[Gitelman syndrome: a crucial role of laboratory medicine for the diagnosis]. / Le syndrome de Gitelman : un diagnostic avant tout biologique.

We described a case of Gitelman syndrome. A 56-year-old healthy man presented with facial paralysis. Initial laboratory tests revealed hypokalemia. Despite potassium supplements, kaliemia remains at low levels. Further investigations showed urinary potassium wasting, hypomagnesemia and hypocalciuria. Diagnosis of Gitelman syndrome has been confirmed by molecular diagnosis with identification of a composite heterozygote mutation on SLC12A3 gene. One of the mutations on exon 1 SCL12A3 gene wasn't yet known. In the patient family, the same genetic disorder has been found in the sister. Treatment and follow up schedule were proposed to patient.

Gitelman syndrome as a cause of psychomotor retardation in a toddler.

INTRODUCTION: Gitelman syndrome (GS) is a very rare autosomal recessive tubulopathy due to loss-of-function or mutation in solute carrier family12, member 3 gene (SLC12A3 gene) encoding thiazide-sensitive NaCl co-transporter in the distal convoluted tubule, leading to hypokalemia, metabolic alkalosis, hypomagnesemia, hypocalciuria and low-to-normal blood pressure. Clinical signs are mostly secondary to chronic hypokalemia and include dizziness, fatigue, constipation and weakness. Patients can also present with muscle cramps, tetany, fatigue and convulsions due to severe metabolic alkalosis or hypomagnesemia. Manifestations of GS are rarely apparent before the age of five, and the syndrome is usually diagnosed during adolescence or adulthood. Here we describe a case of GS presenting in infancy with hypokalemia and psychomotor retardation. CASE REPORT: We present an 18-month-old boy who presented with psychomotor retardation and failure to thrive. Investigations revealed hypokalemia at 2.7 mmol/L, metabolic alkalosis, hypocalciuria and normal serum magnesium level. The diagnoses of Barter syndrome (BS) and Gitelman syndrome (GS) were considered. Genetic studies confirmed the diagnosis of GS and three different mutations of in SLC12A3 gene were detected. Two mutations (c.2576T>C and c.2929C>Ty) were considered as causal ones, with the patient´s parents being the heterozygous carriers. Oral potassium supplementation resulted in normalisation of the hypokalemia and psychomotor improvement. CONCLUSION: We report a rare case of psychomotor retardation occurring at an early age in genetically confirmed GS. In spite of being a rare disorder, GS has to be considered in children with developmental delay and muscle weakness. With adequate treatment, GS patients have an excellent prognosis.

Testosterone protects female embryonic heart H9c2 cells against severe metabolic stress by activating estrogen receptors and up-regulating IES SUR2B.

A recent clinical study demonstrated that a testosterone supplementation improves functional capacity in elderly female patients suffering from heart failure. These findings prompted us to consider possible mechanisms of testosterone-induced cardioprotection in females. To address this question we have used a pure female population of rat heart embryonic H9c2 cells. Pre-treatment of cells with testosterone for 24h significantly increased survival of H9c2 cells exposed to 2,4-dinitrophenol (DNP), an inhibitor of oxidative phosphorylation. These cells expressed low level of androgen receptors and the effect of testosterone was not modified by hydroxyflutamide, an antagonist of androgen receptor. In contrast, cyclohexamide, an inhibitor of protein biosynthesis, and tamoxifene, a partial agonist of estrogen receptors, abolished cardioprotection afforded by testosterone. In addition, finasteride, an inhibitor of 5α-reductase, and anastrazole, an inhibitor of α-aromatase, also blocked testosterone-induced cytoprotection. Real time RT-PCR revealed that testosterone did not regulate the expression of nine subunits and accessory proteins of sarcolemmal ATP-sensitive K(+) (K(ATP)) channels. On the other hand, testosterone, as well as 17ß-estradiol, up-regulated a putative mitochondrial K(ATP) channel subunit, mitochondrial sulfonylurea receptor 2B intraexonics splice variant (IES SUR2B), without affecting expression of IES SUR2A. Tamoxifene inhibited testosterone-induced up-regulation of IES SUR2B without affecting IES SUR2A. In conclusion, this study has shown that testosterone protect female embryonic heart H9c2 cells against severe metabolic stress by its conversion into metabolites that activate estrogen receptors and up-regulate IES SUR2B.

Gitelman syndrome: novel mutation and long-term follow-up.

We report a case of Gitelman syndrome presenting with fatigue, paresthesias, weakness of limbs and neck muscles since 2.5 years of age. Investigations showed hypokalemia and hypomagnesemia with urinary magnesium wasting. Genetic analysis revealed the presence of a novel homozygous mutation in the SLC12A3 gene (c.2879_2883+9ins14bp, p.Val 960 Glu fsx12). Management with potassium and magnesium supplements and spironolactone resulted in a significant improvement in symptoms. Over a follow-up of 11 years, the patient showed satisfactory growth and physical development.

