TMPRSS2-ERG promotes the initiation of prostate cancer by suppressing oncogene-induced senescence

ERG translocations are commonly involved in the initiation of prostate neoplasia, yet previous experimental approaches have not addressed mechanisms of oncogenic inception. Here, in a genetically engineered mouse model, combining TMPRSS2-driven ERG with KrasG12D led to invasive prostate adenocarcinomas, while ERG or KrasG12D alone were non-oncogenic. In primary prostate luminal epithelial cells, following inducible oncogenic Kras expression or Pten depletion, TMPRSS2-ERG suppressed oncogene-induced senescence, independent of TP53 induction and RB1 inhibition. Oncogenic KRAS and TMPRSS2-ERG synergized to promote tumorigenesis and metastasis of primary luminal cells. The presence of TMPRSS2-ERG compared to a wild-type background was associated with a stemness phenotype and with relatively increased RAS-induced differential gene expression for MYC and mTOR-regulated pathways, including protein translation and lipogenesis. In addition, mTOR inhibitors abrogated ERG-dependent senescence resistance. These studies reveal a previously unappreciated function whereby ERG expression primes preneoplastic cells for the accumulation of additional gene mutations by suppression of oncogene-induced senescence.

Cardiac resynchronization therapy reduces expression of inflammation-promoting genes related to interleukin-1β in heart failure

AIMS

In light of recent data regarding inflammatory signalling pathways in cardiovascular disease and the recently demonstrated impact of pharmacologic inhibition of interleukin-1β (IL-1β) in heart failure, the primary aim was to assess the physiologic effects of cardiac resynchronization therapy (CRT) on the expression of systemic inflammatory, immune-modulatory, metabolic, and apoptotic genes in peripheral blood mononuclear cells (PBMCs) of patients with heart failure.

METHODS AND RESULTS

We used RNA sequencing (RNA-Seq) and reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) to identify gene expression changes in PBMCs in response to CRT. In total, 27 patients were analysed: 12 with heart failure undergoing CRT, 6 with heart failure undergoing standard implanted cardioverter defibrillators, and 9 with coronary artery disease but not heart failure. In CRT patients (median age 65.5 years, interquartile range 63.0-66.8 years, 33% female), RNA-Seq analysis identified 40 genes, including multiple genes associated with the IL-1β pathway, with significant correlations (false discovery rate < 0.05) with four key CRT response measures. CRT was associated with suppression of PBMC expression of IL-1β (1.80-fold decrease, P = 0.047), FOS proto-oncogene (FOS) (3.25-fold decrease, P = 0.01), dual specificity phosphatase 1 (DUSP1) (2.05-fold decrease, P = 0.001), and early growth response 1 (EGR1) (7.38-fold decrease, P = 0.03), and suppression was greater in responders vs. non-responders (P = 0.03 for IL-1β, P = 0.02 for FOS, P = 0.02 for DUSP1, and P = 0.11 for EGR1). Baseline FOS and DUSP-1 levels were greater in responders vs. non-responders (6.15-fold higher, FOS, P = 0.002; 2.60-fold higher, DUSP1, P = 0.0001). CRT responders but not non-responders showed higher baseline gene expression of FOS (P = 0.04) and DUSP1 (P = 0.06) compared with control patients without heart failure. Baseline serum high-sensitivity C-reactive protein levels were 3.47-fold higher in CRT responders vs. non-responders (P = 0.008).

CONCLUSION

Treatment of heart failure with CRT resulted in decreased PBMC expression of genes linked to inflammation. Moreover, CRT responders had higher expression of these inflammatory genes prior to CRT and greater suppression of these genes after CRT compared with non-responders.

Targeting the PI3K/AKT Pathway Overcomes Enzalutamide Resistance by Inhibiting Induction of the Glucocorticoid Receptor

The PI3K-AKT pathway has pleiotropic effects and its inhibition has long been of interest in the management of prostate cancer, where a compensatory increase in PI3K signaling has been reported following androgen receptor (AR) blockade. Prostate cancer cells can also bypass AR blockade through induction of other hormone receptors, in particular the glucocorticoid receptor (GR). Here we demonstrate that AKT inhibition significantly decreases cell proliferation through both cytostatic and cytotoxic effects. The cytotoxic effect is enhanced by AR inhibition and is most pronounced in models that induce compensatory GR expression. AKT inhibition increases canonical AR activity and remodels the chromatin landscape, decreasing enhancer interaction at the GR gene (NR3C1) locus. Importantly, it blocks induction of GR expression and activity following AR blockade. This is confirmed in multiple in vivo models, where AKT inhibition of established xenografts leads to increased canonical AR activity, decreased GR expression, and marked antitumor activity. Overall, our results demonstrate that inhibition of the PI3K/AKT pathway can block GR activity and overcome GR-mediated resistance to AR-targeted therapy. Ipatasertib is currently in clinical development, and GR induction may be a biomarker to identify responsive patients or a responsive disease state.

Implementation of Mass Cytometry as a Tool for Mechanism of Action Studies in Inflammatory Bowel Disease

Background

Novel therapeutics for inflammatory bowel disease (IBD) are under development, yet mechanistic readouts at the tissue level are lacking. Techniques to assess intestinal immune composition could represent a valuable tool for mechanism of action (MOA) studies of novel drugs. Mass cytometry enables analysis of intestinal inflammatory cell infiltrate and corresponding molecular fingerprints with unprecedented resolution. Here, we aimed to optimize the methodology for isolation and cryopreservation of cells from intestinal tissue to allow for the potential implementation of mass cytometry in MOA studies.

Methods

We investigated key technical issues, including minimal tissue requirements, cell isolation protocols, and cell storage, using intestinal biopsies and peripheral blood from healthy individuals. High-dimensional mass cytometry was employed for the analyses of biopsy-derived intestinal cellular subsets.

Results

Dithiothreitol and mechanical dissociation decreased epithelial cell contamination and allowed for isolation of adequate cell numbers from 2 to 4 colonic or ileal biopsies (6 × 104±2 × 104) after a 20-minute collagenase digestion, allowing for reliable detection of most major immune cell subsets. Biopsies and antibody-labeled mononuclear cells could be cryopreserved for later processing and acquisition (viability > 70%; P < 0.05).

Conclusions

Mass cytometry represents a unique tool for deep immunophenotyping intestinal cell composition. This technique has the potential to facilitate analysis of drug actions at the target tissue by identifying specific cellular subsets and their molecular signatures. Its widespread implementation may impact not only IBD research but also other gastrointestinal conditions where inflammatory cells play a role in pathogenesis.

Intensive dietary intervention promoting the Mediterranean diet in people with high cardiometabolic risk: a non-randomized study

AIMS

Mediterranean diet (MD) is acknowledged to exert a number of beneficial health effects. We assessed the efficacy and the durability of a 3-month intensive dietary intervention aimed at implementing the MD on body weight and cardiometabolic risk factors in subjects at high risk.

METHODS

One hundred and sixteen subjects participated in the study (71 assigned to the intensive intervention and 45 to the conventional intervention). The intensive intervention consisted of 12 weekly group educational meetings and a free-of-charge supply of meals prepared according to the MD model. The conventional intervention consisted of an individual education session along with monthly reinforcements of nutritional messages by the general practitioner. All participants were followed up for 9 months.

RESULTS

The two groups had similar pre-intervention characteristics. After the intervention, mean body weight decreased significantly in both groups (p < 0.001). However, the intervention group lost more weight (6.8 ± 4.0 vs. 0.7 ± 1.3, p < 0.0001) and showed a greater reduction in plasma glucose, triglycerides, blood pressure and an increase in HDL cholesterol than the control group (p < 0.01-p < 0.002). In the subgroup of participants with type 2 diabetes, there was a significant reduction in HbA1c level following the intensive (p < 0.0001) but not the conventional intervention. At follow-up, weight loss still persisted in the intervention group (p < 0.0001), while it was lost in the control group. Both interventions significantly reduced blood pressure in the long term (p < 0.001). A significant reduction in daily total energy intake was observed in both groups with a greater reduction in saturated fat and a higher increase in fibre intake in the intervention than in the control group (p < 0.009 and p < 0.001, respectively).

CONCLUSIONS

A 3-month intensive dietary intervention inspired to the traditional MD produced greater and more durable weight loss and improvement in cardiometabolic risk profile than the conventional intervention.

Effects of Sleeve Gastrectomy and Gastric Bypass on Postprandial Lipid Profile in Obese Type 2 Diabetic Patients: a 2-Year Follow-up

BACKGROUND

Bariatric surgery (BS) is known to favorably impact fasting lipid profile. Fasting and postprandial lipids were evaluated before and 2 years after BS in obese type 2 diabetic (T2DM) patients.

METHODS

A prospective study was conducted in 19 obese T2DM patients: ten undergoing sleeve gastrectomy (SG) and nine undergoing Roux-en-Y gastric bypass (RYGB). Before and 2 years after BS, clinical parameters and the response of lipid and incretin hormones to a mixed meal (MM) were assessed.

RESULTS

The two groups had similar characteristics at baseline. After BS, weight loss was similar in the two groups (p ≤ 0.01). Fasting glucose, insulin, and triglycerides decreased while HDL cholesterol increased in a similar way (p < 0.05); in contrast, fasting LDL cholesterol decreased only after RYGB (p < 0.05). Post-meal glucose concentrations decreased while early insulin response significantly improved after both procedures (p < 0.001 for both). Postprandial triglycerides decreased after both procedures (p < 0.05) while postprandial LDL cholesterol decreased only after RYGB (p < 0.05). Meal-GLP-1 increased postoperatively in both groups although to a greater extent after RYGB (p < 0.001 vs. SG). GIP decreased after both procedures, especially after RYGB (p = 0.003). At multivariate analysis, GLP-1 peak was the best predictor of LDL reduction (β = -0.552, p = 0.039) while the improvement of HOMA-IR (β = 0.574, p = 0.014) and weight loss (β = 0.418, p = 0.036) predicted triglycerides reduction.

CONCLUSIONS

Both surgical procedures markedly reduce fasting and postprandial triglycerides and increase HDL cholesterol levels. LDL cholesterol decreases only after RYGB through a mechanism likely mediated by the restoration of GLP-1.

Diabetes remission after bariatric surgery is characterized by high glycemic variability and high oxidative stress

BACKGROUND AND AIM

To evaluate glycemic variability (GV) and oxidative stress in patients who achieved type 2 diabetes (T2DM) remission after bariatric surgery (BS).

