Beyond basics: Key mutation selection features for successful tumor-informed ctDNA detection

Tumor-informed mutation-based approaches are frequently used for detection of circulating tumor DNA (ctDNA). Not all mutations make equally effective ctDNA markers. The objective was to explore if prioritizing mutations using mutational features-such as cancer cell fraction (CCF), multiplicity, and error rate-would improve the success rate of tumor-informed ctDNA analysis. Additionally, we aimed to develop a practical and easily implementable analysis pipeline for identifying and prioritizing candidate mutations from whole-exome sequencing (WES) data. We analyzed WES and ctDNA data from three tumor-informed ctDNA studies, one on bladder cancer (Cohort A) and two on colorectal cancer (Cohorts I and N). The studies included 390 patients. For each patient, a unique set of mutations (median mutations/patient: 6, interquartile 13, range: 1-46, total n = 4023) were used as markers of ctDNA. The tool PureCN was used to assess the CCF and multiplicity of each mutation. High-CCF mutations were detected more frequently than low-CCF mutations (Cohort A: odds ratio [OR] 20.6, 95% confidence interval [CI] 5.72-173, p = 1.73e-12; Cohort I: OR 2.24, 95% CI 1.44-3.52, p = 1.66e-04; and Cohort N: OR 1.78, 95% CI 1.14-2.79, p = 7.86e-03). The detection-likelihood was additionally improved by selecting mutations with multiplicity of two or above (Cohort A: OR 1.55, 95% CI 1. 14-2.11, p = 3.85e-03; Cohort I: OR 1.78, 95% CI 1.23-2.56, p = 1.34e-03; and Cohort N: OR 1.94, 95% CI 1.63-2.31, p = 2.83e-14). Furthermore, selecting the mutations for which the ctDNA detection method had the lowest error rates, additionally improved the detection-likelihood, particularly evident when plasma cell-free DNA tumor fractions were below 0.1% (p = 2.1e-07). Selecting mutational markers with high CCF, high multiplicity, and low error rate significantly improve ctDNA detection likelihood. We provide free access to the analysis pipeline enabling others to perform qualified prioritization of mutations for tumor-informed ctDNA analysis.

Unraveling the potential clinical utility of circulating tumor DNA detection in colorectal cancer-evaluation in a nationwide Danish cohort

BACKGROUND

Increasingly, circulating tumor DNA (ctDNA) is proposed as a tool for minimal residual disease (MRD) assessment. Digital PCR (dPCR) offers low analysis costs and turnaround times of less than a day, making it ripe for clinical implementation. Here, we used tumor-informed dPCR for ctDNA detection in a large colorectal cancer (CRC) cohort to evaluate the potential for post-operative risk assessment and serial monitoring, and how the metastatic site may impact ctDNA detection. Additionally, we assessed how altering the ctDNA-calling algorithm could customize performance for different clinical settings.

PATIENTS AND METHODS

Stage II-III CRC patients (N = 851) treated with a curative intent were recruited. Based on whole-exome sequencing on matched tumor and germline DNA, a mutational target was selected for dPCR analysis. Plasma samples (8 ml) were collected within 60 days after operation and-for a patient subset (n = 246)-every 3-4 months for up to 36 months. Single-target dPCR was used for ctDNA detection.

RESULTS

Both post-operative and serial ctDNA detection were prognostic of recurrence [hazard ratio (HR) = 11.3, 95% confidence interval (CI) 7.8-16.4, P < 0.001; HR = 30.7, 95% CI 20.2-46.7, P < 0.001], with a cumulative ctDNA detection rate of 87% at the end of sample collection in recurrence patients. The ctDNA growth rate was prognostic of survival (HR = 2.6, 95% CI 1.5-4.4, P = 0.001). In recurrence patients, post-operative ctDNA detection was challenging for lung metastases (4/21 detected) and peritoneal metastases (2/10 detected). By modifying the cut-off for calling a sample ctDNA positive, we were able to adjust the sensitivity and specificity of our test for different clinical contexts.

CONCLUSIONS

The presented results from 851 stage II-III CRC patients demonstrate that our personalized dPCR approach effectively detects MRD after operation and shows promise for serial ctDNA detection for recurrence surveillance. The ability to adjust sensitivity and specificity shows exciting potential to customize the ctDNA caller for specific clinical settings.

DREAMS: deep read-level error model for sequencing data applied to low-frequency variant calling and circulating tumor DNA detection

Circulating tumor DNA detection using next-generation sequencing (NGS) data of plasma DNA is promising for cancer identification and characterization. However, the tumor signal in the blood is often low and difficult to distinguish from errors. We present DREAMS (Deep Read-level Modelling of Sequencing-errors) for estimating error rates of individual read positions. Using DREAMS, we develop statistical methods for variant calling (DREAMS-vc) and cancer detection (DREAMS-cc). For evaluation, we generate deep targeted NGS data of matching tumor and plasma DNA from 85 colorectal cancer patients. The DREAMS approach performs better than state-of-the-art methods for variant calling and cancer detection.

Error Characterization and Statistical Modeling Improves Circulating Tumor DNA Detection by Droplet Digital PCR

BACKGROUND

Droplet digital PCR (ddPCR) is a widely used and sensitive application for circulating tumor DNA (ctDNA) detection. As ctDNA is often found in low abundance, methods to separate low-signal readouts from noise are necessary. We aimed to characterize the ddPCR-generated noise and, informed by this, create a sensitive and specific ctDNA caller.

METHODS

We built 2 novel complimentary ctDNA calling methods: dynamic limit of blank and concentration and assay-specific tumor load estimator (CASTLE). Both methods are informed by empirically established assay-specific noise profiles. Here, we characterized noise for 70 mutation-detecting ddPCR assays by applying each assay to 95 nonmutated samples. Using these profiles, the performance of the 2 new methods was assessed in a total of 9447 negative/positive reference samples and in 1311 real-life plasma samples from colorectal cancer patients. Lastly, performances were compared to 7 literature-established calling methods.

RESULTS

For many assays, noise increased proportionally with the DNA input amount. Assays targeting transition base changes were more error-prone than transversion-targeting assays. Both our calling methods successfully accounted for the additional noise in transition assays and showed consistently high performance regardless of DNA input amount. Calling methods that were not noise-informed performed less well than noise-informed methods. CASTLE was the only calling method providing a statistical estimate of the noise-corrected mutation level and call certainty.

CONCLUSIONS

Accurate error modeling is necessary for sensitive and specific ctDNA detection by ddPCR. Accounting for DNA input amounts ensures specific detection regardless of the sample-specific DNA concentration. Our results demonstrate CASTLE as a powerful tool for ctDNA calling using ddPCR.

Publisher Correction: MethCORR modelling of methylomes from formalin-fixed paraffin-embedded tissue enables characterization and prognostication of colorectal cancer

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Performance characteristics of thromboelastometry assays using incompletely filled and prolonged stored samples

BACKGROUND

Thromboelastometry (TEM) is often used to guide transfusion therapy in patients with massive bleeding. The effect of testing incompletely filled samples and those stored for a prolonged time at 4°C was investigated.

METHODS

Whole blood samples were collected from 15 healthy blood donors and were pooled according to ABO group. From these pools, aliquots were taken and diluted to produce final whole blood:citrate buffer ratios ranging from 90:10 (fully filled sample) to 40:60 (extremely under filled samples). These samples were then tested by EXTEM, INTEM, and FIBTEM on calibrated ROTEM delta machines. Separately, the four samples at 90:10 dilution were kept at 4°C for 16-20 hours and then retested on the ROTEM machines.

RESULTS

All of the samples at the 90:10 and 80:20 (half-filled sample) whole blood:citrate buffer dilutions demonstrated ROTEM parameters within their respective reference ranges, although the samples from the 80:20 dilution tended to demonstrate slightly longer or slower times, depending on each ROTEM parameter, compared to the completely filled samples. All of the samples with more dilute whole blood to citrate buffer ratios (i.e., 70:30 to 40:60) yielded abnormal TEM results. The TEM results for the 90:10 dilution samples exposed to 16-20 hours of storage at 4°C were within the reference intervals.

