Identification of differentially expressed genes in skeletal muscle of non-diabetic insulin-resistant and insulin-sensitive Pima Indians by differential display PCR

Plant Growth Promoting and Stress Mitigating Abilities of Soil Born Microorganisms

Abiotic stresses affect the plant growth in different ways and at different developmental stages that reduce the crop yields. The increasing world population continually demands more crop yields; therefore it is important to use low-cost technologies against abiotic stresses to increase crop productivity. Soil microorganisms survive in the soil associated with plants in extreme condition. It was demonstrated that these beneficial microorganisms promote plant growth and development under various stresses. The soil microbes interact with the plant through rhizospheric or endophytic association and promote the plant growth through different processes such as nutrients mobilization, disease suppression, and hormone secretions. The microorganisms colonized in the rhizospheric region and imparted the abiotic stress tolerance by producing 1-aminocyclopropane-1- carboxylate (ACC) deaminase, antioxidant, and volatile compounds, inducing the accumulation of osmolytes, production of exopolysaccharide, upregulation or downregulation of stress genes, phytohormones and change the root morphology. A large number of these rhizosphere microorganisms are now patented. In the present review, an attempt was made to throw light on the mechanism of micro-organism that operates during abiotic stresses and promotes plant survival and productivity.

Identification of a Prognostic Signature Based on the Expression of Genes Related to the Insulin Pathway in Early Breast Cancer

Introduction

Insulin and the insulin-like growth factor (IGF) family play a key role in breast cancer (BC).

Objective

In this study, we evaluated on a genomic scale the potential prognostic value of insulin signaling in early BC.

Methods

Candidate genes were selected from the published literature and gene expression profiling experiments. Three publicly available BC datasets, containing gene expression data on 502 cases, were used to test the prognostic ability of the score. The gene signature was developed on GSE1456, containing microarray data from 159 patients, split into a training set (102 breast tumors) and a validation set (n = 57). GSE3494 and GSE2990 (350 patients) were used for external validation. Univariate Mann-Whitney test was used to identify genes differentially expressed between relapsed and nonrelapsed patients. Expression of genes significantly correlated with relapse was combined in a linear score. Patients were classified as low or high risk with respect to the median value.

Results

On the training set, 15 genes turned out to be differentially expressed: 8-year disease-free survival (DFS) was 51 and 91% in the high- and low-risk group (p < 0.001), respectively. In the validation set, DFS was 97 and 54% (p = 0.009), respectively. External validation: 8-year DFS was 72 and 61%, respectively, in GSE3494 (p = 0.03) and 74 and 55% in GSE2990 (p = 0.03). By multivariate analyses, the insulin signature was significantly associated with DFS, independently of age, hormone receptor status, nodal status, and grade.

Conclusions

Our findings indicate that the insulin pathway is involved in BC prognosis at a genomic level and provide a window of selectivity for preventive and treatment strategies targeting the insulin/IGF pathway in BC patients.

Measurement of altered APP isoform expression in adipose tissue of diet-induced obese mice by absolute quantitative real-time PCR

Obesity is associated with increased risk of Alzheimer’s disease. Previous studies have demonstrated that amyloid-beta precursor protein (APP) is expressed in subcutaneous adipose tissue (SAT), upregulated with obesity, and correlates with insulin resistance and adipose tissue inflammation. APP is alternatively spliced into several isoforms, which may be indicative of the pathogenesis of APP-related diseases, but the accurate quantification has been difficult to standardize and reproduce. In light of this, we developed isoform-specific absolute cDNA standards for absolute quantitative real-time PCR (AQ-PCR), and measured transcript copy numbers for three major APP isoforms (APP770, APP751, and APP695), in SAT from C57BL/6 mice fed either a normal or high-fat diet. Expression of all three major APP isoforms was increased in diet-induced obese mice. Transcript copy numbers of APP770 and APP695 correlated with plasma insulin and CCL2 gene expression. The ratios of APP770 and APP751 to APP695 gradually decreased with aging, and correlated with plasma glucose levels. In addition, APP770 was significantly decreased in thiazolidinedione-treated mice. We describe quantification of APP isoform transcripts by AQ-PCR, which allows for direct comparison of gene copy number across isoforms, between experiments, and across studies conducted by independent research groups, which relative quantitative PCR does not allow. Our results suggest a possible role of differential expression of APP isoforms in the development of obesity-related insulin resistance and adipose tissue inflammation. In addition, it is important to determine if altered ratios of APP isoforms in SAT contribute to higher circulating Aβ peptides and increased risk of abnormalities in obesity.

The beneficial effect of soybean (Glycine max (L.) Merr.) leaf extracts in adults with prediabetes: a randomized placebo controlled trial

The present study investigated the effects of soybean leaf extracts (SLEs) on blood glucose, insulin resistance, body fat and dyslipidemia in prediabetes subjects, and compared them with the effects of banaba extracts (BE) which is known to ameliorate diabetes in several animals and clinical studies. Overweight subjects with mild hyperglycemia (fasting blood glucose level of 100-125 mg dL(-1)) were randomly assigned to three groups and administered four capsules containing starch (2 g per day, Placebo), BE (300 mg per day, 0.3% corosolic acid) or SLE (2 g per day) during regular meals for 12 weeks. The SLE as well as BE significantly decreased the baseline-adjusted final blood glucose, HbA1c, HOMA-IR and transaminase levels compared to the placebo group. The body weight, BMI and WHR were not different between the groups, but the baseline-adjusted final body fat content and waist circumference were lower in the BE and SLE groups than in the placebo group. Furthermore, the baseline-adjusted final plasma triglyceride concentration was lower in the BE and SLE groups compared to the placebo group. There were no significant differences in plasma total cholesterol and LDL-cholesterol concentrations between the groups. However, the SLE, but not the BE, significantly increased the plasma HDL-cholesterol concentration and the ratio of HDL-cholesterol to total cholesterol after 12 weeks of supplementation compared to the placebo group, while the atherogenic index was decreased. Taken together, these data suggest that SLE may play an important role in improving blood glucose, insulin resistance, adiposity, and dyslipidemia in prediabetes subjects consuming their habitual diet, similar to or better than BE.

