Increased Plasma Levels of Adenylate Cyclase 8 and cAMP Are Associated with Obesity and Type 2 Diabetes: Results from a Cross-Sectional Study.

Adenylate cyclases (ADCYs) catalyze the conversion of ATP to cAMP, an important co-factor in energy homeostasis. Giving ADCYs role in obesity, diabetes and inflammation, we questioned whether calcium-stimulated ADCY isoforms may be variably detectable in human plasma. We report the results of a cross-sectional study assessing circulating levels of functional ADCY1, -3 and -8 in patients with T2D vs. non-diabetic (ND) controls in association with obesity. ADCY1 levels exhibited no significant change between ND and T2D groups. ADCY3 levels were lower in obese individuals, albeit not statistically significantly. In contrast, ADCY8 plasma levels were significantly higher in obese and T2D patients compared to controls (p = 0.001) and patients with T2D only (p = 0.039). ADCY8 levels correlated positively with body mass index and Hb1Ac levels. Parallel to the increased ADCY8 levels, significantly higher cAMP levels were observed in patients with T2D compared with ND controls, and further elevated in obese individuals, irrespective of T2D status. Additionally, cAMP levels positively correlated with fasting plasma glucose levels. In conclusion, the current cross-sectional study demonstrated elevated levels of circulating plasma ADCY8 and cAMP in obesity and T2D.

Electronic cigarettes increase endothelial progenitor cells in the blood of healthy volunteers.

BACKGROUND AND AIMS: The use of electronic cigarettes is increasing dramatically on a global scale and its effects on human health remain uncertain. In the present study, we measured endothelial progenitor cells (EPCs) and microvesicles (MVs) in healthy young volunteers following short-term exposure to inhalation of e-cigarette vapor (ECV) to determine vascular changes. METHODS: Sixteen healthy seldom smokers were randomized into two groups either exposed or not exposed to 10 puffs of ECV for 10 min, in a crossover design. Blood samples were obtained at baseline and 1, 4 and 24 h following exposure. EPCs (CD34 + CD309) and MVs were analyzed by flow cytometry. MVs were phenotyped according to origin (platelet (CD41), endothelial (CD144), leukocytes (CD45), monocytes (CD14)) and nuclear content (SYTO 13 dye). In addition, expression of inflammation markers such P-selectin (CD62P), E-selectin (CD62E), CD40-ligand (CD154) and HMGB1 was investigated. Fractional exhaled nitric oxide (FeNO) was also measured at baseline and after 24 h. RESULTS: EPC levels in blood were significantly increased 1 h following exposure to ECV and returned to baseline values after 24 h. Only E-selectin positive MVs (endothelial origin) were slightly elevated (p < 0.038). FeNO was unaffected by exposure to ECV. CONCLUSIONS: In healthy volunteers, ten puffs of e-cigarette vapor inhalation caused an increase in EPCs. This increase was of the same magnitude as following smoking of one traditional cigarette, as we previously demonstrated. Taken together, these results may represent signs of possible vascular changes after short e-cigarette inhalation. Further studies analyzing potential cardiovascular health effects are critical as the e-cigarette market continues to burgeon.

TNF stimulation induces VHL overexpression and impairs angiogenic potential in skeletal muscle myocytes.

Decreased skeletal muscle capillarization is considered to significantly contribute to the development of pulmonary cachexia syndrome (PCS) and progressive muscle wasting in several chronic inflammatory diseases, including chronic obstructive pulmonary disease (COPD). It is unclear to which extent the concurrent presence of systemic inflammation contributes to decreased skeletal muscle capillarization under these conditions. The present study was designed to examine in vitro the effects of the pro-inflammatory cytokine, tumor necrosis factor (TNF), on the regulation of hypoxia-angiogenesis signal transduction and capillarization in skeletal muscles. For this purpose, fully differentiated C2C12 skeletal muscle myocytes were stimulated with TNF and maintained under normoxic or hypoxic conditions. The expression levels of the putative elements of the hypoxia-angiogenesis signaling cascade were examined using qPCR, western blot analysis and immunofluorescence. Under normoxic conditinos, TNF stimulation increased the protein expression of anti-angiogenic von-Hippel Lindau (VHL), prolyl hydroxylase (PHD)2 and ubiquitin conjugating enzyme 2D1 (Ube2D1), as well as the total ubiquitin content in the skeletal muscle myocytes. By contrast, the expression levels of hypoxia-inducible factor 1­α (HIF1-α) and those of its transcriptional targets, vascular endothelial growth factor (VEGF)A and glucose transporter 1 (Glut1), were markedly reduced. In addition, hypoxia increased the expression of the VHL transcript and further elevated the VHL protein expression levels in C2C12 myocytes following TNF stimulation. Consequently, an impaired angiogenic potential was observed in the TNF-stimulated myocytes during hypoxia. In conclusion, TNF increases VHL expression and disturbs hypoxia-angiogenesis signal transduction in skeletal muscle myocytes. The current findings provide a mechanism linking systemic inflammation and impaired angiogenesis in skeletal muscle. This is particularly relevant to further understanding the mechanisms mediating muscle wasting and cachexia in patients with chronic inflammatory diseases, such as COPD.

