Metabolic Messengers: Adiponectin

Contribution of specific ceramides to obesity-associated metabolic diseases

Ceramides are a heterogeneous group of bioactive membrane sphingolipids that play specialized regulatory roles in cellular metabolism depending on their characteristic fatty acyl chain lengths and subcellular distribution. As obesity progresses, certain ceramide molecular species accumulate in metabolic tissues and cause cell-type-specific lipotoxic reactions that disrupt metabolic homeostasis and lead to the development of cardiometabolic diseases. Several mechanisms for ceramide action have been inferred from studies in vitro, but only recently have we begun to better understand the acyl chain length specificity of ceramide-mediated signaling in the context of physiology and disease in vivo. New discoveries show that specific ceramides affect various metabolic pathways and that global or tissue-specific reduction in selected ceramide pools in obese rodents is sufficient to improve metabolic health. Here, we review the tissue-specific regulation and functions of ceramides in obesity, thus highlighting the emerging concept of selectively inhibiting production or action of ceramides with specific acyl chain lengths as novel therapeutic strategies to ameliorate obesity-associated diseases.

Effect of Exercise Training on Body Composition and Inflammatory Cytokine Levels in Overweight and Obese Individuals: A Systematic Review and Network Meta-Analysis

Objective

This study aimed to compare and rank the effectiveness of aerobic exercise (AE), resistance training (RT), combined aerobic and resistance training (CT), and high-intensity interval training (HIIT) on body composition and inflammatory cytokine levels in overweight and obese individuals by using network meta-analysis (NMA).

Methods

We searched the PubMed, Cochrane, Embase, Web of Science, and EBSCO databases to identify randomized controlled trials investigating the effects of exercise training on inflammatory cytokines in overweight and obese patients. The retrieval period was from inception to November 2021. Two reviewers independently screened the retrieved articles, extracted the pertinent data, and assessed the risk of bias of the included studies; then, they used Stata 16.0 and Review Manager 5.3 to perform an NMA.

Results

A total of 38 studies involving 1317 patients were included in this study. The results of the NMA indicated that AE had the greatest effect on weight loss (SUCRA=78.3; SMD=−0.51, 95% CI: −0.70, −0.33); CT had the greatest effect on reducing body mass index (SUCRA=70.7; SMD=−0.46, 95% CI: −0.81, −0.10), waist circumference (SUCRA=93.4; SMD=−1.86, 95% CI: −2.80, −0.93), percentage body fat (SUCRA=79.6; SMD=−1.38, 95% CI: −2.29, −0.48), interleukin-6 level (SUCRA=86.4; SMD=−1.98, 95% CI: −3.87, −0.09), and tumor necrosis factor-α level (SUCRA=79.4; SMD=−2.08, 95% CI: −3.75, −0.42); AE (SMD=0.51, 95% CI: −1.68, 2.69), RT (SMD=0.15, 95% CI: −3.01, 3.32), CT (SMD=1.78, 95% CI: −1.35, 4.92), and HIIT (SMD=2.29, 95% CI: −1.27, 5.86) did not significantly increase the adiponectin level.

Conclusion

The current results suggest that CT is the best exercise modality for improving body composition and inflammatory status in overweight and obese individuals. More rigorous randomized control trials are needed for further validation.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022303165.

Current therapies and new developments in NASH

Non-alcoholic steatohepatitis is becoming the most important aetiology for advanced liver disease. There has been important progress in the field in recent years and the complexity of the pathophysiology of NASH is better understood. Multiple non-invasive circulating and imaging biomarkers have been tested. The importance of lifestyle has been recognised and several drugs are being tested in clinical trials. This review addresses the challenges that healthcare professionals face in the management of NASH patients.

Decreased Adiponectin Levels in Early Pregnancy Are Associated with High Risk of Prematurity for African American Women

The relationship of low maternal serum adiponectin levels with preterm delivery among a multi-ethnic group has not been extensively investigated. We examined ethnic differences in cytokine/adipokine profiles and whether they contribute to several adverse pregnancy outcomes, particularly preterm delivery. Data and samples were from a large prospective observational cohort (n = 1776) of young, generally healthy pregnant women (African American 36.4%, Hispanic 48.0%, Caucasian 15.6%). Serum cytokine/adipokine concentrations were measured at entry (mean gestational age of 16.83 weeks) using the Liminex xMap Technology. Multivariable analyses were performed. A significant difference in adiponectin level was observed among ethnic groups. African Americans had a decreased adiponectin and increased resistin levels compared to Hispanics and Caucasians (p < 0.05 to p < 0.0001 for each). Decreased adiponectin (lowest quartile) was positively associated with preterm delivery independent of usual risk factors (adjusted odds ratio (AOR) 1.46, 95% confidence interval (CI) 1.05, 2.04 for all preterm and AOR 1.84, 95% CI 1.07, 3.17 for early preterm births). The results were unchanged when women with preeclampsia were excluded. Similar results were observed in African Americans. Decreased adiponectin levels were not related to preterm birth in either Hispanics or Caucasians. Lower adiponectin levels were also significantly associated with an increased risk of developing gestational diabetes (AOR 1.72, 95% CI 1.05, 2.84) and preeclampsia (AOR 1.45, 95% CI 1.00, 2.14) in the whole cohort and in Caucasians. We did not find any consistent relationships between the other markers with outcome variables. Dysregulation in maternal adiponectin at early gestation is associated with an increased risk of preterm delivery. An ethnic difference in adiponectin levels may contribute to a higher preterm delivery rate in African American women.

Ramulus Mori (Sangzhi) Alkaloids Alleviate High-Fat Diet-Induced Obesity and Nonalcoholic Fatty Liver Disease in Mice

Nonalcoholic fatty liver disease (NAFLD), obesity, and type 2 diabetes mellitus (T2DM) have highly related mechanisms. Ramulus Mori (Sangzhi) alkaloids (SZ-A) from Morus alba L. were approved in 2020 for the treatment of T2DM. In this study, we examined the therapeutic effects and mechanism of SZ-A on obesity and NAFLD in mice. Mice (C57BL/6J) fed a high-fat diet (HFD) for 14 weeks were treated with SZ-A for another 6 weeks. HFD-induced weight gain was reduced by SZ-A in a dose-dependent manner. SZ-A treatment significantly stimulated adiponectin expression and secretion in adipose tissue and 3T3-L1 adipocytes. Additionally, SZ-A markedly reduced hepatic steatosis (triglyceride, total cholesterol) and expression of pro-inflammatory and pro-fibrotic genes. SZ-A regulated lipid metabolism and oxidative stress (malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione (GSH)) in the liver. Palmitic acid-induced insulin resistance and lipid accumulation in HepG2 cells were also repressed by SZ-A. Collectively, SZ-A protected mice from HFD-induced NAFLD through an indirect effect of improved systemic metabolism reducing bodyweight, and a direct effect by enhancing the lipid metabolism of HepG2 cells. The weight-loss effect of SZ-A in mice was partly due to improved fatty oxidation instead of influencing food consumption.

Adipocyte GPX4 protects against inflammation, hepatic insulin resistance and metabolic dysregulation

OBJECTIVES

Metabolic inflammation is a hallmark of obesity and related disorders, afflicting substantial morbidity and mortality to individuals worldwide. White visceral and subcutaneous adipose tissue not only serves as energy storage but also controls metabolism. Adipose tissue inflammation, commonly observed in human obesity, is considered a critical driver of metabolic perturbation while molecular hubs are poorly explored. Metabolic stress evoked by e.g. long-chain fatty acids leads to oxidative perturbation of adipocytes and production of inflammatory cytokines, fuelling macrophage infiltration and systemic low-grade inflammation. Glutathione peroxidase 4 (GPX4) protects against lipid peroxidation, accumulation of oxygen-specific epitopes and cell death, collectively referred to as ferroptosis. Here, we explore the function of adipocyte GPX4 in mammalian metabolism.

