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Biochemical and metabolic aspects of platelet dysfunction in chronic myeloproliferative disorders.

Fifty-two patients with chronic myeloproliferative disorders (13 with polycythemia vera; 23 with primary thrombocythemia; 6 with myelofibrosis and 10 with chronic granulocytic leukemia) had low platelet levels of adenine nucleotides and serotonin and abnormal uptake and storage of the amine. The storage pool deficiency was confined to the substances contained in the platelet dense bodies, because alpha-granule and lysosome markers were present in normal amounts. In chronic granulocytic leukemia the storage defect was usually less marked but was accompanied by a decreased formation of thromboxane B2 and normal platelet aggregation in response to arachidonic acid. There was no clearcut relationship of these biochemical abnormalities to prolongation of bleeding time or to thrombotic and hemorrhagic symptoms. The defect was still present in 15 patients after treatment had returned the cell counts to the normal range. Normal levels of 5HT and adenine nucleotides were observed in 8 patients whose platelet counts were high after splenectomy for non-hematological reasons. These findings suggest that biochemical abnormalities are related to the presence in the bone marrow of abnormal clones, resulting in the production of defective platelets.

Adenine Nucleotides↗

Cell imaging and morphology: application to studies of inherited purine metabolic disorders.

A number of inherited or drug-induced metabolic disorders involving dysfunctions in purines and pyrimidines are strongly associated with neurological dysfunction, e.g., Lesch Nyhan syndrome. Such disorders have been studied extensively using biochemical and molecular techniques in order to examine how such defects occur, sometimes using in vitro models based upon cultured neuroblastoma cell lines. However, these metabolic dysfunctions may manifest their effects in other ways, such as impaired synaptic transmission and gross abnormalities in neuronal growth and differentiation. This review outlines the latter novel facet of purine research. It is proposed that by employing cell imaging techniques and cultured neuroblastoma cell lines, believed to model the nervous system, significant insights into how inherited disorders of purine metabolism affect neuronal development can be obtained. This review provides an example of the application of these techniques to understand the etiology of Lesch Nyhan syndrome, and encourages further study of the role of purines and pyrimidines in the development of the nervous system.

Animals↗

Exercise elicits mitonuclear protein imbalance and UPRmt in the liver of mice with obesity.

Mitochondrial dysfunction plays a critical role in the development of metabolic dysfunction-associated steatotic liver disease (MASLD). It has been proposed that mitochondrial unfolded-protein response (UPRmt) activation improves mitochondrial function in the liver. Growing evidence demonstrates that physical exercise effectively prevents and treats MASLD. However, the effects of exercise on UPRmt activation in the liver are unknown. Thus, we investigated the impact of aerobic training on the mechanisms involved in mitochondrial quality control in the liver in a mouse model of obesity. Liver transcript data from a genetic reference panel of BXD isogenic mice revealed a negative correlation between UPRmt-related genes and hepatic triacylglycerol content. In addition, the liver UPRmt markers were strongly associated with several mitochondrial-related genes in the hepatic tissue of BXD mice and humans. Notably, 4 weeks of aerobic exercise strongly impacted the liver metabolism, preventing intrahepatic lipid accumulation in HFD-fed mice. Physical exercise boosted the NAD-biosynthesis pathway, elicited the mitonuclear protein imbalance, stimulated the protein content of UPRmt-markers, including CLpP, Lonp1, and Yme1L1, and improved the mitochondrial proteostasis and function in the liver in HFD-fed mice. Thus, our findings link the mitonuclear protein imbalance and UPRmt activation in the liver to mitochondrial proteostasis and MASLD prevention in response to physical exercise.

Animals↗

Erectile dysfunction and its correlates among the Ariaal of northern Kenya.

To expand our crosscultural understanding of erectile dysfunction, we investigated erectile dysfunction among Ariaal men, pastoral nomads of northern Kenya. To measure erectile dysfunction, we administered the International Index of Erectile Function (IIEF-5) to 198 men aged 20 y and older during interviews. Marital status and anthropometric measures of body composition were also obtained. Men were classified into 10-y age groups. ANOVA revealed that erectile dysfunction increases with age (P<0.0005), with men 60 y and older showing significantly higher erectile dysfunction compared with men in their 20s, 40s and 50s. In a MANCOVA model, erectile dysfunction increased with age group (P<0.001), was negatively related to right-hand grip strength (P<0.01) and negatively related to number of wives (P<0.05). In addition, there was a significant interaction between age group and marital status (P<0.01). Erectile dysfunction showed no independent relationship to measures of body composition, including body mass index, fat free mass and percentage body fat. These findings provide further evidence of age-related increases in erectile dysfunction, even when factors commonly associated with erectile dysfunction (eg, metabolic complications of obesity, use of medicines causing erectile dysfunction) are absent. The finding that number of wives is negatively related to erectile dysfunction may represent the specific cultural conditions (political power and wealth) associated with polygyny among the Ariaal.

