Distinct Time Course of the Decrease in Hepatic AMP-Activated Protein Kinase and Akt Phosphorylation in Mice Fed a High Fat Diet

Acetyl-11-Keto-Beta-Boswellic Acid Has Therapeutic Benefits for NAFLD Rat Models That Were Given a High Fructose Diet by Ameliorating Hepatic Inflammation and Lipid Metabolism

Acetyl-11-keto-beta-boswellic acid (AKBA), a potent anti-inflammatory compound purified from Boswellia species, was investigated in a preclinical study for its potential in preventing and treating non-alcoholic fatty liver disease (NAFLD), the most common chronic inflammatory liver disorder. The study involved thirty-six male Wistar rats, equally divided into prevention and treatment groups. In the prevention group, rats were given a high fructose diet (HFrD) and treated with AKBA for 6 weeks, while in the treatment group, rats were fed HFrD for 6 weeks and then given a normal diet with AKBA for 2 weeks. At the end of the study, various parameters were analyzed including liver tissues and serum levels of insulin, leptin, adiponectin, monocyte chemoattractant protein-1 (MCP-1), transforming growth factor beta (TGF-β), interferon gamma (INF-ϒ), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α). Additionally, the expression levels of genes related to the inflammasome complex and peroxisome proliferator-activated receptor gamma (PPAR-ϒ), as well as the levels of phosphorylated and non-phosphorylated AMP-activated protein kinase alpha-1 (AMPK-α1) protein, were measured. The results showed that AKBA improved NAFLD-related serum parameters and inflammatory markers and suppressed PPAR-ϒ and inflammasome complex-related genes involved in hepatic steatosis in both groups. Additionally, AKBA prevented the reduction of the active and inactive forms of AMPK-α1 in the prevention group, which is a cellular energy regulator that helps suppress NAFLD progression. In conclusion, AKBA has a beneficial effect on preventing and avoiding the progression of NAFLD by preserving lipid metabolism, improving hepatic steatosis, and suppressing liver inflammation.

Association of dietary intake with body mass index and glycemic profile among newly diagnosed patients with type 2 diabetes mellitus

INTRODUCTION

Dietary intake plays an important role in determining body mass index (BMI) and glycemic profile in patients with type 2 diabetes mellitus (T2DM). Our aim was to describe habitual dietary intake and its associations with BMI and glycemic profile in a cohort of patients with newly diagnosed T2DM in Sri Lanka.

METHODS

A cross-sectional study was carried out among 158 patients with newly diagnosed T2DM in Galle, Sri Lanka. Data on demographic, lifestyle, and family history of diabetes mellitus, and clinical measures were collected. The dietary information was collected using a 24-h dietary recall.

RESULTS

Among the total number of study subjects, only 12.0%, 5.7% and 1.3% met the recommended daily consumption value of protein, fat, and fiber, respectively, whereas 99.4% of subjects had taken carbohydrates that exceeded the recommended consumption. There was a positive association between carbohydrate intake and BMI (0.004, [0.002], p = .048) and carbohydrate intake and glycated hemoglobin (HbA1C ) (0.001, [0.000], p = .049). Fat intake showed positive associations with BMI (0.029, [0.011], p = .006) and HbA1C (0.005, [0.002], p = .050). Protein intake showed a positive association with HbA1C (0.006, [0.003], p = .023). The aforementioned associations were observed after adjusting for demographic, lifestyle, and history of diabetes among the first-degree family members. The carbohydrate intake was positively associated with BMI (0.010, [0.003], p = .003) and HbA1C (0.001, [0.000], p = .050) with further adjustment in nutrient intake (except when used as an independent variable). Furthermore, the fat intake was associated with BMI (0.031, [0.011], p = .004) and HbA1C (0.005 [0.002], p = .050) with additional adjustments.

