MitoNEET-driven alterations in adipocyte mitochondrial activity reveal a crucial adaptive process that preserves insulin sensitivity in obesity. Nat Med. 2012;18:1539-1549. [PMID: 22961109 DOI: 10.1038/nm.2899]

Afadin is a scaffold protein repressing insulin action via HDAC6 in adipose tissue

Insulin orchestrates metabolic homeostasis through a complex signaling network for which the precise mechanisms controlling its fine-tuning are not completely understood. Here, we report that Afadin, a scaffold protein, is phosphorylated on S1795 (S1718 in humans) in response to insulin in adipocytes, and this phosphorylation is impaired with obesity and insulin resistance. In turn, loss of Afadin enhances the response to insulin in adipose tissues via upregulation of the insulin receptor protein levels. This happens in a cell-autonomous and phosphorylation-dependent manner. Insulin-stimulated Afadin-S1795 phosphorylation modulates Afadin binding with interaction partners in adipocytes, among which HDAC6 preferentially interacts with phosphorylated Afadin and acts as a key intermediate to suppress insulin receptor protein levels. Adipose tissue-specific Afadin depletion protects against insulin resistance and improves glucose homeostasis in diet-induced obese mice, independently of adiposity. Altogether, we uncover a novel insulin-induced cellular feedback mechanism governed by the interaction of Afadin with HDAC6 to negatively control insulin action in adipocytes, which may offer new strategies to alleviate insulin resistance.

Impaired skeletal muscle mitochondrial pyruvate uptake rewires glucose metabolism to drive whole-body leanness

Metabolic cycles are a fundamental element of cellular and organismal function. Among the most critical in higher organisms is the Cori Cycle, the systemic cycling between lactate and glucose. Here, skeletal muscle-specific Mitochondrial Pyruvate Carrier (MPC) deletion in mice diverted pyruvate into circulating lactate. This switch disinhibited muscle fatty acid oxidation and drove Cori Cycling that contributed to increased energy expenditure. Loss of muscle MPC activity led to strikingly decreased adiposity with complete muscle mass and strength retention. Notably, despite decreasing muscle glucose oxidation, muscle MPC disruption increased muscle glucose uptake and whole-body insulin sensitivity. Furthermore, chronic and acute muscle MPC deletion accelerated fat mass loss on a normal diet after high fat diet-induced obesity. Our results illuminate the role of the skeletal muscle MPC as a whole-body carbon flux control point. They highlight the potential utility of modulating muscle pyruvate utilization to ameliorate obesity and type 2 diabetes.

Crystal structure of the mitochondrial protein mitoNEET bound to a benze-sulfonide ligand

MitoNEET (gene cisd1) is a mitochondrial outer membrane [2Fe-2S] protein and is a potential drug target in several metabolic diseases. Previous studies have demonstrated that mitoNEET functions as a redox-active and pH-sensing protein that regulates mitochondrial metabolism, although the structural basis of the potential drug binding site(s) remains elusive. Here we report the crystal structure of the soluble domain of human mitoNEET with a sulfonamide ligand, furosemide. Exploration of the high-resolution crystal structure is used to design mitoNEET binding molecules in a pilot study of molecular probes for use in future development of mitochondrial targeted therapies for a wide variety of metabolic diseases, including obesity, diabetes and neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease.

Immune Cells Gate White Adipose Tissue Expansion

The immune system plays a critical role in white adipose tissue (WAT) energy homeostasis and, by extension, whole-body metabolism. Substantial evidence from mouse and human studies firmly establishes that insulin sensitivity deteriorates as a result of subclinical inflammation in the adipose tissue of individuals with diabetes. However, the relationship between adipose tissue expandability and immune cell infiltration remains a complex problem important for understanding the pathogenesis of obesity. Notably, a large body of work challenges the idea that all immune responses are deleterious to WAT function. This review highlights recent advances that describe how immune cells and adipocytes coordinately enable WAT expansion and regulation of energy homeostasis.

Environmental and Nutritional Effects Regulating Adipose Tissue Function and Metabolism Across Generations

The unabated rise in obesity prevalence during the last 40 years has spurred substantial interest in understanding the reasons for this epidemic. Studies in mice and humans have demonstrated that obesity is a highly heritable disease; however genetic variations within specific populations have so far not been able to explain this phenomenon to its full extent. Recent work has demonstrated that environmental cues can be sensed by an organism to elicit lasting changes, which in turn can affect systemic energy metabolism by different epigenetic mechanisms such as changes in small noncoding RNA expression, DNA methylation patterns, as well as histone modifications. These changes can directly modulate cellular function in response to environmental cues, however research during the last decade has demonstrated that some of these modifications might be transmitted to subsequent generations, thus modulating energy metabolism of the progeny in an inter- as well as transgenerational manner. In this context, adipose tissue has become a focus of research due to its plasticity, which allows the formation of energy storing (white) as well as energy wasting (brown/brite/beige) cells within the same depot. In this Review, the effects of environmental induced obesity with a particular focus on adipose tissue are discussed.

Glucagon Receptor Antagonism Improves Glucose Metabolism and Cardiac Function by Promoting AMP-Mediated Protein Kinase in Diabetic Mice

The antidiabetic potential of glucagon receptor antagonism presents an opportunity for use in an insulin-centric clinical environment. To investigate the metabolic effects of glucagon receptor antagonism in type 2 diabetes, we treated Lepr^db/db and Lep^ob/ob mice with REMD 2.59, a human monoclonal antibody and competitive antagonist of the glucagon receptor. As expected, REMD 2.59 suppresses hepatic glucose production and improves glycemia. Surprisingly, it also enhances insulin action in both liver and skeletal muscle, coinciding with an increase in AMP-activated protein kinase (AMPK)-mediated lipid oxidation. Furthermore, weekly REMD 2.59 treatment over a period of months protects against diabetic cardiomyopathy. These functional improvements are not derived simply from correcting the systemic milieu; nondiabetic mice with cardiac-specific overexpression of lipoprotein lipase also show improvements in contractile function after REMD 2.59 treatment. These observations suggest that hyperglucagonemia enables lipotoxic conditions, allowing the development of insulin resistance and cardiac dysfunction during disease progression.

GABA-stimulated adipose-derived stem cells suppress subcutaneous adipose inflammation in obesity

Accumulating evidence suggests that subcutaneous and visceral adipose tissues are differentially associated with metabolic disorders. In obesity, subcutaneous adipose tissue is beneficial for metabolic homeostasis because of repressed inflammation. However, the underlying mechanism remains unclear. Here, we demonstrate that γ-aminobutyric acid (GABA) sensitivity is crucial in determining fat depot-selective adipose tissue macrophage (ATM) infiltration in obesity. In diet-induced obesity, GABA reduced monocyte migration in subcutaneous inguinal adipose tissue (IAT), but not in visceral epididymal adipose tissue (EAT). Pharmacological modulation of the GABA_B receptor affected the levels of ATM infiltration and adipose tissue inflammation in IAT, but not in EAT, and GABA administration ameliorated systemic insulin resistance and enhanced insulin-dependent glucose uptake in IAT, accompanied by lower inflammatory responses. Intriguingly, compared with adipose-derived stem cells (ADSCs) from EAT, IAT-ADSCs played key roles in mediating GABA responses that repressed ATM infiltration in high-fat diet-fed mice. These data suggest that selective GABA responses in IAT contribute to fat depot-selective suppression of inflammatory responses and protection from insulin resistance in obesity.

