Inhibition Of Renal Glucose Reabsorption Research Articles

Sodium-Glucose Co-Transporter 2 Inhibitors and the Risk of Genitourinary Infections at HbA1c ≥10%: A Population Health-Based Retrospective Review.

Sodium-glucose co-transporter 2 inhibitors (SGLT2i) are first-line treatment for type 2 diabetes. Evidence has shown a 3- to 5-fold increase in the risk of genitourinary infections with their use due to inhibition of renal glucose reabsorption, resulting in glucosuria. Increased glucosuria is thought to increase the risk of genitourinary infections at a greater degree in patients with a significantly elevated HbA1c (≥10%), and initiation of SGLT2i is often delayed in these patients. While a limited body of evidence exists indicating that A1c level is not an independent risk factor for SGLT2i-induced genitourinary infection, pragmatically this concern remains a barrier to SGLT2i utilization. Evaluate the real-world genitourinary (GU) infection rate in patients receiving SGLT2i with a baseline HbA1c ≥10% compared to patients with a baseline HbA1c <10%. This retrospective cohort study evaluated data from 5542 adult patients treated between January 2013 and January 2023, who were prescribed an SGLT2i. Data collected included sex, age, race/ethnicity, renal function, date of SGLT2i start, number of SGLT2i orders, name and dose of SGLT2i, HbA1c, and a predetermined set of diagnosis codes related to bacterial and fungal genitourinary infections. The primary outcome was the overall GU infection rate after SGLT2i initiation within groups of baseline HbA1c of ≥10% and <10%, and the secondary outcome was total GU infections within these same groups. The primary outcome was equivalent between those with HbA1c <10% and HbA1c ≥10% (0.0064 ± 0.0565 vs 0.0030 ± 0.0303 infection per month [mean ± standard deviation]; P < 0.0001 for both lower and upper bounds). There was no statistically significant difference in total GU infections between the same groups (0.027 ± 0.21 vs 0.015 ± 0.14, P = 0.11). Female gender and prior recurrent infection were associated with increased GU infection after SGLT2i. A baseline HbA1c ≥ 10% was not significantly associated with an increased risk of GU infection following the initiation of SGLT2i compared to those with a baseline HbA1c of <10%.

Renal effects of SGLT2 inhibitors in cardiovascular patients with and without chronic kidney disease: focus on heart failure and renal outcomes.

The kidney has a prominent role in maintaining glucose homeostasis by using glucose as a metabolic substrate. This occurs by generating glucose through gluconeogenesis, and by reuptaking filtered glucose through the sodium–glucose cotransporters SGLT1 and SGLT2 located in the proximal tubule. In recent studies, the administration of sodium–glucose cotransporters inhibitors demonstrated that inhibition of renal glucose reabsorption significantly reduces adverse renal events and heart failure exacerbations, in type 2 diabetic patients with and without cardiovascular damage as well as in advanced chronic kidney disease and heart failure patients with reduced ejection fraction with and without diabetes. The benefit was consistent throughout the different investigated clinical conditions, ameliorating overall patient outcome. The efficacy of sodium glucose cotransporters inhibitors was prominently linked to the limitation of renal damage as highlighted by the significant reduction on global mortality achieved in the studies investigating diabetic and not diabetic populations with advanced chronic kidney disease. Both studies were halted at the interim analysis because of unquestionable evidence of treatment benefit. In current review, we examine the role of SGLT2 and SGLT1 in the regulation of renal glucose reabsorption in health and disease and the effect of SGLT2 inhibition on clinical outcomes of populations with different cardiovascular conditions investigated with large-scale outcome trials.

Role of DPP-4 and SGLT2 Inhibitors Connected to Alzheimer Disease in Type 2 Diabetes Mellitus.

