bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunobiological Consequence of Regulation of Insulin Receptor on Alloactivated Lymphocytes in Normal and Obese Subjects
Authors: Koffler Michael , Raskin Philip , Womble Debra , Helderman J Harold
Published: September 2013

Acute manipulations of insulin in vivo regulate the display of insulin receptors induced on activated T lymphocytes after presentation of alloantigen. This study explored the immunobiological consequences of regulation of insulin-receptor display by acute manipulations of insulin achieved during the hyperinsulinemic-euglycemic clamp in healthy normal individuals and obese subjects. T lymphocytes were isolated at 0, 1, and 4 h of hyperinsulinemia from seven normal volunteers and seven obese individuals and studied for their capacity to 1) synthesize a complement of insulin receptors on cell membrane, 2) respond to alloantigen in the mixed-lymphocyte culture (an immunologic activity unrelated to manipulations in insulin concentrations in complete medium), and 3) respond to the lymphocyte-mediated cytotoxicity reaction (an immunologic activity known to be modulated by insulin). In the face of a reduction in receptor numbers to 25% of baseline in normal individuals, alloreactivity in the mixed-lymphocyte culture was not affected (95 ± 9% of time 0 after 4 h of hyperinsulinemia), whereas lymphocyte-mediated cytotoxicity fell from 14 ± 4 at time 0 to 2 ± 2% sp Cr release (P < 0.02). Hyperinsulinemia achieved by the clamp in seven obese subjects did not alter the synthesis of insulin receptors on cell membrane after presentation of alloantigen. In the absence of further reduction of insulin-receptor membrane display, neither the mixed-lymphocyte culture nor lymphocyte-mediated cytotoxicity reaction was affected. It is concluded that those immunologic activities of lymphocytes that can be modulated by insulin are affected by regulation of insulin-receptor display on activated lymphocytes. Therefore, receptor regulation is not effete but carries significant immunologic consequence. This study supports the hypothesis that insulin-directed immunologic activity is regulated at the site of receptor display rather than at the locus of regulation of the ligand itself.
Coordinate Reduction of Rat Pancreatic Islet Glucokinase and Proinsulin mRNA by Exercise Training
Authors: Koranyi Laszlo I , Bourey Raymond E , Slentz Cris A , Holloszy John O , Permutt M Alan
Published: September 2013

Exercise training results not only in enhanced insulin sensitivity but also in a reduction in insulin secretion. In this study, we examined the effects of exercise training on the expression of genes potentially related to insulin synthesis and glucose-stimulated insulin release by measuring pancreatic islet proinsulin, glucose-transporter (GLUT2), and glucokinase mRNAs. Female Wistar rats were subjected to 100 min of running at 25 m · min−1 up a 15% incline for 90 min/day for 6 days/wk for 3 wk. Pancreatic mRNA was evaluated by Northern- and dot-blot analysis with [32P]cRNA probes. We found no change in the pancreatic content of GLUT2 mRNA but found marked decreases in the content of proinsulin mRNA (78%, P < 0.005) and glucokinase mRNA (65%, P < 0.001). These results suggest that exercise modulates both islet glucose metabolism and insulin synthesis at the level of gene expression. Furthermore, there was a significant correlation between the decreases in glucokinase and proinsulin mRNA concentrations (r = 0.95, P < 0.001), suggesting that expression of these genes is regulated in parallel.
Molecular Defects in Diabetes Mellitus
Authors: Bell Graeme I
Published: September 2013

The application of molecular biology to problems in diabetes mellitus has begun to reveal the underlying molecular defects contributing to the development of hyperglycemia. Islet amyloid represents the most common pathological lesion occurring in the islets of NIDDM subjects. The use of both biochemistry and molecular biology has lead to the identification of the major protein component of human islet amyloid and elucidation of the structure of its precursor. This protein, termed islet amyloid polypeptide, is related to two neuropeptides, calcitonin gene–related peptides 1 and 2, and represents a new β-cell secretory product whose normal physiological function remains to be determined. The use of molecular biology has also led to a better understanding of the molecular defects contributing to insulin resistance. Characterization of the insulin-receptor gene in patients with extreme forms of insulin resistance has resulted in the identification of mutations that impair its function and lead to tissue resistance to the action of insulin. Molecular biological approaches have also led to a better understanding of the regulation of glucose transport. They have revealed that there is a family of structurally related proteins encoded by distinct genes and expressed in a tissue-specific manner that are responsible for the transport of glucose across the plasma membrane. Moreover, they have shown that specific depletion of the glucose-transporter isoform that mediates insulin-stimulated glucose transport is responsible for decreased transport activity in adipose tissue in insulin-resistant states.
Maternal Diabetes and Retarded Preimplantation Development of Mice
Authors: Beebe Luke F S , Kaye Peter L
Published: September 2013

