Decorin is a secreted protein associated with obesity and type 2 diabetes

Obesity-associated inflammatory macrophage polarization is inhibited by capsaicin and phytolignans

Obesity is often accompanied by increased adipose tissue inflammation, a process that is partially driven by adipose tissue-resident macrophages. In this study, we explored the potential for plant-derived dietary compounds to exert anti-inflammatory effects in macrophages that alleviate obesity-associated adipocyte dysfunction. Capsaicin (CAP), schisandrin A (SA), enterodiol (END), and enterolactone (ENL) treatment polarized J774 macrophages to an "M2" or anti-inflammatory phenotype and inhibited responses to stimulation with lipopolysaccharide (LPS). Furthermore, these compounds blocked inflammasome activation when administered just before ATP-induced NLRP3 activation, as evidenced by the abrogation of IL-1β release in mouse macrophages and human peripheral blood monocytes. The addition of CAP, SA, or ENL during the differentiation of bone marrow-derived macrophages was also sufficient to inhibit LPS-induced IL-6 and TNFα production. Finally, CAP, END, and ENL treatment during differentiation of 3T3-L1 adipocytes induced an adiponectin-high phenotype accompanied by increases in thermogenic gene expression, and conditioned media from these adipocytes inhibited LPS-induced production of IL-1β, IL-6, and TNFα from J774 macrophages. These polarizing effects were partially mediated by the elevated adiponectin and decreased syndecan-4 in the adipocyte-conditioned media. These results implicate the contribution of plant-derived dietary components to the modulation of macrophages and adipocytes in obesity.NEW & NOTEWORTHY The utility of food-based products to prevent or alleviate chronic conditions such as obesity and its associated comorbidities is an attractive approach. Capsaicin, schisandrin A, enterodiol, and enterolactone, phytochemicals present in traditional medicinal food, decreased proinflammatory cytokine production from macrophages that, in turn, reduced obesity-associated adipocyte dysfunction. These results implicate the contribution of plant-derived dietary components to the modulation of macrophages and adipocytes in obesity.

The Role of Adipokines and Myokines in the Pathogenesis of Different Obesity Phenotypes-New Perspectives

Obesity is a characteristic disease of the twenty-first century that is affecting an increasing percentage of society. Obesity expresses itself in different phenotypes: normal-weight obesity (NWO), metabolically obese normal-weight (MONW), metabolically healthy obesity (MHO), and metabolically unhealthy obesity (MUO). A range of pathophysiological mechanisms underlie the occurrence of obesity, including inflammation, oxidative stress, adipokine secretion, and other processes related to the pathophysiology of adipose tissue (AT). Body mass index (BMI) is the key indicator in the diagnosis of obesity; however, in the case of the NWO and MONW phenotypes, the metabolic disturbances are present despite BMI being within the normal range. On the other hand, MHO subjects with elevated BMI values do not present metabolic abnormalities. The MUO phenotype involves both a high BMI value and an abnormal metabolic profile. In this regard, attention has been focused on the variety of molecules produced by AT and their role in the development of obesity. Nesfatin-1, neuregulin 4, myonectin, irisin, and brain-derived neurotrophic factor (BDNF) all seem to have protective effects against obesity. The primary mechanism underlying the action of nesfatin-1 involves an increase in insulin sensitivity and reduced food intake. Neuregulin 4 sup-presses lipogenesis, decreases lipid accumulation, and reduces chronic low-grade inflammation. Myonectin lowers the amount of fatty acids in the bloodstream by increasing their absorption in the liver and AT. Irisin stimulates the browning of white adipose tissue (WAT) and consequently in-creases energy expenditure, additionally regulating glucose metabolism. Another molecule, BDNF, has anorexigenic effects. Decorin protects against the development of hyperglycemia, but may also contribute to proinflammatory processes. Similar effects are shown in the case of visfatin and chemerin, which may predispose to obesity. Visfatin increases adipogenesis, causes cholesterol accumulation in macrophages, and contributes to the development of glucose intolerance. Chemerin induces angiogenesis, which promotes the expansion of AT. This review aims to discuss the role of adipokines and myokines in the pathogenesis of the different obesity phenotypes.

Matricellular Proteins in the Homeostasis, Regeneration, and Aging of Skin

Matricellular proteins are secreted extracellular proteins that bear no primary structural functions but play crucial roles in tissue remodeling during development, homeostasis, and aging. Despite their low expression after birth, matricellular proteins within skin compartments support the structural function of many extracellular matrix proteins, such as collagens. In this review, we summarize the function of matricellular proteins in skin stem cell niches that influence stem cells' fate and self-renewal ability. In the epidermal stem cell niche, fibulin 7 promotes epidermal stem cells' heterogeneity and fitness into old age, and the transforming growth factor-β-induced protein ig-h3 (TGFBI)-enhances epidermal stem cell growth and wound healing. In the hair follicle stem cell niche, matricellular proteins such as periostin, tenascin C, SPARC, fibulin 1, CCN2, and R-Spondin 2 and 3 modulate stem cell activity during the hair cycle and may stabilize arrector pili muscle attachment to the hair follicle during piloerections (goosebumps). In skin wound healing, matricellular proteins are upregulated, and their functions have been examined in various gain-and-loss-of-function studies. However, much remains unknown concerning whether these proteins modulate skin stem cell behavior, plasticity, or cell-cell communications during wound healing and aging, leaving a new avenue for future studies.

[Adipomyokines in children with obesity]

BACKGROUND

Adipomyokines are synthesized and secreted into the bloodstream by cells of both muscle and adipose tissue. They can have both a negative metabolic effect, acting as pro-inflammatory adipokines in obesity, and a positive one, increasing in response to physical exertion in the form of myokines.

AIM

To study the features of adipocytokine secretion in children with constitutionally exogenous obesity.

MATERIALS AND METHODS

The study included 80 patients: 60 adolescents aged 15 [13; 16] years with constitutionally exogenous obesity SDS BMI: 3.0 [2.6; 3.3] and 20 control group children aged 16 [15; 17] years without excess weight SDS BMI: -0.3 [-1.25; 0.33]. Commercial enzyme immunoassay kits were used to determine the level of adipomyokines. The compositional composition of the body was evaluated by bioimpedance analysis (InBody 770 analyzer, South Korea) in the morning, on an empty stomach. Statistical processing was carried out using STATISTICA v.12.0 (StatSoft Inc., USA). The results are presented in the form of median (Me) and quartiles (Q1; Q3) corresponding to 25 and 75 percentiles. The critical significance level (p) was assumed to be <0.05.

RESULTS

Levels of IL-6 and irisin are statistically significantly higher in obese adolescents compared to the control group: 0.55 [0.226; 1.35] pg/ml vs 0.202 [0.128; 0.652] pg/ml (p=0.041) and 11.16 [6.6; 22.76] mcg/ml vs 7.36 [6.48; 9.68] mcg/ml (p=0.043), respectively. Concentrations of IL-6, myostatin and decorin increase with an increase in the degree of obesity: grade I vs III: 0.226 [0.224; 0.398] vs 0.80 [0.36; 1.81] pg/ml (p=0,0197), 25,85 [21,53; 28,23] vs 31.41 [24.36; 35.06] ng/ml (p=0.03), 4065.3 [3244.9; 5245.5] vs 5322.5 [4199.8; 7702.4] pg/ml (p=0.0376), respectively. In obese children, IL-6 levels positively correlate with BMI, SDS BMI and the amount of adipose tissue, and myostatin - with BMI and SDS BMI. The concentration of irisin in the blood serum is significantly higher in obese girls than in obese boys and healthy girls. Obese patients, compared with lean peers, are characterized by a statistically significantly higher content of both fat and lean mass. With the progression of obesity, there is a statistically significant increase in the ratio of fat to lean mass (I degree - 0.66 [0.56; 0.7], III - 0.78 [0.68; 0.98] (p=0.0073).

CONCLUSION

Patients with obesity and normal body weight have different levels of adipomyokines. An increase in the level of IL-6 with the progression of obesity is directly related to an increase in the content of adipose tissue. Further study of the features of adipocytokine secretion, their relationship with the features of the body composition and metabolic complications in obesity is required.

