Tirzepatide as Monotherapy Improved Markers of Beta-cell Function and Insulin Sensitivity in Type 2 Diabetes (SURPASS-1)

Mechanisms of action and therapeutic applications of GLP-1 and dual GIP/GLP-1 receptor agonists

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are two incretins that bind to their respective receptors and activate the downstream signaling in various tissues and organs. Both GIP and GLP-1 play roles in regulating food intake by stimulating neurons in the brain's satiety center. They also stimulate insulin secretion in pancreatic β-cells, but their effects on glucagon production in pancreatic α-cells differ, with GIP having a glucagonotropic effect during hypoglycemia and GLP-1 exhibiting glucagonostatic effect during hyperglycemia. Additionally, GIP directly stimulates lipogenesis, while GLP-1 indirectly promotes lipolysis, collectively maintaining healthy adipocytes, reducing ectopic fat distribution, and increasing the production and secretion of adiponectin from adipocytes. Together, these two incretins contribute to metabolic homeostasis, preventing both hyperglycemia and hypoglycemia, mitigating dyslipidemia, and reducing the risk of cardiovascular diseases in individuals with type 2 diabetes and obesity. Several GLP-1 and dual GIP/GLP-1 receptor agonists have been developed to harness these pharmacological effects in the treatment of type 2 diabetes, with some demonstrating robust effectiveness in weight management and prevention of cardiovascular diseases. Elucidating the underlying cellular and molecular mechanisms could potentially usher in the development of new generations of incretin mimetics with enhanced efficacy and fewer adverse effects. The treatment guidelines are evolving based on clinical trial outcomes, shaping the management of metabolic and cardiovascular diseases.

Tirzepatide Improved Markers of Islet Cell Function and Insulin Sensitivity in People With T2D (SURPASS-2)

CONTEXT

In previous SURPASS studies tirzepatide reduced hemoglobin glycated A1c (HbA1c) and body weight and improved markers of insulin sensitivity and β-cell function to a greater extent than comparators.

OBJECTIVE

Explore changes in biomarkers of β-cell function and insulin sensitivity and in efficacy profiles in baseline biomarker quartile analyses with tirzepatide compared to semaglutide.

DESIGN

Post hoc analysis of SURPASS-2 phase 3 trial (participants randomly assigned to receive weekly subcutaneous tirzepatide or semaglutide for 40 weeks).

SETTING

Post hoc analysis of 128 sites in 8 countries.

PARTICIPANTS

A total of 1879 participants with type 2 diabetes.

INTERVENTIONS

Once-weekly tirzepatide (5, 10, 15 mg) or semaglutide 1 mg.

MAIN OUTCOMES MEASURES

Change in homeostatic model assessment indices for pancreatic β-cell function (HOMA2-B) and for insulin resistance (HOMA2-IR), fasting glucagon, fasting C-peptide, and fasting insulin.

RESULTS

At week 40, a greater increase in HOMA2-B was seen with tirzepatide (5, 10, 15 mg) doses (96.9-120.4%) than with semaglutide 1 mg (84.0%) (P < .05). There was a greater reduction in HOMA2-IR with all doses of tirzepatide (15.5%-24.0%) than with semaglutide 1 mg (5.1%) (P < .05). Tirzepatide 10 and 15 mg resulted in a significant reduction in both fasting C-peptide (5.2%-6.0%) and fasting glucagon (53.0%-55.3%) compared with an increase of C-peptide (3.3%) and a reduction of glucagon (47.7%) with semaglutide 1 mg (P < .05). HbA1c and body weight reductions were greater with all tirzepatide doses than semaglutide within each HOMA2-B and HOMA2-IR baseline quartile.

CONCLUSION

In this post hoc analysis, improvements in HbA1c and weight loss were consistent and significantly higher with tirzepatide, regardless of baseline β-cell function and insulin resistance, compared with semaglutide.

Renal effects of GLP-1 receptor agonists and tirzepatide in individuals with type 2 diabetes: seeds of a promising future

PURPOSE

Chronic kidney disease (CKD) is one of the most common complications of type 2 diabetes (T2D), and CKD-related disability and mortality are increasing despite the recent advances in diabetes management. The dual GIP/GLP-1 receptor agonist tirzepatide is among the furthest developed multi-agonists for diabetes care and has so far displayed promising nephroprotective effects. This review aims to summarize the evidence regarding the nephroprotective effects of glucagon-like peptide-1 receptor agonists (GLP-1RA) and tirzepatide and the putative mechanisms underlying the favorable renal profile of tirzepatide.

