Fibroblast growth factor 21: an endocrine inhibitor of sugar and alcohol appetite

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 study on the early metabolic effects of salt and fructose consumption: the protective role of water

Increasing serum osmolality has recently been linked with acute stress responses, which over time can lead to increased risk for obesity, hypertension, and other chronic diseases. Salt and fructose are two major stimuli that can induce acute changes in serum osmolality. Here we investigate the early metabolic effects of sodium and fructose consumption and determine whether the effects of sodium or fructose loading can be mitigated by blocking the change in osmolality with hydration. Forty-four healthy subjects without disease and medication were recruited into four groups. After overnight fasting, subjects in Group 1 drank 500 mL of salty soup, while those in Group 2 drank 500 mL of soup without salt for 15 min. Subjects in Group 3 drank 500 mL of 100% apple juice in 5 min, while subjects in Group 4 drank 500 mL of 100% apple juice and 500 mL of water in 5 min. Blood pressure (BP), plasma sodium, and glucose levels were measured every 15 min in the first 2 h. Serum and urine osmolarity, serum uric acid, cortisol, fibroblast growth factor 21 (FGF21), aldosterone, adrenocorticotropic hormone (ACTH) level, and plasma renin activity (PRA) were measured at the baseline and 2 h. Both acute intake of salt or fructose increased serum osmolality (maximum ∼4 mOsm/L peaking at 75 min) associated with a rise in systolic and diastolic BP, PRA, aldosterone, ACTH, cortisol, plasma glucose, uric acid, and FGF21. Salt tended to cause greater activation of the renin-angiotensin-system (RAS), while fructose caused a greater rise in glucose and FGF21. In both cases, hydration could prevent the osmolality and largely block the acute stress response. Acute changes in serum osmolality can induce remarkable activation of the ACTH-cortisol, RAS, glucose metabolism, and uric acid axis that is responsive to hydration. In addition to classic dehydration, salt, and fructose-containing sugars can activate these responses. Staying well hydrated may provide benefits despite exposure to sugar and salt. More studies are needed to investigate whether hydration can block the chronic effects of sugar and salt on disease.

Resting energy metabolism and sweet taste preference during the menstrual cycle in healthy women

Differences in blood concentration of sex hormones in the follicular (FP) and luteal (LP) phases may influence energy metabolism in women. We compared fasting energy metabolism and sweet taste preference on a representative day of the FP and LP in twenty healthy women (25·3 (sd 5·1) years, BMI: 22·2 (sd 2·2) kg/m2) with regular self-reported menses and without the use of hormonal contraceptives. From the self-reported duration of the three prior menstrual cycles, the predicted FP and LP visits were scheduled for days 5-12 and 20-25 after menses, respectively. The order of the FP and LP visits was randomly assigned. On each visit, RMR and RQ by indirect calorimetry, sweet taste preference by the Monell two-series forced-choice tracking procedure, serum fibroblast growth factor 21 by a commercial ELISA (FGF21, a liver-derived protein with action in energy balance, fuel oxidation and sugar preference) and dietary food intake by a 24-h dietary recall were determined. Serum progesterone and oestradiol concentrations displayed the expected differences between phases. RMR was lower in the FP v. LP (5042 (sd 460) v. 5197 (sd 490) kJ/d, respectively; P = 0·04; Cohen effect size, d rm = 0·33), while RQ showed borderline significant higher values (0·84 (sd 0·05) v. 0·81 (sd 0·05), respectively; P = 0·07; d rm = 0·62). Also, in the FP v. LP, sweet taste preference was lower (12 (sd 8) v. 16 (sd 9) %; P = 0·04; d rm = 0·47) concomitant with higher serum FGF21 concentration (294 (sd 164) v. 197 (sd 104) pg/ml; P < 0·01; d rm = 0·66). The menstrual cycle is associated with changes in energy expenditure, sweet taste preference and oxidative fuel partitioning.

