The pathogenesis of NIDDM

Identification and characterization of a small molecule that activates thiosulfate sulfurtransferase and stimulates mitochondrial respiration

The enzyme Thiosulfate sulfurtransferase (TST, EC 2.8.1.1), is a positive genetic predictor of diabetes type 2 and obesity. As increased TST activity protects against the development of diabetic symptoms in mice, an activating compound for TST may provide therapeutic benefits in diabetes and obesity. We identified a small molecule activator of human TST through screening of an inhouse small molecule library. Kinetic studies in vitro suggest that two distinct isomers of the compound are required for full activation as well as an allosteric mode of activation. Additionally, we studied the effect of TST protein and the activator on TST activity through mitochondrial respiration. Molecular docking and molecular dynamics (MD) approaches supports an allosteric site for the binding of the activator, which is supported by the lack of activation in the Escherichia coli. mercaptopyruvate sulfurtransferase. Finally, we show that increasing TST activity in isolated mitochondria increases mitochondrial oxygen consumption.

Therapeutic vs. Suprapharmacological Metformin Concentrations: Different Effects on Energy Metabolism and Mitochondrial Function in Skeletal Muscle Cells in vitro

Metformin is an oral antidiabetic agent that has been widely used in clinical practice for over 60 years, and is currently the most prescribed antidiabetic drug worldwide. However, the molecular mechanisms of metformin action in different tissues are still not completely understood. Although metformin-induced inhibition of mitochondrial respiratory chain Complex I and activation of AMP-activated protein kinase have been observed in many studies, published data is inconsistent. Furthermore, metformin concentrations used for in vitro studies and their pharmacological relevance are a common point of debate. The aim of this study was to explore the effects of different metformin concentrations on energy metabolism and activity of relevant signaling pathways in C2C12 muscle cells in vitro. In order to determine if therapeutic metformin concentrations have an effect on skeletal muscle cells, we used micromolar metformin concentrations (50 µM), and compared the effects with those of higher, millimolar concentrations (5 mM), that have already been established to affect mitochondrial function and AMPK activity. We conducted all experiments in conditions of high (25 mM) and low glucose (5.5 mM) concentration, in order to discern the role of glucose availability on metformin action. According to our results, micromolar metformin treatment did not cause Complex I inhibition nor AMPK activation. Also, cells cultured in low glucose medium were more sensitive to Complex I inhibition, mitochondrial membrane depolarization and AMPK activation by millimolar metformin, but cells cultured in high glucose medium were more prone to induction of ROS production. In conclusion, even though suprapharmacological metformin concentrations cause Complex I inhibition and AMPK activation in skeletal muscle cells in vitro, therapeutic concentrations cause no such effect. This raises the question if these mechanisms are relevant for therapeutic effects of metformin in skeletal muscle.

The Genetic Basis of Metabolic Disease

Recent developments in genetics and genomics are providing a detailed and systematic characterization of the genetic underpinnings of common metabolic diseases and traits, highlighting the inherent complexity within systems for homeostatic control and the many ways in which that control can fail. The genetic architecture underlying these common metabolic phenotypes is complex, with each trait influenced by hundreds of loci spanning a range of allele frequencies and effect sizes. Here, we review the growing appreciation of this complexity and how this has fostered the implementation of genome-scale approaches that deliver robust mechanistic inference and unveil new strategies for translational exploitation.

Genetic insights into fetal growth and measures of glycaemic regulation and adiposity in adulthood: a family-based study

Background

The genetics of fetal insulin release and/or action have been suggested to affect fetal growth, adult insulin resistance and adult body composition. The genetic correlation between body composition at birth versus glycaemic regulation and body composition in adulthood have, however, not been well studied. We therefore aimed to investigate these genetic correlations in a family-based cohort.

Methods

A Danish family cohort of 434 individuals underwent an oral glucose tolerance test with subsequent calculation of surrogate measures of serum insulin response and insulin sensitivity. Measures of fetal growth were retrieved from midwife journals. Heritability and genetic correlations were estimated using a variance component model.

Results

A high heritability of 0.80 was found for birth weight, whereas ponderal index had a heritability of 0.46. Adult insulin sensitivity measured as Matsuda index was genetically correlated with both birth weight and ponderal index (ρG = 0.36 (95% CI: 0.03; 0.69) and ρG = 0.52 (95% CI, 0.15; 0.89), respectively). Only birth weight showed a significant genetic correlation with adult weight (ρG = 0.38 (95% CI: 0.09; 0.67)) whereas only ponderal index was genetically inversely correlated with fasting insulin (ρG = - 0.47 (95% CI: - 0.86; - 0.08) and area under the curve for insulin release during the oral glucose tolerance test (ρG = - 0.66 (95% CI: - 1.13; - 0.19)).

Individual as well as combined adjustment for 45 selected birth weight, obesity and type 2 diabetes susceptibility gene variants did not affect the correlations.

Conclusions

The genetics of both birth weight and ponderal index appear to be under the same genetic influence as adult insulin resistance. Furthermore, ponderal index and adult insulin release seem to be partly shared, as well as the genetics of birth weight and adult weight.

Word count abstract: 281.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0718-2) contains supplementary material, which is available to authorized users.

Alteration in pancreatic islet function in human immunodeficiency virus

Molecular mechanisms behind the defects in insulin production and secretion associated with antihuman immunodeficiency virus (anti-HIV) therapy and the development of HIV-associated lipodystrophy syndrome (HALS) are discussed in this article. Data suggesting insulin resistance on the beta cell and defects in first-phase insulin release of HALS patients are presented. Hepatic extraction of insulin, nonglucose insulin secretagogues and insulin-like growth factor release may exert influence on the demand of circulating insulin and on insulin secretion in HIV-infected patients. Finally, the paucity in understanding the incretin effects in HIV and HIV therapy in relation to insulin secretion is highlighted.

Recent progress in the use of genetics to understand links between type 2 diabetes and related metabolic traits

Genome-wide association studies have identified genetic variants associated with increased risk of type 2 diabetes. The aim of this review is to highlight some of the insights into the mechanism underlying type 2 diabetes provided by genetic association studies.

β-cell dysfunction in adolescents and adults with newly diagnosed type 2 diabetes mellitus

OBJECTIVE

To compare β-cell function in adolescents and adults with newly diagnosed type 2 diabetes (T2DM).

STUDY DESIGN

Thirty-nine adolescents with T2DM, 38 age- and weight-matched control subjects, and 19 adults with T2DM were studied. The adolescent subjects with diabetes were divided on the basis of whether they needed insulin to control their initial hyperglycemia. The primary outcome variable was the disposition index, computed from the acute insulin response to glucose corrected for insulin sensitivity (1/Homeostatic model assessment of insulin resistance).

RESULTS

The disposition index was significantly reduced in all 3 diabetic groups (control n=3360, adolescents with T2DM without insulin n=630, adolescents with T2DM with insulin n=120, adults with T2DM n=200; P<.001), and the adolescents with more severe hyperglycemia at diagnosis had lower disposition index than those with a more modest presentation (P<.05).