Breast cancer microenvironment and obesity: challenges for therapy

Women with obesity who develop breast cancer have a worsened prognosis with diminished survival rates and increased rates of metastasis. Obesity is also associated with decreased breast cancer response to endocrine and chemotherapeutic treatments. Studies utilizing multiple in vivo models of obesity as well as human breast tumors have enhanced our understanding of how obesity alters the breast tumor microenvironment. Changes in the complement and function of adipocytes, adipose-derived stromal cells, immune cells, and endothelial cells and remodeling of the extracellular matrix all contribute to the rapid growth of breast tumors in the context of obesity. Interactions of these cells enhance secretion of cytokines and adipokines as well as local levels of estrogen within the breast tumor microenvironment that promote resistance to multiple therapies. In this review, we will discuss our current understanding of the impact of obesity on the breast tumor microenvironment, how obesity-induced changes in cellular interactions promote resistance to breast cancer treatments, and areas for development of treatment interventions for breast cancer patients with obesity.

Intensity Dependent Effects of Interval Resistance Training on Myokines and Cardiovascular Risk Factors in Males With Obesity

OBJECTIVE

To determine the effects of different intensities of interval resistance training (IRT) protocols on the levels of select myokines (decorin, follistatin, myostatin, activin A, transforming growth factor beta-1 [TGF-β1]), and cardiometabolic and anthropometric measures in males with obesity.

METHODS

Forty-four obese males (age: 27.5 ± 9.4 yr.; height: 165.4 ± 2.8 cm; weight: 97.9 ± 2.6 kg and BMI: 35.7 ± 4.3 kg/m²) were randomly assigned to one of four groups (n=11 per group): low-intensity interval resistance training (LIIRT), moderate-intensity interval resistance training (MIIRT), high-intensity interval resistance training (HIIRT) or control (C). The LIIRT group performed 10 exercises in 3 sets of 40% (20 repetitions), the MIIRT group performed 10 exercises in three sets of 60% (13 repetitions), and the HIIRT group performed 10 exercises in three sets of 80% (10 repetitions) of one maximum repetition (1RM), which were followed with active rest of 20% of 1RM and 15 repetitions. The resistance training groups exercised ~70 min per session, 3 days per week, for 12 weeks. Measurements were taken at baseline and after 12 weeks of exercise training.

RESULTS

Baseline levels of myokines, cardiovascular risk factors, anthropometry, body composition, and cardio-respiratory fitness were not different between the four groups (p>0.05). The group x time interactions for decorin, activin A, follistatin, myostatin, and TGF-β1, total cholesterol (TC), triglyceride (TG), high-density cholesterol (HDL), low-density cholesterol (LDL), anthropometry, body composition, and cardio-respiratory fitness were statistically significant (p<0.05). There were increases in post-test values for decorin, follistatin, HDL (p<0.05) and decreases in TC, TG, TGF-β1, LDL, and myostatin levels in the LIIRT, MIIRT, and HIIRT groups compared to pretest values (p<0.05). Changes in fat mass, VO_2peak, HDL, TG, glucose, activin A, decorin were not significant in LIIRT compared to the control group, while changes in activin A, follistatin, and TFG-β1 levels were greater in HIIRT and MIIRT groups compared to the LIIRT group (p<0.05).

CONCLUSION

The LIIRT, MIIRT, and HIIRT protocols all produced beneficial changes in decorin, activin A, follistatin, myostatin, and TGF-β1 levels, and cardiometabolic risk factors, with greater effects from the MIIRT and HIIRT protocols compared to LIIRT.

Decorin Concentrations in Aqueous Humor of Patients with Diabetic Retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes in the retina. Chronic hyperglycemia damages retinal microvasculature embedded into the extracellular matrix (ECM), causing fluid leakage and ischemic retinal neovascularization. Current treatment strategies include intravitreal anti-vascular endothelial growth factor (VEGF) or steroidal injections, laser photocoagulation, or vitrectomy in severe cases. However, treatment may require multiple modalities or repeat treatments due to variable response. Though DR management has achieved great success, improved, long-lasting, and predictable treatments are needed, including new biomarkers and therapeutic approaches. Small-leucine rich proteoglycans, such as decorin, constitute an integral component of retinal endothelial ECM. Therefore, any damage to microvasculature can trigger its antifibrotic and antiangiogenic response against retinal vascular pathologies, including DR. We conducted a cross-sectional study to examine the association between aqueous humor (AH) decorin levels, if any, and severity of DR. A total of 82 subjects (26 control, 56 DR) were recruited. AH was collected and decorin concentrations were measured using an enzyme-linked immunosorbent assay (ELISA). Decorin was significantly increased in the AH of DR subjects compared to controls (p = 0.0034). AH decorin levels were increased in severe DR groups in ETDRS and Gloucestershire classifications. Decorin concentrations also displayed a significant association with visual acuity (LogMAR) measurements. In conclusion, aqueous humor decorin concentrations were found elevated in DR subjects, possibly due to a compensatory response to the retinal microvascular changes during hyperglycemia.

Mammary collagen is under reproductive control with implications for breast cancer

Mammographically-detected breast density impacts breast cancer risk and progression, and fibrillar collagen is a key component of breast density. However, physiologic factors influencing collagen production in the breast are poorly understood. In female rats, we analyzed gene expression of the most abundantly expressed mammary collagens and collagen-associated proteins across a pregnancy, lactation, and weaning cycle. We identified a triphasic pattern of collagen gene regulation and evidence for reproductive state-dependent composition. An initial phase of collagen deposition occurred during pregnancy, followed by an active phase of collagen suppression during lactation. The third phase of collagen regulation occurred during weaning-induced mammary gland involution, which was characterized by increased collagen deposition. Concomitant changes in collagen protein abundance were confirmed by Masson's trichrome staining, second harmonic generation (SHG) imaging, and mass spectrometry. We observed similar reproductive-state dependent collagen patterns in human breast tissue obtained from premenopausal women. SHG analysis also revealed structural variation in collagen across a reproductive cycle, with higher packing density and more collagen fibers arranged perpendicular to the mammary epithelium in the involuting rat mammary gland compared to nulliparous and lactating glands. Involution was also characterized by high expression of the collagen cross-linking enzyme lysyl oxidase, which was associated with increased levels of cross-linked collagen. Breast cancer relevance is suggested, as we found that breast cancer diagnosed in recently postpartum women displayed gene expression signatures of increased collagen deposition and crosslinking compared to breast cancers diagnosed in age-matched nulliparous women. Using publically available data sets, we found this involution-like, collagen gene signature correlated with poor progression-free survival in breast cancer patients overall and in younger women. In sum, these findings of physiologic collagen regulation in the normal mammary gland may provide insight into normal breast function, the etiology of breast density, and inform breast cancer risk and outcomes.

Decorin Suppresses Invasion and EMT Phenotype of Glioma by Inducing Autophagy via c-Met/Akt/mTOR Axis

Decorin exhibits inhibitory effects in tumorigenesis in various types of cancers. The clinical characteristics of 42 patients with GBM were reviewed and analyzed. Lentiviral constructs for decorin overexpression and shRNA-mediated silencing were established for U87MG cells and T98G cells, respectively. The expressions of EMT- and autophagy-associated markers were detected in GBM cell lines. The migration and invasion of the glioma cells were assayed to reflect the malignant behavior of GBM. A mouse xenograft model was used to verify the effect of decorin on autophagy in vivo. Reduced expression of decorin in glioma tissues was associated with a poor survival of the patients. Decorin overexpression suppressed cell migration, invasion and attenuated EMT phenotype in glioma cell lines. Further study indicated that decorin inhibited EMT phenotype through the induction of autophagy. The mechanisms include inhibiting the activation of c-Met/Akt/mTOR signaling and regulating the expressions of mesenchymal markers including Slug, vimentin and Twist, and epithelial marker E-cadherin. In addition, decorin overexpression in a mice model can also suppress the GBM invasion and EMT phenotype. In conclusion, decorin suppresses invasion and EMT phenotype of glioma by inducing autophagy via c-Met/Akt/mTOR axis.

