Serum Adropin Levels Are Reduced in Adult Patients with Nonalcoholic Fatty Liver Disease

Unveiling the multifaceted role of adropin in various diseases (Review)

Adropin is a secreted peptide encoded by the energy homeostasis‑associated gene, which also functions as a membrane‑bound protein facilitating intercellular communication. This peptide has been detected in various tissues and body fluids, including the brain, liver, kidney, heart, pancreas, small intestine, endothelial cells and colostrum. Notably, the amino acid sequences of adropin are identical in humans, mice and rats. Previous studies have demonstrated that adropin levels fluctuate under different physiological and pathological conditions. Adropin plays a role in regulating carbohydrate metabolism, lipid metabolism and intercellular molecular signaling pathways, implicating its involvement in the progression of numerous diseases, such as acute myocardial infarction, lung injury, non‑alcoholic fatty liver disease/non‑alcoholic steatohepatitis, kidney disease, polycystic ovary syndrome, obesity, and diabetes, atherosclerosis, systemic sclerosis and cancer. Despite its significance, the precise role and mechanism of this protein remain inadequately understood and studied. To elucidate the function of adropin and its clinical research status, a systematic review of recent studies on adropin across various diseases was conducted. Additionally, several challenges and limitations associated with adropin research in both animal and clinical contexts were identified, aiming to offer valuable insights for future investigation.

From NAFLD to MASLD: Meta-analysis and systematic review of NAFLD patients in Turkiye in terms of metabolic profile and MASLD potential

Non-alcoholic Fatty Liver Disease (NAFLD) is both a cause and a consequence of metabolic disturbances. Consequently, the disease term has recently changed to Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD). Turkiye is one of the leading countries with high incidences of diseases such as diabetes, obesity, metabolic syndrome, and fatty liver. This study aims to identify the metabolic parameters and MASLD potential of NAFLD in Turkiye. All NAFLD studies conducted in Turkiye were systematically searched using the keywords "fatty liver disease" AND " Turkiye " on PubMed, Scopus, and Web of Science databases. A total of 2653 articles were scanned, and 120 studies were eligible for meta-analysis. The metabolic parameters were meta-analyzed from a broad perspective. According to the meta-analysis results, there were significant increases in waist circumferences (mean difference: 10.90, p<0.00001), HOMA-IR (mean difference: 2.13, p<0.00001), aspartate aminotransferase (AST) (mean difference: 17.82, p<0.00001), systolic blood pressure (SBP) (mean difference: 5.86, p<0.00001), and C-reactive protein (CRP) levels (mean difference: 0.95, p<0.00001). These parameters are representative biochemical findings of disturbed glucose metabolism, lipid profile, blood pressure, and acute phase response mechanisms. Furthermore, the analysis of all related parameters commonly found among the articles confirmed these metabolic dysfunctions. NAFLD is a metabolic disease that encompasses multiple pathways related to glucose and lipid metabolism, vascular function, inflammation, and acute phase responses. Additionally, our results suggest that Turkish NAFLD patients identified in previous studies mostly have MASLD. This is the first meta-analysis study indicating changes in metabolism-related parameters with a cumulative meta-analysis of all Turkish NAFLD studies.

Longitudinal changes in serum adropin levels and liver fat content during liraglutide treatment in newly diagnosed patients with type 2 diabetes mellitus and metabolic dysfunction-associated fatty liver disease

AIMS

To explore the effect of liraglutide treatment on serum adropin and its relationship to the liver fat content in newly diagnosed patients with type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated fatty liver disease (MAFLD).

METHODS

Serum adropin level and liver fat content were assessed in patients with T2DM and MAFLD (n = 22), along with healthy controls (n = 22). Afterward, the patients received liraglutide treatment for 12 weeks. Serum adropin levels were examined by a competitive enzyme-linked immunosorbent assay. Liver fat content was quantified via magnetic resonance imaging-estimated proton density fat fraction (MRI-PDFF).

