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Osmotic diuresis by SGLT2 inhibition stimulates vasopressin-induced water reabsorption to maintain body fluid volume.

ABSTRACT: Most of the filtered glucose is reabsorbed in the early proximal tubule by the sodium-glucose cotransporter SGLT2. The glycosuric effect of the SGLT2 inhibitor ipragliflozin is linked to a diuretic and natriuretic effect that activates compensatory increases in fluid and food intake to stabilize body fluid volume (BFV). However, the compensatory mechanisms that are activated on the level of renal tubules remain unclear. Type 2 diabetic Goto-Kakizaki (GK) rats were treated with vehicle or 0.01% (in diet) ipragliflozin with free access to fluid and food. After 8 weeks, GK rats were placed in metabolic cages for 24-hr. Ipragliflozin decreased body weight, serum glucose and systolic blood pressure, and increased fluid and food intake, urinary glucose and Na+ excretion, urine volume, and renal osmolar clearance, as well as urine vasopressin and solute-free water reabsorption (TcH2O). BFV, measured by bioimpedance spectroscopy, and fluid balance were similar among the two groups. Urine vasopressin in ipragliflozin-treated rats was negatively and positively associated with fluid balance and TcH2O, respectively. Ipragliflozin increased the renal membrane protein expression of SGLT2, aquaporin (AQP) 2 phosphorylated at Ser269 and vasopressin V2 receptor. The expression of SGLT1, GLUT2, AQP1, and AQP2 was similar between the groups. In conclusion, the SGLT2 inhibitor ipragliflozin induced a sustained glucosuria, diuresis, and natriuresis, with compensatory increases in fluid intake and vasopressin-induced TcH2O in proportion to the reduced fluid balance to maintain BFV. These results indicate that the osmotic diuresis induced by SGLT2 inhibition stimulates compensatory fluid intake and renal water reabsorption to maintain BFV.

SUBMITTER: Masuda T

PROVIDER: S-EPMC6987478 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Osmotic diuresis by SGLT2 inhibition stimulates vasopressin-induced water reabsorption to maintain body fluid volume.

Masuda Takahiro T Muto Shigeaki S Fukuda Keiko K Watanabe Minami M Ohara Ken K Koepsell Hermann H Vallon Volker V Nagata Daisuke D

Physiological reports 20200101 2

Most of the filtered glucose is reabsorbed in the early proximal tubule by the sodium-glucose cotransporter SGLT2. The glycosuric effect of the SGLT2 inhibitor ipragliflozin is linked to a diuretic and natriuretic effect that activates compensatory increases in fluid and food intake to stabilize body fluid volume (BFV). However, the compensatory mechanisms that are activated on the level of renal tubules remain unclear. Type 2 diabetic Goto-Kakizaki (GK) rats were treated with vehicle or 0.01% ( ...[more]

