A meta-analysis of GFR slope as a surrogate endpoint for kidney failure

Glomerular filtration rate (GFR) decline is causally associated with kidney failure and is a candidate surrogate endpoint for clinical trials of chronic kidney disease (CKD) progression. Analyses across a diverse spectrum of interventions and populations is required for acceptance of GFR decline as an endpoint. In an analysis of individual participant data, for each of 66 studies (total of 186,312 participants), we estimated treatment effects on the total GFR slope, computed from baseline to 3 years, and chronic slope, starting at 3 months after randomization, and on the clinical endpoint (doubling of serum creatinine, GFR < 15 ml min-1 per 1.73 m2 or kidney failure with replacement therapy). We used a Bayesian mixed-effects meta-regression model to relate treatment effects on GFR slope with those on the clinical endpoint across all studies and by disease groups (diabetes, glomerular diseases, CKD or cardiovascular diseases). Treatment effects on the clinical endpoint were strongly associated with treatment effects on total slope (median coefficient of determination (R2) = 0.97 (95% Bayesian credible interval (BCI) 0.82-1.00)) and moderately associated with those on chronic slope (R2 = 0.55 (95% BCI 0.25-0.77)). There was no evidence of heterogeneity across disease. Our results support the use of total slope as a primary endpoint for clinical trials of CKD progression.

Change in Albuminuria and GFR Slope as Joint Surrogate End Points for Kidney Failure: Implications for Phase 2 Clinical Trials in CKD

SIGNIFICANCE STATEMENT

Changes in albuminuria and GFR slope are individually used as surrogate end points in clinical trials of CKD progression, and studies have demonstrated that each is associated with treatment effects on clinical end points. In this study, the authors sought to develop a conceptual framework that combines both surrogate end points to better predict treatment effects on clinical end points in Phase 2 trials. The results demonstrate that information from the combined treatment effects on albuminuria and GFR slope improves the prediction of treatment effects on the clinical end point for Phase 2 trials with sample sizes between 100 and 200 patients and duration of follow-up ranging from 1 to 2 years. These findings may help inform design of clinical trials for interventions aimed at slowing CKD progression.

BACKGROUND

Changes in log urinary albumin-to-creatinine ratio (UACR) and GFR slope are individually used as surrogate end points in clinical trials of CKD progression. Whether combining these surrogate end points might strengthen inferences about clinical benefit is unknown.

METHODS

Using Bayesian meta-regressions across 41 randomized trials of CKD progression, we characterized the combined relationship between the treatment effects on the clinical end point (sustained doubling of serum creatinine, GFR <15 ml/min per 1.73 m 2 , or kidney failure) and treatment effects on UACR change and chronic GFR slope after 3 months. We applied the results to the design of Phase 2 trials on the basis of UACR change and chronic GFR slope in combination.

RESULTS

Treatment effects on the clinical end point were strongly associated with the combination of treatment effects on UACR change and chronic slope. The posterior median meta-regression coefficients for treatment effects were -0.41 (95% Bayesian Credible Interval, -0.64 to -0.17) per 1 ml/min per 1.73 m 2 per year for the treatment effect on GFR slope and -0.06 (95% Bayesian Credible Interval, -0.90 to 0.77) for the treatment effect on UACR change. The predicted probability of clinical benefit when considering both surrogates was determined primarily by estimated treatment effects on UACR when sample size was small (approximately 60 patients per treatment arm) and follow-up brief (approximately 1 year), with the importance of GFR slope increasing for larger sample sizes and longer follow-up.

CONCLUSIONS

In Phase 2 trials of CKD with sample sizes of 100-200 patients per arm and follow-up between 1 and 2 years, combining information from treatment effects on UACR change and GFR slope improved the prediction of treatment effects on clinical end points.

Evaluation of Variation in the Performance of GFR Slope as a Surrogate End Point for Kidney Failure in Clinical Trials that Differ by Severity of CKD

BACKGROUND

The GFR slope has been evaluated as a surrogate end point for kidney failure in meta-analyses on a broad collection of randomized controlled trials (RCTs) in CKD. These analyses evaluate how accurately a treatment effect on GFR slope predicts a treatment effect on kidney failure. We sought to determine whether severity of CKD in the patient population modifies the performance of GFR slope.

METHODS

We performed Bayesian meta-regression analyses on 66 CKD RCTs to evaluate associations between effects on GFR slope (the chronic slope and the total slope over 3 years, expressed as mean differences in ml/min per 1.73 m2/yr) and those of the clinical end point (doubling of serum creatinine, GFR <15 ml/min per 1.73 m2, or kidney failure, expressed as a log-hazard ratio), where models allow interaction with variables defining disease severity. We evaluated three measures (baseline GFR in 10 ml/min per 1.73 m2, baseline urine albumin-to-creatinine ratio [UACR] per doubling in mg/g, and CKD progression rate defined as the control arm chronic slope, in ml/min per 1.73 m2/yr) and defined strong evidence for modification when 95% posterior credible intervals for interaction terms excluded zero.

RESULTS

There was no evidence for modification by disease severity when evaluating 3-year total slope (95% credible intervals for the interaction slope: baseline GFR [-0.05 to 0.03]; baseline UACR [-0.02 to 0.04]; CKD progression rate [-0.07 to 0.02]). There was strong evidence for modification in evaluations of chronic slope (95% credible intervals: baseline GFR [0.02 to 0.11]; baseline UACR [-0.11 to -0.02]; CKD progression rate [0.01 to 0.15]).

CONCLUSIONS

These analyses indicate consistency of the performance of total slope over 3 years, which provides further evidence for its validity as a surrogate end point in RCTs representing varied CKD populations.

Acute Treatment Effects on GFR in Randomized Clinical Trials of Kidney Disease Progression

BACKGROUND

Acute changes in GFR can occur after initiation of interventions targeting progression of CKD. These acute changes complicate the interpretation of long-term treatment effects.

METHODS

To assess the magnitude and consistency of acute effects in randomized clinical trials and explore factors that might affect them, we performed a meta-analysis of 53 randomized clinical trials for CKD progression, enrolling 56,413 participants with at least one estimated GFR measurement by 6 months after randomization. We defined acute treatment effects as the mean difference in GFR slope from baseline to 3 months between randomized groups. We performed univariable and multivariable metaregression to assess the effect of intervention type, disease state, baseline GFR, and albuminuria on the magnitude of acute effects.

RESULTS

The mean acute effect across all studies was -0.21 ml/min per 1.73 m2 (95% confidence interval, -0.63 to 0.22) over 3 months, with substantial heterogeneity across interventions (95% coverage interval across studies, -2.50 to +2.08 ml/min per 1.73 m2). We observed negative average acute effects in renin angiotensin system blockade, BP lowering, and sodium-glucose cotransporter 2 inhibitor trials, and positive acute effects in trials of immunosuppressive agents. Larger negative acute effects were observed in trials with a higher mean baseline GFR.

CONCLUSION

The magnitude and consistency of acute GFR effects vary across different interventions, and are larger at higher baseline GFR. Understanding the nature and magnitude of acute effects can help inform the optimal design of randomized clinical trials evaluating disease progression in CKD.

Association of Treatment Effects on Early Change in Urine Protein and Treatment Effects on GFR Slope in IgA Nephropathy: An Individual Participant Meta-analysis

RATIONALE & OBJECTIVE

An early change in proteinuria is considered a reasonably likely surrogate end point in immunoglobulin A nephropathy (IgAN) and can be used as a basis for accelerated approval of therapies, with verification in a postmarketing confirmatory trial. Glomerular filtration rate (GFR) slope is a recently validated surrogate end point for chronic kidney disease progression and may be considered as the end point used for verification. We undertook a meta-analysis of clinical trials in IgAN to compare treatment effects on change in proteinuria versus change in estimated GFR (eGFR) slope.

