MGSE Regulates Crosstalk from the Mucin Pathway to the TFE3 Pathway of the Golgi Stress Response.

The Golgi apparatus is an organelle where membrane or secretory proteins receive post-translational modifications such as glycosylation and sulfation, after which the proteins are selectively transported to their final destinations through vesicular transport. When the synthesis of secretory or membrane proteins is increased and overwhelms the capacity of the Golgi (Golgi stress), eukaryotic cells activate a homeostatic mechanism called the Golgi stress response to augment the capacity of the Golgi. Four response pathways of the Golgi stress response have been identified, namely the TFE3, CREB3, HSP47, and proteoglycan pathways, which regulate the general function of the Golgi, apoptosis, cell survival, and proteoglycan glycosylation, respectively. Here, we identified a novel response pathway that augments the expression of glycosylation enzymes for mucins in response to insufficiency in mucin-type glycosylation in the Golgi (mucin-type Golgi stress), and we found that expression of glycosylation enzymes for mucins such as GALNT5, GALNT8, and GALNT18 was increased upon mucin-type-Golgi stress. We named this pathway the mucin pathway. Unexpectedly, mucin-type Golgi stress induced the expression and activation of TFE3, a key transcription factor regulating the TFE3 pathway, suggesting that the activated mucin pathway sends a crosstalk signal to the TFE3 pathway. We identified an enhancer element regulating transcriptional induction of TFE3 upon mucin-type Golgi stress, and named it the mucin-type Golgi stress response element, of which consensus was ACTTCC(N9)TCCCCA. These results suggested that crosstalk from the mucin pathway to the TFE3 pathway has an important role in the regulation of the mammalian Golgi stress response.Key words: Golgi stress, mucin, TFE3, organelle autoregulation, organelle zone.

PGSE Is a Novel Enhancer Regulating the Proteoglycan Pathway of the Mammalian Golgi Stress Response.

The Golgi stress response is a homeostatic mechanism that augments the functional capacity of the Golgi apparatus when Golgi function becomes insufficient (Golgi stress). Three response pathways of the Golgi stress response have been identified in mammalian cells, the TFE3, HSP47 and CREB3 pathways, which augment the capacity of specific Golgi functions such as N-glycosylation, anti-apoptotic activity and pro-apoptotic activity, respectively. On the contrary, glycosylation of proteoglycans (PGs) is another important function of the Golgi, although the response pathway upregulating expression of glycosylation enzymes for PGs in response to Golgi stress remains unknown. Here, we found that expression of glycosylation enzymes for PGs was induced upon insufficiency of PG glycosylation capacity in the Golgi (PG-Golgi stress), and that transcriptional induction of genes encoding glycosylation enzymes for PGs was independent of the known Golgi stress response pathways and ER stress response. Promoter analyses of genes encoding these glycosylation enzymes revealed the novel enhancer elements PGSE-A and PGSE-B (the consensus sequences are CCGGGGCGGGGCG and TTTTACAATTGGTC, respectively), which regulate their transcriptional induction upon PG-Golgi stress. From these observations, the response pathway we discovered is a novel Golgi stress response pathway, which we have named the PG pathway.Key words: Golgi stress, proteoglycan, ER stress, organelle zone, organelle autoregulation.

MLX Is a Transcriptional Repressor of the Mammalian Golgi Stress Response.

The Golgi stress response is a homeostatic mechanism that controls the capacity of the Golgi apparatus in accordance with cellular demands. When the capacity of the Golgi apparatus becomes insufficient (Golgi stress), transcription levels of Golgi-related genes encoding glycosylation enzymes, a Golgi structural protein, and components of vesicular transport are upregulated through a common cis-acting enhancer-the Golgi apparatus stress response element (GASE). Here, we identified the transcription factor MLX as a GASE-binding protein. MLX resides in the cytoplasm and does not bind to GASE in normal growth conditions, whereas MLX translocates into the nucleus and specifically binds to GASE in response to Golgi stress. Suppression of MLX expression increased transcriptional induction of target genes of the Golgi stress response, whereas overexpression of MLX reduced GASE-binding of TFE3 as well as transcriptional induction from GASE, suggesting that MLX is a transcriptional repressor of the mammalian Golgi stress response.