Prohibitin: a prime candidate for a pleiotropic effector that mediates sex differences in obesity, insulin resistance, and metabolic dysregulation

Adipocytes and macrophages, the two major constituents of adipose tissue, exhibit sex differences and work in synergy in adipose tissue physiology and pathophysiology, including obesity-linked insulin resistance and metabolic dysregulation. Sex steroid hormones play a major role in sex differences in adipose tissue biology. However, our knowledge of the molecules that mediate these effects in adipose tissue remains limited. Consequently, it remains unclear whether these effector molecules in different adipose and immune cell types are distinct or if there are also pleiotropic effectors. Recently, a protein named prohibitin (PHB) with cell compartment- and tissue-specific functions has been found to play a role in sex differences in adipose and immune functions. Transgenic (Tg) mouse models overexpressing PHB (PHB-Tg) and a phospho-mutant PHB (mPHB-Tg) from the fatty acid binding protein-4 (Fabp-4) gene promoter display sex-neutral obesity; however, obesity-related insulin resistance and metabolic dysregulation are male-specific. Intriguingly, with aging, the male PHB-Tg mice developed hepatic steatosis and subsequently liver tumors whereas the male mPHB-Tg mice developed lymph node tumors and splenomegaly. Unlike the male transgenic mice, the female PHB-Tg and mPHB-Tg mice remain protected from obesity-related metabolic dysregulation and tumor development. In conclusion, the sex-dimorphic metabolic and immune phenotypes of PHB-Tg and mPHB-Tg mice have revealed PHB as a pleiotropic effector of sex differences in adipose and immune functions. In this mini-review, we will discuss the pleiotropic attributes of PHB and potential mechanisms that may have contributed to the sex-dimorphic metabolic phenotypes in PHB-Tg and mPHB-Tg mice, which warrant future research. We propose that PHB is a prime candidate for a pleiotropic mediator of sex differences in adipose and immune functions in both physiology and pathophysiology, including obesity, insulin resistance, and metabolic dysregulation.

Quantitative Proteomics of Presynaptic Mitochondria Reveal an Overexpression and Biological Relevance of Neuronal MitoNEET in Postnatal Brain Development

Although it has been recognized that energy metabolism and mitochondrial structure and functional activity in the immature brain differs from that of the adult, few studies have examined mitochondria specifically at the neuronal synapse during postnatal brain development. In this study, we examined the presynaptic mitochondrial proteome in mice at postnatal day 7 and 42, a period that involves the formation and maturation of synapses. Application of two independent quantitative proteomics approaches - SWATH-MS and super-SILAC - revealed a total of 40 proteins as significantly differentially expressed in the presynaptic mitochondria. In addition to elevated levels of proteins known to be involved in ATP metabolic processes, our results identified increased levels of mitoNEET (Cisd1), an iron-sulfur containing protein that regulates mitochondrial bioenergetics. We found that mitoNEET overexpression plays a cell-type specific role in ATP synthesis and in neuronal cells promotes ATP generation. The elevated ATP levels in SH-SY5Y neuroblastoma cells were associated with increased mitochondrial membrane potential and a fragmented mitochondrial network, further supporting a role for mitoNEET as a key regulator of mitochondrial function.

The Antioxidant Moiety of MitoQ Imparts Minimal Metabolic Effects in Adipose Tissue of High Fat Fed Mice

Mitochondrial dysfunction is associated with a diverse array of diseases ranging from dystrophy and heart failure to obesity and hepatosteatosis. One of the major biochemical consequences of impaired mitochondrial function is an accumulation of mitochondrial superoxide, or reactive oxygen species (ROS). Excessive ROS can be detrimental to cellular health and is proposed to underpin many mitochondrial diseases. Accordingly, much research has been committed to understanding ways to therapeutically prevent and reduce ROS accumulation. In white adipose tissue (WAT), ROS is associated with obesity and its subsequent complications, and thus reducing mitochondrial ROS may represent a novel strategy for treating obesity related disorders. One therapeutic approach employed to reduce ROS abundance is the mitochondrial-targeted coenzyme Q (MitoQ), which enables mitochondrial specific delivery of a CoQ10 antioxidant via its triphenylphosphonium bromide (TPP+) cation. Indeed, MitoQ has been successfully shown to accumulate at the outer mitochondrial membrane and prevent ROS accumulation in several tissues in vivo; however, the specific effects of MitoQ on adipose tissue metabolism in vivo have not been studied. Here we demonstrate that mice fed high-fat diet with concomitant administration of MitoQ, exhibit minimal metabolic benefit in adipose tissue. We also demonstrate that both MitoQ and its control agent dTPP+ had significant and equivalent effects on whole-body metabolism, suggesting that the dTPP+ cation rather than the antioxidant moiety, was responsible for these changes. These findings have important implications for future studies using MitoQ and other TPP+ compounds.

MitoNEET in Perivascular Adipose Tissue Prevents Arterial Stiffness in Aging Mice

PURPOSE

Arterial stiffness is an inevitable consequence of the aging process and is considered an early stage in the development of cardiovascular diseases. The perivascular adipose tissue (PVAT) is a distinct functional integral layer of the vasculature actively involved in blood pressure regulation and atherosclerosis development via PVAT-derived paracrine/autocrine factors. However, there is little knowledge regarding the relationship between PVAT and arterial stiffness.

METHODS

Using unique mice lacking PVAT, high-fat diet-induced obesity, and in mice overexpressing brown adipocyte selective mitoNEET, we investigated the relationship between PVAT and arterial stiffness in mice.

RESULTS

We found that lack of PVAT enhanced arterial stiffness in aging mice. High-fat diet feeding of aging C57BL/6J wild-type mice significantly induced hypertrophic PVAT and enhanced arterial stiffness. Furthermore, the expression of mitoNEET, a mitochondrial membrane protein related to energy expenditure, was significantly increased by pioglitazone treatment, while reduced in the hypertrophic PVAT induced by high-fat diet. Overexpression of mitoNEET in PVAT reduced the expression of inflammatory genes and was associated with lower pulse wave velocity in aging mice.

CONCLUSIONS

These data indicate that local PVAT homeostasis especially inflammation in PVAT is associated with arterial stiffness development. Pioglitazone-induced mitoNEET in PVAT prevents PVAT inflammation and is negatively associated with arterial stiffness. These findings provide new experimental insight into the roles of pioglitazone on PVAT in arterial stiffness and indicate that PVAT might be a target to treat or prevent cardiovascular disease.

