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.

Metabolic effects of 1-week binge drinking and fast food intake during Roskilde Festival in young healthy male adults.

AIMS/HYPOTHESIS: Metabolic effects of intermittent unhealthy lifestyle in young adults are poorly studied. We investigated the gluco-metabolic and hepatic effects of participation in Roskilde Festival (1 week of binge drinking and junk food consumption) in young, healthy males. METHODS: Fourteen festival participants (FP) were studied before, during and after 1 week's participation in Roskilde Festival. Fourteen matched controls (CTRL) who did not participate in Roskilde Festival or change their lifestyle in other ways were investigated along a similar timeline. RESULTS: The FP group consumed more alcohol compared to their standard living conditions (2.0 ± 3.9 vs 16.3 ± 8.3 units/day, P < 0.001). CTRLs did not change their alcohol consumption. AUC for glucose during OGTT did not change in either group. C-peptide responses increased in the FP group (206 ± 24 vs 236 ± 17 min × nmol/L, P = 0.052) and the Matsuda index of insulin sensitivity decreased (6.2 ± 2.4 vs 4.7 ± 1.4, P = 0.054). AUC for glucagon during oral glucose tolerance test (OGTT) increased in the FP group (1037 ± 90 vs 1562 ± 195 min × pmol/L, P = 0.003) together with fasting fibroblast growth factor 21 (FGF21) (62 ± 30 vs 132 ± 72 pmol/L, P < 0.001), growth differentiation factor 15 (GDF5) (276 ± 78 vs 330 ± 83 pg/mL, P = 0.009) and aspartate aminotransferase (AST) levels (37.6 ± 6.8 vs 42.4 ± 11 U/L, P = 0.043). Four participants (29%) developed ultrasound-detectable steatosis and a mean strain elastography-assessed liver stiffness increased (P = 0.026) in the FP group. CONCLUSIONS/INTERPRETATION: Participation in Roskilde Festival did not affect oral glucose tolerance but was associated with a reduction in insulin sensitivity, increases in glucagon, FGF21, GDF15 and AST and lead to increased liver stiffness and, in 29% of the participants, ultrasound-detectable hepatic steatosis.

Dose-dependent efficacy of the glucose-dependent insulinotropic polypeptide (GIP) receptor antagonist GIP(3-30)NH2 on GIP actions in humans.

The glucose-dependent insulinotropic polypeptide (GIP) fragment GIP(3-30)NH2 is a selective, competitive GIP receptor antagonist, and doses of 800 to 1200 pmol/kg/min inhibit GIP-induced potentiation of glucose-stimulated insulin secretion by >80% in humans. We evaluated the effects of GIP(3-30)NH2 across a wider dose range in eight healthy men undergoing six separate and randomized 10-mmol/L hyperglycaemic clamps (A-F) with concomitant intravenous infusion of GIP (1.5 pmol/kg/min; A-E) or saline (F). Clamps A to E involved double-blinded, infusions of saline (A) and GIP(3-30)NH2 at four rates: 2 (B), 20 (C), 200 (D) and 2000 pmol/kg/min (E), respectively. Mean plasma concentrations of glucose (A-F) and GIP (A-E) were similar. GIP-induced potentiation of glucose-stimulated insulin secretion was reduced by 44 ± 10% and 84 ± 10% during clamps D and E, respectively. Correspondingly, the amounts of glucose required to maintain the clamp during D and E were not different from F. GIP-induced suppression of bone resorption and increase in heart rate were lowered by clamps D and E. In conclusion, GIP(3-30)NH2 provides extensive, dose-dependent inhibition of the GIP receptor in humans, with most pronounced effects of the doses 200 to 2000 pmol/kg/min within the tested range.

The role of endogenous GIP and GLP-1 in postprandial bone homeostasis.