CONCLUSION

Completely and half-filled samples, and completely filled samples after prolonged cold storage, produced normal ROTEM results. Tubes that are less than half-filled should not be used for ROTEM testing.

MethCORR modelling of methylomes from formalin-fixed paraffin-embedded tissue enables characterization and prognostication of colorectal cancer

Transcriptional characterization and classification has potential to resolve the inter-tumor heterogeneity of colorectal cancer and improve patient management. Yet, robust transcriptional profiling is difficult using formalin-fixed, paraffin-embedded (FFPE) samples, which complicates testing in clinical and archival material. We present MethCORR, an approach that allows uniform molecular characterization and classification of fresh-frozen and FFPE samples. MethCORR identifies genome-wide correlations between RNA expression and DNA methylation in fresh-frozen samples. This information is used to infer gene expression information in FFPE samples from their methylation profiles. MethCORR is here applied to methylation profiles from 877 fresh-frozen/FFPE samples and comparative analysis identifies the same two subtypes in four independent cohorts. Furthermore, subtype-specific prognostic biomarkers that better predicts relapse-free survival (HR = 2.66, 95%CI [1.67-4.22], P value < 0.001 (log-rank test)) than UICC tumor, node, metastasis (TNM) staging and microsatellite instability status are identified and validated using DNA methylation-specific PCR. The MethCORR approach is general, and may be similarly successful for other cancer types.

Abstract 466: A novel DNA methylation-based approach for molecular subtyping and improved prognostication of colorectal cancer using formalin-fixed and paraffin-embedded tissue

Background: Colorectal cancer (CRC) is characterized by marked inter-tumor heterogeneity, both molecularly and clinically. Patient stratification using transcriptional subtyping show promise to resolve the heterogeneity and guide precision medicine. This requires high quality RNA, which can be purified from fresh frozen (FF) tissue, but not from clinically collected formalin-fixed paraffin-embedded (FFPE) tissue. Consequently, transcriptional subtyping is not applicable to most CRC patients.

Aim: To establish a DNA methylation-based approach for molecular characterization and subtyping, which is compatible with both FF and FFPE tissue, and use this to improve patient prognostication as compared to histopathological TNM staging.

Methods: Using paired RNA expression and DNA methylation profiles (450K array) from 394 CRCs, we identified 200 CpG sites genome-wide, whose methylation levels correlated best with expression for each gene. With this information, we 1) devised an approach, methCORR, that can infer RNA expression in both FF and FFPE samples using only DNA methylation profiles, 2) established a methCORR network that clusters genes according to overlap in the CpG sites associated with their expression level and 3) used the network to determine and characterize biological traits associated with tumor aggressiveness.

Results: The methCORR-inferred RNA expression profiles in FF tissue consistently exhibited high correlation to matched RNA-seq. profiles (median Pearson r=0.97; range 0.91-0.98). We found a higher correlation between FF RNA-seq. and FFPE inferred RNA profiles (median r= 0.97; range 0.96-0.98) than between FF and FFPE RNA-seq. profiles (median r= 0.78; range 0.51-0.92). Gene expression profiles were inferred in two FF (n=231, n=203), and two FFPE cohorts (n=113, n=56). Clustering of these profiles identified the same two CRC subtypes independently in all cohorts. Characterization using the methCORR network showed that the two subtypes resembled conventional and serrated CRC. Moreover, methCORR network analysis identified subtype-specific traits that associated strongly with tumor aggressiveness, such as T-cell, fibroblast, and epithelial-mesenchymal transition activity, and thus allowed identification of subtype-specific prognostic biomarkers. These better predicted relapse-free survival (HR=3.22, 95%CI 2.00-5.17) than TNM staging (HR=1.99, 95%CI 1.28-3.08). Finally, we derived four simple and clinically applicable DNA methylation-specific PCR assays for subtyping and prognostication of CRC FFPE samples.

Conclusion: We have developed a novel method for characterization, subtyping, and prognostication of CRC, which is compatible with FF and FFPE samples. We envision that application of the methCORR approach to other cancer types will generate similar fruitful results.

Citation Format: Trine B. Mattesen, Mads H. Rasmussen, Juan Sandoval, Halit Ongen, Sigrid S. Árnadóttir, Anders H. Madsen, Søren Laurberg, Emmanouil T. Dermitzakis, Manel Esteller, Claus L. Andersen, Jesper B. Bramsen. A novel DNA methylation-based approach for molecular subtyping and improved prognostication of colorectal cancer using formalin-fixed and paraffin-embedded tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 466.

Abstract 3617: Prediction of irinotecan and flurouracil efficacy in metastatic colorectal cancer by early measurement of circulating tumor DNA

Background: Chemotherapy resistance in metastatic colorectal cancer (mCRC) is a major challenge, and development of biomarkers for determining therapy efficacy is vital to ensure optimal palliative treatment. Recently, quantification of changes in circulating tumor DNA (ctDNA) levels has attracted substantial attention as a predictive marker. Here, we provide evidence that ctDNA has the potential to be used as an early marker of therapeutic efficacy of irinotecan and fluorouracil (FOLFIRI).

Experimental Procedures: Patients diagnosed with mCRC, and with indication for first-line combination chemotherapy, were prospectively enrolled in this phase II study. Blood was drawn at baseline, day 7, 14, 21, 40 and then monthly until progression. Response evaluation was done at eight-week intervals by CT scanning using RECIST criteria. Chemotherapy was administered at day one and two every two weeks. The levels of cell-free DNA (cfDNA) and ctDNA were determined using sensitive digital droplet PCR assays. ctDNA assays were designed either to mutations identified by targeted sequencing or on basis of known tumor mutations detected in primary or metastatic lesions using a panel of mutation-specific qPCR based assays (KRAS, NRAS, BRAF).

Results: Twenty-four patients were enrolled. A KRAS, NRAS or BRAF mutation was observed in tumor tissue of 16 patients. In 12 of these the mutations were confirmed in baseline samples and used for assessing ctDNA. For the remaining 12 patients, a mutation for ctDNA quantification was identified by targeted tumor sequencing. Patients with high baseline ctDNA levels (75th centile) had significantly shorter progression-free survival (PFS) than patients with low baseline ctDNA levels. After first treatment cycle all patients experienced a decline in ctDNA levels demonstrating initial response to treatment; however, the reduction in ctDNA was not associated with prolonged PFS or overall survival (OS). Conversely, change in ctDNA levels from first to second cycle of treatment (three weeks after treatment start) predicted FOLFIRI efficacy. Patients with increasing ctDNA levels at this time point had a significantly shorter PFS and a shorter OS than patients with stable or decreasing ctDNA levels.

Conclusion: In agreement with the literature, we show that baseline tumor DNA levels predicted PFS. The initial observed decline in ctDNA levels upon administration of FOLFIRI indicates that all tumors had cancer cells sensitive to treatment; however, after elimination of these, resistant clones expanded, leading to treatment resistance. Importantly, our study demonstrates that FOLFIRI efficacy can be evaluated as early as three weeks after treatment initiation by measurement of ctDNA levels. This enables early detection of treatment failure and allows for rapid adaptation of the treatment strategy.

Citation Format: Iben Lyskjær, Camilla J. Kronborg, Mads H. Rasmussen, Boe S. Sørensen, Mona Rosenkilde, Michael Knudsen, Søren R. Krag, Karen-Lise G. Spindler, Claus L. Andersen. Prediction of irinotecan and flurouracil efficacy in metastatic colorectal cancer by early measurement of circulating tumor DNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3617.