Caveolin-1/PTRF upregulation constitutes a mechanism for mediating p53-induced cellular senescence: implications for evidence-based therapy of delayed wound healing in diabetes.

A heightened state of oxidative stress and senescence of fibroblasts constitute potential therapeutic targets in nonhealing diabetic wounds. Here, we studied the underlying mechanism mediating diabetes-induced cellular senescence using in vitro cultured dermal fibroblasts and in vivo circular wounds. Our results demonstrated that the total antioxidant capacity and mRNA levels of thioredoxinreductase and glucose-6-phosphate dehydrogenase as well as the ratio of NADPH/NADP were decreased markedly in fibroblasts from patients with type 2 diabetes (DFs). Consistent with this shift in favor of excessive reactive oxygen species, DFs also displayed a significant increase in senescence-associated ß-galactosidase activity and phospho-γ-histone H2AX (pH2AX) level. Moreover, the ability of PDGF to promote cell proliferation/migration and regulate the phosphorylation-dependent activation of Akt and ERK1/2 appears to be attenuated as a function of diabetes. Mechanistically, we found that diabetes-induced oxidative stress upregulated caveolin-1 (Cav-1) and PTRF expression, which in turn sequestered Mdm2 away from p53. This process resulted in the activation of a p53/p21-dependent pathway and the induction of premature senescence in DFs. Most of the aforementioned oxidative stress and senescence-based features observed in DFs were recapitulated in a 10-day-old diabetic wound. Intriguingly, we confirmed that the targeted depletion of Cav-1 or PTRF using siRNA- or Vivo-Morpholino antisense-based gene therapy markedly inhibited diabetes/oxidative stress-induced premature senescence and also accelerated tissue repair in this disease state. Overall, our data illuminate Cav-1/PTRF-1 as a key player of a novel signaling pathway that may link a heightened state of oxidative stress to cellular senescence and impaired wound healing in diabetes.

Exposure to cigarette smoke induces overexpression of von Hippel-Lindau tumor suppressor in mouse skeletal muscle.

Cigarette smoke (CS) is a well-established risk factor in the development of chronic obstructive pulmonary disease (COPD). In contrast, the extent to which CS exposure contributes to the development of the systemic manifestations of COPD, such as skeletal muscle dysfunction and wasting, remains largely unknown. Decreased skeletal muscle capillarization has been previously reported in early stages of COPD and might play an important role in the development of COPD-associated skeletal muscle abnormalities. To investigate the effects of chronic CS exposure on skeletal muscle capillarization and exercise tolerance, a mouse model of CS exposure was used. The 129/SvJ mice were exposed to CS for 6 mo, and the expression of putative elements of the hypoxia-angiogenic signaling cascade as well as muscle capillarization were studied. Additionally, functional tests assessing exercise tolerance/endurance were performed in mice. Compared with controls, skeletal muscles from CS-exposed mice exhibited significantly enhanced expression of von Hippel-Lindau tumor suppressor (VHL), ubiquitin-conjugating enzyme E2D1 (UBE2D1), and prolyl hydroxylase-2 (PHD2). In contrast, hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) expression was reduced. Furthermore, reduced muscle fiber cross-sectional area, decreased skeletal muscle capillarization, and reduced exercise tolerance were also observed in CS-exposed animals. Taken together, the current results provide evidence linking chronic CS exposure and induction of VHL expression in skeletal muscles leading toward impaired hypoxia-angiogenesis signal transduction, reduced muscle fiber cross-sectional area, and decreased exercise tolerance.

