Severely impaired adipsin expression in genetic and acquired obesity

Is the endotoxin-complement cascade the major driver in lipedema?

Lipedema is a poorly understood disorder of adipose tissue characterized by abnormal but symmetrical deposition of subcutaneous white adipose tissue (WAT) in proximal extremities. Here, we propose that the underlying cause for lipedema could be triggered by a selective accumulation of bacterial lipopolysaccharides (LPS; also known as endotoxin) in gluteofemoral WAT. Together with a malfunctioning complement system, this induces low-grade inflammation in the depot and raises its uncontrollable expansion. Correspondingly, more attention should be paid in future research to the endotoxemia prevalent in patients with lipedema. We would like to propose that proper management of endotoxemia can reduce the progression and even improve the state of disease in patients with lipedema.

Association of Serum Adipsin Level with Insulin Resistance and Inflammatory Markers in Newly Diagnosed Type two Diabetes Mellitus Patients

Adipsin is an anti-inflammatory adipokines and its altered level was seen in obesity and type II DM. Our study investigated the clinical significance of serum adipsin levels as a risk marker for type 2 diabetes and its relationships with insulin resistance and various adipo-cytokines. The study included 110 treatment-naïve T2DM cases and 100 controls of similar age and gender from northern India. Clinical, biochemical, and anthropometric characteristics were all profiled. Serum adipo-cytokines were measured using ELISA methods. Adipsin was significantly inversely correlated with body mass index (BMI), waist circumference, fasting plasma glucose, glycated haemoglobin (HbA1C), total cholesterol (TC), triglyceride (TG), homeostasis model assessment-estimated insulin resistance (HOMA-IR), tumour necrosis factor- α (TNF-α) and interleulin-6 (IL-6) and positively correlated with high-density lipoprotein cholesterol (HDL-C) and homeostasis model assessment of β-cell function (HOMA-B) (P < 0.05). T2DM occurrence decreased with increasing concentration of adipsin with an odds ratio (OR) of 0.68 (95% CI = 0.58-0.79), P < 0.001. The area under curve (95% CI) for adipsin was 0.70 (0.63 to 0.76) with P < 0.001. The best cutoff value for adipsin to predict T2DM was < 5.50 µg/ml with 47.27% sensitivity and 82.00% specificity. FPG and WC were both independent predictors of serum adipsin levels. Our findings showed that high adipsin levels reduced the likelihood of T2DM and emerged as a potential risk marker in the prediction of T2DM.

Graphical Abstract

Complement 3a Receptor 1 on Macrophages and Kupffer cells is not required for the Pathogenesis of Metabolic Dysfunction-Associated Steatotic Liver Disease

Together with obesity and type 2 diabetes, metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing global epidemic. Activation of the complement system and infiltration of macrophages has been linked to progression of metabolic liver disease. The role of complement receptors in macrophage activation and recruitment in MASLD remains poorly understood. In human and mouse, C3AR1 in the iver is expressed primarily in Kupffer cells, but is downregulated in humans with MASLD compared to obese controls. To test the role of complement 3a receptor (C3aR1) on macrophages and liver resident macrophages in MASLD, we generated mice deficient in C3aR1 on all macrophages (C3aR1-MφKO) or specifically in liver Kupffer cells (C3aR1-KpKO) and subjected them to a model of metabolic steatotic liver disease. We show that macrophages account for the vast majority of C3ar1 expression in the liver. Overall, C3aR1-MφKO and C3aR1-KpKO mice have similar body weight gain without significant alterations in glucose homeostasis, hepatic steatosis and fibrosis, compared to controls on a MASLD-inducing diet. This study demonstrates that C3aR1 deletion in macrophages or Kupffer cells, the predominant liver cell type expressing C3aR1, has no significant effect on liver steatosis, inflammation or fibrosis in a dietary MASLD model.

Novel mechanisms involved in leptin sensitization in obesity

Leptin is a hormone that is secreted by adipocytes in proportion to adipose tissue size, and that informs the brain about the energy status of the body. Leptin acts through its receptor LepRb, expressed mainly in the hypothalamus, and induces a negative energy balance by potent inhibition of feeding and activation of energy expenditure. These actions have led to huge expectations for the development of therapeutic targets for metabolic complications based on leptin-derived compounds. However, the majority of patients with obesity presents elevated leptin production, suggesting that in this setting leptin is ineffective in the regulation of energy balance. This resistance to the action of leptin in obesity has led to the development of "leptin sensitizers," which have been tested in preclinical studies. Much research has focused on generating combined treatments that act on multiple levels of the gastrointestinal-brain axis. The gastrointestinal-brain axis secretes a variety of different anorexigenic signals, such as uroguanylin, glucagon-like peptide-1, amylin, or cholecystokinin, which can alleviate the resistance to leptin action. Moreover, alternative mechanism such as pharmacokinetics, proteostasis, the role of specific kinases, chaperones, ER stress and neonatal feeding modifications are also implicated in leptin resistance. This review will cover the current knowledge regarding the interaction of leptin with different endocrine factors from the gastrointestinal-brain axis and other novel mechanisms that improve leptin sensitivity in obesity.

Influence of Adipokines on Metabolic Dysfunction and Aging

Currently, 30% of the global population is overweight or obese, with projections from the World Obesity Federation suggesting that this figure will surpass 50% by 2035. Adipose tissue dysfunction, a primary characteristic of obesity, is closely associated with an increased risk of metabolic abnormalities, such as hypertension, hyperglycemia, and dyslipidemia, collectively termed metabolic syndrome. In particular, visceral fat accretion is considered as a hallmark of aging and is strongly linked to higher mortality rates in humans. Adipokines, bioactive peptides secreted by adipose tissue, play crucial roles in regulating appetite, satiety, adiposity, and metabolic balance, thereby rendering them key players in alleviating metabolic diseases and potentially extending health span. In this review, we elucidated the role of adipokines in the development of obesity and related metabolic disorders while also exploring the potential of certain adipokines as candidates for longevity interventions.

Adipose Signals Regulating Distal Organ Health and Disease

Excessive adiposity in obesity is a significant risk factor for development of type 2 diabetes (T2D), nonalcoholic fatty liver disease, and other cardiometabolic diseases. An unhealthy expansion of adipose tissue (AT) results in reduced adipogenesis, increased adipocyte hypertrophy, adipocyte hypoxia, chronic low-grade inflammation, increased macrophage infiltration, and insulin resistance. This ultimately culminates in AT dysfunction characterized by decreased secretion of antidiabetic adipokines such as adiponectin and adipsin and increased secretion of proinflammatory prodiabetic adipokines including RBP4 and resistin. This imbalance in adipokine secretion alters the physiological state of AT communication with target organs including pancreatic β-cells, heart, and liver. In the pancreatic β-cells, adipokines are known to have a direct effect on insulin secretion, gene expression, cell death, and/or dedifferentiation. For instance, impaired secretion of adipsin, which promotes insulin secretion and β-cell identity, results in β-cell failure and T2D, thus presenting a potential druggable target to improve and/or preserve β-cell function. The cardiac tissue is affected by both the classic white AT-secreted adipokines and the newly recognized brown AT (BAT)-secreted BATokines or lipokines that alter lipid deposition and ventricular function. In the liver, adipokines affect hepatic gluconeogenesis, lipid accumulation, and insulin sensitivity, underscoring the importance of adipose-liver communication in the pathogenesis of nonalcoholic fatty liver disease. In this perspective, we outline what is currently known about the effects of individual adipokines on pancreatic β-cells, liver, and the heart.

A single-cell atlas of bovine skeletal muscle reveals mechanisms regulating intramuscular adipogenesis and fibrogenesis

BACKGROUND

Intramuscular fat (IMF) and intramuscular connective tissue (IMC) are often seen in human myopathies and are central to beef quality. The mechanisms regulating their accumulation remain poorly understood. Here, we explored the possibility of using beef cattle as a novel model for mechanistic studies of intramuscular adipogenesis and fibrogenesis.

METHODS

Skeletal muscle single-cell RNAseq was performed on three cattle breeds, including Wagyu (high IMF), Brahman (abundant IMC but scarce IMF), and Wagyu/Brahman cross. Sophisticated bioinformatics analyses, including clustering analysis, gene set enrichment analyses, gene regulatory network construction, RNA velocity, pseudotime analysis, and cell-cell communication analysis, were performed to elucidate heterogeneities and differentiation processes of individual cell types and differences between cattle breeds. Experiments were conducted to validate the function and specificity of identified key regulatory and marker genes. Integrated analysis with multiple published human and non-human primate datasets was performed to identify common mechanisms.