Alzheimer’s disease (AD) is characterized by memory loss and cognitive decline. Additionally, abnormal extracellular amyloid plaques accumulation and nerve damage caused by intracellular neurofibrillary tangles, and tau protein are characteristic of AD. Furthermore, AD is associated with oxidative stress, impaired mitochondrial structure and function, denormalization, and inflammatory responses. Recently, besides the amyloid β hypothesis, another hypothesis linking AD to systemic diseases has been put forth by multiple studies as a probable cause for AD. Particularly, type 2 diabetes mellitus (T2DM) and its features, including hyperinsulinemia, and chronic hyperglycemia with an inflammatory response, have been shown to be closely related to AD through insulin resistance. The brain cannot synthesize or store glucose, but it does require glucose, and the use of glucose in the brain is higher than that in any other organ in the mammalian body. One of the therapeutic drugs for T2DM, dipeptidyl peptidase-4 (DPP-4) inhibitor, suppresses the degradation of incretins, glucagon-like peptides and glucose-dependent insulinotropic peptide. Sodium-glucose cotransporter 2 (SGLT2) inhibitors, recently used in T2DM treatment, have a unique mechanism of action via inhibition of renal glucose reabsorption, and which is different from the mechanisms of previously used medications. This manuscript reviews the pathophysiological relationship between the two diseases, AD and T2DM, and the pharmacological effects of therapeutic T2DM drugs, especially DPP-4 inhibitors, and SGLT2 inhibitors.

Glucose Metabolism in the Kidney: Neurohormonal Activation and Heart Failure Development.

The liver is not the exclusive site of glucose production in humans in the postabsorptive state. Robust data support that the kidney is capable of gluconeogenesis and studies have demonstrated that renal glucose production can increase systemic glucose production. The kidney has a role in maintaining glucose body balance, not only as an organ for gluconeogenesis but by using glucose as a metabolic substrate. The kidneys reabsorb filtered glucose through the sodium‐glucose cotransporters sodium‐glucose cotransporter (SGLT) 1 and SGLT2, which are localized on the brush border membrane of the early proximal tubule with immune detection of their expression in the tubularized Bowman capsule. In patients with diabetes mellitus, the renal maximum glucose reabsorptive capacity, and the threshold for glucose passage into the urine, are higher and contribute to the hyperglycemic state. The administration of SGLT2 inhibitors to patients with diabetes mellitus enhances sodium and glucose excretion, leading to a reduction of the glycosuria threshold and tubular maximal transport of glucose. The net effects of SGLT2 inhibition are to drive a reduction in plasma glucose levels, improving insulin secretion and sensitivity. The benefit of SGLT2 inhibitors goes beyond glycemic control, since inhibition of renal glucose reabsorption affects blood pressure and improves the hemodynamic profile and the tubule glomerular feedback. This action acts to rebalance the dense macula response by restoring adenosine production and restraining renin‐angiotensin‐aldosterone activation. By improving renal and cardiovascular function, we explain the impressive reduction in adverse outcomes associated with heart failure supporting the current clinical perspective.

Risk of Erythrocytosis During Concomitant Testosterone and SGLT2-Inhibitor Treatment: A Warning From Two Clinical Cases

Erythrocytosis is one of the most common side effects occurring during testosterone replacement therapy (TRT) in male hypogonadism. It is well known that all testosterone formulations may cause Hb and hematocrit increase, especially with short-acting injectable formulations. Sodium-glucose cotransporter-2 inhibitors (SGLT2is) are a new class of glucose-lowering agents that reduce hyperglycemia in patients with type 2 diabetes mellitus (T2DM) by inhibition of renal glucose reabsorption, leading to increased urinary glucose excretion. The co-occurrence of T2DM and hypogonadism is known to be increasingly frequent. However, to date, no adverse events with the concomitant use of TRT and SGLT2is are reported. We report two cases of erythrocytosis during testosterone treatment and SGLT2i in patients with hypogonadism and T2DM. Considering that hypogonadism and T2DM are frequently associated, clinicians should carefully monitor the risk of occurrence of erythrocytosis when prescribing TRT and SGLT2i together.

