Aldosterone- and Cortisol Co-secreting Adrenal Cortical Neoplasm With Lipomatous and Myelolipomatous Metaplasia  .

We report a case of a 58-year-old woman with a history of hypertension diagnosed at aged 35 years, on 5 antihypertensive agents and a history of intermittent spontaneous hypokalemia, was found to have a 6-cm left adrenal mass on computed tomography scan of the abdomen. The unenhanced computed tomography attenuation of the adrenal mass was -16 Hounsfield units (HU). The biochemical evaluation showed potassium of 2.8 mEq/L (SI unit, mmol/L) (reference range, 3.5-5.0), plasma aldosterone concentration of 61.3 ng/dL (SI unit, 1701 pmol/L) with plasma renin activity of 0.4 ng/mL/h (SI unit, µg/L/h). An overnight 1-mg dexamethasone suppression test showed nonsuppressible serum cortisol of 10.8 µg/dL (SI unit, 298 nmol/L). Dehydroepiandrosterone sulfate and ACTH were measured at 24.5 µg/dL (age-adjusted, 26-200) (SI unit, 0.66 µmol/L; 0.70-5.43) and <5 pg/mL (SI unit, < 1.1 pmol/L), respectively. Left adrenalectomy was performed and hydrocortisone therapy was initiated. Postoperatively and thereafter, her blood pressure was controlled with no antihypertensive agent. Seven months later, hydrocortisone therapy was stopped once her cortisol level had normalized. Pathology showed adrenal cortical neoplasm of uncertain malignant potential with associated lipomatous and myelolipomatous metaplasia. This is a rare case of aldosterone and cortisol co-secreting adrenal cortical neoplasm of uncertain malignant potential with lipomatous and myelolipomatous metaplasia. Although the majority of cases of myelolipoma are benign and nonfunctioning, this case emphasizes the importance of thorough hormonal and morphologic evaluation of the tumor.

EpiMix is an integrative tool for epigenomic subtyping using DNA methylation.

DNA methylation (DNAme) is a major epigenetic factor influencing gene expression with alterations leading to cancer and immunological and cardiovascular diseases. Recent technological advances have enabled genome-wide profiling of DNAme in large human cohorts. There is a need for analytical methods that can more sensitively detect differential methylation profiles present in subsets of individuals from these heterogeneous, population-level datasets. We developed an end-to-end analytical framework named "EpiMix" for population-level analysis of DNAme and gene expression. Compared with existing methods, EpiMix showed higher sensitivity in detecting abnormal DNAme that was present in only small patient subsets. We extended the model-based analyses of EpiMix to cis-regulatory elements within protein-coding genes, distal enhancers, and genes encoding microRNAs and long non-coding RNAs (lncRNAs). Using cell-type-specific data from two separate studies, we discover epigenetic mechanisms underlying childhood food allergy and survival-associated, methylation-driven ncRNAs in non-small cell lung cancer.

EpiMix: an integrative tool for epigenomic subtyping using DNA methylation.

DNA methylation (DNAme) is a major epigenetic factor influencing gene expression with alterations leading to cancer, immunological, and cardiovascular diseases. Recent technological advances enable genome-wide quantification of DNAme in large human cohorts. So far, existing methods have not been evaluated to identify differential DNAme present in large and heterogeneous patient cohorts. We developed an end-to-end analytical framework named "EpiMix" for population-level analysis of DNAme and gene expression. Compared to existing methods, EpiMix showed higher sensitivity in detecting abnormal DNAme that was present in only small patient subsets. We extended the model-based analyses of EpiMix to cis-regulatory elements within protein-coding genes, distal enhancers, and genes encoding microRNAs and lncRNAs. Using cell-type specific data from two separate studies, we discovered novel epigenetic mechanisms underlying childhood food allergy and survival-associated, methylation-driven non-coding RNAs in non-small cell lung cancer.

Imatinib improves insulin resistance and inhibits injury-induced neointimal hyperplasia in high fat diet-fed mice.

