Liddle syndrome misdiagnosed as primary aldosteronism is caused by inaccurate aldosterone-rennin detection while a novel SCNN1G mutation is discovered

PURPOSE

Through describing the confusing misdiagnosis process of Liddle syndrome, we try to reveal the importance of accurate aldosterone-renin detection and a genetic test for Liddle syndrome.

METHODS

We found a family of hypertension and hypokalaemia with the proband of a 21-year-old female who had been misdiagnosed as primary aldosteronism (PA). She presented with high aldosterone and low renin levels. Aldosterone is not suppressed in the saline infusion test and captopril challenge test. However, treatment with a standard dose of spironolactone has no blood pressure improvement effect. A heterozygous variant of SCNN1G was found with whole exome sequencing and Liddle syndrome is indicated. Treatment with amiloride was effective. We rechecked aldosterone-renin levels with two different aldosterone and renin test kits. Clinical features and the mutant gene SCNN1G of each family member were determined by the Sanger method.

RESULTS

The two kits had nearly opposite results. Among those Liddle syndrome patients confirmed by a genetic test, for Test kit A all ARR were screened positive while for test kit B negative. It seems Test kit B is consistent with the diagnosis while test kit A misleads the diagnosis. A novel SCNN1G mutation, c.1729 C > T, was found in this family, which introduce a premature stop codon in the γ subunit in the epithelial Na⁺ channel (ENaC) and resulted in a deletion of 72 amino acids at the carboxyl end.

CONCLUSION

inaccurate ARR detection might misdiagnose Liddle syndrome. A Gene test is an important method for the diagnosis of Liddle syndrome. A novel SCNN1G missense mutation, c.1729 C > T, is found in a Chinese family.

Safety evaluation of the food enzyme chymosin from the genetically modified Kluyveromyces lactis strain CIN

The food enzyme chymosin (EC 3.4.23.4) is produced with the genetically modified Kluyveromyces lactis strain CIN by DSM Food Specialties B.V. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its recombinant DNA. It is intended to be used in milk processing for cheese production and for the production of fermented milk products. Dietary exposure was estimated to be up to 0.73 mg total organic solids (TOS)/kg body weight (bw) per day in European populations. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90‐day oral toxicity study in rats. The Panel identified a no observed adverse effect level of 1,000 mg TOS/kg bw per day, the highest dose tested, which when compared with the estimated dietary exposure, results in a margin of exposure of at least 1,300. Similarity of the amino acid sequence of the food enzyme to those of known allergens was searched for and four matches were found. The Panel considered that under the intended conditions of use the risk of allergic sensitisation and elicitation reactions by dietary exposure, although unlikely, cannot be excluded, particularly for individuals sensitised to cedar pollen allergens. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme chymosin from the genetically modified Aspergillus niger strain DSM 29544

The food enzyme chymosin (EC 3.4.23.4) is produced with the genetically modified Aspergillus niger strain DSM 29544 by Chr. Hansen. The genetic modifications do not give rise to safety concerns. The food enzyme was considered free from viable cells of the production organism and its DNA. It is intended to be used in milk processing for cheese production and for production of fermented milk products. Based on the maximum use levels, dietary exposure to the food enzyme total organic solids (TOS) was estimated to be up to 0.09 mg TOS/kg body weight (bw) per day in European populations. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90‐day oral toxicity study in rats. The Panel identified a no observed adverse effect level of 84.1 mg TOS/kg bw per day, the highest dose tested, which when compared with the estimated dietary exposure, results in a margin of exposure above 930. A search for similarity of the amino acid sequence of the food enzyme to known allergens was made and two matches with respiratory allergens were found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood for this to occur is considered low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme chymosin from the genetically modified Kluyveromyces lactis strain CHY

