Extracellular metallothionein as a therapeutic target in the early progression of type 1 diabetes.

Type 1 diabetes (T1D) is characterized by lymphocyte infiltration into the pancreatic islets of Langerhans, leading to the destruction of insulin-producing beta cells and uncontrolled hyperglycemia. In the nonobese diabetic (NOD) murine model of T1D, the onset of this infiltration starts several weeks before glucose dysregulation and overt diabetes. Recruitment of immune cells to the islets is mediated by several chemotactic cytokines, including CXCL10, while other cytokines, including SDF-1α, can confer protective effects. Global gene expression studies of the pancreas from prediabetic NOD mice and single-cell sequence analysis of human islets from prediabetic, autoantibody-positive patients showed an increased expression of metallothionein (MT), a small molecular weight, cysteine-rich metal-binding stress response protein. We have shown that beta cells can release MT into the extracellular environment, which can subsequently enhance the chemotactic response of Th1 cells to CXCL10 and interfere with the chemotactic response of Th2 cells to SDF-1α. These effects can be blocked in vitro with a monoclonal anti-MT antibody, clone UC1MT. When administered to NOD mice before the onset of diabetes, UC1MT significantly reduces the development of T1D. Manipulation of extracellular MT may be an important approach to preserving beta cell function and preventing the development of T1D.

Vascular smooth muscle-derived Trpv1+ progenitors are a source of cold-induced thermogenic adipocytes.

Brown adipose tissue (BAT) and beige fat function in energy expenditure in part due to their role in thermoregulation, making these tissues attractive targets for treating obesity and metabolic disorders. While prolonged cold exposure promotes de novo recruitment of brown adipocytes, the exact sources of cold-induced thermogenic adipocytes are not completely understood. Here, we identify transient receptor potential cation channel subfamily V member 1 (Trpv1)+ vascular smooth muscle (VSM) cells as previously unidentified thermogenic adipocyte progenitors. Single-cell RNA sequencing analysis of interscapular brown adipose depots reveals, in addition to the previously known platelet-derived growth factor receptor (Pdgfr)α-expressing mesenchymal progenitors, a population of VSM-derived adipocyte progenitor cells (VSM-APC) expressing the temperature-sensitive cation channel Trpv1. We demonstrate that cold exposure induces the proliferation of Trpv1+ VSM-APCs and enahnces their differentiation to highly thermogenic adipocytes. Together, these findings illustrate the landscape of the thermogenic adipose niche at single-cell resolution and identify a new cellular origin for the development of brown and beige adipocytes.

Brown Fat-Activating Lipokine 12,13-diHOME in Human Milk Is Associated With Infant Adiposity.

CONTEXT: Little is known about the specific breastmilk components responsible for protective effects on infant obesity. Whether 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME), an oxidized linoleic acid metabolite and activator of brown fat metabolism, is present in human milk, or linked to infant adiposity, is unknown. OBJECTIVE: To examine associations between concentrations of 12,13-diHOME in human milk and infant adiposity. DESIGN: Prospective cohort study from 2015 to 2019, following participants from birth to 6 months of age. SETTING: Academic medical centers. PARTICIPANTS: Volunteer sample of 58 exclusively breastfeeding mother-infant pairs; exclusion criteria included smoking, gestational diabetes, and health conditions with the potential to influence maternal or infant weight gain. MAIN OUTCOME MEASURES: Infant anthropometric measures including weight, length, body mass index (BMI), and body composition at birth and at 1, 3, and 6 months postpartum. RESULTS: We report for the first time that 12,13-diHOME is present in human milk. Higher milk 12,13-diHOME level was associated with increased weight-for-length Z-score at birth (ß = 0.5742, P = 0.0008), lower infant fat mass at 1 month (P = 0.021), and reduced gain in BMI Z-score from 0 to 6 months (ß = -0.3997, P = 0.025). We observed similar associations between infant adiposity and milk abundance of related oxidized linoleic acid metabolites 12,13-Epoxy-9(Z)-octadecenoic acid (12,13-epOME) and 9,10-Dihydroxy-12-octadecenoic acid (9,10-diHOME), and metabolites linked to thermogenesis including succinate and lyso-phosphatidylglycerol 18:0. Milk abundance of 12,13-diHOME was not associated with maternal BMI, but was positively associated with maternal height, milk glucose concentration, and was significantly increased after a bout of moderate exercise. CONCLUSIONS: We report novel associations between milk abundance of 12,13-diHOME and adiposity during infancy.

FGF6 and FGF9 regulate UCP1 expression independent of brown adipogenesis.