Different associations between obesity and impaired fasting glucose depending on serum gamma-glutamyltransferase levels within normal range: a cross-sectional study

BACKGROUND

Despite the consistent relationship between serum γ-glutamyltransferase (GGT) and type 2 diabetes (T2D), one unsolved issue is the role of serum GGT in the well-known association between obesity and T2D. This study was performed to investigate whether the association between body mass index (BMI) and impaired fasting glucose (IFG) differed depending on serum GGT levels within the normal range.

METHODS

Study subjects were 2,424 men and 3,652 women aged ≥ 40, participating in the Fifth Korean National Health and Nutrition Examination Survey. Serum GGT levels within the normal range were classified into gender-specific tertiles.

RESULTS

Among men and women belonging to the lowest tertile of serum GGT, BMI showed statistically non-significant weak associations with the risk of IFG. However, among persons in the highest tertile of serum GGT, the risk of IFG was 3 - 4 times higher among persons with BMI ≥ 25 kg/m2 than those with BMI < 23 kg/m2 (Pinteraction = 0.032 in men and 0.059 in women).

CONCLUSIONS

The well-known strong association between BMI and IFG was observed mainly among persons with elevation of serum GGT to certain physiological levels, suggesting a critical role of serum GGT in the pathogenesis of IFG. This finding has an important clinical implication because serum GGT can be used to detect high-risk obese persons.

IL-24 gene polymorphisms are associated with cardiometabolic parameters and cardiovascular risk factors but not with premature coronary artery disease: the genetics of atherosclerotic disease Mexican study

Coronary artery disease (CAD) is a multifactorial and polygenic disorder that results from an excessive inflammatory response. We analyzed whether interleukin-24 (IL-24) gene polymorphisms are associated with premature CAD in a case-control association study. Four polymorphisms (rs1150253, rs1150256, rs1150258, and rs3762344) of the IL-24 gene were analyzed by 5' exonuclease TaqMan genotyping assays in a group of 952 patients with premature CAD, 284 individuals with subclinical atherosclerosis (SA), and 912 controls. The studied polymorphisms were not associated with the risk of premature CAD or SA (P>0.05). Under dominant models adjusted for age, sex, body mass index, and medication, the polymorphisms were associated with cardiometabolic parameters and cardiovascular risk factors. Three polymorphisms (rs1150253, rs1150256, and rs3762344) were associated with hypertension and increased levels of systolic blood pressure in controls. In SA, 2 polymorphisms (rs1150256 and rs3762344) were associated with type 2 diabetes mellitus, gamma-glutamyl transpeptidase (GGT), and alkaline phosphatase, whereas rs1150253 was associated with GGT and type 2 diabetes mellitus and rs1150258 with GGT and alkaline phosphatase. In premature CAD, the 4 polymorphisms were associated with total cholesterol >200 mg/dL, low-density lipoprotein cholesterol (LDL-C), and GGT, whereas rs1150256 was associated also with ApoA. On the other hand, rs1150258 was associated with ApoA, LDL-C >100 mg/dL, and apoB/apoA ratio, and rs3762344 with ApoA, apoB/apoA ratio, LDL-C >100 mg/dL, and total cholesterol. On the basis of single-nucleotide polymorphism functional prediction software, rs1150253 and rs1150258 polymorphisms seem to be functional. The 4 studied polymorphisms were in linkage disequilibrium and had a similar haplotype distribution in patients and controls. Our study demonstrates the association of IL-24 polymorphisms with metabolic and cardiovascular risk factors in individuals with premature CAD, SA, and controls.

The association between liver enzymes and risk of type 2 diabetes: the Namwon study

BACKGROUND

We examined the association between liver enzymes and development of type 2 diabetes in a general Korean population.

METHODS

A total of 10,667 subjects (4,201 males and 6,466 females) aged 45 to 74 years participated in a baseline examination between 2004 and 2007. Among the subjects, 8,157 (3,231 males and 4,926 females) underwent follow-up examination from 2007 to 2011, for a median follow-up period of 4.2 years. Type 2 diabetes was defined as intake of anti-diabetic agents, insulin treatment, fasting glucose concentration of more than 126 mg/dl, or hemoglobin A1c of more than 6.5% at re-examination. Associations of liver enzymes with incidence of type 2 diabetes were analyzed using logistic regression models.

RESULTS

During the follow-up period, 548 subjects (235 males, 313 females) developed type 2 diabetes. After adjusting for comprehensive diabetes risk factor, the risk of type 2 diabetes was significantly higher in the highest alanine aminotransferase (ALT) quartile than in the lowest quartile (odds ratio (OR): 1.95, 95% confidence interval (CI): 1.18-3.21 in males; OR: 1.49, 95% CI: 1.03-2.16 in females). Similar results were observed for gamma-glutamyltransferase (GGT) quartiles, but in the fully adjusted analysis, the OR for the highest versus lowest quartiles was significant only for females (OR: 1.58, 95% CI: 0.95-2.63 in males; OR: 1.85, 95% CI: 1.23-2.79 in females).

