Weight for Gestational Age as a Baseline Predictor of Kidney Function in Adulthood

Study of intercurrent infection pattern in hepatitis C seropositive renal transplant recipients, relationship with T-cell function

BACKGROUND

We assessed the effect of hepatitis C seropositivity on the percentage of various T-cells in living donor renal transplant recipients (LDRTRs) and their association with intercurrent infections post renal transplantation (post-Tx).

METHODS

One hundred and thirty-three matching LDRTRs [A (seronegative) (68 patients) and B (seropositive) (65 patients) by ELISA] were studied prospectively 10 days, 6 months and 12 months post-Tx for intercurrent infections, acute rejection and T-cell% by flow cytometry.

RESULTS

CD4(+), CD8(+), CD4/CD8 were significantly higher 10 days post-Tx in Group B compared to Group A, p < 0.001. A significant increase in CD8% was seen 6-month post-Tx among Group B compared to Group A. No difference was detected between groups in (CD4(+), CD8(+), CD4/CD8, CD3-CD16/65(+)%), rate and severity of intercurrent infection, rate of acute rejection, 12 months post-Tx. A significantly higher rate of severe infections particularly urinary tract infections (UTI) was noted in Group B compared to Group A the first 3 months post-Tx particularly in those who received the combination of antithymocyte globulin (ATG) or basiliximab, tacrolimus, steroids, mycophenolate mofetil (MMF). CD4(+)% correlated negatively with intercurrent infections in Group B 6 months post-Tx.

CONCLUSION

HCV(+) patients are more prone to intercurrent infections the first 3 months post-Tx. Infection rate correlates positively with pre-transplant HCV seropositivity and immunosuppressive regimen.

Smaller kidney size at birth in South Asians: findings from the Born in Bradford birth cohort study

BACKGROUND

Rates of advanced chronic kidney disease and renal replacement therapy are higher in South Asian than in white British populations. Low birth weight is also more frequent in South Asian populations and has been associated with increased risks of kidney disease, perhaps due to a reduced nephron endowment.

METHODS

Using ultrasound scans at 34 weeks of gestation, we measured fetal kidney dimensions (transverse and anteroposterior diameters, length and circumference) and derived volume in a random sample of 872 white British and 715 South Asian participants in the Born in Bradford cohort study. Kidney measurements were compared between ethnic groups.

RESULTS

Birth weight for gestational age at 40 weeks was 200 g less in South Asian babies compared with white British babies. The mean kidney volume for gestational age was 16% lower in South Asian than in white British babies [8.79 versus 10.45 cm(3), difference 1.66 cm(3) (95% confidence interval 1.40-1.93, P < 0.001)]. The difference was robust after adjustment for maternal age, socio-economic factors, marital status, body mass index, smoking and alcohol use in pregnancy, parity, baby's gender and birth weight for gestational age [adjusted difference 1.38 cm(3) (0.97-1.84), P < 0.001]. There were smaller reductions in other fetal measures.

CONCLUSION

South Asian babies have smaller kidneys compared with white British babies, even after adjusting for potential confounders including birth weight. This finding may contribute to increased risks of adult kidney disease in South Asian populations.

Urinary neutrophil gelatinase-associated lipocalin at birth predicts early renal function in very low birth weight infants

