Central serotonin participates in the anorexigenic effect of GLP-1 in rainbow trout (Oncorhynchus mykiss)

A circadian clock controls the daily function of the intestine in rainbow trout. Influence of light and food as synchronizers

Environmental factors (daily light/dark cycles, food availability, etc.) entrain endogenous oscillators in living organisms, thereby allowing them to control the rhythms of behavioral and physiological functions, such as energy homeostasis. The gastrointestinal tract (GIT) is the first site of nutrient contact upon food intake. Thus, the GIT is key in energy homeostasis. Circadian oscillators exist within the GIT of mammals, modulating the daily function of the tissue. However, little information in this respect is available for other vertebrates, such as fish. Thus, we aimed to confirm the presence of a circadian oscillator within the GIT of rainbow trout (Oncorhynchus mykiss) and its interaction with locally released hormones that participate in feeding regulation in this species. We subsequently evaluated the role of food and light in synchronizing the rhythmic functioning of the GIT. According to our results, a circadian oscillator exists throughout the GIT of rainbow trout, based on the daily rhythms of clock gene (clock1a, bmal1b, per1, cry2 and reb-ervβ-like) mRNA abundance. Light influences the function of the circadian oscillator within the GIT, but food is a key factor as a synchronizer. The feeding time and the presence and/or absence of food synchronize the rhythmic function of the GIT, as observed for GIT hormones (Ghrelin, Glp1 and Cck). Understanding the functioning of the circadian machinery in peripheral organs such as the GIT will ultimately help to improve different aspects of aquaculture, from farming strategies to welfare, among others.

Vitamin D3 Regulates Energy Homeostasis under Short-Term Fasting Condition in Zebrafish (Danio Rerio)

Vitamin D3 (VD3) is a steroid hormone that plays pivotal roles in pathophysiology, and 1,25(OH)2D3 is the most active form of VD3. In the current study, the crucial role of VD3 in maintaining energy homeostasis under short-term fasting conditions was investigated. Our results confirmed that glucose-depriving pathways were inhibited while glucose-producing pathways were strengthened in zebrafish after fasting for 24 or 48 h. Moreover, VD3 anabolism in zebrafish was significantly suppressed in a time-dependent manner under short-fasting conditions. After fasting for 24 or 48 h, zebrafish fed with VD3 displayed a higher gluconeogenesis level and lower glycolysis level in the liver, and the serum glucose was maintained at higher levels, compared to those fed without VD3. Additionally, VD3 augmented the expression of fatty acids (FAs) transporter cd36 and lipogenesis in the liver, while enhancing lipolysis in the dorsal muscle. Similar results were obtained in cyp2r1-/- zebrafish, in which VD3 metabolism is obstructed. Importantly, it was observed that VD3 induced the production of gut GLP-1, which is considered to possess a potent gluconeogenic function in zebrafish. Meanwhile, the gene expression of proprotein convertase subtilisin/kexin type 1 (pcsk1), a GLP-1 processing enzyme, was also induced in the intestine of short-term fasted zebrafish. Notably, gut microbiota and its metabolite acetate were involved in VD3-regulated pcsk1 expression and GLP-1 production under short-term fasting conditions. In summary, our study demonstrated that VD3 regulated GLP-1 production in zebrafish by influencing gut microbiota and its metabolite, contributing to energy homeostasis and ameliorating hypoglycemia under short-term fasting conditions.

Glucagon-like Peptide-1 Receptor Agonists and Suicidal Ideation: Analysis of Real-Word Data Collected in the European Pharmacovigilance Database

BACKGROUND

A potential risk of suicide associated with liraglutide or semaglutide treatments has recently emerged. Therefore, we decided to investigate the reporting probability of suicidal events among glucagon-like peptide-1 receptor agonists (GLP-1 RAs).

METHODS

A retrospective pharmacovigilance study of the European Pharmacovigilance database was conducted for the period from 1 January 2018 to 10 July 2023. Disproportionality analyses (reporting odds ratio, ROR) were performed to assess the reporting probability of suicidal events among GLP-1 RAs.

