Holdemanella biformis improves glucose tolerance and regulates GLP-1 signaling in obese mice.

Impaired glucose homeostasis in obesity is mitigated by enhancing the glucoregulatory actions of glucagon-like peptide 1 (GLP-1), and thus, strategies that improve GLP-1 sensitivity and secretion have therapeutic potential for the treatment of type 2 diabetes. This study shows that Holdemanella biformis, isolated from the feces of a metabolically healthy volunteer, ameliorates hyperglycemia, improves oral glucose tolerance and restores gluconeogenesis and insulin signaling in the liver of obese mice. These effects were associated with the ability of H. biformis to restore GLP-1 levels, enhancing GLP-1 neural signaling in the proximal and distal small intestine and GLP-1 sensitivity of vagal sensory neurons, and to modify the cecal abundance of unsaturated fatty acids and the bacterial species associated with metabolic health. Our findings overall suggest the potential use of H biformis in the management of type 2 diabetes in obesity to optimize the sensitivity and function of the GLP-1 system, through direct and indirect mechanisms.

BMPER is upregulated in obesity and seems to have a role in pericardial adipose stem cells.

Pericardial adipose tissue (PAT), a visceral fat depot enveloping the heart, is an active endocrine organ and a source of free fatty acids and inflammatory cytokines. As in other fat adult tissues, PAT contains a population of adipose stem cells; however, whether these cells and/or their environment play a role in physiopathology is unknown. We analyzed several stem cell-related properties of pericardial adipose stem cells (PSCs) isolated from obese and ex-obese mice. We also performed RNA-sequencing to profile the transcriptional landscape of PSCs isolated from the different diet regimens. Finally, we tested whether these alterations impacted on the properties of cardiac mesoangioblasts isolated from the same mice. We found functional differences between PSCs depending on their source: specifically, PSCs from obese PSC (oPSC) and ex-obese PSC (dPSC) mice showed alterations in apoptosis and migratory capacity when compared with lean, control PSCs, with increased apoptosis in oPSCs and blunted migratory capacity in oPSCs and dPSCs. This was accompanied by different gene expression profiles across the cell types, where we identified some genes altered in obese conditions, such as BMP endothelial cell precursor-derived regulator (BMPER), an important regulator of BMP-related signaling pathways for endothelial cell function. The importance of BMPER in PSCs was confirmed by loss- and gain-of-function studies. Finally, we found an altered production of BMPER and some important chemokines in cardiac mesoangioblasts in obese conditions. Our findings point to BMPER as a potential new regulator of PSC function and suggest that its dysregulation could be associated with obesity and may impact on cardiac cells.

Resistin is co-secreted with adiponectin in white mouse adipocytes.

In the current work we have investigated the cellular and molecular regulation of resistin secretion in cultured and primary mouse adipocytes. Resistin is an adipose tissue hormone proposed to contribute to metabolic disease. In rodents, resistin is secreted from white adipocytes whereas it is in humans synthesised and released from other cell types within white adipose tissue. The metabolic importance of resistin has been studied in both mouse and man, but the regulation of its release remains poorly investigated. Here we define that, in mouse adipocytes, resistin secretion is triggered by an intracellular elevation of cAMP and/or Ca2+. Resistin release is stimulated via activation of beta 3 adrenergic receptors (ß3ARs) and the downstream signalling protein exchange protein activated by cAMP (Epac). The secretion of resistin is markedly abrogated in adipocytes isolated from obese and diabetic mice. Immunocytochemical staining demonstrates a significant overlap between signals for resistin and the adipocyte hormone adiponectin. Our data propose that resistin and adiponectin are contained within the same vesicles in mouse adipocytes and that the two hormones are co-secreted in response to the same exocytosis-triggering signals.

Hypothalamic long noncoding RNA AK044061 is involved in the development of dietary obesity in mice.

