Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial.

Importance: The effect of continued treatment with tirzepatide on maintaining initial weight reduction is unknown. Objective: To assess the effect of tirzepatide, with diet and physical activity, on the maintenance of weight reduction. Design, Setting, and Participants: This phase 3, randomized withdrawal clinical trial conducted at 70 sites in 4 countries with a 36-week, open-label tirzepatide lead-in period followed by a 52-week, double-blind, placebo-controlled period included adults with a body mass index greater than or equal to 30 or greater than or equal to 27 and a weight-related complication, excluding diabetes. Interventions: Participants (n = 783) enrolled in an open-label lead-in period received once-weekly subcutaneous maximum tolerated dose (10 or 15 mg) of tirzepatide for 36 weeks. At week 36, a total of 670 participants were randomized (1:1) to continue receiving tirzepatide (n = 335) or switch to placebo (n = 335) for 52 weeks. Main Outcomes and Measures: The primary end point was the mean percent change in weight from week 36 (randomization) to week 88. Key secondary end points included the proportion of participants at week 88 who maintained at least 80% of the weight loss during the lead-in period. Results: Participants (n = 670; mean age, 48 years; 473 [71%] women; mean weight, 107.3 kg) who completed the 36-week lead-in period experienced a mean weight reduction of 20.9%. The mean percent weight change from week 36 to week 88 was -5.5% with tirzepatide vs 14.0% with placebo (difference, -19.4% [95% CI, -21.2% to -17.7%]; P < .001). Overall, 300 participants (89.5%) receiving tirzepatide at 88 weeks maintained at least 80% of the weight loss during the lead-in period compared with 16.6% receiving placebo (P < .001). The overall mean weight reduction from week 0 to 88 was 25.3% for tirzepatide and 9.9% for placebo. The most common adverse events were mostly mild to moderate gastrointestinal events, which occurred more commonly with tirzepatide vs placebo. Conclusions and Relevance: In participants with obesity or overweight, withdrawing tirzepatide led to substantial regain of lost weight, whereas continued treatment maintained and augmented initial weight reduction. Trial Registration: ClinicalTrials.gov Identifier: NCT04660643.

Tirzepatide Once Weekly for the Treatment of Obesity.

BACKGROUND: Obesity is a chronic disease that results in substantial global morbidity and mortality. The efficacy and safety of tirzepatide, a novel glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist, in people with obesity are not known. METHODS: In this phase 3 double-blind, randomized, controlled trial, we assigned 2539 adults with a body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) of 30 or more, or 27 or more and at least one weight-related complication, excluding diabetes, in a 1:1:1:1 ratio to receive once-weekly, subcutaneous tirzepatide (5 mg, 10 mg, or 15 mg) or placebo for 72 weeks, including a 20-week dose-escalation period. Coprimary end points were the percentage change in weight from baseline and a weight reduction of 5% or more. The treatment-regimen estimand assessed effects regardless of treatment discontinuation in the intention-to-treat population. RESULTS: At baseline, the mean body weight was 104.8 kg, the mean BMI was 38.0, and 94.5% of participants had a BMI of 30 or higher. The mean percentage change in weight at week 72 was -15.0% (95% confidence interval [CI], -15.9 to -14.2) with 5-mg weekly doses of tirzepatide, -19.5% (95% CI, -20.4 to -18.5) with 10-mg doses, and -20.9% (95% CI, -21.8 to -19.9) with 15-mg doses and -3.1% (95% CI, -4.3 to -1.9) with placebo (P<0.001 for all comparisons with placebo). The percentage of participants who had weight reduction of 5% or more was 85% (95% CI, 82 to 89), 89% (95% CI, 86 to 92), and 91% (95% CI, 88 to 94) with 5 mg, 10 mg, and 15 mg of tirzepatide, respectively, and 35% (95% CI, 30 to 39) with placebo; 50% (95% CI, 46 to 54) and 57% (95% CI, 53 to 61) of participants in the 10-mg and 15-mg groups had a reduction in body weight of 20% or more, as compared with 3% (95% CI, 1 to 5) in the placebo group (P<0.001 for all comparisons with placebo). Improvements in all prespecified cardiometabolic measures were observed with tirzepatide. The most common adverse events with tirzepatide were gastrointestinal, and most were mild to moderate in severity, occurring primarily during dose escalation. Adverse events caused treatment discontinuation in 4.3%, 7.1%, 6.2%, and 2.6% of participants receiving 5-mg, 10-mg, and 15-mg tirzepatide doses and placebo, respectively. CONCLUSIONS: In this 72-week trial in participants with obesity, 5 mg, 10 mg, or 15 mg of tirzepatide once weekly provided substantial and sustained reductions in body weight. (Supported by Eli Lilly; SURMOUNT-1 ClinicalTrials.gov number, NCT04184622.).

Insulin clearance and incretin hormones following oral and "isoglycemic" intravenous glucose in type 2 diabetes patients under different antidiabetic treatments.