CONCLUSION

At the time of diagnosis, adolescents with T2DM have significant β-cell dysfunction, comparable with adults newly diagnosed with T2DM. Thus, severe β-cell impairment can develop within the first two decades of life and is likely to play a central role in the pathogenesis of T2DM in adolescents.

β-Cell failure in type 2 diabetes

Type 2 diabetic patients are insulin resistant as a result of obesity and a sedentary lifestyle. Nevertheless, it has been known for the past five decades that insulin response to nutrients is markedly diminished in type 2 diabetes. There is now a consensus that impaired glucose regulation cannot develop without insulin deficiency. First-phase insulin response to glucose is lost very early in the development of type 2 diabetes. Several prospective studies have shown that impaired insulin response to glucose is a predictor of future impaired glucose tolerance (IGT) and type 2 diabetes. Recently discovered type 2 diabetes-risk gene variants influence β-cell function, and might represent the molecular basis for the low insulin secretion that predicts future type 2 diabetes. We believe type 2 diabetes develops on the basis of normal but 'weak'β-cells unable to cope with excessive functional demands imposed by overnutrition and insulin resistance. Several laboratories have shown a reduction in β-cell mass in type 2 diabetes and IGT, whereas others have found modest reductions and most importantly, a large overlap between β-cell masses of diabetic and normoglycemic subjects. Therefore, at least initially, the β-cell dysfunction of type 2 diabetes seems more functional than structural. However, type 2 diabetes is a progressive disorder, and animal models of diabetes show β-cell apoptosis with prolonged hyperglycemia/hyperlipemia (glucolipotoxicity). β-Cells exposed in vitro to glucolipotoxic conditions show endoplasmic reticulum (ER) and oxidative stress. ER stress mechanisms might participate in the adaptation of β-cells to hyperglycemia, unless excessive. β-Cells are not deficient in anti-oxidant defense, thioredoxin playing a major role. Its inhibitor, thioredoxin-interacting protein (TXNIP), might be important in leading to β-cell apoptosis and type 2 diabetes. These topics are intensively investigated and might lead to novel therapeutic approaches. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00094.x, 2011).

Novel biological insights emerging from genetic studies of type 2 diabetes and related metabolic traits

PURPOSE OF REVIEW

In the past 3 years, genome-wide association studies have identified many tens of common genetic variants associated with metabolic diseases and traits. Although much further research is needed to identify the target genes, the associations between gene variants and diseases are already providing biological insights. The purpose of this review is to update the reader with the most relevant findings, with a particular emphasis on type 2 diabetes (T2D) and glucose metabolism, and discuss some of the biological implications of the genetic findings.

RECENT FINDINGS

Largely through recent genome-wide association studies, we now know of approximately 20 gene variants associated with T2D, 10 with body mass index (BMI) and obesity, four with fasting glucose levels in the normoglycaemic population and over 30 with lipid levels. These findings are stimulating many new important areas of research related to metabolic diseases. For T2D and glucose metabolism, we discuss a number of aspects and implications of the genetic findings, including the observations that T2D gene variants are not usually in or near obvious candidate genes, highlighting the poor prior knowledge of the biology of the disease; most T2D gene variants are associated with beta-cell function rather than insulin resistance; there is a difference between genes that influence variation in normal glucose levels compared with those influencing onset and progression of diabetes; and there is a genetic link between diabetes and foetal growth.

SUMMARY

Genetic studies in the past 3 years have provided a greatly increased knowledge of the regions of the genome involved in adverse metabolic consequences. There are now over 100 common genetic variants reproducibly associated with metabolic traits, including reduced beta-cell function, obesity, increased lipid levels and increased glucose levels. These genetic findings are already altering perceptions of how these traits develop and interact to result in diseases such as T2D.

Impaired first‐phase insulin response predicts postprandial blood glucose increment in patients with recently diagnosed type 2 diabetes

OBJECTIVE

The aim of the study was to evaluate the relationship between postprandial blood glucose and first-phase insulin response and, furthermore, to assess whether the intravenous glucagon stimulation test can be used as a predictor for increased postprandial glucose in patients with recently diagnosed type 2 diabetes.

MATERIAL AND METHODS

Twenty patients with diet-treated type 2 diabetes, diagnosed within the past 5 years, were included. In random order, on three different days, the patients underwent: 1) a standardized meal tolerance test, 2) an intravenous glucose tolerance test, and 3) an intravenous glucagon stimulation test. The postprandial blood glucose response was defined as the incremental area under the blood glucose curve 0-240 min after the meal.

RESULTS

The first-phase insulin response at an intravenous glucose stimulation test was significantly correlated to the postprandial blood glucose increment (R(2)=0.21, p<0.05) and the maximal increment in plasma glucose concentration (R(2)=0.40, p<0.01) during the meal tolerance test. However, the incremental C-peptide value at 6 min in response to intravenous glucagon stimulation did not correlate to the postprandial blood glucose increment (R(2)=0.09, p=0.14).

CONCLUSION

Impaired first-phase insulin response is a significant predictor of the increase in postprandial blood glucose in patients with type 2 diabetes in near normal metabolic control, whereas beta-cell function, assessed by glucagon stimulation test, is not.

T2D-Db: an integrated platform to study the molecular basis of Type 2 diabetes

Background

Type 2 Diabetes Mellitus (T2DM) is a non insulin dependent, complex trait disease that develops due to genetic predisposition and environmental factors. The advanced stage in type 2 diabetes mellitus leads to several micro and macro vascular complications like nephropathy, neuropathy, retinopathy, heart related problems etc. Studies performed on the genetics, biochemistry and molecular biology of this disease to understand the pathophysiology of type 2 diabetes mellitus has led to the generation of a surfeit of data on candidate genes and related aspects. The research is highly progressive towards defining the exact etiology of this disease.

Results

T2D-Db (Type 2 diabetes Database) is a comprehensive web resource, which provides integrated and curated information on almost all known molecular components involved in the pathogenesis of type 2 diabetes mellitus in the three widely studied mammals namely human, mouse and rat. Information on candidate genes, SNPs (Single Nucleotide Polymorphism) in candidate genes or candidate regions, genome wide association studies (GWA), tissue specific gene expression patterns, EST (Expressed Sequence Tag) data, expression information from microarray data, pathways, protein-protein interactions and disease associated risk factors or complications have been structured in this on line resource.

Conclusion

Information available in T2D-Db provides an integrated platform for the better molecular level understanding of type 2 diabetes mellitus and its pathogenesis. Importantly, the resource facilitates graphical presentation of the gene/genome wide map of SNP markers and protein-protein interaction networks, besides providing the heat map diagram of the selected gene(s) in an organism across microarray expression experiments from either single or multiple studies. These features aid to the data interpretation in an integrative way. T2D-Db is to our knowledge the first publicly available resource that can cater to the needs of researchers working on different aspects of type 2 diabetes mellitus.