Abstract 1590: Personalized circulating tumor DNA analysis to monitor colorectal cancer

Early detection of disease recurrence has shown to improve survival in patients with early-stage colorectal cancer (CRC) (Pita-Fernandez et al., 2015). Detection of circulating tumor DNA (ctDNA) postoperatively in patients with stage II colon cancer provides direct evidence of residual disease and identifies patients at high risk of recurrence (Tie et al., 2016). Previous studies have performed ctDNA analysis to monitor tumor burden in early-stage CRC using small gene panel sequencing or digital droplet PCR (ddPCR) assays to detect specific variants (Tie et al., 2016, Reinert et al., 2016). Building upon these previous studies, here we use a personalized multiplex ctDNA technology measuring 16 mutations specific to each patient's tumor respectively to assess minimal residual disease postoperatively and to monitor treatment response in CRC. Our study includes 130 patients diagnosed with stage I-III CRC treated with intended curative surgery. Of the 130 patients, 80 received adjuvant chemotherapy for a duration of six months. For 119 patients, one pre-operative and one post-operative plasma sample were available. In addition, longitudinally-collected plasma samples were available from 78 of 130 patients for early detection of disease recurrence and to determine their relationship with imaging and carcinoembryonic antigen (CEA) during a 3-year post-operative surveillance period.

To identify patient-specific tumor mutation signatures, whole-exome sequencing of CRC tissue and germline DNA is used. Patient specific multiplex-PCR assay panels are designed to target 16 tumor-specific single-nucleotide variants (SNVs) in plasma. Targeted sequencing is then performed on plasma samples collected pre- and post-operative and during adjuvant therapy. We then correlate ctDNA status to the clinical outcome, including CEA and radiographic imaging, for each patient. Data collection is ongoing and results will be presented at the AACR 2018 meeting.

Conclusion. This study provides a novel methodology to detect minimal residual disease postoperatively and to monitor treatment efficacy in CRC using a personalized multiplex-PCR approach. The performance of this patient-specific ctDNA technology will be compared to the current standard of care for monitoring disease burden.

References:

S. Pita-Fernàndez, et al. Ann. Oncol. 26, 644–656 (2015).

Tie J, et al. Sci Transl Med. 2016 Jul 6;8(346):346ra92.

Reinert T. Gut. 2016 Apr;65(4):625-34.

Citation Format: Thomas Reinert, Tenna V. Henriksen, Mads H. Rasmussen, Himanshu Sethi, Shruti Sharma, Hsin-Ta Wu, Dina Hafez, Prashanthi Natarajan, Scott Dashner, Mustafa Balcioglu, Ann Nguyen, Derrick Renner, Bernhard Zimmermann, Lene H- Iversen, Mogens R. Madsen, Cheng-Ho Jimmy Lin, Claus L. Andersen. Personalized circulating tumor DNA analysis to monitor colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1590.

The incidence of bent dorsal fins in free-ranging cetaceans

Laterally bent dorsal fins are rarely observed in free-ranging populations of cetaceans, contrary to captivity, where most killer whale Orcinus orca adult males have laterally collapsed fins. This topic has been poorly explored, and data/information on its occurrence and possible causes are limited. The present study: (i) undertakes a review of the available information on bent dorsal fins in free-ranging cetaceans, and updates it with new records, (ii) reports on the proportion of bent fins in different study populations, and (iii) discusses possible causes. An empirical approach based on bibliographic research and compilation of 52 new records collected worldwide resulted in a total of 17 species of cetaceans displaying bent dorsal fins. The species with the highest number of records (64%) and from most locations was O. orca. On average, individuals with bent dorsal fins represent < 1% of their populations, with the exception of false killer whales Pseudorca crassidens and O. orca. While line injuries associated with fisheries interactions may be the main cause for P. crassidens, and the vulnerability to health issues caused by the evolutionary enlargement of the fin may be the cause for O. orca adult males, factors contributing to this abnormality for other species are still unclear. The occurrence of bent dorsals could be influenced by a set of variables rather than by a single factor but, irrespective of the cause, it is suggested that it does not directly affect the animals' survivorship. While still rare in nature, this incident is more common (at least 101 known cases) and widespread (geographically and in species diversity) than hypothesized, and is not confined only to animals in captive environments. Investigation into the occurrence of bent fins may be an interesting avenue of research.

A genetically inducible porcine model of intestinal cancer

Transgenic porcine cancer models bring novel possibilities for research. Their physical similarities with humans enable the use of surgical procedures and treatment approaches used for patients, which facilitates clinical translation. Here, we aimed to develop an inducible oncopig model of intestinal cancer. Transgenic (TG) minipigs were generated using somatic cell nuclear transfer by handmade cloning. The pigs encode two TG cassettes: (a) an Flp recombinase‐inducible oncogene cassette containing KRAS‐G12D, cMYC, SV40LT – which inhibits p53 – and pRB and (b) a 4‐hydroxytamoxifen (4‐OHT)‐inducible Flp recombinase activator cassette controlled by the intestinal epithelium‐specific villin promoter. Thirteen viable transgenic minipigs were born. The ability of 4‐OHT to activate the oncogene cassette was confirmed in vitro in TG colonic organoids and ex vivo in tissue biopsies obtained by colonoscopy. In order to provide proof of principle that the oncogene cassette could also successfully be activated in vivo, three pigs were perorally treated with 400 mg tamoxifen for 2 × 5 days. After two months, one pig developed a duodenal neuroendocrine carcinoma with a lymph node metastasis. Molecular analysis of the carcinoma and metastasis confirmed activation of the oncogene cassette. No tumor formation was observed in untreated TG pigs or in the remaining two treated pigs. The latter indicates that tamoxifen delivery can probably be improved. In summary, we have generated a novel inducible oncopig model of intestinal cancer, which has the ability to form metastatic disease already two months after induction. The model may be helpful in bridging the gap between basic research and clinical usage. It opens new venues for longitudinal studies of tumor development and evolution, for preclinical assessment of new anticancer regimens, for pharmacology and toxicology assessments, as well as for studies into biological mechanisms of tumor formation and metastasis.

Abstract 2927: miR-625-3p regulates oxaliplatin resistance by targeting MAP2K6-p38 signalling in human colorectal adenocarcinoma cell

Oxaliplatin (oxPt) resistance in colorectal cancers (CRC) is a major medical problem, and predictive markers are urgently needed. Recently, miR-625-3p was reported as a promising predictive marker. Here, we have used in vitro models to show that miR-625-3p functionally induces oxPt resistance in CRC cells, and have identified signalling networks affected by mir-625-3p. The p38 MAPK activator MAP2K6 was shown to be a direct target of miR-625-3p, and, accordingly, was downregulated in patients not responding to oxPt therapy. miR-625-3p resistance could be reversed in CRC cells by anti-miR-625-3p treatment and by ectopic expression of a miR-625-3p insensitive MAP2K6 variant. In addition, by reducing p38 MAPK signalling using either siRNA technology, chemical inhibitors to p38 or by ectopic expression of dominant negative MAP2K6 protein we induced resistance to oxPt. Transcriptome, proteome and phosphoproteome profiles revealed inactivation of MAP2K6-p38 signalling as a possible driving force behind oxPt resistance.

Our study shows that miR-625-3p induces oxPt resistance by abrogating MAP2K6-p38 regulated apoptosis and cell cycle control networks, and corroborates the predictive power of miR-625-3p.

Citation Format: Mads H. Rasmussen, Iben Lyskjær, Rosa R. Jersie-Christensen, Line S. Tarpgaard, Bjarke Primdal-Bengtson, Morten M. Nielsen, Jakob S. Pedersen, Tine P. Hansen, Flemming Hansen, Jesper V. Olsen, Per Pfeiffer, Torben F. Ørntoft, Claus L. Andersen. miR-625-3p regulates oxaliplatin resistance by targeting MAP2K6-p38 signalling in human colorectal adenocarcinoma cell. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2927.

