Assocoation Between Serum β-Sheet Level And Coronaryartery Heart Disease

BackgroundWith the change of life style and the increase of average life expectancy,coronary artery heart disease(CHD)has become one of the chronic diseases with high morbidity and mortality worldwide.According to China Cardiovascular Health and Disease Report 2020,the number of patients with cardiovascular disease in China has exceeded 290 million,and there are about 11.39 million patients with CHD,and the prevalence of CHD in China is on the rise,with an annual growth rate of 20%.CHD is the second leading cause of death in China and the second leading cause of premature death.A large number of clinical trials have fully confirmed that low density lipoprotein cholesterol(LDL-C)is the most important risk factor of atherosclerosis,promoting the occurrence and development of CHD.However,patients with CHD still have a higher risk of residual vascular disease after active lifestyle improvement,lipid-lowering therapy,blood pressure management and antiplatelet therapy.It has been found that the risk of cardiovascular disease depends on the number of lipoprotein cholesterol particles in circulation,and relevant guidelines have always regarded LDL-C as the primary goal to determine the risk of cardiovascular disease and evaluate lipid-lowering treatment.However,patients still experience adverse cardiovascular events in a portion of the population even after aggressive application of statins or even PCSK9 inhibitors to achieve the LDL-C target,or even control LDL-C at 30 mg/dL.Therefore,looking for risk factors other than elevated LDL-C to reduce the risk of remaining vascular disease is the key to the prevention and treatment of CHD.β-sheet of proteins is one of the most basic structures for proteins to function and participate in life activities,but β-sheet-rich misfolded proteins can lead to abnormal cell function and even death.Misfolded proteins have long been studied in the pathogenesis of neurodegenerative diseases.X-ray powder diffraction patterns have comfirmed that the abundant β-sheet of ApoB in atherosclerosis had the same pathogenic antiparallel structure as Aβ in Alzheimer’s disease.In addition,β-sheet-rich misfolded proteins are prone to form amyloid fibers,which is associated with the conversion of macrophages to a pro-inflammatory phenotype,the increment of reactive oxygen species,and the inflammatory response of atherosclerosis.It has been shown that the initial LDL-C does not cause foaming of macrophages,that is,it does not initiate atherosclerosis,due to the negative feedback regulation mechanism of intracellular cholesterol levels at the low-density lipoprotein receptor(LDLR).However,after oxidative modification of LDL-C,the negative feedback regulation of intracellular cholesterol levels disappears,and the modified LDL-C is continuously taken up by macrophages,which is excessively accumulated in cells to form foam cells.ApoB-100 is the main structural protein of LDL.Pentagonal ApoB-100 is composed of alternating α-helix and β-sheet domains.The β-sheet region of ApoB-100 will be the key structural region to maintain the integrity of LDL.Furthermore,the α2 domain of ApoB-100 is prone to transform from α-helix to a more structurally stable β-sheet during LDL-C oxidation,leading to an increase content of β-sheet in ox-LDL-C.Circular dichroism analysis showed that the α-helix content of LDL-C involved in atherosclerosis(33.5%)was significantly lower than that of natural LDL-C(93.2%),while the β-sheet content of oxidatively modified LDL-C(16.4%)was significantly higher than that of natural LDL-C(6.2%).Therefore,the content of β-sheet in LDL-C can reflect its modification level.In combination with Hierarchical Cluster Analysis(HCA),Fourier Transform Infrared Spectroscopy(FT-IR)technology found that,in ApoE-/-/LDLR-/-mice,the secondary structure of proteins in atherosclerotic vessel wall tissue was changed,and the