New insights into the treatment of obesity

Obesity is a chronic, progressive and relapsing disease with a rising global prevalence associated with increased morbidity and mortality and reduced quality of life. Treatment of obesity requires a comprehensive medical approach that includes behavioural interventions, pharmacotherapy and bariatric surgery. The degree of weight loss with all approaches is highly heterogeneous, and long-term weight maintenance remains challenging. For years, antiobesity medications have been limited in number, often delivering meagre efficacy and raising numerous safety concerns. Therefore, there is a need for the development of highly efficacious and safe new agents. Recent insights into the complex pathophysiology of obesity have increased our understanding of intervenable targets for pharmacotherapies to treat obesity and improve weight-related cardiometabolic complications, namely, type 2 diabetes, hyperlipidaemia and hypertension. As a result, novel potent therapies have emerged, such as semaglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA) recently approved for the treatment of obesity. Semaglutide 2.4 mg once weekly significantly reduces body weight by approximately 15%, with simultaneous improvement in cardiometabolic risk factors and physical functioning in people with obesity. Tirzepatide, the first dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1RA, has recently demonstrated that body weight reduction exceeding 20% in people with obesity and coupled with improved cardiometabolic measures is feasible. Thus, these novel agents promise to narrow the gap between the weight-loss effects of behaviour interventions, previous pharmacotherapies, and bariatric surgery. In this narrative review, we highlight established and emerging therapeutic treatments for long-term obesity management and position them in a framework according to their weight loss effects.     

Efficacy and safety of liraglutide 3.0 mg for weight management are similar across races: subgroup analysis across the SCALE and phase II randomized trials

The efficacy and safety of liraglutide 3.0 mg versus placebo, as adjunct to diet and exercise, was evaluated in racial subgroups. This post hoc analysis of pooled data from five double‐blind randomized, placebo‐controlled trials was conducted in 5325 adults with either a body mass index (BMI) ≥27 kg/m² plus ≥1 comorbidity or a BMI ≥30 kg/m². Statistical interaction tests evaluated possible treatment effect differences between racial subgroups: white (4496, 84.4%), black/African‐American (550, 10.3%), Asian (168, 3.2%) and other (111, 2.1%). Effects of liraglutide 3.0 mg on weight loss, associated metabolic effects and safety profile were generally consistent across racial subgroups. All achieved statistically significant mean weight loss at end‐of‐treatment with liraglutide 3.0 mg versus placebo: white 7.7% versus 2.3%, black/African‐American 6.3% versus 1.4%, Asian 6.3% versus 2.5%, other 7.3% versus 0.49%. Treatment effects on weight and cardiovascular risk markers generally showed no dependence on race (interaction test p > 0.05). Adverse events were similar across racial subgroups.     

The evolving story of incretins (GIP and GLP-1) in metabolic and cardiovascular disease: A pathophysiological update

The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) have their main physiological role in augmenting insulin secretion after their nutrient-induced secretion from the gut. A functioning entero-insular (gut-endocrine pancreas) axis is essential for the maintenance of a normal glucose tolerance. This is exemplified by the incretin effect (greater insulin secretory response to oral as compared to “isoglycaemic” intravenous glucose administration due to the secretion and action of incretin hormones). GIP and GLP-1 have additive effects on insulin secretion. Local production of GIP and/or GLP-1 in islet α-cells (instead of enteroendocrine K and L cells) has been observed, and its significance is still unclear. GLP-1 suppresses, and GIP increases glucagon secretion, both in a glucose-dependent manner. GIP plays a greater physiological role as an incretin. In type 2-diabetic patients, the incretin effect is reduced despite more or less normal secretion of GIP and GLP-1. While insulinotropic effects of GLP-1 are only slightly impaired in type 2 diabetes, GIP has lost much of its acute insulinotropic activity in type 2 diabetes, for largely unknown reasons. Besides their role in glucose homoeostasis, the incretin hormones GIP and GLP-1 have additional biological functions: GLP-1 at pharmacological concentrations reduces appetite, food intake, and—in the long run—body weight, and a similar role is evolving for GIP, at least in animal studies. Human studies, however, do not confirm these findings. GIP, but not GLP-1 increases triglyceride storage in white adipose tissue not only through stimulating insulin secretion, but also by interacting with regional blood vessels and GIP receptors. GIP, and to a lesser degree GLP-1, play a role in bone remodelling. GLP-1, but not GIP slows gastric emptying, which reduces post-meal glycaemic increments. For both GIP and GLP-1, beneficial effects on cardiovascular complications and neurodegenerative central nervous system (CNS) disorders have been observed, pointing to therapeutic potential over and above improving diabetes complications. The recent finding that GIP/GLP-1 receptor co-agonists like tirzepatide have superior efficacy compared to selective GLP-1 receptor agonists with respect to glycaemic control as well as body weight has renewed interest in GIP, which previously was thought to be without any therapeutic potential. One focus of this research is into the long-term interaction of GIP and GLP-1 receptor signalling. A GLP-1 receptor antagonist (exendin [9-39]) and, more recently, a GIP receptor agonist (GIP [3-30] NH₂) and, hopefully, longer-acting GIP receptor agonists for human use will be helpful tools to shed light on the open questions. A detailed knowledge of incretin physiology and pathophysiology will be a prerequisite for designing more effective incretin-based diabetes drugs.     

