Adropin regulates cardiac energy metabolism and improves cardiac function and efficiency

Adropin may regulate ovarian functions by improving antioxidant potential in adult mouse

The corpus luteum (CL) is a temporary endocrine gland that synthesizes progesterone. The luteal progesterone plays a central role in the regulation of the estrous cycle as well as the implantation and maintenance of pregnancy. Our previous study showed the expression of adropin and its receptor, GPR19, in the luteal cells and its significant role in luteinization. The aim of the present study was to investigate the in vitro effect of adropin on hCG-induced ovarian functions in adult mice. We also evaluated the effect of exogenous treatment with adropin on ovarian steroidogenesis and anti-oxidant parameters, with special emphasis on CL function. Our results demonstrated that adropin acts synergistically with hCG to promote ovarian steroidogenesis and survival by increasing the expression of StAR, 3β-HSD, and aromatase proteins and decreasing the BAX/BCL2 ratio. Exogenous adropin treatment increased progesterone production by increasing the expression of GPR19, StAR and 3β-HSD enzymes in the mouse ovary. Also, adropin inhibited the luteal oxidative stress by increasing nuclear translocation of NRF-2 in CL, which resulted in increased HO-1 expression and SOD, catalase activity. Decreased oxidative stress might inhibit the translocation of NF-κB into the nucleus of luteal cells, resulting into increased survival and decreased apoptosis, as evident by decreased lipid peroxidation, BAX/BCL2 ratio, caspase 3, active caspase 3 expression, and TUNEL-positive cells in adropin treated mice. Our findings suggest that adropin can be a promising candidate that can enhance the survivability of the CL.

Low circulating adropin concentrations predict increased risk of cognitive decline in community-dwelling older adults

The secreted peptide adropin is highly expressed in human brain tissues and correlates with RNA and proteomic risk indicators for dementia. Here we report that plasma adropin concentrations predict risk for cognitive decline in the Multidomain Alzheimer Preventive Trial (ClinicalTrials.gov Identifier, NCT00672685; mean age 75.8y, SD = 4.5 years, 60.2% female, n = 452). Cognitive ability was evaluated using a composite cognitive score (CCS) that assessed four domains: memory, language, executive function, and orientation. Relationships between plasma adropin concentrations and changes in CCS (∆CCS) were examined using Cox Proportional Hazards Regression, or by grouping into tertiles ranked low to high by adropin values and controlling for age, time between baseline and final visits, baseline CCS, and other risk factors (e.g., education, medication, APOE4 status). Risk of cognitive decline (defined as a ∆CCS of - 0.3 or more) decreased with increasing plasma adropin concentrations (hazard ratio = 0.873, 95% CI 0.780-0.977, P = 0.018). Between adropin tertiles, ∆CCS was significantly different (P = 0.01; estimated marginal mean ± SE for the 1st to 3rd tertile, - 0.317 ± 0.064; - 0.275 ± 0.063; - 0.042 ± 0.071; n = 133,146, and 130, respectively; P < 0.05 for 1st vs. 2nd and 3rd adropin tertiles). Normalized plasma Aß42/40 ratio and plasma neurofilament light chain, indicators of neurodegeneration, were significantly different between adropin tertile. These differences were consistent with reduced risk of cognitive decline with higher plasma adropin levels. Overall, these results suggest cognitive decline is reduced in community-dwelling older adults with higher circulating adropin levels. Further studies are needed to determine the underlying causes of the relationship and whether increasing adropin levels can delay cognitive decline.

Fatty acid metabolism disorders and potential therapeutic traditional Chinese medicines in cardiovascular diseases

Cardiovascular diseases are currently the primary cause of mortality in the whole world. Growing evidence indicated that the disturbances in cardiac fatty acid metabolism are crucial contributors in the development of cardiovascular diseases. The abnormal cardiac fatty acid metabolism usually leads to energy deficit, oxidative stress, excessive apoptosis, and inflammation. Targeting fatty acid metabolism has been regarded as a novel approach to the treatment of cardiovascular diseases. However, there are currently no specific drugs that regulate fatty acid metabolism to treat cardiovascular diseases. Many traditional Chinese medicines have been widely used to treat cardiovascular diseases in clinics. And modern studies have shown that they exert a cardioprotective effect by regulating the expression of key proteins involved in fatty acid metabolism, such as peroxisome proliferator-activated receptor α and carnitine palmitoyl transferase 1. Hence, we systematically reviewed the relationship between fatty acid metabolism disorders and four types of cardiovascular diseases including heart failure, coronary artery disease, cardiac hypertrophy, and diabetic cardiomyopathy. In addition, 18 extracts and eight monomer components from traditional Chinese medicines showed cardioprotective effects by restoring cardiac fatty acid metabolism. This work aims to provide a reference for the finding of novel cardioprotective agents targeting fatty acid metabolism.

Ontogeny of adropin and its receptor expression during postnatal development and its pro-gonadal role in the ovary of pre-pubertal mouse

Adropin, a highly conserved multifunctional peptide hormone, has a beneficial effect on the maintenance of gluco-lipid homeostasis, endothelial and cardiovascular functions. However, the expression and potential role of adropin in ovarian function are not fully elucidated. The present study aimed to investigate the expression of adropin and GPR19 in the mice ovary during various stages of postnatal development. This study also explored whether the treatment of adropin can modulate the timing of puberty, for which pre-pubertal mice were treated with adropin. The result showed the intense immunoreactivity of adropin in TICs, while GPR19 immunoreactivity was noted in GCs in infantile, pre-pubertal, and pubertal mice ovary. Also, adropin and GPR19 are highly expressed in the CL of the ovary of reproductively active mice. The fact that adropin expression in the ovary at different stages of postnatal development positively correlated with circulating progesterone and estradiol indicated that it has a role in the production of steroid hormones. Furthermore, the results of in vivo studies in pre-pubertal mice showed that adropin promotes early folliculogenesis by enhancing the proliferation (PCNA) of GCs of cortical ovarian follicles and promotes estradiol production by enhancing the expression of GPR19, StAR, CYP11A1 and aromatase proteins. Also, adropin treatment increases the Bax/Bcl2 ratio and expression of cleaved caspase-3 and ERα proteins, which may result in increased apoptosis of medullary follicles leading to the formation of a well-developed interstitium with interstitial glandular cells. Collectively, these findings indicate that adropin may be a factor that accelerates pubertal development in the ovary and could be utilized as a therapeutic approach for treating pubertal delay.