Unmasking and aggravation of polycythemia vera by canagliflozin

Sodium-glucose co-transporter-2 inhibitors are novel antidiabetes drugs that act via inhibition of renal glucose reabsorption. This action causes osmotic diuresis, reduces intravascular volume and is associated with various adverse effects. In the present paper, we describe the first report on the unmasking of underlying polycythemia vera by canagliflozin in a person with Type 2 diabetes mellitus, which was temporally related to the use of the drug. A 51-year-old obese man with Type 2 diabetes was prescribed canagliflozin 100 mg for control of his glycaemia. He presented 6 months later with asymptomatic elevation of his haemogram measurements (haemoglobin: 16.9 g/dl; haematocrit: 55%; red cell number: 8.1 million/mm3 ; total leukocytes: 23010/mm3 ; platelet count: 9.7 *106 /mm3 ). He had no history of smoking, exposure to high altitude or other drugs. Subsequent investigations revealed myeloproliferative neoplasm (polycythemia vera) on trephine biopsy of bone marrow, normal erythropoietin level and JAK2V617F positivity. Because of the possibility that the underlying condition had been unmasked by canagliflozin, the latter was stopped. This led to a remarkable improvement in the man's haematological profile, with no other significant intervention. The man subsequently restarted the drug of his own accord, causing his haematological profile to worsen again and thereby posing a challenge in monitoring of both polycythemia vera as well as diabetes mellitus. This report brings to light unmasking of a new adverse effect of sodium-glucose co-transporter-2 inhibitors in clinical practice caused by volume loss, apart from hypotension and falls.

The Association Between the Dosage of SGLT2 Inhibitor and Weight Reduction in Type 2 Diabetes Patients: A Meta-Analysis.

Sodium glucose cotransporter 2 (SGLT2) inhibitors may induce urinary glucose excretion via the inhibition of renal glucose reabsorption, improve glycemic control, and lower body weight. The aim of this meta-analysis was to evaluate weight changes in patients who received different dosages of SGLT2 inhibitors. Overall, 55 placebo-controlled trials were included. The results indicated that treatment with 2.5 mg, 5 mg, 10 mg, and 20 mg of dapagliflozin led to significant decreases in body weight compared with a placebo (weighted mean difference [WMD], -1.30 kg, -1.51 kg, -1.79 kg, -2.24 kg, respectively; P < 0.001). Treatment with 50 mg, 100 mg, 200 mg, and 300 mg of canagliflozin also led to significant decreases in weight (WMD, -1.20 kg, -1.82 kg, -1.83 kg, -2.37 kg, respectively; P < 0.001). In the treatment with empagliflozin, ipragliflozin, tofogliflozin, and luseogliflozin, body weight also significantly decreased. The decrease in weight was associated with the dosage of dapagliflozin (P < 0.05). Body weight significantly decreased in patients with type 2 diabetes who received different dosages of SGLT2 inhibitors compared with patients who received a placebo. Moreover, in patients treated with dapagliflozin, there was a statistically significant dosage-dependent trend in body weight reduction.

Renal, metabolic and cardiovascular considerations of SGLT2 inhibition.

The kidney has a pivotal role in maintaining glucose homeostasis by using glucose as a metabolic fuel, by producing glucose through gluconeogenesis, and by reabsorbing all filtered glucose through the sodium-glucose cotransporters SGLT1 and SGLT2 located in the proximal tubule. In patients with diabetes, the maximum glucose reabsorptive capacity (TmG) of the kidney, as well as the threshold for glucose spillage into the urine, are elevated, contributing to the pathogenesis of hyperglycaemia. By reducing the TmG and, more importantly, the threshold of glucosuria, SGLT2 inhibitors enhance glucose excretion, leading to a reduction in fasting and postprandial plasma glucose levels and improvements in both insulin secretion and insulin sensitivity. The beneficial effects of SGLT2 inhibition extend beyond glycaemic control, however, with new studies demonstrating that inhibition of renal glucose reabsorption reduces blood pressure, ameliorates glucotoxicity and induces haemodynamic effects that lead to improved cardiovascular and renal outcomes in patients with type 2 diabetes mellitus. In this Review we examine the role of SGLT2 and SGLT1 in the regulation of renal glucose reabsorption in health and disease and the effect of SGLT2 inhibition on renal function, glucose homeostasis, and cardiovascular disease.