RESULTS

We found that patients with newly diagnosed T2DM and MAFLD had lower serum adropin levels [2.79 ± 0.47 vs. 3.27 ± 0.79 ng/mL, P < 0.05] and higher liver fat content [19.12 ± 9.46 vs. 4.67 ± 0.61%, P < 0.001], compared to healthy controls. Following 12-week liraglutide treatment, serum adropin levels increased from 2.83(2.44, 3.24) to 3.65(3.20, 3.85) ng/mL (P < 0.001), and liver fat content decreased from 18.04(11.08, 27.65) to 7.74(6.42, 13.49) % (P < 0.001) in patients with T2DM and MAFLD. Furthermore, increases in serum adropin were strongly associated with decreases in liver fat content (β = - 5.933, P < 0.001), liver enzyme and glucolipid metabolism parameters.

CONCLUSION

The increase in serum adropin level following liraglutide treatment was strongly correlated with the reduction in liver fat content and glucolipid metabolism. Hence, adropin might be a potential marker for the beneficial effects of liraglutide on treating T2DM and MAFLD.

Circulating levels of adropin and diabetes: a systematic review and meta-analysis of observational studies

OBJECTIVE

Adropin, a newly identified regulatory protein has garnered attention given its potential role in metabolism regulation, especially glucose metabolism and insulin resistance. However, studies on the association between adropin and type 2 diabetes mellitus (T2DM) are equivocal. The aim of this study is to assess the association between serum adropin levels and T2DM using a systematic review and meta-analysis of observational studies.

METHODS

PubMed, Scopus, ISI Web of science, and Google Scholar were searched, up to August 2022, for studies that reported the association between serum levels of adropin in adults with T2DM compared to a control group without diabetes. A random-effect model was used to compute the pooled weighted mean difference (WMD) with 95% confidence intervals (CI).

RESULTS

Meta-analysis of 15 studies (n = 2813 participants) revealed that the serum adropin concentrations were significantly lower in patients with T2DM compared with the control group (WMD= -0.60 ng/mL, 95% CI: -0.70 to -0.49; I² = 99.5%). Subgroup analysis also found lower concentration of adropin in patients with T2DM who were otherwise healthy compared to a control group (n = 9; WMD=-0.04 ng/ml, 95% CI= -0.06 to -0.01, p = 0.002; I² = 96.4).

CONCLUSIONS

Our study showed adropin levels are lower in patients with diabetes compared to a control group without diabetes. However, the limitations of observational studies challenge the validity of the results, and further investigations are needed to confirm the veracity of these findings and additionally explore possible mechanisms.

Role of adropin in arterial stiffening associated with obesity and type 2 diabetes

Adropin is a peptide largely secreted by the liver and known to regulate energy homeostasis; however, it also exerts cardiovascular effects. Herein, we tested the hypothesis that low circulating levels of adropin in obesity and type 2 diabetes (T2D) contribute to arterial stiffening. In support of this hypothesis, we report that obesity and T2D are associated with reduced levels of adropin (in liver and plasma) and increased arterial stiffness in mice and humans. Establishing causation, we show that mesenteric arteries from adropin knockout mice are also stiffer, relative to arteries from wild-type counterparts, thus recapitulating the stiffening phenotype observed in T2D db/db mice. Given the above, we performed a set of follow-up experiments, in which we found that 1) exposure of endothelial cells or isolated mesenteric arteries from db/db mice to adropin reduces filamentous actin (F-actin) stress fibers and stiffness, 2) adropin-induced reduction of F-actin and stiffness in endothelial cells and db/db mesenteric arteries is abrogated by inhibition of nitric oxide (NO) synthase, and 3) stimulation of smooth muscle cells or db/db mesenteric arteries with a NO mimetic reduces stiffness. Lastly, we demonstrated that in vivo treatment of db/db mice with adropin for 4 wk reduces stiffness in mesenteric arteries. Collectively, these findings indicate that adropin can regulate arterial stiffness, likely via endothelium-derived NO, and thus support the notion that "hypoadropinemia" should be considered as a putative target for the prevention and treatment of arterial stiffening in obesity and T2D.NEW & NOTEWORTHY Arterial stiffening, a characteristic feature of obesity and type 2 diabetes (T2D), contributes to the development and progression of cardiovascular diseases. Herein we establish that adropin is decreased in obese and T2D models and furthermore provide evidence that reduced adropin may directly contribute to arterial stiffening. Collectively, findings from this work support the notion that "hypoadropinemia" should be considered as a putative target for the prevention and treatment of arterial stiffening in obesity and T2D.