RESULTS

A total of 230 reports of suicidal events were identified. The most reported GLP-1 RA was liraglutide (38.3%), followed by semaglutide (36.5%) and dulaglutide (16.1%). The most reported events were suicidal ideation (65.3%) and suicide attempt (19.5%). Disproportionality analysis found a higher reporting probability of suicidal events for semaglutide than dulaglutide (ROR, 2.05; 95%CI, 1.40-3.01) and exenatide (ROR, 1.81; 95%CI, 1.08-3.05). In the same way, liraglutide was associated with a higher reporting probability of suicidal events than dulaglutide (ROR, 3.98; 95%CI, 2.73-5.82) and exenatide (ROR, 3.52; 95%CI, 2.10-5.92). On the contrary, a lower reporting probability was found for semaglutide than liraglutide (ROR, 0.51; 95%CI, 0.38-0.69).

CONCLUSIONS

Suicidal events were mostly reported with semaglutide and liraglutide, which were also associated with significantly higher reporting probabilities compared to other GLP1 RAs. Although this study provides the reporting frequencies of suicide-related events with GLP-1 RAs, establishing causality requires further investigation, which will probably be addressed by the Pharmacovigilance Risk Assessment Committee of the European Medicine Agency in the future.

Unraveling the periprandial changes in brain serotonergic activity and its correlation with food intake-related neuropeptides in rainbow trout Oncorhynchus mykiss

This study explored changes in brain serotonin content and activity together with hypothalamic neuropeptide mRNA abundance around feeding time in rainbow trout, as well as the effect of one-day fasting. Groups of trout fed at two (ZT2) and six (ZT6) hours after lights on were sampled from 90 minutes before to 240 minutes after feeding, while additional groups of non-fed trout were also included in the study. Changes in brain amine and metabolite contents were measured in hindbrain, diencephalon and telencephalon, while in the diencephalon the mRNA abundance of tryptophan hydroxylase (tph1, tph2), serotonin receptors (5htr1a, 5htr1b and 5htr2c) and several neuropeptides (npy, agrp1, cartpt, pomca1, crfb) involved in the control of food intake were also assessed. The results showed changes in the hypothalamic neuropeptides that were consistent with the expected role for each in the regulation of food intake in rainbow trout. Serotonergic activity increased rapidly at the time of food intake in the diencephalon and hindbrain and remained high for much of the postprandial period. This increase in serotonin abundance was concomitant with elevated levels of pomca1 mRNA in the diencephalon, suggesting that serotonin might act on brain neuropeptides to promote a satiety profile. Furthermore, serotonin synthesis and neuronal activity appear to increase already before the time of feeding, suggesting additional functions for this amine before and during food intake. Exploration of serotonin receptors in the diencephalon revealed only small changes for gene expression of 5htr1b and 5htr2c receptors during the postprandial phase. Therefore, the results suggest that serotonin may play a relevant role in the regulation of feeding behavior in rainbow trout during periprandial time, but a better understanding of its interaction with brain centers involved in receiving and processing food-related signals is still needed.

Obesity Impairs Cognitive Function with No Effects on Anxiety-like Behaviour in Zebrafish

Over the last decade, the zebrafish has emerged as an important model organism for behavioural studies and neurological disorders, as well as for the study of metabolic diseases. This makes zebrafish an alternative model for studying the effects of energy disruption and nutritional quality on a wide range of behavioural aspects. Here, we used the zebrafish model to study how obesity induced by overfeeding regulates emotional and cognitive processes. Two groups of fish (n = 24 per group) were fed at 2% (CTRL) and 8% (overfeeding-induced obesity, OIO) for 8 weeks and tested for anxiety-like behaviour using the novel tank diving test (NTDT). Fish were first tested using a short-term memory test (STM) and then trained for four days for a long-term memory test (LTM). At the end of the experiment, fish were euthanised for biometric sampling, total lipid content, and triglyceride analysis. In addition, brains (eight per treatment) were dissected for HPLC determination of monoamines. Overfeeding induced faster growth and obesity, as indicated by increased total lipid content. OIO had no effect on anxiety-like behaviour. Animals were then tested for cognitive function (learning and memory) using the aversive learning test in Zantiks AD units. Results show that both OIO and CTRL animals were able to associate the aversive stimulus with the conditioned stimulus (conditioned learning), but OIO impaired STM regardless of fish sex, revealing the effects of obesity on cognitive processes in zebrafish. Obese fish did not show a deficiency in monoaminergic transmission, as revealed by quantification of total brain levels of dopamine and serotonin and their metabolites. This provides a reliable protocol for assessing the effect of metabolic disease on cognitive and behavioural function, supporting zebrafish as a model for behavioural and cognitive neuroscience.