Model analysis of effect of canagliflozin (Invokana), a sodium–glucose cotransporter 2 inhibitor, to alter plasma 1,5-anhydroglucitol

BackgroundRenal reabsorption of 1,5-anhydroglucitol (AG) is competitively inhibited by elevated glucose and leads to depleted plasma AG in diabetes. Plasma AG recovery in diabetes normally correlates with improved glycemic control. However, use of sodium–glucose co-transporter 2 (SGLT2) inhibitors (e.g., canagliflozin) to treat diabetes by inhibition of renal glucose reabsorption can negate this correlation, via an indirect effect (increase of renal filtrate glucose concentration) to inhibit AG reabsorption by sodium–glucose co-transporter 4 (SGLT4). Conversely, then, AG measurement might be useful as an independent marker for SGLT2 inhibitor activity. MethodsUsing an AG mass balance model, we analyzed literature data on plasma AG before and after initiation of canagliflozin therapy (CT) to quantitatively characterize the effect of CT on AG reabsorption. ResultsAccording to model calculations, modest decreases (<5%) in fractional reabsorption of AG account for the drastic decrease in [AG] observed during CT. Decreases are predicted to be rapid (t1/2<3days) after CT initiation. ConclusionCT negates the usual premise of AG measurement (that [AG] should increase with improved glycemic control). However, according to model calculations, a substantial and likely rapid effect of CT on [AG] means that AG measurement might provide an early marker for CT activity.

Effect of Sodium-Glucose Cotransport Inhibition on Polycystic Kidney Disease Progression in PCK Rats.

The sodium-glucose-cotransporter-2 (SGLT2) inhibitor dapagliflozin (DAPA) induces glucosuria and osmotic diuresis via inhibition of renal glucose reabsorption. Since increased diuresis retards the progression of polycystic kidney disease (PKD), we investigated the effect of DAPA in the PCK rat model of PKD. DAPA (10 mg/kg/d) or vehicle was administered by gavage to 6 week old male PCK rats (n=9 per group). Renal function, albuminuria, kidney weight and cyst volume were assessed after 6 weeks of treatment. Treatment with DAPA markedly increased glucose excretion (23.6 ± 4.3 vs 0.3 ± 0.1 mmol/d) and urine output (57.3 ± 6.8 vs 19.3 ± 0.8 ml/d). DAPA-treated PCK rats had higher clearances for creatinine (3.1 ± 0.1 vs 2.6 ± 0.2 ml/min) and BUN (1.7 ± 0.1 vs 1.2 ± 0.1 ml/min) after 3 weeks, and developed a 4-fold increase in albuminuria. Ultrasound imaging and histological analysis revealed a higher cyst volume and a 23% higher total kidney weight after 6 weeks of DAPA treatment. At week 6 the renal cAMP content was similar between DAPA and vehicle, and staining for Ki67 did not reveal an increase in cell proliferation. In conclusion, the inhibition of glucose reabsorption with the SGLT2-specific inhibitor DAPA caused osmotic diuresis, hyperfiltration, albuminuria and an increase in cyst volume in PCK rats. The mechanisms which link glucosuria to hyperfiltration, albuminuria and enhanced cyst volume in PCK rats remain to be elucidated.

Use of systems pharmacology modeling to elucidate the operating characteristics of SGLT1 and SGLT2 in renal glucose reabsorption in humans.

In the kidney, glucose in glomerular filtrate is reabsorbed primarily by sodium-glucose cotransporters 1 (SGLT1) and 2 (SGLT2) along the proximal tubules. SGLT2 has been characterized as a high capacity, low affinity pathway responsible for reabsorption of the majority of filtered glucose in the early part of proximal tubules, and SGLT1 reabsorbs the residual glucose in the distal part. Inhibition of SGLT2 is a viable mechanism for removing glucose from the body and improving glycemic control in patients with diabetes. Despite demonstrating high levels (in excess of 80%) of inhibition of glucose transport by SGLT2 in vitro, potent SGLT2 inhibitors, e.g., dapagliflozin and canagliflozin, inhibit renal glucose reabsorption by only 30–50% in clinical studies. Hypotheses for this apparent paradox are mostly focused on the compensatory effect of SGLT1. The paradox has been explained and the role of SGLT1 demonstrated in the mouse, but direct data in humans are lacking. To further explore the roles of SGLT1/2 in renal glucose reabsorption in humans, we developed a systems pharmacology model with emphasis on SGLT1/2 mediated glucose reabsorption and the effects of SGLT2 inhibition. The model was calibrated using robust clinical data in the absence or presence of dapagliflozin (DeFronzo et al., 2013), and evaluated against clinical data from the literature (Mogensen, 1971; Wolf et al., 2009; Polidori et al., 2013). The model adequately described all four data sets. Simulations using the model clarified the operating characteristics of SGLT1/2 in humans in the healthy and diabetic state with or without SGLT2 inhibition. The modeling and simulations support our proposition that the apparent moderate, 30–50% inhibition of renal glucose reabsorption observed with potent SGLT2 inhibitors is a combined result of two physiological determinants: SGLT1 compensation and residual SGLT2 activity. This model will enable in silico inferences and predictions related to SGLT1/2 modulation.

