Inflammatory induction of human resistin causes insulin resistance in endotoxemic mice

The Role of Adipokines in the Control of Pituitary Functions

The pituitary gland is a key endocrine gland in all classes of vertebrates, including mammals. The pituitary gland is an important component of hypothalamus-pituitary-target organ hormonal regulatory axes and forms a functional link between the nervous system and the endocrine system. In response to hypothalamic stimuli, the pituitary gland secretes a number of hormones involved in the regulation of metabolism, stress reactions and environmental adaptation, growth and development, as well as reproductive processes and lactation. In turn, hormones secreted by target organs at the lowest levels of the hormonal regulatory axes regulate the functions of the pituitary gland in the process of hormonal feedback. The pituitary also responds to other peripheral signals, including adipose-tissue-derived factors. These substances are a broad group of peptides known as adipocytokines or adipokines that act as endocrine hormones mainly involved in energy homeostasis. Adipokines, including adiponectin, resistin, apelin, chemerin, visfatin, and irisin, are also expressed in the pituitary gland, and they influence the secretory functions of this gland. This review is an overview of the existing knowledge of the relationship between chosen adipose-derived factors and endocrine functions of the pituitary gland, with an emphasis on the pituitary control of reproductive processes.

Resistin production does not affect outcomes in a mouse model of acute surgical sepsis

Introduction

Because of the strong correlation between the blood concentration of circulating resistin and the illness severity of septic patients, resistin has been proposed as a mediator of sepsis pathophysiology. In vitro data indicate that human resistin directly impairs neutrophil migration and intracellular bacterial killing, although the significance of these findings in vivo remain unclear.

Objective

The objectives of the present study were: (1) to validate the expression of human resistin in a clinically relevant, murine model of surgical sepsis, (2) to assess how sepsis-induced changes in resistin correlate with markers of infection and organ dysfunction, and (3) to investigate whether the expression of human resistin alters immune function or disease outcomes in vivo.

Methods

107 male, C57BL/6 mice transgenic for the human resistin gene and its promoter elements (Retn^+/−/−, or Retn+) were generated on a Retn^−/− (mouse resistin knockout, or Rko) background. Outcomes were compared between age-matched transgenic and knockout mice. Acute sepsis was defined as the initial 24 h following cecal ligation and puncture (CLP). Physiologic and laboratory parameters correlating to the human Sequential Organ Failure Assessment (SOFA) Score were measured in mice, and innate immune cell number/function in the blood and peritoneal cavity were assessed.

Results

CLP significantly increased circulating levels of human resistin. The severity of sepsis-induced leukopenia was comparable between Retn+ and Rko mice. Resistin was associated with increased production of neutrophil reactive oxygen species, a decrease in circulating neutrophils at 6 h and an increase in peritoneal Ly6C^hi monocytes at 6 h and 24 h post-sepsis. However, intraperitoneal bacterial growth, organ dysfunction and mouse survival did not differ with resistin production in septic mice.

Significance

Ex vivo resistin-induced impairment of neutrophil function do not appear to translate to increased sepsis severity or poorer outcomes in vivo following CLP.

Adropin Slightly Modulates Lipolysis, Lipogenesis and Expression of Adipokines but Not Glucose Uptake in Rodent Adipocytes

Adropin is a peptide hormone which modulates energy homeostasis and metabolism. In animals with diet-induced obesity, adropin attenuates adiposity and improves lipid and glucose homeostasis. Adropin promotes the proliferation of rodent white preadipocytes and suppresses their differentiation into adipocytes. By contrast, the effects of adropin on mature white adipocytes are unknown. Therefore, we aimed to evaluate the effects of adropin on lipolysis, lipogenesis and glucose uptake in white rodent adipocytes. We assessed the effects of adropin on the mRNA expression of adiponectin, resistin and visfatin. White preadipocytes were isolated from male Wistar rats. Differentiated 3T3-L1 cells were used as a surrogate model of white adipocytes. Lipolysis was measured by the evaluation of glycerol and free fatty acid secretion using colorimetric kits. The effects of adropin on lipogenesis and glucose uptake were measured using radioactive-labelled glucose. The expression of adipokine mRNA was studied using real-time PCR. Our results show that adropin slightly promotes lipolysis in rat adipocytes and 3T3-L1 cells. Adropin suppresses lipogenesis in rat adipocytes without influencing glucose uptake. In addition, adropin stimulates adiponectin mRNA expression and suppresses the expression of resistin and visfatin. These results indicate that adropin may be involved in controlling lipid metabolism and adipokine expression in white rodent adipocytes.

Adipose tissue in health and disease

Adipose, or fat, tissue (AT) was once considered an inert tissue that primarily existed to store lipids, and was not historically recognized as an important organ in the regulation and maintenance of health. With the rise of obesity and more rigorous research, AT is now recognized as a highly complex metabolic organ involved in a host of important physiological functions, including glucose homeostasis and a multitude of endocrine capabilities. AT dysfunction has been implicated in several disease states, most notably obesity, metabolic syndrome and type 2 diabetes. The study of AT has provided useful insight in developing strategies to combat these highly prevalent metabolic diseases. This review highlights the major functions of adipose tissue and the consequences that can occur when disruption of these functions leads to systemic metabolic dysfunction.

Roles of leptin and resistin in metabolism, reproduction, and leptin resistance

Increased adipose mass can cause insulin resistance and type 2 diabetes mellitus. This phenomenon is related to adipocyte-secreted signaling molecules that affect glucose balance, such as fatty acids, adiponectin, leptin, interleukin-6, tumor necrosis factor-α, and resistin. Among these hormones, leptin and resistin play important roles in regulating weight and glucose metabolism. Leptin and resistin work in both similar and opposite ways, and they interact with each other. Circulating concentrations of leptin and resistin are elevated in models of obesity and rodents fed a high-fat diet. In addition, leptin and resistin are similarly regulated by nutritional status: they are reduced by fasting and increased by feeding. This effect is mediated partially through insulin receptors and glucose transporters. Our latest data provided the first indication that in sheep, intravenous infusion of resistin increases the mean circulating concentrations of leptin and decreases luteinizing hormone in a dose-dependent manner during both the long-day (LD) and short-day seasons. Furthermore, exogenous resistin increased suppressor of cytokine signaling (SOCS)-3 mRNA expression only during the LD season, when the leptin resistance/insensitivity phenomenon was observed in the arcuate nucleus, preoptic area, and anterior pituitary. We concluded that one factor contributing to central leptin resistance is autosuppression, via which leptin and resistin stimulate the expression of SOCS-3, which inhibits leptin signaling. The increased expression of SOCS-3 in response to leptin and resistin may be a pivotal cause of leptin resistance/insensitivity, a pathological situation in obese individuals and a physiological occurrence in sheep during the LD season.