Emerging Evidence Linking the Liver to the Cardiovascular System: Liver-derived Secretory Factors

Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality worldwide. Recently, accumulating evidence has revealed hepatic mediators, termed as liver-derived secretory factors (LDSFs), play an important role in regulating CVDs such as atherosclerosis, coronary artery disease, thrombosis, myocardial infarction, heart failure, metabolic cardiomyopathy, arterial hypertension, and pulmonary hypertension. LDSFs presented here consisted of microbial metabolite, extracellular vesicles, proteins, and microRNA, they are primarily or exclusively synthesized and released by the liver, and have been shown to exert pleiotropic actions on cardiovascular system. LDSFs mainly target vascular endothelial cell, vascular smooth muscle cells, cardiomyocytes, fibroblasts, macrophages and platelets, and further modulate endothelial nitric oxide synthase/nitric oxide, endothelial function, energy metabolism, inflammation, oxidative stress, and dystrophic calcification. Although some LDSFs are known to be detrimental/beneficial, controversial findings were also reported for many. Therefore, more studies are required to further explore the causal relationships between LDSFs and CVDs and uncover the exact mechanisms, which is expected to extend our understanding of the crosstalk between the liver and cardiovascular system and identify potential therapeutic targets. Furthermore, in the case of patients with liver disease, awareness should be given to the implications of these abnormalities in the cardiovascular system. These studies also underline the importance of early recognition and intervention of liver abnormalities in the practice of cardiovascular care, and a multidisciplinary approach combining hepatologists and cardiologists would be more preferable for such patients.

Adropin - A new player in energy regulation predicts long-term prognosis of patients with acute myocardial infarction

Background

As a novel energy homeostasis regulator, Adropin not only plays a vital part in meditating energy metabolism, but also has a certain correlation with atherosclerotic diseases. The purpose of this study was to evaluate the effect of Adropin on the long-term prognosis of patients with acute myocardial infarction (AMI).

Methods

162 recruited patients with AMI were divided into low Adropin group (Adropin<166.3 pg/mL, n = 82) and high Adropin group (Adropin≥166.3 pg/mL, n = 80), according to the mean value of serum Adropin level. Patients were followed up and major adverse cardiac events (MACEs) were recorded. The Kaplan-Meier method and Cox regression model were used to evaluate the survival of patients and the related factors of cardiac events.

Results

Diabetes was more common in low Adropin group than that in high Adropin group (P < 0.05). Patients were followed up for an average of 50.3 ± 19.2 months. MACEs occurred in 37 patients (22.8%), including 6 cardiac deaths (3.7%), 14 recurrent myocardial infarction (8.6%) and 17 rehospitalization of heart failure (10.5%). The incidence of recurrent myocardial infarction in low Adropin group was higher than that in high Adropin group (13.4% vs 3.8%, P < 0.05). There was no significant difference in the overall incidence of MACE, cardiac death and rehospitalization of heart failure between the two groups. Kaplan-Meier method (log rank test) analysis results showed that patients with low Adropin had lower survival rate without recurrent myocardial infarction (log rank P = 0.035).

Conclusion

Low Adropin level was associated with an increased risk of long-term recurrent myocardial infarction in patients with AMI.

Feeding-induced hepatokines and crosstalk with multi-organ: A novel therapeutic target for Type 2 diabetes

Hyperglycemia, which can be caused by either an insulin deficit and/or insulin resistance, is the main symptom of Type 2 diabetes, a significant endocrine metabolic illness. Conventional medications, including insulin and oral antidiabetic medicines, can alleviate the signs of diabetes but cannot restore insulin release in a physiologically normal amount. The liver detects and reacts to shifts in the nutritional condition that occur under a wide variety of metabolic situations, making it an essential organ for maintaining energy homeostasis. It also performs a crucial function in glucolipid metabolism through the secretion of hepatokines. Emerging research shows that feeding induces hepatokines release, which regulates glucose and lipid metabolism. Notably, these feeding-induced hepatokines act on multiple organs to regulate glucolipotoxicity and thus influence the development of T2DM. In this review, we focus on describing how feeding-induced cross-talk between hepatokines, including Adropin, Manf, Leap2 and Pcsk9, and metabolic organs (e.g.brain, heart, pancreas, and adipose tissue) affects metabolic disorders, thus revealing a novel approach for both controlling and managing of Type 2 diabetes as a promising medication.

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.

Adropin’s Role in Energy Homeostasis and Metabolic Disorders

Adropin is a novel 76-amino acid-peptide that is expressed in different tissues and cells including the liver, pancreas, heart and vascular tissues, kidney, milk, serum, plasma and many parts of the brain. Adropin, encoded by the Enho gene, plays a crucial role in energy homeostasis. The literature review indicates that adropin alleviates the degree of insulin resistance by reducing endogenous hepatic glucose production. Adropin improves glucose metabolism by enhancing glucose utilization in mice, including the sensitization of insulin signaling pathways such as Akt phosphorylation and the activation of the glucose transporter 4 receptor. Several studies have also demonstrated that adropin improves cardiac function, cardiac efficiency and coronary blood flow in mice. Adropin can also reduce the levels of serum triglycerides, total cholesterol and low-density lipoprotein cholesterol. In contrast, it increases the level of high-density lipoprotein cholesterol, often referred to as the beneficial cholesterol. Adropin inhibits inflammation by reducing the tissue level of pro-inflammatory cytokines such as tumor necrosis factor alpha and interleukin-6. The protective effect of adropin on the vascular endothelium is through an increase in the expression of endothelial nitric oxide synthase. This article provides an overview of the existing literature about the role of adropin in different pathological conditions.

