bluuebunny/crossref_metadata_2025 huggingface dataset:
Insulin-Independent Acute Restoration of Euglycemia Normalizes the Impaired Glucose Clearance During Exercise in Diabetic Dogs
Authors: Fisher Simon J , Lekas Michael , Shi Z Qing , Bilinski Debra , Carvalho George , Giacca Adria , Vranic Mladen
Published: September 2013

At rest and during exercise, chronic hyperglycemia, high free fatty acid (FFA) oxidation, and insulin deficiency in diabetes are well known to impair glucose clearance (metabolic clearance rate [MCR]). The effect of acute restoration of glycemia per se on MCR has been less well characterized. We therefore studied normal and alloxan-diabetic dogs both at rest and during exercise, as diabetic hyperglycemic or after acutely induced euglycemia (<160 min) generated by infusion of either insulin or phlorizin. Glucose uptake was similar under hyperglycemic and normoglycemic conditions both at rest and during exercise, indicating a precise balance between the mass effect of glucose and decreased MCR. Rest and exercise MCR was fourfold lower under conditions of hyperglycemia, but insulin-independent restoration of euglycemia improved basal MCR threefold and normalized MCR during exercise. High FFA turnover did not affect glucose uptake but was correlated with plasma lactate concentrations (r = 0.72, P < 0.001), suggesting that muscle fuel requirements are controlled by glucose oxidation and not uptake. We conclude that in alloxan-diabetic dogs, the impaired MCR may be an adaptive phenomenon because correction of hyperglycemia corrects MCR despite partial insulin deficiency and high FFA turnover. We speculate that constant glucose uptake despite hyperglycemia in diabetes may protect the muscle from excessive exposure to glucose.
Renal and Ocular Hemodynamic Effects of Insulin
Authors: Schmetterer Leopold , Müller Markus , Fasching Peter , Diepolder Carmen , Gallenkamp Antje , Zanaschka Gabriele , Findl Oliver , Strenn Karin , Mensik Christa , Tschernko Edda , Eichler Hans-Georg , Wolzt Michael
Published: September 2013

There is evidence that the vasodilator action of insulin is mediated by the release of nitric oxide (NO). We hypothesized that euglycemic hyperinsulinemia might increase renal and ocular blood flow, and that the vasodilator capacity of insulin might be NO-dependent. Euglycemic insulin clamps were performed in 10 healthy subjects. Sixty minutes after the start of insulin administration, an intravenous coinfusion of N-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthase, or of norepinephrine (NE), an endothelium-independent vasoconstrictor, was started. Renal plasma flow was measured by para-aminohippurate (PAH) clearance method. Ocular hemodynamics were assessed by laser interferometric measurement of fundus pulsations and Doppler sonographic measurement of blood flow velocity in the ophthalmic artery. Renal plasma flow and ocular fundus pulsations were increased by insulin, L-NMMA almost completely abolished the vasodilative effects of insulin, whereas the effects of combined infusion of insulin and NE were approximately the sum of the hemodynamic changes induced by each agent alone. The results show that during euglycemic hyperinsulinemia, renal and ocular blood flow are increased, which may be mediated either by a local vasodilator effect or a systemic increase in flow. The hemodynamic effects of insulin in the kidney and the eye are at least partially dependent on NO synthesis. Because the insulin plasma levels we obtained are in the high physiological range, it may be assumed that insulin plays a role in renal and ocular blood flow regulation.
Central Leptin Stimulates Corticosterone Secretion at the Onset of the Dark Phase
Authors: Dijk Gertjan van , Donahey Jamie C K , Thiele Todd E , Scheurink Anton J W , Steffens Anton B , Wilkinson Charles W , Tenenbaum Renata , Campfield L Arthur , Burn Paul , Seeley Randy J , Woods Stephen C
Published: September 2013

Leptin, a hormone secreted by adipose tissue in proportion to body adiposity, is proposed to be involved in the central nervous regulation of food intake and body weight. In addition, evidence is emerging that leptin regulates neuroendocrine and metabolic functions as well, presumably via its action in the central nervous system (CNS). To investigate this regulatory effect of leptin, we infused 3.5 μg of human leptin directly into the third cerebral ventricle (i3vt) of lean male Long-Evans rats, 90 min before the onset of their dark phase. Before and after infusion, blood samples were withdrawn through indwelling catheters for assessment of hormonal (plasma corticosterone, insulin, leptin), autonomic (plasma norepinephrine, epinephrine), and metabolic (plasma glucose) parameters. 13vt leptin caused an increase in plasma corticosterone and plasma leptin levels relative to the control condition. The effects of i3vt leptin on corticosterone secretion became particularly apparent after the onset of the dark phase. The results of the present study indicate that i3vt leptin stimulates the hypothalamo-pituitary-adrenal (HPA) axis, particularly when rats normally encounter their largest meals. These results are consistent with the possibility that high circulating leptin levels may underlie the increased activity of the HPA axis that is generally characteristic of human obesity and most animal models of obesity.
Supplemental myo-Inositol Prevents L-Fucose–Induced Diabetic Neuropathy
Authors: Sima Anders A F , Dunlap Joyce A , Davidson Eric P , Wiese Thomas J , Lightle Rhonda L F , Greene Douglas A , Yorek Mark A
Published: September 2013

