Differential regulation of Actn2 and Actn3 expression during unfolded protein response in C2C12 myotubes

ACTN2 and ACTN3 encode sarcomeric α-actinin-2 and α-actinin-3 proteins, respectively, that constitute the Z-line in mammalian skeletal muscle fibers. In human ACTN3, a nonsense mutation at codon 577 that encodes arginine (R) produces the R577X polymorphism. Individuals having a homozygous 577XX genotype do not produce α-actinin-3 protein. The 577XX genotype reportedly occurs in sprint and power athletes in frequency lower than in the normal population, suggesting that α-actinin-3 deficiency diminishes fast-type muscle function. Among humans who carry 577R alleles, varying ACTN3 expression levels under certain conditions can have diverse effects on atheletic and muscle performance. However, the factors that regulate ACTN3 expression are unclear. Here we investigated whether the unfolded protein response (UPR) under endoplasmic reticulum (ER) stress regulates expression of Actn3 and its isoform Actn2 in mouse C2C12 myotubes. Among UPR-related transcription factors, XBP1 upregulated Actn2, whereas XBP1, ATF4 and ATF6 downregulated Actn3 promoter activity. Chemical induction of ER stress increased Actn2 mRNA levels, but decreased those for Actn3. ER stress also decreased α-actinin-3 protein levels, whereas levels of α-actinin-2 were unchanged. The intracellular composition of muscle contraction-related proteins was altered under ER stress, in that expression of parvalbumin (a fast-twitch muscle-specific protein) and troponin I type 1 (skeletal, slow) was suppressed. siRNA-induced suppression of Actn3 mimicked the inhibitory effect of ER stress on parvalbumin levels. Thus, endogenous expression levels of α-actinin-3 can be altered by ER stress, which may modulate muscle performance and athletic aptitudes, particularly in humans who carry ACTN3 577R alleles.

Readthrough of ACTN3 577X nonsense mutation produces full-length α-actinin-3 protein

The ACTN3 gene encodes α-actinin-3 protein, which stabilizes the contractile apparatus at the Z-line in skeletal muscle cell fast fibers. A nonsense mutation of the arginine (R) at the codon for amino acid 577 of the ACTN3 gene generates a premature termination codon (PTC) and produces the R577X polymorphism in humans (X specifies translational termination). The ACTN3 577X genotype abolishes α-actinin-3 protein production due to targeted degradation of the mutant transcript by the cellular nonsense-mediated mRNA decay (NMD) system, which requires mRNA splicing. In humans, α-actinin-3 deficiency can decrease sprinting and power performance as well as skeletal muscle mass and strength. Here we investigated whether suppression of the in-frame PTC induced by treatment with the aminoglycosides gentamicin and G418 that promote termination codon readthrough could allow production of full-length α-actinin-3 protein from ACTN3 577X. We constructed expression plasmids encoding mature mRNA that lacks introns or pre-mRNA, which carries introns for the ACTN3 577X gene (X and X_pre, respectively) and transfected the constructs into HEK293 cells. Similar constructs for the ACTN3 577R gene were used as controls. HEK293 cells carrying the X gene, but not the X_pre gene, expressed exogenous truncated α-actinin-3 protein, indicating NMD-mediated suppression of exogenous X_pre expression. Cells treated with aminoglycosides produced exogenous full-length α-actinin-3 protein in X-transfected cells, but not in X_pre-transfected cells. The NMD inhibitor caffeine prevented suppression of X_pre expression and thereby induced production of full-length α-actinin-3 protein in the presence of aminoglycoside. Together these results indicate that the ACTN3 R577X polymorphism could be a novel target for readthrough therapy, which may affect athletic and muscle performance in humans.

Predictors for the Treatment Effect of Sodium Glucose Co-transporter 2 Inhibitors in Patients with Type 2 Diabetes Mellitus

INTRODUCTION

Predictors for the effect of sodium glucose co-transporter 2 (SGLT2) inhibitors at lowering hemoglobin A1c (HbA1c) levels in type 2 diabetes mellitus patients remain unclear. We therefore aimed to elucidate these predictors in type 2 diabetes patients after 3 months of SGLT2 treatment.

METHODS

A total of 302 consecutive type 2 diabetes patients who had been treated with SGLT2 inhibitors as monotherapy or add-on therapy to existing antidiabetic treatments were enrolled retrospectively. After excluding 27 patients whose HbA1c levels could not be evaluated 3 months after treatment, the glucose-lowering effects of SGLT2 inhibitors were assessed in 275 patients by measuring HbA1c levels before and 3 months after treatment. The predictors for changes in HbA1c levels after 3 months of treatment were evaluated.

RESULTS

SGLT2 inhibitor treatment for 3 months decreased HbA1c levels from 7.8 ± 1.2% to 7.4 ± 1.0% (p < 0.0001). A multiple regression analysis showed that the independent determinants for SGLT2 inhibitor treatment effect included decreased HbA1c levels after 1 month of treatment, high baseline HbA1c levels, and a high estimated glomerular filtration rate (eGFR).

CONCLUSION

We show that type 2 diabetes patients who received the greatest glucose-lowering effect with SGLT2 inhibitor treatment were those with preserved renal function (high baseline eGFR) and high baseline HbA1c levels. Moreover, SGLT2 inhibitor treatment efficacy could be predicted by the patients' initial response to treatment.