CONCLUSIONS

Our results suggest that serum ALT concentrations were independently associated with type 2 diabetes in both sexes, and that GGT was also independently associated but only in females.

The Association of Metabolic Syndrome and Serum γ-Glutamyl Transpeptidase: A 4-Year Cohort Study of 3,698 Korean Male Workers

The aim of the present study was to examine the causal-effect of baseline (year 2004) serum γ-glutamyl transpeptidase (GGT) level with the prevalence of metabolic syndrome (MS) in year 2008. The study was comprised of male workers who underwent a regular health check-up in 2004 and 2008. MS was diagnosed according to the American Association of Clinical Endocrinologists (AACE) criteria. In the subgroup analysis according to serum GGT level, triglyceride (TG), low density lipoprotein cholesterol (LDL-C), and total cholesterol (TC) showed a significant increasing tendency (p < 0.001). In addition, unexpectedly results were consistent in non-drinkers (p < 0.001). GGT level was significantly associated with risk factors of MS (waist circumference [WC]: r = 0.18, p < 0.001; fasting blood glucose [FBG]: r = 0.16, p < 0.001; TG: r = 0.29, p < 0.001). As the secondary biomarker, homeostasis model assessment of insulin sensitivity (HOMA-S) and TC had significant correlations with GGT level (HOMA-S: r = -0.14, p < 0.001; TC: r = 0.21, p < 0.001). In the 4-year prospective analysis, the predictive effect of baseline GGT concentrations on change in MS status was evaluated using Cox proportional model. Elevated GGT concentrations measured in 2004 were associated with the risk of MS incidence after 4 years (GGT: HR 1.7 [95% CI: 1.2-2.3]) (p < 0.01). This observation indicates that an elevated GGT level could be suggested as a subsidiary marker for MS and partially reflects dyslipidemia as a component of MS.

A genome-wide scan of selective sweeps in two broiler chicken lines divergently selected for abdominal fat content

Background

Genomic regions controlling abdominal fatness (AF) were studied in the Northeast Agricultural University broiler line divergently selected for AF. In this study, the chicken 60KSNP chip and extended haplotype homozygosity (EHH) test were used to detect genome-wide signatures of AF.

Results

A total of 5357 and 5593 core regions were detected in the lean and fat lines, and 51 and 57 reached a significant level (P<0.01), respectively. A number of genes in the significant core regions, including RB1, BBS7, MAOA, MAOB, EHBP1, LRP2BP, LRP1B, MYO7A, MYO9A and PRPSAP1, were detected. These genes may be important for AF deposition in chickens.

Conclusions

We provide a genome-wide map of selection signatures in the chicken genome, and make a contribution to the better understanding the mechanisms of selection for AF content in chickens. The selection for low AF in commercial breeding using this information will accelerate the breeding progress.

Diabetes and its chronic complications in the She ethnic minority group of China

OBJECTIVE

According to recent reports, the development of type 2 diabetes in China has soared at an alarming rate. However, most of the investigations were based on Han people, who account for the majority of people in China. Little is known about the prevalence of diabetes its chronic complications in the She people, who have their own traditional lifestyle and hereditable background, different from other Asian population. The present study investigated the prevalence of type 2 diabetes and associated risk factors in the adult population of She nationals.

SUBJECTS AND METHODS

A total of 5,385 participants entered into the analysis eventually, including 2,308 men and 3,077 women. An oral glucose tolerance test was performed in subjects without diagnosed diabetes. Liver function, cardiovascular risk (brachial-ankle pulse wave velocity, estimated glomerular filtration rate, and abnormal Minnesota codes findings), uric acid, and neuropathy were tested to assess the profiles of associated risks.

RESULTS

In general, the self-reported diabetes rate was 9.5%. After age and sex standardization, the prevalence of diabetes was 6.1% (6.7% for men and 5.7% for women) in She Chinese people. In logistic regression models, age, family history of diabetes, alcohol use, total cholesterol, and triglycerides were all significantly associated with the risk of diabetes in this cross-sectional study (all P<0.05). In all, 47.4% had cardiovascular risks, 19.4% had liver dysfunction, and 6.2% had hyperuricemia. For women, compared with the first quartile, log-transformed homeostasis model assessment for insulin resistance of the fourth quartile was significantly higher (P<0.05), and log-transformed homeostasis model assessment for β cells was also higher in the second, third, and fourth quartiles (all P<0.05). The prevalences of polyneuropathy in impaired fasting glucose (IFG), impaired glucose tolerance (IGT), IFG/IGT, and diabetes mellitus (DM) were 16.1%, 13.1%, 18.6%, and 28.4% separately, which was higher than that in normal glucose tolerance. The prevalences of polyneuropathy in IFG/IGT and DM were higher than that in IGT.

CONCLUSIONS

The present study revealed that a total of 6.1% She people suffered from type 2 diabetes, which was lower than the average level of China, but the standardized prevalence of prediabetes was higher, 20.6%. Early peripheral neuropathy screening should be performed in the prediabetes population. The Toronto Clinical Neuropathy Scoring System is convenient to assess diabetic polyneuropathy in clinical practice and should be tested regularly for people in prediabetes. Liver dysfunction, headache, and insomnia, appearing before type 2 diabetes, should be assessed regularly to avoid deterioration.