The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are well known for their insulinotropic effects and they are thought to affect bone homeostasis as mediators in the so-called entero-osseous axis. We examined the contributions of endogenous GIP and GLP-1, respectively, to postprandial bone homeostasis, in healthy subjects in two randomized and double-blind crossover studies. We included healthy men who received either four oral glucose tolerance tests (OGTTs) (n = 18, median age 27 (range 20-70), BMI 27.2 (22.4-37.0) kg/m2) or liquid mixed meal tests (MMTs) (n = 12, age 23 (19-65), BMI 23.7 (20.3-25.5) kg/m2) with infusions of 1) the GIP receptor antagonist GIP(3-30)NH2, 2) the GLP-1 receptor antagonist exendin(9-39)NH2, 3) both GIP(3-30)NH2 and exendin(9-39)NH2, or 4) placebo infusions (saline) on four separate visits. Bone resorption was evaluated from levels of circulating carboxy-terminal collagen crosslinks (CTX) and bone formation from levels of procollagen type 1 amino-terminal propeptide (P1NP). During placebo infusions, baseline-subtracted area under the curve values for CTX were -39 ± 5.0 (OGTT) and -57 ± 4.3 ng/ml × min (MMT). When GIP(3-30)NH2 was administered, CTX suppression was significantly diminished compared to placebo (-30 ± 4.8 (OGTT) and -45 ± 4.6 ng/ml × min (MMT), P = 0.0104 and P = 0.0288, respectively, compared to placebo. During exendin(9-39)NH2 infusion, CTX suppression after OGTT/MMT was similar to placebo (P = 0.28 (OGTT) and P = 0.93 (MMT)). The relative contribution of endogenous GIP to postprandial suppression of bone resorption during both OGTT and MMT was similar and reached 22-25%. There were no differences in P1NP concentrations between interventions. In conclusion, endogenous GIP contributes by up to 25% to postprandial suppression of bone resorption in humans whereas an effect of endogenous GLP-1 could not be demonstrated.

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.

GIP and GLP-1 Receptor Antagonism During a Meal in Healthy Individuals.

CONTEXT: The actions of both endogenous incretin hormones during a meal have not previously been characterized. OBJECTIVE: Using specific receptor antagonists, we investigated the individual and combined contributions of endogenous glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) to postprandial glucose metabolism, energy expenditure, and gallbladder motility. DESIGN: Randomized, double-blinded, placebo-controlled, crossover design. SETTING: On four separate days, four liquid mixed meal tests (1894 kJ) over 270 minutes (min). PATIENTS OR OTHER PARTICIPANTS: Twelve healthy male volunteers. INTERVENTIONS: Infusions of the GIP receptor antagonist GIP(3-30)NH2 (800 pmol/kg/min), the GLP-1 receptor antagonist exendin(9-39)NH2 (0-20 min: 1000 pmol/kg/min; 20-270 min: 450 pmol/kg/min), GIP(3-30)NH2+exendin(9-39)NH2, or placebo/saline. MAIN OUTCOME MEASURE: Baseline-subtracted area under the curve (bsAUC) of C-peptide. RESULTS: Infusion of GIP(3-30)NH2+exendin(9-39)NH2 significantly increased plasma glucose excursions (bsAUC: 261 ± 142 mmol/L × min) during the liquid mixed meals compared with GIP(3-30)NH2 (180 ± 141 mmol/L × min; P = 0.048), exendin(9-39)NH2 (171 ± 114 mmol/L × min; P = 0.046), and placebo (116 ± 154 mmol/L × min; P = 0.015). Correspondingly, C-peptide:glucose ratios during GIP(3-30)NH2+exendin(9-39)NH2 infusion were significantly lower than during GIP(3-30)NH2 (P = 0.0057), exendin(9-39)NH2 (P = 0.0038), and placebo infusion (P = 0.014). GIP(3-30)NH2 resulted in significantly lower AUCs for glucagon than exendin(9-39)NH2 (P = 0.0417). Gallbladder ejection fraction was higher during GIP(3-30)NH2 compared with placebo (P = 0.004). For all interventions, energy expenditure and respiratory quotient were similar. CONCLUSIONS: Endogenous GIP and GLP-1 lower postprandial plasma glucose excursions and stimulate insulin secretion but only endogenous GIP affects gallbladder motility. The two incretin hormones potentiate each other's effects in the control of postprandial glycemia in healthy men.