A novel lipoprotein (a) lowering drug, D-47, decreases neointima thickening after vascular injury

Although Lp(a) have been thought to be a cardiovascular risk factor, it is unclear whether lowering Lp(a) levels reduces the risk of cardiovascular diseases. No pharmacological agents which selectively reduce serum Lp(a) levels, and Lp(a) is present in primate but absent in common laboratory animals such as mice and pigs. In the present study we used transgenic mice of human Lp(a) and tested effect a novel Lp(a) lowering drug D-47 on neointima formation after vascular injury. D-47 successfully decreased plasma levels of Lp(a) and possibly inhibited neointima formation in Lp(a) transgenic mice. The results indicate that we can modulate plasma Lp(a) levels by pharmacologic agents and inhibit atherogenic properties of Lp(a) by reducing plasma levels of Lp(a). J. Med. Invest. 64: 64-67, February, 2017.

Intracerebroventricular injection of ghrelin decreases wheel running activity in rats

There is an increasing interest in elucidating the molecular mechanisms by which voluntary exercise is regulated. In this study, we examined how the central nervous system regulates exercise. We used SPORTS rats, which were established in our laboratory as a highly voluntary murine exercise model. SPORTS rats showed lower levels of serum ghrelin compared with those of the parental line of Wistar rats. Intracerebroventricular and intraperitoneal injection of ghrelin decreased wheel-running activity in SPORTS rats. In addition, daily injection of the ghrelin inhibitor JMV3002 into the lateral ventricles of Wistar rats increased wheel-running activity. Co-administration of obestatin inhibited ghrelin-induced increases in food intake but did not inhibit ghrelin-induced suppression of voluntary exercise in rats. Growth hormone secretagogue receptor (GHSR) in the hypothalamus and hippocampus of SPORTS rats was not difference that in control rats. We created an arcuate nucleus destruction model by administering monosodium glutamate (MSG) to neonatal SPORTS rats. Injection of ghrelin into MSG-treated rats decreased voluntary exercise but did not increase food intake, suggesting that wheel-running activity is not controlled by the arcuate nucleus neurons that regulate feeding. These results provide new insights into the mechanism by which ghrelin regulates voluntary activity independent of arcuate nucleus neurons.

DNA Methylation Suppresses Leptin Gene in 3T3-L1 Adipocytes

Leptin is a key regulator of energy intake and expenditure. This peptide hormone is expressed in mouse white adipose tissue, but hardly expressed in 3T3-L1 adipocytes. Using bisulfite sequencing, we found that CpG islands in the leptin promoter are highly methylated in 3T3-L1cells. 5-azacytidine, an inhibitor of DNA methyltransferase, markedly increased leptin expression as pre-adipocytes matured into adipocytes. Remarkably, leptin expression was stimulated by insulin in adipocytes derived from precursor cells exposed to 5-azacytidine, but suppressed by thiazolidinedione and dexamethasone. In contrast, adipocytes derived from untreated precursor cells were unresponsive to both 5-azacytidine and hormonal stimuli, although lipid accumulation was sufficient to boost leptin expression in the absence of demethylation. Taken together, the results suggest that leptin expression in 3T3-L1 cells requires DNA demethylation prior to adipogenesis, transcriptional activation during adipogenesis, and lipid accumulation after adipogenesis.

Spatial and Temporal Brain Responses to Noxious Heat Thermal Stimuli in Burning Mouth Syndrome

Burning mouth syndrome (BMS) is an idiopathic orofacial pain condition. Although the pathophysiology of BMS is not clearly understood, central and peripheral neuropathic mechanisms are thought to be involved. The authors compared brain response to noxious heat stimuli in 16 right-handed women with primary BMS and 15 sex- and age-matched right-handed healthy female controls. A thermal stimulus sequence of 32 °C to 40 °C to 32 °C to 49 °C was repeated 4 times in a cycle. Warm and noxious heat stimuli were delivered with a Peltier thermode placed on the right palm or right lower lip for 32 s each in a session. Functional magnetic resonance imaging data were obtained by recording echoplanar images with a block design. Statistical Parametric Mapping 8 software was used to analyze the data. Patients and controls both reported feeling more pain during palm stimulation than during lip stimulation. Repetition of noxious heat stimulus on the lower lip but not on the palm induced habituation in brain activity in the cingulate cortex without reduction in pain perception. Multiple regression analysis revealed a correlation between perceived pain intensity and suppression of brain activity in the anterior cingulate cortex when the repeated thermal sequence was applied at the lower lip. Furthermore, the response of the parahippocampal area differed in BMS patients and controls when the same repeated thermal sequence was applied at the palm. The authors’ findings indicate that BMS patients show specific brain responses due to impaired function of the central and peripheral nervous systems (clinical trial registration: UMIN000015002).