TFE3 is a bHLH-ZIP-type transcription factor that regulates the mammalian Golgi stress response.

The Golgi stress response is a mechanism by which, under conditions of insufficient Golgi function (Golgi stress), the transcription of Golgi-related genes is upregulated through an enhancer, the Golgi apparatus stress response element (GASE), in order to maintain homeostasis in the Golgi. The molecular mechanisms associated with GASE remain to be clarified. Here, we identified TFE3 as a GASE-binding transcription factor. TFE3 was phosphorylated and retained in the cytoplasm in normal growth conditions, whereas it was dephosphorylated, translocated to the nucleus and activated Golgi-related genes through GASE under conditions of Golgi stress, e.g. in response to inhibition of oligosaccharide processing in the Golgi apparatus. From these observations, we concluded that the TFE3-GASE pathway is one of the regulatory pathways of the mammalian Golgi stress response, which regulates the expression of glycosylation-related proteins in response to insufficiency of glycosylation in the Golgi apparatus.

New insights into the functions of histidine-rich glycoprotein.

Histidine-rich glycoprotein (HRG) is one of the major plasma proteins; it has been isolated from the plasma of various mammals and chicken. HRG has a multidomain structure consisting of cystatin-like domains 1 and 2, Pro-rich domain 1, His-rich domain, Pro-rich domain 2, and C-terminal domain from its N-terminus. The ability to bind a wide range of ligands suggests the multivalent function of HRG in blood coagulation, fibrinolysis, and innate immune systems. The local structure supports its binding capacities. Herein, the structural characteristics of HRG and its gene structure are described first. The functions of HRG in coagulation and fibrinolysis systems, the recently reported functions of HRG in angiogenesis, and HRG's antibacterial effect are described next. The activities of HRG in immune response are also reviewed.

UBC9 regulates the stability of XBP1, a key transcription factor controlling the ER stress response.

XBP1 is a key transcription factor regulating the mammalian endoplasmic reticulum (ER) stress response, which is a cytoprotective mechanism for dealing with an accumulation of unfolded proteins in the ER (ER stress). The expression of XBP1 is regulated by two different mechanisms: mRNA splicing and protein stability. When ER stress occurs, unspliced XBP1 mRNA is converted to mature mRNA, from which an active transcription factor, pXBP1(S), is translated and activates the transcription of ER-related genes to dispose of unfolded proteins. In the absence of ER stress, pXBP1(U) is translated from unspliced XBP1 mRNA and enhances the degradation of pXBP1(S). Here, we analyzed the regulatory mechanism of pXBP1(S) stability, and found that a SUMO-conjugase, UBC9, specifically bound to the leucine zipper motif of pXBP1(S) and increased the stability of pXBP1(S). Suppression of UBC9 expression by RNA interference reduced both the expression of pXBP1(S) and ER stress-induced transcription by pXBP1(S). Interestingly, overexpression of a UBC9 mutant deficient in SUMO-conjugating activity was able to increase pXBP1(S) expression as well as wild-type UBC9, indicating that UBC9 stabilizes pXBP1(S) without conjugating SUMO moieties. From these observations, we concluded that UBC9 is a novel regulator of the mammalian ER stress response.

The essential biology of the endoplasmic reticulum stress response for structural and computational biologists.

The endoplasmic reticulum (ER) stress response is a cytoprotective mechanism that maintains homeostasis of the ER by upregulating the capacity of the ER in accordance with cellular demands. If the ER stress response cannot function correctly, because of reasons such as aging, genetic mutation or environmental stress, unfolded proteins accumulate in the ER and cause ER stress-induced apoptosis, resulting in the onset of folding diseases, including Alzheimer's disease and diabetes mellitus. Although the mechanism of the ER stress response has been analyzed extensively by biochemists, cell biologists and molecular biologists, many aspects remain to be elucidated. For example, it is unclear how sensor molecules detect ER stress, or how cells choose the two opposite cell fates (survival or apoptosis) during the ER stress response. To resolve these critical issues, structural and computational approaches will be indispensable, although the mechanism of the ER stress response is complicated and difficult to understand holistically at a glance. Here, we provide a concise introduction to the mammalian ER stress response for structural and computational biologists.