The role of resistin and myeloperoxidase in severe sepsis and septic shock: Results from the ALBIOS trial

BACKGROUND

Inflammatory biomarkers are useful in detecting patients with sepsis. The prognostic role of resistin and myeloperoxidase (MPO) has been investigated in sepsis.

MATERIALS AND METHODS

Plasma resistin and MPO were measured on days 1, 2 and 7 in 957 patients enrolled in the Albumin Italian Outcome Sepsis (ALBIOS) trial. The association between resistin and MPO levels on day 1, 2 and 7 and 90-day mortality was assessed.

RESULTS

Plasma resistin and MPO concentrations were higher at day 1 and decreased until day 7. Both biomarkers were positively correlated with each other and with physiological parameters. Higher levels of resistin and MPO on day 1 were associated with the development of new organ failures. Patients experiencing death at 90 days showed higher levels of resistin and MPO compared with survivors. At day 1, only MPO in the 4th quartile (Q4), but not resistin, was found to predict 90-day death (adjusted hazard ratio [aHR] 1.55 vs Q1). At day 2, resistin in the Q3 and Q4 predicted a > 40% increase in mortality as also did MPO in the Q4. On day 7, Q4 resistin was able to predict 90-day mortality, while all quartiles of MPO were not.

CONCLUSIONS

High levels of MPO, but not of resistin, on day 1 were able to predict 90-day mortality. These findings may either suggest that early hyper-activation of neutrophils is detrimental in patients with sepsis or reflect the burden of the inflammatory process caused by sepsis. Further studies are warranted to deepen these aspects (ALBIOS ClinicalTrials.gov Identifier: NCT00707122).

Resistin in metabolism, inflammation, and disease

Resistin is a small secretory protein that has a pleiotropic role in rodents and humans. Both rodent resistin and human resistin have an extremely stable and high-order multimeric structure. Moreover, there is significant variation in the source of secretion and the diversity of functions of resistin. Mouse resistin resists insulin action and contributes to type 2 diabetes mellitus, while human resistin plays a role in inflammation and also functions as a small accessory chaperone. Currently, active research in the area identified a significant role for resistin in stress biology and as a biomarker in diagnostics to evaluate disease status and treatment outcome. This review summarizes recent developments within resistin biology including their association with obesity, inflammation, stress response mechanisms, and its role in clinical diagnostics.

Analysis of serum inflammatory mediators in type 2 diabetic patients and their influence on renal function

Aim

To evaluate the serum concentrations of inflammatory mediators in patients with type 2 diabetes mellitus (T2DM) with or without renal alteration (RA) function.

Methods

Serum samples from 76 patients with T2DM and 24 healthy individuals were selected. Patients with T2DM were divided into two groups according to eGFR (> or < 60mL/min/1.73m²). Cytokines, chemokines and adipokines levels were evaluated using the Multiplex immunoassay and ELISA.

Results

TNFR1 and leptin were higher in the T2DM group with RA than in the T2DM group without RA and control group. All patients with T2DM showed increased resistin, IL-8, and MIP-1α compared to the control group. Adiponectin were higher and IL-4 decreased in the T2DM group with RA compared to the control group. eGFR positively correlated with IL-4 and negatively with TNFR1, TNFR2, and leptin in patients with T2DM. In the T2DM group with RA, eGFR was negatively correlated with TNFR1 and resistin. TNFR1 was positively correlated with resistin and leptin, as well as resistin with IL-8 and leptin.

Conclusion

Increased levels of TNFR1, adipokines, chemokines and decrease of IL-4 play important role in the inflammatory process developed in T2DM and decreased renal function. We also suggest that TNFR1 is a strong predictor of renal dysfunction in patients with T2DM.

Resistin expression in human monocytes is controlled by two linked promoter SNPs mediating NFKB p50/p50 binding and C-methylation

Resistin is a key cytokine associated with metabolic and inflammatory diseases. Especially in East Asian populations, the expression levels are strongly influenced by genetic polymorphisms. Mechanisms and functional implications of this genetic control are still unknown. By employing reporter assays, EMSA, inhibition studies, bisulphite sequencing, ChIP-Seq and gene-editing we show that the p50/p50 homodimer known to act as repressor for a number of pro-inflammatory genes plays a central role in the genetic regulation of resistin in monocytes along with promoter methylation. In the common RETN haplotype p50/p50 constitutively dampens the expression by binding to the promoter. In an Asian haplotype variant however this interaction is disrupted by the A allele of rs3219175. The SNP is in very close linkage to rs34861192, a CpG SNP, located 280 bp upstream which provides an allele-specific C-methylation site. rs34861192 is located in a 100 bp region found to be methylated in the common but not in the Asian haplotype, resulting in the latter having a higher basal expression, which also associates with elevated histone acetylation (H3K27ac). Genotype associations within cohort data of 200 East Asian individuals revealed significant associations between this haplotype and the plasma levels of factors such as TGF-b, S100B, sRAGE and IL-8 as well as with myeloid DC counts. Thus, the common RETN haplotype is tightly regulated by the epigenetic mechanism linked to p50/p50-binding. This control is lost in the Asian haplotype, which may have evolved to balance the antagonistic RETN effects on pathogen protection vs. metabolic and inflammatory disease induction.

Human resistin protects against endotoxic shock by blocking LPS-TLR4 interaction

Helminths trigger multiple immunomodulatory pathways that can protect from sepsis. Human resistin (hRetn) is an immune cell-derived protein that is highly elevated in helminth infection and sepsis. However, the function of hRetn in sepsis, or whether hRetn influences helminth protection against sepsis, is unknown. Employing hRetn-expressing transgenic mice (hRETNTg⁺) and recombinant hRetn, we identify a therapeutic function for hRetn in lipopolysaccharide (LPS)-induced septic shock. hRetn promoted helminth-induced immunomodulation, with increased survival of Nippostrongylus brasiliensis (Nb)-infected hRETNTg⁺ mice after a fatal LPS dose compared with naive mice or Nb-infected hRETNTg^- mice. Employing immunoprecipitation assays, hRETNTg⁺Tlr4^-/- mice, and human immune cell culture, we demonstrate that hRetn binds the LPS receptor Toll-like receptor 4 (TLR4) through its N terminal and modulates STAT3 and TBK1 signaling, triggering a switch from proinflammatory to anti-inflammatory responses. Further, we generate hRetn N-terminal peptides that are able to block LPS proinflammatory function. Together, our studies identify a critical role for hRetn in blocking LPS function with important clinical significance in helminth-induced immunomodulation and sepsis.

CNS Targets of Adipokines

Our understanding of adipose tissue as an endocrine organ has been transformed over the last 20 years. During this time, a number of adipocyte-derived factors or adipokines have been identified. This article will review evidence for how adipokines acting via the central nervous system (CNS) regulate normal physiology and disease pathology. The reported CNS-mediated effects of adipokines are varied and include the regulation of energy homeostasis, autonomic nervous system activity, the reproductive axis, neurodevelopment, cardiovascular function, and cognition. Due to the wealth of information available and the diversity of their known functions, the archetypal adipokines leptin and adiponectin will be focused on extensively. Other adipokines with established CNS actions will also be discussed. Due to the difficulties associated with studying CNS function on a molecular level in humans, the majority of our knowledge, and as such the studies described in this paper, comes from work in experimental animal models; however, where possible the relevant data from human studies are also highlighted. © 2017 American Physiological Society. Compr Physiol 7:1359-1406, 2017.

