Differential In Vitro Effects of SGLT2 Inhibitors on Mitochondrial Oxidative Phosphorylation, Glucose Uptake and Cell Metabolism.

(1) The cardio-reno-metabolic benefits of the SGLT2 inhibitors canagliflozin (cana), dapagliflozin (dapa), ertugliflozin (ertu), and empagliflozin (empa) have been demonstrated, but it remains unclear whether they exert different off-target effects influencing clinical profiles. (2) We aimed to investigate the effects of SGLT2 inhibitors on mitochondrial function, cellular glucose-uptake (GU), and metabolic pathways in human-umbilical-vein endothelial cells (HUVECs). (3) At 100 µM (supra-pharmacological concentration), cana decreased ECAR by 45% and inhibited GU (IC5o: 14 µM). At 100 µM and 10 µM (pharmacological concentration), cana increased the ADP/ATP ratio, whereas dapa and ertu (3, 10 µM, about 10× the pharmacological concentration) showed no effect. Cana (100 µM) decreased the oxygen consumption rate (OCR) by 60%, while dapa decreased it by 7%, and ertu and empa (all 100 µM) had no significant effect. Cana (100 µM) inhibited GLUT1, but did not significantly affect GLUTs' expression levels. Cana (100 µM) treatment reduced glycolysis, elevated the amino acids supplying the tricarboxylic-acid cycle, and significantly increased purine/pyrimidine-pathway metabolites, in contrast to dapa (3 µM) and ertu (10 µM). (4) The results confirmed cana´s inhibition of mitochondrial activity and GU at supra-pharmacological and pharmacological concentrations, whereas the dapa, ertu, and empa did not show effects even at supra-pharmacological concentrations. At supra-pharmacological concentrations, cana (but not dapa or ertu) affected multiple cellular pathways and inhibited GLUT1.

SGLT2 Inhibition by Dapagliflozin Attenuates Diabetic Ketoacidosis in Mice with Type-1 Diabetes.

BACKGROUND: SGLT2 inhibitors increase plasma ketone concentrations. It has been suggested that insulinopenia, along with an increase in the counter-regulatory hormones epinephrine, corticosterone, glucagon and growth hormone, can induce ketoacidosis, especially in type-1 diabetes (T1DM). Dehydration precipitates SGLT2 inhibitor-induced ketoacidosis in type-2 diabetes. We studied the effects of dapagliflozin and water deprivation on the development of ketoacidosis and the associated signaling pathways in T1DM mice. METHODS: C57BL/6 mice were fed a high-fat diet. After 7 days, some mice received intraperitoneal injection of streptozocin + alloxan (STZ/ALX). The treatment groups were control + water at lib; control + dapagloflozin + water at lib; control + dapagloflozin + water deprivation; STZ/ALX + water at lib; STZ/ALX + water deprivation; STZ/ALX + dapagloflozin + water at lib; STZ/ALX + dapagloflozin + water deprivation. Dapagliflozin was given for 7 days. In the morning of day 18, food was removed, and water was removed in the water deprivation groups. ELISA, rt-PCR, and immunoblotting were used to assess blood, heart, liver, white and brown adipose tissues. RESULTS: The T1DM mice had ketoacidosis even without water deprivation. Water deprivation increased plasma levels of ß-hydroxybutyrate, acetoacetate, corticosterone, and epinephrine and reduced the levels of adiponectin in T1DM mice. Interleukin (IL) 1ß, IL-6, IL-8, and TNFα were also increased in the T1DM mice with water deprivation. Dapagliflozin attenuated the changes in the T1DM mice without and with water deprivation. Likewise, water deprivation increased the activation of the inflammasome in the heart, liver, and white fat of the T1DM mice and dapagliflozin attenuated these changes. Dapagliflozin reduced the mRNA levels of glucagon receptors in the liver and the increase in GPR109a in white and brown fat. In the liver, dapagliflozin increased AMPK phosphorylation, and attenuated the phosphorylation of TBK1 and the activation of NFκB. CONCLUSIONS: Dapagliflozin reduced ketone body levels and attenuated the activation of NFκB and the activation of the inflammasome in T1DM mice with ketoacidosis.