Fibroblast Growth Factor 21 Relieves Lipopolysaccharide-Induced Acute Lung Injury by Suppressing JAK2/STAT3 Signaling Pathway

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a life-threatening disease without an effective drug at present. Fibroblast growth factor 21 (FGF21) was reported to be protective against inflammation in metabolic disease in recent studies. However, the role of FGF21 in ALI has been rarely investigated. In this study, it was found that the expression of FGF21 was markedly increased in lung tissue under lipopolysaccharide (LPS) stimulation in vivo, whereas it was decreased in lung epithelial cells under LPS stimulation in vitro. Therefore, our research aimed to elucidate the potential role of FGF21 in LPS-induced ALI and to detect possible underlying mechanisms. The results revealed that the deficiency of FGF21 aggravated pathological damage, inflammatory infiltration, and pulmonary function in LPS-induced ALI, while exogenous administration of FGF21 improved these manifestations. Moreover, through RNA sequencing and enrichment analysis, it was unveiled that FGF21 might play a protective role in LPS-induced ALI via JAK2/STAT3 signaling pathway. The therapeutic effect of FGF21 was weakened after additional usage of JAK2 activator in vivo. Further investigation revealed that FGF21 significantly inhibited STAT3 phosphorylation and impaired the nuclear translocation of STAT3 in vitro. In addition, the aggravation of inflammation caused by silencing FGF21 can be alleviated by JAK2 inhibitor in vitro. Collectively, these findings unveil a potent protective effect of FGF21 against LPS-induced ALI by inhibiting the JAK2/STAT3 pathway, implying that FGF21 might be a novel and effective therapy for ALI.

Development and Characterization of a Cancer Cachexia Rat Model Transplanted with Cells of the Rat Lung Adenocarcinoma Cell Line Sato Lung Cancer (SLC)

Cancer cachexia is a complex malnutrition syndrome that causes progressive dysfunction. This syndrome is accompanied by protein and energy losses caused by reduced nutrient intake and the development of metabolic disorders. As many as 80% of patients with advanced cancer develop cancer cachexia; however, an effective targeted treatment remains to be developed. In this study, we developed a novel rat model that mimics the human pathology during cancer cachexia to elucidate the mechanism underlying the onset and progression of this syndrome. We subcutaneously transplanted rats with SLC cells, a rat lung adenocarcinoma cell line, and evaluated the rats' pathophysiological characteristics. To ensure that our observations were not attributable to simple starvation, we evaluated the characteristics under tube feeding. We observed that SLC-transplanted rats exhibited severe anorexia, weight loss, muscle atrophy, and weakness. Furthermore, they showed obvious signs of cachexia, such as anemia, inflammation, and low serum albumin. The rats also exhibited weight and muscle losses despite sufficient nutrition delivered by tube feeding. Our novel cancer cachexia rat model is a promising tool to elucidate the pathogenesis of cancer cachexia and to conduct further research on the development of treatments and supportive care for patients with this disease.

3-Month Post-Operative Increase in FGF21 is Predictive of One-Year Weight Loss After Bariatric Surgery

PURPOSE

The association between bariatric surgery outcome and blood levels of fibroblast growth factor 21 (FGF21) remains controversial. Many patients displayed stable or decreased FGF21 one year after bariatric surgery. Nevertheless, there is often an early increase FGF21 concentration in the post-surgery period. The aim of this study was to investigate the relationship between 3-month FGF21 response and percentage total weight loss at one year after bariatric surgery.

MATERIALS AND METHODS

In this prospective monocentric study, a total of 144 patients with obesity grade 2-3 were included; 61% of them underwent a sleeve gastrectomy and 39% a Roux-en-Y gastric bypass. Data analysis was carried out to determine the relation between 3-month plasma FGF21 response and weight loss one year after bariatric surgery. Multiple adjustments were done including degree of weight loss after 3 months.

