DOI: https://doi.org/10.21203/rs.3.rs-1914108/v1
This cross-sectional study aimed to investigate the association between plasma homocysteine (Hcy) and chronic kidney disease (CKD) in US patients with type 2 diabetes mellitus (T2DM).
We used data from the 2003–2006 National Health and Nutritional Examination Surveys (NHANES). CKD was defined as an estimated glomerular filtration rate < 60 ml/min/1.73 m2 and/or urinary albumin-creatine ratio ≥ 3 mg/mmol.
This study included 1018 patients with T2DM. The mean Hcy value was 10.2 ± 4.6 µmol/L. Among the patients, 417 (40.96%) had Hyperhomocysteine (HHcy) and 480 (47.15%) had CKD. The Hcy level was higher in patients with CKD than in those without CKD. Compared with patients with normal Hcy, those with HHcy were older and had worse renal function. After full multivariate adjustment, HHcy was positively associated with the risk of CKD in US patients with T2DM (OR, 1.17; 95% CI, 1.11–1.22; P < 0.001). The odds ratio for CKD was 1.15 (95% CI, 1.08 ~ 1.23; P < 0.001) in women and 1.18 (95% CI, 1.1 ~ 1.27; P < 0.001) in men.
HHcy was independently associated with CKD in patients with T2DM. Further prospective studies are warranted to investigate the effect of Hcy on CKD in patients with T2DM.
Type 2 diabetes mellitus (T2DM) is the most common type of diabetes and accounts for over 90% of all diabetes cases worldwide. An estimated 537 million adults aged 20–79 years worldwide (10.5% of all adults in this age group) have diabetes according to the latest International Diabetes Federation (IDF) Diabetes Atlas.1 Up to 40% of patients with diabetes also develop chronic kidney disease (CKD). T2DM patients with CKD also account for most patients with ESKD globally, and CKD is associated with high morbidity, mortality, and poor quality of life.2 The progression of CKD can lead to end-stage kidney disease (ESKD), where patients require either dialysis or a kidney transplant for survival.3 In addition, an increasing number of people are also at high risk of cardiovascular (CV) disease, including myocardial infarction, ischaemic stroke, and all-cause mortality.
Homocysteine (Hcy) may play a role in the development of cardiovascular (CV) diseases. The role of Hcy in the development of the vascular complications associated with DM is not clearly defined.4 The 2006 US Stroke guidelines clearly indicate that plasma Hcy > 10 µmol/L is defined as hyperhomocysteine (HHcy).5 HHcy can reflect the abnormal state of body methylation and vulcanization and can damage cells, tissues and organs.6 It is an important risk factor for the occurrence of many chronic diseases and is one of the important indicators of health risk, such as hypertension, hyperlipidaemia and hyperglycaemia.7 Hcy appears to cause endothelial damage and increase the activity and production of coagulation factors.8 Furthermore, several studies have found that Hcy is associated with eGFR and CKD in the general population.9 However, few studies have reported the association between Hcy and CKD in patients with diabetes.
The aim of this study was to assess the association between Hcy and CKD in T2DM patients in a cross-sectional study while adjusting for various confounding factors that can affect the progression to CKD.
A NHANES dataset was used for this study. NHANES is a nationwide population-based survey of the US that has been conducted since 1999 to assess the health and nutritional status of the US population. For the present study, NHANES data from surveys conducted in 2003–2004 and 2005–2006 surveys used because the two cycles measured plasma homocysteine. Of a total of 16,625 patients, 1112 type 2 diabetes patients were included in this study. A total of 74 patients younger than 18 and older than 80 were excluded. Twenty patients were excluded because 16 had missing data on Hcy and 4 had missing data on eGFR. Finally, the data obtained from 1018 participants were employed for this study (Fig. 1). NHANES was approved by the US National Center for Health Statistics Research Ethics Review Board, and all participants provided informed consent.
We evaluated both clinical characteristics (sex, age, and race) and biochemical parameters (levels of triglycerides [TG], cholesterol [CHO], albumin [ALB], blood urea nitrogen [BUN], serum creatinine [Scr], uric acid [UA], HbA1c, urinary albumin-creatinine ratio [ACR] and plasma homocysteine [Hcy]) collected from the NHANES Laboratory Data. The TG, CHO, ALB, BUN, Scr, and UA analyses were performed using a Beckman Synchron LX20 (Beckman Coulter, Inc).HbA1c measurements were performed by the Diabetes Laboratory at the University of Minnesota using a Tosoh A1c 2.2 Plus Glycohemoglobin Analyser (Tosoh Medics, Inc., San Francisco, CA). Hcy in plasma was measured by the Abbott Homocysteine (Hcy) assay, which is a fully automated fluorescence polarization immunoassay (FPIA) from Abbott Diagnostics.