Swallowing rehabilitation with nutrition therapy improves clinical outcome in patients with dysphagia at an acute care hospital

Dysphagia is associated with nutritional deficits and increased risk of aspiration pneumonia. The aim of the present study was to evaluate the impact of nutrition therapy for the patients with dysphagia at an acute care hospital. We also tried to clarify the factors which improve swallowing function in these patients. Seventy patients with dysphagia were included in the present study. Multidisciplinary nutrition support team evaluated swallowing function and nutrition status. Most patients were fed by parenteral or enteral nutrition at the time of the first round. Of these 70 patients, 36 became able to eat orally. The improvement of swallowing function was associated with higher BMI in both genders and higher AMC in men. Mortality was high in the patients with lower BMI and %AMC, suggesting importance of maintaining muscle mass. Thirteen (38.2%) of 34 patients who did not show any improvement in swallowing function died, but no patients who showed improvement died (p<0.001). In addition, the patients with nutrition intake about<22 kcal/kg/day during follow-up period, showed significantly poorer recovery from dysphagia and poor outcome, compared to those with about>22 kcal/kg/day. These results suggest that it is important to maintain nutritional status to promote rehabilitation in patients with dysphagia even in an acute care hospital.

Serum albumin levels correlate with inflammation rather than nutrition supply in burns patients: a retrospective study

The aim of this retrospective study was to examine whether serum albumin levels offer a good marker of nutritional status in patients with burns. Serum albumin levels have been used to evaluate nutritional status in burns patients, even though these levels are affected by various factors and are not specific to malnutrition. To clarify whether provision of nutrition or presence of inflammation affects serum albumin levels, we studied serum albumin levels, C-reactive protein (CRP) levels and caloric intake over time in 30 patients with burns. Serum albumin levels did not respond to provision of nutrition, but correlated negatively with CRP levels, suggesting that serum albumin levels are more closely associated with inflammation than nutrition. This study also suggests that hypoalbuminemia is a good indicator of the severity of burns or associated complications. We conclude that serum albumin levels do not offer a good nutritional marker in burns patients.

C-terminal region of GADD34 regulates eIF2α dephosphorylation and cell proliferation in CHO-K1 cells

GADD34 is a member of a growth arrest and DNA damage (GADD)-inducible gene family. Here, we established a novel Chinese hamster ovary (CHO)-K1-derived cell line, CHO-K1-G34M, which carries a nonsense mutation (termed the Q525X mutation) in the GADD34 gene. The Q525X mutant protein lacks the C-terminal 66 amino acids required for GADD34 to bind to and activate protein phosphatase 1 (PP1). We investigated the effects of GADD34 with or without the Q525X mutation on the phosphorylation status of PP1 target proteins, including the α subunit of eukaryotic initiation factor 2 (eIF2α) and glycogen synthase kinase 3β (GSK3β). CHO-K1-G34M cells had higher levels of eIF2α phosphorylation compared to the control CHO-K1-normal cells both in the presence and absence of endoplasmic reticulum stress. Overexpression of the wild-type GADD34 protein in CHO-K1-normal cells largely reduced eIF2α phosphorylation, while overexpression of the Q525X mutant did not produce similar reductions. Meanwhile, neither wild type nor Q525X mutation of GADD34 affected the GSK3β phosphorylation status. GADD34 also did not affect the canonical Wnt signaling pathway downstream of GSK3β. Cell proliferation rates were higher, while expression levels of the cyclin-dependent kinase inhibitor p21 were lower in CHO-K1-G34M cells compared to the CHO-K1-normal cells. The GADD34 Q525X mutant had a reduced ability to inhibit cell proliferation and enhance p21 expression of the CHO-K1-normal cells compared to the wild-type GADD34 protein. These results suggest that the GADD34 protein C-terminal plays important roles in regulating not only eIF2α dephosphorylation but also cell proliferation in CHO-K1 cells.

Long-term dietary supplementation with saury oil attenuates metabolic abnormalities in mice fed a high-fat diet: combined beneficial effect of omega-3 fatty acids and long-chain monounsaturated fatty acids

Background

Pacific saury is a common dietary component in East Asia. Saury oil contains considerable levels of n-3 unsaturated fatty acids (PUFA) and long-chain monounsaturated fatty acids (LCMUFA) with aliphatic tails longer than 18 carbons. In our previous study, consumption of saury oil for 4 to 6 wk improved insulin sensitivity and the plasma lipid profile in mice. However, the long-term effects of saury oil on metabolic syndrome (MetS) risk factors remain to be demonstrated. In the current study, we examined the long-term effects of saury oil on mice fed a high-fat diet, and compared the effect of n-3 PUFA EPA and LCMUFA on MetS risk factor in diet-induced obese mice.

Methods and Results

In Experiment 1, male C57BL/6 J mice were fed either a 32 % lard diet (control) or a diet containing 22 % lard plus 10 % saury oil (saury oil group) for 18 weeks. Although no differences were found in body weight and energy expenditure between the control and saury oil groups, the saury oil diet decreased plasma insulin, non–HDL cholesterol, hepatic steatosis, and adipocyte size, and altered levels of mRNA transcribed from genes involved in insulin signaling and inflammation in adipose tissue. Organ and plasma fatty acid profile analysis revealed that consumption of saury oil increased n-3 PUFA and LCMUFA (especially n-11 LCMUFA) levels in multiple organs, and decreased the fatty acid desaturation index (C16:1/C16:0; C18:1/C18:0) in liver and adipose tissue. In Experiment 2, male C57BL/6 J mice were fed a 32 % lard diet (control), a diet containing 28 % lard plus 4 % EPA (EPA group), or a diet containing 20 % lard plus 12 % LCMUFA concentrate (LCMUFA group) for 8 weeks. EPA or LCMUFA intake increased organ levels of EPA and LCMUFA, respectively. Consumption of EPA reduced plasma lipid levels and hepatic lipid deposition, and decreased the fatty acid desaturation index in liver and adipose tissue. Consumption of LCMUFA decreased plasma non–HDL cholesterol, improved hyperinsulinemia, and decreased the fatty acid desaturation index in adipose tissue. EPA accumulated mainly in liver, and LCMUFA (especially n-11 LCMUFA) accumulated mainly in white adipose tissue, suggesting their possible individual biological effects for improving MetS.