Adipokines and free fatty acids regulate insulin sensitivity by increasing microRNA-21 expression in human mature adipocytes

Obesity is a global public health concern and may lead to a variety of complications. Previous studies have indicated that adipokines and energy‑source materials contribute to obesity and obesity‑associated insulin resistance. MicroRNAs (miRs) are endogenous 20‑ to 25‑nucleotide non‑coding RNAs associated with fat metabolism. It has been indicated that miR‑21 is associated with adipogenesis and metabolic syndrome. In the present study, the expression of miR‑21 in human mature adipocytes was analyzed using reverse transcription quantitative‑polymerase chain reaction following treatment with adipokines, including tumor necrosis factor (TNF)‑α, interleukin (IL)‑6, leptin, resistin and energy source materials, including free fatty acids (FFAs) and glucose. The current study demonstrated that the expression of miR‑21 in human mature adipocytes was upregulated following treatment with TNF‑α, IL‑6, leptin, resistin and FFAs. However, low‑ and high‑glucose did not have an effect on miR‑21 expression. These results confirmed that TNF‑α, IL‑6, leptin, resistin and FFAs may contribute to obesity and obesity‑associated insulin resistance via upregulating miR‑21 in human mature adipocytes. Therefore, miR‑21 may be a key regulatory factor of obesity and obesity‑associated insulin resistance, and represents a potential therapeutic target for the treatment of these disorders.

Adipose tissue: an endocrine organ playing a role in metabolic regulation

Adipose tissue is a complex endocrine organ with an intricate role in whole body homeostasis. Beyond storing energy, adipose tissue is fundamental in numerous processes including, but not limited to, metabolism, food intake and immune cell function. Adipokines and cytokines are the signaling factors from adipose tissue. These factors play a role in maintaining health, but are also candidates for pathologies associated with obesity. Indeed excessive adiposity causes dysregulation of these factors which negatively affect health and contribute to numerous obesity-induced co-morbidities. In particular, adipokines are fundamental in regulation of glucose homeostasis and insulin signaling, thus aberrant production of these adipose derived hormones correlates with the development and progression of type 2 diabetes. Therefore, elucidation of adipose regulation is crucial for understanding the pathophysiological basis of obesity and metabolic diseases such as type 2 diabetes. In the present review, we summarize current data on the relation between adipokines and adipose depot derived cytokines in the maintenance of glucose homeostasis. Specifically, physiological and molecular functions of several adipokines are defined with particular focus on interactions within the insulin-signaling pathway and subsequent regulation of glucose uptake in both standard and obesity-induced dysregulated conditions. This same relation will be discussed for cytokines and inflammation as well.

Linking resistin, inflammation, and cardiometabolic diseases

Adipose tissue secretes a variety of bioactive substances that are associated with chronic inflammation, insulin resistance, and an increased risk of type 2 diabetes mellitus. While resistin was first known as an adipocyte-secreted hormone (adipokine) linked to obesity and insulin resistance in rodents, it is predominantly expressed and secreted by macrophages in humans. Epidemiological and genetic studies indicate that increased resistin levels are associated with the development of insulin resistance, diabetes, and cardiovascular disease. Resistin also appears to mediate the pathogenesis of atherosclerosis by promoting endothelial dysfunction, vascular smooth muscle cell proliferation, arterial inflammation, and the formation of foam cells. Thus, resistin is predictive of atherosclerosis and poor clinical outcomes in patients with cardiovascular disease and heart failure. Furthermore, recent evidence suggests that resistin is associated with atherogenic dyslipidemia and hypertension. The present review will focus on the role of human resistin in the pathogeneses of inflammation and obesity-related diseases.

Regulation and function of AMPK in physiology and diseases

5′-adenosine monophosphate (AMP)-activated protein kinase (AMPK) is an evolutionarily conserved serine/threonine kinase that was originally identified as the key player in maintaining cellular energy homeostasis. Intensive research over the last decade has identified diverse molecular mechanisms and physiological conditions that regulate the AMPK activity. AMPK regulates diverse metabolic and physiological processes and is dysregulated in major chronic diseases, such as obesity, inflammation, diabetes and cancer. On the basis of its critical roles in physiology and pathology, AMPK is emerging as one of the most promising targets for both the prevention and treatment of these diseases. In this review, we discuss the current understanding of the molecular and physiological regulation of AMPK and its metabolic and physiological functions. In addition, we discuss the mechanisms underlying the versatile roles of AMPK in diabetes and cancer.

Serum Resistin Levels May Contribute to an Increased Risk of Acute Cerebral Infarction

The objective of this study was to investigate the association between serum resistin levels and acute cerebral infarction (ACI). PubMed, SpringerLink, Wiley, EBSCO, Ovid, Web of Science, Wanfang, China National Knowledge Infrastructure, and VIP databases (last updated search in October 2014) were exhaustively searched, and data from the eligible studies were extracted and analyzed to assess the association between serum resistin levels and ACI. STATA software (version 12.0, Stata Corporation, College Station, TX, USA) was utilized for data analysis. Ten studies including 1829 ACI patients and 1557 healthy controls were eligible for inclusion in the meta-analysis. Our major result revealed that ACI patients exhibited higher serum resistin levels compared with healthy controls. Asubgroup analysis based on ethnicity showed a significant association between serum resistin levels and ACI in Asians, but surprisingly not in Caucasians. The results of our meta-analysis suggest that serum resistin levels are associated with an increased risk of ACI.

Control of Macrophage Dynamics as a Potential Therapeutic Approach for Clinical Disorders Involving Chronic Inflammation

Macrophages are a well recognized player of both innate and adaptive immunity and have emerged as a key regulator of systemicmetabolism, hematopoiesis, vasculogenesis, apoptosis, malignancy, and reproduction. Such pleiotropic roles of macrophages are mirrored by their protean features. Upon environmental. challenges, macrophages redistribute and differentiate in situ and contribute to the multiple disease states by exerting protective and pathogenic effects. The environmental challenges include cytokines, chemokines, lipid mediators, and extrinsic insults, such as food and pathogenic bacteria. In addition, homeostasis and the activation state of macrophages are influenced by various metabolites from a commensal microbe that colonizes epithelial and mucosal surfaces, such as the lungs, intestines, and skin. In this review, we describe macrophage differentiation, polarization, and various functions in chronic disease states, including chronic inflammatory bowel disease, tumorigenesis, metabolism and obesity, and central nervous system demyelinating disorders. Controlling the macrophage dynamics to affect the pathologic states is considered to be an important therapeutic approach for many clinical disorders involving chronic inflammation.