Abstract 2630: Integration of tumor microenvironment and molecular subclassification of colorectal cancer identifies patient subsets with poor prognosis

The patho-molecular diversity of colorectal cancer (CRC) complicates the prediction of patient postoperative prognosis and response to treatment. This calls for methods for CRC stratification beyond clinical features and the few molecular biomarkers currently implemented. Recent studies have highlighted the importance of the tumor microenvironment in CRC. Here we show by integrative transcriptome/methylome analysis of &gt;300 patient samples that CRC generates five arche-typic microenviroments encompassing three molecularly distinct types of cancer cells. The existence of the microenviroments, which we denote “Secretory”, “Stroma”, “Immune”, “ARE”, and “CIN”, could be independently identified in large external CRC datasets and are in concordance with the CRC subtypes recently defined by the CRC Subtyping Consortium (1). Detailed analysis of the five microenvironments reveals striking differences in cell composition and pathway activity. We observe that the microenvironment, particularly immune and stromal cell activity, is closely associated with patient prognosis. In particular, tumors associated with low anti-tumoral immune activity due to poor recruitment of immune cells or immune inhibition by activated stromal cells have poor prognosis. Importantly, we find that microenviroment subtyping is in fact pivotal for molecular prediction of patient prognosis as no single molecular marker carries robust prognostic information in all CRC subtypes and environments. Instead, potent prognostic biomarkers are environment-specific: As an example interferon signaling is deregulated in several microenviroment types, yet the specific interferon response genes deregulated (i.e. biomarker candidates) differ between microenvironments in accordance with their cellular composition. Our approach has allowed us to identify superior, single prognostic biomarkers for each CRC type and, importantly, their prognostic value in external datasets is only observed after environment subtyping. Collectively, these observations may well explain the poor validation rate of prognostic biomarker candidates in the past. In conclusion: we provide a CRC microenvironment framework that has the potential to guide future clinical decision-making primarily in relation to prognosis, but likely also in relation to therapy choice. This work is performed within framework the SYSCOL consortium funded by EU FP7

(1) Guinney, J. et al. “The consensus molecular subtypes of colorectal cancer”, Nature Medicine (2015) doi:10.1038/nm.3967

Citation Format: Jesper B. Bramsen, Mads H. Rasmussen, Halit Ongen, Søren Vang, Philippe Lamy, Manel B. Esteller, Emmanouil T. Dermitzakis, Torben F. Orntoft, Claus L. Andersen. Integration of tumor microenvironment and molecular subclassification of colorectal cancer identifies patient subsets with poor prognosis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2630.

Establishment and characterization of models of chemotherapy resistance in colorectal cancer: Towards a predictive signature of chemoresistance

Current standard treatments for metastatic colorectal cancer (CRC) are based on combination regimens with one of the two chemotherapeutic drugs, irinotecan or oxaliplatin. However, drug resistance frequently limits the clinical efficacy of these therapies. In order to gain new insights into mechanisms associated with chemoresistance, and departing from three distinct CRC cell models, we generated a panel of human colorectal cancer cell lines with acquired resistance to either oxaliplatin or irinotecan. We characterized the resistant cell line variants with regards to their drug resistance profile and transcriptome, and matched our results with datasets generated from relevant clinical material to derive putative resistance biomarkers. We found that the chemoresistant cell line variants had distinctive irinotecan- or oxaliplatin-specific resistance profiles, with non-reciprocal cross-resistance. Furthermore, we could identify several new, as well as some previously described, drug resistance-associated genes for each resistant cell line variant. Each chemoresistant cell line variant acquired a unique set of changes that may represent distinct functional subtypes of chemotherapy resistance. In addition, and given the potential implications for selection of subsequent treatment, we also performed an exploratory analysis, in relevant patient cohorts, of the predictive value of each of the specific genes identified in our cellular models.

Cellular disposal of miR23b by RAB27-dependent exosome release is linked to acquisition of metastatic properties

Exosomes are small secreted vesicles that can transfer their content to recipient cells. In cancer, exosome secretion has been implicated in tumor growth and metastatic spread. In this study, we explored the possibility that exosomal pathways might discard tumor-suppressor miRNA that restricts metastatic progression. Secreted miRNA characterized from isogenic bladder carcinoma cell lines with differing metastatic potential were uncoupled from binding to target transcripts or the AGO2-miRISC complex. In metastatic cells, we observed a relative increase in secretion of miRNA with tumor-suppressor functions, including miR23b, miR224, and miR921. Ectopic expression of miR23b inhibited invasion, anoikis, angiogenesis, and pulmonary metastasis. Silencing of the exocytotic RAB family members RAB27A or RAB27B halted miR23b and miR921 secretion and reduced cellular invasion. Clinically, elevated levels of RAB27B expression were linked to poor prognosis in two independent cohorts of patients with bladder cancer. Moreover, highly exocytosed miRNA from metastatic cells, such as miR23b, were reduced in lymph node metastases compared with patient-matched primary tumors and were correlated with increments in miRNA-targeted RNA. Taken together, our results suggested that exosome-mediated secretion of tumor-suppressor miRNA is selected during tumor progression as a mechanism to coordinate activation of a metastatic cascade.

Putative cis-regulatory drivers in colorectal cancer

The cis-regulatory effects responsible for cancer development have not been as extensively studied as the perturbations of the protein coding genome in tumorigenesis. To better characterize colorectal cancer (CRC) development we conducted an RNA-sequencing experiment of 103 matched tumour and normal colon mucosa samples from Danish CRC patients, 90 of which were germline-genotyped. By investigating allele-specific expression (ASE) we show that the germline genotypes remain important determinants of allelic gene expression in tumours. Using the changes in ASE in matched pairs of samples we discover 71 genes with excess of somatic cis-regulatory effects in CRC, suggesting a cancer driver role. We correlate genotypes and gene expression to identify expression quantitative trait loci (eQTLs) and find 1,693 and 948 eQTLs in normal samples and tumours, respectively. We estimate that 36% of the tumour eQTLs are exclusive to CRC and show that this specificity is partially driven by increased expression of specific transcription factors and changes in methylation patterns. We show that tumour-specific eQTLs are more enriched for low CRC genome-wide association study (GWAS) P values than shared eQTLs, which suggests that some of the GWAS variants are tumour specific regulatory variants. Importantly, tumour-specific eQTL genes also accumulate more somatic mutations when compared to the shared eQTL genes, raising the possibility that they constitute germline-derived cancer regulatory drivers. Collectively the integration of genome and the transcriptome reveals a substantial number of putative somatic and germline cis-regulatory cancer changes that may have a role in tumorigenesis.

Overdiagnosis of dementia in young patients - a nationwide register-based study

BACKGROUND

Little is known about the quality of the diagnostic evaluation and the validity of dementia diagnoses in young patients established in routine clinical practice. The aim of this study was to investigate the validity of the diagnosis of dementia registered in the Danish nationwide hospital registers in young patients.

METHODS

Two hundred patients were randomly selected from 891 patients <65 years registered with a dementia diagnosis for the first time in 2008. The patients' medical records were reviewed to evaluate if they fulfilled ICD-10 and/or DSM-IV criteria for dementia and current clinical criteria for specific dementia subtypes.

RESULTS

A registered diagnosis was found to be correct in only 59%. A misdiagnosis of dementia occurred primarily in patients with depression or alcohol abuse.

CONCLUSION

Our results suggest that dementia is overregistered and overdiagnosed in young patients. This may be due to a different symptom profile of dementia in young patients, lack of knowledge among clinical physicians and the wide range of conditions which may be misinterpreted as dementia.

