Primary hyperoxaluria type 1 (PH1) is a rare life-threatening genetic disease related to glyoxylate metabolism and characterized by accumulation of calcium oxalate crystals. Current therapies involve hepatic and/or renal transplantation, procedures that have significant morbidity and mortality and require long-term immunosuppression. Thus, a pharmacological treatment is urgently needed. We introduce here an unprecedented activity of salicylic acid derivatives as agents capable of decreasing oxalate output in hyperoxaluric hepatocytes at the low micromolar range, which means a potential use in the treatment of PH1. Though correlation of this phenotypic activity with glycolate oxidase (GO) inhibition is still to be verified, most of the salicylic acids described here are GO inhibitors with IC values down to 3 μM. Binding mode of salicylic acids inside GO has been studied using in silico methods, and preliminary structure-activity relationships have been established. The drug-like structure and ease of synthesis of our compounds make them promising hits for structural optimization.

The aim of this study was to evaluate differences in short-chain fatty acids (SCFAs) and the total fatty acid profile of faeces or plasma as possible indicators of FRE in comparison with healthy dogs. FRE dogs had a lower concentration (p = 0.026) of plasma α-tocopherol as an indicator of the oxidative status of the animal, and lower C20:5n-3 (p = 0.033), C22:5n-3 (p = 0.005), polyunsaturated fatty acids (PUFA) (p = 0.021) and n-6 (p = 0.041) when compared with the control dogs; furthermore, sick dogs had higher proportions of plasma C20:3n-6 (p = 0.0056). The dogs with FRE showed a decrease in the production of faecal levels of SCFAs, mainly propionic acid (C3) (p = 0.0001) and isovaleric acid (iC5) (p = 0.014). FRE dogs also had a lower proportion of C15:0 (p = 0.0003), C16:1n-9 (p = 0.0095), C16:1n-7 (p = 0.0001), C20:5n-3 (p = 0.0034) and monounsaturated fatty acids (p = 0.0315), and tended to have lower n-3 (p = 0.058) and a reduced desaturase activity index in the stool when compared with the control group. However, the dogs with chronic enteropathy tended to have greater C20:4n-6 (p = 0.065) in their faeces as signs of damage at the intestinal level. The faecal parameters were better predictors than plasma. The highest correlations between faecal odd-chain, medium- or long-chain fatty acids and SCFAs were observed for C15:0 that correlated positively with faecal acetic acid (C2) (r = 0.72, p = 0.004), propionic acid (r = 0.95, p = 0.0001), isobutyric acid (iC4) (r = 0.59, p = 0.027) and isovaleric acid (r = 0.64, p = 0.0136), as well as with total SCFAs (r = 0.61, p = 0.02). Conversely, faecal C20:4n-6 showed a high inverse correlation (r = −0.83, p = 0.0002) with C2 and C3 (r = −0.59, p = 0.027). Canine inflammatory bowel disease (IBD) activity (CIBDAI) index correlated negatively mainly with faecal measurements, such as C3 (r = −0.869, p = 0.0005) and C15:0 (r = −0.825, p = 0.0018), followed by C16:1/C16:0 (r = −0.66, p= 0.0374) and iC5 (r = −0.648, p = 0.0310), which would indicate that these fatty acids could be good non-invasive indicators of the chronic inflammatory status, specifically FRE.

Dogs suffering from food-responsive enteropathy (FRE) respond to an elimination diet based on hydrolysed protein or novel protein; however, studies regarding the amino acid profile in FRE dogs are lacking. The aim of this pilot study was to evaluate whether the plasma and faecal amino acid profiles differed between control and FRE dogs and whether these could serve as indicators of severity of illness. Blood, faecal samples, body condition score, and severity of clinical signs based on the canine inflammatory bowel disease activity index were collected before starting the elimination diet. FRE dogs had lower proportions of plasma Asparagine, Histidine, Glycine, Cystine, Leucine, and branched-chain/aromatic amino acids; however, Phenylalanine increased. In faecal samples, Cystine was greater whereas Phenylalanine was lesser in sick dogs compared to control. Leucine correlated negatively with faecal humidity (r = −0.66), and Leucine and Phenylalanine with faecal fat (r = −0.57 and r = −0.62, respectively). Faecal Phenylalanine (r = 0.80), Isoleucine (r = 0.75), and Leucine (r = 0.92) also correlated positively with total short-chain fatty acids, whereas a negative correlation was found with Glycine (r = −0.85) and Cystine (r = −0.61). This study demonstrates the importance of Leucine and Phenylalanine amino acids as indicators of the disease severity in FRE dogs.