BACKGROUND: Long noncoding RNAs (lncRNAs) have been implicated in various important biological processes, however, its role in energy balance and obesity remains largely unknown. METHODS: Differentially expressed lncRNAs in the hypothalamus of diet-induced obesity (DIO) mice versus chow-fed mice were identified by RNA sequencing. Lentivirus-mediated overexpression and knockdown of a novel lncRNA, AK044061, were used to assess its role in energy balance and the development of DIO. RNA immunoprecipitation (RIP) and pull down assays were carried out to analyze the interaction between lncRNA AK044061 and RelA, an NF-κB subunit. RESULTS: LncRNA AK044061 was upregulated in the hypothalamus of DIO mice. Acute intracerebroventricular (i.c.v.) infusion of glucose reduced the expression of lncRNA AK044061, whereas an overnight of fasting enhanced its expression. RNA in situ hybridization data showed that AK044061 was expressed in the neurons of the arcuate nucleus (ARC). Lentivirus-mediated overexpression of AK044061 in ARC cells, or in the neurons of the ARC nucleus led to an obesity-like phenotype and related metabolic disorders. Furthermore, knockdown of lncRNA AK044061 in Agouti-related peptide (AgRP)-expressing neurons mitigated DIO and its related metabolic dysregulations. In mechanism, we showed that lncRNA AK044061 was associated with RelA and could enhance the NF-κB reporter activity. The effect of lncRNA AK044061 on energy balance is mediated by NF-κB. CONCLUSIONS: Our findings suggest that excessive lncRNA AK044061 in the ARC nucleus leads to energy imbalance and obesity. LncRNA AK044061 expressed in the AgRP neurons is important in the development of dietary obesity in mice.

Obesity reduces mammary epithelial cell TGFß1 activity through macrophage-mediated extracellular matrix remodeling.

Obesity is a risk factor for breast cancer in postmenopausal and high-risk premenopausal women. Changes within the obese breast microenvironment may increase breast cancer risk. Transforming growth factor beta-1 (TGFß1) is a major regulator of mammary epithelial stem/progenitor cells, and its activity is dysregulated under conditions of obesity. Using a high-fat diet model of obesity in mice and breast tissue from women, we observed that TGFß1 activity is reduced in breast epithelial cells in obesity. Breast ducts and lobules demonstrated increased decorin in the extracellular matrix (ECM) surrounding epithelial cells, and we observed that decorin and latent TGFß1 complexed together. Under conditions of obesity, macrophages expressed higher levels of decorin and were significantly increased in number surrounding breast epithelial cells. To investigate the relationship between macrophages and decorin expression, we treated obese mice with either IgG control or anti-F4/80 antibodies to deplete macrophages. Mice treated with anti-F4/80 antibodies demonstrated reduced decorin surrounding mammary ducts and enhanced TGFß1 activity within mammary epithelial cells. Given the role of TGFß1 as a tumor suppressor, reduced epithelial TGFß1 activity and enhanced TGFß1 within the ECM of obese mammary tissue may enhance breast cancer risk.

Plasma metabolomics analysis of the effects of drinking soda water on hyperglycemia mice using ultrahigh-pressure liquid chromatography-quadrupole-time of flight-mass spectrometry.

The aim of this study was to evaluate the effects of a natural soda water [Shi Han Quan (SHQ)] on hyperglycemia and plasma metabolic profiling and explore the mechanism using metabolomics techniques. Kun-Ming mice weighing 26 ± 2 g were used for the hyperglycemia animal model with alloxan and divided into control, hyperglycemia (HG), and HG + SHQ soda water (SHQ) groups. The experiment lasted for 30 days. The plasma metabolomic profiling of mice was determined using ultrahigh-pressure liquid chromatography-quadrupole-time of flight-mass spectrometry. After the mice drank SHQ soda water, the levels of insulin and blood glucose were significantly lower in the SHQ group compared with the control group, and the level of insulin sensitivity [insulin sensitivity index (ISI)] was significantly higher in the SHQ group compared with the HG group. The mice in the different groups after SHQ intervention could be separated into distinct clusters, and nine major plasma metabolites with significant differences between groups were found closely associated with blood glucose and ISI. The metabolic pathway analysis of these metabolites involved abnormal fatty acid oxidation and phospholipid, acylcarnitine, and corticoid metabolism. The results suggested the metabolic changes and possible mechanism of SHQ improving the alloxan-induced HG, and the findings provided insights into the prevention and control of HG and diabetes.

Deficient Leptin Cellular Signaling Plays a Key Role in Brain Ultrastructural Remodeling in Obesity and Type 2 Diabetes Mellitus.