Routine clinical use of liraglutide 3 mg for the treatment of obesity: Outcomes in non-surgical and bariatric surgery patients

In this study we prospectively collected data on the use of liraglutide 3 mg in obese Arab patients. As part of routine care, 2092 patients were dispensed liraglutide 3 mg. Median age was 38 years and 77% were women. Median baseline weight was 95 kg and body mass index was 36.6 kg/m². Of the patients, 188 (9%) had previous bariatric surgery. Seven hundred and eighty-seven patients were treated for ≥16 weeks and their median (interquartile range) weight loss was 6.0 (2.4-9.4) kg, equivalent to 6.4% (2.6%-9.7%) of baseline weight (P < 0.0001, n = 787). Of those treated for ≥16 weeks, 474 (60%) achieved a weight loss of >5% of baseline weight while 182 (23%) achieved >10% weight loss. There was no difference in percentage weight loss between postbariatric surgery (n = 76) and non-surgical patients (n = 711). As a result of adverse events, mainly gastrointestinal symptoms, 140 (6.7%) of the patients stopped treatment. One patient developed acute pancreatitis in the context of gallstone disease but made an uneventful recovery. Liraglutide 3 mg was well tolerated and resulted in weight loss in routine clinical care similar to that seen in randomized controlled trials.     

Liraglutide changes postprandial responses of gut hormones involved in the regulation of gallbladder motility

Aim

Liraglutide treatment is associated with gallbladder-related disorders and has been shown to delay postprandial gallbladder refilling. The gut hormones cholecystokinin (CCK), fibroblast growth factor 19 (FGF19) and glucagon-like peptide 2 (GLP-2), are known to regulate gallbladder motility and may be implicated in gallbladder-related disorders associated with liraglutide treatment.

Materials and Methods

In a double-blind, 12-week trial, 52 participants [50% male, age 47.6 ± 10.0 years, body mass index 32.6 ± 3.4 kg/m² (mean ± standard deviation)] with obesity were randomized 1:1 to once-daily subcutaneous liraglutide (escalated from 0.6 mg to 3.0 mg once-daily) or placebo. During liquid meal tests performed at baseline, after the first dose and following 12 weeks of treatment, we evaluated postprandial gallbladder dynamics and plasma responses of CCK, FGF19 and GLP-2.

Results

Liraglutide reduced postprandial FGF19 after the first dose [area under the curve (AUC)_{0-240 min} 24.8 vs. 48.0 min × ng/ml, treatment ratio (TR) (95% confidence interval) 0.52 (0.39; 0.69)] and following 12 weeks of treatment [AUC_{0-240 min} 33.7 vs. 48.5 ng/ml × min, TR 0.69 (0.52; 0.93)]. Liraglutide also reduced postprandial GLP-2 responses (AUC_{0-240 min} 3650 vs. 4894 min × pmol/L, TR 0.75 (0.62; 0.90)] following the first dose as well as after 12 weeks [AUC_{0-240 min} 3760 vs. 4882 min × pmol/L, TR 0.77 (0.60; 0.99)]. Liraglutide increased postprandial responses of CCK after the first dose [AUC_{0-240 min} 762 vs. 670 min × pmol/L; TR 1.14 (0.97; 1.33)] and following 12 weeks of treatment [AUC_{0-240 min} 873 vs. 628 min × pmol/L; TR 1.39 (1.12; 1.73)].

Conclusion

Compared with placebo, treatment with liraglutide decreased postprandial FGF19 and GLP-2 concentrations and increased postprandial CCK concentrations, which may explain the delayed postprandial gallbladder refilling observed in individuals with obesity treated with liraglutide.     

Semaglutide for the treatment of overweight and obesity: A review

Obesity is a chronic, relapsing disease associated with multiple complications and a substantial morbidity, mortality and health care burden. Pharmacological treatments for obesity provide a valuable adjunct to lifestyle intervention, which often achieves only limited weight loss that is difficult to maintain. The Semaglutide Treatment Effect in People with obesity (STEP) clinical trial programme is evaluating once-weekly subcutaneous semaglutide 2.4 mg (a glucagon-like peptide-1 analogue) in people with overweight or obesity. Across STEP 1, 3, 4 and 8, semaglutide 2.4 mg was associated with mean weight losses of 14.9%-17.4% in individuals with overweight or obesity without type 2 diabetes from baseline to week 68; 69%-79% of participants achieved ≥10% weight loss with semaglutide 2.4 mg (vs. 12%-27% with placebo) and 51%-64% achieved ≥15% weight loss (vs. 5%-13% with placebo). In STEP 5, mean weight loss was −15.2% with semaglutide 2.4 mg versus −2.6% with placebo from baseline to week 104. In STEP 2 (individuals with overweight or obesity, and type 2 diabetes), mean weight loss was −9.6% with semaglutide 2.4 mg versus −3.4% with placebo from baseline to week 68. Improvements in cardiometabolic risk factors, including high blood pressure, atherogenic lipids and benefits on physical function and quality of life were seen with semaglutide 2.4 mg. The safety profile of semaglutide 2.4 mg was consistent across trials, primarily gastrointestinal adverse events. The magnitude of weight loss reported in the STEP trials offers the potential for clinically relevant improvement for individuals with obesity-related diseases.     