RESULTS

A total of 32 708 cells and 21 clusters were identified, including fibro/adipogenic progenitor (FAP) and other resident and infiltrating cell types. We identified an endomysial adipogenic FAP subpopulation enriched for COL4A1 and CFD (log2FC = 3.19 and 1.92, respectively; P < 0.0001) and a perimysial fibrogenic FAP subpopulation enriched for COL1A1 and POSTN (log2FC = 1.83 and 0.87, respectively; P < 0.0001), both of which were likely derived from an unspecified subpopulation. Further analysis revealed more progressed adipogenic programming of Wagyu FAPs and more advanced fibrogenic programming of Brahman FAPs. Mechanistically, NAB2 drives CFD expression, which in turn promotes adipogenesis. CFD expression in FAPs of young cattle before the onset of intramuscular adipogenesis was predictive of IMF contents in adulthood (R2  = 0.885, P < 0.01). Similar adipogenic and fibrogenic FAPs were identified in humans and monkeys. In aged humans with metabolic syndrome and progressed Duchenne muscular dystrophy (DMD) patients, increased CFD expression was observed (P < 0.05 and P < 0.0001, respectively), which was positively correlated with adipogenic marker expression, including ADIPOQ (R2  = 0.303, P < 0.01; and R2  = 0.348, P < 0.01, respectively). The specificity of Postn/POSTN as a fibrogenic FAP marker was validated using a lineage-tracing mouse line. POSTN expression was elevated in Brahman FAPs (P < 0.0001) and DMD patients (P < 0.01) but not in aged humans. Strong interactions between vascular cells and FAPs were also identified.

CONCLUSIONS

Our study demonstrates the feasibility of beef cattle as a model for studying IMF and IMC. We illustrate the FAP programming during intramuscular adipogenesis and fibrogenesis and reveal the reliability of CFD as a predictor and biomarker of IMF accumulation in cattle and humans.

Absolute Quantification of Pan-Cancer Plasma Proteomes Reveals Unique Signature in Multiple Myeloma

Mass spectrometry based on data-independent acquisition (DIA) has developed into a powerful quantitative tool with a variety of implications, including precision medicine. Combined with stable isotope recombinant protein standards, this strategy provides confident protein identification and precise quantification on an absolute scale. Here, we describe a comprehensive targeted proteomics approach to profile a pan-cancer cohort consisting of 1800 blood plasma samples representing 15 different cancer types. We successfully performed an absolute quantification of 253 proteins in multiplex. The assay had low intra-assay variability with a coefficient of variation below 20% (CV = 17.2%) for a total of 1013 peptides quantified across almost two thousand injections. This study identified a potential biomarker panel of seven protein targets for the diagnosis of multiple myeloma patients using differential expression analysis and machine learning. The combination of markers, including the complement C1 complex, JCHAIN, and CD5L, resulted in a prediction model with an AUC of 0.96 for the identification of multiple myeloma patients across various cancer patients. All these proteins are known to interact with immunoglobulins.

Adipsin alleviates cardiac microvascular injury in diabetic cardiomyopathy through Csk-dependent signaling mechanism

BACKGROUND

Microvascular complications are associated with an overtly increased risk of adverse outcomes in patients with diabetes including coronary microvascular injury which manifested as disruption of adherens junctions between cardiac microvascular endothelial cells (CMECs). However, particular mechanism leading to diabetic coronary microvascular hyperpermeability remains elusive.

METHODS

Experimental diabetes was induced in mice with adipose tissue-specific Adipsin overexpression (Adipsin^LSL/LSL-Cre) and their respective control (Adipsin^LSL/LSL). In addition, cultured CMECs were subjected to high glucose/palmitic acid (HG + PA) treatment to simulate diabetes for a mechanistic approach.

RESULTS

The results showed that Adipsin overexpression significantly reduced cardiac microvascular permeability, preserved coronary microvascular integrity, and increased coronary microvascular density. Adipsin overexpression also attenuated cardiac dysfunction in diabetic mice. E/A ratio, an indicator of cardiac diastolic function, was improved by Adipsin. Adipsin overexpression retarded left ventricular adverse remodeling, enhanced LVEF, and improved cardiac systolic function. Adipsin-enriched exosomes were taken up by CMECs, inhibited CMECs apoptosis, and increased CMECs proliferation under HG + PA treatment. Adipsin-enriched exosomes also accelerated wound healing, rescued cell migration defects, and promoted tube formation in response to HG + PA challenge. Furthermore, Adipsin-enriched exosomes maintained adherens junctions at endothelial cell borders and reversed endothelial hyperpermeability disrupted by HG + PA insult. Mechanistically, Adipsin blocked HG + PA-induced Src phosphorylation (Tyr416), VE-cadherin phosphorylation (Tyr685 and Tyr731), and VE-cadherin internalization, thus maintaining CMECs adherens junctions integrity. LC-MS/MS analysis and co-immunoprecipitation analysis (Co-IP) unveiled Csk as a direct downstream regulator of Adipsin. Csk knockdown increased Src phosphorylation (Tyr416) and VE-cadherin phosphorylation (Tyr685 and Tyr731), while abolishing Adipsin-induced inhibition of VE-cadherin internalization. Furthermore, Csk knockdown counteracted Adipsin-induced protective effects on endothelial hyperpermeability in vitro and endothelial barrier integrity of coronary microvessels in vivo.

CONCLUSIONS

Together, these findings favor the vital role of Adipsin in the regulation of CMECs adherens junctions integrity, revealing its promises as a treatment target against diabetic coronary microvascular dysfunction. Graphical abstract depicting the mechanisms of action behind Adipsin-induced regulation of diabetic coronary microvascular dysfunction.

Extracellular Vesicles in Adipose Tissue Communication with the Healthy and Pathological Heart

Adipose tissue and its diverse cell types constitute one of the largest endocrine organs. With multiple depot locations, adipose tissue plays an important regulatory role through paracrine and endocrine communication, particularly through the secretion of a wide range of bioactive molecules, such as nucleic acids, proteins, lipids or adipocytokines. Over the past several years, research has uncovered a myriad of interorgan communication signals mediated by small lipid-derived nanovesicles known as extracellular vesicles (EVs), in which secreted bioactive molecules are stably transported as cargo molecules and delivered to adjacent cells or remote organs. EVs constitute an essential part of the human adipose secretome, and there is a growing body of evidence showing the crucial implications of adipose-derived EVs in the regulation of heart function and its adaptative capacity. The adipose tissue modifications and dysfunction observed in obesity and aging tremendously affect the adipose-EV secretome, with important consequences for the myocardium. The present review presents a comprehensive analysis of the findings in this novel area of research, reports the key roles played by adipose-derived EVs in interorgan cross-talk with the heart and discusses their implications in physiological and pathological conditions affecting adipose tissue and/or the heart (pressure overload, ischemia, diabetic cardiomyopathy, etc.).

Increased Serum Adipsin Correlates with MAFLD and Metabolic Risk Abnormalities

PURPOSE

A panel of international experts proposed a new definition of fatty liver in 2020, namely metabolic dysfunction-associated fatty liver disease (MAFLD). As an adipokine, adipsin is closely related to metabolic-related diseases. In this study, we aimed to evaluate the relationship among MAFLD, serum adipsin, and metabolic risk abnormalities.

METHODS

Our study was a cross-sectional study based on the first follow-up of the Guangzhou Nutrition and Health Study (GNHS). A total of 908 patients with hepatic steatosis were involved in our study. Detailed data of patients were collected based upon questionnaire information, physical examination, and blood biochemical test.

RESULTS

Among the 908 patients, 789 patients were diagnosed with MAFLD. The levels of serum adipsin in the MAFLD group and non-MAFLD group were (3543.00 (3187.94-3972.50) ng/mL) and (3095.33 (2778.71-3354.77) ng/mL) (P < 0.001), respectively. After adjusting for potential confounders, adipsin levels were found to be associated with MAFLD. The OR was 3.46 (95% CI: 1.57-7.64) for adipsin when comparing subjects in the highest tertile with those in the lowest tertile. With the increase in the number of metabolic risk abnormalities, both the levels of serum adipsin and the proportion of moderate to severe fatty liver increased (all p-trend < 0.001).

CONCLUSION

Increased serum adipsin correlates with MAFLD. Both adipsin levels as well as fatty liver severity increase with higher numbers of metabolic risk abnormalities.