Conclusion

Our results suggest that saury oil-mediated improvement of metabolic syndrome in diet-induced obese mice may possibly be due to a combined effect of n-3 PUFA and LCMUFA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-015-0161-8) contains supplementary material, which is available to authorized users.

Correlations among obesity-associated gene polymorphisms, body composition, and physical activity in patients with type 2 diabetes mellitus

CONTEXT

Various studies have focused on the correlation between β2-adrenergic receptor (β2AR), the β3-adrenergic receptor (β3AR), and the uncoupling protein 1 (UCP1) polymorphisms and obesity in patients with type 2 diabetes mellitus (T2DM).

AIMS

We examined the correlation between these polymorphisms and body composition variables and between body composition and lifestyle variables in Japanese T2DM patients.

MATERIALS AND METHODS

Of the 48, T2DM outpatients in Kanagawa prefecture recruited for participation, 32 (6 men and 26 women) met the study criteria and were enrolled. Obesity-related gene polymorphisms were identified in 3 genes β3AR, UCP1, and β2AR using the SMart amplification process. Body composition variables were measured using a body composition analyzer. Data regarding food and nutrient consumption, family history, and lifestyle factors were collected via administration of questionnaires.

RESULTS

Because significant differences in body composition variables were found between men and women, statistical analysis was performed with data from the 25 female subjects only. On the basis of results of genetic testing, the subjects were divided into genotype groups for two-group and three-group comparison. The β3AR, UCP1, and β2AR polymorphisms and body composition significantly correlated with the percentage of subcutaneous fat in both arms as compared with the wild type or hetero groups with β3AR polymorphisms. However, physical activity correlated with several body composition variables.

CONCLUSIONS

These results suggest that obesity in T2DM patients is not the result of presence of an obesity-related gene polymorphism but rather the absence of daily physical activity.

Propofol-induced relaxation of rat aorta is altered by aging

BACKGROUND

Propofol causes vasodilation via endothelium-dependent and -independent mechanisms. Because endothelial function is impaired with aging, the effects of propofol on endothelium-dependent vasodilation might be altered by aging. The aim of this study was thus to determine the effects of aging on vascular responses to propofol.

METHODS

Young (4-6 weeks old) or adult (16-25 weeks old) rats were anesthetized with sevoflurane. The thoracic aorta was dissected and cut into pieces 3-4 mm in length. In some rings, the endothelium was deliberately removed. The ring segment of the aorta was mounted for isometric force recording at a resting tension of 0.5-1.0 g in a 2 ml organ bath, containing Krebs-Ringer bicarbonate buffer. Arteries were precontracted with phenylephrine, and the function of endothelium was confirmed with acetylcholine. Then, we studied the concentration-dependent effects of propofol in endothelium-intact (control group) and -denuded aortic rings (denuded group), as well as those treated with N(ω)-nitro-L-arginine methylester (L-NAME group).

RESULTS

Relaxation due to propofol was observed in the control groups of both young and adult rats in a concentration-dependent manner, but the magnitude of relaxation was significantly greater in young rats. In addition, in young rats, relaxation due to propofol was significantly and equally reduced in both L-NAME and denuded groups at all propofol concentrations that we studied (10(-6)-10(-3) M). In adult rats, relaxation due to propofol was quite similar between control and L-NAME groups at all propofol concentrations, whereas it was significantly reduced in the denuded group.

CONCLUSION

These results suggest that endothelium-derived nitric oxide plays an important role in propofol-induced vasodilation in young rats, but not in adult rats.

Enhancement of endothelial function inhibits left atrial thrombi development in an animal model of spontaneous left atrial thrombosis

BACKGROUND

Left atrial (LA) thrombosis is an important cause of systemic embolization. The SPORTS rat model of LA thrombi (Spontaneously-Running Tokushima-Shikoku), which have a unique characteristic of high voluntary wheel running, was previously established. The aim of the present study was to investigate how SPORTS rats develop LA thrombi.

METHODS AND RESULTS

Nitric oxide (NO) produced from cardiovascular endothelial cells plays an important protective role in the local regulation of blood flow, vascular tone, and platelet aggregation. No evidence of atrial fibrillation or hypercoagulability in SPORTS rats regardless of age was found; however, SPORTS rats demonstrated endothelial dysfunction and a decrease of NO production from a young age. In addition, endothelial NO synthase activity was significantly decreased in the LA and thoracic aorta endothelia of SPORTS rats. While voluntary wheel running was able to intermittently increase NO levels, running did not statistically decrease the incidence of LA thrombi at autopsy. However, L-arginine treatment significantly increased NO production and provided protection from the development of LA thrombi in SPORTS rats.