METHODS

A comprehensive literature search was performed from inception to July 31st 2023 to select research papers addressing the renal effects of GLP-1RA and tirzepatide.

RESULTS

The pathogenesis of CKD in patients with T2D likely involves many contributors besides hyperglycemia, such as hypertension, obesity, insulin resistance and glomerular atherosclerosis, exerting kidney damage through metabolic, fibrotic, inflammatory, and hemodynamic mechanisms. Tirzepatide displayed an unprecedented glucose and body weight lowering potential, presenting also with the ability to increase insulin sensitivity, reduce systolic blood pressure and inflammation and ameliorate dyslipidemia, particularly by reducing triglycerides levels.

CONCLUSION

Tirzepatide is likely to counteract most of the pathogenetic factors contributing to CKD in T2D, potentially representing a step forward in incretin-based therapy towards nephroprotection. Further evidence is needed to understand its role in renal hemodynamics, fibrosis, cell damage and atherosclerosis, as well as to conclusively show reduction of hard renal outcomes.

Early-Onset Type 2 Diabetes and Tirzepatide Treatment: A Post Hoc Analysis From the SURPASS Clinical Trial Program

OBJECTIVE

We evaluated baseline characteristics of participants with early-onset type 2 diabetes (T2D) from the SURPASS program and tirzepatide's effects on glycemic control, body weight (BW), and cardiometabolic markers.

RESEARCH DESIGN AND METHODS

This post hoc analysis compared baseline characteristics and changes in mean HbA1c, BW, waist circumference (WC), lipids, and blood pressure (BP) in 3,792 participants with early-onset versus later-onset T2D at week 40 (A Study of Tirzepatide [LY3298176] in Participants With Type 2 Diabetes Not Controlled With Diet and Exercise Alone [SURPASS-1] and A Study of Tirzepatide [LY3298176] Versus Semaglutide Once Weekly as Add-on Therapy to Metformin in Participants With Type 2 Diabetes [SURPASS-2]) or week 52 (A Study of Tirzepatide [LY3298176] Versus Insulin Degludec in Participants With Type 2 Diabetes [SURPASS-3]). Analyses were performed by study on data from participants while on assigned treatment without rescue medication in case of persistent hyperglycemia.

RESULTS

At baseline in SURPASS-2, participants with early-onset versus later-onset T2D were younger with longer diabetes duration (9 vs. 7 years, P < 0.001) higher glycemic levels (8.5% vs. 8.2%, P < 0.001), higher BW (97 vs. 93 kg, P < 0.001) and BMI (35 vs. 34 kg/m2, P < 0.001), and a similarly abnormal lipid profile (e.g., triglycerides 167 vs. 156 mg/dL). At week 40, similar improvements in HbA1c (-2.6% vs. -2.4%), BW (-14 vs. -13 kg), WC (-10 vs. -10 cm), triglycerides (-26% vs. -24%), HDL (7% vs. 7%), and systolic BP (-6 vs. -7 mmHg) were observed in both subgroups with tirzepatide.

CONCLUSIONS

Despite younger age, participants with early-onset T2D from the SURPASS program had higher glycemic levels and worse overall metabolic health at baseline versus those with later-onset T2D. In this post hoc analysis, similar improvements in HbA1c, BW, and cardiometabolic markers were observed with tirzepatide, irrespective of age at T2D diagnosis. Future studies are needed to determine long-term outcomes of tirzepatide in early-onset T2D.

Overnutrition, Hyperinsulinemia and Ectopic Fat: It Is Time for A Paradigm Shift in the Management of Type 2 Diabetes