Adropin Inhibits Vascular Smooth Muscle Cell Osteogenic Differentiation to Alleviate Vascular Calcification via the JAK2/STAT3 Signaling Pathway

Vascular calcification is characterized as the deposition of hydroxyapatite mineral in the form of calcium-phosphate complexes in the vasculature. Transdifferentiation between vascular smooth muscle cells (VSMCs) and osteoblast-like cells is considered essential in the progression of vascular calcification. The pathophysiological mechanisms underlying vascular calcification and VSMC osteogenic differentiation remain to be fully elucidated, and the development of novel therapies is required. In the present study, PCR and western blot analysis were conducted to quantify the mRNA and protein expression levels of calcification-associated markers (bone morphogenetic protein 2, alkaline phosphatase, osteoprotegerin, osteocalcin, and runt-related transcription factor 2) and adropin in VSMCs and rat vascular tissues. The calcification of VSMCs was assessed using alizarin red staining. Moreover, adropin expression levels in VSMCs were analyzed using immunofluorescence. Lentiviral transfection and small interfering RNA were used for overexpression and knockdown of adropin in VSMCs, respectively. The results demonstrated that adropin alleviated vascular calcification in vivo. Moreover, adropin also inhibited osteogenic differentiation and the calcification of VSMCs in vitro. Notably, results of the present study revealed that the tyrosine protein kinase JAK2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway played a key role in the aforementioned inhibition. In conclusion, the results of the present study demonstrated that adropin inhibited VSMC osteogenic differentiation to alleviate vascular calcification via the JAK2/STAT3 signaling pathway.

Adropin Improves Radiation-Induced Myocardial Injury via VEGFR2/PI3K/Akt Pathway

Mediastinal cancer radiotherapy exposes the heart and causes myocardial injury. It is of utmost importance to identify effective prevention and treatment targets. In this study, the regulatory role of adropin (Ad) in radiation-induced myocardial injury (RIMI) was explored in mice. After C57BL/6 mice were administered E0771 cells and received radiotherapy, the effects of exogenous Ad intervention on myocardial fibrosis, apoptosis, microvessel density, oxidative stress, and protein expression levels were observed. The results showed that exogenous Ad effectively improved cardiac function, suppressed oxidative stress, inhibited myocardial fibrosis, reduced myocardial apoptosis, and promoted microangiogenesis in RIMI mice. Ad also downregulated the expression levels of transforming growth factor β1 (TGF-β1), NADPH oxidase 4 (NOX4), and cleaved caspase 3 and upregulated the expression of phosphor-endothelial nitric oxide synthase (p-eNOS). However, the above-mentioned effects of Ad were significantly reversed in Ad^−/− mice. Radiotherapy resulted in the downregulation of phosphor-vascular endothelial growth factor receptor (p-VEGFR2) and p-Akt in myocardial tissue, which were upregulated by Ad. However, after targeted inhibition of VEGFR2 with apatinib, the effect of Ad on improving RIMI was significantly reversed. Taken together, exogenous Ad significantly ameliorated RIMI by reducing oxidative stress, promoting microangiogenesis, and inhibiting myocardial fibrosis and apoptosis. The underlying molecular mechanism involved may be elucidated by activation of the VEGFR2/PI3K/Akt pathway.

The effectiveness of serum S100B, TRAIL, and adropin levels in predicting clinical outcome, final infarct core, and stroke subtypes of acute ischemic stroke patients

Introduction:

More than half of all worldwide deaths and disabilities were caused by stroke. Large artery atherosclerosis is identified as a high etiological risk factor because it accounts for 20% of ischemic stroke.

Objectives:

To identify the significance of TRAIL and adropin release and the relative changes related to S100B levels, as well as the relationship between these biomarkers and the final infarct core, the clinical outcome, and the presence of large artery atherosclerosis in acute stroke patients.

Materials and methods:

Over a one-year period, demographic, clinical, and neuroimaging findings of 90 consecutive patients with acute ischemic stroke were evaluated.

Results:

The mean age of participants was 69.28 ± 10 and 39 patients were female. The increased level of S100B and the decreased levels of sTRAIL with adropin were significantly associated with moderate to severe neurologic presentation (p=0.0001, p=0.002, p=0.002, respectively). On the control CT, a large infarct core was significantly associated with decreased serum levels of sTRAIL and adropin (p=0.001 and p=0.000, respectively); however, the levels of S100B were not significantly associated with good ASPECTS score (p=0.684). Disability and an unfavorable outcome were significantly related to the decreased level of sTRAIL and adropin (p=0.001 and p=0.000 for THRIVE score>5, respectively). Decreased sTRAIL and adropin levels and an increased S100B level were correlated with the presence of large artery atherosclerotic etiologic factors (p=0.000, p=0.000, p=0.036, respectively).

Conclusion:

TRAIL and adropin serum levels were associated with poor clinical outcomes and greater infarcted area in acute ischemic stroke patients.

Hepatic Adropin is Regulated by Estrogen and Contributes to Adverse Metabolic Phenotypes in Ovariectomized Mice

Objective

Menopause is associated with visceral adiposity, hepatic steatosis and increased risk for cardiovascular disease. As estrogen replacement therapy is not suitable for all postmenopausal women, a need for alternative therapeutics and biomarkers has emerged.

Methods

9-week-old C57BL/6 J female mice were subjected to ovariectomy (OVX) or SHAM surgery (n = 10 per group), fed a standard diet and sacrificed 6- & 12 weeks post-surgery.

Results

Increased weight gain, hepatic triglyceride content and changes in hepatic gene expression of Cyp17a1, Rgs16, Fitm1 as well as Il18, Rares2, Retn, Rbp4 in mesenteric visceral adipose tissue (VAT) were observed in OVX vs. SHAM. Liver RNA-sequencing 6-weeks post-surgery revealed changes in genes and microRNAs involved in fat metabolism in OVX vs. SHAM mice. Energy Homeostasis Associated gene (Enho) coding for the hepatokine adropin was significantly reduced in OVX mice livers and strongly inversely correlated with weight gain (r = −0.7 p < 0.001) and liver triglyceride content (r = −0.4, p = 0.04), with a similar trend for serum adropin. In vitro, Enho expression was tripled by 17β-estradiol in BNL 1 ME liver cells with increased adropin in supernatant. Analysis of open-access datasets revealed increased hepatic Enho expression in estrogen treated OVX mice and estrogen dependent ERα binding to Enho. Treatment of 5-month-old OVX mice with Adropin (i.p. 450 nmol/kg/twice daily, n = 4,5 per group) for 6-weeks reversed adverse adipokine gene expression signature in VAT, with a trended increase in lean body mass and decreased liver TG content with upregulation of Rgs16.