Clinical potential of resistin as a novel prognostic biomarker for cellulitis

Cellulitis is an acute, subacute or chronic inflammation of the dermis and subdermal tissues, which is typically caused by bacteria, although other causes are possible. The present study aimed to evaluate the association between resistin levels and the recovery time of patients with cellulitis. In addition, the effect of resistin and insulin resistance on the prognosis of cellulitis was investigated. In total, 52 patients with cellulitis (male, 21; female, 31) and an age-matched group of 42 healthy individuals (male, 18; female, 24) were included in the study. The levels of serum resistin, fasting plasma glucose (FPG), homeostasis model assessment-insulin resistance (HOMA-IR), C-reactive protein (CRP) and other biochemical parameters were compared between the groups. The mean resistin levels in the cellulitis and control groups were 9.4±5.3 and 5.8±3.1 ng/ml, respectively. The levels of resistin, FPG, HOMA-IR and CRP were significantly higher in the cellulitis group compared with the control group (P<0.001). Furthermore, the mean recovery time of the patients with cellulitis was 21.2±5.6 days. Thus, increased levels of resistin (P=0.002) and HOMA-IR (P=0.005) could be used as predictive factors for the recovery time. The enhanced levels of resistin and HOMA-IR were shown to correlate with the high CRP levels in the cellulitis group. Therefore, the results indicated that increased levels of resistin may function as a prognostic marker for cellulitis.

Central obesity, type 2 diabetes and insulin: exploring a pathway full of thorns

The prevalence of type 2 diabetes (T2D) is rapidly increasing. This is strongly related to the contemporary lifestyle changes that have resulted in increased rates of overweight individuals and obesity. Central (intra-abdominal) obesity is observed in the majority of patients with T2D. It is associated with insulin resistance, mainly at the level of skeletal muscle, adipose tissue and liver. The discovery of macrophage infiltration in the abdominal adipose tissue and the unbalanced production of adipocyte cytokines (adipokines) was an essential step towards novel research perspectives for a better understanding of the molecular mechanisms governing the development of insulin resistance. Furthermore, in an obese state, the increased cellular uptake of non-esterified fatty acids is exacerbated without any subsequent β-oxidation. This in turn contributes to the accumulation of intermediate lipid metabolites that cause defects in the insulin signaling pathway. This paper examines the possible cellular mechanisms that connect central obesity with defects in the insulin pathway. It discusses the discrepancies observed from studies organized in cell cultures, animal models and humans. Finally, it emphasizes the need for therapeutic strategies in order to achieve weight reduction in overweight and obese patients with T2D.

Clinical potential of resistin as a novel prognostic biomarker for cellulitis

Cellulitis is an acute, subacute or chronic inflammation of the dermis and subdermal tissues, which is typically caused by bacteria, although other causes are possible. The present study aimed to evaluate the association between resistin levels and the recovery time of patients with cellulitis. In addition, the effect of resistin and insulin resistance on the prognosis of cellulitis was investigated. In total, 52 patients with cellulitis (male, 21; female, 31) and an age-matched group of 42 healthy individuals (male, 18; female, 24) were included in the study. The levels of serum resistin, fasting plasma glucose (FPG), homeostasis model assessment-insulin resistance (HOMA-IR), C-reactive protein (CRP) and other biochemical parameters were compared between the groups. The mean resistin levels in the cellulitis and control groups were 9.4±5.3 and 5.8±3.1 ng/ml, respectively. The levels of resistin, FPG, HOMA-IR and CRP were significantly higher in the cellulitis group compared with the control group (P<0.001). Furthermore, the mean recovery time of the patients with cellulitis was 21.2±5.6 days. Thus, increased levels of resistin (P=0.002) and HOMA-IR (P=0.005) could be used as predictive factors for the recovery time. The enhanced levels of resistin and HOMA-IR were shown to correlate with the high CRP levels in the cellulitis group. Therefore, the results indicated that increased levels of resistin may function as a prognostic marker for cellulitis.

Obesity, adipokines and neuroinflammation

Global levels of obesity are reaching epidemic proportions, leading to a dramatic increase in incidence of secondary diseases and the significant economic burden associated with their treatment. These comorbidities include diabetes, cardiovascular disease, and some psychopathologies, which have been linked to a low-grade inflammatory state. Obese individuals exhibit an increase in circulating inflammatory mediators implicated as the underlying cause of these comorbidities. A number of these molecules are also manufactured and released by white adipose tissue (WAT), in direct proportion to tissue mass and are collectively known as adipokines. In the current review we focused on the role of two of the better-studied members of this family namely, leptin and adiponectin, with particular emphasis on their role in neuro-immune interactions, neuroinflammation and subsequent brain diseases. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Macrophage-derived human resistin is induced in multiple helminth infections and promotes inflammatory monocytes and increased parasite burden

Parasitic helminth infections can be associated with lifelong morbidity such as immune-mediated organ failure. A better understanding of the host immune response to helminths could provide new avenues to promote parasite clearance and/or alleviate infection-associated morbidity. Murine resistin-like molecules (RELM) exhibit pleiotropic functions following helminth infection including modulating the host immune response; however, the relevance of human RELM proteins in helminth infection is unknown. To examine the function of human resistin (hResistin), we utilized transgenic mice expressing the human resistin gene (hRetnTg⁺). Following infection with the helminth Nippostrongylus brasiliensis (Nb), hResistin expression was significantly upregulated in infected tissue. Compared to control hRetnTg⁻ mice, hRetnTg⁺ mice suffered from exacerbated Nb-induced inflammation characterized by weight loss and increased infiltration of inflammatory monocytes in the lung, along with elevated Nb egg burdens and delayed parasite expulsion. Genome-wide transcriptional profiling of the infected tissue revealed that hResistin promoted expression of proinflammatory cytokines and genes downstream of toll-like receptor signaling. Moreover, hResistin preferentially bound lung monocytes, and exogenous treatment of mice with recombinant hResistin promoted monocyte recruitment and proinflammatory cytokine expression. In human studies, increased serum resistin was associated with higher parasite load in individuals infected with soil-transmitted helminths or filarial nematode Wuchereria bancrofti, and was positively correlated with proinflammatory cytokines. Together, these studies identify human resistin as a detrimental factor induced by multiple helminth infections, where it promotes proinflammatory cytokines and impedes parasite clearance. Targeting the resistin/proinflammatory cytokine immune axis may provide new diagnostic or treatment strategies for helminth infection and associated immune-mediated pathology.