Ultraviolet a induces endoplasmic reticulum stress response in human dermal fibroblasts.

The endoplasmic reticulum (ER) stress response is a cytoprotective mechanism against the accumulation of unfolded proteins in the ER (ER stress) that consists of three response pathways (the ATF6, IRE1 and PERK pathways) in mammals. These pathways regulate the transcription of ER-related genes through specific cis-acting elements, ERSE, UPRE and AARE, respectively. Because the mammalian ER stress response is markedly activated in professional secretory cells, its main function was thought to be to upregulate the capacity of protein folding in the ER in accordance with the increased synthesis of secretory proteins. Here, we found that ultraviolet A (UVA) irradiation induced the conversion of an ER-localized sensor pATF6α(P) to an active transcription factor pATF6α(N) in normal human dermal fibroblasts (NHDFs). UVA also induced IRE1-mediated splicing of XBP1 mRNA as well as PERK-mediated phosphorylation of an α subunit of eukaryotic initiation factor 2. Consistent with these observations, we found that UVA increased transcription from ERSE, UPRE and AARE elements. From these results, we concluded that UVA irradiation activates all branches of the mammalian ER stress response in NHDFs. This suggests that the mammalian ER stress response is activated by not only intrinsic stress but also environmental stress.

Histidine-rich glycoprotein: a possible modulator of coagulation and fibrinolysis.

Histidine-rich glycoprotein (HRG) is one of the major plasma proteins and thought to function in blood coagulation, fibrinolysis, and innate immune systems. The amino acid sequence of HRG revealed a multidomain structure consisting of cystatin-like domains 1 and 2, a Pro-rich domain 1, a His-rich domain, a Pro-rich domain 2, and a C-terminal domain. Broad ligand-binding properties of HRG are involved in the multivalent functions of HRG. Among various functions of HRG, its interactions with heparin/heparan sulfate, fibrinogen, and plasminogen are thought to be intimately related to its roles in the coagulation and fibrinolytic systems. Recent studies on these topics are mainly reviewed in this article. The newly disclosed abilities of HRG in angiogenesis, its antibacterial effect, its activation of T-cell lines in cooperation with Concanavalin A, and the identification of a putative receptor for HRG on T cell lines are also described.

Novel cis-acting element GASE regulates transcriptional induction by the Golgi stress response.

When increased production of secretory proteins overwhelms the capacity of the endoplasmic reticulum (ER) and the Golgi apparatus, eukaryotic cells expand their capacity to sustain secretory function. The capacity of the ER is enhanced by the mechanism called the ER stress response, but the mechanism regulating Golgi capacity (the Golgi stress response) has remained unclear. Here, we found that transcription of Golgi-related genes, including glycosylation enzymes as well as factors involved in post-Golgi vesicular transport and maintenance of Golgi structure, was upregulated upon treatment with monensin, an ionophore that disrupts the function of acidic organelles, including the Golgi apparatus and lysosomes by neutralizing their lumen. This transcriptional induction was found to be commonly regulated by a novel cis-acting element called the Golgi apparatus stress response element (GASE), whose consensus sequence is ACGTGgc. When the function of the Golgi apparatus was specifically disturbed by overexpression of GCP60, a Golgi-localized protein that binds to giantin, transcription from GASE was significantly induced. These results suggest that mammalian cells have the Golgi stress response, and that GASE regulates transcriptional induction involved in the Golgi stress response.

Relation between serum high molecular weight adiponectin and serum ferritin or prohepcidin in patients with type 2 diabetes.

