Acute endurance exercise lowers serum fibroblast growth factor 21 levels in Japanese men

Fructose-induced FGF21 secretion does not activate brown adipose tissue in Japanese young men: randomized cross-over and randomized controlled trials

BACKGROUND

Human brown adipose tissue (BAT) activity is associated with lower body fatness and favorable glucose metabolism. Previous studies reported that oral fructose loading induces postprandial fibroblast growth factor 21 (FGF21) secretion. FGF21 is a known inducer of adipose tissue thermogenesis; however, the effects of diet-induced FGF21 secretion on BAT thermogenesis remain to be elucidated.

METHODS

The effects of both single load and daily consumption of fructose on BAT activity were examined using a randomized cross-over trial and a 2-week randomized controlled trial (RCT), respectively. In the cross-over trial, 15 young men consumed a single dose of fructose solution or water and then consumed the other on a subsequent day. The RCT enrolled 22 young men, and the participants were allocated to a group that consumed fructose and a group that consumed water daily for 2 weeks. BAT activity was analyzed using thermography with cold exposure. Plasma FGF21 level was determined by enzyme-linked immunosorbent assay.

RESULTS

In the cross-over single-load trial, plasma FGF21 levels were significantly increased at 2 h after oral fructose load (p < 0.01); however, there was no significant difference in BAT activity between the fructose load and drinking water. The 2-week RCT revealed that both plasma FGF21 levels and BAT activity were not significantly increased by daily fructose consumption compared to water. Correlation analyses revealed that BAT activity at the baseline and the final measurements were strongly and positively associated with the RCT (r = 0.869, p < 0.001). Changes in BAT activity were significantly and negatively correlated with changes in plasma glucose levels during the 2-week intervention (r = - 0.497, p = 0.022).

CONCLUSIONS

Oral fructose load induces a temporary increase in circulating FGF21 levels; however, this does not activate BAT thermogenesis in healthy young men. Further studies are needed to elucidate the effect of endogenous FGF21 on physiological function.

TRIAL REGISTRATION

This study is registered with the University Hospital Medical Information Network in Japan (number 000051761, registered 1 August 2023, retrospectively registered, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000052680 ).

Fibroblast growth factor 21 and bone homeostasis

Fibroblast growth factor 21 (FGF21), a member of the FGF subfamily, is produced primarily in the liver and adipose tissue. The main function of FGF21 is to regulate energy metabolism of carbohydrates and lipids in the body through endocrine and other means, making FGF21 have potential clinical value in the treatment of metabolic disorders. Although FGF21 and its receptors play a role in the regulation of bone homeostasis through a variety of signaling pathways, a large number of studies have reported that the abuse of FGF21 and its analogues and the abnormal expression of FGF21 in vivo may be associated with bone abnormalities. Due to limited research information on the effect of FGF21 on bone metabolism regulation, the role of FGF21 in the process of bone homeostasis regulation and the mechanism of its occurrence and development have not been fully clarified. Certainly, the various roles played by FGF21 in the regulation of bone homeostasis deserve increasing attention. In this review, we summarize the basic physiological knowledge of FGF21 and the effects of FGF21 on metabolic homeostasis of the skeletal system in animal and human studies. The information provided in this review may prove beneficial for the intervention of bone diseases.

Attenuated inflammatory profile following single and repeated handgrip exercise and remote ischemic preconditioning in patients with cerebral small vessel disease

