Creation of Apolipoprotein C-II (ApoC-II) Mutant Mice and Correction of Their Hypertriglyceridemia with an ApoC-II Mimetic Peptide

Abstract

Apolipoprotein C-II (apoC-II) is a cofactor for lipoprotein lipase, a plasma enzyme that hydrolyzes triglycerides (TGs). ApoC-II deficiency in humans results in hypertriglyceridemia. We used zinc finger nucleases to create Apoc2 mutant mice to investigate the use of C-II-a, a short apoC-II mimetic peptide, as a therapy for apoC-II deficiency. Mutant mice produced a form of apoC-II with an uncleaved signal peptide that preferentially binds high-density lipoproteins (HDLs) due to a 3-amino acid deletion at the signal peptide cleavage site. Homozygous Apoc2 mutant mice had increased plasma TG (757.5 6 281.2 mg/dl) and low HDL cholesterol (31.4 6 14.7 mg/dl) compared with wild-type mice (TG, 55.9 6 13.3 mg/dl; HDL cholesterol, 55.9 6 14.3 mg/dl). TGs were found in light (density , 1.063 g/ml) lipoproteins in the size range of verylow-density lipoprotein and chylomicron remnants (40-200 nm). Intravenous injection of C-II-a (0.2, 1, and 5 mmol/kg) reduced plasma TG in a dose-dependent manner, with a maximum decrease of 90% occurring 30 minutes after the high dose. Plasma TG did not return to baseline until 48 hours later. Similar results were found with subcutaneous or intramuscular injections. Plasma half-life of C-II-a is 1.33 6 0.72 hours, indicating that C-II-a only acutely activates lipolysis, and the sustained TG reduction is due to the relatively slow rate of new TG-rich lipoprotein synthesis. In summary, we describe a novel mouse model of apoC-II deficiency and show that an apoC-II mimetic peptide can reverse the hypertriglyceridemia in these mice, and thus could be a potential new therapy for apoC-II deficiency.

Apolipoprotein C-II: New findings related to genetics, biochemistry, and role in triglyceride metabolism

“…The recent development of an apoC-II mimetic peptide, which incorporates the third helix of apoC-II, has shown some promise as potential future therapy. Intravenous injection of this peptide normalized TG in a mouse model of apoC-II deficiency 81 . Furthermore, the apoC-II mimetic peptide potentiated LPL activity in other non-apoC-II deficient HTG conditions, suggesting a potential broader utility 93 .…”

“…4A). Retention of the signal peptide in transgenic mice due to a specific mutation has recently been shown to cause the selective binding of apoC-II to HDL, leading to HTG 81 . ApoC-II contains no N-linked glycosylation sites and does not appear to undergo significant O-linked glycosylation.…”

Emerging strategies of targeting lipoprotein lipase for metabolic and cardiovascular diseases

“…Further, in vivo evaluation of the peptide in the APOE −/− mouse model showed significant activity of lowering plasma triglycerides and plasma cholesterol. Further evaluation of the same peptide in APOC2 mutant mice showed the ability to correct the hypertriglyceridemia in these mice [146]. Although preliminary in nature, these studies provide crucial proof-of-concept validation for APOC2 mimetic peptides as pharmacological tools.…”

Loss of Transcription Factor CREBH Accelerates Diet-Induced Atherosclerosis in Ldlr −/− Mice

“…Deficiencies of LPL inhibitors, such as apoC-III or angiopoietin-like proteins, conferred protective effects against atherosclerosis 18, 19 . In contrast, it has been shown that the loss of apoC-II LPL activator increased the risk of CVD in parallel with plasma TG and cholesterol levels 20, 21 .…”