Contribution of animal models to the mechanistic understanding of Alternative Pathway and Amplification Loop (AP/AL)-driven Complement-mediated Diseases

This review aimed to capture the key findings that animal models have provided around the role of the alternative pathway and amplification loop (AP/AL) in disease. Animal models, particularly mouse models, have been incredibly useful to define the role of complement and the alternative pathway in health and disease; for instance, the use of cobra venom factor and depletion of C3 provided the initial insight that complement was essential to generate an appropriate adaptive immune response. The development of knockout mice have further underlined the importance of the AP/AL in disease, with the FH knockout mouse paving the way for the first anti-complement drugs. The impact from the development of FB, properdin, and C3 knockout mice closely follows this in terms of mechanistic understanding in disease. Indeed, our current understanding that complement plays a role in most conditions at one level or another is rooted in many of these in vivo studies. That C3, in particular, has roles beyond the obvious in innate and adaptive immunity, normal physiology, and cellular functions, with or without other recognized AP components, we would argue, only extends the reach of this arm of the complement system. Humanized mouse models also continue to play their part. Here, we argue that the animal models developed over the last few decades have truly helped define the role of the AP/AL in disease.

Acetylation of PPARγ in macrophages promotes visceral fat degeneration in obesity

Obesity is characterized by chronic, low-grade inflammation, which is driven by macrophage infiltration of adipose tissue. PPARγ is well established to have an anti-inflammatory function in macrophages, but the mechanism that regulates its function in these cells remains to be fully elucidated. PPARγ undergoes post-translational modifications (PTMs), including acetylation, to mediate ligand responses, including on metabolic functions. Here, we report that PPARγ acetylation in macrophages promotes their infiltration into adipose tissue, exacerbating metabolic dysregulation. We generated a mouse line that expresses a macrophage-specific, constitutive acetylation-mimetic form of PPARγ (K293Qflox/flox:LysM-cre, mK293Q) to dissect the role of PPARγ acetylation in macrophages. Upon high-fat diet feeding to stimulate macrophage infiltration into adipose tissue, we assessed the overall metabolic profile and tissue-specific phenotype of the mutant mice, including responses to the PPARγ agonist Rosiglitazone. Macrophage-specific PPARγ K293Q expression promotes proinflammatory macrophage infiltration and fibrosis in epididymal white adipose tissue, but not in subcutaneous or brown adipose tissue, leading to decreased energy expenditure, insulin sensitivity, glucose tolerance, and adipose tissue function. Furthermore, mK293Q mice are resistant to Rosiglitazone-induced improvements in adipose tissue remodeling. Our study reveals that acetylation is a new layer of PPARγ regulation in macrophage activation, and highlights the importance and potential therapeutic implications of such PTMs in regulating metabolism.

Pancreatic Islets as a Target of Adipokines

Rising rates of obesity are intricately tied to the type 2 diabetes epidemic. The adipose tissues can play a central role in protection against or triggering metabolic diseases through the secretion of adipokines. Many adipokines may improve peripheral insulin sensitivity through a variety of mechanisms, thereby indirectly reducing the strain on beta cells and thus improving their viability and functionality. Such effects will not be the focus of this article. Rather, we will focus on adipocyte-secreted molecules that have a direct effect on pancreatic islets. By their nature, adipokines represent potential druggable targets that can reach the islets and improve beta-cell function or preserve beta cells in the face of metabolic stress. © 2022 American Physiological Society. Compr Physiol 12:1-27, 2022.

Adipsin – summing up large-scale results: A review

Adipsin is one of the first discovered adipokines hormones produced by adipose tissue. Adipsin performs the function of a regulator of carbohydrate and lipid metabolism and participates in the adaptation of metabolism to the real needs of the body, being a powerful stimulant of anabolic processes. A characteristic feature of adipsin is that it is also a complement factor D, which is necessary for the normal functioning of an alternative pathway of activation of the complement system. Due to this, adipsin is represented in the body as a link between the energy block of the endocrine system and the humoral block of the immune system. Adipsin is known as a regulator of the function of pancreatic beta cells, a stimulator of lipogenesis, a modulator of inflammation processes. Recently, there have been works indicating the effect of adipsin on the microbiota, as well as its role in non-alcoholic fatty liver disease. To date, there are a large number of publications describing the biochemical structure, functions of adipsin, mechanisms of regulation of its synthesis, as well as changes in the level of adipsin in various pathological conditions. Attempts are also described to pharmacologically influence adipsin in order to modulate its functions or use it as a biomarker for the diagnosis of diseases. However, there is currently no structured review that summarizes and systematizes all available information about this adipokine. This is exactly the task we set ourselves in this study. The paper contains the results of all available studies on adipsin. In some cases, they are contradictory in nature, which indicates the need for further research in detecting connections between the body's systems.

Stachydrine derived from fermented rice prevents diet-induced obesity by regulating adipsin and endoplasmic reticulum homeostasis

Makgeolli, a widely consumed traditional alcoholic beverage in Korea, is brewed mainly from rice using Nuruk as a fermentation starter, which contains fungi, yeast, and lactic acid bacteria. Among 58 Makgeolli samples brewed using various Nuruks, we found that one exhibited anti-obesity properties, with stachydrine shown to be responsible for these properties. Stachydrine promotes lipolysis and inhibits lipid accumulation in 3T3-L1 adipocytes; it also reduces weight gain and improves glucose tolerance and insulin resistance in a mouse model. Stachydrine dramatically suppresses adipsin mRNA levels in liver and adipose tissue, whereas serum adipsin levels were elevated in stachydrine-treated mice compared to mice fed a high-fat diet alone. Moreover, stachydrine recovers endoplasmic reticulum homeostasis and regulates adipsin expression. We highlight the potential use of stachydrine as a therapeutic agent for the treatment of obesity and insulin resistance and the use of Makgeolli fermented by Nuruk as a source of novel bioactive compounds.

Plasma and aqueous levels of alarin and adipsin ın patients with and without diabetic retinopathy

Backround

Diabetic retinopathy is a disease seen with microvascular complications as a result of hyperglycemia and insulin resistance. Alarin and Adipsin are molecules with a role in energy and glucose metabolism. The aim of this study was to determine plasma and aqueous levels of Alarin and Adipsin in patients with and without diabetic retinopathy to evaluate their potential roles in diabetic retinopathy.

Methods

The study included one eye from each of 20 cataract patients without diabetes (C), 20 cataract patients with diabetes and without diabetic retinopathy (DM + C), and 20 cataract patients with diabetes and diabetic retinopathy (DR + C). Plasma and aqueous humour samples were taken from all patients during the cataract operation. Alarin and Adipsin levels were examined with the enzyme-linked immunosorbent assay (ELISA) method.

Results

Both plasma and aqueous Alarin levels were significantly higher in the patients with diabetic retinopathy than in the control group (p < 0.001, p = 0.006). Adipsin levels were found to be significantly higher in plasma in the control group than in the DR + C group and significantly higher in aqueous in the DR + C group than in the control group (p < 0.001, p < 0.001).

Conclusion

These findings suggest that Alarin and Adipsin may play important role in diabetic retinopathy.

Adipsin Serum Concentrations and Adipose Tissue Expression in People with Obesity and Type 2 Diabetes

(1) Adipsin is an adipokine that may link increased fat mass and adipose tissue dysfunction to obesity-related cardiometabolic diseases. Here, we investigated whether adipsin serum concentrations and adipose tissue (AT) adipsin mRNA expression are related to parameters of AT function, obesity and type 2 diabetes (T2D). (2) Methods: A cohort of 637 individuals with a wide range of age and body weight (Age: 18–85 years; BMI: 19–70 kg/m2) with (n = 237) or without (n = 400) T2D was analyzed for serum adipsin concentrations by ELISA and visceral (VAT) and subcutaneous (SAT) adipsin mRNA expression by RT-PCR. (3) Results: Adipsin serum concentrations were significantly higher in patients with T2D compared to normoglycemic individuals. We found significant positive univariate relationships of adipsin serum concentrations with age (r = 0.282, p < 0.001), body weight (r = 0.264, p < 0.001), fasting plasma glucose (r = 0.136, p = 0.006) and leptin serum concentrations (r = 0.362, p < 0.001). Neither VAT nor SAT adipsin mRNA expression correlated with adipsin serum concentrations after adjusting for age, sex and BMI. Independent of T2D status, we found significantly higher adipsin expression in SAT compared to VAT (4) Conclusions: Our data suggest that adipsin serum concentrations are strongly related to obesity and age. However, neither circulating adipsin nor adipsin AT expression reflects parameters of impaired glucose or lipid metabolism in patients with obesity with or without T2D.

New Discovered Adipokines Associated with the Pathogenesis of Obesity and Type 2 Diabetes

Obesity is defined as abnormal or excessive accumulation of adipose tissue, closely associated with the increased risk of various comorbidities, especially type 2 diabetes mellitus (T2DM). Adipose tissue is a complex structure responsible for not only fat storage but also releasing adipokines which may play roles in the pathogenesis and could be developed into biomarkers for diagnosis, treatment and prognosis of obesity-related metabolic diseases. This review aims to summarize several adipokines discovered recently that have promising functions in obesity and T2DM. Among them, the levels of FSTL1, WISP1 and Asprosin in subjects with obesity or diabetes are commonly higher than in normal controls, suggesting that they may be pathogenic. Inversely, SFRP5, Metrnl, NRG4 and FAM19A5 may serve as the protective factors.