Impaired proinsulin secretion before and during oral glucose stimulation in HIV-infected patients who display fat redistribution

The beta-cell function of HIV-infected patients on highly active antiretroviral therapy who display lipodystrophy may be impaired. An early defect in beta-cell function may be characterized by an increase in secretion of 32-33 split proinsulin (SP) and intact proinsulin (IP). To address this issue, the secretion patterns of SP and IP of 16 HIV-infected men with lipodystrophy (LIPO) and 15 HIV-infected men without lipodystrophy (NONLIPO) were studied during an oral glucose tolerance test (OGTT). All patients received highly active antiretroviral therapy. Insulin secretion rates were determined by deconvolution of plasma C-peptide concentrations. More LIPO than NONLIPO patients displayed diabetes mellitus and impaired glucose tolerance than normal glucose tolerance (LIPO 2/8/6 vs NONLIPO 1/2/12, P = .05). LIPO patients had increased fasting levels of SP and IP, ratio of SP/IP, and area under the curve of SP and IP during the early phase (0, 10, and 20 minutes) and during the late phase (45, 75, and 105 minutes) of the OGTT compared with NONLIPO patients (Ps < .05). LIPO patients exhibited significantly increased fasting SP/IP ratio, fasting SP/insulin ratio, and total proinsulin to C-peptide ratio during the OGTT. LIPO patients displayed increased incremental secretion of IP during the first 10 minutes of the OGTT (P < .05), although the incremental insulin secretion during this period did not differ between LIPO and NONLIPO patients. These data suggest that HIV-infected patients with lipodystrophy display major perturbations of proinsulin secretion in the fasting state and during an OGTT, which is compatible with the notion of a beta-cell dysfunction of such patients.

Feline diabetes mellitus: low carbohydrates versus high fiber?

Treatment of diabetes mellitus (DM) in the cat relies primarily on the adequate insulin therapy and controlled dietary intake. The goals of managing DM in the cat have changed from attaining glycemic control to achieving diabetic remission (transient diabetes) in a large proportion of cases. Remission rates of up to 68% have been published. The used of low-carbohydrate foods for cats improves the odds of achieving diabetic remission by fourfold. Nonetheless, some cats show an improved response to high-fiber food. Clinical judgement, trial, and personal preference to currently dictate which diet to offer an individual animal.

Hyperproinsulinaemia in normoglycaemic lipodystrophic HIV-infected patients

BACKGROUND

We aimed to investigate whether the insulin precursors, intact (IP) and 32-33 split proinsulin (SP), which are elevated in states of insulin resistance and predict type 2 diabetes, would be elevated in human immunodeficiency virus (HIV)-infected patients with lipodystrophy (LIPO).

MATERIALS AND METHODS

Forty-three normoglycaemic HIV-infected patients [18 LIPO and 18 without lipodystrophy (NONLIPO) receiving antiretroviral drugs, and seven patients naïve to antiretroviral drugs (NAIVE)] were examined. Insulin precursors were measured during fasting, during an intravenous glucose tolerance test and during a hyperinsulinaemic-euglycaemic clamp, respectively. Insulin secretion rates (ISR) were determined by deconvolution of C-peptide concentrations. Disposition index (DI) was calculated as insulin sensitivity (Si(RD)) multiplied by the first-phase insulin response to intravenous glucose.

RESULTS

LIPO exhibited increased fasting IP and SP (P < 0.05), a higher proportion of elevated fasting IP (3.1 pmol L(-1), 66% vs. 33% and 28%, P < 0.05) and SP (7.2 pmol L(-1), 50%, 11% and 0%, P < 0.01), reduced Si(RD) (> 50%, P < 0.001) and increased ISR (P < 0.001) compared with NONLIPO and NAIVE. Fasting SP and IP correlated positively with ISR (P < 0.001) and inversely and hyperbolically with Si(RD) (P < 0.001). Fasting SP/insulin ratio correlated inversely with Si(RD) (P < 0.05). Incremental IP + SP/insulin ratio after an intravenous glucose bolus correlated inversely with DI (P < 0.01), but did not differ between study groups.

CONCLUSIONS

Proinsulin appeared to be increased in HIV-lipodystrophy, but no more than caused by the increased ISR. Nevertheless, the inverse correlations between SP/insulin ratio versus Si(RD) and incremental total proinsulin/insulin ratio versus DI may argue for a subtle beta-cell dysfunction in those patients with insulin resistance and low DI.

Prevention of type 2 diabetes by lifestyle intervention: a Japanese trial in IGT males

Prevention of type 2 diabetes by intensive lifestyle intervention designed to achieve and maintain ideal body weight was assessed in subjects with impaired glucose tolerance (IGT). Male subjects with IGT recruited from health-screening examinees were randomly assigned in a 4:1 ratio to a standard intervention group (control group) and intensive intervention group (intervention group). The final numbers of subjects were 356 and 102, respectively. The subjects in the control group and in the intervention group were advised to maintain body mass index (BMI) of <24.0 kg/m2 and of <22.0 kg/m2, respectively, by diet and exercise. In the intervention group, detailed instructions on lifestyle were repeated every 3-4 months during hospital visits. Diabetes was judged to have developed when two or more consecutive fasting plasma glucose (FPG) values exceeded 140 mg/dl. A 100g oral glucose tolerance test was performed every 6 months to detect improvement of glucose tolerance. The subjects were seen in an ordinary outpatient clinic. The cumulative 4-year incidence of diabetes was 9.3% in the control group, versus 3.0% in the intervention group, and the reduction in risk of diabetes was 67.4% (P < 0.001). Body weight decreased by 0.39 kg in the control group and by 2.18 kg in the intervention group (P < 0.001). The control group was subclassified according to increase and decrease in body weight. The incidence of diabetes was positively correlated with the changes in body weight, and the improvement in glucose tolerance was negatively correlated. Subjects with higher FPG at baseline developed diabetes at a higher rate than those with lower FPG. Higher 2h plasma glucose values and higher BMI values at baseline were also associated with a higher incidence of diabetes, but the differences were not significant. Subjects with a low insulinogenic index (DeltaIRI/DeltaPG 30 min after an oral glucose load) developed diabetes at a significantly higher rate than those with a normal insulinogenic index. Comparison of the BMI data and incidence of diabetes in five diabetes prevention studies by lifestyle intervention revealed a linear correlation between the incidence of diabetes and the BMI values, with the exception of the DaQing Study. However, the slope of the reduction in incidence of diabetes in the intensive intervention groups was steeper than expected simply on the basis of the reduction of BMI, suggesting that the effect of lifestyle intervention cannot be solely ascribed to the body weight reduction. We conclude that lifestyle intervention aimed at achieving ideal body weight in men with IGT is effective and can be conducted in an outpatient clinic setting.

Type 2 diabetes in grandparents and birth weight in offspring and grandchildren in the ALSPAC study

OBJECTIVE

To examine the association between a history of type 2 diabetes and birth weight of offspring and grandchildren.

DESIGN

Prospective observational study. Diabetic status, as reported by mothers (F1 generation) was collected on grandparents (F0) of babies (F2) born to mothers (F1) who participated in a study of maternal and child health. Associations between risk of grandparental diabetes and birth weight in mothers (F1) and grandchildren (F2) were analysed using linear and logistic regression.

SETTING

Avon: comprising of the city of Bristol and surrounding areas.

PARTICIPANTS

12 076 singleton babies (F2), their parents (F1) and maternal and paternal grandparents (F0).