The triad of obesity, metabolic syndrome (MetS), Type 2 diabetes mellitus (T2DM) and advancing age are currently global societal problems that are expected to grow over the coming decades. This triad is associated with multiple end-organ complications of diabetic vasculopathy (maco-microvessel disease), neuropathy, retinopathy, nephropathy, cardiomyopathy, cognopathy encephalopathy and/or late-onset Alzheimer's disease. Further, obesity, MetS, T2DM and their complications are associated with economical and individual family burdens. This review with original data focuses on the white adipose tissue-derived adipokine/hormone leptin and how its deficient signaling is associated with brain remodeling in hyperphagic, obese, or hyperglycemic female mice. Specifically, the ultrastructural remodeling of the capillary neurovascular unit, brain endothelial cells (BECs) and their endothelial glycocalyx (ecGCx), the blood-brain barrier (BBB), the ventricular ependymal cells, choroid plexus, blood-cerebrospinal fluid barrier (BCSFB), and tanycytes are examined in female mice with impaired leptin signaling from either dysfunction of the leptin receptor (DIO and db/db models) or the novel leptin deficiency (BTBR ob/ob model).

Endothelial ADAM17 Expression in the Progression of Kidney Injury in an Obese Mouse Model of Pre-Diabetes.

Disintegrin and metalloproteinase domain 17 (ADAM17) activates inflammatory and fibrotic processes through the shedding of various molecules such as Tumor Necrosis Factor-α (TNF-α) or Transforming Growht Factor-α (TGF-α). There is a well-recognised link between TNF-α, obesity, inflammation, and diabetes. In physiological situations, ADAM17 is expressed mainly in the distal tubular cell while, in renal damage, its expression increases throughout the kidney including the endothelium. The aim of this study was to characterize, for the first time, an experimental mouse model fed a high-fat diet (HFD) with a specific deletion of Adam17 in endothelial cells and to analyse the effects on different renal structures. Endothelial Adam17 knockout male mice and their controls were fed a high-fat diet, to induce obesity, or standard rodent chow, for 22 weeks. Glucose tolerance, urinary albumin-to-creatinine ratio, renal histology, macrophage infiltration, and galectin-3 levels were evaluated. Results showed that obese mice presented higher blood glucose levels, dysregulated glucose homeostasis, and higher body weight compared to control mice. In addition, obese wild-type mice presented an increased albumin-to-creatinine ratio; greater glomerular size and mesangial matrix expansion; and tubular fibrosis with increased galectin-3 expression. Adam17 deletion decreased the albumin-to-creatinine ratio, glomerular mesangial index, and tubular galectin-3 expression. Moreover, macrophage infiltration in the glomeruli of obese Adam17 knockout mice was reduced as compared to obese wild-type mice. In conclusion, the expression of ADAM17 in endothelial cells impacted renal inflammation, modulating the renal function and histology in an obese pre-diabetic mouse model.

Inhibition of PU.1 ameliorates metabolic dysfunction and non-alcoholic steatohepatitis.

BACKGROUND & AIMS: Obesity is a well-established risk factor for type 2 diabetes (T2D) and non-alcoholic steatohepatitis (NASH), but the underlying mechanisms remain incompletely understood. Herein, we aimed to identify novel pathogenic factors (and possible therapeutic targets) underlying metabolic dysfunction in the liver. METHODS: We applied a tandem quantitative proteomics strategy to enrich and identify transcription factors (TFs) induced in the obese liver. We used flow cytometry of liver cells to analyze the source of the induced TFs. We employed conditional knockout mice, shRNA, and small-molecule inhibitors to test the metabolic consequences of the induction of identified TFs. Finally, we validated mouse data in patient liver biopsies. RESULTS: We identified PU.1/SPI1, the master hematopoietic regulator, as one of the most upregulated TFs in livers from diet-induced obese (DIO) and genetically obese (db/db) mice. Targeting PU.1 in the whole liver, but not hepatocytes alone, significantly improved glucose homeostasis and suppressed liver inflammation. Consistently, treatment with the PU.1 inhibitor DB1976 markedly reduced inflammation and improved glucose homeostasis and dyslipidemia in DIO mice, and strongly suppressed glucose intolerance, liver steatosis, inflammation, and fibrosis in a dietary NASH mouse model. Furthermore, hepatic PU.1 expression was positively correlated with insulin resistance and inflammation in liver biopsies from patients. CONCLUSIONS: These data suggest that the elevated hematopoietic factor PU.1 promotes liver metabolic dysfunction, and may be a useful therapeutic target for obesity, insulin resistance/T2D, and NASH. LAY SUMMARY: Expression of the immune regulator PU.1 is increased in livers of obese mice and people. Blocking PU.1 improved glucose homeostasis, and reduced liver steatosis, inflammation and fibrosis in mouse models of non-alcoholic steatohepatitis. Inhibition of PU.1 is thus a potential therapeutic strategy for treating obesity-associated liver dysfunction and metabolic diseases.