STUDY DESIGN

Individual patient-level meta-analysis.

SETTING & STUDY POPULATIONS

Individual data of 1,037 patients from 12 randomized trials.

SELECTION CRITERIA FOR STUDIES

Randomized trials of IgAN with proteinuria measurements at baseline and 6 (range, 2.5-14) months and at least a further 1 year of follow-up for the clinical outcome.

ANALYTICAL APPROACH

For each trial, we estimated the treatment effects on proteinuria and on the eGFR slope, computed as the total slope starting at baseline or the chronic slope starting 3 months after randomization. We used a Bayesian mixed-effects analysis to relate the treatment effects on proteinuria to effects on GFR slope across these studies and developed a prediction model for the treatment effect on the GFR slope based on the effect on proteinuria.

RESULTS

Across all studies, treatment effects on proteinuria accurately predicted treatment effects on the total slope at 3 years (median R2 = 0.88; 95% Bayesian credible interval [BCI], 0.06-1) and on the chronic slope (R2 = 0.98; 95% BCI, 0.29-1). For future trials, an observed treatment effect of approximately 30% reduction in proteinuria would confer probabilities of at least 90% for nonzero treatment benefits on the total and chronic slopes of eGFR. We obtained similar results for proteinuria at 9 and 12 months and total slope at 2 years.

LIMITATIONS

Study population restricted to 12 trials of small sample size, leading to wide BCIs. There was heterogeneity among trials with respect to study design and interventions.

CONCLUSIONS

These results provide new evidence supporting that early reduction in proteinuria can be used as a surrogate end point for studies of chronic kidney disease progression in IgAN.

Performance of GFR Slope as a Surrogate End Point for Kidney Disease Progression in Clinical Trials: A Statistical Simulation

BACKGROUND

Randomized trials of CKD treatments traditionally use clinical events late in CKD progression as end points. This requires costly studies with large sample sizes and long follow-up. Surrogate end points like GFR slope may speed up the evaluation of new therapies by enabling smaller studies with shorter follow-up.

METHODS

We used statistical simulations to identify trial situations where GFR slope provides increased statistical power compared with the clinical end point of doubling of serum creatinine or kidney failure. We simulated GFR trajectories based on data from 47 randomized treatment comparisons. We evaluated the sample size required for adequate statistical power based on GFR slopes calculated from baseline and from 3 months follow-up.

RESULTS

In most scenarios where the treatment has no acute effect, analyses of GFR slope provided similar or improved statistical power compared with the clinical end point, often allowing investigators to shorten follow-up by at least half while simultaneously reducing sample size. When patients' GFRs are higher, the power advantages of GFR slope increase. However, acute treatment effects within several months of randomization can increase the risk of false conclusions about therapies based on GFR slope. Care is needed in study design and analysis to avoid such false conclusions.

CONCLUSIONS

Use of GFR slope can substantially increase statistical power compared with the clinical end point, particularly when baseline GFR is high and there is no acute effect. The optimum GFR-based end point depends on multiple factors including the rate of GFR decline, type of treatment effect and study design.

Observational study on the incidence of nephrogenic systemic fibrosis in patients with renal impairment following gadoterate meglumine administration: the NSsaFe study

BACKGROUND

Nephrogenic systemic fibrosis (NSF) is a rare life-threatening condition strongly associated with the administration of gadolinium-based contrast agents in patients with severe or endstage renal impairment.

PURPOSE

To prospectively determine the incidence of NSF in patients with renal impairment after administration of gadoterate meglumine.

STUDY TYPE

Prospective.

POPULATION

In all, 540 patients with moderate, severe, or endstage renal impairment, scheduled to undergo a routine contrast-enhanced MRI with gadoterate meglumine. Mean age was 69.7 ± 12.7 years (range: 21-95) with 58.4% of males.

FIELD STRENGTH/SEQUENCE

1.5T or 3.0T, sequence according to each site practice.

ASSESSMENT

Medical history, indication(s) for current MRI and adverse events were recorded for each patient. Patients were followed up over 2 years after administration with three visits separated by at least 3 months to detect any signs/symptoms suggestive of NSF.

STATISTICAL TESTS

Descriptive.

RESULTS

Renal impairment was graded as moderate for 69.4% of patients, severe for 16.0% and endstage for 12.1%; 2.6% had undergone a kidney transplant. Estimated glomerular filtration rate ranged from 4 to 59 mL/min/1.73 m² except one value of 74 mL/min/1.73 m² in a patient with kidney transplant. Central nervous system exploration was the main MRI indication (34.7%) and mean dose injected was 0.22 ± 0.09 mL/kg. Overall, 446 patients (82.6%) attended at least one follow-up visit and completed the NSF questionnaire and 329 (60.9%) attended the 2-year visit. No suspicion of NSF was reported in all 446 patients, including 119 patients with severe or endstage renal impairment. No deaths and no adverse events were reported during the MRI examination and the usual period of follow-up after gadoterate meglumine administration.

DATA CONCLUSION

No cases of NSF were observed in the 446 patients with moderate to endstage renal impairment followed up over a maximum of 2 years after injection of gadoterate meglumine.

LEVEL OF EVIDENCE

2 Technical Efficacy Stage: 4 J. Magn. Reson. Imaging 2020;51:607-614.

Targeted-release budesonide versus placebo in patients with IgA nephropathy (NEFIGAN): a double-blind, randomised, placebo-controlled phase 2b trial

BACKGROUND

IgA nephropathy is thought to be associated with mucosal immune system dysfunction, which manifests as renal IgA deposition that leads to impairment and end-stage renal disease in 20-40% of patients within 10-20 years. In this trial (NEFIGAN) we aimed to assess safety and efficacy of a novel targeted-release formulation of budesonide (TRF-budesonide), designed to deliver the drug to the distal ileum in patients with IgA nephropathy.

METHODS

We did a randomised, double-blind, placebo-controlled phase 2b trial, comprised of 6-month run-in, 9-month treatment, and 3-month follow-up phases at 62 nephrology clinics across ten European countries. We recruited patients aged at least 18 years with biopsy-confirmed primary IgA nephropathy and persistent proteinuria despite optimised renin-angiotensin system (RAS) blockade. We randomly allocated patients with a computer algorithm, with a fixed block size of three, in a 1:1:1 ratio to 16 mg/day TRF-budesonide, 8 mg/day TRF-budesonide, or placebo, stratified by baseline urine protein creatinine ratio (UPCR). Patients self-administered masked capsules, once daily, 1 h before breakfast during the treatment phase. All patients continued optimised RAS blockade treatment throughout the trial. Our primary outcome was mean change from baseline in UPCR for the 9-month treatment phase, which was assessed in the full analysis set, defined as all randomised patients who took at least one dose of trial medication and had at least one post-dose efficacy measurement. Safety was assessed in all patients who received the intervention. This trial is registered with ClinicalTrials.gov, number NCT01738035.