METHODS AND RESULTS

Twenty-two patients (M/F10/12, age 50 ± 9 years, BMI 31 ± 6 kg/m²) who were in remission of T2DM (T2DM remitters) after BS since at least 1 year and 22 age-, sex- and BMI-matched control subjects were studied. Of the BS group, eleven subjects had undergone Roux-en-Y gastric bypass (RYGB) and eleven subjects sleeve gastrectomy (SG). Oral glucose tolerance test (OGTT), 7 days-continuous glucose monitoring, 24-h urinary excretion of 8-isoprostaglandin F2α (8-isoPGF2α) and dietary intake evaluation were performed. According to general linear model for repeated measures, glucose and insulin response during OGTT were significantly different in T2DM remitter than in control subjects (p < 0.001, for both). All measures of GV (standard deviation, coefficient of variation and mean amplitude of glucose excursions) were significantly higher in T2DM remitters than in controls, (p < 0.001 for all). These indexes were higher among RYGB than SG patients (p < 0.05). The time spent out of the 60-160 mg/dl range was significantly longer in T2DM remitters undergoing RYGB than in controls (p < 0.02). Mean 24-h urinary 8-isoPGF2α excretion was significantly higher in T2DM remitters than that of control subjects (p = 0.04). All GV indexes were directly correlated with blood glucose levels at 30 and 60 min during OGTT (p < 0.05-0.001).

CONCLUSION

Remission of T2DM after BS is characterized by high GV and high oxidative stress in the face of fasting blood glucose and HbA1c within the normal range.

Comparative Effects of Roux-en-Y Gastric Bypass and Sleeve Gastrectomy on Glucose Homeostasis and Incretin Hormones in Obese Type 2 Diabetic Patients: A One-Year Prospective Study

The aim of the work was to compare the hormonal and the metabolic mechanisms involved in weight loss and remission of T2DM one year after Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) in morbidly obese type 2 diabetic (T2DM) patients. Insulin sensitivity, insulin secretion, and the gastrointestinal (GI) hormone response to a mixed meal test (MMT) were evaluated before and one year after BS (14 RYGB and 19 VSG). RYGB and VSG groups had similar characteristics at baseline. Weight loss at one year was similar in the 2 groups (ΔBMI%: - 32±10 and - 30±7%, p=0.546). Insulin sensitivity and insulin secretion improved similarly after either procedures with a similar rate in T2DM remission (86% in RYGB and 76% in VSG). Meal-stimulated GLP-1 levels increased after both procedures reaching significantly higher levels after RYGB (p=0.0001). GIP response to MMT decreased to a similar extent after the 2 interventions (p=0.977). Both fasting and post-meal ghrelin concentrations were markedly suppressed after VSG and significantly lower than RYGB (p=0.013 to p=0.035). The improvement of insulin sensitivity and beta-cell function was significantly associated with weight loss (p=0.014 to p=0.035), while no relation was found with the changes in GI hormones. In conclusion, in morbidly obese T2DM patients, RYGB and VSG result in similar improvements of the glucose status in the face of different GI hormonal pattern. Weight loss is the key determinant of diabetes remission one year after surgery.

Using mass cytometry to identify novel B cell subsets in red meat allergy

Previous studies have identified a novel food allergy driven by IgE antibodies specific for galactose-α-1,3-galactose (alpha-gal), an oligosaccharide found in red meat. While it is known that B cells play an important role in allergy as the producers of IgE antibodies that drive the allergic response, little is known about the phenotype of these B cells. The number of markers used to identify the major human B cell subsets by flow cytometry has been limited to common B cell proteins and thus precludes high dimensional immune phenotyping of B cell subsets, including unique phenotypes present in allergic individuals. We have addressed this problem by using mass cytometry (CyTOF), which enables the simultaneous analysis of up to 40 markers in a single staining panel. Here we analyzed the expression of 23 cell surface markers in PBMCs from 19 alpha-gal-allergic patients and 20 non-allergic controls by CyTOF. Additionally, we combined our CyTOF data with clinical endpoints to identify markers that may correlate with allergic disease. Our data reveals substantial heterogeneity within major B cells subsets on an individual level. Furthermore, our analysis identifies a number of markers that vary significantly in their expression in allergic versus non-allergic B cells and correlate with serum alpha-gal IgE titers. We hypothesize that B cells with this phenotype play an important role in mediating alpha-gal allergy. These findings demonstrate the power of using CyTOF and analytical tools to extract a hierarchy from high dimensional cytometry data in an unsupervised manner to identify known B cell subsets as well as to find novel B cell populations that differ between alpha-gal allergic and non-allergic individuals.

Combinatorial drug screening and molecular profiling reveal diverse mechanisms of intrinsic and adaptive resistance to BRAF inhibition in V600E BRAF mutant melanomas

Over half of BRAFV600E melanomas display intrinsic resistance to BRAF inhibitors, in part due to adaptive signaling responses. In this communication we ask whether BRAFV600E melanomas share common adaptive responses to BRAF inhibition that can provide clinically relevant targets for drug combinations. We screened a panel of 12 treatment-naïve BRAFV600E melanoma cell lines with MAP Kinase pathway inhibitors in pairwise combination with 58 signaling inhibitors, assaying for synergistic cytotoxicity. We found enormous diversity in the drug combinations that showed synergy, with no two cell lines having an identical profile. Although the 6 lines most resistant to BRAF inhibition showed synergistic benefit from combination with lapatinib, the signaling mechanisms by which this combination generated synergistic cytotoxicity differed between the cell lines. We conclude that adaptive responses to inhibition of the primary oncogenic driver (BRAFV600E) are determined not only by the primary oncogenic driver but also by diverse secondary genetic and epigenetic changes ("back-seat drivers") and hence optimal drug combinations will be variable. Because upregulation of receptor tyrosine kinases is a major source of drug resistance arising from diverse adaptive responses, we propose that inhibitors of these receptors may have substantial clinical utility in combination with inhibitors of the MAP Kinase pathway.

Effects of bariatric surgery on markers of subclinical atherosclerosis and endothelial function: a meta-analysis of literature studies

BACKGROUND/OBJECTIVES

Several studies confirmed a significantly increased carotid intima-media thickness (IMT) and impaired flow-mediated dilation (FMD) and nitrate-mediated dilation (NMD) in obese subjects, but few data are available on the effects of bariatric surgery on these markers of cardiovascular (CV) risk. We performed a meta-analysis of studies evaluating changes in IMT, FMD and NMD in obese patients after bariatric surgery.

METHODS

A systematic search was performed in the PubMed, Web of Science, Scopus and EMBASE databases without any language or publication year restriction. The last search was performed in January 2015. In addition, the reference lists of all retrieved articles were manually reviewed. Prospective studies evaluating the impact of bariatric surgery on the markers of CV risk were included. Changes in IMT, FMD and NMD after bariatric surgery were expressed as mean differences (MD) with pertinent 95% confidence intervals (95% CIs). IMT has been expressed in millimeters (mm); FMD and NMD as percentage (%). Impact of clinical and demographic features on effect size was assessed by meta-regression.

RESULTS

Ten articles (314 obese patients) were included in the analysis. Six studies contained data on IMT (7 data sets; 206 patients), 8 studies on FMD (9 data sets; 269 patients) and 4 on NMD (4 data sets; 149 patients). After bariatric surgery, there was a significant reduction of IMT (MD: -0.17 mm; 95% CI: -0.290, -0.049; P=0.006) and a significant improvement in FMD (MD: 5.65%; 95% CI: 2.87, 8.03; P<0.001), whereas NMD did not change (MD: 2.173%; 95% CI: -0.796, 5.142; P=0.151). Interestingly, percentage of changes in the body mass index were associated with changes in IMT (Z=11.52, P<0.001), FMD (Z=-4.26, P<0.001) and NMD (Z=-3.81, P<0.001).

CONCLUSIONS

Despite heterogeneity among studies, bariatric surgery is associated with improvement of subclinical atherosclerosis and endothelial function. These effects may significantly contribute to the reduction of the CV risk after bariatric surgery.

Synergistic apoptosis in head and neck squamous cell carcinoma cells by co-inhibition of insulin-like growth factor-1 receptor signaling and compensatory signaling pathways

BACKGROUND

In head and neck squamous cell carcinoma (HNSCC), resistance to single-agent targeted therapy may be overcome by co-targeting of compensatory signaling pathways.

METHODS

A targeted drug screen with 120 combinations was used on 9 HNSCC cell lines.

RESULTS

Multiple novel drug combinations demonstrated synergistic growth inhibition. Combining the insulin-like growth factor-1 receptor (IGF-1R) inhibitor, BMS754807, with either the human epidermal growth factor receptor (HER)-family inhibitor, BMS599626, or the Src-family kinase inhibitor, dasatinib, resulted in substantial synergy and growth inhibition. Depending on the cell line, these combinations induced synergistic or additive apoptosis; when synergistic apoptosis was observed, AKT phosphorylation was inhibited to a greater extent than either drug alone. Conversely, when additive apoptosis occurred, AKT phosphorylation was not reduced by the drug combination.

CONCLUSION

Combined IGF-1R/HER family and IGF-1R/Src family inhibition may have therapeutic potential in HNSCC. AKT may be a node of convergence between IGF-1R signaling and pathways that compensate for IGF-1R inhibition.

Clinical efficacy of bariatric surgery versus liraglutide in patients with type 2 diabetes and severe obesity: a 12-month retrospective evaluation

AIMS

To evaluate the clinical efficacy of bariatric surgery vs medical therapy with liraglutide on weight loss, glycemic control and cardiovascular risk profile in patients with type 2 diabetes and severe obesity.

METHODS

A retrospective evaluation was conducted in 31 patients with type 2 diabetes and severe obesity who had undergone bariatric surgery and in 31 patients with type 2 diabetes and comparable body weight who had added liraglutide to their background medical treatment in the period 2009-2013. Anthropometric parameters, glycemic control, treatment of diabetes and other comorbidities, safety and side effects before and 12 months after treatment were assessed.

RESULTS

Age was 47 ± 8 years (mean ± SD) in bariatric surgery and 56 ± 9 years in medical treatment group (p < 0.001); body mass index before treatment was 44 ± 7 and 40 ± 4 kg/m(2) in bariatric surgery and medical treatment, respectively (p = 0.03). Twelve months after treatment, average weight loss was 38 ± 15 kg among bariatric surgery patients, and 5 ± 8 kg in medical treatment group (p < 0.001). Glycemic control improved in both groups with greater improvement in bariatric surgery patients. The UKPDS risk score decreased in both groups, although it remained higher in medical treatment than in bariatric surgery patients (p < 0.001). Of note, almost 60 % of patients on liraglutide met the target of glycated hemoglobin <7 % (53 mmol/mol) and lost ≥5 % of body weight.