Nerve myo-inositol depletion, which has been implicated in the pathogenesis of acute experimental diabetic neuropathy, can be reproduced in normal rats by feeding diets enriched in L-fucose, a competitive inhibitor of sodium-dependent myo-inositol transport. Previously, we reported that L-fucose feeding for 6 weeks reproduces the effect of experimental diabetes on nerve Na+-K+-ATPase activity and conduction velocity, which can be prevented by simultaneous dietary myo-inositol supplementation. To further validate this model of myo-inositol depletion, we examined the effects of long-term (24-week) L-fucose feeding and dietary myo-inositol supplementation on nerve Na+-K+-ATPase, nerve conduction velocity, and myelinated nerve fiber pathology. After 24 weeks of L-fucose enriched (10 or 20%) diets, nerve myo-inositol levels and Na+-K+-ATPase activity decreased significantly (P < 0.05) and were associated with a 25-30% reduction in nerve conduction velocity, all of which were completely prevented by 1% dietary myo-inositol. Twenty percent L-fucose diet resulted in significant axonal atrophy, paranodal swelling (P < 0.001), and paranodal demyelination (P < 0.005), without increasing Wallerian degeneration or nerve fiber loss, a pattern qualitatively similar to that seen in early murine diabetic neuropathy. Dietary myo-inositol supplementation prevented these structural changes and increased nodal remyelination, supporting a role of myo-inositol depletion in the genesis of early diabetic neuropathy. The L-fucose model system may therefore serve as an experimental tool to elucidate the pathophysiological role of isolated myo-inositol depletion and its consequences in the multifactorial pathogenesis of diabetic neuropathy.
Mapping Novel Pancreatic Islet Genes to Human Chromosomes
Authors: Ferrer Jorge , Wasson Jonathon , Schoor Kathleen D , Mueckler Michael , Donis-Keller Helen , Permutt M Alan
Published: September 2013

A strategy was developed to generate expressed sequence tags (ESTs) from human pancreatic islet gene products using differential display of mRNA. Screening of over 2,000 cDNA amplification products identified 42 cDNAs that were preferentially expressed in pancreatic islets relative to exocrine tissue. Public database analysis showed that 29 (69%) corresponded to novel genes, in contrast with only 66 of 250 (26.4%) cDNA clones randomly selected from a human islet library. Reverse transcription–polymerase chain reaction (RTPCR) and/or Northern analysis of RNA from multiple tissues confirmed that expression was enhanced in human islet cell RNA for 11 of 15 tested cDNAs. Sequencetagged sites developed from 19 islet cDNAs were used to map these genes to human chromosomes using a combination of monochromosomal somatic-cell hybrids, genome-wide radiation hybrids, and mega–yeast artificial chromosome analysis. These results indicate that this PCR-based cDNA selection strategy yields information on a distinct subset of pancreatic islet transcribed sequences, which complements ongoing human EST identification efforts based on random cDNA selection. These mapped ESTs may be used to assist in the positional cloning of diabetes susceptibility genes.
Differences Between Nisoldipine and Lisinopril on Glomerular Filtration Rates and Albuminuria in Hypertensive IDDM Patients With Diabetic Nephropathy During the First Year of Treatment
Authors: Rossing Peter , Tarnow Lise , Boelskifte Søren , Jensen Berit R , Nielsen Flemming S , Parving Hans-Henrik
Published: September 2013

Our objective was to compare the effect of a long-acting calcium antagonist (nisoldipine) versus an ACE inhibitor (lisinopril) on albuminuria, arterial blood pressure, and glomerular filtration rate (GFR) in hypertensive IDDM patients with diabetic nephropathy. We performed a 1-year, double-blind, doubledummy, randomized, controlled study comparing nisoldipine (20–40 mg once daily) with lisinopril (10–20 mg once daily) in 52 hypertensive IDDM subjects with diabetic nephropathy. Three patients dropped out, and results for the remaining 49 (25 nisoldipine, 24 lisinopril) are presented. Diuretics were required in 10 nisoldipineand 8 lisinopril-treated patients. Every 3 months, 24-h ambulatory blood pressure (TM2420, A&D, Tokyo, Japan) and albuminuria in three 24-h samples (enzyme immunoassay) were measured; GFR (51Cr-EDTA plasma clearance) was recorded every 6 months. Mean arterial blood pressure (24 h) was reduced from (mean ± SE) 108 ± 3 mmHg at baseline to 101 ± 2 in average during treatment in the lisinopril group and from 105 ± 2 to 103 ± 2 in the nisoldipine group (P = 0.06 comparing changes in the two groups). Albuminuria was reduced 47% (95% CI 21–65) in the lisinopril group versus an increase of 11% (−3 to 27) in the nisoldipine group (P = 0.001). Fractional albumin clearance was reduced 37% (95% CI 4–59%) in the lisinopril versus an increase of 35% (8–69%) in the nisoldipine group (P < 0.01). GFR decreased from 85 ± 5 ml · min−1 · 1.73 m−2 to 73 ± 5 in the lisinopril group and from 84 ± 6 to 80 ± 7 in the nisoldipine group (P < 0.05). The effect of study medication on albuminuria and GFR was independent of changes in systemic blood pressure and baseline variables in multiple regression analyses. In summary, lisinopril reduced albuminuria, but also GFR, to a greater extent than did nisoldipine in hypertensive IDDM patients with diabetic nephropathy during the 1st year of treatment. Longer follow-up is required to clarify whether these drugs have different renoprotective effects.
Elevated Islet Amyloid Pancreatic Polypeptide and Proinsulin in Lean Gestational Diabetes
Authors: Kautzky-Willer A , Thomaseth K , Ludvik B , Nowotny P , Rabensteiner D , Waldhäusl W , Pacini G , Prager R
Published: September 2013

