Effect of the sodium-glucose cotransporter 2 inhibitor luseogliflozin on pancreatic beta cell mass in db/db mice of different ages

Targeting β-Cell Plasticity: A Promising Approach for Diabetes Treatment

The β-cells within the pancreas play a pivotal role in insulin production and secretion, responding to fluctuations in blood glucose levels. However, factors like obesity, dietary habits, and prolonged insulin resistance can compromise β-cell function, contributing to the development of Type 2 Diabetes (T2D). A critical aspect of this dysfunction involves β-cell dedifferentiation and transdifferentiation, wherein these cells lose their specialized characteristics and adopt different identities, notably transitioning towards progenitor or other pancreatic cell types like α-cells. This process significantly contributes to β-cell malfunction and the progression of T2D, often surpassing the impact of outright β-cell loss. Alterations in the expressions of specific genes and transcription factors unique to β-cells, along with epigenetic modifications and environmental factors such as inflammation, oxidative stress, and mitochondrial dysfunction, underpin the occurrence of β-cell dedifferentiation and the onset of T2D. Recent research underscores the potential therapeutic value for targeting β-cell dedifferentiation to manage T2D effectively. In this review, we aim to dissect the intricate mechanisms governing β-cell dedifferentiation and explore the therapeutic avenues stemming from these insights.

Luseogliflozin preserves the pancreatic beta-cell mass and function in db/db mice by improving mitochondrial function

We aimed to determine the mechanism by which the sodium glucose co-transporter 2 inhibitor, luseogliflozin, preserves pancreatic beta-cell mass and function in db/db mice. Six-week-old db/db mice were fed to standard chow or standard chow containing 0.01% luseogliflozin. After 4 weeks, DNA microarray analysis, real-time PCR analysis, and measurement of mitochondrial respiratory capacity and reactive oxygen species (ROS) generation were performed using isolated islets. Immunohistochemistry and electron microscopic analysis were performed using pancreatic tissues. Metabolites extracted from the islets were measured by capillary electrophoresis mass spectrometry. The expression of genes involved in the tricarboxylic acid (TCA) cycle and electron transport chain was upregulated by luseogliflozin. Luseogliflozin improved the mitochondrial complex II-linked oxidative phosphorylation capacity and reduced ROS generation. Mitochondrial morphology was normally maintained by luseogliflozin. Luseogliflozin increased NK6 homeobox 1 (NKX6.1) expression and TCA cycle metabolites. Relief of glucotoxicity by luseogliflozin may involve lower mitochondrial ROS generation and an improvement in complex II-linked mitochondrial respiration. Reducing ROS generation through preventing complex II damage likely increases NKX6.1 expression and ameliorate glucose metabolism in the TCA cycle, contributing to the protection of pancreatic beta-cells. Protection of complex II in pancreatic beta-cells represents a novel therapeutic target for type 2 diabetes.

Effects of Sodium-Glucose Co-Transporter-2 Inhibitors on Pancreatic β-Cell Mass and Function

Sodium-glucose co-transporter-2 inhibitors (SGLT2is) not only have antihyperglycemic effects and are associated with a low risk of hypoglycemia but also have protective effects in organs, including the heart and kidneys. The pathophysiology of diabetes involves chronic hyperglycemia, which causes excessive demands on pancreatic β-cells, ultimately leading to decreases in β-cell mass and function. Because SGLT2is ameliorate hyperglycemia without acting directly on β-cells, they are thought to prevent β-cell failure by reducing glucose overload in this cell type. Several studies have shown that treatment with an SGLT2i increases β-cell proliferation and/or reduces β-cell apoptosis, resulting in the preservation of β-cell mass in animal models of diabetes. In addition, many clinical trials have shown that that SGLT2is improve β-cell function in individuals with type 2 diabetes. In this review, the preclinical and clinical data regarding the effects of SGLT2is on pancreatic β-cell mass and function are summarized and the protective effect of SGLT2is in β-cells is discussed.