CONCLUSIONS

In severely obese type 2 diabetic patients, bariatric surgery reduced body weight and improved overall metabolic control to a greater extent than medical treatment. Randomized clinical studies are necessary.

Early improvement of postprandial lipemia after bariatric surgery in obese type 2 diabetic patients

BACKGROUND

Bariatric surgery (BS) is able to positively influence fasting lipid profile in obese type 2 diabetic patients (T2DM), but no data is available on the impact of BS on postprandial lipid metabolism neither on its relation with incretin hormones. We evaluated the short-term (2 weeks) effects of BS on fasting and postprandial lipid metabolism in obese T2DM patients and the contribution of changes in active GLP-1.

METHODS

We studied 25 obese T2DM patients (age = 46 ± 8 years, BMI = 44 ± 7 kg/m2), of which 15 underwent sleeve gastrectomy and 10 underwent gastric bypass. Lipid and incretin hormone concentrations were evaluated for 3 h after ingestion of a liquid meal before and 2 weeks after BS.

RESULTS

After BS, there was a significant reduction in body weight (p < 0.001), fasting plasma glucose (p < 0.001), fasting plasma insulin (p < 0.05), HOMA-IR (p < 0.001), and fasting plasma lipids (p < 0.05). The meal response of plasma triglycerides, total cholesterol, and HDL cholesterol was significantly lower compared to pre-intervention (p < 0.05, p < 0.001). In particular, the incremental area under the curve (IAUC) of plasma triglycerides decreased by 60% (p < 0.005). The meal-stimulated response of active GLP-1 increased, reaching a statistical significance (p < 0.001).

CONCLUSIONS

BS leads to an early improvement of fasting and postprandial lipemia. The fall in fasting triglycerides is associated with an improvement of insulin resistance, while the reduction of postprandial lipemia is likely related to reduced intestinal lipid absorption consequent to bariatric surgery.

Identification of a new target of miR-16, Vacuolar Protein Sorting 4a

Rationale

The rationale was to utilize a bioinformatics approach to identify miRNA binding sites in genes with single nucleotide mutations (SNPs) to discover pathways in heart failure (HF).

Objective

The objective was to focus on the genes containing miRNA binding sites with miRNAs that were significantly altered in end-stage HF and in response to a left ventricular assist device (LVAD).

Methods and Results

BEDTools v2.14.3 was used to discriminate SNPs within predicted 3′UTR miRNA binding sites. A member of the miR-15/107 family, miR-16, was decreased in the circulation of end-stage HF patients and increased in response to a LVAD (p<0.001). MiR-16 decreased Vacuolar Protein Sorting 4a (VPS4a) expression in HEK 293T cells (p<0.01). The SNP rs16958754 was identified in the miR-15/107 family binding site of VPS4a which abolished direct binding of miR-16 to the 3′UTR of VPS4a (p<0.05). VPS4a was increased in the circulation of end-stage HF patients (p<0.001), and led to a decrease in the number of HEK 293T cells in vitro (p<0.001).

Conclusions

We provide evidence that miR-16 decreases in the circulation of end-stage HF patients and increases with a LVAD. Modeling studies suggest that miR-16 binds to and decreases expression of VPS4a. Overexpression of VPS4a decreases cell number. Together, these experiments suggest that miR-16 and VPS4a expression are altered in end-stage HF and in response to unloading with a LVAD. This signaling pathway may lead to reduced circulating cell number in HF.

Abstract B29: Combinatorial screens with targeted inhibitors reveal diverse compensatory responses and mechanisms of adaptive resistance to therapy

The effectiveness of targeted inhibition of cell signaling can be blunted by compensatory signaling, which generates adaptive resistance mechanisms and reduces therapeutic responses. We have performed high-throughput combinatorial drug screening as a discovery tool to identify compensatory pathways that confer resistance to the cytotoxic effects of targeted therapy. We screened subsets of over 1,000 drug combinations in 14 different epithelial cell lines representing three distinct cancer lineages, and 19 melanoma cell lines, and assessed the ability of each combination to cause synergistic cytotoxicity. We focused on synergistic combinations because they point to mechanistic linkages between the signaling pathways, and also because of the possibility of improved therapeutic index in vivo. Drug substitution studies were used to validate the functionally important drug targets. Of the 84 combinations that caused robust synergy in multiple epithelial cell lines, none were synergistic in more than half of the lines tested, and we observed no pattern with respect to lineage specificity or mutational status of commonly altered oncogenes in the observed synergies. Within the melanoma panel, BRAF mutational status predicted response to single-agent BRAF inhibition, but did not predict synergistic drug combinations, which were different for each cell line. These results reflect the heterogeneity of genetic alterations and the plasticity of cell signaling networks even among cell lines of the same tissue of origin that contain the same predominant driver mutations. We suggest that there is not a sharp dichotomy between “driver” and “passenger” mutations, and that the biological responses to combination therapies are determined by functionally important modifier mutations that we term “back-seat drivers.” This hypothesis is supported by analysis of the transcriptomes and phosphoproteomes of cells treated with drugs singly and in combination, and by exome sequencing. Such analyses also can reveal critical nodes with the potential to function as effective single targets. We found that co-inhibition of EGFR and PI3 Kinase causes synergistic cytotoxicity in some epithelial cancer cell lines, and that phosphoproteomic analysis of signaling pathway responses revealed concordant synergistic inhibition of p70S6 Kinase in KU-7 bladder cancer cells. Using an epistasis paradigm, restoration of p70S6 Kinase signaling by expression of mutationally activated p70S6 Kinase resulted in protection from cytotoxicity, indicating that p70S6 Kinase is a critical node for enhanced cytotoxicity due to combination treatment. AT7867, a potent inhibitor of p70S6 Kinase, was able to inhibit phosphorylation of ribosomal protein S6 and induce cytotoxicity as effectively as the combination drug treatment. We suggest that p70S6 Kinase acts as a functionally important node within the EGFR/PI3 Kinase signaling network and is an attractive target for therapeutic intervention.

Citation Format: Mark J. Axelrod, Devin Roller, Brian Capaldo, Aaron J. Mackey, Mark Conaway, Daniel Gioeli, Michael J. Weber. Combinatorial screens with targeted inhibitors reveal diverse compensatory responses and mechanisms of adaptive resistance to therapy. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Synthetic Lethal Approaches to Cancer Vulnerabilities; May 17-20, 2013; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(5 Suppl):Abstract nr B29.

Cardiometabolic risk in overweight subjects with or without relative fat-free mass deficiency: the Strong Heart Study

BACKGROUND AND AIM

Sarcopenia is a condition mainly due to loss of fat-free mass (FFM) in elderly individuals. RFFMD, however, is also frequent in obese subjects due to abnormal body composition. Objective of this study was to evaluate the impact of relative fat-free mass deficiency (RFFMD) on cardiometabolic (CM) risk in obese normoglycemic individuals.

METHODS AND RESULTS

Overweight/obese American Indians from the Strong Heart Study population, without diabetes and with FBG ≤ 110 mg/dL and with GFR >60 mg/mL/1.73 m(2) were selected for this analysis (n = 742). RFFMD was defined on the basis of a multivariable equation previously reported. Fasting glucose and 2 h-OGTT were measured together with urine albumin/creatinine excretion, laboratory and anthropometric parameters. In addition to lower FFM and greater adipose mass, participants with RFFMD had higher body mass index, waist circumference, C-reactive protein, fibrinogen, insulin resistance and urinary albumin/creatinine than participants with normal FFM (all p < 0.001); they also had a greater prevalence of hypertension, impaired glucose tolerance (IGT) or OGTT-diabetes than participants with normal FFM (all p < 0.003) and a near 2-fold greater probability of significant proteinuria (p < 0.01). RFFMD was more frequent in women than in men: significant sex-RFFMD interactions were found for BMI and waist circumference (both p < 0.0001).

CONCLUSIONS

RFFMD in overweight/obese normoglycemic individuals is associated with greater probability of hypertension, abnormalities of glucose tolerance and proteinuria. Assessment of RFFRMD might, therefore, help stratifying cardiometabolic risk among normoglycemic individuals with overweight/obesity.

Dietary fat differentially modulate the mRNA expression levels of oxidative mitochondrial genes in skeletal muscle of healthy subjects

BACKGROUND AND AIMS

Different types of dietary fats exert differential effects on glucose and lipid metabolism. Our aim was to evaluate the impact of different dietary fats on the expression of skeletal muscle genes regulating mitochondrial replication and function in healthy subjects.

METHODS AND RESULTS

Ten healthy subjects (age 29 ± 3 years; BMI 25.0 ± 3 kg/m(2)) received in a random order a test meal with the same energy content but different composition in macronutrients and quality of fat: Mediterranean (MED) meal, SAFA meal (Lipid 66%, saturated 36%) and MUFA meal (Lipid 63%, monounsaturated 37%). At fast and after 180 min, a fine needle aspiration was performed from the vastus lateralis for determination of mitochondrial gene expression by quantitative PCR. No difference in glucose and triglyceride response was observed between the three meals, while NEFA levels were significantly higher following fat-rich meals compared to MED meal (p < 0.002-0.0001). MED meal was associated with an increased expression, albeit not statistically significant, of some genes regulating both replication and function. Following MUFA meal, a significant increase in the expression of PGC1β (p = 0.02) and a reduction in the transcription factor PPARδ (p = 0.006) occurred with no change in the expression of COX and GLUT4 genes. In contrast, SAFA meal was associated with a marked reduction in the expression of COX (p < 0.001) PFK (p < 0.003), LPL (p = 0.002) and GLUT4 (p = 0.009) genes.

CONCLUSION

Dietary fats differentially modulate gene transcriptional profile since saturated, but not monounsaturated fat, downregulate the expression of genes regulating muscle glucose transport and oxidation.

