Decreased Akt kinase activity and insulin resistance in C57BL/KsJ-Leprdb/db mice

The dose-effect response of combined red and infrared photobiomodulation on insulin resistance in skeletal muscle cells

Obesity is a major public health problem and is a major contributor to the development of insulin resistance. In previous studies we observed that single-wavelength red or infrared photobiomodulation (PBM) improved insulin signaling in adipocytes and skeletal muscle of mice fed a high-fat diet, but information about the combination of different wavelengths, as well as the effect of different light doses (J/cm2) is lacking. Therefore, the aim of this study was to investigate the effects of different doses of dual-wavelength PBM on insulin signaling in muscle cell, and explore potential mechanisms involved. Mouse myoblasts (C2C12) were differentiated into myotubes and cultured in palmitic acid, sodium oleate and l-carnitine (PAL) to induce insulin resistance high or in glucose medium (CTRL). Then, they received SHAM treatment (lights off, 0 J/cm2) or PBM (660 + 850 nm; 2, 4 or 8 J/cm2). PAL induced insulin resistance (assessed by Akt phosphorylation at ser473), attenuated maximal citrate synthase activity, and increased the phosphorylation of c-Jun NH(2) terminal kinase (JNK) (T183/Y185). PBM at doses of 4 or 8 J/cm2 reversed these PAL-induced responses. Furthermore, at doses of 2, 4 or 8 J/cm2, PBM reversed the increase in mitofusin-2 content induced by PAL. In conclusion, the combination of dual-wavelength red and infrared PBM at doses of 4 and 8 J/cm2 improved intracellular insulin signaling in musculoskeletal cells, and this effect appears to involve the modulation of mitochondrial function and the attenuation of the activation of stress kinases.

WNKs regulate mouse behavior and alter central nervous system glucose uptake and insulin signaling

Certain areas of the brain involved in episodic memory and behavior, such as the hippocampus, express high levels of insulin receptors and glucose transporter-4 (GLUT4) and are responsive to insulin. Insulin and neuronal glucose metabolism improve cognitive functions and regulate mood in humans. Insulin-dependent GLUT4 trafficking has been extensively studied in muscle and adipose tissue, but little work has demonstrated either how it is controlled in insulin-responsive brain regions or its mechanistic connection to cognitive functions. In this study, we demonstrate that inhibition of WNK (With-No-lysine (K)) kinases improves learning and memory in mice. Neuronal inhibition of WNK enhances in vivo hippocampal glucose uptake. Inhibition of WNK enhances insulin signaling output and insulin-dependent GLUT4 trafficking to the plasma membrane in mice primary neuronal cultures and hippocampal slices. Therefore, we propose that the extent of neuronal WNK kinase activity has an important influence on learning, memory and anxiety-related behaviors, in part, by modulation of neuronal insulin signaling.

MCC950 Ameliorates Diabetic Muscle Atrophy in Mice by Inhibition of Pyroptosis and Its Synergistic Effect with Aerobic Exercise

Diabetic muscle atrophy is an inflammation-related complication of type-2 diabetes mellitus (T2DM). Even though regular exercise prevents further deterioration of atrophic status, there is no effective mediator available for treatment and the underlying cellular mechanisms are less explored. In this study, we investigated the therapeutic potential of MCC950, a specific, small-molecule inhibitor of NLRP3, to treat pyroptosis and diabetic muscle atrophy in mice. Furthermore, we used MCC950 to intervene in the protective effects of aerobic exercise against muscle atrophy in diabetic mice. Blood and gastrocnemius muscle (GAS) samples were collected after 12 weeks of intervention and the atrophic state was assessed. We initially corroborated a diabetic muscle atrophy phenotype in db/db mice (D) by comparison with control m/m mice (W) by examining parameters such as fasting blood glucose (D vs. W: 24.47 ± 0.45 mmol L-1 vs. 4.26 ± 0.6 mmol L-1, p < 0.05), grip strength (D vs. W: 166.87 ± 15.19 g vs. 191.76 ± 14.13 g, p < 0.05), exercise time (D vs. W: 1082.38 ± 104.67 s vs. 1716 ± 168.55 s, p < 0.05) and exercise speed to exhaustion (D vs. W: 24.25 ± 2.12 m min-1 vs. 34.75 ± 2.66 m min-1, p < 0.05), GAS wet weight (D vs. W: 0.07 ± 0.01 g vs. 0.13 ± 0.01 g, p < 0.05), the ratio of GAS wet weight to body weight (D vs. W: 0.18 ± 0.01% vs. 0.54 ± 0.02%, p < 0.05), and muscle fiber cross-sectional area (FCSA) (D vs. W: 1875 ± 368.19 µm2 vs. 2747.83 ± 406.44 µm2, p < 0.05). We found that both MCC950 (10 mg kg-1) treatment and exercise improved the atrophic parameters that had deteriorated in the db/db mice, inhibited serum inflammatory markers and significantly attenuated pyroptosis in atrophic GAS. In addition, a combined MCC950 treatment with exercise (DEI) exhibited a further improvement in glucose uptake capacity and muscle performance. This combined treatment also improved the FCSA of GAS muscle indicated by Laminin immunofluorescence compared to the group with the inhibitor treatment alone (DI) (DEI vs. DI: 2597 ± 310.97 vs. 1974.67 ± 326.15 µm2, p < 0.05) or exercise only (DE) (DEI vs. DE: 2597 ± 310.97 vs. 2006.33 ± 263.468 µm2, p < 0.05). Intriguingly, the combination of MCC950 treatment and exercise significantly reduced NLRP3-mediated inflammatory factors such as cleaved-Caspase-1, GSDMD-N and prevented apoptosis and pyroptosis in atrophic GAS. These findings for the first time demonstrate that targeting NLRP3-mediated pyroptosis with MCC950 improves diabetic muscle homeostasis and muscle function. We also report that inhibiting pyroptosis by MCC950 can enhance the beneficial effects of aerobic exercise on diabetic muscle atrophy. Since T2DM and muscle atrophy are age-related diseases, the young mice used in the current study do not seem to fully reflect the characteristics of diabetic muscle atrophy. Considering the fragile nature of db/db mice and for the complete implementation of the exercise intervention, we used relatively young db/db mice and the atrophic state in the mice was thoroughly confirmed. Taken together, the current study comprehensively investigated the therapeutic effect of NLRP3-mediated pyroptosis inhibited by MCC950 on diabetic muscle mass, strength and exercise performance, as well as the synergistic effects of MCC950 and exercise intervention, therefore providing a novel strategy for the treatment of the disease.

Smith-Magenis syndrome protein RAI1 regulates body weight homeostasis through hypothalamic BDNF-producing neurons and neurotrophin downstream signalling

Retinoic acid-induced 1 (RAI1) haploinsufficiency causes Smith-Magenis syndrome (SMS), a genetic disorder with symptoms including hyperphagia, hyperlipidemia, severe obesity, and autism phenotypes. RAI1 is a transcriptional regulator with a pan-neural expression pattern and hundreds of downstream targets. The mechanisms linking neural Rai1 to body weight regulation remain unclear. Here we find that hypothalamic brain-derived neurotrophic factor (BDNF) and its downstream signalling are disrupted in SMS (Rai1+/-) mice. Selective Rai1 loss from all BDNF-producing cells or from BDNF-producing neurons in the paraventricular nucleus of the hypothalamus (PVH) induced obesity in mice. Electrophysiological recordings revealed that Rai1 ablation decreased the intrinsic excitability of PVHBDNF neurons. Chronic treatment of SMS mice with LM22A-4 engages neurotrophin downstream signalling and delayed obesity onset. This treatment also partially rescued disrupted lipid profiles, insulin intolerance, and stereotypical repetitive behaviour in SMS mice. These data argue that RAI1 regulates body weight and metabolic function through hypothalamic BDNF-producing neurons and that targeting neurotrophin downstream signalling might improve associated SMS phenotypes.

Integrated omics analysis for characterization of the contribution of high fructose corn syrup to non-alcoholic fatty liver disease in obesity

BACKGROUND

High-Fructose Corn Syrup (HFCS), a sweetener rich in glucose and fructose, is nowadays widely used in beverages and processed foods; its consumption has been correlated to the emergence and progression of Non-Alcoholic Fatty Liver Disease (NAFLD). Nevertheless, the molecular mechanisms by which HFCS impacts hepatic metabolism remain scarce, especially in the context of obesity. Besides, the majority of current studies focuses either on the detrimental role of fructose in hepatic steatosis or compare separately the additive impact of fructose versus glucose in high fat diet-induced NAFLD.

AIM

By engaging combined omics approaches, we sought to characterize the role of HFCS in obesity-associated NAFLD and reveal molecular processes, which mediate the exaggeration of steatosis under these conditions.

METHODS

Herein, C57BL/6 mice were fed a normal-fat-diet (ND), a high-fat-diet (HFD) or a HFD supplemented with HFCS (HFD-HFCS) and upon examination of their metabolic and NAFLD phenotype, proteomic, lipidomic and metabolomic analyses were conducted to identify HFCS-related molecular alterations of the hepatic metabolic landscape in obesity.

RESULTS

Although HFD and HFD-HFCS mice displayed comparable obesity, HFD-HFCS mice showed aggravation of hepatic steatosis, as analysis of the lipid droplet area in liver sections revealed (12,15 % of total section area in HFD vs 22,35 % in HFD-HFCS), increased NAFLD activity score (3,29 in HFD vs 4,86 in HFD-HFCS) and deteriorated hepatic insulin resistance, as compared to the HFD mice. Besides, the hepatic proteome of HFD-HFCS mice was characterized by a marked upregulation of 5 core proteins implicated in de novo lipogenesis (DNL), while an increased phosphatidyl-cholines(PC)/phosphatidyl-ethanolamines(PE) ratio (2.01 in HFD vs 3.04 in HFD-HFCS) was observed in the livers of HFD-HFCS versus HFD mice. Integrated analysis of the omics datasets indicated that Tricarboxylic Acid (TCA) cycle overactivation is likely contributing towards the intensification of steatosis during HFD-HFCS-induced NAFLD.