Molecular Mechanism of Pancreatic β-Cell Failure in Type 2 Diabetes Mellitus

Various important transcription factors in the pancreas are involved in the process of pancreas development, the differentiation of endocrine progenitor cells into mature insulin-producing pancreatic β-cells and the preservation of mature β-cell function. However, when β-cells are continuously exposed to a high glucose concentration for a long period of time, the expression levels of several insulin gene transcription factors are substantially suppressed, which finally leads to pancreatic β-cell failure found in type 2 diabetes mellitus. Here we show the possible underlying pathway for β-cell failure. It is likely that reduced expression levels of MafA and PDX-1 and/or incretin receptor in β-cells are closely associated with β-cell failure in type 2 diabetes mellitus. Additionally, since incretin receptor expression is reduced in the advanced stage of diabetes mellitus, incretin-based medicines show more favorable effects against β-cell failure, especially in the early stage of diabetes mellitus compared to the advanced stage. On the other hand, many subjects have recently suffered from life-threatening coronavirus infection, and coronavirus infection has brought about a new and persistent pandemic. Additionally, the spread of coronavirus infection has led to various limitations on the activities of daily life and has restricted economic development worldwide. It has been reported recently that SARS-CoV-2 directly infects β-cells through neuropilin-1, leading to apoptotic β-cell death and a reduction in insulin secretion. In this review article, we feature a possible molecular mechanism for pancreatic β-cell failure, which is often observed in type 2 diabetes mellitus. Finally, we are hopeful that coronavirus infection will decline and normal daily life will soon resume all over the world.

Glucokinase activation leads to an unsustained hypoglycaemic effect with hepatic triglyceride accumulation in db/db mice

AIM

To investigate how subchronic administration of a glucokinase activator (GKA) results in attenuation of the hypoglycaemic effect in the diabetic condition.

MATERIALS AND METHODS

Six-week-old db/db mice were fed standard chow containing a GKA or the sodium-glucose cotransporter 2 inhibitor ipragliflozin for 1, 6, 14 or 28 days. We performed histological evaluation and gene expression analysis of the pancreatic islets and liver after each treatment and compared the results to those in untreated mice.

RESULTS

The unsustained hypoglycaemic effect of GKAs was reproduced in db/db mice in conjunction with significant hepatic fat accumulation. The initial reactions to treatment with the GKA in the liver were upregulation of the gene expression of carbohydrate response element-binding protein beta (Chrebp-b) and downregulation of phosphoenolpyruvate carboxykinase (Pepck) on day 1. Subsequently, the initial changes in Chrebp-b and Pepck disappeared and increases in the expression of genes involved in lipogenesis, including acetyl-CoA carboxylase and fatty acid synthase, were observed. There were no significant changes in the pancreatic β cells nor in hepatic insulin signalling.

CONCLUSIONS

The GKA showed an unsustained hypoglycaemic effect and promoted hepatic fat accumulation in db/db mice. Dynamic changes in the expression of hepatic genes involved in lipogenesis and gluconeogenesis could affect the unsustained hypoglycaemic effect of the GKA despite no changes in pancreatic β-cell function and mass.

SGLT2 inhibitors therapy protects glucotoxicity-induced β-cell failure in a mouse model of human KATP-induced diabetes through mitigation of oxidative and ER stress