Preterm infants are exposed to conditions that can impair renal function. We evaluated the ability of serum and urinary neutrophil gelatinase-associated lipocalin (sNGAL and uNGAL) to predict renal function in the first weeks of life. From September 2008 to July 2009, infants weighing ≤1500 g at birth with no major congenital anomalies or sepsis were eligible. We measured sNGAL and uNGAL levels at birth. To evaluate renal function, we determined changes in serum creatinine (sCreat) and estimated GFR (eGFR) from birth to d 21. Forty neonates (mean GA, 27 ± 2 wk) completed the study. Renal function improved in 32 of 40 (80%) infants (normal renal function, NRF group) (sCreat, from 0.97 ± 0.2 to 0.53 ± 0.13 mg/dL; eGFR, from 15.3 ± 4.1 to 28.6 ± 7.9 mL/min), whereas renal function worsened in 8 of 40 (20%) infants (impaired renal function, IRF group) (sCreat, from 0.71 ± 0.27 to 0.98 ± 0.43 mg/dL; eGFR from 23 ± 14.7 to 16.4 ± 9.1 mL/min). The uNGAL/urinary creatinine (uCreat) ratio at birth was higher in the IRF group (31.05 ng/mg) than the NRF group (6.0 ng/mg), and uNGAL was significantly higher in IRF group, detecting IRF with a cutoff of 100 ng/mL. uNGAL levels at birth may have a predictive role in very LBW (VLBW) infants.

Low nephron number and its clinical consequences

Epidemiologic studies now strongly support the hypothesis, proposed over two decades ago, that developmental programming of the kidney impacts an individual's risk for hypertension and renal disease in later life. Low birth weight is the strongest current clinical surrogate marker for an adverse intrauterine environment and, based on animal and human studies, is associated with a low nephron number. Other clinical correlates of low nephron number include female gender, short adult stature, small kidney size, and prematurity. Low nephron number in Caucasian and Australian Aboriginal subjects has been shown to be associated with higher blood pressures, and, conversely, hypertension is less prevalent in individuals with higher nephron numbers. In addition to nephron number, other programmed factors associated with the increased risk of hypertension include salt sensitivity, altered expression of renal sodium transporters, altered vascular reactivity, and sympathetic nervous system overactivity. Glomerular volume is universally found to vary inversely with nephron number, suggesting a degree of compensatory hypertrophy and hyperfunction in the setting of a low nephron number. This adaptation may become overwhelmed in the setting of superimposed renal insults, e.g. diabetes mellitus or rapid catch-up growth, leading to the vicious cycle of on-going hyperfiltration, proteinuria, nephron loss and progressive renal functional decline. Many millions of babies are born with low birth weight every year, and hypertension and renal disease prevalences are increasing around the globe. At present, little can be done clinically to augment nephron number; therefore adequate prenatal care and careful postnatal nutrition are crucial to optimize an individual's nephron number during development and potentially to stem the tide of the growing cardiovascular and renal disease epidemics worldwide.

Level and determinants of kidney function in a South Asian population in Pakistan

BACKGROUND

People of South Asian origin are at high risk of chronic kidney disease. Some have suggested that the usual level of glomerular filtration rate (GFR) in South Asians may be lower than in populations of European origin. However, measured GFR in a general adult population of South Asian origin has not been studied.

DESIGN

Cross-sectional observational study.

SETTING & PARTICIPANTS

530 patients 40 years or older randomly selected from communities in Karachi, Pakistan, using multistage cluster sampling. Patients with both diabetes and hypertension were excluded.

PREDICTOR

Age, sex, diabetes, and hypertension.

OUTCOME

Measured GFR using urinary clearance of inulin.

RESULTS

Mean age of participants was 49.7 ± 9.5 (standard deviation [SD]) years, 51% were men, 34.9% had hypertension, and 30.5% had diabetes. Mean measured GFR was 94.1 ± 28.6 mL/min/1.73 m(2). GFR was lower by 0.79 ± 0.11 mL/min/1.73 m(2) for each 1-year older age. The 5-year age- and sex-specific mean GFR of the study population generally was within 1 SD of the mean of previously reported values for US adults. Factors independently associated with GFR were younger age (β coefficient, -3.84 [95% CI, -5.46 to -2.21] mL/min/1.73 m(2) per 5 years older), higher serum albumin level (4.58 [95% CI, 0.74-8.42] mL/min/1.73 m(2) per 0.5-g/dL increase), higher fasting plasma glucose level (0.81 [95% CI, 0.44-1.18] mL/min/1.73 m(2) per 10-mg/dL increase), high versus low meat intake (7.81 [95% CI, 1.14-14.48] mL/min/1.73 m(2) for ≥11 vs ≤5 servings/wk), and higher estimated protein intake (1.46 [95% CI, 0.41-2.51] mL/min/1.73 m(2) per 1.0-g/d increase) from urine urea nitrogen.