A Longitudinal Genetic Study of Uric Acid and Liver Enzymes in Adolescent Twins

Biochemical traits such as plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma glutamyltransferase (GGT) and uric acid are associated with obesity, and with risk of cardiovascular disease, metabolic syndrome and diabetes. Each is subject to genetic influences, but little is known about changes in genetic and environmental influences on these traits over time. We investigated the contribution of genetic and environmental influences to variation in these biochemical traits in adolescent twins and their nontwin siblings from 965 twin families. Twins were studied at ages 12, 14 and 16 years. Multivariate genetic models that included effects of age and sex were fitted to determine whether the same or different genetic or environmental factors influence each trait at different ages. Results showed that the genetic factors influencing AST, ALT, GGT and uric acid change over time during adolescence, and that the magnitude of these effects differs between males and females. The nonshared environment effects were generally time specific. There are developmental changes in genes affecting these traits during adolescence.

The relationship of gamma-glutamyltransferase to aortic elastic properties in young patients with prehypertension

Some cross-sectional studies have demonstrated a positive association between serum gamma-glutamyltransferase (GGT) levels and blood pressure. Accordingly, we aimed to analyze serum GGT levels in patients with prehypertension and examine the relationship with aortic elasticity parameters. The study population consisted of 25 newly diagnosed prehypertensive individuals and 25 healthy control subjects. Aortic strain, distensibility index, and stiffness index beta were calculated from aortic diameters measured by echocardiography and blood pressures simultaneously measured by sphygmomanometry. Prehypertensive patients were detected to have significantly lower aortic distensibility and strain indexes compared to control subjects aortic distensibility. However, aortic stiffness index beta of the prehypertensive group was significantly higher compared to that of the control group (3.73 ± 1.41 vs. 2.97 ± 0.82, p = 0.02). The mean GGT levels were found to be higher in patients with prehypertension compared to those of controls (47.9 ± 15.9 U/L vs. 36.1 ± 9.4 U/L, p = 0.003). When multiple linear regression analysis was done to clarify the contributions of GGT to aortic elasticity adjusting for age, body mass index, uric acid, serum glucose, heart rate, low-density lipoprotein (LDL)-cholesterol, high-density lipoprotein (HDL)-cholesterol, and triglyceride, we observed that only serum GGT levels were significantly associated with aortic elasticity parameters (for aortic strain beta = -0.247, p < 0.001; for aortic distensibility beta = -0.108, p < 0.001; for stiffness index beta = 0.063, p < 0.001). Whatever the mechanism is, young patients with prehypertension have higher serum GGT levels compared to healthy control subjects. More importantly, increased GGT levels are independently associated with impaired aortic elasticity in patients with prehypertension.

Bimodal distribution of RNA expression levels in human skeletal muscle tissue

Background

Many human diseases and phenotypes are related to RNA expression, levels of which are influenced by a wide spectrum of genetic and exposure-related factors. In a large genome-wide study of muscle tissue expression, we found that some genes exhibited a bimodal distribution of RNA expression, in contrast to what is usually assumed in studies of a single healthy tissue. As bimodality has classically been considered a hallmark of genetic control, we assessed the genome-wide prevalence, cause, and association of this phenomenon with diabetes-related phenotypes in skeletal muscle tissue from 225 healthy Pima Indians using exon array expression chips.

Results

Two independent batches of microarrays were used for bimodal assessment and comparison. Of the 17,881 genes analyzed, eight (GSTM1, HLA-DRB1, ERAP2, HLA-DRB5, MAOA, ACTN3, NR4A2, and THNSL2) were found to have bimodal expression replicated in the separate batch groups, while 24 other genes had evidence of bimodality in only one group. Some bimodally expressed genes had modest associations with pre-diabetic phenotypes, of note ACTN3 with insulin resistance. Most of the other bimodal genes have been reported to be involved with various other diseases and characteristics. Association of expression with cis genetic variation in a subset of 149 individuals found all but one of the confirmed bimodal genes and nearly half of all potential ones to be highly significant expression quantitative trait loci (eQTL). The rare prevalence of these bimodally expressed genes found after controlling for batch effects was much lower than the prevalence reported in other studies. Additional validation in data from separate muscle expression studies confirmed the low prevalence of bimodality we observed.

Conclusions

We conclude that the prevalence of bimodal gene expression is quite rare in healthy muscle tissue (<0.2%), and is much lower than limited reports from other studies. The major cause of these clearly bimodal expression patterns in homogeneous tissue appears to be cis-polymorphisms, indicating that such bimodal genes are, for the most part, eQTL. The high frequency of disease associations reported with these genes gives hope that this unique feature may identify or actually be an underlying factor responsible for disease development.

Increased liver fat content and unfavorable glucose profiles in subjects without diabetes

BACKGROUND

Liver fat content (LFC) in subjects without diabetes may be correlated with adverse glucose profiles.

METHODS

LFC was measured by (1)H magnetic resonance spectroscopy in 47 healthy subjects, 35 of whom also completed continuous glucose monitoring (CGM) studies. Subjects were divided into two groups according to LFC, and between-group comparisons of glucose profiles were made.

