Fractional Excretion Research Articles

A Comparative Analysis of Fractional Excretion of Sodium, Potassium and Magnesium among T2DM Patients with Increased Albuminuria and Normal Albuminuria in a Tertiary Care Hospital- An Observational Study

Background: T2DM often leads to diabetic kidney disease, a condition marked by change in GFR and urinary albumin excretion. The renal handling of key electrolytes like sodium, potassium, and magnesium plays a crucial role in the progression of renal tubulointerstitial damage in diabetic patients. Aim of the study: The aim of this study was to compare the fractional excretion of sodium, potassium and magnesium among T2DM patients with increased albuminuria and normal albuminuria. Methods: This observational study was conducted in Department of Nephrology, Chattogram, Bangladesh from February 2021 to January 2022. Total 125 patients with T2DM were included in this study. Result: Baseline characteristics showed no significant differences across the study groups. Biochemically, eGFR decreased non-significantly from 95.5 to 86.1 ml/min/1.73 m² across groups, while UACR significantly increased from 14.3 to 1056 mg/gm (P<0.001). FBG levels were similar, but 2hPPBG showed a significant decrease from 8.2 to 7.4 mmol/l (P=0.0041). HbA1C levels varied slightly. FENa, FEK, and FEMg showed significant differences across groups, with FENa ranging from 0.59% to 0.56% (P=0.0016), FEK from 9.4% to 6.9% (P=0.0358), and FEMg from 2.87% to 5.58% (P=0.001). Correlations revealed significant negative associations of eGFR with FENa, FEK, and FEMg, and a significant positive correlation of FEMg with UACR. No significant correlations were found between FBG, 2hPPBG, HbA1C, and the electrolytes excretion. Conclusion: Significant variations in the fractional excretion of sodium, potassium, and magnesium were observed. Higher eGFR was associated with lower electrolyte excretion, and a significant positive correlation was found between magnesium excretion and UACR.

Short-term effects of small volume saline infusion on acid base equilibrium in critically ill patients.

Short-term acid-base effects of 0.9% saline solution infusion are not well described. Aim of this study was to assess the effects of a fluid challenge with 0.9% saline in critically ill patients according to the Stewart's approach, which allows a precise determination of acid base equilibrium. In 40 mechanically ventilated critically ill patients, acid-base variables according to Stewart's approach were measured before and after 30 minutes from the infusion of 0.5L of 0.9% saline. Patients were divided in saline responder (fractional sodium excretion increase <0.5) and non-responders, and in patients with (estimated glomerular filtration rate >63 mL/min) and without renal impairment. After saline infusion, plasma sodium concentration did not change (138 [135-141] vs. 138 [135-140] mEq/L, P=0.646), while chloride concentration significantly increased (102 [100-106] vs. 104 [191-106] mEq/L, P=0.003), reducing strong ion difference (37.0 [34.9-38.0] vs. 35.4 [32.7-37.5] mEq/L, P=0.004) without any impact on pH, due to the concomitant albumin dilution. In saline non-responders, the increase of plasma chloride concentration caused a reduction in strong ion difference, while in saline responders both plasma chloride concentration and strong ion difference remained similar. Patients with and without renal impairment presented a similar acid-base response. The infusion of 0.9% saline reduced strong ion difference by increasing plasma chloride concentration, with no effect on pH due to concomitant albumin dilution. Saline non-responders, characterized by the ability to excrete the sodium excess, were more likely to suffer the acidifying effects of saline infusion, while renal function did not affect the acid-base response to saline infusion.

Fractional Excretion of Urate is Positively Associated with Type 2 Diabetes in HUA Patients: A Cross-Sectional Study.