Adipose Tissue-Endothelial Cell Interactions in Obesity-Induced Endothelial Dysfunction

Obesity has a strong impact on the pathogenesis of cardiovascular disease, which raises enthusiasm to understand how excess adiposity causes vascular injury. Adipose tissue is an essential regulator of cardiovascular system through its endocrine and paracrine bioactive products. Obesity induces endothelial dysfunction, which often precedes and leads to the development of cardiovascular diseases. Connecting adipose tissue-endothelial cell interplay to endothelial dysfunction may help us to better understand obesity-induced cardiovascular disease. This Mini Review discussed (1) the general interactions and obesity-induced endothelial dysfunction, (2) potential targets, and (3) the outstanding questions for future research.

Complement in metabolic disease: metaflammation and a two-edged sword

We are currently experiencing an enduring global epidemic of obesity and diabetes. It is now understood that chronic low-grade tissue inflammation plays an important role in metabolic disease, brought upon by increased uptake of a so-called Western diet, and a more sedentary lifestyle. Many evolutionarily conserved links exist between metabolism and the immune system, and an imbalance in this system induced by chronic over-nutrition has been termed 'metaflammation'. The complement system is an important and evolutionarily ancient part of innate immunity, but recent work has revealed that complement not only is involved in the recognition of pathogens and induction of inflammation, but also plays important roles in cellular and tissue homeostasis. Complement can therefore contribute both positively and negatively to metabolic control, depending on the nature and anatomical site of its activity. This review will therefore focus on the interactions of complement with mechanisms and tissues relevant for metabolic control, obesity and diabetes.

The Inflammatory Profile of Obesity and the Role on Pulmonary Bacterial and Viral Infections

Obesity is a globally increasing health problem, entailing diverse comorbidities such as infectious diseases. An obese weight status has marked effects on lung function that can be attributed to mechanical dysfunctions. Moreover, the alterations of adipocyte-derived signal mediators strongly influence the regulation of inflammation, resulting in chronic low-grade inflammation. Our review summarizes the known effects regarding pulmonary bacterial and viral infections. For this, we discuss model systems that allow mechanistic investigation of the interplay between obesity and lung infections. Overall, obesity gives rise to a higher susceptibility to infectious pathogens, but the pathogenetic process is not clearly defined. Whereas, viral infections often show a more severe course in obese patients, the same patients seem to have a survival benefit during bacterial infections. In particular, we summarize the main mechanical impairments in the pulmonary tract caused by obesity. Moreover, we outline the main secretory changes within the expanded adipose tissue mass, resulting in chronic low-grade inflammation. Finally, we connect these altered host factors to the influence of obesity on the development of lung infection by summarizing observations from clinical and experimental data.

The complex role of adipokines in obesity, inflammation, and autoimmunity

The global obesity epidemic is a major contributor to chronic disease and disability in the world today. Since the discovery of leptin in 1994, a multitude of studies have characterized the pathological changes that occur within adipose tissue in the obese state. One significant change is the dysregulation of adipokine production. Adipokines are an indispensable link between metabolism and optimal immune system function; however, their dysregulation in obesity contributes to chronic low-grade inflammation and disease pathology. Herein, I will highlight current knowledge on adipokine structure and physiological function, and focus on the known roles of these factors in the modulation of the immune response. I will also discuss adipokines in rheumatic and autoimmune diseases.

Plasticity of Epididymal Adipose Tissue in Response to Diet-Induced Obesity at Single-Nucleus Resolution

Adipose tissues display a remarkable ability to adapt to the dietary status. Here, we have applied single-nucleus RNA-seq to map the plasticity of mouse epididymal white adipose tissue at single-nucleus resolution in response to high-fat-diet-induced obesity. The single-nucleus approach allowed us to recover all major cell types and to reveal distinct transcriptional stages along the entire adipogenic trajectory from preadipocyte commitment to mature adipocytes. We demonstrate the existence of different adipocyte subpopulations and show that obesity leads to disappearance of the lipogenic subpopulation and increased abundance of the stressed lipid-scavenging subpopulation. Moreover, obesity is associated with major changes in the abundance and gene expression of other cell populations, including a dramatic increase in lipid-handling genes in macrophages at the expense of macrophage-specific genes. The data provide a powerful resource for future hypothesis-driven investigations of the mechanisms of adipocyte differentiation and adipose tissue plasticity.

Adipsin deficiency does not impact atherosclerosis development in Ldlr-/- mice

Obesity is a potent risk factor for atherosclerotic morbidity and mortality. Cytokines secreted from adipose tissue, namely, adipokines, have been suggested to be actively involved in atherosclerosis. One of the most abundant adipokines, adipsin, is downregulated in obesity. It catalyzes the rate-limiting step of alternative complement activation, which is one of the three complement pathways potentially involved in inflammation in atherosclerosis. Interestingly, adipsin has been identified as a novel biomarker in human coronary artery disease. However, its role in the development of atherosclerosis remains unexplored. We crossed adipsin^-/- mice onto an Ldlr^-/- background [double-knockout (DKO) mice] and induced atherogenesis by high-fat and high-cholesterol feeding. Metabolic profiles were systemically characterized, and atherosclerotic plaques were measured at both aortic root and arch regions. Western blotting was conducted to assess adipsin level and complement activity. The DKO mice exhibited similar sizes of atherosclerotic lesions as Ldlr^-/- control mice at both the aortic root and arch regions. Accordingly, they displayed comparable metabolic parameters, including body weight, insulin sensitivity, and lipid profiles, along with compensated complement activity. Adipsin deficiency does not impact the development of atherosclerosis in Ldlr^-/- mice despite its crucial function in alternative complement activation. Therefore, it is unlikely to play an important role in mediating the risk of atherosclerotic complications in obesity.NEW & NOTEWORTHY Adipsin deficiency does not impact the development of atherosclerosis in Ldlr^-/- mice despite its crucial function in alternative complement activation. Therefore, it is unlikely to play an important role in mediating the risk of atherosclerotic complications in obesity.

Programming With Varying Dietary Fat Content Alters Cardiac Insulin Receptor, Glut4 and FoxO1 Immunoreactivity in Neonatal Rats, Whereas High Fat Programming Alters Cebpa Gene Expression in Neonatal Female Rats

Fetal programming refers to an intrauterine stimulus or insult that shapes growth, development and health outcomes. Dependent on the quality and quantity, dietary fats can be beneficial or detrimental for the growth of the fetus and can alter insulin signaling by regulating the expression of key factors. The effects of varying dietary fat content on the expression profiles of factors in the neonatal female and male rat heart were investigated and analyzed in control (10% fat), 20F (20% fat), 30F (30% fat) and 40F (40% fat which was a high fat diet used to induce high fat programming) neonatal rats. The whole neonatal heart was immunostained for insulin receptor, glucose transporter 4 (Glut4) and forkhead box protein 1 (FoxO1), followed by image analysis. The expression of 84 genes, commonly associated with the insulin signaling pathway, were then examined in 40F female and 40F male offspring. Maintenance on diets, varying in fat content during fetal life, altered the expression of cardiac factors, with changes induced from 20% fat in female neonates, but from 30% fat in male neonates. Further, CCAAT/enhancer-binding protein alpha (Cebpa) was upregulated in 40F female neonates. There was, however, differential expression of several insulin signaling genes in 40F (high fat programmed) offspring, with some tending to significance but most differences were in fold changes (≥1.5 fold). The increased immunoreactivity for insulin receptor, Glut4 and FoxO1 in 20F female and 30F male neonatal rats may reflect a compensatory response to programming to maintain cardiac physiology. Cebpa was upregulated in female offspring maintained on a high fat diet, with fold increases in other insulin signaling genes viz. Aebp1, Cfd (adipsin), Adra1d, Prkcg, Igfbp, Retn (resistin) and Ucp1. In female offspring maintained on a high fat diet, increased Cebpa gene expression (concomitant with fold increases in other insulin signaling genes) may reflect cardiac stress and an adaptative response to cardiac inflammation, stress and/or injury, after high fat programming. Diet and the sex are determinants of cardiac physiology and pathophysiology, reflecting divergent mechanisms that are sex-specific.