RESULTS

The median LFC value was 3.8% (interquartile range, 2.4-7.6%), and 29.8% of the subjects had LFC values ≥ 5.5%. LFC was positively correlated with triglyceride, aspartate aminotransferase, γ-glutamyltransferase, fasting C-peptide, fasting insulin, insulin concentration at 120 min, area under the time-concentration curve for insulin, and change in insulin from 0 to 30 min, homeostatic model assessment of insulin resistance, fasting plasma glucose, nocturnal mean blood glucose concentration (MBG) (all P < 0.05). The 35 CGM profiles revealed that nocturnal MBG was higher in subjects with LFC ≥ 3.8% (P < 0.05). In subjects with LFC ≥ 5.5%, both diurnal and nocturnal MBG values were elevated compared with subjects with lower LFC (P < 0.05). LFC was the strongest predictive factor of nocturnal MBG.

CONCLUSIONS

Even modestly elevated LFC was associated with unfavorable glucose profiles in subjects without diabetes.

Prevention of type 2 diabetes in a primary healthcare setting: three-year results of lifestyle intervention in Japanese subjects with impaired glucose tolerance

Background

A randomized control trial was performed to test whether a lifestyle intervention program, carried out in a primary healthcare setting using existing resources, can reduce the incidence of type 2 diabetes in Japanese with impaired glucose tolerance (IGT). The results of 3 years' intervention are summarized.

Methods

Through health checkups in communities and workplaces, 304 middle-aged IGT subjects with a mean body mass index (BMI) of 24.5 kg/m² were recruited and randomized to the intervention group or control group. The lifestyle intervention was carried out for 3 years by public health nurses using the curriculum and educational materials provided by the study group.

Results

After 1 year, the intervention had significantly improved body weight (-1.5 ± 0.7 vs. -0.7 ± 2.5 kg in the control; p = 0.023) and daily non-exercise leisure time energy expenditure (25 ± 113 vs. -3 ± 98 kcal; p = 0.045). Insulin sensitivity assessed by the Matsuda index was improved by the intervention during the 3 years. The 3-year cumulative incidence tended to be lower in the intervention group (14.8% vs.8.2%, log-rank test: p = 0.097). In a sub-analysis for the subjects with a BMI > 22.5 kg/m², a significant reduction in the cumulative incidence was found (p = 0.027).

Conclusions

The present lifestyle intervention program using existing healthcare resources is beneficial in preventing diabetes in Japanese with IGT. This has important implications for primary healthcare-based diabetes prevention.

Trial registration number

UMIN000003136

Elevated serum gamma-glutamyltransferase activity is associated with increased risk of mortality, incident type 2 diabetes, cardiovascular events, chronic kidney disease and cancer - a narrative review

Abstract In clinical practice, increased serum gamma-glutamyltransferase (GGT) activity is usually interpreted as a marker of alcohol abuse and liver dysfunction. The knowledge of the GGT's physiological functions has expanded and several important epidemiological associations have been reported. This review examines evidence for an association of high normal serum GGT enzyme activity, mostly within the reference range, with the risk of mortality and major vascular (i.e., cardiovascular morbidity and mortality) and non-vascular outcomes (i.e., incident type 2 diabetes, chronic kidney disease and cancer), independent of alcohol consumption and other prognostic factors.

Using pre-existing microarray datasets to increase experimental power: application to insulin resistance

Although they have become a widely used experimental technique for identifying differentially expressed (DE) genes, DNA microarrays are notorious for generating noisy data. A common strategy for mitigating the effects of noise is to perform many experimental replicates. This approach is often costly and sometimes impossible given limited resources; thus, analytical methods are needed which increase accuracy at no additional cost. One inexpensive source of microarray replicates comes from prior work: to date, data from hundreds of thousands of microarray experiments are in the public domain. Although these data assay a wide range of conditions, they cannot be used directly to inform any particular experiment and are thus ignored by most DE gene methods. We present the SVD Augmented Gene expression Analysis Tool (SAGAT), a mathematically principled, data-driven approach for identifying DE genes. SAGAT increases the power of a microarray experiment by using observed coexpression relationships from publicly available microarray datasets to reduce uncertainty in individual genes' expression measurements. We tested the method on three well-replicated human microarray datasets and demonstrate that use of SAGAT increased effective sample sizes by as many as 2.72 arrays. We applied SAGAT to unpublished data from a microarray study investigating transcriptional responses to insulin resistance, resulting in a 50% increase in the number of significant genes detected. We evaluated 11 (58%) of these genes experimentally using qPCR, confirming the directions of expression change for all 11 and statistical significance for three. Use of SAGAT revealed coherent biological changes in three pathways: inflammation, differentiation, and fatty acid synthesis, furthering our molecular understanding of a type 2 diabetes risk factor. We envision SAGAT as a means to maximize the potential for biological discovery from subtle transcriptional responses, and we provide it as a freely available software package that is immediately applicable to any human microarray study.

Amyloid precursor protein expression is upregulated in adipocytes in obesity

The aim of this study was to determine whether amyloid precursor protein (APP) is expressed in human adipose tissue, dysregulated in obesity, and related to insulin resistance and inflammation. APP expression was examined by microarray expression profiling of subcutaneous abdominal adipocytes (SAC) and cultured preadipocytes from obese and nonobese subjects. Quantitative real-time PCR (QPCR) was performed to confirm differences in APP expression in SAC and to compare APP expression levels in adipose tissue, adipocytes, and stromal vascular cells (SVCs) from subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) specimens. Adipose tissue samples were also examined by western blot and immunofluorescence confocal microscopy. Microarray studies demonstrated that APP mRNA expression levels were higher in SAC (approximately 2.5-fold) and preadipocytes (approximately 1.4) from obese subjects. Real-time PCR confirmed increased APP expression in SAC in a separate group of obese compared with nonobese subjects (P=0.02). APP expression correlated to in vivo indices of insulin resistance independently of BMI and with the expression of proinflammatory genes, such as monocyte chemoattractant protein-1 (MCP-1) (R=0.62, P=0.004), macrophage inflammatory protein-1alpha (MIP-1alpha) (R=0.60, P=0.005), and interleukin-6 (IL-6) (R=0.71, P=0.0005). Full-length APP protein was detected in adipocytes by western blotting and APP and its cleavage peptides, Abeta40 and Abeta42, were observed in SAT and VAT by immunofluorescence confocal microscopy. In summary, APP is highly expressed in adipose tissue, upregulated in obesity, and expression levels correlate with insulin resistance and adipocyte cytokine expression levels. These data suggest a possible role for APP and/or Abeta in the development of obesity-related insulin resistance and adipose tissue inflammation.

