversial reports on UCP genotypes and obesity in adults and children. This study aims to investigate the link between mostly studied UCP polymorphisms (UCP1-3826A/G, UCP2 Insertion/Deletion (Ins/Del) polymorphism of exon 8, and UCP3-55C/T Polymorphisms) and obesity in Turkish children. Furthermore, the relationships of UCP polymorphisms are also analyzed within the scope of metabolic parameters of obese children. METHODS: Molecular screening of the UCP1, UCP2, and UCP3 gene polymorphisms was carried out in 189 children aged 6 to 18 years, 102 of who had exogenous obesity (54 girls) and 87 of whom were healthy controls (48 girls). In the obese group, fasting lipids, glucose and insulin levels were measured. In 60 obese children, an oral glucose tolerance test (OGTT) was performed with 0, 30, 60, 90 and 120 minutes of sampling for plasma glucose and insulin levels. RESULTS: The frequency of UCP polymorphisms was similar in obese and non-obese children. In obese children, fasting lipids, glucose and insulin levels were not different among the UCP 1, 2 and 3 genotypes. While no relationship was found between the UCP 1 and 3 genotypes and glucose/insulin levels during OGTT, carriers of the Insertion allele with UCP2 Ins/Del polymorphism had significantly higher 30-minute insulin levels (p=0.018). CONCLUSIONS: Polymorphisms of the UCP1-3826A/G, UCP2 Ins/Del, and UCP3-55C/T are not associated with obesity and related pathologies in Turkish children. However, the presence of the Ins allele of the UCP2 gene has been found to have an unfavorable influence on early insulin excursion after glucose loading.