Adipose-derived stromal/stem cells from different adipose depots in obesity development

The increasing prevalence of obesity is alarming because it is a risk factor for cardiovascular and metabolic diseases (such as type 2 diabetes). The occurrence of these comorbidities in obese patients can arise from white adipose tissue (WAT) dysfunctions, which affect metabolism, insulin sensitivity and promote local and systemic inflammation. In mammals, WAT depots at different anatomical locations (subcutaneous, preperitoneal and visceral) are highly heterogeneous in their morpho-phenotypic profiles and contribute differently to homeostasis and obesity development, depending on their ability to trigger and modulate WAT inflammation. This heterogeneity is likely due to the differential behavior of cells from each depot. Numerous studies suggest that adipose-derived stem/stromal cells (ASC; referred to as adipose progenitor cells, in vivo) with depot-specific gene expression profiles and adipogenic and immunomodulatory potentials are keys for the establishment of the morpho-functional heterogeneity between WAT depots, as well as for the development of depot-specific responses to metabolic challenges. In this review, we discuss depot-specific ASC properties and how they can contribute to the pathophysiology of obesity and metabolic disorders, to provide guidance for researchers and clinicians in the development of ASC-based therapeutic approaches.

NEET Proteins: A New Link Between Iron Metabolism, Reactive Oxygen Species, and Cancer

SIGNIFICANCE

Cancer cells accumulate high levels of iron and reactive oxygen species (ROS) to promote their high metabolic activity and proliferation rate. However, high levels of iron and ROS can also lead to enhanced oxidative stress and the activation of cell death pathways such as apoptosis and ferroptosis. This has led to the proposal that different drugs that target iron and/or ROS metabolism could be used as anticancer drugs. However, due to the complex role iron and ROS play in cells, the majority of these drugs yielded mixed results, highlighting a critical need to identify new players in the regulation of iron and ROS homeostasis in cancer cells. Recent Advances: NEET proteins belong to a newly discovered class of iron-sulfur proteins (2Fe-2S) required for the regulation of iron and ROS homeostasis in cells. Recent studies revealed that the NEET proteins NAF-1 (CISD2) and mitoNEET (CISD1) play a critical role in promoting the proliferation of cancer cells, supporting tumor growth and metastasis. Moreover, the function of NEET proteins in cancer cells was found to be dependent of the degree of lability of their 2Fe-2S clusters.

CRITICAL ISSUES

NEET proteins could represent a key regulatory link between the maintenance of high iron and ROS in cancer cells, the activation of cell death and survival pathways, and cellular proliferation.

FUTURE DIRECTIONS

Because the function of NEET proteins depends on the lability of their clusters, drugs that target the 2Fe2S clusters of NEET proteins could be used as promising anticancer drugs.

Adipocyte GR Inhibits Healthy Adipose Expansion Through Multiple Mechanisms in Cushing Syndrome

In Cushing syndrome, excessive glucocorticoids lead to metabolic disturbances, such as insulin resistance, adipocyte hypertrophy, and liver steatosis. In vitro experiments have highlighted the importance of adipocyte glucocorticoid receptor (GR), but its metabolic roles in vivo have not been fully elucidated in Cushing syndrome. In this study, using clinical samples from patients with Cushing syndrome and adipocyte-specific GR knockout (AGRKO) mice, we investigated the roles of adipocyte GR and its clinical relevance in Cushing syndrome. Under chronic treatment with corticosterone, AGRKO mice underwent healthy adipose expansion with diminished ectopic lipid deposition and improved insulin sensitivity. These changes were associated with Atgl-mediated lipolysis through a novel intronic glucocorticoid-responsive element. Additionally, integrated analysis with RNA sequencing of AGRKO mice and clinical samples revealed that healthy adipose expansion was associated with dysregulation of tissue remodeling, preadipocyte proliferation, and expression of the circadian gene. Thus, our study revealed the roles of adipocyte GR on healthy adipose expansion and its multiple mechanisms in Cushing syndrome.

Metabolically healthy versus metabolically unhealthy obesity

Obesity-related disease complications reduce life quality and expectancy and increase health-care costs. Some studies have suggested that obesity not always entails metabolic abnormalities and increased risk of cardiometabolic complications. Because of the lack of universally accepted criteria to identify metabolically healthy obesity (MHO), its prevalence varies widely among studies. Moreover, the prognostic value of MHO is hotly debated, mainly because it likely shifts gradually towards metabolically unhealthy obesity (MUO). In this review, we outline the differential factors contributing to the metabolic heterogeneity of obesity by discussing the behavioral, genetic, phenotypical, and biological aspects associated with each of the two metabolic phenotypes (MHO and MUO) of obesity and their clinical implications. Particular emphasis will be laid on the role of adipose tissue biology and function, including genetic determinants of body fat distribution, depot-specific fat metabolism, adipose tissue plasticity and, particularly, adipogenesis. Finally, the emerging role of gut microbiota in obesity and adipose tissue dysfunction as well as the search for novel biomarkers for the obesity-related metabolic traits and associated diseases will be briefly presented. A better understanding of the main determinants of a healthy metabolic status in obesity would allow promotion of this favorable condition by targeting the relevant pathways.

Metabolic Messengers: Adiponectin

Adiponectin is one of the most widely studied adipokines to date. First described in the mid-1990's, studying its regulation, biogenesis and physiological effects has proven to be extremely insightful and improved our understanding of the mechanisms that ensure systemic metabolic homeostasis. Here, we provide a brief overview of the current state of the field with respect to adiponectin, its history, sites and mechanisms of action, and the critical questions that will need to be addressed in the future.

Adipose Tissue Expansion by Overfeeding Healthy Men Alters Iron Gene Expression

CONTEXT

Iron overload has been associated with greater adipose tissue (AT) depots. We retrospectively studied the potential interactions between iron and AT during an experimental overfeeding in participants without obesity.

METHODS

Twenty-six participants (mean body mass index ± SD, 24.7 ± 3.1 kg/m2) underwent a 56-day overfeeding (+760 kcal/d). Serum iron biomarkers (ELISA), subcutaneous AT (SAT) gene expression, and abdominal AT distribution assessed by MRI were analyzed at the beginning and the end of the intervention.

RESULTS

Before intervention: SAT mRNA expression of the iron transporter transferrin (Tf) was positively correlated with the expression of genes related to lipogenesis (lipin 1, ACSL1) and lipid storage (SCD). SAT expression of the ferritin light chain (FTL) gene, encoding ferritin (FT), an intracellular iron storage protein, was negatively correlated to SREBF1, a gene related to lipogenesis. Serum FT (mean, 92 ± 57 ng/mL) was negatively correlated with the expression of SAT genes linked to lipid storage (SCD, DGAT2) and to lipogenesis (SREBF1, ACSL1). After intervention: Overfeeding led to a 2.3 ± 1.3-kg weight gain. In parallel to increased expression of lipid storage-related genes (mitoNEET, SCD, DGAT2, SREBF1), SAT Tf, SLC40A1 (encoding ferroportin 1, a membrane iron export channel) and hephaestin mRNA levels increased, whereas SAT FTL mRNA decreased, suggesting increased AT iron requirement. Serum FT decreased to 67 ± 43 ng/mL. However, no significant associations between serum iron biomarkers and AT distribution or expansion were observed.

CONCLUSION

In healthy men, iron metabolism gene expression in SAT is associated with lipid storage and lipogenesis genes expression and is modulated during a 56-day overfeeding diet.