Abstract 1157: MicroRNA-625-3p is associated with response to first-line oxaliplatin-based treatment of metastatic colorectal cancer

The backbone of current oncologic treatment of metastatic colorectal cancer (mCRC) consists of fluoropyrimidine together with either oxaliplatin (XELOX/FOLFOX) or irinotecan (XELIRI/FOLFIRI). With an overall objective response rate of approximately 50% for either treatment combination, a major unsolved problem is that no predictors of response to these treatments currently are available. To address this issue, we profiled 742 microRNAs in laser-capture microdissected cancer cells from responding and non-responding patients receiving XELOX/FOLFOX as first-line treatment for mCRC, and identified, among others, high expression of miR-625-3p, miR-181b and miR-27b to be associated with poor clinical response. In a validation cohort of 98 mCRC patients treated first-line with XELOX, high expression of miR-625-3p was confirmed to be associated with poor response (OR 6.25, 95%CIOR [1.8; 21.0]). Independent analyses showed that miR-625-3p was not dysregulated between normal and cancer samples, nor was its expression associated with recurrence of stage II or III disease, indicating that miR-625-3p solely is a response marker. Finally, we also found that these miRNAs are up-regulated in oxaliplatin resistant HCT116/oxPt (miR-625-3p, miR-181b and miR-27b) and LoVo/oxPt (miR-181b) CRC cell lines as compared with their isogenic parental cells. Altogether, our results suggest an association between miR-625-3p and response to first-line oxaliplatin based chemotherapy of mCRC.

Citation Format: Mads H. Rasmussen, Niels F. Jensen, Line S. Tarpgaard, Camilla Qvortrup, Maria U. Rømer, Jan Stenvang, Tine P. Hansen, Lise-Lotte Christensen, Jan Lindebjerg, Flemming Hansen, Benny V. Jensen, Torben F. Hansen, Anders M. Jakobsen, Per Pfeiffer, Nils Brünner, Torben F. Ørntoft, Claus L. Andersen. MicroRNA-625-3p is associated with response to first-line oxaliplatin-based treatment of metastatic colorectal cancer. [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 1157. doi:10.1158/1538-7445.AM2013-1157

High expression of microRNA-625-3p is associated with poor response to first-line oxaliplatin based treatment of metastatic colorectal cancer

The backbone of current cytotoxic treatment of metastatic colorectal cancer (mCRC) consists of a fluoropyrimidine together with either oxaliplatin (XELOX/FOLFOX) or irinotecan (XELIRI/FOLFIRI). With an overall objective response rate of approximately 50% for either treatment combination, a major unsolved problem is that no predictors of response to these treatments are available. To address this issue, we profiled 742 microRNAs in laser-capture microdissected cancer cells from responding and non-responding patients receiving XELOX/FOLFOX as first-line treatment for mCRC, and identified, among others, high expression of miR-625-3p, miR-181b and miR-27b to be associated with poor clinical response. In a validation cohort of 94 mCRC patients treated first-line with XELOX, high expression of miR-625-3p was confirmed to be associated with poor response (OR = 6.25, 95%CI [1.8; 21.0]). Independent analyses showed that miR-625-3p was not dysregulated between normal and cancer samples, nor was its expression associated with recurrence of stage II or III disease, indicating that miR-625-3p solely is a response marker. Finally, we also found that these miRNAs were up-regulated in oxaliplatin resistant HCT116/oxPt (miR-625-3p, miR-181b and miR-27b) and LoVo/oxPt (miR-181b) colon cancer cell lines as compared with their isogenic parental cells. Altogether, our results suggest an association between miR-625-3p and response to first-line oxaliplatin based chemotherapy of mCRC.

MiRNA-362-3p induces cell cycle arrest through targeting of E2F1, USF2 and PTPN1 and is associated with recurrence of colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer deaths in Western countries. A significant number of CRC patients undergoing curatively intended surgery subsequently develop recurrence and die from the disease. MicroRNAs (miRNAs) are aberrantly expressed in cancers and appear to have both diagnostic and prognostic significance. In this study, we identified novel miRNAs associated with recurrence of CRC, and their possible mechanism of action. TaqMan(®) Human MicroRNA Array Set v2.0 was used to profile the expression of 667 miRNAs in 14 normal colon mucosas and 46 microsatellite stable CRC tumors. Four miRNAs (miR-362-3p, miR-570, miR-148 a* and miR-944) were expressed at a higher level in tumors from patients with no recurrence (p<0.015), compared with tumors from patients with recurrence. A significant association with increased disease free survival was confirmed for miR-362-3p in a second independent cohort of 43 CRC patients, using single TaqMan(®) microRNA assays. In vitro functional analysis showed that over-expression of miR-362-3p in colon cancer cell lines reduced cell viability, and proliferation mainly due to cell cycle arrest. E2F1, USF2 and PTPN1 were identified as potential miR-362-3p targets by mRNA profiling of HCT116 cells over-expressing miR-362-3p. Subsequently, these genes were confirmed as direct targets by Luciferase reporter assays and their knockdown in vitro phenocopied the effects of miR-362-3p over-expression. We conclude that miR-362-3p may be a novel prognostic marker in CRC, and hypothesize that the positive effects of augmented miR-362-3p expression may in part be mediated through the targets E2F1, USF2 and PTPN1.

Tumor-specific usage of alternative transcription start sites in colorectal cancer identified by genome-wide exon array analysis

BACKGROUND

Approximately half of all human genes use alternative transcription start sites (TSSs) to control mRNA levels and broaden the transcriptional output in healthy tissues. Aberrant expression patterns promoting carcinogenesis, however, may arise from alternative promoter usage.

RESULTS

By profiling 108 colorectal samples using exon arrays, we identified nine genes (TCF12, OSBPL1A, TRAK1, ANK3, CHEK1, UGP2, LMO7, ACSL5, and SCIN) showing tumor-specific alternative TSS usage in both adenoma and cancer samples relative to normal mucosa. Analysis of independent exon array data sets corroborated these findings. Additionally, we confirmed the observed patterns for selected mRNAs using quantitative real-time reverse-transcription PCR. Interestingly, for some of the genes, the tumor-specific TSS usage was not restricted to colorectal cancer. A comprehensive survey of the nine genes in lung, bladder, liver, prostate, gastric, and brain cancer revealed significantly altered mRNA isoform ratios for CHEK1, OSBPL1A, and TCF12 in a subset of these cancer types.To identify the mechanism responsible for the shift in alternative TSS usage, we antagonized the Wnt-signaling pathway in DLD1 and Ls174T colorectal cancer cell lines, which remarkably led to a shift in the preferred TSS for both OSBPL1A and TRAK1. This indicated a regulatory role of the Wnt pathway in selecting TSS, possibly also involving TP53 and SOX9, as their transcription binding sites were enriched in the promoters of the tumor preferred isoforms together with their mRNA levels being increased in tumor samples. Finally, to evaluate the prognostic impact of the altered TSS usage, immunohistochemistry was used to show deregulation of the total protein levels of both TCF12 and OSBPL1A, corresponding to the mRNA levels observed. Furthermore, the level of nuclear TCF12 had a significant correlation to progression free survival in a cohort of 248 stage II colorectal cancer samples.

CONCLUSIONS

Alternative TSS usage in colorectal adenoma and cancer samples has been shown for nine genes, and OSBPL1A and TRAK1 were found to be regulated in vitro by Wnt signaling. TCF12 protein expression was upregulated in cancer samples and correlated with progression free survival.

Evaluation of two commercial global miRNA expression profiling platforms for detection of less abundant miRNAs

Background

microRNAs (miRNA) are short, endogenous transcripts that negatively regulate the expression of specific mRNA targets. miRNAs are found both in tissues and body fluids such as plasma. A major perspective for the use of miRNAs in the clinical setting is as diagnostic plasma markers for neoplasia. While miRNAs are abundant in tissues, they are often scarce in plasma. For quantification of miRNA in plasma it is therefore of importance to use a platform with high sensitivity and linear performance in the low concentration range. This motivated us to evaluate the performance of three commonly used commercial miRNA quantification platforms: GeneChip miRNA 2.0 Array, miRCURY Ready-to-Use PCR, Human panel I+II V1.M, and TaqMan Human MicroRNA Array v3.0.

Results

Using synthetic miRNA samples and plasma RNA samples spiked with different ratios of 174 synthetic miRNAs we assessed the performance characteristics reproducibility, recovery, specificity, sensitivity and linearity. It was found that while the qRT-PCR based platforms were sufficiently sensitive to reproducibly detect miRNAs at the abundance levels found in human plasma, the array based platform was not. At high miRNA levels both qRT-PCR based platforms performed well in terms of specificity, reproducibility and recovery. At low miRNA levels, as in plasma, the miRCURY platform showed better sensitivity and linearity than the TaqMan platform.