FINDINGS

Between Dec 11, 2012, and June 25, 2015, 150 randomised patients were treated (safety set) and 149 patients were eligible for the full analysis set. Overall, at 9 months TRF-budesonide (16 mg/day plus 8 mg/day) was associated with a 24·4% (SEM 7·7%) decrease from baseline in mean UPCR (change in UPCR vs placebo 0·74; 95% CI 0·59-0·94; p=0·0066). At 9 months, mean UPCR had decreased by 27·3% in 48 patients who received 16 mg/day (0·71; 0·53-0·94; p=0·0092) and 21·5% in the 51 patients who received 8 mg/day (0·76; 0·58-1·01; p=0·0290); 50 patients who received placebo had an increase in mean UPCR of 2·7%. The effect was sustained throughout followup. Incidence of adverse events was similar in all groups (43 [88%] of 49 in the TRF-budesonide 16 mg/day group, 48 [94%] of 51 in the TRF-budesonide 8 mg/day, and 42 [84%] of 50 controls). Two of 13 serious adverse events were possibly associated with TRF-budesonide-deep vein thrombosis (16 mg/day) and unexplained deterioration in renal function in follow-up (patients were tapered from 16 mg/day to 8 mg/day over 2 weeks and follow-up was assessed 4 weeks later).

INTERPRETATION

TRF-budesonide 16 mg/day, added to optimised RAS blockade, reduced proteinuria in patients with IgA nephropathy. This effect is indicative of a reduced risk of future progression to end-stage renal disease. TRF-budesonide could become the first specific treatment for IgA nephropathy targeting intestinal mucosal immunity upstream of disease manifestation.

FUNDING

Pharmalink AB.

Early Change in Urine Protein as a Surrogate End Point in Studies of IgA Nephropathy: An Individual-Patient Meta-analysis

BACKGROUND

The role of change in proteinuria as a surrogate end point for randomized trials in immunoglobulin A nephropathy (IgAN) has previously not been thoroughly evaluated.

STUDY DESIGN

Individual patient-level meta-analysis.

SETTING & POPULATION

Individual-patient data for 830 patients from 11 randomized trials evaluating 4 intervention types (renin-angiotensin system [RAS] blockade, fish oil, immunosuppression, and steroids) examining associations between changes in urine protein and clinical end points at the individual and trial levels.

SELECTION CRITERIA FOR STUDIES

Randomized controlled trials of IgAN with measurements of proteinuria at baseline and a median of 9 (range, 5-12) months follow-up, with at least 1 further year of follow-up for the clinical outcome.

PREDICTOR

9-month change in proteinuria.

OUTCOME

Doubling of serum creatinine level, end-stage renal disease, or death.

RESULTS

Early decline in proteinuria at 9 months was associated with lower risk for the clinical outcome (HR per 50% reduction in proteinuria, 0.40; 95% CI, 0.32-0.48) and was consistent across studies. Proportions of treatment effect on the clinical outcome explained by early decline in proteinuria were estimated at 11% (95% CI, -19% to 41%) for RAS blockade and 29% (95% CI, 6% to 53%) for steroid therapy. The direction of the pooled treatment effect on early change in proteinuria was in accord with the direction of the treatment effect on the clinical outcome for steroids and RAS blockade. Trial-level analyses estimated that the slope for the regression line for the association of treatment effects on the clinical end points and for the treatment effect on proteinuria was 2.15 (95% Bayesian credible interval, 0.10-4.32).

LIMITATIONS

Study population restricted to 11 trials, all having fewer than 200 patients each with a limited number of clinical events.

CONCLUSIONS

Results of this analysis offer novel evidence supporting the use of an early reduction in proteinuria as a surrogate end point for clinical end points in IgAN in selected settings.

Comparison of peritoneal dialysis and haemodialysis after renal transplant failure

BACKGROUND

A growing number of patients are returning to dialysis after renal transplant failure. The aim of this study is to determine whether peritoneal dialysis (PD) is a safe and good treatment option for these patients.

METHODS

All patients returning to PD or haemodialysis (HD) after renal transplant failure before 1 October 2002 at the University Hospital Gasthuisberg, Leuven, Belgium, were evaluated. Data were collected until death, retransplantation (reTx), transfer to HD or PD or until 1 January 2003.

RESULTS

Twenty-one patients starting PD (PDpostTx-group) and 39 patients starting HD (HDpostTx-group) after renal transplant failure were included in the study. There were no significant differences in age, sex, serum albumin- and CRP-levels at baseline. The total time on renal replacement therapy at transplant failure and time to transplant failure did not differ between the two groups either. Furthermore, the baseline comorbidity was similar in both groups. During follow-up, the outcome did not differ significantly between the two groups. However, there was a tendency towards higher patient survival and reTx tended to be more frequent in the PDpostTx-group. Moreover, patients in the HDpostTx-group tended to accrue more new comorbidity. The incidence of peritonitis and the evolution of dialysis adequacy (renal and peritoneal Kt/V and creatinine clearances) with time in the PDpostTx-group was similar to that seen in our centre's PD patients who had never undergone transplantation before.

CONCLUSIONS

This study suggests that the outcome in patients starting PD after renal transplant failure is at least as good as the outcome in those starting HD. Although these observational findings warrant further confirmation, PD therefore can be regarded as a safe and good treatment option for patients returning to dialysis after renal transplant failure.

Combined therapy with atorvastatin and calcineurin inhibitors: no interactions with tacrolimus

Increased systemic exposure to statins and consequent risk for complications has been reported in patients concomitantly treated with cyclosporin A (CsA). This has been ascribed to inhibition of drug catabolism by cytochrome P450 3A4 (CYP3A4) or drug transport by P-glycoprotein (PGP) and organic anion transporting polypeptide (OATP1B1). It is not known whether the combination of statins and tacrolimus (Tac) also suffers from this drawback. Therefore, a pharmacokinetic study of atorvastatin and its metabolites was performed in 13 healthy volunteers after 4 days' treatment, and after short (12 h) concomitant exposure to CsA and Tac. A complementary assessment of overall CYP, and hepatic and intestinal CYP3A4+PGP activity was performed after each treatment episode and compared to baseline (no drugs). Systemic exposure to atorvastatin acid and its metabolites was significantly increased when administered with CsA. In contrast, intake of Tac did not have any impact on atorvastatin pharmacokinetics. Concomitantly, a profound decrease of hepatic and intestinal PGP and an increase of intestinal CYP3A4 were noted with CsA, whereas no effect was seen after atorvastatin therapy with or without Tac. Based on these findings treatment with Tac appears a safer option for patients needing a combination of statins and calcineurin inhibitors.

Different evolution of trough and dose levels during the first year after transplantation for tacrolimus versus cyclosporine

At present, the two calcineurin inhibitors-cyclosporine (CsA) and tacrolimus (FK506)-are among the most frequently used immunosuppressants in clinical transplantation. Both drugs share variable oral bioavailability, which necessitates intense drug monitoring. This variability is attributed to large interindividual differences in drug catabolism by cytochrome P450 3A4/5 (CYP3A4/5) and drug efflux by P-glycoprotein (PGP). In addition, the activity of both CYP3A4 and PGP can vary substantially within the same individual due to environmental factors such as concomitant intake of inducing/inhibiting medications (eg, rifampicin/sporanox) or food substances (eg, grapefruit juice). More recently, an inducing effect of methylprednisolone on intestinal and hepatic CYP3A4 has been shown. Also, an influence of gender on CYP3A4 activity (being higher in women) has been reported. Once CsA and FK506 are absorbed and reach the bloodstream, both drugs are avidly bound to erythrocytes (up to 95% for FK506 and 50% for CsA) and plasma proteins, leaving only a small fraction of circulating active drug. This phenomenon also limits further hepatic catabolism and hence clearance of drug, which is influenced by hematocrit and levels of plasma proteins such as albumin. The aim of the present study was to compare the influence of changing steroid doses, hematocrit, and albumin on trough and dose levels of FK506 versus CsA during the first year after transplantation. In addition, the evolution of trough and dose levels of FK506 versus CsA was stratified according to gender.