RESULTS

FGF21 significantly increased between baseline and Month 3 (n = 144, p < 10-3), then decreased between Month 3 and Month 6 (n = 142, p = 0.047) and was not different from baseline at Month 12 (n = 142, p = 0.86). The 3-month-FGF21 response adjusted to body weight loss was not different between types of bariatric surgery. The 3-month-FGF21 response was associated to body weight loss at Month 6 (r = -0.19, p = 0.02) and Month 12 (r = -0.34, p < 10-4). After multiple regression analysis, only Month 12 body weight loss remained associated to 3-month FGF21 response (r = -0.3, p = 0.02).

CONCLUSION

This study showed that the magnitude of changes in FGF21 at 3 months after bariatric surgery emerged as an independent predictor of one-year body weight loss irrespective of the type of surgery.

Potential Correlation between Changes in Serum FGF21 Levels and Lenvatinib-Induced Appetite Loss in Patients with Unresectable Hepatocellular Carcinoma

Lenvatinib, used for unresectable hepatocellular carcinoma (HCC), causes appetite loss, but the underlying mechanisms, clinical impact, and predictive factors have been unclear. The endocrine factor FGF21 modulates appetite and is involved in cachexia. We evaluated the association between FGF21 level changes during lenvatinib treatment for unresectable HCC and appetite loss. Sixty-three eligible unresectable HCC patients who started lenvatinib treatment between 2018 and 2021 were included. We analyzed FGF21 levels at baseline; 1, 2, and 4 weeks after lenvatinib initiation, and before the onset of appetite loss. Grade ≥ 2 lenvatinib-induced appetite loss led to liver functional reserve deterioration at disease progression and a poor prognosis. Baseline characteristics and serum FGF21 levels were similar between patients with and without appetite loss. However, the serum FGF21 change rate increased significantly at 4 weeks post-lenvatinib initiation in patients with grade ≥ 2 appetite loss, as compared to those without appetite loss. Similar significant increases in the serum FGF21 level change rate were observed prior to grade ≥ 2 appetite loss onset. This suggests that changes in FGF21 levels can be used to predict patients with a greater risk of marked appetite loss and provides insights into the mechanisms underlying lenvatinib-induced appetite loss in patients with HCC.

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.

The association of circulating fibroblast growth factor 21 levels with incident heart failure: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Fibroblast growth factor 21 (FGF21) levels are often elevated in heart failure (HF), although this has not been assessed using a longitudinal study design. Therefore, we investigated the association between baseline plasma FGF21 levels and incident HF in the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS

A total of 5408 participants, free of clinically apparent cardiovascular disease, were included in the analysis, of which 342 developed HF over a median follow-up period of 16.7 years. Multivariable Cox regression analysis was performed and the additive value of FGF21 in the performance of risk prediction over other well-established cardiovascular biomarkers was assessed.

RESULTS

The mean age of the participants was 62.6 years with 47.6 % male. Regression spline analysis demonstrated a significant association of FGF21 levels with incident HF among participants with FGF21 levels ≥239.0 pg/mL (hazard ratio = 1.84 [95 % confidence interval 1.21, 2.80] per SD increase in ln-transformed levels) after adjustment for traditional cardiovascular risk factors and biomarkers, but not in participants with FGF21 levels <239.0 pg/mL (p for heterogeneity = 0.004). Among participants with FGF21 levels ≥239.0 pg/mL, FGF21 levels were associated with HF with preserved ejection fraction (HR [95 % CI] = 2.57 [1.51, 4.37]), but not HF with reduced ejection fraction.