Progressive loss of pancreatic β-cell functional mass and anti-diabetic drug responsivity are classic findings in diabetes, frequently attributed to compensatory insulin hypersecretion and β-cell exhaustion. However, loss of β-cell mass and identity still occurs in mouse models of human KATP-gain-of-function induced Neonatal Diabetes Mellitus (NDM), in the absence of insulin secretion. Here we studied the temporal progression and mechanisms underlying glucotoxicity-induced loss of functional β-cell mass in NDM mice, and the effects of sodium-glucose transporter 2 inhibitors (SGLT2i) therapy. Upon tamoxifen induction of transgene expression, NDM mice rapidly developed severe diabetes followed by an unexpected loss of insulin content, decreased proinsulin processing and increased proinsulin at 2-weeks of diabetes. These early events were accompanied by a marked increase in β-cell oxidative and ER stress, without changes in islet cell identity. Strikingly, treatment with the SGLT2 inhibitor dapagliflozin restored insulin content, decreased proinsulin:insulin ratio and reduced oxidative and ER stress. However, despite reduction of blood glucose, dapagliflozin therapy was ineffective in restoring β-cell function in NDM mice when it was initiated at >40 days of diabetes, when loss of β-cell mass and identity had already occurred. Our data from mouse models demonstrate that: i) hyperglycemia per se, and not insulin hypersecretion, drives β-cell failure in diabetes, ii) recovery of β-cell function by SGLT2 inhibitors is potentially through reduction of oxidative and ER stress, iii) SGLT2 inhibitors revert/prevent β-cell failure when used in early stages of diabetes, but not when loss of β-cell mass/identity already occurred, iv) common execution pathways may underlie loss and recovery of β-cell function in different forms of diabetes. These results may have important clinical implications for optimal therapeutic interventions in individuals with diabetes, particularly for those with long-standing diabetes.

Bovine α-lactalbumin-derived peptides attenuate TNF-α-induced insulin resistance and inflammation in 3T3-L1 adipocytes through inhibiting JNK and NF-κB signaling

Bioactive peptides in bovine α-lactalbumin were isolated and identified, and the effects and mechanisms of peptide KILDK on insulin resistance in 3T3-L1 adipocytes were investigated. Mature 3T3-L1 adipocytes were stimulated with TNF-α to induce insulin resistance. Bovine α-lactalbumin hydrolysates (α-LAH) were subjected to stimulated gastrointestinal digestion and Caco-2 absorption, and GD-α-LAH and CA-α-LAH were obtained. Our results demonstrated that α-LAH, GD-α-LAH, and CA-α-LAH increased glucose uptake, enhanced Akt phosphorylation (Ser473), and decreased IRS-1 phosphorylation (Ser307) in insulin resistant 3T3-L1 adipocytes. Gel filtration chromatography and liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI MS/MS) were used to separate and identify bioactive peptides. The identified peptide KILDK attenuated insulin resistance in 3T3-L1 adipocytes, which was attributed to the suppression of JNK phosphorylation (Thr183/Tyr185). Moreover, KILDK downregulated pro-inflammatory genes through blocking NF-κB signaling. Our findings suggested that bovine α-LAH might be a potential ingredient against insulin resistance.

Preservation effect of imeglimin on pancreatic β-cell mass: Noninvasive evaluation using 111In-exendin-4 SPECT/CT imaging and the perspective of mitochondrial involvements

Progressive loss of β-cell mass (BCM) has a pernicious influence on type 2 diabetes mellitus (T2DM); evaluation of BCM has conventionally required an invasive method that provides only cross-sectional data. However, a noninvasive approach to longitudinal assessment of BCM in living subjects using an indium 111-labeled exendin-4 derivative ([Lys12(¹¹¹In-BnDTPA-Ahx)]exendin-4) (¹¹¹In-exendin-4) has been developed recently. Imeglimin is a novel antidiabetic agent that is reported to improve glycemic control and glucose-stimulated insulin secretion (GSIS) via augmentation of mitochondrial function. However, the influence of imeglimin on BCM is not fully understood. We have investigated the effects of imeglimin on BCM in vivo in prediabetic db/db mice using a noninvasive ¹¹¹In-exendin-4 single-photon emission computed tomography/computed tomography (SPECT/CT) technique. During the 5-week study period, imeglimin treatment attenuated the progression of glucose intolerance, and imeglimin-treated mice retained greater BCM than control, which was consistent with the results of ¹¹¹In-exendin-4 SPECT/CT scans. Furthermore, immunohistochemical analysis revealed reduced β-cell apoptosis in the imeglimin-treated db/db mice, and also lowered release of cytosolic cytochrome c protein in the β cells. Furthermore, electron microscopy observation and membrane potential measurement revealed improved structural integrity and membrane potential of the mitochondria of imeglimin-treated islets, respectively. These results demonstrate attenuation of progression of BCM loss in prediabetic db/db mice partly via inhibition of mitochondria-mediated apoptosis.

