Postprandial glucagon-like peptide-1 (GLP-1) response is positively associated with changes in neuronal activity of brain areas implicated in satiety and food intake regulation in humans

Safety and efficacy of glucagon-like peptide-1 (GLP-1) receptor agonists in patients with weight regain or insufficient weight loss after metabolic bariatric surgery: A systematic review and meta-analysis

INTRODUCTION

Weight regain and insufficient weight loss are major challenges after metabolic bariatric surgery (MBS), affecting patients' comorbidities and quality of life. The current systematic review and meta-analysis aim to assess the efficacy and safety of GLP-1 receptor agonists (GLP-1 RA) in patients with weight regain or insufficient weight loss after MBS.

METHODS

A systematic search was conducted across PubMed, Embase, Scopus, and Web of Science databases to find the relevant studies.

RESULTS

A total of 19 articles were included. The highest doses of liraglutide and semaglutide were 3 mg per day and 1 mg once weekly, respectively, in the included studies. The mean differences in weight and body mass index after treatment were -7.02 kg or 3.07 kg/m2, -8.65 or -5.22 kg/m2, and -6.99 kg or -3.09 kg/m2 for treatment durations of ≤ 6 months, 6-12 months, and >12 months with liraglutide, respectively. Additionally, weekly semaglutide showed significantly greater weight loss compared to daily liraglutide, with a mean difference of 4.15 kg. Common complications included nausea (19.1%), constipation (8.6%), abdominal pain (3.7%), and vomiting (2.4%).

CONCLUSION

Using GLP-1 RA is a safe and effective treatment for weight regain and insufficient weight loss after MBS.

GLP-1 programs the neurovascular landscape

Readily available nutrient-rich foods exploit our inherent drive to overconsume, creating an environment of overnutrition. This transformative setting has led to persistent health issues, such as obesity and metabolic syndrome. The development of glucagon-like peptide-1 receptor (GLP-1R) agonists reveals our ability to pharmacologically manage weight and address metabolic conditions. Obesity is directly linked to chronic low-grade inflammation, connecting our metabolic environment to neurodegenerative diseases. GLP-1R agonism in curbing obesity, achieved by impacting appetite and addressing associated metabolic defects, is revealing additional benefits extending beyond weight loss. Whether GLP-1R agonism directly impacts brain health or does so indirectly through improved metabolic health remains to be elucidated. In exploring the intricate connection between obesity and neurological conditions, recent literature suggests that GLP-1R agonism may have the capacity to shape the neurovascular landscape. Thus, GLP-1R agonism emerges as a promising strategy for addressing the complex interplay between metabolic health and cognitive well-being.

Effect of oral semaglutide on energy intake, appetite, control of eating and gastric emptying in adults living with obesity: A randomized controlled trial

AIM

To investigate the effects of once-daily oral semaglutide 50 mg on energy intake, appetite, control of eating and gastric emptying.

METHODS

A clinical pharmacology, double-blind study was conducted in 61 adults with obesity randomized to once-daily oral semaglutide (dose-escalated to 50 mg) or placebo for 20 weeks. Energy intake was measured during an ad libitum lunch, and participant-reported appetite ratings and Control of Eating Questionnaire responses were assessed. Gastric emptying was measured using paracetamol absorption following a standardized breakfast.

RESULTS

The relative change from baseline in ad libitum energy intake at week 20 (primary endpoint) was -39.2% points (95% confidence interval -59.0%, -19.4%) with semaglutide compared with placebo. Body weight was reduced by 9.8% with semaglutide and by 1.5% with placebo. Semaglutide reduced hunger, increased fullness and satiety, and was associated with fewer food cravings and better control of eating versus placebo. No statistically significant difference in gastric emptying was observed at week 20.

CONCLUSIONS

In participants with obesity, once-daily oral semaglutide 50 mg reduced energy intake, body weight and appetite, and improved control of eating. There was no evidence of delayed gastric emptying at week 20, as measured through paracetamol absorption.

The role of glucagon-like peptide 1 receptor agonists for weight control in individuals with acquired hypothalamic obesity-A systematic review

Hypothalamic obesity does not respond well to conventional interventions for obesity. GLP-1 receptor agonists have mechanisms independent of the hypothalamus which may be potentially beneficial for managing hypothalamic obesity. This systematic review summarizes the efficacy and safety of GLP-1 receptor agonists use in hypothalamic obesity. A PRISMA-compliant systematic review was performed. Data was extracted from included studies and analysed based on change in weight, body mass index, glycaemic control, satiety, and safety profile with GLP-1 receptor agonist use. Ten studies comprising 5 case reports, 4 case series and 1 randomized-controlled trial included 54 patients (24 males, 30 females) with mean age of 25.2 (range 13-71) years with hypothalamic obesity who had received GLP-1 receptor agonists (exenatide = 48, liraglutide = 5 and dulaglutide = 1) over a mean duration of treatment of 12 (range 3-51) months. Mean weight reduction of 7.4 (SD 7.92) kg was observed in patients in whom weight was reported, with 85.7% of patients experiencing weight loss. All patients on liraglutide had weight reduction post-therapy. The sole trial had reported a non-significant reduction in BMI post-exenatide. Glycaemic control had either improved/maintained in all patients in whom this was measured. The main side effects of GLP-1 receptor agonist in individuals with hypothalamic obesity were nausea and vomiting; there were no major safety concerns. Based on limited published experience, GLP-1RA may be effective and safe for weight control in hypothalamic obesity, with the added benefit of improved glycaemic control in those with concurrent diabetes mellitus.

State-dependent central synaptic regulation by GLP-1 is essential for energy homeostasis

Central nervous system (CNS) control of metabolism plays a pivotal role in maintaining energy homeostasis. Glucagon-like peptide-1 (GLP-1, encoded by Gcg), secreted by a distinct population of neurons located within the nucleus tractus solitarius (NTS), suppresses feeding through projections to multiple brain targets1-3. Although GLP-1 analogs are proven clinically effective in treating type 2 diabetes and obesity4, the mechanisms of GLP-1 action within the brain remain unclear. Here, we investigate the involvement of GLP-1 receptor (GLP-1R) mediated signaling in a descending circuit formed by GLP-1R neurons in the paraventricular hypothalamic nucleus (PVNGLP-1R) that project to dorsal vagal complex (DVC) neurons of the brain stem in mice. PVNGLP- 1R→DVC synapses release glutamate that is augmented by GLP-1 via a presynaptic mechanism. Chemogenetic activation of PVNGLP-1R→DVC neurons suppresses feeding. The PVNGLP-1R→DVC synaptic transmission is dynamically regulated by energy states. In a state of energy deficit, synaptic strength is weaker but is more profoundly augmented by GLP-1R signaling compared to an energy-replete state. In an obese state, the dynamic synaptic strength changes in the PVNGLP-1R→DVC descending circuit are disrupted. Blocking PVNGLP-1R→DVC synaptic release or ablation of GLP-1R in the presynaptic compartment increases food intake and causes obesity, elevated blood glucose, and impaired insulin sensitivity. These findings suggest that the state-dependent synaptic plasticity in this PVNGLP-1R→DVC descending circuit mediated by GLP-1R signaling is an essential regulator of energy homeostasis.

Pharmacotherapy for obesity: moving towards efficacy improvement

Obesity is a chronic, recurring, progressive disease and a major public health problem associated with several other diseases that lead to disability, morbidity, and mortality. The prevalence of obesity has increased at pandemic levels, along with increasing weight-related comorbidities and deaths worldwide. Lifestyle interventions alone provide clinically significant long-term weight loss in only a small proportion of individuals, and bariatric surgery is not suitable or desirable for all patients. Historically, anti-obesity medications achieved a mean efficacy with weight loss between 5 and 10%, which significantly impacted several comorbidities and risk factors, but the average efficacy of these medications remained lower than that expected by both patients and health care professionals and eventually curbed long-term use. Moreover, there is no direct evidence on the impact of anti-obesity medications on cardiovascular outcomes. Semaglutide is a newer anti-obesity medication that changes the overall landscape, as phase 3 studies show a mean weight loss near the 15% threshold and significant proportions of patients with a weight loss of greater than 20%. In this review, we focus on the currently available anti-obesity medications, discuss the results of semaglutide, and present perspectives on the future of obesity treatment after semaglutide.