People with hyperuricemia (HUA) are often related to metabolic disorders such as diabetes, metabolic syndrome (MetS), and obesity. However, the correlation between excretion of uric acid and these diseases is unclear. Our study aimed to explore the relationship between uric acid excretion and type 2 diabetes (T2D). A total of 228 HUA patients from Tianjin Medical University General Hospital from 2022 to 2023 were included in this study. We collected demographic, biochemical, and anthropometric data on each subject. Urine uric acid excretion (UUAE) was calculated enzymatically from a single urine collection that lasted 24 hours. And fractional excretion of uric acid (FEUA) was calculated from serum uric acid and creatinine and uric acid and creatinine. Binary logistic regression modeling assessed the association between uric acid excretion and T2D. Of the 228 subjects, 13.4% had T2D and 48.7% had obesity. The obesity group had a lower FEUA (p<0.05) and a higher UUAE compared to the control group (p<0.05). And FEUA had a stronger correlation with the risk of T2D (p<0.001). Also, there was a negative association between BMI and FEUA and a positive link between BMI and UUAE in the outpatients. Increased FEUA levels were significantly associated with T2D in HUA patients. Therefore, routine calculating of FEUA is essential for proper diagnosis and appropriate treatment T2D of in HUA patients.

The association between hemoglobin levels and renal function parameters during normothermic machine perfusion: A retrospective cohort study using porcine kidneys.

Ex vivo normothermic machine perfusion (NMP) is a promising tool for assessing an isolated kidney prior to transplantation. However, there is no consensus on the perfusate's optimal oxygen-carrying capacity to support renal function. To investigate the association of hemoglobin levels with renal function parameters, a retrospective analysis of isolated, normothermically, perfused porcine kidneys was performed. Between 2015 and 2021, a total of 228 kidneys underwent 4 h of NMP with perfusates that varied in hemoglobin levels. A generalized linear model was used to determine the association of hemoglobin levels with time-weighted means of renal function markers, such as fractional sodium excretion (FENa) and creatinine clearance (CrCl). Stratified by baseline hemoglobin level (<4.5, 4.5-6, or >6 mmol/L), these markers were modeled over time using a generalized linear mixed-effects model. All models were adjusted for potential confounders. Until a hemoglobin level of around 5 mmol/L was reached, increasing hemoglobin levels were associated with superior FENa and CrCl. Thereafter, this association plateaued. When hemoglobin levels were categorized, hemoglobin <4.5 mmol/L was associated with worse renal function. Hemoglobin levels were neither significantly associated with proteinuria during NMP nor with ATP levels at the end of NMP. Hemoglobin levels >6 mmol/L showed no additional benefits in renal function. In conclusion, we found an association between baseline hemoglobin levels and superior renal function parameters, but not injury, during NMP of porcine kidneys. Furthermore, we show that performing a retrospective cohort study of preclinical data is feasible and able to answer additional questions, reducing the potential use of laboratory animals.

Effect of sodium-glucose cotransporter 2 inhibitor canagliflozin on interstitial glucose concentration in insulin-treated diabetic dogs.

The utility of sodium-glucose cotransporter 2 inhibitors (SGLT2i) has not been reported in insulin-treated diabetic dogs. Canagliflozin, a PO-administered SGLT2i, decreases interstitial glucose concentration (IG) in insulin-treated diabetic dogs. Five insulin-treated diabetic dogs. Uncontrolled open label longitudinal study. Canagliflozin (2-4 mg/kg/day PO) was added to an unchanged insulin dose for 7 days. Fractional excretion of glucose was calculated by dividing the product of urine glucose and serum creatinine concentrations by the product of serum glucose and urine creatinine concentrations. Hypoglycemia was defined as IG <60 mg/dL. Median IG in 2869 measurements obtained while dogs were treated with insulin and canagliflozin was 87 mg/dL (range, 40-500 mg/dL) and was significantly lower than median IG in 1426 measurements obtained while dogs were treated with insulin alone (212 mg/dL; range, 41-500 mg/dL; P < .001). Median fractional excretion of glucose when dogs were treated with insulin and canagliflozin was 1.1% (range, 0.9%-2.0%), significantly higher than when dogs were treated with insulin alone (0.3%; range, 0.01%-1.0%; P = .04). The frequency of hypoglycemia was higher in dogs treated with insulin and canagliflozin (544 of 2869 IG measurements, 19%) compared with the frequency of hypoglycemia in dogs treated with insulin alone (52 of 1426 IG measurements, 4%; P < .001). Canagliflozin may have a role in improving glycemic control in insulin-treated diabetic dogs, but the dose of insulin should be decreased when adding canagliflozin to insulin treatment.