GIP's effect on bone metabolism is reduced by the selective GIP receptor antagonist GIP(3-30)NH2.

Infusion of the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) suppresses the bone resorption marker carboxy-terminal type 1 collagen crosslinks (CTX). Using separate and combined infusions of the selective GIP receptor (GIPR) antagonist, GIP(3-30)NH2, and GIP, we investigated how GIPR inhibition affects bone turnover markers. Ten healthy men (median age 22.5 years (range 21-25), BMI 21.3kg/m2 (19.9-24.7)) participated in a randomized, doubled blinded, placebo-controlled, crossover study with four 1h 12mmol/l-hyperglycemic clamps on four separate study days with concomitant infusions of GIP, GIP+GIP(3-30)NH2, GIP(3-30)NH2, and placebo, respectively, separated by a period of at least one week. GIP was infused at 1.5pmol/kg/min and GIP(3-30)NH2 at 800pmol/kg/min. Plasma glucose was clamped at 12.0±1.2mmol/l and plasma levels of GIP and GIP(3-30)NH2 amounted to ∼80pmol/l and ∼50nmol/l, respectively. GIP suppressed CTX more than placebo (baseline-subtracted AUC -6,811±1,260 vs. -3,012±3,018ng/l×min, P= 0.002) and resulted in CTX values of 53 ± 6.9% (GIP) versus 81 ± 10% of baseline (placebo), respectively (P = 0.0006), at the end of the hyperglycemic clamp. Co-infusion of GIP and GIP(3-30)NH2 attenuated the GIP-induced CTX suppression by 51±33% (P = 0.01). The peak value of the bone formation marker N-terminal propeptide of type 1 procollagen (P1NP) peaked at higher levels during GIP (109±6.7% of baseline) than during GIP(3-30)NH2 infusion (101±8.9%) (P = 0.049) and GIP suppressed PTH levels compared to GIP(3-30)NH2 alone (P = 0.0158). In conclusion, blockade of the GIPR with GIP(3-30)NH2 diminished GIP-induced CTX and P1NP responses, showing that these effects are GIPR-mediated and that GIPR antagonism might interfere with bone resorption.

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

BACKGROUND: Ingestion of the calorically dense compound alcohol may cause metabolic disturbances including hypoglycaemia, hepatic steatosis and insulin resistance, but the underlying mechanisms are uncertain. The gastrointestinal tract is well recognised as a major influencer on glucose, protein and lipid metabolism, but its role in alcohol metabolism remains unclear. OBJECTIVE: To examine the effects of oral and intravenous alcohol, respectively, on plasma concentrations of several gluco-regulatory hormones including serum/plasma insulin, C-peptide, glucagon, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP-1) and fibroblast growth factor 21 (FGF21). DESIGN AND METHODS: In a double-blinded, randomised, crossover design, we subjected 12 healthy men to intragastric ethanol infusion (IGEI) and an isoethanolaemic intravenous ethanol infusion (IVEI) (0.7 g alcohol per kg body weight), respectively, on two separate experimental days. RESULTS: Isoethanolaemia during the two alcohol administration forms was obtained (P = 0.38). During both interventions, plasma glucose peaked after ~30 min and thereafter fell below baseline concentrations. GIP and GLP-1 concentrations were unaffected by the two interventions. Insulin concentrations were unaffected by IGEI but decreased during IVEI. C-peptide, insulin secretion rate and glucagon concentrations were lowered similarly during IGEI and IVEI. FGF21 concentrations increased dramatically (nine-fold) and similarly during IGEI and IVEI. CONCLUSIONS: Alcohol does not seem to affect the secretion of incretin hormones but decreased insulin and glucagon secretion independently of gut-derived factors. IGEI as well as IVEI potently stimulate FGF21 secretion indicating a gut-independent effect of alcohol on FGF21 secretion in humans.

Separate and Combined Glucometabolic Effects of Endogenous Glucose-Dependent Insulinotropic Polypeptide and Glucagon-like Peptide 1 in Healthy Individuals.