CONCLUSIONS

They present study results indicate that NO has an important role in the development of LA thrombus, and endothelia pathways could provide new targets of therapy to prevent LA thrombosis.

Establishment of a model of spontaneously-running-Tokushima-shikoku rats with left atrial thrombosis

Studies that investigate the underlying mechanisms of disease and treatment options typically require the use of a suitable animal model. Few suitable animal models exist for left atrial thrombosis. Here, we demonstrated that the Spontaneously-Running-Tokushima-Shikoku (SPORTS) rat — a Wistar strain known for its running ability—is predisposed to the development of thrombi in the left atrium. We investigated the incidence of left atrial thrombosis in male (n = 16) and female (n = 17) SPORTS rats and observed organized atrial thrombosis in 57% and 38% of males and female rats, respectively. In the male rats, systolic blood pressures and heart rates were significantly higher in SPORTS rats than in control Wistar rats. We could not find any evidence of arrhythmias, such as atrial fibrillation, during electrocardiographic examination of SPORTS rats. We believe that the SPORTS rat could serve as a new research model for left atrial thrombosis; further, it may be suitable for research investigating the development of new antithrombotic approaches for the control of atrial thrombosis or familial thrombophilia in humans.

Islet infiltration, cytokine expression and beta cell death in the NOD mouse, BB rat, Komeda rat, LEW.1AR1-iddm rat and humans with type 1 diabetes

AIMS/HYPOTHESIS

Research on the pathogenesis of type 1 diabetes relies heavily on good animal models. The aim of this work was to study the translational value of animal models of type 1 diabetes to the human situation.

METHODS

We compared the four major animal models of spontaneous type 1 diabetes, namely the NOD mouse, BioBreeding (BB) rat, Komeda rat and LEW.1AR1-iddm rat, by examining the immunohistochemistry and in situ RT-PCR of immune cell infiltrate and cytokine pattern in pancreatic islets, and by comparing findings with human data.

RESULTS

After type 1 diabetes manifestation CD8(+) T cells, CD68(+) macrophages and CD4(+) T cells were observed as the main immune cell types with declining frequency, in infiltrated islets of all diabetic pancreases. IL-1β and TNF-α were the main proinflammatory cytokines in the immune cell infiltrate in NOD mice, BB rats and LEW.1AR1-iddm rats, as well as in humans. The Komeda rat was the exception, with IFN-γ and TNF-α being the main cytokines. In addition, IL-17 and IL-6 and the anti-inflammatory cytokines IL-4, IL-10 and IL-13 were found in some infiltrating immune cells. Apoptotic as well as proliferating beta cells were observed in infiltrated islets. In healthy pancreases no proinflammatory cytokine expression was observed.

CONCLUSIONS/INTERPRETATION

With the exception of the Komeda rat, the animal models mirror very well the situation in humans with type 1 diabetes. Thus animal models of type 1 diabetes can provide meaningful information on the disease processes in the pancreas of patients with type 1 diabetes.

Effect of NS-018, a selective JAK2V617F inhibitor, in a murine model of myelofibrosis

A single somatic mutation, V617F, in Janus kinase 2 (JAK2) is one of the causes of myeloproliferative neoplasms (MPNs), including primary myelofibrosis, and the JAK2V617F mutant kinase is a therapeutic target in MPN. However, inhibition of wild-type (WT) JAK2 can decrease the erythrocyte or platelet (PLT) count. Our selective JAK2 inhibitor, NS-018, suppressed the growth of Ba/F3 cells harboring JAK2V617F more strongly than that of cells harboring WT JAK2. The 4.3-fold JAK2V617F selectivity of NS-018 is higher than the 1.0- to 2.9-fold selectivity of seven existing JAK2 inhibitors. NS-018 also inhibited erythroid colony formation in JAK2V617F transgenic mice at significantly lower concentrations than in WT mice. In keeping with the above results, in a JAK2V617F bone marrow transplantation mouse model with a myelofibrosis-like disease, NS-018 reduced leukocytosis and splenomegaly, improved bone marrow fibrosis and prolonged survival without decreasing the erythrocyte or PLT count in the peripheral blood. By exploring the X-ray co-crystal structure of NS-018 bound to JAK2, we identified unique hydrogen-bonding interactions between NS-018 and Gly993 as a plausible explanation for its JAK2V617F selectivity. These results suggest that NS-018 will have therapeutic benefit for MPN patients through both its efficacy and its reduced hematologic adverse effects.

Interaction of IL-1β and P2X(3) receptor in pathologic masseter muscle pain

The exact mechanism underlying chronic masseter muscle pain, a conspicuous symptom in temporomandibular disorder, remains unclear. We investigated whether expression of P2X3 receptor (P2X3R) is involved in mechanical hyperalgesia after contraction of masseter muscle (CMM). As compared with sham rats, the head-withdrawal threshold (HWT) to mechanical pressure stimulation of masseter muscle (MM) (but not after similar stimulation of facial skin) was significantly lower, and IL-1β level was significantly higher, in CMM rats on day 7 after CMM. The mean percentage of FG-labeled P2X3R-positive neurons was significantly increased in TG following successive IL-1β injections into the MM for 7 days. Successive administration of an IL-1β receptor-antagonist into the MM attenuated the increase of P2X3-IR cells in the TG. ATP release from MM after 300-g pressure stimulation of MM was also significantly enhanced after CMM. Administration into MM of the selective P2X3,2/3 receptor antagonist A-317491 attenuated the decrement of HWT in CMM rats. A significant increase in HWT was also observed at 30 min after A-317491 (60 µg) injection in IL-1β-injected rats. These findings suggest that P2X3R expression associated with enhanced IL-1β expression and ATP release in MM has a possible important role in MM mechanical hyperalgesia after excessive muscular contraction.