Imatinib, a PDGF receptor tyrosine kinase inhibitor, has been shown to suppress intimal hyperplasia in different animal models under normal metabolic milieu, diabetic, and/or hypercholesterolemic conditions. However, the impact of imatinib treatment on injury-induced neointimal hyperplasia has not yet been investigated in the setting of insulin resistance without frank diabetes. Using a mouse model of high fat diet (HFD)-induced insulin resistance and guidewire-induced arterial injury, the present study demonstrates that intraperitoneal administration of imatinib (25 mg/kg/day) for ~3 weeks resulted in a marked attenuation of neointimal hyperplasia (intima/media ratio) by ~78% (n = 6-9 per group; P < 0.05). Imatinib treatment also led to significant improvements in key metabolic parameters. In particular, imatinib improved insulin resistance and glucose tolerance, as revealed by complete inhibition of HFD-induced increase in HOMA-IR index and AUCIPGTT, respectively. In addition, imatinib treatment led to diminutions in HFD-induced increases in plasma total cholesterol and triglycerides by ~73% and ~59%, respectively. Furthermore, imatinib decreased HFD-induced increase in visceral fat accumulation by ~51% (as determined by epididymal white adipose tissue weight). Importantly, imatinib treatment in HFD-fed mice enhanced plasma levels of high-molecular-weight adiponectin by ~2-fold without affecting total adiponectin. However, there were no significant changes in mean arterial pressure in insulin-resistant state or after imatinib exposure, as measured by tail-cuff method. Together, the present findings suggest that targeting PDGF receptor tyrosine kinase using imatinib may provide a realistic treatment option to prevent injury-induced neointimal hyperplasia and diet-induced insulin resistance in obesity.

WNT Signaling Driven by R-spondin 1 and LGR6 in High-grade Serous Ovarian Cancer.

BACKGROUND/AIM: R-spondins control WNT signaling and RSPO1 and LGR6, two of its receptors, are uniquely expressed at high levels in high-grade serous ovarian cancer (HGSOC). The aim of this study was to assess the interrelations between the expression of the RSPOs and LGRs in HGSOC and in the ovarian surface (OSE) and fallopian tube surface epithelium (FTSE) from which HGSOC arises. MATERIALS AND METHODS: Analysis of TCGA (HGSOC), CCLE (ovary), and other publicly accessed RNA-Seq data using UC San Diego Computational Cancer Analysis Library (CCAL) to perform differential expression analysis, association studies, and gene set inspection using the single-sample GSEA method. Additionally, we employed multiple publicly available databases including StringDB, Human Protein Atlas, and cBioPortal to aid the investigation. RESULTS: Among normal tissues, expression of RSPO1, LGR5 and LGR6 was highest in the fallopian tube. The relative levels of expression of the RSPOs and LGRs in the OSE and FTSE matched those in HGSOC. RSPO1 and LGR6 were highly co-expressed in all three tissues. Gene set enrichment analysis (GSEA) showed that expression of RSPO1 was strongly linked to the enrichment of three separate WNT-driven GO pathways. Analysis of genes that impacted overall survival identified two other immediately adjacent genes that control WNT signaling, KREMEN1 and ZNRF3 whose expression and copy number were coordinately linked. CONCLUSION: RSPO1 and LGR6 are coordinately expressed in HGSOC and the two normal tissues from which this tumor arises, and their expression is linked to WNT signaling pathways known the control cell fate and proliferation.

LOCALLY INVASIVE PHEOCHROMOCYTOMA COMBINED WITH PRIMARY MALIGNANT ADRENAL LYMPHOMA.