Parasitic helminths, which infect an estimated two billion people worldwide, represent a significant global public health problem. Infection is associated with life-long morbidity including growth retardation and organ failure. Despite these debilitating conditions, there are currently no successful vaccines against helminths. Further, great variability in the host immune response to helminths exists, with the ability of some individuals to develop immunity, while others are susceptible when re-exposed or maintain life-long chronic infections. Identifying new factors that are differentially expressed in immune versus susceptible individuals could provide new targeting strategies for diagnosis or treatment of helminth infection. Here, we identify an important immunoregulatory function for human resistin in helminth infection. Employing transgenic mice in which the human resistin gene was inserted, we show that human resistin is induced by infection with the helminth Nippostrongylus brasiliensis, where it promotes excessive inflammation and impedes parasite killing. Moreover, analysis of clinical samples from two cohorts of individuals infected with filarial nematodes or soil-transmitted helminths revealed increased resistin and serum proinflammatory cytokines compared to putatively immune individuals. Together, these studies suggest that human resistin is a detrimental cytokine that is expressed in multiple helminth infections, mediates pathogenic inflammation, and delays parasite clearance.

Wild blueberries (Vaccinium myrtillus) alleviate inflammation and hypertension associated with developing obesity in mice fed with a high-fat diet

Background

Low-grade metabolic inflammation and hypertension are primary mechanisms involved in obesity-associated adverse health effects. Berries, especially Nordic wild blueberries (hereafter referred to as bilberries), represent an important source of dietary anthocyanins, a group of polyphenols with potential beneficial effects to combat obesity-associated metabolic disturbances.

Methods

The effects of 5% or 10% (w/w) of whole bilberries (BB) were studied on the development of obesity and its metabolic disturbances in C57BL mice fed with a high-fat diet (HFD) for three months. Cytokines, inflammatory cells, systolic blood pressure, glucose tolerance, insulin sensitivity, weight gain, body fat, food consumption and energy metabolism were assessed.

Results

Bilberries ameliorated type 1 pro-inflammatory responsiveness induced by HFD. This was indicated by the altered cytokine profile and the reduced prevalence of interferon gamma -producing T-cells, in particular T helper type 1 cells. Bilberries also prevented the progression of obesity associated long term increase in systolic blood pressure in mice.

Conclusions

Bilberries reduce the development of systemic inflammation and prevent the progression of chronic hypertension, thus supporting their potential role in alleviating the adverse health effects associated with developing obesity.

Deletion of apoptosis signal-regulating kinase 1 (ASK1) protects pancreatic beta-cells from stress-induced death but not from glucose homeostasis alterations under pro-inflammatory conditions

BACKGROUND

Type 2 diabetes is characterized by pancreatic beta-cell dysfunction and is associated with low-grade inflammation. Recent observations suggest that apoptosis signal-regulating kinase 1 (ASK1) is involved in beta-cell death in response to different stressors. In this study, we tested whether ASK1 deficiency protects beta-cells from glucolipotoxic conditions and cytokines treatment or from glucose homeostasis alteration induced by endotoxemia.

METHODOLOGY/PRINCIPAL FINDINGS

Insulin secretion was neither affected upon shRNA-mediated downregulation of ASK1 in MIN6 cells nor in islets from ASK1-deficient mice. ASK1 silencing in MIN6 cells and deletion in islets did not prevent the deleterious effect of glucolipotoxic conditions or cytokines on insulin secretion. However, it protected MIN6 cells from death induced by ER stress or palmitate and islets from short term caspase activation in response to cytokines. Moreover, endotoxemia induced by LPS infusion increased insulin secretion during hyperglycemic clamps but the response was similar in wild-type and ASK1-deficient mice. Finally, insulin sensitivity in the presence of LPS was not affected by ASK1-deficiency.

CONCLUSIONS/SIGNIFICANCE

Our study demonstrates that ASK1 is not involved in beta-cell function and dysfunction but controls stress-induced beta-cell death.

Maternal diet-induced microRNAs and mTOR underlie β cell dysfunction in offspring

A maternal diet that is low in protein increases the susceptibility of offspring to type 2 diabetes by inducing long-term alterations in β cell mass and function. Nutrients and growth factor signaling converge through mTOR, suggesting that this pathway participates in β cell programming during fetal development. Here, we revealed that newborns of dams exposed to low-protein diet (LP0.5) throughout pregnancy exhibited decreased insulin levels, a lower β cell fraction, and reduced mTOR signaling. Adult offspring of LP0.5-exposed mothers exhibited glucose intolerance as a result of an insulin secretory defect and not β cell mass reduction. The β cell insulin secretory defect was distal to glucose-dependent Ca2+ influx and resulted from reduced proinsulin biosynthesis and insulin content. Islets from offspring of LP0.5-fed dams exhibited reduced mTOR and increased expression of a subset of microRNAs, and blockade of microRNA-199a-3p and -342 in these islets restored mTOR and insulin secretion to normal. Finally, transient β cell activation of mTORC1 signaling in offspring during the last week of pregnancy of mothers fed a LP0.5 rescued the defect in the neonatal β cell fraction and metabolic abnormalities in the adult. Together, these findings indicate that a maternal low-protein diet alters microRNA and mTOR expression in the offspring, influencing insulin secretion and glucose homeostasis.

Elevated resistin levels induce central leptin resistance and increased atherosclerotic progression in mice

AIMS/HYPOTHESIS

Resistin was originally identified as an adipocyte-derived factor upregulated during obesity and as a contributor to obesity-associated insulin resistance. Clinically, resistin has also been implicated in cardiovascular disease in a number of different patient populations. Our aim was to simultaneously address these phenomena.

METHODS

We generated mice with modest adipocyte-specific resistin overexpression. These mice were crossed with mice deficient in the LDL receptor (Ldlr (-/-)) to probe the physiological role of resistin. Both metabolic and atherosclerotic assessments were performed.

RESULTS

Resistin overexpression led to increased atherosclerotic progression in Ldlr (-/-) mice. This was in part related to elevated serum triacylglycerol levels and a reduced ability to clear triacylglycerol upon a challenge. Additional phenotypic changes, such as increased body weight and reduced glucose clearance, independent of the Ldlr (-/-) background, confirmed increased adiposity associated with a more pronounced insulin resistance. A hallmark of elevated resistin was the disproportionate increase in circulating leptin levels. These mice thus recapitulated both the proposed negative cardiovascular correlation and the insulin resistance. A unifying mechanism for this complex phenotype was a resistin-mediated central leptin resistance, which we demonstrate directly both in vivo and in organotypic brain slices. In line with reduced sympathetic nervous system outflow, we found decreased brown adipose tissue (BAT) activity. The resulting elevated triacylglycerol levels provide a likely explanation for accelerated atherosclerosis.

CONCLUSIONS/INTERPRETATION

Resistin overexpression leads to a complex metabolic phenotype driven by resistin-mediated central leptin resistance and reduced BAT activity. Hypothalamic leptin resistance thus provides a unifying mechanism for both resistin-mediated insulin resistance and enhanced atherosclerosis.