Prohibitin: A hypothetical target for sex-based new therapeutics for metabolic and immune diseases

IMPACT STATEMENT

Traditional sex-related biases in research are now obsolete, and it is important to identify the sex of humans, animals, and even cells in research protocols, due to the role of sex as a fundamental facet of biology, predisposition to disease, and response to therapy. Genetic sex, epigenetics and hormonal regulations, generate sex-dimorphisms. Recent investigations acknowledge sex differences in metabolic and immune health as well as chronic diseases. Prohibitin, an evolutionarily conserved molecule, has pleotropic functions in mitochondrial housekeeping, plasma membrane signaling, and nuclear genetic transcription. Studies in adipocytes, macrophages, and transgenic mice indicate that prohibitin interacts with sex steroids and plays a role in mediating sex differences in adipose tissues and immune cell types. Prohibitin may, depending on context, modulate predisposition to chronic metabolic diseases and malignancy and, because of these attributes, could be a target for sex-based therapies of metabolic and immune-related diseases as well as cancer.

Metabolic adaptation and maladaptation in adipose tissue

Adipose tissue possesses the remarkable capacity to control its size and function in response to a variety of internal and external cues, such as nutritional status and temperature. The regulatory circuits of fuel storage and oxidation in white adipocytes and thermogenic adipocytes (brown and beige adipocytes) play a central role in systemic energy homeostasis, whereas dysregulation of the pathways is closely associated with metabolic disorders and adipose tissue malfunction, including obesity, insulin resistance, chronic inflammation, mitochondrial dysfunction, and fibrosis. Recent studies have uncovered new regulatory elements that control the above parameters and provide new mechanistic opportunities to reprogram fat cell fate and function. In this Review, we provide an overview of the current understanding of adipocyte metabolism in physiology and disease and also discuss possible strategies to alter fuel utilization in fat cells to improve metabolic health.

The E3 ligase MARCH5 is a PPARγ target gene that regulates mitochondria and metabolism in adipocytes

Mitochondrial dynamics refers to the constant remodeling of mitochondrial populations by multiple cellular pathways that help maintain mitochondrial health and function. Disruptions in mitochondrial dynamics often lead to mitochondrial dysfunction, which is frequently associated with disease in rodents and humans. Consistent with this, obesity is associated with reduced mitochondrial function in white adipose tissue, partly via alterations in mitochondrial dynamics. Several proteins, including the E3 ubiquitin ligase membrane-associated RING-CH-type finger 5 (MARCH5), are known to regulate mitochondrial dynamics; however, the role of these proteins in adipocytes has been poorly studied. Here, we show that MARCH5 is regulated by peroxisome proliferator-activated receptor-γ (PPARγ) during adipogenesis and is correlated with fat mass across a panel of genetically diverse mouse strains, in ob/ob mice, and in humans. Furthermore, manipulation of MARCH5 expression in vitro and in vivo alters mitochondrial function, affects cellular metabolism, and leads to differential regulation of several metabolic genes. Thus our data demonstrate an association between mitochondrial dynamics and metabolism that defines MARCH5 as a critical link between these interconnected pathways.

The many secret lives of adipocytes: implications for diabetes

Adipose tissue remains a cryptic organ. The ubiquitous presence of adipocytes, the different fat pads in distinct anatomical locations, the many different types of fat, in each case with their distinct precursor populations, and the ability to interchange into other types of fat cells or even de-differentiate altogether, offers a staggering amount of complexity to the adipose tissue organ as a whole. Adipose tissue holds the key to improving our understanding of systemic metabolic homeostasis. As such, understanding adipose tissue physiology offers the basis for a mechanistic understanding of the pathophysiology of diabetes. This review presents some of the lesser known aspects of this fascinating tissue, which consistently still offers much opportunity for the discovery of novel targets for pharmacological intervention.

Isoliquiritigenin Induces Mitochondrial Dysfunction and Apoptosis by Inhibiting mitoNEET in a Reactive Oxygen Species-Dependent Manner in A375 Human Melanoma Cells

The mitochondrial protein mitoNEET is a type of iron-sulfur protein localized to the outer membrane of mitochondria and is involved in a variety of human pathologies including cystic fibrosis, diabetes, muscle atrophy, and neurodegeneration. In the current study, we found that isoliquiritigenin (ISL), one of the components of the root of Glycyrrhiza glabra L., could decrease the expression of mitoNEET in A375 melanoma cells. We also demonstrated that mitoNEET could regulate the content of reactive oxygen species (ROS), by showing that the ISL-mediated increase in the cellular ROS content could be mitigated by the mitoNEET overexpression. We also confirmed the important role of ROS in ISL-treated A375 cells. The increased apoptosis rate and the decreased mitochondrial membrane potential were mitigated by the overexpression of mitoNEET in A375 cells. These findings indicated that ISL could decrease the expression of mitoNEET, which regulated ROS content and subsequently induced mitochondrial dysfunction and apoptosis in A375 cells. Our findings also highlight mitoNEET as a promising mitochondrial target for cancer therapy.

Irisin: A Hope in Understanding and Managing Obesity and Metabolic Syndrome

White adipose tissue (WAT) is an endocrine organ highly integrated in homeostasis and capable of establishing ways of communicating and influencing multiple metabolic processes. Brown adipose tissue promotes energy expenditure by incorporating the uncoupling protein 1 (UCP1), also known as thermogenin, which decouples cellular respiration and heat production, in the mitochondrial membranes. Recent data suggest the presence of a thermogenic cell formation from white adipocytes (beige or brite cells) with a potential role in preventing obesity and metabolic syndrome. The formation of these cells is influenced by physical exertion that induces expression of PPARγ coactivator-1 (PGC1) and downstream membrane protein, fibronectin type III domain-containing protein 5 (FNDC5) in skeletal muscle. Irisin, a thermogenic adipomyokine produced by FNDC5 cleavage is involved in the browning of adipose tissue. While animal studies are congruent with regard to the relationship between physical exertion and irisin release, the results from human studies are less than clear. Therefore, this review focuses on recent advances in our understanding of muscle and adipose tissue thermogenesis. Further, it describes the molecular mechanisms by which irisin impacts exercise, glucose homeostasis and obesity. Finally, the review discusses current gaps and controversies related to irisin release, its mode of action and its future potential as a therapeutic tool in managing obesity and metabolic syndrome.

Knockdown of Ant2 Reduces Adipocyte Hypoxia And Improves Insulin Resistance in Obesity

Decreased adipose tissue oxygen tension and increased HIF-1α expression can trigger adipose tissue inflammation and dysfunction in obesity. Our current understanding of obesity-associated decreased adipose tissue oxygen tension is mainly focused on changes in oxygen supply and angiogenesis. Here, we demonstrate that increased adipocyte O₂ demand, mediated by ANT2 activity, is the dominant cause of adipocyte hypoxia. Deletion of adipocyte Ant2 improves obesity-induced intracellular adipocyte hypoxia by decreasing obesity-induced adipocyte oxygen demand, without effects on mitochondrial number or mass, or oligomycin-sensitive respiration. This led to decreased adipose tissue HIF-1α expression and inflammation with improved glucose tolerance and insulin resistance in both a preventative or therapeutic setting. Our results suggest that ANT2 may be a target for the development of insulin sensitizing drugs and that ANT2 inhibition might have clinical utility.