Conclusion

For profiling clinical samples with low miRNA abundance, such as plasma samples, the miRCURY platform with its better sensitivity and linearity would probably be superior.

Alternative splicing of SLC39A14 in colorectal cancer is regulated by the Wnt pathway

Alternative splicing is a crucial step in the generation of protein diversity and its misregulation is observed in many human cancer types. By analyzing 143 colorectal samples using exon arrays, SLC39A14, a divalent cation transporter, was identified as being aberrantly spliced in tumor samples. SLC39A14 contains two mutually exclusive exons 4A and 4B and the exon 4A/4B ratio was significantly altered in adenomas (p = 3.6 × 10(-10)) and cancers (p = 9.4 × 10(-11)), independent of microsatellite stability status. The findings were validated in independent exon array data sets and by quantitative real-time reverse-transcription PCR (qRT-PCR). Aberrant Wnt signaling is a hallmark of colorectal tumorigenesis and is characterized by nuclear β-catenin. Experimental inactivation of Wnt signaling in DLD1 and Ls174T cells by knockdown of β-catenin or overexpression of dominant negative TCFs (TCF1 and TCF4) altered the 4A/4B ratio, indicating that SLC39A14 splicing is regulated by the Wnt pathway. An altered 4A/4B ratio was also observed in gastric and lung cancer where Wnt signaling is also known to be aberrantly activated. The splicing factor SRSF1 and its regulator, the kinase SRPK1, were found to be deregulated upon Wnt inactivation in colorectal carcinoma cells. SRPK1 was also found up-regulated in both adenoma samples (p = 1.5 × 10(-5)) and cancer samples (p = 5 × 10(-4)). In silico splicing factor binding analysis predicted SRSF1 to bind predominantly to the cancer associated exon 4B, hence, it was hypothesized that SRPK1 activates SRSF1 through phosphorylation, followed by SRSF1 binding to exon 4B and regulation of SLC39A14 splicing. Indeed, siRNA-mediated knockdown of SRPK1 and SRSF1 in DLD1 and SW480 colorectal cancer cells led to a change in the 4A/4B isoform ratio, supporting a role of these factors in the regulation of SLC39A14 splicing. In conclusion, alternative splicing of SLC39A14 was identified in colorectal tumors and found to be regulated by the Wnt pathway, most likely through regulation of SRPK1 and SRSF1.

Alternative splicing of SLC39A14 in colorectal cancer is regulated by the Wnt pathway

Alternative splicing is a crucial step in the generation of protein diversity and its misregulation is observed in many human cancer types. By analyzing 143 colorectal samples using exon arrays, SLC39A14, a divalent cation transporter, was identified as being aberrantly spliced in tumor samples. SLC39A14 contains two mutually exclusive exons 4A and 4B and the exon 4A/4B ratio was significantly altered in adenomas (p = 3.6 × 10(-10)) and cancers (p = 9.4 × 10(-11)), independent of microsatellite stability status. The findings were validated in independent exon array data sets and by quantitative real-time reverse-transcription PCR (qRT-PCR). Aberrant Wnt signaling is a hallmark of colorectal tumorigenesis and is characterized by nuclear β-catenin. Experimental inactivation of Wnt signaling in DLD1 and Ls174T cells by knockdown of β-catenin or overexpression of dominant negative TCFs (TCF1 and TCF4) altered the 4A/4B ratio, indicating that SLC39A14 splicing is regulated by the Wnt pathway. An altered 4A/4B ratio was also observed in gastric and lung cancer where Wnt signaling is also known to be aberrantly activated. The splicing factor SRSF1 and its regulator, the kinase SRPK1, were found to be deregulated upon Wnt inactivation in colorectal carcinoma cells. SRPK1 was also found up-regulated in both adenoma samples (p = 1.5 × 10(-5)) and cancer samples (p = 5 × 10(-4)). In silico splicing factor binding analysis predicted SRSF1 to bind predominantly to the cancer associated exon 4B, hence, it was hypothesized that SRPK1 activates SRSF1 through phosphorylation, followed by SRSF1 binding to exon 4B and regulation of SLC39A14 splicing. Indeed, siRNA-mediated knockdown of SRPK1 and SRSF1 in DLD1 and SW480 colorectal cancer cells led to a change in the 4A/4B isoform ratio, supporting a role of these factors in the regulation of SLC39A14 splicing. In conclusion, alternative splicing of SLC39A14 was identified in colorectal tumors and found to be regulated by the Wnt pathway, most likely through regulation of SRPK1 and SRSF1.

Shipboard measurements of the hearing of the white-beaked dolphin Lagenorhynchus albirostris

This is the first report of an underwater audiogram from a dolphin in a capture-and-release scenario. Two bow-riding white-beaked dolphins Lagenorhynchus albirostris (a female and a male) were captured using the hoop-net technique in Faxaflói Bay, Iceland. The dolphins were transferred to a stretcher and hoisted into a plastic research tank on board a small fishing vessel. Two underwater transducers were used to cover the frequency range from 16 to 215 kHz. Two human EEG electrodes mounted in suction cups, one placed near the blow hole and the other on the dorsal fin, picked up bioelectrical responses to acoustic stimuli. Responses to about 1000 sinusoidal amplitude modulated stimuli for each amplitude/frequency combination were averaged and analyzed using a fast Fourier transform to obtain an evoked auditory response. Threshold was defined as the zero crossing of the response using linear regression. Two threshold frequencies at 50 kHz and 64 kHz were obtained from the female. An audiogram ranging from 16 to 181 kHz was obtained from an adult male and showed the typical ;U' shaped curve for odontocetes. The thresholds for both white-beaks were comparable and demonstrated the most sensitive high frequency hearing of any known dolphin and were as sensitive as the harbor porpoise.

Source levels and harmonic content of whistles in white-beaked dolphins (Lagenorhynchus albirostris)

Recordings of white-beaked dolphin whistles were made in Faxafl6i Bay (Iceland) using a three-hydrophone towed linear array. Signals from the hydrophones were routed through an amplifier to a lunch box computer on board the boat and digitized using a sample rate of 125 kHz per channel. Using this method more than 5000 whistles were recorded. All recordings were made in sea states 0-1 (Beaufort scale). Dolphins were located in a 2D horizontal plane by using the difference of arrival time to the three hydrophones, and source levels were estimated from these positions using two different methods (I and II). Forty-three whistles gave a reliable location for the vocalizing dolphin when using method II and of these 12 when using method I. Source level estimates on the center hydrophone were higher using method I [average source level 148 (rms) +/- 12 dB, n = 36] than for method II [average source level 139 (rms) +/- 12 dB, n = 36]. Using these rms values the maximum possible communication range for whistling dolphins given the local ambient noise conditions was then estimated. The maximum range was 10.5 km for a dolphin whistle with the highest source level (167 dB) and about 140 m for a whistle with the lowest source level (118 dB). Only two of the 43 whistles contained an unequal number of harmonics recorded at the three hydrophones judging from the spectrograms. Such signals could be used to calculate the directionality of whistles, but more recordings are necessary to describe the directionality of white-beaked dolphin whistles.

