Tirzepatide (Zepbound) for chronic weight management

The injectable glucose-dependent insulinotropic polypeptide (GIP)/glucagon-like peptide-1 (GLP-1) receptor agonist tirzepatide, which was approved by the FDA as Mounjaro for treatment of type 2 diabetes in 2022, has now been approved as Zepbound (Lilly) for chronic weight management in adults who have a BMI ≥30 kg/m2 or a BMI ≥27 kg/m2 and at least one weight-related comorbidity.

In brief: GI effects of GLP-1 receptor agonists

Glucagon-like peptide-1 (GLP-1) receptor agonists and the dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonist tirzepatide (Mounjaro) are widely prescribed for treatment of type 2 diabetes and weight management (see Table 1), but they delay gastric emptying and commonly cause nausea and vomiting. Gastroparesis and bowel obstruction (ileus) have also been reported with their use.

Molecular Connectomics Reveals a Glucagon-Like Peptide 1 Sensitive Neural Circuit for Satiety

Liraglutide and other agonists of the glucagon-like peptide 1 receptor (GLP-1RAs) are effective weight loss drugs, but how they suppress appetite remains unclear. GLP-1RAs inhibit hunger-promoting Agouti-related peptide (AgRP) neurons of the arcuate hypothalamus (Arc) but only indirectly, implicating synaptic afferents to AgRP neurons. To investigate, we developed a method combining rabies-based connectomics with single-nuclei transcriptomics. Applying this method to AgRP neurons in mice predicts 21 afferent subtypes in the mediobasal and paraventricular hypothalamus. Among these are Trh+ Arc neurons (TrhArc), which express the Glp1r gene and are activated by the GLP-1RA liraglutide. Activating TrhArc neurons inhibits AgRP neurons and decreases feeding in an AgRP neuron-dependent manner. Silencing TrhArc neurons increases feeding and body weight and reduces liraglutide's satiating effects. Our results thus demonstrate a widely applicable method for molecular connectomics, reveal the molecular organization of AgRP neuron afferents, and shed light on a neurocircuit through which GLP-1RAs suppress appetite.

Effect of Liraglutide on Fat Mass Percentage Among Overweight and Obese Adults with Type 2 Diabetes: A Systematic Review

Background

Obesity and type 2 diabetes mellitus (T2DM) are two global public health problems. Liraglutide, a glucagon-like peptide 1 analogue (GLP-1), is considered an effective option for weight loss. Hence, it is meaningful to understand the impact of GLP-1 therapy on body composition, particularly fat mass percentage (%), in determining health risks associated with obesity. The current meta-analysis and systematic review aimed to appraise and summarize available studies regarding the efficacy of liraglutide on fat mass (%), anthropometrics and glycemic control.

Methods

Three databases were searched up to March 2022 for randomized clinical trials (RCTs) and studies that evaluated the efficacy of liraglutide on T2DM patients: Cochrane Central Register of Controlled Trials, Web of Science, and PUBMED: Cochrane Central Register of Controlled Trials, Web of Science, and PUBMED. If at least two studies had the same outcome and treatment, a random effect model meta-analysis was used to report pooled mean difference (MD) and 95% confidence interval (CI). The protocol of this review was registered in PROSPERO under registration number CRD42022313002.

Results

From the 4031 articles identified and reviewed, only 5 studies (N = 263 patients) matched the inclusion criteria. Only two out of 3 RCTs have complete data to produce forest plots. No significant changes were observed from the pooled MD for body fat % [-0.56 (-2.63, 1.26)] and weight [-0.68 (-2.63, 1.26)]. A significant change in Hba1c with a pooled MD of -1.25 (-2.13, -0.36) (p = 0.006) was observed. I2 tests were above the threshold of 50% for weight and Hba1c, indicating heterogeneity among the included studies.

Conclusion

This review suggests that liraglutide is effective in glycemic control with no significant effect on weight and fat mass % among overweight patients with T2DM. It is important to note, however, that the certainty of the available evidence is weak.

Can we win the war on obesity with pharmacotherapy?