Dapagliflozin and Ticagrelor Have Additive Effects on the Attenuation of the Activation of the NLRP3 Inflammasome and the Progression of Diabetic Cardiomyopathy: an AMPK-mTOR Interplay.

PURPOSE: Ticagrelor, a P2Y12 receptor antagonist, and dapagliflozin, a sodium-glucose-cotransporter-2 inhibitor, suppress the activation of the NLRP3 inflammasome. The anti-inflammatory effects of dapagliflozin depend on AMPK activation. Also, ticagrelor can activate AMPK. We assessed whether dapagliflozin and ticagrelor have additive effects in attenuating the progression of diabetic cardiomyopathy in T2DM mice. METHODS: Eight-week-old BTBR and wild-type mice received no drug, dapagliflozin (1.5 mg/kg/day), ticagrelor (100 mg/kg/day), or their combination for 12 weeks. Heart function was evaluated by echocardiography and heart tissue samples were assessed for fibrosis, apoptosis, qRT-PCR, and immunoblotting. RESULTS: Both drugs attenuated the progression of diabetic cardiomyopathy as evident by improvements in left ventricular end-systolic and end-diastolic volumes and left ventricular ejection fraction, which were further improved by the combination. Both drugs attenuated the activation of the NOD-like receptor 3 (NLRP3) inflammasome and fibrosis. The effect of the combination was significantly greater than each drug alone on myocardial tissue necrotic factorα (TNFα) and interleukin-6 (IL-6) levels, suggesting additive effects. The combination had also a greater effect on ASC, collagen-1, and collagen-3 mRNA levels than each drug alone. While both drugs activated adenosine mono-phosphate kinase (AMPK), only dapagliflozin activated mTOR and increased RICTOR levels. Moreover, only dapagliflozin decreased myocardial BNP and Caspase-1 mRNA levels, and the effects of dapagliflozin on NLRP3 and collagen-3 mRNA levels were significantly greater than those of ticagrelor. CONCLUSIONS: Both dapagliflozin and ticagrelor attenuated the progression of diabetic cardiomyopathy, the activation of the NLRP3 inflammasome, and fibrosis in BTBR mice with additive effects of the combination. While both dapagliflozin and ticagrelor activated AMPK, only dapagliflozin activated mTOR complex 2 (mTORC2) in hearts of BTBR mice.

Deriving functional human enteroendocrine cells from pluripotent stem cells.

Enteroendocrine cells (EECs) are a minor cell population in the intestine yet they play a major role in digestion, satiety and nutrient homeostasis. Recently developed human intestinal organoid models include EECs, but their rarity makes it difficult to study their formation and function. Here, we used the EEC-inducing property of the transcription factor NEUROG3 in human pluripotent stem cell-derived human intestinal organoids and colonic organoids to promote EEC development in vitro An 8-h pulse of NEUROG3 expression induced expression of known target transcription factors and after 7 days organoids contained up to 25% EECs in the epithelium. EECs expressed a broad array of human hormones at the mRNA and/or protein level, including motilin, somatostatin, neurotensin, secretin, substance P, serotonin, vasoactive intestinal peptide, oxyntomodulin, GLP-1 and INSL5. EECs secreted several hormones including gastric inhibitory polypeptide (GIP), ghrelin, GLP-1 and oxyntomodulin. Injection of glucose into the lumen of organoids caused an increase in both GIP secretion and K-cell number. Lastly, we observed formation of all known small intestinal EEC subtypes following transplantation and growth of human intestinal organoids in mice.

Structural basis for GPR40 allosteric agonism and incretin stimulation.

Activation of free fatty acid receptor 1 (GPR40) by synthetic partial and full agonists occur via distinct allosteric sites. A crystal structure of GPR40-TAK-875 complex revealed the allosteric site for the partial agonist. Here we report the 2.76-Å crystal structure of human GPR40 in complex with a synthetic full agonist, compound 1, bound to the second allosteric site. Unlike TAK-875, which acts as a Gαq-coupled partial agonist, compound 1 is a dual Gαq and Gαs-coupled full agonist. compound 1 binds in the lipid-rich region of the receptor near intracellular loop 2 (ICL2), in which the stabilization of ICL2 by the ligand is likely the primary mechanism for the enhanced G protein activities. The endogenous free fatty acid (FFA), γ-linolenic acid, can be computationally modeled in this site. Both γ-linolenic acid and compound 1 exhibit positive cooperativity with TAK-875, suggesting that this site could also serve as a FFA binding site.

