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

CONTEXT: This study addresses the development of a new glucoregulatory mechanism in type 2 diabetes (T2D) patients treated with SGLT-2 inhibitors, which is independent of glucose, insulin and glucagon. The data suggest the presence of a potential trigger factor (s) arising in the kidney that stimulates endogenous glucose production (EGP) during sustained glycosuria. OBJECTIVE: To investigate effects of SGLT-2 inhibitor therapy together with GLP-1 receptor agonist on EGP and glucose kinetics in patients with T2D. Our hypothesis was that increased EGP in response to SGLT2i-induced glycosuria persists for a long period and is not abolished by GLP-1 RA stimulation of insulin secretion and glucagon suppression. METHODS: Seventy-five patients received a 5-hour dual-tracer oral glucose tolerance test (OGTT) (intravenous 3-(3H)-glucose oral (1-14C)-glucose): (1) before/after 1 of dapagliflozin (DAPA); exenatide (EXE), or both, DAPA/EXE (acute study), and (2) after 1 and 4 months of therapy with each drug. RESULTS: In the acute study, during the OGTT plasma glucose (PG) elevation was lower in EXE (Δ = 42 ± 1 mg/dL) than DAPA (Δ = 72 ± 3), and lower in DAPA/EXE (Δ = 11 ± 3) than EXE and DAPA. EGP decrease was lower in DAPA (Δ = -0.65 ± 0.03 mg/kg/min) than EXE (Δ = -0.96 ± 0.07); in DAPA/EXE (Δ = -0.84 ± 0.05) it was lower than EXE, higher than DAPA. At 1 month, similar PG elevations (EXE, Δ = 26 ± 1 mg/dL; DAPA, Δ = 62 ± 2, DAPA/EXE, Δ = 27 ± 1) and EGP decreases (DAPA, Δ = -0.60 ± 0.05 mg/kg/min; EXE, Δ = -0.77 ± 0.04; DAPA/EXE, Δ = -0.72 ± 0.03) were observed. At 4 months, PG elevations (EXE, Δ = 55 ± 2 mg/dL; DAPA, Δ = 65 ± 6; DAPA/EXE, Δ = 46 ± 2) and lower EGP decrease in DAPA (Δ = -0.66 ± 0.04 mg/kg/min) vs EXE (Δ = -0.84 ± 0.05) were also comparable; in DAPA/EXE (Δ = -0.65 ± 0.03) it was equal to DAPA and lower than EXE. Changes in plasma insulin/glucagon could not explain higher EGP in DAPA/EXE vs EXE mg/kg/min. CONCLUSION: Our findings provide strong evidence for the emergence of a new long-lasting, glucose-independent, insulin/glucagon-independent, glucoregulatory mechanism via which SGLT2i-induced glycosuria stimulates EGP in patients with T2D. SGLT2i plus GLP-1 receptor agonist combination therapy is accompanied by superior glycemic control vs monotherapy.

Plasma insulin is required for the increase in plasma angiopoietin-like protein 8 in response to nutrient ingestion.

BACKGROUND: Plasma levels of angiopoietin-like protein 8 (ANGPTL8) are regulated by feeding and they increase following glucose ingestion. Because both plasma glucose and insulin increase following food ingestion, we aimed to determine whether the increase in plasma insulin and glucose or both are responsible for the increase in ANGPTL8 levels. METHODS: ANGPTL8 levels were measured in 30 subjects, 14 with impaired fasting glucose (IFG), and 16 with normal fasting glucose (NFG); the subjects received 75g glucose oral Glucose tolerance test (OGTT), multistep euglycaemic hyperinsulinemic clamp and hyperglycaemic clamp with pancreatic clamp. RESULTS: Subjects with IFG had significantly higher ANGPTL8 than NGT subjects during the fasting state (p < 0.05). During the OGTT, plasma ANGPTL8 concentration increased by 62% above the fasting level (p < 0.0001), and the increase above fasting in ANGPTL8 levels was similar in NFG and IFG individuals. During the multistep insulin clamp, there was a dose-dependent increase in plasma ANGPTL8 concentration. During the 2-step hyperglycaemic clamp, the rise in plasma glucose concentration failed to cause any change in the plasma ANGPTL8 concentration from baseline. CONCLUSIONS: In response to nutrient ingestion, ANGPTL8 level increased due to increased plasma insulin concentration, not to the rise in plasma glucose. The incremental increase above baseline in plasma ANGLPTL8 during OGTT was comparable between people with normal glucose tolerance and IFG.