Kaiyuqingre formula improves insulin secretion via regulating uncoupling protein-2 and KATP channel.

BACKGROUND: Type 2 diabetes mellitus (T2DM) results from the complex association of insulin resistance and pancreatic ß-cell failure. Recent studies have shown that patients diagnosed with T2DM present with a significant decrease in ß-cell function, which can be further compromised during the progression of the disease. Several mechanisms have been shown to play a role in this process such as glucotoxicity and lipotoxicity, which contribute to accelerating insulin secretion. In this regard, Chinese medicine has a certain advantage. This experiment was performed to observe the effect of a Chinese medicine named Kaiyuqingre formula (KYQRF) on ß-cell function and its mechanisms of action therein. METHODS: High glucose was used to set up a model of ß-cell function failure. At the same time, medicated serum of KYQRF with different doses were administered to the cells. Rosiglitazone was taken as a control to observe the changes in insulin secretion, ATP-sensitive K(+) channels (K(ATP) channel) and uncoupling protein-2 (UCP-2) in each group. RESULTS: KYQRF had some effects on the insulin secretion. In a low glucose environment, no effective change in insulin secretion was observed (P > 0.05). However, insulin levels increased significantly when INS-1 cells were exposed to a high glucose environment (P < 0.05). KYQRF could also enhance cell viability (P < 0.05) in an effect similar to rosiglitazone. Although KYQRF had no effect on inwardly rectifying potassium channels (Kir6.2) (P > 0.05), it could decrease the overexpression of both UCP-2 and sulfonylurea receptor 1 (P < 0.05). CONCLUSION: KYQRF can protect islet function by decreasing UCP-2 and sulfonylurea receptor 1.

[An asymptomatic chronic hypokalaemia]. / Une hypokaliémie chronique asymptomatique.

We report the case of an asymptomatic patient presenting a severe chronic renal hypokalaemia. Once being sure of no diuretics use, two hypothesis can be mentioned for a normotensive patient presenting an hypokalaemia associated with a metabolic alcalosis: Bartter syndrome or Gitelman syndrome. The highlighting of low magnesaemia and hypocalciuria strongly concentrates the diagnosis on Gitelman syndrome. First, this has been strengthened by the results of renal function tests and later it has confirmed by molecular diagnosis with the identification of a known homozygous mutation on SLC12A3 gene. In the patient family, the same chromosomal abnormality has been found in the young sister. For these two patients the treatment ordered is an antikaliuretic diuretic, magnesium and potassium supplements. This case shows the difficulty to diagnose Gitelman syndrome: it is frequently mistaken for Bartter syndrome. The main differences between these two syndromes are magnesaemia and calciuria. Furthemore , patients with Gitelman syndrome are often asymptomatic, this explains why prevalence of this illness is probably underestimated.

Similar effects of all WNK3 variants on SLC12 cotransporters.

With-no-lysine kinase 3 (WNK3) is a member of a subfamily of serine/threonine kinases that modulate the activity of the electroneutral cation-coupled chloride cotransporters. WNK3 activates NKCC1/2 and NCC and inhibits the KCCs. Four splice variants are generated from the WNK3 gene. Our previous studies focused on the WNK3-18a variant. However, it has been suggested that other variants could have different effects on the cotransporters. Thus, the present study was designed to define the effects of all WNK3 variants on members of the SLC12 family. By RT-PCR from a fetal brain library, exons 18b and 22 were separately amplified and subcloned into the original WNK3-18a or catalytically inactive WNK3-D294A to obtain all four potential combinations with and without catalytic activity (18a, 18a+22, 18b, and 18b+22). The basal activity of the cotransporters and the effects of WNK3 isoforms were assessed in Xenopus laevis oocytes coinjected with each of the WNK3 variant cRNAs. In isotonic conditions, the basal activity of NCC and NKCC1/2 were increased by coinjection with any of the WNK3. The positive effects occurred even in hypotonic conditions, in which the basal activity of NKCC1 is completely prevented. Consistent with these observations, when expressed in hypotonicity, all KCCs were active, but in the presence of any of the WNK3 variants, KCC activity was completely reduced. That is, NKCC1/2 and NCC were inhibited, even in hypertonicity, while KCCs were activated, even in isotonic conditions. We conclude that the effects of all WNK3 variants toward SLC12 proteins are similar.

Gitelman syndrome in Gypsy paediatric patients carrying the same intron 9 + 1 G>T mutation. Clinical features and impact on quality of life.