METHODS

We studied the regulation and function of GPX4 in differentiated mouse adipocytes derived from 3T3-L1 fibroblasts. We generated two conditional adipocyte-specific Gpx4 knockout mice by crossing Gpx4fl/fl mice with Adipoq-Cre+ (Gpx4-/-AT) or Fabp4-Cre+ (Gpx4+/-Fabp4) mice. Both models were metabolically characterized by a glucose tolerance test and insulin resistance test, and adipose tissue lipid peroxidation, inflammation and cell death were assessed by quantifying oxygen-specific epitopes, transcriptional analysis of chemokines, quantification of F4/80+ macrophages and TUNEL labelling.

RESULTS

GPX4 expression was induced during and required for adipocyte differentiation. In mature adipocytes, impaired GPX4 activity spontaneously evoked lipid peroxidation and expression of inflammatory cytokines such as TNF-α, interleukin 1β (IL-1β), IL-6 and the IL-8 homologue CXCL1. Gpx4-/-AT mice spontaneously displayed adipocyte hypertrophy on a chow diet, which was paralleled by the accumulation of oxygen-specific epitopes and macrophage infiltration in adipose tissue. Furthermore, Gpx4-/-AT mice spontaneously developed glucose intolerance, hepatic insulin resistance and systemic low-grade inflammation, when compared to wildtype littermates, which was similarly recapitulated in Gpx4+/-Fabp4 mice. Gpx4-/-AT mice exhibited no signs of adipocyte death.

CONCLUSION

Adipocyte GPX4 protects against spontaneous metabolic dysregulation and systemic low-grade inflammation independent from ferroptosis, which could be therapeutically exploited in the future.

Role of Obesity, Physical Exercise, Adipose Tissue-Skeletal Muscle Crosstalk and Molecular Advances in Barrett's Esophagus and Esophageal Adenocarcinoma

Both obesity and esophageal adenocarcinoma (EAC) rates have increased sharply in the United States and Western Europe in recent years. EAC is a classic example of obesity-related cancer where the risk of EAC increases with increasing body mass index. Pathologically altered visceral fat in obesity appears to play a key role in this process. Visceral obesity may promote EAC by directly affecting gastroesophageal reflux disease and Barrett’s esophagus (BE), as well as a less reflux-dependent effect, including the release of pro-inflammatory adipokines and insulin resistance. Deregulation of adipokine production, such as the shift to an increased amount of leptin relative to “protective” adiponectin, has been implicated in the pathogenesis of BE and EAC. This review discusses not only the epidemiology and pathophysiology of obesity in BE and EAC, but also molecular alterations at the level of mRNA and proteins associated with these esophageal pathologies and the potential role of adipokines and myokines in these disorders. Particular attention is given to discussing the possible crosstalk of adipokines and myokines during exercise. It is concluded that lifestyle interventions to increase regular physical activity could be helpful as a promising strategy for preventing the development of BE and EAC.

Plasminogen activator inhibitor-1 mediate downregulation of adiponectin in type 2 diabetes patients with metabolic syndrome

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Both Adiponectin and PAI-1 levels are associated with the Metabolic abnormalities.

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This study demonstrates that subjects with MetS have low adiponectin and higher PAI-1 levels compare to non-MetS.

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Higher PAI-1 levels are associated with higher odds of risk and prevalence of MetS.

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Pharmacological targeting of PAI-1 is necessary for MetS management.

Introduction

Metabolic syndrome (MetS) is a multifactorial disease characterized by metabolic abnormalities. Plasminogen activator inhibitor-1(PAI-1) is a key factor of the fibrinolysis its expression is elevated in insulin resistance, obesity, and MetS. In addition, an adiponectin produced by adipocytes is also key factor in MetS. This study aimed to investigate the relationship between PAI-1, adiponectin levels in MetS.

Patients and Methods

A total of 379 subjects were analyse in this cross-sectional study. MetS was defined by NCEP ATP-III criteria. Anthropometric, fasting blood glucose, HbA1c, total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, PAI-1, and adiponectin were measured.

Results

PAI-1 levels were higher in MetS compared with non-MetS. In addition, adiponectin levels were significantly lower in MetS compared to non-MetS. Furthermore, increased level of PAI-1 corresponds with increase in prevalence of MetS. PAI-1 levels were significantly associated with MetS (OR = 2.51, CI = 1.23 – 5.14; p = 0.039).

Conclusion

PAI-1 increases the risk of MetS. PAI-1 and adiponectin regulation is useful in assesing the presence and severity of MetS. Further pharmacological targeting of PAI-1 studies are necessary for MetS management.

Transdermal Photothermal-Pharmacotherapy to Remodel Adipose Tissue for Obesity and Metabolic Disorders

Despite the increasing prevalence of obesity, the current medications, which act indirectly on the central nervous system to suppress appetite or on the gastrointestinal tract to inhibit fat absorption, suffer from poor effectiveness and side effects. Here, we developed a transdermal mild photothermal therapy directly acting on the root of evil (subcutaneous white adipose depot) to induce its ameliorating remodeling (browning, lipolysis, and apoptosis), based on the injectable thermoresponsive hydrogel encapsulated with copper sulfide nanodots. Further, combining pharmaceutical therapy with codelivery of mirabegron leads to a strong therapeutic synergy. This method not only ensures high effectiveness and low side effects due to localized and targeted application but also remotely creates significant improvements in systemic metabolism. Specifically, as compared to the untreated group, it totally inhibits obesity development in high-fat-diet fed mice (15% less in body weight) with decreased masses of both subcutaneous (40%) and visceral fats (54%), reduced serum levels of cholesterol (54%)/triglyceride (18%)/insulin (74%)/glucose (45%), and improved insulin sensitivity (65% less in insulin resistance index). This self-administrable method is amenable for long-term home-based treatment. Finally, multiple interconnected signaling pathways are revealed, providing mechanistic insights to develop effective strategies to combat obesity and associated metabolic disorders.

Diagnostic and Prognostic Protein Biomarkers of β-Cell Function in Type 2 Diabetes and Their Modulation with Glucose Normalization

Development of type-2 diabetes(T2D) is preceded by β-cell dysfunction and loss. However, accurate measurement of β-cell function remains elusive. Biomarkers have been reported to predict β-cell functional decline but require validation. Therefore, we determined whether reported protein biomarkers could distinguish patients with T2D (onset < 10-years) from controls. A prospective, parallel study in T2D (n = 23) and controls (n = 23) was undertaken. In T2D subjects, insulin-induced blood glucose normalization from baseline 7.6 ± 0.4 mmol/L (136.8 ± 7.2 mg/dL) to 4.5 ± 0.07 mmol/L (81 ± 1.2 mg/dL) was maintained for 1-h. Controls were maintained at 4.9 ± 0.1 mmol/L (88.2 ± 1.8 mg/dL). Slow Off-rate Modified Aptamer (SOMA) -scan plasma protein measurement determined a 43-protein panel reported as diagnostic and/or prognostic for T2D. At baseline, 9 proteins were altered in T2D. Three of 13 prognostic/diagnostic proteins were lower in T2D: Adiponectin (p < 0.0001), Endocan (p < 0.05) and Mast/stem cell growth factor receptor-Kit (KIT) (p < 0.01). Two of 14 prognostic proteins [Cathepsin-D (p < 0.05) and Cadherin-E (p < 0.005)], and four of 16 diagnostic proteins [Kallikrein-4 (p = 0.001), Aminoacylase-1 (p = 0.001), Insulin-like growth factor-binding protein-4 (IGFBP4) (p < 0.05) and Reticulon-4 receptor (RTN4R) (p < 0.001)] were higher in T2D. Protein levels were unchanged following glucose normalization in T2D. Our results suggest that a focused biomarker panel may be useful for assessing β-cell dysfunction and may complement clinical decision-making on insulin therapy. Unchanged post-glucose normalization levels indicate these are not acute-phase proteins or affected by glucose variability.