A CYP26B1 polymorphism enhances retinoic acid catabolism and may aggravate atherosclerosis.

All-trans retinoic acid, controlled by cytochrome P450, family 26 (CYP26) enzymes, potentially has beneficial effects in atherosclerosis treatment. This study investigates CYP26 subfamily B, polypeptide 1 (CYP26B1) in atherosclerosis and the effects of a genetic polymorphism in CYP26B1 on retinoid catabolism. We found that CYP26B1 mRNA was induced by retinoic acid in human atherosclerotic arteries, and CYP26B1 and the macrophage marker CD68 were colocalized in human atherosclerotic lesions. In mice, Cyp26B1 mRNA was higher in atherosclerotic arteries than in normal arteries. Databases were queried for nonsynonymous CYP26B1 single nucleotide polymorphisms (SNPs) and rs2241057 selected for further studies. Constructs of the CYP26B1 variants were created and used for production of purified proteins and transfection of macrophagelike cells. The minor variant catabolized retinoic acid with significantly higher efficiency, indicating that rs2241057 is functional and suggesting reduced retinoid availability in tissues with the minor variant. rs2241057 was investigated in a Stockholm Coronary Atherosclerosis Risk Factor (SCARF) subgroup. The minor allele was associated with slightly larger lesions, as determined by angiography. In summary, this study identifies the first CYP26B1 polymorphism that alters CYP26B1 capacity to metabolize retinoic acid. CYP26B1 was expressed in macrophage-rich areas of human atherosclerotic lesions, induced by retinoic acid and increased in murine atherosclerosis. Taken together, the results indicate that CYP26B1 capacity is genetically regulated and suggest that local CYP26B1 activity may influence atherosclerosis.

Alterations in the muscle-to-capillary interface in patients with different degrees of chronic obstructive pulmonary disease.

BACKGROUND: It is hypothesized that decreased capillarization of limb skeletal muscle is implicated in the decreased exercise tolerance in COPD patients. We have recently demonstrated decreased number of capillaries per muscle fibre (CAF) but no changes in CAF in relation to fibre area (CAFA), which is based on the diffusion distance between the capillary and muscle fibre. The aim of the current study is to investigate the muscle-to-capillary interface which is an important factor involved in oxygen supply to the muscle that has previously been suggested to be a more sensitive marker for changes in the capillary bed compared to CAF and CAFA. METHODS: 23 COPD patients and 12 age-matched healthy subjects participated in the study. Muscle-to-capillary interface was assessed in muscle biopsies from the tibialis anterior muscle using the following parameters:1) The capillary-to-fibre ratio (C:Fi) which is defined as the sum of the fractional contributions of all capillary contacts around the fibre2) The ratio between C:Fi and the fibre perimeter (CFPE-index)3) The ratio between length of capillary and fibre perimeter (LC/PF) which is also referred to as the index of tortuosity.Exercise capacity was determined using the 6-min walking test. RESULTS: A positive correlation was found between CFPE-index and ascending disease severity with CFPE-index for type I fibres being significantly lower in patients with moderate and severe COPD. Furthermore, a positive correlation was observed between exercise capacity and CFPE-index for both type I and type IIa fibres. CONCLUSION: It can be concluded that the muscle-to-capillary interface is disturbed in the tibialis anterior muscle in patients with COPD and that interface is strongly correlated to increased disease severity and to decreased exercise capacity in this patient group.

Inflammation and apoptosis in aortic tissues of aged type II diabetes: amelioration with alpha-lipoic acid through phosphatidylinositol 3-kinase/Akt- dependent mechanism.