It has not been elucidated whether incretins affect insulin clearance in type 2 diabetes (T2D). We aimed exploring possible associations between insulin clearance and endogenously secreted or exogenously administered incretins in T2D patients. Twenty T2D patients were studied (16 males/4 females, 59 ± 2 years (mean ± standard error), BMI = 31 ± 1 kg/m2, HbA1c = 7.0 ± 0.1%). Patients were treated with metformin, sitagliptin, metformin/sitagliptin combination, and placebo (randomized order). On each treatment period, oral and isoglycemic intravenous glucose infusion tests were performed (OGTT, IIGI, respectively). We also studied twelve T2D patients (9 males/3 females, 61 ± 3 years, BMI = 30 ± 1 kg/m2, HbA1c = 7.3 ± 0.4%) that underwent infusion of GLP-1(7-36)-amide, GIP, GLP-1/GIP combination, and placebo. Plasma glucose, insulin, C-peptide, and incretins were measured. Insulin clearance was assessed as insulin secretion to insulin concentration ratio. In the first study, we found OGTT/IIGI insulin clearance ratio weakly inversely related to OGTT/IIGI total GIP and intact GLP-1 (R2 = 0.13, p < 0.02). However, insulin clearance showed some differences between sitagliptin and metformin treatment (p < 0.02). In the second study we found no difference in insulin clearance following GLP-1 and/or GIP infusion (p > 0.5). Thus, our data suggest that in T2D there are no relevant incretin effects on insulin clearance. Conversely, different antidiabetic treatments may determine insulin clearance variations.

Effect of Subcutaneous Tirzepatide vs Placebo Added to Titrated Insulin Glargine on Glycemic Control in Patients With Type 2 Diabetes: The SURPASS-5 Randomized Clinical Trial.

Importance: The effects of tirzepatide, a dual glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist, as an addition to insulin glargine for treatment of type 2 diabetes have not been described. Objective: To assess the efficacy and safety of tirzepatide added to insulin glargine in patients with type 2 diabetes with inadequate glycemic control. Design, Setting, and Participants: Randomized phase 3 clinical trial conducted at 45 medical research centers and hospitals in 8 countries (enrollment from August 30, 2019, to March 20, 2020; follow-up completed January 13, 2021) in 475 adults with type 2 diabetes and inadequate glycemic control while treated with once-daily insulin glargine with or without metformin. Interventions: Patients were randomized in a 1:1:1:1 ratio to receive once-weekly subcutaneous injections of 5-mg (n = 116), 10-mg (n = 119), or 15-mg (n = 120) tirzepatide or volume-matched placebo (n = 120) over 40 weeks. Tirzepatide was initiated at 2.5 mg/week and escalated by 2.5 mg every 4 weeks until the assigned dose was achieved. Main Outcomes and Measures: The primary end point was mean change from baseline in glycated hemoglobin A1c (HbA1c) at week 40. The 5 key secondary end points included mean change in body weight and percentage of patients achieving prespecified HbA1c levels. Results: Among 475 randomized participants (211 [44%] women; mean [SD] age, 60.6 [9.9] years; mean [SD] HbA1c, 8.31% [0.85%]), 451 (94.9%) completed the trial. Treatment was prematurely discontinued by 10% of participants in the 5-mg tirzepatide group, 12% in the 10-mg tirzepatide group, 18% in the 15-mg tirzepatide group, and 3% in the placebo group. At week 40, mean HbA1c change from baseline was -2.40% with 10-mg tirzepatide and -2.34% with 15-mg tirzepatide vs -0.86% with placebo (10 mg: difference vs placebo, -1.53% [97.5% CI, -1.80% to -1.27%]; 15 mg: difference vs placebo, -1.47% [97.5% CI, -1.75% to -1.20%]; P < .001 for both). Mean HbA1c change from baseline was -2.11% with 5-mg tirzepatide (difference vs placebo, -1.24% [95% CI, -1.48% to -1.01%]; P < .001]). Mean body weight change from baseline was -5.4 kg with 5-mg tirzepatide, -7.5 kg with 10-mg tirzepatide, -8.8 kg with 15-mg tirzepatide and 1.6 kg with placebo (5 mg: difference, -7.1 kg [95% CI, -8.7 to -5.4]; 10 mg: difference, -9.1 kg [95% CI, -10.7 to -7.5]; 15 mg: difference, -10.5 kg [95% CI, -12.1 to -8.8]; P < .001 for all). Higher percentages of patients treated with tirzepatide vs those treated with placebo had HbA1c less than 7% (85%-90% vs 34%; P < .001 for all). The most common treatment-emergent adverse events in the tirzepatide groups vs placebo group were diarrhea (12%-21% vs 10%) and nausea (13%-18% vs 3%). Conclusions and Relevance: Among patients with type 2 diabetes and inadequate glycemic control despite treatment with insulin glargine, the addition of subcutaneous tirzepatide, compared with placebo, to titrated insulin glargine resulted in statistically significant improvements in glycemic control after 40 weeks. Trial Registration: ClinicalTrials.gov Identifier: NCT04039503.

Effects of Tirzepatide, a Dual GIP and GLP-1 RA, on Lipid and Metabolite Profiles in Subjects With Type 2 Diabetes.