CONCLUSIONS

The diet of the majority of newly diagnosed T2DM patients in this cohort consisted of a higher carbohydrate intake than the recommended level. However, they did not meet the recommended daily intake of protein, fat, and fiber. Both carbohydrate and fat intake were significantly and positively associated with BMI and HbA1C in patients with newly diagnosed T2DM.

Protein Phosphatase 2A Regulates Phenotypic and Metabolic Alteration of Microglia Cells in HFD-Associated Vascular Dementia Mice via TNF-α/Arg-1 Axis

Protein phosphatase 2A (PP2A), the activity of which is dictated by the composition of its regulatory subunit, is strongly related to the progression of neurodegenerative disease. The potential role of PP2A on the phenotypic transition of microglial cells under obese conditions is poorly explored. An understanding of the role of PP2A and identification of regulatory subunits contributing to microglial phenotypic transitions in obese condition may serve as a therapeutic target for obesity-associated neurodegeneration. C57BL/6 mice were exposed to obese-associated vascular dementia conditions by performing unilateral common carotid artery occlusion on obese mice of microglial polarization and PP2A activity using flow cytometry, real-time PCR, western blotting, and immunoprecipitation enzymatic assay, followed identifications of PP2A regulatory subunits using LCMS and RT-PCR. Chronic HFD feeding significantly increased the populations of infiltrated macrophages, showing a high percentage of CD86⁺ in VaD mice, and the expression of pro-inflammatory cytokines, and we observed that PP2A modulates metabolic reprogramming of microglia by regulating OXPHOS/ECAR activity. Using Co-IP and LCMS, we identified the six specific regulatory subunits, namely PPP2R2A, PPP2R2D, PPP2R5B, PPP2R5C, PPP2R5D, and PPP2R5E, that are associated with microglial-activation during obesity-associated-VaD. Interestingly, pharmacological up-regulation of PP2A more significantly suppressed the expression of TNF-alpha than other pro-inflammatory-cytokines and increased the expression of Arginase-1, suggesting that PP2A modulates microglial-phenotypic transitions through TNF-α/Arg-1 axis. Our present findings demonstrate microglial polarization in HFD associated with VaD, and point towards a therapeutic target by providing specific PP2A regulatory-subunits implicated in microglial activation during obesity-related-vascular-dementia.

Nutrition, metabolism, and epigenetics: pathways of circadian reprogramming

Food intake profoundly affects systemic physiology. A large body of evidence has indicated a link between food intake and circadian rhythms, and ~24-h cycles are deemed essential for adapting internal homeostasis to the external environment. Circadian rhythms are controlled by the biological clock, a molecular system remarkably conserved throughout evolution. The circadian clock controls the cyclic expression of numerous genes, a regulatory program common to all mammalian cells, which may lead to various metabolic and physiological disturbances if hindered. Although the circadian clock regulates multiple metabolic pathways, metabolic states also provide feedback on the molecular clock. Therefore, a remarkable feature is reprogramming by nutritional challenges, such as a high-fat diet, fasting, ketogenic diet, and caloric restriction. In addition, various factors such as energy balance, histone modifications, and nuclear receptor activity are involved in the remodeling of the clock. Herein, we review the interaction of dietary components with the circadian system and illustrate the relationships linking the molecular clock to metabolism and critical roles in the remodeling process.

Role of Plin5 Deficiency in Progression of Non-Alcoholic Fatty Liver Disease Induced by a High-Fat Diet in Mice

Characterized by steatosis, inflammation and fibrosis, non-alcoholic fatty liver disease (NAFLD) is a metabolic disorder. As a major lipid droplet-binding protein, Plin5 has been reported to have multiple effects on metabolism, but the effect of Plin5 deficiency on NAFLD is unknown. Plin5 knockout mice and wild-type mice were used to investigate the role of Plin5 in the progression of NAFLD by feeding a high-fat diet (HFD) for 20 weeks. Plin5 deficiency improved obesity induced by the HFD and altered glucose tolerance. Histological examination revealed that Plin5 deficiency alleviated hepatic steatosis and fibrosis induced by the HFD. Plin5 deficiency was also associated with a significant change in lipid metabolism-associated molecules. Further studies of these molecules indicated that Plin5 deficiency activated the expression of AMP-activated protein kinase and inhibited the core regulator of lipogenesis, sterol regulatory element binding protein 1 and its downstream lipid synthesis-related genes. These findings suggest that Plin5 deficiency ameliorates NAFLD by regulating lipid metabolism and inhibiting lipogenesis, and may provide a new strategy for the treatment of NAFLD.