The Gα12/13-coupled receptor LPA4 limits proper adipose tissue expansion and remodeling in diet-induced obesity

White adipose tissue (WAT) can dynamically expand and remodel through adipocyte hypertrophy and hyperplasia. The relative contribution of these 2 mechanisms to WAT expansion is a critical determinant of WAT function and dysfunction in obesity. However, little is known about the signaling systems that determine the mechanisms of WAT expansion. Here, we show that the GPCR LPA4 selectively activates Gα12/13 proteins in adipocytes and limits continuous remodeling and healthy expansion of WAT. LPA4-KO mice showed enhanced expression of mitochondrial and adipogenesis genes and reduced levels of inhibitory phosphorylation of PPARγ in WAT, along with increased production of adiponectin. Furthermore, LPA4-KO mice showed metabolically healthy obese phenotypes in a diet-induced obesity model, with continuous WAT expansion, as well as protection from WAT inflammation, hepatosteatosis, and insulin resistance. These findings unravel a potentially new signaling system that underlies WAT plasticity and expandability, providing a promising therapeutic approach for obesity-related metabolic disorders.

miR-30a Remodels Subcutaneous Adipose Tissue Inflammation to Improve Insulin Sensitivity in Obesity

Chronic inflammation accompanies obesity and limits subcutaneous white adipose tissue (WAT) expandability, accelerating the development of insulin resistance and type 2 diabetes mellitus. MicroRNAs (miRNAs) influence expression of many metabolic genes in fat cells, but physiological roles in WAT remain poorly characterized. Here, we report that expression of the miRNA miR-30a in subcutaneous WAT corresponds with insulin sensitivity in obese mice and humans. To examine the hypothesis that restoration of miR-30a expression in WAT improves insulin sensitivity, we injected adenovirus (Adv) expressing miR-30a into the subcutaneous fat pad of diabetic mice. Exogenous miR-30a expression in the subcutaneous WAT depot of obese mice coupled improved insulin sensitivity and increased energy expenditure with decreased ectopic fat deposition in the liver and reduced WAT inflammation. High-throughput proteomic profiling and RNA-Seq suggested that miR-30a targets the transcription factor STAT1 to limit the actions of the proinflammatory cytokine interferon-γ (IFN-γ) that would otherwise restrict WAT expansion and decrease insulin sensitivity. We further demonstrated that miR-30a opposes the actions of IFN-γ, suggesting an important role for miR-30a in defending adipocytes against proinflammatory cytokines that reduce peripheral insulin sensitivity. Together, our data identify a critical molecular signaling axis, elements of which are involved in uncoupling obesity from metabolic dysfunction.

Genes that make you fat, but keep you healthy

Obesity prevalence continues to rise worldwide, posing a substantial burden on people's health. However, up to 45% of obese individuals do not suffer from cardiometabolic complications, also called the metabolically healthy obese (MHO). Concurrently, up to 30% of normal-weight individuals demonstrate cardiometabolic risk factors that are generally observed in obese individuals, the metabolically obese normal weight (MONW). Besides lifestyle, environmental factors and demographic factors, innate biological mechanisms are known to contribute to the aetiology of the MHO and MONW phenotypes, as well. Experimental studies in animal models have shown that adipose tissue expandability, fat distribution, adipogenesis, adipose tissue vascularization, inflammation and fibrosis, and mitochondrial function are the main mechanisms that uncouple adiposity from its cardiometabolic comorbidities. We reviewed current genetic association studies to expand insights into the biology of MHO/MONW phenotypes. At least four genetic loci were identified through genome-wide association studies for body fat percentage (BF%) of which the BF%-increasing allele was associated with a protective effect on glycemic and lipid outcomes. For some, this association was mediated through favourable effects on body fat distribution. Other studies that characterized the genetic susceptibility of insulin resistance found that a higher susceptibility was associated with lower overall adiposity due to less fat accumulation at hips and legs, suggesting that an impaired capacity to store fat subcutaneously or a preferential storage in the intra-abdominal cavity may be metabolically harmful. Clearly, more work remains to be done in this field, first through gene discovery and subsequently through functional follow-up of identified genes.

A reduced M1-like/M2-like ratio of macrophages in healthy adipose tissue expansion during SGLT2 inhibition

The adipose tissue includes various stromal cells, such as preadipocytes, endothelial cells, fibroblasts, and immune cells, which are involved in adipose tissue functions. We previously reported that, in obese mice, the sodium–glucose cotransporter 2 inhibitor ipragliflozin (Ipra) promoted the expansion of the epididymal adipose tissue (Epi) with increase of serum ketone body concentration. The Ipra-induced adipose tissue expansion did not deteriorate adipose inflammation, or systemic glucose/lipid metabolism, referred to as “healthy adipose tissue expansion.” Here we found that Ipra promoted healthy adipose tissue expansion with a reduced ratio of pro-inflammatory M1-like adipose tissue macrophages (ATMs) to anti-inflammatory M2-like ATMs. Ipra downregulated the gene expression of interleukin (IL)−15 (Il15) in stromal cells of Epi. IL-15 inhibited lipogenesis in 3T3-L1 cells associated with downregulation of the lipogenic gene. Ketone body β-hydroxybutyrate suppressed Il15 gene induction in M1-polarized cultured macrophages, and a ketogenic diet reproduced the adipose tissue expansion without deteriorating systemic glucose metabolism in mice. Our data indicate that the phenotypic switch of ATMs could mediate healthy adipose tissue expansion by treatment with Ipra, and it may offer new insights into the pathophysiological mechanisms of adipose tissue expansion.

Altered DNA Methylation Sites in Peripheral Blood Leukocytes from Patients with Simple Steatosis and Nonalcoholic Steatohepatitis (NASH)

Background

The aim of this study was to identify DNA methylation sites in peripheral blood leukocytes from patients with histologically confirmed nonalcoholic fatty liver disease (NAFLD) that included simple hepatic steatosis and nonalcoholic steatohepatitis (NASH).

Material/Methods

DNA was isolated from peripheral blood leukocytes from patients with histologically diagnosed NAFLD (n=35), including simple hepatic steatosis (n=18) and NASH (n=17). Healthy controls included individuals without liver disease (n=30). DNA was hybridized, and DNA methylation was interrogated in an epigenome-wide association study (EWAS). DNA methylation levels (β-values) were correlated with serum lipid profiles, liver enzymes, and liver histology.

Results

Circulating blood leukocytes from 35 patients with NAFLD (simple steatosis and NASH) contained 65 CpG sites, which represented 60 genes that were differentially methylated when compared with healthy controls. In the simple hepatic steatosis group (n=18), 42 methylated CpG sites were found to be associated with increased levels of serum alanine aminotransferase (ALT), and 32 methylated CpG sites were associated with increased serum lipid profiles. In the NASH group (n=17), when compared with the simple hepatic steatosis group, methylated CpG sites showed significant correlations with the presence of lobular inflammation compared with hepatic steatosis and fibrosis. Six differentially methylated CpG sites were identified in the ACSL4, CRLS1, CTP1A, SIGIRR, SSBP1 and ZNF622 genes, which were associated with histologically confirmed simple hepatic steatosis and NASH.

Conclusions

The study identified some key methylated CpG sites from peripheral blood leukocytes, which might be used as serum biomarkers to stratify NAFLD patients into simple hepatic steatosis and NASH.

