Familial renal glycosuria and modifications of glucose renal excretion

Emergence of a New Glucoregulatory Mechanism for Glycemic Control With Dapagliflozin/Exenatide Therapy in Type 2 Diabetes

CONTEXT

This study addresses the development of a new glucoregulatory mechanism in type 2 diabetes (T2D) patients treated with SGLT-2 inhibitors, which is independent of glucose, insulin and glucagon. The data suggest the presence of a potential trigger factor (s) arising in the kidney that stimulates endogenous glucose production (EGP) during sustained glycosuria.

OBJECTIVE

To investigate effects of SGLT-2 inhibitor therapy together with GLP-1 receptor agonist on EGP and glucose kinetics in patients with T2D. Our hypothesis was that increased EGP in response to SGLT2i-induced glycosuria persists for a long period and is not abolished by GLP-1 RA stimulation of insulin secretion and glucagon suppression.

METHODS

Seventy-five patients received a 5-hour dual-tracer oral glucose tolerance test (OGTT) (intravenous 3-(3H)-glucose oral (1-14C)-glucose): (1) before/after 1 of dapagliflozin (DAPA); exenatide (EXE), or both, DAPA/EXE (acute study), and (2) after 1 and 4 months of therapy with each drug.

RESULTS

In the acute study, during the OGTT plasma glucose (PG) elevation was lower in EXE (Δ = 42 ± 1 mg/dL) than DAPA (Δ = 72 ± 3), and lower in DAPA/EXE (Δ = 11 ± 3) than EXE and DAPA. EGP decrease was lower in DAPA (Δ = -0.65 ± 0.03 mg/kg/min) than EXE (Δ = -0.96 ± 0.07); in DAPA/EXE (Δ = -0.84 ± 0.05) it was lower than EXE, higher than DAPA. At 1 month, similar PG elevations (EXE, Δ = 26 ± 1 mg/dL; DAPA, Δ = 62 ± 2, DAPA/EXE, Δ = 27 ± 1) and EGP decreases (DAPA, Δ = -0.60 ± 0.05 mg/kg/min; EXE, Δ = -0.77 ± 0.04; DAPA/EXE, Δ = -0.72 ± 0.03) were observed. At 4 months, PG elevations (EXE, Δ = 55 ± 2 mg/dL; DAPA, Δ = 65 ± 6; DAPA/EXE, Δ = 46 ± 2) and lower EGP decrease in DAPA (Δ = -0.66 ± 0.04 mg/kg/min) vs EXE (Δ = -0.84 ± 0.05) were also comparable; in DAPA/EXE (Δ = -0.65 ± 0.03) it was equal to DAPA and lower than EXE. Changes in plasma insulin/glucagon could not explain higher EGP in DAPA/EXE vs EXE mg/kg/min.

CONCLUSION

Our findings provide strong evidence for the emergence of a new long-lasting, glucose-independent, insulin/glucagon-independent, glucoregulatory mechanism via which SGLT2i-induced glycosuria stimulates EGP in patients with T2D. SGLT2i plus GLP-1 receptor agonist combination therapy is accompanied by superior glycemic control vs monotherapy.

A transcriptional regulatory network of HNF4α and HNF1α involved in human diseases and drug metabolism

HNF4α and HNF1α are core transcription factors involved in the development and progression of a variety of human diseases and drug metabolism. They play critical roles in maintaining the normal growth and function of multiple organs, mainly the liver, and in the metabolism of endogenous and exogenous substances. The twelve isoforms of HNF4α may exhibit different physiological functions, and HNF4α and HNF1α show varying or even opposing effects in different types of diseases, particularly cancer. Additionally, the regulation of CYP450, phase II drug-metabolizing enzymes, and drug transporters is affected by several factors. This article aims to review the role of HNF4α and HNF1α in human diseases and drug metabolism, including their structures and physiological functions, affected diseases, regulated drug metabolism genes, influencing factors, and related mechanisms. We also propose a transcriptional regulatory network of HNF4α and HNF1α that regulates the expression of target genes related to disease and drug metabolism.