CONTEXT: Tirzepatide substantially reduced hemoglobin A1c (HbA1c) and body weight in subjects with type 2 diabetes (T2D) compared with the glucagon-like peptide 1 receptor agonist dulaglutide. Improved glycemic control was associated with lower circulating triglycerides and lipoprotein markers and improved markers of beta-cell function and insulin resistance (IR), effects only partially attributable to weight loss. OBJECTIVE: Assess plasma metabolome changes mediated by tirzepatide. DESIGN: Phase 2b trial participants were randomly assigned to receive weekly subcutaneous tirzepatide, dulaglutide, or placebo for 26 weeks. Post hoc exploratory metabolomics and lipidomics analyses were performed. SETTING: Post hoc analysis. PARTICIPANTS: 259 subjects with T2D. INTERVENTION(S): Tirzepatide (1, 5, 10, 15 mg), dulaglutide (1.5 mg), or placebo. MAIN OUTCOME MEASURE(S): Changes in metabolite levels in response to tirzepatide were assessed against baseline levels, dulaglutide, and placebo using multiplicity correction. RESULTS: At 26 weeks, a higher dose tirzepatide modulated a cluster of metabolites and lipids associated with IR, obesity, and future T2D risk. Branched-chain amino acids, direct catabolic products glutamate, 3-hydroxyisobutyrate, branched-chain ketoacids, and indirect byproducts such as 2-hydroxybutyrate decreased compared to baseline and placebo. Changes were significantly larger with tirzepatide compared with dulaglutide and directly proportional to reductions of HbA1c, homeostatic model assessment 2-IR indices, and proinsulin levels. Proportional to metabolite changes, triglycerides and diglycerides were lowered significantly compared to baseline, dulaglutide, and placebo, with a bias toward shorter and highly saturated species. CONCLUSIONS: Tirzepatide reduces body weight and improves glycemic control and uniquely modulates metabolites associated with T2D risk and metabolic dysregulation in a direction consistent with improved metabolic health.

The effect of 6-day subcutaneous glucose-dependent insulinotropic polypeptide infusion on time in glycaemic range in patients with type 1 diabetes: a randomised, double-blind, placebo-controlled crossover trial.

AIMS/HYPOTHESIS: Type 1 diabetes is characterised by reduced glucagon response to hypoglycaemia, increasing the risk of insulin treatment-associated hypoglycaemia known to hamper glycaemic control. We previously reported a glucagonotropic effect of exogenous glucose-dependent insulinotropic polypeptide (GIP) during insulin-induced hypoglycaemia in individuals with type 1 diabetes. Here we investigate the effect of a 6-day s.c. GIP infusion on time in glycaemic range as assessed by continuous glucose monitoring (CGM) in individuals with type 1 diabetes. METHODS: In a randomised, placebo-controlled, double-blind crossover study, time in glycaemic range (assessed by double-blinded CGM) was evaluated in 20 men with type 1 diabetes (18-75 years, stable insulin treatment ≥3 months, diabetes duration 2-15 years, fasting plasma C-peptide below 200 pmol/l, BMI 20-27 kg/m2, HbA1c <69 mmol/mol [8.5%]) during two × 6 days of continuous s.c. GIP (6 pmol kg-1 min-1) and placebo (saline [154 mmol/l NaCl]) infusion, respectively, with an interposed 7-day washout period. The primary outcome was glycaemic time below range, time in range and time above range. RESULTS: There were no significant differences in time below range (<3.9 mmol/l, p = 0.53) or above range (>10 mmol/l, p = 0.32) during night-time or daytime, in mean glucose, or in hypoglycaemic events as assessed by CGM. GIP altered neither self-reported hypoglycaemia nor safety measures. Compared with placebo, GIP significantly increased time in tight range (3.9-7.8 mmol/l) during daytime (06:00-23:59 hours) by [mean ± SEM] 11.2 ± 5.1% [95% CI 0.41, 21.9] (p = 0.02). CONCLUSIONS/INTERPRETATION: Six-day s.c. GIP infusion in men with type 1 diabetes did not procure convincing effect on overall time in range, but increased time in tight glycaemic range during daytime by ~2 h per day. TRIAL REGISTRATION: ClinicalTrials.gov NCT03734718. FUNDING: The study was funded by grants from The Leona M. and Harry B. Helmsley Charitable Trust and Aase og Ejnar Danielsens Fond.

Once-weekly tirzepatide versus once-daily insulin degludec as add-on to metformin with or without SGLT2 inhibitors in patients with type 2 diabetes (SURPASS-3): a randomised, open-label, parallel-group, phase 3 trial.