OBJECTIVE: Pheochromocytoma (PHEO) combined with primary adrenal lymphoma is extremely rare. We describe a case of locally invasive PHEO combined with primary malignant lymphoma. METHODS: We provide a case description with biochemical analyses, imaging, and pathologic findings. RESULTS: A 79-year-old male presented with a 17-cm, complex mass in the left adrenal gland with non-contrast Hounsfield units of 100 and left para-aortic enlarged lymph nodes imaged by computed tomography. Biochemical evaluation showed plasma and 24-hour urinary normetanephrine significantly elevated about 22 times (about 13.5 times above the normal upper limit) while metanephrine levels were normal. With adequate perioperative preparation, en bloc resection of the left adrenal gland was performed. The pathology revealed a tumor consisting of B-cell lymphoma, a PHEO forming a large adrenal mass with soft tissue invasion with extensive sclerosis and a separate nodule with PHEO without sclerosis. Immunohistochemistry and in situ hybridization of the lymphoma were consistent with Epstein-Barr virus-positive, diffuse large B-cell lymphoma. Immunohistochemistry of the PHEO was positive for chromogranin, synaptophysin, and S100. The Ki67 index was 8.7% and PHEO of the adrenal gland scaled score was 8 (≥4 is considered potentially malignant). CONCLUSION: To the best of our knowledge this is the first case demonstrating locally invasive and potentially malignant PHEO combined with primary malignant lymphoma in the same adrenal gland.

Sulforaphane improves dysregulated metabolic profile and inhibits leptin-induced VSMC proliferation: Implications toward suppression of neointima formation after arterial injury in western diet-fed obese mice.

Sulforaphane (SFN), a dietary phase-2 enzyme inducer that mitigates cellular oxidative stress through nuclear factor erythroid 2-related factor 2 (Nrf2) activation, is known to exhibit beneficial effects in the vessel wall. For instance, it inhibits vascular smooth muscle cell (VSMC) proliferation, a major event in atherosclerosis and restenosis after angioplasty. In particular, SFN attenuates the mitogenic and pro-inflammatory actions of platelet-derived growth factor (PDGF) and tumor necrosis factor-α (TNFα), respectively, in VSMCs. Nevertheless, the vasoprotective role of SFN has not been examined in the setting of obesity characterized by hyperleptinemia and insulin resistance. Using the mouse model of western diet-induced obesity, the present study demonstrates for the first time that subcutaneous delivery of SFN (0.5mg/Kg/day) for~3weeks significantly attenuates neointima formation in the injured femoral artery [↓ (decrease) neointima/media ratio by~60%; n=5-8]. This was associated with significant improvements in metabolic parameters, including ↓ weight gain by~52%, ↓ plasma leptin by~42%, ↓ plasma insulin by~63%, insulin resistance [↓ homeostasis model assessment of insulin resistance (HOMA-IR) index by~73%], glucose tolerance (↓ AUCGTT by~24%), and plasma lipid profile (e.g., ↓ triglycerides). Under in vitro conditions, SFN significantly decreased leptin-induced VSMC proliferation by~23% (n=5) with associated diminutions in leptin-induced cyclin D1 expression and the phosphorylation of p70S6kinase and ribosomal S6 protein (n=3-4). The present findings reveal that, in addition to improving systemic metabolic parameters, SFN inhibits leptin-induced VSMC proliferative signaling that may contribute in part to the suppression of injury-induced neointima formation in diet-induced obesity.

Moo1 obesity quantitative trait locus in BTBR T+ Itpr3tf/J mice increases food intake.

The rising prevalence of obesity is one of the greatest health challenges facing the world today. Discovery of genetic factors affecting obesity risk will provide important insight to its etiology that could suggest new therapeutic approaches. We have previously identified the Modifier of obese 1 (Moo1) quantitative trait locus (QTL) in a cross between leptin-deficient BTBR T(+) Itpr3(tf)/J (BTBR) and C57BL/6J (B6) mice. Understanding the mechanism by which this locus acts will aid in the identification of candidate genes. Here we refined the location of this QTL and sought to determine the mechanism by which Moo1 affects body weight. We found that the effects of Moo1 also alter high fat diet-induced obesity in mice having functional leptin. In detailed metabolic analyses we determined that this locus acts by increasing food intake in BTBR mice, without affecting energy expenditure. The expression levels of the main molecular mediators of food intake in the hypothalamus were not altered, suggesting this locus affects an independent pathway, consistent with its identification in mice lacking functional leptin. Finally, we show that the increased adiposity resulting from Moo1 is sufficient to affect glucose tolerance. These studies show that the Moo1 obesity QTL affects food intake, likely through a novel mechanism, and indicate that modulation of the underlying pathway may not only ameliorate obesity but also its clinical consequences.