Blockade of High-Fat Diet Proteomic Phenotypes Using Exercise as Prevention or Treatment

The increasing consumption of high-fat foods combined with a lack of exercise is a major contributor to the burden of obesity in humans. Aerobic exercise such as running is known to provide metabolic benefits, but how the overconsumption of a high-fat diet (HFD) and exercise interact is not well characterized at the molecular level. Here, we examined the plasma proteome in mice for the effects of aerobic exercise as both a treatment and as a preventative regimen for animals on either a HFD or a healthy control diet. This analysis detected large changes in the plasma proteome induced by the HFD, such as increased abundance of SERPINA7, ALDOB, and downregulation of SERPINA1E and complement factor D (CFD; adipsin). Some of these changes were significantly reverted using exercise as a preventative measure but not as a treatment regimen. To determine if either the intensity or duration of exercise influenced the outcome, we compared high-intensity interval training and endurance running. Endurance running slightly outperformed high-intensity interval training exercise, but overall, both provided similar reversion in abundance of plasma proteins modulated by the HFD, including SERPINA7, apolipoprotein E, SERPINA1E, and CFD. Finally, we compared the changes induced by overconsumption of a HFD with previous data from mice fed on an isocaloric high-saturated fatty acid or polyunsaturated fatty acid diet. This identified several common changes, including not only increased apolipoprotein C-II and apolipoprotein E but also highlighted changes specific for overconsumption of a HFD (fructose-bisphosphate aldolase B, SERPINA7, and CFD), saturated fatty acid-based diets (SERPINA1E), or polyunsaturated fatty acid-based diets (haptoglobin). Together, these data highlight the importance of early intervention with exercise to revert HFD-induced phenotypes and suggest some of the molecular mechanisms leading to the changes in the plasma proteome generated by HFD consumption. Web-based interactive visualizations are provided for this dataset (larancelab.com/hfd-exercise), which give insight into diet and exercise phenotypic interactions on the plasma proteome.

Predictors of HbA1c among Adipocytokine Biomarkers in African-American Men with Varied Glucose Tolerance

This study explored adipocytokine associations with acute and chronic hyperglycemia in African-American men (AAM). Fourteen adipocytokines were measured from men with normal glucose tolerance (NGT) or type 2 diabetes (T2D, drug-naïve MF(-) or using metformin MF(+)). Acute and chronic hyperglycemia were evaluated by 120 min oral glucose tolerance test (OGTT) and glycohemoglobin A1c (HbA1c). AAM with T2D (n = 21) compared to NGT (n = 20) were older, had higher BMI and slightly higher glucose and insulin. In the fasted state, TNF-α, IL-6, PAI-1, IL-13, adiponectin, adipsin, and lipocalin were lower in T2D vs. NGT. At 120 min post-glucose load, TNF-α, IL-6, IL-13, IL-8, PAI-1, adiponectin, adipsin, lipocalin, and resistin were lower in T2D vs. NGT. There were no statistical differences for GM-CSF, IL-7, IL-10, IP-10, and MCP-1. Regression analysis showed that fasting IL-8, TNF-α, adiponectin, lipocalin, resistin, adipsin, and PAI-1 were associated with HbA1c. After adjusting for age, BMI, glucose tolerance, and metformin use, only adipsin remained significantly associated with HbA1c (p = 0.021). The model including adipsin, TNF-α, age, BMI, and group designation (i.e., NGT, MF(-), MF(+)) explained 86% of HbA1c variability. The data suggested that adipsin could be associated with HbA1c in AAM with varied glucose tolerance.

Possible mechanisms involved in improved beta cell function in pregnant women with type 1 diabetes

Pregnancy is known to be associated with an increased demand for insulin that is normally compensated by an increased beta cell mass and insulin secretion. Recent studies have suggested enhanced beta cell function during pregnancy in women with type 1 diabetes (T1D). To explore the possible mechanisms behind enhanced beta cell function during pregnancy in women with T1D we investigated the impact of circulating factors in serum from nine women from each group of pregnant women with and without T1D, after pregnancy and non-diabetic non-pregnant women on rat islet cell proliferation and apoptosis, and on T-lymphocyte activation. In addition, circulating levels of pancreatic hormones and selected cytokines and adipokines were measured. Rat islet cell proliferation was higher in serum from pregnant women with T1D (p < 0.05) compared to T1D women after pregnancy. Apoptosis in INS-1E cell was lower (p < 0.05) in serum from pregnant women with T1D compared to T1D women after pregnancy. T-lymphocyte cell (Jurkat) proliferation was reduced by serum from pregnant women without T1D only (p < 0.05). Higher C-peptide levels and lower levels of ghrelin, IL-6, MCP-1, IL-8 and adipsin were observed in pregnant women with T1D compared to T1D women after pregnancy. In conclusion, the improved beta cell function in women with T1D during pregnancy may be due to lower levels of proinflammatory cytokines and/or higher levels of pregnancy-associated growth factors.

Fat-Produced Adipsin Regulates Inflammatory Arthritis

We explored the relationship of obesity and inflammatory arthritis (IA) by selectively expressing diphtheria toxin in adipose tissue yielding "fat-free" (FF) mice completely lacking white and brown fat. FF mice exhibit systemic neutrophilia and elevated serum acute phase proteins suggesting a predisposition to severe IA. Surprisingly, FF mice are resistant to K/BxN serum-induced IA and attendant bone destruction. Despite robust systemic basal neutrophilia, neutrophil infiltration into joints of FF mice does not occur when challenged with K/BxN serum. Absence of adiponectin, leptin, or both has no effect on joint disease, but deletion of the adipokine adipsin (complement factor D) completely prevents serum-induced IA. Confirming that fat-expressed adipsin modulates the disorder, transplantation of wild-type (WT) adipose tissue into FF mice restores susceptibility to IA, whereas recipients of adipsin-deficient fat remain resistant. Thus, adipose tissue regulates development of IA through a pathway in which adipocytes modify neutrophil responses in distant tissues by producing adipsin.

Overexpression of Adiponectin Receptors in Opium Users with and without Cancer

Aim

Opium addiction is a serious public health concern in the Middle East countries causing various illnesses. Opium use is associated with an increased risk of several cancers; however, the underlying mechanisms are not yet fully elucidated. Altered levels of adiponectin and its related main receptors, Adiponectin receptor 1 and 2 (AdipoR1 and AdipoR2) have been associated with several malignancies. Opium users are at risk of various cancers. All together let us to the hypothesis that probable overexpression of AdipoRs in opium users might be linked to the occurrence of cancer in this population.

Methods

One hundred opium users along with 100 healthy non-opium users were enrolled in the study. Opium users were followed up for 5 years (2014–2019) to evaluate the occurrence of malignancies. AdipoR1 and AdipoR2 expressions were measured using a flow cytometry method.

Results

Expression of AdipoR1 and AdipoR2 was significantly higher in opium users compared with the healthy control group (P=0.0001 and 0.0001, respectively). Eight opium users developed cancer during the follow-up period. Subjects abusing opium developed cancer by 8.6 folds comparing to non-opium users (P=0.034; OR=8.6; 95% CI (1.06–70.1)). Expression of these two receptors was significantly higher in opium users developing cancer compared with cancer-free opium (P=0.001).

Conclusion

Considering the significant overexpression of AdipoR1 and AdipoR2 in opium users and in opium users who developed malignancies and the association between upregulation of these receptors in most cancers affecting opium users and assessment of AdipoRs may serve as an early detection tool of cancer in this population.

Adipokines as key players in β cell function and failure

The growing prevalence of obesity and its related metabolic diseases, mainly Type 2 diabetes (T2D), has increased the interest in adipose tissue (AT) and its role as a principal metabolic orchestrator. Two decades of research have now shown that ATs act as an endocrine organ, secreting soluble factors termed adipocytokines or adipokines. These adipokines play crucial roles in whole-body metabolism with different mechanisms of action largely dependent on the tissue or cell type they are acting on. The pancreatic β cell, a key regulator of glucose metabolism due to its ability to produce and secrete insulin, has been identified as a target for several adipokines. This review will focus on how adipokines affect pancreatic β cell function and their impact on pancreatic β cell survival in disease contexts such as diabetes. Initially, the "classic" adipokines will be discussed, followed by novel secreted adipocyte-specific factors that show therapeutic promise in regulating the adipose-pancreatic β cell axis.