Fractional excretion of urea nitrogen can identify true worsening renal function in patients with heart failure.

Fractional excretion of urea nitrogen (FEUN), used to differentiate the cause of acute kidney injury, has emerged as a useful fluid index in patients with heart failure (HF). We hypothesized that FEUN could be useful in identifying worsening renal function (WRF) associated with poor outcomes in patients with acute HF (AHF). Overall, 1103 patients with AHF (median age, 78years; male proportion, 60%) were categorized into six groups according to the presence of WRF and FEUN values (low, ≤32.1%; medium, >32.1% and ≤38.0%; and high, >38.0%) at discharge. WRF was defined as an increase of ≥0.3mg/dL in the serum creatinine level from admission to discharge. FEUN was calculated by the following formula: (urinary urea×serum creatinine)×100/(serum urea×urinary creatinine). The cut-off values for low, medium, and high FEUN were based on a previous study. The primary outcome of this study was HF readmission after hospital discharge. During the 1year follow-up, 170 HF readmissions occurred. Kaplan-Meier analysis revealed significantly higher HF readmission rates in patients with WRF than in those without WRF (log-rank test, P<0.001). Additionally, among patients with WRF, HF readmission rates were lowest in those with medium FEUN values, followed by those with low FEUN values and those with high FEUN values. On multivariable analysis, the presence of WRF with low or high FEUN values was independently associated with increased HF readmission, as compared with the absence of WRF with medium FEUN values. Notably, no association was noted between WRF with medium FEUN values and HF readmission. The prognostic impact of WRF was significantly mediated by the FEUN values and was associated with worse outcomes only when the FEUN values were either low or high. Our study suggests that FEUN can identify prognostically relevant WRF in patients with AHF.

Low serum carnitine level is associated with increased urinary carnitine excretion in late pregnancy.

Carnitine is essential for fatty acid metabolism. Free carnitine (FCA) is excreted in the urine in the glomerulus, but is partly reabsorbed by a carnitine transporter. The mechanism underlying the decrease in serum carnitine level during pregnancy is unclear. To investigate whether low carnitine level is associated with increased renal excretion in pregnant women. We recruited 43 healthy pregnant and 25 non-pregnant women. Total carnitine (TCA) and FCA levels were measured using the enzymatic cycling method, and the acylcarnitine (ACA) level was calculated. Fractional excretion (FE) was calculated as carnitine clearance divided by creatinine clearance. The mean TCA, FCA, and ACA levels were lower at 12weeks of gestation in pregnant than non-pregnant women (P < .001); the levels decreased further at 36weeks, reaching 39%, 36%, and 52% of those in non-pregnant women, respectively (P < .001). The FEs were 3-4-fold higher in pregnant women than non-pregnant women. Pregnant women had a lower serum FCA/TCA ratio than non-pregnant women (0.788±0.098 vs 0.830±0.074, respectively; P < .05), whereas the urine FCA/TCA ratio was similar between the groups. Low carnitine level is associated with increased renal excretion during late pregnancy.

Fractional excretion of total protein predicts renal prognosis in Japanese patients with primary membranous nephropathy

Abstract Background Primary membranous nephropathy (pMN) is one of the most common types of glomerulonephritis, with a third of patients progressing to renal insufficiency. Various prognostic factors have been reported, of which urinary protein and renal function are the most critical parameters. Fractional excretion of total protein (FETP) indicates protein leakage that accounts for creatinine kinetics and serum protein levels. In this study, we investigated the association between FETP and renal prognosis in pMN. Methods We retrospectively identified 150 patients with pMN. FETP was calculated as follows: (serum creatinine × urine protein)/(serum protein × urine creatinine) %. We divided the patients into three groups according to FETP values and compared the clinicopathological findings. The primary outcome was an estimated glomerular filtration rate (eGFR) decrease of ≥ 30% from the baseline level. Results FETP was associated with urinary protein and renal function, Ehrenreich and Churg stage, and global glomerulosclerosis. The primary outcome was observed in 38 patients (25.3%), and the frequency of the primary outcome was higher in the higher FETP group (P = 0.001). FETP is higher than protein–creatinine ratio (PCR) in the area under the curve. In the multivariate analysis adjusted for age, eGFR, PCR, and treatment, FETP was significantly associated with primary outcome (adjusted hazard ratio, 8.19; P &amp;lt; 0.019). Conclusions FETP is a valuable indicator that can reflect the pathophysiology and is more useful than PCR as a predictor of renal prognosis in patients with Japanese pMN.