Ablation of Akt2 and AMPKα2 rescues high fat diet-induced obesity and hepatic steatosis through Parkin-mediated mitophagy

Given the opposing effects of Akt and AMP-activated protein kinase (AMPK) on metabolic homeostasis, this study examined the effects of deletion of Akt2 and AMPKα2 on fat diet-induced hepatic steatosis. Akt2-Ampkα2 double knockout (DKO) mice were placed on high fat diet for 5 months. Glucose metabolism, energy homeostasis, cardiac function, lipid accumulation, and hepatic steatosis were examined. DKO mice were lean without anthropometric defects. High fat intake led to adiposity and decreased respiratory exchange ratio (RER) in wild-type (WT) mice, which were ablated in DKO but not Akt2 -/- and Ampkα2 -/- mice. High fat intake increased blood and hepatic triglycerides and cholesterol, promoted hepatic steatosis and injury in WT mice. These effects were eliminated in DKO but not Akt2 -/- and Ampkα2 -/- mice. Fat diet promoted fat accumulation, and enlarged adipocyte size, the effect was negated in DKO mice. Fat intake elevated fatty acid synthase (FAS), carbohydrate-responsive element-binding protein (CHREBP), sterol regulatory element-binding protein 1 (SREBP1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), peroxisome proliferator-activated receptor-α (PPARα), PPARγ, stearoyl-CoA desaturase 1 (SCD-1), phosphoenolpyruvate carboxykinase (PEPCK), glucose 6-phosphatase (G6Pase), and diglyceride O-acyltransferase 1 (DGAT1), the effect was absent in DKO but not Akt2 -/- and Ampkα2 -/- mice. Fat diet dampened mitophagy, promoted inflammation and phosphorylation of forkhead box protein O1 (FoxO1) and AMPKα1 (Ser485), the effects were eradicated by DKO. Deletion of Parkin effectively nullified DKO-induced metabolic benefits against high fat intake. Liver samples from obese humans displayed lowered microtubule-associated proteins 1A/1B light chain 3B (LC3B), Pink1, Parkin, as well as enhanced phosphorylation of Akt, AMPK (Ser485), and FoxO1, which were consolidated by RNA sequencing (RNAseq) and mass spectrometry analyses from rodent and human livers. These data suggest that concurrent deletion of Akt2 and AMPKα2 offers resilience to fat diet-induced obesity and hepatic steatosis, possibly through preservation of Parkin-mediated mitophagy and lipid metabolism.

Temporal metabolic and transcriptomic characteristics crossing islets and liver reveal dynamic pathophysiology in diet-induced diabetes

To investigate the molecular mechanisms underlying islet dysfunction and insulin resistance in diet-induced diabetes, we conducted temporal RNA sequencing of tissues responsible for insulin secretion (islets) and action (liver) every 4 weeks in mice on high-fat (HFD) or chow diet for 24 weeks, linking to longitudinal profile of metabolic characteristics. The diverse responses of α, β, and δ cells to glucose and palmitate indicated HFD-induced dynamic deterioration of islet function from dysregulation to failure. Insulin resistance developed with variable time course in different tissues. Weighted gene co-expression network analysis and Ingenuity Pathway Analysis implicated islets and liver jointly programmed β-cell compensatory adaption via cell proliferation at early phase and irreversible islet dysfunction by inappropriate immune response at later stage, and identified interconnected molecules including growth differentiation factor 15. Frequencies of T cell subpopulation showed an early decrement in Tregs followed by increases in Th1 and Th17 cells during progression to diabetes.