Regulation of Adipsin Expression by Endoplasmic Reticulum Stress in Adipocytes

Adpsin is an adipokine that stimulates insulin secretion from β-cells and improves glucose tolerance. Its expression has been found to be markedly reduced in obese animals. However, it remains unclear what factors lead to downregulation of adipsin in the context of obesity. Endoplasmic reticulum (ER) stress response is activated in various tissues under obesity-related conditions and can induce transcriptional reprogramming. Therefore, we aimed to investigate the relationship between adipsin expression and ER stress in adipose tissues during obesity. We observed that obese mice exhibited decreased levels of adipsin in adipose tissues and serum and increased ER stress markers in adipose tissues compared to lean mice. We also found that ER stress suppressed adipsin expression via adipocytes-intrinsic mechanisms. Moreover, the ER stress-mediated downregulation of adipsin was at least partially attributed to decreased expression of peroxisome proliferator-activated receptor γ (PPARγ), a key transcription factor in the regulation of adipocyte function. Finally, treatment with chemical chaperones recovered the ER stress-mediated downregulation of adipsin and PPARγ in vivo and in vitro. Our findings suggest that activated ER stress in adipose tissues is an important cause of the suppression of adipsin expression in the context of obesity.

Incendiary Leptin

Leptin is a hormone released by adipose tissue that plays a key role in the control of energy homeostasis through its binding to leptin receptors (LepR), mainly expressed in the hypothalamus. Most scientific evidence points to leptin’s satiating effect being due to its dual capacity to promote the expression of anorexigenic neuropeptides and to reduce orexigenic expression in the hypothalamus. However, it has also been demonstrated that leptin can stimulate (i) thermogenesis in brown adipose tissue (BAT) and (ii) the browning of white adipose tissue (WAT). Since the demonstration of the importance of BAT in humans 10 years ago, its study has aroused great interest, mainly in the improvement of obesity-associated metabolic disorders through the induction of thermogenesis. Consequently, several strategies targeting BAT activation (mainly in rodent models) have demonstrated great potential to improve hyperlipidemias, hepatic steatosis, insulin resistance and weight gain, leading to an overall healthier metabolic profile. Here, we review the potential therapeutic ability of leptin to correct obesity and other metabolic disorders, not only through its satiating effect, but by also utilizing its thermogenic properties.

The role of adipose tissue in cardiovascular health and disease

Accumulating knowledge on the biology and function of the adipose tissue has led to a major shift in our understanding of its role in health and disease. The adipose tissue is now recognized as a crucial regulator of cardiovascular health, mediated by the secretion of several bioactive products, including adipocytokines, microvesicles and gaseous messengers, with a wide range of endocrine and paracrine effects on the cardiovascular system. The adipose tissue function and secretome are tightly controlled by complex homeostatic mechanisms and local cell-cell interactions, which can become dysregulated in obesity. Systemic or local inflammation and insulin resistance lead to a shift in the adipose tissue secretome from anti-inflammatory and anti-atherogenic towards a pro-inflammatory and pro-atherogenic profile. Moreover, the interplay between the adipose tissue and the cardiovascular system is bidirectional, with vascular-derived and heart-derived signals directly affecting adipose tissue biology. In this Review, we summarize the current knowledge of the biology and regional variability of adipose tissue in humans, deciphering the complex molecular mechanisms controlling the crosstalk between the adipose tissue and the cardiovascular system, and their possible clinical translation. In addition, we highlight the latest developments in adipose tissue imaging for cardiovascular risk stratification and discuss how therapeutic targeting of the adipose tissue can improve prevention and treatment of cardiovascular disease.

Identification of Adipsin as a Novel Prognostic Biomarker in Patients With Coronary Artery Disease

Background

Circulating proteins are exposed to vascular endothelial layer and influence their functions. Among them, adipsin is a member of the trypsin family of peptidases and is mainly secreted from adipocytes, monocytes, and macrophages, catalyzing the rate‐limiting step of the alternative complement pathway. However, its pathophysiological role in cardiovascular disease remains to be elucidated. Here, we examined whether serum adipsin levels have a prognostic impact in patients with coronary artery disease.

Methods and Results

In 370 consecutive patients undergoing diagnostic coronary angiography, we performed a cytokine array analysis for screening serum levels of 50 cytokines/chemokines and growth factors. Among them, classification and regression analysis identified adipsin as the best biomarker for prediction of their long‐term prognosis (median 71 months; interquartile range, 55–81 months). Kaplan–Meier curve showed that higher adipsin levels (≥400 ng/mL) were significantly associated with all‐cause death (hazard ratio [HR], 4.2; 95% CI, 1.7–10.6 [P<0.001]) and rehospitalization (HR, 2.4; 95% CI, 1.7–3.5 [P<0.001]). Interestingly, higher high‐sensitivity C‐reactive protein levels (≥1 mg/L) were significantly correlated with all‐cause death (HR, 3.2; 95% CI, 1.7–5.9 [P<0.001]) and rehospitalization (HR, 1.5, 95% CI, 1.1–1.9 [P<0.01]). Importantly, the combination of adipsin (≥400 ng/mL) and high‐sensitivity C‐reactive protein (≥1 mg/L) was more significantly associated with all‐cause death (HR, 21.0; 95% CI, 2.9–154.1 [P<0.001]). Finally, the receiver operating characteristic curve demonstrated that serum adipsin levels predict the death caused by acute myocardial infarction in patients with coronary artery disease (C‐statistic, 0.847).

Conclusions

These results indicate that adipsin is a novel biomarker that predicts all‐cause death and rehospitalization in patients with coronary artery disease, demonstrating the novel aspects of the alternative complementary system in the pathogenesis of coronary artery disease.

Association between plasma adipsin level and mild cognitive impairment in Chinese patients with type 2 diabetes: a cross-sectional study

BACKGROUND

The adipokine adipsin contributes to insulin resistance (IR), inflammation, and obesity, which are all regarded as high-risk factors for mild cognitive impairment (MCI) in patients with type 2 diabetes mellitus. This research aimed to uncover the role of adipsin in Chinese type 2 diabetes mellitus (T2DM) population with early cognitive dysfunction and determine whether adipsin contributes to diabetic MCI caused by IR.

METHODS

In our study, 126 patients with T2DM were enrolled. The Montreal Cognitive Assessment (MoCA) was used to assess cognitive impairment. Demographic data and neuropsychological test results were evaluated. Plasma adipsin level was measured by enzyme-linked immunosorbent assay.

RESULTS

The MCI group (n = 57) presented higher plasma adipsin levels compared with the healthy controls (p = 0.018). After adjustment for educational attainment, and age, begative correlations were found between plasma adipsin levels and MoCA, Mini Mental State Exam, and Verbal Fluency Test scores(r = - 0.640, p < 0.001; r = - 0.612, p < 0.001; r = - 0.288, p = 0.035; respectively). Correlation analysis demonstrated that adipsin levels were significantly positively correlated with fasting C-peptide; homeostasis model of assessment for insulin resistance (HOMA-IR) (r = 0.368, p < 0.001; r = 0.494, p < 0.001; respectively). Multivariable regression analysis further indicated that high plasma adipsin level was a significant independent determinant of MCI in the Chinese population withT2DM (p = 0.017).

CONCLUSIONS

Elevated plasma adipsin level was associated with MCI in Chinese T2DM patients. Further large-scale studies should be designed to determine whether adipsin is linked to IR-associated susceptibility to early cognitive decline in T2DM patients.

High Dose of Dietary Nicotinamide Riboside Induces Glucose Intolerance and White Adipose Tissue Dysfunction in Mice Fed a Mildly Obesogenic Diet

Nicotinamide riboside (NR) is a nicotinamide adenine dinucleotide (NAD⁺) precursor vitamin. The scarce reports on the adverse effects on metabolic health of supplementation with high-dose NR warrant substantiation. Here, we aimed to examine the physiological responses to high-dose NR supplementation in the context of a mildly obesogenic diet and to substantiate this with molecular data. An 18-week dietary intervention was conducted in male C57BL/6JRccHsd mice, in which a diet with 9000 mg NR per kg diet (high NR) was compared to a diet with NR at the recommended vitamin B3 level (control NR). Both diets were mildly obesogenic (40 en% fat). Metabolic flexibility and glucose tolerance were analyzed and immunoblotting, qRT-PCR and histology of epididymal white adipose tissue (eWAT) were performed. Mice fed with high NR showed a reduced metabolic flexibility, a lower glucose clearance rate and aggravated systemic insulin resistance. This was consistent with molecular and morphological changes in eWAT, including sirtuin 1 (SIRT1)-mediated PPARγ (proliferator-activated receptor γ) repression, downregulated AKT/glucose transporter type 4 (GLUT4) signaling, an increased number of crown-like structures and macrophages, and an upregulation of pro-inflammatory gene markers. In conclusion, high-dose NR induces the onset of WAT dysfunction, which may in part explain the deterioration of metabolic health.

