Plasma homocysteine levels in living kidney donors before and after uninephrectomy

Kidney function decline is associated with an accelerated increase in plasma homocysteine in older adults: a longitudinal study

Few studies have been conducted to investigate the association of kidney function decline with the trajectories of homocysteine (Hcy) over time, using repeated measurements. We aimed to investigate the association of kidney function with changes in plasma Hcy levels over time. Data were collected from the Rugao Longevity and Ageing Study. In detail, plasma Hcy and creatinine levels were measured in both waves (waves 2, 3 and 4) during the 3·5-year follow-up (n 1135). Wave 2 was regarded as the baseline survey. The estimated glomerular filtration rate (eGFR) was calculated based on creatinine. Subjects were categorised into four groups according to quartiles of eGFR at baseline. Linear mixed-effect models were used to investigate the association of eGFR with subsequent plasma Hcy levels. The mean eGFR at baseline was 90·84 (sd 11·42) ml/min per 1·73 m2. The mean plasma Hcy level was 14·09 (sd 6·82) at baseline and increased to 16·28 (sd 8·27) and 17·36 (sd 10·39) μmol/l during follow-ups. In the crude model, the interaction between time and eGFR at baseline was significant (β = -0·02, 95 % CI -0·02, -0·01, P = 0·002). After adjusting for confounding factors, a significant relationship remained (β = -0·02, 95 % CI -0·02, -0·01, P = 0·003), suggesting that kidney function decline at baseline was associated with a faster increase in Hcy levels. Kidney function decline is associated with a more pronounced increase in plasma Hcy levels. Further studies with longer follow-up periods and larger sample sizes are needed to validate our findings.

Homocysteine and diabetes: Role in macrovascular and microvascular complications

Diabetes mellitus (DM) can lead to the development of macro- and microvascular complications. Homocysteine (Hcy) may play a role in the development of cardiovascular (CV) diseases (CVDs). The role of Hcy in the development of the vascular complications associated with DM is not clearly defined. Despite a strong initial assumption regarding the importance of Hcy in DM and its complications, over time "enthusiasm has waned" because several studies showed unconvincing and occasionally contradictory results. A universal conclusion is not easy to draw given the diversity of studies (e.g. number of patients, design, folic acid and vitamin B status, ethnic differences, genetic background). For some complications, most results encourages further investigation. Impaired renal function is a major independent determinant of high total Hcy (tHcy) levels. However, the role of hyperhomocysteinaemia (HHcy) in the development of diabetic kidney disease (DKD) has yet to be determined. Hcy-lowering therapies can significantly decrease Hcy levels but their effects on CVD risk reduction are conflicting. Further studies are needed to determine the influence of Hcy-lowering therapy on CVD risk reduction, especially in patients with DM.

Assessment of long-term cardiovascular effects of unilateral nephrectomy

PURPOSE

There is conflicting evidence regarding long-term effects of unilateral nephrectomy such as cardiovascular diseases. Excessive increase in blood pressure (BP) during exercise called "hypertensive response to exercise" may be a sign of unborn hypertension and increased cardiovascular risk. Decrease in glomerular filtration rate (GFR) in patients with unilateral nephrectomy may be associated with disturbance of circadian BP changes without affecting the absolute levels of BP. We aimed to investigate the circadian BP changes and hypertensive response to exercise in normotensive patients with preserved renal functions who had undergone unilateral nephrectomy for other causes rather than organ donation.

METHODS

This study enrolled 32 patients (mean age 43.4 ± 9.9 years, male 15) with unilateral nephrectomy and 40 healthy controls (mean age 47 ± 6.1 years, male 17). All patients were undergone both office and ambulatory BP measurements and treadmill stress test.

RESULTS

The median time since nephrectomy was 12 (9-22) years in the patient group. The median GFR of the patient group was lower than that of the controls without significance [85.1 (76.0-97.9) vs. 93.2 (84.5-104.9), respectively; p = 0.14]. There was no significant difference between groups in terms of office BP measurements, night time diastolic and systolic BP, mean arterial pressure (MAP), night/day time ratio of MAP in ambulatory BP measurements. The results of treadmill stress tests and hypertensive response to exercise ratios were also similar between the groups.

CONCLUSION

This study revealed that there was no increase in long-term cardiovascular risks one decade after unilateral nephrectomy based on circadian BP changes and hypertensive response to exercise in normotensive patients.

A prospective controlled study of living kidney donors: three-year follow-up

BACKGROUND

There have been few prospective controlled studies of kidney donors. Understanding the pathophysiologic effects of kidney donation is important for judging donor safety and improving our understanding of the consequences of reduced kidney function in chronic kidney disease.

STUDY DESIGN

Prospective, controlled, observational cohort study.

SETTING & PARTICIPANTS

3-year follow-up of kidney donors and paired controls suitable for donation at their donor's center.

PREDICTOR

Kidney donation.

OUTCOMES

Medical history, vital signs, glomerular filtration rate, and other measurements at 6, 12, 24, and 36 months after donation.