CONCLUSION

Our results imply that HFCS significantly contributes to steatosis aggravation during obesity-related NAFLD, likely deriving from DNL upregulation, accompanied by TCA cycle overactivation and deteriorated hepatic insulin resistance.

iNOS contributes to heart failure with preserved ejection fraction through mitochondrial dysfunction and Akt S-nitrosylation

INTRODUCTION

Despite the high morbidity and mortality of heart failure with preserved fraction (HFpEF), there are currently no effective therapies for this condition. Moreover, the pathophysiological basis of HFpEF remains poorly understood.

OBJECTIVE

The aim of the present study was to investigate the role of inducible nitric oxide synthase (iNOS) and its underlying mechanism in a high-fat diet and N^ω-nitro-L-arginine methyl ester-induced HFpEF mouse model.

METHODS

The selective iNOS inhibitor L-NIL was used to examine the effects of short-term iNOS inhibition, whereas the long-term effects of iNOS deficiency were evaluated using iNOS-null mice. Cardiac and mitochondrial function, oxidative stress and Akt S-nitrosylation were then measured.

RESULTS

The results demonstrated that both pharmacological inhibition and iNOS knockout mitigated mitochondrial dysfunction, oxidative stress and Akt S-nitrosylation, leading to an ameliorated HFpEF phenotype in mice. In vitro, iNOS directly induced Akt S-nitrosylation at cysteine 224 residues , leading to oxidative stress, while inhibiting insulin-mediated glucose uptake in myocytes.

CONCLUSION

Altogether, the present findings suggested an important role for iNOS in the pathophysiological development of HFpEF, indicating that iNOS inhibition may represent a potential therapeutic strategy for HFpEF.

Reduced Birth Weight and Exposure to Per- and Polyfluoroalkyl Substances: A Review of Possible Underlying Mechanisms Using the AOP-HelpFinder

Prenatal exposure to per- and polyfluorinated substances (PFAS) may impair fetal growth. Our knowledge of the underlying mechanisms is incomplete. We used the Adverse Outcome Pathway (AOP)-helpFinder tool to search PubMed for studies published until March 2021 that examined PFAS exposure in relation to birth weight, oxidative stress, hormones/hormone receptors, or growth signaling pathways. Of these 1880 articles, 106 experimental studies remained after abstract screening. One clear finding is that PFAS are associated with oxidative stress in in vivo animal studies and in vitro studies. It appears that PFAS-induced reactive-oxygen species (ROS) generation triggers increased peroxisome proliferator-activated receptor (PPAR)γ expression and activation of growth signaling pathways, leading to hyperdifferentiation of pre-adipocytes. Fewer proliferating pre-adipocytes result in lower adipose tissue weight and in this way may reduce birth weight. PFAS may also impair fetal growth through endocrine effects. Estrogenic effects have been noted in in vivo and in vitro studies. Overall, data suggest thyroid-damaging effects of PFAS affecting thyroid hormones, thyroid hormone gene expression, and histology that are associated in animal studies with decreased body and organ weight. The effects of PFAS on the complex relationships between oxidative stress, endocrine system function, adipogenesis, and fetal growth should be further explored.

Changes Induced by Aging and Long-Term Exercise and/or DHA Supplementation in Muscle of Obese Female Mice

Obesity and aging promote chronic low-grade systemic inflammation. The aim of the study was to analyze the effects of long-term physical exercise and/or omega-3 fatty acid Docosahexaenoic acid (DHA) supplementation on genes or proteins related to muscle metabolism, inflammation, muscle damage/regeneration and myokine expression in aged and obese mice. Two-month-old C57BL/6J female mice received a control or a high-fat diet for 4 months. Then, the diet-induced obese (DIO) mice were distributed into four groups: DIO, DIO + DHA, DIO + EX (treadmill training) and DIO + DHA + EX up to 18 months. Mice fed a control diet were sacrificed at 2, 6 and 18 months. Aging increased the mRNA expression of Tnf-α and decreased the expression of genes related to glucose uptake (Glut1, Glut4), muscle atrophy (Murf1, Atrogin-1, Cas-9) and myokines (Metrnl, Il-6). In aged DIO mice, exercise restored several of these changes. It increased the expression of genes related to glucose uptake (Glut1, Glut4), fatty acid oxidation (Cpt1b, Acox), myokine expression (Fndc5, Il-6) and protein turnover, decreased Tnf-α expression and increased p-AKT/AKT ratio. No additional effects were observed when combining exercise and DHA. These data suggest the effectiveness of long-term training to prevent the deleterious effects of aging and obesity on muscle dysfunction.

Mechanisms by which smoothelin-like protein 1 reverses insulin resistance in myotubules and mice

Insulin resistance (InR) is manifested in skeletal muscle by decreased insulin-stimulated glucose uptake due to impaired insulin signaling and multiple post-receptor intracellular defects. Chronic glucose-induced insulin resistance leads to the activation of Ser/Thr kinases and elevated phosphorylation of insulin receptor substrate 1 (IRS1) on Ser residues. Phosphorylation of IRS1 triggers the dissociation of IRS1 and its downstream effector, phosphatidylinositol 3-kinase. In the present study, we provide evidence for the insulin-sensitizing role of smoothelin-like protein 1 (SMTNL1) that is a ligand-dependent co-regulator of steroid receptors, predominantly the progesterone receptor. SMTNL1 was transiently overexpressed in insulin-resistant C2C12 myotubes. A proteome profiler array revealed that mTOR and Ser/Thr kinases were SMTNL1-dependent signaling pathways. In the presence of progesterone, overexpression was coupled to decreased Ser phosphorylation of IRS1 at Ser307, Ser318, and Ser612 residues. SMTNL1 also induced the expression and activity of the p85 subunit of PI3K. SMTNL1 regulated the expression of PKCε, which phosphorylates IRS1 at Ser318 residue. SMTNL1 also regulated ERK1/2 and JNK, which phosphorylate IRS1 at Ser612 and Ser307, respectively. Real-time metabolic measurements of oxygen consumption rate and extracellular acidification rate revealed that SMTNL1 improved glycolysis and promoted the utilization of alternative carbon fuels. SMTNL1 also rescued the mitochondrial respiration defect induced by chronic insulin exposure. Collectively, SMTNL1 plays a crucial role in maintaining the physiological ratio of Tyr/Ser IRS1 phosphorylation and attenuates the insulin-signaling cascade that contributes to impaired glucose disposal, which makes it a potential therapeutic target for improving InR.

Type-2 diabetic rat heart: The effect of kolaviron on mTOR-1, P70S60K, PKC-α, NF-kB, SOD-2, NRF-2, eNOS, AKT-1, ACE, and P38 MAPK gene expression profile

It has been established that genetic factors partially contribute to type-2 diabetes and vascular disease development. This study determined the effect of kolaviron on the expression profile of genes associated with the insulin signaling pathway and involved in regulating glucose and lipid metabolism, oxidative stress, inflammation, vascular functions, pro-survival and the apoptosis pathway in the heart of type-2 diabetic rats. After induction and confirmation of type-2 diabetes seven days after, the rats were treated with kolaviron for twenty-eight days before being euthanized. Organs were harvested and stored at - 80 °C in a biofreezer. Total RNA was extracted from the ventricle, reverse transcribed to cDNA followed by a real-time quantitative polymerase chain reaction (RT-qPCR) analysis of the expression of mTOR-1, P70S60K, PKC-α, NF-kB, SOD-2, NRF-2, eNOS, AKT-1, ACE, p38 MAPK and the reference gene (GAPDH), after which they were normalized/standardized. The results show an increase in the relative mRNA expression of mTOR/P70S60K/PKCα /P38MAPK/NF-KB/ACE and a decrease in the relative mRNA expression of NRF2/SOD/AKT/eNOS in the heart of the diabetic rats. Nevertheless, kolaviron modulated the expression profile of these genes, which suggest a therapeutic effect and target for vascular dysfunction and complications in type-2 diabetes through the activation of the NRF-2/AKT-1/eNOS signaling pathway and suppression of the NF-kB/PKC signaling pathway.

Angiogenin Released from ABCB5+ Stromal Precursors Improves Healing of Diabetic Wounds by Promoting Angiogenesis

Severe angiopathy is a major driver for diabetes associated secondary complications. Knowledge on underlying mechanisms essential for advanced therapies to attenuate these pathologies is limited. Injection of ABCB5⁺ stromal precursors (SPs) at the edge of non-healing diabetic wounds in a murine db/db model, closely mirroring human type II diabetes, profoundly accelerates wound closure. Strikingly, enhanced angiogenesis was substantially enforced by the release of the ribonuclease angiogenin from ABCB5⁺ SPs. This compensates for the profoundly reduced angiogenin expression in non-treated murine chronic diabetic wounds. Silencing of angiogenin in ABCB5⁺ SPs prior to injection significantly reduced angiogenesis and delayed wound closure in diabetic db/db mice implying an unprecedented key role for angiogenin in tissue regeneration in diabetes. These data hold significant promise for further refining SPs-based therapies of non-healing diabetic foot ulcers and other pathologies with impaired angiogenesis.

