Gluco-metabolic effects of oral and intravenous alcohol administration in men

Alcohol-induced fibroblast growth factor 21 secretion is increased in individuals with alcohol use disorder

BACKGROUND

Alcohol use disorder (AUD) affects 5% of the global population. Despite its high prevalence, the pathophysiology of AUD remains enigmatic, hindering the development of novel therapeutics. Interestingly, the liver hormone fibroblast growth factor 21 (FGF21), which is currently in late-stage clinical trials for the treatment of non-alcoholic steatohepatitis, has been implicated by recent genome-wide association studies as a regulator of alcohol consumption.

METHODS

This study aimed to evaluate plasma responses of FGF21 to an alcohol challenge in three groups: 15 males with AUD, 15 healthy males with a father with AUD (Predisposed), and 15 healthy males without any predisposition to AUD (Controls). All participants were investigated after an overnight fast. Assessments, including blood sampling and visual analog scale-assessed desire for alcohol intake, were performed before and for 10 h after ingesting 0.5 g alcohol per kg body weight over 10 min.

RESULTS

The three groups were age and body-mass index-matched and had normal plasma concentrations of transaminases and FibroScan®-assessed elastography. Baseline FGF21 concentrations did not differ between groups, but individuals with AUD exhibited greater FGF21 responses to alcohol (area under the curve (AUC0-600 min): 954 ± 665 ng/ml × min (mean (standard deviation)) compared to Controls (AUC0-600 min: 453 ± 333 ng/ml × min, P = 0.03) but not Predisposed (AUC0-600 min: 556 ± 429 ng/ml × min, P = 0.11).

CONCLUSION

In conclusion, we demonstrate greater alcohol-induced FGF21 responses in individuals with AUD compared to healthy individuals without paternal predisposition to AUD, suggesting a role for FGF21 in AUD pathophysiology.

The glucagon-like peptide-1 and other endocrine responses to alcohol ingestion in women with versus without metabolic surgery

Glucagon-like peptide-1 (GLP-1)-based therapies, effective in treating obesity and type 2 diabetes, hold potential for reducing alcohol-seeking behaviour. However, the understanding of how alcohol consumption affects endogenous GLP-1 responses-important for understanding GLP-1-based therapies' potential in addressing alcohol misuse-is limited, given the absence of placebo-controlled studies examining these effects. This study aimed to determine the acute effects of alcohol ingestion on GLP-1 and other peptides and evaluate whether metabolic surgery, which increases GLP-1 responses, blood alcohol concentrations (BAC) and alcohol misuse risk, influences this effect. Additionally, we assessed the acute effects of alcohol on plasma glucose and insulin concentrations. Using a placebo-controlled crossover study, we examined hormonal and glucose responses after oral alcohol consumption (0.5 g/kg of fat-free mass) versus placebo drinks in 18 women who underwent metabolic surgery <5 years ago and in 14 non-operated controls (equivalent in age, body mass index [BMI], race and alcohol consumption patterns). Women had a mean (SD) age of 41 (10) years and a BMI of 33 (5) kg/m2. Compared with the control group, the surgery group exhibited a higher peak BAC (0.99 [0.20] g/L vs. 0.75 [0.16] g/L; P < 0.005). Alcohol decreased GLP-1 by 34% (95% CI, 16%-52%) in both groups and decreased ghrelin more in the control (27%) than in the surgery group (13%). Alcohol modestly decreased plasma glucose and transiently increased insulin secretion in both groups (P < 0.05). However, alcohol lowered blood glucose concentrations to the hypoglycaemic range in 28% of the women in the surgery group versus none in the control group. These findings provide compelling evidence that acute alcohol consumption decreases GLP-1, a satiation signal, elucidating alcohol's 'apéritif' effect. This study also highlights the potential increase in alcohol-related hypoglycaemic effects after metabolic surgery.

IUPHAR review - Glucagon-like peptide-1 (GLP-1) and substance use disorders: An emerging pharmacotherapeutic target

Addiction is a chronic relapsing disease with high morbidity and mortality. Treatments for addiction include pharmacological and psychosocial interventions; however, currently available medications are limited in number and efficacy. The glucagon-like-peptide-1 (GLP-1) system is emerging as a potential novel pharmacotherapeutic target for alcohol and other substance use disorders (ASUDs). In this review, we summarize and discuss the wealth of available evidence from testing GLP-1 receptor (GLP-1R) agonist medications in preclinical models and humans with ASUDs, possible mechanisms underlying the impact of GLP-1R agonists on alcohol/substance use, gaps in knowledge, and future directions. Most of the research with GLP-1R agonists has been conducted in relation to alcohol use; psychostimulants, opioids, and nicotine have also been investigated. Preclinical evidence suggests that GLP-1R agonists reduce alcohol/substance use and other related outcomes. The main proposed mechanisms are related to reward processing, stress, and cognitive function, as well as broader mechanisms related to satiety, changes in gastric motility, and glucose homeostasis. More in-depth mechanistic studies are warranted. Clinical studies have been limited and their findings have been less conclusive; however, most support the safety and potential efficacy of GLP-1R agonists in ASUD treatment. Identifying preferred compounds, as well as possible subgroups who are most responsive to GLP-1R agonists are some of the key research questions to translate the promising preclinical data into clinical settings. Several clinical trials are underway to test GLP-1R agonists in people with ASUDs.