INTRODUCTION

Obesity is a major health concern for several countries. The United States (U.S.) has arguably led the world in the percentage of overweight and/or obese per capita for several decades. As a result, numerous FDA-approved pharmacotherapeutic options are available for the long-term treatment of obesity. Although most of these medications have been on the U.S. market for a few years and have demonstrated efficacy for long-term weight loss in clinical trials, the impact of these medications on obesity in the U.S. has yet to be realized. Areas covered: We will review and evaluate why pharmacotherapy for obesity has not produced a meaningful reduction in the number of overweight and obese adults in the U.S. Expert commentary: Several obstacles, such as adverse drug effects, poor insurance coverage, not treating obesity as a chronic disease, and availability of other weight loss alternatives, has resulted in poor performance of pharmacotherapy for obesity in the U.S. market.

Liraglutide: A New Option for the Treatment of Obesity

Obesity continues to pose a major public health risk to the United States and across the world, with an estimated one-third of adult Americans being defined as obese. Obesity treatment guidelines recommend the use of pharmacologic therapy in adults who have a body mass index (BMI) of 30 kg/m(2) or higher or in patients with a BMI of 27 kg/m(2) or higher who have at least one weight-related comorbid condition (e.g., hypertension, dyslipidemia, insulin resistance, type 2 diabetes mellitus). Liraglutide is a glucagon-like peptide-1 receptor agonist that has been successfully used in the treatment of type 2 diabetes for several years. Weight loss has been well described as an additional benefit with liraglutide therapy, which prompted the manufacturer to evaluate and develop a higher dose formulation specifically for the treatment of obesity. Liraglutide 3 mg/day was approved by the U.S. Food and Drug Administration for this indication in December 2014. We performed a search of the Medline database to identify relevant literature focused on liraglutide's role specifically in treating obesity. Five clinical trials with this primary end point were identified. Data demonstrated that liraglutide can successfully achieve weight-loss benchmarks of 5% or more and 10% or more loss from baseline. The most common adverse effects were gastrointestinal and mild to moderate in intensity. The cost of therapy is high, averaging over $1000/month for out-of-pocket expenses if insurance coverage is not available. Liraglutide is also available for delivery only by subcutaneous injection, which may represent a barrier for patients. Liraglutide 3 mg/day represents another pharmacologic option for the treatment of obesity.

GLP-1 and weight loss: unraveling the diverse neural circuitry

Glucagon-like peptide-1 (GLP-1) is currently one of the most promising biological systems for the development of effective obesity pharmacotherapies. Long-acting GLP-1 analogs potently reduce food intake and body weight, and recent discoveries reveal that peripheral administration of these drugs reduces food intake largely through humoral pathways involving direct action on brain GLP-1 receptors (GLP-1R). Thus, it is of critical importance to understand the neural systems through which GLP-1 and long-acting GLP-1 analogs reduce food intake and body weight. In this review, we discuss several neural, physiological, cellular and molecular, as well as behavioral mechanisms through which peripheral and central GLP-1R signaling reduces feeding. Particular attention is devoted to discussion regarding the numerous neural substrates through which GLP-1 and GLP-1 analogs act to reduce food intake and body weight, including various hypothalamic nuclei (arcuate nucleus of the hypothalamus, periventricular hypothalamus, lateral hypothalamic area), hindbrain nuclei (parabrachial nucleus, medial nucleus tractus solitarius), hippocampus (ventral subregion; vHP), and nuclei embedded within the mesolimbic reward circuitry [ventral tegmental area (VTA) and nucleus accumbens (NAc)]. In some of these nuclei [VTA, NAc, and vHP], GLP-1R activation reduces food intake and body weight without concomitant nausea responses, suggesting that targeting these specific pathways may be of particular interest for future obesity pharmacotherapy. The widely distributed neural systems through which GLP-1 and GLP-1 analogs act to reduce body weight highlight the complexity of the neural systems regulating energy balance, as well as the challenges for developing effective obesity pharmacotherapies that reduce feeding without producing parallel negative side effects.