Oxygenated Water Inhibits Adipogenesis and Attenuates Hepatic Steatosis in High-Fat Diet-Induced Obese Mice.

The expansion of adipose tissue mass is the primary characteristic of the process of becoming obesity, which causes chronic adipose inflammation and is closely associated with type 2 diabetes mellitus (T2DM). Adipocyte hypertrophy restricts oxygen availability, leading to microenvironmental hypoxia and adipose dysfunction. This study aimed at investigating the effects of oxygenated water (OW) on adipocyte differentiation (adipogenesis) and the metabolic function of mature adipocytes. The effects of OW on adipogenesis and the metabolic function of mature adipocytes were examined. Meanwhile, the in vivo metabolic effects of long-term OW consumption on diet-induced obesity (DIO) mice were investigated. OW inhibited adipogenesis and lipid accumulation through down-regulating critical adipogenic transcription factors and lipogenic enzymes. While body weight, blood and adipose parameters were not significantly improved by long-term OW consumption, transient circulatory triglyceride-lowering and glucose tolerance-improving effects were identified. Notably, hepatic lipid contents were significantly reduced, indicating that the DIO-induced hepatic steatosis was attenuated, despite no improvements in fibrosis and lipid contents in adipose tissue being observed in the OW-drinking DIO mice. The study provides evidence regarding OW's effects on adipogenesis and mature adipocytes, and the corresponding molecular mechanisms. OW exhibits transient triglyceride-lowering and glucose tolerance-improving activity as well as hepatic steatosis-attenuating functions.

Exercise prevents the adverse effects of maternal obesity on placental vascularization and fetal growth.

KEY POINTS: Maternal exercise improves the metabolic health of maternal mice challenged with a high-fat diet. Exercise intervention of obese mothers prevents fetal overgrowth. Exercise intervention reverses impaired placental vascularization in obese mice. Maternal exercise activates placental AMP-activated protein kinase, which was inhibited as a result of maternal obesity. ABSTRACT: More than one-third of pregnant women in the USA are obese and maternal obesity (MO) negatively affects fetal development, which predisposes offspring to metabolic diseases. The placenta mediates nutrient delivery to fetuses and its function is impaired as a result of MO. Exercise ameliorates metabolic dysfunction resulting from obesity, although its effect on placental function of obese mothers has not been explored. In the present study, C57BL/6J female mice were randomly assigned into two groups fed either a control or a high-fat diet (HFD) and then the mice on each diet were further divided into two subgroups with/without exercise. In HFD-induced obese mice, daily treadmill exercise during pregnancy reduced body weight gain, lowered serum glucose and lipid concentration, and improved insulin sensitivity of maternal mice. Importantly, maternal exercise prevented fetal overgrowth (macrosomia) induced by MO. To further examine the preventive effects of exercise on fetal overgrowth, placental vascularization and nutrient transporters were analysed. Vascular density and the expression of vasculogenic factors were reduced as a result of MO but were recovered by maternal exercise. On the other hand, the contents of nutrient transporters were not substantially altered by MO or exercise, suggesting that the protective effects of exercise in MO-induced fetal overgrowth were primarily a result of the alteration of placental vascularization and improved maternal metabolism. Furthermore, exercise enhanced downstream insulin signalling and activated AMP-activated protein kinase in HFD placenta. In sum, maternal exercise prevented fetal overgrowth induced by MO, which was associated with improved maternal metabolism and placental vascularization in obese mothers with exercise.

Fluorescent blood-brain barrier tracing shows intact leptin transport in obese mice.