Abstract 3400: Small molecule biological screens and global analytical approaches reveal the complexity of cancer cell signaling networks and the challenge of personalized medicine

BRAF is mutationally activated in 50% of melanomas with a variety of data indicating its role as a driver of malignancy. However, while patients with BRAF mutations respond to vemurafenib, most responses are not long lasting. Moreover, the 25% of melanomas harboring an NRAS activating mutation are resistant de novo to BRAF inhibitors. In order to identify effective drug combinations that increase the effectiveness of BRAF inhibition, we used combinatorial small molecule biological screens and global analytical approaches to identify compensatory and redundant pathways. We screened a drug library for combinations with BRAF or MEK inhibitors that cause synergistic cytotoxicity in melanoma cell lines. Although BRAF mutational status predicted sensitivity to inhibitors of BRAF, each BRAF mutant line differed in the combination of drugs that induced synergistic cytotoxicity. One robust and clinically relevant pair identified was the BRAF inhibitor PLX4720 and the EGFR/HER2 inhibitor lapatinib. This drug combination was synergistic in half of the BRAF mutant cell lines tested, including a line that was completely resistant to PLX4720. The combination was also effective in the two NRAS mutant lines tested. Xenograft experiments testing the combination of PLX4720 and lapatinib revealed a significant reduction in tumor volume compared to either single agent alone in both PLX4720 sensitive and resistant BRAF mutant tumors, providing preclinical data supporting the efficacy of this drug combination. Synergy of the PLX4720-lapatinib combination did not correlate with EGFR/HER2 expression, activity state, or mutational status. This further indicates that sensitivity of melanoma to drug combinations is not determined by the targeted oncogenic drivers, but by the existence of unique secondary, compensatory survival responses. We hypothesize that mutationally activated BRAF is wired into the constitutive signaling network differently in each of these cells, presumably a consequence of the diverse secondary mutations that characterize melanomas. Consistent with this, whole exome-sequencing data revealed a diversity of somatic variation among the synergistic and non-synergistic melanomas, while gene expression analysis demonstrated both distinct, line-specific basal transcriptional profiles and the lack of common gene expression signatures in melanomas synergistically inhibited by treatment with PLX4720-lapatinib. Collectively, these data point out the extraordinary robustness of cancer cell signaling networks and the challenges of individualizing therapies. This study has uncovered novel functional drug combinations and suggests that the underlying signaling networks that control responses to targeted agents can vary substantially depending on unexplored components of the cell genotype and cell signaling network.

Citation Format: Devin Roller, Brian Capaldo, Aaron J. Mackey, Mark Conaway, Michael J. Weber, Daniel G. Gioeli. Small molecule biological screens and global analytical approaches reveal the complexity of cancer cell signaling networks and the challenge of personalized medicine. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3400. doi:10.1158/1538-7445.AM2013-3400

Clinical efficacy of laparoscopic sleeve gastrectomy vs laparoscopic gastric bypass in obese type 2 diabetic patients: a retrospective comparison

BACKGROUND

Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) are performed in patients with obesity and type 2 diabetes mellitus (T2DM). The aim of this study is to evaluate retrospectively the clinical efficacy of RYGB and SG in two groups of obese T2DM patients.

METHODS

From the hospital database, we extracted the clinical records of 31 obese T2DM patients, of whom 15 (7 F/8 M) had undergone laparoscopic SG (LSG) and 16 (7 F/9 M) laparoscopic RYGB (LRYGB) in the period 2005-2008. The groups were comparable for age (range 33-59 years) and BMI (range 38-57 kg/m(2)). LRYGB alimentary limb was 150 cm, and biliopancreatic limb was 150 cm from the Treitz ligament. LSG vertical transection was calibrated on a 40-Fr orogastric bougie. Data were analysed at 6, 12 and 18-24 months with reference to weight loss and remission of comorbidities.

RESULTS

The reduction in body weight was comparable in the two groups. At 18-24 months the percent BMI reduction was 29 ± 8 and 33 ± 11 % in LSG and LRYGB, respectively. Percent excess weight loss was 53 ± 16 and 52 ± 19 % in LSG and LRYGB, respectively. Thirteen patients in LSG and 14 patients in LRYGB discontinued their hypoglycaemic medications. Five (55 %) patients in LSG and eight (89 %) in LRYGB discontinued antihypertensive drugs. Three out of five patients in LSG and one out of two patients in LRYGB withdrew lipid-lowering agents.

CONCLUSIONS

LSG and LRYGB are equally effective in terms of weight loss and remission of obesity-related comorbidities. Controlled long-term comparisons are needed to establish the optimal procedure in relation to patients' characteristics.

Effects of meals with different glycaemic index on postprandial blood glucose response in patients with Type 1 diabetes treated with continuous subcutaneous insulin infusion

OBJECTIVE

To evaluate the impact of high-glycaemic index and low-glycaemic index meals on postprandial blood glucose in patients with Type 1 diabetes treated with continuous subcutaneous insulin infusion.

METHODS

Sixteen patients with Type 1 diabetes under continuous subcutaneous insulin infusion treatment, age 36±0.5 years (mean±sem), HbA(1c) 7.6±0.2% (56±1.1 mmol/mol), consumed two test meals with an identical macronutrient composition, but with a different glycaemic index: 59 vs. 90. Blood glucose was checked before the test meal and every 30 min thereafter for 180 min. The same preprandial insulin dose was administered on the two occasions.

RESULTS

Blood glucose concentrations following the low-glycaemic index meal were significantly lower than those of the high-glycaemic index meal (P<0.05 to P<0.01). The blood glucose area under the curve after the low-glycaemic index meal was 20% lower than after the high-glycaemic meal (P=0.006).

CONCLUSIONS

  Our data show that meals with the same carbohydrate content but a different glycaemic index produce clinically significant differences in postprandial blood glucose.

Impact of sleeve gastrectomy on weight loss, glucose homeostasis, and comorbidities in severely obese type 2 diabetic subjects

This study was undertaken to assess medium-term effects of laparoscopic sleeve gastrectomy (LSG) on body weight and glucose homeostasis in severely obese type 2 diabetic (T2DM) subjects. Twenty-five obese T2DM subjects (10 M/15 F, age 45 ± 9 years, BMI 48 ± 8 kg/m(2), M ± SD) underwent evaluation of anthropometric/clinical parameters and glucose homeostasis before, 3 and 9-15 months after LSG. Mean BMI decreased from 48 ± 8 kg/m(2) to 40 ± 9 kg/m(2) (P < .001) at 3 months and 34 ± 6 kg/m(2) (P < .001) at 9-15 months after surgery. Remission of T2DM (fasting plasma glucose < 126 mg/dL and HbA1c < 6.5% in the absence of hypoglycemic treatment) occurred in all patients but one. There was a remarkable reduction in the percentage of patients requiring antihypertensive and hypolipidemic drugs. Our study shows that LSG is effective in producing a significant and sustained weight loss and improving glucose homeostasis in severely obese T2DM patients.

Coronary vasoreactivity is not altered in young people with type 1 diabetes

BACKGROUND AND AIM

Abnormal coronary microvascular circulation has been demonstrated in diabetes and is associated with increased rate of cardiovascular events. Our objective was to evaluate coronary vasoreactivity in young people with type 1 diabetes with and without microvascular complications.

METHODS AND RESULTS

Twenty-five type 1 diabetic patients without microvascular complications (DC-), 23 with microvascular complications (DC+), and 18 control subjects (C) were studied. Coronary vasoreactivity was assessed by means of coronary flow reserve (CFR). Blood flow velocity in the left anterior descending coronary artery was measured at rest and after high-dose dipyridamole using transthoracic color-guided pulsed Doppler echocardiography. CFR was defined as the ratio of hyperaemic to resting diastolic peak flow velocities. The three groups had similar cardiac function parameters, and also systolic and diastolic blood pressure at rest, which remained unchanged during dipyridamole infusion. Resting coronary flow velocity was comparable in C, DC-, and DC+ (p=ns). Dipyridamole infusion produced a threefold increase in coronary diastolic peak velocity, which reached similar values in C (0.69±0.16 m/s), DC- (0.69±0.18 m/s), and DC+ (0.66±0.11 m/s). Mean CFR ratio was similar in C (3.33±0.66), DC- (3.30±0.51), and DC+ (3.24±0.60). At multiple linear regression analysis, no association was found between CFR and age, sex, HbA(1c), duration of diabetes, and complications.

CONCLUSION

Coronary vasodilatory function is preserved in young D patients, even those with early microvascular complications, suggesting that coronary vasoreactivity deteriorates at more advanced stages of microvascular complications and/or in the presence of other cardiovascular risk factors.

Prevalence of the metabolic syndrome using ATP-derived definitions and its relation to insulin-resistance in a cohort of Italian outpatient children

OBJECTIVE

To analyze the prevalence of the metabolic syndrome (MetS) defined by three sets of Adult Treatment Panel III (ATPIII)-derived criteria, and the ability of each definition to identify insulin-resistance (IR) in a wide cohort of outpatient children.

SUBJECTS AND METHODS

Seven hundred and twenty-four children consecutively observed in the Outpatient Pediatric Clinic of Pozzuoli Hospital during the period 2004-2009 were included in the study. Diagnosis of the MetS was made using three definitions: Cook, Jolliffe (which adopt age- and gender-specific cut-points) and de Ferranti. Insulin sensitivity was evaluated by homeostasis model assessment of insulin resistance (HOMA-IR). IR was defined by the 90th percentile of HOMA-IR in healthy non-obese Italian children grouped by gender and Tanner stage. The ability of each definition to identify IR was evaluated in terms of sensitivity and specificity.

RESULTS

The prevalence of the MetS in the overall cohort was 11, 12 and 24% using Cook, Jolliffe and de Ferranti criteria, respectively. Sensitivity and specificity in relation to IR were 19 and 94% with Cook criteria, 21 and 92% with Jolliffe criteria, and 39 and 84% with de Ferranti criteria.

CONCLUSIONS

The prevalence of the MetS in children increases with increasing body weight. Among the three definitions analyzed, de Ferranti identifies a larger number of children with the MetS. The prediction of IR is weak with all definitions; on the contrary, the absence of MetS identifies fairly well children with low degree of IR.

Myasthenia gravis in a patient affected by glycogen storage disease type Ib: a further manifestation of an increased risk for autoimmune disorders?

Glycogen storage disease type Ib (GSD Ib, OMIM 232220) is an inborn disorder of glucose metabolism, caused by mutations in the G6PT gene, encoding a glucose 6-phosphate transporter (G6PT). GSD Ib is mainly associated with fasting hypoglycaemia and hepatomegaly. Most GSD Ib patients also show neutropenia and neutrophil dysfunction and therefore are at risk of developing severe infections and inflammatory bowel disease (IBD). An increased risk for autoimmune disorders, such as thyroid autoimmunity and Crohn-like disease, has also been demonstrated, but no systematic study on the prevalence of autoimmune disorders in GSD Ib patients has ever been performed. We describe a 25-year-old patient affected by GSD Ib who developed 'seronegative' myasthenia gravis (MG), presenting with bilateral eyelid ptosis, diplopia, dysarthria, severe dysphagia, dyspnoea and fatigue. The repetitive stimulation of peripheral nerves test showed signs of exhaustion of neuromuscular transmission, particularly evident in the cranial area. Even in the absence of identifiable anti-acetylcholine receptor antibodies, seronegative MG is considered an autoimmune disorder and may be related to the disturbed immune function observed in GSD Ib patients.