Expression of conventional and novel glucose transporters, GLUT1, -9, -10, and -12, in vascular smooth muscle cells.

Intimal hyperplasia is characterized by exaggerated proliferation of vascular smooth muscle cells (VSMCs). Enhanced VSMC growth is dependent on increased glucose uptake and metabolism. Facilitative glucose transporters (GLUTs) are comprised of conventional GLUT isoforms (GLUT1-5) and novel GLUT isoforms (GLUT6-14). Previous studies demonstrate that GLUT1 overexpression or GLUT10 downregulation contribute to phenotypic changes in VSMCs. To date, the expression profile of all 14 GLUT isoforms has not been fully examined in VSMCs. Using the proliferative and differentiated phenotypes of human aortic VSMCs, the present study has determined the relative abundance of GLUT1-14 mRNAs by quantitative real-time PCR analysis. Twelve GLUT mRNAs excluding GLUT7 and GLUT14 were detectable in VSMCs. In the proliferative phenotype, the relative abundance of key GLUT mRNAs was GLUT1 (∼43%)>GLUT10 (∼26%)>GLUT9 (∼13%)>GLUT12 (∼4%), whereas in the differentiated phenotype the relative abundance was GLUT10 (∼28%)>GLUT1 (∼25%)>GLUT12 (∼20%)>GLUT9 (∼14%), together constituting 86-87% of total GLUT transcripts. To confirm the expression of key GLUT proteins, immunoblot and immunocytochemical analyses were performed using GLUT isoform-specific primary antibodies. The protein bands characteristic of GLUT1, -9, -10, and -12 were detected in VSMCs in parallel with respective positive controls. In particular, GLUT1 protein expression showed different molecular forms representative of altered glycosylation. While GLUT1 protein displayed a predominant distribution in the plasma membrane, GLUT9, -10, and -12 proteins were mostly distributed in the intracellular compartments. The present study provides the first direct evidence for GLUT9 and GLUT12 expression in VSMCs in conjunction with the previously identified GLUT1 and GLUT10.

Leptin treatment inhibits the progression of atherosclerosis by attenuating hypercholesterolemia in type 1 diabetic Ins2(+/Akita):apoE(-/-) mice.

AIMS: The impact of leptin deficiency and its replacement in T1D remain unclear in the context of dyslipidemia and atherosclerosis. The current study has investigated the physiologic role of leptin in lipid metabolism and atherosclerosis in T1D. METHODS AND RESULTS: The present study has employed Ins2(+/Akita):apoE(-/-) mouse model that spontaneously develops T1D, hypercholesterolemia, and atherosclerosis. At age 13 weeks, diabetic Ins2(+/Akita):apoE(-/-) mice showed leptin deficiency by ~92% compared with nondiabetic Ins2(+/+):apoE(-/-) mice. From 13 weeks to 25 weeks of age, diabetic Ins2(+/Akita):apoE(-/-) mice were treated with low-dose leptin (at 0.4 µg/g body weight daily). Leptin treatment diminished food intake by 22-27% in diabetic mice without affecting body weight and lean mass throughout the experiment. Importantly, leptin therapy substantially reduced plasma cholesterol concentrations by ~41%, especially in LDL fractions, in diabetic Ins2(+/Akita):apoE(-/-) mice. Moreover, leptin therapy decreased atherosclerotic lesion in diabetic mice by ~62% comparable to that seen in nondiabetic mice. In addition, leptin restored repressed expression of hepatic sortilin-1, a receptor for LDL clearance, and reversed altered expression of several hepatic genes involved in lipogenesis and cholesterol synthesis characteristic of diabetic mice. These findings were accompanied by normalization of reduced hepatic expression of Irs1 and Irs2 mRNA as well as their protein levels, and improved hepatic insulin-receptor signaling. CONCLUSIONS: The present findings suggest that leptin administration may be useful to improve dyslipidemia and reduce atherosclerosis-related cardiovascular disease in human subjects with T1D.