BACKGROUND: Tirzepatide is a novel dual glucose-dependent insulinotropic polypeptide and GLP-1 receptor agonist under development for the treatment of type 2 diabetes. We aimed to assess the efficacy and safety of tirzepatide versus titrated insulin degludec in people with type 2 diabetes inadequately controlled by metformin with or without SGLT2 inhibitors. METHODS: In this open-label, parallel-group, multicentre (122 sites), multinational (13 countries), phase 3 study, eligible participants (aged ≥18 years) had a baseline glycated haemoglobin (HbA1c) of 7·0-10·5%, body-mass index of at least 25 kg/m2, stable weight, and were insulin-naive and treated with metformin alone or in combination with an SGLT2 inhibitor for at least 3 months before screening. Participants were randomly assigned (1:1:1:1), using an interactive web-response system, to once-weekly subcutaneous injection of tirzepatide (5, 10, or 15 mg) or once-daily subcutaneous injection of titrated insulin degludec, and were stratified by country, HbA1c, and concomitant use of oral antihyperglycaemic medications. Tirzepatide was initially given at 2·5 mg and the dose was escalated by 2·5 mg every 4 weeks until the assigned dose was reached. Insulin degludec was initially given at 10 U per day and was titrated once weekly to a fasting self-monitored blood glucose of less than 5·0 mmol/L (<90 mg/dL), following a treat-to-target algorithm, for 52 weeks. The primary efficacy endpoint was non-inferiority of tirzepatide 10 mg or 15 mg, or both, versus insulin degludec in mean change from baseline in HbA1c at week 52. Key secondary efficacy endpoints were non-inferiority of tirzepatide 5 mg versus insulin degludec in mean change from baseline in HbA1c at week 52, superiority of all doses of tirzepatide versus insulin degludec in mean change from baseline in HbA1c and bodyweight, and the proportion of participants achieving HbA1c of less than 7·0% (<53 mmol/mol) at week 52. We used a boundary of 0·3% to establish non-inferiority in HbA1c difference between treatments. Efficacy and safety analyses were assessed in the modified intention-to-treat population (all participants who received at least one dose of study drug). This trial is registered with ClinicalTrials.gov, number NCT03882970, and is complete. FINDINGS: Between April 1 and Nov 15, 2019, we assessed 1947 participants for eligibility, 1444 of whom were randomly assigned to treatment. The modified intention-to-treat population was 1437 participants from the tirzepatide 5 mg (n=358), tirzepatide 10 mg (n=360), tirzepatide 15 mg (n=359), and insulin degludec (n=360) groups. From a mean baseline HbA1c of 8·17% (SD 0·91), the reductions in HbA1c at week 52 were 1·93% (SE 0·05) for tirzepatide 5 mg, 2·20% (0·05) for tirzepatide 10 mg, and 2·37% (0·05) for tirzepatide 15 mg, and 1·34% (0·05) for insulin degludec. The non-inferiority margin of 0·3% was met. The estimated treatment difference (ETD) versus insulin degludec ranged from -0·59% to -1·04% for tirzepatide (p<0·0001 for all tirzepatide doses). The proportion of participants achieving a HbA1c of less than 7·0% (<53 mmol/mol) at week 52 was greater (p<0·0001) in all three tirzepatide groups (82%-93%) versus insulin degludec (61%). At week 52, from a baseline of 94·3 kg (SD 20·1), all three tirzepatide doses decreased bodyweight (-7·5 kg to -12·9 kg), whereas insulin degludec increased bodyweight by 2·3 kg. The ETD versus insulin degludec ranged from -9·8 kg to -15·2 kg for tirzepatide (p<0·0001 for all tirzepatide doses). The most common adverse events in tirzepatide-treated participants were mild to moderate gastrointestinal events that decreased over time. A higher incidence of nausea (12-24%), diarrhoea (15-17%), decreased appetite (6-12%), and vomiting (6-10%) was reported in participants treated with tirzepatide than in those treated with insulin degludec (2%, 4%, 1%, and 1%, respectively). Hypoglycaemia (<54 mg/dL or severe) was reported in five (1%), four (1%), and eight (2%) participants on tirzepatide 5, 10, and 15 mg, respectively, versus 26 (7%) on insulin degludec. Treatment discontinuation due to an adverse event was more common in the tirzepatide groups than in the insulin degludec group. Five participants died during the study; none of the deaths were considered by the investigators to be related to the study treatment. INTERPRETATION: In patients with type 2 diabetes, tirzepatide (5, 10, and 15 mg) was superior to titrated insulin degludec, with greater reductions in HbA1c and bodyweight at week 52 and a lower risk of hypoglycaemia. Tirzepatide showed a similar safety profile to that of GLP-1 receptor agonists. FUNDING: Eli Lilly and Company.

Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes.

BACKGROUND: Tirzepatide is a dual glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 (GLP-1) receptor agonist that is under development for the treatment of type 2 diabetes. The efficacy and safety of once-weekly tirzepatide as compared with semaglutide, a selective GLP-1 receptor agonist, are unknown. METHODS: In an open-label, 40-week, phase 3 trial, we randomly assigned 1879 patients, in a 1:1:1:1 ratio, to receive tirzepatide at a dose of 5 mg, 10 mg, or 15 mg or semaglutide at a dose of 1 mg. At baseline, the mean glycated hemoglobin level was 8.28%, the mean age 56.6 years, and the mean weight 93.7 kg. The primary end point was the change in the glycated hemoglobin level from baseline to 40 weeks. RESULTS: The estimated mean change from baseline in the glycated hemoglobin level was -2.01 percentage points, -2.24 percentage points, and -2.30 percentage points with 5 mg, 10 mg, and 15 mg of tirzepatide, respectively, and -1.86 percentage points with semaglutide; the estimated differences between the 5-mg, 10-mg, and 15-mg tirzepatide groups and the semaglutide group were -0.15 percentage points (95% confidence interval [CI], -0.28 to -0.03; P = 0.02), -0.39 percentage points (95% CI, -0.51 to -0.26; P<0.001), and -0.45 percentage points (95% CI, -0.57 to -0.32; P<0.001), respectively. Tirzepatide at all doses was noninferior and superior to semaglutide. Reductions in body weight were greater with tirzepatide than with semaglutide (least-squares mean estimated treatment difference, -1.9 kg, -3.6 kg, and -5.5 kg, respectively; P<0.001 for all comparisons). The most common adverse events were gastrointestinal and were primarily mild to moderate in severity in the tirzepatide and semaglutide groups (nausea, 17 to 22% and 18%; diarrhea, 13 to 16% and 12%; and vomiting, 6 to 10% and 8%, respectively). Of the patients who received tirzepatide, hypoglycemia (blood glucose level, <54 mg per deciliter) was reported in 0.6% (5-mg group), 0.2% (10-mg group), and 1.7% (15-mg group); hypoglycemia was reported in 0.4% of those who received semaglutide. Serious adverse events were reported in 5 to 7% of the patients who received tirzepatide and in 3% of those who received semaglutide. CONCLUSIONS: In patients with type 2 diabetes, tirzepatide was noninferior and superior to semaglutide with respect to the mean change in the glycated hemoglobin level from baseline to 40 weeks. (Funded by Eli Lilly; SURPASS-2 ClinicalTrials.gov number, NCT03987919.).