Transforming growth factor β1 signaling links extracellular matrix remodeling to intracellular lipogenesis upon physiological feeding events

Adipose tissue dynamically changes its mass in response to external nutritional status, which plays an important role in maintaining the lipid homeostasis. Physiologically, feeding events are associated with the expansion of adipose tissue, but little is known about the detailed molecular mechanisms of this expansion. Here, using comprehensive transcriptome analysis, we found that levels of transforming growth factor β1 (TGF-β1), a key regulator of extracellular matrix (ECM) remodeling, were increased in adipose tissue under feeding conditions and associated with the lipogenic pathway. In addition, TGF-β receptors are highly expressed in adipose tissue, and pharmacological inhibition of TGF-β1 reduced adipose tissue mass and caused ectopic lipid accumulation in the liver. This reduced fat mass was associated with decreased gene expression in ECM remodeling and lipogenesis. Furthermore, similar results were observed in the adipose tissue of SMAD family member 3 knockout mice or upon systemic TGF-β neutralization, with significant reductions in both ECM remodeling and lipogenesis-related genes. Mechanistically, we found that insulin-induced TGF-β1 and cell-autonomous action remodels the ECM of adipocytes, which controls the downstream focal adhesion kinase–AKT signaling cascades and enhances the lipogenic pathway. Of note, destruction of collagens or matrix metalloproteinase/a disintegrin and metalloprotease activities, critical components of ECM remodeling, blocked TGF-β1-mediated focal adhesion kinase–AKT signaling and the lipogenic pathway. Taken together, this study identifies a previously unknown lipogenic role of TGF-β1 by which adipocytes can expand to adapt to physiological feeding events.

Anti-depressive-like behaviors of APN KO mice involve Trkb/BDNF signaling related neuroinflammatory changes

Major depression disorder is a severe mental illness often linked with metabolic disorders. Adiponectin is an adipocyte-secreted circulatory hormone with antidiabetic and glucose/lipid modulation capacities. Studies have demonstrated the pathophysiological roles of adiponectin involved in various neurological disorders, including depression. However, the underlying mechanisms are poorly understood. Here we showed that adiponectin deprivation enhanced antidepressive-like behaviors in the LPS-induced model of depression. APN KO mice displayed increased cytokines (both pro and anti-inflammatory), accompanied by an impaired expression of adiponectin receptors (mRNA/protein level) and decreasing IBA-1 level in the cortex and primary microglia of LPS treated APN KO mice. Further, LPS-treatment significantly reduced p-NFκB expression in the microglia of APN KO mice. However, the Bay11-7082 treatment recovered p-NFκB expression in the cortex of APN KO mice in the presence of LPS. Interestingly, the antidepressant potentials of APN KO mice were abolished by TrkB antagonist K252a, IKK inhibitor Bay11-7082, and AdipoRon suggesting crosstalk between TrkB/BDNF signaling and NFκB in depression. Furthermore, the effects of Bay11-7082 were abolished by a TrkB/BDNF activator (7,8-DHF), indicating a critical role of TrkB/BDNF signaling. Taken together, these findings showed that dysregulated neuroinflammatory status and BDNF signaling might underlie the antidepressive-like behaviors of APN KO mice. NFκB elicited BDNF changes may be accountable for the pathogenesis of LPS induced depression, where APN might present an alternative therapeutic target for depressive disorders.

Why does obesity cause diabetes?

The accumulation of an excessive amount of body fat can cause type 2 diabetes, and the risk of type 2 diabetes increases linearly with an increase in body mass index. Accordingly, the worldwide increase in the prevalence of obesity has led to a concomitant increase in the prevalence of type 2 diabetes. The cellular and physiological mechanisms responsible for the link between obesity and type 2 diabetes are complex and involve adiposity-induced alterations in β cell function, adipose tissue biology, and multi-organ insulin resistance, which are often ameliorated and can even be normalized with adequate weight loss.

Tetrahydrocurcumin Upregulates the Adiponectin-AdipoR Pathway and Improves Insulin Signaling and Pancreatic β-Cell Function in High-Fat Diet/Streptozotocin-Induced Diabetic Obese Mice

Impairment of adiponectin production and function is closely associated with insulin resistance and type 2 diabetes, which are linked to obesity. Studies in animal models have documented the anti-diabetic effects of tetrahydrocurcumin (THC). Although several possible mechanisms have been proposed, the contribution of adiponectin signaling on THC-mediated antihyperglycemic effects remains unknown. Here, we report that adiposity, steatosis, and hyperglycemia were potently attenuated in high-fat diet/streptozotocin-induced diabetic obese mice after they received 20 and 100 mg/kg THC for 14 weeks. THC upregulated UCP-1 in adipose tissue and elevated adiponectin levels in the circulation. THC upregulated the AdipoR1/R2-APPL1-mediated pathway in the liver and skeletal muscle, which contributes to improved insulin signaling, glucose utilization, and lipid metabolism. Furthermore, THC treatment significantly (p < 0.05) preserved islet mass, reduced apoptosis, and restored defective insulin expression in the pancreatic β-cells of diabetic obese mice, which was accompanied by an elevation of AdipoR1 and APPL1. These results demonstrated a potential mechanism underlying the beneficial effects of THC against hyperglycemia via the adiponectin-AdipoR pathway, and thus, may lead to a novel therapeutic use for type 2 diabetes.

An Explanation for the Adiponectin Paradox

The adipokine adiponectin improves insulin sensitivity. Functional signal transduction of adiponectin requires at least one of the receptors AdipoR1 or AdipoR2, but additionally the glycosyl phosphatidylinositol-anchored molecule, T-cadherin. Overnutrition causes a reduction in adiponectin synthesis and an increase in the circulating levels of the enzyme glycosyl phosphatidylinositol-phospholipase D (GPI-PLD). GPI-PLD promotes the hydrolysis of T-cadherin. The functional consequence of T-cadherin hydrolysis is a reduction in adiponectin sequestration by responsive tissues, an augmentation of adiponectin levels in circulation and a (further) reduction in signal transduction. This process creates the paradoxical situation that adiponectin levels are augmented, whereas the adiponectin signal transduction and insulin sensitivity remain strongly impaired. Although both hypoadiponectinemia and hyperadiponectinemia reflect a situation of insulin resistance, the treatments are likely to be different.

Adiponectin Ameliorates Cognitive Behaviors and in vivo Synaptic Plasticity Impairments in 3xTg-AD Mice

BACKGROUND

Cognitive deficit is mainly clinical characteristic of Alzheimer's disease (AD). Recent reports showed adiponectin and its analogues could reverse cognitive impairments, lower amyloid-β protein (Aβ) deposition, and exert anti-inflammatory effects in different APP/PS1 AD model mice mainly exhibiting amyloid plaque pathology. However, the potential in vivo electrophysiological mechanism of adiponectin protecting against cognitive deficits in AD and the neuroprotective effects of adiponectin on 3xTg-AD mice including both plaque and tangle pathology are still unclear.

OBJECTIVE

To observe the effects of adiponectin treatment on cognitive deficits in 3xTg-AD mice, investigate its potential in vivo electrophysiological mechanism, and testify its anti-inflammatory effects.

METHODS

Barnes maze test, Morris water maze test, and fear conditioning test were used to evaluate the memory-ameliorating effects of adiponectin on 3xTg-AD mice. In vivo hippocampal electrophysiological recording was used to observe the change of basic synaptic transmission, long-term potentiation, and long-term depression. Immunohistochemistry staining and western blot were used to observe the activation of microglia and astroglia, and the expression levels of proinflammatory factors and anti-inflammtory factor IL-10.

RESULTS

Adiponectin treatment could alleviate spatial memory and conditioned fear memory deficits observed in 3xTg-AD mice, improve in vivo LTP depression and LTD facilitation, inhibit overactivation of microglia and astroglia, decrease the expression of proinflammatory factors NF- κB and IL-1β, and increase the expression level of IL-10 in the hippocampus of 3xTg-AD mice.

CONCLUSION

Adiponectin could ameliorate cognitive deficits in 3xTg-AD mice through improving in vivo synaptic plasticity impairments and alleviating neuroinflammation in the hippocampus of 3xTg-AD mice.