Ulk1, Not Ulk2, Is Required for Exercise Training-Induced Improvement of Insulin Response in Skeletal Muscle

Unc51 like autophagy activating kinase 1 (Ulk1), the primary autophagy regulator, has been linked to metabolic adaptation in skeletal muscle to exercise training. Here we compared the roles of Ulk1 and homologous Ulk2 in skeletal muscle insulin action following exercise training to gain more mechanistic insights. Inducible, skeletal muscle-specific Ulk1 knock-out (Ulk1-iMKO) mice and global Ulk2 knock-out (Ulk2^–/–) mice were subjected to voluntary wheel running for 6 weeks followed by assessment of exercise capacity, glucose tolerance, and insulin signaling in skeletal muscle after a bolus injection of insulin. Both Ulk1-iMKO and Ulk2^–/– mice had improved endurance exercise capacity post-exercise. Ulk1-iMKO did not improve glucose clearance during glucose tolerance test, while Ulk2^–/– had only marginal improvement. However, exercise training-induced improvement of insulin action in skeletal muscle, indicated by Akt-S473 phosphorylation, was only impaired in Ulk1-iMKO. These data suggest that Ulk1, but not Ulk2, is required for exercise training-induced improvement of insulin action in skeletal muscle, implicating crosstalk between catabolic and anabolic signaling as integral to metabolic adaptation to energetic stress.

Dynamic control of mitochondria-associated membranes by kinases and phosphatases in health and disease

Membrane-contact sites are getting more and more credit for their indispensable role in maintenance of cell function and homeostasis. In the last decades, the ER-mitochondrial contact sites in particular received a lot of attention. While our knowledge of ER-mitochondrial contact sites increases steadily, the focus often lies on a static exploration of their functions. However, it is increasingly clear that these contact sites are very dynamic. In this review, we highlight the dynamic nature of ER-mitochondrial contact sites and the role of kinases and phosphatases therein with a focus on recent findings. Phosphorylation events allow for rapid integration of information on the protein level, impacting protein function, localization and interaction at ER-mitochondrial contact sites. To illustrate the importance of these events and to put them in a broader perspective, we connect them to pathologies like diabetes type II, Parkinson's disease and cancer.

Hyperglycaemia up-regulates placental growth factor (PlGF) expression and secretion in endothelial cells via suppression of PI3 kinase-Akt signalling and activation of FOXO1

Placenta growth factor (PlGF) is a pro-inflammatory angiogenic mediator that promotes many pathologies including diabetic complications and atherosclerosis. Widespread endothelial dysfunction precedes the onset of these conditions. As very little is known of the mechanism(s) controlling PlGF expression in pathology we investigated the role of hyperglycaemia in the regulation of PlGF production in endothelial cells. Hyperglycaemia stimulated PlGF secretion in cultured primary endothelial cells, which was suppressed by IGF-1-mediated PI3K/Akt activation. Inhibition of PI3K activity resulted in significant PlGF mRNA up-regulation and protein secretion. Similarly, loss or inhibition of Akt activity significantly increased basal PlGF expression and prevented any further PlGF secretion in hyperglycaemia. Conversely, constitutive Akt activation blocked PlGF secretion irrespective of upstream PI3K activity demonstrating that Akt is a central regulator of PlGF expression. Knock-down of the Forkhead box O-1 (FOXO1) transcription factor, which is negatively regulated by Akt, suppressed both basal and hyperglycaemia-induced PlGF secretion, whilst FOXO1 gain-of-function up-regulated PlGF in vitro and in vivo. FOXO1 association to a FOXO binding sequence identified in the PlGF promoter also increased in hyperglycaemia. This study identifies the PI3K/Akt/FOXO1 signalling axis as a key regulator of PlGF expression and unifying pathway by which PlGF may contribute to common disorders characterised by endothelial dysfunction, providing a target for therapy.

Curcumin Improved Glucose Intolerance, Renal Injury, and Nonalcoholic Fatty Liver Disease and Decreased Chromium Loss through Urine in Obese Mice

Obesity-associated hyperglycemia underlies insulin resistance, glucose intolerance, and related metabolic disorders including type 2 diabetes, renal damage, and nonalcoholic fatty liver disease. Turmeric root is commonly used in Asia, and curcumin, one of its pharmacological components, can play a role in preventing and treating certain chronic physiological disorders. Accordingly, this study examined how high-fat diet (HFD)-induced hyperglycemia and hyperlipidemia are reduced by curcumin through changes in fatty liver scores, chromium distribution, and renal injury in mice. Relative to the control group, also fed an HFD, the curcumin group weighed less and had smaller adipocytes; it also had lower daily food efficiency, blood urea nitrogen and creatinine levels, serum alanine aminotransferase and aspartate aminotransferase levels, serum and hepatic triglyceride levels, and hepatic lipid regulation marker expression. The curcumin-treated obese group exhibited significantly lower fasting blood glucose, was less glucose intolerant, had higher Akt phosphorylation and glucose transporter 4 (GLUT4) expression, and had greater serum insulin levels. Moreover, the group showed renal damage with lower TNF-α expression along with more numerous renal antioxidative enzymes that included superoxide dismutase, glutathione peroxidase, and catalase. The liver histology of the curcumin-treated obese mice showed superior lipid infiltration and fewer FASN and PNPLA3 proteins in comparison with the control mice. Curcumin contributed to creating a positive chromium balance by decreasing the amount of chromium lost through urine, leading to the chromium mobilization needed to mitigate hyperglycemia. Thus, the results suggest that curcumin prevents HFD-induced glucose intolerance, kidney injury, and nonalcoholic fatty liver disease.

Exercise-A Panacea of Metabolic Dysregulation in Cancer: Physiological and Molecular Insights

Metabolic dysfunction is a comorbidity of many types of cancers. Disruption of glucose metabolism is of concern, as it is associated with higher cancer recurrence rates and reduced survival. Current evidence suggests many health benefits from exercise during and after cancer treatment, yet only a limited number of studies have addressed the effect of exercise on cancer-associated disruption of metabolism. In this review, we draw on studies in cells, rodents, and humans to describe the metabolic dysfunctions observed in cancer and the tissues involved. We discuss how the known effects of acute exercise and exercise training observed in healthy subjects could have a positive outcome on mechanisms in people with cancer, namely: insulin resistance, hyperlipidemia, mitochondrial dysfunction, inflammation, and cachexia. Finally, we compile the current limited knowledge of how exercise corrects metabolic control in cancer and identify unanswered questions for future research.

Metformin downregulates miR223 expression in insulin-resistant 3T3L1 cells and human diabetic adipose tissue

AIMS AND DESIGNS

Metformin, an anti-diabetic drug, is the first line medication for the treatment of type 2 diabetes mellitus and some studies show its relationship with micro-RNAs. This study set up to determine the effect of metformin on miR223 expression and content of AKT/GLUT4 proteins in insulin resistant signaling in 3T3L1 cells and adipocyte of human diabetic patients.

MATERIALS AND METHODS

Subcutaneous adipose tissues were taken from newly diagnosed diabetic patients (HOMA-IR > 1.8), before and after three months treatment with 500 mg of metformin twice a day. Cellular homogenate was prepared and miR223 expression and AKT/GLUT4 protein expression were determined by quantitative real-time PCR and western blotting. The results were compared to insulin resistant 3T3L1 adipocytes that were treated with 10 mM Metformin.

RESULTS

MiR223 expression was significantly overexpressed both in insulin-resistant 3T3L1 adipocytes compared to non-insulin resistant adipocytes and in human diabetic adipose tissue, compared to non-diabetics (P value < 0.01). Metformin treatment downregulated miR223 expression in both adipocytes and human diabetic adipose tissue. In contrast the IRS/PI3-K/AKT pathway signaling components, Akt and GLUT4 increased in insulin-resistant 3T3L1 adipocytes and human diabetic adipose tissue after three months of metformin treatment.

CONCLUSIONS

Metformin reduced insulin resistance in adipocytes by reduction of miR223 expression and improving of IRS/Akt/GLUT4 signaling pathways. Plasma miR223 expression of human diabetic patients was reduced by metformin treatment. These results point to a novel mechanism of miR223 in insulin resistance.

The Effect of Chrysin-Loaded Phytosomes on Insulin Resistance and Blood Sugar Control in Type 2 Diabetic db/db Mice

Although a variety of beneficial health effects of natural flavonoids, including chrysin, has been suggested, poor solubility and bioavailability limit their practical use. As a promising delivery system, chrysin-loaded phytosomes (CPs) were prepared using egg phospholipid (EPL) at a 1:3 molar ratio and its antidiabetic effects were assessed in db/db diabetic mice. Male C57BLKS/J-db/db mice were fed a normal diet (control), chrysin diet (100 mg chrysin/kg), CP diet (100 mg chrysin equivalent/kg), metformin diet (200 mg/kg) or EPL diet (vehicle, the same amount of EPL used for CP preparation) for 9 weeks. Administration of CP significantly decreased fasting blood glucose and insulin levels in db/db mice compared with the control. An oral glucose tolerance test and homeostatic model assessment for insulin resistance were significantly improved in the CP group (p < 0.05). CP treatment suppressed gluconeogenesis via downregulation of phosphoenolpyruvate carboxykinase while it promoted glucose uptake in the skeletal muscle and liver of db/db mice (p < 0.05). The CP-mediated improved glucose utilization in the muscle was confirmed by upregulation of glucose transporter type 4, hexokinase2 and peroxisome proliferator-activated receptor γ during treatment (p < 0.05). The CP-induced promotion of GLUT4 plasma translocation was confirmed in the skeletal muscle of db/db mice (p < 0.05). Based on the results, CP showed greater antidiabetic performance compared to the control by ameliorating insulin resistance in db/db mice and phytosome can be used as an effective antidiabetic agent.