Novel roles of Tsukushi in signaling pathways and multiple disease processes

Tsukushi (TSK), a newly identified hepatokine, is a member of the small leucine-rich proteoglycans (SLRPs) family. TSK was originally isolated and identified in the lens of the chicken. Preliminary research on TSK has focused on its role in various physiological processes such as growth and development, wound healing, and cartilage formation. In recent years, the role of TSK in regulating cell signaling pathways, cell proliferation, and differentiation has been studied. In addition, the research has gradually expanded to the fields of glycolipid metabolism and energy balance. This article briefly reviews the role of TSK in the physiological and pathological process.

A Panel of 6 Biomarkers Significantly Improves the Prediction of Type 2 Diabetes in the MONICA/KORA Study Population

CONTEXT

Improved strategies to identify persons at high risk of type 2 diabetes are important to target costly preventive efforts to those who will benefit most.

OBJECTIVE

This work aimed to assess whether novel biomarkers improve the prediction of type 2 diabetes beyond noninvasive standard clinical risk factors alone or in combination with glycated hemoglobin A1c (HbA1c).

METHODS

We used a population-based case-cohort study for discovery (689 incident cases and 1850 noncases) and an independent cohort study (262 incident cases, 2549 noncases) for validation. An L1-penalized (lasso) Cox model was used to select the most predictive set among 47 serum biomarkers from multiple etiological pathways. All variables available from the noninvasive German Diabetes Risk Score (GDRSadapted) were forced into the models. The C index and the category-free net reclassification index (cfNRI) were used to evaluate the predictive performance of the selected biomarkers beyond the GDRSadapted model (plus HbA1c).

RESULTS

Interleukin-1 receptor antagonist, insulin-like growth factor binding protein 2, soluble E-selectin, decorin, adiponectin, and high-density lipoprotein cholesterol were selected as the most relevant biomarkers. The simultaneous addition of these 6 biomarkers significantly improved the predictive performance both in the discovery (C index [95% CI], 0.053 [0.039-0.066]; cfNRI [95% CI], 67.4% [57.3%-79.5%]) and the validation study (0.034 [0.019-0.053]; 48.4% [35.6%-60.8%]). Significant improvements by these biomarkers were also seen on top of the GDRSadapted model plus HbA1c in both studies.

CONCLUSION

The addition of 6 biomarkers significantly improved the prediction of type 2 diabetes when added to a noninvasive clinical model or to a clinical model plus HbA1c.

A novel ocular function for decorin in the aqueous humor outflow

Primary open-angle glaucoma, a neurodegenerative disorder characterized by degeneration of optic nerve axons, is a frequent cause of vision loss and blindness worldwide. Several randomized multicenter studies have identified intraocular pressure as the major risk factor for its development, caused by an increased outflow resistance to the aqueous humor within the trabecular meshwork. However, the molecular mechanism for increased outflow resistance in POAG has not been fully established. One of the proposed players is the pro-fibrotic transforming growth factor (TGF)-β2, which is found in higher amounts in the aqueous humor of patients with POAG. In this study we elucidated the role of decorin, a small leucine-rich proteoglycan and known antagonist of TGF-β, in the region of aqueous humor outflow tissue. Utilizing decorin deficient mice, we discovered that decorin modulated TGF-β signaling in the canonical outflow pathways and the lack of decorin in vivo caused an increase in intraocular pressure. Additionally, the Dcn^-/- mice showed significant loss of optic nerve axons and morphological changes in the glial lamina, typical features of glaucoma. Moreover, using human trabecular meshwork cells we discovered that soluble decorin attenuated TGF-β2 mediated synthesis and expression of typical downstream target genes including CCN2/CTGF, FN and COL IV.  Finally, we found a negative reciprocal regulation of decorin and TGF-β, with a dramatic downregulation of decorin in the canonical outflow pathways of patients with primary open-angle glaucoma. Collectively, our results indicate that decorin plays an important role in the pathogenesis of primary open-angle glaucoma and offers novel perspectives in the treatment of this serious disease.

Glycosaminoglycan Modification of Decorin Depends on MMP14 Activity and Regulates Collagen Assembly

Proper processing of collagens COL1 and COL6 is required for normal function of adipose tissue and skeletal muscle. Proteoglycan decorin (DCN) regulates collagen fiber formation. The amino-terminus of DCN is modified with an O-linked glycosaminoglycan (GAG), the function of which has remained unclear. Previously, non-glycanated DCN (ngDCN) was identified as a marker of adipose stromal cells. Here, we identify MMP14 as the metalloprotease that cleaves DCN to generate ngDCN. We demonstrate that mice ubiquitously lacking DCN GAG (ngDCN mice) have reduced matrix rigidity, enlarged adipocytes, fragile skin, as well as skeletal muscle hypotrophy, fibrosis, and dysfunction. Our results indicate that DCN deglycanation results in reduced intracellular DCN—collagen binding and increased production of truncated COL6 chains, leading to aberrant procollagen processing and extracellular localization. This study reveals that the GAG of DCN functions to regulate collagen assembly in adipose tissue and skeletal muscle and uncovers a new mechanism of matrix dysfunction in obesity and aging.

Sarcopenic obesity: Myokines as potential diagnostic biomarkers and therapeutic targets?

Sarcopenic obesity (SO) is a condition characterized by the occurrence of both sarcopenia and obesity and imposes a heavy burden on the health of the elderly. Controversies and challenges regarding the definition, diagnosis and treatment of SO still remain because of its complex pathogenesis and limitations. Over the past few decades, numerous studies have revealed that myokines secreted from skeletal muscle play significant roles in the regulation of muscle mass and function as well as metabolic homeostasis. Abnormalities in myokines may trigger and promote the pathogenesis underlying age-related and metabolic diseases, including obesity, sarcopenia, type 2 diabetes (T2D), and SO. This review mainly focuses on the role of myokines as potential biomarkers for the early diagnosis and therapeutic targets in SO.

Proteoglycans in Obesity-Associated Metabolic Dysfunction and Meta-Inflammation

Proteoglycans are a specific subset of glycoproteins found at the cell surface and in the extracellular matrix, where they interact with a plethora of proteins involved in metabolic homeostasis and meta-inflammation. Over the last decade, new insights have emerged on the mechanism and biological significance of these interactions in the context of diet-induced disorders such as obesity and type-2 diabetes. Complications of energy metabolism drive most diet-induced metabolic disorders, which results in low-grade chronic inflammation, thereby affecting proper function of many vital organs involved in energy homeostasis, such as the brain, liver, kidney, heart and adipose tissue. Here, we discuss how heparan, chondroitin and keratan sulfate proteoglycans modulate obesity-induced metabolic dysfunction and low-grade inflammation that impact the initiation and progression of obesity-associated morbidities.

Obesity reduces mammary epithelial cell TGFβ1 activity through macrophage-mediated extracellular matrix remodeling

Obesity is a risk factor for breast cancer in postmenopausal and high‐risk premenopausal women. Changes within the obese breast microenvironment may increase breast cancer risk. Transforming growth factor beta‐1 (TGFβ1) is a major regulator of mammary epithelial stem/progenitor cells, and its activity is dysregulated under conditions of obesity. Using a high‐fat diet model of obesity in mice and breast tissue from women, we observed that TGFβ1 activity is reduced in breast epithelial cells in obesity. Breast ducts and lobules demonstrated increased decorin in the extracellular matrix (ECM) surrounding epithelial cells, and we observed that decorin and latent TGFβ1 complexed together. Under conditions of obesity, macrophages expressed higher levels of decorin and were significantly increased in number surrounding breast epithelial cells. To investigate the relationship between macrophages and decorin expression, we treated obese mice with either IgG control or anti‐F4/80 antibodies to deplete macrophages. Mice treated with anti‐F4/80 antibodies demonstrated reduced decorin surrounding mammary ducts and enhanced TGFβ1 activity within mammary epithelial cells. Given the role of TGFβ1 as a tumor suppressor, reduced epithelial TGFβ1 activity and enhanced TGFβ1 within the ECM of obese mammary tissue may enhance breast cancer risk.