The worldwide incidence of prediabetes/type 2 has continued to rise the last 40 years. In the same period, the mean daily energy intake has increased, and the quality of food has significantly changed. The chronic exposure of pancreatic β-cells to calorie excess (excessive energy intake) and food additives may increase pancreatic insulin secretion, decrease insulin pulses and/or reduce hepatic insulin clearance, thereby causing chronic hyperinsulinemia and peripheral insulin resistance. Chronic calorie excess and hyperinsulinemia may promote lipogenesis, inhibit lipolysis and increase lipid storage in adipocytes. In addition, calorie excess and hyperinsulinemia can induce insulin resistance and contribute to progressive and excessive ectopic fat accumulation in the liver and pancreas by the conversion of excess calories into fat. The personal fat threshold hypothesis proposes that in susceptible individuals, excessive ectopic fat accumulation may eventually lead to hepatic insulin receptor resistance, the loss of pancreatic insulin secretion, hyperglycemia and the development of frank type 2 diabetes. Thus, type 2 diabetes seems (partly) to be caused by hyperinsulinemia-induced excess ectopic fat accumulation in the liver and pancreas. Increasing evidence further shows that interventions (hypocaloric diet and/or bariatric surgery), which remove ectopic fat in the liver and pancreas by introducing a negative energy balance, can normalize insulin secretion and glucose tolerance and induce the sustained biochemical remission of type 2 diabetes. This pathophysiological insight may have major implications and may cause a paradigm shift in the management of type 2 diabetes: avoiding/reducing ectopic fat accumulation in the liver and pancreas may both be essential to prevent and cure type 2 diabetes.

Diabetic Cardiomyopathy-From Basics through Diagnosis to Treatment

Diabetic cardiomyopathy (DCM) is the development of myocardial dysfunction in patients with diabetes despite the absence of comorbidities such as hypertension, atherosclerosis or valvular defect. The cardiovascular complications of poorly controlled diabetes are very well illustrated by the U.K. Prospective Diabetes Study (UKPDS), which showed a clear association between increasing levels of glycated hemoglobin and the development of heart failure (HF). The incidence of HF in patients with diabetes is projected to increase significantly, which is why its proper diagnosis and treatment is so important. Providing appropriate therapy focusing on antidiabetic and hypolipemic treatment with the consideration of pharmacotherapy for heart failure reduces the risk of CMD and reduces the incidence of cardiovascular complications. Health-promoting changes made by patients such as a low-carbohydrate diet, regular exercise and weight reduction also appear to be important in achieving appropriate outcomes. New hope for the development of therapies for DCM is offered by novel methods using stem cells and miRNA, which, however, require more thorough research to confirm their efficacy.

Reduction of prevalence of patients meeting the criteria for metabolic syndrome with tirzepatide: a post hoc analysis from the SURPASS Clinical Trial Program

BACKGROUND

Metabolic syndrome is characterized as the co-occurrence of interrelated cardiovascular risk factors, including insulin resistance, hyperinsulinemia, abdominal obesity, dyslipidemia and hypertension. Once weekly tirzepatide is approved in the US and EU for the treatment of type 2 diabetes (T2D) and obesity. In the SURPASS clinical trial program for T2D, tirzepatide demonstrated greater improvements in glycemic control, body weight reduction and other cardiometabolic risk factors versus placebo, subcutaneous semaglutide 1 mg, insulin degludec, and insulin glargine. This post hoc analysis assessed the effect of tirzepatide use on the prevalence of patients meeting the criteria for metabolic syndrome across SURPASS 1-5.

METHODS

Metabolic syndrome was defined as having ≥ 3 of 5 criteria according to the US National Cholesterol Education Program: Adult Treatment Panel III. Analyses were based on on-treatment data at the primary endpoint from patients adherent to treatment (taking ≥ 75% study drug). A logistic regression model with metabolic syndrome status as the response variable, metabolic syndrome status at the baseline visit as an adjustment, and randomized treatment as fixed explanatory effect was used. The effect of tirzepatide use on the prevalence of patients meeting the criteria for metabolic syndrome by categorical weight loss, background medication and gender were assessed.

RESULTS

In SURPASS, the prevalence of patients meeting the criteria for metabolic syndrome at baseline was 67-88% across treatment groups with reductions at the primary endpoint to 38-64% with tirzepatide versus 64-82% with comparators. Reductions in the prevalence of patients meeting the criteria for metabolic syndrome was significantly greater with all tirzepatide doses versus placebo, semaglutide 1 mg, insulin glargine, and insulin degludec (p < 0.001). Individual components of metabolic syndrome were also reduced to a greater extent with tirzepatide vs comparators. Greater reductions in body weight were associated with greater reductions in the prevalence of patients meeting the criteria for metabolic syndrome and its individual components. Background SGLT2i or sulfonylurea use or gender did not impact the change in prevalence of patients meeting the criteria for metabolic syndrome.