Combined therapy with atorvastatin and calcineurin inhibitors: no interactions with tacrolimus

Increased systemic exposure to statins and consequent risk for complications has been reported in patients concomitantly treated with cyclosporin A (CsA). This has been ascribed to inhibition of drug catabolism by cytochrome P450 3A4 (CYP3A4) or drug transport by P-glycoprotein (PGP) and organic anion transporting polypeptide (OATP1B1). It is not known whether the combination of statins and tacrolimus (Tac) also suffers from this drawback. Therefore, a pharmacokinetic study of atorvastatin and its metabolites was performed in 13 healthy volunteers after 4 days' treatment, and after short (12 h) concomitant exposure to CsA and Tac. A complementary assessment of overall CYP, and hepatic and intestinal CYP3A4+PGP activity was performed after each treatment episode and compared to baseline (no drugs). Systemic exposure to atorvastatin acid and its metabolites was significantly increased when administered with CsA. In contrast, intake of Tac did not have any impact on atorvastatin pharmacokinetics. Concomitantly, a profound decrease of hepatic and intestinal PGP and an increase of intestinal CYP3A4 were noted with CsA, whereas no effect was seen after atorvastatin therapy with or without Tac. Based on these findings treatment with Tac appears a safer option for patients needing a combination of statins and calcineurin inhibitors.

Impact of gastric acid suppressants on cytochrome P450 3A4 and P-glycoprotein: consequences for FK506 assimilation

BACKGROUND

Cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (PGP) are important determinants of the oral bioavailability and clearance of tacrolimus. Cimetidine and omeprazole are known modulators of several CYPs in vitro. In the present study, the impact of cimetidine and omeprazole on tacrolimus exposure and on CYP3A4/PGP activity in vivo was examined.

METHODS

In a cohort of 48 renal transplant recipients who switched standard ulcer prophylaxis with 400 mg of cimetidine daily to 20 mg of omeprazole, dose/weight normalized trough levels of tacrolimus during a 5-day interval before and after switch were compared and further studied using multivariate analysis. In a cohort of 6 healthy volunteers, the effect of a 5-day course of ranitidine, cimetidine, and omeprazole on overall CYP, CYP3A4, and PGP activity in vivo was assessed with the (13)C-aminopyrin breath test and the combined per oral and intravenous (14)C-erythromycin breath and urine test.

RESULTS

Dose/weight normalized trough levels of tacrolimus decreased significantly (-15%) after switch from cimetidine to omeprazole. In healthy volunteers, a significant increase of intestinal CYP3A4 activity was observed after omeprazole, whereas no change was noted after cimetidine/ranitidine. Overall CYP activity was significantly decreased after cimetidine and remained unchanged after omeprazole/ranitidine. No effects on PGP or hepatic CYP3A4 were seen.

CONCLUSION

Switching treatment with cimetidine to omeprazole in renal transplant recipients is associated with a decrease of dose/weight normalized trough levels of tacrolimus. Studies in healthy volunteers suggest that this may be explained by an increase of intestinal CYP3A4 activity.

Localised plasma-cell type Castleman's disease and AA-amyloidosis cured by resection. A case report and review of the literature

Castleman's disease (CD) is a rare atypical lymphoproliferative disorder with frequent, yet less well known renal involvement. We describe the case of a 58-year-old woman with localised abdominal plasma-cell type CD complicated by nephrotic syndrome due to renal amyloidosis. 18Fluorodeoxyglucose (FDG) positron emission tomography (PET) confirmed the unicentric nature. Resection of the mass resulted in regression of the signs of inflammation, a negative FDG-PET and complete remission of the nephrotic syndrome. A review of the literature of renal involvement (incidence, clinical and pathological manifestations, treatment and prognosis) in CD is provided.

Crohn's-like changes in the colon due to mycophenolate?

OBJECTIVE

Mycophenolate mofetil (MMF) is used for prevention of allograft rejection in kidney transplant patients. A subset of patients suffers from chronic diarrhoea of unknown origin. The aim of the study was to investigate the effect of MMF on the colonic mucosa.

MATERIALS AND METHODS

Colonic mucosal biopsies from 24 kidney transplant patients receiving MMF and presenting with chronic diarrhoea were analysed using routine stainings and immunohistochemistry for Ki67 and E-cadherin. Results were compared with a control group of 19 kidney transplant patients not receiving MMF. In all patients routine clinical and laboratory investigations were performed in order to explain the diarrhoea.

RESULTS

In 11 patients, the diarrhoea seemed to be of infectious origin. Furthermore, 19/24 of MMF-patients showed characteristic histological alterations of the mucosa that were Crohn's disease-like: discontinuous crypt architectural distortion, increased epithelial mucin secretion, mildly active inflammation and focal presence of dilated and inflamed crypts. Ki67 staining was abnormal in 6/24 MMF patients but also in 4/19 control patients. E-Cadherin staining was normal in most MMF and control patients.

CONCLUSIONS

Diarrhoea following MMF treatment is frequently infectious in origin and associated with morphological changes with a Crohn's-like pattern in the colonic mucosa in a subset of patients. MMF does not induce major alteration in the proliferative compartment of colonic epithelium. The diarrhoea is not associated with altered E-cadherin expression in the colonic epithelium.

Mycophenolate mofetil in IgA nephropathy: results of a 3-year prospective placebo-controlled randomized study

BACKGROUND

Because humoral immunity is believed to play a pivotal role in the pathogenesis of IgA nephropathy (IgAN), a prospective placebo-controlled randomized study was started in patients with IgAN using mycophenolate mofetil (MMF).

METHODS

A total of 34 patients with IgAN were treated with salt intake restriction, angiotensin-converting enzyme (ACE) inhibition and MMF 2 g per day (N= 21) or placebo (N= 13). After 36 months of follow-up clinical, biochemical, and radiologic data were analyzed using linear mixed models for longitudinal data and Kaplan-Meier survival analysis.

RESULTS

Therapy had to be stopped prematurely in five patients. Two patients (MMF group) evolved to end-stage renal disease (ESRD). There was no difference between groups in the percentage of patients with a decrease of 25% or more in the inulin clearance or with a serum creatinine increase of 50% or more over 3 years. There was also no significant difference between groups in annualized rate of change of serum creatinine, computed by linear regression analysis. No significant difference was noted between groups for inulin clearance, serum creatinine, proteinuria, blood pressure, or other parameters of renal function. Hemoglobin and C-reactive protein were significantly lower in the MMF group compared with the placebo group. As a function of time, a significant decline in both groups was noted of proteinuria, parenchymal thickness of the kidneys and C3d.

CONCLUSION

In patients with IgAN at risk for progressive disease, no beneficial effect of 3-year treatment with MMF 2 g per day could be demonstrated on renal function/outcome or proteinuria. However, larger randomized studies are needed to confirm or reject these results.