Study on the Hyperglycemic Effect of GLP-1 in Spinibarbus denticulatus by Oral Administration and Intraperitoneal Injection Methods

Glucagon-like peptide-1 (GLP-1), one of the expression products of the proglucagon (pg) gene, is an incretin mainly secreted by the gastrointestinal system. In mammals, GLP-1 has hypoglycemic and food-inhibiting effects; while in some fish species, it has been confirmed to increase blood glucose by promoting gluconeogenesis and stimulating glycogenolysis. In order to more deeply understand the role of GLP-1 in the process of glycometabolism in herbivorous fish, the pg gene was cloned from Spinibarbus denticulatus to obtain its sequence characteristics, and the changes in blood glucose level and pg gene expression in S. denticulatus were further explored by feeding with three kinds of carbohydrates and intraperitoneal injection of GLP-1. Basal and temporal blood glucose levels and pg gene expression of S. denticulatus (91.68 ± 10.79 g) were measured at 0, 1, 3, 5, 7, and 12 h after oral administration (n = 4). Then, the changes of blood glucose levels and pg and glucokinase (gk) gene expressions of S. denticulatus (94.29 ± 10.82 g) were determined at 0, 30, 60, and 120 min after intraperitoneal injection (n = 4). It was shown that polysaccharides could induce the upregulation of pg gene expression faster than monosaccharides and stimulate the secretion of GLP-1 in the intestine. Intraperitoneal injection of GLP-1 peptide rapidly raised blood glucose levels, and pg gene expression in the anterior intestine, whole brain, and hepatopancreas decreased continuously after 30 minutes. These results showed that S. denticulatus might inhibit the excessive accumulation of blood glucose by reducing the expression of the pg gene and increasing the expression of gk gene in a short time. It was speculated that GLP-1 of S. denticulatus might have a "gut-brain-liver" pathway similar to mammals in glycemia regulation. Therefore, this study provided a novel perspective for explaining the functional differences of GLP-1 in herbivorous fish and mammals.

Efficacy of non-pharmacological interventions to reduce pain in people with dementia: A systematic review and meta-analysis

AIMS AND OBJECTIVES

To identify the efficacy of non-pharmacological interventions designed to reduce pain in people with dementia.

BACKGROUND

Pain is prevalent among patients with dementia but frequently remains untreated. Although non-pharmacological interventions have been used to reduce pain in people with dementia, the efficacy of these interventions for pain management in people with dementia has not been thoroughly synthesised.

DESIGN

Systematic review and meta-analysis.

METHODS

The study was conducted in accordance with PRISMA guidelines and Cochrane criteria for systematic reviews. A comprehensive search was performed using the Academic Search Complete, CINAHL, Cochrane Library, EMBASE, MEDLINE, PubMed, OVID and Web of Science databases, from databases inception to 13 March 2022. The modified Cochrane risk-of-bias tool (ROB-2) was used to evaluate the methodological quality of each included study. Standardised mean differences (SMDs) with 95% confidence intervals (CIs) were synthesised using a random-effects model to assess the efficacy of non-pharmacological interventions for reducing pain in people with dementia (using Stata 16.0).

RESULTS

The final analysis assessed 12 studies, including 989 persons with dementia. Non-pharmacological interventions were found to reduce pain in 4-8 weeks after the interventions (SMD: -0.32; 95% CI: -0.62 to -0.02). However, the effects of intervention frequency and patient age remain unknown.

CONCLUSIONS

Non-pharmacological interventions are effective for reducing pain in people with dementia. Further investigations remain necessary to explore the effectiveness of specific non-pharmacological therapies for pain reduction in people with dementia (e.g. aromatherapy, play activity, singing or robotic care).

RELEVANCE TO CLINICAL PRACTICE

The findings of this study can guide healthcare practitioners when considering the use of non-pharmacological pain management methods for people with dementia and may improve the implementation of these methods in clinical practice.

PATIENT OR PUBLIC CONTRIBUTIONS

The study suggests non-pharmacological interventions to reduce pain and underlines the relevance of health provider's viewpoints. The types, duration and length of follow-up of non-pharmacological interventions can be offered based on patient's conditions and the standard of clinical practice.