CONCLUSIONS

In this post hoc analysis, tirzepatide at all doses studied was associated with a greater reduction in the prevalence of patients meeting the criteria for metabolic syndrome compared to placebo, semaglutide 1 mg, insulin degludec, and insulin glargine. Although more evidence is needed, these data would support greater potential improvement in cardiovascular risk factor profile with tirzepatide treatment in people across the continuum of T2D.

Tirzepatide: A Review in Type 2 Diabetes

Tirzepatide (Mounjaro®), a first-in-class dual incretin agonist of the glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors, is approved for use as an adjunct to diet and exercise to improve glycaemic control in adults with type 2 diabetes mellitus (T2DM) in the USA, EU, Japan and other countries. It comes as single-dose prefilled pens and single-dose vials. In phase III SURPASS trials, once-weekly subcutaneous tirzepatide, as monotherapy or add-on-therapy to oral glucose-lowering medications and insulin, was superior to the GLP-1 receptor agonists (RAs) dulaglutide 0.75 mg and semaglutide 1 mg as well as basal and prandial insulin for glycaemic control and weight loss in adults with inadequately controlled T2DM. Tirzepatide was generally well tolerated, with a safety profile consistent with that of GLP-1 RAs. Tirzepatide was associated with a low risk of clinically significant or severe hypoglycaemia and no increased risk of major adverse cardiovascular events. Adverse events were mostly mild to moderate in severity, with the most common being gastrointestinal events including nausea, diarrhoea, decreased appetite and vomiting. In conclusion, tirzepatide is a valuable addition to the treatment options for T2DM.

Achieving Normoglycemia With Tirzepatide: Analysis of SURPASS 1-4 Trials

OBJECTIVE

Tirzepatide is a novel single-molecule glucose-dependent insulinotropic polypeptide/glucagon-like peptide 1 receptor agonist, which demonstrated unprecedented improvements in glycemic control and body weight reduction, in the SURPASS phase 3 program. In this exploratory analysis, we aimed to characterize tirzepatide-treated participants who achieved HbA1c <5.7% and evaluate changes in clinical markers associated with long-term cardiometabolic health.

RESEARCH DESIGN AND METHODS

Baseline characteristics and change from baseline to week 40 for several efficacy and safety parameters were analyzed according to HbA1c attainment category (<5.7%, 5.7-6.5%, and >6.5%) using descriptive statistics in participants taking ≥75% of treatment doses, without rescue medication, in the SURPASS 1-4 trials (N = 3,229). Logistic regression models with tirzepatide doses adjusted as a covariate were used to obtain odds ratios and assess the impact of patient characteristics achieving an HbA1c <5.7%.

RESULTS

Tirzepatide-treated participants who achieved HbA1c <5.7% were slightly younger, with a shorter duration of diabetes and lower HbA1c value at baseline compared with those who did not achieve HbA1c <5.7%. In addition, they showed greater improvements in HbA1c, body weight, waist circumference, blood pressure, liver enzymes, and lipid parameters without increasing hypoglycemia risk.

CONCLUSIONS

Normoglycemia was unprecedently achieved in a significant proportion of participants in the SURPASS clinical program, without increasing hypoglycemia risk, and was associated with an overall improvement in metabolic health.

Novel Dual Incretin Receptor Agonists in the Spectrum of Metabolic Diseases with a Focus on Tirzepatide: Real Game-Changers or Great Expectations? A Narrative Review

The prevalence of metabolic diseases including type 2 diabetes (T2D), obesity and non-alcoholic fatty liver disease (NAFLD) increases globally. This highlights an unmet need for identifying optimal therapies for the management of these conditions. Tirzepatide is a novel dual incretin receptor agonist (twincretin) that activates both glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptors. The aim of this narrative review was to examine the impact of novel twincretins, focusing on tirzepatide, on the management of a wide spectrum of metabolic diseases. Data from preclinical and clinical trials have shown that twincretins significantly reduce blood glucose levels in T2D, and tirzepatide is the first agent of this class that has been approved for the management of T2D. Additionally, the beneficial impact of tirzepatide on weight reduction has been corroborated in several studies, showing that this agent can achieve substantial and sustained weight loss in obese patients with or without T2D. Data also suggest that tirzepatide could be a promising drug for hepatic steatosis reduction in individuals with NAFLD. The remarkable effects of tirzepatide on glycaemic control, weight loss and liver-related outcomes have posed new research questions that are likely to lead to further advancements in the treatment of T2D, obesity and related metabolic disorders.