Background: Similar to remote ischemic preconditioning bouts of exercise may possess immediate protective effects against ischemia-reperfusion injury. However, underlying mechanisms are largely unknown. This study compared the impact of single and repeated handgrip exercise versus remote ischemic preconditioning on inflammatory biomarkers in patients with cerebral small vessel disease (cSVD). Methods: In this crossover study, 14 patients with cSVD were included. All participants performed 4-day of handgrip exercise (4x5-minutes at 30% of maximal handgrip strength) and remote ischemic preconditioning (rIPC; 4x5-minutes cuff occlusion around the upper arm) twice daily. Patients were randomized to start with either handgrip exercise or rIPC and the two interventions were separated by > 9 days. Venous blood was drawn before and after one intervention, and after 4-day of repeated exposure. We performed a targeted proteomics on inflammation markers in all blood samples. Results: Targeted proteomics revealed significant changes in 9 out of 92 inflammatory proteins, with four proteins demonstrating comparable time-dependent effects between handgrip and rIPC. After adjustment for multiple testing we found significant decreases in FMS-related tyrosine kinase-3 ligand (Flt3L; 16.2% reduction; adjusted p-value: 0.029) and fibroblast growth factor-21 (FGF-21; 32.8% reduction adjusted p-value: 0.029) after single exposure. This effect did not differ between handgrip and rIPC. The decline in Flt3L after repeated handgrip and rIPC remained significant (adjusted p-value = 0.029), with no difference between rIPC and handgrip (adjusted p-value = 0.98). Conclusion: Single handgrip exercise and rIPC immediately attenuated plasma Flt3L and FGF-21, with the reduction of Flt3L remaining present after 4-day of repeated intervention, in people with cSVD. This suggests that single and repeated handgrip exercise and rIPC decrease comparable inflammatory biomarkers, which suggests activation of shared (anti-)inflammatory pathways following both stimuli. Additional studies will be needed to exclude the possibility that this activation is merely a time effect.

Association of serum fibroblast growth factor 21 with diabetic complications and insulin dose in patients with type 1 diabetes mellitus

Introduction

Fibroblast growth factor (FGF) 21 is an important regulator of glycemic control, but the association between circulating FGF21 and diabetic complications is poorly understood. Moreover, basal FGF21 secretion, especially in response to insulin dose, in patients with type 1 diabetes mellitus (T1DM), has not been well examined. Therefore, this study aimed to determine the association of circulating FGF21 levels with diabetic complications and insulin dosage in middle-aged and elderly patients with T1DM.

Materials and methods

A total of 127 middle-aged and elderly patients with T1DM, including 68 patients with diabetic complications, and 106 non-diabetic individuals were analyzed in this cross-sectional study. Information on demographic characteristics and T1DM was extracted from their electronic medical records. Serum FGF21 levels were determined using ELISA.

Results

Serum FGF21 levels were significantly lower in T1DM patients (75.2 [37.4–135.1] pg/mL) than in non-diabetic participants (151.6 [92.0–224.6] pg/mL; P < 0.001). No diabetic complications were associated with serum FGF21 concentrations. Both basal and bolus insulin doses were significantly and positively correlated with serum FGF21 levels (P < 0.05). Stepwise multiple regression analysis showed that FGF21 level was associated with age and body mass index (P < 0.05), while the basal insulin dose was an independent positive predictor of serum FGF21 levels (β = 0.197, P = 0.032).

Conclusions

Circulating FGF21 levels are reduced in patients with T1DM; however, they are not associated with diabetic complications. In addition, aging, obesity, and insulin dosage are positive determinants of circulating FGF21.

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.

Impact of acute exercise on immediate and following early post-exercise FGF-21 concentration in adults: systematic review and meta-analysis

PURPOSE/OBJECTIVE

The aim of this study was to quantify circulating fibroblast growth factor 21 (FGF-21) changes during and immediately after acute exercise and, based on body weight, to identify the subgroups exhibiting the largest response.

METHODS

The PubMed, Web of Science, and Cochrane Library electronic databases were searched up to December 2019 for studies published in English peer-reviewed journals. Studies that evaluated the effects of acute exercise on FGF-21 concentrations immediately after and 1 and 3 h post-exercise in adults were included. Random effects models were used for analyses, with data reported as standardized mean difference (SMD) and 95% confidence interval, and the risk of heterogeneity was evaluated. Subgroup analysis of subjects with normal weight and obesity/overweight was performed.

RESULTS

A total of seven studies involving 125 participants (age 35.95 (21-64) years and BMI 25.89 (21.30-35.46) kg/m²) were included. Overall, acute exercise increased FGF-21 (d = 0.18; 95% CI 0.01 to 0.35, p = 0.02) and this remained for 1 h post-exercise FGF-21 (d = 0.59; 95% CI 0.33 to 0.86, p = 0.001). Three hours after exercise, FGF-21 was restored to near baseline values (d = - 0.05; 95% CI - 0.34 to 0.22, p = 0.68). Acute exercise raised FGF-21 concentrations in normal weight participants (d = 0.57, p = 0.001) and tended to increase in overweight and obese participants (d = 0.79, p = 0.05) 1 h post-exercise.