The role of extracellular matrix in the pathophysiology of diabetic wounds

Impaired healing leading to the formation of ulcerated wounds is a critical concern in patients with diabetes. Abnormalities in extracellular matrix (ECM) production and remodeling contribute to tissue dysfunction and delayed healing. Specifically, diabetes-induced changes in the expression and/or activity of structural proteins, ECM-modifying enzymes, proteoglycans, and matricellular proteins have been reported. In this review, we provide a summary of the key ECM molecules and associated changes in skin and diabetic wounds. Such information should allow for new insights in the understanding of impaired wound healing and lead to the development of ECM-based therapeutic strategies.

Functional and Structural Adaptations of Skeletal Muscle in Long-Term Juvenile Dermatomyositis: A Controlled Cross-Sectional Study

OBJECTIVE

To compare muscle strength and endurance of the knee extensors between patients with long-term juvenile dermatomyositis (DM) and controls and between patients with active disease and those with inactive disease, and to explore associations between strength/endurance and 1) clinical parameters, 2) physical activity, and 3) humoral/structural adaptation in the skeletal muscle of patients.

METHODS

In a cross-sectional study (44 patients and 44 age- and sex-matched controls), we tested isometric muscle strength (peak torque, in Nm) and dynamic muscle endurance (total work, in Joules) of the knee extensors, physical activity (measured by accelerometer), and serum myokine levels (by enzyme-linked immunosorbent assay). Patients were examined with validated tools (clinical muscle tests and measures of disease activity/damage and inactive disease) and using magnetic resonance imaging of the thigh muscles, which included evaluation of the quadriceps cross-sectional area (CSA). Needle biopsy samples of the vastus lateralis muscle (obtained from 12 patients ages ≥18 years) were assessed by histochemistry.

RESULTS

After a mean ± SD disease duration of 21.8 ± 11.8 years, peak torque was lower in patients with juvenile DM compared to controls (mean difference 29 Nm, 95% confidence interval 13-46; P = 0.001). Similarly, total work of the knee extensors was lower in patients compared to controls (median 738J [interquartile range 565-1,155] versus 1,249J [interquartile range 815-1,665]; P < 0.001). Both peak torque and total work were lower in patients with active juvenile DM compared to those with inactive disease (both P < 0.019); in analyses controlled for quadriceps CSA, only total work remained lower in patients with active disease. Moreover, peak torque and total work correlated with findings from clinical muscle tests in patients with active disease (r = 0.57-0.84). Muscle biopsy results indicated that the fiber type composition was different, but capillary density was similar, between patients with active disease and those with inactive disease.

CONCLUSION

In patients with long-term juvenile DM, both muscle strength and endurance of the knee extensors were lower when compared to matched controls, and also lower in patients with active disease compared to those with inactive disease. Our results indicate a need for more sensitive muscle tests in this clinical setting. We hypothesize that impaired muscle endurance in patients with active juvenile DM may be influenced by structural/functional adaptations of muscle tissue independent of muscle size.

Adipose tissue loss and lipodystrophy in xylosyltransferase II deficient mice

BACKGROUND/OBJECTIVES

The cellular and extracellular matrix (ECM) interactions that regulate adipose tissue homeostasis are incompletely understood. Proteoglycans (PGs) and their sulfated glycosaminoglycans (GAGs) provide spatial and temporal signals for ECM organization and interactions with resident cells by impacting growth factor and cytokine activity. Therefore, PGs and their GAGs could be significant to adipose tissue homeostasis. The purpose of this study was to determine the role of ECM sulfated GAGs in adipose tissue homeostasis.

METHODS

Adipose tissue and metabolic homeostasis in mice deficient in xylosyltransferase 2 (Xylt2-/-) were examined by histologic analyses, gene expression analyses, whole body fat composition measurements, and glucose tolerance test. Adipose tissue inflammation and adipocyte precursors were characterized by flow cytometry and in vitro culture of mesenchymal stem cells.

RESULTS

Xylt2-/- mice have low body weight due to overall reductions in abdominal fat deposition. Histologically, the adipocytes are reduced in size and number in both gonadal and mesenteric fat depots of Xylt2-/- mice. In addition, these mice are glucose intolerant, insulin resistant, and have increased serum triglycerides as compared to Xylt2 + / + control mice. Furthermore, the adipose tissue niche has increased inflammatory cells and enrichment of proinflammatory factors IL6 and IL1β, and these mice also have a loss of adipose tissue vascular endothelial cells. Lastly, xylosyltransferease-2 (XylT2) deficient mesenchymal stem cells from gonadal adipose tissue and bone marrow exhibit impaired adipogenic differentiation in vitro.

CONCLUSIONS

Decreased GAGs due to the loss of the key GAG assembly enzyme XylT2 causes reduced steady state adipose tissue stores leading to a unique lipodystrophic model. Accumulation of an adipocytic precursor pool of cells is discovered indicating an interruption in differentiation. Therefore, adipose tissue GAGs are important in the homeostasis of adipose tissue by mediating control of adipose precursor development, tissue inflammation, and vascular development.

Ginkgo biloba Extract Modulates the Retroperitoneal Fat Depot Proteome and Reduces Oxidative Stress in Diet-Induced Obese Rats

The rapid increase in the number of individuals with obesity, over the past four decades, is triggered by a number of complex interactions among factors. Despite the plethora of treatments available, side effects are commonly observed and, in this context, herbal medicines have been employed as an alternative form of therapy. Ginkgo biloba extract (GbE) has been described as a promising new pharmacological approach to treat obesity. In order to better comprehend the mechanisms involved with this potential effect, the present study evaluated the effects of GbE treatment on diet-induced obese rats, focusing on the proteome and the oxidative stress defense system of visceral adipose tissue. After 14 days treatment, GbE significantly modulated 25 proteins. Retroperitoneal adipose tissue of treated animals exhibited higher amounts of proteins associated with adipogenesis (decorin), carbon metabolism and mitochondrial function (citrate synthase), and a concomitant reduction in adipocyte hypertrophy. In parallel, GbE down-regulated proteins involved in oxidative stress (peroxiredoxin) and the inflammatory response (complement C3, mast cell protease 1, and Ig gamma-2B chain C region). Moreover, also related to oxidative stress defense, GbE stimulated catalase activity, reduced malondialdehyde levels (lipid peroxidation indicator), and increased lactoylglutathione lyase levels. It was concluded that GbE acts as an antioxidant agent, and improved the proteome profile and oxidative stress response in the adipose tissue of diet-induced obese rats.

The beneficial effects of 15 units of high-intensity circuit training in women is modified by age, baseline insulin resistance and physical capacity

AIM

To investigate the effect of a single and 15 units of high-intensity circuit training (HICT) programme on glucose metabolism, myokines' response and selected genes' expression in women.

METHODS

Thirty-three, non-active women (mean age: 38 ± 12) were split into a HICT (n = 20) or a control group (CON, n = 13). The training protocol included three circuits of nine exercises with own body weight as a workload performed 3 times a week for five weeks. The CON group performed HICT twice. Blood samples were taken before, 1 h and 24 h after the first and last unit to determine IGF-1, myostatin, irisin, decorin, HSP27, interleukin-15 concentrations using the ELISA immunoenzymatic method. To evaluate HSPB1, TNF-α and DCN mRNA, real-time PCR was used. Pre- and post-intervention, the oral glucose test and body composition assessment were completed.

RESULTS

The following parameters tended to decrease after the 5-week HICT program: insulin and HOMA-IR Training diminished insulin/IGF-1 ratio (51% CI: -63% to -34%) and induced the drop of myostatin concentration but significantly only among middle-aged women and at baseline insulin resistance.

CONCLUSION

Obtained data revealed that HICT improved an insulin sensitivity and diminished myostatin concentration among older, insulin-resistant women with lower baseline physical capacity.