Recent research indicates that islet amyloid pancreatic polypeptide (IAPP) might have a regulatory effect on (β-cell insulin processing and secretion. To study such interaction in more detail, IAPP secretion and kinetics and the serum concentrations of proinsulin were assessed both before and after delivery in lean pregnant women with gestational diabetes mellitus (GDM patients) in comparison to those with normal glucose tolerance (NGT) and to nonpregnant healthy lean (control) and obese insulin-resistant women during oral glucose tolerance tests. Kinetic analysis of IAPP was performed with mathematical modeling, providing indirect estimates of its secretion and fractional clearance. Total insulin secretion per 180 min was elevated by 30% in GDM patients (35 ± 3 pmol/1) versus control subjects (27 ± 1 pmol/1) (P < 0.05), but increased even more (190–250%) in obese insulin-resistant women, compared with all other groups (68 ± 7 pmol/l, P < 0.0005). Pregnancy induced a more marked fourfold increase in apparent total IAPP secretion rate (TIR) (GDM patients, 172 ± 31 pmol · 1−1 · 3 h−1; NGT subjects, 166 ± 31 pmol · 1−1 · 3 h−1; control subjects, 40 ± 1 pmol · 1−1 · 3 h−1) and a twofold rise in its fractional clearance versus control subjects (P < 0.01), whereas in GDM patients a 30% increase of IAPP secretion and a decreased clearance was found, compared with obese insulin-resistant women (TIR, 112 ± 14 pmol · 1−1 · 3 h−1). The increase in IAPP secretion in both pregnant groups was much higher than that of the insulin groups, resulting in a marked change of the IAPP-insulin cosecretion factor when compared with lean or obese nonpregnant women (P < 0.0005). Associated serum proinsulin and the postprandial (total divided by 180 min) proinsulinto-insulin ratio were greater in GDM patients versus NGT and control subjects (0.11 ± 0.01 vs. 0.07 ± 0.01 and 0.08 ± 0.01 pmol/1, P < 0.05), while the fasting proinsulin-to-insulin ratio was only increased in GDM patients versus control subjects (0.22 ± 0.03 vs. 0.13 ± 0.01 pmol/l, P < 0.05). After delivery, total IAPP secretion (52.4 ± 1.5 pmol/l) was completely normalized in the GDM group, as were the clearance rate and the IAPP-insulin cosecretion factor. Similarly, serum proinsulin concentrations returned to normal, whereas proinsulin-to-insulin ratios remained elevated. In conclusion, IAPP hypersecretion is characteristic for pregnancy and might partially decrease hyperinsulinemia in pregnancy by inhibiting insulin secretion. Increased proinsulin concentrations and a raised proinsulin-toinsulin ratio, which did not abate following delivery, are specific to GDM and might thus serve as its marker and potentially even identify subjects at high risk for the development of NIDDM.
Novel Mutations and a Mutational Hotspot in the M0DY3 Gene
Authors: Glucksmann M Alexandra , Lehto Markku , Tayber Olga , Scotti Susan , Berkemeier Lucy , Pulido Jacqueline C , Wu Ye , Nir Waan-Jeng , Fang Lei , Markel Paul , Munnelly Kevin D. , Goranson Jill , Orho Marju , Young Brian M , Whitacre Jennifer L , McMenimen Cheryl , Wantman Michael , Tuomi Tlinamija , Warram James , Forsblom Carol M , Carlsson Martin , Rosenzweig James , Kennedy Giulia , Duyk Geoffrey M , Krolewski Andrzej S , Groop Leif C , Thomas Jeffrey D
Published: September 2013

Maturity-onset diabetes of the young 3 (MODY3) is a type of NIDDM caused by mutations in the transcription factor hepatocyte nuclear factor-1a (HNF-1α) located on chromosome 12q. We have identified four novel HNF-1α missense mutations in M0DY3 families. In four additional and unrelated families, we observed an identical insertion mutation that had occurred in a polycytidine tract in exon 4. Among those families, one exhibited a de novo mutation at this location. We propose that instability of this sequence represents a general mutational mechanism in M0DY3. We observed no HNF-1α mutations among 86 unrelated late-onset diabetic patients with relative insulin deficiency. Hence mutations in this gene appear to be most strongly associated with early-onset diabetes.
Regulation of Insulin Secretion From Novel Engineered Insulinoma Cell Lines
Authors: Hohmeier Hans E , BeltrandelRio Hector , Clark Samuel A , Henkel-Rieger Rosemarie , Normington Karl , Newgard Christopher B
Published: September 2013

In the accompanying article, we describe the creation of novel cell lines derived from RIN 1046-38 rat insulinoma cells by stable transfection with combinations of genes encoding human insulin, GLUT2, and glucokinase. Herein we describe the regulation of insulin secretion and glucose metabolism in these new cell lines. A cell line (βG I/17) expressing only the human proinsulin transgene exhibits a clear increase in basal insulin production (measured in the absence of secretagogues) relative to parental RIN 1046-38 cells. βG I/17 cells engineered for high levels of GLUT2 expression and a twofold increase in glucokinase activity ([βG 49/206) or engineered for a 10-fold increase in glucokinase activity alone (βG 40/110) exhibit a 66% and 80% suppression in basal insulin secretion relative to βG I/17 cells, respectively. As a result, βG 49/206 and βG 40/110 cells exhibit potent insulin-secretory responses to glucose alone (6.1- and 7.6-fold, respectively) or to glucose plus isobutylmethylxanthine (10.8- and 15.1-fold, respectively) that are clearly larger than the corresponding responses of βG I/17 or parental RIN 1046-38 cells. βG 49/206 and βG 40/110 cells also exhibit a rapid and sustained response to glucose plus isobutylmethylxanthine in perifusion studies that is clearly larger in magnitude than that of the two control lines. Glucose dose-response studies show that both engineered and non-engineered lines respond maximally to submillimolar concentrations of glucose and that βG 49/206 cells are the most sensitive to low concentrations of the hexose, consistent with their clearly elevated rate of ]5-3H]glucose usage. Finally, 5-thioglucose, a potent inhibitor of low-Km hexokinases, most effectively normalizes glucose concentration dependence for insulin secretion in the cell line with highest glucokinase expression (βG 40/110). We conclude that GLUT2 and/or glucokinase expression imposes tight regulation of basal insulin secretion in cell lines that overexpress human proinsulin, allowing a marked improvement in the range of secretagogue responsiveness in such cells.
Preserved GLP-I Effects on Glycogen Synthase a Activity and Glucose Metabolism in Isolated Hepatocytes and Skeletal Muscle From Diabetic Rats
Authors: Morales Mónica , López-Delgado María I. , Alcántara Ana , Luque Miguel A , Clemente Felipe , Márquez Luis , Puente Jesús , Viñmbres Concepción , Malaisse Willy J , Wlanueva-Peñacarrillo María L , Valverde Isabel
Published: September 2013