CYP3A4 and P-glycoprotein activity in healthy controls and transplant patients on cyclosporin vs. tacrolimus vs. sirolimus

This study aimed to determine the impact of maintenance immunosuppressive therapy with cyclosporin A (CsA), tacrolimus (FK506) and sirolimus (Rapa) on the in vivo activity of both intestinal and hepatic cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (PGP) in renal transplant patients. The activity of these four elimination pathways was measured by the recently validated intravenous (iv) and per oral (po)14C erythromycin breath and urine test. In addition, overall hepatic P450 activity was measured by the (13)C aminopyrin breath test. Three groups of stable renal transplant patients on maintenance therapy with corticosteroids (CS) and mycophenolate mofetil (MMF) plus either CsA or FK506 or Rapa were examined. A significant increase in intestinal CYP3A4 activity and a significant decrease in hepatic and intestinal PGP activity was seen in patients on CsA in comparison with those on FK506 or Rapa (p < 0.01). A similar analysis in six healthy volunteers at baseline and after intake of CsA, FK506 and Rapa confirmed the results seen in the patients. There was no difference in CYP3A4 and PGP activity in the patients taking either FK506 or Rapa and healthy controls. These data suggest that a different pattern of drug interactions might be expected in patients treated with CsA vs. FK506/Rapa.

Alterations of CYP3A4 and P-glycoprotein activity in vivo with time in renal graft recipients

BACKGROUND

Catabolism by intestinal and hepatic cytochrome P450 3A4 (CYP3A4), and excretion by P-glycoprotein (PGP), has a major influence on oral bioavailability of calcineurin inhibitors. In this study, the activity of intestinal and hepatic CYP3A4 and PGP in vivo was assessed in renal transplant recipients during the first year after transplantation (Tx).

METHODS

Stable Caucasian renal transplant patients were tested at 1 week, 3 months, and 1 year after Tx, and compared with the results obtained in drug-free healthy volunteers. Intestinal and hepatic CYP3A4 and PGP activity were determined by measurement of (14)C-excretion dynamics in breath and urine after oral and intravenous administration of [N-methyl-(14)C]-erythromycin.

RESULTS

Compared with 1 week after Tx, intestinal and hepatic CYP3A4 activity significantly decreased at 3 months and 1 year after Tx (-33% and -45%; -7% and -33%, respectively). Compared with the healthy volunteers, intestinal and hepatic CYP3A4 activity of the patients was significantly increased at 1 week after Tx, but normalized at 1 year after Tx. A similar pattern, though not significant, was seen for intestinal PGP activity.

CONCLUSION

Phenotypic expression of hepatic and intestinal CYP3A4 was increased immediately after Tx, but gradually decreased to basal levels toward the end of the first year after Tx. The most plausible explanation for this evolution was the tapering of corticosteroid (CS) doses. These findings may also explain the increasing bioavailability of tacrolimus with time after Tx.

Cyclosporine: advantages versus disadvantages vis-à-vis tacrolimus

Despite a different molecular structure and biochemical properties, cyclosporine and tacrolimus--by inhibiting calcineurin activity--have been shown in the previous two decades of solid organ transplantation to be well tolerated and effective immunosuppressants. Initial randomized clinical trials showed a lower incidence of acute rejection in tacrolimus than in cyclosporine-treated patients, in combination with steroids and azathioprine. But in conjunction with mycophenolate mofetil, the difference in the incidence of acute rejection episodes is less clear. In general, short- and medium-term outcome variables (1-year serum creatinine, graft and patient survival) with cyclosporine and tacrolimus are excellent, and (almost) identical, with both substances having the same intrinsic nephrotoxic potential. On the other hand, cyclosporine and tacrolimus have a different impact on cardiovascular risk factors with tacrolimus having a better profile on arterial tension and lipid metabolism and cyclosporine on glucose metabolism. However, at present no data are available to discern that these differences in risk profile alter patient or graft survival or long-term cardiovascular morbidity/mortality. Therefore, prospective long-term trials are needed to study the quantitative impact of different immunosuppressive agents and concomitant cardiovascular risk factors on long-term patient and graft survival, before evidence-based (patient, graft, or cardiovascular) risk reduction can be firmly claimed by tailoring calcineurin inhibitors.

The value of tuberculin skin testing in haemodialysis patients

BACKGROUND

Chronic haemodialysis patients are at increased risk for developing tuberculosis (TB). Appropriate screening methods to detect latent Mycobacterium tuberculosis infection are required. The aim of this prospective multi-centre study was to evaluate the tuberculin skin test (TST) as a screening method for detection of M.tuberculosis infection in haemodialysis patients.

METHODS

A total of 224 patients in two haemodialysis centres were prospectively tested, using 2 units of tuberculin PPD RT23. Up to three booster injections were given with a 7 day interval to patients not responding to the previous test. The results were compared with clinical and radiological data.

RESULTS

The cumulative prevalence of a positive TST was 14.7% for the first test, 27.8% for the second test and 32.6% for the fourth test. There was no influence of age, gender, haemodialysis centre, dialysis efficiency, nutritional state, levels of zinc, vitamin D therapy, primary renal disease, (previous or active) immunosuppressive therapy or response to hepatitis B vaccination. There was a significant, but weak, correlation between TST positivity and a history of positive TST or TB. Chest radiography and positive TST were not correlated, yet a positive chest X-ray increased the detection of patients with latent M.tuberculosis infection up to 47.8%.

CONCLUSIONS

In haemodialysis patients, a positive response of >30% to repeated TST was obtained. Two consecutive TSTs were sufficient to recruit most of the booster reactions. Since only a weak correlation was found with anamnestic data, regular TST evaluation in combination with a chest X-ray, is a useful tool to detect infection with M.tuberculosis in haemodialysis patients.

Cessation of steroids in stable renal transplant patients: the Leuven experience

Because of the major long-term impact of steroids on the quality of life of renal allograft recipients, physicians are attempting to avoid, reduce or eliminate steroids from the immunosuppressive regimen after renal transplantation. In 311 stable renal transplant recipients, transplanted more than one year and with low immunological risk for rejection, an attempt was made to stop steroids. A permanent cessation of steroids succeeded in 274. Cessation of steroids in stable renal transplant patients resulted in a transient rise of serum creatinine over 3 months. This was reflected in a decreased GFR in the first month. A concomitant change in potassium and weight suggested a minor mineralocorticoid deficiency as plausible explanation. After 4 years, serum creatinine again rose slightly; however, this was not reflected in a decreased GFR. This might reflect a metabolic phenomenon rather than immunological one because patients with acute rejection were excluded from this group and also because there was a small rise in weight and blood pressure noted after the second year following cessation of steroids. Only a mild and transient drop in lipids was present after cessation of steroids. Steroid withdrawal was unsuccessful in 12% of patients, and was twice as high in female patients as in males. Adrenal cortical deficiency was the most prominent reason (3%); acute rejection developed in only 5 patients (1.6%) and chronic rejection was documented in only 4 (1.3%). A better graft and patient survival rate and similar renal function, degree of proteinuria and blood pressure 10 years after renal transplantation (and 6 years after cessation of steroids) compared with patients in whom steroids were never stopped, are very promising despite the selection bias. Although longer follow-up is needed to determine whether stopping steroids will result in altered long-term transplant function, these results are reassuring that steroids can be withdrawn in stable renal transplant patients with a low immunological risk in order to diminish the long-term morbidity associated with corticosteroid therapy.

Measurement of hepatic and intestinal CYP3A4 and PGP activity by combined po + iv [14C]erythromycin breath and urine test

The aim of the present study was to develop a test for measuring hepatic and intestinal removal of cytochrome p-450 3A4 (CYP3A4)- and P-glycoprotein (PGP)-dependent xenobiotics that would be applicable for clinical use in humans. Orally and intravenously administered [N-methyl-14C]erythromycin was used for evaluation of 14C-labeled excretion dynamics in breath and urine. Simultaneous breath and urine test measurements were performed in 32 healthy volunteers and in 23 renal transplant recipients. Mathematical analysis of the excretion rate of labeled CO2 in breath and labeled carbon in urine resulted in 1). separation of both CYP3A4 and PGP activity in the liver and the intestinal mucosa and 2). numerical calculation of the dynamics of the different processes. The test was sufficiently sensitive to detect theoretically predicted process-specific pharmacological modulations by different drugs in healthy volunteers and after recent renal transplantation. It is concluded that the combined oral and intravenous erythromycin breath and urine test is a reliable and noninvasive test to measure phenotypic intestinal and hepatic CYP3A4 and PGP activity and may be a promising tool for prediction of drug interactions and dose adjustment of many pharmacotherapeutics in clinical practice, e.g., immunosuppressive agents after renal transplantation.