LIMITATIONS

Moderate sample size, lack of validation of some items in the dietary assessment for this study population.

CONCLUSIONS

Mean measured GFR in South Asian adults from the general population in Karachi, Pakistan, is only modestly lower than in European-origin counterparts, with similar age association. This may reflect lower dietary protein intake in South Asians.

The clinical importance of nephron mass

Abundant evidence supports the association between low birth weight (LBW) and renal dysfunction in humans. Anatomic measurements of infants, children, and adults show significant inverse correlation between LBW and nephron number. Nephron numbers are also lower in individuals with hypertension compared with normotension among white and Australian Aboriginal populations. The relationship between nephron number and hypertension among black individuals is still unclear, although the high incidence of LBW predicts low nephron number in this population as well. LBW, a surrogate for low nephron number, also associates with increasing BP from childhood to adulthood and increasing risk for chronic kidney disease in later life. Because nephron numbers can be counted only postmortem, surrogate markers such as birth weight, prematurity, adult height, reduced renal size, and glomerulomegaly are potentially useful for risk stratification, for example, during living-donor assessment. Because early postnatal growth also affects subsequent risk for higher BP or reduced renal function, postnatal nutrition, a potentially modifiable factor, in addition to intrauterine effects, has significant influence on long-term cardiovascular and renal health.

Renal transplant: nonenhanced renal MR angiography with magnetization-prepared steady-state free precession

The institutional review board approved this HIPAA-compliant study and waived informed consent. The purpose was to investigate nonenhanced magnetic resonance (MR) angiography with steady-state free precession (SSFP) with inversion recovery for assessing renal arteries in patients with renal transplants. Thirteen recipients of renal transplants underwent SSFP MR angiography before contrast material-enhanced MR angiography. Three stenoses (two mild, one severe) were identified at SSFP MR angiography in agreement with findings at contrast-enhanced MR angiography. There was no significant difference in image quality between the two methods. Results suggest SSFP MR angiography permits image quality of renal transplant arteries and detection of arterial stenosis comparable with those at contrast-enhanced MR angiography.

Regulation of renal 12(S)-hydroxyeicosatetraenoic acid in diabetes by angiotensin AT1 and AT2 receptors

Diabetes is associated with increased production of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE]. The mechanisms involved in this process remain unclear. We hypothesized that hyperglycemia and angiotensin II (ANG II) regulate renal 12(S)-HETE production via a balance between angiotensin AT(1) and AT(2) receptors activities. Using a microdialysis technique, renal interstitial fluid (RIF) levels of ANG II and 12(S)-HETE were monitored in normal control and streptozotocin-induced diabetic rats at baseline and then weekly thereafter for 12 wk. In a second group of normal and diabetic rats, 3 wk after development of diabetes, we monitored RIF 12(S)-HETE levels in response to acute AT(1) receptor blockade with valsartan or AT(2) receptor blockade with PD123319 individually or combined. Two weeks after induction of diabetes there was a 404% increase in ANG II (P < 0.05), a 149% increase in 12S-HETE (P < 0.05), and a 649% increase in urinary albumin excretion (P < 0.05). These levels remained elevated throughout the study. PD123319 given alone had no effect on 12(S)-HETE. Valsartan decreased 12(S)-HETE by 61.6% (P < 0.0001), a response that was abrogated when PD123319 was given with valsartan. These data demonstrate that hyperglycemia increases renal ANG II and 12(S)-HETE levels. The increase in 12(S)-HETE is mediated via AT(1) receptor. The attenuation of the effects of AT(1) receptor blockade by PD123319 suggests that AT(2) receptor contributes to the downregulation of renal 12(S)-HETE production.