Prevalence of hyperhomocysteinaemia in chronic kidney disease and ...

ORIGINAL ARTICLE

JIACM 2013; 14(1): 33-6

Prevalence of hyperhomocysteinaemia in chronic kidney disease and effect of supplementation of folic acid and vitamin B12 on cardiovascular mortality N Nand*, M Sharma**, N Mittal***

Abstract Objectives: Cardiovascular disease (CVD) mortality is 16-times more in cases of chronic kidney disease (CKD). Elevated plasma homocysteine is an important risk factor for increased cardiovascular morbidity and mortality. It is elevated in 85 to 100% patients of CKD and can be an important modifiable risk factor for increased CVD risk. The present study was undertaken to see homocysteine levels in CKD and effect of folic acid and B12 supplementation on homocysteine and cardiovascular outcome. Methods: A randomised placebo-controlled trial on 100 cases was carried-out at our tertiary care hospital from May 2009 to November 2010. Adult patients of CKD having glomerular filtration rate (GFR) < 60ml/min were enrolled for the study. Patients were randomly assigned into two groups. Control group was given placebo and the interventional group was given folic acid and vitamin B12 supplementation for 6 months. Results: Mean baseline homocysteine levels were similar in the two groups. It was 32.61 µmol/L in the interventional group and 29.48 µmol/L in the placebo group (p > 0.05). The level decreased significantly to 19.69 µmol/L (p 0.05) in the placebo group after 6 months. The homocysteine level had a negative corelation with haemoglobin (r = -0.19), GFR (r = - 0.16), folic acid (r = -0.19) and vitamin B12 (r = -0.35). There was no significant effect on total mortality, deaths due to CVD, total ischaemic events, hospitalisation due to unstable angina, heart failure, or venous thrombotic events after 6 months of supplementation therapy. Conclusion: Serum homocysteine is elevated in patients of CKD. Folic acid and vitamin B12 supplementation lowered homocysteine, but it did not reduce cardiovascular disease mortality. Key words: Glomerular filtration rate, unstable angina, venous thrombotic events.

Introduction Patients of CKD are at higher risk of mortality from cardiovascular disease1. Homocysteine is an independent risk factor for CVD 2 . In people with CKD, plasma homocysteine levels tend to increase with decreasing GFR3 and may reach high levels in end-stage renal disease4. Folic acid, vitamin B12, and vitamin B6 play a critical role in the metabolism of homocysteine 5 . Although epidemiological studies have confirmed the association between homocysteine and cardiovascular risk, interventional studies designed to lower homocysteine have not shown any consistent benefit on clinical outcomes6,7. Several randomised control trials of lowering homocysteine with folic acid and B vitamins failed to find any reduction of major cardiovascular events or death in high risk patients6,7. However, most of the studies done were in Caucasian population8. There are no data available regarding their role in Indian population8. The present study was therefore conducted to evaluate the prevalence of hyperhomocysteinaemia in CKD patients and to see the effect of supplementation of folic acid and vitamin

B12 on homocysteine level and CVD mortality in these Indian patients.

Materials and methods This was a randomised placebo-controlled trial carried over the period from May 2009 till November 2010. It included 100 adult patients of CKD having GFR < 60 ml/ min/1.73m2. Patients taking vitamin supplementation more than 2.5 mg of folic acid and normal homocysteine level were excluded from the study. Pre-informed consent was obtained in each case and patients were divided into two group. Group A (interventional group) included 50 patients and they were given daily supplementation of 2.5mg folic acid, 50mg vitamin B6 and 1.5mg of vitamin B12, whereas Group B (control group) patients were given placebo. All the patients were examined in detail and all basal laboratory investigations were done with a special emphasis on renal and cardiovascular parameters. Serum homocysteine, vitamin B12 and folic acid were measured at baseline, at 3 months and at 6 months alongwith other renal parameters.

* Senior Professor & Head, Department of Nephrology, ** Formerly Associate Professor of Biochemistry, *** Resident, Department of Medicine, Pandit B.D. Sharma Post-Graduate Institute of Medical Sciences (PGIMS), Rohtak, Haryana.

Patients were evaluated every month for adherence to treatment, adverse effects, and clinical outcome. Homocysteine, vitamin B12 and folic acid levels were measured by ADVIA CENTOUR CP model using Siemen’s kit.9 Data was analysed by using student t – test (paired and unpaired), chi-square test and Pearson’s correlation coefficient (r). Paired t-test was used for comparison within the same group and unpaired t-test was used for comparison in between two groups.