Portulaca oleracea L. extract reduces hyperglycemia via PI3k/Akt and AMPK pathways in the skeletal muscles of C57BL/Ksj-db/db mice

HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE

Portulaca oleracea L. is a succulent annual herb, which has various pharmacological effects including antidiabetic property. However, in vivo the reducing effect of P. oleracea on hyperglycemia and its mechanism of action have not been clarified in a mouse model of type 2 diabetes.

AIM OF THE STUDY

The effects of Portulaca oleracea L. extract (POE) on hyperglycemia were investigated in an animal model of type 2 diabetes.

MATERIALS AND METHODS

C57BL/Ksj-db/db mice were randomly divided into three groups: db/db-control group was fed a standard semi-synthetic diet (AIN-93 G), db/db-RG group was fed AIN-93 G supplemented with rosiglitazone (RG) (0.005%, w/w), and db/db-POE group was fed AIN-93 G supplemented with POE (0.4%, w/w) for 6 weeks. Diabetes-related physical and biochemical indicators and the phosphorylation of components of PI3k/Akt and AMPK pathways were measured.

RESULTS

The blood glucose and the glycosylated hemoglobin levels (HbA1c) in db/db-POE group were significantly lower than those in db/db-control group. In db/db-POE group, The homeostatic index of insulin resistance (HOMA-IR) decreased significantly, whereas the quantitative insulin sensitivity check index (QUICKI) was higher than those in db/db-control group. POE significantly elicited the phosphorylation of IRS-1^Tyr612, Akt^Ser473, and AS160^Thr642, and the activation of PI3K in the skeletal muscle of mice. Additionally, POE significantly stimulated the phosphorylation of AMPK^Thr172, TBC1D1^Ser231, and ACC^Ser79 and elevated the expression of plasma membrane-glucose transporter type 4 (GLUT4).

CONCLUSIONS

These results indicate that POE reduces hyperglycemia by improving insulin resistance through the PI3k/Akt and AMPK pathways in the skeletal muscle of C57BL/Ksj-db/db mice.

Sea cucumbers-derived sterol sulfate alleviates insulin resistance and inflammation in high-fat-high-fructose diet-induced obese mice

Sea cucumbers are widely consumed in traditional medicine and food. Sea cucumbers-derived sulfated sterol exhibits a sulfate group at C-3 position, which is different from phytosterol with a hydroxyl group. However, the effect of sterol sulfate on metabolic syndrome remains unknown. The purpose of the present study is to investigate the alleviation of sterol sulfate on high-fat-high-fructose diet (HFFD)-induced insulin resistance and inflammation. After 2 weeks feeding with HFFD, male C57BL/6J mice were continuously fed with HFFD plus 0.4 % (w/w) sterol sulfate or phytosterol for 6 weeks. The OGTT was carried out at 7 weeks. At the end of the experimental period, the changes of glycogen, circulating glucose, insulin, pro-inflammatory cytokine and adiponectin were measured. H&E staining was used to observe the morphological changes in adipose tissue. Furthermore, the underlying molecular mechanisms were investigated. Dietary sterol sulfate was superior to phytosterol in reducing body weight gain, adipocyte hypertrophy, and levels of circulating glucose and insulin, as well as increasing the glycogen content of tissues. Furthermore, sterol sulfate ameliorated insulin resistance mainly due to the inhibition of gluconeogenesis, the promotion of glycogen synthesis and GLUT4 translocation by activating PI3K/Akt signaling pathway. Additionally, sterol sulfate effectively attenuated inflammation by increasing serum adiponectin and reducing pro-inflammatory cytokine release. Sterol sulfate exhibited a more significant effect than phytosterol in alleviating HFFD -induced insulin resistance and inflammation, which might be closely related to the sulfate group. The results might provide insights into the prevention and alleviation of metabolic syndrome.

Red Pepper (Capsicum annuum L.) Seed Extract Improves Glycemic Control by Inhibiting Hepatic Gluconeogenesis via Phosphorylation of FOXO1 and AMPK in Obese Diabetic db/db Mice

Obesity is a notable risk factor for developing type 2 diabetes, augmenting the concern of obese diabetes (ObD). Anti-obesity and antioxidant effects of red pepper seeds extract (RPSE) have increased our expectations that RPSE would also improve the pathological phenotypes of obese diabetes. Therefore, we hypothesized that RPSE would have an anti-diabetic effect in ObD mice. Animals were assigned either as follows: (1) db/+, (2) db/db control, (3) RPSE (200 mg/kg bw), or (4) a comparative control (metformin 150 mg/kg bw). RPSE was orally administered daily for 8 weeks. As a result, RPSE supplementation improved diabetic phenotypes, including fasting glucose, hemoglobin (HbA1c), and insulin levels. Pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6), and triglycerides were reduced in RPSE-treated mice. RPSE supplementation also diminished the rate-limiting enzymes of gluconeogenesis, including glucose 6-phosphatas (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK), in the liver. RPSE supplementation increased the phosphorylation of forkhead box protein O1 (FOXO1) and AMP-activated protein kinase (AMPK), which underlined the mechanism of the anti-diabetic effects of RPSE. Taken together, RPSE has the potential to improve glycemic control by repressing hepatic gluconeogenesis via the phosphorylation of FOXO1 and AMPK in ObD mice.

Assessment of insulin resistance in the skeletal muscle of mice using positron emission tomography/computed tomography imaging

Measuring glucose uptake in the skeletal muscle in vivo is an effective method to determine glucose metabolism abnormalities as the skeletal muscle is the principal tissue responsible for glucose disposal and is a major site of peripheral insulin resistance. In this study, we investigated the pathological glucose metabolism dynamics of the skeletal muscle of C57BL/6J mice in a noninvasive and time-sequential manner using positron emission tomography/computed tomography (PET/CT), an imaging technique that uses radioactive substances to visualize and measure metabolic processes in the body, with [¹⁸F]-fluoro-2-deoxy-D-glucose (FDG). FDG-PET/CT imaging revealed that insulin administration and exercise load significantly increased FDG accumulation in the skeletal muscle of C57BL/6J mice. FDG accumulation was lower in the skeletal muscle of 14-week-old db/db diabetic model mice exhibiting remarkable insulin resistance compared to that of 7-week-old db/db mice. Based on the continuous observation of FDG accumulation over time in diet-induced obese (DIO) mice, FDG accumulation significantly decreased in 17-week-old mice after the acquisition of insulin resistance. Although insulin-induced glucose uptake in the skeletal muscle was markedly attenuated in 20-week-old DIO mice that had already developed insulin resistance, exercise load effectively increased FDG uptake in the skeletal muscle. Thus, we successfully confirmed that glucose uptake accompanied by insulin administration and exercise load increased in the skeletal muscle using PET-CT. FDG-PET/CT might be an effective tool that could noninvasively capture the chronological changes of metabolic abnormalities in the skeletal muscle of mice.

Vanadium coordination compounds loaded on graphene quantum dots (GQDs) exhibit improved pharmaceutical properties and enhanced anti-diabetic effects

Vanadium compounds are promising anti-diabetic agents, and graphene quantum dots (GQDs) are emerging as potential drug delivery systems to improve drug solubility in water and membrane transport. Using highly dispersible and water-soluble GQDs, we herein prepared a novel GQD-VO (p-dmada) complex, in which vanadium coordination compounds [VO(p-dmada)] were packed closely on one side of the GQD sheets possibly via the π-π stacking mechanism. The in vitro tests showed that GQD-VO(p-dmada) exhibited membrane permeability (Papp) as good as that of GQDs with reduced cytotoxicity. In vivo tests on type 2 diabetic mice demonstrated that GQD-VO(p-dmada) exhibited a delayed glucose lowering profile but more profound effects on insulin enhancement and β-cell protection after three-week treatment compared to VO(p-dmada) alone. In addition, GQD alone was observed for the first time to effectively lower the blood lipid levels of the db/db mice. Overall, GQD-VO(p-dmada) showed improved pharmacokinetic performance and hypoglycemic effects, and using GQD as a nanoplatform for drug delivery may provide vast opportunities for the further design of metal-based pharmaceutical agents.

Cancer causes metabolic perturbations associated with reduced insulin-stimulated glucose uptake in peripheral tissues and impaired muscle microvascular perfusion

BACKGROUND

Redirecting glucose from skeletal muscle and adipose tissue, likely benefits the tumor's energy demand to support tumor growth, as cancer patients with type 2 diabetes have 30% increased mortality rates. The aim of this study was to elucidate tissue-specific contributions and molecular mechanisms underlying cancer-induced metabolic perturbations.

METHODS

Glucose uptake in skeletal muscle and white adipose tissue (WAT), as well as hepatic glucose production, were determined in control and Lewis lung carcinoma (LLC) tumor-bearing C57BL/6 mice using isotopic tracers. Skeletal muscle microvascular perfusion was analyzed via a real-time contrast-enhanced ultrasound technique. Finally, the role of fatty acid turnover on glycemic control was determined by treating tumor-bearing insulin-resistant mice with nicotinic acid or etomoxir.

RESULTS

LLC tumor-bearing mice displayed reduced insulin-induced blood-glucose-lowering and glucose intolerance, which was restored by etomoxir or nicotinic acid. Insulin-stimulated glucose uptake was 30-40% reduced in skeletal muscle and WAT of mice carrying large tumors. Despite compromised glucose uptake, tumor-bearing mice displayed upregulated insulin-stimulated phosphorylation of TBC1D4^Thr642 (+18%), AKT^Ser474 (+65%), and AKT^Thr309 (+86%) in muscle. Insulin caused a 70% increase in muscle microvascular perfusion in control mice, which was abolished in tumor-bearing mice. Additionally, tumor-bearing mice displayed increased (+45%) basal (not insulin-stimulated) hepatic glucose production.

