Adipose tissue loss and lipodystrophy in xylosyltransferase II deficient mice

mRNA Degradation as a Therapeutic Solution for Mucopolysaccharidosis Type IIIC: Use of Antisense Oligonucleotides to Promote Downregulation of Heparan Sulfate Synthesis

Mucopolysaccharidosis type IIIC is a neurodegenerative lysosomal storage disorder (LSD) characterized by the accumulation of undegraded heparan sulfate (HS) due to the lack of an enzyme responsible for its degradation: acetyl-CoA:α-glucosaminide N-acetyltransferase (HGSNAT). Classical treatments are ineffective. Here, we attempt a new approach in genetic medicine, genetic substrate reduction therapy (gSRT), to counteract this neurological disorder. Briefly, we used synthetic oligonucleotides, particularly gapmer antisense oligonucleotides (ASOs), to target the synthesis of the accumulated compounds at the molecular level, downregulating a specific gene involved in the first step of HS biosynthesis, XYLT1. Our goal was to reduce HS production and, consequently, its accumulation. Initially, five gapmer ASOs were designed and their potential to decrease XYLT1 mRNA levels were tested in patient-derived fibroblasts. Subsequent analyses focused on the two best performing molecules alone. The results showed a high inhibition of the XYLT1 gene mRNA (around 90%), a decrease in xylosyltransferase I (XT-I) protein levels and a reduction in HS storage 6 and 10 days after transfection (up to 21% and 32%, respectively). Overall, our results are highly promising and may represent the initial step towards the development of a potential therapeutic option not only for MPS IIIC, but virtually for every other MPS III form. Ultimately, the same principle may also apply to other neuropathic MPS.

Genetic variability in proteoglycan biosynthetic genes reveals new facets of heparan sulfate diversity

Heparan sulfate (HS) and chondroitin sulfate (CS) proteoglycans (PG) consist of a core protein to which the glycosaminoglycan (GAG) chains, HS or CS, are attached through a common linker tetrasaccharide. In the extracellular space, they are involved in the regulation of cell communication, assuring development and homeostasis. The HSPG biosynthetic pathway has documented 51 genes, with many diseases associated to defects in some of them. The phenotypic consequences of this genetic variation in humans, and of genetic ablation in mice, and their expression patterns, led to a phenotypically centered HSPG biosynthetic pathway model. In this model, HS sequences produced by ubiquitous NDST1, HS2ST and HS6ST enzymes are essential for normal development and homeostasis, whereas tissue restricted HS sequences produced by the non-ubiquitous NDST2-4, HS6ST2-3, and HS3ST1-6 enzymes are involved in adaptative behaviors, cognition, tissue responsiveness to stimuli, and vulnerability to disease. The model indicates that the flux through the HSPG/CSPG pathways and its diverse branches is regulated by substrate preferences and protein-protein-interactions. This results in a privileged biosynthesis of HSPG over that of CSPGs, explaining the phenotypes of linkeropathies, disease caused by defects in genes involved in the biosynthesis of the common tetrasaccharide linker. Documented feedback loops whereby cells regulate HS sulfation, and hence the interactions of HS with protein partners, may be similarly implemented, e.g., protein tyrosine sulfation and other posttranslational modifications in enzymes of the HSPG pathway. Together, ubiquitous HS, specialized HS, and their biosynthesis model can facilitate research for a better understanding of HSPG roles in physiology and pathology.

The effects of WWP1 overexpression on the golgi apparatus stress response and proteoglycan production in adipocytes

White adipocytes are a major component of white adipose tissue (WAT) and help to maintain systemic metabolic homeostasis by storing energy and secreting adipokines. In mice deficient in the protein WWP1 (WW domain-containing E3 ubiquitin protein ligase 1), oxidative stress in adipocytes increases but insulin resistance induced by obesity improves. However, the specific roles of WWP1 in adipocytes remain unclear. Here, we show that in 3T3L1 adipocytes, WWP1 localized in the Golgi apparatus via its C2 domain, where it protected the Golgi apparatus from monensin-induced disruption. By contrast, WWP1 knockdown by short hairpin RNA failed to protect the Golgi apparatus and enhanced Golgi apparatus disruption by monensin. The Golgi apparatus acts as a central organelle to establish accurate protein glycosylation of proteoglycans containing glycosaminoglycans, including chondroitin sulfate and heparan sulfate (HS). WWP1 overexpression increased chondroitin sulfate and HS levels, whereas WWP1 knockdown decreased them. Furthermore, obesity-related increases in HS were prevented by WWP1 knockout in adipose tissue. In summary, our results demonstrate a novel role for WWP1 in maintaining Golgi apparatus morphology and proteoglycan synthesis in adipocytes.