Uncoupling protein-1 (UCP1) plays a central role in energy dissipation in brown adipose tissue (BAT). Using high-throughput library screening of secreted peptides, we identify two fibroblast growth factors (FGF), FGF6 and FGF9, as potent inducers of UCP1 expression in adipocytes and preadipocytes. Surprisingly, this occurs through a mechanism independent of adipogenesis and involves FGF receptor-3 (FGFR3), prostaglandin-E2 and interaction between estrogen receptor-related alpha, flightless-1 (FLII) and leucine-rich-repeat-(in FLII)-interacting-protein-1 as a regulatory complex for UCP1 transcription. Physiologically, FGF6/9 expression in adipose is upregulated by exercise and cold in mice, and FGF9/FGFR3 expression in human neck fat is significantly associated with UCP1 expression. Loss of FGF9 impairs BAT thermogenesis. In vivo administration of FGF9 increases UCP1 expression and thermogenic capacity. Thus, FGF6 and FGF9 are adipokines that can regulate UCP1 through a transcriptional network that is dissociated from brown adipogenesis, and act to modulate systemic energy metabolism.

TGF-ß2 is an exercise-induced adipokine that regulates glucose and fatty acid metabolism.

Exercise improves health and well-being across diverse organ systems, and elucidating mechanisms underlying the beneficial effects of exercise can lead to new therapies. Here, we show that transforming growth factor-ß2 (TGF-ß2) is secreted from adipose tissue in response to exercise and improves glucose tolerance in mice. We identify TGF-ß2 as an exercise-induced adipokine in a gene expression analysis of human subcutaneous adipose tissue biopsies after exercise training. In mice, exercise training increases TGF-ß2 in scWAT, serum, and its secretion from fat explants. Transplanting scWAT from exercise-trained wild type mice, but not from adipose tissue-specific Tgfb2-/- mice, into sedentary mice improves glucose tolerance. TGF-ß2 treatment reverses the detrimental metabolic effects of high fat feeding in mice. Lactate, a metabolite released from muscle during exercise, stimulates TGF-ß2 expression in human adipocytes. Administration of the lactate-lowering agent dichloroacetate during exercise training in mice decreases circulating TGF-ß2 levels and reduces exercise-stimulated improvements in glucose tolerance. Thus, exercise training improves systemic metabolism through inter-organ communication with fat via a lactate-TGF-ß2-signaling cycle.

Deciphering adipose tissue heterogeneity.

Obesity is an excess accumulation of adipose tissue mass, and, together with its sequelae, in particular type II diabetes and metabolic syndrome, obesity presents a major health crisis. Although obesity is simply caused by increased adipose mass, the heterogeneity of adipose tissue in humans means that the response to increased energy balance is highly complex. Individual subjects with similar phenotypes may respond very differently to the same treatments; therefore, obesity may benefit from a personalized precision medicine approach. The variability in the development of obesity is indeed driven by differences in sex, genetics, and environment, but also by the various types of adipose tissue as well as the different cell types that compose it. By describing the distinct cell populations that reside in different fat depots, we can interpret the complex effect of these various players in the maintenance of whole-body energy homeostasis. To further understand adipose tissue, adipogenic differentiation and the transcriptional program of lipid accumulation must be investigated. As the cell- and depot-specific functions are described, they can be placed in the context of energy excess to understand how the heterogeneity of adipose tissue shapes individual metabolic status and condition.

Loss of BMP receptor type 1A in murine adipose tissue attenuates age-related onset of insulin resistance.

AIMS/HYPOTHESIS: Adipose tissue dysfunction is a prime risk factor for the development of metabolic disease. Bone morphogenetic proteins (BMPs) have previously been implicated in adipocyte formation. Here, we investigate the role of BMP signalling in adipose tissue health and systemic glucose homeostasis. METHODS: We employed the Cre/loxP system to generate mouse models with conditional ablation of BMP receptor 1A in differentiating and mature adipocytes, as well as tissue-resident myeloid cells. Metabolic variables were assessed by glucose and insulin tolerance testing, insulin-stimulated glucose uptake and gene expression analysis. RESULTS: Conditional deletion of Bmpr1a using the aP2 (also known as Fabp4)-Cre strain resulted in a complex phenotype. Knockout mice were clearly resistant to age-related impairment of insulin sensitivity during normal and high-fat-diet feeding and showed significantly improved insulin-stimulated glucose uptake in brown adipose tissue and skeletal muscle. Moreover, knockouts displayed significant reduction of variables of adipose tissue inflammation. Deletion of Bmpr1a in myeloid cells had no impact on insulin sensitivity, while ablation of Bmpr1a in mature adipocytes partially recapitulated the initial phenotype from aP2-Cre driven deletion. Co-cultivation of macrophages with pre-adipocytes lacking Bmpr1a markedly reduced expression of proinflammatory genes. CONCLUSIONS/INTERPRETATION: Our findings show that altered BMP signalling in adipose tissue affects the tissue's metabolic properties and systemic insulin resistance by altering the pattern of immune cell infiltration. The phenotype is due to ablation of Bmpr1a specifically in pre-adipocytes and maturing adipocytes rather than an immune cell-autonomous effect. Mechanistically, we provide evidence for a BMP-mediated direct crosstalk between pre-adipocytes and macrophages.