AIMS: Endothelial dysfunction is a key triggering event in the development of cardiovascular diseases and the current study explored this phenomenon in the context of inflammation, apoptosis, reactive oxygen species (ROS) and the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway during chronic diabetes. MAIN METHODS: alpha-Lipoic acid (ALA) and wortmannin (WM) were chronically administered to aged Goto Kakizaki (GK) rats, a genetic model of non-obese type II diabetes. Key indices of inflammation, apoptosis and oxidative stress were assessed using western blotting, real-time PCR and immunofluoresence-based techniques. KEY FINDINGS: A chronic inflammation (e.g., increased mRNA/protein levels of TNF-alpha, ICAM, fractalkine, CD-68, myeloperoxidase) in connection with increased caspase-based apoptotic cell death and heightened state of oxidative stress (HSOS)- appear to exist in diabetic cardiovascular tissues. An assessment of NF-kappaB dynamics in aged diabetic vessels revealed not only a marked increase in cytosolic phosphorylated levels of IkappaB-alpha, NIK, IKK but also an enhancement in nuclear localization of p65 concomitantly with augmented NF-kappaB-DNA binding activity. Most of the aforementioned cardiovascular-based diabetic abnormalities including reduced activities of PI3K and Akt kinase were ameliorated following chronic ALA therapy. WM, given to GK rats negated the anti-inflammatory and anti-apoptotic actions of ALA. SIGNIFICANCE: Our data highlight a unifying mechanism whereby HSOS through an induction of NF-kappaB activity together with an impairment in PI3K/Akt pathway favors pro-inflammatory/pro-apoptotic diabetic vascular milieu that culminate in the onset of endothelial dysfunction, a phenomenon which appears to be amenable to treatment with antioxidants and/or PI3/Akt mimetics (e.g., ALA).

Increased serum inflammatory markers in the absence of clinical and skeletal muscle inflammation in patients with chronic obstructive pulmonary disease.

BACKGROUND: Muscle wasting and cachexia are common occurrences in patients with chronic obstructive pulmonary disease (COPD). OBJECTIVES: The current study aimed to investigate markers of inflammation in the circulation and skeletal muscle that might be associated with development of muscle wasting. METHODS: Three groups of patients with mild, moderate and severe COPD and matched healthy controls were recruited. Serum levels of C-reactive protein (CRP), high-sensitivity CRP (hs-CRP), IL-6, IL-8, TNF-alpha, cortisol, insulin-like growth factor 1 (IGF-1), leptin and ghrelin were analysed. Skeletal muscle inflammation was investigated microscopically using a panel of antibodies and standard staining for inflammatory cell infiltration. RESULTS: All COPD patients were clinically stable, with no sign of inflammation and normal CRP values. Compared to controls, significantly increased hs-CRP levels were observed in all COPD patient groups. Significant rises in IL-6 levels were first observed in moderate COPD, while IL-8 levels were significantly elevated at the late severe stage. Circulating levels of TNF-alpha, cortisol, IGF-1, leptin and ghrelin were similar to control levels. No microscopic signs of skeletal muscle inflammation were observed. CONCLUSION: Our results identify hs-CRP as an early marker of inflammation that is significantly increased in the circulation even in mild COPD. Serum interleukin levels appear to be increased with disease progress. These changes were manifested in the absence of any clinical signs of disease exacerbation, evidence of skeletal muscle inflammation or hormonal changes.

PACAP is expressed in secretory granules of insulin and glucagon cells in human and rodent pancreas. Evidence for generation of cAMP compartments uncoupled from hormone release in diabetic islets.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an islet neuropeptide with potent insulinotropic action. The current study investigates PACAP expression in normal human and rat pancreatic islets, and whether it is altered in diabetic state. To that end, PACAP immunoreactivity was studied by immunofluorescence methods enhanced by the catalyzed reporter deposition (CARD) technique. Insulin and cyclic adenosine monophosphate (cAMP) generation induced by PACAP were investigated in islets isolated from the spontaneously diabetic Goto-Kakizaki (GK) rat. PACAP immunoreactivity was observed in virtually all insulin and glucagon cells in both species, but not in somatostatin or pancreatic polypeptide (PP) cells; this co-localization pattern was unaltered in diabetic pancreata. In normal human pancreas, PACAP was further localized ultrastructurally to the secretory granules of insulin and glucagon cells. PACAP significantly potentiated glucose-stimulated insulin release in isolated islets of normal but not of GK rats. PACAP failed to enhance cAMP generation in normal islets, but induced approximately 5-folds exaggeration in the diabetic islets. In conclusion, using improved immunocytochemistry techniques and electron microscopy (EM), PACAP was shown to be expressed both in normal and diabetic islet cells and localized to secretory granules of insulin and glucagon cells. Furthermore, the insulinotropic action of PACAP was markedly impaired in diabetic islets in spite of exaggerated cAMP response.