RESULTS

Women (F1) who had no parents with type 2 diabetes had lower birth weights than women with one or two diabetic parents, after controlling for the age of both parents. There was a U shaped association between maternal birth weight and grandmaternal diabetes, but no evidence of an association with grandpaternal diabetes. The grandchildren of maternal grandparents with type 2 diabetes were more likely to be in the top tertile of birth weight than grandchildren of non-diabetics. There was evidence for an inverted U shaped association between birth weight of grandchildren and diabetes in paternal grandmothers.

CONCLUSIONS

This is the first study to show intergenerational associations between type 2 diabetes in one generation and birth weight in the subsequent two generations. While the study has limitations mainly because of missing data, the findings nevertheless provide some support for the role of developmental intrauterine effects and genetically determined insulin resistance in impaired insulin mediated growth in the fetus.

Pathogenesis of type 2 diabetes mellitus

This article provides an overview of the pathogenesis of type 2 diabetes mellitus. Discussion begins by describing normal glucose homeostasis and ingestion of a typical meal and then discusses glucose homeostasis in diabetes. Topics covered include insulin secretion in type 2 diabetes mellitus and insulin resistance, the site of insulin resistance, the interaction between insulin sensitivity and secretion, the role of adipocytes in the pathogenesis of type 2 diabetes, cellular mechanisms of insulin resistance including glucose transport and phosphorylation, glycogen and synthesis,glucose and oxidation, glycolysis, and insulin signaling.

An increase in insulin sensitivity and basal beta-cell function in diabetic subjects treated with pioglitazone in a placebo-controlled randomized study

AIMS

To investigate the effect of treatment with pioglitazone on beta-cell function and insulin sensitivity in Type 2 diabetes.

METHODS

Thirty subjects with diet-controlled Type 2 diabetes were randomized to 3 months treatment with pioglitazone (n = 19) or placebo (n = 11). All subjects underwent basal sampling for homeostatic model assessment (HOMA), followed by an intravenous glucose tolerance test and hyperglycaemic clamp, followed by an euglycaemic hyperinsulinaemic clamp; at baseline and after treatment.

RESULTS

All results are expressed as mean (sem). Pioglitazone increased basal insulin sensitivity by 24.7% (7.8) HOMA-%S vs. 2.1% (5.9) in the placebo group (P = 0.02). Stimulated insulin sensitivity, M/I, increased in the pioglitazone group compared with placebo: +15.1 (2.8) l kg(-1) min(-1) vs. +3.2 (2.9) l kg(-1) min(-1), respectively (P = 0.009). Pioglitazone increased adiponectin by 39.3 (6.3), ng/ml compared with a decrease of 0.8 (1.3) ng/ml with placebo (P = 0.00004). HOMA-%B increased with pioglitazone, +11.5% (4.8) vs. -2.0% (4.8) with placebo (P = 0.049), but there was no change in stimulated beta-cell function as determined by hyperglycaemic clamps. There was a significant reduction in the proinsulin/insulin ratio in the pioglitazone group, -0.057 (0.02) compared with placebo, +0.004 (0.02) (P = 0.03). There was a significant reduction in HbA(1c) of 0.6% (0.1) in the pioglitazone group compared with placebo (P = 0.003). There was no significant weight gain associated with pioglitazone therapy: +0.7 (sem 0.6) kg vs. +1.1 (sem 0.5) kg in placebo group (P = NS).

CONCLUSIONS

Basal beta-cell function and insulin sensitivity improved following pioglitazone therapy. The improvement in proinsulin to insulin ratio suggests that beta-cells are under less stress.

Evaluation of the site(s) of glycation in human proinsulin by ion-trap LCQ electrospray ionization mass spectrometry

The glycation of beta cell proteins is known to occur under hyperglycemic states. The site(s) of glycation in human proinsulin was investigated following exposure to a hyperglycemic environment under reducing conditions in vitro. Proinsulin and glycated proinsulin were separated by reversed-phase high-performance liquid chromatography (RP-HPLC) and identified using LCQ ion-trap electrospray ionization mass spectrometry. This revealed a major peak (>70% total) of monoglycated proinsulin (M(r) 9552.2 Da), a second peak (approximately 27%) of nonglycated proinsulin (M(r) 9389.8 Da), and a third minor peptide peak (approximately 3%) corresponding to diglycated proinsulin (M(r) 9717.9 Da). Following reduction of disulphide bridges with dithiothreitol, intact peptides were incubated with endoproteinase Glu-C to release nine daughter fragments for LC-MS analysis. This strategy revealed an N-terminal fragment of monoglycated proinsulin Phe(1)-Glu(13), which contained a single glucitol adduct (M(r) 1642.0 Da). A similar treatment of small amounts of purified diglycated proinsulin revealed a fragment with Phe(1)-Glu(13) linked by a disulphide bridge to Gln(70)-Glu(82) containing two glucitol adducts (M(r) 3292.7 Da). In summary, these studies indicate that the major site of glycation in proinsulin, like insulin, is the amino terminal Phe(1) residue. However, small amounts of diglycated proinsulin occur naturally, involving an additional site of glycation located between Gln(70) and Glu(82).

Prevention of type 2 diabetes in young people: a theoretical perspective

Type 2 diabetes in youth is an increasing public health concern, especially in certain minority populations. The current paper consists of four sections. First, we establish the significance of the problem by presenting an overview of epidemiological and physiological evidence. Second, we discuss behavioral issues relevant to the prevention of type 2 diabetes in youth. Third, a qualitative review of existing prevention interventions specific to type 2 diabetes in youth is presented. Results suggest that modest improvements in social cognitive, dietary, and exercise outcomes are possible with diabetes intervention studies, although beneficial changes are difficult to sustain over the long term. Although theoretical frameworks are not always explicit, most studies have utilized elements of the social cognitive theory. Less attention has been paid to sociocultural and community organization variables. Finally, the paper discusses issues of risk definition and intervention sustainability, and presents a comprehensive, theoretically diverse model for the prevention of type 2 diabetes in youth. In summary, we suggest that theories of the natural history and pathophysiology of type 2 diabetes are important to identify modifiable risk factors, while theories of behavioral change are essential to modify the risk factors identified. The combination of sound physiological and behavioral theories should form the basis of prevention intervention design. In addition, an ecologic approach that takes into consideration the dynamic interactions of personal, social, and environmental factors would best promote the long-term adoption of healthful behaviors in a supportive, meaningful, and personally enjoyable context.

Regulation of in vitro maturation of stimulus-secretion coupling in fetal rat islet beta-cells

We have studied the maturation of a glucose-responsive insulin release from fetal rat islets, and specifically investigated the impact of nutrients, alpha-adrenoceptors, imidazoline receptors, and cyclic adenosine monophosphate (cAMP). Islets were isolated from 21 -d-old fetal rats and maintained for 7 d in tissue culture at 3.3 or 11.1 mM glucose and various supplements. Culture in the presence of the nonglucidic nutrient alpha-ketoisocaproic acid (KIC), markedly enhanced both basal and stimulated insulin release from islets cultured at either low or high glucose. Additionally, KIC significantly elevated the insulin content of islets maintained in low glucose, whereas it slightly lowered it in islets cultured at high glucose. Culture with phentolamine, an antagonist of alpha-adrenergic and imidazoline receptors, markedly amplified both basal and glucose-stimulated insulin secretion when added with islets cultured in either low or high glucose. By contrast, the pure alpha2-adrenoceptor antagonist benextramine had no such effects. Addition to culture media of a membrane-permeant agonist (Sp-cAMP[S]) or antagonist (Rp-cAMP[S]) of cAMP-dependent protein kinases types I and II failed to influence basal or glucose-responsive insulin secretory rates at either glucose concentration during culture as well as islet insulin content. In conclusion, islet beta-cell differentiation and functional maturation of the stimulus-secretion coupling can be accelerated in vitro in fetal rat pancreatic tissue by nutrient stimulation, and by interference with imidazoline receptors, whereas cAMP seems virtually ineffective in this respect. These effectors may be of regulatory significance in the in vivo development of glucose-sensitive beta-cells.