Bromocriptine-QR Therapy Reduces Sympathetic Tone and Ameliorates a Pro-Oxidative/Pro-Inflammatory Phenotype in Peripheral Blood Mononuclear Cells and Plasma of Type 2 Diabetes Subjects.

Bromocriptine-QR is a sympatholytic dopamine D2 agonist for the treatment of type 2 diabetes that has demonstrated rapid (within 1 year) substantial reductions in adverse cardiovascular events in this population by as yet incompletely delineated mechanisms. However, a chronic state of elevated sympathetic nervous system activity and central hypodopaminergic function has been demonstrated to potentiate an immune system pro-oxidative/pro-inflammatory condition and this immune phenotype is known to contribute significantly to the advancement of cardiovascular disease (CVD). Therefore, the possibility exists that bromocriptine-QR therapy may reduce adverse cardiovascular events in type 2 diabetes subjects via attenuation of this underlying chronic pro-oxidative/pro-inflammatory state. The present study was undertaken to assess the impact of bromocriptine-QR on a wide range of immune pro-oxidative/pro-inflammatory biochemical pathways and genes known to be operative in the genesis and progression of CVD. Inflammatory peripheral blood mononuclear cell biology is both a significant contributor to cardiovascular disease and also a marker of the body's systemic pro-inflammatory status. Therefore, this study investigated the effects of 4-month circadian-timed (within 2 h of waking in the morning) bromocriptine-QR therapy (3.2 mg/day) in type 2 diabetes subjects whose glycemia was not optimally controlled on the glucagon-like peptide 1 receptor agonist on (i) gene expression status (via qPCR) of a wide array of mononuclear cell pro-oxidative/pro-inflammatory genes known to participate in the genesis and progression of CVD (OXR1, NRF2, NQO1, SOD1, SOD2, CAT, GSR, GPX1, GPX4, GCH1, HMOX1, BiP, EIF2α, ATF4, PERK, XBP1, ATF6, CHOP, GSK3ß, NFkB, TXNIP, PIN1, BECN1, TLR2, TLR4, TLR10, MAPK8, NLRP3, CCR2, GCR, L-selectin, VCAM1, ICAM1) and (ii) humoral measures of sympathetic tone (norepinephrine and normetanephrine), whole-body oxidative stress (nitrotyrosine, TBARS), and pro-inflammatory factors (IL-1ß, IL-6, IL-18, MCP-1, prolactin, C-reactive protein [CRP]). Relative to pre-treatment status, 4 months of bromocriptine-QR therapy resulted in significant reductions of mRNA levels in PBMC endoplasmic reticulum stress-unfolded protein response effectors [GRP78/BiP (34%), EIF2α (32%), ATF4 (29%), XBP1 (25%), PIN1 (14%), BECN1 (23%)], oxidative stress response proteins [OXR1 (31%), NRF2 (32%), NQO1 (39%), SOD1 (52%), CAT (26%), GPX1 (33%), GPX4 (31%), GCH1 (30%), HMOX1 (40%)], mRNA levels of TLR pro-inflammatory pathway proteins [TLR2 (46%), TLR4 (20%), GSK3ß (19%), NFkB (33%), TXNIP (18%), NLRP3 (32%), CCR2 (24%), GCR (28%)], mRNA levels of pro-inflammatory cellular receptor proteins CCR2 and GCR by 24% and 28%, and adhesion molecule proteins L-selectin (35%) and VCAM1 (24%). Relative to baseline, bromocriptine-QR therapy also significantly reduced plasma levels of norepinephrine and normetanephrine by 33% and 22%, respectively, plasma pro-oxidative markers nitrotyrosine and TBARS by 13% and 10%, respectively, and pro-inflammatory factors IL-18, MCP1, IL-1ß, prolactin, and CRP by 21%,13%, 12%, 42%, and 45%, respectively. These findings suggest a unique role for circadian-timed bromocriptine-QR sympatholytic dopamine agonist therapy in reducing systemic low-grade sterile inflammation to thereby reduce cardiovascular disease risk.

