Defects In Glucose Metabolism Research Articles

Olanzapine effects on body composition, food preference, glucose metabolism and insulin sensitivity in the rat

The atypical antipsychotic drug olanzapine induces weight gain and defects in glucose metabolism in patients. Using a rat model we investigated the effects of acute and long term olanzapine treatment on weight gain, food preference and glucose metabolism. Olanzapine treated rats fed a chow diet grew more slowly than vehicle controls but olanzapine treated animals fed a high fat/sugar diet grew faster than control animals on the same diet. These changes in weight were paralleled by changes in fat mass. Olanzapine also induced a strong preference for a high fat/high sugar diet. Acute exposure to olanzapine rapidly induced severe impairments of glucose tolerance and increased insulin secretion but did not impair insulin tolerance. These results indicate the defect in glucose metabolism induced by acute olanzapine treatment was most likely due to increased hepatic glucose output associated with a reduction in active GLP-1 levels and correspondingly high glucagon levels.

ENPP1 Affects Insulin Action and Secretion: Evidences from In Vitro Studies

The aim of this study was to deeper investigate the mechanisms through which ENPP1, a negative modulator of insulin receptor (IR) activation, plays a role on insulin signaling, insulin secretion and eventually glucose metabolism. ENPP1 cDNA (carrying either K121 or Q121 variant) was transfected in HepG2 liver-, L6 skeletal muscle- and INS1E beta-cells. Insulin-induced IR-autophosphorylation (HepG2, L6, INS1E), Akt-Ser473, ERK1/2-Thr202/Tyr204 and GSK3-beta Ser9 phosphorylation (HepG2, L6), PEPCK mRNA levels (HepG2) and 2-deoxy-D-glucose uptake (L6) was studied. GLUT 4 mRNA (L6), insulin secretion and caspase-3 activation (INS1E) were also investigated. Insulin-induced IR-autophosphorylation was decreased in HepG2-K, L6-K, INS1E-K (20%, 52% and 11% reduction vs. untransfected cells) and twice as much in HepG2-Q, L6-Q, INS1E-Q (44%, 92% and 30%). Similar data were obtained with Akt-Ser473, ERK1/2-Thr202/Tyr204 and GSK3-beta Ser9 in HepG2 and L6. Insulin-induced reduction of PEPCK mRNA was progressively lower in untransfected, HepG2-K and HepG2-Q cells (65%, 54%, 23%). Insulin-induced glucose uptake in untransfected L6 (60% increase over basal), was totally abolished in L6-K and L6-Q cells. GLUT 4 mRNA was slightly reduced in L6-K and twice as much in L6-Q (13% and 25% reduction vs. untransfected cells). Glucose-induced insulin secretion was 60% reduced in INS1E-K and almost abolished in INS1E-Q. Serum deficiency activated caspase-3 by two, three and four folds in untransfected INS1E, INS1E-K and INS1E-Q. Glyburide-induced insulin secretion was reduced by 50% in isolated human islets from homozygous QQ donors as compared to those from KK and KQ individuals. Our data clearly indicate that ENPP1, especially when the Q121 variant is operating, affects insulin signaling and glucose metabolism in skeletal muscle- and liver-cells and both function and survival of insulin secreting beta-cells, thus representing a strong pathogenic factor predisposing to insulin resistance, defective insulin secretion and glucose metabolism abnormalities.

T-Lymphocyte Responses to Intestinally Absorbed Antigens Can Contribute to Adipose Tissue Inflammation and Glucose Intolerance during High Fat Feeding