Combined SGLT2 and DPP4 Inhibition Reduces the Activation of the Nlrp3/ASC Inflammasome and Attenuates the Development of Diabetic Nephropathy in Mice with Type 2 Diabetes.

BACGROUND: Sodium-glucose cotransporter 2 (SGLT2) inhibitors and dipeptidyl peptidase-4 inhibitors (DPP4I) are used to treat type 2 diabetes (T2DM). DPP4 inhibitors (DPP4) attenuate Nlrp3 inflammasome activation in the kidney. SGLT2 inhibition reduces inflammation and attenuates the progression of diabetic nephropathy (DN). The effects of dapagliflozin (Dapa) on the activation of the Nlrp3 inflammasome and the combined effect of SGLT2 and DPP4 on T2DM-induced inflammasome activation and progression of DN have not been previously studied. We assessed whether Dapa attenuates the inflammasome activation and progression of DN in T2DM mice and whether these effects can be augmented by adding DPP4I saxagliptin (Saxa). METHODS AND RESULTS: Male BTBR ob/ob and wild-type (WT) mice received vehicle, Dapa, or Dapa+Saxa for 8 weeks. Serum BUN in the WT mice was 16.9 ± 0.8 mg/dl. It increased to 55.7 ± 2.8 mg/dl in the BTBR mice. Dapa alone reduced BUN to 31.4 ± 1.2 mg/dl. A greater effect was seen in the Dapa+Saxa combination (24.8 ± 0.8 mg/dl). Serum creatinine was 0.16 ± 0.02 and 1.01 ± 0.04 mg/dl in the WT and BTBR mice, respectively. Dapa and Dapa+Saxa attenuated the increase of creatinine to 0.65 ± 0.02 and 0.40 ± 0.03 mg/dl, respectively. Serum cystatin C was elevated in the BTBR mice (3.9 ± 0.1 vs. 0.6 ± 0.2 ng/ml) as compared to WT mice. Dapa (2.4 ± 0.1) and Dapa+Saxa (1.4 ± 0.1) attenuated this increase. Kidney weight was higher in the BTBR than that of WT mice. Dapa reduced the kidney/body weight ratio in the BTBR mice. Dapa+Saxa tended to have greater effect, but the difference was not significant. mRNA levels of NALP3, ASC, IL-1ß, IL-6, caspase-1, TNF-α, collagen-1, and collagen-3 significantly increased in the kidneys of the BTBR compared to the WT mice. Dapa alone and to a greater extent, Dapa+Saxa, attenuated the activation of the inflammasome. Yet, the combination did not result in greater attenuation of the collagen-1 and collagen-3 mRNA levels. The P-AMPK/total AMPK ratio was lower in the BTBR mice than in the WT mice. Dapa and Dapa+ Saxa equally increased the ratio. CONCLUSIONS: Dapa attenuates T2DM-induced activation of the inflammasome and progression of DN in BTBR ob/ob mice. Adding Saxa to Dapa augmented attenuation of the inflammasome, but had no significant effect on kidney weight or collagen-1 and collagen-3 mRNA levels. Future clinical trials are necessary to study the effect of combined SGLT2 inhibitor and incretin therapy on renal outcomes in patients with T2DM.

Optimization of Hydroxyethylamine Transition State Isosteres as Aspartic Protease Inhibitors by Exploiting Conformational Preferences.

NMR conformational analysis of a hydroxyethylamine peptide isostere developed as an aspartic protease inhibitor shows that it is a flexible architecture. Cyclization to form pyrrolidines, piperidines, or morpholines results in a preorganization of the whole system in solution. The resulting conformation is similar to the conformation of the inhibitor in the active site of BACE-1. This entropic gain results in increased affinity for the enzyme when compared with the acyclic system. For morpholines 27 and 29, the combination of steric and electronic factors is exploited to orient substituents toward S1, S1', and S2' pockets both in the solution and in the bound states. These highly preorganized molecules proved to be the most potent compounds of the series. Additionally, the morpholines, unlike the pyrrolidine and piperidine analogues, have been found to be brain penetrant BACE-1 inhibitors.