Revisiting the multiple roles of T-cadherin in health and disease

As a non-canonical member of cadherin superfamily, T-cadherin was initially described as a molecule involved in homophilic recognition in the nervous and vascular systems. The ensuing decades clearly demonstrated that T-cadherin is a remarkably multifunctional molecule. It was validated as a bona fide receptor for both: LDL exerting adverse atherogenic action and adiponectin mediating many protective metabolic and cardiovascular effects. Motivated by the latest progress and accumulated data unmasking important roles of T-cadherin in blood vessel function and tissue regeneration, here we revisit the original function of T-cadherin as a guidance receptor for the growing axons and blood vessels, consider the recent data on T-cadherin-induced exosomes' biogenesis and their role in myocardial regeneration and revascularization. The review expands upon T-cadherin contribution to mesenchymal stem/stromal cell compartment in adipose tissue. We also dwell upon T-cadherin polymorphisms (SNP) and their possible therapeutic applications. Furthermore, we scrutinize the molecular hub of insulin and adiponectin receptors (AdipoR1 and AdipoR2) conveying signals to their downstream targets in quest for defining a putative place of T-cadherin in this molecular circuitry.

In vitro and in silico characterization of adiponectin-receptor agonist dipeptides

The aim of this study is to develop a dipeptide showing an adiponectin receptor 1 (AdipoR1) agonistic effect in skeletal muscle L6 myotubes. Based on the structure of the AdipoR1 agonist, AdipoRon, 15 synthetic dipeptides were targeted to promote glucose uptake in L6 myotubes. Tyr-Pro showed a significant increase in glucose uptake among the dipeptides, while other dipeptides, including Pro-Tyr, failed to exert this effect. Tyr-Pro induces glucose transporter 4 (Glut4) expression in the plasma membrane, along with adenosine monophosphate-activated protein kinase (AMPK) activation. In AdipoR1-knocked down cells, the promotion by Tyr-Pro was ameliorated, indicating that Tyr-Pro may directly interact with AdipoR1 as an agonist, followed by the activation of AMPK/Glut4 translocation in L6 myotubes. Molecular dynamics simulations revealed that a Tyr-Pro molecule was stably positioned in the two potential binding pockets (sites 1 and 2) of the seven-transmembrane receptor, AdipoR1, anchored in a virtual 1-palmitoyl-2-oleoyl-phosphatidylcholine membrane. In conclusion, we demonstrated the antidiabetic function of the Tyr-Pro dipeptide as a possible AdipoR1 agonist.

Alternatives for the worse: Molecular insights into adverse effects of bisphenol a and substitutes during human adipocyte differentiation

Bisphenol A (BPA), which is used in a variety of consumer-related plastic products, was reported to cause adverse effects, including disruption of adipocyte differentiation, interference with obesity mechanisms, and impairment of insulin- and glucose homeostasis. Substitute compounds are increasingly emerging but are not sufficiently investigated.We aimed to investigate the mode of action of BPA and four of its substitutes during the differentiation of human preadipocytes to adipocytes and their molecular interaction with peroxisome proliferator-activated receptor γ (PPARγ), a pivotal regulator of adipogenesis.Binding and effective biological activation of PPARγ were investigated by surface plasmon resonance and reporter gene assay, respectively. Human preadipocytes were continuously exposed to BPA, BPS, BPB, BPF, BPAF, and the PPARγ-antagonist GW9662. After 12 days of differentiation, lipid production was quantified via Oil Red O staining, and global protein profiles were assessed using LC-MS/MS-based proteomics. All tested bisphenols bound to human PPARγ with similar efficacy as the natural ligand 15d-PGJ2in vitroand provoked an antagonistic effect on PPARγ in the reporter gene assay at non-cytotoxic concentrations. During the differentiation of human preadipocytes, all bisphenols decreased lipid production. Global proteomics displayed a down-regulation of adipogenesis and metabolic pathways, similar to GW9662. Interestingly, pro-inflammatory pathways were up-regulated, MCP1 release was increased, and adiponectin decreased. pAKT/AKT ratios revealed significantly reduced insulin sensitivity by BPA, BPB, and BPS upon insulin stimulation.Thus, our results show that not only BPA but also its substitutes disrupt crucial metabolic functions and insulin signaling in adipocytes under low, environmentally relevant concentrations. This effect, mediated through inhibition of PPARγ, may promote hypertrophy of adipose tissue and increase the risk of developing metabolic syndrome, including insulin resistance.

An automated platform for structural analysis of membrane proteins through serial crystallography

Membrane proteins are central to many pathophysiological processes, yet remain very difficult to analyze structurally. Moreover, high-throughput structure-based drug discovery has not yet been exploited for membrane proteins because of lack of automation. Here, we present a facile and versatile platform for in meso membrane protein crystallization, enabling rapid atomic structure determination at both cryogenic and room temperatures. We apply this approach to human integral membrane proteins, which allowed us to identify different conformational states of intramembrane enzyme-product complexes and analyze by molecular dynamics simulations the structural dynamics of the ADIPOR2 integral membrane protein. Finally, we demonstrate an automated pipeline combining high-throughput microcrystal soaking, automated laser-based harvesting, and serial crystallography, enabling screening of small-molecule libraries with membrane protein crystals grown in meso. This approach brings needed automation to this important class of drug targets and enables high-throughput structure-based ligand discovery with membrane proteins.

Role of adipokines in embryo implantation

Embryo implantation is a complex process in which multiple molecules acting together under strict regulation. Studies showed the production of various adipokines and their receptors in the embryo and uterus, where they can influence the maternal-fetal transmission of metabolites and embryo implantation. Therefore, these cytokines have opened a novel area of study in the field of embryo-maternal crosstalk during early pregnancy. In this respect, the involvement of adipokines has been widely reported in the regulation of both physiological and pathological aspects of the implantation process. However, the information about the role of some recently identified adipokines is limited. This review aims to highlight the role of various adipokines in embryo-maternal interactions, endometrial receptivity, and embryo implantation, as well as the underlying molecular mechanisms.

Obesity and Pancreatic Cancer: Insight into Mechanisms

Simple Summary

Obesity is recognized as a chronic progressive disease and risk factor for many human diseases. The high and increasing number of obese people may underlie the expected increase in pancreatic cancer cases in the United States. There are several pathways discussed that link obesity with pancreatic cancer. Adipose tissue and adipose tissue-released factors may thereby play an important role. This review discusses selected mechanisms that may accelerate pancreatic cancer development in obesity.

Abstract

The prevalence of obesity in adults and children has dramatically increased over the past decades. Obesity has been declared a chronic progressive disease and is a risk factor for a number of metabolic, inflammatory, and neoplastic diseases. There is clear epidemiologic and preclinical evidence that obesity is a risk factor for pancreatic cancer. Among various potential mechanisms linking obesity with pancreatic cancer, the adipose tissue and obesity-associated adipose tissue inflammation play a central role. The current review discusses selected topics and mechanisms that attracted recent interest and that may underlie the promoting effects of obesity in pancreatic cancer. These topics include the impact of obesity on KRAS activity, the role of visceral adipose tissue, intrapancreatic fat, adipose tissue inflammation, and adipokines on pancreatic cancer development. Current research on lipocalin-2, fibroblast growth factor 21, and Wnt5a is discussed. Furthermore, the significance of obesity-associated insulin resistance with hyperinsulinemia and obesity-induced gut dysbiosis with metabolic endotoxemia is reviewed. Given the central role that is occupied by the adipose tissue in obesity-promoted pancreatic cancer development, preventive and interceptive strategies should be aimed at attenuating obesity-associated adipose tissue inflammation and/or at targeting specific molecules that mechanistically link adipose tissue with pancreatic cancer in obese patients.

Discovery of a transdermally deliverable pentapeptide for activating AdipoR1 to promote hair growth

Alopecia induced by aging or side effects of medications affects millions of people worldwide and impairs the quality of life; however, there is a limit to the current medications. Here, we identify a small transdermally deliverable 5-mer peptide (GLYYF; P5) that activates adiponectin receptor 1 (AdipoR1) and promotes hair growth. P5 sufficiently reproduces the biological effect of adiponectin protein via AMPK signaling pathway, increasing the expression of hair growth factors in the dermal papilla cells of human hair follicle. P5 accelerates hair growth ex vivo and induces anagen hair cycle in mice in vivo. Furthermore, we elucidate a key spot for the binding between AdipoR1 and adiponectin protein using docking simulation and mutagenesis studies. This study suggests that P5 could be used as a topical peptide drug for alleviating pathological conditions, which can be improved by adiponectin protein, such as alopecia.