The streptozocin-induced diabetic (STZ-D) mouse was found to be a suitable model for studying the effects of maternal diabetes on the preimplantation embryo. This study looked at the effects of maternal diabetes on embryonic growth. Female Quakenbush mice were made diabetic (plasma glucose levels >20 mM) by injection of 190 mg/kg i.p. STZ and were superovulated by standard methods. The blastocysts collected on day 4 from diabetic mothers had 8.5% fewer cells and a 35% lower protein synthetic rate than control embryos. Their cellular protein synthetic rate was 19% less than that in controls. Morulae from diabetic mothers also displayed a reduced protein synthetic rate, but this reduction was not seen in the two-cell embryo. Furthermore, blastocysts cultured in vitro from two-cell embryos from diabetic and control mothers displayed similar protein synthetic rates. This infers that the two-cell embryos from diabetic mothers are normal, and the retardation seen in later development in vivo occurs after the two-cell stage while the embryo is still free in the oviductal and uterine environment. Treatment of the diabetic mice with ultralente insulin every 12 h raised the protein synthetic rate of those blastocysts toward control levels, whereas treatment with lente insulin every 8 h recovered the embryo to the same rate as the control embryos. Because insulin has been shown to be mitogenic and stimulates protein synthesis of morulae and blastocysts in vitro, the absence of insulin in the diabetic mothers may be the cause of the retardation observed in their preimplantation embryos.
Vanadate Induction of L-type Pyruvate Kinase mRNA in Adult Rat Hepatocytes in Primary Culture
Authors: Miralpeix Montserrat , Decaux Jean-François , Kahn Axel , Bartrons Ramon
Published: September 2013

In primary culture of adult rat hepatocytes, vanadate in the presence of glucose stimulates the expression of the liver (L-type) pyruvate kinase gene. Glucose by itself was inactive, and vanadate, like insulin, was also inefficient in the absence of glucose. Similar results were obtained on glucokinase gene expression. An analogue of cAMP, 8-(4-chlorophenylthio)-cAMP, inhibited the production of L-type pyruvate kinase and glucokinase mRNAs in the presence of glucose plus vanadate.
Adipose Tissue Glucose Transporters in NIDDM: Decreased Levels of Muscle/Fat Isoform
Authors: Sinha Madhur K , Raineri-Maldonado Carla , Buchanan Cresada , Pories Walter J , Carter-Su Christin , Pilch Paul F , Caro José F
Published: September 2013

We investigated the mechanism of peripheral insulin resistance in the adipose tissue of obese and non-insulin-dependent diabetes mellitus (NIDDM) patients at the level of the glucose-transport effector system. Freshly isolated adipocytes from obese nondiabetic and obese NIDDM subjects had decreased insulin sensitivity and responsiveness for glucose-transport stimulation compared with control subjects, with more pronounced changes associated with obese NIDDM patients. The relative abundance of muscle/fat glucose-transporter isoform in the three groups of subjects was determined by Western-blot analysis of detergent-soluble adipose tissue extracts with monoclonal antibody 1F8. Obesity per se had no effect on adipose tissue muscle/fat glucose-transporter isoform (3150 ± 660 vs. 4495 ± 410 counts/min [cpm]/mg protein). Furthermore, decreased levels of muscle/fat isoform was observed in adipose tissue of NIDDM patients (1560 ± 600 cmp/mg protein.) Furthermore, decreased levels of muscle/fat isoform in adipose tissue of NIDDM patients were also reflected in isolated adipocytes. Our results demonstrate that insulin resistance in isolated adipocytes of NIDDM patients could at least partly be due to a significant depletion of adipose tissue muscle/fat glucose-transporter isoform.
Antidiabetic Action of Vanadyl in Rats Independent of in Vivo Insulin-Receptor Kinase Activity
Authors: Venkatesan Natarajan , Avidan Alon , Davidson Mayer B
Published: September 2013

The effects of oral vanadyl sulfate administration for 9–12 days on carbohydrate and lipid metabolism in the basal state and on glucose dynamics during submaximal hyperinsulinemic clamps were investigated in nondiabetic and streptozocin-induced diabetic rats. Decreases in growth rate and water and food consumption were the only significant alterations noted in control animals receiving vanadyl. Administration of vanadyl to diabetic rats resulted in weight loss; a significant decrease in plasma glucose, triglyceride, and cholesterol levels; and decreases in food and water intake, without a concomitant change in plasma insulin concentrations. Vanadyl treatment did not modify either peripheral glucose utilization or hepatic glucose production in control rats during submaximal insulin clamps. In contrast, vanadyl therapy increased insulin-induced glucose utilization significantly and had a small but nonsignificant effect on insulin-mediated suppression of glucose production in diabetic rats. The tyrosine kinase activity of liver- and muscle-derived insulin receptors from diabetic rats that underwent clamp study, which reflected the in vivo phosphorylation state of insulin receptor, was not altered by vanadyl treatment. In conclusion, these results show that augmentation of peripheral glucose utilization is the major determinant of the antidiabetic action of vanadyl and support the notion that the action of vanadyl is independent of insulin-receptor kinase activity.
Study in Tanzania of Impaired Glucose Tolerance: Methodological Myth?
Authors: Swai Andrew B M , McLarty Donald G , Kitange Henry M , Kilima Peter M , Masuki Gabriel , Mtinangi Bernard I , Chuwa Linus , Alberti K George M M
Published: September 2013