SGLT-2 Inhibition with Dapagliflozin Reduces the Activation of the Nlrp3/ASC Inflammasome and Attenuates the Development of Diabetic Cardiomyopathy in Mice with Type 2 Diabetes. Further Augmentation of the Effects with Saxagliptin, a DPP4 Inhibitor.

PURPOSE: We assessed whether (1) dapagliflozin (Dapa, an SGLT2-inhibitor) attenuates the deterioration of heart function Nlrp3 and inflammasome activation in diabetic mice. (2) The effects can be augmented with saxagliptin (Saxa), a DDP4-inhibitor. (3) Dapa effect is possibly SGLT2-independent on cardiofibroblasts in vitro. METHODS: Type 2 diabetic (BTBR ob/ob) and wild-type (WT) mice received vehicle, Dapa, or Dapa+Saxa for 8 weeks. Glucose tolerance test and echocardiogram were performed. Cardiofibroblasts from WT and BTBR hearts were incubated with Dapa and exposed to LPS. RESULTS: Left ventricular ejection fraction (LVEF) was 81 ± 1% in the WT and 53 ± 1% in the T2D-cont mice. Dapa and Dapa+Saxa improved LVEF to 68 ± 1 and 74.6 ± 1% in the BTBR mice (p < 0.001). The mRNA levels of NALP3, ASC, IL-1ß, IL-6, caspase-1, and TNFα were significantly higher in the BTBR compared to the WT hearts; and Dapa and Dapa+Saxa significantly attenuated these levels. Likewise, protein levels of NLRP3, TNFα, and caspase-1 were higher in the BTBR compared to the WT hearts and Dapa, and to a greater extent Dapa+Saxa, attenuated the increase in the BTBR mice. Collagen-1 and collagen-3 mRNA levels significantly increased in the BTBR mice and these increases were attenuated by Dapa and Dapa+Saxa. P-AMPK/total-AMPK ratio was significantly lower in the BTBR mice than in the WT mice. Dapa and Dapa+Saxa equally increased the ratio in the BTBR mice. This in vitro study showed that NALP3, ASC, IL-1ß, and caspase-1 mRNA levels were higher in the BTBR cardiofibroblasts and attenuated with Dapa. The effect was AMPK-dependent and SGLT1-independent. CONCLUSIONS: Dapa attenuated the activation of the inflammasome, fibrosis, and deterioration of LVEF in BTBR mice. The anti-inflammatory, anti-fibrotic effects are likely SGLT2- and glucose-lowering-independent, as they were replicated in the in vitro model. The effects on remodeling were augmented when Saxa was added to Dapa. Yet, adding Saxa to Dapa did not result in a greater effect on myocardial fibrosis and collagen levels.

Does des-acyl ghrelin improve glycemic control in obese diabetic subjects by decreasing acylated ghrelin levels?

OBJECTIVE: The objective of this study was to assess the effects of a continuous overnight infusion of des-acyl ghrelin (DAG) on acylated ghrelin (AG) levels and glucose and insulin responses to a standard breakfast meal (SBM) in eight overweight patients with type 2 diabetes. Furthermore, in the same patients and two additional subjects, the effects of DAG infusion on AG concentrations and insulin sensitivity during a hyperinsulinemic-euglycemic clamp (HEC) were assessed. RESEARCH DESIGN AND METHODS: A double-blind, placebo-controlled cross-over study design was implemented, using overnight continuous infusions of 3 and 10  µg DAG/kg per h and placebo to study the effects on a SBM. During a HEC, we studied the insulin sensitivity. RESULTS: We observed that, compared with placebo, overnight DAG administration significantly decreased postprandial glucose levels, both during continuous glucose monitoring and at peak serum glucose levels. The degree of improvement in glycemia was correlated with baseline plasma AG concentrations. Concurrently, DAG infusion significantly decreased fasting and postprandial AG levels. During the HEC, 2.5  h of DAG infusion markedly decreased AG levels, and the M-index, a measure of insulin sensitivity, was significantly improved in the six subjects in whom we were able to attain steady-state euglycemia. DAG administration was not accompanied by many side effects when compared with placebo. CONCLUSIONS: DAG administration improves glycemic control in obese subjects with type 2 diabetes through the suppression of AG levels. DAG is a good candidate for the development of compounds in the treatment of metabolic disorders or other conditions with a disturbed AG:DAG ratio, such as type 2 diabetes mellitus or Prader-Willi syndrome.