The food enzyme chymosin (EC 3.4.23.4) is produced with the genetically modified Kluyveromyces lactis strain CHY by DSM Food Specialties B.V. It is intended to be used in milk processing for cheese production and for production of fermented milk products. Dietary exposure was estimated to be up to 0.69 mg total organic solids (TOS)/kg body weight (bw) per day in European populations. The production strain contains multiple copies of known antimicrobial resistance genes and consequently, it does not fully fulfil the requirements for the qualified presumption of safety (QPS) approach to safety assessment. However, considering the absence of viable cells and DNA from the production organism in the food enzyme, this is not considered to be a risk. As no other concerns arising from the microbial source and its subsequent genetic modification or from the manufacturing process have been identified, the Panel considered that toxicological tests were not needed for the assessment of this food enzyme. Similarity of the amino acid sequence of the food enzyme to those of known allergens was searched and four matches were found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure, although unlikely, cannot be excluded, particularly for individuals sensitised to cedar pollen allergens. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Baseline Plasma Aldosterone Level and Renin Activity Allowing Omission of Confirmatory Testing in Primary Aldosteronism

CONTEXT

Previous studies have proposed cutoff value of baseline plasma aldosterone concentration (bPAC) under renin suppression that could diagnose primary aldosteronism (PA) without confirmatory testing. However, those studies are limited by selection bias due to a small number of patients and a single-center study design.

OBJECTIVE

This study aimed to determine cutoff value of bPAC and baseline plasma renin activity (bPRA) for predicting positive results in confirmatory tests for PA.

DESIGN

The multi-institutional, retrospective, cohort study was conducted using the PA registry in Japan (JPAS/JRAS). We compared bPAC in patients with PA who showed positive and negative captopril challenge test (CCT) or saline infusion test (SIT) results.

PATIENTS

Patients with PA who underwent CCT (n = 2256) and/or SIT (n = 1184) were studied.

MAIN OUTCOME MEASURES

The main outcomes were cutoff value of bPAC (ng/dL) and bPRA (ng/mL/h) for predicting positive CCT and/or SIT results.

RESULTS

In patients with renin suppression (bPRA ≤ 0.3), the cutoff value of bPAC that would give 100% specificity for predicting a positive SIT result was lower than that for predicting a positive CCT result (30.85 vs 56.35, respectively). Specificities of bPAC cutoff values ≥ 30.85 for predicting positive SIT and CCT results remained high (100.0% and 97.0%, respectively) in patients with bPRA ≤ 0.6. However, the specificities of bPAC cutoff values ≥ 30.85 for predicting positive SIT and CCT results decreased when patients with bPRA > 0.6 were included.

CONCLUSION

Confirmatory testing could be omitted in patients with bPAC ≥ 30.85 in the presence of bPRA ≤ 0.6.

Aldosterone and renin in cardiac patients referred for catheterization

Little is known regarding alterations of the renin-angiotensin system in patients referred for cardiac catheterization. Here, we measured plasma levels of active renin and aldosterone in patients referred for cardiac catheterization in order to determine the prevalence of elevated renin, aldosterone, and the aldosterone-renin ratio.A chemiluminescence assay was used to measure plasma aldosterone concentration (PAC) and active renin levels in 833 consecutive patients, after an overnight fasting and without any medication for least 12 hours. We evaluated associations of the hormonal elevations in relation to hypertension, atrial fibrillation (AF), hypertensive cardiomyopathy, coronary artery disease (CAD), valvular disease, impaired left ventricular ejection fraction (LVEF < 35%), and pulmonary hypertension (arterial pulmonary mean pressure >25 mm Hg).Hyperaldosteronism occurred in around one-third of all examined patients, without significant differences between patients with or without the named cardiac diseases. In a comparison between patients with or without any given cardiac disease condition, renin was significantly elevated in patients with either hypertension (36.4% vs 15.9%), CAD (33.9% vs 22.1%), or impaired LVEF (47.3% vs 24.8%). The angiotensin-renin ratio was elevated in AF patients and in patients with hypertensive cardiomyopathy. Patients with AF and coexisting hypertension had elevated renin more frequently than AF patients without coexisting hypertension (35.3% vs 16.5%; P  =  .005). Patients with persistent/permanent AF more frequently had elevated renin than patients with paroxysmal AF (34.1% vs 15.8%; P  =  .007).This prospective study of consecutive cardiac disease patients referred for cardiac catheterization has revealed distinct cardiac disease condition-associated differences in the frequencies of elevations in plasma renin, PAC, and the aldosterone-renin ratio.