BACKGROUND/OBJECTIVES: Individuals carrying loss-of-function gene mutations for the adipocyte hormone leptin are morbidly obese, but respond favorably to replacement therapy. Recombinant leptin is however largely ineffective for the vast majority of obese individuals due to leptin resistance. One theory underlying leptin resistance is impaired leptin transport across the blood-brain-barrier (BBB). Here, we aim to gain new insights into the mechanisms of leptin BBB transport, and its role in leptin resistance. METHODS: We developed a novel tool for visualizing leptin transport using infrared fluorescently labeled leptin, combined with tissue clearing and light-sheet fluorescence microscopy. We corroborated these data using western blotting. RESULTS: Using 3D whole brain imaging, we display comparable leptin accumulation in circumventricular organs of lean and obese mice, predominantly in the choroid plexus (CP). Protein quantification revealed comparable leptin levels in microdissected mediobasal hypothalami (MBH) of lean and obese mice (p = 0.99). We further found increased leptin receptor expression in the CP (p = 0.025, p = 0.0002) and a trend toward elevated leptin protein levels in the MBH (p = 0.17, p = 0.078) of obese mice undergoing weight loss interventions by calorie restriction or exendin-4 treatment. CONCLUSIONS: Overall, our findings suggest a crucial role for the CP in controlling the transport of leptin into the cerebrospinal fluid and from there to target areas such as the MBH, potentially mediated via the leptin receptor. Similar leptin levels in circumventricular organs and the MBH of lean and obese mice further suggest intact leptin BBB transport in leptin resistant mice.

Ubiquitin-Specific Peptidase 10 (USP10) Inhibits Hepatic Steatosis, Insulin Resistance, and Inflammation Through Sirt6.

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis, insulin resistance and inflammation, and the pathogenic mechanism of NAFLD is poorly understood. Ubiquitin-specific peptidase 10 (USP10), a member of the ubiquitin-specific protease family, is involved in environmental stress responses, tumor growth, inflammation, and cellular metabolism. However, the role of USP10 in hepatic steatosis, insulin resistance, and inflammation remains largely unexplored. USP10 expression was detected in livers of patients with NAFLD, mice with high-fat diet (HFD)-induced obesity, and genetically obese (ob/ob) mice, as well as in palmitate-induced hepatocytes. The function of USP10 in hepatic steatosis, insulin resistance, and inflammation was investigated using hepatocyte-specific USP10 deficiency or overexpression in mice induced by HFD treatment or genetic defect. The molecular mechanisms underlying USP10-regulated hepatic steatosis were further investigated in HFD-treated mice. USP10 expression was significantly decreased in the fatty livers of NAFLD patients and obese mice and in palmitate-treated hepatocytes. USP10 deficiency exacerbated the metabolic dysfunction induced by HFD treatment for 12 weeks. Conversely, USP10 overexpression significantly suppressed metabolic dysfunction in mice after HFD treatment and inhibited the development of NAFLD in ob/ob mice. Further investigation indicated that USP10 regulates hepatic steatosis by interacting with Sirt6 and inhibiting its ubiquitination and degradation. Sirt6 overexpression markedly ameliorated the effects of USP10 deficiency in hepatic steatosis, insulin resistance, and inflammation. Conversely, Sirt6 deficiency decreased the ameliorative effects of USP10 overexpression in response to HFD treatment. Conclusion: USP10 inhibits hepatic steatosis, insulin resistance, and inflammation through Sirt6.

Effects and mechanisms of apolipoprotein A-V on the regulation of lipid accumulation in cardiomyocytes.

BACKGROUND: Apolipoprotein (apo) A-V is a key regulator of triglyceride (TG) metabolism. We investigated effects of apoA-V on lipid metabolism in cardiomyocytes in this study. METHODS: We first examined whether apoA-V can be taken up by cardiomyocytes and whether low density lipoprotein receptor family members participate in this process. Next, triglyceride (TG) content and lipid droplet changes were detected at different concentrations of apoA-V in normal and lipid-accumulation cells in normal and obese animals. Finally, we tested the levels of fatty acids (FAs) taken up into cardiomyocytes and lipid secretion through [14C]-oleic acid. RESULTS: Our results show that heart tissue has apoA-V protein, and apoA-V is taken up by cardiomyocytes. When HL-1 cells were transfected with low density lipoprotein receptor (LDLR)-related protein 1(LRP1) siRNA, apoA-V intake decreased by 53% (P<0.05), while a 37% lipid accumulation in HL-1 cells remain unchanged. ApoA-V localized to the cytoplasm and was associated with lipid droplets in HL-1 cells. A 1200 and 1800 ng/mL apoA-V intervention decreased TG content by 28% and 45% in HL-1 cells, respectively and decreased TG content by 39% in mouse heart tissue (P<0.05). However, apoA-V had no effects on TG content in either normal HL-1 cells or mice. The levels of FAs taken up into cardiomyocytes decreased by 43% (P < 0.05), and the levels of TG and cholesterol ester secretion increased by 1.2-fold and 1.6-fold, respectively (P < 0.05). CONCLUSION: ApoA-V is a novel regulator of lipid metabolism in cardiomyocytes.