The albumin in the urine was measured via a fluorescent immunoassay. The urinary creatinine analysis uses a Jaffé rate reaction, in which creatinine reacts with picrate in an alkaline solution to form a red creatinine-picrate complex.
We used ACR and eGFR values as parameters to determine CKD.10 To calculate the eGFR, the following CKD-EPI formula was applied11:
eGFR CKD−EPI (mL/min/1.73 m2)
GFR = a × (Scr/b)c × (0.993)age
In this formula, Scr denotes the serum creatinine level (µmol/L);a is 166 for black females and 163 for males;a is 144 for non-black females and 141 for males; b is 0.7 for females and 0.9 for males, and c is − 0.329 for females with serum creatinine ≤ 62 µmol/L and − 0.411 for males with serum creatinine ≤ 80 µmol/L. c is -1.209 for females with serum creatinine ≥ 62 µmol/L and for males with serum creatinine ≥ 80 µmol/L. The ACR was calculated as the urinary albumin/creatinine ratio. Participants with an ACR above 3 mg/mmoL or an ALFF below 60 mL/min/1.73 m2 were classified as CKD patients according to the Kidney Disease Outcome Quality Initiative clinical practice guidelines for CKD.
Data are presented as the mean ± standard deviation (SD) for normally distributed variables or the median (interquartile range) for nonnormally distributed variables and as the frequency or percentage for categorical variables. For the baseline characteristics analysis, the significant differences between two groups were tested based on t test, nonparametric tests for continuous variables and chi-square or Fisher tests for categorical variables. Multiple logistic regression analysis was performed to evaluate the associations between Hcy and CKD, with the results expressed as odds ratios (ORs) and 95% confidence intervals (CIs). The covariates entered into the model were based on univariate analyses and a literature review.12 All analyses were performed using R Statistical Software (http://www.R-project.org, The R Foundation) and the Free Statistics analysis platform. P values < 0.05 (two-tailed) were considered statistically significant.
The baseline clinical characteristics of the included patients are summarized in Table 1. The mean age of the included patients was 59.9 ± 13.1 years, and 51.2% were male. Of all patients, 480 (47.1%) had CKD. Patients with CKD were older (P < 0.001). Levels of Hcy (P < 0.001), ACR (P < 0.001), Scr (P < 0.001), BUN (P < 0.001) and UA (P < 0.001) were higher in patients with CKD than in those without CKD. No significant differences were found in the proportion of Race, HbA1c, TG and CHO between the two groups. Table 2 compares the characteristics of the normal plasma homocysteine and hyperhomocysteinemia groups in which the plasma homocysteine concentration exceeded 10 µmol/L. Compared with patients with normal Hcy, those with HHcy were older (P < 0.001). They also had higher levels of ACR and worse renal function (P < 0.001) but had lower HbA1c (P < 0.001) and CHO (P = 0.002).
Table 3 shows the results of the univariate logistic regression analysis for the associations between Hcy and CKD. In the multivariate model that included age, race, HbA1c, ALB, CHO, TG and UA, the prevalence of CKD increased with increasing Hcy in all patients (OR, 1.17; 95% CI, 1.11–1.22; P < 0.001). For male and female patients, the ORs for CKD all tended to increase with increasing Hcy levels (male OR, 1.18; 95% CI, 1.1 ~ 1.27; P < 0.001; female OR, 1.15; 95% CI, 1.08 ~ 1.23; P < 0.001). Figure 2 shows the homocysteine plasma levels at different stages of renal impairment in type 2 diabetes. Significant differences were observed among the five groups (P < 0.001), and the mean value of Hcy in the CKD5 stage was the highest.
In this cross-sectional study of 1018 patients with T2DM, we investigated the association between Hcy and the prevalence of CKD. We found that the prevalence of CKD in T2DM patients increased with increasing Hcy, independent of age, race, sex, and other clinical variables. To our knowledge, this is the first study with a large patient population to demonstrate the association between Hcy and CKD in US patients with T2DM. Previously, diabetes, hypertension, hyperuricaemia, obesity, and hyperlipidaemia were identified as risk factors for CKD.Except for Hcy, our study showed that male sex, age, UA, TG, and HbA1c were associated with CKD. However, the associations among HbA1c, TG, and CKD were not significant.