Effects of Long-Term DHA Supplementation and Physical Exercise on Non-Alcoholic Fatty Liver Development in Obese Aged Female Mice

Obesity and aging are associated to non-alcoholic fatty liver disease (NAFLD) development. Here, we investigate whether long-term feeding with a docosahexaenoic acid (DHA)-enriched diet and aerobic exercise, alone or in combination, are effective in ameliorating NAFLD in aged obese mice. Two-month-old female C57BL/6J mice received control or high fat diet (HFD) for 4 months. Then, the diet-induced obese (DIO) mice were distributed into four groups: DIO, DIO + DHA (15% dietary lipids replaced by a DHA-rich concentrate), DIO + EX (treadmill running), and DIO + DHA + EX up to 18 months. The DHA-rich diet reduced liver steatosis in DIO mice, decreasing lipogenic genes (Dgat2, Scd1, Srebp1c), and upregulated lipid catabolism genes (Hsl/Acox) expression. A similar pattern was observed in the DIO + EX group. The combination of DHA + exercise potentiated an increase in Cpt1a and Ppara genes, and AMPK activation, key regulators of fatty acid oxidation. Exercise, alone or in combination with DHA, significantly reversed the induction of proinflammatory genes (Mcp1, Il6, Tnfα, Tlr4) in DIO mice. DHA supplementation was effective in preventing the alterations induced by the HFD in endoplasmic reticulum stress-related genes (Ern1/Xbp1) and autophagy markers (LC3II/I ratio, p62, Atg7). In summary, long-term DHA supplementation and/or exercise could be helpful to delay NAFLD progression during aging in obesity.

Coordinated regulation of miR-27 by insulin/CREB/Hippo contributes to insulin resistance

MicroRNA-27 is a critical non-coding metabolic gene that is often aberrantly overexpressed in non-alcoholic fatty livers (NAFLD). However, the pathogenic role of miR-27 in NAFLD remains unknown. In this study, we attempted to identify the mechanism by which miR-27 was regulated in the context of insulin resistance, a predisposed metabolic disorder in NAFLD. Our data from cell culture and animal studies showed that insulin, CREB, and Hippo signalings coordinately regulated miR-27. First, miR-27 was upregulated in palmitate-treated cells and high fat diet-fed mouse livers, which exhibited insulin resistance and CREB overexpression. Second, miR-27 peaked in the mouse liver at the post-absorptive phase when CREB activity was increased. Also, miR-27 was increased rapidly in cell lines when CREB was deactivated by insulin treatment. Third, miR-27 was decreased in cultured cells when CREB was downregulated by siRNA or metformin treatment. In contrast, Forskolin-mediated activation of CREB promoted miR-27 expression. Fourth, Hippo signaling repressed miR-27 in a CREB-independent manner: miR-27 was reduced in cells at full confluence but was inhibited in cells transfected with siRNA against Lats2 and Nf2, which were two positive regulators of Hippo signaling. Lastly, bioinformatics and luciferase assay showed that miR-27 inhibited Akt phosphorylation by targeting Pdpk1 and Pik3r1. Overexpression of miR-27 impaired Akt phosphorylation in cell lines and primary mouse hepatocytes upon insulin stimulation. In conclusion, our data suggest that insulin, CREB, and Hippo signalings contribute to aberrant miR-27 overexpression and eventually lead to insulin resistance in NAFLD.