Production of Bioactive Recombinant Bovine Chymosin in Tobacco Plants

Chymosin (also known as rennin) plays an essential role in the coagulation of milk in the cheese industry. Chymosin is traditionally extracted from the rumen of calves and is of high cost. Here, we present an alternative method to producing bovine chymosin from transgenic tobacco plants. The CYM gene, which encodes a preprochymosin from bovine, was introduced into the tobacco nuclear genome under control of the viral 35S cauliflower mosaic promoter. The integration and transcription of the foreign gene were confirmed with Southern blotting and reverse transcription PCR (RT-PCR) analyses, respectively. Immunoblotting analyses were performed to demonstrate expression of chymosin, and the expression level was quantified by enzyme-linked immunosorbent assay (ELISA). The results indicated recombinant bovine chymosin was successfully expressed at an average level of 83.5 ng/g fresh weight, which is 0.52% of the total soluble protein. The tobacco-derived chymosin exhibited similar native milk coagulation bioactivity as the commercial product extracted from bovine rumen.

Effects of intensive low-salt diet education on albuminuria among nondiabetic patients with hypertension treated with olmesartan: a single-blinded randomized, controlled trial

BACKGROUND AND OBJECTIVES

The antiproteinuric effect of a renin-angiotensin-aldosterone system blockade can be magnified by dietary salt restriction. This study sought to determine the effect of intensive low-salt diet education on BP and urine albumin excretion in nondiabetic patients with hypertension and albuminuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study was conducted between March of 2012 and March of 2013 as an open-label, randomized, controlled trial. After a run-in period of 8 weeks, all patients received the angiotensin II receptor blocker olmesartan (40 mg daily). Patients were then divided into two groups. One group was treated for another 8 weeks with angiotensin II receptor blocker plus conventional low-salt diet education, and the other group was treated for 8 weeks with angiotensin II receptor blocker plus intensive low-salt diet education. The final analyses was performed with 245 completed patients.

RESULTS

The amount of daily albuminuria was significantly decreased from 0 (566.0 [25.0-5398.6] mg/d) to 8 weeks (282.5 [16.1-4898.5] mg/d; P<0.001). From 8 to 16 weeks, the 24-hour urinary sodium excretion was decreased by 36.0±5.9 mmol/d in the intensive education group and 8.8±4.9 mmol/d in the conventional education group (interaction P<0.001). Patients who completed intensive low-salt diet education exhibited greater decreases in urinary albumin excretion than the control group (change in albuminuria from 8 to 16 weeks, -154.0 versus 0.4 mg/d; P=0.01). Urinary albumin excretion tended to decrease as the 24-hour urinary sodium excretion amount decreased (R=0.32; 95% confidence interval, 0.20 to 0.43; P<0.001).

CONCLUSIONS

The 24-hour urinary albumin excretion was decreased more in patients in the intensive low-salt diet education group than patients in the conventional education group. Weekly intensive education on a low-salt diet would be a suitable method for clinical practice.

The succinate receptor as a novel therapeutic target for oxidative and metabolic stress-related conditions

The succinate receptor (also known as GPR91) is a G protein-coupled receptor that is closely related to the family of P2Y purinoreceptors. It is expressed in a variety of tissues, including blood cells, adipose tissue, the liver, retina, and kidney. In these tissues, this receptor and its ligand succinate have recently emerged as novel mediators in local stress situations, including ischemia, hypoxia, toxicity, and hyperglycemia. Amongst others, the succinate receptor is involved in recruitment of immune cells to transplanted tissues. Moreover, it was shown to play a key role in the development of diabetic retinopathy. However, most prominently, the role of locally increased succinate levels and succinate receptor activation in the kidney, stimulating the systemic and local renin-angiotensin system, starts to unfold: the succinate receptor is a key mediator in the development of hypertension and possibly fibrosis in diabetes mellitus and metabolic syndrome. This makes the succinate receptor a promising drug target to counteract or prevent cardiovascular and fibrotic defects in these expanding disorders. Recent development of SUCNR1-specific antagonists opens novel possibilities for research in models for these disorders and may eventually provide novel opportunities for the treatment of patients.