TRPM2 Ca2+ channel regulates energy balance and glucose metabolism.

TRPM2 Ca(2+)-permeable cation channel is widely expressed and activated by markers of cellular stress. Since inflammation and stress play a major role in insulin resistance, we examined the role of TRPM2 Ca(2+) channel in glucose metabolism. A 2-h hyperinsulinemic euglycemic clamp was performed in TRPM2-deficient (KO) and wild-type mice to assess insulin sensitivity. To examine the effects of diet-induced obesity, mice were fed a high-fat diet for 4-10 mo, and metabolic cage and clamp studies were conducted in conscious mice. TRPM2-KO mice were more insulin sensitive partly because of increased glucose metabolism in peripheral organs. After 4 mo of high-fat feeding, TRPM2-KO mice were resistant to diet-induced obesity, and this was associated with increased energy expenditure and elevated expressions of PGC-1α, PGC-1ß, PPARα, ERRα, TFAM, and MCAD in white adipose tissue. Hyperinsulinemic euglycemic clamps showed that TRPM2-KO mice were more insulin sensitive, with increased Akt and GSK-3ß phosphorylation in heart. Obesity-mediated inflammation in adipose tissue and liver was attenuated in TRPM2-KO mice. Overall, TRPM2 deletion protected mice from developing diet-induced obesity and insulin resistance. Our findings identify a novel role of TRPM2 Ca(2+) channel in the regulation of energy expenditure, inflammation, and insulin resistance.

Spontaneously diabetic Ins2(+/Akita):apoE-deficient mice exhibit exaggerated hypercholesterolemia and atherosclerosis.

Type 1 diabetes (T1D) increases the risk of adverse coronary events. Among risk factors, dyslipidemia due to altered hepatic lipoprotein metabolism plays a central role in diabetic atherosclerosis. Nevertheless, the likely alterations in plasma lipid/lipoprotein profile remain unclear, especially in the context of spontaneously developed T1D and atherosclerosis. To address this question, we generated Ins2(+/Akita):apoE(-/-) mouse by cross-breeding Ins2(+/Akita) mouse (which has Ins2 gene mutation, causing pancreatic ß-cell apoptosis and insulin deficiency) with apoE(-/-) mouse. Ins2(+/Akita):apoE(-/-) mice developed T1D spontaneously at 4-5 wk of age. At 25 wk of age and while on a standard chow diet, diabetic Ins2(+/Akita):apoE(-/-) mice exhibited an approximately threefold increase in atherosclerotic plaque in association with an approximatelty twofold increase in plasma non-HDL cholesterol, predominantly in the LDL fraction, compared with nondiabetic controls. To determine factors contributing to the exaggerated hypercholesterolemia, we assessed hepatic VLDL secretion and triglyceride content, expression of hepatic lipoprotein receptors, and plasma apolipoprotein composition. Diabetic Ins2(+/Akita):apoE(-/-) mice exhibited diminished VLDL secretion by ~50%, which was accompanied by blunted Akt phosphorylation in response to insulin infusion and decreased triglyceride content in the liver. Although the expression of hepatic LDL receptor was not affected, there was a significant reduction in the expression of lipolysis-stimulated lipoprotein receptor (LSR) by ~28%. Moreover, there was a marked decrease in plasma apoB-100 with a significant increase in apoB-48 and apoC-III levels. In conclusion, exaggerated hypercholesterolemia and atherosclerosis in spontaneously diabetic Ins2(+/Akita):apoE(-/-) mice may be attributable to impaired lipoprotein clearance in the setting of diminished expression of LSR and altered apolipoprotein composition of lipoproteins.

PDGF-induced vascular smooth muscle cell proliferation is associated with dysregulation of insulin receptor substrates.