BACKGROUND AND AIMS Patients with primary hyperoxaluria type I (PH I) are prone to develop early end-stage kidney failure (ESKF). Systemic deposition of calcium-oxalate (CaOx) crystals starts when renal function declines and plasma oxalate (Pox) increases >30 µmol/L. It is anticipated that all parenchymal organs, but also bone (marrow), retina and the central nervous system can be involved. However, liver involvement, either as CaOx deposition or as chronic hepatitis/fibrosis, was never reported. METHOD We now examined liver involvement in 19 patients with PH I aged 1.5–52 years. Liver specimen was obtained by biopsy for diagnostic purposes (1), at autopsy (1) or at the time of combined or sequential liver kidney transplantation (17). RESULTS With polarization microscopy, crystals with the typical star-like appearance of CaOx were found in 3/19 patients. The crystals were located in small arteries but not within hepatocytes. Cirrhosis was seen in one patient. Fibrosis was seen in 10/19 patients, with porto-portal and nodular fibrosis (n = 1), and a limitation of fibrosis to the portal field in eight and/or to central areas in five patients. Unspecific hepatitis features were observed in seven patients. Fiber proliferations were detectable in 10 cases, and in one sample, transformed Ito-cells (myofibroblasts) were found. Iron deposition but also megakaryocytes as a sign of extramedullary erythropoiesis were found in nine and three patients, respectively. CONCLUSION Overall, liver involvement in patients with PH I was more pronounced, as previously described. However, compared with CaOx deposition in other organs/tissue, such crystal accumulations were only minimal in the liver, although the oxalate concentration must be the highest.

BACKGROUND AND AIMS Primary hyperoxaluria type 1 (PH1) is a rare metabolic disorder of the glyoxylate metabolism in the liver inducing severe endogenous oxalate overproduction. Massive hyperoxaluria leads to recurrent urolithiasis and/or nephrocalcinosis and often early end-stage kidney failure. Current treatment options were scarce until the first RNA interference drug, Oxlumo® (Lumasiran, Alnylam Pharmaceuticals, USA) can now be prescribed. Oxlumo® targets the mRNA of glycolate oxidase and, thus, prevents its translation. This reduces production of glyoxylate (i.e. the precursor to oxalate) and thus oxalate production. However, glycolate production increases. METHOD We herein report our current clinical experience with s.c. administration of Oxlumo adhering to provide dosage recommendation. A total of 25 PH1 patients were included. Seven patients were on haemodialysis, 1 patient on peritoneal dialysis and 17 were on stable kidney function at start of Oxlumo medication (eGFR > 30 and <55 mL/min in 2 patients and >70 mL/min in all others). The male: female ratio was 15:10, and the age range was 1–62 years of age at start of treatment. In both groups plasma oxalate (Pox) and glycolate (Pglyc) were determined before the first and every next Oxlumo dosage. In non-dialysis patients, urinary oxalate (Uox) and urinary glycolate in 24 h urines were analysed at same interval plus monthly collection until month 6 of treatment and thereafter in 6 weeks’ intervals, if Uox did not reach near normalisation, or had increased again at end of dosing interval (3 monthly). Oxalate and glycolate were determined using ion chromatography/mass spectrometry in the same lab. RESULTS We now report data of those patients, who have received at least four dosages of Oxlumo (n = 15). Non-dialysis patients: Uox was normal (<0.5 mmol/1.73 m2/d) in two patients, in five patients it was near normal (1.5 times the upper limit, <0.75) and in three patients Uox was above 0.75 mmol/1.73 m2/d. Pox was normal in seven and above 7.4 µmol/L in three patients. In seven patients data were available at fifth to seventh dosage interval. Here, one patient had a normal Uox; in all other patients Uox was above 0.75 mmol/1.73 m2/d before next dosage. In the seven dialysis patients median Pox did not really decline over time (median of 45.1 at baseline, n = 7; and 39.9 post fourth dosage, n = 5), as was median Pglyc (86.05/71.1). Patient-specific follow-up differed and must also be related to co-medication with B6. For example, one dialysis patient remained stable with Pglyc below 2 µmol/L (under B6) and another patient experienced Pglyc > 1 mmol/L (without B6). CONCLUSION Oxlumo® has reduced Uox in 7/10 patients after the fourth dosage. However, adjustment of dosage intervals or dosage per se are necessary in the majority of patients to reach the goal of treatment, e.g. at least near normalisation of urinary oxalate excretion. In dialysis patients lack of reduction of Pox maybe because patients dissolve systemic oxalate deposits. However, specific imaging (bone MRI) in three of the dialysis patients did not show improvement of oxalate osteopathy over 6 and 9 months, respectively.