A New Dietary Fiber Can Enhance Satiety and Reduce Postprandial Blood Glucose in Healthy Adults: A Randomized Cross-Over Trial

BACKGROUND

Dietary fiber plays a potential role in regulating energy intake and stabilizing postprandial blood glucose levels. Soluble dietary fiber has become an important entry point for nutritional research on the regulation of satiety.

METHODS

this was a double-blind, randomized cross-over trial enrolling 12 healthy subjects to compare the effects of RPG (R+PolyGly) dietary fiber products (bread, powder, and capsule) and pectin administered with a standard meal on satiety, blood glucose, and serum insulin level.

RESULTS

Adding 3.8% RPG dietary fiber to bread significantly increased the volume, water content, hardness, and chewiness of bread compared to 3.8% pectin bread and white bread and significantly improved the sensory quality of bread. RPG bread had better appetite suppression effects at some time points than the other two groups and the best postprandial blood glucose lowering effects among the three groups. Administration of RPG capsules containing 5.6 g of RPG dietary fiber with meals improved satiety and reduced hunger compared to 6 g of RPG powder and 6 g of pectin, which had the greatest effect on suppressing appetite and reducing prospective food consumption. The peak level of serum glucagon-like peptide-1 (GLP-1) in the RPG capsule group (578.17 ± 19.93 pg/mL) was significantly higher than that in other groups at 0 min and 30 min after eating. RPG powder had the best effect in reducing postprandial blood glucose and increasing serum insulin levels; the total area under the curve (AUC) of serum insulin with RPG powder was higher than other groups (5960 ± 252.46 μU min/mL).

CONCLUSION

RPG dietary fiber products can improve the sensory properties of food, reduce postprandial blood glucose, and enhance satiety, especially in capsule and powder forms. Further research on the physiological effects of RPG dietary fiber is required to facilitate its use as a functional ingredient in food products.

Current Insights into the Potential Role of fMRI in Discovering the Mechanisms Underlying Obesity

Obesity is becoming one of the major global health concerns. This chronic disease affects around 650 million people worldwide and is an underlying cause of a number of significant comorbidities. According to the World Health Organization (WHO) report on obesity from 2022, this disorder became the fourth leading cause of deaths in Europe. Thus, understanding the mechanisms underlying obesity is of essential importance to successfully prevent and treat this disease. The aim of this study was to review the current insights into the potential role of fMRI in discovering the mechanisms underlying obesity on the basis of recent scientific literature published up to December 2022 and searches of the PubMed, Google Scholar and Web of Science databases. The literature assessed indicated that a growing body of evidence suggests that obesity leads to changes in both structure and connectivity within the central nervous system. Emerging data from recent functional magnetic resonance imaging (fMRI) studies prove that obese individuals present an increased motivational drive to eat as well as impaired processing in reward- and control-related brain regions. Apart from this, it is clear that fMRI might be a useful tool in detection of obesity-induced changes within the central nervous system.

Emerging Role of GLP-1 Agonists in Obesity: A Comprehensive Review of Randomised Controlled Trials

Obesity is a chronic disease with high prevalence and associated comorbidities, making it a growing global concern. These comorbidities include type 2 diabetes, hypertension, ventilatory dysfunction, arthrosis, venous and lymphatic circulation diseases, depression, and others, which have a negative impact on health and increase morbidity and mortality. GLP-1 agonists, used to treat type 2 diabetes, have been shown to be effective in promoting weight loss in preclinical and clinical studies. This review summarizes numerous studies conducted on the main drugs in the GLP-1 agonists class, outlining the maximum achievable weight loss. Our aim is to emphasize the active role and main outcomes of GLP-1 agonists in promoting weight loss, as well as in improving hyperglycemia, insulin sensitivity, blood pressure, cardio-metabolic, and renal protection. We highlight the pleiotropic effects of these medications, along with their indications, contraindications, and precautions for both diabetic and non-diabetic patients, based on long-term follow-up studies.

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.

Speech-Encoding Deficits in Neonates Born Large-for-Gestational Age as Revealed With the Envelope Frequency-Following Response

OBJECTIVES

The present envelope frequency-following response (FFRENV) study aimed at characterizing the neural encoding of the fundamental frequency of speech sounds in neonates born at the higher end of the birth weight continuum (>90th percentile), known as large-for-gestational age (LGA).

DESIGN

Twenty-five LGA newborns were recruited from the maternity unit of Sant Joan de Déu Barcelona Children's Hospital and paired by age and sex with 25 babies born adequate-for-gestational age (AGA), all from healthy mothers and normal pregnancies. FFRENVs were elicited to the/da/ syllable and recorded while the baby was sleeping in its cradle after a successful universal hearing screening. Neural encoding of the stimulus' envelope of the fundamental frequency (F0ENV) was characterized through the FFRENV spectral amplitude. Relationships between electrophysiological parameters and maternal/neonatal variables that may condition neonatal neurodevelopment were assessed, including pregestational body mass index (BMI), maternal gestational weight gain and neonatal BMI.

RESULTS

LGA newborns showed smaller spectral amplitudes at the F0ENV compared to the AGA group. Significant negative correlations were found between neonatal BMI and the spectral amplitude at the F0ENV.

CONCLUSIONS

Our results indicate that in spite of having a healthy pregnancy, LGA neonates' central auditory system is impaired in encoding a fundamental aspect of the speech sounds, namely their fundamental frequency. The negative correlation between the neonates' BMI and FFRENV indicates that this impaired encoding is independent of the pregnant woman BMI and weight gain during pregnancy, supporting the role of the neonatal BMI. We suggest that the higher adipose tissue observed in the LGA group may impair, via proinflammatory products, the fine-grained central auditory system microstructure required for the neural encoding of the fundamental frequency of speech sounds.

Differential association between the GLP1R gene variants and brain functional connectivity according to the severity of alcohol use

Growing evidence suggests that the glucagon-like peptide-1 (GLP-1) system is involved in mechanisms underlying alcohol seeking and consumption. Accordingly, the GLP-1 receptor (GLP-1R) has begun to be studied as a potential pharmacotherapeutic target for alcohol use disorder (AUD). The aim of this study was to investigate the association between genetic variation at the GLP-1R and brain functional connectivity, according to the severity of alcohol use. Participants were 181 individuals categorized as high-risk (n = 96) and low-risk (n = 85) alcohol use, according to their AUD identification test (AUDIT) score. Two uncommon single nucleotide polymorphisms (SNPs), rs6923761 and rs1042044, were selected a priori for this study because they encode amino-acid substitutions with putative functional consequences on GLP-1R activity. Genotype groups were based on the presence of the variant allele for each of the two GLP-1R SNPs of interest [rs6923761: AA + AG (n = 65), GG (n = 116); rs1042044: AA + AC (n = 114), CC (n = 67)]. Resting-state functional MRI data were acquired for 10 min and independent component (IC) analysis was conducted. Multivariate analyses of covariance (MANCOVA) examined the interaction between GLP-1R genotype group and AUDIT group on within- and between-network connectivity. For rs6923761, three ICs showed significant genotype × AUDIT interaction effects on within-network connectivity: two were mapped onto the anterior salience network and one was mapped onto the visuospatial network. For rs1042044, four ICs showed significant interaction effects on within-network connectivity: three were mapped onto the dorsal default mode network and one was mapped onto the basal ganglia network. For both SNPs, post-hoc analyses showed that in the group carrying the variant allele, high versus low AUDIT was associated with stronger within-network connectivity. No significant effects on between-network connectivity were found. In conclusion, genetic variation at the GLP-1R was differentially associated with brain functional connectivity in individuals with low versus high severity of alcohol use. Significant findings in the salience and default mode networks are particularly relevant, given their role in the neurobiology of AUD and addictive behaviors.