Parental obesity-induced changes in developmental programming

Many studies support the link between parental obesity and the predisposition to develop adult-onset metabolic syndromes that include obesity, high blood pressure, dyslipidemia, insulin resistance, and diabetes in the offspring. As the prevalence of obesity increases in persons of childbearing age, so does metabolic syndrome in their descendants. Understanding how parental obesity alters metabolic programs in the progeny, predisposing them to adult-onset metabolic syndrome, is key to breaking this cycle. This review explores the basis for altered metabolism of offspring exposed to overnutrition by focusing on critical developmental processes influenced by parental obesity. We draw from human and animal model studies, highlighting the adaptations in metabolism that occur during normal pregnancy that become maladaptive with obesity. We describe essential phases of development impacted by parental obesity that contribute to long-term alterations in metabolism in the offspring. These encompass gamete formation, placentation, adipogenesis, pancreas development, and development of brain appetite control circuits. Parental obesity alters the developmental programming of these organs in part by inducing epigenetic changes with long-term consequences on metabolism. While exposure to parental obesity during any of these phases is sufficient to alter long-term metabolism, offspring often experience multiple exposures throughout their development. These insults accumulate to increase further the susceptibility of the offspring to the obesogenic environments of modern society.

The Endometrial Transcriptome of Metabolic and Inflammatory Pathways During the Window of Implantation Is Deranged in Infertile Obese Polycystic Ovarian Syndrome Women

Introduction and Aim: Obese women with polycystic ovarian syndrome (PCOS) have a reduced rate of spontaneous conception even when their cycles are ovulatory. Endometrial receptivity is an important factor for poor implantation and increased miscarriage rates. Mechanisms in which both pathologies modify the endometrium are not fully clarified. The aim of our study was to compare the endometrial transcriptomic profiles between infertile obese PCOS (O-PCOS) women and infertile normal weight subjects during the window of implantation in ovulatory menstrual cycles. Methods: We conducted a prospective transcriptomic analysis of the endometrium using RNA sequencing. In this way, potential endometrial mechanisms leading to the poor reproductive outcome in O-PCOS patients could be characterized. Endometrial samples during days 21-23 of the menstrual cycle were collected from infertile O-PCOS women (n = 11) and normal weight controls (n = 10). Subgroups were defined according to the ovulatory/anovulatory status in the natural cycles, and O-PCOS women were grouped into the O-PCOS ovulatory (O-PCOS-ovul) subgroup. RNA isolation, sequencing with library reparation, and subsequent RNAseq data analysis were performed. Results: Infertile O-PCOS patients had 610 differentially expressed genes (DEGs), after adjustment for multiple comparisons with normal weight infertile controls, related to obesity (MXRA5 and ECM1), PCOS (ADAMTS19 and SLC18A2), and metabolism (VNN1 and PC). In the ovulatory subgroup, no DEGs were found, but significant differences in canonical pathways and the upstream regulator were revealed. According to functional and upstream analyses of ovulatory subgroup comparisons, the most important biological processes were related to inflammation (TNFR1 signaling), insulin signaling (insulin receptor signaling and PI3/AKT), fatty acid metabolism (stearate biosynthesis I and palmitate biosynthesis I), and lipotoxicity (unfolded protein response pathway). Conclusions: We demonstrated that endometrial transcription in ovulatory O-PCOS patients is deranged in comparison with the control ovulatory endometrium. The most important pathways of differentiation include metabolism and inflammation. These processes could also represent potential mechanisms for poor embryo implantation, which prevent the development of a successful pregnancy. ClinicalTrials.gov ID: NCT03353948.

An Overview of in vivo Functions of Chondroitin Sulfate and Dermatan Sulfate Revealed by Their Deficient Mice

Chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS) are covalently attached to specific core proteins to form proteoglycans in their biosynthetic pathways. They are constructed through the stepwise addition of respective monosaccharides by various glycosyltransferases and maturated by epimerases as well as sulfotransferases. Structural diversities of CS/DS and HS are essential for their various biological activities including cell signaling, cell proliferation, tissue morphogenesis, and interactions with a variety of growth factors as well as cytokines. Studies using mice deficient in enzymes responsible for the biosynthesis of the CS/DS and HS chains of proteoglycans have demonstrated their essential functions. Chondroitin synthase 1-deficient mice are viable, but exhibit chondrodysplasia, progression of the bifurcation of digits, delayed endochondral ossification, and reduced bone density. DS-epimerase 1-deficient mice show thicker collagen fibrils in the dermis and hypodermis, and spina bifida. These observations suggest that CS/DS are essential for skeletal development as well as the assembly of collagen fibrils in the skin, and that their respective knockout mice can be utilized as models for human genetic disorders with mutations in chondroitin synthase 1 and DS-epimerase 1. This review provides a comprehensive overview of mice deficient in CS/DS biosyntheses.