Dapagliflozin Impairs the Suppression of Endogenous Glucose Production in Type 2 Diabetes Following Oral Glucose.

OBJECTIVE: To examine the effect of SGLT2 inhibitors (SGLT2i) on endogenous glucose production (EGP) in patients with type 2 diabetes after an oral glucose load. RESEARCH DESIGN AND METHODS: Forty-eight patients with type 2 diabetes received an 8-h [3-3H]-glucose infusion (protocol I) to assess EGP response to: 1) dapagliflozin (DAPA), 10 mg; 2) exenatide (EXE), 5 µg s.c.; 3) DAPA/EXE; and 4) placebo (PCB). After 2 weeks (protocol II), patients were restudied with a 5-h double-tracer (i.v. [3-3H]-glucose and oral [1-14C]-glucose) oral glucose tolerance test (OGTT) preceded by PCB, DAPA, EXE, or DAPA/EXE. RESULTS: Protocol I: EGP decreased (P < 0.01) with PCB (2.16 ± 0.15 to 1.57 ± 0.08 mg/kg/min) and EXE (2.13 ± 0.16 to 1.58 ± 0.03) and remained unchanged (P = NS) with DAPA (2.04 ± 0.17 vs. 1.94 ± 0.18) and DAPA/EXE (2.13 ± 0.10 vs. 2.09 ± 0.03). During OGTT, EGP decreased (P < 0.01) with PCB (2.30 ± 0.05 to. 1.45 ± 0.06 mg/kg/min) and EXE (2.53 ± 0.08 to 1.36 ± 0.06); with DAPA (2.20 ± 0.04 vs. 1.71 ± 0.07) and DAPA/EXE (2.48 ± 0.05 vs. 1.64 ± 0.07), the decrease in EGP was attenuated (both P < 0.05). During OGTT, the insulin/glucagon (INS/GCN) ratio increased in PCB (0.26 ± 0.03 vs. 0.71 ± 0.06 µU/mL per pg/mL), whereas in DAPA (0.26 ± 0.02 to 0.50 ± 0.04), the increase was blunted (P < 0.05). In EXE, INS/GCN increased significantly (0.32 ± 0.03 to 1.31 ± 0.08) and was attenuated in DAPA/EXE (0.32 ± 0.03 vs. 0.78 ± 0.08) (P < 0.01). CONCLUSIONS: These findings provide novel evidence that the increase in EGP induced by SGLT2i is present during an oral glucose load. The fact that stimulation of EGP occurs despite elevated plasma insulin and glucagon suggests that additional factors must be involved.

Combination therapy with pioglitazone/exenatide/metformin reduces the prevalence of hepatic fibrosis and steatosis: The efficacy and durability of initial combination therapy for type 2 diabetes (EDICT).