Central adiposity and left ventricular mass in obese children

AIM

The impact of central adiposity on left ventricular (LV) mass in childhood obesity has been little explored. This study evaluates whether central obesity influences LV mass and function in obese children.

METHODS AND RESULTS

Biochemical, anthropometric and echocardiographic measurements were taken in obese (n=111, mean age 10.6+/-2.5 years) and non-obese children (n=30, mean age 10.8+/-3.0 years). Left ventricular function was analyzed by conventional and tissue Doppler echocardiography. LV mass was calculated according to the Penn convention and indexed for height(2.7) (LVM(i)). The obese group showed increased levels of LVM(i) as compared to the non-obese group (35.7+/-8.5 vs 23.5+/-2.8 g/h(2.7), p<0.0001). Among obese children, we observed a significant increase of LVM(i) across tertile of waist-height ratio (WHtR). The subjects identified by the highest tertile of WHtR, as compared to subjects identified by the lowest tertile, showed higher levels of BMI (29.5+/-5.4 vs 31.0+/-5.0 kg/m(2), p<0.0001) and LVM(i) (32.1+/-6.5 vs 37.1+/-8.5 g/h(2.7), p<0.01). Among obese children a positive correlation (standardized for age and gender) was found between LVM(i) and BMI (r=0.282, p<0.01) and WHtR (r=0.334, p<0.0001). To analyze the independent predictors of LVM(i), a stepwise linear regression analysis was performed using age, gender, BMI, blood pressure, heart rate, HOMA-IR and WHtR as independent variables. LVM(i) was independently associated only with WHtR (beta=0.309, t=3.238, p=0.002).

CONCLUSION

Obese children show an increased LVM(i) and a preserved LV function. Central adiposity is the major determinant of left ventricular mass.

Prevalence of elevated liver enzymes in Type 2 diabetes mellitus and its association with the metabolic syndrome

The occurrence of liver disease and raised liver enzymes is common in Type 2 diabetes, and may be multifactorial in origin. Very few studies are available on the exact prevalence of the phenomenon, however. We carried out an observational point-prevalence study of elevated liver enzymes in eight hospital-based Italian diabetes units. Data of 9621 consecutive Type 2 diabetes patients (males, 52.4%; median age, 65 yr) were analyzed, and alanine and aspartate aminotransferase (ALT, AST) and gamma-glutamyltransferase (GGT) levels were related to body mass index (BMI), metabolic control and the presence of the metabolic syndrome. ALT, AST, and GGT levels exceeding the upper limit of normal were present in 16.0%, 8.8%, 23.1%, respectively, the prevalence being higher in males, increasing with obesity class and poor metabolic control, and decreasing with age. Elevated enzymes were systematically associated with most parameters of the metabolic syndrome. After correction for age, gender, BMI, and differences across centers, elevated triglyceride levels/fibrate treatment [odds ratio (OR), 1.57; 95% confidence interval (CI), 1.34- 1.84] and an enlarged waist circumference (OR, 1.47; 95% CI, 1.17-1.85) were the only parameters independently associated with high ALT. In a separate analysis, the presence of metabolic syndrome (Adult Treatment Panel III criteria) was highly predictive of raised liver enzymes. After exclusion of hepatitis B and C positive cases, tested in 2 centers, the prevalence of raised enzymes decreased by approximately 4%, but the association with the metabolic syndrome did not change significantly. In conclusion, the high prevalence of elevated liver enzymes in Type 2 diabetes is in keeping with the well-demonstrated risk of progressive liver disease. A large amount of diabetes patients may require a thorough clinical, laboratory and histological investigation.

Upper airway obstructive disease in mucopolysaccharidoses: polysomnography, computed tomography and nasal endoscopy findings

In mucopolysaccharidoses, upper airway obstruction has multiple causative factors and progressive respiratory disease may severely affect morbidity and mortality. In a cross-sectional study over 2 years we evaluated upper airway obstructive disease through overnight polysomnography, upper airway computed tomography and nasal endoscopy in 5 children and 6 adults with mucopolysaccharidoses of various types. Measurements of apnoea and apnoea-hypopnoea index, arousal index, and sleep efficiency were obtained through polysomnography. Retropalatal and retroglossal spaces were calculated through computed tomography, and the degree of adenoid hypertrophy was assessed through endoscopy. Apnoea index and apnoea-hypopnoea index were significantly higher in children than in adults with mucopolysaccharidoses (p = 0.03 and p = 0.03, respectively). Compared to healthy controls, retropalatal and retroglossal spaces were significantly smaller in children (p = 0.03 and p = 0.004, respectively) or adults with mucopolysaccharidoses (p = 0.004 and p = 0.004, respectively). All subjects had adenoid hypertrophy causing first-degree (36%) or second-degree (64%) obstruction at endoscopy. Overnight polysomnography, upper airway computed tomography and nasal endoscopy are useful tools for diagnosing obstructive sleep apnoea syndrome in mucopolysaccharidoses, and identifying the site and severity of airway obstruction.

Impact of impaired fasting glucose and other metabolic factors on cognitive function in elderly people

AIM

The present study was undertaken to evaluate the impact of impaired fasting glucose (IFG), insulin resistance (IR) and hyperhomocysteinaemia (Hhcy) on cognitive function (CF) in a sample of non-diabetic elderly subjects.

METHODS AND RESULTS

One hundred and eighty-two non-diabetic subjects, aged > or = 65 years, without signs of previous stroke were included in the study. CF was evaluated by the Mini Mental State Examination (MMSE) score, corrected for age and education. Since diagnostic criteria for IFG have been recently lowered from 110 to 100 mg/dl, subjects were categorized according to old (IFG1997) and new (IFG2003) criteria. IR and Hhcy were defined by the upper quartile of insulin (11.0 UI/L) and Hcy (18.6 micromol/L) distribution, respectively. The frequency of IFG1997, Hhcy, and IR, but not of IFG2003, showed a linear trend across tertiles of MMSE (p<0.001). The odds ratio (95% CI) for impaired CF (MMSE<24.3) was 9.08 (2.97-27.74) for IFG1997, 3.66 (1.28-10.45) for Hhcy, 2.83 (1.25-6.37) for IR and 1.32 (0.61-2.89) for IFG2003.

CONCLUSIONS

Our study shows that IFG1997, Hhcy and IR are powerful metabolic markers of impaired CF among elderly people.

Early detection of diabetic cardiomyopathy: usefulness of tissue Doppler imaging

OBJECTIVE

The aim of the study was to evaluate whether tissue Doppler imaging (TDI) detects a pre-clinical impairment of diastolic function in subjects with Type 2 diabetes with short duration of disease and normal cardiac function with conventional echocardiography (CE), and whether echocardiographic parameters are related to metabolic abnormalities.

PATIENTS AND METHODS

We studied 40 non-obese, normotensive, uncomplicated Type 2 diabetic subjects with short duration of disease and 20 control subjects. All participants underwent both CE and TDI echocardiography. With TDI, early velocity (Ea), atrial velocity (Aa), their ratio (Ea/Aa) and systolic velocity (Sa) were measured at the lateral corner of mitral annulus. Glycosylated haemoglobin, fasting plasma glucose and insulin were determined and homeostasis model assessment (HOMA-IR), as an index of insulin resistance, was calculated.

RESULTS

Cardiac function with CE was similar in the two groups. Using TDI, diabetic subjects showed a lower Ea velocity (15.5+/-3.9 vs. 19.4+/-3.5 cm/s, P<0.0001), an increased Aa velocity (15.5+/-2.4 vs. 14.1+/-2.4 cm/s, P<0.05) and a reduced Ea/Aa ratio (1.00+/-0.2 vs. 1.39+/-0.3, P<0.0001), compared with control subjects. Linear regression analysis in the diabetic group showed that only HOMA-IR was negatively associated with Ea/Aa ratio (P=0.026). No significant association was observed with other metabolic variables.

CONCLUSION

An early stage of diabetic cardiomyopathy can be evidenced by TDI in Type 2 diabetic subjects even in the presence of a normal cardiac function with CE. This abnormality is associated with insulin resistance.

Impact of known and unknown diabetes on in-hospital mortality from ischemic stroke

BACKGROUND AND AIMS

The effect of known diabetes on in-hospital mortality from ischemic stroke is still debated whereas the role of unknown diabetes is virtually unexplored. This study evaluates the impact of known and unknown diabetes on in-hospital mortality from ischemic stroke.

METHODS AND RESULTS

We have retrospectively evaluated the records of 286 consecutive cases of ischemic stroke hospitalized from January 1998 to December 2000 at the Department of Internal Medicine of the General Hospital located in the western area of Naples. Fasting plasma glucose level < 7 mmol/L identified non diabetic subjects. Known diabetes mellitus was diagnosed by history of diabetes and/or hypoglycemic therapy, unknown diabetes was defined as a random plasma glucose level > or = 11 mmol/L and/or in-hospital fasting glucose > or = 7 mmol/L on two or more occasions. Severity of stroke was defined using the Canadian Neurological Score (CNS). According to these criteria, 144 subjects were non diabetics, 99 had known diabetes and 43 had unknown diabetes. Subjects with known diabetes showed a higher prevalence of female sex, hypertension and increased triglyceride levels as compared with non diabetic subjects (p < 0.01). Subjects with unknown diabetes were older (p < 0.01) and showed a more severe CNS (3.4 +/- 2.7) than non diabetic and diabetic subjects (5.8 +/- 2.6 and 5.8 +/- 2.6, respectively; p < 0.01). In-hospital mortality was significantly higher in the unknown diabetic group (44%) as compared with known diabetic (15%) and non diabetic groups (12%) (p < 0.001). This finding was independent of neurological deficit, age, atrial fibrillation and history of previous stroke.

CONCLUSIONS

Our study shows that unknown diabetes, more than known diabetes, is a strong risk factor for in-hospital mortality in subjects with acute ischemic stroke.