Peptidergic regulation of maturation of the stimulus-secretion coupling in fetal islet beta cells

The stimulus-secretion coupling of the insulin-producing pancreatic islet beta cell is subject to functional maturation during fetal life. We studied the maturation of a glucose-responsive insulin release from fetal rat islets and specifically investigated the impact of peptidergic regulation. To this end, islets were isolated from 21-day-old fetal rats and maintained for 7 days in tissue culture at 3.3 or 11.1 mM glucose and various supplements. In islets cultured in low glucose, acutely raising the ambient glucose concentration to 16.7 mM evoked a modest stimulation of short-term insulin release that was more pronounced in islets maintained in high glucose. Moreover, the insulin content was much higher in islets cultured in high than in low glucose. Culture with growth hormone (GH) markedly amplified both basal and stimulated short-term insulin secretion from islets maintained in either low or high glucose. Additionally, GH significantly elevated the insulin content in islets maintained in low glucose. Transforming growth factor alpha (TGF-alpha) increased basal, but not glucose-stimulated, insulin release and insulin content in islets cultured in low glucose. Gastrin, expressed in islets during fetal life, did not affect basal or glucose-stimulated insulin release, or insulin content, in islets maintained in either low or high glucose. The addition of gastrin to TGF-alpha did not affect the results obtained with the latter peptide. Gastrin-releasing peptide failed to influence basal or glucose-responsive insulin secretory rates, and insulin content, at either glucose concentration during culture. The somatostatin analog Sandostatin (octreotide acetate) neither influenced basal nor stimulated short-term insulin release at any glucose concentration present during culture, whereas the hormone significantly decreased the insulin content of islets cultured in high glucose. Pancreastatin, produced by porcine islet beta and delta cells, failed to influence basal or glucose-responsive insulin secretory rates, and islet insulin content, at either glucose concentration during culture. Culture with gastric inhibitory peptide (GIP) or glucagon-like peptide I (GLP-1), two proposed incretins, did not affect short-term insulin secretion in response to 3.3 or 16.7 mM glucose irrespective of the ambient glucose concentration during culture. To the contrary, GLP-1, but not GIP, increased the content of insulin in islets cultured in low glucose. We conclude that islet beta-cell differentiation and functional maturation of the stimulus-secretion coupling can be modulated in vitro in fetal rat pancreatic tissue by peptidergic regulation and glycemic stimulation. We suggest that GH and TGF-alpha stimulate, while somatostatin, through paracrine interaction, may inhibit, these processes. These effectors may be of regulatory significance in the in vivo development of glucose-sensitive beta cells, and defects in these mechanisms may result in glucose intolerance in adult subjects.

Infant feeding and adult glucose tolerance, lipid profile, blood pressure, and obesity

BACKGROUND

It is generally accepted that breast feeding has a beneficial effect on the health of infants and young children. Recently, a few studies have shown that the method of infant feeding is also associated with cardiovascular disease and its risk factors in adult life.

AIMS

To examine the association between the method of infant feeding in the first weeks after birth and glucose tolerance, plasma lipid profile, blood pressure, and body mass in adults aged 48-53 years.

METHODS

Subjects born at term between 1 November 1943 and 28 February 1947 in the Wilhelmina Gasthuis in Amsterdam around the time of a severe period of famine (late November 1944 to early May 1945). For 625 subjects, information was available about infant feeding at the time of discharge from hospital (on average 10.4 days after birth), and at least one blood sample after an overnight fast.

RESULTS

Subjects who were bottle fed had a higher mean 120 minute plasma glucose concentration after a standard oral glucose tolerance test than those who were exclusively breast fed. They also had a higher plasma low density lipoprotein (LDL) cholesterol concentration, a lower high density lipoprotein (HDL) cholesterol concentration, and a higher LDL/HDL ratio. Systolic blood pressure and body mass index were not affected by the method of infant feeding.

CONCLUSIONS

Exclusive breast feeding seems to have a protective effect against some risk factors for cardiovascular disease in later life.

Autonomic dysfunction is related to impaired pancreatic beta cell function in patients with coronary artery disease

OBJECTIVE

To assess the role of beta cell failure in the development of autonomic dysfunction in patients with coronary artery disease.

DESIGN

Autonomic function was measured by standard clinical methods and by heart rate variability in 24 type II diabetic and 24 non-diabetic subjects with coronary artery disease. Quantitative estimates of pancreatic beta cell function (%beta) and insulin resistance were made from basal plasma glucose and insulin concentrations using a computer solved model. Fasting proinsulin levels provided an independent measure of beta cell function.

RESULTS

The circadian rhythm of sympathovagal balance (ratio of low to high frequency spectral components of heart rate variability) was significantly attenuated in patients with below median (%beta </= 63. 3) compared with above median pancreatic beta cell function. Multiple measures of autonomic function showed positive associations with %beta (low frequency: r = 0.41, p = 0.004; high frequency: r = 0.27, p = 0.07; lying/standing fall in systolic pressure: r = -0.30, p = 0.04) and negative associations with proinsulin (low frequency: r = -0.35, p = 0.03; high frequency: r = -0.36, p = 0.02; standard deviation of RR intervals: r = -0.43, p = 0.007). Associations tended to be stronger in non-diabetic than diabetic patients. In contrast, there was no association between insulin resistance and either autonomic function or the circadian rhythm of sympathovagal balance, regardless of diabetes status.

CONCLUSIONS

The data are consistent with the hypothesis that beta cell failure plays a pathogenic role in the development of autonomic dysfunction in patients with coronary artery disease.

The fetal insulin hypothesis: an alternative explanation of the association of low birthweight with diabetes and vascular disease

Low birthweight is associated with insulin resistance, hypertension, coronary-artery disease, and non-insulin-dependent diabetes (NIDDM). A suggested explanation for this association is intrauterine programming in response to maternal malnutrition. We propose, however, that genetically determined insulin resistance results in impaired insulin-mediated growth in the fetus as well as insulin resistance in adult life. Low birthweight, measures of insulin resistance in life, and ultimately glucose intolerance, diabetes, and hypertension could all be phenotypes of the same insulin-resistant genotype. There is evidence to support this hypothesis. Insulin secreted by the fetal pancreas in response to maternal glucose concentrations is a key growth factor. Monogenic diseases that impair sensing of glucose, lower insulin secretion, or increase insulin resistance are associated with impaired fetal growth. Polygenic influences resulting in insulin resistance in the normal population are therefore likely to result in lower birthweight. Abnormal vascular development during fetal life and early childhood, as a result of genetic insulin resistance, could also explain the increased risk of hypertension and vascular disease. The predisposition to NIDDM and vascular disease is likely to be the result of both genetic and fetal environmental factors.