Diospyros kaki and Citrus unshiu Mixture Improves Disorders of Lipid Metabolism in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) has been a major cause of a chronic liver disease over recent decades and increasing worldwide in parallel with the remarkable growth of obesity. In the present study, we investigate the ameliorative effects of PCM, a combination of Diospyros kaki fruit and Citrus unshiu peel mixture, on high-fat diet- (HFD-) induced NAFLD and clarify the potential mechanisms. PCM in HFD-fed mice was orally administered at a dose of 50 or 100 mg/kg subsequently for 2 months. Thereafter, lipid metabolism parameters and fat synthesis-related genes in the mouse liver were evaluated. Subsequently, body weight changes, liver weight, serum liver function and lipid profiles, and liver pathology were examined, and the relative levels of fatty acid synthesis and β-oxidation gene expression were evaluated by western blot. Serum AST, ALT, and TG levels in the HFD control mice were significantly higher than those of normal mice. Compared with HFD control mice, PCM supplementation increased phosphorylation of AMP-activated protein kinase (AMPK). Peroxisome proliferator-activated receptor (PPAR) α was significantly increased by PCM administration. Continuously, the activation of PPARα significantly elevated carnitine palmitoyltransferase 1 (CPT-1), a key enzyme in fatty acid β-oxidation, and mitochondrial uncoupling protein 2 (UCP-2), thermogenic regulatory genes, in PCM-treated mice compared with those of HFD control mice. Moreover, PCM inhibits lipogenesis and cholesterol synthesis via suppression of sterol regulatory element binding protein-1 (SREBP-1) and SREBP-2 and its target genes such as acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), stearoyl-CoA desaturase-1 (SCD-1), and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR). Taken together, these effects were mediated through activation of AMPK. In the conclusion, PCM improved liver damage in HFD-fed mice and attenuated NAFLD by the activation of PPARα and the inhibition of SREBPs expression via AMPK-dependent pathways.

GR-C/EBPα-IGF1 axis mediated azithromycin-induced liver developmental toxicity in fetal mice

Azithromycin is considered an effective drug to treat the perinatal mycoplasma infection. However, there is a lack of studies on developmental toxicity of azithromycin. In this study, we observed the developmental toxicity of fetal liver induced by prenatal azithromycin exposure (PAE) in mice and explored the potential mechanism. Pregnant Kunming mice were intraperitoneally injected with azithromycin (37.5 and 150 mg/kg·d) from gestational day (GD) 9 to 18. After PAE, the bodyweight gain rates of pregnant mice and the birthweights of the offspring were decreased, and the liver morphology, development indexes and metabolic function were all altered in different degree in the PAE fetuses. Meanwhile, PAE decreased the fetal serum insulin-like growth factor 1 (IGF1) levels and liver IGF1 signal pathway expression, accompanied by glucocorticoid receptor-CCAAT enhancer-binding protein α (GR-C/EBPα) signal enhancement. Furthermore, azithromycin disturbed hepatocyte differentiation, maturation and metabolic function via upregulating GR-C/EBPα signal and reducing the expression and secretion levels of IGF1 in HepG2 cells. These changes could be reversed by GR siRNA or exogenous IGF1. These results indicated that PAE could cause fetal liver developmental toxicity in mice, and one of the main mechanisms was that azithromycin activated the GR-C/EBPα signal, inhibited the IGF1 signal pathway, and then disturbed the hepatic proliferation, apoptosis, differentiation, and glycose and lipid metabolism.

Associations of nutrient intakes with obesity and diabetes mellitus in the longitudinal medical surveys of Japanese Americans

AIMS/INTRODUCTION

Our previous survey of two Japanese populations, with different lifestyles but identical genetic dispositions, showed that Japanese Americans had different dietary intakes and higher prevalences of obesity and diabetes mellitus, compared with the native Japanese population. The present study examined whether Westernized dietary habits could affect the development of obesity or diabetes.

MATERIALS AND METHODS

This study included 765 individuals with normal glucose tolerance at baseline medical examinations (1986 or 1989 in Los Angeles and in 1988 or 1992 in Hawaii) who subsequently completed follow-up medical examinations several years later. The participants were categorized at baseline as "lean" (576 individuals, body mass index of <25 kg/m2 ) or "obese" (189 individuals, body mass index of ≥25 kg/m2 ). Nutrient intakes were analyzed for associations with the development of obesity or diabetes using Cox's proportional hazard model.