To search if biological effects of GLP-I on glucose metabolism in extrapancreatic tissue are present in diabetic states, we have studied the action of GLP-I and insulin on glycogen-enzyme activity, glycogen synthesis, and glucose metabolism in isolated hepatocytes and soleus muscle from adult streptozotocin (STZ)- and neonatal STZ- treated diabetic rats. This work confirms the previously reported insulin-like effects of GLP-I on glucose metabolism in both muscle and liver tissue from normal rats (control). The present study extends those observations to the muscle and liver tissue of diabetic animals. In both muscle and liver tissue, the metabolism of d-glucose, in the absence of added peptides, was more severely affected in adult STZ (IDDM model) than in neonatal STZ (nSTZ; NIDDM model) rats, and the magnitude of hormonal effect on metabolic variables was lower in diabetic rats than in control rats, as a rule. Nevertheless, in liver and muscle tissue of diabetic rats, GLP-I was able to increase glycogen synthase activity, augment the net rate of d-[U-14C]glucose incorporation into glycogen, and increase d-[5-3H]glucose utilization, d-[U-14C]glucose oxidation, and lactate production. In conclusion, GLP-I exerts insulin-like effects on d-glucose metabolism in both muscle and liver tissue in IDDM or NIDDM animal models, and present observations reinforce the view that GLP-I may represent a most promising tool in the treatment of diabetic patients.
Effects of Differing Antecedent Hypoglycemia on Subsequent Counterregulation in Normal Humans
Authors: Davis Stephen N , Shavers Chris , Mosqueda-Garcia Rogelio , Costa Fernando
Published: September 2013

The aim of the study was to determine the effects of specific levels of antecedent hypoglycemia on subsequent autonomic, neuroendocrine, and metabolic counter-regulatory responses. Eight healthy, overnight-fasted male subjects were studied during 2-day protocols on four separate randomized occasions separated by at least 2 months. On day 1, insulin was infused at a rate of 9 pmol · kg−1 · min−1 and 2-h clamped euglycemia (plasma glucose 5.2 ± 0.2 mmol/l) or differing hypoglycemia (plasma glucose 3.9 ± 0.1, 3.3 ± 0.1, or 2.9 ± 0.1 mmol/l) was obtained during morning and afternoon. The next morning after an evening meal and 10-h overnight fast, each subject underwent a 2-h hyperin-sulinemic (9 pmol · kg−1 · min−1) hypoglycemic (2.9 ± 0.1 mmol/l) clamp study. Despite equivalent day 2 plasma glucose and insulin levels, differing levels of antecedent hypoglycemia produced specific blunting of subsequent counterregulatory responses. Day 1 hypoglycemia of 3.9 mmol/l resulted in significantly (P < 0.01) blunted epinephrine, muscle sympathetic nerve activity, and glucagon responses. Day 1 hypoglycemia of 3.3 mmol/l resulted in additional significant blunting (P < 0.01) of pancreatic polypeptide, norepinephrine, growth hormone, endogenous glucose production, and lipolytic responses. Deeper day 1 hypoglycemia of 2.9 mmol/l produced similar day 2 counterregulatory failure as day 1 hypoglycemia of 3.3 mmol/l. In summary, in healthy overnight-fasted men, mild antecedent hypoglycemia of 3.9 mmol/l significantly blunts sympathoadrenal and glucagon, but not other forms of neuroendocrine counterregulatory responses, to subsequent hypoglycemia. Antecedent hypoglycemia of 3.3 mmol/l resulted in additional significant blunting of all major neuroendocrine and metabolic responses to subsequent hypoglycemia. We conclude that in normal humans, there is a hierarchy of blunted counterregulatory responses that are determined by the depth of antecedent hypoglycemia.
Skeletal Muscle Myosin Heavy Chain Synthesis in Type 1 Diabetes
Authors: Charlton Michael R , Balagopal P , Nair K Sreekumaran
Published: September 2013

Although insulin's anticatabolic effect on protein metabolism in type 1 diabetes has been clearly shown to be related to the inhibition of protein breakdown, insulin's effect on muscle protein synthesis remains controversial. Cross-limb studies and measurements of synthesis rates of mixed muscle protein have yielded conflicting results. These measurements represent the mean synthesis of several muscle proteins and may miss changes in the synthesis rates of individual muscle proteins. We measured the fractional synthesis rates of myosin heavy chain (MHC), the principal muscle contractile protein, and mixed muscle protein (MMP) in six type 1 diabetic patients during insulin deprivation and insulin treatment. Comparisons were made with six healthy control subjects. Muscle biopsies were taken at 2 h and 8 h during a primed continuous infusion of l-[1- 13C]leucine. MHC was purified by a preparative continuous elution gel electrophoresis, and fractional synthesis rates were calculated. We found that in type 1 diabetic subjects, the fractional synthesis rates of MHC and MMP during insulin treatment are similar to those of control subjects. Acute insulin deprivation did not affect either the synthesis rate or the ratio of MHC to MMP in type 1 diabetic subjects. In the postabsorptive state, acute insulin deprivation has no effect on MHC or MMP synthesis in type 1 diabetic patients.
Evidence for Acute Stimulation of Fibrinogen Production by Glucagon in Humans
Authors: Tessari P , Iori E , Vettore M , Zanetti M , Kiwanuka E , Davanzo G , Barazzoni R
Published: September 2013

