Role of beta-cell dysfunction, ectopic fat accumulation and insulin resistance in the pathogenesis of type 2 diabetes

n the natural history of type 2 diabetes (T2DM), individuals progress from normal glucose tolerance (NGT) to impaired glucose tolerance (IGT) to overt T2DM and this progression has been demonstrated in populations of diverse ethnic background. It is widely recognised that both insulin resistance and beta-cell dysfunction are important in the pathogenesis of glucose intolerance. In populations with a high prevalence of T2DM, insulin resistance is well established long before the development of any impairment in glucose homeostasis, particularly in subjects with ectopic fat accumulation. However, as long as the beta cell is able to secrete sufficient amounts of insulin to offset the severity of insulin resistance, glucose tolerance remains normal. This dynamic interaction between insulin secretion and insulin resistance is essential to the maintenance of NGT and interruption of this crosstalk between the beta cell and peripheral tissues results in the progressive deterioration of glucose homeostasis. In this paper the role of beta-cell function is reviewed, as well as the role of ectopic fat accumulation and insulin resistance in the development of type 2 diabetes

Protective role of adiponectin on endothelial dysfunction induced by AGEs: A clinical and experimental approach

Objective: Obesity is characterized by low levels of adiponectin, an adipocytes derived hormone, and by an inflammatory component. Endothelial dysfunction is often found in overweight/obesity, diabetes, and atherosclerosis. Advanced glycation end products (AGEs) induce endothelial dysfunction and are linked to diabetes and increased atherogenicity and inflammation. The aim of the study was to investigate the possible link between adiponectin and N(epsilon)-(carboxymethyl) lysine (CML), the predominant adduct of circulating AGEs in overweight patients, and, in an in vitro model, to test the hypothesis that adiponectin acts as modulator of endothelial dysfunction, induced by AGEs. Results: In 108 overweight patients, plasma levels of CML correlated inversely with adiponectin levels. Preincubation of human vein endothelial cells (HUVECs) with physiological concentrations of adiponectin, followed by stimulation with AGEs, reduced vascular adhesion molecule-1 (VCAM-1) and E-selectin expression, as assessed by surface enzyme immunoassay. Conclusions: Taken together, these findings demonstrate an inverse correlation between CML and adiponectin levels in overweight patients and a protective role of adiponectin on endothelial dysfunction induced by AGEs, suggesting its key role in the treatment of the vascular complications of obesity/metabolic syndrome