Sphingosine 1-phosphate counteracts insulin signaling in pancreatic ß-cells via the sphingosine 1-phosphate receptor subtype 2.

Glucolipotoxic stress has been identified as a key player in the progression of pancreatic ß-cell dysfunction contributing to insulin resistance and the development of type 2 diabetes mellitus (T2D). It has been suggested that bioactive lipid intermediates, formed under lipotoxic conditions, are involved in these processes. Here, we show that sphingosine 1-phosphate (S1P) levels are not only increased in palmitate-stimulated pancreatic ß-cells but also regulate ß-cell homeostasis in a divergent manner. Although S1P possesses a prosurvival effect in ß-cells, an enhanced level of the sphingolipid antagonizes insulin-mediated cell growth and survival via the sphingosine 1-phosphate receptor subtype 2 (S1P2) followed by an inhibition of Akt-signaling. In an attempt to investigate the role of the S1P/S1P2 axis in vivo, the New Zealand obese (NZO) diabetic mouse model, characterized by ß-cell loss under high-fat diet (HFD) conditions, was used. The occurrence of T2D was accompanied by an increase of plasma S1P levels. To examine whether S1P contributes to the morphologic changes of islets via S1P2, the receptor antagonist JTE-013 was administered. Most interestingly, JTE-013 rescued ß-cell damage clearly indicating an important role of the S1P2 in ß-cell homeostasis. Therefore, the present study provides a new therapeutic strategy to diminish ß-cell dysfunction and the development of T2D.

Obesity resistance and increased hepatic expression of catabolism-related mRNAs in Cnot3+/- mice.

Obesity is a life-threatening factor and is often associated with dysregulation of gene expression. Here, we show that the CNOT3 subunit of the CCR4-NOT deadenylase complex is critical to metabolic regulation. Cnot3(+/-) mice are lean with hepatic and adipose tissues containing reduced levels of lipids, and show increased metabolic rates and enhanced glucose tolerance. Cnot3(+/-) mice remain lean and sensitive to insulin even on a high-fat diet. Furthermore, introduction of Cnot3 haplodeficiency in ob/ob mice ameliorated the obese phenotype. Hepatic expression of most mRNAs is not altered in Cnot3(+/-) vis-à-vis wild-type mice. However, the levels of specific mRNAs, such as those coding for energy metabolism-related PDK4 and IGFBP1, are increased in Cnot3(+/-) hepatocytes, having poly(A) tails that are longer than those seen in control cells. We provide evidence that CNOT3 is involved in recruitment of the CCR4-NOT deadenylase to the 3' end of specific mRNAs. Finally, as CNOT3 levels in the liver and white adipose tissues decrease upon fasting, we propose that CNOT3 responds to feeding conditions to regulate deadenylation-specific mRNAs and energy metabolism.

Inositol 1,4,5-trisphosphate receptor type II (InsP3R-II) is reduced in obese mice, but metabolic homeostasis is preserved in mice lacking InsP3R-II.

Inositol 1,4,5-trisphosphate receptor type II (InsP3R-II) is the most prevalent isoform of the InsP3R in hepatocytes and is concentrated under the canalicular membrane, where it plays an important role in bile secretion. We hypothesized that altered calcium (Ca(2+)) signaling may be involved in metabolic dysfunction, as InsP3R-mediated Ca(2+) signals have been implicated in the regulation of hepatic glucose homeostasis. Here, we find that InsP3R-II, but not InsP3R-I, is reduced in the livers of obese mice. In our investigation of the functional consequences of InsP3R-II deficiency, we found that organic anion secretion at the canalicular membrane and Ca(2+) signals were impaired. However, mice lacking InsP3R-II showed no deficits in energy balance, glucose production, glucose tolerance, or susceptibility to hepatic steatosis. Thus, our results suggest that reduced InsP3R-II expression is not sufficient to account for any disruptions in metabolic homeostasis that are observed in mouse models of obesity. We conclude that metabolic homeostasis is maintained independently of InsP3R-II. Loss of InsP3R-II does impair secretion of bile components; therefore, we suggest that conditions of obesity would lead to a decrease in this Ca(2+)-sensitive process.

Induction of receptor for advanced glycation end products by insufficient leptin action triggers pancreatic ß-cell failure in type 2 diabetes.