Isolation of progenitors that exhibit myogenic/osteogenic bipotency in vitro by fluorescence-activated cell sorting from human fetal muscle.

Fluorescence-activated cell sorting (FACS) strategies to purify distinct cell types from the pool of fetal human myofiber-associated (hMFA) cells were developed. We demonstrate that cells expressing the satellite cell marker PAX7 are highly enriched within the subset of CD45(-)CD11b(-)GlyA(-)CD31(-)CD34(-)CD56(int)ITGA7(hi) hMFA cells. These CD45(-)CD11b(-)GlyA(-)CD31(-)CD34(-)CD56(int)ITGA7(hi) cells lack adipogenic capacity but exhibit robust, bipotent myogenic and osteogenic activity in vitro and engraft myofibers when transplanted into mouse muscle. In contrast, CD45(-)CD11b(-)GlyA(-)CD31(-)CD34(+) fetal hMFA cells represent stromal constituents of muscle that do not express PAX7, lack myogenic function, and exhibit adipogenic and osteogenic capacity in vitro. Adult muscle likewise contains PAX7(+) CD45(-)CD11b(-)GlyA(-)CD31(-)CD34(-)CD56(int)ITGA7(hi) hMFA cells with in vitro myogenic and osteogenic activity, although these cells are present at lower frequency in comparison to their fetal counterparts. The ability to directly isolate functionally distinct progenitor cells from human muscle will enable novel insights into muscle lineage specification and homeostasis.

Increased mitochondrial activity in BMP7-treated brown adipocytes, due to increased CPT1- and CD36-mediated fatty acid uptake.

AIMS: Brown adipose tissue dissipates chemical energy in the form of heat and regulates triglyceride and glucose metabolism in the body. Factors that regulate fatty acid uptake and oxidation in brown adipocytes have not yet been fully elucidated. Bone morphogenetic protein 7 (BMP7) is a growth factor capable of inducing brown fat mitochondrial biogenesis during differentiation from adipocyte progenitors. Administration of BMP7 to mice also results in increased energy expenditure. To determine if BMP7 is able to affect the mitochondrial activity of mature brown adipocytes, independent of the differentiation process, we delivered BMP7 to mature brown adipocytes and measured mitochondrial activity. RESULTS: We found that BMP7 increased mitochondrial activity, including fatty acid oxidation and citrate synthase activity, without increasing the mitochondrial number. This was accompanied by an increase in fatty acid uptake and increased protein expression of CPT1 and CD36, which import fatty acids into the mitochondria and the cell, respectively. Importantly, inhibition of either CPT1 or CD36 resulted in a blunting of the mitochondrial activity of BMP7-treated cells. INNOVATION: These findings uncover a novel pathway regulating mitochondrial activities in mature brown adipocytes by BMP7-mediated fatty acid uptake and oxidation. CONCLUSION: In conclusion, BMP7 increases mitochondrial activity in mature brown adipocytes via increased fatty acid uptake and oxidation, a process that requires the fatty acid transporters CPT1 and CD36.

Gene profiling of scleroderma skin reveals robust signatures of disease that are imperfectly reflected in the transcript profiles of explanted fibroblasts.

OBJECTIVE: To determine whether biopsy specimens obtained from systemic sclerosis (SSc) lesions show a distinctive gene profile, whether that gene profile is maintained in fibroblasts cultured from SSc skin biopsy specimens, and whether results from tissue obtained from multiple clinical centers can be combined to yield useful observations in this rare disease. METHODS: Biopsy samples and passaged fibroblasts were stored in RNAlater solution prior to processing for RNA. RNA from SSc and control skin biopsy specimens, as well as SSc and control explanted passage 4 fibroblasts, from 9 patients and 9 controls was hybridized to Affymetrix HG-U133A arrays. Data were analyzed using the BRB ArrayTools system. When appropriate, findings were followed up with immunohistochemical analysis or TaqMan studies. RESULTS: Biopsy samples obtained from patients with SSc had a robust and distinctive gene profile, with approximately 1,800 qualifiers distinguishing normal skin from SSc skin at a significant level. The SSc phenotype was the major driver of sample clusters, independent of origin. Alterations in transforming growth factor beta and Wnt pathways, extracellular matrix proteins, and the CCN family were prominent. Explanted fibroblasts from SSc biopsy samples showed a far smaller subset of changes that were relatively variable between samples, suggesting that either nonfibroblast cell types or other aspects of the dermal milieu are required for full expression of the SSc phenotype. CONCLUSION: SSc has a distinct gene profile that is not confounded by geographic location, indicating that extended multicenter studies may be worthwhile to identify distinct subsets of disease by transcript profiling. Explanted SSc fibroblasts show an incomplete reflection of the SSc phenotype.