content ofβ-sheet in conformation was significantly increased,especially in the lesion plaque and middle membrane region,while the content of α-helix was generally decreased,suggesting that there were a large number of misfolded proteins in the lesion region that could not be removed.Therefore,we hypothesized that elevated serum β-sheet level may be a risk factor for atherosclerosis.In patients with CHD,the β-sheet level of serum proteins was increased,and the deposition of β-sheet-rich LDL-C promoted the occurrence and development of CHD.This study will explore the correlation between serum β-sheet level and CHD,and analyze various risk factors affecting serum β-sheet level.Objectives(1)Analysis of the relationship between serum β-sheet level and CHD;(2)To explore various risk factors affecting serum β-sheet level.Study methodsA total of 223 patients with CHD(stenosis of at least 1 or more major coronary arteries≥50%in diameter)admitted to Qilu Hospital of Shandong University from June 2018 to June 2019 and 56 normal people who received physical examination in Qilu Hospital of Shandong University during the same period were selected as the research objects.Gender,age,blood pressure,heart rate,body mass index,smoking,drinking,hypertension,diabetes,hyperlipidemia,past myocardial infarction,physical examinations and blood specimens were collected.Serum protein β-sheet content was determined by thioflavin T fluorescence.SPSS 24.0 was used to analyze data.Results(1)Compared with the normal control group,male,systolic blood pressure,diastolic blood pressure,BMI,smoking history rate,drinking history rate,hypertension history rate,diabetes history rate,hyperlipidemia history rate,white blood cell count,red blood cell count,ALT,TG,sdLDL-C,ALB,PA,Glu,Cr,Hcy,UA and cTnI were significantly increased in CHD group(P<0.05～0.01).The heart rate,TC,VLDL,HDL-C,LDL-C,C1q and LDH were statistically significantly lower than those of the control group(P<0.05～0.01).(2)Compared with the normal control group,serum ThT fluorescence intensity in the CHD group was significantly increased,as well as after correction for LDL-C,small dense LDL-C(sdLDL-C)and total cholesterol(TC)(P<0.05～0.01).After removing the fluorescence effect of albumin,the fluorescence intensity of the CHD group was still significantly higher than that of the control group,as well as after correction for LDL-C,sdLDL-C and TC(P<0.05～0.01).These results suggested that the serum β-sheet level was increased in patients with CHD.(3)The level of serum β-sheet was positively correlated with Waist-to-Hip Ratio(WHR)(β=2.636,P＜0.001),age(β=0.014,P＜0.001),heart rate(β=0.007,P<0.001),diastolic blood pressure(β=0.004,P<0.05),glycosylated hemoglobin(HbA1C)(β=0.511,P<0.001),low density lipoprotein cholesterol(LDL-C)(β=0.216,P<0.01),sodium(Na)(β=0.026,P<0.001),white blood cell(WBC)(β=0.037,P<0.01)and lactic dehydrogenase(LDH)(β=0.001,P<0.05),as well as with the history of hypertension(β=2.332,P<0.001),smoking(β=2.054,P<0.001),diabetes(β=1.204,P<0.001),hyperlipidemia(β=1.078,P<0.01)and family history of CHD(β=1.149,P<0.01).(4)Serum β-sheet level(OR=27.28,P<0.01),sex(OR=2.830,P<0.05),systolic blood pressure(OR=1.057,P<0.001),triglyceride(TG)(OR=15,926,P<0.001),glucose(Glu)(OR=1.545,P<0.05)and homocysteine(Hcy)(OR=1.105,P<0.05)were independent risk factors for CHD.C1q(OR=0.972,P<0.001)was a protective factor for CHD.The above results showed that the serum β-sheet level was an independent risk factor for CHD.Conclusions(1)The serum β-sheet level was increased in patients with CHD.(2)CHD patients with a history of hypertension,smoking,diabetes,hyperlipidemia,and a family history of CHD were more likely to have elevated serum β-sheet levels in increased age,diastolic blood pressure,waist-to-hip ratio,heart rate,and elevated levels of HbA1C,LDL-C,Na,WBC,and LDH.(3)The serum β-sheet level was an independent risk factor for CHD,and independent of known risk factors such as LDL-C.