An increase of serum ferritin, an indicator of body iron store, is associated with insulin resistance and with an increased risk of type 2 diabetes in the general population. A low serum adiponectin is also associated with insulin resistance. Recently, hepcidin was identified as a regulator of iron metabolism. We investigated whether serum adiponectin was associated with serum ferritin or prohepcidin, a precursor of hepcidin, in healthy subjects and patients with type 2 diabetes. We studied 65 healthy subjects and 104 patients with type 2 diabetes. A serum ferritin concentration ≥ 300 ng/ml for men or ≥ 150 ng/ml for women was defined as hyperferritinemia. Serum ferritin was significantly higher and serum prohepcidin was significantly lower in diabetic patients than in control subjects. Serum total and high molecular weight (HMW) adiponectin correlated negatively with serum ferritin in control subjects or diabetic patients, while serum total and HMW adiponectin correlated positively with serum prohepcidin in diabetic patients, but not in control subjects. Serum total and HMW adiponectin were lower in patients with hyperferritinemia than in those without it. In conclusion, serum ferritin was increased in type 2 diabetic patients, while serum prohepcidin was decreased. A high serum ferritin was associated with insulin resistance, and with low serum total and HMW adiponectin in patients with type 2 diabetes.

D-Amino acid dehydrogenase from Helicobacter pylori NCTC 11637.

Helicobacter pylori is a microaerophilic bacterium, associated with gastric inflammation and peptic ulcers. D-Amino acid dehydrogenase is a flavoenzyme that digests free neutral D-amino acids yielding corresponding 2-oxo acids and hydrogen. We sequenced the H. pylori NCTC 11637 D-amino acid dehydrogenase gene, dadA. The primary structure deduced from the gene showed low similarity with other bacterial D-amino acid dehydrogenases. We purified the enzyme to homogeneity from recombinant Escherichia coli cells by cloning dadA. The recombinant protein, DadA, with 44 kDa molecular mass, possessed FAD as cofactor, and showed the highest activity to D-proline. The enzyme mediated electron transport from D-proline to coenzyme Q(1), thus distinguishing it from D-amino acid oxidase. The apparent K(m) and V(max) values were 40.2 mM and 25.0 micromol min(-1) mg(-1), respectively, for dehydrogenation of D-proline, and were 8.2 microM and 12.3 micromol min(-1) mg(-1), respectively, for reduction of Q(1). The respective pH and temperature optima were 8.0 and 37 degrees C. Enzyme activity was inhibited markedly by benzoate, and moderately by SH reagents. DadA showed more similarity with mammalian D-amino acid oxidase than other bacterial D-amino acid dehydrogenases in some enzymatic characteristics. Electron transport from D-proline to a c-type cytochrome was suggested spectrophotometrically.

Anemia is associated with an elevated serum level of high-molecular-weight adiponectin in patients with type 2 diabetes independently of renal dysfunction.

Low serum adiponectin is associated with a high incidence of type 2 diabetes or coronary artery disease in the general population. Paradoxically, serum adiponectin is elevated in patients with chronic kidney disease (CKD), such as overt diabetic nephropathy. The current study aimed to investigate whether anemia was independently associated with the serum level of high-molecular-weight (HMW) adiponectin in patients with type 2 diabetes. We studied 207 type 2 diabetic patients (92 women and 115 men). Anemia was defined as a hemoglobin (Hb) <13.0g/dL in men and <12.0g/dL in women according to the guidelines of the World Health Organization (WHO). Overt nephropathy (CKD) was defined as clinical proteinuria and /or estimated glomerular filtration rate (eGFR) lower than 60mL/min for more than 3 months. The diabetic patients were divided into 4 groups according to the presence or absence of anemia and/or CKD. Serum HMW adiponectin levels were measured by a sandwich enzyme-linked immunosorbent assay. In all 207 patients with type 2 diabetes, serum total and HMW adiponectin levels were correlated positively with age, the duration of diabetes, high-density lipoprotein (HDL) cholesterol, urinary albumin, and serum erythropoietin, whereas negative correlations were found with body mass index, triglyceride, eGFR, Hb, hematocrit, and high sensitivity C-reactive protein. A stepwise regression analysis demonstrated that among several significant variables, Hb had the strongest independent influence on HMW adiponectin (beta =-0.487, P < 0.001). Diabetic patients of both sexes with anemia and CKD had the highest serum levels of HMW adiponectin among the 4 groups. In conclusion, anemia is associated with marked elevation of serum HMW adiponectin levels in diabetic patients who have CKD, and this elevation is independent of renal function.