Absence of the proteoglycan decorin reduces glucose tolerance in overfed male mice

Studies have implicated the extracellular matrix (ECM) of adipose tissue in insulin resistance. The proteoglycan decorin, a component of ECM, has been associated with glucose tolerance, but possible causal effects on metabolism remain to be explored. We here sought to determine metabolic consequences of loss of decorin in mice (DcnKO). DcnKO mice were fed a low-fat (LF) or high-fat (HF) diet for 10 weeks and body weight and food intake was recorded. An intraperitoneal glucose tolerance test was performed after eight weeks. Blood samples and adipose, liver and muscle tissues were collected at sacrifice. Global gene expression was measured in adipose tissue, and expression of decorin was also analyzed in human adipose samples. DcnKO mice showed increased feed efficiency during overfeeding and impaired glucose tolerance. Adipose leptin mRNA and circulating leptin levels were elevated in DcnKO mice, along with a downregulation of genes involved in ECM organization and triglyceride biosynthesis, and an upregulation of adipose genes involved in complement and coagulation cascades. Consistent with a protective metabolic role for decorin, in obese patients we found increased adipose decorin expression after profound fat loss, particularly in the stromal vascular fraction. Loss of decorin in mice caused impaired glucose tolerance in association with increased feed efficiency and altered gene expression in adipose tissue. Our data provide evidence that decorin is an important factor for maintaining glucose tolerance.

A Modified Random Survival Forests Algorithm for High Dimensional Predictors and Self-Reported Outcomes

We present an ensemble tree-based algorithm for variable selection in high dimensional datasets, in settings where a time-to-event outcome is observed with error. The proposed methods are motivated by self-reported outcomes collected in large-scale epidemiologic studies, such as the Women's Health Initiative. The proposed methods equally apply to imperfect outcomes that arise in other settings such as data extracted from electronic medical records. To evaluate the performance of our proposed algorithm, we present results from simulation studies, considering both continuous and categorical covariates. We illustrate this approach to discover single nucleotide polymorphisms that are associated with incident Type II diabetes in the Women's Health Initiative. A freely available R package icRSF (R Core Team, 2018; Xu et al., 2018) has been developed to implement the proposed methods.

Metabolic reprogramming of murine cardiomyocytes during autophagy requires the extracellular nutrient sensor decorin

The extracellular matrix is a master regulator of tissue homeostasis in health and disease. Here we examined how the small, leucine-rich, extracellular matrix proteoglycan decorin regulates cardiomyocyte metabolism during fasting in vivo First, we validated in Dcn ^-/- mice that decorin plays an essential role in autophagy induced by fasting. High-throughput metabolomics analyses of cardiac tissue in Dcn ^-/- mice subjected to fasting revealed striking differences in the hexosamine biosynthetic pathway resulting in aberrant cardiac O-β-N-acetylglycosylation as compared with WT mice. Functionally, Dcn ^-/- mice maintained cardiac function at a level comparable with nonfasted animals whereas fasted WT mice showed reduced ejection fraction. Collectively, our results suggest that reduced sensing of nutrient deprivation in the absence of decorin preempts functional adjustments of cardiac output associated with metabolic reprogramming.

Loss of periostin ameliorates adipose tissue inflammation and fibrosis in vivo

Recent evidence suggests that the accumulation of macrophages as a result of obesity-induced adipose tissue hypoxia is crucial for the regulation of tissue fibrosis, but the molecular mechanisms underlying adipose tissue fibrosis are still unknown. In this study, we revealed that periostin (Postn) is produced at extraordinary levels by adipose tissue after feeding with a high-fat diet (HFD). Postn was secreted at least from macrophages in visceral adipose tissue during the development of obesity, possibly due to hypoxia. Postn-/- mice had lower levels of crown-like structure formation and fibrosis in adipose tissue and were protected from liver steatosis. These mice also showed amelioration in systemic insulin resistance compared with HFD-fed WT littermates. Mice deficient in Postn in their hematopoietic compartment also had lower levels of inflammation in adipose tissue, in parallel with a reduction in ectopic lipid accumulation compared with the controls. Our data indicated that the regulation of Postn in visceral fat could be beneficial for the maintenance of healthy adipose tissue in obesity.

Egr1 deficiency induces browning of inguinal subcutaneous white adipose tissue in mice

Beige adipocyte differentiation within white adipose tissue, referred to as browning, is seen as a possible mechanism for increasing energy expenditure. The molecular regulation underlying the thermogenic browning process has not been entirely elucidated. Here, we identify the zinc finger transcription factor EGR1 as a negative regulator of the beige fat program. Loss of Egr1 in mice promotes browning in the absence of external stimulation and leads to an increase of Ucp1 expression, which encodes the key thermogenic mitochondrial uncoupling protein-1. Moreover, EGR1 is recruited to the proximal region of the Ucp1 promoter in subcutaneous inguinal white adipose tissue. Transcriptomic analysis of subcutaneous inguinal white adipose tissue in the absence of Egr1 identifies the molecular signature of white adipocyte browning downstream of Egr1 deletion and highlights a concomitant increase of beige differentiation marker and a decrease in extracellular matrix gene expression. Conversely, Egr1 overexpression in mesenchymal stem cells decreases beige adipocyte differentiation, while increasing extracellular matrix production. These results reveal a role for Egr1 in blocking energy expenditure via direct Ucp1 transcription repression and highlight Egr1 as a therapeutic target for counteracting obesity.

Podocan Is Expressed in Blood and Adipose Tissue and Correlates Negatively With the Induction of Diabetic Nephropathy

Podocan, a member of the small leucine-rich repeat proteoglycans (SLRPs), is expressed in vascular endothelial cells with high levels of expression in the sclerotic glomerular lesions of experimental HIV-associated nephropathy. It is also found in vascular smooth muscle cells and is involved in atherosclerosis. Decorin, a protein similar to podocan, also belongs to the SLRP family and is highly expressed in adipose tissues. It is a secreted protein associated with obesity, type 2 diabetes, and diabetic nephropathy. Based on the similarity of podocan to decorin and its functions reported in the renal and cardiovascular systems, we hypothesized that podocan levels might correlate with the occurrence of metabolic syndromes such as obesity, diabetes, and diabetic nephropathy. We found that podocan was highly expressed in the adipose tissue of mice and humans and its expression was regulated by tumor necrosis factor-α in mouse 3T3-L1 adipocytes. In addition, podocan was detected in the plasma, and its levels tended to increase in diet-induced obese C57BL/6J mice and decrease in obese-diabetic KKA^y and db/db mice. Podocan messenger RNA (mRNA) levels in the renal cortex correlated negatively with the urinary albumin-to-creatinine ratio, a surrogate marker of glomerular injury in uninephrectomized db/db mice used as a model of diabetic nephropathy. Our results suggest that podocan is involved in kidney function and could be a unique therapeutic target for diabetic nephropathy.

Decorin over-expression by decidual cells in preeclampsia: a potential blood biomarker

BACKGROUND

Decorin, a leucine-rich proteoglycan that is produced by decidual cells, limits invasion and endovascular differentiation of extravillous trophoblast cells during early placentation by binding to multiple tyrosine kinase receptors, in particular, vascular endothelial growth factor receptor-2.

OBJECTIVE

Because many studies have reported an association between poor trophoblast invasion and endovascular differentiation with preeclampsia, the studies reported here tested (1) whether decorin over-expression in the chorionic villi and/or basal decidua is associated with preeclampsia and, if so, (2) whether this association results in a hypoinvasive placenta, and (3) whether elevated plasma decorin concentration in the second trimester is a predictive biomarker for preeclampsia.

STUDY DESIGN

Decorin messenger RNA expression was measured with quantitative polymerase chain reaction at the tissue level and with in situ hybridization at the cellular level using (35)S-labeled antisense complimentary RNA probe in placentas from healthy control subjects and subjects with preeclampsia (14 each, 23-40 weeks of gestation). Tissue sections of the same placentas were also immunostained for decorin protein. A decorin over-expressing human endometrial stromal cell line was tested for invasion-regulatory effects on an invasive first-trimester extravillous trophoblast cell line HTR-8/SVneo plated in cocultures that were separated by a semipermeable membrane. Furthermore, we conducted retrospective measurements of plasma decorin levels during the second trimester (15-18 weeks of gestation) in a cohort of 28 body mass index-matched pairs of control subjects and subjects with preeclampsia before the onset of clinical disease.