In the last 10 years, Hcy has been regarded as a marker of cardiovascular disease and a definite risk factor for many other diseases. HHcy is a trigger for many diseases, such as atherosclerosis, congestive heart failure, age-related macular degeneration, Alzheimer’s disease and hearing loss.13 Several previous reports have assessed the association between Hcy and CKD. Li reported that Hcy is associated with tubular interstitial lesions in the early stages of IgA nephropathy.14 Wang found that HHcy was more prevalent in patients with IgA nephropathy than in patients with other primary glomerular diseases, especially in the early stages of CKD, and may be a predictor of accelerated decline in renal function and future incidence of CKD.15 Spence has shown that Hcy plays a significant role in the effect of renal dysfunction on atherosclerosis.16
Diabetes mellitus is the most common cause of CKD. The hemodynamic changes and abnormal glucose metabolism caused by hyperglycemia are the basis of renal damage.However, The exact mechanisms underlying the association between HHcy and renal disease progression are not fully understood. Possible reasons are that HHcy inhibits vasodilation of renal arteries, promoting acceleration of progression of renal damage, and promotes sclerotic process in glomeruli.17–19 Increasing evidence indicates that the potential causes of Hcy excretion are reduced in CKD patients.20Fig. 2 indicates that renal function gradually deteriorated with increasing Hcy levels. An Israeli study found that subjects with homocysteine > 15 µmol/L were more likely to have an eGFR < 60 ml/min and proteinuria. At a GFR < 60 ml/min, homocysteine was progressively elevated in stages 3 and 4 of CKD.9,21 This is consistent with our findings.It was found that the greater the duration of T2DM, the higher the levels of Hcy in the plasma.
This study had several limitations. First, this was a retrospective cross-sectional study that did not confirm the causal relationship between Hcy and CKD in patients with T2DM. Second, the covariates in this study did not include medications that might affect the results of Hcy detection.
Nevertheless, the strength of this study is the relatively large sample size in patients with T2DM. This study provides useful and convincing epidemiological evidence for the association between Hcy and CKD in patients with T2DM. In conclusion, Hcy was found to be independently associated with CKD in patients with T2DM. In the future, a prospective cohort study needs to be conducted to further investigate the impact of Hcy on CKD in patients with T2DM.
Acknowledgements
We gratefully thank Dr. Jing Hu of Beijing Institute of Traditional Chinese Medicine for her contribution to the study design and comments regarding the manuscript.
Authors’ contributions
Zilong Shen contributed to the conception and design, wrote the manuscript, contributed to the research data discussion, reviewed the data and wrote the initial draft. Zhengmei Zhang contributed to the research data and editing. Wenjing Zhao contributed to the conception, design and critical review of the manuscript.
Funding
Natural Science Foundation of Beijing.The funding source had no involvement in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication.
Availability of data and materials
Data can be downloaded from the ‘NHANES’database (https://www.cdc.gov/nchs/nhanes/index.htm).
Ethics approval and consent to participate
NHANES study protocols were approved by the research ethics review board of the National Center for Health Statistics. Written informed consent was obtained from the legal guardians of participants younger than 18 years of age.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Table 1. Characteristics of the study participants grouped by CKD status
|
Variables |
Total (n = 1018) |
0 (n = 538) |
1 (n = 480) |
p |
|
Male, n (%) 521 (51.2) |
249 (46.3) |
272 (56.7) |
0.001 |
|
|
Age, years |
59.9 ± 13.1 |
57.0 ± 13.3 |
63.1 ± 12.0 |
< 0.001 |
|
Race, n (%) |
|
|
0.114 |
|
|
Mexican American |
290 (28.5) |
162 (30.1) |
128 (26.7) |
|
|
Other Hispanic |
30 (2.9) |
18 (3.3) |
12 (2.5) |
|
|
Non-Hispanic White |
378 (37.1) |
207 (38.5) |
171 (35.6) |
|
|
Non-Hispanic Black |
278 (27.3) |
128 (23.8) |
150 (31.2) |
|
|
Other Race |
42 (4.1) |
23 (4.3) |
19 (4) |
|
|
HbA1c, % |
7.5 ± 1.8 |
7.4 ± 1.7 |
7.6 ± 1.9 |
0.091 |
|
ALB, g/L |
40.7 ± 3.7 |
41.2 ± 3.2 |
40.2 ± 4.1 |
< 0.001 |
|
BUN, mmol/L |
5.6 ± 3.2 |
4.6 ± 1.5 |
6.9 ± 4.0 |
< 0.001 |
|
Scr, μmol/L |
91.3 ± 55.1 |
73.7 ± 15.5 |
111.0 ± 73.7 |
< 0.001 |
|
eGFR, ml/min/1.73 m2 |
82.4 ± 39.7 |
94.4 ± 35.2 |
69.1 ± 40.1 |
< 0.001 |
|
ACR, mg/mmol |
1.6 (0.8, 5.1) |
0.9 (0.6, 1.5) |
5.4 (2.7, 15.6) |
< 0.001 |
|
CHO, mmol/L |
5.2 ± 1.3 |
5.2 ± 1.2 |
5.1 ± 1.4 |
0.305 |
|
TG, mmol/L |
2.2 ± 2.1 |
2.1 ± 1.9 |
2.3 ± 2.2 |
0.068 |
|
UA, μmol/L |
334.2 ± 94.3 |
310.0 ± 79.5 |
361.2 ± 101.9 |
< 0.001 |
|
Hcy, μmol/L |
10.2 ± 4.6 |
8.8 ± 3.0 |
11.8 ± 5.5 |
< 0.001 |
Abbreviations: CKD, chronic kidney disease; ALB, albumin; BUN, blood urea nitrogen; Scr, serum creatinine; ACR, albumin-creatinine ratio; CHO, cholesterol; TG, triglycerides; UA, uric acid; Hcy, plasma homocysteine concentrations.