AIM: To compare the efficacy of triple therapy (metformin/exenatide/pioglitazone) versus stepwise conventional therapy (metformin → glipizide → glargine insulin) on liver fat content and hepatic fibrosis in newly diagnosed, drug-naïve patients with type 2 diabetes. METHODS: Sixty-eight patients completed the 6-year follow-up and had an end-of-study (EOS) FibroScan to provide measures of steatosis (controlled attenuation parameter [CAP] in dB/m) and fibrosis (liver stiffness measurement [LSM] in kPa); 59 had magnetic resonance imaging-proton density fat fraction (MRI-PDFF) to measure liver fat. RESULTS: At EOS, HbA1c was 6.8% and 6.0% in triple and conventional therapy groups, respectively (P = .0006). Twenty-seven of 39 subjects (69%) receiving conventional therapy had grade 2/3 steatosis (CAP, FibroScan) versus nine of 29 (31%) in triple therapy (P = .0003). Ten of 39 (26%) subjects receiving conventional therapy had stage 3/4 fibrosis (LSM) versus two of 29 (7%) in triple therapy (P = .04). Conventional therapy subjects had more liver fat (MRI-PDFF) than triple therapy (12.9% vs. 8.8%, P = .03). The severity of steatosis (CAP) (r = 0.42, P < .001) and fibrosis (LSM) (r = -0.48, P < .001) correlated inversely with the Matsuda Index of insulin sensitivity, but not with percentage body fat. Aspartate aminotransferase (AST) to Platelet Ratio Index (APRI), non-alcoholic fatty liver disease fibrosis score (NFS), plasma AST, and alanine aminotransferase (ALT) all decreased significantly with triple therapy, but only the decrease in plasma AST and ALT correlated with the severity of steatosis and fibrosis at EOS. CONCLUSIONS: At EOS, subjects with type 2 diabetes treated with triple therapy had less hepatic steatosis and fibrosis versus conventional therapy; the severity of hepatic steatosis and fibrosis were both strongly and inversely correlated with insulin resistance; and changes in liver fibrosis scores (APRI, NFS, Fibrosis-4, and AST/ALT ratio) have limited value in predicting response to therapy.

Increase in Endogenous Glucose Production With SGLT2 Inhibition Is Unchanged by Renal Denervation and Correlates Strongly With the Increase in Urinary Glucose Excretion.

OBJECTIVE: Sodium-glucose cotransporter 2 (SGLT2) inhibition causes an increase in endogenous glucose production (EGP). However, the mechanisms are unclear. We studied the effect of SGLT2 inhibitors on EGP in subjects with type 2 diabetes (T2D) and without diabetes (non-DM) in kidney transplant recipients with renal denervation. RESEARCH DESIGN AND METHODS: Fourteen subjects who received a renal transplant (six with T2D [A1C 7.2 ± 0.1%] and eight non-DM [A1C 5.6 ± 0.1%) underwent measurement of EGP with [3-3H]glucose infusion following dapagliflozin (DAPA) 10 mg or placebo. Plasma glucose, insulin, C-peptide, glucagon, and titrated glucose-specific activity were measured. RESULTS: Following placebo in T2D, fasting plasma glucose (FPG) (143 ± 14 to 124 ± 10 mg/dL; P = 0.02) and fasting plasma insulin (12 ± 2 to 10 ± 1.1 µU/mL; P < 0.05) decreased; plasma glucagon was unchanged, and EGP declined. After DAPA in T2D, FPG (143 ± 15 to 112 ± 9 mg/dL; P = 0.01) and fasting plasma insulin (14 ± 3 to 11 ± 2 µU/mL; P = 0.02) decreased, and plasma glucagon increased (all P < 0.05 vs. placebo). EGP was unchanged from baseline (2.21 ± 0.19 vs. 1.96 ± 0.14 mg/kg/min) in T2D (P < 0.001 vs. placebo). In non-DM following DAPA, FPG and fasting plasma insulin decreased, and plasma glucagon was unchanged. EGP was unchanged from baseline (1.85 ± 0.10 to 1.78 ± 0.10 mg/kg/min) after DAPA, whereas EGP declined significantly with placebo. When the increase in EGP production following DAPA versus placebo was plotted against the difference in urinary glucose excretion (UGE) for all patients, a strong correlation (r = 0.824; P < 0.001) was observed. CONCLUSIONS: Renal denervation in patients who received a kidney transplant failed to block the DAPA-mediated stimulation of EGP in both individuals with T2D and non-DM subjects. The DAPA-stimulated rise in EGP is strongly related to the increase in UGE, blunting the decline in FPG.

