P704Nanoliposomal anti-PCSK9 vaccine ameliorates glucose intolerance and insulin resistance in diabetic rats

Abstract Background PCSK9 inhibitors have emerged as an effective lipid-lowering approach. Although the results of available studies suggest a positive association of plasma PCSK9 levels with glycemic parameters and risk of DM, the effects of PCSK9 inhibitors on glucose intolerance and insulin resistance as the key features of DM remain unclear. Purpose The present study was directed to determine effect of vaccine-mediated PCSK9 inhibition on glucose intolerance and insulin resistance in experimental diabetic rats. Methods Nanoliposomal vaccine composing from PCSK9-linked nanoliposome particles mixed in Alum adjuvant was subcutaneously injected four times with bi-weekly intervals in Wistar-Albino rats. Two weeks after the last immunization, vaccinated and non-vaccinated rats were subjected to diabetes experiment induced by single intraperitoneal injection of streptozotocin (STZ). One week after STZ injection, glucose tolerance ability of each animal was evaluated by using oral glucose tolerance test (OGTT) on the overnight fasted rats with glucose dose at 2 g/kg. Two weeks after STZ injection, insulin tolerance test (ITT) viaintraperitoneal injection of insulin (0.8 U/kg) was performed to determine the measure of peripheral utilization of glucose. The plasma concentrations of total cholesterol (TC), LDL-C, HDL-C, and TG were measured. Results Nanoliposomal vaccine exposing PCSK9 peptide was found to provoke high-titers IgG antibody response against PCSK9 in rats, which was associated with the decrease plasma levels and function of plasma PCSK9. During the first week after STZ injection, it was indicated that the fasting blood glucose (FBG) level was 49% (−171.7±35 mg/dL, p<0.0001) lower in the vaccinated diabetic (VD) rats, when compared to the diabetic control (DC) rats. OGTT assessment revealed that the VS rats had significantly improved glucose tolerance ability and recorded significant reduction in the level of blood glucose over the period of 180 min, when compared with the DC rats. Measurement of integrated areas under the glucose curve values demonstrated that blood glucose levels were significantly (p<0.0001) decreased by 34.5% in the VS rats than the DC rats. In addition, ITT analysis showed that after insulin administration blood glucose level was decreased by 49.3% in the VS group compared with the DC group. The VS rats showed significantly lower (−26.65%, p=0.02) plasma LDL-C levels than the DC rats (Figure). Histopathology examination indicated that the pancreatic islet of the VS rats had a slightly decreased population of β-cells and few α-cells. Histopathology examination of the liver tissues of both VS and DC rats exhibited the normal histology with the normal hepatic architecture composed of hepatic lobules with normal central vein. Conclusions PCSK9 inhibition using liposomal vaccine can protect from glucose and insulin tolerance impairments in diabetic rats through an unknown and pancreatic-independent mechanism.