Fibrinogen, an acute-phase protein, and glucagon, a stress hormone, are often elevated in many conditions of physical and metabolic stress, including uncontrolled diabetes. However, the possible mechanisms for this association are poorly known. We have studied the acute effects of selective hyperglucagonemia (raised from ∼200 to ∼350 pg/ml for 3 h) on fibrinogen fractional secretion rate (FSR) in eight normal subjects during infusion of somatostatin and replacement doses of insulin, glucagon, and growth hormone. Fibrinogen FSR was evaluated by precursor-product relationships using either Phe (n = 8) or Leu (n = 2) tracers. Hyperglucagonemia did not change either plasma Phe or Tyr specific activity. After hyperglucagonemia, fibrinogen FSR increased by ∼65% (from 12.9 ± 3.6 to 21.5 ± 6.1% per day, P < 0.025) using plasma Phe specific activity as the precursor pool. FSR increased by ∼80% (from 16.6 ± 4.8 to 29.4 ± 8.8% per day, P < 0.025) if plasma Phe specific activity was corrected for the ketoisocaproate/Leu enrichment (or specific activity) ratio to obtain an approximate estimate of intrahepatic Phe specific activity. FSR increased by ∼60% when using plasma Tyr specific activity as precursor pool (n = 8) (P < 0.05), as well as when using the Leu tracer precursorproduct relationship (n = 2). In conclusion, selective hyperglucagonemia for ∼3 h acutely stimulated fibrinogen FSR using a Phe tracer method. Thus, glucagon may be involved in the increase of fibrinogen concentration and FSR observed under stressed or pathologic conditions.
Insulin Administration Enhances Growth of the β-Cell Mass in Streptozotocin-Treated Newborn Rats
Authors: Movassat Jamileh , Saulnier Catherine , Portha Bernard
Published: September 2013

We have previously reported that the damage caused by streptozotocin (STZ) administration to the β-cells in newborn rats was followed by spontaneous recovery from neonatal diabetes. Our present data indicate that STZ administration on the day of birth (day 1) reduced the total β-cell mass on day 4 to only 10% of the normal value and that after sucb damage, 27% of the corresponding normal β-cell mass was spontaneously regained on day 7. During days 4–7, the contribution of the predicted β-cell growth (due to the replication of preexisting differentiated β-cells) to the total β-cell growth represented only 56%. Therefore, recruitment of new β-cells from a precursor pool indeed represents a significant mechanism for β-cell regeneration after STZ during this period of life. Here, we report for the first time that 1) insulin therapy from days 2 to 4 did not significantly influence the occurrence of β-cell damage after STZ administration (total β-cell mass on day 4 was reduced to 12% of the normal value) and 2) insulin therapy from days 2 to 6 did improve the otherwise spontaneous β-cell regeneration, since on day 7 total β-cell mass was 44% of the corresponding normal β-cell mass. During days 4-7, the contribution of the predicted β-cell growth to the total β-cell growth represented only 32% in the insulin-treated STZ group. Finally the insulin-favored regeneration of the β-cells reflects both an increased replication from differentiated β-cells and an increased neogenesis from precursor/stem cells, with this last pathway being preferentially activated.
Myocardial Glucose Uptake in Patients with NIDDM and Stable Coronary Artery Disease
Authors: Mäki Maija , Nuutila Pirjo , Laine Hanna , Voipio-Pulkki Liisa-Maria , Haaparanta Merja , Solin Olof , Knuuti Juhani M
Published: September 2013

Whole body insulin resistance characterizes patients with NIDDM, but it is not known whether insulin also has impaired ability to stimulate myocardial glucose uptake (MGU) in these patients. This study was designed to evaluate MGU as measured by 2-[l8F]flu-oro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) in patients with NIDDM and stable coronary artery disease (CAD) under standardized metabolic conditions. Eight patients with NIDDM, 11 nondiabetic patients with CAD, and 9 healthy control subjects were enrolled in the study. MGU was quanti-tated in the normal myocardial regions with [18F]FDG and PET and the whole body glucose disposal by glucose-insulin clamp technique (serum insulin, ∼430 pmol/l). Plasma glucose and serum insulin concentrations were comparable in all groups during PET studies. The whole body glucose uptake was 45% lower in NIDDM patients (22 ± 9 pmol · min−1 · kg−1 body wt [mean ± SD]), compared with healthy control subjects (40 ± 17 pmol · min−1 · kg−1 body wt, P < 0.05). In CAD patients, whole body glucose uptake was 30 ± 9 pmol · min−1 · kg−1 body wt (NS between the other groups). MGU was similar in the normal segments in all three groups (69 ± 28 pmol · min−1 · 100 g−1 in NIDDM patients, 72 ± 17 pmol · min−1 · 100 g−1 in CAD patients, and 76 ± 10 pmol. min−1 · 100 g−1 in healthy control subjects, NS). No correlation was found between whole body glucose uptake and MGU. As studied by [18F]FDG PET under stable normoglycemic hyperinsulinemic conditions, MGU is not reduced in patients with NIDDM and CAD in spite of peripheral insulin resistance. These findings suggest that there is no significant defect in MGU in patients with NIDDM.
Elevated Free Fatty Acids Induce Uncoupling Protein 3 Expression in Muscle: A Potential Explanation for the Effect of Fasting
Authors: Weigle David S , Selfridge Leah E , Schwartz Michael W , Seeley Randy J , Cummings David E , Havel Peter J , Kuijper Joseph L , BeltrandelRio Hector
Published: September 2013

The newly described uncoupling protein 3 (UCP3) may make an important contribution to thermogenesis in humans because of its high level of expression in skeletal muscle. Contrary to expectations, fasting, a condition that reduces resting energy expenditure, has been reported to increase UCP3 expression in muscle. We have confirmed that a 10-fold increase in UCP3 mRNA levels occurs in rat quadriceps muscle between 12 and 24 h of food removal. A less consistent twofold increase in muscle UCP2 mRNA levels was observed in animals fasted for up to 72 h. Administration of recombinant leptin to prevent a fall in circulating leptin levels did not eliminate the fasting-induced increase in quadriceps UCP3 expression. Administration of a high dose of glucocorticoid to fed animals to mimic the increase in corticosterone induced by fasting did not reproduce the increase in UCP3 expression observed in fasted animals. In contrast, elevation of circulating free fatty acid levels in fed animals by Intralipid plus heparin infusion caused significant increases in the UCP3/actin mRNA ratio compared with saline-infused fed controls in both extensor digitorum longus (2.01 ± 0.34 vs. 0.68 ± 0.11, P = 0.002) and soleus muscles (0.31 ± 0.07 vs. 0.09 ± 0.02, P = 0.014). We conclude that free fatty acids are a potential mediator of the increase in muscle UCP3 expression that occurs during fasting. This seemingly paradoxical induction of UCP3 may be linked to the use of free fatty acid as a fuel rather than an increased need of the organism to dissipate energy.
Glucagon-Like Peptide 1 Improves the Ability of the β-Cell to Sense and Respond to Glucose in Subjects With Impaired Glucose Tolerance
Authors: Byrne Maria M , Gliem Katja , Wank Uwe , Arnold Rudolf , Katschinski Martin , Polonsky Kenneth S , Goke Burkhard
Published: September 2013