RESULTS

A total of 41 lean participants developed diabetes, which was not associated with any nutrient intakes (mean follow up 10.8 ± 6.6 years). A total of 36 obese participants developed diabetes, which was positively associated with intakes of animal protein, animal fat and saturated fatty acid (mean follow up 10.7 ± 6.3 years). A total of 85 lean participants became obese, which was positively associated with intakes of simple carbohydrates, sugar and fructose, as well as inversely associated with intakes of vegetable protein and complex carbohydrates (mean follow up 10.4 ± 6.5 years).

CONCLUSIONS

In the Japanese Americans, different nutrient intakes affected the development of obesity and diabetes. Furthermore, the associations of nutrient intakes with diabetes development varied according to the presence or absence of obesity.

Two-week administration of engineered Escherichia coli establishes persistent resistance to diet-induced obesity even without antibiotic pre-treatment

Adverse alterations in the composition of the gut microbiota have been implicated in the development of obesity and a variety of chronic diseases. Re-engineering the gut microbiota to produce beneficial metabolites is a potential strategy for treating these chronic diseases. N-acyl-phosphatidylethanolamines (NAPEs) are a family of bioactive lipids with known anti-obesity properties. Previous studies showed that administration of Escherichia coli Nissle 1917 (EcN) engineered with Arabidopsis thaliana NAPE synthase to produce NAPEs imparted resistance to obesity induced by a high-fat diet that persisted after ending their administration. In prior studies, mice were pre-treated with ampicillin prior to administering engineered EcN for 8 weeks in drinking water. If use of antibiotics and long-term administration are required for beneficial effects, implementation of this strategy in humans might be problematic. Studies were therefore undertaken to determine if less onerous protocols could still impart persistent resistance and sustained NAPE biosynthesis. Administration of engineered EcN for only 2 weeks without pre-treatment with antibiotics sufficed to establish persistent resistance. Sustained NAPE biosynthesis by EcN was required as antibiotic treatment after administration of the engineered EcN markedly attenuated its effects. Finally, heterologous expression of human phospholipase A/acyltransferase-2 (PLAAT2) in EcN provided similar resistance to obesity as heterologous expression of A. thaliana NAPE synthase, confirming that NAPEs are the bioactive mediator of this resistance.

Interleukin-37 treatment of mice with metabolic syndrome improves insulin sensitivity and reduces pro-inflammatory cytokine production in adipose tissue

Obesity and the metabolic syndrome are characterized by chronic, low-grade inflammation mainly originating from expanding adipose tissue and resulting in inhibition of insulin signaling and disruption of glycemic control. Transgenic mice expressing human interleukin 37 (IL-37), an anti-inflammatory cytokine of the IL-1 family, are protected against metabolic syndrome when fed a high-fat diet (HFD) containing 45% fat. Here, we examined whether treatment with recombinant IL-37 ameliorates established insulin resistance and obesity-induced inflammation. WT mice were fed a HFD for 22 weeks and then treated daily with IL-37 (1 μg/mouse) during the last 2 weeks. Compared with vehicle only-treated mice, IL-37-treated mice exhibited reduced insulin in the plasma and had significant improvements in glucose tolerance and in insulin content of the islets. The IL-37 treatment also increased the levels of circulating IL-1 receptor antagonist. Cultured adipose tissues revealed that IL-37 treatment significantly decreases spontaneous secretions of IL-1β, tumor necrosis factor α (TNFα), and CXC motif chemokine ligand 1 (CXCL-1). We also fed mice a 60% fat diet with concomitant daily IL-37 for 2 weeks and observed decreased secretion of IL-1β, TNFα, and IL-6 and reduced intracellular levels of IL-1α in the liver and adipose tissue, along with improved plasma glucose clearance. Compared with vehicle treatment, these IL-37-treated mice had no apparent weight gain. In human adipose tissue cultures, the presence of 50 pm IL-37 reduced spontaneous release of TNFα and 50% of lipopolysaccharide-induced TNFα. These findings indicate that IL-37's anti-inflammatory effects can ameliorate established metabolic disturbances during obesity.