BACKGROUND: Gitelman syndrome is a primary tubular disorder causing hypokalaemic metabolic alkalosis with hypocalciuria. Its prevalence is high in Gypsies, who harbour an identical mutation, intron 9 + 1 G>T, in the SLC12A3 gene. METHODS: To better define the Gitelman syndrome in Gypsies, the clinical and biochemical features of 34 Spanish paediatric Gypsy patients were analysed. At diagnosis, symptoms, height and weight as well as serum and urinary biochemical data were collected. During a follow-up of 4.5 ± 2.4 years [X ± standard deviation (SD)], therapy, treatment compliance, symptoms, frequency of hospital admissions and, at the last visit, growth and biochemical work-up of 29 patients followed for at least 6 months were analysed. Quality of life items were also assessed by a questionnaire. RESULTS: Muscle cramps (41%) and asthenia (35%) were the most frequent presenting symptoms. Biochemical data at diagnosis were serum K 2.76 ± 0.46 mEq/L, serum Mg 1.32 ± 0.28 mg/dL, blood pH 7.45 ± 0.06, serum bicarbonate 28.2 ± 2.9 mEq/L, urinary calcium/creatinine ratio 0.03 ± 0.04 mg/mg, fractional K excretion 24.4 ± 17.1% and fractional Mg excretion 8.9 ± 8.3%. During follow-up, Mg and K supplements were prescribed to 79 and 86% of patients, respectively; compliance with treatment was good in 35%. Hospital admission rate was 0.03/patient/month. Muscle cramps were the symptom most often referred by the patients (45%) during the follow-up, and 71% of patients considered their health status as excellent or good. Twenty-one patients stated that their disease did not adversely interfere with their mood or social relationships. Height and weight of patients at diagnosis were -0.60 ± 1.17 and -0.49 ± 1.32 SD, respectively, and improved to -0.44 ± 1.28 (P < 0.05) and 0.18 ± 1.79 SD (P < 0.01) at the last visit. CONCLUSIONS: Gypsy children with Gitelman syndrome mostly exhibit muscle symptoms and asthenia although the disease is not particularly severe in this ethnic group. Body growth improves with treatment and close follow-up.

The mitochondrial bioenergetic phenotype for protection from cardiac ischemia in SUR2 mutant mice.

The sulfonylurea receptor-2 (SUR2) is a subunit of ATP-sensitive potassium channels (K(ATP)) in heart. Mice with the SUR2 gene disrupted (SUR2m) are constitutively protected from ischemia-reperfusion (I/R) cardiac injury. This was surprising because K(ATP), either sarcolemmal or mitochondrial or both, are thought to be important for cardioprotection. We hypothesized that SUR2m mice have an altered mitochondrial phenotype that protects against I/R. Mitochondrial membrane potential (ΔΨ(m)), tolerance to Ca(2+) load, and reactive oxygen species (ROS) generation were studied by fluorescence-based assays, and volumetric changes in response to K(+) were measured by light scattering in isolated mitochondria. For resting SUR2m mitochondria compared with wild type, the ΔΨ(m) was less polarized (46.1 ± 0.4 vs. 51.9 ± 0.6%), tolerance to Ca(2+) loading was increased (163 ± 2 vs. 116 ± 2 µM), and ROS generation was enhanced with complex I [8.5 ± 1.2 vs. 4.9 ± 0.2 arbitrary fluorescence units (afu)/s] or complex II (351 ± 51.3 vs. 166 ± 36.2 afu/s) substrates. SUR2m mitochondria had greater swelling in K(+) medium (30.2 ± 3.1%) compared with wild type (14.5 ± 0.6%), indicating greater K(+) influx. Additionally, ΔΨ(m) decreased and swelling increased in the absence of ATP in SUR2m, but the sensitivity to ATP was less compared with wild type. When the mitochondria were subjected to hypoxia-reoxygenation, the decrease in respiration rates and respiratory control index was less in SUR2m. ΔΨ(m) maintenance in the SUR2m intact myocytes was also more tolerant to metabolic inhibition. In conclusion, the cardioprotection observed in the SUR2m mice is associated with a protected mitochondrial phenotype resulting from enhanced K(+) conductance that partially dissipated ΔΨ(m). These results have implications for possible SUR2 participation in mitochondrial K(ATP).

Network systems biology for drug discovery.

Systems biology provides a platform for integrating multiple components and interactions underlying cell, organ, and organism processes in health and disease. Beyond traditional approaches focused on individual molecules or pathways, bioinformatic network analysis of high-throughput data sets offers an opportunity for integration of biological complexity and multilevel connectivity. Emerging applications in rational drug discovery range from targeting and modeling disease-corrupted networks to screening chemical or ligand libraries to identification/validation of drug-target interactions for improved efficacy and safety.