Glucose effectiveness: Lessons from studies on insulin-independent glucose clearance in mice.

Besides insulin-mediated transport of glucose into the cells, an important role is also played by the non-insulin-mediated transport. This latter process is called glucose effectiveness (acronym SG ), which is estimated by modeling of glucose and insulin data after an intravenous glucose administration, and accounts for ≈70% of glucose disposal. This review summarizes studies on SG , mainly in humans and rodents with focus on results achieved in model experiments in mice. In humans, SG is reduced in type 2 diabetes, in obesity, in liver cirrhosis and in some elderly populations. In model experiments in mice, SG is independent from glucose levels, but increases when insulin secretion is stimulated, such as after administration of the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide. SG is reduced in insulin resistance induced by high-fat feeding and by exogenous administration of glucagon. Glucose-dependent (insulin-independent) glucose disposal is therefore important for glucose elimination, and it is also well regulated. It might be of pathophysiological relevance for the development of type 2 diabetes, in particular during insulin resistance, and might also be a target for glucose-reducing therapy. Measuring SG is essentially important when carrying out metabolic studies to understand glucose homeostasis.

Different mechanisms of GIP and GLP-1 action explain their different therapeutic efficacy in type 2 diabetes.

BACKGROUND AND AIMS: The reduced action of incretin hormones in type 2 diabetes (T2D) is mainly attributed to GIP insensitivity, but efficacy estimates of GIP and GLP-1 differ among studies, and the negligible effects of pharmacological GIP doses remain unexplained. We aimed to characterize incretin action in vivo in subjects with normal glucose tolerance (NGT) or T2D and provide an explanation for the different insulinotropic activity of GIP and GLP-1 in T2D subjects. METHODS: We used in vivo data from ten studies employing hormone infusion or an oral glucose test (OGTT). To homogeneously interpret and compare the results of the studies we performed the analysis using a mathematical model of the ß-cell incorporating the effects of incretins on the triggering and amplifying pathways. The effect on the amplifying pathway was quantified by a time-dependent factor that is greater than one when insulin secretion (ISR) is amplified by incretins. To validate the model results for GIP in NGT subjects, we performed an extensive literature search of the available data. RESULTS: a) the stimulatory effects of GIP and GLP-1 differ markedly: ISR potentiation increases linearly with GLP-1 over the whole dose range, while with GIP infusion it reaches a plateau at ~100 pmol/L GIP, with ISR potentiation of ~2 fold; b) ISR potentiation in T2D is reduced by ~50% for GIP and by ~40% for GLP-1; c) the literature search of GIP in NGT subjects confirmed the saturative effect on insulin secretion. CONCLUSION: We show that incretin potentiation of ISR is reduced in T2D, but not abolished, and that the lack of effects of pharmacological GIP doses is due to saturation of the GIP effect more than insensitivity to GIP in T2D.

Gut Hormone GIP Induces Inflammation and Insulin Resistance in the Hypothalamus.

The hypothalamus plays a critical role in controlling energy balance. High-fat diet (HFD) feeding increases the gene expression of proinflammatory mediators and decreases insulin actions in the hypothalamus. Here, we show that a gut-derived hormone, glucose-dependent insulinotropic polypeptide (GIP), whose levels are elevated during diet-induced obesity, promotes and mediates hypothalamic inflammation and insulin resistance during HFD-induced obesity. Unbiased ribonucleic acid sequencing of GIP-stimulated hypothalami revealed that hypothalamic pathways most affected by intracerebroventricular (ICV) GIP stimulation were related to inflammatory-related responses. Subsequent analysis demonstrated that GIP administered either peripherally or centrally, increased proinflammatory-related factors such as Il-6 and Socs3 in the hypothalamus, but not in the cortex of C57BL/6J male mice. Consistently, hypothalamic activation of IκB kinase-ß inflammatory signaling was induced by ICV GIP. Further, hypothalamic levels of proinflammatory cytokines and Socs3 were significantly reduced by an antagonistic GIP receptor (GIPR) antibody and by GIPR deficiency. Additionally, centrally administered GIP reduced anorectic actions of insulin in the brain and diminished insulin-induced phosphorylation of Protein kinase B and Glycogen synthase kinase 3ß in the hypothalamus. Collectively, these findings reveal a previously unrecognized role for brain GIP signaling in diet-induced inflammation and insulin resistance in the hypothalamus.

GIP and GLP-1 Receptor Antagonism During a Meal in Healthy Individuals.

