Ablation of Plasma Prekallikrein Decreases Low-Density Lipoprotein Cholesterol by Stabilizing Low-Density Lipoprotein Receptor and Protects Against Atherosclerosis.

BACKGROUND: High blood cholesterol accelerates the progression of atherosclerosis, which is an asymptomatic process lasting for decades. Rupture of atherosclerotic plaques induces thrombosis, which results in myocardial infarction or stroke. Lowering cholesterol levels is beneficial for preventing atherosclerotic cardiovascular disease. METHODS: Low-density lipoprotein (LDL) receptor (LDLR) was used as bait to identify its binding proteins in the plasma, and the coagulation factor prekallikrein (PK; encoded by the KLKB1 gene) was revealed. The correlation between serum PK protein content and lipid levels in young Chinese Han people was then analyzed. To investigate the effects of PK ablation on LDLR and lipid levels in vivo, we genetically deleted Klkb1 in hamsters and heterozygous Ldlr knockout mice and knocked down Klkb1 using adeno-associated virus-mediated shRNA in rats. The additive effect of PK and proprotein convertase subtilisin/kexin 9 inhibition also was evaluated. In addition, we applied the anti-PK neutralizing antibody that blocked the PK and LDLR interaction in mice. Mice lacking both PK and apolipoprotein e (Klkb1-/-Apoe-/-) were generated to assess the role of PK in atherosclerosis. RESULTS: PK directly bound LDLR and induced its lysosomal degradation. The serum PK concentrations positively correlated with LDL cholesterol levels in 198 young Chinese Han adults. Genetic depletion of Klkb1 increased hepatic LDLR and decreased circulating cholesterol in multiple rodent models. Inhibition of proprotein convertase subtilisin/kexin 9 with evolocumab further decreased plasma LDL cholesterol levels in Klkb1-deficient hamsters. The anti-PK neutralizing antibody could similarly lower plasma lipids through upregulating hepatic LDLR. Ablation of Klkb1 slowed the progression of atherosclerosis in mice on Apoe-deficient background. CONCLUSIONS: PK regulates circulating cholesterol levels through binding to LDLR and inducing its lysosomal degradation. Ablation of PK stabilizes LDLR, decreases LDL cholesterol, and prevents atherosclerotic plaque development. This study suggests that PK is a promising therapeutic target to treat atherosclerotic cardiovascular disease.

IDOL G51S Variant Is Associated With High Blood Cholesterol and Increases Low-Density Lipoprotein Receptor Degradation.

OBJECTIVE: A high level of LDL-C (low-density lipoprotein cholesterol) is a major risk factor for cardiovascular disease. The E3 ubiquitin ligase named IDOL (inducible degrader of the LDLR [LDL receptor]; also known as MYLIP [myosin regulatory light chain interacting protein]) mediates degradation of LDLR through ubiquitinating its C-terminal tail. But the expression profile of IDOL differs greatly in the livers of mice and humans. Whether IDOL is able to regulate LDL-C levels in humans remains to be determined. Approach and Results: By using whole-exome sequencing, we identified a nonsynonymous variant rs149696224 in the IDOL gene that causes a G51S (Gly-to-Ser substitution at the amino acid site 51) from a Chinese Uygur family. Large cohort analysis revealed IDOL G51S carriers (+/G51S) displayed significantly higher LDL-C levels. Mechanistically, the G51S mutation stabilized IDOL protein by inhibiting its dimerization and preventing self-ubiquitination and subsequent proteasomal degradation. IDOL(G51S) exhibited a stronger ability to promote ubiquitination and degradation of LDLR. Adeno-associated virus-mediated expression of IDOL(G51S) in mouse liver decreased hepatic LDLR and increased serum levels of LDL-C, total cholesterol, and triglyceride. CONCLUSIONS: Our study demonstrates that IDOL(G51S) is a gain-of-function variant responsible for high LDL-C in both humans and mice. These results suggest that IDOL is a key player regulating cholesterol level in humans.

Discovery of a potent HMG-CoA reductase degrader that eliminates statin-induced reductase accumulation and lowers cholesterol.