Human resistin promotes neutrophil proinflammatory activation and neutrophil extracellular trap formation and increases severity of acute lung injury

Although resistin was recently found to modulate insulin resistance in preclinical models of type II diabetes and obesity, recent studies also suggested that resistin has proinflammatory properties. We examined whether the human-specific variant of resistin affects neutrophil activation and the severity of LPS-induced acute lung injury. Because human and mouse resistin have distinct patterns of tissue distribution, experiments were performed using humanized resistin mice that exclusively express human resistin (hRTN(+/-)(/-)) but are deficient in mouse resistin. Enhanced production of TNF-α or MIP-2 was found in LPS-treated hRtn(+/-/-) neutrophils compared with control Rtn(-/-/-) neutrophils. Expression of human resistin inhibited the activation of AMP-activated protein kinase, a major sensor and regulator of cellular bioenergetics that also is implicated in inhibiting inflammatory activity of neutrophils and macrophages. In addition to the ability of resistin to sensitize neutrophils to LPS stimulation, human resistin enhanced neutrophil extracellular trap formation. In LPS-induced acute lung injury, humanized resistin mice demonstrated enhanced production of proinflammatory cytokines, more severe pulmonary edema, increased neutrophil extracellular trap formation, and elevated concentration of the alarmins HMGB1 and histone 3 in the lungs. Our results suggest that human resistin may play an important contributory role in enhancing TLR4-induced inflammatory responses, and it may be a target for future therapies aimed at reducing the severity of acute lung injury and other inflammatory situations in which neutrophils play a major role.

Resistin in rodents and humans

Obesity is characterized by excess accumulation of lipids in adipose tissue and other organs, and chronic inflammation associated with insulin resistance and an increased risk of type 2 diabetes. Obesity, type 2 diabetes, and cardiovascular diseases are major health concerns. Resistin was first discovered as an adipose-secreted hormone (adipokine) linked to obesity and insulin resistance in rodents. Adipocyte-derived resistin is increased in obese rodents and strongly related to insulin resistance. However, in contrast to rodents, resistin is expressed and secreted from macrophages in humans and is increased in inflammatory conditions. Some studies have also suggested an association between increased resistin levels and insulin resistance, diabetes and cardiovascular disease. Genetic studies have provided additional evidence for a role of resistin in insulin resistance and inflammation. Resistin appears to mediate the pathogenesis of atherosclerosis by promoting endothelial dysfunction, vascular smooth muscle cell proliferation, arterial inflammation, and formation of foam cells. Indeed, resistin is predictive of atherosclerosis and poor clinical outcomes in patients with coronary artery disease and ischemic stroke. There is also growing evidence that elevated resistin is associated with the development of heart failure. This review will focus on the biology of resistin in rodents and humans, and evidence linking resistin with type 2 diabetes, atherosclerosis, and cardiovascular disease.

Human resistin in chemotherapy-induced heart failure in humanized male mice and in women treated for breast cancer

Resistin is a circulating mediator of insulin resistance mainly expressed in human monocytes and responsive to inflammatory stimuli. Recent clinical studies have connected elevated resistin levels with the development and severity of heart failure. To further our understanding of the role of human resistin in heart failure, we studied a humanized mouse model lacking murine resistin but transgenic for the human Retn gene (Hum-Retn mice), which exhibits basal and inflammation-stimulated resistin levels similar to humans. Specifically, we explored whether resistin underlies acute anthracycline-induced cardiotoxicity. Remarkably, doxorubicin (25mg/kg ip) led to a 4-fold induction of serum resistin levels in Hum-Retn mice. Moreover, doxorubicin-induced cardiotoxicity was greater in the Hum-Retn mice than in littermate controls not expressing human resistin (Retn(-/-)). Hum-Retn mice showed increased cardiac mRNA levels of inflammatory and cell adhesion genes compared with Retn(-/-) mice. Macrophages, but not cardiomyocytes, from Hum-Retn mice treated with doxorubicin in vitro showed dramatic induction of hRetn (human resistin) mRNA and protein expression. We also examined resistin levels in anthracycline-treated breast cancer patients with and without cardiotoxicity. Intriguingly, serum resistin levels in women undergoing anthracycline-containing chemotherapy increased significantly at 3 months and remained elevated at 6 months in those with subsequent cardiotoxicity. Further, elevation in resistin correlated with decline in ejection fraction in these women. These results suggest that elevated resistin is a biomarker of anthracycline-induced cardiotoxicity and may contribute in the development of heart failure via its direct effects on macrophages. These results further implicate resistin as a link between inflammation, metabolism, and heart disease.

Resistin affects lipid metabolism during adipocyte maturation of 3T3-L1 cells

Resistin, an adipose-tissue-specific secretory factor, aggravates metabolic syndrome through impairment of glucose metabolism. Previously, we demonstrated that resistin expression was induced in both 3T3-L1 cells and primary pre-adipocytes derived from Zucker obese rats during the process of differentiation and maturation (Ikeda Y, Hama S, Kajimoto K, Okuno T, Tsuchiya H & Kogure K (2011) Biol Pharm Bull 34, 865-870). However, the biological function of resistin in adipocytes is poorly understood. In the present study, we examined the effects of resistin knockdown on the biological features of 3T3-L1 cells. We found that lipid content was significantly decreased in 3T3-L1 cells transfected with anti-resistin small interfering RNA (siRNA) after adipocyte differentiation. While expression of peroxisome proliferator activated receptor γ and CCAAT/enhancer-binding protein α was not affected, protein expression and transcriptional activity levels of carbohydrate response element binding protein (ChREBP), which upregulates transcription of lipogenic genes, decreased after anti-resistin siRNA treatment. Moreover, gene expression of fatty acid synthase and acetyl-CoA carboxylase 2, which are known to be regulated by ChREBP, were also suppressed by resistin knockdown. In contrast, activity of the fatty acid β-oxidation-regulating protein carnitine palmitoyltransferase 1 increased. These results suggest that resistin knockdown induces suppression of lipid production and activation of fatty acid β-oxidation. Consequently, resistin may affect lipid metabolism during adipocyte maturation.

Rapid cloning and comparative sequence analysis of full-length cDNA of Rhesus monkey (Macaca mulatta) resistin

Resistin protein is thought to link insulin resistance in murine models of obesity and type-2 diabetes, but the role of resistin in human studies of inflammatory metabolic disorders have generated conflicting data. Here, we describe the structure of the resistin gene using adipose tissue from non-human primates (NHPs), which have been used extensively to model a host of human diseases. Full-length cDNA from rhesus macaque resistin obtained by rapid amplification of cDNA ends (RACE) is comprised of 526 nucleotides covering an open-reading frame (ORF) that encodes a 108-amino-acid protein that is 92% homologous with the human counterpart but only 60% homologous with the murine counterpart. Using a modified polymerase chain reaction technique, we identified single nucleotide polymorphisms and a 78-bp deletion within resistin cDNA of nine rhesus macaques. Comparisons of the full-length cDNA sequence and an amplified 569-bp genomic DNA sequence revealed an error in published predictions arising from genomic studies about the gene's exon 3 region. Our data show, for the first time, the full-length macaque resistin cDNA sequence (GenBank: JF740676.1). These findings will illuminate future studies into the role of resistin in NHP models of inflammatory metabolic diseases.