During study of diabetes prevalence in six rural Tanzanian communities, a repeat oral glucose tolerance test (OGTT) was carried out in 514 subjects ≥ 15 yr of age within 1 wk of an initial 75-g OGTT. In 498 subjects, blood glucose was measured 2 h after the glucose load on both occasions, and in 175 subjects, fasting blood glucose measurement was also repeated. Of the 498 subjects, 245 had normal glucose tolerance in the first test and were selected at random for further testing; 223 subjects had impaired glucose tolerance (IGT), and 30 had diabetic values. Diabetes and IGT were diagnosed on the basis of the 2-h blood glucose values. In the second test, 241 (98.4%) of the 245 subjects with normal tolerance continued in this category and 4 (1.6%) showed IGT. Of the 223 with IGT in the first test, 171 (76.2%) reverted to normal on the second test, 7 (3.1%) had diabetic values, and 45 (20.2%) persisted with IGT. Of the 30 subjects diagnosed as diabetic in the first test, 8 (26.7%) remained with diabetic values, 11 (36.7%) had IGT, and 11 (36.7%) were normal. Based on the second test, the population-prevalence rates of diabetes and IGT would have been 0.5 and 3.3% vs. 1 and 7.6% based on the first test. There was a significant downward trend in the mean 2-h blood glucose values in all three diagnostic groups. Regression toward the mean could not account for the downward shift in blood glucose values observed on retesting. It is postulated that a phenomenon occurred similar to the acclimatizing reflex observed in measurement of blood pressure. Therefore, single 2-h postload values may be inadequate for the accurate assessment of IGT and diabetes-prevalence rates within communities, particularly those unused to blood sampling. Because of the instability of the category of IGT, it may be advisable to discontinue use of this term or to restrict the term to those who show impaired tolerance on more than one occasion.
T-Lymphocyte Changes Linked to Autoantibodies: Association of Insulin Autoantibodies With CD4+CD45R+ Lymphocyte Subpopulation in Prediabetic Subjects
Authors: Faustman Denise , Schoenfeld David , Ziegler Ralph
Published: September 2013

The onset of insulin-dependent (type I) diabetes is predictable before hyperglycemia by the presence of islet cell autoantibodies (ICAs) and competitive insulin autoantibodies (CIAAs). CIAA+ICA+ first-degree relatives of individuals with type I diabetes have increased numbers of CD4 cells bearing the CD45R antigen and reciprocal depressions of the CD4 cells bearing the CD29 determinant. In addition, depressed CD4/CD8 ratios are present. In this study, we investigated the correlation between autoantibody levels and T-lymphocyte changes in the prediabetic state. The data demonstrate a clear linear relationship between rising CIAA levels, a marker of disease rate, and rising elevations in the CD4+CD45R+/CD4+CD29+ ratio in 37 CIAA+ICA+ and CIAA+ICA− relatives (r = 0.93). In marked contrast, the degree of CD4/CD8 depression found in individuals with prediabetes or long-term diabetes failed to correlate with either CIAA (r = 0.32) or ICA (r = 0.29) levels. The investigation of T-lymphocyte changes in siblings of individuals with type I diabetes with different stable autoantibody patterns (CIAAs and/or ICAs), and thus varying risks for diabetes, revealed differences in the prediabetic groups. Fifteen CIAA+ICA− relatives with high CIAA levels (>80 nU/ml) had high CD4+CD45R+/CD4+CD29+ ratios (P = 0.03) and depressed CD4/CD8 ratios (P = 0.008). In contrast, CIAA+ICA− relatives with low CIAA levels (39–80 nU/ml), and thus low risk of diabetes, had no alteration in their CD4/CD8 ratio (P = 0.75) or CD4+CD45R+/CD4+CD29+ ratio (P = 0.33). Nineteen CIAA−ICA+ siblings with a predicted intermediate risk for diabetes showed heterogeneity in the presence of T-lymphocyte abnormalities. No statistically significant trend was observed in the peripheral T-lymphocyte composition with all CIAA−ICA+ relatives combined. This study links the magnitude of the well-described CIAA production to the magnitude of altered numbers of T lymphocytes bearing the CD45R+ and CD29+ antigens in the prediabetic stage. We conclude that prediabetic relatives prone to frank hyperglycemia represent a heterogeneous population now definable by autoantibody production and the newly described T-lymphocyte changes. This study represents an initial delineation of a link between abnormal alterations in the humoral and cellular immune response.
Increased Matrix Gene Expression by Glucose in Rat Neural Connective Tissue Cells in Culture
Authors: Muona Päivi , Peltonen Juha , Jaakkola Sirkku , Uitto Jouni
Published: September 2013

The effects of different glucose concentrations on the expression of extracellular matrix genes were examined in primary cell cultures initiated from sciatic nerves of nondiabetic Sprague-Dawley rats. The cells were incubated in medium containing 5.5, 15, or 25 mM D-glucose, and the expression of type I and IV collagens, laminin, and fibronectin genes was examined at mRNA steady-state levels by Northern hybridizations. Incubation of cell cultures, consisting of Schwann cells, perineurial cells, and fibroblasts, in high glucose concentrations (15 or 25 mM D-glucose) resulted in elevation of pro-α 1(IV), pro-α 2(IV), and pro-α 1(I) collagen chain and fibronectin mRNAs after only 3 days of incubation, whereas laminin B2 chain mRNA levels appeared unaltered. These observations suggest that hyperglycemia may partially contribute to basement membrane thickening in peripheral nerves of diabetic individuals by increasing the expression of genes coding for basement membrane components, e.g., type IV collagen.
Effects of Insulin Deprivation and Replacement on In Vivo Subcutaneous Adipose Tissue Substrate Metabolism in Humans
Authors: Hagström-Toft Eva , Arner Peter , Näslund Birgitta , Ungerstedt Urban , Bolinder Jan
Published: September 2013