CONCLUSIONS

Cancer can result in marked perturbations on at least six metabolically essential functions; i) insulin's blood-glucose-lowering effect, ii) glucose tolerance, iii) skeletal muscle and WAT insulin-stimulated glucose uptake, iv) intramyocellular insulin signaling, v) muscle microvascular perfusion, and vi) basal hepatic glucose production in mice. The mechanism causing cancer-induced insulin resistance may relate to fatty acid metabolism.

Targeting the Inositol Pyrophosphate Biosynthetic Enzymes in Metabolic Diseases

In mammals, a family of three inositol hexakisphosphate kinases (IP6Ks) synthesizes the inositol pyrophosphate 5-IP7 from IP6. Genetic deletion of Ip6k1 protects mice from high fat diet induced obesity, insulin resistance and fatty liver. IP6K1 generated 5-IP7 promotes insulin secretion from pancreatic β-cells, whereas it reduces insulin signaling in metabolic tissues by inhibiting the protein kinase Akt. Thus, IP6K1 promotes high fat diet induced hyperinsulinemia and insulin resistance in mice while its deletion has the opposite effects. IP6K1 also promotes fat accumulation in the adipose tissue by inhibiting the protein kinase AMPK mediated energy expenditure. Genetic deletion of Ip6k3 protects mice from age induced fat accumulation and insulin resistance. Accordingly, the pan IP6K inhibitor TNP [N2-(m-trifluorobenzyl), N6-(p-nitrobenzyl)purine] ameliorates obesity, insulin resistance and fatty liver in diet induced obese mice by improving Akt and AMPK mediated insulin sensitivity and energy expenditure. TNP also protects mice from bone loss, myocardial infarction and ischemia reperfusion injury. Thus, the IP6K pathway is a potential target in obesity and other metabolic diseases. Here, we summarize the studies that established IP6Ks as a potential target in metabolic diseases. Further studies will reveal whether inhibition of this pathway has similar pleiotropic benefits on metabolic health of humans.

Differential protein phosphorylation is responsible for hypoxia-induced regulation of the Akt/mTOR pathway in naked mole rats

Naked mole rats (NMRs, Heterocephalus glaber) are among the most hypoxia-tolerant mammals known. They can reduce their metabolic rate (>85%) under severe hypoxia, remain moderately active and recover with no obvious signs of damage. Hence, NMRs are an excellent model for studying mammalian hypoxia tolerance. The current study characterized the involvement of posttranslational modifications in regulating the Akt/mTOR pathway that regulates protein synthesis, and the responses of key ribosomal proteins in order to assess tissue-specific responses to 4 h exposure to 7% O₂ (compared to controls at 21% O₂). Results showed a tissue-specific regulation of the Akt/mTOR pathway via differential phosphorylation. Relative amounts of p-TSC(S939) in brain and of p-TSC(S939), p-Akt(473) and p-PTEN(S380) in liver increased under hypoxia, whereas levels of IGF1R(Y1135/1136) in liver decreased. In skeletal muscle, levels of p-Akt(S473) and p-PTEN(S380) decreased during hypoxia, whereas lungs showed an increase in p-mTOR(S2884) content but a decrease in p-RPS6(S235-236) under the same conditions. Analysis of the phosphorylation states of ribosomal proteins revealed increases in p-4E-BP1(T37/46) content in brain and lungs under hypoxia, as well as a rise in total 4E-BP1 protein level in liver. Phosphorylated eIF-4B(S422) content also increased in liver while levels of p-eIF-2α(S51), and eIF-4E(S209) decreased during hypoxia in liver. Overall, hypoxia altered the Akt/mTOR pathway, which correlated with a general decrease in activity of the ribosomal protein biosynthesis machinery in muscle, lung, and brain of NMRs. However, the increase in eIF-4B in liver suggests the potential promotion of cap-independent mRNA translation mechanism operating under hypoxic stress.

The role of skeletal muscle Akt in the regulation of muscle mass and glucose homeostasis

OBJECTIVE

Skeletal muscle insulin signaling is a major determinant of muscle growth and glucose homeostasis. Protein kinase B/Akt plays a prominent role in mediating many of the metabolic effects of insulin. Mice and humans harboring systemic loss-of-function mutations in Akt2, the most abundant Akt isoform in metabolic tissues, are glucose intolerant and insulin resistant. Since the skeletal muscle accounts for a significant amount of postprandial glucose disposal, a popular hypothesis in the diabetes field suggests that a reduction in Akt, specifically in skeletal muscle, leads to systemic glucose intolerance and insulin resistance. Despite this common belief, the specific role of skeletal muscle Akt in muscle growth and insulin sensitivity remains undefined.

METHODS

We generated multiple mouse models of skeletal muscle Akt deficiency to evaluate the role of muscle Akt signaling in vivo. The effects of these genetic perturbations on muscle mass, glucose homeostasis and insulin sensitivity were assessed using both in vivo and ex vivo assays.

RESULTS

Surprisingly, mice lacking Akt2 alone in skeletal muscle displayed normal skeletal muscle insulin signaling, glucose tolerance, and insulin sensitivity despite a dramatic reduction in phosphorylated Akt. In contrast, deletion of both Akt isoforms (M-AktDKO) prevented downstream signaling and resulted in muscle atrophy. Despite the absence of Akt signaling, in vivo and ex vivo insulin-stimulated glucose uptake were normal in M-AktDKO mice. Similar effects on insulin sensitivity were observed in mice with prolonged deletion (4 weeks) of both skeletal muscle Akt isoforms selectively in adulthood. Conversely, short term deletion (2 weeks) of skeletal muscle specific Akt in adult muscles impaired insulin tolerance paralleling the effect observed by acute pharmacological inhibition of Akt in vitro. Mechanistically, chronic ablation of Akt induced mitochondrial dysfunction and activation of AMPK, which was required for insulin-stimulated glucose uptake in the absence of Akt.

CONCLUSIONS

Together, these data indicate that chronic reduction in Akt activity alone in skeletal muscle is not sufficient to induce insulin resistance or prevent glucose uptake in all conditions. Therefore, since insulin-stimulated glucose disposal in skeletal muscle is markedly impaired in insulin-resistant states, we hypothesize that alterations in signaling molecules in addition to skeletal muscle Akt are necessary to perturb glucose tolerance and insulin sensitivity in vivo.

Insulin-Mediated Changes in Tau Hyperphosphorylation and Autophagy in a Drosophila Model of Tauopathy and Neuroblastoma Cells

Almost 50 million people in the world are affected by dementia; the most prevalent form of which is Alzheimer’s disease (AD). Although aging is considered to be the main risk factor for AD, growing evidence from epidemiological studies suggests that type 2 diabetes mellitus (T2DM) increases the risk of dementia including AD. Defective brain insulin signaling has been suggested as an early event in AD and other tauopathies but the mechanisms that link these diseases are largely unknown. Tau hyperphosphorylation is a hallmark of neurofibrillary pathology and insulin resistance increases the number of neuritic plaques particularly in AD. Utilizing a combination of our Drosophila models of tauopathy (expressing the 2N4R-Tau) and neuroblastoma cells, we have attempted to decipher the pathways downstream of the insulin signaling cascade that lead to tau hyperphosphorylation, aggregation and autophagic defects. Using cell-based, genetic, and biochemical approaches we have demonstrated that tau phosphorylation at AT8 and PHF1 residues is enhanced in an insulin-resistant environment. We also show that insulin-induced changes in total and phospho-tau are mediated by the crosstalk of AKT, glycogen synthase kinase-3β, and extracellular regulating kinase located downstream of the insulin receptor pathway. Finally, we demonstrate a significant change in the levels of the key proteins in the mammalian target of rapamycin/autophagy pathway, implying an increased impairment of aggregated protein clearance in our transgenic Drosophila models and cultured neuroblastoma cells.

Dietary chokeberry and dried jujube fruit attenuates high-fat and high-fructose diet-induced dyslipidemia and insulin resistance via activation of the IRS-1/PI3K/Akt pathway in C57BL/6 J mice

Background

The incidence of metabolic syndrome linked to dyslipidemia and insulin resistance has increased; thus, studies must be conducted to elucidate this phenomenon. The present study aimed to investigate the protective effects of chokeberry and dried jujube diet on high-fat and high-fructose diet-induced dyslipidemia in mice.

Methods

Male C57BL/6 J mice were divided into five groups: ND, mice fed normal diet and tap water; HFFD, mice fed 60% high-fat and 10% fructose diet (HFFD) in tap water; HFFD+C, mice fed HFFD with 1% chokeberry powder; HFFD+J, mice fed HFFD with 1% jujube fruit powder; and HFFD+M, mice fed HFFD with 0.5% chokeberry + 0.5% jujube fruit powder mixture.

Results

After 10 weeks of dietary treatment, chokeberry and dried jujube fruits reduced HFFD-induced weight gain and central obesity and decreased liver weight and abdominal and epididymal fat mass. Furthermore, such fruits attenuated HFFD-induced dyslipidemia; decreased triglyceride, total cholesterol, non-high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, and very-low-density lipoprotein-cholesterol levels. Insulin resistance was improved via the consumption of dietary chokeberry and dried jujube fruits according to various indicators (serum insulin level, fasting blood glucose level, homeostatic model assessment-insulin resistance score, and oral glucose tolerance test value). These treatments were found to lower serum triglyceride levels. Moreover, the consumption of chokeberry and dried jujube changed the hepatic protein expression of insulin receptor, insulin receptor substrate 1, phosphoinositide 3-kinase, Akt, and catalase, which are associated with insulin resistance.

Conclusions

Chokeberry and dried jujube could be used in the management of dyslipidemia and insulin resistance associated with metabolic syndrome by reducing risk parameters in mice with HFFD.