Association of liver enzymes with incident type 2 diabetes: A nested case control study in an Iranian population

BACKGROUND

To investigate the association of Aspartate aminotransferase (AST), Alanin aminotranferase (ALT) and Gamma glutamyl transferase (GGT) with incident type 2 diabetes.

METHODS

In a nested case-control study, AST, ALT, GGT as well as classic diabetes risk factors, insulin and C-reactive protein (CRP) were measured in 133 non-diabetic subjects at baseline of which 68 were cases and 65 were controls. Incident diabetes was defined by the WHO 1999 criteria. Conditional logistic regression was used to calculate the odds ratio (OR) of incident diabetes associated with different hepatic markers. We used factor analysis for clustering of classic diabetes risk factors.

RESULTS

In Univariate analysis both ALT and GGT were associated with diabetes with ORs of 3.07(1.21-7.79) and 2.91(1.29-6.53) respectively. After adjustment for CRP and insulin, ALT and GGT were still predictive of incident diabetes. When the model was further adjusted for anthropometric, blood pressure and metabolic factors, only ALT was independently associated with diabetes [OR = 3.18 (1.02-9.86)]. No difference was found between the area under the receiver operating characteristic curves of the models with and without ALT (0.820 and 0.802 respectively, P = 0.4)

CONCLUSION

ALT is associated with incident type 2 diabetes independent of classic risk factors. However, its addition to the classic risk factors does not improve the prediction of diabetes.

Relationship between gamma-glutamyltransferase and metabolic syndrome in a Korean population

AIMS

To investigate associations between gamma-glutamyltransferase (GGT) and components of metabolic syndrome (MS), insulin resistance and inflammatory markers in the Korean population.

METHODS

The 3508 subjects enrolled in this survey participated in the Korean Rural Genomic Cohort (KRGC) study. Written consent was obtained from the local ethical committee. Of these participants, 1437 were men (mean age 56.9 +/- 7.9 years) and 2071 were women (mean age 55.8 +/- 8.1 years). We measured GGT levels and various biochemical markers. To examine insulin resistance status, we used the homeostasis assessment method for insulin resistance (HOMA-IR). For inflammatory marker, we used C-reactive protein (CRP) levels.

RESULTS

Serum GGT levels were significantly higher in the MS group compared to the healthy patient group [23 (5-1403) vs. 19 (5-1920) IU/l; P = 0.01]. The prevalence of MS and adjusted relative risk were both significantly increased from the lowest to highest GGT quartiles; these results persisted after adjustments for multiple confounders. Positive correlations were established between GGT and HOMA-IR or CRP.

CONCLUSION

These results suggest that GGT levels may be a surrogate marker of insulin resistance, inflammation and MS.

Fatty liver is an independent risk factor for the development of Type 2 diabetes in Korean adults

AIMS

To investigate whether fatty liver per se is an independent risk factor of incident type 2 diabetes mellitus (T2DM) in Koreans.

METHODS

We examined the clinical and laboratory data of 5372 non-diabetic participants (3670 men and 1702 women; age 46.8 +/- 8.4 years, range 20-79 years) who underwent voluntary medical check-ups in 2000 and follow-up examinations in 2005.

RESULTS

Two hundred and thirty-three participants (4.3%) developed T2DM after 5 years. Univariate analysis showed that the development of diabetes was associated with: male sex; family history of diabetes; smoking; older age; higher body mass index (BMI), systolic and diastolic blood pressure, fasting plasma glucose (FPG), hepatic enzymes, total cholesterol and triglycerides; lower HDL cholesterol; and the presence of fatty liver on ultrasonography at baseline. In multiple logistic regression models, after adjusting for age, sex and alcohol consumption, patients with fatty liver were at significantly higher risk of developing T2DM compared to those without fatty liver [relative risk (RR) 3.92, 95% confidence interval (CI) 2.89-5.31]. After further adjustment for smoking, BMI, triglycerides, HDL cholesterol, FPG, alanine aminotransferase and ultrasonographer, fatty liver remained significantly associated with the development of T2DM (RR 1.51, 95% CI 1.04-2.20). Patients with moderate to severe fatty liver had higher risk ratios than patients with mild fatty liver. Exclusion of frequent drinkers did not attenuate the association.

CONCLUSIONS

Fatty liver on ultrasonography is associated with the development of T2DM, independently of classical risk factors, in Korean adults.

Can persistent organic pollutants explain the association between serum gamma-glutamyltransferase and type 2 diabetes?