NAD+-dependent deacetylase SIRT3 in adipocytes is dispensable for maintaining normal adipose tissue mitochondrial function and whole body metabolism

Mitochondrial dysfunction in adipose tissue is involved in the pathophysiology of obesity-induced systemic metabolic complications, such as type 2 diabetes, insulin resistance, and dyslipidemia. However, the mechanisms responsible for obesity-induced adipose tissue mitochondrial dysfunction are not clear. The aim of present study was to test the hypothesis that nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylase sirtuin-3 (SIRT3) in adipocytes plays a critical role in adipose tissue mitochondrial biology and obesity. We first measured adipose tissue SIRT3 expression in obese and lean mice. Next, adipocyte-specific mitochondrial Sirt3 knockout (AMiSKO) mice were generated and metabolically characterized. We evaluated glucose and lipid metabolism in adult mice fed either a regular-chow diet or high-fat diet (HFD) and in aged mice. We also determined the effects of Sirt3 deletion on adipose tissue metabolism and mitochondrial biology. Supporting our hypothesis, obese mice had decreased SIRT3 gene and protein expression in adipose tissue. However, despite successful knockout of SIRT3, AMiSKO mice had normal glucose and lipid metabolism and did not change metabolic responses to HFD-feeding and aging. In addition, loss of SIRT3 had no major impact on putative SIRT3 targets, key metabolic pathways, and mitochondrial function in white and brown adipose tissue. Collectively, these findings suggest that adipocyte SIRT3 is dispensable for maintaining normal adipose tissue mitochondrial function and whole body metabolism. Contrary to our hypothesis, loss of SIRT3 function in adipocytes is unlikely to contribute to the pathophysiology of obesity-induced metabolic complications.

Iron overload by transferrin receptor protein 1 regulation plays an important role in palmitate-induced insulin resistance in human skeletal muscle cells

Free fatty acid is considered to be one of the major pathogenic factors of inducing insulin resistance. The association between iron disturbances and insulin resistance has recently begun to receive a lot of attention. Although skeletal muscles are a major tissue for iron utilization and storage, the role of iron in palmitate (PA)-induced insulin resistance is unknown. We investigated the molecular mechanism underlying iron dysregulation in PA-induced insulin resistance. Interestingly, we found that PA simultaneously increased intracellular iron and induced insulin resistance. The iron chelator deferoxamine dramatically inhibited PA-induced insulin resistance, and iron donors impaired insulin sensitivity by activating JNK. PA up-regulated transferrin receptor 1 (tfR1), an iron uptake protein, which was modulated by iron-responsive element-binding proteins 2. Knockdown of tfR1 and iron-responsive element-binding proteins 2 prevented PA-induced iron uptake and insulin resistance. PA also translocated the tfR1 by stimulating calcium influx, but the calcium chelator, BAPTA-AM, dramatically reduced iron overload by inhibiting tfR1 translocation and ultimately increased insulin sensitivity. Iron overload may play a critical role in PA-induced insulin resistance. Blocking iron overload may thus be a useful strategy for preventing insulin resistance and diabetes.-Cui, R., Choi, S.-E., Kim, T. H., Lee, H. J., Lee, S. J., Kang, Y., Jeon, J. Y., Kim, H. J., Lee, K.-W. Iron overload by transferrin receptor protein 1 regulation plays an important role in palmitate-induced insulin resistance in human skeletal muscle cells.

Electron transfer kinetics of the mitochondrial outer membrane protein mitoNEET

Increasing evidence suggests that the mitochondrial outer membrane protein mitoNEET is a key regulator of energy metabolism, iron homeostasis, and production of reactive oxygen species in mitochondria. Previously, we reported that mitoNEET is a redox enzyme that catalyzes electron transfer from the reduced flavin mononucleotide (FMNH₂) to oxygen or ubiquinone via its unique [2Fe-2S] clusters. Here, we explore the reduction and oxidation kinetics of the mitoNEET [2Fe-2S] clusters under anaerobic and aerobic conditions. We find that the mitoNEET [2Fe-2S] clusters are rapidly reduced by a catalytic amount of FMNH₂ which is reduced by flavin reductase and an equivalent amount of NADH under anaerobic conditions. When the reduced mitoNEET [2Fe-2S] clusters are exposed to air, the [2Fe-2S] clusters are slowly oxidized by oxygen at a rate constant of about 6.0 M^-1 s^-1. Compared with oxygen, ubiquinone-2 has a much higher activity to oxidize the reduced mitoNEET [2Fe-2S] clusters at a rate constant of about 3.0 × 10³ M^-1 s^-1 under anaerobic conditions. Under aerobic conditions, the mitoNEET [2Fe-2S] clusters can still be reduced by FMNH₂ in the presence of flavin reductase and excess NADH. However, when NADH is completely consumed, the reduced mitoNEET [2Fe-2S] clusters are gradually oxidized by oxygen. Addition of ubiquinone-2 also rapidly oxidizes the pre-reduced mitoNEET [2Fe-2S] clusters and effectively prevents the FMNH₂-mediated reduction of the mitoNEET [2Fe-2S] clusters under aerobic conditions. The results suggest that ubiquinone may act as an intrinsic oxidant of the reduced mitoNEET [2Fe-2S] clusters in mitochondria under aerobic and anaerobic conditions.

Body Composition and Metabolic Caging Analysis in High Fat Fed Mice

Alterations to body composition (fat or lean mass), metabolic parameters such as whole-body oxygen consumption, energy expenditure, and substrate utilization, and behaviors such as food intake and physical activity can provide important information regarding the underlying mechanisms of disease. Given the importance of body composition and metabolism to the development of obesity and its subsequent sequelae, it is necessary to make accurate measures of these parameters in the pre-clinical research setting. Advances in technology over the past few decades have made it possible to derive these measures in rodent models in a non-invasive and longitudinal fashion. Consequently, these metabolic measures have proven useful when assessing the response of genetic manipulations (for example knockout or transgenic mice, viral knock-down or overexpression of genes), experimental drug/compound screening and dietary, behavioral or physical activity interventions. Herein, we describe the protocols used to measure body composition and metabolic parameters using an animal monitoring system in chow-fed and high fat diet-fed mice.

Endocrine Adiponectin-FGF15/19 Axis in Ethanol-Induced Inflammation and Alcoholic Liver Injury

Alcoholic liver disease (ALD) is the most prevalent form of liver disease, encompassing a spectrum of progressive pathological changes from steatosis to steatohepatitis to fibrosis/cirrhosis and hepatocellular carcinoma. Alcoholic steatosis/steatohepatitis is the initial stage of ALD and a major risk factor for advanced liver injuries. Adiponectin is a hormone secreted from adipocytes. Fibroblast growth factor (FGF) 15 (human homolog, FGF19) is an ileum-derived hormone. Adipocyte-derived adiponectin and gut-derived FGF15/19 regulate each other, share common signaling cascades, and exert similar beneficial functions. Emerging evidence has revealed that dysregulated adiponectin-FGF15/19 axis and impaired hepatic adiponectin-FGF15/19 signaling are associated with alcoholic liver damage in rodents and humans. More importantly, endocrine adiponectin-FGF15/19 signaling confers protection against ethanol-induced liver damage via fine tuning the adipose-intestine-liver crosstalk, leading to limited hepatic inflammatory responses, and ameliorated alcoholic liver injury. This review is focused on the recently discovered endocrine adiponectin-FGF15/19 axis that is emerging as an essential adipose-gut-liver coordinator involved in the development and progression of alcoholic steatohepatitis.