Toxicokinetics of homosalate in humans after dermal application: applicability of oral-route data for exposure assessment by human biomonitoring

Homosalate (HMS) is a UV filter used in sunscreens and personal care products as a mixture of cis- and trans-isomers. Systemic absorption after sunscreen use has been demonstrated in humans, and concerns have been raised about possible endocrine activity of HMS, making a general population exposure assessment desirable. In a previous study, it was shown that the oral bioavailability of cis-HMS (cHMS) is lower than that of trans-HMS (tHMS) by a factor of 10, calling for a separate evaluation of both isomers in exposure and risk assessment. The aim of the current study is the investigation of HMS toxicokinetics after dermal exposure. Four volunteers applied a commercial sunscreen containing 10% HMS to their whole body under regular-use conditions (18–40 mg HMS (kg bw)−1). Parent HMS isomers and hydroxylated and carboxylic acid metabolites were quantified using authentic standards and isotope dilution analysis. Further metabolites were investigated semi-quantitatively. Elimination was delayed and slower compared to the oral route, and terminal elimination half-times were around 24 h. After dermal exposure, the bioavailability of cHMS was a factor of 2 lower than that of tHMS. However, metabolite ratios in relation to the respective parent isomer were very similar to the oral route, supporting the applicability of the oral-route urinary excretion fractions for dermal-route exposure assessments. Exemplary calculations of intake doses showed margins of safety between 11 and 92 (depending on the approach) after single whole-body sunscreen application. Human biomonitoring can reliably quantify oral and dermal HMS exposures and support the monitoring of exposure reduction measures.

Nutrient Composition and Feed Hygiene of Alfalfa, Comparison of Feed Intake and Selected Metabolic Parameters in Horses Fed Alfalfa Haylage, Alfalfa Hay or Meadow Hay.

The aim of this study was to examine the nutrient composition and feed hygiene of alfalfa as well as investigate the feed intake, blood, urine and faecal parameters of horses fed alfalfa haylage (AS) compared with alfalfa hay (AH) and meadow hay (MH). A total of 11 geldings were fed ad libitum (2.1% dry matter (DM) of body weight (BW)) with alfalfa haylage, alfalfa hay and meadow hay (MH) in a Latin square design. On days 0 and 21 of the feeding period, blood samples were analysed for kidney and liver parameters. Faecal samples were analysed for pH, DM and short-chain fatty acids (SCFAs). Spontaneous urine was collected during the feeding period to analyse selected parameters. Forage was analysed in terms of feed hygiene and crude nutrients. In several feed samples of AS, AH and MH, the microbial reference ranges were exceeded for product-typical and spoilage-indicating bacteria and fungi. Crude nutrient analyses revealed a median crude protein content of 139 (138/142) g/kg DM for AS, which was similar to that in AH (127-135 g/kg DM) and substantially higher than in MH (79.1-87.7 g/kg DM). The calcium level in AS (11.3 g/kg DM) was significantly higher than that in MH (4.00-4.95 g/kg DM) but not compared with that in AH (9.80-10.4 g/kg DM). All blood parameters were within the reference ranges. Fractional excretion (FE)Ca for AS-fed horses ranged from 8.13 to 22.0%; the FECa for AH-fed horses ranged from 6.48 to 24.8%; the FECa for MH-fed horses ranged from 6.69 to 53.2%. No significant differences were found in faecal pH or SCFA content in AS-fed horses compared with AH-fed and MH-fed horses. We concluded that alfalfa haylage provides an alternative forage for equine nutrition.