Influence of SDZ RAD vs. MMF on gastric emptying in renal transplant recipients

SDZ RAD and mycophenolate mofetil (MMF) are increasingly used in the prevention of renal allograft rejection. SDZ RAD, having a macrolide structure, and MMF, known with gastrointestinal side-effects, may have gastric motility modifying properties. Gastric emptying was examined 1 yr after renal transplantation in eight patients taking corticosteroids (CS), cyclosporin A (CsA) and SDZ RAD and six patients treated with CS, CsA and MMF. Comparing the two groups, no significant differences in gastric emptying of solids and liquids were noted. Compared with normal volunteers, solid gastric emptying was faster in the SDZ RAD group and similar in the MMF group. It is concluded that in stable renal transplant recipients treated with MMF, gastric emptying was normal. Because of the impact on drug absorption and gastrointestinal symptoms, further studies are indicated to corroborate the potential prokinetic properties of SDZ RAD.

Erosive enterocolitis in mycophenolate mofetil-treated renal-transplant recipients with persistent afebrile diarrhea

BACKGROUND

Diarrhea is the most frequently reported adverse event in mycophenolate mofetil (MMF)-treated transplant patients. The aim of this study was to explore the gastrointestinal tract in MMF-treated renal transplant recipients with persistent afebrile diarrhea to characterize its nature and etiology.

METHODS

Renal transplant recipients with persistent afebrile diarrhea (daily fecal output >200 g) were prospectively investigated for infections, morphologic, and functional (gastrointestinal motility and intestinal absorptive capacity) integrity of the gastrointestinal tract; 26 patients met the inclusion criteria.

RESULTS

All but one patient had an erosive enterocolitis. Seventy percent of the patients had malabsorption of nutrients, contributing to the diarrhea. In +/-60%, an infectious origin was demonstrated and successfully treated with antimicrobial agents without changes in immunosuppressive regimen. In +/-40%, no infection occurred, but a Crohn's disease-like pattern of inflammation was noted. These patients also had a less pronounced bile-acid malabsorption but a significant faster colonic transit time, correlating with the trough level of mycophenolic acid (MPA). Cessation of MMF, however, was associated with allograft rejection in one third of these patients.

CONCLUSIONS

Persistent afebrile diarrhea in renal transplant recipients is characterized by erosive enterocolitis, which is of infectious origin in +/-60%. In +/-40%, a Crohn's disease-like (entero-)colitis was present. Because reduction or cessation of MMF was the only effective therapy, MPA or one of its metabolites may be suggested as a possible cause. However, reduction or cessation of MMF was associated with an increased risk for rejection.

Differential effect of diarrhea on FK506 versus cyclosporine A trough levels and resultant prevention of allograft rejection in renal transplant recipients

Diarrhea is the most frequently reported adverse event in patients treated with mycophenolate mofetil. Twenty-six renal transplant patients on a mycophenolate mofetil-based immunosuppressive regime with persistent afebrile diarrhea were examined. Diarrhea caused a significant rise in FK-506 trough levels despite intake of stable doses, necessitating FK-506 dose reductions of 30% to obtain pre-diarrhea trough levels. In contrast, trough levels of cyclosporine A remained stable without dose adjustments. This suggests that absorption and/or metabolism is differentially altered for FK506 compared with cyclosporine A in patients with diarrhea. In nine patients mycophenolate mofetil was reduced or stopped because of persistent diarrhea without identifiable cause. This resulted in end-stage renal disease because of chronic rejection in two patients, and in acute rejection in two patients, all taking FK506 and steroids. Therefore, dose adjustments of FK506 in patients with diarrhea must be carefully monitored, especially when doses of mycophenolate mofetil are also reduced.

Posttransplantation diabetes mellitus in FK-506-treated renal transplant recipients: analysis of incidence and risk factors

BACKGROUND

The development of posttransplantation diabetes mellitus has a major impact on the quality of life and long-term outcome.

METHODS

One hundred thirty-nine patients without known glucose metabolism abnormalities and treated with FK-506, methylprednisolone, and mycophenolate mofetil/azathioprine were analyzed for incidence of and risk factors for developing impaired fasting glycemia (IFG) and diabetes mellitus (DM).

RESULTS

Using the American Diabetes Association criteria, 15% developed IFG and 32% developed DM in the first year after transplantation. High trough levels of FK-506 during the first month after transplantation (especially >15 ng/ml) and high body mass index (BMI) were significant risk factors for IFG or DM. Patients with (steroid-treated) acute rejections in addition to high trough levels of FK-506 were most prone to develop DM, whereas high BMI conferred risk of developing IFG. Patients with posttransplantation glycemic abnormalities also had higher levels of serum triglycerides at the time of transplantation, but they needed a lower dose of FK-506 to obtain higher trough levels of FK-506, suggesting metabolic differences already present before transplantation. The only risk factor retained for persistent IFG or DM beyond the first year was a higher number of trough levels of FK-506 >15 ng/ml during the first month after transplantation.

CONCLUSIONS

Induction with an FK-506 based immunosuppressive regimen resulted in a high incidence of glucose metabolism disorders in renal transplantation recipients. Higher trough levels of FK-506 during the first month, acute rejections, and higher BMI were the most obvious risk factors.

Differences in gastric motor activity in renal transplant recipients treated with FK-506 versus cyclosporine

BACKGROUND

Little is known concerning gastric motility after renal transplantation and on the impact of immunosuppressants on gastric emptying.

METHODS

Gastric emptying was measured in renal transplant recipients, taking different immunosuppressive therapy (steroids and cyclosporine/azathioprine/FK-506), and compared with normal volunteers.

RESULTS

After renal transplantation, gastric emptying of liquids was normal, irrespective of the type of immunosuppression. However, solid gastric emptying was significantly faster in FK-506-treated patients compared with patients taking cyclosporine for all measured emptying parameters. Compared with normal volunteers solid gastric emptying was slower in patients taking cyclosporine, comparable in azathioprine treated patients, and characterized by an unusual short lag phase in patients taking FK-506.

CONCLUSIONS

In stable renal transplant recipients gastric emptying of solids was significantly faster in patients on FK-506 compared with patients taking cyclosporine. Therefore, FK-506 may be the immunosuppressant of choice after solid organ transplantation in patients with problems related to gastroparesis.

Gastric emptying in hyperemesis gravidarum and non-dyspeptic pregnancy

BACKGROUND

Emesis and hyperemesis are significant problems associated with early pregnancy. However, gastric emptying of solids has never been studied during early pregnancy in humans.

AIM

To investigate gastric emptying of solids in patients recovering from hyperemesis gravidarum and in non-dyspeptic pregnant women and to compare these results with a group of healthy non-pregnant women.

METHODS

Fourteen patients with hyperemesis gravidarum, 10 non-dyspeptic pregnant women and 36 non-pregnant women in the first half of the menstrual cycle underwent a gastric emptying study. Seven non-pregnant women repeated the test in the post-ovulatory period.