Chondrodysplasias With Multiple Dislocations Caused by Defects in Glycosaminoglycan Synthesis

Chondrodysplasias with multiple dislocations form a group of severe disorders characterized by joint laxity and multiple dislocations, severe short stature of pre- and post-natal onset, hand anomalies, and/or vertebral anomalies. The majority of chondrodysplasias with multiple dislocations have been associated with mutations in genes encoding glycosyltransferases, sulfotransferases, and transporters implicated in the synthesis or sulfation of glycosaminoglycans, long and unbranched polysaccharides composed of repeated disaccharide bond to protein core of proteoglycan. Glycosaminoglycan biosynthesis is a tightly regulated process that occurs mainly in the Golgi and that requires the coordinated action of numerous enzymes and transporters as well as an adequate Golgi environment. Any disturbances of this chain of reactions will lead to the incapacity of a cell to construct correct glycanic chains. This review focuses on genetic and glycobiological studies of chondrodysplasias with multiple dislocations associated with glycosaminoglycan biosynthesis defects and related animal models. Strong comprehension of the molecular mechanisms leading to those disorders, mostly through extensive phenotypic analyses of in vitro and/or in vivo models, is essential for the development of novel biomarkers for clinical screenings and innovative therapeutics for these diseases.

Enlarged adipocytes from subcutaneous vs. visceral adipose tissue differentially contribute to metabolic dysfunction and atherogenic risk of patients with obesity

Morphological characteristics and source of adipose tissue as well as adipokines may increase cardiometabolic risk. This study aimed to explore whether adipose tissue characteristics may impact metabolic and atherogenic risks. Subcutaneous Adipose Tissue (SAT), Visceral Adipose Tissue (VAT) and peripheral blood were obtained from obese patients submitted to bariatric surgery. Adipose tissue (morphometry), plasma adiponectin, TNF-α, resistin (multiplexing) and biochemical chemistry were analyzed; as well as endothelial dysfunction (Flow Mediated Dilation, FMD) and atherogenesis (Carotid Intima Media Thickness, CIMT). Subgroups divided by adipocyte size and source were compared; as well as correlation and multivariate analysis. Sixty patients 36.6% males, aged 44 years-old, BMI 46.7 kg/m² were included. SAT's adipocytes showed a lower range of size expandability than VAT's adipocytes. Independent from their source, larger adipocytes were associated with higher glucose, lower adiponectin and higher CIMT. Particularly, larger adipocytes from SAT were associated with higher blood pressure, lower insulin and HDL-cholesterol; and showed positive correlation with glucose, Hb_A1c, systolic/diastolic values, and negatively correlated with insulin and adiponectin. VAT's larger adipocytes particularly associated with lower resistin and lower FMD values. Gender and Diabetes Mellitus significantly impacted the relation of adipocyte size/source with the metabolic and atherogenic risk. Multivariable analysis suggested hypertension-resistin-Hb_A1c interactions associated with SAT's larger adipocytes; whereas potential insulin-adiponectin associations were observed for VAT's larger adipocytes. Adipocyte morphology and source are differentially related with cardiometabolic and atherogenic risk in population with obesity, which are potentially affected by gender and Diabetes Mellitus.

Xylosyltransferase 2 deficiency and organ homeostasis

In this paper we characterize the function of Xylosyltransferase 2 (XylT2) in different tissues to investigate the role XylT2 has in the proteoglycan (PG) biochemistry of multiple organs. The results show that in all organs examined there is a widespread and significant decrease in total XylT activity in Xylt2 knock out mice (Xylt2-/-). This decrease results in increased organ weight differences in lung, heart, and spleen. These findings, in addition to our previous findings of increased liver and kidney weight with loss of serum XylT activity, suggest systemic changes in organ function due to loss of XylT2 activity. The Xylt2-/- mice have splenomegaly due to enlargement of the red pulp area and enhanced pulmonary response to bacterial liposaccharide. Tissue glycosaminoglycan composition changes are also found. These results demonstrate a role of XylT2 activity in multiple organs and their PG content. Because the residual XylT activity in the Xylt2-/- is due to xylosyltransferase 1 (XylT1), these studies indicate that both XylT1 and XylT2 have important roles in PG biosynthesis and organ homeostasis.

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.