The adiponectin signalling pathway - A therapeutic target for the cardiac complications of type 2 diabetes?

Diabetes is associated with an increased risk of heart failure (HF). This is commonly termed diabetic cardiomyopathy and is often characterised by increased cardiac fibrosis, pathological hypertrophy, increased oxidative and endoplasmic reticulum stress as well as diastolic dysfunction. Adiponectin is a cardioprotective adipokine that is downregulated in settings of type 2 diabetes (T2D) and obesity. Furthermore, both adiponectin receptors (AdipoR1 and R2) are also downregulated in these settings which further results in impaired cardiac adiponectin signalling and reduced cardioprotection. In many cardiac pathologies, adiponectin signalling has been shown to protect against cardiac remodelling and lipotoxicity, however its cardioprotective actions in T2D-induced cardiomyopathy remain unresolved. Diabetic cardiomyopathy has historically lacked effective treatment options. In this review, we summarise the current evidence for links between the suppressed adiponectin signalling pathway and cardiac dysfunction, in diabetes. We describe adiponectin receptor-mediated signalling pathways that are normally associated with cardioprotection, as well as current and potential future therapeutic approaches that could target this pathway as possible interventions for diabetic cardiomyopathy.

Self-Organization Provides Cell Fate Commitment in MSC Sheet Condensed Areas via ROCK-Dependent Mechanism

Multipotent mesenchymal stem/stromal cells (MSC) are one of the crucial regulators of regeneration and tissue repair and possess an intrinsic program from self-organization mediated by condensation, migration and self-patterning. The ability to self-organize has been successfully exploited in tissue engineering approaches using cell sheets (CS) and their modifications. In this study, we used CS as a model of human MSC spontaneous self-organization to demonstrate its structural, transcriptomic impact and multipotent stromal cell commitment. We used CS formation to visualize MSC self-organization and evaluated the role of the Rho-GTPase pathway in spontaneous condensation, resulting in a significant anisotropy of the cell density within the construct. Differentiation assays were carried out using conventional protocols, and microdissection and RNA-sequencing were applied to establish putative targets behind the observed phenomena. The differentiation of MSC to bone and cartilage, but not to adipocytes in CS, occurred more effectively than in the monolayer. RNA-sequencing indicated transcriptional shifts involving the activation of the Rho-GTPase pathway and repression of SREBP, which was concordant with the lack of adipogenesis in CS. Eventually, we used an inhibitory analysis to validate our findings and suggested a model where the self-organization of MSC defined their commitment and cell fate via ROCK1/2 and SREBP as major effectors under the putative switching control of AMP kinase.

Adipocyte iron levels impinge on a fat-gut crosstalk to regulate intestinal lipid absorption and mediate protection from obesity

Iron overload is positively associated with diabetes risk. However, the role of iron in adipose tissue remains incompletely understood. Here, we report that transferrin-receptor-1-mediated iron uptake is differentially required for distinct subtypes of adipocytes. Notably, adipocyte-specific transferrin receptor 1 deficiency substantially protects mice from high-fat-diet-induced metabolic disorders. Mechanistically, low cellular iron levels have a positive impact on the health of the white adipose tissue and can restrict lipid absorption from the intestine through modulation of vesicular transport in enterocytes following high-fat diet feeding. Specific reduction of adipocyte iron by AAV-mediated overexpression of the iron exporter Ferroportin1 in adult mice effectively mimics these protective effects. In summary, our studies highlight an important role of adipocyte iron in the maintenance of systemic metabolism through an adipocyte-enterocyte axis, offering an additional level of control over caloric influx into the system after feeding by regulating intestinal lipid absorption.

The Troubling Link Between Non-alcoholic Fatty Liver Disease (NAFLD) and Extrahepatic Cancers (EHC)

Non-alcoholic fatty liver disease (NAFLD) is a fast-spreading epidemic across the globe and has serious implications far beyond that of a "benign" liver condition. It is usually an outcome of ectopic fat storage due to chronic positive energy balance leading to obesity and is associated with multiple health problems. While association with cardiovascular disease and hepatocellular cancer is well recognized, it is becoming clear the NAFLD carries with it an increased risk of cancers of extrahepatic tissues. Studies have reported a higher risk for cancers of the colon, breast, prostate, lung, and pancreas. Fatty liver is associated with increased mortality; there is an urgent need to understand that fatty liver is not always benign, and not always associated with obesity. It is, however, a reversible condition and early recognition and intervention can alter its natural history and associated complications.

The mitochondrial dicarboxylate carrier prevents hepatic lipotoxicity by inhibiting white adipocyte lipolysis

BACKGROUND & AIMS

We have previously reported that the mitochondrial dicarboxylate carrier (mDIC [SLC25A10]) is predominantly expressed in the white adipose tissue (WAT) and subject to regulation by metabolic cues. However, the specific physiological functions of mDIC and the reasons for its abundant presence in adipocytes are poorly understood.

METHODS

To systemically investigate the impact of mDIC function in adipocytes in vivo, we generated loss- and gain-of-function mouse models, selectively eliminating or overexpressing mDIC in mature adipocytes, respectively.

RESULTS

In in vitro differentiated white adipocytes, mDIC is responsible for succinate transport from the mitochondrial matrix to the cytosol, from where succinate can act on the succinate receptor SUCNR1 and inhibit lipolysis by dampening the cAMP- phosphorylated hormone-sensitive lipase (pHSL) pathway. We eliminated mDIC expression in adipocytes in a doxycycline (dox)-inducible manner (mDIC^iKO) and demonstrated that such a deletion results in enhanced adipocyte lipolysis and promotes high-fat diet (HFD)-induced adipocyte dysfunction, liver lipotoxicity, and systemic insulin resistance. Conversely, in a mouse model with dox-inducible, adipocyte-specific overexpression of mDIC (mDIC^iOE), we observed suppression of adipocyte lipolysis both in vivo and ex vivo. mDIC^iOE mice are potently protected from liver lipotoxicity upon HFD feeding. Furthermore, they show resistance to HFD-induced weight gain and adipose tissue expansion with concomitant improvements in glucose tolerance and insulin sensitivity. Beyond our data in rodents, we found that human WAT SLC25A10 mRNA levels are positively correlated with insulin sensitivity and negatively correlated with intrahepatic triglyceride levels, suggesting a critical role of mDIC in regulating overall metabolic homeostasis in humans as well.

CONCLUSIONS

In summary, we highlight that mDIC plays an essential role in governing adipocyte lipolysis and preventing liver lipotoxicity in response to a HFD.

LAY SUMMARY

Dysfunctional fat tissue plays an important role in the development of fatty liver disease and liver injury. Our present study identifies a mitochondrial transporter, mDIC, which tightly controls the release of free fatty acids from adipocytes to the liver through the export of succinate from mitochondria. We believe this mDIC-succinate axis could be targeted for the treatment of fatty liver disease.

The associations of leptin and adiponectin with the metabolic syndrome in an Indonesian and a Dutch population

BACKGROUND AND AIMS

At the same BMI, Asian populations develop cardiometabolic complications earlier than Western populations. We hypothesized that a different secretion of the adipocyte-derived hormones leptin and adiponectin plays a role and investigated the associations of the two hormones with the metabolic syndrome (MetS) in an Indonesian and a Dutch population.