Study of microRNAs targeted Dvl2 on the osteoblasts differentiation of rat BMSCs in hyperlipidemia environment

Dishevelled 2 (Dvl-2), a key mediator of the wnt/β-catenin signaling pathway, plays critical roles in osteoblasts differentiation in hyperlipidemia environment. In our previous study, we observed a strong correlation between increased dvl2 expression and decreased new bone formation around implants in a rat hyperlipidemia implant surgery model. However, transcriptional regulation of Dvl2 by microRNAs in this process remains unknown. In the current study, we searched in online database and identified four significantly up-regulated miRNAs, miR-21-5p, miR-29c-3p, miR-138-5p, and miR-351-5p that could potentially regulate Dvl2. Using Western blot and dual-luciferase assays, we confirmed that miR29c-3p suppresses Dvl2 expression by binding to its 3'-UTR. Our results suggest a novel transcriptional regulation mechanism of Dvl2 by miR-29c-3p in osteoblasts differentiation of BMSCs.

[Disheveled 2 around the implant at an early stage of hyperlipidemic rats]

OBJECTIVE

This study aims to investigate the expression of disheveled 2 (Dvl2) around the implant of hyperlipidemic rats at an early stage after the implantation.

METHODS

A total of 24 Wistar rats were divided equally into the experimental group fed with high-fat diet group and control group fed with a normal diet. After 8 weeks, the serum lipid levels were detected, and rats received implants in the femur metaphysis. Rats were sacrificed at 1, 3, and 5 days after implantation, and the bones around implants were obtained. Methylene blue-acid fuchsin staining was performed to observe the implant-bone interface. Real-time polymerase chain reaction was performed on runt-related transcription factor 2 (Runx2), cathepsin K (CatK), and Dvl2. Dvl2 Western blot or immunoprecipitation, phosphorylation, and ubiquitination were also conducted.

RESULTS

In the experimental group, less osteoblasts, lower expression of Runx2 and Dvl2, and lower Dvl2 phosphorylation (P<0.05) than those of the control group were observed; furthermore, the CatK expression and Dvl2 ubiquitination were higher than those in the control group (P<0.05).

CONCLUSIONS

Hyperlipidemia may suppress bone remodeling around the implant at an early stage by Dvl2 down-regulation, phosphorylation, and up-regulated ubiquitination.

Increased intracellular Ca2+ concentrations prevent membrane localization of PH domains through the formation of Ca2+-phosphoinositides

Insulin resistance is a metabolic disorder in which target cells fail to respond to physiological levels of circulating insulin, leading to hyperinsulinemia and glucose intolerance. The molecular mechanism underlying insulin resistance is still largely unknown. Here, we found that intracellular Ca²⁺ overloading in obesity attenuates insulin-stimulated phosphorylation of protein kinase B and its downstream signaling by preventing membrane localization of various pleckstrin homology (PH) domains. When at high intracellular levels, Ca²⁺ binds tightly with phosphoinositides to yield Ca²⁺-phosphoinositides (PIPs), abrogating the membrane targeting of PH domains and disrupting insulin signaling. Thus, we identified a previously unknown physiological function of intracellular Ca²⁺ as a critical negative regulator of insulin signaling, especially through the formation of Ca²⁺-PIPs.