Data are shown as the mean ± standard deviation, number (percentage) or median (interquartile range).
Table 2. Characteristics of the study participants grouped by with and without hyperhomocysteinemia
|
Variables |
Total (n = 1018) |
Normal Hcy (n = 601) |
HHcy (n = 417) |
p |
|
Male, n (%) 521 (51.2) |
271 (45.1) |
250 (60) |
< 0.001 |
|
|
Age, |
59.9 ± 13.1 |
56.0 ± 13.5 |
65.5 ± 10.0 |
< 0.001 |
|
Race, n (%) |
|
|
< 0.001 |
|
|
Mexican American |
290 (28.5) |
194 (32.3) |
96 (23) |
|
|
Other Hispanic |
30 (2.9) |
27 (4.5) |
3 (0.7) |
|
|
Non-Hispanic White |
378 (37.1) |
202 (33.6) |
176 (42.2) |
|
|
Non-Hispanic Black |
278 (27.3) |
148 (24.6) |
130 (31.2) |
|
|
Other Race |
42 (4.1) |
30 (5) |
12 (2.9) |
|
|
HbA1c, % |
7.5 ± 1.8 |
7.6 ± 1.9 |
7.2 ± 1.6 |
< 0.001 |
|
ALB, g/L |
40.7 ± 3.7 |
41.0 ± 3.3 |
40.4 ± 4.1 |
0.023 |
|
BUN, mmol/L |
5.6 ± 3.2 |
4.6 ± 1.5 |
7.2 ± 4.1 |
< 0.001 |
|
Scr, μmol/L |
91.3 ± 55.1 |
74.3 ± 18.6 |
116.0 ± 76.9 |
< 0.001 |
|
eGFR, ml/min/1.73 m2 |
91.3 ± 55.1 |
74.3 ± 18.6 |
116.0 ± 76.9 |
< 0.001 |
|
ACR, g/mmol |
1.6 (0.8, 5.1) |
1.3 (0.7, 3.6) |
2.5 (1.0, 10.1) |
< 0.001 |
|
CHO, mmol/L |
5.2 ± 1.3 |
5.3 ± 1.3 |
5.0 ± 1.3 |
0.002 |
|
TG, mmol/L |
2.2 ± 2.1 |
2.2 ± 2.2 |
2.2 ± 1.9 |
0.671 |
|
UA, μmol/L |
334.2 ± 94.3 |
306.9 ± 79.1 |
373.5 ± 100.4 |
< 0.001 |
Data are shown as the mean ± standard deviation, number (percentage) or median (interquartile range).
Table 3. Logistic regression analysis of Hcy in relation to CKD risk.
|
Variable |
Male |
|
Female |
|
Total |
|
|
OR (95% CI) |
P value |
OR (95% CI) |
P value |
OR (95% CI) |
P value |
|
|
Hcy |
|
|
|
|
|
|
|
Model 1 |
1.26(1.18~ 1.34) |
<0.001 |
1.2 (1.14~ 1.27) |
<0.001 |
1.23(1.18~ 1.29) |
<0.001 |
|
Mode 2 |
1.22(1.15~ 1.3) |
<0.001 |
1.17(1.11~ 1.24) |
<0.001 |
1.2 (1.15~ 1.25) |
<0.001
|
|
Model 3 |
1.18(1.1~ 1.27) |
<0.001 |
1.15(1.08~ 1.23) |
<0.001 |
1.17(1.11~ 1.22) |
<0.001 |
The data are presented as odds ratios (95% confidence intervals) and P values. Model 1: unadjusted; Model 2: adjusted for age and race; Model 3: adjusted for age, race, HbA1c, ALB, CHO, TG, and UA.