Glucokinase activation or inactivation: Which will lead to the treatment of type 2 diabetes?

Glucokinase, which phosphorylates glucose to form glucose-6-phosphate, plays a critical role in regulating blood glucose levels. On the basis of data of glucokinase-knockout and transgenic mice and humans with glucokinase mutations, glucokinase was targeted for drug development aiming to augment its activity, and thereby reduce hyperglycaemia in patients with diabetes. In fact, various small molecule compounds have been developed and clinically tested as glucokinase activators. However, some have been discontinued because of efficacy and safety issues. One of these issues is loss of the drug's efficacy over time. This unsustained glycaemic efficacy may be associated with the excess glycolysis by glucokinase activation in pancreatic beta cells, resulting in beta-cell failure. Recently, we have shown that glucokinase haploinsufficiency ameliorated glucose intolerance by increasing beta-cell function and mass in a mouse model of diabetes. Given that a similar phenotype has been observed in glucokinase-activated beta cells and diabetic beta cells, glucokinase inactivation may be a new therapeutic target for type 2 diabetes.

Effects of Dapagliflozin Adjunct to Insulin on Glycemic Variations in Patients with Newly Diagnosed Type 2 Diabetes: A Randomized, Controlled, Open-Labeled Trial

Background

This study is aimed at investigating whether dapagliflozin adjunct to insulin therapy further improves glycemic control compared to insulin therapy alone in patients with newly diagnosed type 2 diabetes (T2D).

Methods

This single-centre, randomized, controlled, open-labeled trial recruited newly diagnosed T2D patients. Subjects were randomized 1 : 1 to the dapagliflozin add-on to continuous subcutaneous insulin infusion (CSII) group (DAPA) or the CSII therapy group for 5 weeks. Standard meal tests were performed 3 times at days -3, 7, and 35 for glucose, C-peptide, and insulin level determination. Two-time continuous glucose monitoring (CGM) was performed at baseline and at the end of the study. The primary endpoint was the difference in the mean amplitude of glycemic excursions (MAGEs) between the groups.

Results

A total of 66 subjects completed the study, with 34 and 32 patients in the DAPA and CSII groups, respectively. Patients in the DAPA group exhibited significant decreases in MAGE levels at the endpoint. We also observed that patients in the DAPA group had a lower homoeostasis model assessment insulin resistance (HOMA-IR) and a higher homoeostasis model assessment B (HOMA-B) value at 1 week and 5 weeks compared to those with insulin therapy, respectively. In addition, our data showed that patients in the DAPA group showed a significantly lower insulin dose (0.07 U/kg) and weighed less than those in the CSII group.

Conclusion

Our data indicate that dapagliflozin adjunct to insulin is a safe and effective therapy for improving glycemic variations, insulin sensitivity, and weight loss in newly diagnosed T2D patients.

The Role of the α Cell in the Pathogenesis of Diabetes: A World beyond the Mirror