BackgroundObesity is associated with inflammation of visceral adipose tissues, which increases the risk for insulin resistance. Animal models suggest that T-lymphocyte infiltration is an important early step, although it is unclear why these cells are attracted. We have recently demonstrated that dietary triglycerides, major components of high fat diets, promote intestinal absorption of a protein antigen (ovalbumin, “OVA”). The antigen was partly transported on chylomicrons, which are prominently cleared in adipose tissues. We hypothesized that intestinally absorbed gut antigens may cause T-lymphocyte associated inflammation in adipose tissue.Methodology/Principal FindingsTriglyceride absorption promoted intestinal absorption of OVA into adipose tissue, in a chylomicron-dependent manner. Absorption tended to be higher in mesenteric than subcutaneous adipose tissue, and was lowest in gonadal tissue. OVA immunoreactivity was detected in stromal vascular cells, including endothelial cells. In OVA-sensitized mice, OVA feeding caused marked accumulation of CD3+ and osteopontin+ cells in mesenteric adipose tissue. The accumulating T-lymphocytes were mainly CD4+. As expected, high-fat (60% kCal) diets promoted mesenteric adipose tissue inflammation compared to low-fat diets (10% Kcal), as reflected by increased expression of osteopontin and interferon-gamma. Immune responses to dietary OVA further increased diet-induced osteopontin and interferon-gamma expression in mesenteric adipose. Inflammatory gene expression in subcutaneous tissue did not respond significantly to OVA or dietary fat content. Lastly, whereas OVA responses did not significantly affect bodyweight or adiposity, they significantly impaired glucose tolerance.Conclusions/SignificanceOur results suggest that loss or lack of immunological tolerance to intestinally absorbed T-lymphocyte antigens can contribute to mesenteric adipose tissue inflammation and defective glucose metabolism during high-fat dieting.

Zebrafish fat-free, a novel Arf effector, regulates phospholipase D to mediate lipid and glucose metabolism

Zebrafish fat-free mutants ( ffr) exhibit defective intestinal lipid metabolism and fat-free protein (Ffr) is involved in Golgi-related vesicular trafficking. In this study, we show that ffr mutants also display defective glucose metabolism. Using microarray and real-time PCR, we found that a ffr mutant with a nonsense mutation exhibits increased transcript level of ADP-ribosylation factor gene ( arfs). Further analysis indicated that Ffr contains a putative Arf binding motif and can bind GTP-bound Arfs. In addition, ffr exhibited increased transcript and activity levels of the Arf downstream effector phospholipase D (PLD). Inhibition of PLD partially restored lipid and glucose metabolism in ffr, suggesting that Ffr is involved in a pathway regulating PLD activity by regulating Arfs. We propose that local over-production of phosphatidic acid (PA) by excess PLD promotes membrane curvature, which affects Golgi membrane structure and secretory processes, contributing to impairment of lipid and glucose metabolism.

Occult impaired glucose regulation in patients with atherosclerosis is associated to the number of affected vascular districts and inflammation

ObjectiveThe role of inflammatory adipokines has clear mechanistic effects in the promotion of both DM2 and cardiovascular diseases (CVDs), but it is unknown to what extent atherosclerosis-related inflammation might promote defects of glucose metabolism. The purpose of this study was to test the hypothesis that in subjects with atherosclerotic vascular disease and no previous medical record of type 2 diabetes mellitus (DM2), the diagnosis of occult impaired glucose regulation (IGR) is related to the severity of atherosclerosis, measured as the single or combined presence of an history of coronary artery disease (CAD), carotid atherosclerosis (Car-ATS) and peripheral artery disease (PAD). MethodsIn a population of 551 subjects (440 men and 111 women) with a previous history of atherosclerosis, we investigated the presence of IGR (including both impaired glucose tolerance and DM2). To test the correlation between conventional and non-conventional risk factors for cardiovascular disease and diabetes we used logistic and regression analysis models. ResultsIGR was more prevalent in patients with a documented vascular disease in two or three vessel districts compared with patients with only one symptomatic district (p=0.016). Among classic risk factors we found that waist circumference was correlated neither to IGR nor to symptomatic vascular disease extension. By contrast, adiponectin level was independently associated to vascular and glucose regulation status (p=0.012 and p<0.001, respectively). ConclusionIn subjects affected by atherosclerotic vascular diseases, the presence of impaired glucose regulation is associated to the number of vascular districts affected and to a reduced adiponectin level.

Clear Cell Change in Eccrine Glands Is Not Associated With Diabetes

The significance of clear cell change (clear reticulated cytoplasmic change) in the secretory portion of eccrine glands remains an enigma. It has been postulated to be a product of defective cellular glucose metabolism and potentially a predictor of diabetes. A series of 61 specimens from 38 patients were assessed to establish any demographic, seasonal, or metabolic associations. Sixty-one specimens from 38 patients with eccrine clear cell changes were identified prospectively by one of the authors (T.W.B.). Each specimen was stratified by site, age, sex, and season. For each patient, the general practitioner was contacted and diabetes status was ascertained. This was possible in 34 of 38 patients. Fifty routine consecutive cases from the archive in both summer and winter were studied for possible clear cell changes, looking for any seasonal variance. No clear association between the presence of eccrine clear cell change and any demographic or seasonal pattern was found. Specifically, there did not seem to be any significant association between diabetes and this histological finding. The prevalence of diabetes in cases with eccrine clear cell change was similar to the background population prevalence of diabetes in Australia (7.9% vs. 7.4%). The incidence of this finding is approximately 1 case in 189 specimens (0.5%) examined in this practice. Clear cell change within the secretory portion of eccrine glands seems to be an incidental finding, with no clear clinicopathological implication. In particular, there does not seem to be any association with diabetes.