The effects of insulin deprivation and replacement on adipose tissue metabolism were investigated in vivo with microdialysis in nine insulin-dependent diabetic patients with no residual insulin secretion. Dialysis probes, implanted in abdominal subcutaneous fat, were continuously perfused, and tissue dialysate concentrations of glycerol (lipolysis index), glucose, lactate, and pyruvate were determined. Comparisons were made with respective metabolite levels in venous plasma. After termination of intravenous insulin infusion, free insulin in plasma fell from 130 to 70 pM. At the same time, glucose levels in plasma and adipose tissue rose in parallel. However, the relative increase in glucose levels was greater in adipose tissue than in blood. On the other hand, the increase in glycerol concentration in adipose tissue (35%) was markedly < that in venous plasma (250%). Lactate and pyruvate levels in adipose tissue and blood remained unchanged. After the resumption of intravenous insulin, free insulin in plasma rose to ∼600 pM. At the same time, the glucose levels in blood and adipose tissue decreased rapidly, and the glycerol concentration in these tissues decreased to 50% of the baseline levels. The lactate and pyruvate levels in subcutaneous tissue increased briefly after insulin replacement, whereas the lactate but not pyruvate levels in blood showed a similar increase. The α- or β-blocking agents phentolamine and propranolol in the ingoing tissue perfusate did not influence tissue glycerol at any time during the experiment. We concluded that insulin-induced changes in circulating metabolites only partly reflect variations in adipose tissue substrate kinetics. During insulin deprivation, glucose is accumulated in the adipose tissue extracellular compartment, probably because of reduced utilization by the adipocytes. The increase in lactate and pyruvate levels in adipose tissue after insulin replacement may be explained by local metabolite production. The lipolytic activity in abdominal subcutaneous adipose tissue is only modestly enhanced during relative insulin deficiency, which is in contrast to overall lipolytic activity. Finally, adrenergic mechanisms do not seem to be involved in the changes in the lipolysis rate, which are induced by hypoinsulinemia and hyperinsulinemia.
Opposing Actions of Dehydroepiandrosterone and Testosterone on Insulin Sensitivity: In Vivo and In Vitro Studies of Hyperandrogenic Females
Authors: Buffington Cynthia K , Givens James R , Kitabchi Abbas E
Published: September 2013

It has been hypothesized that the androgens testosterone and dehydroepiandrosterone (DHEA) may have opposing actions on insulin sensitivity. To test this hypothesis, we selected patients with polycystic ovary syndrome (PCO) and hypertestosteronemia and a group of individuals with adrenal hyperplasia (AH) and elevated DHEA and studied their 1) insulin and glucose responses to a 75-g oral glucose tolerance test, 2) insulin resistance by hypoglycemic responses to a standard dose of intravenous (IV) insulin, and 3) insulin binding and pyruvate dehydrogenase (PDH) responsiveness to insulin in phytohemagglutinin (PHA)-activated T lymphocytes. PCO patients exhibited elevated basal and glucose-challenged insulin levels and had blunted hypoglycemic responses to IV insulin. Conversely, AH patients had hypoglycemic responses to IV insulin significantly > and basal and glucose-challenged insulin levels lower than the PCO patients and weight-matched control subjects. In vitro, T-lymphocyte insulin binding of the PCO patients was 40–60% below control values; in AH patients, insulin binding and PDH insulin sensitivity were above those of the control subjects. Testosterone levels in all study subjects were negatively correlated to T-lymphocyte insulin binding and positively correlated to basal insulin, insulin area under the curve (AUC), and insulin-glucose indices. DHEA levels were positively correlated to insulin binding and inversely related to basal insulin, insulin AUC, and insulin-glucose indices. In all instances, the parameters of insulin sensitivity were more strongly correlated to individuals' ratios of DHEA to testosterone than to either of these androgens alone. From the above in vivo and in vitro studies, we conclude that, in hyperandrogenic women, the ratio of DHEA to testosterone may be an important modulator of insulin sensitivity.
HLA-DQA1 and -DQB1 Alleles Associated With Genetic Susceptibility to IDDM in a Black Population
Authors: Mijovic Catherine H , Jenkins David , Jacobs Karen H , Penny Michelle A , Fletcher Jeremy A , Barnett Anthony H
Published: September 2013

Transracial analysis provides a method of distinguishing primary associations between insulin-dependent diabetes mellitus (IDDM) and HLA class II alleles from those secondary to linkage disequilibrium. Blacks show DR-DQ relationships that are different from other races and are a useful group in which to investigate HLA-D region associations with IDDM. In this study, the frequencies of HLA-DQA1 and -DQB1 alleles in Afro-Caribbean IDDM and control subjects were compared. Alleles were identified with sequence-specific oligonucleotide probing. The DQA1 allele A3 was positively associated with IDDM (relative risk [RR] = 25.3, corrected P [Pc] < 7.0 × 10−6. The DQB1 alleles DQw2 and DQw8 were also positively associated (RR = 4.7, Pc < 6.5 × 10−3 and RR = 12.3, Pc = 3.4 × 10−3, respectively). The A1.2 and DQw6 alleles were negatively associated (RR = 0.16, Pc < 3.5 × 10−3 and RR = 0.15, Pc = 2.4 × 10−2, respectively). These findings were compared to data from other races. The positive associations with A3 and DQw2 are consistent with all racial groups investigated. The negative association with DQw6 is present in all racial groups in which it is a common allele. These findings suggest that DQ alleles, and hence DQ molecules, may directly affect predisposition to IDDM.
Role of Postglomerular Microvessels in Pathophysiology of Diabetic Nephropathy: Assessment and Hypothesis
Authors: Pinter G G , Atkins J L
Published: September 2013