Genetic Variability of Incretin Receptors and Alcohol Dependence: A Pilot Study

Alcohol dependence is a chronic mental disorder that leads to decreased quality of life for patients and their relatives and presents a considerable burden to society. Incretin hormones, such as glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are endogenous gut-brain peptides, which can travel across the blood-brain barrier and access the nervous system. Their respective receptors, GIPR and GLP-1R, are expressed in the reward-related brain areas and are involved in memory formation and neurogenesis, which results in behavioral changes in rodent models. The current study investigated the potential association of genetic variability of incretin receptors with alcohol dependence and alcohol-related psychosymptomatology. Alcohol dependence and comorbid psychosymptomatology were assessed in a cohort of Slovenian male participants, comprised of 89 hospitalized alcohol-dependent patients, 98 abstinent alcohol-dependent patients, and 93 healthy blood donors. All participants were genotyped for GIPR rs1800437 and GLP1R rs10305420 and rs6923761 polymorphisms. For the statistical analysis Kruskal-Wall and Mann-Whitney tests were used in additive and dominant genetic models. Our findings indicated that GIPR rs1800437 genotypes were associated with an increased risk of alcohol dependence. Statistically significant association between GIPR rs1800437 GG genotype and Brief Social Phobia Scale scores were observed in the abstinent alcohol-dependent patients, while GLP1R rs6923761 GG genotype was associated with Zung anxiety scores in healthy controls. Our pilot study indicates that GIPR rs1800437 may play some role in susceptibility to alcohol dependence, as well as in alcohol-related psychosymptomatology symptoms. To our knowledge, this is the first study that indicates the involvement of GIPR in alcohol dependence. However, studies with larger cohorts are needed to confirm these preliminary findings.

Mapping brain activity of gut-brain signaling to appetite and satiety in healthy adults: A systematic review and functional neuroimaging meta-analysis

Understanding how neurohormonal gut-brain signaling regulates appetite and satiety is vital for the development of therapies for obesity and altered eating behavior. However, reported brain areas associated with appetite or satiety regulators show inconsistency across functional neuroimaging studies. The aim of this study was to systematically assess the convergence of brain regions modulated by appetite and satiety regulators. Twenty-five studies were considered for qualitative synthesis, and 14 independent studies (20-experiments) found eligible for coordinate-based neuroimaging meta-analyses across 212 participants and 123 foci. We employed two different meta-analysis approaches. The results from the systematic review revealed the modulation of insula, amygdala, hippocampus, and orbitofrontal cortex (OFC) with appetite regulators, where satiety regulators were more associated with caudate nucleus, hypothalamus, thalamus, putamen, anterior cingulate cortex in addition to the insula and OFC. The two neuroimaging meta-analyses methods identified the caudate nucleus as a key area associated with satiety regulators. Our results provide quantitative brain activation maps of neurohormonal gut-brain signaling in heathy-weight adults that can be used to define alterations with eating behavior.

A molecular link between diabetes and breast cancer: Therapeutic potential of repurposing incretin-based therapies for breast cancer

Female breast cancer recently surpassed lung cancer and became the most commonly diagnosed cancer worldwide. As per the recent data from WHO, breast cancer accounts for one out of every 8 cancer cases diagnosed among an estimated 2.3 million new cancer cases. Breast cancer is the most prevailing cancer type among women causing the highest number of cancer-related mortality. It has been estimated that in 2020, 68,5000 women died due to this disease. Breast cancers have varying degrees of molecular heterogeneity; therefore, they are divided into various molecular clinical sub types. Recent reports suggest that type 2 diabetes (one of the common chronic diseases worldwide) is linked to the higher incidence, accelerated progression, and aggressiveness of different cancers; especially breast cancer. Breast cancer is hormone-dependent in nature and has a cross-talk with metabolism. A number of antidiabetic therapies are known to exert beneficial effects on various types of cancers, including breast cancer. However, only a few reports are available on the role of incretin-based antidiabetic therapies in cancer as a whole and in breast cancer in particular. The present review sheds light on the potential of incretin based therapies on breast cancer and explores the plausible underlying mechanisms. Additionally, we have also discussed the sub types of breast cancer as well as the intricate relationship between diabetes and breast cancer.

Can GLP-1 Be a Target for Reward System Related Disorders? A Qualitative Synthesis and Systematic Review Analysis of Studies on Palatable Food, Drugs of Abuse, and Alcohol

The role of glucagon-like peptide 1 (GLP-1) in insulin-dependent signaling is well-known; GLP-1 enhances glucose-dependent insulin secretion and lowers blood glucose in diabetes. GLP-1 receptors (GLP-1R) are also widely expressed in the brain, and in addition to its role in neuroprotection, it affects reward pathways. This systematic review aimed to analyze the studies on GLP-1 and reward pathways and its currently identified mechanisms.

Methods: “Web of Science” and “Pubmed” were searched to identify relevant studies using GLP-1 as the keyword. Among the identified 26,539 studies, 30 clinical, and 71 preclinical studies were included. Data is presented by grouping rodent studies on palatable food intake, drugs of abuse, and studies on humans focusing on GLP-1 and reward systems.

Results: GLP-1Rs are located in reward-related areas, and GLP-1, its agonists, and DPP-IV inhibitors are effective in decreasing palatable food intake, along with reducing cocaine, amphetamine, alcohol, and nicotine use in animals. GLP-1 modulates dopamine levels and glutamatergic neurotransmission, which results in observed behavioral changes. In humans, GLP-1 alters palatable food intake and improves activity deficits in the insula, hypothalamus, and orbitofrontal cortex (OFC). GLP-1 reduces food cravings partially by decreasing activity to the anticipation of food in the left insula of obese patients with diabetes and may inhibit overeating by increasing activity to the consumption of food in the right OFC of obese and left insula of obese with diabetes.

Conclusion: Current preclinical studies support the view that GLP-1 can be a target for reward system related disorders. More translational research is needed to evaluate its efficacy on human reward system related disorders.

A plant-based meal affects thalamus perfusion differently than an energy- and macronutrient-matched conventional meal in men with type 2 diabetes, overweight/obese, and healthy men: A three-group randomized crossover study

BACKGROUND & AIMS

Reward circuitry in the brain plays a key role in weight regulation. We tested the effects of a plant-based meal on these brain regions.

METHODS

A randomized crossover design was used to test the effects of two energy- and macronutrient-matched meals: a vegan (V-meal) and a conventional meat (M-meal) on brain activity, gastrointestinal hormones, and satiety in participants with type 2 diabetes (T2D; n = 20), overweight/obese participants (O; n = 20), and healthy controls (H; n = 20). Brain perfusion was measured, using arterial spin labeling functional brain imaging; satiety was assessed using a visual analogue scale; and plasma concentrations of gut hormones were determined at 0 and 180 min. Repeated-measures ANOVA was used for statistical analysis. Bonferroni correction for multiple comparisons was applied. The Hedge's g statistic was used to measure the effect size for means of paired difference between the times (180-0 min) and meal types (M-V meal) for each group.