Diet and Exercise in the Treatment of Fatty Liver

In recent years, we came to realize that obesity, broadly defined as increased body mass index or increased total body fat, is not necessarily associated with metabolic dysfunction and greater risk for cardiometabolic disease. In fact, there are several obese persons who are "metabolically healthy," as there are nonobese persons who are "metabolically abnormal." Although the reason(s) underlying this phenomenon are still not entirely clear, a number of studies conducted over the past several years indicate that the anatomical location of excess fat is more important than total body adiposity in determining metabolic outcomes. Ectopic fat accumulation, particularly in the liver, is frequently observed in obese persons and is strongly associated with metabolic dysfunction, including multiorgan insulin resistance and dyslipidemia. Intrahepatic fat, possibly more than visceral or intramyocellular fat, may thus be a prominent factor modifying the metabolic risk associated with increasing whole-body adiposity. However, cause-and-effect relationships have not yet been established, and it is also possible that intrahepatic triglyceride content is not a determinant but merely a marker of metabolic health. Understanding the regulation of fat accumulation in the liver will thus have important implications in both research and clinical practice. Little is known regarding the specific effects of lifestyle factors such as diet and exercise in regulating the accumulation of fat in the liver and its depletion thereof. In this special issue, we have invited a few papers in an attempt to partly fill this gap in our knowledge. In the first paper of this issue, "Putative factors that may modulate the effect of exercise on liver fat: insights from animal studies," several studies in animals are reviewed in order to highlight putative factors that may modulate the effect of exercise on liver fat. This includes the fat content of the diet (exercise appears to be more effective under high-fat feeding), the role of concurrent exercise-induced loss of body weight or visceral fat, sex (males versus females), prandial status (fasted versus fed), and the duration of training, as well as the time elapsed from the last bout of exercise. The potential importance of these factors in modifying the exercise-induced changes in liver fat has not yet been formally tested in man, thereby providing a wide array of opportunities for future research. The second paper of this issue, "Nafld, estrogens, and physical exercise: the animal model," focuses on the effects of exercise on liver fat in relation to estrogen availability. Estrogen deficiency, such as that occurring naturally after menopause in women, is strongly associated with fatty liver in animals. Exercise training exerts an estrogenic-like effect on the expression of genes involved in hepatic lipid metabolism and is a powerful means for preventing liver fat accumulation in estrogen-deficient animals. The third paper of this special issue, "Dietary conjugated linoleic acid and hepatic steatosis: species specific effects on liver and adipose lipid metabolism and gene expression," reviews the effects of dietary conjugated linoleic acid on liver fat content and hepatic and adipose tissue fatty acid metabolism in animals. Conjugated linoleic acids, particularly the trans-10, cis-12, lead to hepatic steatosis owing to increased de novo lipogenesis and increased hepatic fatty acid uptake, at rates far exceeding the rates of disposal of intrahepatic fatty acids towards oxidation, esterification, and triglyceride export. The fourth paper of this issue, "Effects of exercise training on molecular markers of lipogenesis and lipid partitioning in fructose-induced liver fat accumulation," examines the effects of exercise training on liver fat in starved and subsequently fructose-refed animals. Fructose, a simple sugar, is a potent dietary trigger for liver fat accretion. Exercise training in this model is not able to reverse the fructose-induced changes in lipogenic enzymes and does not reduce intrahepatic fat content. Thus, contrary to the large body of evidence demonstrating that exercise is effective in alleviating hepatic steatosis induced by high-fat feeding, exercise is not able to reverse the changes induced by fructose feeding. The final paper of this special issue, "Exercise and omega-3 polyunsaturated fatty acid supplementation for the treatment of hepatic steatosis in hyperphagic OLETF rats," evaluates the effects of exercise on a hyperphagic model of obesity, with or without concurrent omega-3 polyunsaturated fatty acid supplementation. Exercise training in this animal model alleviates hepatic steatosis even under low-fat feeding conditions, predominantly by increasing hepatic fatty acid oxidation, whereas supplementation with omega-3 fatty acids slightly increases liver-fat content and attenuates the liver-fat-depleting effect of exercise. It is noteworthy that omega-3 fatty acid supplementation in this study accounted for only 3% of total dietary energy, whereas in several previous studies showing that omega-3 fatty acids reduce liver fat the supplement was administered at much greater doses. Research presented and reviewed in this special issue not only highlights the independent effects of exercise and diet on liver fat accumulation but also, more importantly, raises the intriguing possibility of interactive effects between exercise and diet on the mechanisms regulating liver fat accretion and depletion. It seems that several dietary factors are able to either augment or attenuate the intrahepatic triglyceride-depleting effect of exercise

The barec of "Piani del Monte Avaro" (Bergamo, Italy)

This article outlines some archaeoastronomical results about an Iron Age site gained during the "Practical Archeoastronomy Course" held the 24th and 25th of June 2017 by Prof. Adriano Gaspani. The Iron Age settlement is called "Barec dei Piani del Monte Avaro". On it where found a closed enclosure of stones formed by an elliptical drywall inside which there are some megalithic structures: a monolith on a lithic platform, another monolith on which was placed on purpose a big rock with a perfectly vertical vein of white quartz oriented astronomically in accordance with the megalithic structure. At the top of the barec there is a large erratic monolith that overhangs all the stones of the drywall. The dry stone enclosure was found to be contemporary to monolithic structures. Within the enclosure lie, in the lower area, the remainders of a probable hut bottom. The site was active during the 6th century BC and the people that most likely attended to it was the celtic tribe of the Orobi who belonged, as well as all the tribes spread in the area now known as Lombardy (located between 45 deg and 46 deg North geographical latitude) to the Golasecca Culture. This civilization dates back to the first part of Iron Age and derives from the Canegrate culture of the 13th century BC which in turn is linked to the ancient culture of Halstatt, the oldest Celts lived in Northern Europe. The results of this astronomical survey are the detection of three alignments directed toward important directions, associated with the rising and the setting of the Moon at the southern extreme standstill, that proved this complex to be a Moon Sanctuary

Protective role of adiponectin on endothelial dysfunction induced by AGEs: a clinical and experimental approach