Adult↗

Serum cytokines and bone metabolism in patients with thyroid dysfunction.

Hyperthyroidism is associated with increased bone turnover. Besides the hormones of calcium metabolism, locally produced factors are important in maintaining normal bone metabolism. Interleukin-6 (IL-6), in particular, has a major influence on bone turnover. In this study, serum IL-6 and tumor necrosis factor-alpha (TNF-alpha) levels, as well as bone turnover markers and relationships between them, were investigated in hyperthyroidism and hypothyroidism. A total of 20 female patients with hyperthyroidism, 15 with subclinical hyperthyroidism, 16 with hypothyroidism, and 15 with subclinical hypothyroidism constituted the patient groups. In all, 15 age-matched healthy female volunteers were recruited as controls. When compared with controls, serum TNF-alpha levels showed no significant difference in any of the patient groups (P>.05). In the groups with hyperthyroidism and subclinical hyperthyroidism, IL-6 levels were significantly higher compared with control group values (P<.05). Hyperthyroid patients showed higher levels of alkaline phosphatase (ALP) and osteocalcin, and a higher urinary deoxypyridinoline/creatinine ratio, compared with controls (P<.05). In subclinical hyperthyroidism, only ALP was found to be higher compared with control values. No significant correlations were made in any group between serum IL-6 or TNF-alpha level and bone turnover markers. Results suggest that serum IL-6 level and markers of bone turnover rate seem to be increased in hyperthyroidism. This finding may support the role of IL-6 in induction of bone turnover in hyperthyroid states.

Biomarkers↗

Remnant lipoproteinemia is a risk factor for endothelial vasomotor dysfunction and coronary artery disease in metabolic syndrome.

This study aimed to determine whether elevated levels of remnant lipoprotein, an atherogenic triglyceride-rich lipoprotein, might be associated with coronary artery disease (CAD) and endothelial vasomotor dysfunction in metabolic syndrome. The fasting serum levels of remnant lipoproteins (remnant-like lipoprotein particles cholesterol; RLP-C) were measured by an immunoseparation method in 210 patients with metabolic syndrome meeting ATP III criteria. Flow-mediated endothelium-dependent dilatation (FMD) in the brachial artery during reactive hyperemia was examined by high-resolution ultrasound technique. This study found that elevated RLP-C levels were a significant and independent risk factor for impaired FMD and angiographically proven coronary artery disease (CAD). Treatment with bezafibrate (n = 20) or atorvastatin (n = 20) for 4 weeks significantly reduced RLP-C levels, with a concomitant improvement in FMD. The % reduction in RLP-C levels from baseline after the treatment was independently correlated with the magnitude of improvement in FMD after adjustment for the % changes in levels of triglyceride, hsCRP, and IL-6, and HOMA index. Thus, elevated levels of RLP-C are a risk factor for CAD and endothelial vasomotor dysfunction, a predictor of coronary events, in metabolic syndrome. Measurement of RLP-C is useful for assessment of CAD risk and therapeutic effects in metabolic syndrome.

Aged↗

Can brain dysfunction be a predisposing factor for metabolic syndrome?