Prolonged renal function impairment in infants born during the peri-viable period: A retrospective longitudinal cohort study

BackgroundThe number of infants born during the peri-viable period who survive has been increasing. AimTo clarify renal function in infants from the time of birth during the peri-viable period until their due date. Study designThis retrospective cohort study was conducted at a single center. SubjectsWe reviewed the data of infants born at ≤28 weeks of gestation between 2018 and 2022 at our hospital. The infants were divided into the following groups: born at 22–24 weeks vs. 25–28 weeks (appropriate-for-gestational age [AGA] infants), and AGA infants vs. small-for-gestational age (SGA) infants (born at 22–28 weeks). Outcome measuresWe compared the perinatal data and renal function of the infants from birth until their due date. ResultsEighty-one infants were included. Their serum creatinine, fractional excretion of sodium, and urine glucose levels were high or positive soon after birth but gradually improved. The urine albumin level was significantly higher among AGA infants born at 22–24 weeks, even at term equivalent age, than among those born at 25–28 weeks. ConclusionsPersistent renal insufficiency was observed even around the term equivalent age in peri-viable infants. Follow-up data collected after the neonatal period should be investigated in these infants.

Association between Regular Exercise and Urinary Uric Acid Excretion in Chinese Adults: A Cross-sectional Study.

Regular exercise decreases the risk of hyperuricemia, which is related to reduced urinary uric acid excretion (UUA/UAE). However, few studies have assessed the association between regular exercise and UAE. We conducted this study to investigate their associations in the general population. This was a cross-sectional study that involved a total of 5513 Chinese community-dwellers, who reported data on physical exercise. Fasting morning spot urine was used to measure UUA and creatinine. UAE was primarily assessed by UUA to creatinine ratio (UCr) and secondly by excretion of uric acid per volume of glomerular filtration (EurGF) and fractional excretion of uric acid (FEua). Linear regression analysis was used to assess their associations. Of the included participants, their mean age was 55.1 ± 13.0 years, and 1984 (36.0%) undertook regular exercise. Compared with participants with regular exercise, those with irregular exercise or no exercise had higher UUA/UCr (0.36 ± 0.15 vs. 0.39 ± 0.15, P < 0.001), EurGF (0.23 ± 0.10 vs. 0.24 ± 0.11 mg/dL, P < 0.001), and FEua (0.07 ± 0.04 vs. 0.08 ± 0.04, P = 0.006). These associations remained significant after controlling for multivariable including serum uric acid (SUA) or upon the exclusion of participants with renal dysfunction or urinary tract infection. In conclusion, regular exercise might be associated with decreased UAE, independent of SUA, in Chinese community-dwellers.

Hepatorenal Syndrome Type 1: Diagnosis and Treatment.

Hepatorenal syndrome (HRS)is a feared complication in patients with advanced cirrhosis and is associated with significant morbidity and mortality. While recognized as a distinct physiologic condition for well over one hundred years, a lack of objective diagnostic tests has made the diagnosis one of exclusion. Since 1979, multiple sets of diagnostic criteria have been proposed. Though varying in detail, the principal intent of these criteria is to identify patients with severe, functional acute kidney injury that is unresponsive to volume resuscitation and exclude those with structural injury. However, accurate differential diagnosis remains challenging. Recently, multiple urinary biomarkers of kidney injury, including neutrophil gelatinase-associated lipocalin, have been studied as a means of objectively phenotyping etiologies of acute kidney injury in patients with cirrhosis. Along with markers reflecting tubular functional integrity, includingthe fractional excretion of sodium, injury markers will likely be incorporated into future diagnostic criteria. Making an accurate diagnosis is critical, as therapeutic options exist for HRS but must be given in a timely manner and only to those patients likely to benefit. Terlipressin, an analog of vasopressin, is the first line of therapy for HRS in much of the world and has recently been approved for use in the United States. Significant questions remain regarding the optimal dosing strategy, metrics for titration, and the potential role of point-of-care ultrasound to help guide concurrent albumin administration.