Inhibition of the intestinal sodium-coupled glucose transporter 1 (SGLT1) by extracts and polyphenols from apple reduces postprandial blood glucose levels in mice and humans.

There is a growing interest in food constituents that could reduce intestinal glucose absorption to prevent overshooting plasma glucose and insulin levels in patients with prediabetes and diabetes mellitus type 2. We here demonstrate that an extract and individual polyphenols from apple diminish sodium-coupled glucose transporter 1 (SGLT1) mediated glucose uptake in vitro and in vivo. Inhibition of transport of sugars by SGLT1 was shown in Xenopus oocytes and in mice jejunal segments. Strongest inhibition was observed for phlorizin with IC50 values for transport inhibition of 0.46 ± 0.19 and 4.1 ± 0.6 μM in oocytes and intestinal segments, respectively. An oral glucose tolerance test performed in volunteers with prior administration of the apple extract reduced venous blood glucose and plasma insulin levels, similar to findings obtained in C57BL/6N mice. Analysis of human urine samples revealed that the extract increased modestly renal glucose loss that is most likely a result of inhibition of renal glucose reabsorption by phloretin derivatives found in plasma of the volunteers. Although the apple extract substantially decreased intestinal glucose absorption in all test systems, the finding that there are systemic effects that relate to inhibition of glucose transport processes beyond the intestine addresses safety issues that need further exploitation.

Inhibition of renal glucose reabsorption as a novel treatment for diabetes patients

The importance of the kidney in glucose homeostasis has been recognized for many years. Recent observations indicating a greater role of renal glucose metabolism in various physiologic and pathologic conditions have rekindled the interest in renal glucose handling as a potential target for the treatment of diabetes. The enormous capacity of the proximal tubular cells to reabsorb the filtered glucose load entirely, utilizing the sodium-glucose co-transporter system (primarily SGLT-2), became the focus of attention. Original studies conducted in experimental animals with the nonspecific SGLT inhibitor phlorizin showed that hyperglycemia after pancreatectomy decreased as a result of forced glycosuria. Subsequently, several compounds with more selective SGLT-2 inhibition properties ("second-generation") were developed. Some agents made it into pre-clinical and clinical trials and a few have already been approved for commercial use in the treatment of type 2 diabetes. In general, a 6-month period of therapy with SGLT-2 inhibitors is followed by a mean urinary glucose excretion rate of ~80 g/day accompanied by a decline in fasting and postprandial glucose with average decreases in HgA1C ~1.0%. Concomitant body weight loss and a mild but consistent drop in blood pressure also have been reported. In contrast, transient polyuria, thirst with dehydration and occasional hypotension have been described early in the treatment. In addition, a significant increase in the occurrence of uro-genital infections, particularly in women has been documented with the use of SGLT-2 inhibitors. Although long-term cardiovascular, renal and bone/mineral effects are unknown SGLT-2 inhibitors, if used with caution and in the proper patient provide a unique insulin-independent therapeutic option in the management of obese type 2 diabetes patients.