The various mechanisms that may explain the association between brain dysfunction and the pathogenesis of metabolic syndrome (MS) leading to cardiovascular disease and type 2 diabetes have been reviewed. A Medline search was conducted until September 2003, and articles published in various national and international journals were reviewed. Experts working in the field were also consulted. Compelling evidence was found that saturated and total fat and low dietary n-3 fatty acids and other long-chain polyunsaturated fatty acids (PUFAs) in conjunction with sedentary behavior and mental stress combined with various personality traits can enhance sympathetic activity and increase the secretion of catecholamine, cortisol and serotonin, all of which appear to be underlying mechanisms involved in MS. Excess secretion of these neurotransmitters in conjunction with underlying long-chain PUFA deficiency may damage the neurons in the ventromedial hypothalamus and insulin receptors in the brain, in particular during fetal life, infancy and childhood, and lead to their dysfunction. Since 30-50% of the fatty acids in the brain are long-chain PUFAs, especially omega-3 fatty acids which are incorporated in the cell membrane phospholipids, it is possible that their supplementation may have a protective effect. Omega-3 fatty acids are also known to enhance parasympathetic activity and to increase the secretion of anti-inflammatory cytokines as well as acetylecholine in the hippocampus. It is possible that a marginal deficiency of long-chain PUFAs, especially n-3 fatty acids, due to poor dietary intake during the critical period of brain growth and development in the fetus, and later in the infant and also possibly in the child, adolescent and adult may enhance the release of tumor necrosis factor-alpha (TNF-alpha) interleukin (IL)-1, 2 and 6 and cause neuronal dysfunction. Experimental studies indicate that ventromedial hypothalamic lesions in rats induce hyperphagia, resulting in glucose intolerance and insulin resistance. Treatment with neuropeptide Y abolished hyperphagia and ob mRNA (leptin mRNA) in this animal model. Long-term infusion of norepinephrine and serotonin into the ventromedial hypothalamus impaired pancreatic islet function inasmuch as ventromedial hypothalamic norepinephrine and serotonin levels were elevated in hyperinsulinemic and insulin-resistant animals. Treatment with insulin was associated with restoration of hypothalamic neurotransmitter abnormalities, indicating that ventromedial hypothalamus dysfunction can impair pancreatic beta cells resulting in metabolic abnormalities consistent with MS. Treatment with omega-3 fatty acids, beta blockers, ACE inhibitors, estrogen, and meditation may have a beneficial effect on insulin receptors and ventromedial hypothalamic dysfunction. However, no definite or precise insight into the pathophysiological link between MS, brain function and nutrition is available. Despite this, epidemiological studies and intervention trials indicate that treatment with n-3 fatty acids may be adopted in clinical practice and used to direct therapy for prevention of type 2 diabetes, hypertension, coronary artery disease (CAD), and atherosclerosis, thereby indicating that MS may also respond to this treatment.

Animals↗

Hemodynamic and myocardial metabolic effects of the beta-agonist prenalterol in ischemic left ventricular dysfunction.

Hemodynamic and myocardial metabolic parameters in ischemic left ventricular (LV) dysfunction were evaluated in response to the beta-agonist prenalterol. Twenty micrograms/kg intravenous prenalterol increased resting heart rate and cardiac output and decreased LV filling pressure, systemic vascular resistance, and pulmonary artery pressure. Resting coronary blood flow and myocardial oxygen consumption increased but net myocardial lactate and oxygen extraction did not change significantly. During pacing induced tachycardia (121 +/- 4 beats/min), prenalterol improved cardiac index and stroke work index; whereas, LV filling pressure, systemic vascular resistance, and pulmonary artery pressure decreased. Coronary blood flow and myocardial oxygen extraction did not change significantly. Net myocardial lactate extraction during pacing decreased insignificantly; one patient developed overt lactate production. Thus, prenalterol improves cardiovascular function at rest and during pacing-induced tachycardia in ischemic LV failure, but at the cost of higher resting myocardial oxygen consumption. The majority of subjects had no adverse metabolic response.

Adrenergic beta-Agonists↗

Homocysteine metabolism and B-vitamins in schizophrenic patients: low plasma folate as a possible independent risk factor for schizophrenia.

Two apparently unrelated disorders, neural tube defects (NTD) and schizophrenia showed increased risks in birth cohorts exposed to famine during early gestation. NTD is associated with impaired folate metabolism. We investigated whether schizophrenia is also linked with a dysfunctional folate metabolism. In addition to the prevalence of the 677C-->T mutation in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, we compared plasma and red blood cell (RBC) folate, vitamin B6, vitamin B12, and homocysteine (Hcy) concentrations of 35 schizophrenic patients with those of 104 unrelated controls. Schizophrenic patients had significantly lower plasma folate concentrations after adjustment for Hcy levels, and elevated RBC folate levels compared to controls. Vitamin B6, vitamin B12, and Hcy levels did not differ from control values. Plasma folate levels below the 10th percentile of controls were associated with an approximate 4-7-fold (before and after adjustment of folate levels for Hcy, respectively) risk of having schizophrenia. In addition, a significant dose-response relation between plasma folate concentrations and risk for schizophrenia suggested a protective effect by high plasma folate concentrations. Elevated Hcy levels and, in line with this finding, homozygosity for the 677C-->T mutation in the MTHFR gene were not associated with an increased risk for schizophrenia. Evidence is presented suggesting that folate metabolism is disturbed in schizophrenic patients, independently of Hcy.