CONCLUSIONS

The present study suggests baseline FGF21 levels could predict the development of incident HF with preserved ejection fraction, among participants with elevated FGF21 levels at baseline. This study may suggest a pathophysiological role of FGF21 resistance in HF with preserved ejection fraction.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Fibroblast Growth Factor 21 Facilitates the Homeostatic Control of Feeding Behavior

Fibroblast growth factor 21 (FGF21) is a stress hormone that is released from the liver in response to nutritional and metabolic challenges. In addition to its well-described effects on systemic metabolism, a growing body of literature now supports the notion that FGF21 also acts via the central nervous system to control feeding behavior. Here we review the current understanding of FGF21 as a hormone regulating feeding behavior in rodents, non-human primates, and humans. First, we examine the nutritional contexts that induce FGF21 secretion. Initial reports describing FGF21 as a ‘starvation hormone’ have now been further refined. FGF21 is now better understood as an endocrine mediator of the intracellular stress response to various nutritional manipulations, including excess sugars and alcohol, caloric deficits, a ketogenic diet, and amino acid restriction. We discuss FGF21’s effects on energy intake and macronutrient choice, together with our current understanding of the underlying neural mechanisms. We argue that the behavioral effects of FGF21 function primarily to maintain systemic macronutrient homeostasis, and in particular to maintain an adequate supply of protein and amino acids for use by the cells.

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.

Physiological Changes and Pathological Pain Associated with Sedentary Lifestyle-Induced Body Systems Fat Accumulation and Their Modulation by Physical Exercise

A sedentary lifestyle is associated with overweight/obesity, which involves excessive fat body accumulation, triggering structural and functional changes in tissues, organs, and body systems. Research shows that this fat accumulation is responsible for several comorbidities, including cardiovascular, gastrointestinal, and metabolic dysfunctions, as well as pathological pain behaviors. These health concerns are related to the crosstalk between adipose tissue and body systems, leading to pathophysiological changes to the latter. To deal with these health issues, it has been suggested that physical exercise may reverse part of these obesity-related pathologies by modulating the cross talk between the adipose tissue and body systems. In this context, this review was carried out to provide knowledge about (i) the structural and functional changes in tissues, organs, and body systems from accumulation of fat in obesity, emphasizing the crosstalk between fat and body tissues; (ii) the crosstalk between fat and body tissues triggering pain; and (iii) the effects of physical exercise on body tissues and organs in obese and non-obese subjects, and their impact on pathological pain. This information may help one to better understand this crosstalk and the factors involved, and it could be useful in designing more specific training interventions (according to the nature of the comorbidity).

Does FGF21 Mediate the Potential Decrease in Sweet Food Intake and Preference Following Bariatric Surgery?

The liver-derived hormone fibroblast growth factor 21 (FGF21) has recently been linked to preference for sweet-tasting food. We hypothesized, that surgery-induced changes in FGF21 could mediate the reduction in sweet food intake and preference following bariatric surgery. Forty participants (35 females) with severe obesity (BMI ≥ 35 kg/m²) scheduled for roux-en-y gastric bypass (n = 30) or sleeve gastrectomy (n = 10) were included. Pre- and postprandial responses of intact plasma FGF21 as well as intake of sweet-tasting food assessed at a buffet meal test, the hedonic evaluation of sweet taste assessed using an apple juice with added sucrose and visual analog scales, and sweet taste sensitivity were assessed before and 6 months after bariatric surgery. In a cross-sectional analysis pre-surgery, pre- and postprandial intact FGF21 levels were negatively associated with the hedonic evaluation of a high-sucrose juice sample (p = 0.03 and p = 0.02). However, no changes in pre- (p = 0.24) or postprandial intact FGF21 levels were found 6 months after surgery (p = 0.11), and individual pre- to postoperative changes in pre- and postprandial intact FGF21 levels were not found to be associated with changes in intake of sweet foods, the hedonic evaluation of sweet taste or sweet taste sensitivity (all p ≥ 0.10). In conclusion, we were not able to show an effect of bariatric surgery on circulating FGF21, and individual postoperative changes in FGF21 were not found to mediate an effect of surgery on sweet food intake and preference.