Background and Aims Primary Hyperoxaluria type 3 (PH3) is said to be the less problematic form of PH and with low risk of chronic kidney disease (CKD) and end stage renal disease. However, a recent OxalEurope registry evaluation reported both urine and plasma oxalate levels in a comparable range as in PH1 and PH2 patients. In addition, PH3 patients remain symptomatic with recurrent kidney stones, even in adulthood, and 24% of the 95 patients evaluated were on CKD ≥ 2 at last follow up. Hence, it was speculated, that PH3 patients may also be on risk to develop systemic oxalate deposition. Method We retrospectively analyzed the imaging procedures performed so far in patients regularly seen at the German Hyperoxaluria Center, which included: eye exams; x-rays of the hand; bone MRI (3 Thesla of the left knee and proximal tibia); and Speckle tracking echocardiography using 2D Cardiac Performance Analysis VC (TomTec Imaging Systems GmbH, Germany), which measures changes in global longitudinal strain (GLS), an index of left ventricular contractibility. The normal range for GLS is ≤18%. All patients or parents signed an informed consent. Results From the 49 PH3 patients registered at the German Hyperoxaluria center, 12 pediatric and 4 adult patients are seen on a regular basis, at least twice a year, and the rest are followed in other centers. All the 16 patients were in stable kidney function and in no less than CKD 2. Eye examination was performed in six patients and was normal in all. Four patients received an x-ray of the left hand, which was normal in 3, but in one patient with a problematic clinical course (multiple stone removal procedures, decline in GFR), tiny sclerosing areas, although no true metaphyseal bands, were seen at caput MCP IV and the thumb. Therefore, MRI of the left knee and proximal tibia was performed in this and another patient, which showed no signs of systemic oxalate deposition. Speckle tracking echocardiography was done in 6 patients and was abnormal in one (GLS – 17.3 and left ventricular hypertrophy) and borderline in the twin sibling (GLS – 18.6). The patient with the abnormal GLS also had salivary stones in the parotid gland, as were also found in his other, older sibling in a routine x-ray of the jaw before orthodontic treatment. Conclusion Although this is currently only data of a small cohort of patients, the parameters available so far show, that systemic oxalate deposition may also occur in PH3. Based on our experience on PH1, we regard Speckle tracking echocardiography as the best parameter to detect early systemic calcium-oxalate depositions. Hence the reduction in global longitudinal strain, thus ventricular contractability, is a clear proof of such deposits. Of course, data in more patients are needed to elucidate the true risk of systemic oxalate deposition and we are therefore currently screening all our PH3 patients.