Activation of Akt through 5-HT2A receptor ameliorates serotonin-induced degradation of insulin receptor substrate-1 in adipocytes

Serotonin (5-hydroxytryptamine, 5-HT) was found to be elevated in the serum of diabetic patients. In this study, we investigate the mechanism of insulin desensitization caused by 5-HT. In 3T3-L1 adipocytes, 5-HT treatment induced the translocation of insulin receptor substrate-1 (IRS-1) from low density microsome (LDM), the important intracellular compartment for its functions, to cytosol, inducing IRS-1 ubiquitination and degradation. Moreover, inhibition of 5-HT-stimulated Akt activation by either ketanserin (a specific 5-HT2A receptor antagonist) or knocking-down the expression of 5-HT2A receptor promoted 5-HT-stimulated IRS-1 dissociation from 14-3-3β in LDM, leading to drastic ubiquitination. Interestingly, sarpogrelate, another antagonist of 5-HT2A receptor, protected IRS-1 from degradation through activation of Akt. This implicates the importance of Akt activation in extending IRS-1 life span through maintaining their optimal sub-location into adipocytes. Taken together, this study suggest that activation of Akt may be able to compensate the adverse effects of 5-HT by stabilizing IRS-1 in LDM.

Taurine Alters Respiratory Gas Exchange and Nutrient Metabolism in Type 2 Diabetic Rats

OBJECTIVE

To assess the effect of taurine supplementation on respiratory gas exchange, which might reflect the improved metabolism of glucose and/or lipid in the type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats.

RESEARCH METHODS AND PROCEDURES

Male OLETF rats (16 weeks of age) were randomly divided into two groups: unsupplemented group and taurine-supplemented (3% in drinking water) group. After 9 weeks of treatment, indirect calorimetry and insulin tolerance tests were conducted. The amounts of visceral fat pads, tissue glycogen, the blood concentrations of glucose, triacylglycerol, taurine, and electrolytes, and the level of hematocrit were compared between groups. A nondiabetic rat strain (Long-Evans Tokushima Otsuka) was used as the age-matched normal control.

RESULTS

The indirect calorimetry showed that the treatment of OLETF rats with taurine could reduce a part of postprandial glucose oxidation possibly responsible for the increase of triacylglycerol synthesis in the body. Taurine supplementation also improved hyperglycemia and insulin resistance and increased muscle glycogen content in the OLETF rats. Supplementation with taurine increased the blood concentration of taurine and electrolyte and fluid volume, all of which were considered to be related to the improvement of metabolic disturbance in OLETF rats.

DISCUSSION

Taurine supplementation may be an effective treatment for glucose intolerance and fat/lipid accumulation observed in type 2 diabetes associated with obesity. These metabolic changes might be ascribed, in part, to the alteration of circulating blood profiles, where the improved hyperglycemia and/or the blood accumulation of taurine itself would play roles.

Activation of AMPK-Sirt1 pathway by telmisartan in white adipose tissue: A possible link to anti-metabolic effects

Telmisartan exerts anti-metabolic effects beyond its angiotensin receptor blockade activities, but the mechanisms have hitherto remained elusive. We sought to elucidate the peroxisome proliferator-activated receptor-γ (PPAR-γ)-dependent and PPAR-γ-independent mechanisms underlying the anti-metabolic effects of telmisartan in white adipose tissue. Nine-week-old male C57BL/6 mice were fed with a 60% high-fat diet for 6 weeks, with 1mg/kg telmisartan or vehicle administrated orally during the last 3 weeks. 3T3-L1 adipocytes were cultured with telmisartan either with 2-chloro-5-nitro-N-phenylbenzamide (GW9662), a selective irreversible antagonist of PPAR-γ, or compound C, an ATP-competitive inhibitor of AMPK. Western blotting and semiquantitative RT-PCR analysis were used to assess adiponectin, Sirt1, and AMPK levels. Lipid accumulation was assessed by Oil red O staining. The activation of transcription factor PPAR-γ2 was evaluated by using a luciferase reporter assay for mPPAR-γ2 expression plasmid vector. Treatment with telmisartan increased serum adiponectin levels in high-fat diet-fed mice concomitantly with an upregulation of adiponectin mRNA in visceral adipose tissue. In vitro telmisartan treatment dose-dependently increased adiponectin mRNA in 3T3-L1 cells; the increase was inhibited by compound C, but not by GW9662. Telmisartan increased expression of Sirt1 mRNA and Sirt1 protein as well as the phosphorylation of AMPK in 3T3-L1 cells. Telmisartan can increase adiponectin production in white adipose tissue partly via a PPAR-γ2-independent mechanism. Precise understanding of this molecular mechanism will require further investigation.