Type 2 Diabetes Mellitus (T2DM) is one of the most prevalent chronic metabolic disorders, and insulin has been placed at the epicentre of its pathophysiological basis. However, the involvement of impaired alpha (α) cell function has been recognized as playing an essential role in several diseases, since hyperglucagonemia has been evidenced in both Type 1 and T2DM. This phenomenon has been attributed to intra-islet defects, like modifications in pancreatic α cell mass or dysfunction in glucagon's secretion. Emerging evidence has shown that chronic hyperglycaemia provokes changes in the Langerhans' islets cytoarchitecture, including α cell hyperplasia, pancreatic beta (β) cell dedifferentiation into glucagon-positive producing cells, and loss of paracrine and endocrine regulation due to β cell mass loss. Other abnormalities like α cell insulin resistance, sensor machinery dysfunction, or paradoxical ATP-sensitive potassium channels (KATP) opening have also been linked to glucagon hypersecretion. Recent clinical trials in phases 1 or 2 have shown new molecules with glucagon-antagonist properties with considerable effectiveness and acceptable safety profiles. Glucagon-like peptide-1 (GLP-1) agonists and Dipeptidyl Peptidase-4 inhibitors (DPP-4 inhibitors) have been shown to decrease glucagon secretion in T2DM, and their possible therapeutic role in T1DM means they are attractive as an insulin-adjuvant therapy.

Early combination therapy of empagliflozin and linagliptin exerts beneficial effects on pancreatic β cells in diabetic db/db mice

Effects of combination therapy of dipeptidyl peptidase-4 (DPP-4) inhibitor and sodium-glucose co-transporter 2 (SGLT2) inhibitor on β-cells are still unclear, although combination agent of these two drugs has become common in clinical practice. Therefore, we aimed to elucidate the effects of DPP-4 inhibitor and/or SGLT2 inhibitor on β-cell mass and function and compared their effects between in an early and advanced phase of diabetes. We used 7-week-old db/db mice as an early phase and 16-week-old mice as an advanced phase and treated them for 2 weeks with oral administration of linagliptin, empagliflozin, linagliptin + empagliflozin (L + E group), and 0.5% carboxymethylcellulose (Cont group). Blood glucose levels in Empa and L + E group were significantly lower than Cont group after treatment. In addition, β-cell mass in L + E group was significantly larger than Cont group only in an early phase, accompanied by increased Ki67-positive β-cell ratio. In isolated islets, mRNA expression levels of insulin and its transcription factors were all significantly higher only in L + E group in an early phase. Furthermore, mRNA expression levels related to β-cell differentiation and proliferation were significantly increased only in L + E group in an early phase. In conclusion, combination of DPP-4 inhibitor and SGLT2 inhibitor exerts more beneficial effects on β-cell mass and function, especially in an early phase of diabetes rather than an advanced phase.

β-cell replenishment: Possible curative approaches for diabetes mellitus

AIMS

Diabetes mellitus (DM) is a disorder of heterogeneous etiology marked by persistent hyperglycemia. Exogenous insulin is the only treatment for type 1 diabetes (T1D). Islet transplantation is a potential long cure for T1D but is disapproved due to the possibility of immune rejection in the later stage. The approaches used for treating type 2 diabetes (T2D) include diet restrictions, weight management and pharmacological interventions. These procedures have not been able to boost the quality of life for diabetic patients owing to the complexity of the disorder.

DATA SYNTHESIS

Hence, research has embarked on permanent ways of managing, or even curing the disease. One of the possible approaches to restore the pancreas with new glucose-responsive β-cells is by their regeneration. Regeneration of β-cells include islet neogenesis, dedifferentiation, and trans-differentiation of the already differentiated cells.

CONCLUSIONS

This review briefly describes the islet development, functions of β-cells, mechanism and factors involved in β-cell death. It further elaborates on the potential of the existing and possible therapeutic modalities involved in the in-vivo replenishment of β-cells with a focus on exercise, diet, hormones, small molecules, and phytochemicals.

Diet intake control is indispensable for the gluconeogenic response to sodium-glucose cotransporter 2 inhibition in male mice

Aims/Introduction

Sodium–glucose cotransporter 2 inhibitor (SGLT2i) lowers blood glucose and causes a whole‐body energy deficit by boosting renal glucose excretion, thus affecting glucose and energy metabolism. This energy deficit not only decreases bodyweight, but also increases food intake. This food intake increase offsets the SGLT2i‐induced bodyweight decrease, but the effect of the food intake increase on the SGLT2i regulation of glucose metabolism remains unclear.