RESULTS

First, decorin messenger RNA expression at the cellular level measured with in situ hybridization exhibited profoundly higher expression levels in basal plate decidual cells within the placentas from preeclamptic subjects than those from control subjects at all gestational ages, whereas no difference between the 2 subject groups was noted in villus mesenchymal cells. Similarly decorin messenger RNA expression at the tissue level in chorionic villi (primarily resulting from fetally derived mesenchymal cells) did not differ significantly between control and preeclampsia placentas. These findings were validated with immunostaining for decorin protein. Second, knocking down decorin gene in a decorin over-expressing endometrial cell line (used as an in vitro surrogate of decorin over-expressing decidual cells) in cocultures with extravillous trophoblast cells abrogated its invasion-restraining actions on trophoblast cells, which indicated paracrine contribution of decorin over-expressing decidua to the poor trophoblast invasiveness in situ. Finally, retrospective measurement of plasma decorin levels during the second trimester in 28 body mass index-matched pairs of control subjects and subjects with preeclampsia revealed elevated plasma decorin levels in all subjects with preeclampsia in all body mass index groups. A receiver operating characteristic curve analysis revealed strong diagnostic performance of plasma decorin in the prediction of preeclampsia status. Although there was no significant gestational age-related change in decorin levels during the second trimester in control or subjects with preeclampsia, we found that plasma decorin had a significant inverse relationship with body mass index or bodyweight.

CONCLUSION

We conclude that decorin over-expression by basal decidual cells is associated with hypoinvasive phenotype and poor endovascular differentiation of trophoblast cells in preeclampsia and that elevated plasma decorin concentration is a potential predictive biomarker for preeclampsia before the onset of clinical signs.

The miR-181d-regulated metalloproteinase Adamts1 enzymatically impairs adipogenesis via ECM remodeling

The extracellular matrix (ECM) maintenance is crucial to the structural integrity of adipocytes and whole adipose tissue formation. However, the potential impact of the ECM on adipocyte lineage commitment is unclear. Herein, we demonstrate that forced expression of matrix-associated metalloproteinase Adamts1 (a disintegrin and metalloproteinase with thrombospondin motifs 1), which we show is targeted by microRNA-181d (miR-181d) during BMP4-induced adipocytic lineage commitment, markedly impairs adipocyte commitment. Conversely, siRNA-induced inhibition of Adamts1 promotes adipocyte commitment. Adamst1 metalloprotease activity is required for this inhibition and is determined to function via remodeling ECM components followed by activating FAK-ERK signaling pathway during the commitment process. Furthermore, ablation of Adamts1 in adipose tissue increases adipose tissue mass, reduces insulin sensitivity, and disrupts lipid homeostasis. This finding is consistent with Adamts1 decreased expression in the adipose tissue of obese mice and an inverse correlation of Adamts1 expression with body mass index in humans. Collectively, our results indicate that Adamts1 acts as an ECM 'modifier', with miR-181d-induced downregulation, that regulates adipocyte lineage commitment and obesity.

Decorin as a multivalent therapeutic agent against cancer

Decorin is a prototypical small leucine-rich proteoglycan that epitomizes the multifunctional nature of this critical gene family. Soluble decorin engages multiple receptor tyrosine kinases within the target-rich environment of the tumor stroma and tumor parenchyma. Upon receptor binding, decorin initiates signaling pathways within endothelial cells downstream of VEGFR2 that ultimately culminate in a Peg3/Beclin 1/LC3-dependent autophagic program. Concomitant with autophagic induction, decorin blunts capillary morphogenesis and endothelial cell migration, thereby significantly compromising tumor angiogenesis. In parallel within the tumor proper, decorin binds multiple RTKs with high affinity, including Met, for a multitude of oncosuppressive functions including growth inhibition, tumor cell mitophagy, and angiostasis. Decorin is also pro-inflammatory by modulating macrophage function and cytokine secretion. Decorin suppresses tumorigenic growth, angiogenesis, and prevents metastatic lesions in a variety of in vitro and in vivo tumor models. Therefore, decorin would be an ideal therapeutic candidate for combating solid malignancies.

DNA methylation and gene expression patterns in adipose tissue differ significantly within young adult monozygotic BMI-discordant twin pairs

BACKGROUND

Little is known about epigenetic alterations associated with subcutaneous adipose tissue (SAT) in obesity. Our aim was to study genome-wide DNA methylation and gene expression differences in SAT in monozygotic (MZ) twin pairs who are discordant for body mass index (BMI). This design completely matches lean and obese groups for genetic background, age, gender and shared environment.

METHODS

14We analyzed DNA methylome and gene expression from SAT, together with body composition (magnetic resonance imaging/spectroscopy) and glucose tolerance test, lipids and C-reactive protein from 26 rare BMI-discordant (intrapair difference in BMI ⩾3 kg m(-2)) MZ twin pairs identified from 10 birth cohorts of young adult Finnish twins.

RESULTS

We found 17 novel obesity-associated genes that were differentially methylated across the genome between heavy and lean co-twins. Nine of them were also differentially expressed. Pathway analyses indicated that dysregulation of SAT in obesity includes a paradoxical downregulation of lipo/adipogenesis and upregulation of inflammation and extracellular matrix remodeling. Furthermore, CpG sites whose methylation correlated with metabolically harmful fat depots (intra-abdominal and liver fat) also correlated with measures of insulin resistance, dyslipidemia and low-grade inflammation, thus suggesting that epigenetic alterations in SAT are associated with the development of unhealthy obesity.

CONCLUSION

This is the first study in BMI-discordant MZ twin pairs reporting genome-wide DNA methylation and expression profiles in SAT. We found a number of novel genes and pathways whose methylation and expression patterns differ within the twin pairs, suggesting that the pathological adaptation of SAT to obesity is, at least in part, epigenetically regulated.

Analysis of the Human Proteome in Subcutaneous and Visceral Fat Depots in Diabetic and Non-diabetic Patients with Morbid Obesity

No longer regarded as simply a storage depot, fat is a dynamic organ acting locally and systemically to modulate energy homeostasis, glucose sensitivity, insulin resistance, and inflammatory pathways. Here, mass spectrometry was used to survey the proteome of patient matched subcutaneous fat and visceral fat in 20 diabetic vs 22 nondiabetic patients with morbid obesity. A similar number of proteins (~600) were identified in each tissue type. When stratified by diabetic status, 19 and 41 proteins were found to be differentially abundant in subcutaneous fat and omentum, respectively. These proteins represent pathways known to be involved in metabolism. Five of these proteins were differentially abundant in both fat depots: moesin, 78 kDa glucose-regulated protein, protein cordon-bleu, zinc finger protein 611, and cytochrome c oxidase subunit 6B1. Three proteins, decorin, cytochrome c oxidase subunit 6B1, and 78 kDa glucose-regulated protein, were further tested for validation by western blot analysis. Investigation of the proteins reported here is expected to expand on the current knowledge of adipose tissue driven biochemistry in diabetes and obesity, with the ultimate goal of identifying clinical targets for the development of novel therapeutic interventions in the treatment of type 2 diabetes mellitus. To our knowledge, this study is the first to survey the global proteome derived from each subcutaneous and visceral adipose tissue obtained from the same patient in the clinical setting of morbid obesity, with and without diabetes. It is also the largest study of diabetic vs nondiabetic patients with 42 patients surveyed.

Proteoglycan form and function: A comprehensive nomenclature of proteoglycans

We provide a comprehensive classification of the proteoglycan gene families and respective protein cores. This updated nomenclature is based on three criteria: Cellular and subcellular location, overall gene/protein homology, and the utilization of specific protein modules within their respective protein cores. These three signatures were utilized to design four major classes of proteoglycans with distinct forms and functions: the intracellular, cell-surface, pericellular and extracellular proteoglycans. The proposed nomenclature encompasses forty-three distinct proteoglycan-encoding genes and many alternatively-spliced variants. The biological functions of these four proteoglycan families are critically assessed in development, cancer and angiogenesis, and in various acquired and genetic diseases where their expression is aberrant.