The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are secreted postprandially and contribute importantly to postprandial glucose tolerance. In this study, we assessed the individual and combined contributions of endogenous GIP and GLP-1 to the postprandial changes in glucose and glucoregulatory hormones using the novel GIP receptor antagonist GIP(3-30)NH2 and the well-established GLP-1 receptor antagonist exendin(9-39)NH2 During 4-h oral glucose tolerance tests (75 g) combined with an ad libitum meal test, 18 healthy men received on four separate days in randomized, double-blinded order intravenous infusions of A) GIP(3-30)NH2 (800 pmol/kg/min) plus exendin(9-39)NH2 (0-20 min: 1,000 pmol/kg/min; 20-240 min: 450 pmol/kg/min), B) GIP(3-30)NH2, C) exendin(9-39)NH2, and D) saline, respectively. Glucose excursions were significantly higher during A than during B, C, and D, while glucose excursions during B were higher than during C and D. Insulin secretion (assessed by C-peptide/glucose ratio) was reduced by 37 ± 16% (A), 30 ± 17% (B), and 8.6 ± 16% (C) compared with D (mean ± SD). A and C resulted in higher glucagon levels and faster gastric emptying. In conclusion, endogenous GIP affects postprandial plasma glucose excursions and insulin secretion more than endogenous GLP-1, but the hormones contribute additively to postprandial glucose regulation in healthy individuals.

GIP(3-30)NH2 is an efficacious GIP receptor antagonist in humans: a randomised, double-blinded, placebo-controlled, crossover study.

AIMS/HYPOTHESIS: Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone secreted postprandially from enteroendocrine K cells, but despite therapeutically interesting effects, GIP physiology in humans remains incompletely understood. Progress in this field could be facilitated by a suitable GIP receptor antagonist. For the first time in humans, we investigated the antagonistic properties of the naturally occurring GIP(3-30)NH2 in in vivo and in in vitro receptor studies. METHODS: In transiently transfected COS-7 cells, GIP(3-30)NH2 was evaluated with homologous receptor binding and receptor activation (cAMP accumulation) studies at the glucagon-like peptide 1 (GLP-1), glucagon-like peptide-2 (GLP-2), glucagon, secretin and growth hormone-releasing hormone (GHRH) receptors. Ten healthy men (eligibility criteria: age 20-30 years, HbA1c less than 6.5% [48 mmol/mol] and fasting plasma glucose [FPG] less than 7 mmol/l) were included in the clinical study. Data were collected as plasma and serum samples from a cubital vein cannula. As primary outcome, insulin secretion and glucose requirements were evaluated together with in a randomised, four-period, crossover design by infusing GIP(3-30)NH2 (800 pmol kg-1 min-1), GIP (1.5 pmol kg-1 min-1), a combination of these or placebo during hyperglycaemic clamp experiments. The content of the infusions were blinded to the study participants and experimental personnel. No study participants dropped out. RESULTS: GIP(3-30)NH2 neither bound, stimulated nor antagonised a series of related receptors in vitro. The elimination plasma half-life of GIP(3-30)NH2 in humans was 7.6 ± 1.4 min. Markedly larger amounts of glucose were required to maintain the clamp during GIP infusion compared with the other days. GIP-induced insulin secretion was reduced by 82% (p < 0.0001) during co-infusion with GIP(3-30)NH2, and the need for glucose was reduced to placebo levels. There were no effects of GIP(3-30)NH2 alone or of GIP with or without GIP(3-30)NH2 on plasma glucagon, GLP-1, somatostatin, triacylglycerols, cholesterol, glycerol or NEFA. GIP(3-30)NH2 administration was well tolerated and without side effects. CONCLUSIONS/INTERPRETATION: We conclude that GIP(3-30)NH2 is an efficacious and specific GIP receptor antagonist in humans suitable for studies of GIP physiology and pathophysiology. TRIAL REGISTRATION: ClinicalTrials.gov registration no. NCT02747472. FUNDING: The study was funded by Gangstedfonden, the European Foundation for the Study of Diabetes, and Aase og Ejnar Danielsens fond.