CONTEXT: The actions of both endogenous incretin hormones during a meal have not previously been characterized. OBJECTIVE: Using specific receptor antagonists, we investigated the individual and combined contributions of endogenous glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) to postprandial glucose metabolism, energy expenditure, and gallbladder motility. DESIGN: Randomized, double-blinded, placebo-controlled, crossover design. SETTING: On four separate days, four liquid mixed meal tests (1894 kJ) over 270 minutes (min). PATIENTS OR OTHER PARTICIPANTS: Twelve healthy male volunteers. INTERVENTIONS: Infusions of the GIP receptor antagonist GIP(3-30)NH2 (800 pmol/kg/min), the GLP-1 receptor antagonist exendin(9-39)NH2 (0-20 min: 1000 pmol/kg/min; 20-270 min: 450 pmol/kg/min), GIP(3-30)NH2+exendin(9-39)NH2, or placebo/saline. MAIN OUTCOME MEASURE: Baseline-subtracted area under the curve (bsAUC) of C-peptide. RESULTS: Infusion of GIP(3-30)NH2+exendin(9-39)NH2 significantly increased plasma glucose excursions (bsAUC: 261 ± 142 mmol/L × min) during the liquid mixed meals compared with GIP(3-30)NH2 (180 ± 141 mmol/L × min; P = 0.048), exendin(9-39)NH2 (171 ± 114 mmol/L × min; P = 0.046), and placebo (116 ± 154 mmol/L × min; P = 0.015). Correspondingly, C-peptide:glucose ratios during GIP(3-30)NH2+exendin(9-39)NH2 infusion were significantly lower than during GIP(3-30)NH2 (P = 0.0057), exendin(9-39)NH2 (P = 0.0038), and placebo infusion (P = 0.014). GIP(3-30)NH2 resulted in significantly lower AUCs for glucagon than exendin(9-39)NH2 (P = 0.0417). Gallbladder ejection fraction was higher during GIP(3-30)NH2 compared with placebo (P = 0.004). For all interventions, energy expenditure and respiratory quotient were similar. CONCLUSIONS: Endogenous GIP and GLP-1 lower postprandial plasma glucose excursions and stimulate insulin secretion but only endogenous GIP affects gallbladder motility. The two incretin hormones potentiate each other's effects in the control of postprandial glycemia in healthy men.

No Acute Effects of Exogenous Glucose-Dependent Insulinotropic Polypeptide on Energy Intake, Appetite, or Energy Expenditure When Added to Treatment With a Long-Acting Glucagon-Like Peptide 1 Receptor Agonist in Men With Type 2 Diabetes.

OBJECTIVE: Dual incretin receptor agonists in clinical development have shown reductions in body weight and hemoglobin A1c (HbA1c) in patients with type 2 diabetes, but the impact of glucose-dependent insulinotropic polypeptide (GIP) receptor activation remains unclear. Here, we evaluated the effects of high-dose exogenous GIP on energy intake, energy expenditure, plasma glucose, and glucose-regulating hormones in patients with type 2 diabetes treated with a long-acting glucagon-like peptide 1 receptor (GLP-1R) agonist. RESEARCH DESIGN AND METHODS: In a randomized, double-blind design, men with type 2 diabetes (n = 22, mean ± SEM HbA1c 6.8 ± 0.1% [51 ± 1.5 mmol/mol]) treated with metformin and long-acting GLP-1R agonists were subjected to two 5-h continuous infusions (separated by a washout period of ≥3 days): one with GIP (6 pmol/kg/min) and another with saline (placebo). After 60 min of infusion, a liquid mixed-meal test was performed, and after 270 min of infusion, an ad libitum meal was served for evaluation of energy intake (primary end point). RESULTS: Energy intake was similar during GIP and placebo infusion (648 ± 74 kcal vs. 594 ± 55 kcal, respectively; P = 0.480), as were appetite measures and energy expenditure. Plasma glucagon and glucose were higher during GIP infusion compared with placebo infusion (P = 0.026 and P = 0.017) as assessed by area under the curve. CONCLUSIONS: In patients with type 2 diabetes, GIP infusion on top of treatment with metformin and a long-acting GLP-1R agonist did not affect energy intake, appetite, or energy expenditure but increased plasma glucose compared with placebo. These results indicate no acute beneficial effects of combining GIP and GLP-1.

A GIP/xenin hybrid in combination with exendin-4 improves metabolic status in db/db diabetic mice and promotes enduring antidiabetic benefits in high fat fed mice.

The current study has determined the ability of exendin-4 to augment the antidiabetic benefits of the recently characterised GIP/xenin hybrid, (DAla2)GIP/xenin-8-Gln. As such, combined activation of metabolic pathways linked to various gut derived hormones has been shown to exert complementary beneficial metabolic effects in diabetes. (DAla2)GIP/xenin-8-Gln and exendin-4 were administered twice daily to high fat fed (HFF) or db/db mice for 28 days and antidiabetic benefits assessed. Persistence of beneficial metabolic effects in HFF mice was also examined. Twice-daily injection of (DAla2)GIP/xenin-8-Gln for 28 days in HFF mice significantly reduced energy intake, body weight, circulating glucose, HbA1c and improved glucose tolerance and insulin sensitivity. Overall pancreatic islet, alpha- and beta-cell areas were reduced, with concurrent reduction in alpha- and beta-cell proliferation that was more apparent in the combined treatment group. Addition of exendin-4 to (DAla2)GIP/xenin-8-Gln therapy did not significantly improve metabolic control. Remarkably, beneficial effects were still evident 14 days following complete cessation of peptide administration. Thus, circulating glucose and insulin, HbA1c concentrations and glucose tolerance were still significantly improved when compared to control HFF mice on day 42, with minimal changes to pancreatic islet architecture. In contrast to HFF mice, combined treatment of db/db mice with (DAla2)GIP/xenin-8-Gln plus exendin-4 was required to induce beneficial effects on key metabolic parameters, which were not observed with either treatment alone. This included improvements in glucose tolerance and insulin sensitivity, but no effect on pancreatic architecture. These studies highlight the clear, and persistent, metabolic advantages of sustained activation of GLP-1 receptors, alongside concurrent activation of related GIP and xenin cell signalling pathways, in diabetes.

Effects of combined GIP and GLP-1 infusion on energy intake, appetite and energy expenditure in overweight/obese individuals: a randomised, crossover study.