Materials and Methods

We administered SGLT2i (luseogliflozin) for 4 weeks to hepatic gluconeogenic enzyme gene G6pc reporter mice with/without obesity, which were either fed freely or under a 3‐hourly dietary regimen. The effect of feeding condition on the gluconeogenic response to SGLT2i was evaluated by plasma Gaussia luciferase activity, an index of the hepatic gluconeogenic response, in G6pc reporter mice. Energy expenditure was measured by indirect calorimetry.

Results

In the lean mice under controlled feeding, SGLT2i decreased bodyweight and plasma glucose, and increased the hepatic gluconeogenic response while decreasing blood insulin. SGLT2i also increased oxygen consumption under controlled feeding. However, free feeding negated all of these effects of SGLT2i. In the obese mice, SGLT2i decreased bodyweight, blood glucose and plasma insulin, ameliorated the upregulated hepatic gluconeogenic response, and increased oxygen consumption under controlled feeding. Under free feeding, although blood glucose was decreased and plasma insulin tended to decrease, the effects of SGLT2i – decreased bodyweight, alleviation of the hepatic gluconeogenic response and increased oxygen consumption – were absent.

Conclusions

Food intake management is crucial for SGLT2i to affect glucose and energy metabolism during type 2 diabetes treatment.

Favourable effect of the sodium-glucose co-transporter-2 inhibitor canagliflozin plus the dipeptidyl peptidase-4 inhibitor teneligliptin in combination on glycaemic fluctuation: An open-label, prospective, randomized, parallel-group comparison trial (the CALMER study)

This multicentre, prospective, randomized, open-label, blinded-endpoint, parallel-group, short-term (4-5 weeks) controlled trial was conducted to investigate the superiority of the effect of reducing mean amplitude of glycaemic excursions (MAGE) during meal tolerance tests (MTTs) for the combination of dipeptidyl peptidase-4 (DPP-4) inhibitor and sodium-glucose co-transporter-2 (SGLT2) inhibitor compared with SGLT2 inhibitor monotherapy. Ninety-nine patients with type 2 diabetes who were taking teneligliptin (20 mg/d) were randomized to one of the following two groups: those who switched to 100 mg/d of canagliflozin (SWITCH group) or those who added 100 mg/d of canagliflozin (COMB group). MAGE in the COMB group was significantly decreased compared with that in the SWITCH group (COMB 117.5 ± 39.8 to 92.2 ± 28.0 mg/dL vs SWITCH 110.7 ± 29.8 to 104.2 ± 27.6 mg/dL; P<0.01). Mean blood glucose decreased significantly during MTTs in both groups, although the extent of the reduction was significantly greater in the COMB group (COMB 142.3 ± 28.7 to 119.5 ± 25.1 mg/dL vs SWITCH 146.4 ± 25.5 to 135.5 ± 22.4 mg/dL; P < 0.01). SGLT2 inhibitor combined with DPP-4 inhibitor therapy strongly reduced glycaemic fluctuation compared with SGLT2 inhibitor monotherapy.

Effect of Dapagliflozin on Glycemic Variability in Patients with Type 2 Diabetes under Insulin Glargine Combined with Other Oral Hypoglycemic Drugs

AIM

To evaluate the effect of an inhibitor of sodium-glucose cotransporter 2 (SGLT-2 inhibitor, dapagliflozin) on glycemic variability in type 2 diabetes mellitus (T2D) under insulin glargine combined with oral hypoglycemic drugs, using a continuous glucose monitoring system (CGMS).

METHODS

This prospective, self-controlled, single-center clinical trial recruited 36 patients with T2D under combined insulin glargine and oral hypoglycemic drugs. General clinical data were collected. Fasting blood glucose (FBG), postprandial blood glucose (PBG), glycosylated hemoglobin (HbA1c), and C-peptide levels were assessed before and four weeks of dapagliflozin (10 mg per day) treatment. Blood glucose was monitored for 72 hours before and after treatment using CGMS.