Tumor model-specific proviral insertional mutagenesis of the Fos/Jdp2/Batf locus

Retroviral activation of the AP-1/ATF super family member Jdp2 was recently reported to be a common event in M-MLV-induced T cell lymphoma in p27-null C57x129 mice as compared to wild type-inoculated mice but has not been found important in other models. On the basis of retroviral tag retrieval from 1190 individual Akv- and SL3-3-induced lymphomas, we here report that insertional mutagenesis into the 250-kb Fos/Jdp2/Batf locus is associated with SL3-3 MLV-induced T but not Akv-induced B cell lymphomas of NMRI and SWR mice. Integration pattern and clonality analyses suggest that Jdp2 participates in SL3-3-induced tumorigenesis distinctly as compared to the M-MLV setting. Northern blot analysis showed Jdp2 to be alternatively spliced in various normal tissues as well as MLV-induced lymphomas. Interestingly, in some tumors, proviral insertion seems to activate different mRNA sub-species. Whereas elevated mRNA levels of the Fos gene could not be correlated with provirus presence, in one case, Northern blot analysis as well as quantitative real-time PCR indicated proviral activation of the AP-1 super family member Batf, a gene not previously reported to be a target of insertional mutagenesis. A novel integration cluster between Jdp2 and Batf apparently did not influence the expression level of either gene, underscoring the importance of addressing expression effects to identify target genes of insertion. Altogether, such distinct insertion patterns point to different mechanism of activation of specific proto-oncogenes and are consequently of importance for the understanding of proviral activation mechanisms as well as the specific role of individual oncogenes in tumor development.

Minor long-term changes in weight have beneficial effects on insulin sensitivity and beta-cell function in obese subjects

AIM

To evaluate the long-term effect of changes in body composition induced by weight loss on insulin sensitivity (SI), non-insulin mediated glucose disposal, glucose effectiveness (SG)and beta-cell function.

DESIGN

Glucose metabolism was evaluated before and after participation in a two-year weight loss trial of Orlistat vs. placebo, combined with an energy and fat restricted diet.

SUBJECTS

Twelve obese patients (11 women, 1 man), age 45.8 +/- 10.5 years, body weight (BW) 99.7 +/- 13.3 kg, BMI 35.3 +/- 2.8 kg/m(2).

MEASUREMENTS

At inclusion and 2 years later an oral glucose tolerance test (OGTT) and a frequently sampled intravenous glucose tolerance test (FSIGT) were performed. Body composition was estimated by a dual-energy X-ray absorptiometry (DXA) whole body scanning.

RESULTS

The patients obtained varying changes in BW ranging from a weight loss of 17.8 kg to a weight gain of 6.0 kg. Corresponding changes in fat mass (FM) varied from a 40% reduction to a19% increase. A significant decrease in both fasting (p = 0.038) and 2 h (p = 0.047) blood glucose at OGTT was found. The improvement in insulin sensitivity (SI) estimated by means of Bergmans Minimal Model, was significantly and linearly correlated to change in total FM (r = - 0.83,p = 0.0026). A multiple regression analysis showed that changes in truncal FM was the strongest predictor of change in S(I) explaining 67% of the variation. First phase insulin response (AIRg)remained unchanged whereas insulin disposition index increased significantly (p = 0.044). At inclusion five patients had impaired glucose tolerance of which four, who lost weight, were normalized at the retest 2 years later.

CONCLUSION

In obese subjects long-term minimal or moderate changes in weight were found to be linearly associated with changes in insulin sensitivity. In obese subjects with impaired glucose tolerance even a minor weight loss was able to normalize glucose tolerance.

GH administration and discontinuation in healthy elderly men: effects on body composition, GH-related serum markers, resting heart rate and resting oxygen uptake

BACKGROUND AND OBJECTIVES

GH administration results in increased lean body mass (LBM), decreased fat mass (FM) and increased energy expenditure (EE). GH therapy may therefore have potential benefits, especially in the elderly, who are known to have decreased function of the GH/IGF-I axis. Several studies have focused on effects of GH administration in the elderly in the last decade. However, very limited information is available regarding changes in body composition and EE upon GH discontinuation in the elderly. The present study therefore investigated the effects of 12 weeks of GH administration and subsequent discontinuation on body composition, resting oxygen uptake (VO2), resting heart rate (HR) and GH related serum markers in healthy elderly men.

SUBJECTS AND METHODS

Sixteen healthy men [age 74 +/- 1 years (mean +/- SEM), height 174.2 +/- 1.6 cm, body weight 80.7 +/- 2.6 kg, body fat 27.5 +/- 1.1%] completed the study protocol. Recombinant human GH (1.80 +/- 0.24 IU/day) was administered for 12 weeks in a single-blinded, placebo-controlled design. Body composition (dual energy X-ray absorptiometry), resting VO2 (indirect calorimetry), resting HR (telemetry) and serum IGF-I, IGF-II, IGFBP-3 and acid labile subunit (ALS) were measured at baseline, after 12 weeks of GH administration and, additionally in the GH group, 1, 2, 3, 4, 5 and 9 days after GH discontinuation.

RESULTS

Body weight was unchanged from baseline to 12 weeks in both groups. However, GH administration caused a decrease in FM (3.4 +/- 1.0 kg, P < 0.012), paralleled by a similar increase in LBM (3.2 +/- 0.4 kg, P < 0.0002). Resting VO2 and resting HR increased by 31 +/- 3.6% and 7.3 +/- 1.9 per minute, respectively, in the GH-group, where significant increases in serum IGF-I, IGFBP-3 and ALS also were noted. None of the above parameters changed in the placebo group. Within 2-3 days after GH discontinuation, the GH related serum markers and resting HR returned to baseline levels, whereas resting VO2 remained elevated even 9 days after GH discontinuation. In addition, GH discontinuation caused a significant decrease in body weight (1.86 +/- 0.35 kg), derived exclusively from a decrease in LBM (1.63 +/- 0.43 kg), while the decreased FM was maintained (12 weeks: 17.93 +/- 1.65 kg, +9 days: 17.74 +/- 1.62 kg).

CONCLUSIONS

The increases in serum IGF-I, IGFBP-3, ALS and resting heart rate induced by 12 weeks of GH administration in elderly men returned to baseline levels within 2-3 days after GH discontinuation. However, resting VO2 remained elevated for a longer period. GH administration reduced fat mass but maintained body weight by increasing lean body mass. In contrast, 9 days of GH discontinuation reduced body weight exclusively by reducing lean body mass.

Endurance training and GH administration in elderly women: effects on abdominal adipose tissue lipolysis

In the present study, the effect of endurance training alone and endurance training combined with recombinant human growth hormone (rhGH) administration on subcutaneous abdominal adipose tissue lipolysis was investigated. Sixteen healthy women [age 75 +/- 2 yr (mean +/- SE)] underwent a 12-wk endurance training program on a cycle ergometer. rhGH was administered in a randomized, double-blinded, placebo-controlled design in addition to the training program. Subcutaneous abdominal adipose tissue lipolysis was estimated by means of microdialysis combined with measurements of subcutaneous abdominal adipose tissue blood flow (ATBF; (133)Xe washout). Whole body fat oxidation was estimated simultaneously by indirect calorimetry. Before and after completion of the training program, measurements were performed both at rest and during 60 min of continuous cycling at a workload corresponding to 60% of pretraining peak oxygen uptake. Endurance training alone did not affect subcutaneous abdominal adipose tissue lipolysis either at rest or during exercise, as reflected by identical levels of interstitial adipose tissue glycerol, subcutaneous abdominal ATBF, and plasma nonesterified fatty acids before and after completion of the training program. Similarly, no effect on subcutaneous abdominal adipose tissue lipolysis was observed when combining endurance training with rhGH administration. However, in both the placebo and the GH groups, fat oxidation was significantly increased during exercise performed at the same absolute workload after completion of the training program. We conclude that the changed lipid metabolism during exercise observed after endurance training alone or after endurance training combined with rhGH administration is not due to alterations in subcutaneous abdominal adipose tissue metabolism in elderly women.