Oncosuppressive functions of decorin

The extracellular matrix is rapidly emerging as a prominent contributor to various fundamental processes of tumorigenesis. In particular, decorin, a member of the small leucine-rich proteoglycan gene family, is assuming a central role as a potent soluble tumor repressor. Decorin binds and antagonizes various receptor tyrosine kinases and inhibits downstream oncogenic signaling in several solid tumors. Among other functions, decorin evokes cell cycle arrest, apoptosis, and antimetastatic, and antiangiogenic programs. Recent work has revealed a paradigmatic shift in our understanding of the molecular mechanisms underlying its tumoricidal properties. Decorin adversely compromises the genetic signature of the tumor microenvironment and induces endothelial cell autophagy downstream of VEGFR2. Moreover, decorin selectively evokes destruction of tumor cell mitochondria downstream of Met through mitophagy. Acting as a partial agonist, decorin signals via proautophagic receptors and triggers procatabolic processes that parallel the classical tumoricidal properties of this multifaceted proteoglycan.

Beneficial effects of soluble dietary Jerusalem artichoke (Helianthus tuberosus) in the prevention of the onset of type 2 diabetes and non-alcoholic fatty liver disease in high-fructose diet-fed rats

Jerusalem artichoke (JA) has the potential to attenuate lipid disturbances and insulin resistance (IR), but the underlying mechanisms are not well understood. In the present study, we elucidated the physiological responses and mechanisms of JA intervention with a comprehensive transcriptome analysis. Wistar rats were fed a control diet, a 60 % fructose-enriched diet (FRU), or a FRU with 10 % JA (n 6-7) for 4 weeks. An oral glucose tolerance test was carried out on day 21. Liver samples were collected for biochemical and global gene expression analyses (GeneChip® Rat Genome 230 2.0 Array, Affymetrix). Fructose feeding resulted in IR and hepatic TAG accumulation; dietary JA supplementation significantly improved these changes. Transcriptomic profiling revealed that the expression of malic enzyme 1 (Me1), associated with fatty acid synthesis; decorin (Dcn), related to fibrosis; and cytochrome P450, family 1, subfamily a, polypeptide 2 (Cyp1a2) and nicotinamide phosphoribosyltransferase (Nampt), associated with inflammation, was differentially altered by the FRU, whereas dietary JA supplementation significantly improved the expression of these genes. We established for the first time the molecular mechanisms driving the beneficial effects of JA in the prevention of type 2 diabetes and non-alcoholic fatty liver disease. We propose that 10 % JA supplementation may be beneficial for the prevention of the onset of these diseases.

Extracellular matrix and cytochrome P450 gene expression can distinguish steatohepatitis from steatosis in mice

One of the main questions regarding nonalcoholic fatty liver disease is the molecular background of the transition from simple steatosis (SS) to the inflammatory and fibrogenic condition of steatohepatitis (NASH). We examined the gene expression changes during progression from histologically normal liver to SS and NASH in models of obesity caused by hyperphagia or a high-fat diet. Microarray-based analysis revealed that the expression of 1445 and 264 probe sets was changed exclusively in SS and NASH samples, respectively, and 1577 probe sets were commonly altered in SS and NASH samples. Functional annotations indicated that transcriptome alterations that were common for NASH and SS, as well as exclusive for NASH, involved extracellular matrix (ECM)-related processes, although they differed in the type of matrix structure change. The expression of 80 genes was significantly changed in all three comparisons: SS versus control, NASH versus control and NASH versus SS. Of these genes, epithelial membrane protein 1, IKBKB interacting protein and decorin were progressively up-regulated in both SS and NASH compared to normal tissue. The molecular context of interactions of encoded 80 proteins revealed that they are highly interconnected and significantly enriched for processes involving metabolism by cytochrome P450. Validation of 10 selected mRNAs encoding genes related to ECM and cytochrome P450 with quantitative RT-PCR analysis showed consistent changes in their expression during NASH development. The expression profile of these genes has the potential to distinguish NASH from SS and normal tissue and may possibly be beneficial in the clinical diagnosis of NASH.

Decorin causes autophagy in endothelial cells via Peg3

Soluble decorin affects the biology of several receptor tyrosine kinases by triggering receptor internalization and degradation. We found that decorin induced paternally expressed gene 3 (Peg3), an imprinted tumor suppressor gene, and that Peg3 relocated into autophagosomes labeled by Beclin 1 and microtubule-associated light chain 3. Decorin evoked Peg3-dependent autophagy in both microvascular and macrovascular endothelial cells leading to suppression of angiogenesis. Peg3 coimmunoprecipitated with Beclin 1 and LC3 and was required for maintaining basal levels of Beclin 1. Decorin, via Peg3, induced transcription of Beclin 1 and microtubule-associated protein 1 light chain 3 alpha genes, thereby leading to a protracted autophagic program. Mechanistically, decorin interacted with VEGF receptor 2 (VEGFR2) in a region overlapping with its natural ligand VEGFA, and VEGFR2 was required for decorin-evoked Beclin 1 and microtubule-associated protein 1 light chain 3 alpha expression as well as for Peg3 induction in endothelial cells. Moreover, decorin induced VEGFR2-dependent mitochondrial fragmentation and loss of mitochondrial membrane potential. Thus, we have unveiled a mechanism for a secreted proteoglycan in inducing Peg3, a master regulator of macroautophagy in endothelial cells.

Identification and validation of novel contraction-regulated myokines released from primary human skeletal muscle cells

Proteins secreted by skeletal muscle, so called myokines, have been shown to affect muscle physiology and additionally exert systemic effects on other tissues and organs. Although recent profiling studies have identified numerous myokines, the amount of overlap from these studies indicates that the secretome of skeletal muscle is still incompletely characterized. One limitation of the models used is the lack of contraction, a central characteristic of muscle cells. Here we aimed to characterize the secretome of primary human myotubes by cytokine antibody arrays and to identify myokines regulated by contraction, which was induced by electrical pulse stimulation (EPS). In this study, we validated the regulation and release of two selected myokines, namely pigment epithelium derived factor (PEDF) and dipeptidyl peptidase 4 (DPP4), which were recently described as adipokines. This study reveals that both factors, DPP4 and PEDF, are secreted by primary human myotubes. PEDF is a contraction-regulated myokine, although PEDF serum levels from healthy young men decrease after 60 min cycling at VO2max of 70%. Most interestingly, we identified 52 novel myokines which have not been described before to be secreted by skeletal muscle cells. For 48 myokines we show that their release is regulated by contractile activity. This profiling study of the human skeletal muscle secretome expands the number of myokines, identifies novel contraction-regulated myokines and underlines the overlap between proteins which are adipokines as well as myokines.

Identification of a genetic locus on chromosome 4q34-35 for type 2 diabetes with overweight

The incidence of type 2 diabetes is rising rapidly because of an increase in the incidence of being overweight and obesity. Identification of genetic determinants for complex diseases, such as type 2 diabetes, may provide insight into disease pathogenesis. The aim of the study was to investigate the shared genetic factors that predispose individuals to being overweight and developing type 2 diabetes. We conducted genome-wide linkage analyses for type 2 diabetes in 386 affected individuals (269 sibpairs) from 171 Korean families and association analyses with single-nucleotide polymorphisms of candidate genes within linkage regions to identify genetic variants that predispose individuals to being overweight and developing type 2 diabetes. Through fine-mapping analysis of chromosome 4q34-35, we detected a locus potentially linked (nonparametric linkage 2.81, logarithm of odds 2.27, P=6 × 10⁻⁴) to type 2 diabetes in overweight or obese individuals (body mass index, BMI⩾23 kg m⁻²). Multiple regression analysis with type 2 diabetes-related phenotypes revealed a significant association (false discovery rate (FDR) P=0.006 for rs13144140; FDR P=0.002 for rs6830266) between GPM6A (rs13144140) and BMI and waist–hip ratio, and between NEIL3 (rs6830266) and insulin level from 1314 normal individuals. Our systematic search of genome-wide linkage and association studies, demonstrate that a linkage peak for type 2 diabetes on chromosome 4q34-35 contains two type 2 diabetes-related genes, GPM6A and NEIL3.