Identification and functional characterization of human glycerol-3-phosphate acyltransferase 1 gene promoters

Glycerol-3-phosphate acyltransferase 1 (GPAT1) acts as a rate limiting enzyme in triacylglycerol and phospholipid synthesis in mammals. GPAT1 regulates hepatic lipid accumulation associated with metabolic disorders. Here we have identified two transcriptional initiation sites and two promoters (promoter I and II) required for expression of the human GPAT1 (hGPAT1) gene. Promoter I regulates transcription of three alternative hGPAT1 mRNA variants, hGPAT1-V1, V2, and V3, while promoter II induces expression of a fourth variant, hGPAT1-V4. RT-PCR analysis and luciferase reporter assays revealed that promoter II acts in lipogenic tissues like the liver (and liver-derived HepG2 cells), whereas promoter I is differentially regulated and also acts in non-liver HeLa cells. Among liver-enriched transcription factors, HNF4α and C/EBPα slightly activated hGPAT1 promoter I, while factors including HNF1α altered promoter II activity. The lipogenic transcription factor SREBP1c greatly increased promoter II activity in HepG2 cells. The use of various truncated or mutated fragments of promoter II revealed that one sterol regulatory element-like motif and one inverted CCAAT box on promoter II contributed to the SREBP1c response. These cis-acting elements and trans-acting factors can be potential targets for manipulation of hepatic GPAT1 levels in humans.

Cortactin, an actin binding protein, regulates GLUT4 translocation via actin filament remodeling

Insulin regulates glucose uptake into fat and skeletal muscle cells by modulating the translocation of GLUT4 between the cell surface and interior. We investigated a role for cortactin, a cortical actin binding protein, in the actin filament organization and translocation of GLUT4 in Chinese hamster ovary (CHO-GLUT4myc) and L6-GLUT4myc myotube cells. Overexpression of wild-type cortactin enhanced insulin-stimulated GLUT4myc translocation but did not alter actin fiber formation. Conversely, cortactin mutants lacking the Src homology 3 (SH3) domain inhibited insulin-stimulated formation of actin stress fibers and GLUT4 translocation similar to the actin depolymerizing agent cytochalasin D. Wortmannin, genistein, and a PP1 analog completely blocked insulin-induced Akt phosphorylation, formation of actin stress fibers, and GLUT4 translocation indicating the involvement of both PI3-K/Akt and the Src family of kinases. The effect of these inhibitors was even more pronounced in the presence of overexpressed cortactin suggesting that the same pathways are involved. Knockdown of cortactin by siRNA did not inhibit insulin-induced Akt phosphorylation but completely inhibited actin stress fiber formation and glucose uptake. These results suggest that the actin binding protein cortactin is required for actin stress fiber formation in muscle cells and that this process is absolutely required for translocation of GLUT4-containing vesicles to the plasma membrane.

The characteristics of food intake in patients with type II citrullinemia

Some patients with citrin deficiency caused by SLC25A13 gene mutations develop adult-onset type II citrullinemia (CTLN2) with hepatic encephalopathy. A recent nutritional survey of 18 citrin-deficient subjects (age 1-33 y) confirmed a marked decrease in carbohydrate intake compared to an age-matched general Japanese population. However, a quantitative understanding of food intake in CTLN2 patients remains unclear, although qualitative dietary information has been reported. In order to elucidate the characteristics of daily nutrition of CTLN2 patients, the food intake of 5 male patients (age 39-52 y) was investigated in detail by the Food Frequency Questionnaire. In the present survey, the mean energy ratio of protein : fat : carbohydrate (PFC ratio) of the 5 patients was 19±3% : 44±5% : 37±4%, which was almost identical to previously reported data in younger citrin-deficient subjects (19±2% : 44±5% : 37±7%). Cereal intake was especially low in all CTLN2 patients at 309±33 g/d (56% of control), compared to that in an age-matched general Japanese population (553±197 g/d). Additionally, CTLN2 patients preferred high fat and protein foods. Commonly, fat intake declines with age in the general Japanese population, but this tendency was not observed in the 5 CTLN2 patients. The present results suggest that intakes of low-carbohydrate, high-protein and high-fat food was characteristic the 5 CTLN2 patients surveyed, as has been previously reported in younger citrin-deficient subjects, and that the PFC ratio may not be influenced by age or CTLN2-onset.

Dietary phosphate restriction ameliorates endothelial dysfunction in adenine-induced kidney disease rats

Hyperphosphatemia causes endothelial dysfunction as well as vascular calcification. Management of serum phosphate level by dietary phosphate restriction or phosphate binders is considered to be beneficial to prevent chronic kidney disease patients from cardiovascular disease, but it has been unclear whether keeping lower serum phosphate level can ameliorate endothelial dysfunction. In this study we investigated whether low-phosphate diet can ameliorate endothelial dysfunction in adenine-induced kidney disease rats, one of useful animal model of chronic kidney disease. Administration of 0.75% adenine-containing diet for 21 days induced renal failure with hyperphosphatemia, and impaired acetylcholine-dependent vasodilation of thoracic aortic ring in rats. Then adenine-induced kidney disease rats were treated with either control diet (1% phosphate) or low-phosphate diet (0.2% phosphate) for 16 days. Low-phosphate diet ameliorated not only hyperphosphatemia but also the impaired vasodilation of aorta. In addition, the activatory phosphorylation of endothelial nitric oxide synthase at serine 1177 and Akt at serine 473 in the aorta were inhibited by in adenine-induced kidney disease rats. The inhibited phosphorylations were improved by the low-phosphate diet treatment. Thus, dietary phosphate restriction can improve aortic endothelial dysfunction in chronic kidney disease with hyperphosphatemia by increase in the activatory phosphorylations of endothelial nitric oxide synthase and Akt.