Impaired glucose tolerance (IGT) and NIDDM are both associated with an impaired ability of the β-Cell to sense and respond to small changes in plasma glucose concentrations. The aim of this study was to establish if glucagon-like peptide 1 (GLP-1), a natural enteric peptide and potent insulin secretagogue, improves this defect. Two weight-matched groups, one with eight subjects having IGT (2-h glucose, 10.1 ± 0.3 mmol/l) and another with seven subjects with diet-treated NIDDM (2-h glucose, 14.5 ± 0.9 mmol/l), were studied on two occasions during a 12-h oscillatory glucose infusion, a sensitive test of the ability of the β-Cell to sense and respond to glucose. Glucose was infused with a mean rate of 4 mg · kg−1 · min−1, amplitude 33% above and below the mean rate, and periodicity of 144 min, with infusion of saline or GLP-1 at 0.4 pmol · kg−1 · min−1 for 12 h. Mean glucose levels were significantly lower in both groups during the GLP-1 infusion compared with during saline infusion: 9.2 ± 0.4 vs. 6.4 ±0.1 mmol/l in the IGT subjects (P < 0.0004) and 14.6 ± 1.0 vs. 9.3 ± 0.7 mmol/L in NIDDM subjects (P < 0.0002). Despite this significant reduction in plasma glucose concentration, insulin secretion rates (ISRs) increased significantly in IGT subjects (513.3 ± 77.6 vs. 583.1 ± 100.7 pmol/min; P < 0.03), with a trend toward increasing in NIDDM subjects (561.7 ± 122.16 vs. 642.8 ± 128 pmol/min; P = 0.1). These results were compatible with enhanced insulin secretion in the presence of GLP-1. Spectral power was used as a measure of the ability of the β-Cell to secrete insulin in response to small changes in the plasma glucose concentration during the oscillatory infusion. Spectral power for ISR increased from 2.1 ± 0.9 during saline infusion to 7.4 ±1.3 during GLP-1 infusion in IGT subjects (P < 0.004), but was unchanged in NIDDM subjects (1.0 ± 0.4 to 1.5 ± 0.6; P = 0.3). We concluded that low dosage GLP-1 improves the ability of the β-Cell to secrete insulin in both IGT and NIDDM subjects, but that the ability to sense and respond to subtle changes in plasma glucose is improved in IGT subjects, with only a variable response in NIDDM subjects. β-Cell dysfunction was improved by GLP-1 infusion, suggesting that early GLP-1 therapy may preserve β-Cell function in subjects with IGT or mild NIDDM
Evidence for 5′AMP-Activated Protein Kinase Mediation of the Effect of Muscle Contraction on Glucose Transport
Authors: Hayashi Tatsuya , Hirshman Michael F , Kurth Emily J , Winder William W , Goodyear Laurie J
Published: September 2013

The intracellular signaling proteins that lead to exercise-stimulated glucose transport in skeletal muscle have not been identified, although it is clear that there are separate signaling mechanisms for exercise- and insulinstimulated glucose transport. We have hypothesized that the 5′AMP-activated protein kinase (AMPK) functions as a signaling intermediary in exercise-stimulated glucose uptake. This hypothesis was based on recent studies showing the following: 1) muscle contraction increases AMPK activity and 2) perfusion of rat hindlimb skeletal muscles with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a compound that results in increased AMPK activity, increased insulin-stimulated glucose uptake. In the current study, isolated rat epitrochlearis muscles were treated to contract in vitro (via electrical stimulation for 10 min) and/or incubated in the absence or presence of AICAR (2 mmol/l), insulin (1 μmol/1), or wortmannin (100 nmolA). Both contraction and AICAR significantly increased AMPK activity, while the enzyme was not activated by insulin. AICAR, contraction, and insulin all increased 3-O-methylglucose (3MG) transport by threefold to fivefold above basal. The phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin completely blocked insulin-stimulated transport, but did not inhibit AICAR- or contraction-stimulated transport. The increase in glucose transport with the combination of maximal AICAR plus maximal insulin treatments was partially additive, suggesting that these stimuli increase glucose transport by different mechanisms. In contrast, there was no additive effect on glucose transport with the combination of AICAR plus contraction. These data suggest that AICAR and contraction stimulate glucose transport by a similar insulin-independent signaling mechanism and are consistent with the hypothesis that AMPK is involved in exercise-stimulated glucose uptake.
Pulsatile Insulin Secretion in Isolated Rat Islets
Authors: Chou Hsu-Fang , Ipp Eli
Published: September 2013