CONCLUSION

Acute exercise increases circulating FGF-21, irrespective of body weight.

Effect of Various Exercise Regimens on Selected Exercise-Induced Cytokines in Healthy People

Different forms of physical activity—endurance, resistance or dynamic power—stimulate cytokine release from various tissues to the bloodstream. Receptors for exercise-induced cytokines are present in muscle tissue, adipose tissue, liver, brain, bones, cardiovascular system, immune system, pancreas, and skin. They have autocrine, paracrine and endocrine activities. Many of them regulate the myocyte growth and differentiation necessary for muscle hypertrophy and myogenesis. They also modify energy homeostasis, lipid, carbohydrate, and protein metabolism, regulate inflammation and exchange information (crosstalk) between remote organs. So far, interleukin 6 and irisin have been the best studied exercise-induced cytokines. However, many more can be grouped into myokines, hepatokines and adipomyokines. This review focuses on the less known exercise-induced cytokines such as myostatin, follistatin, decorin, brain-derived neurotrophic factor, fibroblast growth factor 21 and interleukin 15, and their relation to various forms of exercise, i.e., acute vs. chronic, regular training in healthy people.

Endocrine Mechanisms Connecting Exercise to Brown Adipose Tissue Metabolism: a Human Perspective

PURPOSE OF REVIEW

To summarize the state-of-the-art regarding the exercise-regulated endocrine signals that might modulate brown adipose tissue (BAT) activity and/or white adipose tissue (WAT) browning, or through which BAT communicates with other tissues, in humans.

RECENT FINDINGS

Exercise induces WAT browning in rodents by means of a variety of physiological mechanism. However, whether exercise induces WAT browning in humans is still unknown. Nonetheless, a number of protein hormones and metabolites, whose signaling can influence thermogenic adipocyte's metabolism, are secreted during and/or after exercise in humans from a variety of tissues and organs, such as the skeletal muscle, the adipose tissue, the liver, the adrenal glands, or the cardiac muscle. Overall, it seems plausible to hypothesize that, in humans, exercise secretes an endocrine cocktail that is likely to induce WAT browning, as it does in rodents. However, even if exercise elicits a pro-browning endocrine response, this might result in a negligible effect if blood flow is restricted in thermogenic adipocyte-rich areas during exercise, which is still to be determined. Future studies are needed to fully characterize the exercise-induced secretion (i.e., to determine the effect of the different exercise frequency, intensity, type, time, and volume) of endocrine signaling molecules that might modulate BAT activity and/or WAT browning or through which BAT communicates with other tissues, during exercise. The exercise effect on BAT metabolism and/or WAT browning could be one of the still unknown mechanisms by which exercise exerts beneficial health effects, and it might be pharmacologically mimicked.

Relationship between FGF21 and drug or nondrug therapy of type 2 diabetes mellitus

Sedentary and high-calorie diets are associated with increased risk of obesity and type 2 diabetes mellitus, while exercise and diet control are also important nondrug treatments for diabetes. Fibroblast growth factor 21 (FGF21) is an important cytokine, which is mainly expressed in liver, fat and muscle tissue responding to nutrition and exercise, and plays an important role in the improvement of glucose and lipid metabolism. Due to the increasing serum FGF21 level in obesity and diabetes, FGF21 can be used as a predictor or biomarker of diabetes. A variety of clinical antidiabetic drugs can reduce the content of FGF21, possibly for the improvement of FGF21 sensitivity. In this paper, we reviewed the interactions between FGF21 and nondrug therapy (diet and exercise) for diabetes and explored the potential value of the combined application of clinical antidiabetic drugs and FGF21.