Histidine-rich glycoprotein and concanavalin A synergistically stimulate the phosphatidylinositol 3-kinase-independent signaling pathway in leukocytes leading to increased cell adhesion and changes in cell morphology.

Histidine-rich glycoprotein (HRG) promoted the adhesion and morphological changes of human T-cell line MOLT-4 in a Con A-dependent manner. This morphological change-promoting activity was specific for HRG and the Arg23-Lys66 glycopeptide from human HRG. The carbohydrate chain at Asn45 was essential for this activity. The morphological changes of MOLT-4 cells caused by HRG and Con A (HRG/Con A) were not inhibited by phosphatidylinositol 3-kinase inhibitor, wortmannin or LY294002, while the changes by Con A alone were completely inhibited by these reagents, suggesting that HRG/Con A cooperate to activate leukocytes via a signaling pathway distinct from that by Con A alone. The morphological changes by Con A were associated with pseudopodia like structure. On the other hand, the morphological changes caused by HRG/Con A were associated not only with pseudopodia like structure but also with an increase of the F-actin-rich surface protrusions. Wortmannin inhibited only the formation of pseudopodia like structure.

High affinity interaction between histidine-rich glycoprotein and the cell surface type ATP synthase on T-cells.

Histidine-rich glycoprotein (HRG) is a plasma protein implicated in the innate immune system. In recent studies, we showed that either HRG, or the Arg23-Lys66 glycopeptide derived from HRG, in concert with concanavalin A (Con A), promotes a morphological change and adhesion of the human leukemic T-cell line MOLT-4 to culture dishes, and that cell surface glycosaminoglycan or Fcgamma receptors do not participate in this cellular event. In the present study, we identified the alpha-subunit of ATP synthase as one of the HRG-binding proteins on the surface of T-cells by HRG-derived glycopeptide affinity chromatography and by a peptide mass finger printing method. HRG specifically interacted with mitochondrial ATP synthase with a dissociation constant of 66 nM. The presence of alpha- and beta-subunits of ATP synthase on the plasma membrane of MOLT-4 cell was demonstrated by immunofluorescent staining and FACS analysis. The HRG/Con A-induced morphological changes of MOLT-4 cells were specifically inhibited by a monoclonal antibody against the beta-subunit of ATP synthase. These results strongly suggest that the cell surface ATP synthase functions as a binding protein for HRG on MOLT-4 cells, which is required for the morphological changes observed in MOLT-4 cells following treatment with HRG/Con A.

Purification and characterization of serine racemase from a hyperthermophilic archaeon, Pyrobaculum islandicum.

Pyrobaculum islandicum is an anaerobic hyperthermophilic archaeon that is most active at 100 degrees C. A pyridoxal 5'-phosphate-dependent serine racemase called Srr was purified from the organism. The corresponding srr gene was cloned, and recombinant Srr was purified from Escherichia coli. It showed the highest racemase activity toward L-serine, followed by L-threonine, D-serine, and D-threonine. Like rodent and plant serine racemases, Srr is bifunctional, showing high L-serine/L-threonine dehydratase activity. The sequence of Srr is 87% similar to that of Pyrobaculum aerophilum IlvA (a putative threonine dehydratase) but less than 32% similar to any other serine racemases and threonine dehydratases. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration analyses revealed that Srr is a homotrimer of a 44,000-molecular-weight subunit. Both racemase and dehydratase activities were highest at 95 degrees C, while racemization and dehydration were maximum at pH 8.2 and 7.8, respectively. Unlike other, related Ilv enzymes, Srr showed no allosteric properties: neither of these enzymatic activities was affected by either L-amino acids (isoleucine and valine) or most of the metal ions. Only Fe2+ and Cu2+ caused 20 to 30% inhibition and 30 to 40% stimulation of both enzyme activities, respectively. ATP inhibited racemase activity by 10 to 20%. The Km and Vmax values of the racemase activity of Srr for L-serine were 185 mM and 20.1 micromol/min/mg, respectively, while the corresponding values of the dehydratase activity of L-serine were 2.2 mM and 80.4 micromol/min/mg, respectively.