In vascular smooth muscle cells (VSMCs), platelet-derived growth factor (PDGF) plays a major role in inducing phenotypic switching from contractile to proliferative state. Importantly, VSMC phenotypic switching is also determined by the phosphorylation state/expression levels of insulin receptor substrate (IRS), an intermediary signaling component that is shared by insulin and IGF-I. To date, the roles of PDGF-induced key proliferative signaling components including Akt, p70S6kinase, and ERK1/2 on the serine phosphorylation/expression of IRS-1 and IRS-2 isoforms remain unclear in VSMCs. We hypothesize that PDGF-induced VSMC proliferation is associated with dysregulation of insulin receptor substrates. Using human aortic VSMCs, we demonstrate that prolonged PDGF treatment led to sustained increases in the phosphorylation of protein kinases such as Akt, p70S6kinase, and ERK1/2, which mediate VSMC proliferation. In addition, PDGF enhanced IRS-1/IRS-2 serine phosphorylation and downregulated IRS-2 expression in a time- and concentration-dependent manner. Notably, phosphoinositide 3-kinase (PI 3-kinase) inhibitor (PI-103) and mammalian target of rapamycin inhibitor (rapamycin), which abolished PDGF-induced Akt and p70S6kinase phosphorylation, respectively, blocked PDGF-induced IRS-1 serine phosphorylation and IRS-2 downregulation. In contrast, MEK1/ERK inhibitor (U0126) failed to block PDGF-induced IRS-1 serine phosphorylation and IRS-2 downregulation. PDGF-induced IRS-2 downregulation was prevented by lactacystin, an inhibitor of proteasomal degradation. Functionally, PDGF-mediated IRS-1/IRS-2 dysregulation resulted in the attenuation of insulin-induced IRS-1/IRS-2-associated PI 3-kinase activity. Pharmacological inhibition of PDGF receptor tyrosine kinase with imatinib prevented IRS-1/IRS-2 dysregulation and restored insulin receptor signaling. In conclusion, strategies to inhibit PDGF receptors would not only inhibit neointimal growth but may provide new therapeutic options to prevent dysregulated insulin receptor signaling in VSMCs in nondiabetic and diabetic states.

Early hepatic insulin resistance precedes the onset of diabetes in obese C57BLKS-db/db mice.

OBJECTIVE: To identify metabolic derangements contributing to diabetes susceptibility in the leptin receptor-deficient obese C57BLKS/J-db/db (BKS-db) mouse strain. RESEARCH DESIGN AND METHODS: Young BKS-db mice were used to identify metabolic pathways contributing to the development of diabetes. Using the diabetes-resistant B6-db strain as a comparison, in vivo and in vitro approaches were applied to identify metabolic and molecular differences between the two strains. RESULTS: Despite higher plasma insulin levels, BKS-db mice exhibit lower lipogenic gene expression, rate of lipogenesis, hepatic triglyceride and glycogen content, and impaired insulin suppression of gluconeogenic genes. Hepatic insulin receptor substrate (IRS)-1 and IRS-2 expression and insulin-stimulated Akt-phosphorylation are decreased in BKS-db primary hepatocytes. Hyperinsulinemic-euglycemic clamp studies indicate that in contrast to hepatic insulin resistance, skeletal muscle is more insulin sensitive in BKS-db than in B6-db mice. We also demonstrate that elevated plasma triglyceride levels in BKS-db mice are associated with reduced triglyceride clearance due to lower lipase activities. CONCLUSIONS: Our study demonstrates the presence of metabolic derangements in BKS-db before the onset of beta-cell failure and identifies early hepatic insulin resistance as a component of the BKS-db phenotype. We propose that defects in hepatic insulin signaling contribute to the development of diabetes in the BKS-db mouse strain.

Deficiency of phosphoinositide 3-kinase enhancer protects mice from diet-induced obesity and insulin resistance.