Plasma resistin is associated with single nucleotide polymorphisms of a possible resistin receptor, the decorin gene, in the general Japanese population

Resistin is an adipokine secreted from adipocytes in mice. We previously reported that a single nucleotide polymorphism (SNP) -420 (rs1862513) in the human resistin gene (RETN), is correlated with plasma resistin. Decorin is a multifunctional proteoglycan, and its isoform, lacking 14 amino acids from the N terminal region of mature core decorin, recently was identified as a resistin receptor in mice. To examine whether SNPs in the vicinity of the human decorin gene (DCN) are associated with plasma resistin, we cross-sectionally analyzed six tag SNPs selected around DCN in the same linkage disequilibrium block in 2,078 community-dwelling Japanese subjects. Plasma resistin was associated with the rs7139228, rs7956537, rs516115, and rs3138167 genotypes in DCN. A multiple regression analysis revealed that the genotype of rs7308752 (G/G) or rs516115 (C/C) was associated with decreased plasma resistin after adjusted for age, sex, BMI, and the RETN SNP rs1862513. The effect of rs7139228 and rs1862513 seemed to be additive without synergistic interaction. Therefore, plasma resistin was associated with some tag SNPs around DCN in the general Japanese population. The possibility that human decorin is a human resistin receptor should be pursued.

Microvesicles/exosomes as potential novel biomarkers of metabolic diseases

Biomarkers are of tremendous importance for the prediction, diagnosis, and observation of the therapeutic success of common complex multifactorial metabolic diseases, such as type II diabetes and obesity. However, the predictive power of the traditional biomarkers used (eg, plasma metabolites and cytokines, body parameters) is apparently not sufficient for reliable monitoring of stage-dependent pathogenesis starting with the healthy state via its initiation and development to the established disease and further progression to late clinical outcomes. Moreover, the elucidation of putative considerable differences in the underlying pathogenetic pathways (eg, related to cellular/tissue origin, epigenetic and environmental effects) within the patient population and, consequently, the differentiation between individual options for disease prevention and therapy - hallmarks of personalized medicine - plays only a minor role in the traditional biomarker concept of metabolic diseases. In contrast, multidimensional and interdependent patterns of genetic, epigenetic, and phenotypic markers presumably will add a novel quality to predictive values, provided they can be followed routinely along the complete individual disease pathway with sufficient precision. These requirements may be fulfilled by small membrane vesicles, which are so-called exosomes and microvesicles (EMVs) that are released via two distinct molecular mechanisms from a wide variety of tissue and blood cells into the circulation in response to normal and stress/pathogenic conditions and are equipped with a multitude of transmembrane, soluble and glycosylphosphatidylinositol-anchored proteins, mRNAs, and microRNAs. Based on the currently available data, EMVs seem to reflect the diverse functional and dysfunctional states of the releasing cells and tissues along the complete individual pathogenetic pathways underlying metabolic diseases. A critical step in further validation of EMVs as biomarkers will rely on the identification of unequivocal correlations between critical disease states and specific EMV signatures, which in future may be determined in rapid and convenient fashion using nanoparticle-driven biosensors.

The small leucine-rich proteoglycan, biglycan, is highly expressed in adipose tissue of Psammomys obesus and is associated with obesity and type 2 diabetes

We have previously demonstrated that the small leucine-rich proteoglycan decorin may play a role in adipose tissue homeostasis and the pathophysiology of obesity. Biglycan is highly similar in structure to decorin, therefore we hypothesized it would have a similar expression profile and role to decorin in adipose tissue. Real time polymerase chain reaction was used to measure biglycan mRNA levels in adipose tissue from normal glucose tolerant and impaired glucose tolerant and type 2 diabetic (T2D) Psammomys obesus. Biglycan mRNA was found to be highly expressed in adipose tissue, and gene expression was significantly higher in visceral compared to subcutaneous adipose tissue, with elevated levels in obese, T2D compared to lean normal glucose tolerant P. obesus (P < 0.04). Biglycan mRNA was predominantly expressed by stromal/vascular cells of fractionated adipose tissue (P = 0.023). Biglycan expression in adipose tissue, particularly in the obese state, was markedly upregulated. Collectively, our data suggest that the small leucine-rich proteoglycan family proteins biglycan and decorin may play a role in the development of obesity and T2D, possibly by facilitating expansion of adipose tissue mass.

Regulation of pre-adipocyte proliferation and apoptosis by the small leucine-rich proteoglycans, biglycan and decorin

Evidence for a functional role for extracellular matrix (ECM) proteins in adipose tissue is demonstrated in dynamic changes in expression of ECM genes during adipocyte differentiation and in obesity. Components of the ECM may regulate adipose cell number expansion by restricting pre-adipocyte proliferation, regulating apoptosis and inhibiting adipogenesis. Although pre-adipocytes express multiple proteoglycans, their role in pre-adipocyte proliferation up to now has remained unknown. The study described here was conducted to characterize roles of small leucine-rich proteoglycans (SLRPs) in adipocyte proliferation. Pre-adipocytes were seeded on plates coated with biglycan and decorin and were allowed to differentiate. In addition, pre-adipocytes were incubated on plates coated with biglycan, decorin, or fibronectin and measurements were made of cell proliferation and apoptosis. We are able to report that SLRPs decorin and biglycan did not affect differentiation of our 3T3-L1 cells; however, biglycan and decorin did reduce proliferation of pre-adipocytes, partly by induction of apoptosis. Furthermore, anti-proliferative capabilities of decorin and biglycan were nullified with removal of GAG side-chains suggesting that the chains played key roles in anti-proliferative effects of the SLRPs. We also found that co-treatment of decorin or biglycan with the proteoglycan fibronectin restored normal proliferation, an indication that multiple ECM proteins may act in concert to regulate overall proliferation rates of pre-adipocytes. These studies indicate that SLRPs may compose a regulatory factor in adipose tissue expansion, through hyperplasia.

Prospecting for adipose progenitor cell biomarkers: biopanning for gold with in vivo phage display

In this issue of Cell Stem Cell, Daquinag et al. (2011) take a lesson from the oncology field to search for stromal progenitor cells within adipose tissue. Their use of phage display biopanning in vivo identified an isoform of the extracellular matrix protein decorin as a receptor for the adipokine resistin.

An isoform of decorin is a resistin receptor on the surface of adipose progenitor cells

Adipose stromal cells (ASCs) serve as mesenchymal progenitors in white adipose tissue (WAT). Intercellular interactions involving ASCs have remained obscure. By merging phage display technology with fluorescence-activated cell sorting (FACS), we screened a combinatorial library for peptides that target mouse ASCs in vivo. We isolated peptide CSWKYWFGEC that specifically homes to ASCs, used it as bait to purify the corresponding ASC surface receptor, and identified it as a previously unreported cleavage product of decorin (DCN) lacking the glycanation site (termed ΔDCN). We demonstrate that ΔDCN is differentially expressed on ASC surface. In a screen for ΔDCN-binding proteins, we identified resistin, an adipokine for which the receptor has been unknown. Expression of ΔDCN in 3T3-L1 cells promoted proliferation and migration but suppressed lipid accumulation upon adipogenesis induction, which was resistin dependent. We conclude that ΔDCN serves as a functional receptor of resistin in adipocyte progenitors and may regulate WAT expansion.

Architecture and the extracellular matrix: the still unappreciated components of the adipose tissue

Fibrosis is usually characterized by the modification of both the amount and composition of a wide panel of extracellular matrix (ECM) proteins. In the liver, pancreas, kidney and lung the accumulation of fibrosis disrupts cellular processes and appears detrimental for organ function. This review highlights the available evidence supporting an important ECM remodelling in adipose tissue (AT) and, in particular, during the development of obesity. The modifications and occurrence of new adipose ECM components leads to an abnormal accumulation of fibrosis in this tissue. This phenomenon was well described in rodent models and evidence is beginning to emerge in humans; however, the origin and potential impact of these depots in AT biology are unclear. Two animal models with disruptions in ECM components (secreted proteins acidic in nature rich in cysteine null mice and ob/ob collagen VI null mice) suggest that fibrosis limits adipocyte hypertrophy and may cause the metabolic disorders associated with obesity. Over-expression of Hypoxia-inducible factor 1 leading to an increase in collagen expression suggests a role for hypoxia in fibrosis development. We conclude this review with possible hypotheses regarding the cellular and molecular contributors of fibrosis initiation.