Retinol binding protein-4 levels and clinical features of type 2 diabetes patients.

CONTEXT: Retinol binding protein (RBP)-4 is a recently identified adipocytokine that is associated with insulin resistance. OBJECTIVES: The aim was to investigate the association between RBP4 and various markers related to insulin resistance and diabetic complications in type 2 diabetic patients. The effect on RBP4 of the addition of pioglitazone to other diabetic medications was also examined. DESIGN, SETTING, PATIENTS, INTERVENTION, AND MAIN OUTCOME MEASURES: RBP4 levels were measured in 101 hospitalized patients with type 2 diabetes and in 22 nonhospitalized control subjects. Endothelial function was evaluated using flow-mediated vasodilatation. In a further 22 nonhospitalized type 2 diabetic patients, pioglitazone (30 mg/d) was administered for 12 wk while other medications for diabetes were continued. RESULTS: There was a significant elevation of RBP4 levels in diabetic patients compared with healthy subjects. RBP4 showed significant positive correlations with triglyceride, systolic blood pressure, and log urinary albumin excretion, and significant negative correlations with high-density lipoprotein cholesterol and flow-mediated vasodilatation. In stepwise regression analysis, log urinary albumin excretion, triglyceride, and gender showed a significant association with RBP4. RBP4 was significantly elevated in patients with proliferative-diabetic retinopathy compared with nondiabetic retinopathy and simple-diabetic retinopathy patients. The addition of pioglitazone for 12 wk to other diabetic medications the patients were already taking did not affect the serum RBP4 concentration. CONCLUSIONS: The current study shows that RBP4 is associated with variables related to insulin resistance and diabetic complications. The addition of pioglitazone for 12 wk to other diabetic medications the patients were already taking did not affect serum RBP4 levels.

Association between plasma visfatin and vascular endothelial function in patients with type 2 diabetes mellitus.

Visfatin is a newly identified adipocytokine that mimics insulin action. However, the pathophysiological role of visfatin in diabetic patients is not fully understood. The main purpose of this study was to investigate the association of plasma visfatin with endothelial function in patients with type 2 diabetes mellitus. In addition, the relationships of visfatin with oxidative stress, low-grade inflammation, atherosclerosis, adiponectin, plasma renin activity, and aldosterone were also explored, and the effect of pioglitazone on visfatin was examined. Visfatin levels were measured in 80 patients with type 2 diabetes mellitus and in 28 age-matched healthy subjects. Endothelial function was evaluated by using flow-mediated vasodilatation (FMD), oxidative stress was assessed by the level of urinary 8-iso-prostaglandin F2alpha, and atherosclerosis and inflammation were measured by using the intimal-medial complex thickness and the levels of high-sensitivity C-reactive protein and fibrinogen. Pioglitazone was administered for 12 weeks at a dose of 30 mg/d in a further 20 patients with type 2 diabetes mellitus. There was a significant negative correlation between the log10-transformed (log) plasma visfatin concentration and FMD or creatinine clearance (R=-0.2672, P=.0167; R=-0.2750, P=.0136). Log visfatin was also positively correlated with log urinary albumin excretion (R=0.2305, P=.0397). In addition, it was also found that visfatin had a significant negative correlation with plasma aldosterone (R=-0.2432, P=.0297). In stepwise regression analysis, creatinine clearance, log aldosterone, FMD, and sex showed a significant association with log visfatin (P=.0040, P=.0069, P=.0444, and P=.0487, respectively), and log 8-iso-prostaglandin F2alpha showed a tendency for an association (P=.0515). Pioglitazone therapy did not affect the visfatin concentration in the 20 pioglitazone-treated patients with diabetes, although a significant elevation of visfatin was obtained in a subgroup of 11 female patients (P=.0381). In conclusion, the current study showed that visfatin is negatively associated with vascular endothelial function evaluated by FMD and creatinine clearance, and positively associated with log urinary albumin excretion. Visfatin was also negatively correlated with circulating aldosterone. Pioglitazone therapy for 12 weeks did not affect the plasma visfatin concentration significantly in all diabetic patients, but a significant elevation in visfatin was obtained in women only.