Conclusions

OVX is sufficient to induce deranged metabolism in adult female mice. Hepatic adropin is regulated by estrogen, negatively correlated with adverse OVX-induced metabolic phenotypes, which were partially reversed with adropin treatment. Adropin should be further explored as a potential therapeutic target and biomarker for menopause-related metabolic derangement.

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OVX increased body weight, liver fat & adverse visceral fat adipokine signature.

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OVX altered liver transcriptome & miRNA profile including fat metabolism pathways.

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Enho was downregulated by OVX & inversely correlated with weight gain & liver fat.

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Hepatic adropin expression was upregulated by estrogen in-vitro & in-vivo.

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Adropin treatment partially reversed OVX induced adverse metabolic phenotypes.

Current Knowledge of Selected Cardiovascular Biomarkers in Pediatrics: Kidney Injury Molecule-1, Salusin-α and -β, Uromodulin, and Adropin

Cardiovascular diseases are the leading cause of morbidity and mortality in the modern world. Their common denominator is atherosclerosis, a process beginning in childhood. In pediatrics, the aim of preventive measures is to recognize children and adolescents at risk for accelerated atherosclerosis and possible premature cardiovascular events in adulthood. Several diagnostic procedures and biomarkers are available for cardiovascular risk assessment in adults. However, reliable markers in pediatrics are still insufficiently studied. In this contribution, we discuss five potential biomarkers of particular interest: kidney injury molecule-1, salusin-α and -β, uromodulin, and adropin. Studies regarding the pediatric population are scarce, but they support the evidence from studies in the adult population. These markers might entail both a prognostic and a therapeutic interest.

Diet-induced obese mice are resistant to improvements in cardiac function resulting from short-term adropin treatment

Previous studies have shown that treatment with recombinant adropin, a circulating peptide secreted by the liver and brain, restores glucose utilization in the hearts of diet-induced obese mice. This restoration of fuel substrate flexibility, which is lost in obese and diabetic animals, has the potential to improve contractile function in the diabetic heart. Using an ex vivo approach, we examined whether short-term adropin treatment could enhance cardiac function in a mouse model of diet-induced obesity. Our study showed that acute adropin treatment reduces inhibitory phosphorylation of pyruvate dehydrogenase in primary neonatal cardiomyocytes, and leads to moderate improvements in ex vivo cardiac function in mice fed a low fat diet. Conversely, short-term exposure to adropin led to a small decrease in cardiac function in mice fed a long-term high fat diet. Insulin treatment did not significantly alter cardiac function in adropin treated hearts from either low or high fat diet mice, however acute adropin treatment did moderately restore some aspects of downstream insulin signaling in high fat diet fed mice. Overall, these data suggest that in an ex vivo setting, acute adropin treatment alone is not sufficient to promote improved cardiac function in obese animals.

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Adropin promotes cardiac glucose utilization in hearts from diet-induced obese mice.

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In this study, we examined whether adropin treatment improves ex vivo cardiac function in obesity.

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While adropin improves contractile function in lean mice, its impact is lost after exposure to a long-term high fat diet.

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Adropin fails to fully restore cardiac insulin signaling in obese mouse hearts.

Deletion of BCATm increases insulin-stimulated glucose oxidation in the heart

BACKGROUNDS

Branched chain amino acid (BCAA) oxidation is impaired in cardiac insulin resistance, leading to the accumulation of BCAAs and the first products of BCAA oxidation, the branched chain ketoacids. However, it is not clear whether it is the BCAAs, BCKAs or both that are mediating cardiac insulin resistance. To determine this, we produced mice with a cardiac-specific deletion of BCAA aminotransferase (BCATm^-/-), the first enzyme in the BCAA oxidation pathway that is responsible for converting BCAAs to BCKAs.

METHODS

Eight-week-old BCATm cardiac specific knockout (BCATm^-/-) male mice and their α-MHC (myosin heavy chain) - Cre expressing wild type littermates (WT-Cre^+/+) received tamoxifen (50 mg/kg i.p. 6 times over 8 days). At 16-weeks of age, cardiac energy metabolism was assessed in isolated working hearts.

RESULTS

BCATm^-/- mice have decreased cardiac BCAA oxidation rates, increased cardiac BCAAs and a reduction in cardiac BCKAs. Hearts from BCATm^-/- mice showed an increase in insulin stimulation of glucose oxidation and an increase in p-AKT. To determine the impact of reversing these events, we perfused isolated working mice hearts with high levels of BCKAs, which completely abolished insulin-stimulated glucose oxidation rates, an effect associated with decreased p-AKT and inactivation of pyruvate dehydrogenase (PDH), the rate-limiting enzyme in glucose oxidation.

CONCLUSION

This implicates the BCKAs, and not BCAAs, as the actual mediators of cardiac insulin resistance and suggests that lowering cardiac BCKAs can be used as a therapeutic strategy to improve insulin sensitivity in the heart.

Adropin and insulin resistance: Integration of endocrine, circadian, and stress signals regulating glucose metabolism

Dysregulation of hepatic glucose production (HGP) and glucose disposal leads to hyperglycemia and type 2 diabetes. Hyperglycemia results from the declining ability of insulin to reduce HGP and increase glucose disposal, as well as inadequate ß-cell compensation for insulin resistance. Hyperglucagonemia resulting from reduced suppression of glucagon secretion by insulin contributes to hyperglycemia by stimulating HGP. The actions of pancreatic hormones are normally complemented by peptides secreted by cells distributed throughout the body. This regulatory network has provided new therapeutics for obesity and type 2 diabetes (e.g., glucagon-like peptide 1). Other peptide hormones under investigation show promise in preclinical studies. Recent experiments using mice and nonhuman primates indicate the small secreted peptide hormone adropin regulates glucose metabolism. Here, recent expression profiling data indicating hepatic adropin expression increases with oxidative stress and declines with fasting or in the presence of hepatic insulin resistance and how adropin interacts with the pancreatic hormones, insulin, and glucagon to modulate glycemic control are discussed.