Statins are inhibitors of HMG-CoA reductase, the rate-limiting enzyme of cholesterol biosynthesis, and have been clinically used to treat cardiovascular disease. However, a paradoxical increase of reductase protein following statin treatment may attenuate the effect and increase the side effects. Here we present a previously unexplored strategy to alleviate statin-induced reductase accumulation by inducing its degradation. Inspired by the observations that cholesterol intermediates trigger reductase degradation, we identify a potent degrader, namely Cmpd 81, through structure-activity relationship analysis of sterol analogs. Cmpd 81 stimulates ubiquitination and degradation of reductase in an Insig-dependent manner, thus dramatically reducing protein accumulation induced by various statins. Cmpd 81 can act alone or synergistically with statin to lower cholesterol and reduce atherosclerotic plaques in mice. Collectively, our work suggests that inducing reductase degradation by Cmpd 81 or similar chemicals alone or in combination with statin therapy can be a promising strategy for treating cardiovascular disease.

The interleukin 3 gene (IL3) contributes to human brain volume variation by regulating proliferation and survival of neural progenitors.

One of the most significant evolutionary changes underlying the highly developed cognitive abilities of humans is the greatly enlarged brain volume. In addition to being far greater than in most other species, the volume of the human brain exhibits extensive variation and distinct sexual dimorphism in the general population. However, little is known about the genetic mechanisms underlying normal variation as well as the observed sex difference in human brain volume. Here we show that interleukin-3 (IL3) is strongly associated with brain volume variation in four genetically divergent populations. We identified a sequence polymorphism (rs31480) in the IL3 promoter which alters the expression of IL3 by affecting the binding affinity of transcription factor SP1. Further analysis indicated that IL3 and its receptors are continuously expressed in the developing mouse brain, reaching highest levels at postnatal day 1-4. Furthermore, we found IL3 receptor alpha (IL3RA) was mainly expressed in neural progenitors and neurons, and IL3 could promote proliferation and survival of the neural progenitors. The expression level of IL3 thus played pivotal roles in the expansion and maintenance of the neural progenitor pool and the number of surviving neurons. Moreover, we found that IL3 activated both estrogen receptors, but estrogen didn't directly regulate the expression of IL3. Our results demonstrate that genetic variation in the IL3 promoter regulates human brain volume and reveals novel roles of IL3 in regulating brain development.

A common SNP of MCPH1 is associated with cranial volume variation in Chinese population.

Microcephaly (MCPH) genes are informative in understanding the genetics and evolution of human brain volume. MCPH1 and abnormal spindle-like MCPH associated (ASPM) are the two known MCPH causing genes that were suggested undergone recent positive selection in human populations. However, previous studies focusing only on the two tag single nucleotide polymorphisms(SNPs) of MCPH1 and ASPM failed to detect any correlation between gene polymorphisms and variations of brain volume and cognitive abilities. We conducted an association study on eight common SNPs of MCPH1 and ASPM in a Chinese population of 867 unrelated individuals. We demonstrate that a non-synonymous SNP (rs1057090, V761A in BRCA1 C-terminus (BRCT) domain) of MCPH1 other than the two known tag SNPs is significantly associated with cranial volume in Chinese males. The haplotype analysis confirmed the association of rs1057090 with cranial volume, and the homozygote males containing the derived alleles of rs1057090 have larger cranial volumes compared with those containing the ancestral alleles. No recent selection signal can be detected on this SNP, suggesting that the brain volume variation in human populations is likely neutral or under very weak selection in recent human history.

[Change of vascular endothelial growth factor and its receptors expression in acute myeloid leukemia before and after treatment].

OBJECTIVE: To explore the role of angiogenesis in bone marrow in acute myeloid leukemia (AML). METHODS: Bone marrow culture supernatant was assayed for vascular endothelial growth factor (VEGF) by ELISA, bone marrow biopsies from 28 newly diagnosed AML patients were assayed for microvessel density (MVD), VEGF and its receptors KDR, Flt-1 by immunohistochemical staining before and after induction chemotherapy. RESULTS: Culture supernatant of AML bone marrow mononuclear cells showed higher amount of VEGF (425.31 ng/L) than that of control (140.12 ng/L). The VEGF and KDR expressions and MVD were significantly higher in newly diagnosed AML patients (78.6%, 78.6% and 7.1%, respectively) than that of control group (P < 0.05). There was a positive correlation between VEGF, KDR and MVD. The positive rate of VEGF, KDR and MVD reduced to normal after the patients achieved complete remission, while in non-remission patients did not. Kaplan-Meier analysis showed that the survival time was longer in VEGF negative group than in VEGF positive group. The pre-treatment MVD and VEGF had no correlation with survival time. CONCLUSIONS: There is remarkable angiogenesis in AML and VEGF/KDR signaling pathway takes an important role in the pathological angiogenesis. VEGF could be used as a prognostic factor in AML.