Although glomerular damage plays a well-established and important role in the pathomechanism of diabetic nephropathy, it alone does not fully explain the progression of renal complications in long-term diabetes mellitus. We discuss experimental evidence showing involvement of the postglomerular microvessels (peritubular capillaries and venules) in diabetic microangiopathy. This involvement is manifest in increased permeability of these vessels to plasma proteins and in highly augmented lymphatic drainage of the extravasated proteins from the renal interstitium. We suggest that in the advanced phase of diabetic nephropathy, proteinuria (corresponding to excess leakage of proteins through the glomerular capillary wall) indicates the probability that postglomerular microvessels have also allowed leakage of plasma proteins. As long as lymphatic drainage is capable of removing the increased quantity of extravasated plasma proteins from the interstitium, renal function should not be deleteriously affected. However, if the excess amount of extravasated proteins exceeds the capacity of lymphatic drainage, increases in interstitial volume and pressure are unavoidable with detrimental consequences for glomerular filtration and tubular reabsorption. Under these conditions, a potential positive-feedback loop can be visualized that involves increased extravasation of plasma proteins leading to increased interstitial pressure that through dilation of the afferent and efferent arterioles results in a further increase in protein extravasation. These conditions combined with glomerular damage should lead to the eventual collapse of renal function.
Impaired Autophosphorylation of Insulin Receptors From Abdominal Skeletal Muscles in Nonobese Subjects With NIDDM
Authors: Maegawa Hiroshi , Shigeta Yukio , Egawa Katsuya , Kobayashi Masashi
Published: September 2013

We studied both autophosphorylation and phosphotransferase activity of insulin receptors from abdominal skeletal muscles of nonobese subjects with non-insulin-dependent diabetes mellitus (NIDDM). Partially purified insulin receptors were labeled on their α-subunit with 125I-labeled insulin by chemical cross-linking and on their β-subunit by autophosphorylation with 1000 μM ATP. Thereafter, phosphorylated insulin receptors were separated from total receptors with the anti-phosphotyrosine antibody. Thus, the percentage of phosphorylated receptors in total receptors revealed the autophosphorylation activity. Using this method, we studied the function of insulin receptors from muscle obtained by biopsy during surgery in 10 nonobese NIDDM and 8 control subjects. In diabetic subjects, insulin binding capacity from abdominal skeletal muscles was 69.4% of the control subjects. Furthermore, the percentage of phosphorylated insulin receptors stimulated by 8.3 nM insulin was significantly lower than the control subjects (mean ± SD, 29.0 ± 12.0 vs. 56.0 ± 7.4%, P < 0.01), and there was a significant inverse correlation between fasting plasma glucose levels and the percentage of phosphorylated receptors among diabetic subjects (r = 0.73, P < 0.025). Moreover, the insulin-stimulated kinase activity toward a synthetic peptide (Glu80Tyr20) was also impaired in diabetic subjects (28.5% of control). In summary, this is the first demonstration that the autophosphorylation step of insulin receptors from abdominal skeletal muscles is impaired in nonobese NIDDM subjects.
Risk of Diabetes in Siblings and Other Relatives of IDDM Subjects
Authors: Allen Catherine , Palta Mari , D'Alessio Donn J
Published: September 2013

The risk of insulin-dependent diabetes mellitus (IDDM) was examined in siblings of an unselected population (n = 194) of newly diagnosed diabetic individuals <30 yr old. From 1 July 1984 to 30 June 1987, diabetic subjects (proband) identified within a geographically defined area of southern Wisconsin were studied. IDDM occurred among siblings of probands in 13.5% of families and was associated with proband age at diagnosis. The highest risk was found for diabetic subjects <10 yr old at diagnosis (P = 0.04). We did not find an association between sibling IDDM and proband sex, HLA-DR3/4, duration of symptoms, or ketosis at diagnosis. In addition, the odds ratio (OR) for the association of IDDM in the proband with IDDM in parents and second- and third-degree family members was examined by case-control methodology. Diabetic subjects were matched to two types of control subjects (friends and general population) by age stratum and sex. The OR for IDDM was not increased significantly if parental IDDM or non-insulin-dependent diabetes mellitus (NIDDM) was reported. However, there were very few parents with diabetes among diabetic or control subjects. In 6.4% of diabetic subjects, one parent had IDDM, 54% of whom were fathers. In 4.3% of diabetic subjects, one parent had NIDDM, and 57.1% of these were fathers. The OR for IDDM was significantly increased if second- and/or third-degree relatives had IDDM (OR diabetic subjects vs. general population 2.33 [P < 0.05]) or NIDDM (OR diabetic subjects vs. friends 2.05 [P < 0.01]). We conclude that the increased risk of sibling IDDM for younger probands suggests variation in etiological factors by family.
Nutrition and Somatomedin: XXV. Regulation of Insulinlike Growth Factor Binding Protein 1 in Primary Cultures of Normal Rat Hepatocytes
Authors: Villafuerte Betty C , Goldstein Steven , Murphy Liam J , Phillips Lawrence S
Published: September 2013

Although mRNAs encoding insulinlike growth factor (IGF) binding proteins (BPs) are present in adult rat liver and IGF BP-1 circulates at elevated levels in diabetic animals, there is little knowledge of the metabolic regulation of IGF BPs in normal tissues. We examined the release of IGF BPs by adult rat hepatocytes maintained in primary culture. When cultured for 2 days in the absence of added insulin, hepatocytes released a BP identified as BP-1 on the basis of ∼30,000-Mr on ligand blotting and reactivity with antiserum to human BP-1 in immunoblotting and immunoprecipitation studies. Release of BP-1 was sensitive to insulin with suppression of 24 ± 4, 73 ± 5, and 64 ± 14% at 10−10, 10−8, and 10−6 M insulin, respectively; ED50 was ∼1.7 × 10−9 M, which is within the physiological range. Suppression by insulin was reversible and began within 3 h. Because normal hepatocytes in primary culture exhibit insulin-responsive release of both BP-1 and IGF-1, this system may be an ideal model for studies of molecular mechanisms of metabolic regulation.
Effect of Linogliride on Hormone release From Perfused Rat Pancreas: Fuel Dependence and Desensitization by Tolbutamide
Authors: Ronner Peter , Cheong Erlinda , Khalid Parwaiz , Tuman Robert W , Matschinsky Franz M
Published: September 2013