Role of Adropin in Cardiometabolic Disorders: From Pathophysiological Mechanisms to Therapeutic Target

Although a large amount of data supports the crucial role of endothelial dysfunction (ED) in cardiovascular diseases (CVDs), there is a large bench-to-bedside chasm between basic and clinical research of ED, limiting the implementation of these findings in everyday clinical settings. Hence, it is important to further investigate the pathophysiological mechanisms underlying ED and find modalities that will alleviate its clinical implementation. Adropin, a highly conserved peptide hormone secreted primarily by the liver, recently emerged as an important regulatory component of the vascular endothelium. Specifically, the vasoprotective role of adropin is achieved mainly by affecting endothelial NO synthesis. Thus, in this review, we aimed to summarize the current knowledge regarding the role of adropin in physiological processes and address the protective role of adropin in endothelium with consequent implications to CV pathologies. We focused on data regarding the role of adropin in the clinical setting, with concurrent implications to future clinical use of adropin. Studies suggest that plasma levels of adropin correlate with indices of ED in various pathologies and enhanced disease progression, implying that adropin may serve as a useful biomarker of ED in the upcoming future. On the other hand, despite notable results with respect to therapeutic potential of adropin in preliminary experiments, further well-designed studies are warranted in order to establish if adropin might be beneficial in this setting.

Adropin and spexin hormones regulate the systemic inflammation in adenine-induced chronic kidney failure in rat

Chronic kidney disease is one of the major global health problems. Chronic renal failure is stimulated by many cytokines and chemokines. Adropin and spexin (SPX) are peptides hormones. These peptides could affect inflammatory conditions, but this is unclear. Due to the limited information, we planned to investigate the impact of adropin and SPX hormones on systemic inflammation in adenine induced chronic kidney failure rat model. Chronic kidney failure was induced by administering adenine hemisulfate. Renal functions were measured by an autoanalyzer. Granulocyte colony-stimulating factor (G-CSF), interferon-gamma (IFN-γ), interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-10, IL-12, IL-13, IL-17A, tumor necrosis factor-alpha, Eotaxin, growth-regulated oncogene-alpha, IP-10, monocyte chemoattractant protein (MCP)-1, MCP-3, macrophage inflammatory protein (MIP)-1α, MIP-2, and RANTES levels were determined by Luminex. We observed an increase in 24-h urine volume and serum creatinine. Blood urea nitrogen (BUN) and urine protein levels were also significantly higher in the chronic kidney failure (CKF) group. Urine protein and 24-h urine volume were reduced with adropin and SPX treatments. Furthermore, G-CSF, IFN-γ, IL-4, IL-5, IL-10, IL-12, IL-17A, and GRO-α significantly increased by CKF induction; however, these cytokines and chemokines significantly decreased by adropin treatment in the CKF group. Furthermore, adropin increased IP-10, MCP-1, MIP-1α, and MIP-2 levels. In addition, SPX treatment had a more limited effect, decreasing only G-CSF, IFN-γ, and IL-5 levels. The combined adropin + SPX treatment significantly reduced G-CSF, IFN-γ, IL-4, IL-5, IL-12, and IL-17A. Furthermore, IP-10, MCP-1, MCP-3, and MIP-2 were significantly increased by these combined treatments. Our findings indicate that renal functions and inflammatory response were modulated by adropin and SPX peptides. These peptides may have protective effects on systemic inflammation and renal failure progression.

Inflammatory response and matrix metalloproteinases in chronic kidney failure: Modulation by adropin and spexin

Chronic kidney disease is a major global public health problem. The peptide hormones adropin and spexin modulate many physiological functions such as energy balance and glucose, lipid and protein metabolism. However, it is unclear whether these peptides may exert effects on renal damage, tissue remodeling, and inflammatory conditions. In view of the limited information, we aimed to investigate the effect of adropin and spexin on matrix metalloproteinase and inflammatory response genes a rat model of adenine-induced chronic kidney failure. Chronic kidney failure was induced in rats by administering adenine hemisulfate. Renal function was determined in an autoanalyzer. Histopathological modifications were assessed by H&E staining. mRNA expression levels of ALOX 15, COX 1, COX 2, IL-1β, IL-10, IL-17A, IL-18 IL-21, IL-33, KIM-1, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, MMP-13, NGAL, TGFβ1, TIMP-1, and TNFα in kidney tissue were measured by qPCR. Our results showed an increase of 24-h urine volume, serum creatinine, BUN, and urine protein levels in group with adenine-induced CKF. Adropin and spexin treatments decreased urine protein and 24-h urine volume. Renal damage, TIMP-1, IL-33, and MMP-2 increased after CKF induction, while COX 1, MMP-9, and MMP-13 levels were significantly reduced. Furthermore, KIM-1, TIMP-1, IL-33, and MMP-2 were downregulated by spexin treatment. Renal damage, NGAL, TIMP-1 IL-17A, IL-33, MMP-2, and MMP-3 decreased after adropin treatment, while MMP-13 levels were upregulated. Treatment with adropin+spexin decreased KIM-1, NGAL, TIMP-1, IL-1β, IL-17A, IL-18, IL-33, ALOX 15, COX 1, COX 2, TGFβ1, TNFα, MMP-2, MMP-3, and MMP-7, but increased MMP-13 levels. Our findings revealed that inflammatory response and MMP genes were modulated by adropin and spexin. These peptides may have protective effects on inflammation and chronic kidney damage progression.