The Association of Cardiometabolic, Diet and Lifestyle Parameters With Plasma Glucagon-like Peptide-1: An IMI DIRECT Study

CONTEXT

The role of glucagon-like peptide-1 (GLP-1) in type 2 diabetes (T2D) and obesity is not fully understood.

OBJECTIVE

We investigate the association of cardiometabolic, diet, and lifestyle parameters on fasting and postprandial GLP-1 in people at risk of, or living with, T2D.

METHODS

We analyzed cross-sectional data from the two Innovative Medicines Initiative (IMI) Diabetes Research on Patient Stratification (DIRECT) cohorts, cohort 1 (n = 2127) individuals at risk of diabetes; cohort 2 (n = 789) individuals with new-onset T2D.

RESULTS

Our multiple regression analysis reveals that fasting total GLP-1 is associated with an insulin-resistant phenotype and observe a strong independent relationship with male sex, increased adiposity, and liver fat, particularly in the prediabetes population. In contrast, we showed that incremental GLP-1 decreases with worsening glycemia, higher adiposity, liver fat, male sex, and reduced insulin sensitivity in the prediabetes cohort. Higher fasting total GLP-1 was associated with a low intake of wholegrain, fruit, and vegetables in people with prediabetes, and with a high intake of red meat and alcohol in people with diabetes.

CONCLUSION

These studies provide novel insights into the association between fasting and incremental GLP-1, metabolic traits of diabetes and obesity, and dietary intake, and raise intriguing questions regarding the relevance of fasting GLP-1 in the pathophysiology T2D.

The crosstalk between fibroblast growth factor 21 (FGF21) system and substance use

Existing literature indicates that communication between the central nervous system and the peripheral nervous system is disrupted by substance use disorders (SUDs), including alcohol use disorder (AUD). Fibroblast growth factor 21 (FGF21), a liver-brain axis hormone governing energy homeostasis, has been shown to modulate alcohol intake/preference and other substances. To further elucidate the relationship between FGF21, alcohol use, and other substance use, we conducted a scoping review to explore the association between FGF21 and SUDs. Increases in FGF21 reduce alcohol consumption while suppressing FGF21 increases alcohol consumption, demonstrating an inverse relationship. Alcohol elevates FGF21 levels primarily via the liver, subsequently promoting neuronal signals to curb alcohol intake. FGF21 activation engages molecular pathways that defend against alcohol-induced fat accumulation, oxidative stress, and inflammation. Considering the bidirectional association between FGF21 and alcohol, further studies on the FGF21 system as a potential pharmacotherapy for AUD and alcohol-associated liver disease are warranted.

A human laboratory study on the link between alcohol administration and circulating fibroblast growth factor 21 (FGF21) in individuals with alcohol use disorder

Growing evidence indicates that the crosstalk between the central nervous system and the periphery plays an important role in the pathophysiology of neuropsychiatric conditions, including addictive disorders. Fibroblast growth factor 21 (FGF21) is part of the liver-brain axis and regulates energy homeostasis, metabolism, and macronutrient intake. In addition, FGF21 signaling modulates alcohol intake and preference, and changes in FGF21 levels are observed following alcohol consumption. To further elucidate the relationship between alcohol use and FGF21, we assessed serum FGF21 concentrations in 16 non-treatment seeking individuals with alcohol use disorder (AUD) in a naturalistic outpatient setting, as well as a controlled laboratory experiment that included alcohol cue-reactivity, alcohol priming, and alcohol self-administration in a bar-like setting. FGF21 levels were stable during the outpatient phase when participants received placebo and had no significant lifestyle changes. During the bar-like laboratory experiment, a robust increase in serum FGF21 concentrations was found after the 2-hr alcohol self-administration session (F3, 49 = 23.39, p < 0.001). Percent change in FGF21 levels positively correlated with the amount of alcohol self-administered but did not reach statistical significance. No significant changes in FGF21 levels were found after exposure to alcohol cues or consuming the priming drink. Given the bidirectional link between FGF21 and alcohol, targeting the FGF21 system may be further examined as a potential pharmacotherapy for AUD.

Close association between lifestyle and circulating FGF21 levels: A systematic review and meta-analysis

Background

The impact of lifestyle factors on circulating fibroblast growth factor 21 (cFGF21) remains unclear. We conducted this systematic review and meta-analysis to evaluate the association between lifestyle factors and cFGF21 levels.

Methods

We included studies that evaluated the effects of different lifestyles on cFGF21 concentration in adults, which included smoking, exercise, diets, alcohol consumption and weight loss. Random effects models or fixed effects models were used for meta-analysis to calculate the standardized mean difference (SMD) and 95% confidence interval according to the heterogeneity among studies. Study quality was assessed using the Newcastle-Ottawa Scale for cohort studies, the Joanna Briggs Institution Checklist for cross-sectional studies, and the PEDro scale for experimental studies.