RESULTS

Thalamus perfusion was the highest in patients with T2D and the lowest in overweight/obese individuals (p = 0.001). Thalamus perfusion decreased significantly after ingestion of the M-meal in men with T2D (p = 0.04) and overweight/obese men (p = 0.004), and it decreased significantly after ingestion of the V-meal in healthy controls (p < 0.001; Group x Meal x Time: F = 3.4; p = 0.035). The effect size was -0.41 (95% CI, -1.14 to 0.31; p = 0.26) for men with diabetes; -0.72 (95% CI, -1.48 to 0.01; p = 0.05) for overweight/obese men; and 0.82 (95% CI, 0.09 to 1.59; p = 0.03) for healthy men. Postprandial secretion of active GLP-1 increased after the V-meal compared with the M-meal by 42% (95% CI 25-62%; p = 0.003) in men with T2D and by 41% (95% CI 24-61%; p = 0.002) in healthy controls. Changes in thalamus perfusion after ingestion of both test meals correlated with changes in satiety (r = +0.68; p < 0.01), fasting plasma insulin (r = +0.40; p < 0.01), C-peptide (r = +0.48; p < 0.01) and amylin (r = +0.55; p < 0.01), and insulin secretion at 5 mmol/l (r = +0.77; p < 0.05).

CONCLUSIONS

The higher postprandial GLP-1 secretion after the V-meal in men with T2D, with concomitant greater satiety and changes in thalamus perfusion, suggest a potential use of plant-based meals in addressing the key pathophysiologic mechanisms of food intake regulation. Trial registration ClinicalTrials.gov number, NCT02474147.

The altered enteroendocrine reportoire following roux-en-Y-gastric bypass as an effector of weight loss and improved glycaemic control

The alarming rise in obesity and relative lack of pharmacotherapies to treat, what is becoming a global epidemic, has necessitated that an increasing number of bariatric procedures be performed. Several surgical techniques have been developed during the last 50 years and the advent of laparoscopic surgery has increased the safety and efficacy of these procedures. Bariatric surgery is by a substantial margin, the most efficacious means of achieving sustained weight loss maintenance in patients with obesity. Roux-en-Y gastric bypass surgery (RYGB) elicits the most favourable metabolic outcomes with attendant benefits for type 2 diabetes and, cardiovascular disease as well as endocrine disorders and cancers in females. RYGB is the most extensively studied bariatric procedure regarding mechanism of action. In this review we catalogue the multiple alterations in secretion of gut hormones (ghrelin, obestatin, cholecystokinin, GLP-1, PYY, GIP, oxyntomodulin, glicentin and GLP-2) occurring after RYGB and summarise evidence indicating that these changes play a role in the reduction of food intake and improvements in glucose homeostasis.

Repurposing GLP1 agonists for neurodegenerative diseases

There is a large unmet medical need to find disease modifying therapies against neurodegenerative diseases. This review summarizes data indicating that insulin resistance occurs in neurodegeneration and strategies to normalize insulin sensitivity in neurons may provide neuroprotective actions. In particular, recent preclinical and clinical studies in Parkinson's disease and Alzheimer's disease have indicated that glucagon-like peptide 1 (GLP1) agonism and dipeptidyl peptidase-4 inhibition may exert neuroprotection. Mechanistic insights from these studies and future directions for drug development against neurodegeneration based on GLP1 agonism are discussed.

Social jetlag and sleep deprivation are associated with altered activity in the reward-related brain areas: an exploratory resting-state fMRI study

OBJECTIVE

The aim of this research was to assess the effect of social jetlag (SJL) and its interaction with partial sleep deprivation on resting-state brain activity using the fractional amplitude of low-frequency fluctuation (fALFF) during free-living conditions.

METHODS

A total of 28 normal weight healthy subjects were enrolled in four study groups (with SJL [with sleep deprivation and without sleep deprivation] and without SJL [with sleep deprivation and without sleep deprivation]), matched 1:1:1:1 for age, gender, and body mass index (BMI). Resting-state functional magnetic resonance imaging (fMRI) scans were collected with SIEMENS 3T scanner while subjects were in a fasting state.

RESULTS

Participants with SJL had significantly higher fALFF values in right lingual gyrus and right putamen and significantly lower fALFF values in left and right inferior parietal lobe in comparison with participants without SJL and without sleep deprivation. Subjects with sleep deprivation had significantly higher fALFF in the thalamus and left superior frontal gyrus. In those with both SJL and sleep deprivation, we observed higher fALFF values in right Brodmann Area (BA)18 and lower values in left and right parietal inferior lobe. Subjects with SJL alone had significantly lower fALFF values in left frontal mid gyrus (BA6) than those with sleep deprivation alone.

CONCLUSIONS

SJL was associated with altered resting-state brain activity in regions that have been shown to be involved in hedonic feeding. The effect of SJL was independent of effects induced by short sleep duration. These alterations might represent the substrate for the increased risk of obesity observed in those with SJL.

Neurological Manifestation of Incretin-Based Therapies in Patients with Type 2 Diabetes: A Systematic Review and Network Meta-Analysis

As a new class of antidiabetic drug, incretin-based therapies, which include dipeptidyl peptidase-4 inhibitors (DPP-4Is) and glucagon-like peptide-1 receptor agonists (GLP-1 RAs), have raised concerns about symptoms of withdrawal in patients with type 2 diabetes mellitus (T2DM), such as dizziness and headache. To systematically evaluate whether incretin-based therapies may lead to dizziness and headache in patients with T2DM compared to other traditional antidiabetic drugs or placebo. We searched Medline, Embase, the Cochrane library, and clinicaltrials.gov from inception through June 23, 2017, to identify randomized controlled trials of the safety of DPP-4Is or GLP-1 RAs versus placebo or other antidiabetic drugs in T2DM patients. We used the network meta-analysis under the frequentist framework to compare the association between multiple antidiabetic drugs and dizziness and headache. A total of 233 clinical trials with nine treatments and 147,710 patients were included: two incretin-based therapies, one placebo, and six traditional antidiabetic drugs (metformin, insulin, sulfonylurea, thiazolidinediones, alpha-glucosidase inhibitor, and sodium-glucose co-transporter 2). Compared to insulin, thiazolidinediones, or placebo, GLP-1 RAs statistically significantly increased the risk of dizziness (odds ratios [ORs]: 1.92, 1.57, and 1.40, respectively) and headache (ORs: 1.34, 1.41, and 1.18, respectively). DPP-4Is increased the risk of headache (OR: 1.22, 95% confidence interval [CI]: 1.02 to 1.46; moderate quality) and dizziness (OR: 1.46, 95% CI: 1.05 to 2.03; moderate quality) compared to insulin. Of the incretin-based therapies, DPP-4Is had a lower risk of dizziness than GLP-1 RAs (OR: 0.76, 95% CI: 0.67 to 0.87; high quality). Ranking probability analysis indicated that GLP-1 RAs may have the greatest risk of both dizziness and headache among the nine treatments (22.5% and 23.4%, respectively), whereas DPP-4Is were in the middle (46.2% and 45.0%, respectively). Incretin-based therapies increase the risk of dizziness and headache compared to insulin, thiazolidinediones, and placebo.

Interaction of circulating GLP-1 and the response of the dorsolateral prefrontal cortex to food-cues predicts body weight development

OBJECTIVES

This study evaluated the impact of the interaction between the anorexigenic incretin hormone glucagon-like peptide-1 (GLP-1) and reward-related brain activity in the dorsolateral prefrontal cortex (DLPFC), a key area of behavioral control, on future weight loss in obese individuals.

METHODS

We performed a weight loss-weight maintenance intervention study over 27 months. We applied an fMRI food-cue reactivity paradigm during which the participants were passively exposed to food pictures to evaluate neuronal activity in the DLPFC. Additionally, we measured concentrations of circulating GLP-1 levels during a standard oral glucose tolerance test. Phenotyping was performed consecutively before and after a 3-month low-calorie diet as well as after a randomized 12-month trial, investigating the effect of a combined behavioral intervention on body weight maintenance. Participants were then followed-up for another 12 months without further intervention.