AIMS/HYPOTHESIS: Glucagon-like peptide 1 (GLP-1) reduces appetite and energy intake in humans, whereas the other incretin hormone, glucose-dependent insulinotropic polypeptide (GIP), seems to have no effect on eating behaviour. Interestingly, studies in rodents have shown that concomitant activation of GIP and GLP-1 receptors may potentiate the satiety-promoting effect of GLP-1, and a novel dual GLP-1/GIP receptor agonist was recently shown to trigger greater weight losses compared with a GLP-1 receptor agonist in individuals with type 2 diabetes. The aim of this study was to delineate the effects of combined GIP and GLP-1 receptor activation on energy intake, appetite and resting energy expenditure in humans. METHODS: We examined 17 overweight/obese men in a crossover design with 5 study days. On day 1, a 50 g OGTT was performed; on the following 4 study days, the men received an isoglycaemic i.v. glucose infusion (IIGI) plus saline (154 mmol/l NaCl; placebo), GIP (4 pmol kg-1 min-1), GLP-1 (1 pmol kg-1 min-1) or GIP+GLP-1 (4 and 1 pmol kg-1 min-1, respectively). All IIGIs were performed in a randomised order blinded for the participant and the investigators. The primary endpoint was energy intake as measured by an ad libitum meal after 240 min. Secondary endpoints included appetite ratings and resting energy expenditure, as well as insulin, C-peptide and glucagon responses. RESULTS: Energy intake was significantly reduced during IIGI+GLP-1 compared with IIGI+saline infusion (2715 ± 409 vs 4483 ± 568 kJ [mean ± SEM, n = 17], p = 0.014), whereas there were no significant differences in energy intake during IIGI+GIP (4062 ± 520 kJ) or IIGI+GIP+GLP-1 (3875 ± 451 kJ) infusion compared with IIGI+saline (p = 0.590 and p = 0.364, respectively). Energy intake was higher during IIGI+GIP+GLP-1 compared with IIGI+GLP-1 infusion (p = 0.039). CONCLUSIONS/INTERPRETATION: While GLP-1 infusion lowered energy intake in overweight/obese men, simultaneous GIP infusion did not potentiate this GLP-1-mediated effect. TRIAL REGISTRATION: ClinicalTrials.gov NCT02598791 FUNDING: This study was supported by grants from the Innovation Fund Denmark and the Vissing Foundation.

Cholinergic signaling mediates the effects of xenin-25 on secretion of pancreatic polypeptide but not insulin or glucagon in humans with impaired glucose tolerance.

We previously demonstrated that infusion of an intestinal peptide called xenin-25 (Xen) amplifies the effects of glucose-dependent insulinotropic polypeptide (GIP) on insulin secretion rates (ISRs) and plasma glucagon levels in humans. However, these effects of Xen, but not GIP, were blunted in humans with type 2 diabetes. Thus, Xen rather than GIP signaling to islets fails early during development of type 2 diabetes. The current crossover study determines if cholinergic signaling relays the effects of Xen on insulin and glucagon release in humans as in mice. Fasted subjects with impaired glucose tolerance were studied. On eight separate occasions, each person underwent a single graded glucose infusion- two each with infusion of albumin, Xen, GIP, and GIP plus Xen. Each infusate was administered ± atropine. Heart rate and plasma glucose, insulin, C-peptide, glucagon, and pancreatic polypeptide (PP) levels were measured. ISRs were calculated from C-peptide levels. All peptides profoundly increased PP responses. From 0 to 40 min, peptide(s) infusions had little effect on plasma glucose concentrations. However, GIP, but not Xen, rapidly and transiently increased ISRs and glucagon levels. Both responses were further amplified when Xen was co-administered with GIP. From 40 to 240 min, glucose levels and ISRs continually increased while glucagon concentrations declined, regardless of infusate. Atropine increased resting heart rate and blocked all PP responses but did not affect ISRs or plasma glucagon levels during any of the peptide infusions. Thus, cholinergic signaling mediates the effects of Xen on insulin and glucagon release in mice but not humans.

A novel GLP-1/xenin hybrid peptide improves glucose homeostasis, circulating lipids and restores GIP sensitivity in high fat fed mice.

Combined modulation of peptide hormone receptors including, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and xenin, have established benefits for the treatment of diabetes. The present study has assessed the biological actions and therapeutic efficacy of a novel exendin-4/xenin-8-Gln hybrid peptide, both alone and in combination with the GIP receptor agonist (DAla2)GIP. Exendin-4/xenin-8-Gln was enzymatically stable and exhibited enhanced insulin secretory actions when compared to its parent peptides. Exendin-4/xenin-8-Gln also possessed ability to potentiate the in vitro actions of GIP. Acute administration of exendin-4/xenin-8-Gln in mice induced appetite suppressive effects, as well as significant and protracted glucose-lowering and insulin secretory actions. Twice daily administration of exendin-4/xenin-8-Gln, alone or in combination with (DAla2)GIP, for 21-days significantly reduced non-fasting glucose and increased circulating insulin levels in high fat fed mice. In addition, all exendin-4/xenin-8-Gln treated mice displayed improved glucose tolerance, insulin sensitivity and metabolic responses to GIP. Combination therapy with (DAla2)GIP did not result in any obvious further benefits. Metabolic improvements in all treatment groups were accompanied by reduced pancreatic beta-cell area and insulin content, suggesting reduced insulin demand. Interestingly, body weight, food intake, circulating glucagon, metabolic rate and amylase activity were unaltered by the treatment regimens. However, all treatment groups, barring (DAla2)GIP alone, exhibited marked reductions in total- and LDL-cholesterol. Furthermore, exendin-4 therapy also reduced circulating triacylglycerol. This study highlights the positive antidiabetic effects of exendin-4/xenin-8-Gln, and suggests that combined modulation of GLP-1 and xenin related signalling pathways represents an exciting treatment option for type 2 diabetes.