Heterogeneous relationship of early insulin response and fasting insulin level with development of non-insulin-dependent diabetes mellitus in non-diabetic Japanese subjects with or without obesity

The aim of this study was to investigate the association of insulin secretion and insulin resistance with the development of non-insulin-dependent diabetes mellitus (NIDDM) in obese (body mass index (BMI) > or = 25 kg/m2) and non-obese Japanese. Subjects were selected from persons participating a health survey, and a 100 g oral glucose tolerant test was performed. A total of 1604 non-diabetic subjects were followed for 2-8 years (mean 4.5 years). The fasting insulin level and the homeostasis model insulin resistance index (HOMA-R = fasting glucose [mmol/l] x fasting insulin [microU/ml]/22.5) were used as the index of insulin resistance, and insulinogenic index (the ratio of increment of insulin to that of blood glucose 30 min after glucose load) as a measure of early insulin response. Cox's proportional hazards analysis in the whole group showed that BMI, fasting blood glucose (FBG) and 2-h blood glucose (2-h BG) were positive predictors, and age and insulinogenic index were negative predictors of diabetes. Sex, family history, fasting insulin level and HOMA-R were not predictive of developing diabetes. In subgroup analysis, the same variables as in the whole group were predictors in non-obese, whereas only FBG and 2-h BG predicted diabetes in obese subjects. Fasting insulin level and HOMA-R were not predictive of diabetes both in non-obese and obese subjects. Eleven obese subjects, who developed diabetes despite a normal initial insulinogenic index, had significantly higher BMI, fasting insulin level and HOMA-R, compared with 258 obese subjects who did not develop diabetes. We conclude that most cases of diabetes in Japanese begin with decreased insulin secretion, but a small group of diabetes patients may start with insulin resistance, especially obese subjects.

Tissue-specific knockout of the insulin receptor in pancreatic beta cells creates an insulin secretory defect similar to that in type 2 diabetes

Dysfunction of the pancreatic beta cell is an important defect in the pathogenesis of type 2 diabetes, although its exact relationship to the insulin resistance is unclear. To determine whether insulin signaling has a functional role in the beta cell we have used the Cre-loxP system to specifically inactivate the insulin receptor gene in the beta cells. The resultant mice exhibit a selective loss of insulin secretion in response to glucose and a progressive impairment of glucose tolerance. These data indicate an important functional role for the insulin receptor in glucose sensing by the pancreatic beta cell and suggest that defects in insulin signaling at the level of the beta cell may contribute to the observed alterations in insulin secretion in type 2 diabetes.

Abnormally high nourishment during sensitive periods results in body weight changes across generations

OBJECTIVE

This study asked whether a brief period of overnutrition during a developmentally sensitive time could impact the individual's adult weight and that of succeeding generations.

RESEARCH METHODS AND PROCEDURES

Female rat pups (F1 generation) were randomly assigned to 1 of 3 groups: (1) a control group that was naturally reared by mothers; (2) another control group implanted with chronic gastric fistulas on postnatal day 4 and fed enough formula to match the growth of the mother-reared group; and (3) an experimental group gastrostomized and infused from day 8 through day 16 with a greater quantity of food than gastrostomy-reared controls (OF). On postnatal day 16, both gastrostomy-reared groups were returned to normal litters. Adult F1 females from overfed and mother-reared groups were bred with normal males to yield an F2 generation. F2 adult females were bred to normal males to produce an F3 generation.

RESULTS

When adult, the F1 experimental group was heavier than control groups. F2 adults from OF mothers were smaller than those from the control group. F3 animals from OF grandmothers were heavier at weaning than F3 descendants from mother-reared animals.

DISCUSSION

Excess nourishment during a developmentally sensitive period changed the metabolic phenotype of one generation so dramatically that the gestational development and subsequent phenotype of two succeeding generations were also changed. The experiment models fetal effects of gestational diabetes in humans and may help to elucidate how, independent of genetic anomalies, secular changes can be detected across generations.

Mutations in the glucokinase gene of the fetus result in reduced birth weight

Low birth weight and fetal thinness have been associated with non-insulin dependent diabetes mellitus (NIDDM) and insulin resistance in childhood and adulthood. It has been proposed that this association results from fetal programming in response to the intrauterine environment. An alternative explanation is that the same genetic influences alter both intrauterine growth and adult glucose tolerance. Fetal insulin secretion in response to maternal glycaemia plays a key role in fetal growth, and adult insulin secretion is a primary determinant of glucose tolerance. We hypothesized that a defect in the sensing of glucose by the pancreas, caused by a heterozygous mutation in the glucokinase gene, could reduce fetal growth and birth weight in addition to causing hyperglycaemia after birth. In 58 offspring, where one parent has a glucokinase mutation, the inheritance of a glucokinase mutation by the fetus resulted in a mean reduction of birth weight of 533 g (P=0.002). In 19 of 21 sibpairs discordant for the presence of a glucokinase mutation, the child with the mutation had a lower birth weight, with a mean difference of 521 g (P=0.0002). Maternal hyperglycaemia due to a glucokinase mutation resulted in a mean increase in birth weight of 601 g (P=0.001). The effects of maternal and fetal glucokinase mutations on birth weight were additive. We propose that these changes in birth weight reflect changes in fetal insulin secretion which are influenced directly by the fetal genotype and indirectly, through maternal hyperglycaemia, by the maternal genotype. This observation suggests that variation in fetal growth could be used in the assessment of the role of genes which modify either insulin secretion or insulin action.

The clinical importance of postprandial glucose

Atherosclerotic lesions develop over a long period of time and result from complex changes in the arterial wall. Although these changes are not fully understood, there is much evidence to suggest that elevated plasma glucose levels contribute to the development of atherosclerotic lesions. Many studies have shown that there is a strong correlation between elevated plasma glucose levels and the risk of developing cardiovascular disease. Effects of glucose on the arterial wall include immediate effects, which occur rapidly in response to elevated plasma glucose levels, and long-term effects, which result from non-enzymatic glycosylation of various proteins. These adverse effects of elevated plasma glucose levels suggest that tight control of blood glucose levels in patients with diabetes could possibly reduce the risk of cardiovascular complications. This is borne out by the results of clinical studies in patients with type 1 diabetes. Therapy to reduce blood glucose levels may also be appropriate in individuals with impaired glucose tolerance, as this condition is associated with postprandial hyperglycaemia and a significant risk of developing cardiovascular disease.

Insulin resistance: current concepts

Insulin sensitivity varies greatly within the general population; factors contributing to this variability include genetic pre-disposition, obesity, unfavorable body fat distribution, and lack of physical activity. Impaired insulin sensitivity may lead to impaired glucose tolerance and, even in individuals with modest insulin deficiency, to the development of type 2 diabetes mellitus. Of equal concern in patients with impaired insulin sensitivity is the development of the insulin resistance syndrome, in which hypertension, dyslipidemia, and impaired glucose tolerance form a cluster of risk factors for cardiovascular disease. Treatment of insulin resistance includes metformin and the thiazolidinedione troglitazone. Both drugs have been shown to be effective in the treatment of insulin resistance, one of the central abnormalities in type 2 diabetes mellitus. The purpose of this study was to review the current understanding of insulin resistance and its implications for the treatment of type 2 diabetes mellitus. To do this, a MEDLINE search of the clinical literature was conducted and the content analyzed.