The results of several epidemiological studies of serum gamma-glutamyltransferase (GGT) led us to hypothesise that associations of GGT within its normal range with type 2 diabetes may reflect detrimental effects of xenobiotics found in the environment, such as persistent organic pollutants (POPs). Epidemiological observations showed that serum GGT activity within its normal range strongly predicted future type 2 diabetes; the predictability of diabetes from obesity was low with GGT at the low end of the normal range; and GGT showed a positive association with known markers of oxidative stress or inflammation. Experimental findings on cellular GGT suggest that serum GGT levels within the normal range may reflect oxidative stress related to the re-synthesis of intracellular glutathione; however, this interpretation is not completely satisfying because, in its role of regenerating intracellular glutathione, GGT activity should be antioxidative. Alternatively, serum GGT activity may reflect amounts of glutathione conjugates formed during the metabolism of xenobiotics. Accordingly, we postulate a two-part hypothesis: that the association of serum GGT with type 2 diabetes reflects exposure to POPs, as these substances, which have a very long half-life, may influence diabetes risk by residing in adipose tissue as endocrine disruptors; and that POPs or similar substances may interact with obesity to cause type 2 diabetes. Supporting this hypothesis, cross-sectional investigation of background exposure to POPs in the National Health and Nutrition Examination Survey showed relationships similar to those observed for GGT, including a powerful association with prevalent diabetes and no association between obesity and diabetes for very low POP concentrations. Our hypothesis can be tested in both prospective studies and toxicological studies.

The associations between birthweight and adult markers of liver damage and function

Evidence suggesting an effect of fetal growth on liver development and function stems from both animal and human studies. The association of birthweight with adult markers of liver damage and function was examined in a random sample of 2101 British women aged 60-79 years. Age-adjusted natural logged levels of alanine aminotransferase (ALT) and gamma glutamyltransferase (GGT) decreased linearly across increasing thirds of birthweight. Alkaline phosphatase (ALP) levels were higher in women of the lowest third of the birthweight distribution compared with other women. No evidence was found for associations of birthweight with aspartate aminotransferase (AST), total bilirubin and albumin. After full adjustment for social class, physical activity, smoking and alcohol consumption, an increase in one standard deviation of birthweight (691 g) was associated with a 2% ([95% CI 0%, 4%], P = 0.021) decrease in the geometric mean of ALT, a 4% decrease in GGT ([95% CI 1%, 6%], P = 0.008) and a 2% decrease in ALP ([95% CI 0%, 3%], P = 0.001). Associations of birthweight with ALT and GGT, but not with ALP, were attenuated when adjusting for components of the metabolic syndrome. These findings suggest that factors affecting intrauterine growth may increase the propensity for adult liver damage. The attenuation of associations with adjustment for components of the metabolic syndrome is in line with non-alcoholic fatty liver disease, indicated by elevated ALT and GGT, being the hepatic manifestation of the metabolic syndrome, and of the influence of perinatal factors on this syndrome.

Glucose abnormalities are an independent risk factor for nonresponse to antiviral treatment in chronic hepatitis C

OBJECTIVES

The influence of glucose abnormalities on the efficacy of antiviral treatment is unknown. This study investigated whether glucose abnormalities (impaired fasting glucose and type 2 diabetes) influence the response to antiviral therapy with interferon plus ribavirin in patients with chronic hepatitis C.

METHODS

A total of 178 treatment-naïve patients with chronic hepatitis C treated with combination therapy were retrospectively studied. SVR was assessed after completing treatment. Fasting plasmatic glucose was measured prior to therapy.

RESULTS

Compared with nonresponders (N = 111), patients with SVR (N = 67) had lower plasma glucose (94.1 +/- 12.7 vs 104.4 +/- 25.8 mg/dL, P= 0.001) and a lower prevalence of glucose abnormalities (24.24%vs 44.14%, P= 0.012). The SVR rate was 45.13% in patients with normoglycemia (N = 113), 28.26% in patients with impaired fasting glucose (N = 46), and 15.78% in type 2 diabetic patients (N = 19) (P < 0.001). Multivariate logistic regression identified genotype 1 (OR 1.55, 95% CI 1.01-2.41, P= 0.05), gamma-glutamyltranspeptidase level (OR 6.41, 95% CI 1.86-22.07, P= 0.003), and presence of glucose abnormalities (OR 2.33, 95% CI 1.04-5.20, P= 0.039) as being independently associated with the absence of an SVR. In addition, patients with glucose abnormalities (N = 65) showed a lower virological response rate when compared with a subgroup of normoglycemic patients (N = 65) matched for sex, age, and liver fibrosis (24.6%vs 44.6%, P= 0.001).

CONCLUSIONS

Glucose abnormalities are an independent predictor of poor virological response to combined therapy in hepatitis C virus infected patients.

Genotype-by-sex interaction in the aetiology of type 2 diabetes mellitus: support for sex-specific quantitative trait loci in Hypertension Genetic Epidemiology Network participants

AIMS/HYPOTHESIS

While there are sex-related differences in both the prevalence of type 2 diabetes mellitus and disease risk factors, there is only limited research on sex-specific influences on type 2 diabetes aetiology within the same study population. Thus, we assessed genotype-by-sex interaction using a liability threshold model in an attempt to localise sex-specific type 2 diabetes quantitative trait loci (QTLs).

SUBJECTS, MATERIALS AND METHODS

Hypertensive siblings and their offspring and/or parents in the Hypertension Genetic Epidemiology Network of the Family Blood Pressure Program were recruited from five field centres. The diabetic phenotype was adjusted for race, study centre, age and non-linear age effects. In total, 567 diabetic individuals were identified in 385 families. Variance component linkage analyses in the combined sample and stratified by sex and race were performed (SOLAR program) using race-specific marker allele frequencies derived from a random sample of participants at each centre.