Results The age of the patients ranged from 20 - 80 years.The mean age of the patients in group A was 50.48 ± 12.45 years and it was 46.68 ± 14.94 years in group B. There were 66 men and 34 women. Chronic glomerulonephritis was the commonest cause (46.6%), followed by diabetic nephropathy (15%). Anaemia was present in all the patients (mean Hb 9.38gm%) and was more severe in stage 5 CKD. There were 18 patients on dialysis in group A, and 16 in group B. Baseline biochemical parameters of two groups were alike/comparable and are shown in Table I. Homocysteine levels were elevated in 94.4% of the patients. Serum homocysteine levels decreased significantly (Fig. 1) in group A (interventional group) from 32.61 µmol/l to 23.64 µmol/l at 3 months (p < 0.001) and 19.69 µmol/l at 6 months (p < 0.001). In group B (control group) homocysteine continued to increase from 29.48 µmol/l at baseline to 30.13 µmol/l at 3 months (p > 0.05) and 34.41 µmol/l at 6 months (p > 0.05). The rise was more in patients receiving renal replacement therapy (RRT) in group B from 32.28 µmol/l at baseline to 33.58 µmol/l at 3 months (p < 0.05) and 41.25 µmol/l at 6 months (p < 0.05) in comparison to patients of group B, who were not receiving RRT (p > 0.05). The homocysteine levels had negative co-relation (Fig. 2 & 3) with haemoglobin (r = -0.19), GFR (r = - 0.16), folic acid (r = -0.19) and vitamin B12 (r = -0.35). The p value was significant with vitamin B12 (p < 0.05).

Fig. 2: Showing negative correlation of homocysteine with GFR.

Table I: Baseline characteristics of the participants in the two groups.

Age (years) Sex (M:F) Patients on RRT SBP (mmHg) DBP (mmHg) Haemoglobin (gm%) Blood urea (mg%) Serum creatinine (mg%) Serum uric acid (mg%) GFR (ml/min/1.73m2) Serum calcium (mg%) Serum phosphorus (mg%)

Group A

Group B

Unpaired p value

50.48 ± 12.45 32:18 18 138 ± 22.32 86.04 ± 11.68 9.38 ± 1.74 108.87 ± 52.25 4.45 ± 3.58 7.96 ± 2.32 15.92 ± 12.51 9.06 ± 0.86 5.07 ± 1.47

46.68 ± 14.94 34:16 16 140.44 ± 26.44 88.76 ± 15.97 9.89 ± 1.86 105.78 ± 51.69 4.50 ± 3.09 7.85 ± 2.23 17.77 ± 14.22 8.98 ± 0.91 5.64 ± 2.24

> 0.05 > 0.05 > 0.05 > 0.05 > 0.05 > 0.05 > 0.05 > 0.05 > 0.05 > 0.05 > 0.05 > 0.05

SBP = Systolic blood pressure; DBP = Diastolic blood pressure.

Fig. 1: Showing homocysteine levels at the onset of the study and after 3 and 6 months of supplementation/placebo therapy.

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Serum folic acid levels were within the normal range in both the groups (Table II). Following supplementation, folic acid levels increased significantly in Group A both at 3 months and at 6 months (p < 0.001), while there was no significant change observed in folic acid levels of control group (p > 0.05). There was a significant fall in folic acid level in group B patients who were on RRT (p < 0.05). Serum vitamin B12 levels were in lower range in both the groups. Following supplementation, B12 levels increased significantly in Group A – both at 3 months (p < 0.001), and at 6 months (p < 0.001), while there was no significant

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Table III: Clinical events at 6-months follow-up in the two groups. Clinical events

Group A

Group B

Unpaired p value

Total no. of deaths Death from CVD Total ischaemic events Hospitalisation due to USA Hospitalisation due to CHF Venous thrombotic events

10 3 6 3 3 0

11 4 7 4 3 0

> 0.05 > 0.05 > 0.05 > 0.05 > 0.05 > 0.05

Discussion

Fig. 3: Showing negative correlation of homocysteine with vitamin B12.

change in control group (p > 0.05).There was no significant difference observed in blood urea, serum creatinine, and GFR during follow-up in any group. Table II: Plasma concentration of homocysteine, folic acid, and vitamin B12 at baseline, at 3 months, and at 6 months. Parameters

Group A

Group B

Unpaired p value

Homocysteine (µmol/l) Baseline 32.61±14.14 3 months 23.64±11.84* 6 months 19.69±8.41*

29.48±13.89 30.13±13.41** 34.41±12.2**

>0.05