Evidence Against an Important Role of Plasma Insulin and Glucagon Concentrations in the Increase in EGP Caused by SGLT2 Inhibitors.

Sodium-glucose cotransport 2 inhibitors (SGLT2i) lower plasma glucose but stimulate endogenous glucose production (EGP). The current study examined the effect of dapagliflozin on EGP while clamping plasma glucose, insulin, and glucagon concentrations at their fasting level. Thirty-eight patients with type 2 diabetes received an 8-h measurement of EGP ([3-3H]-glucose) on three occasions. After a 3-h tracer equilibration, subjects received 1) dapagliflozin 10 mg (n = 26) or placebo (n = 12); 2) repeat EGP measurement with the plasma glucose concentration clamped at the fasting level; and 3) repeat EGP measurement with inhibition of insulin and glucagon secretion with somatostatin infusion and replacement of basal plasma insulin and glucagon concentrations. In study 1, the change in EGP (baseline to last hour of EGP measurement) in subjects receiving dapagliflozin was 22% greater (+0.66 ± 0.11 mg/kg/min, P < 0.05) than in subjects receiving placebo, and it was associated with a significant increase in plasma glucagon and a decrease in the plasma insulin concentration compared with placebo. Under glucose clamp conditions (study 2), the change in plasma insulin and glucagon concentrations was comparable in subjects receiving dapagliflozin and placebo, yet the difference in EGP between dapagliflozin and placebo persisted (+0.71 ± 0.13 mg/kg/min, P < 0.01). Under pancreatic clamp conditions (study 3), dapagliflozin produced an initial large decrease in EGP (8% below placebo), followed by a progressive increase in EGP that was 10.6% greater than placebo during the last hour. Collectively, these results indicate that 1) the changes in plasma insulin and glucagon concentration after SGLT2i administration are secondary to the decrease in plasma glucose concentration, and 2) the dapagliflozin-induced increase in EGP cannot be explained by the increase in plasma glucagon or decrease in plasma insulin or glucose concentrations.

Glucose-Mediated Glucose Disposal at Baseline Insulin Is Impaired in IFG.

Objective: To quantify glucose-mediated glucose disposal with and without basal insulin replacement and insulin-mediated glucose disposal in subjects with impaired fasting glucose (IFG). Research Design and Methods: We used the hyperglycemic/pancreatic clamp and stepped euglycemic clamp techniques to quantify glucose disposal and suppression of endogenous glucose production (EGP) in those with normal glucose tolerance (NGT; n = 14) and those with IFG (n = 14). Results: Total body glucose-mediated glucose uptake, measured with the hyperglycemic/pancreatic clamp, was not significantly affected by the basal plasma insulin levels in subjects with IFG and those with NGT. Compared with subjects with NGT, those with IFG had significantly lower glucose-mediated glucose uptake (by 15%) during the hyperglycemic clamp performed with and without basal insulin replacement. In contrast, insulin-mediated glucose disposal was comparable in both groups. The suppression of EGP by hyperglycemia was similar in both groups. However, the suppression of EGP by insulin was attenuated in those with IFG compared with those with NGT. Conclusions: The results of the present study have demonstrated that (i) glucose-mediated glucose disposal is impaired in those with IFG; (ii) insulin-mediated glucose uptake in IFG is normal; and (iii) insulin action to suppress EGP is impaired.

Glucose lowering and vascular protective effects of cycloset added to GLP-1 receptor agonists in patients with type 2 diabetes.