RESULTS

At 36 months, 182 of 203 (89.7%) original donors and 173 of 201 (86.1%) original controls continue to participate in follow-up visits. The linear slope of the glomerular filtration rate measured by plasma iohexol clearance declined 0.36±7.55mL/min per year in 194 controls, but increased 1.47±5.02mL/min per year in 198 donors (P=0.005) between 6 and 36 months. Blood pressure was not different between donors and controls at any visit, and at 36 months, all 24-hour ambulatory blood pressure parameters were similar in 126 controls and 135 donors (mean systolic blood pressure, 120.0±11.2 [SD] vs 120.7±9.7mmHg [P=0.6]; mean diastolic blood pressure, 73.4±7.0 vs 74.5±6.5mmHg [P=0.2]). Mean arterial pressure nocturnal dipping was manifest in 11.2% ± 6.6% of controls and 11.3% ± 6.1% of donors (P=0.9). Urinary protein-creatinine and albumin-creatinine ratios were not increased in donors compared with controls. From 6 to 36 months postdonation, serum parathyroid hormone, uric acid, homocysteine, and potassium levels were higher, whereas hemoglobin levels were lower, in donors compared with controls.

LIMITATIONS

Possible bias resulting from an inability to select controls screened to be as healthy as donors, short follow-up duration, and dropouts.

CONCLUSIONS

Kidney donors manifest several of the findings of mild chronic kidney disease. However, at 36 months after donation, kidney function continues to improve in donors, whereas controls have expected age-related declines in function.

Immediate and long-term high levels of plasma homocysteine after extracorporeal shock wave lithotripsy in patients with renal stone disease

BACKGROUND

Plasma homocysteine levels increase in patients with chronic renal failure. Numerous studies have demonstrated that kidney function is one of the most important determinants of plasma total homocysteine (tHcy) concentration. In this study we aimed to evaluate the relationship between tHcy levels and extracorporeal shock wave lithotripsy (ESWL) for patients with renal stones and to see if the change in homocysteine levels continued if renal dysfunction improved.

MATERIALS AND METHODS

The study consisted of 20 patients who underwent first-time ESWL for renal stones. Every patient gave 3 blood samples at 24 h before surgery and at 2 days and at 3 months after ESWL for measurement of plasma levels of tHcy, creatinine, vitamin B6, and vitamin B12.

RESULTS

The 20 patients (12 male, 8 female) had a mean age of 42.8 ± 11.7 years. tHcy levels showed a statistically significant increase from 9.4 ± 1.4 to 18 ± 4.8 and 11.2 ± 2.1 at 2 days and at 3 months, respectively. Serum creatinine also showed a statistically significant increase compared to baseline at 2 days and at 3 months after ESWL.

CONCLUSION

After first-time ESWL, the increase in serum levels of creatinine and tHcy due to renal injury, such as ischemia/reperfusion injury, may be severe and continue for a long period, such as 3 months. According to baseline levels, the increase in homocysteine levels as an indicator of oxidant stress was more severe than the creatinine levels after ESWL for renal stones. Our patients were first-time ESWL patients; however, in patients who undergo EWSL more than once long-term high tHcy levels should also be considered as renal.

Cardiovascular disease and hypertension risk in living kidney donors: an analysis of health administrative data in Ontario, Canada

BACKGROUND

Knowledge of any harm associated with living kidney donation guides informed consent and living donor follow-up. Risk estimates in the literature are variable, and most studies did not use a healthy control group to assess outcomes attributable to donation.

METHODS

We observed a retrospective cohort using health administrative data for donations which occurred in Ontario, Canada between the years 1993 and 2005. There were a total of 1278 living donors and 6359 healthy adults who acted as a control group. Individuals were followed for a mean of 6.2 years (range, 1-13 years) after donation. The primary outcome was a composite of time to death or first cardiovascular event (myocardial infarction, stroke, angioplasty, and bypass surgery). The secondary outcome was time to a diagnosis of hypertension.

RESULTS

There was no significant difference in death or cardiovascular events between donors and controls (1.3% vs. 1.7%; hazard ratio 0.7, 95% confidence interval 0.4-1.2). Donors were more frequently diagnosed with hypertension than controls (16.3% vs. 11.9%, hazard ratio 1.4, 95% confidence interval 1.2-1.7) but were also seen more often by their primary care physicians (median [interquartile range] 3.6 [1.9-6.1] vs. 2.6 [1.4-4.3] visits per person year, P<0.001).

CONCLUSIONS

Based on administrative data, the risk of cardiovascular disease was unchanged in the first decade after kidney donation. The observed increase in diagnosed hypertension may be due to nephrectomy or more blood pressure measurements received by donors in follow-up and requires prospective study.

Do Biochemical Measures Change in Living Kidney Donors?