Adropin correlates with aging-related neuropathology in humans and improves cognitive function in aging mice

The neural functions of adropin, a secreted peptide highly expressed in the brain, have not been investigated. In humans, adropin is highly expressed in astrocytes and peaks during critical postnatal periods of brain development. Gene enrichment analysis of transcripts correlating with adropin expression suggests processes relevant to aging-related neurodegenerative diseases that vary with age and dementia state, possibly indicating survivor bias. In people aged <40 y and 'old-old' (>75 y) diagnosed with dementia, adropin correlates positively with genes involved in mitochondrial processes. In the 'old-old' without dementia adropin expression correlates positively with morphogenesis and synapse function. Potent neurotrophic responses in primary cultured neurons are consistent with adropin supporting the development and function of neural networks. Adropin expression in the 'old-old' also correlates positively with protein markers of tau-related neuropathologies and inflammation, particularly in those without dementia. How variation in brain adropin expression affects neurological aging was investigated using old (18-month) C57BL/6J mice. In mice adropin is expressed in neurons, oligodendrocyte progenitor cells, oligodendrocytes, and microglia and shows correlative relationships with groups of genes involved in neurodegeneration and cellular metabolism. Increasing adropin expression using transgenesis improved spatial learning and memory, novel object recognition, resilience to exposure to new environments, and reduced mRNA markers of inflammation in old mice. Treatment with synthetic adropin peptide also reversed age-related declines in cognitive functions and affected expression of genes involved in morphogenesis and cellular metabolism. Collectively, these results establish a link between adropin expression and neural energy metabolism and indicate a potential therapy against neurological aging.

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.

Molecular cloning and characterization of the novel adropin from tilapia (Oreochromis niloticus): Involvement in the control of food intake

Adropin has been shown to be involved in the regulation of food intake in mice. However, the mechanism of adropin in feeding regulation is still largely unknown. Using the tilapia, Oreochromis niloticus, we identified and characterized a novel form of adropin (designated adropin-b) encoding a 68-amino acid precursor. Although adropin-b shared low amino acid identities with its tilapia paralog (designated adropin-a), synteny analysis proved that tilapia adropin is orthologous to its human counterpart. The transcripts of adropin-b were ubiquitously expressed in various tissues with the highest levels in the olfactory bulb. A decrease in adropin-b mRNA levels was observed 1 h following a meal in the olfactory bulb, hypothalamus, and optic tectum, whereas fasting for 7 days induced an increase in adropin-b mRNA levels in the olfactory bulb, hypothalamus, and optic tectum of tilapia brain. However, no changes in adropin-a mRNA levels were observed in the postprandial and fasting state. Intraperitoneal injection of tilapia adropin-b was shown to increase food consumption, but adropin-a did not affect feeding. Co-treatment of the fish with adropin-b and neuropeptide Y (NPY) had no additive effects on appetite. The appetite stimulatory effects of adropin-b appeared to be mediated by upregulating the orexigenic Npy, Orexin, and Proapelin gene expression, paralleled by inhibition of the mRNA levels of anorexigenic proopiomelanocortin (Pomc) and cocaine-amphetamine-regulated transcript (Cart) in vivo and in vitro. These observations suggested that adropin-b participated in appetite control and gene regulation of central orexigenic and anorexigenic factors in a fish model.

Adropin Alleviates Myocardial Fibrosis in Diabetic Cardiomyopathy Rats: A Preliminary Study

Aim: Adropin (ADR) is a novel regulatory polypeptide and has important effects on energy metabolism in the heart. However, it is still unclear whether ADR can relieve ventricular remodeling in DCM. Therefore, this study was conducted to assess the effect of ADR on myocardial fibrosis in DCM rats.

Materials and Methods: Twenty Wistar rats were randomly assigned into four groups: healthy control group (CON), DCM model group (DCM), DCM model treated with ADR group (ADR) and DCM model treated with perindopril group (PER). Collagen volume fraction (CVF) and perivascular collagen area (PVCA) were calculated. Diastolic function was assessed by echocardiography. The mitochondrial membrane potential assay was conducted by Rhodamine 123 staining. The protein expression levels of Col I, Col III, Mitofusin-1, Mitofusin-2 and Drp1 were evaluated using western blot.

Results: Compared to CON group, CVF, PVCA and the relative protein expression of Col I, Col III and Drp1 increased in DCM group. And the relative expression of Mitofusin-1 and Mitofusin-2 proteins decreased. During our investigations, CVF, PVCA and the relative protein expression of Col I, Col III and Drp1 decreased in ADR treated rats compared to DCM group. The diastolic function was elevated in ADR group. The fluorescence of Rhodamine 123 and the expression of Mitofusin-1 and Mitofusin-2 also increased in ADR group.

Conclusion: Our study demonstrated that ADR could alleviate myocardial fibrosis and improve diastolic function in DCM rats. ADR may be a putative candidate for the treatment of DCM.

Pyruvate dehydrogenase kinases (PDKs): an overview toward clinical applications

Pyruvate dehydrogenase kinase (PDK) can regulate the catalytic activity of pyruvate decarboxylation oxidation via the mitochondrial pyruvate dehydrogenase complex, and it further links glycolysis with the tricarboxylic acid cycle and ATP generation. This review seeks to elucidate the regulation of PDK activity in different species, mainly mammals, and the role of PDK inhibitors in preventing increased blood glucose, reducing injury caused by myocardial ischemia, and inducing apoptosis of tumor cells. Regulations of PDKs expression or activity represent a very promising approach for treatment of metabolic diseases including diabetes, heart failure, and cancer. The future research and development could be more focused on the biochemical understanding of the diseases, which would help understand the cellular energy metabolism and its regulation by pharmacological effectors of PDKs.

