LPS infusion suppresses serum FGF21 levels in healthy adult volunteers

Metformin Improves the Prerequisites for FGF21 Signaling in Patients With Type 2 Diabetes

CONTEXT

Fibroblast growth factor (FGF) 21 acts as a metabolic regulator and its therapeutic use is under investigation. FGF21 signaling requires binding to surface receptors, FGFR1c and β-klotho. FGF21 resistance is observed in metabolic diseases and FGF21 signaling is regulated by fibroblast activation protein (FAP). Metformin is reported to influence expression and secretion of FGF21 in preclinical models, but the effect of metformin on FGF21 in a clinical trial remains unknown.

OBJECTIVE

To investigate how 12 weeks of treatment with metformin affects the FGF21 signaling pathway in patients with type 2 diabetes (T2D).

METHODS

Randomized, placebo-controlled study in patients with T2D (n = 24) receiving either metformin (1000 mg twice daily) or placebo. A control group of body mass index- and age-matched healthy individuals (n = 12) received a similar dose of metformin. Blood samples and muscle and fat biopsies were collected at study entry and after 12 weeks.

METHODS

Plasma levels of FGF21 (total and intact) and FAP (total and activity) were measured. Muscle and fat biopsies were analyzed for mRNA and protein expression of targets relevant for activation of the FGF21 signaling pathway.

RESULTS

Circulating FAP activity decreased after metformin treatment compared with placebo (P = .006), whereas FGF21 levels were unchanged. Metformin treatment increased gene and protein expression of β-klotho, FGFR1c, and pFGFR1c in adipose tissue. FGF21 mRNA expression increased in muscle tissue after metformin and the FGF21 protein, but not mRNA levels, were observed in adipose tissue.

CONCLUSION

Our findings suggest that metformin suppresses the circulating FAP activity and upregulates the expression of FGFR1c and β-klotho for increased FGF21 signaling in adipose tissue, thus improving peripheral FGF21 sensitivity.

Glucose and lipopolysaccharide differentially regulate fibroblast growth factor 21 in healthy male human volunteers - A prospective cross-over trial

Fibroblast growth factor 21 (FGF21) affects the regulation of metabolism. Additionally, anti-inflammatory properties are attributed to FGF21, and studies in animals and humans show conflicting results. This study aimed to investigate how FGF21 is affected by glucose and lipopolysaccharide (LPS) in humans. Therefore, FGF21 was measured eight times at different time points within 48 h in this prospective cross-over trial after glucose and LPS on two different study days. The study included ten healthy, non-smoking male subjects aged 18-40. Repeated measures analysis of variance and paired t-test as post hoc analysis were applied. The administration of glucose and LPS resulted in a significant difference in regulating FGF21 (p < 0.001). After glucose administration, FGF21 declined sharply at 360 min, with a subsequent steep increase that exceeded baseline levels. LPS induced a drop in FGF21 after 180 min, while the baseline concentrations were not reached. After 180 min and 24 h, a statistically significant difference was demonstrated after adjusting the Bonferroni-Holm method. So, our results support the hypothesis that glucose and LPS differentially affect the human expression of FGF21 over 48 h.

Sitagliptin reduces FAP-activity and increases intact FGF21 levels in patients with newly detected glucose abnormalities

INTRODUCTION

Fibroblast growth factor 21 (FGF21), a hormone with pleiotropic metabolic effects, is inactivated by fibroblast activation protein (FAP), a member of the dipeptidyl peptidase-IV (DPP-IV) family. We investigate if sitagliptin (DPP-IV inhibitor) inhibits FAP-activity and increases intact FGF21.

METHODS

Patients with impaired glucose metabolism were randomized to 100 mg sitagliptin (n = 34) or placebo (n = 37) treatment for 12 weeks. Plasma samples obtained at study entry and at 12-weeks were analysed for FAP-activity, FAP, total FGF21 and intact FGF21.