PMID: 31994353

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Project description:The effects of canagliflozin, a sodium glucose co-transporter 2 inhibitor, on blood pressure (BP) and osmotic diuresis- and intravascular volume reduction-related adverse events (AEs) were evaluated using pooled data from four placebo-controlled, phase 3 studies in patients with type 2 diabetes mellitus (T2DM; N=2313). At baseline, 1332 (57.6%) patients were taking an antihypertensive medication. Canagliflozin 100 mg and 300 mg provided reductions (95% confidence interval [CI]) from baseline in systolic BP (SBP) compared with placebo (-4.3 mm Hg [-5.0 to -3.5], -5.0 mm Hg [-5.8 to -4.2], and -0.3 mm Hg [-1.2 to 0.5], respectively) and in diastolic BP (DBP; -2.5 mm Hg [-2.9 to -2.0], -2.4 mm Hg [-2.9 to -1.9], and -0.6 mm Hg [-1.1 to -0.02], respectively). Placebo-subtracted reductions (95% CI) in SBP with canagliflozin 100 mg and 300 mg were -4.0 mm Hg (-5.1 to -2.8) and -4.7 mm Hg (-5.8 to -3.5) and reductions in DBP were -1.9 mm Hg (-2.6 to -1.2) and -1.9 mm Hg (-2.6 to -1.1), respectively. Compared with the overall population, patients with elevated baseline SBP (≥140 mm Hg) had numerically greater absolute SBP reductions (95% CI) with canagliflozin 100 mg and 300 mg and placebo (-12.8 mm Hg [-15.2 to -10.5], -14.2 mm Hg [-16.4 to -12.0], and -6.8 mm Hg [-9.1 to -4.5], respectively). Numerically greater DBP reductions were seen in patients with DBP ≥90 mm Hg at baseline (-5.9 mm Hg [-8.2 to -3.6], -9.0 mm Hg [-11.1 to -6.9], and -7.4 mm Hg [-9.6 to -5.1], respectively). In patients with elevated SBP at baseline, placebo-subtracted reductions (95% CI) in SBP with canagliflozin 100 mg and 300 mg were -6.0 mm Hg (-9.1 to -2.9) and -7.4 mm Hg (-10.4 to -4.4), respectively. Placebo-subtracted changes in DBP were 1.5 mm Hg (-1.6 to 4.5) and -1.6 mm Hg (-4.5 to 1.2), respectively, in those with elevated DBP at baseline. Canagliflozin 100 mg and 300 mg were associated with increased incidence of osmotic diuresis-related AEs (e.g., pollakiuria [increased urine volume] and polyuria [increased urine frequency]) vs placebo (6.7%, 5.6%, and 0.8%). The incidence of intravascular volume reduction-related AEs (eg, orthostatic hypotension and postural dizziness) was low across groups (1.2%, 1.3%, and 1.1%). In summary, canagliflozin was associated with reduced BP in patients with T2DM across a range of baseline BPs, with increased incidence of AEs related to osmotic diuresis but not intravascular volume reduction.

Project description:Healthy kidneys filter ?160 g/day of glucose (?30% of daily energy intake) under euglycaemic conditions. To prevent valuable energy from being lost in the urine, the proximal tubule avidly reabsorbs filtered glucose up to a limit of ?450 g/day. When blood glucose levels increase to the point that the filtered load exceeds this limit, the surplus is excreted in the urine. Thus, the kidney provides a safety valve that can prevent extreme hyperglycaemia as long as glomerular filtration is maintained. Most of the capacity for renal glucose reabsorption is provided by sodium glucose cotransporter (SGLT) 2 in the early proximal tubule. In the absence or with inhibition of SGLT2, the renal reabsorptive capacity for glucose declines to ?80 g/day (the residual capacity of SGLT1), i.e. the safety valve opens at a lower threshold, which makes it relevant to glucose homeostasis from day-to-day. Several SGLT2 inhibitors are now approved glucose lowering agents for individuals with type 2 diabetes and preserved kidney function. By inducing glucosuria, these drugs improve glycaemic control in all stages of type 2 diabetes, while their risk of causing hypoglycaemia is low because they naturally stop working when the filtered glucose load falls below ?80 g/day and they do not otherwise interfere with metabolic counterregulation. Through glucosuria, SGLT2 inhibitors reduce body weight and body fat, and shift substrate utilisation from carbohydrates to lipids and, possibly, ketone bodies. Because SGLT2 reabsorbs sodium along with glucose, SGLT2 blockers are natriuretic and antihypertensive. Also, because they work in the proximal tubule, SGLT2 inhibitors increase delivery of fluid and electrolytes to the macula densa, thereby activating tubuloglomerular feedback and increasing tubular back pressure. This mitigates glomerular hyperfiltration, reduces the kidney's demand for oxygen and lessens albuminuria. For reasons that are less well understood, SGLT2 inhibitors are also uricosuric. These pleiotropic effects of SGLT2 inhibitors are likely to have contributed to the results of the EMPA-REG OUTCOME trial in which the SGLT2 inhibitor, empagliflozin, slowed the progression of chronic kidney disease and reduced major adverse cardiovascular events in high-risk individuals with type 2 diabetes. This review discusses the role of SGLT2 in the physiology and pathophysiology of renal glucose reabsorption and outlines the unexpected logic of inhibiting SGLT2 in the diabetic kidney.

Dataset Information

Osmotic diuresis by SGLT2 inhibition stimulates vasopressin-induced water reabsorption to maintain body fluid volume.

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Osmotic diuresis by SGLT2 inhibition stimulates vasopressin-induced water reabsorption to maintain body fluid volume.

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