Construction Of Biological Age Equation And Evaluation Of Kidney Aging In Healthy Population

Background: Kidney aging is accompanied with series of functional and structural changes.The prevention of kidney function decline may be one of the key determinants of successful aging.Stem cell factor(SCF),also called as c-kit,is found to participate in organ reconstruction and fibrosis of various diseases.However,whether SCF participates in the kidney aging is unkown.Kidney is a high-flow organ and associated with cardiovascular system.The decreasing function of cardiovascular system is one of the inducements of kidney diseases,while kidney diseases also increase the mortality of cardiovascular diseases patients.Brachial-ankle pulse wave velocity(ba PWV)is a measurement of pulse wave velocity.Some researchers reported a close relation between ba PWV and kidney function in aging.While others found no correlation between them.Aging is a complex physical process.Chronological age is often used to evaluate aging status.Because aging is an individual process,biological age(BA)has been proposed to evaluate the aging status in an objective way instead of chronological age(CA).Objective:(1)We investigated the relationship of stem cell factor and the renal function in the ageing process,and we tried to find new biomarkers of kidney ageing.(2)We aimed to investigate the association between renal function and arterial stiffness in a Chinese Han population.(3)The purpose of our study is to construct a precise formula of BA based on a large sample of our studies.Method:(1)In the first part,we collected the data of serum SCF,e GFR and other biological indicators in a population of 892 Chinese in 2014 as baseline and 289 Chinese in 2016 as follow-up.In the cross-sectional analysis,correlation analysis and multiple linear regression were done to select potential indicators to estimate renal function decline.In the longitudinal analysis,we discussed the relations between SCF and e GFR among different genders and age groups.(2)In the second part,we collected the data of the brachium-ankle pulse wave velocity(ba PWV),blood pressure,blood chemistry and so on.Then,the multiple linear regression was done to explore the relationship between estimated glomerular filtration(e GFR)and ba PWV.Further,the parameters were compared among the four groups divided according to the quartiles of ba PWV.(3)In the third part,a total of 1,316 healthy Chinese(age range,23-93 years)were recruited from Beijing in China,including 563 males and 753 females.Physical examination,blood routine,and other lab tests were performed to obtain a total of 100 clinical variables.Then,principal component analysis(PCA)was used to select variables and estimate BA.Results:(1)In cross-sectional study,only chronological age and SCF were left(|r|>0.30 and P<0.05).When age increases,e GFR decreases and SCF increases.In longitudinal anlysis,people with SCF increasing displayed a trend of e GFR decreasing.(2)ba PWV was associated with e GFR in the correlation analysis and univariate linear regression model,but after adjustment,the pulse pressure instead of ba PWV showed a significant association with e GFR;Some blood lipids do not vary according to ba PWV.(3)BA formula was constructed as follows: BA = 0.293(pulse pressure)-0.266(digital symbol test)+ 0.758(diameter of ascending aorta)– 6.118(mitral valve E/A peak)+ 12.61(minimum intima-media thickness)– 6.916(25% of maximal expiratory flow)+ 0.277(CA)+ 20.51.The BA values accelerate faster in the middle-aged population than in the elderly population(>60 years).Conclusion:(1)SCF is an ideal biomarker of renal aging and estimated the changes of e GFR with age in the aging process.(2)PP but not ba PWV is a predictor of declined renal function.(3)This BA formula can reflect health condition changes of aging in a Chinese population.