Selective SGLT2 inhibition by tofogliflozin reduces renal glucose reabsorption under hyperglycemic but not under hypo- or euglycemic conditions in rats

To understand the risk of hypoglycemia associated with urinary glucose excretion (UGE) induced by sodium-glucose cotransporter (SGLT) inhibitors, it is necessary to know the relationship between the ratio of contribution of SGLT2 vs. SGLT1 to renal glucose reabsorption (RGR) and the glycemic levels in vivo. To examine the contributions of SGLT2 and SGLT1 in normal rats, we compared the RGR inhibition by tofogliflozin, a highly specific SGLT2 inhibitor, and phlorizin, an SGLT1 and SGLT2 (SGLT1/2) inhibitor, at plasma concentrations sufficient to completely inhibit rat SGLT2 (rSGLT2) while inhibiting rSGLT1 to different degrees. Under hyperglycemic conditions by glucose titration, tofogliflozin and phlorizin achieved ≥50% inhibition of RGR. Under hypoglycemic conditions by hyperinsulinemic clamp, RGR was reduced by 20-50% with phlorizin and by 1-5% with tofogliflozin, suggesting the smaller contribution of rSGLT2 to RGR under hypoglycemic conditions than under hyperglycemic conditions. Next, to evaluate the hypoglycemic potentials of SGLT1/2 inhibition, we measured the plasma glucose (PG) and endogenous glucose production (EGP) simultaneously after UGE induction by SGLT inhibitors. Tofogliflozin (400 ng/ml) induced UGE of about 2 mg·kg⁻¹·min⁻¹ and increased EGP by 1-2 mg·kg⁻¹·min⁻¹, resulting in PG in the normal range. Phlorizin (1,333 ng/ml) induced UGE of about 6 mg·kg⁻¹·min⁻¹ and increased EGP by about 4 mg·kg⁻¹·min⁻¹; this was more than with tofogliflozin, but the minimum PG was lower. These results suggest that the contribution of SGLT1 to RGR is greater under lower glycemic conditions than under hyperglycemic conditions and that SGLT2-selective inhibitors pose a lower risk of hypoglycemia than SGLT1/2 inhibitors.

The Role of the Kidney and Sodium-Glucose Cotransporter-2 Inhibition in Diabetes Management

IN BRIEF The kidney plays an important role in glucose homeostasis and has become a target for the treatment of hyperglycemia in type 2 diabetes. This review discusses the role of the kidney in glucose homeostasis and how inhibition of renal glucose reabsorption may become a novel treatment option for type 2 diabetes.

Kidney in Diabetes: from Organ Damage Target to Therapeutic Target

Despite the growing of pharmacological options for the treatment of diabetes, epidemiological studies suggest that a substantial proportion of patients does not achieve glycemic goals and so suffers from the risk of chronic complications. This review explores the inhibition of renal glucose reabsorption as a novel approach to treat hyperglycemia. Sodium-glucose cotransporter 2 (SGLT2), a low-affinity high-capacity transporter located in the brush-border membrane of the early segment (S1) of the proximal renal tubule, accounts for about 90% of the reabsorption of glucose from tubular fluid. Competitive inhibitors of SGLT2 that are responsible for renal excretion of glucose provide a unique mechanism to potentially lower the elevated blood glucose levels in patients with diabetes. They act independently of insulin secretion, thereby minimizing the risk of hypoglycemia and weight gain, to control energy balance in a negative direction, a distinctive advantage of this class of drugs over existing oral hypoglycemic agents. Although this group of medications is still under investigation, it appears to be safe and generally well tolerated and it would be expected to improve the treatment of type 2 diabetes as monotherapy or in combination with other oral or parenteral agents. Dapagliflozin is the first agent within this class, which induces clinically meaningful reductions in FPG, PPG, HbA1c, and body weight in type 2 diabetes.

Renal glucose transporters: novel targets for hyperglycemia management

The naturally occurring substance phlorizin has long been recognized to block the reabsorption of glucose from the glomerular ultrafiltrate into the systemic circulation. The poor oral bioavailability and adverse effects associated with this agent, however, have prevented its use in clinical practice and restricted its use to that of a physiological tool. The development of novel agents that are able to block the principal glucose transporter in the kidney has allowed the inhibition of renal glucose reabsorption to be re-evaluated as a therapeutic tool in patients with diabetes mellitus. This Perspectives article summarizes current knowledge pertaining to glucose transport in the kidney and describes the evidence regarding glucose transport blockade as a novel target for the management of hyperglycemia in the context of existing treatment strategies.