Adropin inhibits the phenotypic modulation and proliferation of vascular smooth muscle cells during neointimal hyperplasia by activating the AMPK/ACC signaling pathway

In-stent restenosis (ISR) remains an inevitable problem for some patients receiving drug-eluting stent (DES) implantation. Intimal hyperplasia is an important biological cause of ISR. It has been previously reported that adropin is a potentially protective factor in cardiovascular disease. Therefore, the present study investigated the function of adropin in inhibiting smooth muscle cell (SMC) phenotype modulation and proliferation, causing intimal hyperplasia. A total of 56 patients who visited the hospital consecutively (25 with ISR and 31 without ISR), who were followed up between April 2016 and March 2019, 1 year following DES, were analyzed to evaluate the association between in-stent neointimal volume and adropin serum levels. Rat aorta smooth muscle cells (RASMCs) were used to determine the effects of adropin on their phenotypic modulation and proliferation using western blot, MTT, PCR and immunofluorescence analyses. Adropin serum levels in the ISR group were significantly lower than those in the non-ISR group. Furthermore, linear regression analysis revealed that only adropin levels were negatively associated with neointimal volume in both groups. The overall adropin levels of the 56 patients and the percentages of neointimal volume revealed a strong negative association. In vitro, adropin suppressed angiotensin II (Ang II)-induced phenotypic modulation in RASMCs by restoring variations of osteopontin and α-smooth muscle actin. Furthermore, compared with the Ang II group, adropin markedly decreased the percentage of G₂/M-phase cells. Finally, adropin negatively regulated the phenotypic modulation and proliferation of RASMCs via the AMP-activated protein kinase/acetyl-CoA carboxylase (AMPK/ACC) signaling pathway. In conclusion, an independent, negative association was revealed between adropin and intimal hyperplasia; specifically, adropin inhibited the phenotypic modulation and proliferation of RASMCs by activating the AMPK/ACC signaling pathway. Therefore, adropin may be used as a potential predictor and therapeutic target for intimal hyperplasia and ISR.

Hepatocardiac or Cardiohepatic Interaction: From Traditional Chinese Medicine to Western Medicine

There is a close relationship between the liver and heart based on "zang-xiang theory," "five-element theory," and "five-zang/five-viscus/five-organ correlation theory" in the theoretical system of Traditional Chinese Medicine (TCM). Moreover, with the development of molecular biology, genetics, immunology, and others, the Modern Medicine indicates the existence of the essential interorgan communication between the liver and heart (the heart and liver). Anatomically and physiologically, the liver and heart are connected with each other primarily via "blood circulation." Pathologically, liver diseases can affect the heart; for example, patients with end-stage liver disease (liver failure/cirrhosis) may develop into "cirrhotic cardiomyopathy," and nonalcoholic fatty liver disease (NAFLD) may promote the development of cardiovascular diseases via multiple molecular mechanisms. In contrast, heart diseases can affect the liver, heart failure may lead to cardiogenic hypoxic hepatitis and cardiac cirrhosis, and atrial fibrillation (AF) markedly alters the hepatic gene expression profile and induces AF-related hypercoagulation. The heart can also influence liver metabolism via certain nonsecretory cardiac gene-mediated multiple signals. Moreover, organokines are essential mediators of organ crosstalk, e.g., cardiomyokines link the heart to the liver, while hepatokines link the liver to the heart. Therefore, both TCM and Western Medicine, and both the basic research studies and the clinical practices, all indicate that there exist essential "heart-liver axes" and "liver-heart axes." To investigate the organ interactions between the liver and heart (the heart and liver) will help us broaden and deepen our understanding of the pathogenesis of both liver and heart diseases, thus improving the strategies of prevention and treatment in the future.

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.

Dendrobium officinale Attenuates Myocardial Fibrosis via Inhibiting EMT Signaling Pathway in HFD/STZ-Induced Diabetic Mice

Cardiac fibrosis is a major contributor for diabetic cardiomyopathy and Dendrobium officinale possessed therapeutic effects on hyperglycemia and diabetic cardiomyopathy. To further investigate the possible mechanisms of the Dendrobium officinale on diabetic myocardial fibrosis in mice. Water-soluble extracts of Dendrobium officinale (DOE) from dry stem was analyzed by HPLC and phenol-sulfuric acid method. Diabetic mice were induced by intraperitoneal injection of streptozotocin (STZ) (30 mg/kg) for 4 consecutive days after intragastric administration of a high-fat diet (HFD) for 2 weeks. The groups were as follows: control group, model group, DOE low, medium, high dose group (75, 150, 300 mg/kg) and Metformin positive group (125 mg/kg). The results showed that DOE dose-dependently lower serum insulin, total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and grew the high-density lipoprotein cholesterol (HDL-C) after 12 weeks of daily administration with DOE. Hematoxylin-eosin staining and Sirius red staining showed obvious amelioration of cardiac injury and fibrosis. In addition, the result of immunoblot indicated that DOE increased the expression of peroxisome proliferator activated receptor-α (PPAR-α), phosphorylation of insulin receptor substrate 1 (p-IRS1) and E-cadherin and repressed the expression of transforming growth factor β1 (TGF-β1), phosphorylation of c-Jun N-terminal kinase (p-JNK), Twist, Snail1 and Vimentin. The present findings suggested that DOE ameliorated HFD/STZ-induced diabetic cardiomyopathy (DCM). The possible mechanism mainly associated with DOE accelerating lipid transport, inhibiting insulin resistant and suppressing fibrosis induced by epithelial mesenchymal transition (EMT).

The effect of thyroid dysfunction and treatment on adropin, asprosin and preptin levels in rats

OBJECTIVES

Thyroid hormones have important roles in normal development and energy regulating mechanisms as well as signaling mechanisms that affect energy consumption through central and peripheral pathways. The aim of this study was to determine the effects of thyroid dysfunction on adropin, asprosin and preptin levels in rat.

METHODS

The study was performed on the 38 male Wistar-albino rats. Experiment groups were designed as follows. 1-Control, 2-Hypothyroidism; To induce hypothyroidism PTU was applied by intraperitoneal as 10 mg/kg/day for 2 weeks. 3-Hypothyroidism + Thyroxine; Previously animals were made with hypothyroidism by 1 week PTU application and then 1 week l-thyroxine was given by intraperitoneal as 1.5 mg/kg/day. 4-Hyperthyroidism; Rats were made with hyperthyroidism by 3 weeks l-thyroxine (0.3 mg/kg/day). 5-Hyperthyroidism + PTU; Animals were made hyperthyroisim by l-thyroxine as groups 4, then 1 week PTU was applied to treatment of hiperthyrodism. At the end of supplementation animals were sacrificed and blood samples were collected for FT3, FT4, adropin, asprosin, preptin analysis.