Non-insulin dependent diabetes in children and adolescents: the therapeutic challenge

Data are presented comparing non-insulin dependent diabetes mellitus (NIDDM) and insulin dependent diabetes mellitus (IDDM) in youth. Children and adolescents with NIDDM were predominantly Mexican-American, presented less frequently in ketoacidosis, had a greater frequency of family history of diabetes, had higher BMIs (27.4 vs 16.6 kg/m2), and had higher frequency of acanthosis nigricans (67% vs 1.2%). Logistical, social, and cultural challenges facing the physician treating children and adolescents with NIDDM are discussed, and treatment options for NIDDM in youth are briefly reviewed.

Insulin and coronary artery disease: is syndrome X the unifying hypothesis?

OBJECTIVE

To review data supporting the hypothesis that syndrome X plays a major role in the pathogenesis of coronary artery disease (CAD), and the effects of lifestyle factors and pharmacologic interventions on insulin, other metabolic parameters, and outcomes.

DATA SOURCES

MEDLINE (January 1966-August 1997) and Current Contents database searches identified applicable English-language experimental trials, epidemiologic studies, reviews, and editorials.

STUDY SELECTION AND DATA EXTRACTION

Studies that were included addressed the role of insulin resistance and hyperinsulinemia in the pathogenesis of CAD or the effects of lifestyle factors and pharmacologic interventions on metabolic parameters and outcomes.

DATA SYNTHESIS

The main characteristics of syndrome X are hyperinsulinemia and insulin resistance. These result in secondary syndrome X features, including hyperglycemia, increased very-low-density lipoprotein concentrations, decreased high-density lipoprotein cholesterol, and hypertension. Insulin resistance is worsened by obesity, and insulin has been shown to contribute to the development of hypertension. Other studies demonstrate that smoking adversely affects glucose and insulin concentrations. Animal studies have linked hyperinsulinemia and atherogenesis. These animal data have been confirmed by several large prospective and population studies that have identified associations between hyperinsulinemia and CAD.

CONCLUSIONS

Strong evidence links insulin resistance and hyperinsulinemia to CAD. Lifestyle modifications play an important role in decreasing cardiovascular risk, and clinicians should strongly encourage such changes. Clinicians must also carefully consider the effects of antihypertensive, antihyperglycemic, and antidyslipidemic agents on patients' metabolic profiles when choosing appropriate therapeutic regimens. However, outcome data on many potentially beneficial agents, including calcium antagonists, alpha 1-adrenergic antagonists, angiotensin-converting enzyme inhibitors, metformin, acarbose, and troglitazone, are not yet available.

Glucose tolerance in adults after prenatal exposure to famine

BACKGROUND

Reduced growth in utero is associated with type 2 (non-insulin-dependent) diabetes and impaired glucose tolerance in adult life. There is no direct evidence in human beings that maternal nutrition during gestation affects insulin-glucose metabolism. We investigated glucose tolerance in people born around the time of famine in the Netherlands during 1944-45.

METHODS

We included 702 people born between Nov 1, 1943, and Feb 28, 1947, in Amsterdam, for whom we had detailed prenatal and birth records. We compared glucose and insulin responses to a standard oral glucose load in participants exposed to famine at any stage during gestation (exposed participants) with those who were born in the year before or conceived in the year after the famine (non-exposed participants).

FINDINGS

Glucose concentrations were increased 2 h after a standard glucose load among exposed participants (p = 0.006), and were highest in men and women exposed during mid and late gestation. Mean 2 h glucose concentration among non-exposed participants was 5.8 mmol/L; concentrations were 0.5 mmol/L (95% CI 0.1-0.9) higher among participants exposed during late gestation, 0.4 mmol/L (0-0.8) higher among those exposed during mid gestation, and 0.1 mmol/L (-0.4 to 0.6) among those exposed during early gestation. Participants born as thin babies to mothers with low bodyweights had the highest concentrations and concentrations were especially high among people exposed to famine who became obese as adults. Prenatal exposure to famine was related to increased fasting proinsulin (p = 0.05) and 2 h insulin concentrations (p = 0.04), which suggests an association with insulin resistance.

INTERPRETATION

Prenatal exposure to famine, especially during late gestation, is linked to decreased glucose tolerance in adults. Poor nutrition in utero may lead to permanent changes in insulin-glucose metabolism, even if the effect on fetal growth is small. This effect of famine on glucose tolerance is especially important in people who become obese.

Deficiency of phosphofructo-1-kinase/muscle subtype in humans impairs insulin secretion and causes insulin resistance

Non-insulin-dependent diabetes mellitus (NIDDM) is caused by peripheral insulin resistance and impaired beta cell function. Phosphofructo-1-kinase (PFK1) is a rate-limiting enzyme in glycolysis, and its muscle subtype (PFK1-M) deficiency leads to the autosomal recessively inherited glycogenosis type VII Tarui's disease. It was evaluated whether PFK1-M deficiency leads to alterations in insulin action or secretion in humans. A core family of four members was evaluated for PFK1-M deficiency by DNA and enzyme-activity analyses. All members underwent oral and intravenous glucose tolerance tests (oGTT and ivGTT) and an insulin-sensitivity test (IST) using octreotide. Enzyme activity determinations in red blood cells showed that the father (46 yr, body mass index [BMI] 22. 4 kg/m2) and older son (19 yr, BMI 17.8 kg/m2) had a homozygous, while the mother (47 yr, BMI 28.4 kg/m2) and younger son (13 yr, BMI 16.5 kg/m2) had a heterozygous PFK1-M deficiency. DNA analyses revealed an exon 5 missense mutation causing missplicing of one allele in all four family members, and an exon 22 frameshift mutation of the other allele of the two homozygously affected individuals. The father showed impaired glucose tolerance, and the mother showed NIDDM. By ivGTT, both parents and the older son had decreased first-phase insulin secretion and a diminished glucose disappearance rate. The IST showed marked insulin resistance in both parents and the older, homozygous son, and moderate resistance in the younger son. PFK1-M deficiency causes impaired insulin secretion in response to glucose, demonstrating its participation in islet glucose metabolism, and peripheral insulin resistance. These combined metabolic sequelae of PFK-1 deficiency identify it as a candidate gene predisposing to NIDDM.