Insulin resistance, a key etiological factor in metabolic syndrome, is closely linked to ectopic lipid accumulation and increased intracellular Ca²⁺ concentrations in muscle and liver. However, the mechanism by which dysregulated intracellular Ca²⁺ homeostasis causes insulin resistance remains elusive. Here, we show that increased intracellular Ca²⁺ acts as a negative regulator of insulin signaling. Chronic intracellular Ca²⁺ overload in hepatocytes during obesity and hyperlipidemia attenuates the phosphorylation of protein kinase B (Akt) and its key downstream signaling molecules by inhibiting membrane localization of pleckstrin homology (PH) domains. Pharmacological approaches showed that elevated intracellular Ca²⁺ inhibits insulin-stimulated Akt phosphorylation and abrogates membrane localization of various PH domain proteins such as phospholipase Cδ and insulin receptor substrate 1, suggesting a common mechanism inhibiting the membrane targeting of PH domains. PH domain-lipid overlay assays confirmed that Ca²⁺ abolishes the binding of various PH domains to phosphoinositides (PIPs) with two adjacent phosphate groups, such as PI(3,4)P₂, PI(4,5)P₂, and PI(3,4,5)P₃. Finally, thermodynamic analysis of the binding interaction showed that Ca²⁺-mediated inhibition of targeting PH domains to the membrane resulted from the tight binding of Ca²⁺ rather than PH domains to PIPs forming Ca²⁺-PIPs. Thus, Ca²⁺-PIPs prevent the recognition of PIPs by PH domains, potentially due to electrostatic repulsion between positively charged side chains in PH domains and the Ca²⁺-PIPs. Our findings provide a mechanistic link between intracellular Ca²⁺ dysregulation and Akt inactivation in insulin resistance.

Rapid Eye Movement Sleep Deprivation Produces Long-Term Detrimental Effects in Spatial Memory and Modifies the Cellular Composition of the Subgranular Zone

Sleep deprivation (SD) affects spatial memory and proliferation in the dentate gyrus. It is unknown whether these deleterious effects persist in the long run. The aim of this study was to evaluate the proliferation, differentiation and maturation of neural progenitors as well as spatial memory 21 days after suffering SD. Sixty-day old male Balb/C mice were exposed to 72-h REM-SD. Spatial memory, cell fate, apoptosis and expression levels of insulin-like growth factor 1 receptor (IGF-1R) were evaluated in the hippocampus at 0, 14, and 21 days after SD or control conditions. After 21-days recovery period, memory performance was assessed with the Barnes maze, we found a significant memory impairment in SD mice vs. control (94.0 ± 10.2 s vs. 25.2 ± 4.5 s; p < 0.001). The number of BrdU+ cells was significantly decreased in the SD groups at day 14 (controls = 1.6 ± 0.1 vs. SD mice = 1.2 ± 0.1 cells/field; p = 0.001) and at day 21 (controls = 0.2 ± 0.03 vs. SD mice = 0.1 ± 0.02 cells/field; p < 0.001). A statistically significant decrease was observed in neuronal differentiation (1.4 ± 0.1 cells/field vs. 0.9 ± 0.1 cells/field, p = 0.003). Apoptosis was significantly increased at day 14 after SD (0.53 ± 0.06 TUNEL+ cells/field) compared to controls (0.19 ± 0.03 TUNEL+ cells/field p < 0.001) and at 21-days after SD (SD mice 0.53 ± 0.15 TUNEL+ cells/field; p = 0.035). At day 0, IGF-1R expression showed a statistically significant reduction in SD animals (64.6 ± 12.2 units) when compared to the control group (102.0 ± 9.8 units; p = 0.043). However, no statistically significant differences were found at days 14 and 21 after SD. In conclusion, a single exposition to SD for 72-h can induce deleterious effects that persist for at least 3 weeks. These changes are characterized by spatial memory impairment, reduction in the number of hippocampal BrdU+ cells and persistent apoptosis rate. In contrast, changes IGF-1R expression appears to be a transient event. Highlight Sleep deprivation affects spatial memory and proliferation in the dentate gyrus. To date it is unknown whether these deleterious effects are persistent over a long period of time. We analyzed the effects of sleep deprivation in the hippocampus after 21 days of recovery sleep. Our findings indicate that after sleep recovery, the detrimental effects of SD can be observed for at least 2 weeks, as shown by a reduction in memory performance, changes in the hippocampal cellular composition and higher apoptotic rate over a long period of time.