The Same Metabolic Response to FGF21 Administration in Male and Female Obese Mice Is Accompanied by Sex-Specific Changes in Adipose Tissue Gene Expression

The preference for high-calorie foods depends on sex and contributes to obesity development. Fibroblast growth factor 21 (FGF21) beneficially affects taste preferences and obesity, but its action has mainly been studied in males. The aim of this study was to compare the effects of FGF21 on food preferences and glucose and lipid metabolism in C57Bl/6J male and female mice with diet-induced obesity. Mice were injected with FGF21 or vehicle for 7 days. Body weight, choice between standard (SD) and high-fat (HFD) diets, blood parameters, and gene expression in white (WAT) and brown (BAT) adipose tissues, liver, muscles, and the hypothalamus were assessed. Compared to males, females had a greater preference for HFD; less WAT; lower levels of cholesterol, glucose, and insulin; and higher expression of Fgf21, Insr, Ppara, Pgc1, Acca and Accb in the liver and Dio2 in BAT. FGF21 administration decreased adiposity; blood levels of cholesterol, glucose, and insulin; hypothalamic Agrp expression, increased SD intake, decreased HFD intake independently of sex, and increased WAT expression of Pparg, Lpl and Lipe only in females. Thus, FGF21 administration beneficially affected mice of both sexes despite obesity-associated sex differences in metabolic characteristics, and it induced female-specific activation of gene expression in WAT.

The Interaction of Single Nucleotide Polymorphisms on Fibroblast Growth Factor 19 Superfamily Genes Is Associated With Alcohol Dependence-Related Aggression

Alcohol dependence (AD) is characterized by compulsive alcohol consumption, which involves behavioral impairments such as aggression. Members of fibroblast growth factor (FGF) 19 superfamily, including FGF19, FGF21, and FGF23, are major endocrine mediators that play an important role in alcohol metabolism and alcohol related disorders. The objective of the present study is to explore the possible associations among the interaction of single nucleotide polymorphisms (SNPs) of the FGF 19 superfamily, AD occurrence, and aggression in patients with AD. A total of 956 subjects were enrolled in this study, including 482 AD patients and 474 healthy controls (HCs). Michigan alcoholism screening test (MAST) was used to measure the level of AD, a Chinese version of the Buss–Perry Aggression Questionnaire was used to evaluate the aggressive behavior of subjects, and MassARRAY^@ system was used to genotype rs948992 of FGF19, rs11665841 and rs11665896 of FGF21, rs7955866 and rs11063118 of FGF23. The results showed that AD patients presented a significantly higher level of aggression compared to HCs, and MAST scores were significantly positively associated Buss–Perry aggression scores (r = 0.402, p < 0.001) in AD patients. The interaction of FGF19 rs948992 TC × FGF21 rs11665896 GG presented the high-risk genotype combination predicting the high level of AD. In addition, the interaction of FGF19 rs948992 TC × FGF21 rs11665896 TG × FGF23 rs11063118 TT presented the high-risk genotype combination predicting the high level of aggression in AD patients. Our results added evidence linking the combination of rs948992 TC × rs11665896 TG × rs11063118 TT to aggressive behavior in AD patients and pointed out the potential usefulness of the SNPs of FGF19 superfamily as a predictor for the aggression in AD patients.

Fibroblast Growth Factor 21 Response in a Preclinical Alcohol Model of Acute-on-Chronic Liver Injury

BACKGROUND AND AIMS

Fibroblast growth factor (FGF) 21 has recently been shown to play a potential role in bile acid metabolism. We aimed to investigate the FGF21 response in an ethanol-induced acute-on-chronic liver injury (ACLI) model in Abcb4-/- mice with deficiency of the hepatobiliary phospholipid transporter.

METHODS

Total RNA was extracted from wild-type (WT, C57BL/6J) and Abcb4-/- (KO) mice, which were either fed a control diet (WT-Cont and KO-Cont groups; n = 28/group) or ethanol diet, followed by an acute ethanol binge (WT-EtOH and KO-EtOH groups; n = 28/group). A total of 58 human subjects were recruited into the study, including patients with alcohol-associated liver disease (AALD; n = 31) and healthy controls (n = 27). The hepatic and ileal expressions of genes involved in bile acid metabolism, plasma FGF levels, and bile acid and its precursors 7α- and 27-hydroxycholesterol (7α- and 27-OHC) concentrations were determined. Primary mouse hepatocytes were isolated for cell culture experiments.