Alanine racemase from Helicobacter pylori NCTC 11637: purification, characterization and gene cloning.

The Helicobacter pylori NCTC 11637 alanine racemase gene, alr1, was cloned based on a putative alanine racemase gene, alr, of H. pylori 26695. The protein, Alr1, was purified to homogeneity from Escherichia coli MB2795 cells harboring the alr1 gene. The protein exclusively catalyzes the conversion of l-alanine to the d-isomer with K(m) and V(max) values of 100 mM and 909 mumol min(-1) mg(-1), respectively. The values are 16-fold higher than those for the reaction in the reverse direction. The molecular weight of Alr1 is 42,000 by SDS-PAGE, and 68,000 by gel-filtration analysis. The optimal pH and temperature are pH 8.3 and 37 degrees C, respectively, in good accordance with the characteristics shown by the alanine racemase purified from H. pylori NCTC 11637 cells. Pyridoxal 5'-phosphate was suggested to be the cofactor. The physiological function of Alr1 is discussed regarding energy production in the microbial cells.

High serum high-sensitivity C-reactive protein concentrations are associated with relative cardiac sympathetic overactivity during the early morning period in type 2 diabetic patients with metabolic syndrome.

Sympathetic activation is associated with metabolic syndrome (MS) and increased risk of cardiovascular disease. The aim of this study was to investigate whether cardiac autonomic activity or sympathovagal balance, as estimated by a 24-hour power spectral analysis of heart rate variation, is associated with serum concentrations of high-sensitivity C-reactive protein (hs-CRP), a sensitive predictor for cardiovascular events, in type 2 diabetic patients with and without MS. We studied 104 type 2 diabetic patients (50 female and 54 male). The diagnosis of MS was based on the National Cholesterol Education Program Adult Treatment Panel III criteria. Based on the serum hs-CRP, diabetic patients were also divided into 3 groups: low risk (CRP < 1.0 mg/L), moderate risk (1.0 < or = CRP < or = 3.0), and high risk (CRP > 3.0). Heart rate variation was determined automatically every 5 minutes over 24 hours using an ambulatory Holter electrocardiographic recording. Power spectral analysis of the R-R intervals was performed by fast Fourier transformation. Low frequency (LF, both sympathetic and parasympathetic activities), high frequency (HF, pure parasympathetic activity), and the ratio of LF to HF, an index of sympathovagal balance, were used as indices of cardiac autonomic activity. Blood concentrations of hs-CRP, interleukin 6, and plasminogen activator inhibitor 1 were higher in diabetic patients with than in those without MS (P < .0001, P = .0056, and P < .0001, respectively). Both the 24-hour mean LF and the LF-to-HF ratio were also significantly higher in diabetic patients with than in those without MS (P = .0397 and P = .0483, respectively). The LF-to-HF ratio at 6:00 am was significantly higher in diabetic patients with a high CRP concentration than in those with a low or moderate CRP concentration (P < .001 and P < .01, respectively). Only urinary albumin and hs-CRP were independent factors predicting the LF-to-HF ratio at 6:00 am in diabetic patients. In conclusion, type 2 diabetic patients with MS have elevated markers of inflammation and evidence of cardiac sympathetic predominance. High serum concentrations of hs-CRP are associated with relative cardiac sympathetic overactivity during the early morning in type 2 diabetic patients.