Association between urinary uric acid excretion and kidney outcome in patients with CKD

Inhibiting tubular urate reabsorption may protect the kidney from urate-induced tubular injury. However, this approach may promote intratubular uric acid crystallization, especially in acidified urine, which could be toxic to the kidney. To assess how tubular urate handling affects kidney outcomes, we conducted a retrospective cohort study including 1042 patients with estimated glomerular filtration rates (eGFR) of 15–60 mL/min/1.73 m2. The exposures were fractional excretion of uric acid (FEUA) and urinary uric acid-to-creatinine ratio (UUCR). The kidney outcome was defined as a halving of eGFR from baseline or initiating kidney replacement therapy. The median FEUA and UUCR were 7.2% and 0.33 g/gCre, respectively. During a median follow-up of 1.9 years, 314 kidney outcomes occurred. In a multivariate Cox model, the lowest FEUA quartile exhibited a 1.68-fold higher rate of kidney outcome than the highest FEUA quartile (95% confidence interval, 1.13–2.50; P = 0.01). Similarly, lower UUCR was associated with a higher rate of kidney outcome. Notably, patients in the highest quartile of FEUA and UUCR were at the lowest risk of kidney outcome even among those with aciduria. In conclusion, lower FEUA and UUCR were associated with a higher risk of kidney failure, suggesting that increased urate reabsorption is harmful to the kidney.

The Uricosuric Effect of SGLT2 Inhibitors Is Maintained in the Long Term in Patients with Chronic Kidney Disease and Type 2 Diabetes Mellitus.

(1) Background: Sodium-glucose co-transporter 2 inhibitors (SGLT2is) increase uric acid excretion. The intensity of uricosuria is linked to glycosuria. (2) Methods: We aim to analyze the effect of SGLT2 inhibitors on urinary fractional excretion (FE) of uric acid and glucose in patients with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) in a single-center retrospective study with patients with T2DM and CKD who started on treatment with SGLT2is. Patients on renal replacement therapy or with glucagon-like peptide-1 (GLP1) analogs were excluded. Subgroup analysis was performed according to the estimated glomerular filtration rate (eGFR), the SGLT2i molecule, the main comorbidities, and concomitant treatment. As a secondary objective, the study analyzed the effect of SGLT2 inhibitors on uricemia levels. (3) Results: Seventy-three patients were analyzed, with a mean follow-up of 1.2 years. Uric acid and glucose FE significantly increased after the initiation of SGLT2is. This increase remained stable during the follow-up without differences among eGFR groups. No significant reduction in uricemia was observed. However, a trend towards a decrease was observed. (4) Conclusion: The use of SGLT2is in patients with CKD and T2DM is associated with an increase in uric acid FE, which maintains stability irrespective of glomerular filtration loss at least during 24 months of follow-up.

Assessing city-wide pharmaceutical emissions to wastewater via modelling and passive sampling

With increasing numbers of chemicals used in modern society, assessing human and environmental exposure to them is becoming increasingly difficult. Recent advances in wastewater-based epidemiology enable valuable insights into public exposure to data-poor compounds. However, measuring all >26,000 chemicals registered under REACH is not just technically unfeasible but would also be incredibly expensive. In this paper, we argue that estimating emissions of chemicals based on usage data could offer a more comprehensive, systematic and efficient approach than repeated monitoring. Emissions of 29 active pharmaceutical ingredients (APIs) to wastewater were estimated for a medium-sized city in the Netherlands. Usage data was collected both on national and local scale and included prescription data, usage in health-care institutions and over-the-counter sales. Different routes of administration were considered as well as the excretion and subsequent in-sewer back-transformation of conjugates into respective parent compounds. Results suggest model-based emission estimation on a city-level is feasible and in good agreement with wastewater measurements obtained via passive sampling. Results highlight the need to include excretion fractions in the conceptual framework of emission estimation but suggest that the choice of an appropriate excretion fraction has a substantial impact on the resulting model performance.