Simple resistance exercise decreases cytokeratin 18 and fibroblast growth factor 21 levels in patients with nonalcoholic fatty liver disease: A retrospective clinical study

Cytokeratin 18 (CK18) and fibroblast growth factor 21 (FGF21) are elevated in patients with nonalcoholic fatty liver disease (NAFLD) and are useful markers for identifying or monitoring outcomes. Exercise therapy is one of the established treatments for NAFLD; however, few studies have investigated the effectiveness of exercise therapy on CK18 and FGF21 levels. Therefore, the aim of the present study was to assess the effects of 12 weeks of simple resistance exercise on CK18 and FGF21 levels in patients with NAFLD.Fifty patients with NAFLD were assigned to a resistance exercise group (n = 23) or a control group (n = 27) for a trial period of 12 weeks. During the study, the resistance exercise group performed two exercises (push-ups and squats) three times a week on nonconsecutive days, whereas the control group proceeded with regular physical activities under a restricted diet. We then compared serum levels of CK18 fragments (M65) and FGF21 between groups just before and after the 12-week period.Serum M65 levels (880.0 ± 503.6 vs 648.9 ± 450.2 U/L; P < .01) were significantly decreased in the exercise group. However, no significant differences were observed in body mass index or skeletal muscle. The decreases in serum M65 (-231.1 ± 354.7 vs 56.2 ± 375.0 U/L; P = .02), and FGF21 levels (-41.7 ± 98.2 vs. 33.2 ± 127.6 pg/mL; P = .03) were significantly greater in the exercise than in the control group. Changes in M65 levels in the exercise group were significantly correlated with changes in alanine aminotransferase levels (r = 0.618, P < .01).Simple resistance exercise reduced CK18 and FGF21 levels in patients with NAFLD. These findings suggest that resistance exercise consisting of push-ups and squats helps prevent the progression of NAFLD.

Fibroblast Growth Factor 21 Is Associated With Bone Mineral Density, but not With Bone Turnover Markers and Fractures in Chinese Postmenopausal Women

Fibroblast growth factor 21 (FGF21) is a member of the endocrine FGF subfamily and an important metabolic regulator that has multiple beneficial effects on glucose homeostasis and lipid metabolism. However, it was unclear whether FGF21 would induce bone defects in humans. This study evaluated the associations of FGF21 levels, bone mineral density (BMD), osteoporotic fracture, and bone turnover marks (BTMs) in postmenopausal women. A total of 1342 postmenopausal Chinese Han women (511 cases of fragility fracture in the case group and 831 cases in nonfragility fracture group) were enrolled. Serum FGF21 concentration was measured by ELISA (Quantikine), serum calcium (Ca), phosphate (P), alkaline phosphatase, 25-hydroxyvitamin D, parathyroid hormone, β-crosslinked C-telopeptide of type l collagen, were measured using an automated Roche electro-chemiluminescence system. BMD was measured using dual-energy X-ray absorptiometry. The association with age, BMD, 25-hydroxyvitamin D, parathyroid hormone, β-crosslinked C-telopeptide of type l collagen, and FGF21 levels were also evaluated in postmenopausal women. In nonfracture group and fragility fracture group, postmenopausal women's FGF21 level was 226.57pg/mL (149.11-354.43 pg/mL) and 219.43pg/mL (147.21-323.74 pg/mL), respectively. There is no significant difference in serum FGF21 levels between the fragility fracture group and the nonfracture group (p = 0.160). There was a significant statistical difference in BMD between the fragility fracture group and the nonfracture group (p = 0.000). In multiple linear regression analysis, FGF21 levels were significantly positive associated with lumbar BMD in postmenopausal women (L1-4, p = 0.007), independent of other factors, especially in fragility fracture group (L1-4, p = 0.001). In addition, a significant positive association was also observed between serum FGF21 levels and age in postmenopausal women (p < 0.05). We reveal a positive correlation between serum FGF21 concentrations with lumbar BMD in Chinese Han postmenopausal women. No significant correlations are present between serum FGF21 and bone turnover marks or serum FGF21 and fragility fracture in our study.

Adiposity Is a Key Correlate of Circulating Fibroblast Growth Factor-21 Levels in African Males with or without Type 2 Diabetes Mellitus

BACKGROUND

Fibroblast growth factor-21 is an endocrine regulator with therapeutic and diagnostic potential. The levels and pattern of circulating FGF-21 have been described mainly in European and Asian populations. Given its strong association with adiposity, and the reported ethnic variabilities in body composition, examining FGF-21 in an African population is crucial.