Adult↗

Is the metabolic syndrome an independent risk factor for erectile dysfunction?

PURPOSE: We determined the role of the metabolic syndrome as an independent risk factor for erectile dysfunction. MATERIALS AND METHODS: Men participating in a health screening project completed the International Index of Erectile Function-5. The metabolic syndrome was defined according to the 2005 International Diabetes Federation consensus definition. Multiple linear regression, ANOVA and chi-square tests were used to investigate the impact of the metabolic syndrome on erectile dysfunction. RESULTS: A total of 2,371 men with a mean age of 46.1 years (SD 9.9, range 30 to 69) were analyzed. Of the men 33.4% (652) had no erectile dysfunction (International Index of Erectile Function-5 score 22 to 25), 59.7% (1,166) had mild erectile dysfunction (International Index of Erectile Function-5 score 17 to 21) and 6.9% (134) had moderate to severe erectile dysfunction (International Index of Erectile Function-5 score 5 to 16). The metabolic syndrome was present in 33.8% (794). In a multiple linear regression analysis an increased waist-to-hip ratio (p = 0.01) and metabolic syndrome (p = 0.01) turned out to be independently associated with a decreased International Index of Erectile Function-5 score. When stratified according to age, the metabolic syndrome was correlated to erectile dysfunction only in men 50 years old or older with an increase of severe erectile dysfunction by 48% (p = 0.01). CONCLUSIONS: The metabolic syndrome and an increased waist-to-hip ratio are independently associated with a decreased International Index of Erectile Function-5 score. The metabolic syndrome in men older than 50 years is significantly associated with a higher proportion of moderate to severe erectile dysfunction.

Adult↗

Inositols prevent and reverse endothelial dysfunction in diabetic rat and rabbit vasculature metabolically and by scavenging superoxide.

Endothelial dysfunction (ED) is an early feature of cardiovascular risk and diabetes. Hyperglycemia and hyperlipidemia are causative factors. Excessive endothelial mitochondrial superoxide (ROS) production with hyperglycemia and hyperlipidemia is a key mechanism. Inositol components of an insulin inositol glycan mediator, d-chiro-inositol (DCI) and 3-O-methyl DCI (pinitol), decrease hyperglycemia and hyperlipidemia. We tested whether these, myoinositol and dibutyryl DCI (db-DCI), would prevent or reverse ED in diabetic rats and rabbits. Oral inositols reduced hyperglycemia and hypertriglyceridemia with different potencies and prevented ED in rat aortic rings and mesenteric beds. Inositols added in vitro to five diabetic tissues reversed ED. Relaxation by Ach, NO, and electrical field stimulation was potentiated by inositols in vitro in rabbit penile corpus cavernosa. Inositols in vitro restored impaired contraction by the eNOS inhibitor l-NAME and increased NO effectiveness. DCI and db-DCI decreased elevated ROS in endothelial cells in high glucose and db-DCI reduced PKC activation, hexosamine pathway activity, and advanced glycation end products to basal levels. Xanthine/xanthine oxidase generated superoxide was reduced by superoxide dismutase or inositols, with db-DCI efficacious in a mechanism requiring chelated Fe(3+). Histochemical examination of rat aortic rings for protein SNO demonstrated a decrease in diabetic rings with restoration by inositols. In summary, inositols prevented and reversed ED in rat and rabbit vessels, reduced elevated ROS in endothelial cells, potentiated nitrergic or vasculo-myogenic relaxations, and preserved NO signaling. These effects are related to their metabolic actions, direct superoxide scavenging, and enhancing and protecting NO signaling. Of the inositols tested, db-DCI was most effective.

Animals↗

Beneficial effects of dilazep on the palmitoyl-L-carnitine-induced derangements in isolated, perfused rat heart: comparison with tetrodotoxin.