Results

A total of 50 studies with 1438 individuals were included. Overall, smoking, a hypercaloric carbohydrate-rich diet, a hypercaloric fat-rich diet, amino acid or protein restriction, excessive fructose intake and alcohol consumption significantly upregulated cFGF21 levels (p<0.05), whereas fish oil intake and calorie restriction with sufficient protein intake significantly decreased cFGF21 (p<0.05). Compared to the preexercise cFGF21 level, the cFGF21 level significantly increased within 3 hours postexercise (p<0.0001), while it significantly decreased in the blood sampled >6 h postexercise (p=0.01). Moreover, higher exercise intensity resulted in higher upregulation of cFGF21 at 1-hour post exercise (p=0.0006).

Conclusion

FGF21 could serve as a potential biomarker for the assessment of different lifestyle interventions. When it is used for this purpose, a standard study protocol needs to be established, especially taking into consideration the intervention types and the sampling time post-intervention.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021254758, identifier CRD42021254758.

The role of glucagon-like peptide 1 (GLP-1) in addictive disorders

Drug-, alcohol- and tobacco use disorders are a global burden affecting millions of people. Despite decades of research, treatment options are sparse or missing, and relapse rates are high. Glucagon-like peptide-1 (GLP-1) is released in the small intestines, promotes blood glucose homeostasis, slows gastric emptying, and reduces appetite. GLP-1 receptor agonists approved for treating type 2 diabetes mellitus and obesity, have received attention as a potential anti-addiction treatment. Studies in rodents and non-human primates have demonstrated a reduction in intake of alcohol and drugs of abuse, and clinical trials have been initiated to investigate whether the preclinical findings can be translated to patients. This review will give an overview of current findings and discuss the possible mechanisms of action. We suggest that effects of GLP-1 in alcohol- and substance use disorder is mediated centrally, at least partly through dopamine signalling, but precise mechanisms are still to be uncovered.

The effect of acute intragastric vs. intravenous alcohol administration on inflammation markers, blood lipids and gallbladder motility in healthy men

Ethanol intake increases plasma concentrations of triglycerides and chronic ethanol use impairs lipid metabolism and causes chronic inflammation. The gut plays an important role in metabolic handling of nutrients, including lipids, and a leaky gut associated with alcohol intake, allowing inflammatory signals to the portal vein, has been proposed to constitute a mechanism by which ethanol induces hepatic inflammation. We compared the effects of enteral and parenteral administration of ethanol on a range of circulating inflammation markers (including soluble CD163, a marker of liver macrophage activation), lipids, cholecystokinin (CCK) and fibroblast growth factor 19 (FGF19) as well as gallbladder volume. On two separate and randomized study days, we subjected healthy men (n = 12) to double-blinded intragastric ethanol infusion (IGEI) and isoethanolemic intravenous ethanol infusion (IVEI). Blood was sampled and ultrasonographic evaluation of gallbladder volume was performed at frequent intervals for 4 h after initiation of ethanol administration on both days. Little or no effects were observed on plasma levels of inflammation markers during IGEI and IVEI, respectively. Circulating levels of total, low-density lipoprotein and high-density lipoprotein cholesterol decreased after ethanol administration independently of the administration form. Triglyceride and very low-density lipoprotein (VLDL) cholesterol concentrations increased more after IGEI compared to IVEI. IVEI had no effect on plasma CCK and caused an increased gallbladder volume whereas IGEI elicited a CCK response (P < 0.0001) without affecting gallbladder volume. Circulating FGF19 concentrations decreased equally in response to both ethanol administration forms. In conclusion, by evaluating a range of circulating inflammation markers during IGEI and IVEI we were not able to detect signs of systemic low-grade inflammation originating from the presence of ethanol in the gut. IVEI increased gallbladder volume whereas IGEI increased plasma CCK (with neutral effect on gallbladder volume), increased plasma VLDL cholesterol and triglyceride concentrations; indicating that the enteral route of administration may influence ethanol's effects on lipid metabolism.

FGF21 and the Physiological Regulation of Macronutrient Preference

The ability to respond to variations in nutritional status depends on regulatory systems that monitor nutrient intake and adaptively alter metabolism and feeding behavior during nutrient restriction. There is ample evidence that the restriction of water, sodium, or energy intake triggers adaptive responses that conserve existing nutrient stores and promote the ingestion of the missing nutrient, and that these homeostatic responses are mediated, at least in part, by nutritionally regulated hormones acting within the brain. This review highlights recent research that suggests that the metabolic hormone fibroblast growth factor 21 (FGF21) acts on the brain to homeostatically alter macronutrient preference. Circulating FGF21 levels are robustly increased by diets that are high in carbohydrate but low in protein, and exogenous FGF21 treatment reduces the consumption of sweet foods and alcohol while alternatively increasing the consumption of protein. In addition, while control mice adaptively shift macronutrient preference and increase protein intake in response to dietary protein restriction, mice that lack either FGF21 or FGF21 signaling in the brain fail to exhibit this homeostatic response. FGF21 therefore mediates a unique physiological niche, coordinating adaptive shifts in macronutrient preference that serve to maintain protein intake in the face of dietary protein restriction.