Glucolipotoxicity, which is exerted by free fatty acids (FFA) and prolonged hyperglycemia, is implicated in pancreatic ß-cell failure in diabetes. Pattern recognition receptors such as receptor for advanced glycation end products (RAGE) and toll-like receptors 2 and 4 could mediate danger signals in ß-cells. We examined whether RAGE contributes to ß-cell failure in a type 2 diabetes mouse model. Pancreatic islets were isolated from ob/ob, db/db, diet-induced obesity (DIO), RAGE-null (RAGE(-/-) ), and RAGE(+/+) wild-type (WT) control mice and dispersed into single cells for flow cytometry. RAGE expression was detected in insulin-positive ß-cells of ob/ob and db/db mice, but not of WT, DIO, or RAGE(-/-) mice: thus, inadequate leptin receptor signaling and RAGE expression may be linked. Compared with RAGE(+/+) db/db mice, RAGE(-/-) db/db mice showed higher ß-cell number and mass with less apoptosis as well as glucose tolerance with higher insulin secretion without any differences in serum levels of FFA and adiponectin. Palmitate or oleate pretreatment combined with a leptin antagonist induced RAGE expression, AGE-elicited apoptosis, and impaired glucose-stimulated insulin secretion by advanced glycation end products (AGE) in MIN6 cells. FFA elevation with concomitant AGE formation during prolonged hyperglycemia could cause ß-cell damage through insufficient leptin action and subsequent RAGE induction in type 2 diabetes.

Effects of acute exercise over heart proteome from monogenic obese (ob/ob) mice.

Exercise is recognized to prevent and attenuate several metabolic and cardiovascular disorders. Obesity is commonly related to cardiovascular diseases, frequently resulting in heart failure and death. To elucidate the effects of acute exercise in heart tissue from obese animals, 12-week-old C57BL6/J obese (ob/ob) and non-obese (ob/OB) mice were submitted to a single bout of swimming and had their hearts analyzed by proteomic techniques. Mice were divided into three groups: control (ob/ob, n = 3; ob/OB, n = 3); a moderate intensity consisting of 20 min of swimming around 90% of Maximal Lactate Steady State (ob/ob, n = 3; ob/OB, n = 3), and a high intensity exercise performed as an incremental overload test (ob/ob, n = 3; ob/OB, n = 3). Obesity modulations were analyzed by comparing ob/ob and ob/OB control groups. Differential 2-DE analysis revealed that single session of exercise was able to up-regulate: myoglobin (ob/ob), aspartate aminotransferase (ob/OB) and zinc finger protein (ob/OB) and down-regulate: nucleoside diphosphate kinase B (ob/OB), mitochondrial aconitase (ob/ob and ob/OB) and fatty acid binding protein (ob/ob). Zinc finger protein and α-actin were up-regulated by the effect of obesity on heart proteome. These data demonstrate the immediate response of metabolic and stress-related proteins after exercise so as contractile protein by obesity modulation on heart proteome.

Longitudinal evaluation of hepatic lipid deposition and composition in ob/ob and ob/+ control mice.

Obesity is associated with insulin resistance (IR) and hepatosteatosis. Understanding the link between IR and hepatosteatosis could be relevant to chronic clinical outcomes. The objective of this study was to quantitatively assess lipid deposition (fractional lipid mass, fLM) and composition (fraction of polyunsaturated lipids, fPUL and mean chain length, MCL) in livers of ob/ob mice, a genetic model of obesity and mild diabetes, and ob/+ heterozygous control animals in a noninvasive manner using (1) H-MRS at 9.4T. For accurate quantification, intensity values were corrected for differences in T2 values while T1 effects were considered minimal due to the long TR values used. Values of fLM, fPUL and MCL were derived from T2 -corrected signal intensities of lipids and water resonance. Hepatic lipid signals were compared with fasted plasma insulin, glucose and lipid levels. Statistically significant correlations between fPUL and fasting plasma insulin/glucose levels were found in adolescent ob/ob mice. A similar correlation was found between fLM and fasting plasma insulin levels; however, the correlation between fLM and fasting plasma glucose levels was less obvious in adolescent ob/ob mice. These correlations were lost in adult ob/ob mice. The study showed that in adolescent ob/ob mice, there was an obvious link between lipid deposition/composition in the liver and plasma insulin/glucose levels. This correlation was lost in adult animals, probably due to the limited lipid storage capacity of the liver.