Nutrient Stress Activates Inflammation and Reduces Glucose Metabolism by Suppressing AMP-Activated Protein Kinase in the Heart

OBJECTIVEHeart failure is a major cause of mortality in diabetes and may be causally associated with altered metabolism. Recent reports indicate a role of inflammation in peripheral insulin resistance, but the impact of inflammation on cardiac metabolism is unknown. We investigated the effects of diet-induced obesity on cardiac inflammation and glucose metabolism in mice.RESEARCH DESIGN AND METHODSMale C57BL/6 mice were fed a high-fat diet (HFD) for 6 weeks, and heart samples were taken to measure insulin sensitivity, glucose metabolism, and inflammation. Heart samples were also examined following acute interleukin (IL)-6 or lipid infusion in C57BL/6 mice and in IL-6 knockout mice following an HFD.RESULTSDiet-induced obesity reduced cardiac glucose metabolism, GLUT, and AMP-activated protein kinase (AMPK) levels, and this was associated with increased levels of macrophages, toll-like receptor 4, suppressor of cytokine signaling 3 (SOCS3), and cytokines in heart. Acute physiological elevation of IL-6 suppressed glucose metabolism and caused insulin resistance by increasing SOCS3 and via SOCS3-mediated inhibition of insulin receptor substrate (IRS)-1 and possibly AMPK in heart. Diet-induced inflammation and defects in glucose metabolism were attenuated in IL-6 knockout mice, implicating the role of IL-6 in obesity-associated cardiac inflammation. Acute lipid infusion caused inflammation and raised local levels of macrophages, C-C motif chemokine receptor 2, SOCS3, and cytokines in heart. Lipid-induced cardiac inflammation suppressed AMPK, suggesting the role of lipid as a nutrient stress triggering inflammation.CONCLUSIONSOur findings that nutrient stress activates cardiac inflammation and that IL-6 suppresses myocardial glucose metabolism via inhibition of AMPK and IRS-1 underscore the important role of inflammation in the pathogenesis of diabetic heart.

Impaired Insulin Exocytosis in Neural Cell Adhesion Molecule−/− Mice Due to Defective Reorganization of the Submembrane F-Actin Network

The neural cell adhesion molecule (NCAM) is required for cell type segregation during pancreatic islet organogenesis. We have investigated the functional consequences of ablating NCAM on pancreatic beta-cell function. In vivo, NCAM(-/-) mice exhibit impaired glucose tolerance and basal hyperinsulinemia. Insulin secretion from isolated NCAM(-/-) islets is enhanced at glucose concentrations below 15 mM but inhibited at higher concentrations. Glucagon secretion from pancreatic alpha-cells evoked by low glucose was also severely impaired in NCAM(-/-) islets. The diminution of insulin secretion is not attributable to defective glucose metabolism or glucose sensing (documented as glucose-induced changes in intracellular Ca(2+) and K(ATP)-channel activity). Resting K(ATP) conductance was lower in NCAM(-/-) beta-cells than wild-type cells, and this difference was abolished when F-actin was disrupted by cytochalasin D (1 muM). In wild-type beta-cells, the submembrane actin network disassembles within 10 min during glucose stimulation (30 mM), an effect not seen in NCAM(-/-) beta-cells. Cytochalasin D eliminated this difference and normalized insulin and glucagon secretion in NCAM(-/-) islets. Capacitance measurements of exocytosis indicate that replenishment of the readily releasable granule pool is suppressed in NCAM(-/-) alpha- and beta-cells. Our data suggest that remodeling of the submembrane actin network is critical to normal glucose regulation of both insulin and glucagon secretion.

Deletion of the von Hippel-Lindau gene in pancreatic beta cells impairs glucose homeostasis in mice.