New Peptides as Potential Players in the Crosstalk Between the Brain and Obesity, Metabolic and Cardiovascular Diseases

According to the World Health Organization report published in 2016, 650 million people worldwide suffer from obesity, almost three times more than in 1975. Obesity is defined as excessive fat accumulation which may impair health with non-communicable diseases such as diabetes, cardiovascular diseases (hypertension, coronary artery disease, stroke), and some cancers. Despite medical advances, cardiovascular complications are still the leading causes of death arising from obesity. Excessive fat accumulation is caused by the imbalance between energy intake and expenditure. The pathogenesis of this process is complex and not fully understood, but current research is focused on the role of the complex crosstalk between the central nervous system (CNS), neuroendocrine and immune system including the autonomic nervous system, adipose tissue, digestive and cardiovascular systems. Additionally, special attention has been paid to newly discovered substances: neuropeptide 26RFa, preptin, and adropin. It was shown that the above peptides are synthesized both in numerous structures of the CNS and in many peripheral organs and tissues, such as the heart, adipose tissue, and the gastrointestinal tract. Recently, particular attention has been paid to the role of the presented peptides in the pathogenesis of obesity, metabolic and cardiovascular system diseases. This review summarizes the role of newly investigated peptides in the crosstalk between brain and peripheral organs in the pathogenesis of obesity, metabolic, and cardiovascular diseases.

Serum Adropin as a Potential Biomarker for Predicting the Development of Type 2 Diabetes Mellitus in Individuals With Metabolic Dysfunction-Associated Fatty Liver Disease

Background: Adropin, a peptide translated from the Energy Homeostasis Associated gene (ENHO), was mainly expressed in the liver and was a regulator in metabolic and energy homeostasis. This study aims to investigate the correlation between adropin and histological characteristics of the liver, and the clinical relevance of adropin in patients with metabolic dysfunction-associated fatty liver disease (MAFLD). Methods: A total of 62 subjects, including 32 healthy controls and 30 MAFLD patients, were enrolled in this case-control study. The MAFLD patients were further divided into two subgroups, including NGT-M group and T2DM-M group. Serum adropin levels, metabolic parameters and intrahepatic lipids, the liver ENHO mRNA expressions and histological characteristics were investigated. Results: MAFLD patients showed significantly lower circulating adropin compared with healthy controls (2.02 ± 2.92 vs. 5.52 ± 0.65 ng/mL, P < 0.0001). Subgroup analysis exhibited dramatically declined serum adropin levels in T2DM-M patients compared with NGT-M group (0.51 ± 0.73 vs. 4.00 ± 3.52 ng/mL, P < 0.001). H&E and Oil Red O staining show exacerbated steatohepatitis in T2DM-M patients in contrast with NGT-M group. Furthermore, serum adropin concentrations were negatively correlated with intrahepatic triglyceride (TG), total cholesterol (TC), and NAFLD activity score (NAS) (TG: r = -0.495; TC: r = -0.392; NAS: r = -0.451; all P < 0.05). Conclusions: MAFLD patients showed significantly lower adropin levels than the healthy controls, especially in T2DM patients. Adropin maybe a potential biomarker for predicting the development of MAFLD, especially in T2DM individuals.