METHODS AND RESULTS

We performed cross-sectional analyses of the Netherlands Epidemiology of Obesity Study (n = 6602) and the SUGAR Scientific Programme Indonesia-Netherlands Study (n = 1461). We examined sex-stratified associations of leptin and adiponectin with MetS, using multivariate logistic regression including adjustment for total body fat. The mean (SD) leptin (mcg/L) were 4.7 (6.0) in Indonesian men, 18.6 (12.0) in Indonesian women, 9.1 (7.7) in Dutch men, and 23.4 (17.4) in Dutch women. The mean (SD) adiponectin (mg/L) were 5.7 (5.4), 7.5 (7.1), 6.6 (3.3), and 11.3 (4.9), respectively. Within the same BMI category, leptin concentrations were similar in the two populations, whereas adiponectin was lower in the Indonesian population. Per SD of leptin, adjusted prevalence odds ratios (ORs, 95%CI) of MetS were 0.9 (0.6-1.2) in Indonesian men, 1.1 (0.9-1.4) in Indonesian women, 2.2 (1.6-2.8) in Dutch men, and 1.2 (1.0-1.5) in Dutch women. Per SD of adiponectin, the ORs were 0.9 (0.7-1.2), 0.8 (0.7-1.0), 0.6 (0.6-0.8), and 0.4 (0.4-0.5), respectively.

CONCLUSIONS

Despite lower adiponectin levels, adiponectin was not related to the MetS in the Indonesian population and can not explain their increased cardiometabolic risk at the same BMI.

Retinol-binding protein 4 in obesity and metabolic dysfunctions

Excessive increased adipose tissue mass in obesity is associated with numerous co-morbid disorders including increased risk of type 2 diabetes, fatty liver disease, hypertension, dyslipidemia, cardiovascular diseases, dementia, airway disease and some cancers. The causal mechanisms explaining these associations are not fully understood. Adipose tissue is an active endocrine organ that secretes many adipokines, cytokines and releases metabolites. These biomolecules referred to as adipocytokines play a significant role in the regulation of whole-body energy homeostasis and metabolism by influencing and altering target tissues function. Understanding the mechanisms of adipocytokine actions represents a hot topic in obesity research. Among several secreted bioactive signalling molecules from adipose tissue and liver, retinol-binding protein 4 (RBP4) has been associated with systemic insulin resistance, dyslipidemia, type 2 diabetes and other metabolic diseases. Here, we aim to review and discuss the current knowledge on RBP4 with a focus on its role in the pathogenesis of obesity comorbid diseases.

PEGylated AdipoRon derivatives improve glucose and lipid metabolism under insulinopenic and high-fat diet conditions

The pleiotropic actions of adiponectin in improving cell survival and metabolism have motivated the development of small-molecule therapeutic agents for treating diabetes and lipotoxicity. AdipoRon is a synthetic agonist of the adiponectin receptors, yet is limited by its poor solubility and bioavailability. In this work, we expand on the protective effects of AdipoRon in pancreatic β-cells and examine how structural modifications could affect the activity, pharmacokinetics, and bioavailability of this small molecule. We describe a series of AdipoRon analogs containing amphiphilic ethylene glycol (PEG) chains. Among these, AdipoRonPEG5 induced pleiotropic effects in mice under insulinopenic and high-fat diet (HFD) conditions. While both AdipoRon and AdipoRonPEG5 substantially attenuate palmitate-induced lipotoxicity in INS-1 cells, only AdipoRonPEG5 treatment is accompanied by a significant reduction in cytotoxic ceramides. In vivo, AdipoRonPEG5 can substantially reduce pancreatic, hepatic, and serum ceramide species, with a concomitant increase in the corresponding sphingoid bases and improves insulin sensitivity of mice under HFD feeding conditions. Furthermore, hyperglycemia in streptozotocin (STZ)-induced insulinopenic adiponectin-null mice is also attenuated upon AdipoRonPEG5 treatment. Our results suggest that AdipoRonPEG5 is more effective in reducing ceramides and dihydroceramides in the liver of HFD-fed mice than AdipoRon, consistent with its potent activity in activating ceramidase in vitro in INS-1 cells. Additionally, these results indicate that the beneficial effects of AdipoRonPEG5 can be partially attributed to improved pharmacokinetics as compared with AdipoRon, thus suggesting that further derivatization may improve affinity and tissue-specific targeting.

AdipoRon: A Novel Insulin Sensitizer in Various Complications and the Underlying Mechanisms: A Review

BACKGROUND

AdipoRon is the first synthetic analog of endogenous adiponectin, an adipose tissue-derived hormone. AdipoRon possesses pharmacological properties similar to adiponectin and its ability to bind and activate the adipoR1 and adipoR2 receptors makes it a suitable candidate for the treatment of a multitude of disorders.

OBJECTIVE

In the present review, an attempt was made to compile and discuss the efficacy of adipoRon against various disorders.

RESULTS

AdipoRon is a drug that acts not only in metabolic diseases but in other conditions unrelated to energy metabolism. It is well- reported that adipoRon exhibits strong anti-obesity, anti-diabetic, anticancer, anti-depressant, anti-ischemic, anti-hypertrophic properties and also improves conditions like post-traumatic stress disorder, anxiety, and systemic sclerosis.

CONCLUSION

A lot is known about its effects in experimental systems, but the translation of this knowledge to the clinic requires studies which, for many of the potential target conditions, have yet to be carried out. The beneficial effects of AdipoRon in novel clinical conditions will suggest an underlying pathophysiological role of adiponectin and its receptors in previously unsuspected settings.

The bifurcated role of adiponectin in colorectal cancer

The association of adiponectin with metabolism and cancer is well established. Since its discovery in 1990, adiponectin, as one of the adipose tissue-secreted adipokines, has been very widely studied in biomedical research. Low levels of circulatory adiponectin have been reported in obesity, inflammatory diseases and various types of cancers including colorectal cancer (CRC), which is highly linked with obesity and gut inflammation. However, the function and underlying mechanisms of adiponectin in CRC is not well understood. In addition, there are contradictory reports on the role of adiponectin in cancer. Therefore, further investigation is needed. In this review, we explore the information available on the relationship between adiponectin and CRC with respect to proliferation, cell survival, angiogenesis and inflammation. We also highlighted the knowledge gaps, filling in which could help us better understand the function and mechanisms of adiponectin in CRC.

Cancer-Associated Adipocytes in Breast Cancer: Causes and Consequences

Breast cancer progression is highly dependent on the heterotypic interaction between tumor cells and stromal cells of the tumor microenvironment. Cancer-associated adipocytes (CAAs) are emerging as breast cancer cell partners favoring proliferation, invasion, and metastasis. This article discussed the intersection between extracellular signals and the transcriptional cascade that regulates adipocyte differentiation in order to appreciate the molecular pathways that have been described to drive adipocyte dedifferentiation. Moreover, recent studies on the mechanisms through which CAAs affect the progression of breast cancer were reviewed, including adipokine regulation, metabolic reprogramming, extracellular matrix remodeling, and immune cell modulation. An in-depth understanding of the complex vicious cycle between CAAs and breast cancer cells is crucial for designing novel strategies for new therapeutic interventions.

Rosmarinic acid attenuates obesity and obesity-related inflammation in human adipocytes

Chronic low-grade inflammation is a hallmark of obesity and its related metabolic disorders. At the same time signaling from pro-inflammatory factors such as transforming growth factor beta (TGF-β) or interleukin 17A (IL-17A) are proposed as crucial for the commitment of fibroblast progenitor cells towards adipogenic differentiation. Modulation of inflammation during adipogenic differentiation is incompletely explored as a potential approach to prevent metabolic disorders. Rosmarinic acid (RA) is a caffeic acid derivative known for its anti-inflammatory effects. Experimental studies of its activity on adipogenic factors or in vivo obesity models are, however, controversial and hence insufficient. Here, we investigated the anti-adipogenic action of RA in human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes. Gene expression levels of key players in adipogenesis and lipid metabolism were assessed. Furthermore, a molecular mechanism of action was proposed. The most prominent effect was found on the translation of C/EBPα, PPARγ and adiponectin, as well as on the modulation of TGF1B and IL17A. Interestingly, involvement of NRF2 signaling was identified upon RA treatment. In summary, our findings indicate that RA prevents inflammation and excessive lipid accumulation in human adipocytes. Data from the molecular analysis demonstrate that RA has potential for treatment of obesity and obesity-related inflammation.