Defective insulin secretion in response to glucose is an important component of the beta cell dysfunction seen in type 2 diabetes. As mitochondrial oxidative phosphorylation plays a key role in glucose-stimulated insulin secretion (GSIS), oxygen-sensing pathways may modulate insulin release. The von Hippel-Lindau (VHL) protein controls the degradation of hypoxia-inducible factor (HIF) to coordinate cellular and organismal responses to altered oxygenation. To determine the role of this pathway in controlling glucose-stimulated insulin release from pancreatic beta cells, we generated mice lacking Vhl in pancreatic beta cells (betaVhlKO mice) and mice lacking Vhl in the pancreas (PVhlKO mice). Both mouse strains developed glucose intolerance with impaired insulin secretion. Furthermore, deletion of Vhl in beta cells or the pancreas altered expression of genes involved in beta cell function, including those involved in glucose transport and glycolysis, and isolated betaVhlKO and PVhlKO islets displayed impaired glucose uptake and defective glucose metabolism. The abnormal glucose homeostasis was dependent on upregulation of Hif-1alpha expression, and deletion of Hif1a in Vhl-deficient beta cells restored GSIS. Consistent with this, expression of activated Hif-1alpha in a mouse beta cell line impaired GSIS. These data suggest that VHL/HIF oxygen-sensing mechanisms play a critical role in glucose homeostasis and that activation of this pathway in response to decreased islet oxygenation may contribute to beta cell dysfunction.

Genetic interaction network of the Saccharomyces cerevisiae type 1 phosphatase Glc7

BackgroundProtein kinases and phosphatases regulate protein phosphorylation, a critical means of modulating protein function, stability and localization. The identification of functional networks for protein phosphatases has been slow due to their redundant nature and the lack of large-scale analyses. We hypothesized that a genome-scale analysis of genetic interactions using the Synthetic Genetic Array could reveal protein phosphatase functional networks. We apply this approach to the conserved type 1 protein phosphatase Glc7, which regulates numerous cellular processes in budding yeast.ResultsWe created a novel glc7 catalytic mutant (glc7-E101Q). Phenotypic analysis indicates that this novel allele exhibits slow growth and defects in glucose metabolism but normal cell cycle progression and chromosome segregation. This suggests that glc7-E101Q is a hypomorphic glc7 mutant. Synthetic Genetic Array analysis of glc7-E101Q revealed a broad network of 245 synthetic sick/lethal interactions reflecting that many processes are required when Glc7 function is compromised such as histone modification, chromosome segregation and cytokinesis, nutrient sensing and DNA damage. In addition, mitochondrial activity and inheritance and lipid metabolism were identified as new processes involved in buffering Glc7 function. An interaction network among 95 genes genetically interacting with GLC7 was constructed by integration of genetic and physical interaction data. The obtained network has a modular architecture, and the interconnection among the modules reflects the cooperation of the processes buffering Glc7 function.ConclusionWe found 245 genes required for the normal growth of the glc7-E101Q mutant. Functional grouping of these genes and analysis of their physical and genetic interaction patterns bring new information on Glc7-regulated processes.

Adiponectin isoforms are not associated with the severity of coronary atherosclerosis but with undiagnosed diabetes in patients affected by stable CAD

Background and aims Total adiponectin is emerging as an independent risk factor for cardiovascular diseases, but the role of adiponectin isoforms in coronary artery disease (CAD) is still unknown. We investigated the role of adiponectin isoforms with respect to the severity of coronary disease and to the presence of undiagnosed diabetes in patients with CAD. Methods and results We recruited 205 CAD patients, all living in the central area of Italy, with a history of a previous myocardial infarction but apparently not affected by type 2 diabetes (DM2). We compared the CAD patients to a control population ( n = 100) matched for age, sex, BMI and cardiovascular risk factors, but without overt diabetes and cardiovascular disease. In all patients we measured Total Adiponectin (Tot-Ad) and its isoforms, metabolic, pro- and anti-inflammatory markers and we performed an oral glucose tolerance test (OGTT). CAD patients underwent a coronary angiography and/or coronary multi-slice computed tomography. Based on the severity of CAD they were divided into mono-vessel versus multi-vessel patients. Tot-Ad levels and its isoforms were comparable in patients with mono-vessel versus multi-vessel CAD. After the OGTT, in CAD patients, the results showed that 19% of patients were affected by unknown DM2, 36.1% by unknown impaired glucose tolerance (IGT), and only 43.9% were truly normoglycemic (NGT). Low levels of high molecular weight-adiponectin (HMW-Ad) were significantly associated with undiagnosed IGT or DM2 status ( p < 0.01). Conclusions In our cohort of CAD patients, Tot-Ad and its isoforms do not correlate with severity of CAD, but with undiagnosed defects of glucose metabolism.