Acute loss of adipose tissue-derived adiponectin triggers immediate metabolic deterioration in mice

AIM/HYPOTHESIS

Adiponectin (APN), a circulating hormone secreted by mature adipocytes, has been extensively studied because it has beneficial metabolic effects. While many studies have focused on the congenital loss of APN and its effects on systemic body glucose and lipid metabolism, little is known about the effects triggered by acute loss of APN in the adult mouse. We anticipated that genetically induced acute depletion of APN in adult mice would have a more profound effect on systemic metabolic health than congenital deletion of Adipoq, the gene encoding APN, with its associated potential for adaptive responses that may mask the phenotypes.

METHODS

Mice carrying loxP-flanked regions of Adipoq were generated and bred to the Adipoq (APN) promoter-driven reverse tetracycline-controlled transactivator (rtTA) (APN-rtTA) gene and a tet-responsive Cre line (TRE-Cre) to achieve acute depletion of APN. Upon acute removal of APN in adult mice, systemic glucose and lipid homeostasis were assessed under basal and insulinopenic conditions.

RESULTS

The acute depletion of APN results in more severe systemic insulin resistance and hyperlipidaemia than in mice with congenital loss of APN. Furthermore, the acute depletion of APN in adult mice results in a much more dramatic reduction in survival rate, with 50% of inducible knockouts dying in the first 5 days under insulinopenic conditions compared with 0% of congenital Adipoq knockout mice under similar conditions.

CONCLUSIONS/INTERPRETATION

Acute systemic removal of APN results in a much more negative metabolic phenotype compared with congenital knockout of Adipoq. Specifically, our data demonstrate that acute depletion of APN is especially detrimental to lipid homeostasis, both under basal and insulinopenic conditions. This suggests that compensatory mechanisms exist in congenital knockout mice that offset some of the metabolic actions covered by APN.

Cardiovascular and Metabolic Heterogeneity of Obesity: Clinical Challenges and Implications for Management

The prevalence of obesity has increased globally over the last 2 decades. Although the body mass index has been a convenient and simple index of obesity at the population level, studies have shown that obesity defined by body mass index alone is a remarkably heterogeneous condition with varying cardiovascular and metabolic manifestations across individuals. Adipose tissue is an exquisitely active metabolic organ engaged in cross-talk between various systems; perturbation of adipose tissue results in a pathological response to positive caloric balance in susceptible individuals that directly and indirectly contributes to cardiovascular and metabolic disease. Inadequate subcutaneous adipose tissue expansion in the face of dietary triglycerides leads to visceral and ectopic fat deposition, inflammatory/adipokine dysregulation, and insulin resistance. Conversely, preferential fat storage in the lower body depot may act as a metabolic buffer and protect other tissues from lipotoxicity caused by lipid overflow and ectopic fat. Translational, epidemiological, and clinical studies over the past 30 years have clearly demonstrated a strong link between visceral and ectopic fat and the development of a clinical syndrome characterized by atherogenic dyslipidemia, hyperinsulinemia/glucose intolerance, hypertension, atherosclerosis, and adverse cardiac remodeling/heart failure. This relationship is even more nuanced when clinical entities such as metabolically healthy obesity phenotype and the obesity paradox are considered. Although it is clear that the accumulation of visceral/ectopic fat is a major contributor to cardiovascular and metabolic risk above and beyond the body mass index, implementation of fat distribution assessment into clinical practice remains a challenge. Anthropometric indexes of obesity are easily implemented, but newer imaging-based methods offer improved sensitivity and specificity for measuring specific depots. Lifestyle, pharmacological, and surgical interventions allow a multidisciplinary approach to overweight/obesity that may improve outcomes and align with a public health message to combat the growing epidemic of obesity worldwide and to build healthier lives free of cardiovascular diseases.

Phylogenetic analysis of the CDGSH iron-sulfur binding domain reveals its ancient origin

The iron-sulfur (2Fe-2S) binding motif CDGSH appears in many important plant and animal proteins that regulate iron and reactive oxygen metabolism. In human it is found in CISD1-3 proteins involved in diabetes, obesity, cancer, aging, cardiovascular disease and neurodegeneration. Despite the important biological role of the CDGSH domain, its origin, evolution and diversification, are largely unknown. Here, we report that: (1) the CDGSH domain appeared early in evolution, perhaps linked to the heavy use of iron-sulfur driven metabolism by early organisms; (2) a CISD3-like protein with two CDGSH domains on the same polypeptide appears to represent the ancient archetype of CDGSH proteins; (3) the origin of the human CISD3 protein is linked to the mitochondrial endosymbiotic event; (4) the CISD1/2 type proteins that contain only one CDGSH domain, but function as homodimers, originated after the divergence of bacteria and archaea/eukaryotes from their common ancestor; and (5) the human CISD1 and CISD2 proteins diverged about 650–720 million years ago, and CISD3 and CISD1/2 share their descent from an ancestral CISD about 1–1.1 billion years ago. Our findings reveal that the CDGSH domain is ancient in its origin and shed light on the complex evolutionary path of modern CDGSH proteins.

Iron-sulfur clusters: from metals through mitochondria biogenesis to disease

Iron–sulfur clusters are ubiquitous inorganic co-factors that contribute to a wide range of cell pathways including the maintenance of DNA integrity, regulation of gene expression and protein translation, energy production, and antiviral response. Specifically, the iron–sulfur cluster biogenesis pathways include several proteins dedicated to the maturation of apoproteins in different cell compartments. Given the complexity of the biogenesis process itself, the iron–sulfur research area constitutes a very challenging and interesting field with still many unaddressed questions. Mutations or malfunctions affecting the iron–sulfur biogenesis machinery have been linked with an increasing amount of disorders such as Friedreich’s ataxia and various cardiomyopathies. This review aims to recap the recent discoveries both in the yeast and human iron–sulfur cluster arena, covering recent discoveries from chemistry to disease.

Evidence of the Possible Harm of Endocrine-Disrupting Chemicals in Humans: Ongoing Debates and Key Issues

Evidence has emerged that endocrine-disrupting chemicals (EDCs) can produce adverse effects, even at low doses that are assumed safe. However, systemic reviews and meta-analyses focusing on human studies, especially of EDCs with short half-lives, have demonstrated inconsistent results. Epidemiological studies have insuperable methodological limitations, including the unpredictable net effects of mixtures, non-monotonic dose-response relationships, the non-existence of unexposed groups, and the low reliability of exposure assessment. Thus, despite increases in EDC-linked diseases, traditional epidemiological studies based on individual measurements of EDCs in bio-specimens may fail to provide consistent results. The exposome has been suggested as a promising approach to address the uncertainties surrounding human studies, but it is never free from these methodological issues. Although exposure to EDCs during critical developmental periods is a major concern, continuous exposure to EDCs during non-critical periods is also harmful. Indeed, the evolutionary aspects of epigenetic programming triggered by EDCs during development should be considered because it is a key mechanism for developmental plasticity. Presently, living without EDCs is impossible due to their omnipresence. Importantly, there are lifestyles which can increase the excretion of EDCs or mitigate their harmful effects through the activation of mitohormesis or xenohormesis. Effectiveness of lifestyle interventions should be evaluated as practical ways against EDCs in the real world.