RESULTS

We observed a QTL-specific genotype-by-sex interaction (p=0.009) on chromosome 17 at 31 cM, with females displaying a robust adjusted logarithm of odds (LOD) of 3.0 compared with 0.2 in males and 1.3 in the combined sample. Three additional regions demonstrating suggestive evidence for linkage were detected: chromosomes 2 and 5 in the female sample and chromosome 22 (adjusted LOD=1.9) in the combined sample.

CONCLUSIONS/INTERPRETATION

These findings suggest that multiple genes may regulate susceptibility to type 2 diabetes, demonstrating the importance of considering the interaction of genes and environment in the aetiology of common complex traits.

Gamma-(monophenyl)phosphono glutamate analogues as mechanism-based inhibitors of gamma-glutamyl transpeptidase

Gamma-glutamyl transpeptidase (GGT, EC 2.3.2.2) catalyzes the hydrolysis and transpeptidation of extracellular glutathione and plays a central role in glutathione homeostasis. We report here the synthesis and evaluation of a series of hydrolytically stable gamma-(monophenyl)phosphono glutamate analogues with varying electron-withdrawing para substituents on the leaving group phenols as mechanism-based and transition-state analogue inhibitors of Escherichia coli and human GGTs. The monophenyl phosphonates caused time-dependent and irreversible inhibition of both the E. coli and human enzymes probably by phosphonylating the catalytic Thr residue of the enzyme. The inactivation rate of E. coli GGT was highly dependent on the leaving group ability of phenols with electron-withdrawing groups substantially accelerating the rate (Brønsted betalg = -1.4), whereas the inactivation of human GGT was rather slow and almost independent on the nature of the leaving group. The inhibition potency and profiles of the phosphonate analogues were compared to those of acivicin, a classical inhibitor of GGT, suggesting that the phosphonate-based glutamate analogues served as a promising candidate for potent and selective GGT inhibitors.

γ-Glutamyl transpeptidase acylation with peptidic substrates: free energy relationships measured by an HPLC kinetic assay

gamma-Glutamyl transpeptidase (GGT, EC 2.3.2.2) is a highly glycosylated heterodimeric enzyme linked to the external cellular membrane that catalyzes the hydrolysis of glutathione as well as the transfer of its gamma-glutamyl group to amino acids and dipeptides in a transpeptidation reaction. The measurement of both the hydrolytic and transpeptidation activity of this important enzyme is a challenge, since its native substrates are not highly chromogenic. We have developed an HPLC-based method for the quantitative photometric detection of numerous enzyme substrates and products, after their pre-column derivation with dabsyl chloride. The broad applicability of this method was demonstrated in the kinetic investigation of transpeptidation reactions of rat kidney GGT with glutathione, its native substrate, as well as a series of pertinent glutathione analogues. The pH-rate profile constructed for glutathione confirmed the dependence on the ionisation state of at least two residues. Analysis of the free-energy relationships in the series of synthetic peptidic substrate analogues revealed the importance of enzyme-substrate interactions unrelated to amine leaving group basicity during the acylation step. These results are further interpreted in the context of the recently published structure for a similar GGT.

Serum gamma-glutamyltransferase and risk of type 2 diabetes mellitus in men and women from the general population

OBJECTIVES

To examine gender-specific associations between gamma-glutamyltransferase (GGT) and incident type 2 diabetes mellitus in a representative population-based sample in Germany.

DESIGN

Prospective population-based study.

METHODS

The study was based on 1851 men and 1836 women (aged 25-64 years) who participated in the first Monitoring Trends and Determinants on Cardiovascular Diseases (MONICA) Augsburg Survey 1984/1985, and who were free of diabetes at baseline. Incident cases of type 2 diabetes were assessed using follow-up questionnaires in 1987/1988, 1997/1998 and 2002/2003 and were validated with medical records. Gender-specific hazard ratios (HRs) were estimated from Cox proportional hazard models.

RESULTS

A total of 172 cases of incident type 2 diabetes amongst men and 109 amongst women were registered during a mean follow-up period of 14.7 years. In both sexes the risk of type 2 diabetes increased with increasing levels of serum GGT. After multivariable adjustment HRs for incident type 2 diabetes across GGT categories (<25th, <50th, <75th, <87.5th and > or =87.5th percentiles) were 1.0, 1.81, 2.37, 3.41 and 4.24 (P-value for trend <0.0001) in men and 1.0, 1.42, 1.48, 1.95 and 2.41 (P-value for trend 0.0179) in women. Obesity appeared to be more strongly associated with type 2 diabetes in women with GGT equal or greater than the median compared to women with GGT below the median. However, in men the association between obesity and type 2 diabetes was almost identical in the two groups.

CONCLUSIONS

The GGT is an important predictor for incident type 2 diabetes in men and women from the general population.

Target discovery in metabolic disease

The prevalence of metabolic diseases is taking on epidemic proportions and poses a serious threat to human health. Current treatment options have proven insufficient to cope with obesity and diabetes because they rarely restore normal metabolism and thus leave patients exposed to life-threatening complications. Successful management of these diseases depends on novel, improved therapeutic strategies targeting early intervention in disease progression. Discovery of novel metabolic disease targets has been hampered by the complexity of contributing environmental and genetic factors, as well as the need for potent but safe treatments suitable for chronic diseases. Genomic approaches are excellent tools to manage genetic complexity and have been applied successfully to identify candidate target genes that will lead to the development of novel therapies for metabolic diseases.