Evaluation of the insulinotropic and glucose-lowering actions of zebrafish GIP in mammalian systems: Evidence for involvement of the GLP-1 receptor.

The insulinotropic properties of zebrafish GIP (zfGIP) were assessed in vitro using clonal pancreatic ß-cell lines and isolated mouse islets and acute effects on glucose tolerance and insulin release in vivo were evaluated in mice. The peptide produced a dose-dependent increase in the rate of insulin release from BRIN-BD11 rat clonal ß-cells at concentrations ≥30nM. Insulin release from 1.1 B4 human clonal ß-cells and mouse islets was significantly increased by zfGIP (10nM and 1µM). The in vitro insulinotropic activity of zfGIP was decreased after incubating BRIN-BD11 cells with the GLP-1 receptor antagonist, exendin-4(9-39) (p<0.001) and the GIP receptor antagonist, GIP (6-30) Cex-K40[Pal] (p<0.05) but the glucagon receptor antagonist [des-His1,Pro4,Glu9]glucagon amide was without effect. zfGIP (10nM and 1µM) produced significant increases in cAMP concentration in CHL cells transfected with the human GLP-1 receptor but was without effect on HEK293 cells transfected with the human glucagon receptor. Conversely, zfGIP, but not human GIP, significantly stimulated insulin release from CRISPR/Cas9-engineered INS-1 clonal ß-cells from which the GIP receptor had been deleted. Intraperitoneal administration of zfGIP (25 and 75nmol/kg body weight) to mice together with an intraperitoneal glucose load (18mmol/kg body weight) produced a significant decrease in plasma glucose concentrations concomitant with an increase in insulin concentrations. The study provides evidence that the insulinotropic action of zfGIP in mammalian systems involves activation of both the GLP-1 and the GIP receptors but not the glucagon receptor.

Sodium-glucose cotransporter-2 inhibition improves incretin sensitivity of pancreatic ß-cells in people with type 2 diabetes.

AIM: To test the hypothesis that dapagliflozin, a sodium-glucose cotransporter-2 inhibitor, improves ß-cell responses to incretin hormones (or ß-cell incretin sensitivity) by alleviating glucose toxicity in people with type 2 diabetes mellitus (T2DM). METHODS: A total of 19 people with T2DM underwent a 3-hour hyperglycaemic clamp study with incretin infusion before and after 8-week treatment with dapagliflozin added to the background treatment. In addition, 10 people with normal glucose tolerance (NGT) underwent a single hyperglycaemic clamp study. The hyperglycaemic clamp was targeted at 15.5 mmol/L for 3 hours, with synthetic glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) infusion over a 60- to 180-minute and a 120- to 180-minute period, respectively. RESULTS: Compared with baseline, the C-peptide response to GLP-1 (incremental area under the curve [iAUC] of C-peptide60-120 minutes ) significantly increased (83.6 ± 42.1 to 106.6 ± 45.7 nmol/L × min; P = .011), and the C-peptide response to GIP/GLP-1 (iAUC of C-peptide120-180 minutes ) tended to increase after dapagliflozin treatment (82.5 ± 58.4 to 101.9 ± 50.3 nmol/L × min; P = .087), whereas both the insulin responses to GLP-1 and GIP/GLP-1 increased significantly. First-phase C-peptide response, which reflects ß-cell function, significantly increased after dapagliflozin treatment; however, all these improved values in the participants with T2DM were far lower than those in the participants with NGT. In addition, the improvement in insulin responses to hyperglycaemia was correlated with the improvement in insulin responses to incretin infusion. CONCLUSIONS: Dapagliflozin improved ß-cell responses to incretin hormones as well as glucose during the hyperglycaemic clamp in patients with inadequately controlled T2DM.

Comparative effects of intraduodenal fat and glucose on the gut-incretin axis in healthy males.

BACKGROUND: The interaction of nutrients with the small intestine stimulates the secretion of numerous enteroendocrine hormones that regulate postprandial metabolism. However, differences in gastrointestinal hormonal responses between the macronutrients are incompletely understood. In the present study, we compared blood glucose and plasma hormone concentrations in response to standardised intraduodenal (ID) fat and glucose infusions in healthy humans. METHODS: In a parallel study design, 16 healthy males who received an intraduodenal fat infusion were compared with 12 healthy males who received intraduodenal glucose, both at a rate of 2kcal/min over 120min. Venous blood was sampled at frequent intervals for measurements of blood glucose, and plasma total and active glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), insulin and glucagon. RESULTS: Plasma concentrations of the incretin hormones (both total and active GLP-1 and GIP) and glucagon were higher, and plasma insulin and blood glucose concentrations lower, during intraduodenal fat, when compared with intraduodenal glucose, infusion (treatment by time interaction: P<0.001 for each). CONCLUSIONS: Compared with glucose, intraduodenal fat elicits substantially greater GLP-1, GIP and glucagon secretion, with minimal effects on blood glucose or plasma insulin in healthy humans. These observations are consistent with the concept that fat is a more potent stimulus of the 'gut-incretin' axis than carbohydrate.