Hereditary renal glycosuria, diabetes and responses to SGLT2 inhibitor.

AIMS: To present the clinical features of two rare cases with hereditary renal glycosuria and diabetes, explore their responses to sodium-glucose cotransporter 2 (SGLT2) inhibitor, and summarize the reported solute carrier family 5 member 2 (SLC5A2) mutations and related phenotypes. METHODS: Two patients were followed up for 6.5 and 3 years respectively. SLC5A2 and hepatocyte nuclear factor 1-alpha (HNF1A) gene were sequenced. We used the flash glucose monitoring system to evaluate the efficacy of SGLT2 inhibitor treatment. Then we retrieved all the literature and analyzed SLC5A2 gene mutations and the phenotypes. RESULTS: During long-time follow up, the two patients had frequent unproportional renal glycosuria in the morning even when their fasting serum glucose was only slightly increased. A novel rare mutation V359G and a pathogenic rare mutation ivs7 + 5G > A in SLC5A2 gene were found respectively. In Case 1, the 24 h glucose excretion was 2.2 g/d and increased to 103 g/d after dapaglifozin treatment, whereas the average glucose (6.33 ± 1.56 vs. 6.28 ± 1.74 mmol/L), and time in range (TIR) (95% vs. 93%) were similar. In Case 2, the 24 h glycosuria was 121.4 g/d and increased to 185.8 g/day after dapaglifozin add-on therapy, with a further reduction of average glucose (9.11 ± 2.63 vs. 7.54 ± 2.39 mmol/L, p < 0.001) and better TIR (70% vs. 84%). We reviewed 139 cases with hereditary renal glycosuria and SLC5A2 gene mutation. The urine glucose was highest in patients with homozygous mutations [64.0(36.6-89.6)g/24 h] compared with compound heterozygous mutations [25.9(14.4-41.2)g/24 h] and heterozygous mutations [3.45(1.41-7.50)g/24 h] (p < 0.001). CONCLUSIONS: Genetic renal glycosuria could not protect individuals completely from developing diabetes. Patients with SGLT2 gene mutations are still responsive to the SGLT2 inhibitor treatment.

[Sodium-glucose cotransporter type 2 inhibitors (SGLT2): from familial renal glucosuria to the treatment of type 2 diabetes mellitus]. / Inhibidores del cotransportador sodio-glucosa tipo 2 (SGLT2): de la glucosuria renal familiar al tratamiento de la diabetes mellitus tipo 2.

For centuries, the kidney has been considered primarily an organ of elimination and a regulator of salt and ion balance. Although once thought that the kidney was the structural cause of diabetes, which in recent years has been ignored as a regulator of glucose homeostasis, is now recognized as a major player in the field of metabolic regulation carbohydrate. During fasting, 55% of the glucose comes from gluconeogenesis. Only 2 organs have this capability: the liver and kidney. The latter is responsible for 20% of total glucose production and 40% of that produced by gluconeogenesis. Today we have a better understanding of the physiology of renal glucose transport via specific transporters, such as type 2 sodium-glucose cotransporter  (SGLT2). A natural compound, phlorizin, was isolated in early 1800 and for decades played an important role in diabetes and renal physiology research. Finally, at the nexus of these findings mentioned above, recognized the effect of phlorizin-like compounds in the renal glucose transporter, which has offered a new mechanism to treat hyperglycemia. This has led to the development of several potentially effective treatment modalities for the treatment of diabetes.

Aglycone exploration of C-arylglucoside inhibitors of renal sodium-dependent glucose transporter SGLT2.

Inhibition of sodium-dependent glucose transporter 2 (SGLT2), the transporter that is responsible for renal re-uptake of glucose, leads to glucosuria in animals. SGLT-mediated glucosuria provides a mechanism to shed excess plasma glucose to ameliorate diabetes-related hyperglycemia and associated complications. The current study demonstrates that the proper relationship of a 4'-substituted benzyl group to a beta-1C-phenylglucoside is important for potent and selective SGLT2 inhibition. The lead C-arylglucoside (7a) demonstrates superior metabolic stability to its O-arylglucoside counterpart (4) and it promotes glucosuria when administered in vivo.