Comparative Transcriptome Profile between Iberian Pig Varieties Provides New Insights into Their Distinct Fat Deposition and Fatty Acids Content

The high deposition of intramuscular fat and the content of oleic fatty acid are characteristic of the Iberian pig. These two parameters present great variability and are differentiated amongst the varieties that make up the Iberian pig population. Although previous studies generated evidence for causal genes and polymorphisms associated to the adipogenic potential of the Iberian pig, there is little information about how genetic expression influences this trait's variability. The aim of this study was to analyses the expression profile between two varieties of Iberian pig (Torbiscal and Retinto) and their reciprocal crosses differentiated in their intramuscular fat (IMF) content and fatty acid (FA) composition in the Longissimus thoracis muscle using an RNA-seq approach. Our results corroborate that the Retinto variety is the fattiest amongst all studied varieties as its upregulated genes, such as FABP3 and FABP5, SLC27A1 and VEGFA among others, contribute to increasing adiposity. In its turn, Torbiscal pigs showed an upregulation of genes associated with the inhibition of fat deposition such as ADIPOQ and CPT1A. Further genetic variation analysis in these Iberian varieties showed relevant associations for SNP located within the differentially expressed genes with IMF and FA content. Thus, the differences found in the genetic architecture and the muscle transcriptome of these Iberian varieties might explain the variability in their fat content and composition and hence, their meat quality.

Circulating Adiponectin and Its Association with Metabolic Traits and Type 2 Diabetes: Gene-Diet Interactions Focusing on Selected Gene Variants and at the Genome-Wide Level in High-Cardiovascular Risk Mediterranean Subjects

Adiponectin is gaining renewed interest since, in addition to its possible protective role against insulin resistance and arteriosclerosis, recent studies suggest other additional favorable effects. However, the influence of gene-diet interactions on plasma adiponectin levels is still little understood. We analyzed the association between plasma adiponectin levels and various metabolic traits in a high-cardiovascular risk Mediterranean population, as well as the genetic effect of four candidate single-nucleotide polymorphisms (SNPs) in the adiponectin gene (ADIPOQ) and their interactions with the Mediterranean dietary pattern. Additionally, we explored, at the genome-wide level, the SNPs most associated with plasma adiponectin levels, as well as gene-diet interactions with the Mediterranean diet. In the 954 participants studied (aged 55-80 years), plasma adiponectin levels were strongly associated with plasma HDL-C concentrations (p = 6.6 × 10^-36) and inversely related to triglycerides (p = 4.7 × 10^-18), fasting glucose (p = 3.5 × 10^-16) and type 2 diabetes (p = 1.4 × 10^-7). Of the four pre-selected ADIPOQ candidate SNPs, the one most associated with plasma adiponectin was the -11391G > A (rs17300539) promoter SNP (p = 7.2 × 10^-5, in the multivariable adjusted model). No significant interactions with the Mediterranean diet pattern were observed for these SNPs. Additionally, in the exploratory genome-wide association study (GWAS), we found new SNPs associated with adiponectin concentrations at the suggestive genome-wide level (p < 1 × 10^-5) for the whole population, including the lead SNP rs9738548 (intergenic) and rs11647294 in the VAT1L (Vesicle Amine Transport 1 Like) gene. We also found other promising SNPs on exploring different strata such as men, women, diabetics and non-diabetics (p = 3.5 × 10^-8 for rs2850066). Similarly, we explored gene-Mediterranean diet interactions at the GWAS level and identified several SNPs with gene-diet interactions at p < 1 × 10^-5. A remarkable gene-diet interaction was revealed for the rs2917570 SNP in the OPCML (Opioid Binding Protein/Cell Adhesion Molecule Like) gene, previously reported to be associated with adiponectin levels in some populations. Our results suggest that, in this high-cardiovascular risk Mediterranean population, and even though adiponectin is favorably associated with metabolic traits and lower type 2 diabetes, the gene variants more associated with adiponectin may be population-specific, and some suggestive gene-Mediterranean diet interactions were detected.

Adiponectin, Leptin and Cardiovascular Disorders

The landmark discoveries of leptin and adiponectin firmly established adipose tissue as a sophisticated and highly active endocrine organ, opening a new era of investigating adipose-mediated tissue crosstalk. Both obesity-associated hyperleptinemia and hypoadiponectinemia are important biomarkers to predict cardiovascular outcomes, suggesting a crucial role for adiponectin and leptin in obesity-associated cardiovascular disorders. Normal physiological levels of adiponectin and leptin are indeed essential to maintain proper cardiovascular function. Insufficient adiponectin and leptin signaling results in cardiovascular dysfunction. However, a paradox of high levels of both leptin and adiponectin is emerging in the pathogenesis of cardiovascular disorders. Here, we (1) summarize the recent progress in the field of adiponectin and leptin and its association with cardiovascular disorders, (2) further discuss the underlying mechanisms for this new paradox of leptin and adiponectin action, and (3) explore the possible application of partial leptin reduction, in addition to increasing the adiponectin/leptin ratio as a means to prevent or reverse cardiovascular disorders.

Interactive association between dietary fat and sex on CDH13 cg02263260 methylation

BACKGROUND

DNA methylation of Cadherin 13 (CDH13), a tumor suppressor gene is associated with gene repression and carcinogenesis. We determined the relation of dietary fat and sex with CDH13 cg02263260 methylation in Taiwanese adults.

METHODS

Data of 870 eligible participants (430 men and 440 women) between 30 and 70 years were obtained from the Taiwan Biobank (TWB) database. The association of dietary fat and sex with CDH13 cg02263260 methylation was determined using multiple linear regression.

RESULTS

The association between sex and cg02263260 methylation was significant: beta-coefficient (β) = 0.00532; 95% confidence interval (CI) = 0.00195-0.00868. Moreover, the interaction between sex and dietary fat on cg02263260 methylation was significant (P-value = 0.0145). After stratification by sex, the association of dietary fat with cg02263260 methylation was significant only in women. Specifically, high dietary fat was positively associated with cg02263260 methylation in women (β = 0.00597; 95% CI = 0.00061-0.01133) and the test for trend was significant (P-value = 0.0283).

CONCLUSION

High fat intake was significantly associated with higher cg02263260 methylation in women and the test for trend was significant. These findings suggest that the association of fat intake and CDH13 cg02263260 might vary by sex and CDH13 cg02263260 methylation levels in women might increase as fat intake increases.

Adipocyte-Endothelium Crosstalk in Obesity

Obesity is characterized by pathological adipose tissue (AT) expansion. While healthy AT expansion enhances systemic insulin sensitivity, unhealthy AT expansion through increased adipocyte size is associated with insulin resistance, fibrosis, hypoxia, and reduced adipose-derived adiponectin secretion. The mechanisms causing the unhealthy AT expansion are not fully elucidated; yet, dysregulated crosstalk between cells within the AT is an important contributor. Evidence from animal and human studies suggests a crucial role of the crosstalk between vascular endothelium (the innermost cell type in blood vessels) and adipocytes for metabolic homeostasis. Arterial endothelial cells are directly involved in maintaining normal organ functions through local blood flow regulation. The endothelial-dependent regulation of blood flow in AT is hampered in obesity, which negatively affects the adipocyte. Moreover, endothelial cells secrete extracellular vesicles (EVs) that target adipocytes in vivo. The endothelial EVs secretion is hampered in obesity and may be affected by the adipocyte-derived adipokine adiponectin. Adiponectin targets the vascular endothelium, eliciting organ-protective functions through binding to T-cadherin. The reduced obesity-induced adiponectin binding of T-cadherin reduces endothelial EV secretion. This affects endothelial health and cell-cell communication between AT cells and distant organs, influencing systemic energy homeostasis. This review focuses on the current understanding of endothelial and adipocyte crosstalk. We will discuss how obesity changes the AT environment and how these changes contribute to obesity-associated metabolic disease in humans. Particularly, we will describe and discuss the EV-dependent communication and regulation between adipocytes, adiponectin, and the endothelial cells regulating systemic energy homeostasis in health and metabolic disease in humans.

Puberty Status Modifies the Effects of Genetic Variants, Lifestyle Factors and Their Interactions on Adiponectin: The BCAMS Study

BACKGROUND

Hypoadiponectinemia has been associated with various cardiometabolic disease states. Previous studies in adults have shown that adiponectin levels were regulated by specific genetic and behavioral or lifestyle factors. However, little is known about the influence of these factors on adiponectin levels in children, particularly as mitigated by pubertal development.