Hereditary tubulopathies accompanying polyuia

Tubulopathies are a group of heterogeneous diseases that are manifested in the malfunction of the renal tubules. This review addresses tubulopathies associated with polyuria syndrome, namely renal glucosuria syndrome, nephrogenic diabetes insipidus and pseudohyperaldosteronism. Types of renal glucosuria are described, namely: type A, type B and the most severe type 0. Type A is characterized by a low filtration threshold and low glucose reabsorption. The type of inheritance is autosomal recessive. Type B, autosomal dominant, is characterized by uneven activity of glucose transport, in which its reabsorption is reduced only in some nephrons. That is, normal reabsorption of glucose is maintained, but the filtration threshold of the latter is reduced. Type 0 with a severe course is characterized by complete inability of epithelial cells of the proximal tubules to reabsorb glucose. Nephrogenic diabetes insipidus is a rare inherited disease caused by impaired response of the renal tubules to antidiuretic hormone (ADH). Depending on the degree of inability to concentrate urine, there are complete and partial forms. It is divided into nephrogenic diabetes insipidus type I (X-linked recessive); nephrogenic diabetes insipidus type II (autosomal recessive and autosomal dominant) and nephrogenic diabetes insipidus syndrome with dementia and intracerebral calcifications (type of inheritance remains unknown). Children with autosomal recessive type of inheritance suffer from the more severe disease course. Pseudohypoaldosteronism is characterized by a special condition of the renal tubules which is due to insufficient sensitivity of the tubular epithelium to aldosterone, which in turn leads to hyperaldosteronism, the development of hyponatremia, metabolic acidosis with hyperkalemia, polydipsia and polyuria, decreased sodium reabsorption and retardation of the child's physical development. The classification includes three syndromes of pseudohypoaldosteronism, namely: type I (PHA1), which is divided into PHA1A (autosomal dominant, renal), PHA1B (autosomal recessive, systemic); type II (PHA2; Gordon’s syndrome), type III (secondary), which develops as a result of renal pathology.

[Reactive hypoglycemia - an interdisciplinary approach of the disease of XXI Century]

Reactive hypoglycemia is characterized by low blood glucose level in non-diabetic patients. It manifests as a syndrome of adrenergic and neuroglycopenic symptoms in the postprandial period, and their resolution occurs after consuming carbohydrates. The etiology of reactive hypoglycemia is not fully understood. It may occur in patients after gastrointestinal surgery due to too fast gastric emptying. Decreases in postprandial glucose are also observed in people with a pre-diabetes condition in which insulin secretion is disturbed. Hypoglycaemia can also be seen in patients with insulin resistance and hyperinsulinism. The aim of this study was to summarize existing knowledge about reactive hypoglycemia - etiology, diagnostic model and treatment.

Renal injury in Seipin-deficient lipodystrophic mice and its reversal by adipose tissue transplantation or leptin administration alone: adipose tissue-kidney crosstalk

Seipin deficiency is responsible for type 2 congenital generalized lipodystrophy with severe loss of adipose tissue (AT) and could lead to renal failure in humans. However, the effect of Seipin on renal function is poorly understood. Here we report that Seipin knockout (SKO) mice exhibited impaired renal function, enlarged glomerular and mesangial surface areas, renal depositions of lipid, and advanced glycation end products. Elevated glycosuria and increased electrolyte excretion were also detected. Relative renal gene expression in fatty acid oxidation and reabsorption pathways were impaired in SKO mice. Elevated glycosuria might be associated with reduced renal glucose transporter 2 levels. To improve renal function, AT transplantation or leptin administration alone was performed. Both treatments effectively ameliorated renal injury by improving all of the parameters that were measured in the kidney. The treatments also rescued insulin resistance and low plasma leptin levels in SKO mice. Our findings demonstrate for the first time that Seipin deficiency induces renal injury, which is closely related to glucolipotoxicity and impaired renal reabsorption in SKO mice, and is primarily caused by the loss of AT and especially the lack of leptin. AT transplantation and leptin administration are two effective treatments for renal injury in Seipin-deficient mice.-Liu, X.-J., Wu, X.-Y., Wang, H., Wang, S.-X., Kong, W., Zhang, L., Liu, G., Huang, W. Renal injury in Seipin-deficient lipodystrophic mice and its reversal by adipose tissue transplantation or leptin administration alone: adipose tissue-kidney crosstalk.

[Role of the kidneys in glucose homeostasis. Implication of sodium-glucose cotransporter 2 (SGLT2) in diabetes mellitus treatment]

Kidney plays an important role in glucose homeostasis, both in the post-absorptive and postprandial period. Kidney produces glucose by gluconeogenesis in the renal cortex and uses glucose for covering energy needs of the medulla. Kidney participates also to the reabsorption of filtered glucose in order the terminal urine was devoided of glucose, as long as blood glucose did not exceed 180mg/dL. Reabsorption of glucose is mediated by sodium-glucose cotransporters (SGLT1 et SGLT2) expressed in S1 and S3 segments of proximal tubule. SGLT2 is the main sodium-glucose cotransporter responsible for 90% of glucose reabsorption. In type 2 diabetics, renal gluconeogenesis and glucose utilisation are increased by 30%. Surprisingly, renal glucose reabsorption is increased, participating to worsening of hyperglycemia. This results from the increase in the renal threshhold of glucose reabsorption (220mg/dL) and from an overexpression of SGLT2 in response to hyperglycemia and of cytokine secretion. The administration of SGLT2 inhibitors to type 2 diabetic patients induced a decreased in the renal threshhold of glucose reabsorption (80mg/dL) and strongly reduced kidney glucose reabsorption. The inhibitors of SGLT2 are the only antidiabetic molecules able to correct the excessive renal glucose reabsorption in type 2 diabetics and thus to contribute, by an original mechanism, to the lowering of blood glucose level.