RESULTS

Using voxel-wise linear mixed-effects regression analyses, we evaluated 56 measurements and identified a strong interaction between circulating, endogenous GLP-1 levels and DLPFC activity predicting body weight change over the total observation period (t = -6.17, p = 1.6 · 10-7). While neither the GLP-1 nor the DLPFC response individually predicted the subsequent weight change, participants achieved body weight loss when the GLP-1 and the DLPFC responses occurred concurrently.

CONCLUSIONS

Our data demonstrate an interaction between a peripheral hormonal signal and central nervous activity as robust predictor of body weight change throughout the different periods of a long-term life-style intervention. The preeminent role of their interdependency compared to the partly ambivalent effects of the single components argues for integrative approaches to improve sensitivity and reliability of weight prediction conventionally based on individual biomarkers.

Neuroendocrinological mechanisms underlying impulsive and compulsive behaviors in obesity: a narrative review of fMRI studies

Impulsivity and compulsivity are multidimensional constructs that are increasingly considered determinants of obesity. Studies using functional magnetic resonance imaging (fMRI) have provided insight on how differences in brain response during tasks exploring facets of impulsivity and compulsivity relate to the ingestive behaviors that support the etiology and maintenance of obesity. In this narrative review, we provide an overview of neuroimaging studies exploring impulsivity and compulsivity factors as they relate to weight status. Special focus will be placed on studies examining the impulsivity-related dimensions of attentional bias, delayed gratification and emotion regulation. Discussions of compulsivity within the context of obesity will be restricted to fMRI studies investigating habit formation and response flexibility under shifting contingencies. Further, we will highlight neuroimaging research demonstrating how alterations in neuroendocrine functioning are linked to excessive food intake and may serve as a driver of the impulsive and compulsive behaviors observed in obesity. Research on the associations between brain response with neuroendocrine factors, such as insulin, peptide YY (PYY), leptin, ghrelin and glucagon-like peptide 1 (GLP-1), will be reviewed.

Determining the Effects of Combined Liraglutide and Phentermine on Metabolic Parameters, Blood Pressure, and Heart Rate in Lean and Obese Male Mice

Liraglutide, a glucagon-like peptide 1 (GLP-1) receptor agonist, and phentermine, a psychostimulant structurally related to amphetamine, are drugs approved for the treatment of obesity and hyperphagia. There is significant interest in combination use of liraglutide and phentermine for weight loss; however, both drugs have been reported to induce systemic hemodynamic changes, and as such the therapeutic window for this drug combination needs to be determined. To understand their impact on metabolic and cardiovascular physiology, we tested the effects of these drugs alone and in combination for 21 days in lean and obese male mice. The combination of liraglutide and phentermine, at 100 μg/kg/day and 10 mg/kg/day, respectively, produced the largest reduction in body weight in both lean and diet-induced obese (DIO) mice, when compared with both vehicle and monotherapy-treated mice. In lean mice, combination treatment at the aforementioned doses significantly increased heart rate and reduced blood pressure, whereas in DIO mice, combination therapy induced a transient increase in heart rate and decreased blood pressure. These studies demonstrate that in obese mice, the combination of liraglutide and phentermine may reduce body weight but only induce modest improvements in cardiovascular functions. Conversely, in lean mice, the additional weight loss from combination therapy does not improve cardiovascular parameters.

Resistance Exercise Training Attenuates the Loss of Endogenous GLP-1 Receptor in the Hypothalamus of Type 2 Diabetic Rats

The aim of this study was to investigate the effects of resistance exercise training on hypothalamic GLP-1R levels and its related signaling mechanisms in T2DM. The animals were separated into three groups: a non-diabetic control (CON), diabetic control (DM), and diabetic with resistance exercise (DM + EXE) group. The resistance exercise training group performed ladder climbing (eight repetitions, three days per week for 12 weeks). Body weight was slightly lower in the DM + EXE group than the DM group, but difference between the groups was not significant. Food intake and glucose were significantly lower in the DM + EXE group than in the DM group. The blood insulin concentration was significantly higher and glucagon was significantly lower in the DM + EXE group. The DM + EXE group in the hypothalamus showed significant increases in GLP-1R mRNA, protein kinase A (PKA), glucose transporter 2 (GLUT2), and protein kinase B (AKT) and significant decrease in protein kinase C-iota (PKC-iota). Antioxidant enzymes and apoptosis factors were significantly improved in the DM + EXE group compared with the DM group in the hypothalamus. The results suggest that resistance exercise contributes to improvements the overall health of the brain in diabetic conditions.

Cigarette smoking, type 2 diabetes mellitus, and glucagon-like peptide-1 receptor agonists as a potential treatment for smokers with diabetes: An integrative review

Tobacco use disorder (TUD), in particular cigarette smoking, contributes significantly to the macro- and micro-vascular complications of type 2 diabetes mellitus (DM). Persons with DM who regularly use tobacco products are twice as likely to experience mortality and negative health outcomes. Despite these risks, TUD remains prevalent in persons with DM. The objective of this integrative review is to summarize the relationship between TUD and DM based on epidemiological and preclinical biological evidence. We conclude with a review of the literature on the glucagon-like peptide-1 (GLP-1) as a potential treatment target for addressing comorbid TUD in smokers with DM.

Glucagon-like peptide-1 receptors within the nucleus of the solitary tract regulate alcohol-mediated behaviors in rodents

The ability of glucagon-like peptide-1 (GLP-1) to reduce food intake involves activation of GLP-1 receptors (GLP-1R) in the nucleus of the solitary tract (NTS). It has also been demonstrated that systemic administration of GLP-1R agonists attenuates alcohol-mediated behaviors via, to date, unknown mechanisms. Therefore, we evaluated the effects of NTS-GLP-1R activation by exendin-4 (Ex4) on alcohol-induced locomotor stimulation, accumbal dopamine release and memory of alcohol reward in the conditioned place preference (CPP) model in mice. Moreover, the ability of Ex4 infusion into the NTS on alcohol intake was explored in rats. Ex4 into the NTS inhibits the acute effects of alcohol as measured by alcohol-induced locomotor stimulation, accumbal dopamine release and the memory consolidation of alcohol reward in the CPP paradigm. In addition, NTS-Ex4 dose-dependently decreases alcohol intake in rats consuming alcohol for 12 weeks. Pharmacological suppression of GLP-1R in the NTS prevents the ability of systemic Ex4 to block the alcohol-induced locomotor stimulation in mice. These data add a functional role of GLP-1R within the NTS, involving alcohol-related behaviors. In addition, they may provide insight into the GLP-1R containing brain areas that modulate the ability of GLP-1R agonists to reduce alcohol reinforcement. Collectively, this further supports GLP-1R as potential treatment targets for alcohol use disorder.

The Role of Glucagon-Like Peptide-1 in Energy Homeostasis

Energy homeostasis is coordinated by bidirectional communication pathways between the brain and peripheral organs, including adipose tissue, muscle, the pancreas, liver, and gut. Disruption of the integrated chemical, hormonal, and neuronal signals that constitute the gut-brain axis significantly contributes to disorders of metabolism and body weight. Initial studies of glucagon-like peptide-1 (GLP-1), a gut hormone released in response to the ingestion of nutrients, focused on its incretin actions to improve postprandial glucose homeostasis by enhancing meal-induced insulin secretion. However, GLP-1 is also a key player in the gut-brain regulatory axis with multiple effects on appetite and energy metabolism outside of its peripheral glucoregulatory actions. In this review, we explore the function of GLP-1 as a component of the gut-brain axis in the regulation of energy homeostasis, and consider the implications of this role for the development of therapeutic treatment options for obesity.