Nelumbo nucifera leaves extract attenuate the pathological progression of diabetic nephropathy in high-fat diet-fed and streptozotocin-induced diabetic rats

Diabetic nephropathy is not only a common and severe microvascular complication of diabetes mellitus but also the leading cause of renal failure. Lotus (Nelumbo nucifera) possesses antioxidative and anticancer properties. The present study aimed to investigate the antidiabetic and renoprotective effects of N. nucifera leaf extract (NLE) in a rat model of type 2 diabetic mellitus. Male Sprague–Dawley rats with type 2 diabetes induced by a high-fat diet (HFD)/streptozotocin (STZ) were treated with NLE at dosages of 0.5% and 1% (w/w) daily for 6 weeks. At the end of the experimental period, body weight, serum glucose levels, insulin levels, and kidney function were assessed. Furthermore, antioxidant enzyme and lipid peroxide levels were determined in the kidney, and histopathological examination was performed using hematoxylin and eosin staining, periodic acid Schiff staining, and Masson trichrome staining. To shed light on the molecular mechanism underlying the functioning of NLE, mouse glomerular mesangial cells (MES-13) treated with high glucose (HG, 25 mM glucose) were chosen as a model for an examination of the signal transduction pathway of NLE. The results revealed that NLE improved diabetic kidney injury by reducing blood glucose, serum creatinine, and blood urea nitrogen levels and enhanced antioxidant enzyme activities in kidney tissue. Treatment with NLE significantly reduced the malondialdehyde and 8-hydroxy-2-deoxyguanosine levels and increased serum insulin levels; expression of renal superoxide dismutase, catalase, and glutathione peroxidase activities; and glutathione content. Histological studies have also demonstrated that NLE treatment inhibited the dilation of Bowman’s capsule, which confirmed its renoprotective action in diabetes. In addition, treatment with NLE and its major component quercetin 3-glucuronide attenuated 25 mM HG-induced suppressed nuclear factor erythroid 2-related factor 2 and antioxidant enzyme expression in MES-13 cells. Collectively, these findings indicate that NLE may have antidiabetic and renoprotective effects against HFD/STZ-induced diabetes, at least in part, through antioxidative pathways.

Subcutaneous adipose tissue imaging of human obesity reveals two types of adipocyte membranes: Insulin-responsive and -nonresponsive

In adipose tissue, resistance to insulin's ability to increase glucose uptake can be induced by multiple factors, including obesity. Impaired insulin action may take place at different spatial loci at the cellular or subcellular level. To begin to understand the spatial response to insulin in human subcutaneous adipose tissue (hSAT), we developed a quantitative imaging method for activation of a major signaling node in the glucoregulatory insulin signaling pathway. After treatment with insulin or control media, biopsied tissues were immunostained for Akt phosphorylation at Thr-308/9 (pAkt) and then imaged by confocal fluorescence microscopy automated to collect a large grid of high resolution fields. In hSAT from 40 men and women with obesity, substantial heterogeneity of pAkt densities in adipocyte membranes were quantified in each image mosaic using a spatial unit of at least twice the size of the point spread function. Statistical analysis of the distribution of pAkt spatial units was best fit as the weighted sum of two separate distributions, corresponding to either a low or high pAkt density. A "high pAkt fraction" metric was calculated from the fraction of high pAkt distributed units over the total units. Importantly, upon insulin stimulation, tissues from the same biopsy showed either a minimal or a substantial change in the high pAkt fraction. Further supporting a two-state response to insulin stimulation, subjects with similar insulin sensitivity indices are also segregated into either of two clusters identified by the amount of membrane-localized pAkt.

Intact glucose uptake despite deteriorating signaling in adipocytes with high-fat feeding

To capture immediate cellular changes during diet-induced expansion of adipocyte cell volume and number, we characterized mature adipocytes during a short-term high-fat diet (HFD) intervention. Male C57BL6/J mice were fed chow diet, and then switched to HFD for 2, 4, 6 or 14 days. Systemic glucose clearance was assessed by glucose tolerance test. Adipose tissue was dissected for RNA-seq and cell size distribution analysis using coulter counting. Insulin response in isolated adipocytes was monitored by glucose uptake assay and Western blotting, and confocal microscopy was used to assess autophagic activity. Switching to HFD was accompanied by an immediate adipocyte size expansion and onset of systemic insulin resistance already after two days, followed by recruitment of new adipocytes. Despite an initially increased non-stimulated and preserved insulin-stimulated glucose uptake, we observed a decreased phosphorylation of insulin receptor substrate-1 (IRS-1) and protein kinase B (PKB). After 14 days of HFD, both the insulin-stimulated phosphorylation of Akt substrate of 160 kDa (AS160) and glucose uptake was blunted. RNA-seq analysis of adipose tissue revealed transient changes in gene expression at day four, including highly significant upregulation of Trp53inp, previously demonstrated to be involved in autophagy. We confirmed increased autophagy, measured as an increased density of LC3-positive puncta and decreased p62 expression after 14 days of HFD. In conclusion, HFD rapidly induced systemic insulin resistance, whereas insulin-stimulated glucose uptake remained intact throughout 6 days of HFD feeding. We also identified autophagy as an early cellular process that potentially influences adipocyte function upon switching to HFD.

Effect of gastric bypass combined with ileal transportation on type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a chronic progressive disease, which manifests as an endocrine disorder. Among the different methods of surgery available to treat patients with T2DM, Roux-en-Y gastric bypass (RYGBP) and ileal transposition (IT) are the most commonly performed. The aim of the present study was to investigate the effects of RYGBP combined with IT on rats with T2DM. A total of 8 healthy male rats were used as a control group and 40 GK rats were randomly divided into 5 groups: A diabetes mellitus (DM) group, a sham operative group (SO), a RYGBP group, an IT group and a RYGBP+IT group. The results demonstrated that fasting blood glucose, triglyceride, total cholesterol and gastric inhibitory polypeptide levels in all treatment groups were significantly lower than those of the SO and DM groups. Furthermore, levels TC and TG in the RYGBP+IT group were significantly lower than in the RYGBP and IT groups. Levels of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase mRNA and IRS-2 protein in all treatment groups were also significantly lower than those of the SO group; and they were significantly lower in the RYGBP+IT group compared with the RYGBP and IT groups. The expression of phosphorylated Akt in the treatment groups was significantly higher than the SO group and was significantly higher in the RYGBP+IT group compared with the RYGBP and IT groups. These results indicate that RYGBP and IT surgical treatment can induce T2DM remission by mediating the expression of insulin-related factors to reverse insulin resistance. The current study also indicated that the effect of RYGBP combined with IT may be developed as a novel first-line method of treating T2DM.

Insulin-signalling dysregulation and inflammation is programmed trans-generationally in a female rat model of poor maternal nutrition

Developmental programming phenotypes can be recapitulated in subsequent generations not directly exposed to the initial suboptimal intrauterine environment. A maternal low-protein diet during pregnancy and postnatal catch-up growth (‘recuperated’) alters insulin signaling and inflammation in rat offspring (F1-generation). We aimed to establish if this phenotype is also present in F2-generation females. Insulin-receptor-substrate-1 protein expression was decreased in para-ovarian adipose tissue at 3 months in offspring exposed to a grand-maternal low-protein diet (F2-recuperated), vs. F2-control animals (p < 0.05). There was no effect of grand-maternal diet upon Insulin-receptor-substrate-1 mRNA. Protein-kinase C-zeta protein levels were increased at 3 and 6 months in F2-recuperated animals (p < 0.01 at both ages). Phosphorylated-Akt^ser473 levels were decreased in F2-recuperated animals (p < 0.001). Interleukin-1β protein levels were increased at 3 (p < 0.01) and (p < 0.001) 6 months in F2-recuperated animals. Vastus-lateralis insulin-receptor-β protein expression (p < 0.001) and pAkt^ser473 (p < 0.01) were increased at 3 months in F2-recuperated animals compared to controls. At 6 months, PAkt^ser473 was lower in F2-recuperated animals (p < 0.001). Aspects of insulin signalling dysregulation and inflammation present in offspring of low-protein fed dams can be transmitted to subsequent generations without further exposure to a suboptimal maternal diet. These findings contribute to our understanding of insulin-resistance in grandchildren of sub-optimally nourished individuals during pregnancy.

Inhibition of C1-Ten PTPase activity reduces insulin resistance through IRS-1 and AMPK pathways

Insulin resistance causes type 2 diabetes; therefore, increasing insulin sensitivity is a therapeutic approach against type 2 diabetes. Activating AMP-activated protein kinase (AMPK) is an effective approach for treating diabetes, and reduced insulin receptor substrate-1 (IRS-1) protein levels have been suggested as a molecular mechanism causing insulin resistance. Thus, dual targeting of AMPK and IRS-1 might provide an ideal way to treat diabetes. We found that 15,16-dihydrotanshinone I (DHTS), as a C1-Ten protein tyrosine phosphatase inhibitor, increased IRS-1 stability, improved glucose tolerance and reduced muscle atrophy. Identification of DHTS as a C1-Ten inhibitor revealed a new function of C1-Ten in AMPK inhibition, possibly through regulation of IRS-1. These findings suggest that C1-Ten inhibition by DHTS could provide a novel therapeutic strategy for insulin resistance-associated metabolic syndrome through dual targeting of IRS-1 and AMPK.

Transcriptomic analysis identifies a role of PI3K-Akt signalling in the responses of skeletal muscle to acute hypoxia in vivo

KEY POINTS

Changes in gene expression that occur within hours of exposure to hypoxia in in vivo skeletal muscles remain unexplored. Two hours of hypoxia caused significant down-regulation of extracellular matrix genes followed by a shift at 6 h to altered expression of genes associated with the nuclear lumen while respiratory and blood gases were stabilized. Enrichment analysis of mRNAs classified by stability rates suggests an attenuation of post-transcriptional regulation within hours of hypoxic exposure, where PI3K-Akt signalling was suggested to have a nodal role by pathway analysis. Experimental measurements and bioinformatic analyses suggested that the dephosphorylation of Akt after 2 h of hypoxic exposure might deactivate RNA-binding protein BRF1, hence resulting in the selective degradation of mRNAs.