The pancreas secretes insulin in an oscillatory fashion, but the precise site of the pacemaker for pulsatile insulin secretion has not been identified. These studies were designed to determine whether islets also secrete insulin in a pulsatile fashion if they are isolated from their pancreatic milieu. Isolated rat islets (80–100) were perifused 8 h in culture medium after overnight incubation, and samples were collected at 3.3-min intervals. Insulin secretion was evaluated for pulsatility with the Clifton Cycle Detection Program. Perifusion of islets was associated with a spontaneous, persistent, and regular pulsatility of insulin secretion, which was observed in all conditions tested. Perifusion with medium containing 5.5 mM glucose (n = 11) demonstrated oscillations with a mean periodicity of 17.6 ±1.1 min and a mean amplitude of 4.8 ± 0.4 μU/ml when overall mean insulin concentration was 16.7 ± 2.4 μU/ml. When the glucose concentration was 16.7 mM (n = 9), overall mean insulin concentration was 54.4 ± 2.6 μU/ml, with increases in periodicity (22.0 ±1.3 min) and amplitude (10.7 ± 0.5 μU/ml). All measurements were significantly different from those observed during perifusion with 5.5 mM glucose (P < 0.02−0.001). Theophylline (1 mM) also enhanced the overall mean insulin concentration and amplitude (69.4 ± 10.4 and 14.2 ±1.2 μU/ml, respectively) compared with control studies without theophylline (16.7 ± 5.3 and 4.3 ± 0.5 μU/ml) (P < 0.01). The period of the cycle was also increased from 17.5 ± 1.1 to 26.4 ± 6.3 min, but this was not significantly different from the control group. When glucose was delivered in rhythmic fashion with a period of 40 min, the characteristics of the insulin cycling approximated those of the glucose oscillation rather than the spontaneously generated insulin pulsatility. We conclude that a pacemaker for pulsatile insulin secretion is located within the islets of Langerhans and is subject to influence by both glucose concentration and pattern of delivery and cAMP-mediated mechanisms.
Relative Hyperproinsulinemia of NIDDM Persists Despite the Reduction of Hyperglycemia With Insulin or Sulfonylurea Therapy
Authors: Rachman Jonathan , Levy Jonathan C , Barrow Beryl A , Manley Susan E , Turner Robert C
Published: September 2013

Subjects with NIDDM have increased plasma proinsulin concentrations, compared with nondiabetic subjects, both in absolute terms and as a proportion of circulating insulin-like molecules. It remains uncertain whether this reflects a primary β-cell defect in proinsulin processing or is secondary to hyperglycemia. We addressed this question by assessing the effects of reducing hyperglycemia on relative hyperproinsulinemia in subjects with NIDDM. Eight subjects with NIDDM underwent three 8-week periods in a randomized crossover design of therapy with diet alone, sulfonylurea (gliclazide), or insulin (ultralente). The effects on β-cell peptide concentrations were assessed 1) fasting, 2) in response to hyperglycemie clamping, and 3) in response to an injection of the nonglucose secreto-gogue arginine and compared with measurements in seven nondiabetic control subjects. Both sulfonylurea and insulin therapy substantially reduced fasting plasma glucose and glycosylated hemoglobin (HbA1c) concentrations, compared with diet therapy alone. The diabetic subjects on diet therapy had relative hyperproinsulinemia, assessed relative to C-peptide concentrations, fasting and in response to hyperglycemie clamping and arginine, compared with control subjects. Neither sulfonylurea nor insulin therapy altered the relative hyperproinsulinemia. Insulin therapy reduced fasting proinsulin concentrations from geometric mean 29.4 (1 SD range, 14.6-59.0) pmol/l on diet therapy to 18.7 (7.3-48.1) pmol/l (P < 0.05). A similar trend was evident with fasting C-peptide concentrations with a reduction from 0.9 (0.6-1.4) nmol/l on diet therapy to 0.6 (0.4-0.9) nmol/l (P = 0.06), so that the relative hyperproinsulinemia, assessed as the ratio of fasting proinsulin to C-peptide, was unchanged by insulin. Similarly, insulin therapy failed to reduce the ratio of proinsulin to C-peptide concentrations in response to a hyperglycemie clamp and in the acute incremental response to arginine. Failure to improve the relative hyperproinsulinemia of NIDDM, despite significant reduction of hyperglycemia with exogenous insulin therapy, supports the hypothesis that relative hyperproinsulinemia in NIDDM is a reflection of a primary β-cell defect rather than being secondary to hyperglycemia.
Effects of Nonesterified Fatty Acids on Glucose Metabolism After Glucose Ingestion
Authors: Kruszynska Yolanta T , Mulford Mim I , Yu Joseph G , Armstrong Debra A , Olefsky Jerrold M
Published: September 2013

Impaired suppression of plasma nonesterified fatty acids (NEFAs) after glucose ingestion may contribute to glucose intolerance, but the mechanisms are unclear. Evidence that insulin inhibits hepatic glucose output (HGO), in part by suppressing plasma NEFA levels, suggests that impaired suppression of plasma NEFA after glucose ingestion would impair HGO suppression and increase the systemic delivery of glucose. To test this hypothesis, we studied glucose kinetics (constant intravenous [3-H]glucose [0.4 μCi/min], oral [1-14C]glucose [100 μCi]), whole-body substrate oxidation, and leg glucose uptake in eight normal subjects (age, 39 ± 9 years [mean ± SD]; BMI, 24 ± 2 kg/m2) in response to 75 g oral glucose on two occasions. In one study, plasma NEFAs were prevented from falling by infusion of 20% Liposyn (45 ml/h) and heparin (750 U/h). Plasma glucose rose more rapidly during lipid infusion (P < 0.05), and mean levels tended to be higher after 120 min (6.45 ± 0.41 vs. 5.81 ± 0.25 SE, 0.1 < P < 0.05, NS); peak glucose levels were similar. Total glucose appearance (Ra) was higher during lipid infusion due to a higher HGO (28.4 ± 1.0 vs. 21.2 ± 1.5 g over 4 h, P < 0.005). Total glucose disposal CRd) was also higher (88 ± 2 vs. 81 ± 3 g in 4 h, P < 0.05). Plasma insulin rose more rapidly after glucose ingestion with lipid infusion, and leg glucose uptake was 33% higher (P < 0.05) during the 1st hour. During lipid infusion, subjects oxidized less glucose (47 ± 3 vs. 55 ± 2 g, P < 0.05) and more fat (7.1 ± 0.8 vs. 3.9 ± 0.9 g, P < 0.02). In summary, 1) impaired suppression of NEFAs after oral glucose impairs insulin's ability to suppress HGO, and 2) in normal subjects the greater insulin response compensates for the increased systemic glucose delivery by increasing peripheral glucose Rd.
Organization and Partial Sequence of the Hepatocyte Nuclear Factor-4α/MODY1 Gene and Identification of a Missense Mutation, R127W, in a Japanese Family With MODY
Authors: Furuta Hiroto , Iwasaki Naoko , Oda Naohisa , Hinokio Yoshinori , Horikawa Yukio , Yamagata Kazuya , Yano Nobuki , Sugahiro Jun , Ogata Makiko , Ohgawara Hisako , Omori Yasue , Iwamoto Yasuhiko , Bell Graeme I
Published: September 2013