Role of Complement and Complement-Related Adipokines in Regulation of Energy Metabolism and Fat Storage

Adipose tissue releases many cytokines and inflammatory factors described as adipokines. In obesity, adipokines released from expanding adipose tissue are implicated in disease progression and metabolic dysfunction. However, mechanisms controlling the progression of adiposity and metabolic complications are not fully understood. It has been suggested that expanding fat mass and sustained release of inflammatory adipokines in adipose tissue lead to hypoxia, oxidative stress, apoptosis, and cellular damage. These changes trigger an immune response involving infiltration of adipose tissue with immune cells, complement activation and generation of factors involved in opsonization and clearance of damaged cells. Abundant evidence now indicates that adipose tissue is an active secretory source of complement and complement-related adipokines that, in addition to their inflammatory role, contribute to the regulation of metabolic function. This article highlights advances in knowledge regarding the role of these adipokines in energy regulation of adipose tissue through modulating lipogenic and lipolytic pathways. Several adipokines will be discussed including adipsin, Factor H, properdin, C3a, Acylation-Stimulating Protein, C1q/TNF-related proteins, and response gene to complement-32 (RGC-32). Interactions between these factors will be described considering their immune-metabolic roles in the adipose tissue microenvironment and their potential contribution to progression of adiposity and metabolic dysfunction. The differential expression and the role of complement factors in gender-related fat partitioning will also be addressed. Identifying lipogenic adipokines and their specific autocrine/paracrine roles may provide means for adipose-tissue-targeted therapeutic interventions that may disrupt the vicious circle of adiposity and disease progression. © 2019 American Physiological Society. Compr Physiol 9:1411-1429, 2019.

Association of salivary C-reactive protein with the obesity measures and markers in children

OBJECTIVE

Overweight and obesity is a pro-inflammatory state. This study aimed to examine the level of the salivary obesity markers in normal weight (NW) and overweight/obese (OW/OB) children, association with the obesity measures and the interrelations between the biomarkers.

SUBJECTS AND METHODS

Seventy-six children (40 normal weight and 36 overweight/obese) were recruited for this study. Body weight, height, and waist circumference measurement were obtained. The saliva sample was collected from all the participants. According to the Center for Disease Control and Prevention (CDC), the participants were classified into the normal weight or overweight/obese depending upon the body mass index (BMI) percentile ranking. The obesity panel of salivary markers resistin, C-C Motif Chemokine Ligand 2 (CCL2)/monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP), complement factor D, and interleukin-10 (IL-10) were determined using human magnetic Luminex performance assay. The receiver operating characteristics (ROC) analysis was used to determine the area under the curve (AUC) to identify the best salivary biomarker in children. Linear regression and Pearson's correlation analyses to determine the association between the parameters.

RESULTS

The obesity biomarkers resistin, MCP-1, TNF-α, IL-6 and CRP were significantly high in overweight/obese compared to normal weight. Salivary CRP (AUC: 0.866, 95% CI: 0.780-0.952; p<0.0001) showed superiority area under ROC curves with good discriminatory power than resistin, MCP-1, TNF-α, and IL-6. BMI z-score, WC z-score, and WHtR z-score showed a significant association (p<0.0001) with CRP. The CRP significantly (p<0.0001) correlated with resistin, CCL2/MCP-1, TNF-α, IL-6, and IL-10 by linear regression and Pearson's correlation analysis.

CONCLUSION

Increased level of salivary CRP in children may be considered as a non-invasive marker for childhood obesity for detection of the risk factors for the development of metabolic dysregulation.

An overview of lipodystrophy and the role of the complement system

The complement system is a major component of innate immunity playing essential roles in the destruction of pathogens, the clearance of apoptotic cells and immune complexes, the enhancement of phagocytosis, inflammation, and the modulation of adaptive immune responses. During the last decades, numerous studies have shown that the complement system has key functions in the biology of certain tissues. For example, complement contributes to normal brain and embryonic development and to the homeostasis of lipid metabolism. However, the complement system is subjected to the effective balance between activation-inactivation to maintain complement homeostasis and to prevent self-injury to cells or tissues. When this control is disrupted, serious pathologies eventually develop, such as C3 glomerulopathy, autoimmune conditions and infections. Another heterogeneous group of ultra-rare diseases in which complement abnormalities have been described are the lipodystrophy syndromes. These diseases are characterized by the loss of adipose tissue throughout the entire body or partially. Complement over-activation has been reported in most of the patients with acquired partial lipodystrophy (also called Barraquer-Simons Syndrome) and in some cases of the generalized variety of the disease (Lawrence Syndrome). Even so, the mechanism through which the complement system induces adipose tissue abnormalities remains unclear. This review focuses on describing the link between the complement system and certain forms of lipodystrophy. In addition, we present an overview regarding the clinical presentation, differential diagnosis, classification, and management of patients with lipodystrophy associated with complement abnormalities.

Molecular characterization, expression and antimicrobial activity of complement factor D in Megalobrama amblycephala

Complement factor D (Df) is a serine protease, which can activate the alternative pathway by cleaving complement factor B, and involves in the innate defense against pathogens infection in teleost. In this study, we cloned, characterized the Df gene from blunt snout bream (Megalobrama amblycephala) (Mamdf), and examined its expression pattern and antimicrobial activity. The open reading frame (ORF) of Mamdf was 753 bp, encoding 250 amino acids with a molecular mass of 27.2 kDa. Mamdf consisted of a single serine protease trypsin superfamily domain, 3 substrate binding sites and 3 active sites, but no potential N-glycosylation site. Pairwise alignment showed that Mamdf shared the highest identity (94%) with grass carp (Ctenopharyngodon idellus). Phylogenetic analysis indicated that Mamdf and other vertebrate Df had a common ancestral origin. Mamdf structured with 4 introns and 5 exons. The Mamdf mRNA expressed relatively high at the intestine appearance stage during early development and constitutively expressed in various tissues with the highest expression in the kidney in healthy adults. After challenged with Aeromonas hydrophila, significant changes of Mamdf at both mRNA and protein levels in the kidney, spleen, liver and head-kidney were observed. The recombinant Mamdf protein showed antimicrobial activity against both gram-positive bacteria and gram-negative bacteria. The above results suggested the immune function of Mamdf, and would benefit further detailed Df function research in the immune process in teleost.

Fibro-Adipogenic Remodeling of the Diaphragm in Obesity-Associated Respiratory Dysfunction

Respiratory dysfunction is a common complication of obesity, conferring cardiovascular morbidity and increased mortality and often necessitating mechanical ventilatory support. While impaired lung expansion in the setting of increased adipose mass and reduced central response to hypercapnia have been implicated as pathophysiological drivers, the impact of obesity on respiratory muscles-in particular, the diaphragm-has not been investigated in detail. Here, we demonstrate that chronic high-fat diet (HFD) feeding impairs diaphragm muscle function, as assessed in vivo by ultrasonography and ex vivo by measurement of contractile force. During an HFD time course, progressive adipose tissue expansion and collagen deposition within the diaphragm parallel contractile deficits. Moreover, intradiaphragmatic fibro-adipogenic progenitors (FAPs) proliferate with long-term HFD feeding while giving rise to adipocytes and type I collagen-depositing fibroblasts. Thrombospondin 1 (THBS1), a circulating adipokine, increases with obesity and induces FAP proliferation. These findings suggest a novel role for FAP-mediated fibro-adipogenic diaphragm remodeling in obesity-associated respiratory dysfunction.

Association Between Serum Adipsin Levels and Insulin Resistance in Subjects With Various Degrees of Glucose Intolerance

Context

The association between adipsin and glucose metabolism in human subjects remains unclear.

Objective

We investigated the associations between adipsin and insulin resistance/β-cell function in subjects with various degrees of glucose intolerance.

Design

Fasting blood samples were collected for measurements of fasting plasma glucose (FPG), insulin, and adipsin. An oral glucose tolerance test was conducted in subjects with no history of diabetes.

Setting

This study was conducted at a medical center.

Patients

We enrolled 240 subjects with no history of diabetes and 80 patients with known type 2 diabetes (T2D) on diet control or metformin monotherapy.

Main Outcome Measure

β-cell function and insulin resistance were assessed using the homeostasis model assessment (HOMA-β and HOMA-IR, respectively).

Results

Levels of serum adipsin were higher in subjects with normal glucose tolerance (4.0 ± 1.1 µg/mL) or prediabetes (4.0 ± 1.5 µg/mL) compared with subjects with newly diagnosed diabetes (3.8 ± 1.1 µg/mL) or with known T2D on diet control (3.4 ± 1.0 µg/mL) or metformin monotherapy (3.0 ± 1.0 µg/mL, P < 0.001). There was no significant association between adipsin and HOMA-β. In contrast, there was an independent negative association between adipsin and HOMA-IR (β coefficient −0.414, 95% CI −0.720 to −0.109, P = 0.008). The association was more prominent in subjects with a body mass index (BMI) ≥25 kg/m² or an FPG ≥100 mg/dL (P interaction < 0.001 and 0.014, respectively).