AMP-activated Protein Kinase and p38 MAPK Activate O-GlcNAcylation of Neuronal Proteins during Glucose Deprivation

We have demonstrated previously that a wide array of stress signals induces O-GlcNAc transferase (OGT) expression and increases O-GlcNAcylation of many intracellular proteins, a response that is critical for cell survival. Here, we describe a mechanism by which glucose deprivation induces OGT expression and activity in Neuro-2a neuroblastoma cells. Glucose deprivation increases OGT mRNA and protein expression in an AMP-activated protein kinase-dependent manner, whereas OGT enzymatic activity is regulated in a p38 MAPK-dependent manner. OGT is not phosphorylated by p38, but rather it interacts directly with p38 through its C terminus; this interaction increases with p38 activation during glucose deprivation. Surprisingly, the catalytic activity of OGT, as measured toward peptide substrates, is not altered by glucose deprivation. Instead, p38 regulates OGT activity within the cell by recruiting it to specific targets, including neurofilament H. Neurofilament H is O-GlcNAcylated during glucose deprivation in a p38-dependent manner. Interestingly, neurofilament H solubility is increased by glucose deprivation in an O-GlcNAc-dependent manner, suggesting that O-GlcNAcylation of neurofilament H regulates its disassembly from filaments. Not only do these data help to reveal how OGT is regulated by stress, but these findings also describe a possible mechanism by which defective brain glucose metabolism, as found in aging and ischemia, may directly affect axonal structure.

The implication of proinflammatory cytokines in type 2 diabetes

The incidence of type 2 diabetes (T2D) is rapidly expanding. Some of the more obvious pathologies associated with it include: defective glucose metabolism, obesity, cardiovascular disease and an inability to mount an effective immune response to infection by certain pathogenic organisms, leading to sepsis and death. A common tie linking these seemingly disparate complications is chronic inflammation. Today we know that inflammation is regulated locally and systemically by numerous biochemical signals. One of the most important of these signals is a class of molecules called cytokines. Cytokines can be generally classified as proinflammatory or anti-inflammatory and allow an organism to respond rapidly to an immune challenge by coordinating an appropriate immune response. In T2D, the balance between proinflammatory and anti-inflammatory cytokines is shifted toward proinflammation, potentially causing or exacerbating the health complications found in T2D. Over-nutrition has been shown to trigger the innate immune system but activation of the innate immune system, itself, induces hyperglycemia and insulin resistance. In all likelihood, diabetes and chronic inflammation are inseparable and act as a reciprocal feed-forward loop.

Considerations for the Pharmacological Treatment of Diabetes in Older Adults

More than 20 million people in America are estimated to have diabetes, with the prevalence in adults > 60 years of age now > 20%.1 The increased prevalence in older adults may be the result of several factors, including physiological changes in glucose metabolism that occur with aging, reduced physical activity, and increased prevalence of the metabolic syndrome with aging. As the proportion of the population of older adults increases with the aging of the Baby Boomer generation, so will the proportion of those who are older and have diabetes. This older population will also be faced with increasing prevalence of many other conditions, such as arthritis and high blood pressure, underscoring the need for effective management of diabetes in this population to optimize health. This article reviews the normal physiological and pharmacodynamic changes of aging and relates this information to the process of making optimal therapeutic decisions for the pharmacological treatment of diabetes in older adults. The evidence basis for treatment of older adults, or lack thereof, is discussed, and a general approach to therapy is suggested. Aging is associated with defects in glucose metabolism. In healthy older adults, glucose metabolism is characterized by reduced non–insulin-mediated glucose uptake under basal conditions, with normal response during hyperglycemia compared with younger adults.2 In older adults with diabetes, the defect in basal glucose uptake is further accentuated, and there is a weaker uptake response during hyperglycemia.3 In addition to this effect on basal conditions, glucose-stimulated insulin response is diminished in older adults with diabetes compared with nondiabetic younger adults and nondiabetic older adults or those with impaired glucose tolerance.4 β-Cell sensitivity to the incretin hormones may also be reduced with aging, and delayed gastric emptying or gastroparesis is frequently reported for older adults with diabetes.5,6 …