Glucose intolerance is associated with altered calcium homeostasis: a possible link between increased serum calcium concentration and cardiovascular disease mortality

Serum calcium concentration has recently been shown to predict cardiovascular mortality in a large health-screening program. Since impaired glucose tolerance (IGT) is an independent cardiovascular risk factor, we examined the association between glucose intolerance and serum calcium in a population-based cohort study. To characterize this association, we measured total serum calcium, parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD), and 1,25-dihydroxyvitamin D (1,25-(OH)2D) levels in a cohort of 1,071 randomly selected white individuals aged 40 to 65 years in whom an oral glucose tolerance test had been completed. In multivariate analyses, the 2-hour plasma glucose was positively associated with increasing total serum calcium and PTH in men and women after adjustment for age, obesity, season, and 25OHD. The adjusted odds ratio (OR) between increasing quintiles of total serum calcium and IGT was 1.63 (95% confidence interval [CI], 1.42 to 1.88). The OR comparing the top with the bottom quintile was 8.5 (95% CI, 4.5 to 16.0). The association with quintile of serum PTH was 1.30 (95% CI, 1.14 to 1.49). These data suggest that IGT is associated with an increase in both total serum calcium and PTH that cannot be explained by confounding by aging, obesity, or 25OHD. This relationship may explain the previously observed association between serum calcium and cardiovascular mortality. Whether this association is a manifestation of a shared cellular defect or represents a common relationship with an unknown etiologic factor are important questions for further research.

Do high proinsulin and C-peptide levels play a role in autonomic nervous dysfunction?: Power spectral analysis in patients with non-insulin-dependent diabetes and nondiabetic subjects

BACKGROUND

Immunoreactive insulin has been shown to predict the development of parasympathetic autonomic neuropathy. It is possible that constituents of immunoreactive insulin could explain this association. In this cross-sectional study, the relationship of specific insulin, C-peptide, and proinsulin with autonomic nervous dysfunction was evaluated in 57 NIDDM patients and 108 control subjects.

METHODS AND RESULTS

The frequency-domain analysis of heart rate variability was determined by using spectral analysis from stationary regions of registrations while the subjects breathed spontaneously in a supine position. Total power was divided into three frequency bands: low (0 to 0.07 Hz), medium (MFP, 0.07 to 0.15 Hz), and high (HFP, 0.15 Hz to 0.50 multiplied by the frequency equal to the mean RR interval). In NIDDM patients, total power, the three frequency bands (P<.001 for each), and the MFP/HFP ratio (P=.016), which expresses sympathovagal balance, were reduced compared with control subjects. Fasting proinsulin (r(s)=-.324, P=.014 for diabetics and r(s)=-.286, P=.003 for control subjects), C-peptide (r(s)=-.492, P<.001 for diabetics and r(s)=-.304, P=.001 for control subjects), and total immunoreactive insulin (r(s)=-.291, P=.028 for diabetics and r(s)=-.228, P=.017 for control subjects) were inversely related to MFP/HFP. For proinsulin and C-peptide the results did not change after controlling for the effects of age, body mass index, and fasting glucose.

CONCLUSIONS

Both proinsulin and C-peptide levels were significantly associated with the sympathovagal balance of autonomic nervous function in NIDDM patients and control subjects, but this study cannot determine whether these compounds are directly involved in autonomic nervous dysfunction.

Effect of acarbose on glucose intolerance in patients with non-insulin-dependent diabetes mellitus

We evaluated the effect of acarbose, an alpha-glucosidase inhibitor, on glucose intolerance in patients with non-insulin-dependent diabetes mellitus (NIDDM). Acarbose was given orally (300 mg/day) for 24 weeks to 20 NIDDM patients. Data in an oral glucose tolerance test (OGTT) were evaluated before and after 24 weeks of treatment using principal component analysis. Acarbose administration significantly reduced the postprandial plasma glucose level over 24 weeks of treatment. Principal component analysis suggested that the patients were separated into responders and non-responders. There was a significant improvement of fasting and postprandial glucose levels after 12 and 24 weeks in the responders, but not in the non-responders. Plasma glucose level following the OGTT improved significantly after 24 weeks of treatment in the responders (Hotelling T2 value = 47.098, P = 0.022500), but not in the non-responders. The immunoreactive insulin level did not change in either group. Results thus suggest that acarbose improved insulin resistance in some patients with NIDDM (responders as classified by principal component analysis).

Non-insulin-dependent diabetes mellitus in childhood and adolescence

NIDDM in children and adolescents represents a heterogeneous group of disorders with different underlying pathophysiologic mechanisms. Most subtypes of NIDDM that occur in childhood are uncommon, but some, such as early onset of "classic" NIDDM, seem to be increasing in prevalence. This observed increase is thought to be caused by societal factors that lead to sedentary lifestyles and an increased prevalence of obesity. In adults, hyperglycemia frequently exists for years before a diagnosis of NIDDM is made and treatment is begun. Microvascular complications, such as retinopathy, are often already present at the time of diagnosis. Children are frequently asymptomatic at the time of diagnosis, so screening for this disorder in high-risk populations is important. Screening should be considered for children of high-risk ethnic populations with a strong family history of NIDDM with obesity or signs of hyperinsulinism, such as acanthosis nigricans. Even for children in these high-risk groups who do not yet manifest hyperglycemia, primary care providers can have an important role in encouraging lifestyle modifications that might delay or prevent onset of NIDDM.

Carotid artery intima-media thickness in elderly patients with NIDDM and in nondiabetic subjects

BACKGROUND AND PURPOSE

The risk of atherosclerotic vascular disease is increased both in subjects with non-insulin-dependent diabetes mellitus (NIDDM) and in those with impaired glucose tolerance compared with nondiabetic subjects. Although classic cardiovascular risk factors are operative in subjects with NIDDM, other factors closely related to insulin resistance syndrome such as diabetic dyslipidemia and hyperglycemia itself may contribute to an excessive cardiovascular disease risk in subjects with NIDDM. The purpose of this study was to investigate the carotid intimal-medial thicknesses (IMTs) and their determinants in elderly patients with NIDDM and in control subjects.

METHODS

We investigated the common carotid and carotid bifurcation IMTs and their determinants in groups of elderly patients (n = 84, age 67.2 +/- 0.6 years) with NIDDM and in 119 control subjects (21 with impaired and 98 with normal glucose tolerance; ages 67.5 +/- 1.0 and 65.1 +/- 0.6 years, respectively).

RESULTS

Common carotid and carotid bifurcation IMTs were greater in the NIDDM group than in control subjects (P < .05 to .01). In NIDDM patients, the mean carotid IMT correlated with postglucose 1-hour plasma insulin (r = .305, P = .01, adjusted for age and sex), serum LDL triglyceride (r = .237, P < .05), and apolipoprotein B concentrations (r = .263, P < .05). Fasting plasma immunoreactive insulin, proinsulin, or specific insulin levels were not significantly associated with carotid IMT. Both diabetic status (P < .05) and the presence of clinical macrovascular disease (P < .01) contributed independently to carotid IMT.

CONCLUSIONS

Carotid IMT was greater in NIDDM patients than in control subjects. The main determinants of IMT in NIDDM patients were related to both postglucose insulin levels and abnormal lipoprotein profiles characteristic of NIDDM and insulin resistance syndrome. Treatment of these factors is likely to reduce the atherosclerotic burden in NIDDM.

Pathophysiology of canine diabetes

Diabetes is a fascinating, disease complex. Although much progress has been made in the last three decades to unravel the mysteries behind its multifaceted expressions, much work lies ahead. In dogs diabetes is not identified until late in the disease process. Future research might be directed at identifying early markers of the disease as an aid to improving current modes of treatment.