Applying REWIND cardiovascular disease criteria to SUSTAIN 6 and PIONEER 6: An exploratory analysis of cardiovascular outcomes with semaglutide

In the REWIND trial, dulaglutide reduced cardiovascular (CV) risk versus placebo in patients with type 2 diabetes in both the “established CV disease” (CVD) and “CV risk factor” subgroups. The SUSTAIN 6 and PIONEER 6 trials of semaglutide used different criteria for established CVD from those used in REWIND. The present post hoc analysis assessed the effect of semaglutide on major adverse CV events (MACE) in a pooled population of SUSTAIN 6 and PIONEER 6 patients, re-categorized into CV risk subgroups using the REWIND CVD criteria. In the pooled analysis (n = 6480), a lower percentage of patients were in the established CVD subgroup, when using the REWIND CVD criteria, compared with the original trial CVD criteria (66.5% vs. 83.8%, respectively). After re-categorization, the risk of MACE was significantly lower with semaglutide versus placebo in the established CVD subgroup (hazard ratio [HR] 0.74, 95% confidence interval [CI] 0.59, 0.92) and nonsignificantly lower in the CV risk factor subgroup (HR 0.84, 95% CI 0.55, 1.28) (P-interaction = 0.60). These results suggest that the CV effects of semaglutide may extend to patients with type 2 diabetes across the CV risk continuum.     

Semaglutide single-dose pen-injector: Post hoc analysis of summative usability testing for weight management

Subcutaneous semaglutide, at a 2.4 mg once-weekly maintenance dose, is approved in the United States for weight management in individuals with a body mass index (BMI) of 30 kg/m² or higher, or with a BMI of 27 kg/m² or higher and at least one obesity-related co-morbidity. To investigate the usability of the semaglutide pen-injector in individuals who met these criteria, we report post hoc analysis of the summative (human factors validation) usability testing and safety analysis involving patients with type 2 diabetes (an obesity-related co-morbidity) with the same pen-injector, limited to the 26 out of 30 patients with a BMI of 27 kg/m² or higher (11 pen-injector–naïve, 15 pen-injector–experienced) and 15 non-pharmacist healthcare professionals (HCPs). Participants performed two simulated injections into an injection pad. No potentially serious use errors occurred. Mean subjective ease-of-use rating on a seven-point scale, where 1 = difficult and 7 = easy, was 6.9 for the second injection in all three groups. These results suggest that the semaglutide pen-injector is easy to use and not associated with serious use errors when used by pen-injector–naïve or pen-injector–experienced patients meeting the requirement for weight management with semaglutide treatment, and by non-pharmacist HCPs.     

Tripeptide gut hormone infusion does not alter food preferences or sweet taste function in volunteers with obesity and prediabetes/diabetes but promotes restraint eating: A secondary analysis of a randomized single-blind placebo-controlled study

Aims

To investigate whether the elevation in postprandial concentrations of the gut hormones glucagon-like peptide-1 (GLP-1), oxyntomodulin (OXM) and peptide YY (PYY) accounts for the beneficial changes in food preferences, sweet taste function and eating behaviour after Roux-en-Y gastric bypass (RYGB).

Materials and methods

This was a secondary analysis of a randomized single-blind study in which we infused GLP-1, OXM, PYY (GOP) or 0.9% saline subcutaneously for 4 weeks in 24 subjects with obesity and prediabetes/diabetes, to replicate their peak postprandial concentrations, as measured at 1 month in a matched RYGB cohort ( ClinicalTrials.gov NCT01945840). A 4-day food diary and validated eating behaviour questionnaires were completed. Sweet taste detection was measured using the method of constant stimuli. Correct sucrose identification (corrected hit rates) was recorded, and sweet taste detection thresholds (EC50s: half maximum effective concencration values) were derived from concentration curves. The intensity and consummatory reward value of sweet taste were assessed using the generalized Labelled Magnitude Scale.

Results

Mean daily energy intake was reduced by 27% with GOP but no significant changes in food preferences were observed, whereas a reduction in fat and increase in protein intake were seen post-RYGB. There was no change in corrected hit rates or detection thresholds for sucrose detection following GOP infusion. Additionally, GOP did not alter the intensity or consummatory reward value of sweet taste. A significant reduction in restraint eating, comparable to the RYGB group was observed with GOP.

Conclusion

The elevation in plasma GOP concentrations after RYGB is unlikely to mediate changes in food preferences and sweet taste function after surgery but may promote restraint eating.