We examined the effect of the hypoglycemic drug linogliride on hormone release from the in vitro perfused rat pancreas. Linogliride stimulated insulin release in the absence of glucose either in the presence or absence of a physiological mixture of amino acids. In addition, linogliride inhibited amino acid-induced glucagon release. Half-maximal effects of linogliride on insulin and glucagon release were achieved at concentrations as low as 26 and 3 μM, respectively. The effects of linogliride on hormone release largely resembled those of tolbutamide. In the absence of amino acids, the stimulation of insulin release by linogliride or tolbutamide was transient. When the pancreas had been preperfused for 20 min with tolbutamide, linogliride no longer had an effect on hormone release. Likewise, tolbutamide remained without effect in pancreases preperfused with linogliride. These data suggest that linogliride and tolbutamide may have a similar mechanism of action.
Inhibition of ATP-Sensitive K+ Channels in Pancreatic β-Cells by Nonsulfonylurea Drug Linogliride
Authors: Ronner Peter , Higgins Timothy J , Kimmich George A
Published: September 2013

Linogliride is a nonsulfonylurea drug that lowers blood glucose levels in nondiabetic and diabetic humans and animals. Linogliride also stimulates insulin release in vitro. In the perfused pancreas, pretreatment with tolbutamide desensitizes β-cells to the action of linogliride. We tested the hypothesis that linogliride, like tolbutamide, affects the activity of ATP-sensitive K+ channels, which are thought to control insulin release. We used the whole-cell voltage-clamping technique to measure the K+ current through ATP-sensitive K+ channels in the plasma membrane of single rat β-cells, which were dialyzed with 30 μM ATP. Linogliride (10–300 μM) inhibited the K+ current; half-maximal inhibition was observed at 6–25 μM, depending on how much time was allowed for equilibration of the drug. Reversal of the inhibition was slow (t½ ∼4 min). In summary, linogliride leads to a decrease in the activity of ATP-sensitive K+ channels.
Role of Glycation in Modification of Lens Crystallins in Diabetic and Nondiabetic Senile Cataracts
Authors: Lyons Timothy J , Silvestri Giuliana , Dunn John A , Dyer Daniel G , Baynes John W
Published: September 2013

To assess the significance of glycation, nonenzymatic browning, and oxidation of lens crystallins in cataract formation in elderly diabetic patients, we measured three distinct products of glycation, browning, and oxidation reactions in cataractous lens crystallins from 29 diabetic patients (mean ± SD age 72.8 ± 8.8 yr) and 24 nondiabetic patients (age 73.5 ± 8.3 yr). Compounds measured included 1) fructoselysine (FL), the first stable product of glycation; 2) pentosidine, a fluorescent, carbohydrate-derived protein cross-link between lysine and arginine residues formed during nonenzymatic browning; and 3) N ε-(carboxymethyl)lysine (CML), a product of autoxidation of sugar adducts to protein. In diabetic compared with nondiabetic patients, there were significant increases (P < 0.001) in HbA1 (10.2 ± 3.1 vs. 7.1 ± 0.7%), FL (7.6 ± 5.4 vs. 1.7 ± 1.2 mmol/mol lysine), and pentosidine (6.3 ± 2.8 vs. 3.8 ± 1.9 μmol/mol lysine). The disproportionate elevation of FL compared with HbA1 suggests a breakdown in the lens barrier to glucose in diabetes, whereas the increase in pentosidine is indicative of accelerated nonenzymatic browning of diabetic lens crystallins. CML levels were similar in the two groups (7.1 ± 2.4 vs. 6.8 ± 3.0 mmol/mol lysine), providing no evidence for increased oxidative stress in the diabetic cataract. Thus, although the modification of lens crystallins by autoxidation reactions was not increased in diabetes, the increase in glycation and nonenzymatic browning suggests that these processes may acclerate the development of cataracts in diabetic patients.
Tissue-Specific Effects of Aldose Reductase Inhibition on Fluorescence and Cross-Linking of Extracellular Matrix in Chronic Galactosemia: Relationship to Pentosidine Cross-Links
Authors: Richard Stephanie , Tamas Christine , Sell David R , Monnier Vincent M
Published: September 2013

Chronic experimental hyperglycemia mediated by galactose has been shown to induce browning and cross-linking of rat tail tendon collagen that could be duplicated in vitro by nonenzymatic galactosylation. To investigate the nature of these changes, Sprague-Dawley rats were placed on a 33% galactose diet without and with sorbinil for 6 and 12 mo. Collagen-linked fluorescence and pentosidine cross-links increased with age and galactosemia in tail tendons (P < 0.001) and skin but were essentially unresponsive to aldose reductase inhibition (ARI). In contrast, tendon breaking time in urea, a likely parameter of cross-linking, was markedly improved (P < 0.001) by ARI. Fluorescence that was inhibited by sorbinil treatment was increased in pepsin and proteinase K digest of aortic tissue from galactosemic rats (P < 0.001), but impaired enzymatic digestibility was not observed. Systolic blood pressure as potential consequence of aortic stiffening was not increased in galactosemia. These data suggest that fluorescence in skin and tendon might be in part due to advanced glycosylation and pentosidine formation because these were not decreased by ARI. However, they also suggest that nonfluorescent cross-links may also be forming because, in contrast to fluorescence, tail tendon breaking time was partly corrected by ARI. Thus, it appears that extracellular matrix changes in chronic galactosemia are complex, being partly attributable to advanced glycosylation and partly to polyol-pathway activation.
Importance of Insulin in Subjective, Cognitive, and Hormonal Responses to Hypoglycemia in Patients With IDDM
Authors: Kerr David , Reza Mansur , Smith Nicola , Leatherdale Brian A
Published: September 2013