RESULTS

Sitagliptin significantly inhibited FAP-activity (497 ± 553 vs. 48 ± 712 RFU/min, p < 0.01) and correspondingly increased intact FGF21 (253 ± 182 vs 141 ± 80 ng/L, p < 0.01) compared to placebo in plasma. Sitagliptin dose-dependently inhibited the FAP-activity in vitro. Intact FGF21 was higher in patients obtaining a normal glucose tolerance regardless of treatment (p = 0.03).

CONCLUSION

A sitagliptin-induced increase of intact FGF21 may contribute to an improved metabolic effect in patients with impaired glucose metabolism.

Cytokine Drizzle-The Rationale for Abandoning "Cytokine Storm"

BACKGROUND

"Cytokine storm" has been used to implicate increased cytokine levels in the pathogenesis of serious clinical conditions. Similarities with Severe Acute Respiratory Syndrome Coronoavirus-2 (SARS CoV-2) and the 2012 Middle Eastern Respiratory Syndrome led early investigators to suspect a "cytokine storm" resulting in an unregulated inflammatory response associated with the significant morbidity and mortality induced by SARS CoV-2. The threshold of blood cytokines necessary to qualify as a "cytokine storm" has yet to be defined.

METHODS

A literature review was conducted to identify cytokine levels released during 11 assorted clinical conditions or diseases. Weighted averages for various cytokines were calculated by multiplying the number of patients in the paper by the average concentration of each cytokine. Correlation between cytokine levels for individual conditions or diseases were assessed using Pearson correlation coefficient.

RESULTS

The literature was reviewed to determine blood levels of cytokines in a wide variety of clinical conditions. These conditions ranged from exercise and autoimmune disease to septic shock and therapy with chimeric antigen receptor T cells. The most frequently measured cytokine was IL-6 which ranged from 24,123 pg/mL in septic shock to 11 pg/mL after exercise. In patients with severe SARS CoV-2 infections, blood levels of IL-6 were only 43 pg/mL, nearly three magnitudes lower than IL-6 levels in patients with septic shock. The clinical presentations of these different diseases do not correlate with blood levels of cytokines. Additionally, there is poor correlation between the concentrations of different cytokines among the different diseases. Specifically, blood levels of IL-6 did not correlate with levels of IL-8, IL-10, or TNF. Septic shock had the highest concentrations of cytokines, yet multiple cytokine inhibitors have failed to demonstrate improved outcomes in multiple clinical trials. Patients with autoimmune diseases have very low blood levels of cytokines (rheumatoid arthritis, IL-6 = 34 pg/mL; Crohn's disease, IL-6 = 5 pg/mL), yet respond dramatically to cytokine inhibitors.

CONCLUSION

The misleading term "cytokine storm" implies increased blood levels of cytokines are responsible for a grave clinical condition. Not all inflammatory conditions resulting in worsened disease states are correlated with significantly elevated cytokine levels, despite an association with the term "cytokine storm". "Cytokine storm" should be removed from the medical lexicon since it does not reflect the mediators driving the disease nor does it predict which diseases will respond to cytokine inhibitors.

Impact of Acutely Increased Endogenous- and Exogenous Ketone Bodies on FGF21 Levels in Humans

PURPOSE

Fibroblast growth factor (FGF) 21 is a circulating hormone with metabolic regulatory importance. In mice, FGF21 increases in response to a ketogenic diet and fasting. In humans, a similar increase is only observed after prolonged starvation. We aim to study the acute effects of ketone bodies on circulating FGF21 levels in humans.

METHODS

Participants from three randomized, placebo-controlled crossover studies, with increased endogenous or exogenous ketone bodies, were included. Study 1: patients with type 1 diabetes (T1D) (n = 9) were investigated after a) insulin deprivation and lipopolysaccharide (LPS) injection and b) insulin-controlled euglycemia. Study 2: patients with T1D (n = 9) were investigated after a) total insulin deprivation for 9 hours and b) insulin-controlled euglycemia. Study 3: Healthy adults (n = 9) were examined during a) 3-hydroxybutyrate (OHB) infusion and b) saline infusion. Plasma FGF21 was measured with immunoassay in serial samples.