RESULTS

After treatment with dapagliflozin, FBG decreased from 6.74 ± 1.78 to 5.95 ± 1.13 mmol/L (p < 0.05); PBG decreased from 13.04 ± 2.99 to 10.92 ± 3.26 mmol/L (p < 0.05); HbA1c decreased from 7.37 ± 0.96% to 6.94 ± 0.80%. The proportion of patients with HbA1c < 7% increased from 27.8% to 58.3%, and the proportion of patients with HbA1c < 7% and without level 2 hypoglycemia increased from 27.8% to 55.6% (p < 0.05). CGMS data showed reduction of the 24 h MBG, MAGE, time-above-range (TAR, >10 mmol/L), high blood glucose index (HBGI), glucose management indicator (GMI), and incremental area under the curve of the glucose level more than 10 mmol/L (AUC > 10) and an increase of time-in-range (TIR, 3.9-10 mmol/L) with treatment. Homeostasis model assessment for pancreatic beta-cell function (HOMA-beta) increased significantly with treatment (p < 0.05), and fewer insulin doses were required after the treatment, without increasing in hypoglycemia and urinary tract infection. Further, a stratified analysis showed that patients with higher pretreatment HbA1c and waist-to-hip ratio (WHR) had greater improvement in glycemic control.

CONCLUSION

Dapagliflozin may reduce blood glucose levels, ameliorate glycemic variability, and improve pancreatic beta-cell function in patients with T2D under insulin glargine combined with other oral hypoglycemic drugs, especially in those with poor glucose control and abdominal obesity.

Hepatic Gluconeogenic Response to Single and Long-Term SGLT2 Inhibition in Lean/Obese Male Hepatic G6pc-Reporter Mice

Sodium-glucose cotransporter 2 inhibitor (SGLT2i) consistently reduces blood glucose levels in type 2 diabetes mellitus but increases hepatic gluconeogenic gene expression and glucose production, offsetting its glucose-lowering effect. This study aimed to elucidate the effect of SGLT2i on hepatic gluconeogenic response and its mechanism in both insulin-sensitive and insulin-resistant states. A hepatic mouse model was generated to show liver-specific expression of Gaussia luciferase (GLuc) driven by the gluconeogenic enzyme gene G6pc promoter. Hepatic gluconeogenic response was evaluated by measuring plasma GLuc activity. SGLT2i was given to lean and obese mice in single gavage administration or 4-week dietary administration with controlled feeding every 3 hours. In lean mice, single-dose SGLT2i increased plasma GLuc activity from 2 hours after administration, decreasing blood glucose and plasma insulin from 1 to 2 hours after administration. In obese mice, which had higher plasma GLuc activity than lean ones, SGLT2i did not further increase GLuc activity despite decreased blood glucose and plasma insulin. Hepatic Akt and GSK3β phosphorylation was attenuated by single-dose SGLT2i in lean mice in accordance with the plasma insulin decrease, but not in obese mice. Long-term SGLT2i administration, which increased plasma GLuc activity in lean mice, decreased it in obese mice from 3 weeks after initiation, with increased hepatic Akt and GSK3β phosphorylation. In conclusion, single SGLT2i administration increases hepatic gluconeogenic response in lean insulin-sensitive mice, but not in obese insulin-resistant mice. Long-term SGLT2i administration relieves obesity-induced upregulation of the hepatic gluconeogenic response by restoring impeded hepatic insulin signaling in obese insulin-resistant mice.

Effects of dapagliflozin and/or insulin glargine on beta cell mass and hepatic steatosis in db/db mice

OBJECTIVE

To explore the beneficial effects of dapagliflozin and/or insulin glargine on the pancreatic beta cell mass and hepatic steatosis in db/db mice.

METHODS

Six-week-old db/db mice were assigned to one of four groups: untreated (Placebo), treated with dapagliflozin (Dapa), treated with insulin glargine (Gla), or treated with dapagliflozin and insulin glargine (Dapa+Gla). After 8 weeks of treatment, we determined glucose tolerance, beta cell mass, hepatic lipid content and gene expression.