Conclusions

Serum adipsin levels were negatively associated with insulin resistance, especially in subjects with a BMI ≥25 kg/m² or an FPG ≥100 mg/dL.

Relationship between serum adipsin and the first phase of glucose-stimulated insulin secretion in individuals with different glucose tolerance

AIMS/INTRODUCTION

To detect serum adipsin levels in individuals with different glucose tolerance, and investigate the relationship between adipsisn and the first phase of insulin secretion.

MATERIALS AND METHODS

A total of 56 patients with newly diagnosed type 2 diabetes mellitus, 36 patients with impaired glucose tolerance (IGT) and 45 individuals with normal glucose tolerance were enrolled. Intravenous glucose tolerance tests were carried out to evaluate pancreatic β-cell function. The serum levels of adipsin, interleukin-1β and high-sensitivity C-reactive protein were assayed.

RESULTS

Serum adipsin levels were significantly lower in the type 2 diabetes mellitus and the IGT patients than those in the normal glucose tolerance group (P < 0.05). The acute insulin response and area under the curve showed a progressive decrease in the normal glucose tolerance and IGT groups, and decreased to the lowest levels in the type 2 diabetes mellitus group (P < 0.05). Adipsin was found to be negatively correlated with waist-to-hip ratio, free fatty acid, fasting plasma glucose, 2-h postprandial plasma glucose, glycated hemoglobin, homeostasis model assessment of insulin resistance, interleukin-1β and high-sensitivity C-reactive protein (P < 0.05 or P < 0.001), and positively correlated with homeostasis model assessment of β-cell function, high-density lipoprotein cholesterol, the area under the curve of the first phase insulin secretion and acute insulin response (P < 0.05 or P < 0.001). Stepwise multiple regression analysis showed that homeostasis model assessment for β-cell function and acute insulin response were independently related to adipsin (P < 0.05).

CONCLUSIONS

Serum adipsin levels were lower in type 2 diabetes mellitus and IGT patients, and correlated with the first phase of insulin secretion. Adipsin might be involved in the pathology of type 2 diabetes mellitus.

Type 2 diabetes - An autoinflammatory disease driven by metabolic stress

Type 2 diabetes has traditionally been viewed as a metabolic disorder characterised by chronic high glucose levels, insulin resistance, and declining insulin secretion from the pancreas. Modern lifestyle, with abundant nutrient supply and reduced physical activity, has resulted in dramatic increases in the rates of obesity-associated disease conditions, including diabetes. The associated excess of nutrients induces a state of systemic low-grade chronic inflammation that results from production and secretion of inflammatory mediators from the expanded pool of activated adipocytes. Here, we review the mechanisms by which obesity induces adipose tissue dysregulation, detailing the roles of adipose tissue secreted factors and their action upon other cells and tissues central to glucose homeostasis and type 2 diabetes. Furthermore, given the emerging importance of adipokines, cytokines and chemokines in disease progression, we suggest that type 2 diabetes should now be viewed as an autoinflammatory disease, albeit one that is driven by metabolic dysregulation.

Contribution of Adipose-Derived Factor D/Adipsin to Complement Alternative Pathway Activation: Lessons from Lipodystrophy

Factor D (FD) is an essential component of the complement alternative pathway (AP). It is an attractive pharmaceutical target because it is an AP-specific protease circulating in blood. Most components of the complement activation pathways are produced by the liver, but FD is highly expressed by adipose tissue. Two critical questions are: 1) to what degree does adipose tissue contribute to circulating FD levels and 2) what quantity of FD is sufficient to maintain a functional AP? To address these issues, we studied a novel mouse strain with complete lipodystrophy (LD), the fld mouse with partial LD, an FD-deficient mouse, and samples from lipodystrophic patients. FD was undetectable in the serum of LD mice, which also showed minimal AP function. Reconstitution with purified FD, serum mixing experiments, and studies of partial LD mice all demonstrated that a low level of serum FD is sufficient for normal AP activity in the mouse system. This conclusion was further supported by experiments in which wild-type adipose precursors were transplanted into LD mice. Our results indicate that almost all FD in mouse serum is derived from adipose tissue. In contrast, FD levels were reduced ∼50% in the sera of patients with congenital generalized LD. Our studies further demonstrate that a relatively small amount of serum FD is sufficient to facilitate significant time-dependent AP activity in humans and in mice. Furthermore, this observation highlights the potential importance of obtaining nearly complete inhibition of FD in treating alternative complement activation in various autoimmune and inflammatory human diseases.

Distinct Shift in Beta-Cell Glutaredoxin 5 Expression Is Mediated by Hypoxia and Lipotoxicity Both In Vivo and In Vitro

Histomorphological and functional alterations in pancreatic islet composition directly correlate with hyperglycemia severity. Progressive deterioration of metabolic control in subjects suffering from type 2 diabetes is predominantly caused by impaired beta-cell functionality. The glutaredoxin system is supposed to wield protective properties for beta-cells. Therefore, we sought to identify a correlation between the structural changes observed in diabetic pancreatic islets with altered glutaredoxin 5 expression, in order to determine an underlying mechanism of beta-cell impairment. Islets of db/db mice presenting with uncontrolled diabetes were assessed in terms of morphological structure and insulin, glucagon, and glutaredoxin 5 expression. MIN6 cell function and glutaredoxin 5 expression were analyzed after exposure to oleic acid and hypoxia. Islets of diabese mice were marked by typical remodeling and distinct reduction of, and shifts, in localization of glutaredoxin 5-positive cells. These islets featured decreased glutaredoxin 5 as well as insulin and glucagon content. In beta-cell culture, glutaredoxin 5 protein and mRNA expression were decreased by hypoxia and oleic acid but not by leptin treatment. Our study demonstrates that glutaredoxin 5 expression patterns are distinctively altered in islets of rodents presenting with uncontrolled diabesity. In vitro, reduction of islet-cell glutaredoxin 5 expression was mediated by hypoxia and oleic acid. Thus, glutaredoxin 5-deficiency in islets during diabetes may be caused by lipotoxicity and hypoxia.

Longitudinal associations of the alternative and terminal pathways of complement activation with adiposity: The CODAM study

OBJECTIVE

To investigate longitudinal associations of components of the alternative (C3, C3a, Bb, factor D [FD], factor H [FH], and properdin) and the terminal complement pathway (C5a, sC5b-9) with adiposity.

METHODS

A prospective human cohort study (n=574 at baseline, n=489 after 7 years follow-up) was analyzed. Generalized estimating equations were used to evaluate the longitudinal associations between complement components (standardized values) and adiposity (main outcome BMI [kg/m²]). Multiple linear regression models were used to investigate the associations between change in complement levels and change in BMI. Analyses were adjusted for age, sex, medication and lifestyle.

RESULTS

Over the 7-year period, baseline C3 was positively associated with BMI (β=1.72 [95% confidence interval (CI): 1.35; 2.09]). Positive associations were also observed for C3a (β=0.64 [0.31; 0.97]), FD (β=1.00 [0.59; 1.42]), FH (β=1.17 [0.82; 1.53]), and properdin (β=0.60 [0.28; 0.92]), but not for Bb, C5a or sC5b-9. Moreover, changes in C3 (β=0.52 [0.34; 0.71]) and FH (β=0.51 [0.32; 0.70]) were significantly associated with changes in BMI.

CONCLUSIONS

The complement system, particularly activation of the alternative pathway, may be involved in development of adiposity. Whether individual aspects of alternative pathway activation have a causal role in human obesity, remains to be investigated.

The complement system is dysfunctional in metabolic disease: Evidences in plasma and adipose tissue from obese and insulin resistant subjects

The relationship among chronic low-grade inflammation, insulin resistance and other obesity-associated metabolic disturbances is increasingly recognized. The possible mechanisms that trigger these immunologic alterations remain to be fully understood. The complement system is a crucial element of immune defense system, being important in the activation of innate and adaptative immune response, promoting the clearance of apoptotic and damaged endogenous cells and participating in processes of tissue development, degeneration, and regeneration. Circulating components of the complement system appear to be dysregulated in obesity-associated metabolic disturbances. The activation of the complement system is also evident in adipose tissue from obese subjects, in association with subclinical inflammation and alterations in glucose metabolism. The possible contribution of some components of the complement system in the development of insulin resistance and obesity-associated metabolic disturbances, and the possible role of complement system in adipose tissue physiology is reviewed here. The modulation of the complement system could constitute a potential target in the pathophysiology and therapy of obesity and associated metabolic disease.