RESULTS

Circulating OHB levels were significantly increased to 1.3, 1.5, and 5.5 mmol/l in the three studies, but no correlations with FGF21 levels were found. Also, no correlations between FGF21, insulin, or glucagon were found. Insulin deprivation and LPS injection resulted in increased plasma FGF21 levels at t = 120 min (p = .005) which normalized at t = 240 min.

CONCLUSION

We found no correlation between circulating FGF21 levels and levels of ketone bodies. This suggests that it is not ketosis per se which controls FGF21 production, but instead a rather more complex regulatory mechanism.

TRIAL REGISTRATION

clinicaltrials.gov ID number: Study 1: NCT02157155 (5/6-2014), study 2: NCT02077348 (4/3-2014), and study 3: NCT02357550 (6/2-2015).

Changes in insulin sensitivity and insulin secretion during pregnancy and post partum in women with gestational diabetes

INTRODUCTION

The metabolic abnormalities underlying gestational diabetes mellitus (GDM) include increased insulin resistance and beta cell defects, but it is essential to clarify how insulin resistance and insulin secretion develop post partum in order to decide when and how to screen for type 2 diabetes. The purpose of the present study was to characterize and compare changes in insulin sensitivity, insulin secretion and hormonal status around parturition and 6 months post partum in women with gestational diabetes.

RESEARCH DESIGN AND METHODS

A longitudinal experimental study was performed at Aarhus University Hospital, Denmark. Eight women with GDM were examined at three identical visits: in late pregnancy (LP) between gestational age 34+0 and 36+6, early post partum (EPP) between 12 and 34 days post partum, and late post partum (LPP) 6 months post partum. An intravenous glucose tolerance test was performed, followed by a hyperinsulinemic euglycemic clamp. Blood samples were collected to assess metabolic, hormonal and inflammatory markers at each visit.

RESULTS

First and second phase insulin secretion and C-peptide concentrations were higher in late pregnancy than post partum (p<0.001). Insulin sensitivity index (ISI) was different at all three visits: ISI_LP=0.03±0.004, ISI_EPP=0.09±0.008 and ISI_LPP=0.07±0.008) (p<0.001). Also, significant changes in lipids, leptin, glucagon, growth hormone and insulin-like growth factor-1 were seen when comparing the visits.

CONCLUSIONS

Insulin sensitivity improves immediately after delivery in women with GDM but seems to deteriorate within the first 6 months post partum. Our findings underline the importance of having an increased awareness of the profound risk of developing type 2 diabetes after GDM.

TRIAL REGISTRATION NUMBER

NCT02770079.

Fibroblast Activation Protein is a GH Target: A Prospective Study of Patients with Acromegaly Before and After Treatment

BACKGROUND

Fibroblast growth factor 21 (FGF21) is a circulating hormone with pleiotropic metabolic effects, which is inactivated by fibroblast activation protein (FAP). Data regarding interaction between FGF21, FAP, and growth hormone (GH) are limited, but it is noteworthy that collagens are also FAP substrates, since GH potently stimulates collagen turnover.

AIM

To measure circulating FGF21 components, including FAP, in patients with acromegaly before and after disease control.

METHODS

Eighteen patients with active acromegaly were studied at the time of diagnosis and ≥ 6 months after disease control by either surgery or medical treatment. Serum levels of total and active FGF21, β-klotho, FAP, and collagen turnover markers were measured by immunoassays. Expression of putative FGF21-dependent genes were measured in adipose tissue by reverse transcriptase-polymerase chain reaction, body composition assessed by dual-energy x-ray absorptiometry scan, and insulin sensitivity estimated with homeostatic model assessment of insulin resistance (HOMA-IR).

RESULTS

Total FGF21, active FGF21 and β-klotho remained unchanged. Insulin sensitivity and body fat mass increased after disease control but neither correlated with active FGF21. Expression of FGF21-dependent genes did not change after treatment. FAP levels (µg/L) were markedly reduced after treatment [105.6 ± 29.4 vs 62.2 ± 32.4, P < 0.000]. Collagen turnover markers also declined significantly after treatment and ΔFAP correlated positively with ΔProcollagen Type I (P < 0.000) and Type III (P < 0.000).