RESULTS

FT3 ve FT4 levels were reduced significantly in hypothyroidism while increased in hyperthyroidism (p<0.001). Hipothyrodism led to reduces adropin, asprosin and preptin levels. And also hyperthyroidism reduced adropin and preptin levels (p<0.001).

CONCLUSIONS

The results of study show that experimental hypothyroidism and hyperthyroidism lead to significantly change to adropin, asprosin and preptin levels. However, correction of thyroid function caused to normals levels in asprosin and preptin.

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.

Hepatocyte expression of the micropeptide adropin regulates the liver fasting response and is enhanced by caloric restriction

The micropeptide adropin encoded by the clock-controlled energy homeostasis-associated gene is implicated in the regulation of glucose metabolism. However, its links to rhythms of nutrient intake, energy balance, and metabolic control remain poorly defined. Using surveys of Gene Expression Omnibus data sets, we confirm that fasting suppresses liver adropin expression in lean C57BL/6J (B6) mice. However, circadian rhythm data are inconsistent. In lean mice, caloric restriction (CR) induces bouts of compulsive binge feeding separated by prolonged fasting intervals, increasing NAD-dependent deacetylase sirtuin-1 signaling important for glucose and lipid metabolism regulation. CR up-regulates adropin expression and induces rhythms correlating with cellular stress-response pathways. Furthermore, adropin expression correlates positively with phosphoenolpyruvate carboxokinase-1 (Pck1) expression, suggesting a link with gluconeogenesis. Our previous data suggest that adropin suppresses gluconeogenesis in hepatocytes. Liver-specific adropin knockout (LAdrKO) mice exhibit increased glucose excursions following pyruvate injections, indicating increased gluconeogenesis. Gluconeogenesis is also increased in primary cultured hepatocytes derived from LAdrKO mice. Analysis of circulating insulin levels and liver expression of fasting-responsive cAMP-dependent protein kinase A (PKA) signaling pathways also suggests enhanced responses in LAdrKO mice during a glucagon tolerance test (250 µg/kg intraperitoneally). Fasting-associated changes in PKA signaling are attenuated in transgenic mice constitutively expressing adropin and in fasting mice treated acutely with adropin peptide. In summary, hepatic adropin expression is regulated by nutrient- and clock-dependent extrahepatic signals. CR induces pronounced postprandial peaks in hepatic adropin expression. Rhythms of hepatic adropin expression appear to link energy balance and cellular stress to the intracellular signal transduction pathways that drive the liver fasting response.

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.

Role of angiopoietin-like protein 3 in sugar-induced dyslipidemia in rhesus macaques: suppression by fish oil or RNAi

Angiopoietin-like protein 3 (ANGPTL3) inhibits lipid clearance and is a promising target for managing cardiovascular disease. Here we investigated the effects of a high-sugar (high-fructose) diet on circulating ANGPTL3 concentrations in rhesus macaques. Plasma ANGPTL3 concentrations increased ∼30% to 40% after 1 and 3 months of a high-fructose diet (both P < 0.001 vs. baseline). During fructose-induced metabolic dysregulation, plasma ANGPTL3 concentrations were positively correlated with circulating indices of insulin resistance [assessed with fasting insulin and the homeostatic model assessment of insulin resistance (HOMA-IR)], hypertriglyceridemia, adiposity (assessed as leptin), and systemic inflammation [C-reactive peptide (CRP)] and negatively correlated with plasma levels of the insulin-sensitizing hormone adropin. Multiple regression analyses identified a strong association between circulating APOC3 and ANGPTL3 concentrations. Higher baseline plasma levels of both ANGPTL3 and APOC3 were associated with an increased risk for fructose-induced insulin resistance. Fish oil previously shown to prevent insulin resistance and hypertriglyceridemia in this model prevented increases of ANGPTL3 without affecting systemic inflammation (increased plasma CRP and interleukin-6 concentrations). ANGPTL3 RNAi lowered plasma concentrations of ANGPTL3, triglycerides (TGs), VLDL-C, APOC3, and APOE. These decreases were consistent with a reduced risk of atherosclerosis. In summary, dietary sugar-induced increases of circulating ANGPTL3 concentrations after metabolic dysregulation correlated positively with leptin levels, HOMA-IR, and dyslipidemia. Targeting ANGPTL3 expression with RNAi inhibited dyslipidemia by lowering plasma TGs, VLDL-C, APOC3, and APOE levels in rhesus macaques.

The peptide hormone adropin regulates signal transduction pathways controlling hepatic glucose metabolism in a mouse model of diet-induced obesity

The peptide hormone adropin regulates energy metabolism in skeletal muscle and plays important roles in the regulation of metabolic homeostasis. Besides muscle, the liver has an essential role in regulating glucose homeostasis. Previous studies have reported that treatment of diet-induced obese (DIO) male mice with adropin34-76 (the putative secreted domain) reduces fasting blood glucose independently of body weight changes, suggesting that adropin suppresses glucose production in the liver. Here, we explored the molecular mechanisms underlying adropin's effects on hepatic glucose metabolism in DIO mice. Male DIO B6 mice maintained on a high-fat diet received five intraperitoneal injections of adropin34-76 (450 nmol/kg/injection) over a 48-h period. We found that adropin34-76 enhances major intracellular signaling activities in the liver that are involved in insulin-mediated regulation of glucose homeostasis. Moreover, treatment with adropin34-76 alleviated endoplasmic reticulum stress responses and reduced activity of c-Jun N-terminal kinase in the liver, explaining the enhanced activities of hepatic insulin signaling pathways observed with adropin34-76 treatment. Furthermore, adropin34-76 suppressed cAMP activated protein kinase A (PKA) activities, resulting in reduced phosphorylation of inositol trisphosphate receptor, which mediates endoplasmic reticulum calcium efflux, and of cAMP-responsive element-binding protein, a key transcription factor in hepatic regulation of glucose metabolism. Adropin34-76 directly affected liver metabolism, decreasing glucose production and reducing PKA-mediated phosphorylation in primary mouse hepatocytes in vitro Our findings indicate that major hepatic signaling pathways contribute to the improved glycemic control achieved with adropin34-76 treatment in situations of obesity.