Treating obesity in patients with cardiovascular disease: the pharmacotherapeutic options

INTRODUCTION

Obesity is a growing health problem that has numerous comorbidities, including cardiovascular disease (CVD). The multi-disciplinary treatment of obesity now includes the use of pharmacotherapy. When treating patients with obesity and CVD, certain medications may be more appropriate than others.

AREAS COVERED

Herein, the authors review the most commonly used FDA approved medications for the treatment of obesity, describing their mechanism of action, and the efficacy and safety of the medications as seen in recent studies, particularly in patients with CVD.

EXPERT OPINION

In the population of patients with obesity and CVD, the medications orlistat, lorcaserin and liraglutide are considered the most appropriate options for their treatment, in terms of safety. Sympathomimetic medications, such as phentermine, should be avoided in this group. The recent CAMELLIA-TIMI 61 trial supports the safety of lorcaserin in patients with CVD. Until there are more studies, it is reasonable to extrapolate the findings of the LEADER trial, which found improved CV outcomes in subjects with type 2 diabetes taking liraglutide, to the population of nondiabetic patients being treated for obesity. Further cardiovascular outcomes trials (CVOT) are needed to assess the safety of other pharmacotherapeutic options for weight loss.

Liraglutide-Induced Weight Loss May be Affected by Autonomic Regulation in Type 1 Diabetes

The role of the autonomic nervous system in the efficacy of glucagon-like peptide-1 receptor agonists (GLP-1 RA) in patients with type 1 diabetes is unknown. We assessed the association between autonomic function and weight loss induced by the GLP-1 RA liraglutide. Methods: Lira-1 was a randomized, double-blind, placebo-controlled trial assessing the efficacy and safety of 1.8 mg liraglutide once-daily for 24 weeks in overweight patients with type 1 diabetes. Autonomic function was assessed by heart rate response to deep breathing (E/I ratio), to standing (30/15 ratio), to the Valsalva maneuver and resting heart rate variability (HRV) indices. Associations between baseline the cardiovascular autonomic neuropathy (CAN) diagnosis (> 1 pathological non-resting test) and levels of test outcomes on liraglutide-induced weight loss was assessed by linear regression models. Results: Ninety-nine patients with mean age 48 (SD 12) years, HbA_1c 70 (IQR 66;75) mmol/mol and BMI of 30 (SD 3) kg/m² were assigned to liraglutide (N = 50) or placebo (N = 49). The CAN diagnosis was not associated with weight loss. A 50% higher baseline level of the 30/15 ratio was associated with a larger weight reduction by liraglutide of -2.65 kg during the trial (95% CI: -4.60; -0.69; P = 0.009). Similar significant associations were found for several HRV indices. Conclusions: The overall CAN diagnosis was not associated with liraglutide-induced weight loss in overweight patients with type 1 diabetes. Assessed separately, better outcomes for several CAN measures were associated with higher weight loss, indicating that autonomic involvement in liraglutide-induced weight loss may exist.

Salem A. Metformin, sitagliptin, and liraglutide modulate serum retinol-binding protein-4 level and adipocytokine production in type 2 diabetes mellitus rat model

Many adipocytokines correlate with obesity and insulin resistance. We examined the effects of metformin, sitagliptin, and liraglutide in diabetic rats. Group 1: control normal (CN) rats received oral saline daily. Group 2: diabetic non-treated (DNT) rats were injected with streptozotocin (STZ) to get diabetic then after 72 h received oral saline daily. Group 3: rats were injected with STZ then after 72 h were treated with metformin (200 mg/kg) orally. Group 4: rats were injected with STZ then after 72 h received sitagliptin 6 mg/kg orally twice daily. Group 5: rats were injected with STZ then after 72 h were treated with liraglutide at a dose of 0.3 mg/kg every 12 h subcutaneous injection. After 8 weeks, body mass, fasting blood glucose, adipocytokines, and lipid profile were assessed. From the results, we concluded that the 3 drugs improved blood glucose and insulin resistance with correction of adipocytokines serum levels; however, the liraglutide-treated group was the only group that showed significant body mass reduction.

Endogenous GLP-1 alters postprandial functional connectivity between homeostatic and reward-related brain regions involved in regulation of appetite in healthy lean males: A pilotstudy

AIMS

Peripheral infusion of glucagon-like peptide-1 (GLP-1) can affect brain activity in areas involved in the regulation of appetite, including hypothalamic and reward-related brain regions. In contrast, the physiological role of endogenous GLP-1 in the central regulation of appetite has hardly been investigated.

MATERIALS AND METHODS

This was a randomized, cross-over trial that involved 12 healthy volunteers who received an intragastric (ig) glucose (gluc) load, with or without intravenous (iv) exendin9-39 (ex9-39; specific GLP-1 receptor antagonist). Functional magnetic resonance imaging was used to investigate the effect of endogenous GLP-1 on resting state functional connectivity (rsFC) between homeostatic and reward-related brain regions. Visual analogue scales were used to rate appetite-related sensations. Blood samples were collected for GI hormone measurements.

RESULTS

Administration of iv-ex9-39/ig-gluc induced a significantly higher rsFC, relative to ig-gluc administration, between the hypothalamus and the left lateral orbitofrontal cortex (OFC) as well as the left amygdala (P ≤ .001, respectively). Administration of iv-ex9-39/ig-gluc induced a significantly higher rsFC, relative to ig-gluc administration, between the right nucleus accumbens and the right lateral OFC (P < .001). Administration of iv-ex9-39/ig-gluc induced a significantly lower rsFC, relative to ig-gluc administration, between the midbrain and the right caudate nucleus (P = .001). Administration of ig-gluc significantly decreased prospective food consumption and increased sensations of fullness compared to pre-infusion baseline (P = .028 and P = .019, respectively); these effects were not present in the iv-ex9-39/ig-gluc condition.

CONCLUSIONS

This pilot trial provides preliminary experimental evidence that glucose-induced endogenous GLP-1 affects central regulation of appetite by modulating rsFC in homeostatic and reward-related brain regions in healthy lean male participants in a GLP-1 receptor-mediated fashion.

Impact of Early-Life Weight Status on Cognitive Abilities in Children

OBJECTIVE

Whether obesity is associated with childhood cognition is unknown. Given the sensitivity of the developing brain to environmental factors, this study examined whether early-life weight status was associated with children's cognition.

METHODS

Using data from mother-child pairs enrolled in the Health Outcomes and Measures of the Environment (HOME) Study (2003-2006), children's early-life weight status was assessed using weight-for-length/height standard deviation (SD) scores. A battery of neuropsychological tests was administered to assess cognition, executive function, and visual-spatial abilities at ages 5 and 8 years. Using linear mixed models, associations between early-life weight status and cognition were estimated.

RESULTS

Among 233 children, 167 were lean (≤1 SD) and 48 were nonlean (>1 SD). After covariate adjustment, the results suggest that full-scale intelligence quotient scores decreased with a 1-unit increase in weight-for-height SD score (β = -1.4, 95% CI: -3.0 to 0.1). For individual component scores, with a 1-unit increase in weight-for-height SD score, perceptual reasoning (β = -1.7, 95% CI: -3.3 to 0.0) and working memory (β: -2.4, CI: -4.4 to -0.4) scores decreased. Weight status was generally not associated with other cognition measures.

CONCLUSIONS

Within this cohort of typically developing children, early-life weight status was inversely associated with children's perceptual reasoning and working memory scores and possibly with full-scale intelligent quotient scores.

Hyaluronic acid-based biopharmaceutical delivery and tumor-targeted drug delivery system

Hyaluronic acid (HA) is a natural polysaccharide with good biocompatibility and degradability. HA and its derivatives can be used as sustained-release carriers for drugs, which can delay the release of drugs and have a long-acting effect. They can be used for the delivery of various drugs such as proteins, nucleic acids and anti-tumor drugs. HA and its derivatives can specifically bind to multiple receptors on the cell surface and can be used for targeted drug delivery, especially for the delivery of anti-tumor drugs. Thus, there are different forms of tumor-targeted drug delivery systems based on HA.