Decline in anthropometric evaluation predicts a poor prognosis in geriatric patients

OBJECTIVE

Malnutrition is frequent in the geriatric population and is often undetected and untreated. Although we often use serum albumin as a nutritional marker, it has limitations in elderly patients in terms of predicting diseases and infections. Anthropometric measurements are not commonly used, despite their simple, easy, and effective characteristics. We evaluated the associations between anthropometric measurements with other nutritional factors and examined its relationship with mortality, decubitus ulcer, length of hospital stay and antibiotic usage.

RESEARCH METHODS AND PROCEDURES

We enrolled 223 patients, performed anthropometric measurements and then followed them for a mean of 24 months.

RESULTS

Patients with hypoalbuminemia but with normal body measurements tended to increase serum albumin levels over the next 24 months and had more favorable outcomes including being discharged. Patients with normal albumin but decreased body measurements resulted in a progressive drop in serum albumin and had a higher mortality rate. Additionally, patients with hypoalbuminemia had higher antibiotic usage than patients without hypoalbuminemia. Decreases in anthropometric measurements were related to mortality, length of hospital stay, and decubitus ulcer.

CONCLUSIONS

Anthropometric measurements are easily obtained and closely associated with mortality, decubitus ulcer, and length of hospital stay. Anthropometric measurements used in conjunction with serum albumin are more predictive of patient outcome then serum albumin alone.

Heparin-binding EGF-like growth factor (HB-EGF) mediates 5-HT-induced insulin resistance through activation of EGF receptor-ERK1/2-mTOR pathway

Although an inverse correlation between insulin sensitivity and the level of Gq/11-coupled receptor agonists, such as endothelin-1, thrombin, and 5-hydroxytryptamine (5-HT), has been reported, its precise mechanism remains unclear. In this report, we provide evidence that 5-HT induced production of heparin-binding epidermal growth factor-like growth factor (HB-EGF) and caused insulin resistance in 3T3-L1 adipocytes, primary adipocytes, and C2C12 myotubes. In 3T3-L1 adipocytes, 5-HT stimulated HB-EGF production by promoting metalloproteinase-dependent shedding of transmembrane protein pro-HB-EGF. HB-EGF then bound and tyrosine-phosphorylated EGF receptors, which activated the mammalian target of rapamycin pathway through ERK1/2 phosphorylation. Mammalian target of rapamycin activation caused serine phosphorylation of insulin receptor substrate-1, which attenuated insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 and glucose uptake. Pharmacological inhibition of either Gq/11-coupled receptors or metalloproteinases, as well as either inhibition or knockdown of HB-EGF or Gαq/11, restored insulin signal transduction impaired by 5-HT. Inhibition of metalloproteinase activity also abolished HB-EGF production and subsequent EGF receptor activation by other Gq/11-coupled receptor agonists known to cause insulin resistance, such as endothelin-1 and thrombin. These results suggest that transactivation of the EGF receptor through HB-EGF processing plays a pivotal role in 5-HT-induced insulin resistance.

Coronary atherosclerosis is associated with macrophage polarization in epicardial adipose tissue

OBJECTIVES

The purpose of this report was to assess the link between macrophage polarization in epicardial adipose tissue and atherosclerosis in patients with coronary artery disease (CAD).

BACKGROUND

Macrophage accumulation enhances chronic inflammation in adipose tissue, but macrophage phenotypic change in human epicardial adipose tissue and its role in atherogenesis are unknown.

METHODS

Samples were obtained from epicardial and subcutaneous adipose tissue during elective cardiac surgery (CAD, n = 38; non-CAD, n = 40). Infiltration of M1/M2 macrophages was investigated by immunohistochemical staining with antibodies against CD11c and CD206, respectively. Expression of pro- and anti-inflammatory adipocytokines in adipose tissue was evaluated by real-time quantitative polymerase chain reaction.

RESULTS

Infiltration of macrophages and expression of pro- and anti-inflammatory cytokines were enhanced in epicardial fat of patients with CAD compared with that in non-CAD patients (p < 0.05). The ratio of M1/M2 macrophages was positively correlated with the severity of CAD (r = 0.312, p = 0.039). Furthermore, the expression of pro-inflammatory cytokines was positively correlated, and the expression of anti-inflammatory cytokines was negatively correlated with the ratio of M1/M2 macrophages in epicardial adipose tissue of CAD patients. By contrast, there was no significant difference in macrophage infiltration and cytokine expression in subcutaneous adipose tissue between the CAD and non-CAD groups.

CONCLUSIONS

The ratio of M1/M2 macrophages in epicardial adipose tissue of CAD patients is changed compared with that in non-CAD patients. Human coronary atherosclerosis is associated with macrophage polarization in epicardial adipose tissue.