Acquired renal glucosuria in an undifferentiated connective tissue disease patient with a SLC5A2 heterozygous mutation: A case report.

INTRODUCTION: Renal glucosuria is a renal tubular disorder caused by genetic conditions, drugs, and poisons. Mutations in the SLC5A2 gene are recently found to be responsible for the inherited renal glucosuria, while undifferentiated connective tissue disease (UCTD) was not considered pathogenic for renal glucosuria. Here, we present a case of acquired renal glucosuria in a UCTD patient. PATIENT CONCERNS: A 30-year-old woman was seen in the outpatient clinic for complaints of frequent urination and dysuria. Laboratory tests showed a urinary tract infection (UTI) and persistent renal glucosuria. After antibiotic treatment, the UTI symptoms were relieved, but the renal glucosuria remained. DIAGNOSIS: Laboratory tests ruled out renal tubular acidosis and diabetes mellitus. Genetic analysis showed a heterozygous mutations in the SLC5A2 gene. Meanwhile, immunological tests showed a high antinuclear antibody titer (1:160) and an elevated anti-Rho/SSA antibody level. Schirmer test, tear breakup time, and lip biopsy results were all negative. The patient did not meet the criteria for any known connective diseases. Therefore, she was diagnosed with UCTD. INTERVENTIONS: The patient was started with the treatment of Hydroxychloroquine. OUTCOMES: Hydroxychloroquine treatment resolved the renal glucosuria. The patient's follow- up urinalysis showed no glucosuria at all. LESSONS: This is the first case report to demonstrate that UCTD may induce renal glucosuria in a patient with a heterozygous mutation in SLC5A2. This case suggests that during the process of diagnosing renal glucosuria, in addition to familial renal glucosuria (FRG), autoimmune diseases, though rare, should also be taken into consideration.

Reversible renal glycosuria in acute interstitial nephritis.

Renal glycosuria is defined as the excretion of glucose in urine in a normoglycemic state. It results from renal tubular dysfunction or immaturity of tubular function in the newborn. Etiologically, renal glycosuria is of 3 types-benign renal glycosuria, glycosuria with diabetes mellitus (including gestational diabetes) and tubular defects (Fanconi syndrome). Prognosis of benign renal glycosuria is excellent and reversible. Acute interstitial nephritis (AIN) is one of the main causes of acute renal failure and may often result in tubular dysfunction. In this study, the authors report the occurrence of AIN with acute renal failure that contributed to reversible renal glycosuria. The glycosuria observed in the patient of this study was an isolated tubular defect, with no phosphaturia, aminoaciduria or bicarbonaturia. Such a presentation is very rare in adults and has not been previously reported. These findings confirm that AIN with acute renal failure can cause an isolated tubular defect with benign reversible glycosuria in an adult.

[Renal dlabetes and chemical diabetes. Course in young subjects with normal weight (author's transl)]. / Diabète rénal et diabète chimique. Evolution chez des sujets jeunes de poids normal.

Ninety-two young patients of normal weight with glycosuria were classified according to the results of glucose tolerance tests into renal diabetes (32 cases) and chemical diabetes (53 cases). After 5 years or more 17 of the patients with renal diabetes were located. In only one case had the development of chemical diabetes led to correction of the initial diagnosis to that of potential diabetes with a reduced renal glucose threshold. Family histories of diabetes were identical in both groups (renal and chemical diabetes) (35 %) and did not provide any means for distinguishing renal diabetes from diabetes mellitus with a reduced renal glucose threshold. Amongst the 34 subjects with chemical diabetes who were located, 3 had become frank diabetics (9 %). Chemical diabetes persisted in 14 patients (42 %) and 17 (50 %) could be considered to be normal. In addition to the three subjects with frank diabetes, only 9 patients (5 with chemical diabetes and 4 normal) continued to take oral therapy at the time of the final examination. However, 13 of these patients who were not taking any treatment had abandoned it relatively recently. Even if the effectiveness of oral therapy is not fully clear, it should be remembered that continued treatment renders the patient less neglectful as far as diet is concerned. Tests for microangiopathy in the three diabetic patients were negative.