RESULTS

Gastric emptying of solids was not significantly delayed in non-dyspeptic pregnant women compared with non-pregnant women. The emptying rate tended to be impaired in the post-ovulatory period of the menstrual cycle. Solid emptying was significantly accelerated in patients recovering from hyperemesis gravidarum, correlating well with thyroid function in the latter group.

CONCLUSION

Pregnancy in humans is not associated with decreased solid gastric emptying. In subjects recovering from hyperemesis gravidarum, solid emptying is increased, correlating well with thyroid function abnormalities. Nausea and vomiting in hyperemesis are therefore probably not due to upper gastrointestinal disorders.

Gastric emptying flow curves separated from carbon-labeled octanoic acid breath test results

Recently, we developed the [13/14C]octanoic acid breath test to measure gastric emptying of solids. Although the method has been validated extensively, absorption, metabolism, and excretion of the label in the breath need to be corrected for. In this study a mathematical model was developed that allows for 1) separation of the global CO2 excretion after ingestion of the labeled test meal into the emptying rate of the labeled test meal from mouth to pylorus and the postgastric processing of absorption, metabolism, and excretion of the label, and 2) numerical calculation of the half-emptying time and lag phase of the emptied meal. The model was applied to the gastric emptying results obtained by simultaneous scintigraphic and breath test measurements. An excellent correlation was found between the gastric half-emptying time (r = 0.98) and lag phase (r = 0.85) determined scintigraphically and via breath test. There was also a good agreement between the two methods [mean values and confidence limits for differences: t1/2 = 10 min (-20 to 41) and tlag = -3 min (-39 to 34)]. Moreover, the separated gastric emptying curves, lacking the influence of postgastric processing of the label, showed real patterns of gastric outflow, which changes from moment to moment.

Gastric emptying of the liquid, solid and oil phase of a meal in normal volunteers and patients with Billroth II gastrojejunostomy

BACKGROUND

The relationship between gastric emptying of different phases of a meal in humans has only been partly studied in normal subjects and in patients with previous gastric surgery.

METHODS

In the present study, gastric emptying of the liquid, solid and oil phase and the relationship between the phases was evaluated in 10 normal control subjects and in seven patients with Billroth II gastrojejunostomy using breath test technology.

RESULTS

Gastric emptying in normal subjects showed a clear separation between the emptying of the liquid, solid and oil phase. In healthy volunteers, the liquid phase emptied in the same manner in the presence of a solid phase as in the presence of an oil phase. In contrast, the oil phase emptied more slowly with liquids than with solids. The emptying rate of the oil phase was not only inversely related to the amount administered but was also dependent on its chemical composition. Gastric emptying in patients with Billroth II gastroenterostomy was characterized by a complete loss of discrimination between the different phases of the meal, with an extremely fast emptying of the oil phase compared with normal control subjects.

CONCLUSION

In normal subjects, the liquid, solid and oil phase of a meal are emptied differently. In patients with Billroth II gastrojejunostomy, dumping of the oil phase is the most pronounced difference from the normal physiology of gastric emptying. This could be one of the reasons why Billroth II gastrectomy may be associated with fat malabsorption.

Gastric emptying rate of solids in patients with nonulcer dyspepsia

The underlying role of motility disorders and delayed gastric emptying in nonulcer dyspepsia is still questioned. This study aimed to determine the role of the gastric emptying rate of solids in patients with nonulcer dyspepsia. By means of breath test technology, gastric emptying results of 344 consecutive patients with nonulcer dyspepsia were compared with those of 70 normal healthy volunteers. Although gastric emptying was significantly delayed in patients with nonulcer dyspepsia compared with normal volunteers, there was a great overlap between the two groups. Using 5-95% confidence intervals of the control group in about 30% of the patients with nonulcer dyspepsia gastric emptying was delayed. No correlation was found between gastric emptying rate and age, weight, height, or sex of the subjects in both groups. These findings suggest that, apart from gastric emptying, other mechanisms are very important in the etiology of nonulcer dyspepsia.

Gastric emptying and Helicobacter pylori infection in duodenal ulcer disease

The pathogenetic link between Helicobacter pylori gastritis and duodenal ulcer is still unknown. Fast gastric emptying of liquids might be important in the pathogenesis of gastric metaplasia of the duodenum and duodenal ulcer through an increased exposure of the duodenum to gastric acid. In H. pylori-infected subjects, an abnormal gastric emptying could affect urea breath test results and correlate with histological gastritis. This study was performed to evaluate the gastric emptying of liquids in duodenal ulcer patients with H. pylori infection and the possible relation between the bacterial load, gastric emptying, and urea breath test results. Seventeen duodenal ulcer patients with H. pylori gastritis and 15 healthy volunteers were studied by a [14C]octanoic acid and [13C]urea breath test to evaluate gastric emptying rate and H. pylori status simultaneously. Endoscopy with antral biopsies were performed in all duodenal ulcer patients. Duodenal ulcer patients with H. pylori infection have a normal liquid gastric emptying that is unrelated with histological severity of gastritis. The urea breath test results and the gastric emptying parameters do not correlate with histology. A significant correlation between the gastric emptying and the urea hydrolysis rate is found. It is concluded that H. pylori infection and duodenal ulcer disease is not associated with abnormally fast liquid gastric emptying, and this finding should be taken into account when a casual link between H. pylori infection and duodenal ulcer disease is searched for. The correlation between gastric emptying and urea hydrolysis rate explains why no conclusions on intragastric bacterial load can be drawn from the urea breath test results.

Relation between gastric emptying rate and rate of intraluminal lipolysis

The variable gastric emptying rate of a test meal is one of the major problems in evaluating accurately gastrointestinal physiological functions beyond the stomach. The aim of this study was to evaluate the effect of the gastric emptying rate on the rate of intraluminal lipolysis. Thirty four subjects without pancreatic disease (21 with a normal gastric emptying and 13 with a known slow gastric emptying) and 14 subjects with pancreatic disease (four without and 10 with pancreatic insufficiency) were studied using a dual labelled breath test. The test meal consisted of one egg, 60 grams of white bread, 10 grams of margarine, and 150 ml of water (350 kcal). The egg yolk was labelled with 91 mg of 13C-octanoic acid, the margarine was labelled with 296 kBq of distearyl-2-14C-octanoyl-glycerol. Breath samples were taken every 15 minutes during six hours and analysed for 13CO2 and 14CO2 content. The gastric emptying rate of the meal was evaluated by the gastric emptying coefficient, the half emptying time, and the lag phase; the rate of intraluminal lipolysis was evaluated by the six hours cumulative 14CO2 excretion. Despite a clear distinction in the rate of intraluminal lipolysis, no difference could be detected in gastric emptying rate of the test meal between subjects without and with pancreatic disease. In subjects with pancreatic insufficiency, intraluminal hydrolysis was the rate limiting process in fat assimilation; in patients without pancreatic insufficiency, however, gastric emptying could be rate limiting. Therefore, patients with known slow gastric emptying, displayed a significantly decreased rate of intraluminal lipolysis compared with normal controls. This decrease could be corrected for accurately using a correction factor based on the gastric emptying coefficient. In conclusion, the combined 13C-octanoic acid and 14C-mixed triglyceride breath test permits the measurement of gastric emptying rate and intraluminal lipolysis simultaneously in a minimally invasive way. Correction of intraluminal lipolysis rate for gastric emptying rate of the given test meal permits evaluation of fat assimilation rates in a physiological way regardless of gastric emptying disorders.