METHODS

We performed a cross-sectional analysis of data from 3,402 children aged 6-18 years from the Beijing Child and Adolescent Metabolic Syndrome (BCAMS) study. Pubertal progress was classified as prepubertal, midpuberty, and postpuberty. Six relevant single nucleotide polymorphisms (SNPs) were selected from previous genome-wide association studies of adiponectin in East Asians. Individual SNPs and two weighted genetic predisposition scores, as well as their interactions with 14 lifestyle factors, were analyzed to investigate their influence on adiponectin levels across puberty. The effect of these factors on adiponectin was analyzed using general linear models adjusted for age, sex, and BMI.

RESULTS

After adjustment for age, sex, and BMI, the associations between adiponectin levels and diet items, and diet score were significant at prepuberty or postpuberty, while the effect of exercise on adiponectin levels was more prominent at mid- and postpuberty. Walking to school was found to be associated with increased adiponectin levels throughout puberty. Meanwhile, the effect of WDR11-FGFR2-rs3943077 was stronger at midpuberty (P = 0.002), and ADIPOQ-rs6773957 was more effective at postpuberty (P = 0.005), while CDH13-rs4783244 showed the strongest association with adiponectin levels at all pubertal stages (all P < 3.24 × 10^-15). We further found that effects of diet score (P_interaction = 0.022) and exercise (P_interaction = 0.049) were stronger in children with higher genetic risk of hypoadiponectinemia, while higher diet score and exercise frequency attenuated the differences in adiponectin levels among children with different genetic risks.

CONCLUSIONS

Our study confirmed puberty modulates the associations between adiponectin, and genetic variants, lifestyle factors, and gene-by-lifestyle interactions. These findings provide new insight into puberty-specific lifestyle suggestions, especially in genetically susceptible individuals.

A feed-forward regulatory loop in adipose tissue promotes signaling by the hepatokine FGF21

In this study, Han et al. demonstrate that JNK signaling in adipocytes causes an increased circulating concentration of the hepatokine fibroblast growth factor 21 (FGF21) that regulates systemic metabolism. This regulatory loop represents a novel signaling paradigm that connects autocrine and endocrine signaling modes of the same hormone in different tissues.

The cJun NH₂-terminal kinase (JNK) signaling pathway is activated by metabolic stress and promotes the development of metabolic syndrome, including hyperglycemia, hyperlipidemia, and insulin resistance. This integrated physiological response involves cross-talk between different organs. Here we demonstrate that JNK signaling in adipocytes causes an increased circulating concentration of the hepatokine fibroblast growth factor 21 (FGF21) that regulates systemic metabolism. The mechanism of organ crosstalk is mediated by a feed-forward regulatory loop caused by JNK-regulated FGF21 autocrine signaling in adipocytes that promotes increased expression of the adipokine adiponectin and subsequent hepatic expression of the hormone FGF21. The mechanism of organ cross-talk places circulating adiponectin downstream of autocrine FGF21 expressed by adipocytes and upstream of endocrine FGF21 expressed by hepatocytes. This regulatory loop represents a novel signaling paradigm that connects autocrine and endocrine signaling modes of the same hormone in different tissues.

Pioglitazone Prevents Hemorrhagic Infarction After Transient Focal Ischemia in Type 2 Diabetes

Pioglitazone (PGZ), a PPARγ agonist, has been used for diabetic patients as an insulin-sensitizing agent. Recent studies have demonstrated that PGZ increases adiponectin (APN) levels and provides vascular protection in ischemic conditions. This study was designed to assess the neuroprotective effects of PGZ against cerebral ischemia-reperfusion injury via an APN-related mechanism. Type 2 diabetic leptin-deficient mice (db/db) were administered PGZ for 1 week, and plasma insulin and APN levels were measured. These mice received a middle cerebral artery occlusion and reperfusion injury, and they were evaluated for the infarct volume and by immunohistochemistry and western blotting analysis at several time points after ischemia. PGZ-administered db/db mice showed improved insulin sensitivity, and the hemorrhagic rate and infarct volume were decreased (P < 0.05). In the PGZ-administered group, plasma APN levels increased compared with the vehicle group. In the db/db group, PGZ administration significantly suppressed inflammatory reactions and oxidative stress after reperfusion (P < 0.05). PGZ may be applicable for acute cerebral ischemia treatment in metabolic syndrome patients as well as antidiabetic agents.

Adiponectin/leptin ratio increases after a 12-week very low-carbohydrate, high-fat diet, and exercise training in healthy individuals: A non-randomized, parallel design study

This study aimed to investigate the effect of a 12-week very low-carbohydrate, high-fat (VLCHF) diet and exercise on biomarkers of inflammation in healthy individuals. Since the anti-inflammatory effects of a ketogenic diet have been established, we hypothesized that the VLCHF diet, along with exercise, would have an additional favorable effect on biomarkers of inflammation. Twenty-four healthy individuals were allocated to the VLCHF diet (VLCHF: N = 12, age 25.3 ± 2.0 years, body mass 66.7 ± 9.8 kg, fat mass 21.5% ± 4.9%), or habitual diet (HD: N = 12, age 23.9 ± 3.8 years, body mass 72.7 ± 15.0 kg, fat mass 23.4 ± 8.4 %) group. Biomarkers of inflammation (adiponectin, leptin, and high-sensitive interleukin-6 [hs-IL-6]) and substrate metabolism (glycated hemoglobin, fasting glucose, triacylglycerides, and cholesterol) were analyzed from blood at baseline and after 12 weeks. The adiponectin-leptin ratio significantly increased in the VLCHF group after the intervention period (ES [95% CL]: -0.90 [-0.96, -0.77], P ≤ .001, BF₁₀ = 22.15). The adiponectin-leptin ratio changes were associated with both a significant increase in adiponectin (-0.79 [-0.91, -0.54], P ≤ .001, BF₁₀ = 9.43) and a significant decrease in leptin (0.58 [0.19, 0.81], P = .014, BF₁₀ = 2.70). There was moderate evidence of changes in total cholesterol (-1.15 [-2.01, -0.27], P = .010, BF₁₀ = 5.20), and LDL cholesterol (-1.12 [-2.01, -0.21], P = .016, BF₁₀ = 4.56) in the VLCHF group. Body weight (kg) and fat mass (%) decreased in the VLCHF group by 5.4% and 14.9%, respectively. We found that in healthy young individuals, consuming a VLCHF diet while performing regular exercise over a 12-week period produced favorable changes in body weight and fat mass along with beneficial changes in serum adiponectin and leptin concentrations. These data support the use of a VLCHF diet strategy for the primary prevention of chronic diseases associated with systemic low-grade inflammation.

Understanding Mechanisms Underlying Non-Alcoholic Fatty Liver Disease (NAFLD) in Mental Illness: Risperidone and Olanzapine Alter the Hepatic Proteomic Signature in Mice

Patients with severe mental illness have increased mortality, often linked to cardio-metabolic disease. Non-alcoholic fatty liver disease (NAFLD) incidence is higher in patients with schizophrenia and is exacerbated with antipsychotic treatment. NAFLD is associated with obesity and insulin resistance, both of which are induced by several antipsychotic medications. NAFLD is considered an independent risk factor for cardiovascular disease, the leading cause of death for patients with severe mental illness. Although the clinical literature clearly defines increased risk of NAFLD with antipsychotic therapy, the underlying mechanisms are not understood. Given the complexity of the disorder as well as the complex pharmacology associated with atypical antipsychotic (AA) medications, we chose to use a proteomic approach in healthy mice treated with a low dose of risperidone (RIS) or olanzapine (OLAN) for 28 days to determine effects on development of NAFLD and to identify pathways impacted by AA medications, while removing confounding intrinsic effects of mental illness. Both AA drugs caused development of steatosis in comparison with vehicle controls (p < 0.01) and affected multiple pathways relating to energy metabolism, NAFLD, and immune function. AA-associated alteration in autonomic function appears to be a unifying theme in the regulation of hepatic pathology.