Not all episodes of hypoglycemia are recognized as such by diabetic patients, suggesting that it is possible for them to adapt to a low blood glucose level, although the mechanism involved is not known. The aim of this study was to examine whether insulin has an effect, independent of blood glucose, on the subjective, cognitive, and hormonal responses to hypoglycemia. Nine patients with insulin-dependent diabetes mellitus (IDDM) participated in three hyperinsulinemic glucose-clamp studies. After 60 min at 4.5 mM, blood glucose was randomized to be 1) maintained at 4.5 mM for 240 min, 2) lowered to 2.8 mM for 180 min followed by 60 min at 2 mM with an insulin infusion rate of 40 mU · m−2 · m−1, and 3) fitted to the same protocol as 2 but with an infusion rate of 120 mU · m−2 · min−1. Symptoms and awareness of hypoglycemia (100-mm visual analogue scales), cognitive function, and counterregulatory hormone levels were assessed every 30 min. There were no subjective or cognitive changes during the euglycemic study. Awareness and hypoglycemic symptoms (hunger, facial flushing, trembling, and sweating) were attenuated by the higher insulin infusion rate (P < 0.05 and P < 0.01, respectively). Cognition was significantly impaired after 60 min at 2.8 mM (P < 0.001) and deteriorated further when the blood glucose level was lowered to 2 mM (P < 0.01). Levels of cortisol (P < 0.01) and growth hormone (P < 0.05) but not epinephrine were suppressed by the higher insulin infusion rate. We conclude that the prevailing insulin level does influence the perception of symptomatic and hormonal responses to low blood glucose levels. Cognitive impairment is dependent on level and duration of hypoglycemia.
Abnormalities of Cognitive Functions in IDDM Revealed by P300 Event-Related Potential Analysis: Comparison With Short-Latency Evoked Potentials and Psychometric Tests
Authors: Pozzessere Giuseppe , Valle Elvira , de Crignis Silva , Cordischi Virginia M , Fattapposta Francesco , Rizzo Paolo A , Pietravalle Patrizia , Cristina Giuseppe , Morano Susanna , Di Mario Umberto
Published: September 2013

The possible influence of diabetes on the higher mnestic and cognitive functions has been investigated. The P300 wave latency, an endogenous electrophysiological event, was explored and compared with the multimodal short-latency evoked potential (EP) recordings (visual [VEP], brainstem auditory [BAEP], and median and tibial nerve somatosensory EPs [mSEP and tSEP, respectively]) and psychometric test measures in 16 insulin-dependent diabetic (IDDM) patients, in 16 age- and (IDDM) sex-matched nondiabetic subjects, and in a large normal reference population. The age of subjects, the duration of IDDM, and the metabolic control of patients were taken into account. P300 values were significantly increased in IDDM versus matched control subjects (P < 0.001), and 3 patients showed values above the reference value range. Abnormal VEP recordings were present in 1 of 16 patients, BAEP in 3 of 16, mSEP in 7 of 16, and tSEP in 6 of 16. Digit-span backward test results were significantly (P < 0.02) modified in the diabetic cohort. There was no tendency for anomalies of P300, short-latency EPs, and psychometric test values to be contemporarily present, except in 1 patient. Electrophysiological or psychometric abnormalities were not clearly correlated with the duration of IDDM or the degree of short-term metabolic control. These findings give evidence that 1) higher cognitive functions may be affected in diabetes as documented by P300 analysis and short-term memory tests, 2) endogenous electrophysiological analysis highlights neuropsychological changes not detectable by psychometric tests, 3) an alteration of evoked potentials was present in half of the IDDM subjects studied, and 4) anomalies of the CNS are patchily distributed in diabetes.
Progression to Type I Diabetess in Autoimmune Endocrine Patients With Islet Cell Antibodies
Authors: Bosi Emanuele , Becker Frank , Bonifacio Ezio , Wagner Richard , Collins Peter , Gale Edwin A M , Bottazzo Gian Franco
Published: September 2013

In an 11-yr screening program carried out on serum samples sent to an autoimmune serology laboratory, 158 patients with clinical or subclinical autoimmune endocrine manifestations and islet cell antibodies (ICAs) in the absence of overt diabetes were identified and followed for the development of insulin-dependent (type I) diabetes. Twenty-two (13.9%) developed type I diabetes in a follow-up of up to 12 yr (mean ± SE 4.8 ± 3.2 yr). The probability of being free of type I diabetes was 69.8% at 10 yr after the first detection of ICAs. Progression to disease was influenced by 1) the amount of ICAs represented by high titers (63% of those with ICAs ≥20 Juvenile Diabetes Foundation units being free of type I diabetes at 10 yr), ICA persistency (59% being free of type I diabetes; P < 0.02 vs. nonpersistent ICA), and complement-fixing (CF)-ICAs (63% being free of type I diabetes; P < 0.05 vs. non–CF-ICA); 2) the coexistence of insulin autoantibodies (IAAs) (25% being free of type I diabetes; P < 0.005 vs. IAA−); and 3) a positive family history (1st-degree relative) for type I diabetes (32% being free of type I diabetes; P < 0.005 vs. no family history). There was a trend for diabetes to develop earlier in males of a younger age. No relationships were found with the number, type, or clinical expression of the associated autoimmunities or with a family history of such disorders. These data confirm the predictive ability of ICAs and lAAs for type I diabetes and indicate that the events that lead to disease in individuals with ICAs are influenced by the level of the humoral response and by a familial association of type I diabetes. This study identified a large cohort of individuals with high ICA levels who have not progressed to type I diabetes. A study of these individuals will be valuable in identifying factors important for the ultimate progression to disease.
Detection of Inner Retina Dysfunction by Steady-State Focal Electroretinogram Pattern and Flicker in Early IDDM
Authors: Ghirlanda Giovanni , Di Leo Mauro A S , Caputo Salvatore , Falsini Benedetto , Porciatti Vittorio , Marietti Giovanni , Greco Aldo V
Published: September 2013