ABSTRACT

The effects of acute hypoxia have been widely studied, but there are few studies of transcriptional responses to hours of hypoxia in vivo, especially in hypoxia-tolerant tissues like skeletal muscles. We used RNA-seq to analyse gene expression in plantaris muscles while monitoring respiration, arterial blood gases, and blood glucose in mice exposed to 8% O2 for 2 or 6 h. Rapid decreases in blood gases and a slower reduction in blood glucose suggest stress, which was accompanied by widespread changes in gene expression. Early down-regulation of genes associated with the extracellular matrix was followed by a shift to genes associated with the nuclear lumen. Most of the early down-regulated genes had mRNA half-lives longer than 2 h, suggesting a role for post-transcriptional regulation. These transcriptional changes were enriched in signalling pathways in which the PI3K-Akt signalling pathway was identified as a hub. Our analyses indicated that gene targets of PI3K-Akt but not HIF were enriched in early transcriptional responses to hypoxia. Among the PI3K-Akt targets, 75% could be explained by a deactivation of adenylate-uridylate-rich element (ARE)-binding protein BRF1, a target of PI3K-Akt. Consistent decreases in the phosphorylation of Akt and BRF1 were experimentally confirmed following 2 h of hypoxia. These results suggest that the PI3K-Akt signalling pathway might play a role in responses induced by acute hypoxia in skeletal muscles, partially through the dephosphorylation of ARE-binding protein BRF1.

Downregulation of Lysyl Oxidase Protects Retinal Endothelial Cells From High Glucose-Induced Apoptosis

Purpose

To investigate the effect of reducing high glucose (HG)-induced lysyl oxidase (LOX) overexpression and increased activity on retinal endothelial cell apoptosis.

Methods

Rat retinal endothelial cells (RRECs) were grown in normal (N) or HG (30 mM glucose) medium for 7 days. In parallel, RRECs were grown in HG medium and transfected with LOX small interfering RNA (siRNA), scrambled siRNA as control, or exposed to β-aminopropionitrile (BAPN), a LOX inhibitor. LOX expression, AKT activation, and caspase-3 activity were determined by Western blot (WB) analysis and apoptosis by differential dye staining assay. Moreover, to determine whether diabetes-induced LOX overexpression alters AKT activation and promotes apoptosis, changes in LOX expression, AKT phosphorylation, caspase-3 activation, and Bax expression were assessed in retinas of streptozotocin (STZ)-induced diabetic mice and LOX heterozygous knockout (LOX+/-) mice.

Results

WB analysis indicated significant LOX overexpression and reduced AKT activation under HG condition in RRECs. Interestingly, when cells grown in HG were transfected with LOX siRNA or exposed to BAPN, the number of apoptotic cells was significantly decreased concomitant with increased AKT phosphorylation. Diabetic mouse retinas exhibited LOX overexpression, decreased AKT phosphorylation, and increased Bax and caspase-3 activation compared to values in nondiabetic mice. In LOX+/- mice, reduced LOX levels were observed with increased AKT activity, and reduced Bax and caspase-3 activity. Furthermore, decreased levels of LOX in the LOX+/- mice was protective against diabetes-induced apoptosis.

Conclusions

Findings from this study indicate that preventing LOX overexpression may be protective against HG-induced apoptosis in retinal vascular cells associated with diabetic retinopathy.

17β-Estradiol protects against the effects of a high fat diet on cardiac glucose, lipid and nitric oxide metabolism in rats

The aim of this study was to investigate the in vivo effects of 17β-estradiol (E₂) on myocardial metabolism and inducible nitric oxide synthase (iNOS) expression/activity in obese rats. Male Wistar rats were fed with a normal or a high fat (HF) diet (42% fat) for 10 weeks. Half of the HF fed rats were treated with a single dose of E₂ while the other half were placebo-treated. 24 h after treatment animals were sacrificed. E₂ reduced cardiac free fatty acid (FFA) (p < 0.05), L-arginine (p < 0.01), iNOS mRNA (p < 0.01), and protein (p < 0.05) levels and translocation of the FFA transporter (CD36) (p < 0.01) to the plasma membrane (PM) in HF fed rats. In contrast, Akt phosphorylation at Thr³⁰⁸ (p < 0.05) and translocation of the glucose transporter GLUT4 (p < 0.05) to the PM increased after E₂ treatment in HF rats. Our results indicate that E₂ acts via the PI3K/Akt signalling pathway to partially protect myocardial metabolism by attenuating the detrimental effects of increased iNOS expression/activity in HF fed rats.

miR-24-mediated knockdown of H2AX damages mitochondria and the insulin signaling pathway

Mitochondrial deficits or altered expressions of microRNAs are associated with the pathogenesis of various diseases, and microRNA-operated control of mitochondrial activity has been reported. Using a retrovirus-mediated short-hairpin RNA (shRNA) system, we observed that miR-24-mediated H2AX knockdown (H2AX-KD) impaired both mitochondria and the insulin signaling pathway. The overexpression of miR-24 decreased mitochondrial H2AX and disrupted mitochondrial function, as indicated by the ATP content, membrane potential and oxygen consumption. Similar mitochondrial damage was observed in shH2AX-mediated specific H2AX-KD cells. The H2AX-KD reduced the expression levels of mitochondrial transcription factor A (TFAM) and mitochondrial DNA-dependent transcripts. H2AX-KD mitochondria were swollen, and their cristae were destroyed. H2AX-KD also blocked the import of precursor proteins into mitochondria and the insulin-stimulated phosphorylation of IRS-1 (Y632) and Akt (S473 and T308). The rescue of H2AX, but not the nuclear form of ΔC24-H2AX, restored all features of miR-24- or shH2AX-mediated impairment of mitochondria. Hepatic miR-24 levels were significantly increased in db/db and ob/ob mice. A strong feedback loop may be present among miR-24, H2AX, mitochondria and the insulin signaling pathway. Our findings suggest that H2AX-targeting miR-24 may be a novel negative regulator of mitochondrial function and is implicated in the pathogenesis of insulin resistance.

Hepatic Expression of Adenovirus 36 E4ORF1 Improves Glycemic Control and Promotes Glucose Metabolism Through AKT Activation

Considering that impaired proximal insulin signaling is linked with diabetes, approaches that enhance glucose disposal independent of insulin signaling are attractive. In vitro data indicate that the E4ORF1 peptide derived from human adenovirus 36 (Ad36) interacts with cells from adipose tissue, skeletal muscle, and liver to enhance glucose disposal, independent of proximal insulin signaling. Adipocyte-specific expression of Ad36E4ORF1 improves hyperglycemia in mice. To determine the hepatic interaction of Ad36E4ORF1 in enhancing glycemic control, we expressed E4ORF1 of Ad36 or Ad5 or fluorescent tag alone by using recombinant adeno-associated viral vector in the liver of three mouse models. In db/db or diet-induced obesity (DIO) mice, hepatic expression of Ad36E4ORF1 but not Ad5E4ORF1 robustly improved glycemic control. In normoglycemic wild-type mice, hepatic expression of Ad36E4ORF1 lowered nonfasting blood glucose at a high dose of expression. Of note, Ad36E4ORF1 significantly reduced insulin levels in db/db and DIO mice. The improvement in glycemic control was observed without stimulation of the proximal insulin signaling pathway. Collectively, these data indicate that Ad36E4ORF1 is not a typical sensitizer, mimetic, or secretagogue of insulin. Instead, it may have insulin-sparing action, which seems to reduce the need for insulin and, hence, to reduce insulin levels.

Aryl hydrocarbon receptor-deficient mice are protected from high fat diet-induced changes in metabolic rhythms

High fat diet (HFD) consumption alters the synchronized circadian timing system resulting in harmful loss, gain or shift of transcriptional oscillations. The aryl hydrocarbon receptor (AhR) shares structural homology to clock genes, containing both PAS domains and basic helix-loop helix structural motifs, allowing for interaction with components of the primary circadian feedback loop. Activation of AhR alters circadian rhythmicity, primarily through inhibition of Clock/Bmal1-mediated regulation of Per1. AhR-deficient mice are protected from diet-induced metabolic dysfunction, exhibiting enhanced insulin sensitivity and glucose tolerance. This study examined whether AhR haploinsufficiency can also protect against diet-induced alterations in rhythm. After feeding AhR+/+ and AhR+/- mice an HFD (60% fat) for 15 weeks, samples were collected every 4 hours over a 24-hour period. HFD altered the rhythm of serum glucose and the metabolic transcriptome, including hepatic nuclear receptors Rev-erbα and PPARγ in wild-type c57bl6/j mice. AhR reduction provided protection against diet-induced transcriptional oscillation changes; serum glucose and metabolic gene rhythms were protected from the disruption caused by HFD feeding. These data highlight the critical role of AhR signaling in the regulation of metabolism and provide a potential therapeutic target for diseases characterized by rhythmic desynchrony.