CONCLUSION

1) Circulating FGF21 and β-klotho do not change in response to acromegaly treatment, 2) FAP concentrations in serum decrease after disease control and correlate positively with collagen turnover markers, and 3) FAP is a hitherto unrecognized GH target linked to collagen turnover.

CLINICAL TRIALS REGISTRATION

NCT00647179.

Fibroblast growth factor 21 is required for the therapeutic effects of Lactobacillus rhamnosus GG against fructose-induced fatty liver in mice

Objectives

High fructose feeding changes fibroblast growth factor 21 (FGF21) regulation. Lactobacillus rhamnosus GG (LGG) supplementation reduces fructose-induced non-alcoholic fatty liver disease (NAFLD). The aim of this study was to determine the role of FGF21 and underlying mechanisms in the protective effects of LGG.

Methods

FGF21 knockout (KO) mice and C57BL/6 wild type (WT) mice were fed 30% fructose for 12 weeks. LGG was administered to the mice in the last 4 weeks during fructose feeding. FGF21-adiponectin (ADPN)-mediated hepatic lipogenesis and inflammation were investigated.

Results

FGF21 expression was robustly increased after 5-weeks of feeding and significantly decreased after 12-weeks of feeding in fructose-induced NAFLD mice. LGG administration reversed the depressed FGF21 expression, increased adipose production of ADPN, and reduced hepatic fat accumulation and inflammation in the WT mice but not in the KO mice. Hepatic nuclear carbohydrate responsive-element binding protein (ChREBP) was increased by fructose and reduced by LGG, resulting in a reduction in the expression of lipogenic genes. The methylated form of protein phosphatase 2A (PP2A) C, which dephosphorylates and activates ChREBP, was upregulated by fructose and normalized by LGG. Leucine carboxyl methyltransferase-1, which methylates PP2AC, was also increased by fructose and decreased by LGG. However, those beneficial effects of LGG were blunted in the KO mice. Hepatic dihydrosphingosine-1-phosphate, which inhibits PP2A, was markedly increased by LGG in the WT mice but attenuated in the KO mice. LGG decreased adipose hypertrophy and increased serum levels of ADPN, which regulates sphingosine metabolism. This beneficial effect was decreased in the KO mice.

Conclusion

LGG administration increases hepatic FGF21 expression and serum ADPN concentration, resulting in a reduced ChREBP activation through dihydrosphingosine-1-phosphate-mediated PP2A deactivation, and subsequently reversed fructose-induced NAFLD. Thus, our data suggest that FGF21 is required for the beneficial effects of LGG in reversal of fructose-induced NAFLD.

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Lactobacillus rhamnosus GG (LGG) attenuates fructose-induced NAFLD.

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LGG increases FGF21 and adiponectin expression.

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LGG inhibits fructose-activated ChREBP and reduces hepatic lipogenesis.

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FGF21 is required for the therapeutic effects of LGG against fructose-induced NAFLD.

FGF21 and glycemic control in patients with T1D

PURPOSE

Fibroblast growth factor (FGF) 21 is a circulating hormone with an important role in metabolic regulation. FGF21 production in humans responds positively to glucose consumption and we hypothesize that serum FGF21 concentration is associated to glycemic control.

METHODS

We enrolled 31 patients with type 1 diabetes (T1D) based on their HbA1c (well-regulated (HbA1c <53 mmol/mol), (n = 18) or poorly-regulated (HbA1c >69 mmol/mol), (n = 13). Twelve patients (39%) were diagnosed with retinopathy. Twenty healthy individuals comparable for age and gender distribution were included as a reference group. Serum FGF21, intact FGF21, fibroblast activation protein (FAP), adiponectin, and C-Reactive Protein (CRP) were measured by immunoassays.