Characterization of hepatic and brain metabolism in young adults with glycogen storage disease type 1: a magnetic resonance spectroscopy study

In glycogen storage disease type 1 (GSD1), children present with severe hypoglycemia, whereas the propensity for hypoglycemia may decrease with age in these patients. It was the aim of this study to elucidate the mechanisms for milder hypoglycemia symptoms in young adult GSD1 patients. Four patients with GSD1 [body mass index (BMI) 23.2 +/- 6.3 kg/m, age 21.3 +/- 2.9 yr] and four healthy controls matched for BMI (23.1 +/- 3.0 kg/m) and age (24.0 +/- 3.1 yr) were studied. Combined (1)H/(31)P nuclear magnetic resonance spectroscopy (NMRS) was used to assess brain metabolism. Before and after administration of 1 mg glucagon, endogenous glucose production (EGP) was measured with d-[6,6-(2)H(2)]glucose and hepatic glucose metabolism was examined by (1)H/(13)C/(31)P NMRS. At baseline, GSD1 patients exhibited significantly lower rates of EGP (0.53 +/- 0.04 vs. 1.74 +/- 0.03 mg.kg(-1).min(-1); P < 0.01) but an increased intrahepatic glycogen (502 +/- 89 vs. 236 +/- 11 mmol/l; P = 0.05) and lipid content (16.3 +/- 1.1 vs. 1.4 +/- 0.4%; P < 0.001). After glucagon challenge, EGP did not change in GSD1 patients (0.53 +/- 0.04 vs. 0.59 +/- 0.24 mg.kg(-1).min(-1); P = not significant) but increased in healthy controls (1.74 +/- 0.03 vs. 3.95 +/- 1.34; P < 0.0001). In GSD1 patients, we found an exaggerated increase of intrahepatic phosphomonoesters (0.23 +/- 0.08 vs. 0.86 +/- 0.19 arbitrary units; P < 0.001), whereas inorganic phosphate decreased (0.36 +/- 0.08 vs. -0.43 +/- 0.17 arbitrary units; P < 0.01). Intracerebral ratios of glucose and lactate to creatine were higher in GSD1 patients (P < 0.05 vs. control). Therefore, hepatic defects of glucose metabolism persist in young adult GSD1 patients. Upregulation of the glucose and lactate transport at the blood-brain barrier could be responsible for the amelioration of hypoglycemic symptoms.

Causes and consequences of hyperglycemia in critical illness

This article reviews recent epidemiologic and intervention studies addressing the impact of hyperglycemia on morbidity and mortality in critically ill patients. It also discusses a growing body of literature examining why elevated blood glucose occurs in hospitalized patients without previously recognized diabetes. Hyperglycemia is highly prevalent in the intensive care unit. Numerous observational studies have demonstrated the association between hyperglycemia and adverse outcomes, independent of pre-existing diabetes. Intervention trials of insulin therapy are limited but overall demonstrate that glucose lowering significantly improves outcomes. The ideal target for blood glucose and the population that would benefit most from intervention remain controversial. Less frequently studied than the consequences, the causes of hyperglycemia occurring during critical illness remain unclear. Although glucose abnormalities in hospitalized patients have traditionally been explained by mediators of stress, a growing body of evidence has examined whether underlying defects in glucose metabolism may also be important contributors. In general, evidence suggests that hyperglycemia is a potentially correctable abnormality that has deleterious effects in critically ill individuals. Hyperglycemic patients without previously recognized diabetes appear to be particularly vulnerable, and thus further examination of the mechanisms underlying the development of elevated blood glucose is warranted.

Regulation of FAT/CD36 mRNA gene expression by long chain fatty acids in the differentiated 3T3-L1 cells

Defects in fatty acid translocase (FAT/CD36) have been identified as a major factor in insulin resistance and defective fatty acid and glucose metabolism. Therefore, understanding of the regulation of FAT/CD36 expression and function is important for a potential therapeutic target for type II diabetes. We differentiated 3T3-L1 preadipocytes into matured adipocytes and examined the roles of insulin and long chain fatty acids on FAT/CD36 expression and function. Our results indicate that FAT/CD36 mRNA expression was not detected at preadipocyte but was significantly increased at matured adipocyte. In fully differentiated 3T3-L1 adipocytes, insulin significantly increased FAT/CD36 mRNA and protein expression in a dose dependent manner. The free fatty acid stearic acid reduced FAT/CD36 mRNA expression while the non-metabolizable free fatty acid alpha-bromopalmitate (2-BP) significantly increased FAT/CD36 mRNA and protein expression. Isoproterenol, in contrast, dose-dependently reduced FAT/CD36 mRNA expression and increased free fatty acid release. Mechanism analysis indicated that the effect of insulin and 2-BP on the FAT/CD36 mRNA gene expression may be mediated through activation of PPAR-gamma, suggesting that FAT/CD36 may have important implications in the pathophysiology of defective fatty acid metabolism.