Blood-brain barrier transport and brain metabolism of glucose during acute hyperglycemia in humans

It is controversial whether transport adaptation takes place in chronic or acute hyperglycemia. Blood-brain barrier glucose permeability and regional brain glucose metabolism (CMR(glc)) was studied in acute hyperglycemia in six normal human subjects (mean age, 23 yr) using the double indicator method and positron emission tomography and [(18)F]fluorodeoxyglucose as tracer. The Kety-Schmidt technique was used for measurement of cerebral blood flow (CBF). After 2 h of hyperglycemia (15.7 +/- 0.7 mmol/L), the glucose permeability-surface area product from blood to brain remained unchanged (0.050 +/- 0.008 vs. 0.059 +/- 0.031 mL/100 g.min). The unidirectional clearance of [(18)F]fluorodeoxyglucose (K(1)*) was reduced from 0.108 +/- 0.011 to 0.061 +/- 0.005 mL/100 g.min (P < 0.0004). During hyperglycemia, global CMR(glc) remained constant (21.4 +/- 1.2 vs. 23.1 +/- 2.2 micromol/100 g.min, normo- and hyperglycemia, respectively). Except for a significant increase in white matter CMR(glc), no regional difference in CMR(glc) was found. Likewise, CBF remained unchanged. The reduction in K(1)* was compatible with Michaelis-Menten kinetics for facilitated transport. Our findings indicate no major adaptational changes in the maximal transport velocity or affinity to the blood-brain barrier glucose transporter. Finally, hyperglycemia did not change global CBF or CMR(glc).

Abnormal vascular reactivity in growth hormone deficiency

BACKGROUND

The reason why patients with growth hormone (GH) deficiency (GHD) are at increased risk for premature cardiovascular death is still unclear. Although a variety of vascular risk factors have been identified in GHD, little is known regarding vascular reactivity and its contribution to premature arteriosclerosis.

METHODS AND RESULTS

We assessed vascular function in 7 childhood-onset, GH-deficient nontreated patients (age 22+/-3 years, body mass index [BMI] 25+/-1 kg/m(2)) and 10 healthy subjects (age 24+/-0.4 years, BMI 22+/-1 kg/m(2)) by using strain gauge plethysmography to measure forearm blood flow in response to vasodilatory agents. The increase in forearm blood flow to intrabrachial infusion of the endothelium-dependent vasodilator acetylcholine was significantly lower in GH-deficient nontreated patients than in control subjects (P:<0.05). Likewise, forearm release of nitrite and cGMP during acetylcholine stimulation was reduced in GH-deficient nontreated patients (P:<0.05 and P:<0.002 versus controls). The response to the endothelium-independent vasodilator sodium nitroprusside was also markedly blunted in GH-deficient patients compared with control subjects (P:<0.005). To confirm that abnormal vascular reactivity was due to GHD, we also studied 8 patients with childhood-onset GHD (age 31+/-2 years, BMI 24+/-1 kg/m(2)) who were receiving stable GH replacement therapy. In these patients, the response to both endothelium-dependent and -independent vasodilators, as well as forearm nitrite and cGMP, release was not different from that observed in normal subjects. Peak hyperemic response to 5-minute forearm ischemia was significantly reduced in GH-deficient nontreated patients (17.2+/-2.6 mL x dL(-1) x min(-1), P:<0.01) but not in GH-treated patients (24.8+/-3.3 mL x dL(-1) x min(-1)) compared with normal subjects (29.5+/-3.2 mL x dL(-1) x min(-1)).

CONCLUSIONS

The data support the concept that GH plays an important role in the maintenance of a normal vascular function in humans.

Muscle sympathetic nerve activity in patients with acromegaly

Muscle sympathetic nerve activity was measured in nine acromegalic patients (age, 35 +/- 4 yr; body mass index, 28 +/- 2 kg/m2) and eight healthy subjects (age, 32 +/- 3 yr; body mass index, 25 +/- 2 kg/m2) by combining the forearm arterial-venous difference technique with the tracer method [infusion of tritiated norepinephrine (NE)]. Muscle NE release was quantified both at rest and during physiological hyperinsulinemia while maintaining euglycemia (approximately 90 mg/dL) by means of the euglycemic clamp. Arterial plasma NE was similar in the two groups at rest (197 +/- 28 and 200 +/- 27 pg/mL (-1) and slightly increased during insulin infusion. Forearm NE release was 2.33 +/- 0.55 ng x liter(-1) x min(-1) in healthy subjects and 2.67 +/- 0.61 ng x liter(-1) x min(-1) in acromegalic subjects in the basal state and increased to a similar extent during insulin infusion in both groups (3.13 +/- 0.71 and 3.32 +/- 0.75 ng x L(-1) x min(-1), P < 0.05 vs. basal), indicating a normal stimulatory effect of insulin on muscle sympathetic activity. In contrast, insulin-stimulated forearm glucose uptake was markedly lower in acromegalic patients (2.3 +/- 0.4 mg x L(-1) x min(-1)) than in control subjects (7.9 +/- 1.3 mg x L(-1) x min(-1), P < 0.001), indicating the presence of severe insulin resistance involving glucose metabolism. Our data demonstrate that patients with long-term acromegaly have normal sympathetic activity in the skeletal muscle in the basal, postabsorptive state and normal increments in NE spillover in response to the sympatho-excitatory effect of insulin. Thus, the presence of severe insulin resistance in acromegaly is not accounted for by adrenergic mechanisms.

The IR1152 mutant insulin receptor selectively impairs insulin action in skeletal muscle but not in liver

In patients harboring the IR1152 mutant insulin receptor, hepatic glucose production was normally suppressed by insulin. Hepatocytes without the insulin receptor gene and expressing IR1152 (Hep(MUT)) also showed normal insulin suppression of glucose production and full insulin response of glycogen synthase. In contrast, expression of the IR1152 mutant in skeletal muscle maximally increased glucose uptake and storage, preventing further insulin stimulation. IRS-1 phosphorylation was normally stimulated by insulin in both intact Hep(MUT) and L6 skeletal muscle cells expressing the IR1152 mutant (L6(MUT)). At variance, IRS-2 phosphorylation exhibited high basal levels with no further insulin-dependent increase in L6(MUT) but almost normal phosphorylation, both basal and insulin-stimulated, in the Hep(MUT) cells. In vitro, IR1152 mutant preparations from both the L6(MUT) and the Hep(MUT) cells exhibited increased basal and no insulin-stimulated phosphorylation of IRS-2 immobilized from either muscle or liver cells. IR1152 internalization in liver and muscle cells closely paralleled the ability of this mutant to phosphorylate IRS-2 in vivo in these cells. Block of receptor internalization (wild-type and mutant) in the liver and muscle cells also inhibited IRS-2, but not IRS-1, phosphorylation. Thus, the mechanisms controlling insulin receptor internalization differ in liver and skeletal muscle cells and may enable IR1152 to control glucose metabolism selectively in liver. In both cell types, receptor internalization seems necessary for IRS-2 but not IRS-1 phosphorylation.

Splanchnic and leg substrate exchange after ingestion of a natural mixed meal in humans

The disposal of a mixed meal was examined in 11 male subjects by multiple (splanchnic and femoral) catheterization combined with double-isotope technique (intravenous [2-3H]glucose plus oral U-[14C]starch). Glucose kinetics and organ substrate balance were measured basally and for 5 h after eating pizza (600 kcal) containing carbohydrates 75 g as starch, proteins 37 g, and lipids 17 g. The portal appearance of ingested carbohydrate was maximal (1.0 mmol/min) between 30 and 60 min after the meal and gradually declined thereafter, but was still incomplete at 300 min (0.46+/-0.08 mmol/min). The total amount of glucose absorbed by the gut over the 5 h of the study was 247+/-26 mmol (45+/-6 g), corresponding to 60+/-6% of the ingested starch. Net splanchnic glucose balance (-6.7+/-0.5 micromol x kg(-1) x min(-1), basal) rose by 250-300% between 30 and 60 min and then returned to baseline. Hepatic glucose production (HGP) was suppressed slightly and only tardily in response to meal ingestion (approximately 30% between 120 and 300 min). Splanchnic glucose uptake (3.7+/-0.6 micromol x kg(-1) x min(-1), basal) peaked to 9.8+/-2.0 micromol x kg(-1) x min(-1) (P<0.001) at 120 min and then returned slowly to baseline. Leg glucose uptake (34+/-5 micromol x leg(-1) x min(-1), basal) rose to 151+/-29 micromol x leg(-1) x min(-1) at 30 min (P<0.001) and remained above baseline until the end of the study, despite no increase in leg blood flow. The total amount of glucose taken up by the splanchnic area and total muscle mass was 161+/-16 mmol (29+/-3 g) and 128 mmol (23 g), respectively, which represent 39 and 30% of the ingested starch. Arterial blood lactate increased by 30% after meal ingestion. Net splanchnic lactate balance switched from a basal net uptake (3.2+/-0.6 micromol kg(-1) x min(-1) to a net output between 60 and 120 min and tended to zero thereafter. Leg lactate release (25+/-11 micromol x leg(-1) x min(-1), basal) drastically decreased postprandially. Arterial concentration of both branched-chain amino acids (BCAA) and non-branched-chain amino acids (N-BCAA) increased significantly after meal ingestion (P<0.001). The splanchnic area switched from a basal net amino acid uptake (31+/-16 and 92+/-48 micromol/min for BCAA and N-BCAA, respectively) to a net amino acid release postprandially. The net splanchnic amino acid release over 5 h was 11.3+/-4.2 mmol for BCAA and 37.8+/-9.7 mmol for N-BCAA. Basally, the net leg balance of BCAA was neutral (-3+/-5 micromol x leg(-1) x min(-1)), whereas that of N-BCAA indicated a net release (54+/-14 micromol x leg(-1) x min(-1)). After meal ingestion, there was a net leg uptake of BCAA (20+/-6 micromol x leg(-1) x min(-1)), whereas leg release of N-BCAA decreased by 50%. It is concluded that in human subjects, 1) the absorption of a natural mixed meal is still incomplete at 5 h after ingestion; 2) HGP is only marginally and tardily inhibited; 3) splanchnic and peripheral tissues contribute to the disposal of meal carbohydrate to approximately the same extent; 4) the splanchnic area transfers >30% of the ingested proteins to the systemic circulation; and 5) after meal ingestion, skeletal muscle takes up BCAA to replenish muscle protein stores.

Controlled study of the effect of angiotensin converting enzyme inhibition versus calcium-entry blockade on insulin sensitivity in overweight hypertensive patients: Trandolapril Italian Study (TRIS)

OBJECTIVE

The aim of this study was to evaluate the effect of trandolapril, an angiotensin converting enzyme inhibitor, on blood pressure, forearm blood flow and insulin sensitivity in comparison with nifedipine gastrointestinal therapeutic system.

