[Pancreatic β-cell Dysfunction and Apoptosis Induced by Elevated Free Fatty Acids Synergize with Hyperglycemia]

To analysis the effects of glucoxicity and lipotoxicity on the function and apoptosis of pancreatic β-cells.

The levels of circulating glucose and free fat acids (FFAs) were elevated by infusion dextrose and fat emulsion in high-fat obese rats. The insulin resistance model obese rats were divided into four gourp: obese group with saline infusion (OB-NS group, n=7), obese group with glucose infusion (OB-GS group, n=9), obese group with Lipid emulsion infusion (OB-FFA group, n=8), obese group with glucose and lipid emulsion infusion (OB-FG group, n=9). Five rats fed with general diet were taken as normal group (NC group).Plasma FFAs and β-hydroxybutyric acid (β-HBA) concentrations were determined by an enzymatic colorimetric method. An intravenous glucose tolerance test (IVGTT) was performed to examine the glucose-stimulated insulin secretion in vivo and immunohistochemical staining to detect the storage volume of insulin. FFA and β-HBA concentrations were measured at baseline and post-infusion. The apoptosis of pancreatic β-cell was detected byin situ end labeling technique (TUNEL).

Glucose infusion rate (GIR) of obese rats was significantly lower than that in NC group [(10.82±1.8) mg/(kg·min) vs. (25.21±1.7) mg/(kg·min), P<0.05], confirming insulin resistance rat model successfully established. The insulin secretion peak load time of OB-FG group rats delayed, and the serum insulin level was significantly lower than that of NC group and OB-NS group during IVGTT. The differences were statistically significant ( P<0.05). Compared with OB-NS and NC groups, storage volume of insulin of OB-GS group reduced, and β cell apoptosis rate elevated significantly.

Glucolipotoxicity could induce ketone overproduction, insulin resistance and defective insulin secretion.