Pharmacotherapy for obesity in individuals with type 2 diabetes

INTRODUCTION

Type 2 diabetes (T2DM) is associated with significant morbidity and mortality. Obesity is one of the main risk factors for T2DM and its management requires a multidisciplinary approach, which may include pharmacotherapy.

AREAS COVERED

In this paper, data on efficacy, tolerability and safety of FDA-approved pharmacotherapies for obesity (orlistat, phentermine/topiramate extended-release, lorcaserin, bupropion sustained release/naltrexone sustained release and liraglutide) are reviewed, focusing on individuals with type 2 diabetes.

EXPERT OPINION

Obesity is the major pathophysiologic driver of T2DM; conversely 5-10% weight loss leads to significant improvement in glycemic control, lipids and blood pressure. Weight loss maintenance is difficult with lifestyle interventions alone and may require adjunctive therapies. There is good evidence for the efficacy and tolerability of approved anti-obesity pharmacotherapies in individuals with T2DM, with current cardiovascular safety data being most favorable for liraglutide, orlistat and lorcaserin. Given the link between obesity and T2DM, a weight-centric therapeutic approach including use of weight reducing anti-diabetic therapies, and anti-obesity pharmacotherapies is both intuitive and rational to improve glycemic and other metabolic outcomes in patients with T2DM.

Liraglutide inhibits the proliferation and promotes the apoptosis of MCF-7 human breast cancer cells through downregulation of microRNA-27a expression

The use of glucagon-like peptide-1 analogues, such as liraglutide, as hypoglycemic drugs has been widely employed in clinical practice. Liraglutide is reported to exert potential anti-breast cancer effects, however the specific mechanisms of this action remain unknown. In the present study, MCF-7 human breast cancer cells were cultured in vitro and treated with various concentrations of liraglutide. Cell Counting Kit-8, colony formation and flow cytometry assays were performed to determine the proliferation and apoptosis of cells following treatment. Furthermore, reverse transcription-quantitative polymerase chain reaction was employed to measure the expression level of microRNA (miRNA/miR)-27a. In addition, miR-27a mimics, inhibitors and negative controls were transfected into MCF-7 cells and the proliferation and apoptosis of cells following transfection was subsequently determined. Western blotting was performed to detect alterations in the protein expression of AMP-activated protein kinase catalytic subunit α2 (AMPKα2), proliferating cell nuclear antigen and cleaved-caspase-3 following treatments. The results demonstrated that, following treatment with liraglutide, the proliferation of MCF-7 cells was reduced and the apoptosis was increased, compared with the control group; this effect was increased with increasing concentrations of liraglutide. In addition, liraglutide treatment downregulated miR-27a expression in MCF-7 cells. While the overexpression of miR-27a promoted cell proliferation and inhibited apoptosis, knockdown of endogenous miR-27a inhibited cell proliferation and promoted apoptosis in MCF-7 cells. Furthermore, the expression of AMPKα2 protein in the group transfected with miR-27a mimics was decreased, while it was increased in MCF-7 cells transfected with miR-27a inhibitors. In conclusion, liraglutide may have a role in the inhibition of proliferation and promotion of apoptosis in MCF-7 cells. Concerning the mechanism of these effects, liraglutide may inhibit miR-27a expression, which subsequently increases the expression of AMPKα2 protein. The present study provides an experimental basis for the clinical treatment strategies of T2DM patients with breast cancer.

The impact of gut hormones on the neural circuit of appetite and satiety: A systematic review

The brain-gut-axis is an interdependent system affecting neural functions and controlling our eating behaviour. In recent decades, neuroimaging techniques have facilitated its investigation. We systematically looked into functional and neurochemical brain imaging studies investigating how key molecules such as ghrelin, glucagon-like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY), cholecystokinin (CCK), leptin, glucose and insulin influence the function of brain regions regulating appetite and satiety. Of the 349 studies published before July 2016 identified in the database search, 40 were included (27 on healthy and 13 on obese subjects). Our systematic review suggests that the plasma level of ghrelin, the gut hormone promoting appetite, is positively correlated with activation in the pre-frontal cortex (PFC), amygdala and insula and negatively correlated with activation in subcortical areas such as the hypothalamus. In contrast, the plasma levels of glucose, insulin, leptin, PYY, GLP-1 affect the same brain regions conversely. Our study integrates previous investigations of the gut-brain matrix during food-intake and homeostatic regulation and may be of use for future meta-analyses of brain-gut interactions.

A brief review of salient factors influencing adult eating behaviour

A better understanding of the factors that influence eating behaviour is of importance as our food choices are associated with the risk of developing chronic diseases such as obesity, CVD, type 2 diabetes or some forms of cancer. In addition, accumulating evidence suggests that the industrial food production system is a major contributor to greenhouse gas emission and may be unsustainable. Therefore, our food choices may also contribute to climate change. By identifying the factors that influence eating behaviour new interventions may be developed, at the individual or population level, to modify eating behaviour and contribute to society’s health and environmental goals. Research indicates that eating behaviour is dictated by a complex interaction between physiology, environment, psychology, culture, socio-economics and genetics that is not fully understood. While a growing body of research has identified how several single factors influence eating behaviour, a better understanding of how these factors interact is required to facilitate the developing new models of eating behaviour. Due to the diversity of influences on eating behaviour this would probably necessitate a greater focus on multi-disciplinary research. In the present review, the influence of several salient physiological and environmental factors (largely related to food characteristics) on meal initiation, satiation (meal size) and satiety (inter-meal interval) are briefly discussed. Due to the large literature this review is not exhaustive but illustrates the complexity of eating behaviour. The present review will also highlight several limitations that apply to eating behaviour research.

Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) in the Brain-Adipocyte Axis

The complexity of neural circuits that control food intake and energy balance in the hypothalamic nuclei explains some of the constraints involved in the prevention and treatment of obesity. Two major neuronal populations present in the arcuate nucleus control caloric intake and energy expenditure: one population co-expresses orexigenic agouti-related peptide (AgRP) and neuropeptide Y and the other expresses the anorexigenic anorectic neuropeptides proopiomelanocortin and cocaine- and amphetamine-regulated transcript (POMC/CART). In addition to integrating signals from neurotransmitters and hormones, the hypothalamic systems that regulate energy homeostasis are affected by nutrients. Fat-rich diets, for instance, elicit hypothalamic inflammation (reactive activation and proliferation of microglia, a condition named gliosis). This process generates resistance to the anorexigenic hormones leptin and insulin, contributing to the genesis of obesity. Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs) have increasingly been used to treat type 2 diabetes mellitus. One compound (liraglutide) was recently approved for the treatment of obesity. Although most studies suggest that GLP-1RAs promote weight loss mainly due to their inhibitory effect on food intake, other central effects that have been described for native GLP-1 and some GLP-1RAs in rodents and humans encourage future clinical trials to explore additional mechanisms that potentially underlie the beneficial effects observed with this drug class. In this article we review the most relevant data exploring the mechanisms involved in the effects of GLP-1RAs in the brain–adipocyte axis.