METHODS

We measured levels of circulating FGF-21 in 207 overweight and obese Tanzanian males with or without type 2 diabetes mellitus (T2DM), and using statistical approaches, we explored their relationship with anthropometric and biochemical parameters.

RESULTS

Consistent with previous reports from European and Asian populations, we found higher levels of FGF-21 in people with T2DM compared to those without the disease. Based on statistical models, measures of adiposity explained up to 59% of the variability in FGF-21 levels in the circulation.

CONCLUSION

Levels of circulating FGF-21 in overweight and obese African males are higher in T2DM and strongly correlate with measures of adiposity.

Anti-inflammatory effects of exercise training in adipose tissue do not require FGF21

Exercise enhances insulin sensitivity; it also improves adipocyte metabolism and reduces adipose tissue inflammation through poorly defined mechanisms. Fibroblast growth factor 21 (FGF21) is a pleiotropic hormone-like protein whose insulin-sensitizing properties are predominantly mediated via receptor signaling in adipose tissue (AT). Recently, FGF21 has also been demonstrated to have anti-inflammatory properties. Meanwhile, an association between exercise and increased circulating FGF21 levels has been reported in some, but not all studies. Thus, the role that FGF21 plays in mediating the positive metabolic effects of exercise in AT are unclear. In this study, FGF21-knockout (KO) mice were used to directly assess the role of FGF21 in mediating the metabolic and anti-inflammatory effects of exercise on white AT (WAT) and brown AT (BAT). Male FGF21KO and wild-type mice were provided running wheels or remained sedentary for 8 weeks (n = 9-15/group) and compared for adiposity, insulin sensitivity (i.e., HOMA-IR, Adipo-IR) and AT inflammation and metabolic function (e.g., mitochondrial enzyme activity, subunit content). Adiposity and Adipo-IR were increased in FGF21KO mice and decreased by EX. The BAT of FGF21KO animals had reduced mitochondrial content and decreased relative mass, both normalized by EX. WAT and BAT inflammation was elevated in FGF21KO mice, reduced in both genotypes by EX. EX increased WAT Pgc1alpha gene expression, citrate synthase activity, COX I content and total AMPK content in WT but not FGF21KO mice. Collectively, these findings reveal a previously unappreciated anti-inflammatory role for FGF21 in WAT and BAT, but do not support that FGF21 is necessary for EX-mediated anti-inflammatory effects.

Effect of an Acute Bout of Endurance Exercise on Serum 25(OH)D Concentrations in Young Adults

CONTEXT

Regular exercise or high physical activity levels are associated with higher serum 25-hydroxyvitamin D [25(OH)D] concentrations; however, the effect of acute exercise on serum 25(OH)D concentrations remains unclear.

OBJECTIVE

We aimed to clarify whether acute endurance exercise has a direct effect on the circulating 25(OH)D concentrations in young adults.

DESIGN AND SETTING

Exercise intervention trial in an institutional practice.

PATIENTS

Twenty young, active adults (males, n = 10; females, n = 10).

INTERVENTIONS

Participants were asked to perform a cycling exercise for 30 minutes at 70% maximal oxygen uptake.

MAIN OUTCOME MEASURES

The serum concentrations of 25(OH)D and other blood parameters were assessed before exercise and at 0, 0.5, 1, 3, and 24 hours after exercise.

RESULTS

The serum 25(OH)D concentrations were significantly increased not only at 0 (P < 0.01), 1 (P < 0.05), and 3 hours (P < 0.01) after exercise, but they were also increased at 24 hours (P < 0.05) after acute endurance exercise in young adults. A significant sex × time interaction effect was observed (P < 0.05), and the incremental areas under the curve for the 25(OH)D concentrations were significantly higher in men than in the women (P < 0.01).

CONCLUSIONS

There is a direct effect of endurance exercise on serum 25(OH)D concentrations. In addition, sex disparity was observed in the serum 25(OH)D response to acute endurance exercise, and the increase in 25(OH)D concentrations was greater in men than in women.