RESULTS

Alcohol feeding significantly induced plasma FGF21 and decreased hepatic Cyp7a1 levels. Hepatic expression levels of Fibroblast growth factor receptor 1 (Fgfr1), Fgfr4, Farnesoid X-activated receptor (Fxr), and Small heterodimer partner (Shp) and plasma FGF15/FGF19 levels did not differ with alcohol challenge. Exogenous FGF21 treatment suppressed Cyp7a1 in a dose-dependent manner in vitro. AALD patients showed markedly higher FGF21 and lower 7α-OHC plasma levels while FGF19 did not differ.

CONCLUSIONS

The simultaneous upregulation of FGF21 and downregulation of Cyp7a1 expressions upon chronic plus binge alcohol feeding together with the invariant plasma FGF15 and hepatic Shp and Fxr levels suggest the presence of a direct regulatory mechanism of FGF21 on bile acid homeostasis through inhibition of CYP7A1 by an FGF15-independent pathway in this ACLI model. Lay Summary: Alcohol challenge results in the upregulation of FGF21 and repression of Cyp7a1 expressions while circulating FGF15 and hepatic Shp and Fxr levels remain constant both in healthy and pre-injured livers, suggesting the presence of an alternative FGF15-independent regulatory mechanism of FGF21 on bile acid homeostasis through the inhibition of Cyp7a1.

Long-Acting Glucagon-Like Peptide-1 Receptor Agonists Suppress Voluntary Alcohol Intake in Male Wistar Rats

Alcohol use disorder (AUD) is a chronic relapsing condition characterized by compulsive alcohol-seeking behaviors, with serious detrimental health consequences. Despite high prevalence and societal burden, available approved medications to treat AUD are limited in number and efficacy, highlighting a critical need for more and novel pharmacotherapies. Glucagon-like peptide-1 (GLP-1) is a gut hormone and neuropeptide involved in the regulation of food intake and glucose metabolism via GLP-1 receptors (GLP-1Rs). GLP-1 analogs are approved for clinical use for diabetes and obesity. Recently, the GLP-1 system has been shown to play a role in the neurobiology of addictive behaviors, including alcohol seeking and consumption. Here we investigated the effects of different pharmacological manipulations of the GLP-1 system on escalated alcohol intake and preference in male Wistar rats exposed to intermittent access 2-bottle choice of 10% ethanol or water. Administration of AR231453 and APD668, two different agonists of G-protein receptor 119, whose activation increases GLP-1 release from intestinal L-cells, did not affect voluntary ethanol intake. By contrast, injections of either liraglutide or semaglutide, two long-acting GLP-1 analogs, potently decreased ethanol intake. These effects, however, were transient, lasting no longer than 48 h. Semaglutide, but not liraglutide, also reduced ethanol preference on the day of injection. As expected, both analogs induced a reduction in body weight. Co-administration of exendin 9-39, a GLP-1R antagonist, did not prevent liraglutide- or semaglutide-induced effects in this study. Injection of exendin 9-39 alone, or blockade of dipeptidyl peptidase-4, an enzyme responsible for GLP-1 degradation, via injection of sitagliptin, did not affect ethanol intake or preference. Our findings suggest that among medications targeting the GLP-1 system, GLP-1 analogs may represent novel and promising pharmacological tools for AUD treatment.

Consequences of Obesity on the Sense of Taste: Taste Buds as Treatment Targets?