PATIENTS AND METHODS

This is a multicentre, two-way parallel-group, open-label comparative study in 90 overweight hypertensive patients, who were randomly assigned to treatment for 8 weeks with either trandolapril or nifedipine. At baseline and after treatment, all patients underwent an oral glucose tolerance test, an evaluation of their metabolic profiles and a euglycaemic hyperinsulinaemic clamp test. In a subgroup of 18 patients, a forearm study was carried out.

RESULTS

Blood pressure fell by the second week of treatment and remained significantly reduced compared with baseline in both treatment groups. Plasma triglyceride levels were also significantly reduced after trandolapril therapy, but no significant changes occurred in the other metabolic parameters during treatment with either drug. During the euglycaemic hyperinsulinaemic clamp, whole-body glucose use was similar in the two treatment groups at baseline, and a moderate but statistically significant increase in insulin sensitivity was observed after trandolapril treatment (trandolapril: 5.0 +/- 0.2 versus 4.5 +/- 0.2 mg/kg per min; nifedipine: 4.1 +/- 0.3 versus 4.2 +/- 0.3 mg/kg per min; P < 0.05, versus baseline and trandolapril versus nifedipine treatment). Skeletal muscle glucose uptake was significantly higher after trandolapril than after nifedipine therapy (5.0 +/- 0.7 and 3.0 +/- 0.4 mg/min, respectively; P < 0.01). As forearm blood flow was similar in the two treatment groups at baseline and was unchanged after 8 weeks of therapy, skeletal muscle glucose extraction was significantly greater in the ACE inhibitor treated-group than in the nifedipine comparative group (trandolapril: baseline 21 +/- 2, treatment 24 +/- 3 mg/dl; nifedipine: baseline 18 +/- 3, treatment 16 +/- 2 mg/dl; P < 0.05, trandolapril versus nifedipine treatment).

CONCLUSIONS

During short-term treatment, ACE inhibition with trandolapril was able to moderately improve insulin sensitivity, in comparison with calcium blockade, and this effect appeared to be independent of the haemodynamic action of the drug.

Sympathetic deactivation by growth hormone treatment in patients with dilated cardiomyopathy

AIMS

We examined the effects of growth hormone administration on the sympathetic nervous system in patients with idiopathic dilated cardiomyopathy.

BACKGROUND

Growth factor therapy is emerging as a new potential option in the treatment of heart failure. Although growth hormone provides functional benefit in the short term, it is unknown whether it affects the sympathetic nervous system, which plays a role in the progression of heart failure.

METHODS

Seven patients with idiopathic cardiomyopathy received 3 months treatment with recombinant human growth hormone (0.15-0.20 IU.kg-1.week-1). Standard medical therapy was unchanged. Myocardial norepinephrine release, both at rest and during submaximal physical exercise, plasma aldosterone, and plasma volume were measured before and after growth hormone treatment. Myocardial norepinephrine release was assessed from arterial and coronary venous plasma concentrations of unlabelled and tritiated norepinephrine and coronary plasma flow (thermodilution).

RESULTS

Growth hormone induced a significant fall in myocardial norepinephrine release in response to physical exercise (from 180 +/- 64 to 99 +/- 34 ng.min-1; P < 0.05). Basally, plasma aldosterone was 189 +/- 28 and 311 +/- 48 pg.ml-1 in the supine and upright position, respectively, and fell to 106 +/- 16 (P < 0.01) and 182 +/- 29 pg.ml-1 (P < 0.05) after growth hormone therapy. Growth hormone increased plasma volume from 3115 +/- 493 ml to 3876 +/- 336 ml (P < 0.05), whereas serum sodium and potassium concentrations were unaffected.

CONCLUSIONS

The data demonstrate that growth hormone administration to patients with idiopathic cardiomyopathy reduces myocardial sympathetic drive and circulating aldosterone levels. This neurohormonal deactivation may be relevant to the potential, long-term use of growth hormone in the treatment of patients with heart failure.

Insulin resistance, hyperinsulinemia, and blood pressure: role of age and obesity. European Group for the Study of Insulin Resistance (EGIR)

In population surveys, blood pressure and plasma insulin concentration are related variables, but the association is confounded by age and obesity. Whether insulin resistance is independently associated with higher blood pressure in normal subjects is debated. We analyzed the database of the European Group for the Study of Insulin Resistance, made up of nondiabetic men and women from 20 centers, in whom insulin sensitivity was measured by the euglycemic insulin clamp. After excluding subjects aged > or =70 years, those with severe obesity (body mass index [BMI] >40 kg x m[-2]), and those with abnormal blood pressure values (> or =140/90 mm Hg), 333 cases (ages 18 to 70 years; BMI, 18.4 to 39.8 kg x m[-2]) were available for analysis. In univariate analysis, both systolic and diastolic blood pressures were inversely related to insulin sensitivity, with r values of 0.18 (P<.005) and 0.34 (P<.0001), respectively. In a multivariate model simultaneously accounting for sex, age, BMI, and fasting insulin, systolic and diastolic blood pressures were still inversely related to insulin sensitivity (partial r, 0.15 and 0.19; P<.01 for both). In this model, age was positively related to blood pressure levels independently of insulin sensitivity, whereas BMI was not. The predicted impact on blood pressure of a decrease in insulin sensitivity of 10 micromol x min(-1) x kg(-1) was +1.4 mm Hg, similar to that associated with a 10-year difference in age. Although insulin levels and insulin action were reciprocally interrelated, diastolic blood pressure varied as a simultaneous function of both. In normotensive, nondiabetic Europeans, insulin sensitivity and age are significant, mutually independent correlates of blood pressure, whereas body mass is not. The relation of blood pressure to both insulin action and circulating insulin levels is compatible with distinct influences on blood pressure by insulin resistance and compensatory hyperinsulinemia.

Insulin resistance, hyperinsulinemia, and blood pressure: role of age and obesity. European Group for the Study of Insulin Resistance (EGIR)

In population surveys, blood pressure and plasma insulin concentration are related variables, but the association is confounded by age and obesity. Whether insulin resistance is independently associated with higher blood pressure in normal subjects is debated. We analyzed the database of the European Group for the Study of Insulin Resistance, made up of nondiabetic men and women from 20 centers, in whom insulin sensitivity was measured by the euglycemic insulin clamp. After excluding subjects aged > or =70 years, those with severe obesity (body mass index [BMI] >40 kg x m[-2]), and those with abnormal blood pressure values (> or =140/90 mm Hg), 333 cases (ages 18 to 70 years; BMI, 18.4 to 39.8 kg x m[-2]) were available for analysis. In univariate analysis, both systolic and diastolic blood pressures were inversely related to insulin sensitivity, with r values of 0.18 (P<.005) and 0.34 (P<.0001), respectively. In a multivariate model simultaneously accounting for sex, age, BMI, and fasting insulin, systolic and diastolic blood pressures were still inversely related to insulin sensitivity (partial r, 0.15 and 0.19; P<.01 for both). In this model, age was positively related to blood pressure levels independently of insulin sensitivity, whereas BMI was not. The predicted impact on blood pressure of a decrease in insulin sensitivity of 10 micromol x min(-1) x kg(-1) was +1.4 mm Hg, similar to that associated with a 10-year difference in age. Although insulin levels and insulin action were reciprocally interrelated, diastolic blood pressure varied as a simultaneous function of both. In normotensive, nondiabetic Europeans, insulin sensitivity and age are significant, mutually independent correlates of blood pressure, whereas body mass is not. The relation of blood pressure to both insulin action and circulating insulin levels is compatible with distinct influences on blood pressure by insulin resistance and compensatory hyperinsulinemia.

Increased arterial intima-media thickness in childhood-onset growth hormone deficiency

Very little is known about the atherosclerotic risk in patients with childhood-onset growth hormone deficiency (GHD). Such data may be relevant to reconstructing the natural course of the cardiovascular abnormalities associated with GHD. To this end, the intima-media thickness (IMT) of the carotid arteries and the vascular risk factors were evaluated in 14 childhood-onset GHD patients (age 25 +/- 1 yr, BMI 22 +/- 0.6 Kg/m2) and in 14 age-, sex-, and BMI-matched control subjects. IMT was greater in GHD patients (0.83 +/- 0.06 and 0.81 +/- 0.06 mmol/L for the right and left carotid artery) than in controls (0.64 +/- 0.03 and 0.64 +/- 0.04 mmol/L, P < 0.01 and P < 0.02, respectively). Serum total and lipoprotein cholesterol, and serum total triglycerides did not differ between the two groups. However, a significant increase in low density lipid triglycerides was present in GHD patients (0.27 +/- 0.02 mmol/L) compared with controls (0.19 +/- 0.01; P = 0.007). No difference was found in plasma fibrinogen and serum Lp(a) levels. Plasma glucose and insulin concentrations were similar in GHD and control subjects both in the fasted state and after an oral glucose load. In conclusion, young patients with childhood-onset GHD show an increased IMT in the absence of clear-cut abnormalities of the classic vascular risk factors. This suggests a role for GH deficiency per se in increasing the atherosclerotic risk.

In skeletal muscle, glucose storage and oxidation are differentially impaired by the IR1152 mutant receptor

L6 myotubes expressing the constitutively active Arg1152-->Gln insulin receptor (L6(1152)) featured a 31% increased glucose consumption as compared with L6 cells expressing wild-type receptors (L6(WT)). However, insulin treatment decreased glucose consumption of the mutant cells by 20% while increasing that of the L6(WT) by 30%. In the L6(WT), insulin elicited a significant increase in glucose transport and GLUT1 and GLUT4 plasma membrane expression, while in the L6(1152), all of these functions were constitutively activated and not further stimulated by insulin. Similarly, glycogen content and glycogen synthase activity were increased by 80 and 125%, respectively, in the L6(1152 )versus the L6(WT) and unaffected by insulin (while a 2-fold increase was measured in insulin-exposed L6(WT)). Glucose oxidation and pyruvate dehydrogenase activity were also 25% higher in the mutant compared with the L6(WT). However, in the L6(1152), both functions decreased by 35% in response to insulin (while increasing by 60 and 80%, respectively, in the L6(WT)). Similarly as in the L6(1152), in vivo, forearm glucose uptake in IR1152 patients was 2-fold higher than in control subjects. This difference was not accounted for by higher plasma glucose levels. We conclude that, in skeletal muscle, glucose storage and oxidation are differentially impaired by the expression of IR1152, suggesting that their regulation by insulin involves divergent signaling pathways. Muscle expression of IR1152 may contribute to impairing glucose tolerance in IR1152 individuals.