Correlation of Serum Adropin Levels with Risk Factors of Cardiovascular Disease in Hemodialysis Patients

Background: Many preclinical studies have shown that adropin has physiological effects such as regulating glucose, lipid, and energy metabolism, protecting endothelial cells and antiatherosclerosis. Our aim is to explore whether adropin is correlated with risk factors of cardiovascular disease (CVD) in hemodialysis (HD) patients. Methods: We recruited 170 HD patients and 120 healthy controls. The serum adropin concentration and clinical characteristics were measured. Results: The serum adropin concentration in HD patients was significantly lower than that in healthy controls and which in HD patients with CVD or diabetes mellitus (DM) was significantly lower than that in patients without CVD or DM. The correlation analysis showed that serum adropin levels were correlated negatively with Age, CVD history, DM history, C-reactive protein, type B natriuretic peptide, phosphorus, intact parathyroid hormone, carotid artery plaque amount and carotid intima-media thickness (CIMT), left ventricular septal thickness (LVSTd), and left ventricular posterior wall thickness, whereas it was correlated positively with albumin, hemoglobin, serum creatinine and Kt/V, and ejection fraction value. Partial correlation analysis verified that serum adropin levels were correlated negatively with CIMT, and multiple linear regression analysis revealed that low serum adropin levels may be one independent predictors of CIMT. However, the partial correlation analysis and multiple linear regression analysis did not identify the significant correlation between serum adropin levels and LVSTd. Conclusions: Our study revealed that serum adropin level is significantly correlated with risk factors of CVD and low serum adropin levels may be a potential predictor of CVD in HD patients.

Effect of Long-Term Continuous Light Exposure and Western Diet on Adropin Expression, Lipid Metabolism, and Energy Homeostasis in Rats

Long-term continuous light exposure (CL) and western diet (WD) effects on Adropin expression, RORα, and Rev-erb-α nuclear receptors and energy homeostasis were studied in rats. Thirty-two male Wistar rats (250-290 g) were enrolled for 3 months in the following groups (n = 8/group): (a) Normal control group (NC), (b) CL group, (c) WD group, and (d) CL + WD group. Then, indirect calorimetry and food intake (FI) were measured. Finally, Adropin, hormone-sensitive lipase (HSL), adipocyte triglyceride lipase (ATGL), and free fatty acids (FFA) were measured. Additionally, the histopathology and gene expression of Enho, RORα, and Rev-erb-α genes were done. The CL alone elevated the Adropin plasma level and gene expression, increased RORα expression, and decreased the Rev-erb-α nuclear receptor expression mainly in the liver and kidney. Besides, CL increased the total energy expenditure (TEE) and decreased the respiratory quotient. WD alone or in combination with the CL reversed gene expression of Enho, RORα, and Rev-erb-α. Combined CL and WD increased the TEE, reduced the food intake, increased the ATGL, and reduced the Adropin level in addition to widespread degenerative changes in the liver, spleen, and renal tissues. The deleterious effects of CL and WD on energy homeostasis may include Adropin with the involvement of the RORα and Rev-erb-α nuclear receptors.

Exercise suppresses NLRP3 inflammasome activation in mice with diet-induced NASH: a plausible role of adropin