Premature obesity-related mortality is caused by cardiovascular and pulmonary diseases, type 2 diabetes mellitus, physical disabilities, osteoarthritis, and certain types of cancer. Obesity is caused by a positive energy balance due to hyper-caloric nutrition, low physical activity, and energy expenditure. Overeating is partially driven by impaired homeostatic feedback of the peripheral energy status in obesity. However, food with its different qualities is a key driver for the reward driven hedonic feeding with tremendous consequences on calorie consumption. In addition to visual and olfactory cues, taste buds of the oral cavity process the earliest signals which affect the regulation of food intake, appetite and satiety. Therefore, taste buds may play a crucial role how food related signals are transmitted to the brain, particularly in priming the body for digestion during the cephalic phase. Indeed, obesity development is associated with a significant reduction in taste buds. Impaired taste bud sensitivity may play a causal role in the pathophysiology of obesity in children and adolescents. In addition, genetic variation in taste receptors has been linked to body weight regulation. This review discusses the importance of taste buds as contributing factors in the development of obesity and how obesity may affect the sense of taste, alterations in food preferences and eating behavior.

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.

Increased fructose consumption has sex-specific effects on fibroblast growth factor 21 levels in humans

OBJECTIVE

Fibroblast growth factor 21 (FGF21), a primarily hepatic hormone with pleotropic metabolic effects, is regulated by fructose in humans. Recent work has established that 75 g of oral fructose robustly stimulates FGF21 levels in humans with peak levels occurring 2 h following ingestion; this has been termed an oral fructose tolerance test (OFTT). It is unknown whether prolonged high-fructose consumption influences the FGF21 response to acute fructose or whether biological sex influences FGF21-fructose dynamics.

METHODS

Thirty-nine healthy adults underwent baseline OFTT following an overnight fast. For the high-fructose exposure protocol, 20 subjects ingested 75 g of fructose daily for 14 ± 3 d, followed by repeat OFTT. For the control group, an OFTT was repeated following 14 ± 3 d of ad lib diet. For all subjects, FGF21 levels, glucose, insulin, non-esterified fatty acids and triglyceride levels were measured at baseline and 2 h following OFTT. All subjects maintained 3-d food logs prior to OFTT testing.

RESULTS

Women demonstrated significantly higher baseline and peak stimulated total and intact FGF21 levels compared with men both before and after high-fructose exposure. Baseline total and intact FGF21 levels decreased following ongoing fructose exposure, maintaining a stable ratio. This decrease was sex specific, with only women demonstrating decreased baseline FGF21 levels. There were no changes in metabolic or anthropometric parameters following the high-fructose exposure.

CONCLUSIONS

Daily ingestion of 75 g of fructose for 2 weeks results in a sex-specific decrease in baseline FGF21 levels without change in body weight or biochemical evidence of metabolic injury. There were also sex-specific differences in peak fructose-stimulated FGF21 levels, which do not change with high-fructose consumption. The role of FGF21 in the development of metabolic disease caused by fructose consumption may differ based on biological sex. Future long-term studies should consider sex differences in FGF21-fructose dynamics.

Fructose and metabolic health: governed by hepatic glycogen status?

Fructose is a commonly ingested dietary sugar which has been implicated in playing a particularly harmful role in the development of metabolic disease. Fructose is primarily metabolised by the liver in humans, and increases rates of hepatic de novo lipogenesis. Fructose increases hepatic de novo lipogenesis via numerous mechanisms: by altering transcriptional and allosteric regulation, interfering with cellular energy sensing, and disrupting the balance between lipid synthesis and lipid oxidation. Hepatic de novo lipogenesis is also upregulated by the inability to synthesise glycogen, either when storage is inhibited in knock‐down animal models or storage is saturated in glycogen storage disease. Considering that fructose has the capacity to upregulate hepatic glycogen storage, and replenish these stores more readily following glycogen depleting exercise, the idea that hepatic glycogen storage and hepatic de novo lipogenesis are linked is an attractive prospect. We propose that hepatic glycogen stores may be a key factor in determining the metabolic responses to fructose ingestion, and saturation of hepatic glycogen stores could exacerbate the negative metabolic effects of excessive fructose intake. Since physical activity potently modulates glycogen metabolism, this provides a rationale for considering nutrient–physical activity interactions in metabolic health.