Overexpression of Gs proteins and adenylyl cyclase in normal and diabetic islets.

INTRODUCTION: Knowledge about the relation between G proteins and adenylyl cyclases (ACs) is important for the construction of signaling paradigms to increase our understanding of signal transduction in the normal state and its alterations in pathologic states, such as type-2 diabetes. AIMS AND METHODOLOGY: The immunocytochemical expression patterns of the stimulatory Gs proteins (G alpha-s and G alpha-olf) and the in vitro Ca2+-stimulated ACs (AC1, 3, and 8) were studied in normal and spontaneously diabetic Goto-Kakizaki (GK) rat pancreatic islets with use of well-characterized antibodies. The expressions of G alpha-11 and AC2, abundant in pancreatic islets, were also studied. RESULTS: G alpha-s and G alpha-olf were mainly expressed in insulin cells, and G alpha-11 in glucagon cells. The immunoreactivity to G alpha-s and G alpha-olf and to AC1 and AC3 was higher in the GK islets than in the controls, whereas AC8 was found only in the diabetic islets. Strong G alpha-11 and AC2 immunoreactivity was seen equally in both animal groups. G alpha-s was colocalized with all ACs, whereas G alpha-olf was mainly colocalized with AC3, and G alpha-11 with AC1. CONCLUSION: The current findings may help in drawing a more specific signaling paradigm coupling Gs proteins to ACs.

Increased expression of adenylyl cyclase isoforms in the adrenal gland of diabetic Goto-Kakizaki rat.

The spontaneously diabetic Goto-Kakizaki rat harbors the same defects expressed in human type 2 diabetes. It is not clear, however, whether stress factors emanating from the adrenal glands are involved in causing the diabetic state. For that reason, the authors studied gland size and expression of adenylyl cyclase isoforms in adrenal glands from Goto-Kakizaki and normal rats. Goto-Kakizaki rat adrenals were found to weigh only about half as much as those of control rats. This decrease was the result of a reduction of the cortex, especially of the zona fasciculata, whereas the medulla was unaffected. Cell density measurements showed that the total number of medullary cells in Goto-Kakizaki rats was lower than that in controls. In the cortex, the cell density did not differ between the two groups; thus, our results point to a marked hypotrophy. In the medulla of Goto-Kakizaki rats, the nuclear size was significantly increased, and there was also an overexpression of adenylyl cyclase 1, 2, 4, 6, and 8 isoforms in the adrenalin-producing cells, indicating an increased functional capacity. In the cortex, despite the cortical hypotrophy, adenylyl cyclase 5 immunoreactivity was markedly increased in Goto-Kakizaki rats, especially in the zona reticularis. It is unclear whether this morphologic change in the diabetic adrenal glands together with the overexpression of different adenylyl cyclase isoforms plays a role in the pathogenesis of this diabetic state or is a genetic defect or compensatory mechanism of diabetes in this spontaneous rodent model of type 2 diabetes.

Insulinotropic activity of the imidazoline derivative RX871024 in the diabetic GK rat.

The insulinotropic activity of the imidazoline derivative RX871024 was compared in pancreatic islets from nondiabetic Wistar rats and spontaneously diabetic Goto-Kakizaki (GK) rats. RX871024 significantly stimulated insulin secretion in islets from both animal groups. The insulinotropic activity of RX871024 was higher than that of the sulfonylurea glibenclamide. This difference was more pronounced in islets from GK rats compared with Wistar rat islets. More importantly, RX871024 substantially improved glucose sensitivity in diabetic beta-cells, whereas glibenclamide stimulated insulin secretion about twofold over a broad range of glucose concentrations in nondiabetic and diabetic rats. RX871024 induced a faster increase in cytosolic free Ca(2+) concentration and faster inhibition of ATP-dependent K(+) channel activity in GK rat islets compared with Wistar rat islets. RX871024 also induced a more pronounced increase in diacylglycerol concentration in GK rat islets. These data support the idea that imidazoline compounds can form the basis for the development of novel drugs for treatment of type 2 diabetes, which can restore glucose sensitivity in diabetic beta-cells.