A261 INVESTIGATING THE RELATIONSHIP BETWEEN AIR POLLUTION AND BIOMARKERS OF CROHN’S DISEASE IN CANADA

Abstract Background The cause of Crohn's disease (CD) remains unclear. Studies suggest a potential connection between CD and air pollution, with a higher occurrence of CD found in areas with higher pollution levels. Aims Our study sought to explore this potential connection by investigating the relationship between components of air pollution and biomarkers indicative of CD risk. Methods In total, 2,256 healthy first-degree relatives of patients with CD were recruited as part of the CCC-GEM Project. We assessed baseline samples of gut permeability using the urinary fractional excretion ratio of lactulose-to-mannitol (LMR), subclinical inflammation via fecal calprotectin (FCP), and stool microbiome using 16S-rRNA sequencing. Air pollutant (n=8) concentrations were obtained from the National Air Pollution Surveillance Database. We used postal code to estimate air pollutant exposure via inverse distance weighting, averaging data for one (pollutant1-month), three (pollutant3-months), and twelve months (pollutant12-months) prior to recruitment. We used generalized estimating equation models to find associations between pollutant exposure and LMR, FCP, and microbiome composition, adjusting for age, sex, air pollutant seasonality, familial income, and familial relationships. Significance was set at pampersand:003C0.05, and false discovery rate (q) correction was applied to microbiome analysis. Results We observed a negative association between particulate matter (PMµg/m3), PM101-month, and PM103-months and LMR (β=-0.06[-0.09, -0.01], p=6.0×10-3 and β=-0.05[-0.07, -0.01], p=7.6×10-4), and a positive association between PM103-months and FCP (β=0.05[0.001, 0.10], p=0.04). 12-month pollutant exposure was associated with seven microbial taxa in a logit model. Notably, Carbon monoxide (CO)12-months was associated with Oscillospiraceae UCG_003 (β=3.49[1.53, 5.46], q=0.03). PM2512-months was associated with Marvinbryantia (β=0.12[0.06, 0.18], q=0.02). PM1012-months was associated with Moryella (β=0.07[0.03, 0.10], q=0.02). Nitrogen dioxide (NO)12-months was associated with Coprobacter and Ruminococcaceae UBA1819 (β=0.05[0.02, 0.07], q=0.03 and β=0.05[0.02, 0.08], q=0.04). NOX12-months was also associated with Ruminococcaceae_UBA1819 as well as Intestinimonas (β=0.03[0.01, 0.04], q=0.04 and β=0.03[0.01, 0.04], q=0.02). Conclusions Air pollutant exposure was associated with biomarkers of gut inflammation, barrier function, and microbiome composition. A shorter exposure (1/3 months) primarily affected FCP and LMR, while longer-term exposure (12 months) exerted a discernible impact on the microbiome. These findings suggest that exposure to air pollution may modulate the gut barrier function, inflammation, and the gut microbiome, biomarkers that are associated with the development of CD. Funding Agencies Crohn’s and Colitis Canada Genetics Environment Microbial (CCC-GEM) III, Leona M. and Harry B. Helmsley Charitable Trust, Dr. Croitoru is the recipient of the Canada Research Chair in Inflammatory Bowel Diseases

A18 EARLY LIFE EXPOSURE TO PARENTAL CROHN'S DISEASE IS ASSOCIATED WITH GUT MICROBIAL COMPOSITION AND FUNCTION, GUT PERMEABILITY AND INCREASED RISK OF FUTURE CROHN'S DISEASE

Abstract Background Previous studies show that offspring of persons with Crohn’s disease (CD) have a 7-fold higher risk of incident CD than the general population. Newborns of women with CD (vs healthy women) have altered stool microbiome composition and elevated fecal calprotectin (FCP). The perinatal period (pregnancy and first year postpartum) is critical for the development of the gut microbiome and immune system. Aims We investigated whether perinatal exposure to parental CD (compared to exposure later in life) has an impact on offspring’s gut barrier function, microbiome composition, and risk of future CD. Methods We assessed 1252 healthy offspring of persons with CD who were recruited in the CCC-GEM Project. We classified offspring into "perinatally exposed (pregnancy and first year postpartum)" vs "exposed later in life" to parental CD diagnosis. We measured baseline FCP and urinary fractional excretion ratio of lactulose to mannitol (marker of intestinal permeability, LMR). Fecal microbiome composition was determined by 16S rRNA gene sequencing. Microbiome function was imputed by PICRUSt2 (q value defined as false discovery rate-adjusted p&amp;lt;0.05). Multivariable regression and Cox proportional-hazards analyses were used to assess if peri-natal exposure to parental CD is associated with LMR, FCP, altered microbial composition, and future CD onset. Results Offspring exposed to a CD parent perinatally had a 4.7-fold higher risk (aHR 95%CI 1.3-17.5) of developing CD compared to those exposed to a parent who developed CD later in life (11/586 vs 3/666). LMR was significantly higher in the offspring exposed to parental CD perinatally (p=0.003), while no significant difference was observed for FCP at recruitment (p=0.94). Five bacterial taxa were significantly increased in the perinatally exposed group (q&amp;lt;0.05). The microbial functions such as glycine amidinotransferase, serine protein kinase and cyanophycin synthase were significantly increased in the perinatally exposed group (q&amp;lt;0.05). Conclusions Offspring exposed to parental CD perinatally had a higher risk of developing CD than those exposed to parental CD later in life. Early life exposure to parental CD was associated with higher baseline LMR, altered bacterial taxa and functional capacities. Environmental exposure during the perinatal period may determine the offspring’s risk of developing CD. Funding Agencies CAG, CCC, CIHRCanada Research Chair