RESULTS

No correlation between FGF21 concentration and HbA1c was found. Patients with T1D had lower levels of circulating FGF21 as compared with the reference group, but the difference was nonsignificant (p = 0.12). Dividing the patients according to retinopathy, we found that T1D patients with retinopathy had significantly lower FGF21 concentrations (10.0 ng/L) as compared with the healthy reference group (37.1 ng/L), (p = 0.02). We found significantly higher levels of the FGF21 cleaving enzyme, FAP, in patients with T1D (97.2 μg/L) as compared with the healthy control group (78.5 μg/L), (p = 0.006). Interestingly, serum FAP levels correlated significantly with circulating FGF21 levels in T1D patients, but this correlation was not found in the healthy controls.

CONCLUSIONS

We found no association between circulating FGF21 levels and HbA1c. T1D patients with retinopathy had significantly lower FGF21 levels as compared with healthy individuals, but it remains unclear if the lower levels of FGF21 are pathogenically related to the development of microvascular complications. Of note, serum FAP levels were significantly higher in all T1D patients as compared with the healthy individuals.

Effects of Insulin Treatment with Glargine or Premixed Insulin Lispro Programs in Type 2 Diabetes Mellitus Patients: A Meta-analysis of Randomized Clinical Trials

BACKGROUND

The purpose of this study was to compare the efficacy and safety of intensive insulin therapy (premixed insulin lispro vs. insulin glargine) in patients with type 2 diabetes mellitus (T2DM).

METHODS

MEDLINE, EMBASE, the Cochrane Library, and www.clinicaltrials.gov were systematically searched for randomized clinical trials (RCTs) of patients with T2DM treated with either premixed insulin lispro or insulin glargine for a duration of 24 weeks.

RESULTS

A total of 13 RCTs and 5401 patients were included in this study. In parallel trials and crossover trials, premixed insulin lispro was found to be superior to insulin glargine at reducing glycosylated hemoglobin (HbA1c) (parallel trials: weighted mean difference [WMD] -0.18%; 95% confidence interval [CI] -0.31 to -0.06; P = 0.004; crossover trials: WMD 0.37%; 95% CI -0.51 to -0.23; P < 0.00001). Premixed insulin lispro resulted in more weight gain than insulin glargine (parallel trials: WMD +0.64 kg; 95% CI +0.14 to +1.15; P = 0.01; crossover trials: WMD +0.74 kg; 95% CI +0.19 to +1.29; P = 0.009), and premixed insulin lispro was associated with a higher risk of hypoglycemia than insulin glargine (parallel trials: odds ratio [OR] 1.20; 95% CI 1.06-1.36; P = 0.005; crossover trials: OR 2.24; 95% CI 1.45-3.46; P = 0.0003).

CONCLUSIONS

Premixed insulin lispro provides a larger reduction in HbA1c and is associated with a significantly higher risk of hypoglycemia and greater weight gain in patients with T2DM. These findings may be helpful in selecting therapy for individual subjects.

Rush to the fire: FGF21 extinguishes metabolic stress, metaflammation and tissue damage

FGF21 is a master regulator of homeostasis of local and systemic lipid, glucose and energy metabolism. Since its discovery a decade ago, significant progress has been made in understanding the basic molecular, cellular and physiological mechanisms underlying its metabolic roles, and characterizing its beneficial pharmacological activities and possible pathological roles in obesity, diabetes, dyslipidemia, fatty liver disease and their collateral complications and tissue damage. Under basal or normal conditions, FGF21 appears to play a dispensable role in metabolism. However, in response to a variety of cellular and metabolic stress, FGF21 is significantly upregulated to serve as a potent catabolic factor leading to the clearance of excessive lipids and glucose, and therefore, antagonizes metabolic and energy imbalance in a negative fashion. Furthermore, FGF21 treatment ameliorates tissue damage resulted from the harmful effects of metabolic abnormalities, which often ensue an oxidative, pro-inflammatory, inflammatory and/or immune stress state, the so-called metaflammation. Most notably, studies focusing on the liver, pancreas, cardio-vasculature and kidney have revealed its significant protective effects against the structural and functional damages induced by the obese, diabetic or other abnormal metabolic conditions. In this review, we will summarize the current progress on the roles of FGF21 against metaflammation and metabolic tissue damage.