OBJECTIVE: Phosphoinositide 3-kinase enhancer A (PIKE-A) is a proto-oncogene that promotes tumor growth and transformation by enhancing Akt activity. However, the physiological functions of PIKE-A in peripheral tissues are unknown. Here, we describe the effect of PIKE deletion in mice and explore the role of PIKE-A in obesity development. RESEARCH DESIGN AND METHODS: Whole-body PIKE knockout mice were generated and subjected to high-fat-diet feeding for 20 weeks. The glucose tolerance, tissue-specific insulin sensitivity, adipocyte differentiation, and lipid oxidation status were determined. The molecular mechanism of PIKE in the insulin signaling pathway was also studied. RESULTS: We show that PIKE-A regulates obesity development by modulating AMP-activated protein kinase (AMPK) phosphorylation. PIKE-A is important for insulin to suppress AMPK phosphorylation. The expression of PIKE-A is markedly increased in adipose tissue of obese mice, whereas depletion of PIKE-A inhibits adipocyte differentiation. PIKE knockout mice exhibit a prominent phenotype of lipoatrophy and are resistant to high-fat diet-induced obesity, liver steatosis, and diabetes. PIKE knockout mice also have augmented lipid oxidation, which is accompanied by enhanced AMPK phosphorylation in both muscle and adipose tissue. Moreover, insulin sensitivity is improved in PIKE-A-deficient muscle and fat, thus protecting the animals from diet-induced diabetes. CONCLUSIONS: Our results suggest that PIKE-A is implicated in obesity and associated diabetes development by negatively regulating AMPK activity.

Grp78 heterozygosity promotes adaptive unfolded protein response and attenuates diet-induced obesity and insulin resistance.

OBJECTIVE: To investigate the role of the endoplasmic reticulum (ER) chaperone glucose-regulated protein (GRP) 78/BiP in the pathogenesis of obesity, insulin resistance, and type 2 diabetes. RESEARCH DESIGN AND METHODS: Male Grp78(+/-) mice and their wild-type littermates were subjected to a high-fat diet (HFD) regimen. Pathogenesis of obesity and type 2 diabetes was examined by multiple approaches of metabolic phenotyping. Tissue-specific insulin sensitivity was analyzed by hyperinsulinemic-euglycemic clamps. Molecular mechanism was explored via immunoblotting and tissue culture manipulation. RESULTS: Grp78 heterozygosity increases energy expenditure and attenuates HFD-induced obesity. Grp78(+/-) mice are resistant to diet-induced hyperinsulinemia, liver steatosis, white adipose tissue (WAT) inflammation, and hyperglycemia. Hyperinsulinemic-euglycemic clamp studies revealed that Grp78 heterozygosity improves glucose metabolism independent of adiposity and following an HFD increases insulin sensitivity predominantly in WAT. As mechanistic explanations, Grp78 heterozygosity in WAT under HFD stress promotes adaptive unfolded protein response (UPR), attenuates translational block, and upregulates ER degradation-enhancing alpha-mannosidase-like protein (EDEM) and ER chaperones, thus improving ER quality control and folding capacity. Further, overexpression of the active form of ATF6 induces protective UPR and improves insulin signaling upon ER stress. CONCLUSIONS: HFD-induced obesity and type 2 diabetes are improved in Grp78(+/-) mice. Adaptive UPR in WAT could contribute to this improvement, linking ER homeostasis to energy balance and glucose metabolism.

Prevention of steatosis by hepatic JNK1.

Nonalcoholic steatosis (fatty liver) is a major cause of liver dysfunction that is associated with insulin resistance and metabolic syndrome. The cJun NH(2)-terminal kinase 1 (JNK1) signaling pathway is implicated in the pathogenesis of hepatic steatosis and drugs that target JNK1 may be useful for treatment of this disease. Indeed, mice with defects in JNK1 expression in adipose tissue are protected against hepatic steatosis. Here we report that mice with specific ablation of Jnk1 in hepatocytes exhibit glucose intolerance, insulin resistance, and hepatic steatosis. JNK1 therefore serves opposing actions in liver and adipose tissue to both promote and prevent hepatic steatosis. This finding has potential implications for the design of JNK1-selective drugs for the treatment of metabolic syndrome.