Oral Angiotensin-(1-7) prevented obesity and hepatic inflammation by inhibition of resistin/TLR4/MAPK/NF-κB in rats fed with high-fat diet

Obesity is characterized by a pro-inflammatory state commonly associated with type 2 diabetes and fat-liver disease. In the last few years, different studies pointed out the role of Angiotensin (Ang)-(1-7) in the metabolic regulation. The aim of the present study was to evaluate the effect of oral-administration of Ang-(1-7) in metabolism and inflammatory state of high-fat feed rats. Twenty-four male Sprague Dawley rats were randomized into three groups: High Fat Diet (HFD); Standard Diet (ST); High Fat Diet+Angiotensin-(1-7) [HFD+Ang-(1-7)]. Glycemic profile was evaluated by glucose tolerance and insulin sensitivity tests, plasmatic glucose and insulin. Cholesterol, HDL and triglycerides analyses presented lipidic profile. RT-PCR evaluated mRNA expression to ACE, ACE2, resistin, TLR4, IL-6, TNF-α and NF-κB genes. The main results showed that oral Ang-(1-7) decreased body weight and abdominal fat-mass. In addition, HFD+Ang-(1-7) treated rats presented enhanced glucose tolerance, insulin-sensitivity and decreased plasma-insulin levels, as well as a significant decrease in circulating lipid levels. These alterations were accompanied by a marked decreased expression of resistin, TLR4, ACE and increased ACE2 expression in liver. Furthermore, Ang-(1-7) decreases phosphorylation of MAPK and increases NF-κB expression. These alterations diminished expression of interleukin-6 and TNF-α, ameliorate inflammatory state in liver. In summary, the present study showed that oral-treatment with Ang-(1-7) in high-fat feed rats improved metabolism down-regulating resistin/TLR4/NF-κB-pathway.

Significant interaction between RETN -420 G/G genotype and lower BMI on decreased risk of type 2 diabetes mellitus (T2DM) in Japanese--the J-MICC Study

We examined the association of the RETN (resistin) -420 C>G polymorphism (rs1862513) with risk of diabetes mellitus (DM), considering lifestyle factors, in Japanese. Subjects were participants of J-MICC Study, where 2,651 participants aged 35-69 years provided their blood for genotyping and lifestyle data after informed consent. Odds ratio (OR) of DM for RETN-420 G/G genotype was estimated using unconditional logistic regression model. Statistically significant interaction on risk of DM was observed between RETN-420 G/G genotype and BMI<25 (OR for interaction = 0.12; P = 0.046), and when subjects with RETN-420 C/C+C/G and BMI ≥ 25 (n = 69 for DM and 544 for non-DM) were defined as the reference, the adjusted ORs for subjects with RETN-420 G/G genotype and BMI>25 (n = 10 for DM and 111 for non-DM), RETN-420 C/C+C/G and BMI<25 (n = 81 for DM and 1,605 for non-DM), and RETN-420 G/G and BMI<25 (n = 1 for DM and 230 for non-DM) were demonstrated to be 0.72 (95% confidence interval: 0.36-1.46), 0.40 (0.28-0.56) and 0.03 (0.005-0.25), respectively. The present study revealed the significant interaction of RETN-420 G/G genotype with lower BMI on the decreased risk of DM, but the direction was opposite to the reported ones in Japanese. We should be careful in interpretation of the present study results because of the limited sample sizes. Further investigation of this association as well as of the actual biological roles of RETN in the genesis of human metabolic disorders including DM will be required.

Long-term interdisciplinary therapy reduces endotoxin level and insulin resistance in obese adolescents

AIM

The purpose of the present study was to assess the dietary fat intake, glucose, insulin, Homeostasis model assessment for insulin resistance HOMA-IR, and endotoxin levels and correlate them with adipokine serum concentrations in obese adolescents who had been admitted to long-term interdisciplinary weight-loss therapy.

DESIGN

The present study was a longitudinal clinical intervention of interdisciplinary therapy. Adolescents (n = 18, aged 15-19 y) with a body mass index > 95th percentile were admitted and evaluated at baseline and again after 1 year of interdisciplinary therapy. We collected blood samples, and IL-6, adiponectin, and endotoxin concentrations were measured by ELISA. Food intake was measured using 3-day diet records. In addition, we assessed glucose and insulin levels as well as the homeostasis model assessment for insulin resistance (HOMA-IR).

RESULTS

The most important finding from the present investigation was that the long-term interdisciplinary lifestyle therapy decreased dietary fat intake and endotoxin levels and improved HOMA-IR. We observed positive correlations between dietary fat intake and endotoxin levels, insulin levels, and the HOMA-IR. In addition, endotoxin levels showed positive correlations with IL-6 levels, insulin levels and the HOMA-IR. Interestingly, we observed a negative correlation between serum adiponectin and both dietary fat intake and endotoxin levels.

CONCLUSIONS

The present results indicate an association between dietary fat intake and endotoxin level, which was highly correlated with a decreased pro-inflammatory state and an improvement in HOMA-IR. In addition, this benefits effect may be associated with an increased adiponectin level, which suggests that the interdisciplinary therapy was effective in improving inflammatory pathways.

High leptin and resistin expression in chronic heart failure: adverse outcome in patients with dilated and inflammatory cardiomyopathy

AIM

The expression of leptin and resistin is known to be positively correlated with the incidence of chronic heart failure (CHF). Both adipokines have been implicated in immunomodulation and cardiac remodelling. Therefore, we performed for the first time a clinical study to elucidate the effects of leptin and resistin on progression of CHF in patients with non-ischaemic dilated (DCM) and inflammatory (DCMi) cardiomyopathy.

METHODS AND RESULTS

For the clinical study 120 patients were divided into a control (n = 16), DCM (n = 52), and DCMi (n = 52) group to determine the effect of leptin and resistin on CHF progression. Nuclear factor-κB (NF-κB) activation, reactive oxygen species generation, and tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) expression following adipokine exposition were determined in vitro in cardiomyocytes. Leptin and resistin systemic plasma levels and not cardiac expression were significantly elevated in patients with DCM (leptin, 13.12 ± 17.2 ng/mL, P < 0.05; resistin, 6.87 ± 2.25 ng/mL, P < 0.05) and DCMi (leptin, 13.63 ± 16 ng/mL, P < 0.05; resistin, 7.27 ± 2.2 ng/mL, P < 0.05) compared with the control group (leptin, 7.34 ± 5.7 ng/mL; resistin, 4.4 ± 1.18 ng/mL). A multivariate linear regression model revealed low leptin and resistin plasma levels as contributors for favourable cardiac functional parameters at 6-month follow-up independent of inflammatory conditions. Cell culture experiments in vitro showed leptin and resistin to be potent regulators of TNF-α and IL-6 expression in cardiomyocytes, leading to significantly increased redox stress in cardiac cells.