Insulin Resistance and Metabolic Syndrome in Children of Parents with Diabetes Mellitus

The aim of this prospective study was to research features of insulin resistance and metabolic syndrome in offspring of diabetic parents and to find out whether there is a risk of developing type 2 diabetes mellitus (DM) in these children. Study participants were 30 children of parents with type 1 DM (DM1) (Group I) and 11 children of parents with type 2 DM (DM2) (Group II) who were being followed up in the Diabetes Department of Haseki Research and Training Hospital. The results were compared with a control group of 17 children in the same age group (Group III). There were no statistically significant differences between the Group I and the control group in fasting blood glucose, oral glucose tolerance test values, 1st 2nd and hour insulin, homeostasis model assessment (HOMA) values, body mass index (BMI), systolic and diastolic blood pressure, and lipid parameters, i.e. HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, total cholesterol, and triglycerides. Fasting, 1st and 2nd hour blood insulin levels, HOMA values, BMI, and systolic blood pressure values were significantly higher in Group II compared to the control group (p < 0.05). There were no statistically significant differences between Group II and the control group in lipid parameters, fasting blood glucose, OGTT values, or diastolic blood pressure. We conclude that in our population there is a tendency of insulin resistance and metabolic syndrome in the offspring of parents with DM2, and a risk for developing DM2. Thus, children of patients with DM2 should be followed up so as to recognize early metabolic defects of glucose metabolism and to plan effective preventive efforts to reduce cardiovascular and atherosclerotic risk factors.

Separately Inherited Defects in Insulin Exocytosis and β-Cell Glucose Metabolism Contribute to Type 2 Diabetes

The effects of genetic variation on molecular functions predisposing to type 2 diabetes are still largely unknown. Here, in a specifically designed diabetes model, we couple separate gene loci to mechanisms of beta-cell pathology. Niddm1i is a major glucose-controlling 16-Mb region in the diabetic GK rat that causes defective insulin secretion and corresponds to loci in humans and mice associated with type 2 diabetes. Generation of a series of congenic rat strains harboring different parts of GK-derived Niddm1i enabled fine mapping of this locus. Congenic strains carrying the GK genotype distally in Niddm1i displayed reduced insulin secretion in response to both glucose and high potassium, as well as decreased single-cell exocytosis. By contrast, a strain carrying the GK genotype proximally in Niddm1i exhibited both intact insulin release in response to high potassium and intact single-cell exocytosis, but insulin secretion was suppressed when stimulated by glucose. Islets from this strain also failed to respond to glucose by increasing the cellular ATP-to-ADP ratio. Changes in beta-cell mass did not contribute to the secretory defects. We conclude that the failure of insulin secretion in type 2 diabetes includes distinct functional defects in glucose metabolism and insulin exocytosis of the beta-cell and that their genetic fundaments are encoded by different loci within Niddm1i.

Idiopathic Complex Polysaccharide Storage Disease in an Abyssinian Cat

A glycogen storage disease affecting primarily the skeletal muscle and, to a lesser degree, the cardiac muscle, spinal cord, and brain was diagnosed in a 10-year-old neutered Abyssinian cat with a 4-year history of paresis progressing to acute paralysis. Microscopically, these tissues contained inclusions that were pale basophilic in hematoxylin and eosin-stained slides, diastase resistant, periodic acid-Schiff positive, and blue-to-almost black with iodine stain. By transmission electron microscopy, the inclusions consisted of cytosolic, usually sharply demarcated, nonmembrane-bound deposits of finely granular and filamentous material. On the basis of the structural and histochemical staining characteristics, the inclusions were believed to be aggregates of abnormally stored, unbranched glycogen. A defect in glucose metabolism is suspected to be the underlying pathologic process, but an exact cause remains elusive.