NLRP3 inflammasome activation, which can be triggered by reactive oxygen species (ROS), contributes to nonalcoholic steatohepatitis (NASH) progression. Exercise is an effective therapeutic strategy for NASH. However, whether exercise prevents NLRP3 activation in NASH has not been investigated. Here, we investigated the effect of exercise on NLRP3 inflammasome in mice with high-fat diet (HFD)-induced or methionine and choine-deficient (MCD) diet-induced NASH and explored whether adropin, a metabolic peptide hormone shown to inhibit inflammation, mediates an exercise-induced benefit against NLRP3 inflammasome activation. Exercise alleviated diet-induced hepatic steatosis, inflammation, and fibrosis. Importantly, exercise significantly reduced the expression of NLRP3 inflammasome components, decreased Caspase-1 enzymatic activity, normalized IL-1β production, and suppressed ROS overproduction in HFD-fed and MCD diet-fed mice. The exercise-elicited NLRP3 inflammasome inhibition was accompanied by increased adropin levels. Moreover, serum adropin levels were negatively correlated with serum IL-1β levels. We further explored the effect of adropin on the NLRP3 inflammasome in palmitic acid (PA)-treated hepatocytes and Kupffer cells. Although adropin treatment did not significantly decrease the levels of all inflammasome components, it reduced the active Caspase-1 level, decreased Caspase-1 activity and downregulated IL-1β expression in hepatocytes and Kupffer cells (KCs) treated with PA. Moreover, ROS levels in PA-stimulated hepatocytes and Kupffer cells were reduced upon adropin treatment. In summary, we demonstrated that the inhibitory effect of exercise on NLRP3 inflammasome activation was associated with adropin induction, resulting in NASH improvement.

Adropin as a potential mediator of the metabolic system-autonomic nervous system-chronobiology axis: Implementing a personalized signature-based platform for chronotherapy

Adropin is a peptide hormone, which plays a role in energy homeostasis and controls glucose and fatty acid metabolism. Its levels correlate with changes in carbohydrate-lipid metabolism, metabolic diseases, central nervous system function, endothelial function and cardiovascular disease. Both metabolic pathways and adropin are regulated by the circadian clocks. Here, we review the roles of the autonomic nervous system and circadian rhythms in regulating metabolic pathways and energy homeostasis. The beneficial effects of chronotherapy in various systems are discussed. We suggest a potential role for adropin as a mediator of the metabolic system-autonomic nervous system axis. We discuss the possibility of establishing an individualized adropin and circadian rhythm-based platform for implementing chronotherapy, and variability signatures for improving the efficacy of adropin-based therapies are discussed.

Lower adropin expression is associated with oxidative stress and severity of nonalcoholic fatty liver disease

BACKGROUND & AIMS

Adropin has been reported to be involved in metabolic disorders, including nonalcoholic fatty liver disease (NAFLD). However, the clinical relevance of adropin expression to the histological severity of NAFLD is unclear. This study aimed to investigate adropin expression in biopsy-proven NAFLD patients.

METHODS

This case-control study enrolled a total of 109 participants, including 15 normal histological controls, 26 nonalcoholic fatty liver (NAFL), 21 nonalcoholic steatohepatitis (NASH) subjects and B-ultrasound NAFLD-free normal controls matched to the cases based on age and sex (the case:control ratio was 1:1). Liver biopsies were obtained and histological characteristics were assessed. Primary murine hepatocytes were isolated from C57BL/6J mice and incubated with doses of palmitate to induce oxidative stress.

RESULTS

The serum adropin level in NASH patients was 9.99 ± 5.51 ng/ml, significantly lower than that in B-ultrasound normal controls (22.70 ± 6.32 ng/ml), histological normal controls (21.93 ± 6.63 ng/ml) and NAFL patients (17.82 ± 6.90 ng/ml). Serum adropin levels were negatively correlated with the histological severity of NAFLD. The lower serum adropin level predicted NASH (area under the ROC curve: 87.1%). Adropin expression in serum and liver was also negatively associated with hepatic MDA and serum 8-iso-PGF2α levels. Furthermore, palmitate rather than oleate induced oxidative stress in a dose-dependent manner with a gradient decrease in adropin expression in primary murine hepatocytes. Adropin overexpression or treatment ameliorated palmitate-induced oxidative stress in hepatocytes.

CONCLUSIONS

Circulating adropin was inversely associated with the oxidative stress and histological severity of NAFLD. It may play an important role in the development of NAFLD.