CONCLUSIONS

High leptin and resistin expression in patients with DCM and DCMi is associated with CHF progression, i.e. severe cardiac dysfunction, independent of immune responses.

Serial changes in adiponectin and resistin in critically ill patients with sepsis: associations with sepsis phase, severity, and circulating cytokine levels

PURPOSE

The aim of the present study was to describe the variation in adiponectin and resistin levels, 2 adipokines with opposing effects on metabolism, in mechanically ventilated patients with sepsis and their relationships to disease severity and cytokine levels.

MATERIALS AND METHODS

An observational prospective study was conducted in a secondary/tertiary unit. Forty-one mechanically ventilated patients diagnosed as having sepsis were included in the study. The Acute Physiology and Chronic Health Evaluation II and Sequential Organ Failure Assessment scores were estimated. Adiponectin, resistin, and cytokines were measured upon sepsis diagnosis and every 3 to 4 days thereafter until day 30. Adiponectin and resistin were also measured in 40 controls.

RESULTS

The patients had higher adiponectin (10.9 ± 6.1 μg/mL vs 6.0 ± 2.9 μg/mL, P < .001) and resistin (24.7 ng/mL vs 3.8 ng/mL, P < .001) levels compared with the controls. Adiponectin increased and resistin decreased significantly over time in the entire cohort. Resistin correlated with Acute Physiology and Chronic Health Evaluation II, Sequential Organ Failure Assessment, interleukin (IL)-6, IL-8, and IL-10 and was significantly higher in severe sepsis/septic shock compared with sepsis. No correlations between adiponectin and clinical scores were noted.

CONCLUSIONS

Adiponectin and resistin change reciprocally during the course of sepsis. Resistin relates to the severity of sepsis and the degree of inflammatory response. Adiponectin and resistin may play a critical role in the metabolic adaptations observed in sepsis.

Visceral fat mass is always, but adipokines (adiponectin and resistin) are diversely associated with insulin resistance in Chinese type 2 diabetic and normoglycemic subjects

AIMS

The present study investigated alteration of abdominal visceral fat mass (VFM) and its relationship to adipokines and insulin resistance (IR) in obese and non-obese type 2 diabetes and normoglycemic subjects.

METHODS

Twenty-two diabetic patients and 37 normoglycemic controls were subgrouped into obese and non-obese according to their BMI. VFM was quantified by computed tomography. Plasma adiponectin and resistin, two adipokines exert contrary effects on insulin sensitivity were measured. Insulin sensitivity was evaluated by an established HOMA model.

RESULTS

Obese subjects showed remarkably expanded VFM, while non-obese diabetes obtained more abundant VFM than non-obese controls (104 ± 50 cm(2)vs. 77 ± 26 cm(2), P<0.05). Plasma adiponectin was only significantly decreased in obese diabetes. Plasma resistin was increased in diabetes, but compared between obese and non-obese subjects. Diabetic patients and obese controls were significantly insulin resistant. HOMA-IR index positively correlated to VFM in both groups (r=0.563, P=0.011 for diabetes and r=0.671, P=0.000 for controls). In diabetes but not controls, plasma adiponectin negatively related to VFM (r=-0.687, P=0.000) and HOMA-IR index (r=-0.659, P=0.002), while resistin had no relation to IR and VFM in both groups.

CONCLUSIONS

Increased VFM may lead to IR by mechanisms beyond adipokines in Chinese type 2 diabetic and normoglycemic subjects.

Disassociation of muscle insulin signaling and insulin-stimulated glucose uptake during endotoxemia

Lipopolysaccharide (LPS) elicits a strong immune response, which leads to the release of inflammatory cytokines. Increased cytokine production has been shown to impair insulin-mediated glucose disposal. LPS can alter other factors, such as muscle blood flow and insulin signaling in the myocyte,that can influence glucose disposal. We hypothesize that LPS induced impairments in cardiovascular function contribute to the associated impairments in insulin action in vivo. Male wild-type C57BL/6J mice had a catheter implanted in the jugular vein for infusions and the carotid artery for sampling 5 days prior to the hyperinsulinemic-euglycemic clamp. Mice were treated with vehicle, low-(1 ug/gBW) or high-dose (10 ug/gBW) LPS 4 hours prior to the clamp. Muscle glucose uptake (MGU) was assessed using [2-¹⁴C] deoxyglucose. While both low- and high-dose LPS inhibited insulin-stimulated MGU compared to vehicle-treated mice, the impairment was more significant with the high-dose treatment (∼25% in soleus and ∼70% in both gastrocnemius and vastus lateralis). Interestingly, insulin signaling through the PI3-kinase pathway in the muscle was not affected by this treatment suggesting that the decrease in MGU is not directly due to impairments in muscle insulin action. Echocardiography demonstrated that high-dose LPS treatment significantly decreased stroke volume (∼30%), heart rate (∼35%), and cardiac output (∼50%). These observations were not seen with vehicle or low-dose LPS treatment. High-dose LPS treatment also significantly decreased muscle blood flow (∼70%) and whole body oxygen consumption (∼50%). Thus, in vivo acute endotoxemia does not impair insulin signaling through the PI3-kinase pathway in skeletal muscle and decreased tissue blood flow likely plays a central role in the impairment of glucose uptake in the muscle.

Effect of volatile oil from Cinnamomi Cortex on blood glucose and lipid metabolism in insulin-resistant mice

AIM: To investigate the effect of volatile oil from Cinnamomi Cortex (VOCC) on blood glucose and lipid metabolism in insulin-resistant mice and to investigate the possible mechanisms involved.

METHODS: Insulin resistance was induced by feeding a high-fat diet. After insulin-resistant mice were treated orally with VOCC, oral glucose tolerance test and insulin tolerance test were performed. The body weight, blood glucose, serum insulin, total cholesterol, triglyceride, leptin, resistin, and adiponectin were determined using biochemical methods.

RESULTS: VOCC administration decreased body weight gain (30.3 ± 3.6 vs 34.6 ± 3.1, P < 0.05), blood glucose (7.6 ± 2.2 vs 9.2 ± 1.3, P < 0.05), serum insulin (1.3 ± 0.1 vs 1.7 ± 0.2, P < 0.05), total cholesterol (70.1 ± 10.9 vs 65.4 ± 19.5, P < 0.05), triglyceride (93.2 ± 13.8 vs 102.3 ± 21.5, P < 0.05), leptin, and resistin levels. Treatment with VOCC also decreased insulin resistance by improving oral glucose tolerance and insulin tolerance.

CONCLUSION: VOCC improved blood glucose and lipid metabolism by reducing serum leptin and resistin in insulin-resistant mice, thereby enhancing insulin sensitivity.