BACKGROUND

Living kidney donation provides a unique opportunity to assess possible biochemical changes attributable to small decrements in glomerular filtration rate. We reviewed studies which followed 5 or more healthy donors, where changes in biochemical measures or anemia were assessed at least 4 months after nephrectomy.

METHODS

We searched MEDLINE, EMBASE, and Science Citation databases, and reviewed reference lists from 1966 through June 2006. We abstracted data on study and donor characteristics and biochemical outcomes of interest.

RESULTS

Eight studies examined at least one outcome of interest. The average time after donation ranged from 0.4 to 11 years, the postdonation creatinine clearance ranged from 73 to 99 ml/min, and the decrement after donation ranged from 11 to 38 ml/min. Nephrectomy did not change hemoglobin, erythropoietin, serum phosphate, calcium or C-reactive protein levels. The studies were inconsistent as to whether parathyroid hormone levels increased and 1,25-dihydroxyvitamin D levels decreased after nephrectomy. Uric acid levels increased variably post-donation. Plasma homocysteine increased in the single study included in this review.

CONCLUSIONS

The mechanistic changes described above and their prognostic significance need clarification. Based on existing evidence, it is not necessary to routinely monitor living kidney donors for changes in these biochemical measures.

Living Kidney Donation: Anemia and Inflammation in the Early Postoperative Period

Studies on living donor kidney transplantation primarily address the recipients; few publications focus on kidney donors. The aim of the present study was to detect changes in and compensations of defined parameters of anemia and inflammation in the immediate postnephrectomy period. We included six living kidney donors who underwent an open anterior-extraperitoneal nephrectomy. We excluded donors with complications, such as significant blood loss or infection. Blood samples were taken before nephrectomy as well as on postoperative days 1, 3, 5, and 7, and at discharge for measurements of hemoglobin (Hb), serum erythropoietin (Epo), reticulocytes (Reti), pentraxin 3 (PTX3), and C-reactive protein (CRP). There was a significant decrease in Hb (>3 g/dL), reaching a maximum on day 3 followed by a significant threefold increase in Epo levels on day 5 and a nonsignificant elevation of Reti count. CRP increased approximately 80-fold on day 3. PTX3 showed a similar course, peaking on day 3 with an approximate 70-fold increase. After living donor nephrectomy, there was an unexpectedly pronounced inflammatory reaction in the absence of any signs of bacterial infection simultaneous with a significant decrease in Hb. These parameters improved during the hospital stay, in some cases they achieved the prenephrectomy level at discharge. These data may assist in interpreting laboratory results after nephrectomy among living kidney donors.

Disturbed homocysteine and methionine cycle intermediates S-adenosylhomocysteine and S-adenosylmethionine are related to degree of renal insufficiency in type 2 diabetes

BACKGROUND

Diabetic nephropathy is a common complication in patients with type 2 diabetes that may increase atherothrombotic risk. Hyperhomocysteinemia (HHcy) further increases the risk in those patients. We studied concentrations of total homocysteine (tHcy) and its related metabolites S-adenosylmethionine (AdoMet) and S-adenosylhomocysteine (AdoHcy) in relation to B-vitamin status and renal function in patients with type 2 diabetes who developed diabetic nephropathy.

METHODS

The study included 93 patients with renal failure and type 2 diabetes. Chronic kidney disease was classified into four subgroups according to the National Kidney Foundation based on glomerular filtration rate plus pathologic abnormalities or markers of kidney damage.

RESULTS

Serum or plasma concentrations of the metabolites increased significantly with worsening of renal function, whereas serum concentrations of the B vitamins (folate, vitamins B12 and B6) did not differ appreciably between the groups. Moreover, plasma concentrations of AdoHcy and AdoMet were markedly increased in patients with kidney failure compared with those in stage 2 (median AdoHcy, 112.7 vs 10.5 nmol/L; median AdoMet, 162.0 vs 80.0 nmol/L). The AdoMet/AdoHcy ratio was more than 80% lower in patients with renal failure compared with stage 2. Vitamin B12 was a significant determinant of concentrations of AdoMet, tHcy, methylmalonic acid (MMA), and cystathionine.

CONCLUSIONS

Increased plasma concentrations of tHcy and methionine cycle intermediates (AdoMet, AdoHcy) are related to disturbed renal function in patients with type 2 diabetes. Vitamin B12 and/or folate are significant predictors of tHcy, cystathionine, MMA, and AdoMet. The effect of therapeutic doses of the B vitamins on AdoMet, AdoHcy, and their ratio should be tested in renal patients.

Hyperhomocysteinemia and response of methionine cycle intermediates to vitamin treatment in renal patients

The role of hyperhomocysteinemia (HHcy) as a risk marker for cardiovascular diseases in renal patients is a matter of controversy. The remethylation of homocysteine (Hcy) to methionine in the kidneys is of great importance for Hcy clearance. Hcy remethylation is markedly decreased in patients on hemodialysis, but transsulfuration remains mostly unaffected. Markedly increased concentrations of methylmalonic acid (MMA), as a metabolic marker of vitamin B