Adropin: a hepatokine modulator of vascular function and cardiac fuel metabolism

Adropin is a nutritionally regulated peptide hormone, secreted primarily by the liver, which modulates metabolic homeostasis in a number of tissues. Growing evidence suggests that adropin is an important regulatory component in a number of cardiovascular pathologies, and may be central to the control of cardiac fuel metabolism and vascular function. In this mini-review, we examine the known facets of adropin biology, discuss open questions in the field, and speculate on the therapeutic potential of targeting adropin-related signaling pathways in cardiovascular diseases.

Adropin as A Fat-Burning Hormone with Multiple Functions-Review of a Decade of Research

Adropin is a unique hormone encoded by the energy homeostasis-associated (Enho) gene. Adropin is produced in the liver and brain, and also in peripheral tissues such as in the heart and gastrointestinal tract. Furthermore, adropin is present in the circulatory system. A decade after its discovery, there is evidence that adropin may contribute to body weight regulation, glucose and lipid homeostasis, and cardiovascular system functions. In this review, we summarize and discuss the physiological, metabolic, and pathophysiological factors regulating Enho as well as adropin. Furthermore, we review the literature addressing the role of adropin in adiposity and type 2 diabetes. Finally, we elaborate on the role of adropin in the context of the cardiovascular system, liver diseases, and cancer.

Promotion of Adropin Expression by Hyperglycemia Is Associated with STAT3 Activation in Diabetic Rats

BACKGROUND

Adropin is a secreted polypeptide that has been demonstrated to play an important role in energy homeostasis and lipid metabolism. Signal transducer and activator of transcription 3 (STAT3) may promote the transcription of target genes including adropin. In the current study, we investigated the effect of adropin on glucose metabolism in diabetic rats and the mechanism that governs this effect was subsequently assessed.

MATERIALS AND METHODS

Rats received a single injection of streptozotocin to induce type 1 diabetes. The diabetic rats were treated with insulin or phloridzin, another antidiabetic agent through inhibition of glucose reabsorption, for 7 days. Plasma glucose levels and adropin levels were measured. The interaction between STAT3 and adropin was evaluated using the human hepatoma HepG2 cell line. HepG2 cells were pretreated with the specific antagonist Stattic or with STAT3-specific siRNAs to knockout STAT3. Changes in energy homeostasis-associated gene expression were measured using real-time PCR. The protein expression levels of pSTAT3 and STAT3 were measured using Western blotting.

RESULTS

In diabetic rats, the serum concentrations of adropin were increased in the vehicle-treated group and decreased in the insulin- or phloridzin-treated group. In liver tissues, the Enho expression level and the activity of STAT3 also showed similar tendencies. After HepG2 cells were treated with medium containing high glucose, the ratio of p-STAT3 to STAT3, Enho mRNA levels and reactive oxygen species expression levels in HepG2 cells were significantly increased in conjunction with increased glucose levels. The effect was inhibited after pretreatment with Stattic or knockdown with STAT3-specific siRNAs.

CONCLUSION

STAT3 is involved in the genetic regulation of adropin, increasing the levels of circulating adropin and promoting Enho expression in the livers of diabetic rats.

Inter-organ cross-talk in metabolic syndrome

Maintenance of systemic homeostasis and the response to nutritional and environmental challenges require the coordination of multiple organs and tissues. To respond to various metabolic demands, higher organisms have developed a system of inter-organ communication through which one tissue can affect metabolic pathways in a distant tissue. Dysregulation of these lines of communication contributes to human pathologies, including obesity, diabetes, liver disease and atherosclerosis. In recent years, technical advances such as data-driven bioinformatics, proteomics and lipidomics have enabled efforts to understand the complexity of systemic metabolic cross-talk and its underlying mechanisms. Here, we provide an overview of inter-organ signals and their roles in metabolic control, and highlight recent discoveries in the field. We review peptide, small-molecule and lipid mediators secreted by metabolic tissues, as well as the role of the central nervous system in orchestrating peripheral metabolic functions. Finally, we discuss the contributions of inter-organ signalling networks to the features of metabolic syndrome.