Hepatocyte nuclear factor-4α (HNF-4α) is a member of the nuclear receptor superfamily, a class of ligand-activated transcription factors. A nonsense mutation in the gene encoding this transcription factor was recently found in a white family with one form of maturity-onset diabetes of the young, MODY1. Here, we report the exonintron organization and partial sequence of the human HNF-4α gene. In addition, we have screened the 12 exons, flanking introns and minimal promoter region for mutations in a group of 57 unrelated Japanese subjects with early-onset NIDDM/MODY of unknown cause. Eight nucleotide substitutions were noted, of which one resulted in the mutation of a conserved arginine residue, Argl27 (CGG)→Trp (TGG) (designated R127W), located in the T-box, a region of the protein that may play a role in HNF-4α dimerization and DNA binding. This mutation was not found in 214 unrelated nondiabetic subjects (53 Japanese, 53 Chinese, 51 white, and 57 African-American). The R127W mutation was only present in three of five diabetic members in this family, indicating that it is not the only cause of diabetes in this family. The remaining seven nucleotide substitutions were located in the proximal promoter region and introns. They are not predicted to affect the transcription of the gene or mRNA processing and represent polymorphisms and rare variants. The results suggest that mutations in the HNF-4α gene may cause early-onset NIDDM/MODY in Japanese but they are less common than mutations in the HNF-1α/MODY3 gene. The information on the sequence of the HNF-4α gene and its promoter region will facilitate the search for mutations in other populations and studies of the role of this gene in determining normal pancreatic β-cell function.
Liver Pathology in Infantile Mitochondrial DNA Depletion Syndrome
Authors: Hazard Florette K. , Ficicioglu Can H. , Ganesh Jaya , Ruchelli Eduardo D.
Published: September 2013

Mitochondrial DNA (mtDNA) depletion syndrome is a relatively novel cause of hepatic dysfunction in the pediatric population. It is caused by mutations in either mtDNA or nuclear DNA (nDNA) that result in a quantitative reduction in mtDNA and, in turn, dysfunctional oxidative phosphorylation. In infants, it results in the hepatocerebral phenotype, characterized by hyperbilirubinemia, coagulopathy, lactic acidosis, hypoglycemia, lethargy, encephalopathy, developmental delay, and hypotonia. Three infants diagnosed with mtDNA depletion syndrome at The Children's Hospital of Philadelphia were identified, and their clinical presentation, disease course, and histologic and ultrastructural features of liver samples (pre- and postmortem) were characterized. While a different mutant gene was identified in each child, they all showed clinical evidence of metabolic dysfunction soon after birth and expired by 1 year of age. Steatosis, cholestasis, and cytoplasmic crowding by atypical mitochondria were consistent pathologic liver findings. Other findings included hepatocyte hypereosinophilia, fibrosis, and hemosiderosis. This analysis provides insight into the important clinical signs/symptoms and histopathologic and ultrastructural features of mtDNA depletion syndrome in infants and young children. Knowledge of these characteristics will facilitate early recognition and appropriate treatment of this rare disorder. Additionally, ultrastructural evaluation of liver samples by electron microscopy is an important diagnostic component of hepatic dysfunction caused by metabolic abnormalities. This type of analysis should be routinely employed in the setting of unexplained cholestasis, especially when accompanied by steatosis and hepatocyte hypereosinophilia.
Acquisition and persistence of antimicrobial-resistant bacteria isolated from dogs and cats admitted to a veterinary teaching hospital
Authors: Hamilton Elizabeth , Kruger John M. , Schall William , Beal Matthew , Manning Shannon D. , Kaneene John B.
Published: September 2013

Objective—To assess antimicrobial resistance among bacteria isolated from dogs and cats admitted to a veterinary teaching hospital (VTH), determine the incidence of acquisition of and frequency of persistent colonization by antimicrobial-resistant organisms among these animals, and identify risk factors associated with these variables.

Design—Prospective longitudinal study.

Animals—622 dogs and 92 cats admitted to a VTH and expected to stay ≥ 48 hours.

Procedures—Samples were collected with rectal and nasal or oropharyngeal swabs at admission and discharge. Isolates of enterococci, staphylococci, and Escherichia coli were tested for antimicrobial resistance via microbroth dilution methods. A subset of isolates was analyzed with pulsed-field gel electrophoresis and multilocus sequence typing. Significant trends in proportions of organisms with antimicrobial resistance over the 3-year study period were assessed.

Results—The proportion of staphylococci with antimicrobial resistance increased, whereas the proportion of E coli with resistance decreased, over time; resistance among enterococci was more variable. For 506 dogs with paired admission and discharge samples, multidrug-resistant (MDR) E coli was acquired by 40 (8%) and methicillin-resistant Staphylococcus aureus (MRSA) was acquired by 7 (1.4%); hospitalization for > 3 days was significantly associated with both variables. Most (5/7 isolates) acquired MRSA was of sequence type (ST) 5.

Conclusions and Clinical Relevance—Extended hospitalization was associated with increased risk of acquiring MDR E coli or MRSA, although few animals acquired MRSA. It is unclear whether associations were confounded by illness severity or use of infection control measures. Additionally, MRSA of ST5, which has been associated with small animal medicine, was the most commonly acquired MRSA in this study.