Impaired glucose tolerance after streptozotocin microinjection into the mediodorsal prefrontal cortex of the rat

The mediodorsal prefrontal cortex (mdPFC) is a key structure of the central glucose-monitoring (GM) neural network. Previous studies indicate that intracerebral streptozotocin (STZ) microinjection-induced destruction of local chemosensory neurons results in feeding and metabolic alterations. The present experiments aimed to examine whether STZ microinjection into the mdPFC causes metabolic deficits. To do so, glucose tolerance test (GTT) and measurements of plasma metabolites were performed in STZ-treated or control rats. Intraperitoneal D-glucose load was delivered 20 min or 4 weeks following the intracerebral microinjection of STZ or saline (acute or subacute GTT, respectively). The STZ-treated rats displayed acute glucose intolerance: at the 120th min of the test, blood glucose level of these rats was significantly higher than that of the ones in the control group. When determining the plasma level of various metabolites, 30 min following the intracerebral STZ or saline microinjection, the triglyceride concentration of the STZ-treated rats was found to be reduced compared with that of the control rats. The GM neurons of the mdPFC are suggested to be involved in the organization of complex metabolic processes by which these chemosensory cells contribute to adaptive control mechanisms of the maintenance of homeostasis.

The Hypothalamic Glucagon-Like Peptide 1 Receptor Is Sufficient but Not Necessary for the Regulation of Energy Balance and Glucose Homeostasis in Mice

Pharmacological activation of the hypothalamic glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) promotes weight loss and improves glucose tolerance. This demonstrates that the hypothalamic GLP-1R is sufficient but does not show whether it is necessary for the effects of exogenous GLP-1R agonists (GLP-1RA) or endogenous GLP-1 on these parameters. To address this, we crossed mice harboring floxed Glp1r alleles to mice expressing Nkx2.1-Cre to knock down Glp1r expression throughout the hypothalamus (GLP-1RKD^ΔNkx2.1cre). We also generated mice lacking Glp1r expression specifically in two GLP-1RA-responsive hypothalamic feeding nuclei/cell types, the paraventricular nucleus (GLP-1RKD^ΔSim1cre) and proopiomelanocortin neurons (GLP-1RKD^ΔPOMCcre). Chow-fed GLP-1RKD^ΔNkx2.1cre mice exhibited increased food intake and energy expenditure with no net effect on body weight. When fed a high-fat diet, these mice exhibited normal food intake but elevated energy expenditure, yielding reduced weight gain. None of these phenotypes were observed in GLP-1RKD^ΔSim1cre and GLP-1RKD^ΔPOMCcre mice. The acute anorectic and glucose tolerance effects of peripherally dosed GLP-1RA exendin-4 and liraglutide were preserved in all mouse lines. Chronic liraglutide treatment reduced body weight in chow-fed GLP-1RKD^ΔNkx2.1cre mice, but this effect was attenuated with high-fat diet feeding. In sum, classic homeostatic control regions are sufficient but not individually necessary for the effects of GLP-1RA on nutrient homeostasis.

Harnessing glucagon-like peptide-1 receptor agonists for the pharmacological treatment of overweight and obesity

Over the past 30 years, there has been a dramatic rise in global obesity prevalence, resulting in significant economic and social consequences. Attempts to develop pharmacological agents to treat obesity have met with many obstacles including the lack of long-term effectiveness and the potential for adverse effects. Historically, there have been limited treatment options for overweight and obesity; however, since 2012, a number of new drugs have become available. A number of peptides produced in the gut act as key mediators of the gut-brain axis, which is involved in appetite regulation. This review discusses the role of the gut-brain axis in appetite regulation with special focus on glucagon-like peptide-1. Liraglutide 3.0 mg, a glucagon-like peptide-1 receptor agonist that targets this pathway, is now approved for the treatment of obesity and overweight (body mass index ≥27 kg/m² ) with comorbidities such as type 2 diabetes, high blood pressure, high cholesterol or obstructive sleep apnoea. In addition, other glucagon-like peptide-1 receptor agonists offer promise for obesity management in the future. This review examines how glucagon-like peptide-1 receptor agonists promote weight loss and summarizes the clinical data on weight loss with glucagon-like peptide-1 receptor agonists.

Glucagon-like peptide 1 in the pathophysiology and pharmacotherapy of clinical obesity

Though the pathophysiology of clinical obesity is undoubtedly multifaceted, several lines of clinical evidence implicate an important functional role for glucagon-like peptide 1 (GLP-1) signalling. Clinical studies assessing GLP-1 responses in normal weight and obese subjects suggest that weight gain may induce functional deficits in GLP-1 signalling that facilitates maintenance of the obesity phenotype. In addition, genetic studies implicate a possible role for altered GLP-1 signalling as a risk factor towards the development of obesity. As reductions in functional GLP-1 signalling seem to play a role in clinical obesity, the pharmacological replenishment seems a promising target for the medical management of obesity in clinical practice. GLP-1 analogue liraglutide at a high dose (3 mg/d) has shown promising results in achieving and maintaining greater weight loss in obese individuals compared to placebo control, and currently licensed anti-obesity medications. Generally well tolerated, provided that longer-term data in clinical practice supports the currently available evidence of superior short- and long-term weight loss efficacy, GLP-1 analogues provide promise towards achieving the successful, sustainable medical management of obesity that remains as yet, an unmet clinical need.

The glucagon-like peptide 1 receptor agonist liraglutide attenuates the reinforcing properties of alcohol in rodents

The incretin hormone, glucagon-like peptide 1 (GLP-1), regulates gastric emptying, glucose-dependent stimulation of insulin secretion and glucagon release, and GLP-1 analogs are therefore approved for treatment of type II diabetes. GLP-1 receptors are expressed in reward-related areas such as the ventral tegmental area and nucleus accumbens, and GLP-1 was recently shown to regulate several alcohol-mediated behaviors as well as amphetamine-induced, cocaine-induced and nicotine-induced reward. The present series of experiments were undertaken to investigate the effect of the GLP-1 receptor agonist, liraglutide, on several alcohol-related behaviors in rats that model different aspects of alcohol use disorder in humans. Acute liraglutide treatment suppressed the well-documented effects of alcohol on the mesolimbic dopamine system, namely alcohol-induced accumbal dopamine release and conditioned place preference in mice. In addition, acute administration of liraglutide prevented the alcohol deprivation effect and reduced alcohol intake in outbred rats, while repeated treatment of liraglutide decreased alcohol intake in outbred rats as well as reduced operant self-administration of alcohol in selectively bred Sardinian alcohol-preferring rats. Collectively, these data suggest that GLP-1 receptor agonists could be tested for treatment of alcohol dependence in humans.

Effects of Incretin-Based Therapies on Neuro-Cardiovascular Dynamic Changes Induced by High Fat Diet in Rats

Background and Aims

Obesity promotes cardiac and cerebral microcirculatory dysfunction that could be improved by incretin-based therapies. However, the effects of this class of compounds on neuro-cardiovascular system damage induced by high fat diet remain unclear. The aim of this study was to investigate the effects of incretin-based therapies on neuro-cardiovascular dysfunction induced by high fat diet in Wistar rats.

Methods and Results

We have evaluated fasting glucose levels and insulin resistance, heart rate variability quantified on time and frequency domains, cerebral microcirculation by intravital microscopy, mean arterial blood pressure, ventricular function and mitochondrial swelling. High fat diet worsened biometric and metabolic parameters and promoted deleterious effects on autonomic, myocardial and haemodynamic parameters, decreased capillary diameters and increased functional capillary density in the brain. Biometric and metabolic parameters were better improved by glucagon like peptide-1 (GLP-1) compared with dipeptdyl peptidase-4 (DPP-4) inhibitor. On the other hand, both GLP-1 agonist and DPP-4 inhibitor reversed the deleterious effects of high fat diet on autonomic, myocardial, haemodynamic and cerebral microvascular parameters. GLP-1 agonist and DPP-4 inhibitor therapy also increased mitochondrial permeability transition pore resistance in brain and heart tissues of rats subjected to high fat diet.

Conclusion

Incretin-based therapies improve deleterious cardiovascular effects induced by high fat diet and may have important contributions on the interplay between neuro-cardiovascular dynamic controls through mitochondrial dysfunction associated to metabolic disorders.