Macrocyclic peptidomimetic inhibitors of beta-secretase (BACE): first X-ray structure of a macrocyclic peptidomimetic-BACE complex.

The synthesis of novel macrocyclic peptidomimetic inhibitors of the enzyme BACE1 is described. These macrocycles are derived from a hydroxyethylene core structure. Compound 7 was co-crystallized with BACE1 and the X-ray structure of the complex elucidated at 1.6 Angstrom resolution. This molecule inhibits the production of the Abeta peptide in HEK293 cells overexpressing APP751sw.

Biochemical and kinetic characterization of BACE1: investigation into the putative species-specificity for beta- and beta'-cleavage sites by human and murine BACE1.

Beta-amyloid peptides (Abeta) are produced by a sequential cleavage of amyloid precursor protein (APP) by beta- and gamma-secretases. The lack of Abeta production in beta-APP cleaving enzyme (BACE1)(-/-) mice suggests that BACE1 is the principal beta-secretase in mammalian neurons. Transfection of human APP and BACE1 into neurons derived from wild-type and BACE1(-/-) mice supports cleavage of APP at the canonical beta-secretase site. However, these studies also revealed an alternative BACE1 cleavage site in APP, designated as beta', resulting in Abeta peptides starting at Glu11. The apparent inability of human BACE1 to make this beta'-cleavage in murine APP, and vice versa, led to the hypothesis that this alternative cleavage was species-specific. In contrast, the results from human BACE1 transgenic mice demonstrated that the human BACE1 is able to cleave the endogenous murine APP at the beta'-cleavage site. To address this discrepancy, we designed fluorescent resonance energy transfer peptide substrates containing the beta- and beta'-cleavage sites within human and murine APP to compare: (i) the enzymatic efficiency; (ii) binding kinetics of a BACE1 active site inhibitor LY2039911; and (iii) the pharmacological profiles for human and murine recombinant BACE1. Both BACE1 orthologs were able to cleave APP at the beta- and beta'-sites, although with different efficiencies. Moreover, the inhibitory potency of LY2039911 toward recombinant human and native BACE1 from mouse or guinea pig was indistinguishable. In summary, we have demonstrated, for the first time, that recombinant BACE1 can recognize and cleave APP peptide substrates at the postulated beta'-cleavage site. It does not appear to be a significant species specificity to this cleavage.

Phe*-Ala-based pentapeptide mimetics are BACE inhibitors: P2 and P3 SAR.

We describe herein the syntheses and evaluation of a series of C-termini pyridyl containing Phe*-Ala-based BACE inhibitors (5-19). In conjunction with four fixed residues at the P1 (Phe), P1' (Ala), P2' (Val), and P2' cap (Pyr.), rather detailed SAR modifications at P2 and P3 positions were pursued. The promising inhibitors emerging from this SAR investigation, 12 and 17 demonstrated very good enzyme potency (IC(50)=45 nM) and cellular activity (IC(50)=0.4 microM).

P3 cap modified Phe*-Ala series BACE inhibitors.

With the aim of reducing molecular weight and adjusting log D value of BACE inhibitors to more favorable range for BBB penetration and better bioavailability, we synthesized and evaluated several series of P3 cap modified BACE inhibitors obtained via replacement of the P3NHBoc moiety as seen in 3 with other polar functional groups such as amino, hydroxyl and fluorine. Several promising inhibitors emerging from this P3 cap SAR study (e.g., 15 and 19) demonstrated good enzyme inhibitory potencies (BACE-1 IC(50) <50 nM) and whole cell activities (IC(50) approximately 1 microM).

Design and synthesis of statine-containing BACE inhibitors.

Utilizing structure-based techniques and solid-phase synthesis, statine-based tetrapeptide BACE inhibitors were designed and synthesized using a heptapeptide BACE transition-state mimetic, 1, as the starting point. Structure-activity relationship studies at the P(3), P(2), and P(2)' positions as well as the N-terminal capping group on scaffold 5 led to the discovery of potent inhibitors 27, 32, and 34 (IC(50) <100 nM). In addition, computational analysis and the X-ray structure of BACE-inhibitor 38 are discussed.