KSR2 is an essential regulator of AMP kinase, energy expenditure, and insulin sensitivity.

Kinase suppressors of Ras 1 and 2 (KSR1 and KSR2) function as molecular scaffolds to potently regulate the MAP kinases ERK1/2 and affect multiple cell fates. Here we show that KSR2 interacts with and modulates the activity of AMPK. KSR2 regulates AMPK-dependent glucose uptake and fatty acid oxidation in mouse embryonic fibroblasts and glycolysis in a neuronal cell line. Disruption of KSR2 in vivo impairs AMPK-regulated processes affecting fatty acid oxidation and thermogenesis to cause obesity. Despite their increased adiposity, ksr2(-/-) mice are hypophagic and hyperactive but expend less energy than wild-type mice. In addition, hyperinsulinemic-euglycemic clamp studies reveal that ksr2(-/-) mice are profoundly insulin resistant. The expression of genes mediating oxidative phosphorylation is also downregulated in the adipose tissue of ksr2(-/-) mice. These data demonstrate that ksr2(-/-) mice are highly efficient in conserving energy, revealing a novel role for KSR2 in AMPK-mediated regulation of energy metabolism.

Nutrient stress activates inflammation and reduces glucose metabolism by suppressing AMP-activated protein kinase in the heart.

OBJECTIVE: Heart failure is a major cause of mortality in diabetes and may be causally associated with altered metabolism. Recent reports indicate a role of inflammation in peripheral insulin resistance, but the impact of inflammation on cardiac metabolism is unknown. We investigated the effects of diet-induced obesity on cardiac inflammation and glucose metabolism in mice. RESEARCH DESIGN AND METHODS: Male C57BL/6 mice were fed a high-fat diet (HFD) for 6 weeks, and heart samples were taken to measure insulin sensitivity, glucose metabolism, and inflammation. Heart samples were also examined following acute interleukin (IL)-6 or lipid infusion in C57BL/6 mice and in IL-6 knockout mice following an HFD. RESULTS: Diet-induced obesity reduced cardiac glucose metabolism, GLUT, and AMP-activated protein kinase (AMPK) levels, and this was associated with increased levels of macrophages, toll-like receptor 4, suppressor of cytokine signaling 3 (SOCS3), and cytokines in heart. Acute physiological elevation of IL-6 suppressed glucose metabolism and caused insulin resistance by increasing SOCS3 and via SOCS3-mediated inhibition of insulin receptor substrate (IRS)-1 and possibly AMPK in heart. Diet-induced inflammation and defects in glucose metabolism were attenuated in IL-6 knockout mice, implicating the role of IL-6 in obesity-associated cardiac inflammation. Acute lipid infusion caused inflammation and raised local levels of macrophages, C-C motif chemokine receptor 2, SOCS3, and cytokines in heart. Lipid-induced cardiac inflammation suppressed AMPK, suggesting the role of lipid as a nutrient stress triggering inflammation. CONCLUSIONS: Our findings that nutrient stress activates cardiac inflammation and that IL-6 suppresses myocardial glucose metabolism via inhibition of AMPK and IRS-1 underscore the important role of inflammation in the pathogenesis of diabetic heart.

A stress signaling pathway in adipose tissue regulates hepatic insulin resistance.

A high-fat diet causes activation of the regulatory protein c-Jun NH2-terminal kinase 1 (JNK1) and triggers development of insulin resistance. JNK1 is therefore a potential target for therapeutic treatment of metabolic syndrome. We explored the mechanism of JNK1 signaling by engineering mice in which the Jnk1 gene was ablated selectively in adipose tissue. JNK1 deficiency in adipose tissue suppressed high-fat diet-induced insulin resistance in the liver. JNK1-dependent secretion of the inflammatory cytokine interleukin-6 by adipose tissue caused increased expression of liver SOCS3, a protein that induces hepatic insulin resistance. Thus, JNK1 activation in adipose tissue can cause insulin resistance in the liver.