Background and Aims PHIII is seen as the less problematic type of autosomal recessive inherited PH. This group of disorders in glyoxylate metabolism is clinically characterized by recurrent urolithiasis and/or progressive nephrocalcinosis, and, in type I and II, end-stage renal failure. The cause of PHIII was identified only in 2010 and unlike in PHI/II a remarkable low prevalence of symptomatic adults was observed, hence long-term clinical data are scarce. This phenomenon is commonly attributed to reduced penetrance of causative hydroxy-oxo-glutarate aldolase 1 gene (HOGA1) variants and a still unexplained tendency for clinical remission with age. Most PHIII patients present in early childhood with recurrent urolithiasis and undergo (repeated) stone removal procedures. We now hypothesized that repeated stone removal procedures may be associated with decline in kidney function. Method We retrospectively analyzed clinical and laboratory data of 41 genetically confirmed PHIII patients (0.5-29.3 years of age, with (20 different) biallelic mutations in the HOGA1 gene). Period of follow-up ranged from just diagnosed to 22 years. Results Recurrent urolithiasis was most prominently found in the first 3 years of life (>25% of patients). Not all patients experienced clinical remission, 3/6 patients > 20 years of age have ongoing kidney stone development. In addition, patients presented with nephrocalcinosis and/or urolithiasis. A high amount of stone removal procedures during the first years, but also later in life was observed. Urinary oxalate excretion is significantly elevated, and within the range of PHI/II. A decline in kidney function was observed, which is related to a decreased clearance of oxalate (figure). Two patients each post multiple stone removal procedures had CKD stages 2 or 3. Seven further patients had CKD stage 2, which was not related to stone removal. Conclusion PHIII is said to be the most favorable PH type, but early diagnosis is mandatory to treat the patients adequately and to avoid repeated stone removal procedures, which may have an influence on decline in kidney function. This decline may also be related to hyperoxaluria per se, as reported for PHI and II.

Background and Aims In the primary hyperoxalurias (PH; types 1-3) recurrent urolithiasis (UL) and/or progressive nephrocalcinosis (NC) are the clinical hallmarks. Three different enzyme defects lead to endogenous oxalate overproduction and to extremely elevated urinary oxalate excretion (UOx). Thus, it seems logical that urine is supersaturated for calcium-oxalate (CaOx). It was, hence, speculated that urinary CaOx saturation (ßCaOx), calculated by computed programs, is significantly higher as compared to that of patients with idiopathic CaOx stones. We now aimed to evaluate and calculate urinary ßCaOx in PH patients according to type, as well as in non-PH patients with UL or NC. Method The computed equilibrium program EQUIL2 was used for the calculation of ßCaOx. For this, 24 h urine specimen of 70 patients with non-PH NC (46 male, 24 female, median age 6.06 (range 0.3-31.4 years)), of 149 idiopathic CaOx UL (90/59 m/f, age 8.5 (0.1-68.6)), of 51 PH 1 patients (31/21, age 12.33 (0.8-63.8)), of 5 PH 2 patients (3/2, age 5.41 (4.3-12.9)) and of 14 PH 3 patients (8/6, age 8.5 (2.9-29.3)) were analyzed for all necessary components. All patients were in stable kidney function (eGFR > 45 ml/min). Results Uox was higher in the PH patients as compared to the non-PH UL or NC patients (p < 0.05). However, there was no statistical difference between the Uox in PH 1 vs PH 2 or PH 3 patients, although, a clear effect of B6 medication was visible in PH1 patients. Urinary calcium excretion was lower (not significant) in PH patients as compared to NC/UL. There was no difference in ßCaOx when PH were compared to non-PH patients and it mostly remained in the normal range. Conclusion Urine ßCaOx is similar in PH and non-PH stone formers. Therefore, calculation of ßCaOx using computed programs is not a reliable parameter to define the definitively extreme CaOx supersaturation of urine from PH patients. This miscalculation is related to a rather lowish urinary calcium excretion in PH as compared to other UL/NC patients. Therefore, we recommend not to use such programs to express the risk of recurrent stone disease or nephrocalcinosis in PH.