Effectiveness and safety of Glycyrrhizae Decoction for Purging Stomach-Fire in Behcet disease patients: Study protocol for a randomized controlled and double-blinding trail

BACKGROUND

Behcet disease (BD) is a worldwide-occurred autoimmune disorder and currently lack of optional successful treatment. An ancient traditional Chinese medical formula called Glycyrrhizae Decoction for Purging Stomach-Fire (GDPSF) was recorded and nowadays has been observed to be effective for BD patients. However, the strict randomized controlled and double-blinding trail is needed to further assess this alternative medicine.

METHODS

To ascertain the potential effects and safety of GDPSF for BD patients and to determine whether combination application of GDPSF and thalidomide could possibly reduce the side effects and increase effectiveness for BD management, we will conduct a randomized, double blind, controlled clinical trial. Patients enrolled will be randomly assigned into 3 groups: GDPSF group, thalidomide group, and integrative group (treated by both GDPSF and thalidomide). Participants will receive treatment for 6 months and accept a 12 months follow-up. Before and after treatment, clinical manifestations, blood tests, thalidomide dosage, remission levels, quality of life, and satisfactory levels will be assessed. The data of assessments on each group before and after treatments will be collected and analyzed through historical control, while between groups through intergroup control. Then statistical analysis will be applied to assess the effects and safety.

DISCUSSION

This study protocol will assess the effects and safety of GDPSF for BD patients GDPSF. Combination application of GDPSF and thalidomide might be a new integrative medical method for BD patients.

TRIAL REGISTRATION

Chinese Clinical Registry (ChiCTR-ONC-16009621) on Oct. 2016 http://www.chictr.org.cn/showproj.aspx?proj=16395.

De novo adipocyte differentiation from Pdgfrβ+ preadipocytes protects against pathologic visceral adipose expansion in obesity

Pathologic expansion of white adipose tissue (WAT) in obesity is characterized by adipocyte hypertrophy, inflammation, and fibrosis; however, factors triggering this maladaptive remodeling are largely unknown. Here, we test the hypothesis that the potential to recruit new adipocytes from Pdgfrβ⁺ preadipocytes determines visceral WAT health in obesity. We manipulate levels of Pparg, the master regulator of adipogenesis, in Pdgfrβ⁺ precursors of adult mice. Increasing the adipogenic capacity of Pdgfrβ⁺ precursors through Pparg overexpression results in healthy visceral WAT expansion in obesity and adiponectin-dependent improvements in glucose homeostasis. Loss of mural cell Pparg triggers pathologic visceral WAT expansion upon high-fat diet feeding. Moreover, the ability of the TZD class of anti-diabetic drugs to promote healthy visceral WAT remodeling is dependent on mural cell Pparg. These data highlight the protective effects of de novo visceral adipocyte differentiation in these settings, and suggest Pdgfrβ⁺ adipocyte precursors as targets for therapeutic intervention in diabetes.

Adipocyte hyperplasia is thought to have beneficial metabolic effects in obesity, but definitive evidence is lacking. Here, Shao et al. promote de novo formation of adipocytes in visceral white adipose tissue (WAT) of adult mice through inducible overexpression of Pparg in Pdgfrβ⁺ preadipocytes and show that this protects from pathological WAT remodeling.

Causes and mechanisms of adipocyte enlargement and adipose expansion

Adipose tissue plays a significant role in whole body energy homeostasis. Obesity-associated diabetes, fatty liver and metabolic syndrome are closely linked to adipose stress and dysfunction. Genetic predisposition, overeating and physical inactivity influence the expansion of adipose tissues. Under conditions of constant energy surplus, adipocytes become hypertrophic and adipose tissues undergo hyperplasia so as to increase their lipid storage capacity, thereby keeping circulating blood glucose and fatty acids below toxic levels. Nonetheless, adipocytes have a saturation point where they lose capacity to store more lipids. At this stage, when adipocytes are fully lipid-engorged, they express stress signals. Adipose depots (particularly visceral compartments) from obese individuals with a severe metabolic phenotype are characterized by the high proportion of hypertrophic adipocytes. This review focuses on the mechanisms of adipocyte enlargement in relation to adipose fatty acid and cholesterol metabolism, and considers how this may be related to adipose dysfunction.

The unique fold and lability of the [2Fe-2S] clusters of NEET proteins mediate their key functions in health and disease

NEET proteins comprise a new class of [2Fe-2S] cluster proteins. In human, three genes encode for NEET proteins: cisd1 encodes mitoNEET (mNT), cisd2 encodes the Nutrient-deprivation autophagy factor-1 (NAF-1) and cisd3 encodes MiNT (Miner2). These recently discovered proteins play key roles in many processes related to normal metabolism and disease. Indeed, NEET proteins are involved in iron, Fe-S, and reactive oxygen homeostasis in cells and play an important role in regulating apoptosis and autophagy. mNT and NAF-1 are homodimeric and reside on the outer mitochondrial membrane. NAF-1 also resides in the membranes of the ER associated mitochondrial membranes (MAM) and the ER. MiNT is a monomer with distinct asymmetry in the molecular surfaces surrounding the clusters. Unlike its paralogs mNT and NAF-1, it resides within the mitochondria. NAF-1 and mNT share similar backbone folds to the plant homodimeric NEET protein (At-NEET), while MiNT's backbone fold resembles a bacterial MiNT protein. Despite the variation of amino acid composition among these proteins, all NEET proteins retained their unique CDGSH domain harboring their unique 3Cys:1His [2Fe-2S] cluster coordination through evolution. The coordinating exposed His was shown to convey the lability to the NEET proteins' [2Fe-2S] clusters. In this minireview, we discuss the NEET fold and its structural elements. Special attention is given to the unique lability of the NEETs' [2Fe-2S] cluster and the implication of the latter to the NEET proteins' cellular and systemic function in health and disease.

Loss of mitochondrial protease ClpP protects mice from diet-induced obesity and insulin resistance

Caseinolytic peptidase P (ClpP) is a mammalian quality control protease that is proposed to play an important role in the initiation of the mitochondrial unfolded protein response (UPR^mt), a retrograde signaling response that helps to maintain mitochondrial protein homeostasis. Mitochondrial dysfunction is associated with the development of metabolic disorders, and to understand the effect of a defective UPR^mt on metabolism, ClpP knockout (ClpP^-/-) mice were analyzed. ClpP^-/- mice fed ad libitum have reduced adiposity and paradoxically improved insulin sensitivity. Absence of ClpP increased whole-body energy expenditure and markers of mitochondrial biogenesis are selectively up-regulated in the white adipose tissue (WAT) of ClpP^-/- mice. When challenged with a metabolic stress such as high-fat diet, despite similar caloric intake, ClpP^-/- mice are protected from diet-induced obesity, glucose intolerance, insulin resistance, and hepatic steatosis. Our results show that absence of ClpP triggers compensatory responses in mice and suggest that ClpP might be dispensable for mammalian UPR^mt initiation. Thus, we made an unexpected finding that deficiency of ClpP in mice is metabolically beneficial.