The effects of diabetes on the neural retina before the onset of clinically detectable retinopathy can be investigated with electrophysiological methods. Our aim was to detect early retinal dysfunctions in 60 patients with insulin-dependent diabetes mellitus (IDDM) and with a short duration of disease. We used the steady-state focal (9° field size) electroretinogram (ERG) of the macula in response to luminance modulation of a uniform field (flicker ERG) or to counterphase-modulated sinusoidal gratings (pattern ERG). The harmonic analysis of flicker ERG and pattern ERG yielded three main components: a first and a second harmonic to flicker (1F and 2F, respectively) and a second harmonic to pattern (2P). The 1F is believed to be correlated to photoreceptor activity, whereas 2F and 2P represent different subsets of generators in the inner retina. Results of focal ERG in IDDM patients with no or early retinopathy were compared with age-matched control subjects. Mean 2F and 2P amplitudes were significantly reduced in IDDM patients compared with the control group (P = 0.0001 by analysis of variance). 2P but not 2F amplitude was significantly more reduced in patients with retinopathy than in those without retinopathy (P < 0.05). 2F but not 2P phase abnormalities were observed in some patients. 2F and 2P alterations were slightly correlated with metabolic control (r = 0.22, P = 0.02) and disease duration (r = 0.28, P = 0.003). 1F was not significantly altered in IDDM patients. Our results suggest that early diabetes causes selective neurosensory deficits of inner retina layers, whereas the photoreceptors appear unaffected.
Renal Adaptation to Dietary Phosphate Restriction in Rats: Interactions With Insulin and Calcitriol
Authors: Allon Michael , Hruska Keith A
Published: September 2013

Insulin may contribute to the increase in tubular reabsorption of phosphate during dietary phosphate restriction. Moreover, insulin is required for the stimulation of calcitriol under this experimental condition. To evaluate whether calcitriol plays a role in the antiphosphaturic effect of insulin during phosphate restriction, phosphate uptake was measured in brush border membrane vesicles (BBMVs) obtained from the following six experimental groups of rats: normal (0.8%)-phosphate diet for 1 wk, low (0.03%)-phosphate diet for 1 wk, normal-phosphate diet for 1 wk and streptozocin 48 h before the experiment, low-phosphate diet for 1 wk and streptozocin 48 h before the experiment, low-phosphate diet and streptozocin and exogenous insulin, and low-phosphate diet and streptozocin and exogenous calcitriol. BBMV phosphate uptake was higher in the nondiabetic rats on a low-phosphate diet than in the controls on a normal-phosphate diet. BBMV phosphate uptake was not different between diabetic rats on a normal-phosphate diet than in nondiabetic controls on the same diet. In contrast, BBMV was significantly lower in diabetic rats on a low-phosphate diet than in nondiabetic controls on the same diet. Exogenous insulin but not calcitriol restored the increase in BBMV phosphate uptake in diabetic rats on a low-phosphate diet. Plasma calcitriol levels were increased threefold in nondiabetic rats fed a low-phosphate diet. Streptozocin-induced diabetes abolished the adaptive increase in plasma calcitriol. Exogenous insulin and calcitriol administration to diabetic rats on a low-phosphate diet resulted in similar increases in plasma calcitriol levels. These results suggest that, during dietary phosphate restriction, insulin stimulates renal phosphate retention independently of its effect on calcitriol.
Effect of Somatostatin-28 on Dynamics of Insulin Secretion in Perfused Rat Pancreas
Authors: Ensinck John W , Laschansky Ellen C , Vogel Robin E , D'Alessio David A
Published: September 2013

Somatostatin-28 (S-28), originating in gastrointestinal cells, is secreted into the circulatory system and rises in human plasma after ingestion of a mixed meal. Pancreatic β-cells contain specific, high-affinity receptors for S-28, and it is plausible that this peptide is a physiological modulator of insulin secretion. To evaluate the effects of physiological concentrations of S-28 on glucose-mediated insulin secretion, we used the perfused in situ rat pancreas under two conditions: 1) “square-wave” glucose infusion from 2.8 to 11.1 mM and 2) ramping of glucose at 0.28 mM/min throughout 45 min. S-28 concentrations of 16, 32, and 80 pM were separately coinfused for 40 min in the first condition and at 16 pM in the second condition. During square-wave glucose infusion, biphasic insulin secretion was elicited with marked attenuation of both phases during coinfusion with the two higher concentrations of S-28. At 16 pM S-28, which approximates postprandial At 16 pM S-28, which approximates postprandial concentrations, only first-phase secretion was suppressed. During ramping of glucose, insulin was released gradually and, in the presence of 16 pM S-28, was shifted to the right, indicating an increase in threshold glucose levels for insulin secretion. We concluded that S-28, at levels achieved postprandially, modulates the release of insulin by altering the threshold of sensitivity to glucose.