RESULTS

Glucose tolerance was significantly ameliorated in the three treated groups to the same degree compared with the Placebo group. Immunohistochemical analysis revealed that the pancreatic beta cell mass was significantly maintained in the Dapa and Dapa+Gla groups, but not in the Gla group, compared with the Placebo group (Placebo 2.25 ± 1.44 mg, Dapa 5.01 ± 1.63 mg, Gla 3.79 ± 0.96 mg, Dapa+Gla 5.19 ± 1.78 mg). However, the triglyceride content of the liver was markedly elevated in the Gla group compared with that in the other three groups (Placebo 24.1 ± 11.5 mg, Dapa 30.6 ± 12.9 mg, Gla 128 ± 49.7 mg, Dapa+Gla 54.4 ± 14.1 mg per gram liver). The expression levels of genes related to fatty acid synthesis and lipid storage were significantly upregulated in the Gla group.

CONCLUSIONS

Our results showed that beta cell mass was sustained and hepatic steatosis was prevented, after 8 weeks of treatment with either dapagliflozin or dapagliflozin plus insulin glargine, but not with insulin glargine alone, in db/db mice.

Modulatory effect of empagliflozin on cellular parameters of endocrine pancreas in experimental pre-diabetes

The effect of empagliflozin (EMPA), a sodium-glucose cotransporter 2 inhibitor (SGLT2i), on the structure of endocrine pancreas in pre-diabetes (Pre-DM) is not yet elucidated. In the current study the relatively enlarged islets of Langerhans seen in the Pre-DM group was restored to control size by administration of EMPA. In addition the disbalance in the percentage of β-cells and α-cells in islets of the Pre-DM was corrected in the Pre-DM + EMPA group with reversal of the significantly increased islet mass, β-cell mass and neogenesis. Administrating EMPA in Pre-DM decreased level of caspase-3, increased that of Bcl-2 to control level and reduced the significantly increased inflammatory cytokines to levels approximated to those of the control group. In Pre-DM + EMPA group, EMPA had efficiently restored the significantly impaired glucose hemostasis to levels nearly similar to those of the control animals. This may indicate that the modulatory effect of EMPA on cells of the islets in Pre-DM is associated with a local pleotropic effect on inflammatory cytokines.

Early administration of dapagliflozin preserves pancreatic β-cell mass through a legacy effect in a mouse model of type 2 diabetes

AIMS/INTRODUCTION

The preservation of pancreatic β-cell mass is an essential factor in the onset and development of type 2 diabetes mellitus. Recently, sodium-glucose cotransporter 2 inhibitors have been launched as antihyperglycemic agents, and their organ-protective effects are attracting attention. They are also reported to have favorable effects on the preservation of pancreatic β-cell mass, but the appropriate timing for the administration of sodium-glucose cotransporter 2 inhibitors is obscure.

MATERIALS AND METHODS

In the present study, we administered a sodium-glucose cotransporter 2 inhibitor, dapagliflozin, to an animal model of type 2 diabetes mellitus, db/db mice, and investigated the adequate timing and duration for its administration. We also carried out microarray analysis using pancreatic islets from db/db mice.

RESULTS

We found that dapagliflozin preserved pancreatic β-cell mass depending on the duration of administration and markedly improved blood glucose levels. If the duration was the same, the earlier administration of dapagliflozin was more effective in preserving pancreatic β-cell mass, increasing serum insulin levels and improving blood glucose levels. From microarray analysis, we discovered that the expression of Agr2, Tff2 and Gkn3 was significantly upregulated after the early administration of dapagliflozin. This upregulated gene expression might provide a legacy effect for the preservation of pancreatic β-cell mass.

CONCLUSIONS

We expect that the early administration of dapagliflozin would provide a long-lasting effect in preserving pancreatic β-cell mass.