A275 THE POTENTIAL MECHANISTIC ROLES OF SPHINGOLIPIDS IN HEALTHY FIRST-DEGREE RELATIVES OF PATIENTS WITH CROHN'S DISEASE

Abstract Background Crohn's Disease(CD) features a complex etiology intertwining genetic, environmental, and immunological dimensions. Sphingolipids (SPs) are pivotal lipid molecules within cell membranes and various biological processes, including cell growth, apoptosis, and inflammatory responses. While our prior research identified SPs as significant risk factors for CD onset, their pre-clinical influence on CD risk biomarkers and potential role in pathogenesis remains unclear Aims To identify the relationship between SPs and established CD risk factors Methods We used samples from healthy first-degree relatives(FDRs), followed in a nested case-control cohort from the Crohn's Colitis Canada- Genes, Environment, Microbial(GEM) project, matching those who developed CD(n=77) with control FDRs(n=303) based on age, sex, follow-up time, and geographic location. 59 SPs were selected from serum metabolites measured via an untargeted metabolomics platform. We used partial Spearman correlation to identify relationships between SPs and CD risk factors: i)intestinal permeability via the urinary fractional excretion ratio of lactulose to mannitol(LMR); ii)gut subclinical inflammation using fecal calprotectin(FCP); iii)systemic inflammation with C-reactive protein(CRP); iv)microbiome composition through fecal 16S rRNA sequencing and v)serum protein profile using the Olink® Proximity Extension Assay platform. A two-sided qampersand:003C0.05 was considered significant Results We identified 38 positive correlations between CRP and SPs across various sub-pathways, including Ceramides, Sphingomyelins and Hexosylceramides(0.117≤rho≤0.342, 1.37×10−09≤q≤0.042). One SP Ceramide(d18:1/16:0) correlated positively with FCP(rho=0.201, q=0.012). Moreover, two SPs, N-palmitoyl-sphingosine (d18:1/16:0) and glycosyl-N-(2-hydroxynervonoyl)-sphingosine (d18:1/24:1(2OH)), correlationed with Peptoclostridium genus (rho=0.465 and -0.245, q=1.47×10−16 and 0.028 respectively). All SPs correlated with one or more proteins, most positively between Sphingosine-1-phosphate and non-receptor tyrosine kinase(rho=0.637, q=1.98 ×10−36) and most negatively between sphingadienine and Chymotrypsin-C protein(rho=-0.334, q=4.11×10−8). No significant correlations emerged between SPs and LMR Conclusions We identified correlations between SPs and CD risk factors. The correlation with CRP suggests SPs might contribute to systemic inflammatory pathways related to CD. Moreover, correlations with the bacterial taxa highlight SPs' potential role in regulating microbial composition. Extensive correlations with proteins emphasize the pivotal impact of SPs on their function. This study may offer new insights into CD prevention Funding Agencies CCC, CIHR

767 - Fractional excretion of urinary sodium and urinary sediment microscopy for prediction of response to vasoconstrictors in hepatorenal syndrome type 1

767 - Fractional excretion of urinary sodium and urinary sediment microscopy for prediction of response to vasoconstrictors in hepatorenal syndrome type 1