OBJECTIVE: Obesity is characterized by low levels of adiponectin, an adipocytes derived hormone, and by an inflammatory component. Endothelial dysfunction is often found in overweight/obesity, diabetes, and atherosclerosis. Advanced glycation end products (AGEs) induce endothelial dysfunction and are linked to diabetes and increased atherogenicity and inflammation. The aim of the study was to investigate the possible link between adiponectin and N(epsilon)-(carboxymethyl) lysine (CML), the predominant adduct of circulating AGEs in overweight patients, and, in an in vitro model, to test the hypothesis that adiponectin acts as modulator of endothelial dysfunction, induced by AGEs. RESULTS: In 108 overweight patients, plasma levels of CML correlated inversely with adiponectin levels. Pre-incubation of human vein endothelial cells (HUVECs) with physiological concentrations of adiponectin, followed by stimulation with AGEs, reduced vascular adhesion molecule-1 (VCAM-1) and E-selectin expression, as assessed by surface enzyme immunoassay. CONCLUSIONS: Taken together, these findings demonstrate an inverse correlation between CML and adiponectin levels in overweight patients and a protective role of adiponectin on endothelial dysfunction induced by AGEs, suggesting its key role in the treatment of the vascular complications of obesity/metabolic syndrom

Effect of Oral Sebacic Acid on Postprandial Glycemia, Insulinemia, and Glucose Rate of Appearance in Type 2 Diabetes

Dicarboxylic acids are natural products with the potential of being an alternate dietary source of energy. We aimed to evaluate the effect of sebacic acid (a 10-carbon dicarboxylic acid; C10) ingestion on postprandial glycemia and glucose rate of appearance (Ra) in healthy and type 2 diabetic subjects. Furthermore, the effect of C10 on insulin-mediated glucose uptake and on GLUT4 expression was assessed in L6 muscle cells in vitro

Genetic reconstitution of the human Adenovirus type 2 temperature-sensitive 1 mutant defective in endosomal escape

Human Adenoviruses infect the upper and lower respiratory tracts, the urinary and digestive tracts, lymphoid systems and heart, and give rise to epidemic conjunctivitis. More than 51 human serotypes have been identified to-date, and classified into 6 species A-F. The species C Adenoviruses Ad2 and Ad5 (Ad2/5) cause upper and lower respiratory disease, but how viral structure relates to the selection of particular infectious uptake pathways is not known. An adenovirus mutant, Ad2-ts1 had been isolated upon chemical mutagenesis in the past, and shown to have unprocessed capsid proteins. Ad2-ts1 fails to package the viral protease L3/p23, and Ad2-ts1 virions do not efficiently escape from endosomes. It had been suggested that the C22187T point mutation leading to the substitution of the conserved proline 137 to leucine (P137L) in the L3/p23 protease was at least in part responsible for this phenotype. To clarify if the C22187T mutation is necessary and sufficient for the Ad2-ts1 phenotype, we sequenced the genes encoding the structural proteins of Ad2-ts1, and confirmed that the Ad2-ts1 DNA carries the point mutation C22187T. Introduction of C22187T to the wild-type Ad2 genome in a bacterial artificial chromosome (Ad2-BAC) gave Ad2-BAC46 virions with the full Ad2-ts1 phenotype. Reversion of Ad2-BAC46 gave wild-type Ad2 particles indicating that P137L is necessary and sufficient for the Ad2-ts1 phenotype. The kinetics of Ad2-ts1 uptake into cells were comparable to Ad2 suggesting similar endocytic uptake mechanisms. Surprisingly, infectious Ad2 or Ad5 but not Ad2-ts1 uptake required CALM (clathrin assembly lymphoid myeloid protein), which controls clathrin-mediated endocytosis and membrane transport between endosomes and the trans-Golgi-network. The data show that no other mutations than P137L in the viral protease are necessary to give rise to particles that are defective in capsid processing and endosomal escape. This provides a basis for genetic analyses of distinct host requirements for Ad endocytosis and escape from endosomes

Bariatric surgery as a treatment of type 2 diabetes

Obesity has reached epidemic proportions, predisposing to the development of type 2 diabetes and cardiovascular diseases. Weight loss is a major objective, although often difficult to achieve with medical treatments. Bariatric surgery has proven its efficacy in obtaining marked and sustained weight loss, and is also associated with a significant improvement in insulin resistance, beta cell function, lipid metabolism, blood pressure and even diabetes remission. We examined the long-term effect of Roux-en-Y gastric bypass (RYGB, a predominantly restrictive procedure) in a patient with uncontrolled type 2 diabetes. One year after surgery, the patient had lost 30% of initial weight with a significant improvement in blood pressure, withdrawal of cholesterol-lowering therapy, complete remission of diabetes