OBJECTIVE: To determine the glucose-lowering mechanism of action and the effects of a quick-release bromocriptine-QR, a D2-dopamine agonist (Cycloset) on vascular function in patients with type 2 diabetes (T2D). STUDY DESIGN AND METHODS: Fifteen poorly controlled T2D treated with metformin plus glucagon-like peptide-1 receptor agonists (GLP-1RA) were studied after 4 months of Cycloset, 3.2 mg/d. Subjects received a 5-hour double-tracer (iv 3-3H-glucose and oral 14C-glucose) mixed meal test (MMT) to quantitate rates of endogenous glucose production (EGP), oral glucose appearance (RaO) and disappearance (Rd) pre- and post-Cycloset. Vascular assessments included 2-day continuous BP monitoring, reactive hyperaemia index (RHI) and arterial stiffness (AS). RESULTS: HbA1c decreased from 8.3 ± 0.3% to 7.7 ± 0.2% (P < 0.05), fasting plasma glucose did not change (143 ± 4 vs 147 ± 5) and mean plasma glucose during MTT decreased from 223 ± 3 to 210 ± 4 mg/dL (P < 0.05) after Cycloset. Basal EGP (2.2 ± 0.2 vs 2.1 ± 0.2 mg/kg min) was unchanged, but there was greater MMT suppression (1.1 ± 0.1 vs 0.7 ± 0.1, P < 0.05). After Cycloset, RaO declined from 2.0 ± 0.1 to 1.7 ± 0.2 mg/kg min and peripheral oral glucose appearance from 53.1 ± 3.2 to 44.4 ± 3.1 g (P < 0.01). There were no changes in plasma insulin or glucagon concentration. Systolic (134 ± 4 vs 126 ± 6), diastolic (78 ± 3 vs 73 ± 4), mean BP (97 ± 5 vs 90 ± 4) and pulse pressure (54 ± 2 vs 51 ± 2 mm Hg) were reduced; RHI increased from 1.4 ± 0.1 to 1.9 ± 0.3 au and AS decreased modestly (19.8 ± 4.1 to 16.2 ± 3.7 au, P = NS). CONCLUSIONS: Addition of Cycloset to GLP-1 RA improved vascular indices and postprandial hyperglycaemia in T2DM primarily by lowering oral glucose appearance, suggesting that hepatic glucose uptake was enhanced. Improved vascular indices may explain the reduction in cardiovascular events observed with Cycloset therapy in patients with T2DM.

Decreased basal hepatic glucose uptake in impaired fasting glucose.

AIMS/HYPOTHESIS: This research aimed to define the pathophysiological defects responsible for the elevated fasting plasma glucose (FPG) concentration and excessive rise in post-load plasma glucose observed in individuals with impaired fasting glucose (IFG). METHODS: We used tracer techniques to quantify basal splanchnic (primarily hepatic) glucose uptake and glucose fluxes following glucose ingestion in individuals with normal glucose tolerance (NGT; n = 10) and IFG (n = 10). RESULTS: Individuals with IFG had a comparable basal rate of hepatic glucose production to those with NGT (15.2 ± 0.2 vs 18.0 ± 0.8 µmol min-1 [kg lean body mass (LBM)]-1; p = 0.09). However, they had a significantly reduced glucose clearance rate during the fasting state compared with NGT (2.64 ± 0.11 vs 3.62 ± 0.20 ml min-1 [kg LBM]-1; p < 0.01). The difference between the basal rate of glucose appearance measured with [3-3H]glucose and [1-14C]glucose, which represent basal splanchnic glucose uptake, was significantly reduced in IFG compared with NGT (1.39 ± 0.28 vs 3.16 ± 0.44 µmol min-1 [kg LBM]-1; p = 0.02). Following glucose ingestion, the total amount of exogenous glucose that appeared in the systemic circulation was not significantly different between groups. However, suppression of endogenous glucose production (EGP) was markedly impaired in individuals with IFG. CONCLUSIONS/INTERPRETATION: These results demonstrate that decreased tissue (liver) glucose uptake, not enhanced EGP, is the cause for elevated FPG concentration in individuals with IFG, while the excessive rise in plasma glucose concentration following a glucose load in these individuals is the result of impaired suppression of hepatic glucose production.