Doxorubicin caused severe hyperglycaemia and insulin resistance, mediated by inhibition in AMPk signalling in skeletal muscle

BACKGROUND

Cancer is considered the second leading cause of death in the world, and for the treatment of this disease, pharmacological intervention strategies are frequently based on chemotherapy. Doxorubicin (DOX) is one of the most widely used chemotherapeutic agents in clinical practice for treating a number of solid tumours. The treatment with DOX mimics some effects of cancer cachexia, such as anorexia, asthenia, decreases in fat and skeletal muscle mass and fatigue. We observed that treatment with DOX increased the systemic insulin resistance and caused a massive increase in glucose levels in serum. Skeletal muscle is a major tissue responsible for glucose uptake, and the positive role of AMPk protein (AMP-activated protein kinase) in GLUT-4 (Glucose Transporter type 4) translocation, is well established. With this, our aim was to assess the insulin sensitivity after treatment with DOX and involvement of AMPk signalling in skeletal muscle in this process.

METHODS

We used Wistar rats which received a single dose of doxorubicin (DOX group) or saline (CT group) intraperitoneally at a dose of 15 mg/kg b.w. The expression of proteins involved in insulin sensitivity, glucose uptake, inflammation, and activity of electron transport chain was assessed in extensor digitorum longus muscle, as well as the histological evaluation. In vitro assays were performed in L6 myocytes to assess glucose uptake after treatment with DOX. Agonist of AMPk [5-aminoimidazole-4-carboxamide (AICAR)] and the antioxidant n-acetyl cysteine were used in L6 cells to evaluate its effect on glucose uptake and cell viability.

RESULTS

The animals showed a significant insulin resistance, hyperglycaemia, and hyperinsulinemia. A decrease in the expression of AMKP and GLUT-4 was observed in the extensor digitorum longus muscle. Also in L6 cells, DOX leads to a decrease in glucose uptake, which is reversed with AICAR.

CONCLUSIONS

DOX leads to conditions similar to cachexia, with severe glucose intolerance both in vivo and in vitro. The decrease of AMPk activity of the protein is modulated negatively with DOX, and treatment with agonist of AMPk (AICAR) has proved to be a possible therapeutic target, which is able to recover glucose sensitivity in skeletal muscle.

Endothelial Fcγ Receptor IIB Activation Blunts Insulin Delivery to Skeletal Muscle to Cause Insulin Resistance in Mice

Modest elevations in C-reactive protein (CRP) are associated with type 2 diabetes. We previously revealed in mice that increased CRP causes insulin resistance and mice globally deficient in the CRP receptor Fcγ receptor IIB (FcγRIIB) were protected from the disorder. FcγRIIB is expressed in numerous cell types including endothelium and B lymphocytes. Here we investigated how endothelial FcγRIIB influences glucose homeostasis, using mice with elevated CRP expressing or lacking endothelial FcγRIIB. Whereas increased CRP caused insulin resistance in mice expressing endothelial FcγRIIB, mice deficient in the endothelial receptor were protected. The insulin resistance with endothelial FcγRIIB activation was due to impaired skeletal muscle glucose uptake caused by attenuated insulin delivery, and it was associated with blunted endothelial nitric oxide synthase (eNOS) activation in skeletal muscle. In culture, CRP suppressed endothelial cell insulin transcytosis via FcγRIIB activation and eNOS antagonism. Furthermore, in knock-in mice harboring constitutively active eNOS, elevated CRP did not invoke insulin resistance. Collectively these findings reveal that by inhibiting eNOS, endothelial FcγRIIB activation by CRP blunts insulin delivery to skeletal muscle to cause insulin resistance. Thus, a series of mechanisms in endothelium that impairs insulin movement has been identified that may contribute to type 2 diabetes pathogenesis.

Hyperprolactinemia induced by hCG leads to metabolic disturbances in female mice

The metabolic syndrome is a growing epidemic; it increases the risk for diabetes, cardiovascular disease, fatty liver, and several cancers. Several reports have indicated a link between hormonal imbalances and insulin resistance or obesity. Transgenic (TG) female mice overexpressing the human chorionic gonadotropin β-subunit (hCGβ+ mice) exhibit constitutively elevated levels of hCG, increased production of testosterone, progesterone and prolactin, and obesity. The objective of this study was to investigate the influence of hCG hypersecretion on possible alterations in the glucose and lipid metabolism of adult TG females. We evaluated fasting serum insulin, glucose, and triglyceride levels in adult hCGβ+ females and conducted intraperitoneal glucose and insulin tolerance tests at different ages. TG female mice showed hyperinsulinemia, hypertriglyceridemia, and dyslipidemia, as well as glucose intolerance and insulin resistance at 6 months of age. A 1-week treatment with the dopamine agonist cabergoline applied on 5-week-old hCGβ+ mice, which corrected hyperprolactinemia, hyperandrogenism, and hyperprogesteronemia, effectively prevented the metabolic alterations. These data indicate a key role of the hyperprolactinemia-induced gonadal dysfunction in the metabolic disturbances of hCGβ+ female mice. The findings prompt further studies on the involvement of gonadotropins and prolactin on metabolic disorders and might pave the way for the development of new therapeutic strategies.

The necroptosis-inducing kinase RIPK3 dampens adipose tissue inflammation and glucose intolerance

Receptor-interacting protein kinase 3 (RIPK3) mediates necroptosis, a form of programmed cell death that promotes inflammation in various pathological conditions, suggesting that it might be a privileged pharmacological target. However, its function in glucose homeostasis and obesity has been unknown. Here we show that RIPK3 is over expressed in the white adipose tissue (WAT) of obese mice fed with a choline-deficient high-fat diet. Genetic inactivation of Ripk3 promotes increased Caspase-8-dependent adipocyte apoptosis and WAT inflammation, associated with impaired insulin signalling in WAT as the basis for glucose intolerance. Similarly to mice, in visceral WAT of obese humans, RIPK3 is overexpressed and correlates with the body mass index and metabolic serum markers. Together, these findings provide evidence that RIPK3 in WAT maintains tissue homeostasis and suppresses inflammation and adipocyte apoptosis, suggesting that systemic targeting of necroptosis might be associated with the risk of promoting insulin resistance in obese patients.

Phosphoprotein network analysis of white adipose tissues unveils deregulated pathways in response to high-fat diet

Despite efforts in the last decade, signaling aberrations associated with obesity remain poorly understood. To dissect molecular mechanisms that define this complex metabolic disorder, we carried out global phosphoproteomic analysis of white adipose tissue (WAT) from mice fed on low-fat diet (LFD) and high-fat diet (HFD). We quantified phosphorylation levels on 7696 peptides, and found significant differential phosphorylation levels in 282 phosphosites from 191 proteins, including various insulin-responsive proteins and metabolic enzymes involved in lipid homeostasis in response to high-fat feeding. Kinase-substrate prediction and integrated network analysis of the altered phosphoproteins revealed underlying signaling modulations during HFD-induced obesity, and suggested deregulation of lipogenic and lipolytic pathways. Mutation of the differentially-regulated novel phosphosite on cytoplasmic acetyl-coA forming enzyme ACSS2 (S263A) upon HFD-induced obesity led to accumulation of serum triglycerides and reduced insulin-responsive AKT phosphorylation as compared to wild type ACSS2, thus highlighting its role in obesity. Altogether, our study presents a comprehensive map of adipose tissue phosphoproteome in obesity and reveals many previously unknown candidate phosphorylation sites for future functional investigation.

Imbalanced insulin action in chronic over nutrition: Clinical harm, molecular mechanisms, and a way forward

The growing worldwide prevalence of overnutrition and underexertion threatens the gains that we have made against atherosclerotic cardiovascular disease and other maladies. Chronic overnutrition causes the atherometabolic syndrome, which is a cluster of seemingly unrelated health problems characterized by increased abdominal girth and body-mass index, high fasting and postprandial concentrations of cholesterol- and triglyceride-rich apoB-lipoproteins (C-TRLs), low plasma HDL levels, impaired regulation of plasma glucose concentrations, hypertension, and a significant risk of developing overt type 2 diabetes mellitus (T2DM). In addition, individuals with this syndrome exhibit fatty liver, hypercoagulability, sympathetic overactivity, a gradually rising set-point for body adiposity, a substantially increased risk of atherosclerotic cardiovascular morbidity and mortality, and--crucially--hyperinsulinemia. Many lines of evidence indicate that each component of the atherometabolic syndrome arises, or is worsened by, pathway-selective insulin resistance and responsiveness (SEIRR). Individuals with SEIRR require compensatory hyperinsulinemia to control plasma glucose levels. The result is overdrive of those pathways that remain insulin-responsive, particularly ERK activation and hepatic de-novo lipogenesis (DNL), while carbohydrate regulation deteriorates. The effects are easily summarized: if hyperinsulinemia does something bad in a tissue or organ, that effect remains responsive in the atherometabolic syndrome and T2DM; and if hyperinsulinemia might do something good, that effect becomes resistant. It is a deadly imbalance in insulin action. From the standpoint of human health, it is the worst possible combination of effects. In this review, we discuss the origins of the atherometabolic syndrome in our historically unprecedented environment that only recently has become full of poorly satiating calories and incessant enticements to sit. Data are examined that indicate the magnitude of daily caloric imbalance that causes obesity. We also cover key aspects of healthy, balanced insulin action in liver, endothelium, brain, and elsewhere. Recent insights into the molecular basis and pathophysiologic harm from SEIRR in these organs are discussed. Importantly, a newly discovered oxide transport chain functions as the master regulator of the balance amongst different limbs of the insulin signaling cascade. This oxide transport chain--abbreviated 'NSAPP' after its five major proteins--fails to function properly during chronic overnutrition, resulting in this harmful pattern of SEIRR. We also review the origins of widespread, chronic overnutrition. Despite its apparent complexity, one factor stands out. A sophisticated junk food industry, aided by subsidies from willing governments, has devoted years of careful effort to promote overeating through the creation of a new class of food and drink that is low- or no-cost to the consumer, convenient, savory, calorically dense, yet weakly satiating. It is past time for the rest of us to overcome these foes of good health and solve this man-made epidemic.