Relation between gastric emptying rate and energy intake in children compared with adults

Measurement of gastric emptying rate of solids in children is difficult because the available methods are either invasive or induce a substantial radiation burden. In this study the newly developed 13C octanoic acid breath test was used to examine the gastric emptying rate of solids and milk in healthy children and to compare gastric emptying in children and adults. Fifteen healthy children and three groups of nine healthy adults were studied, using three different test meals labelled with 50 mg of 13C octanoic acid: a low caloric pancake (150 kcal), a high caloric pancake (250 kcal), and 210 ml of milk (134 kcal). Breath samples were taken before and at regular intervals after ingestion of the test meal, and analysed by isotope ratio mass spectrometry. The gastric emptying parameters were derived from the 13CO2 excretion curves by non-linear regression analysis. No significant difference was found between children and adults in the emptying rate of the low caloric solid test meal. In children as well as in adults, increasing the energy content of the solid meal resulted in a significantly slower emptying rate. The milk test meal, however, was emptied at a faster rate in adults and at slower rate in children compared with the low caloric solid test meal. Moreover, the emptying rate of milk in children was significantly slower than in adults. In conclusion, a similar gastric emptying rate of solids but a slower emptying of full cream milk was shown in children of school age compared with adults, using the non-radioactive 13C octanoic acid breath test.

Influence of octreotide on the gastric emptying of solids and liquids in normal healthy subjects

BACKGROUND

The effects of octreotide on small intestinal and gall-bladder motility are well established. However, the influence of octreotide on the gastric emptying rate of both solids and liquids in normal healthy volunteers has never been studied.

METHODS

In nine healthy subjects, the gastric emptying rate of liquids and solids was studied in basal condition and 30 min after subcutaneous administration of 50 micrograms of octreotide, using the combined 14C-octanoic acid/13C-glycine breath test. To determine if the results were entirely due to alterations in gastric emptying, 14/13CO2 excretion rates of intraduodenally administered 14C-octanoic acid and 13C-glycine were measured in basal condition and after subcutaneous injection of octreotide.

RESULTS

After subcutaneous injection of octreotide, the gastric emptying rate of solids was decreased in all but one subject, while the gastric emptying rate of fluids was decreased in all subjects. Nevertheless, 14/13CO2 excretion rates in the breath after intraduodenally administered 14C-octanoic acid and 13C-glycine, were similar in basal condition and after subcutaneous injection of octreotide.

CONCLUSIONS

Subcutaneous injection of a single physiological dose of octreotide induces a marked delay in the gastric emptying of solids and liquids in young healthy volunteers. The combined 14C-octanoic acid/13C-glycine breath test is very well suited to demonstrate this effect, since the absorption and metabolism of octanoic acid and glycine remains unaltered after administration of octreotide.

[*C]octanoic acid breath test to measure gastric emptying rate of solids

We have developed a breath test to measure solid gastric emptying using a standardized scrambled egg test meal (250 kcal) labeled with [14C]octanoic acid or [13C]octanoic acid. In vitro incubation studies showed that octanoic acid is a reliable marker of the solid phase. The breath test was validated in 36 subjects by simultaneous radioscintigraphic and breath test measurements. Nine healthy volunteers were studied after intravenous administration of 200 mg erythromycin and peroral administration of 30 mg propantheline, respectively. Erythromycin significantly enhanced gastric emptying, while propantheline significantly reduced gastric emptying rates. We conclude that the [*C]octanoic breath test is a promising and reliable test for measuring the gastric emptying rate of solids.

Combined carbon-13-glycine/carbon-14-octanoic acid breath test to monitor gastric emptying rates of liquids and solids

The aim of the present study was to develop a dual-carbon-labeled breath test for simultaneously measuring gastric emptying rates of liquids and solids with significantly less radiation burden to the patient than the radioscintigraphic technique.

METHODS

A test meal was used in which the liquid phase was labeled with two markers, i.e., 3.7 MBq of 111In-DTPA and 100 mg of 13C-glycine; the solid phase also was dually labeled with 110 MBq of 99mTc-albumin colloid and 74 kBq of 14C-octanoic acid. Simultaneous radioscintigraphic and breath-test measurements were performed in 27 subjects, 10 normal controls and 17 patients with dyspeptic symptoms. Mathematic analysis of the excretion rate of labeled CO2 allowed the definition of four parameters, i.e., the gastric emptying coefficient, the gastric half-emptying time, the peak excretion time and the lag phase.

RESULTS

There was a good to excellent correlation between the gastric emptying coefficient and the scintigraphic half-emptying time (r = 0.74 for liquids and r = 0.88 for solids), between the half-emptying time determined by breath test and the scintigraphic half-emptying time (r = 0.91 for liquids and r = 0.92 for solids), between the peak excretion time and the scintigraphic half-emptying time (r = 0.91 for liquids and r = 0.96 for solids) and between the lag phase of solid emptying determined by both techniques (r = 0.89).

CONCLUSION

The dual carbon-labeled breath test is a valid, minimally invasive technique to measure the gastric emptying rate of both liquids and solids.

Pharmacological modulation of gastric emptying rate of solids as measured by the carbon labelled octanoic acid breath test: influence of erythromycin and propantheline

The *C (13C or 14C) labelled octanoic acid breath test was recently developed to measure the gastric emptying rate of solids. This study aimed to investigate whether it is sensitive enough to detect pharmacologically induced changes in the gastric emptying rate. Nine healthy volunteers were studied in basal condition, after intravenous administration of 200 mg erythromycin, and after peroral administration of 30 mg propantheline. Erythromycin significantly enhanced gastric emptying in all subjects, with an increase of the gastric emptying coefficient (p = 0.0043) in eight of nine and a fall in both the gastric half emptying time (p = 0.0020) and the lag phase (p = 0.0044) in all nine. Propantheline significantly reduced the gastric emptying rate, with a decreased gastric emptying coefficient (p = 0.0007) and an increased gastric half emptying time (p = 0.0168) in all subjects, but no change in the lag phase (p = 0.1214). Further mathematical analysis showed that breath sampling at 15 minutes intervals over a four hour period is recommended to guarantee accuracy and the discriminative value of the breath test in various gastric emptying patterns. In conclusion the *C labelled octanoic acid breath test is sufficiently sensitive to show pharmacologically induced changes of gastric emptying rates of solids.

Measurement of gastric emptying rate of solids by means of a carbon-labeled octanoic acid breath test

BACKGROUND

The aim of the present study was to develop a breath test for measuring gastric emptying rate of solids that would induce less radiation exposure than radioscintigraphy and would be applicable to field testing.

METHODS

A test meal was used in which [14C]-octanoic acid was mixed with egg yolk and prepared as a scrambled egg. The test meal was labeled with a second marker, 99mTc-albumin colloid, and simultaneous radioscintigraphic and breath test measurements were performed in 36 subjects, 16 normal controls, and 20 patients with dyspeptic symptoms. Mathematical analysis of the excretion rate of labeled CO2 resulted in the definition of three parameters, i.e., gastric emptying coefficient, gastric half-emptying time, and lag phase.

RESULTS

There was an excellent correlation between the gastric emptying coefficient and the scintigraphic half-emptying time (r = -0.88); between the half-emptying time determined by the breath test and the scintigraphic half-emptying time (r = 0.89); and between the lag phases determined by scintigraphy and those determined by breath test (r = 0.92). 14C can be replaced by 13C for labeling the octanoic acid used in the breath test.

CONCLUSIONS

It is concluded that the octanoic acid breath test is a reliable noninvasive test to measure gastric emptying rate of solids.