The present study was carried out to determine the effect of dilazep, having an inhibitory effect on the Na+ channel, on the mechanical dysfunction and metabolic derangements induced by palmitoyl-L-carnitine in isolated rat heart and to compare the effect of dilazep with that of tetrodotoxin, a specific inhibitor of the Na+ channel. Rat hearts were perfused aerobically at a constant flow according to Langendorff's technique and paced electrically. Palmitoyl-L-carnitine (5 microM) decreased the left ventricular developed pressure and increased the left ventricular end diastolic pressure (i.e., it produced mechanical dysfunction), decreased the tissue level of adenosine triphosphate and increased the tissue level of adenosine monophosphate (i.e., it produced metabolic derangements). These mechanical and metabolic alterations induced by palmitoyl-L-carnitine were attenuated by either dilazep (1 microM) or tetrodotoxin (3 microM). On the other hand, neither dilazep nor tetrodotoxin modified the mechanical function and energy metabolism of the normal (palmitoyl-L-carnitine-untreated) heart. These results suggest that inhibition of the Na+ channel with dilazep or tetrodotoxin is responsible, at least in part, for attenuating the palmitoyl-L-carnitine-induced mechanical dysfunction and metabolic derangements in the heart.

Adenosine Diphosphate↗

Role of nitric oxide in the circulatory failure and organ injury in a rodent model of gram-positive shock.

1. The pathological features of Gram-positive shock can be mimicked by the co-administration of two cell wall components of Staphylococcus aureus, namely lipoteichoic acid (LTA) and peptidoglycan (PepG). This is associated with the expression of the inducible isoform of nitric oxide synthase (iNOS) in various organs. We have investigated the effects of dexamethasone (which prevents the expression of iNOS protein) or aminoguanidine (an inhibitor of iNOS activity) on haemodynamics, multiple organ dysfunction syndrome (MODS) as well as iNOS activity elicited by LTA + PepG in anaesthetized rats. 2. Co-administration of LTA (3 mg kg-1, i.v.) and PepG (10 mg kg-1, i.v.) resulted in a significant increase in the plasma levels of tumour necrosis factor-alpha (TNF alpha, maximum at 90 min) as well as a biphasic fall in mean arterial blood pressure (MAP) from 120 +/- 3 mmHg (time 0) to 77 +/- 5 mmHg (at 6 h, n = 8; P < 0.05). This hypotension was associated with a significant tachycardia (4-6 h, P < 0.05) and a reduction of the pressor response elicited by noradrenaline (NA, 1 microgram kg-1, i.v., at 1-6 h; n = 8, P < 0.05). Furthermore, LTA + PepG caused time-dependent increases in the serum levels of markers of hepatocellular injury, glutamate-pyruvate-transminase (GPT) and glutamate-oxalacetate-transaminase (GOT). In addition, urea and creatinine (indicators of renal dysfunction) were increased. There was also a fall in arterial oxygen tension (PaO2), indicating respiratory dysfunction, and metabolic acidosis as shown by the significant drop in pH, PaCO2 and HCO3-. These effects caused by LTA + PepG were associated with the induction of iNOS activity in aorta, liver, kidney and lungs as well as increases in serum levels of nitrite+nitrate (total nitrite). 3. Pretreatment of rats with dexamethasone (3 mg kg-1, i.p.) at 120 min before LTA + PepG administration significantly attenuated these adverse effects as well as the increases in the plasma levels of TNF alpha caused by LTA + PepG. The protective effects of dexamethasone were associated with a prevention of the increase in iNOS activity (in aorta, liver, lung, kidney), the expression of iNOS protein (in lungs), as well as in the increase in the plasma levels of total nitrite. 4. Treatment of rats with aminoguanidine (5 mg kg-1 + 10 mg kg-1 h-1) starting at 120 min after LTA + PepG attenuated most of the adverse effects and gave a significant inhibition of iNOS activity (in various organs) as well as an inhibition of the increase in total plasma nitrite. However, aminoguanidine did not improve renal function although this agent caused a substantial inhibition of NOS activity in the kidney. 5. Thus, an enhanced formation of NO by iNOS importantly contributes to the circulatory failure, hepatocellular injury, respiratory dysfunction and the metabolic acidosis, but not the renal failure, caused by LTA + PepG in the anaesthetized rat.

Acid-Base Equilibrium↗

Metabolic myopathies.

Metabolic myopathies are disorders of muscle energy production that result in skeletal muscle dysfunction. Cardiac and systemic metabolic dysfunction may coexist. Symptoms are often intermittent and provoked by exercise or changes in supply of lipid and carbohydrate fuels. Specific disorders of lipid and carbohydrate metabolism in muscle are reviewed. Evaluation often requires provocative exercise testing. These tests may include ischemic forearm exercise, aerobic cycle exercise, and 31P magnetic resonance spectroscopy with exercise.

Carnitine↗