Soluble CD8 antigen, stimulated C-peptide and islet cell antibodies are predictors of insulin requirement in newly diagnosed patients with unclassifiable diabetes

To evaluate the predictive factors of insulin requirement in newly diagnosed patients with unclassifiable diabetes, 54 consecutive patients, aged less than 35 years, were prospectively followed for 3 years or more. At entry, haemoglobin HbA1c, basal and stimulated C-peptide concentrations, HLA phenotype, islet cell antibodies (ICA) status, and serum levels of soluble CD8 antigen (sCD8) were evaluated. After a median time of 9 (range 2-32) months, 31 patients (group 1) required insulin therapy, whereas 23 patients (group 2) remained non-insulin-requiring after 36 months. Group 1 patients were younger (P < 0.05) and had higher HbA1c and sCD8 serum levels (P < 0.0001), respectively), a higher frequency of ICA positivity and of HLA DR3 and/or DR4 phenotype (P < 0.005 and P < 0.0001, respectively), and lower C-peptide concentrations (P < 0.005 and P < 0.0001, basal and stimulated, respectively) than group 2. The sensitivity, specificity, positive and negative predictive value, and overall accuracy for the subsequent insulin requirement were: sCD8 serum levels (> 737 U/ml), 100%, 65%, 79%, 100% and 85%, respectively; stimulated C-peptide (< 0.60 nmol/l), 71%, 96%, 96%, 74% and 81%, respectively; and ICA positivity (> 20 JDFU), 45%, 91%, 87%, 55% and 65%, respectively. Thus, higher sCD8 serum levels, low stimulated C-peptide concentrations and ICA positivity are the most powerful predictors of subsequent recourse to insulin therapy in young, newly detected patients with unclassifiable diabetes.

Transport of D-glucose and 2-fluorodeoxyglucose across the blood-brain barrier in humans

The deoxyglucose method for calculation of regional cerebral glucose metabolism by PET using 18F-2-fluoro-2-deoxy-d-glucose (FDG) requires knowledge of the lumped constant, which corrects for differences in the blood-brain barrier (BBB) transport and phosphorylation of FDG and glucose. The BBB transport rates of FDG and glucose have not previously been determined in humans. In the present study these transport rates were measured with the intravenous double-indicator method in 24 healthy subjects during normoglycemia (5.2 +/- 0.7 mM). Nine subjects were restudied during moderate hypoglycemia (3.4 +/- 0.4 mM) and five subjects were studied once during hyperglycemia (15.0 +/- 0.7 mM). The global ratio between the unidirectional clearances of FDG and glucose (K1*/K1) was similar in normoglycemia (1.48 +/- 0.22), moderate hypoglycemia (1.41 +/- 0.23), and hyperglycemia (1.44 +/- 0.20). This ratio is comparable to what has been obtained in rats. We argue that the global ratio is constant throughout the brain and may be applied for the regional determination of LC. We also determined the transport parameters of the two hexoses from brain back to blood and, assuming symmetrical transport across the BBB, we found evidence of a larger initial distribution volume of FDG in brain (0.329 +/- 0.236) as compared with that of glucose (0.162 +/- 0.098, p < 0.005). The difference can be explained by the very short experimental time, in which FDG may distribute both intra- and extracellularly, whereas glucose remains in a volume comparable to the interstitial fluid of the brain.

Diastolic dysfunction in patients with non-insulin-dependent diabetes mellitus of short duration

To determine whether abnormal left ventricular diastolic function is present at an early stage of non-insulin-dependent diabetes mellitus (NIDDM), left ventricular diastolic filling was evaluated by pulsed doppler echocardiography in 16 normotensive patients with NIDDM of short duration (1.8 +/- 1 years, mean +/- SD) and no evidence of microangiopathy, and in 16 healthy volunteers comparable for age, body mass index, and sex distribution. All patients showed normal systolic function. The interventricular septum thickness, left atrial diameter, and left ventricular mass index were increased in the diabetic as compared with the control group (p < 0.01, p < 0.01, and p < 0.02, respectively). Isovolumic relaxation time and atrial peak filling velocity were greater in diabetic patients (p < 0.001, and p < 0.01, respectively), whereas early to atrial peak filling velocity ratio was significantly reduced (p < 0.05). This study demonstrates that an impairment of left ventricular diastolic function occurs early in the natural history of NIDDM, and that this abnormality is unlikely to be related to clinical evidence of microangiopathic complications.

A preliminary study of growth hormone in the treatment of dilated cardiomyopathy

BACKGROUND

Cardiac hypertrophy is a physiologic response that allows the heart to adapt to an excess hemodynamic load. We hypothesized that inducing cardiac hypertrophy with recombinant human growth hormone might be an effective approach to the treatment of idiopathic dilated cardiomyopathy, a condition in which compensatory cardiac hypertrophy is believed to be deficient.

METHODS

Seven patients with idiopathic dilated cardiomyopathy and moderate-to-severe heart failure were studied at base line, after three months of therapy with human growth hormone, and three months after the discontinuation of growth hormone. Standard therapy for heart failure was continued throughout the study. Cardiac function was evaluated with Doppler echocardiography, right-heart catheterization, and exercise testing.

RESULTS

When administered at a dose of 14 IU per week, growth hormone doubled the serum concentrations of insulin-like growth factor I. Growth hormone increased left-ventricular-wall thickness and reduced chamber size significantly. Consequently, end-systolic wall stress (a function of both wall thickness and chamber size) fell markedly (from a mean [+/-SE] of 144+/-11 to 85+/-8 dyn per square centimeter, P<0.001). Growth hormone improved cardiac output, particularly during exercise (from 7.4+/-0.7 to 9.7+/-0.9 liters per minute, P=0.003), and enhanced ventricular work, despite reductions in myocardial oxygen consumption (from 56+/-6 to 39+/-5 ml per minute, P=0.005) and energy production (from 1014+/-100 to 701+/-80 J per minute, P=0.002). Thus, ventricular mechanical efficiency rose from 9+/-2 to 21+/-5 percent (P=0.006). Growth hormone also improved clinical symptoms, exercise capacity, and the patients' quality of life. The changes in cardiac size and shape, systolic function, and exercise tolerance were partially reversed three months after growth hormone was discontinued.

CONCLUSIONS

Recombinant human growth hormone administered for three months to patients with idiopathic dilated cardiomyopathy increased myocardial mass and reduced the size of the left ventricular chamber, resulting in improvement in hemodynamics, myocardial energy metabolism, and clinical status.

Forearm muscle insulin resistance during hypoglycemia: role of adrenergic mechanisms and hypoglycemia per se

The forearm perfusion technique was used 1) to quantify the muscle metabolism of glucose and gluconeogenic precursors in response to insulin-induced hypoglycemia and 2) to assess the role of catecholamines and glucose concentration, pe se. Insulin (0.5 mU.kg-1.min-1) was infused for 4 h in three groups of healthy volunteers. In group I (n = 6), blood glucose (BG) was maintained at its basal level (4.5 +/- 0.1 mmol/l). In group II (n = 7), BG was allowed to fall to approximately 3 mmol/l. Group III (n = 6) was similar to group II except that propranolol was infused also. In addition, at 240 min, hypoglycemia was locally corrected by intrabrachial glucose infusion while maintaining the systemic milieu unperturbed. In group I, forearm glucose uptake (FGU) increased from 4.7 +/- 1.3 to a mean value of 37.8 +/- 5.0 mumol.l-1.min-1, whereas in group II it remained unchanged (8.3 +/- 2.0 mumol.l-1.min-1). In group III, propranolol partially prevented the suppression of FGU that increased to 21.6 +/- 5.2 mumol.l-1.min-1 (P < 0.05 vs. group II). Local correction of hypoglycemia normalized the FGU response (36.5 +/- 8.0 mumol.l-1.min-1). Muscle release of lactate, but not of alanine, was slightly higher during hypoglycemia (P = not significant). Forearm blood flow remained unchanged in groups I and III, whereas it increased by approximately 40% in group II (P < 0.05). It is concluded that, during mild hypoglycemia 1) extreme insulin resistance develops in the skeletal muscle, mediated by beta-adrenergic stimulation and reduced glucose mass effect and 2) mobilization of gluconeogenic precursors is only weakly activated.

Role of insulin and free fatty acid (FFA) availability on regional FFA kinetics in the human forearm

To determine the role of insulin and free fatty acid (FFA) concentration in the regulation of FFA metabolism, forearm FFA fluxes were quantified in 16 healthy volunteers by combining the forearm perfusion technique with the infusion of [3H]palmitate. Three groups of studies were performed. In study 1 (n = 6), a systemic insulin infusion (1.2 mU/kg.min) was performed for 120 min while euglycemia was maintained by a variable glucose infusion. In Study 2 (n = 5), insulin (0.05 mU/kg.min) was infused into the brachial artery to expose the forearm tissues to the same insulin level as in study 1. In study 3 (n = 5), heparin was infused to raise plasma FFA concentration to 1-1.5 mmol/L. At 60 min, an intrabrachial insulin infusion was added as in study 2 and maintained for 60 min. During systemic insulin infusion, plasma FFA concentration fell to 0.09 +/- 0.02 mmol/L. Forearm FFA uptake (FFA-U) decreased from the basal value of 2.54 +/- 0.52 to 0.95 +/- 0.10 mumol/L.min (P < 0.05). Likewise, forearm FFA release (FFA-R) fell to 1.0 +/- 0.31 mumol/L.min (P < 0.05). With local insulin administration, both FFA levels and FFA-U remained unchanged, whereas FFA-R was markedly inhibited (from 1.78 +/- 0.23 to 1.04 +/- 0.24 mumol/L.min; P < 0.05). In study 3 (heparin infusion), FFA levels rose to 1.17 +/- 0.12 mmol/L due to a 4-fold increase in FFA-R (from 1.18 +/- 0.36 to 6.92 +/- 2.40 mumol/L.min; P < 0.05). FFA-U rose from the basal value of 2.50 +/- 0.82 to 6.92 +/- 1.95 mumol/L.min (P < 0.05). Addition of intrabrachial insulin did not modify FFA-U, whereas heparin activation of FFA-R was only partially antagonized (4.53 +/- 2.40 mumol/L.min; 0.01 < P < 0.05 vs. heparin alone). The data demonstrate that plasma FFA concentration is the main determinant of forearm FFA transport. Insulin exerts a direct inhibitory effect on FFA release and affects tissue FFA transport only indirectly through the fall in circulating FFA.