Role of the kidney in normal glucose homeostasis and in the hyperglycaemia of diabetes mellitus: therapeutic implications

Considerable data have accumulated over the past 20 years, indicating that the human kidney is involved in the regulation of glucose via gluconeogenesis, taking up glucose from the circulation, and by reabsorbing glucose from the glomerular filtrate. In light of the development of glucose-lowering drugs involving inhibition of renal glucose reabsorption, this review summarizes these data. Medline was searched from 1989 to present using the terms ‘renal gluconeogenesis’, ‘renal glucose utilization’, ‘diabetes mellitus’ and ‘glucose transporters’. The human liver and kidneys release approximately equal amounts of glucose via gluconeogenesis in the post-absorptive state. In the postprandial state, although overall endogenous glucose release decreases substantially, renal gluconeogenesis increases by approximately twofold. Glucose utilization by the kidneys after an overnight fast accounts for ∼10% of glucose utilized by the body. Following a meal, glucose utilization by the kidney increases. Normally each day, ∼180 g of glucose is filtered by the kidneys; almost all of this is reabsorbed by means of sodium–glucose co-transporter 2 (SGLT2), expressed in the proximal tubules. However, the capacity of SGLT2 to reabsorb glucose from the renal tubules is finite and, when plasma glucose concentrations exceed a threshold, glucose appears in the urine. Handling of glucose by the kidney is altered in Type 2 diabetes mellitus (T2DM): renal gluconeogenesis and renal glucose uptake are increased in both the post-absorptive and postprandial states, and renal glucose reabsorption is increased. Specific SGLT2 inhibitors are being developed as a novel means of controlling hyperglycaemia in T2DM.Diabet. Med. 27, 136–142 (2010)

Preventive Effects of Flavonoids on Alloxan-Induced Diabetes Mellitus in Rats

The aim of the present study was the evaluation of possible protective effects of quercetin and chrysin in experimental alloxan-induced diabetes in rats. Alloxan was injected at a single dose of 60 mg/kg (into the tail vein) for diabetes induction. Quercetin (50 and 100 mg/kg; orally) and chrysin (50 and 100 mg/kg; orally) were administered daily for 3 days prior and 7 days after alloxan injection. Alloxan induced a significant increase of glycaemia (p &lt; 0.001) in comparison with control animals. Quercetin at both doses prevented serum glucose elevation (p &lt; 0.001). However, the protective effect of chrysin was weaker and surprisingly, most prominent at the lower dose (p &lt; 0.05; p &lt; 0.01). On the other hand, glycosuria was increased in all groups of animals receiving alloxan. We suggest that the protective effect of the used flavonoids in experimental diabetes mellitus may be related to their antioxidative/chelatory properties. Increased glycosuria indicated that inhibition of renal glucose reabsorption may also play a role in the hypoglycaemic effect of both flavonoids.

Effect of Lepidium sativum L. on renal glucose reabsorption and urinary TGF‐β1 levels in diabetic rats

The purpose of this study was to determine the mechanism underlying the hypoglycaemic activity of the aqueous extract perfusion of Lepidium sativum L. (LS) in normal and streptozotocin-induced diabetic rats. The aqueous LS extract was administered intravenously and the blood glucose levels were determined within 4 h of treatment. Plasma insulin concentrations and glycosuria were determined. The 24 h urinary transforming growth factor-beta1 (ELISA) was evaluated in diabetic and control rats 15 days after oral treatment with the aqueous LS extract at a dose of 20 mg/kg. The study showed that LS at a dose of 10 mg/kg/h reduced blood glucose levels both in normal and diabetic rats (p < 0.001). At the same time as a potent increase of glycosuria was observed both in normal and diabetic rats (p < 0.001). In addition, oral administration of LS for 15 days normalized glycaemia (p < 0.001), enhanced glycosuria (p < 0.05 vs diabetic control) and decreased the amount of urinary TGF-beta1 (p < 0.01) in diabetic rats. It is concluded that the aqueous LS extract caused a potent inhibition of renal glucose reabsorption which in turn reduced blood sugar. This renal effect is at least one mechanism explaining the observed hypoglycaemic activity of this plant in normal and diabetic rats.