Growth hormone enhances effects of endurance training on oxidative muscle metabolism in elderly women

The present study investigated whether recombinant human (rh) growth hormone (GH) combined with endurance training would have a larger effect on oxidative capacity, metabolism, and body fat than endurance training alone. Sixteen healthy, elderly women, aged 75 yr, performed closely monitored endurance training on a cycle ergometer over 12 wk. rhGH was given in a randomized, double-blinded, placebo-controlled design in addition to the training program. GH administration resulted in a doubling of serum insulin-like growth factor I levels. With endurance training, peak oxygen uptake increased by approximately 18% in both groups, whereas the marked increase in muscle citrate synthase activity was 50% larger in the GH group compared with the placebo group. In addition, only the GH group revealed an increase in muscle L-3-hydroxyacyl-CoA dehydrogenase activity. Body weight remained unchanged in both groups, but the GH group showed significant changes in body composition with a decrease in fat mass and an increase in lean body mass. Twenty-four-hour indirect calorimetry performed in four subjects showed a marked increase in energy expenditure with increased relative and absolute fat combustion in the two subjects receiving rhGH. In conclusion, rhGH adds to the effects of endurance training on muscle oxidative enzymes and causes a reduction in body fat in elderly women.

Bioequivalence between ready-to-use recombinant human growth hormone (rhGH) in liquid formulation and rhGH for reconstitution

The bioequivalence of recombinant human growth hormone (rhGH) for reconstitution, at either 24 IU or 8 mg, and three strengths of liquid formulation of rhGH (5, 10 or 15 mg per 1.5 ml, hGH) was tested in two randomized, single-blind, four-period, crossover studies in healthy subjects. The study drugs were administered by subcutaneous injection at a dose of 2.5 mg rhGH/m(2)body surface area or as a fixed dose of 5 mg rhGH. Endogenous hGH release was suppressed by a continuous somatostatin infusion. The 90% confidence intervals for the estimated mean ratios of AUC(0-24 h)and C(max)(analysis of variance) between all products were within 80-125% in both studies. Also, no significant differences (P> 0.05; Wilcoxon signed rank test) were found between t(max)for the liquid formulations of rhGH. These data demonstrate that there is bioequivalence between rhGH for reconstitution and the liquid formulations of rhGH.

Normal spontaneous and stimulated GH levels despite decreased IGF-I concentrations in cystic fibrosis patients

OBJECTIVE

The aim of the present study was to investigate whether patients with cystic fibrosis (CF) are GH resistant with increased GH release and decreased concentrations of IGF-I as a result of malabsorption, increased catabolism and impaired glucose tolerance.

DESIGN

Twenty CF patients were included, ten with normal glucose tolerance (five male, five female, median age 25.5 years (range 20-31)) and ten with diabetes mellitus (five male, five female, median age 25.3 years (range 17-45). Twenty healthy individuals served as controls (ten male, ten female, median age 28.4 years (range 18-36)).

METHODS

GH status was evaluated by 12h spontaneous GH release during the night time, arginine-stimulated GH release and the basal concentrations of IGF-I and insulin-like growth factor-binding protein-3 (IGFBP-3). Twelve hour spontaneous GH profiles were estimated using a constant blood withdrawal technique with sampling every 30min and the Pulsar method was used for the analysis of profiles.

RESULTS

No significant differences were found in spontaneous and stimulated GH release in CF patients compared with healthy controls, whereas IGF-I and IGFBP-3 were significantly decreased in CF patients compared with healthy controls. The combination of reduced IGF-I and IGFBP-3 with normal GH release points to a relative GH resistance or a disturbance in the pituitary axis in patients with CF. The spontaneous GH release, the stimulated GH release and the basal concentrations of IGF-I and IGFBP-3 were not significantly different in diabetic CF patients compared with CF patients with normal glucose tolerance and the presence of diabetes mellitus was not consistent with increased GH resistance in CF patients.

CONCLUSION

CF patients with normal glucose tolerance and diabetic CF patients had normal GH release and decreased concentrations of IGF-I indicating a relative GH resistance.

The acid-labile subunit of human ternary insulin-like growth factor binding protein complex in serum: hepatosplanchnic release, diurnal variation, circulating concentrations in healthy subjects, and diagnostic use in patients with growth hormone deficiency

Circulating insulin-like growth factor-I (IGF-I) is predominantly bound in the trimeric complex comprised of IGF binding protein-3 (IGFBP-3) and acid-labile subunit (ALS). Circulating concentrations of IGF-I, IGFBP-3 and ALS are believed to reflect the GH secretory status, but the clinical use of ALS determination is not known. We therefore, determined the: 1) hepatosplanchnic release of ALS by liver vein catheterization (n=30); 2) 24-h diurnal variation of ALS (n=8); 3) normal age-related ranges of circulating ALS (n=1158); 4) diagnostic value of ALS in 108 patients with childhood-onset GH deficiency (GHD). We found: 1) no significant arteriovenous gradient over the liver ofALS, IGF-I, and IGFBP-3; 2) the diurnal variation of ALS was 12% (mean coefficient of variation percent); 3) ALS levels increased throughout childhood with maximal levels in puberty, with a subsequent decrease with age in adults; and 4) ALS levels were below -2 SD in 57 of 79 GHD patients (sensitivity 72%) and above 2 SD in 22 of 29 patients with normal GH response (specificity 76%), which was similar, compared with the diagnostic utility of IGF-I and IGFBP-3. Finally, our findings indicate that hepatic ALS production is not measurable by this approach or, alternatively, that the liver is not the primary source of circulating ALS, IGF-I, or IGFBP-3 in humans. In conclusion, we have provided extensive normal data for a novel ALS assay and found that circulating ALS levels exhibit minor diurnal variation. We suggest that ALS determination may be used in future classification of adults suspected of GHD.

Fasting gall bladder volume and lithogenicity in relation to glucose tolerance, total and intra-abdominal fat masses in obese non-diabetic subjects

OBJECTIVE

To investigate whether total body fat mass or fat distribution and associated metabolic disturbances in glucose and lipid metabolism influence the well known gallstone pathogenetic factors in obese subjects in order to explain why some obese subjects develop gallstones and some do not.

DESIGN

Cross sectional study of gallstone pathogenetic factors, body composition, fat distribution, glucose and lipid metabolism.

SUBJECTS

57 healthy overweight subjects (aged 26-64y, body mass index (BMI) 30-45 kg/m2).

MEASUREMENTS

Total and intra-abdominal fat masses were measured by dual X-ray absorptiometry and abdominal CT scanning, respectively. The lithogenic index was measured in aspirated bile. The gallbladder volume was determined by ultrasound and the gallbladder ejection fraction% by dynamic cholescintigraphy. Plasma cholecystokinin (CCK) concentrations during a meal were measured with a specific radioimmunoassay. Insulin sensitivity was measured by the Minimal Model and glucose tolerance by an oral glucose tolerance test (OGTT). Serum lipid concentrations were measured by standard methods.

RESULTS

The gallbladder volume in the fasting state increased with increasing intra-abdominal fat mass (P=0.006) and was increased in subjects with impaired glucose tolerance (41 vs 27 ml, P=0.001). The lithogenic index was > 1 in all subjects and correlated with total fat mass (P=0.04).

CONCLUSION

Gallstone pathogenesis in obesity seems to be influenced by the total body fat mass and its regional distribution possibly via mutual association with the glucose tolerance.

The novel oxygenated chalcone, 2,4-dimethoxy-4'-butoxychalcone, exhibits potent activity against human malaria parasite Plasmodium falciparum in vitro and rodent parasites Plasmodium berghei and Plasmodium yoelii in vivo

Previous studies have shown that licochalcone A, an oxygenated chalcone, exhibits antileishmanial and antimalarial activities. The present study was designed to examine the antimalarial activity of an analog of licochalcone A, 2,4-dimethoxy-4'-butoxychalcone (2,4mbc). 2,4mbc inhibited the in vitro growth of both a chloroquine-susceptible (3D7) and a chloroquine-resistant (Dd2) strain of Plasmodium falciparum in a [3H]hypoxanthine uptake assay. The in vivo activity of 2,4mbc was tested in mice infected with Plasmodium berghei or Plasmodium yoelii and in rats infected with P. berghei. 2,4mbc administered either orally, intraperitoneally, or subcutaneously for 5 days protected the mice from otherwise lethal infections of these parasites. 2,4mbc administered orally for 5 days reduced parasitemia in the rats infected with P. berghei. These results demonstrate that 2,4mbc exhibits potent antimalarial activity and might be developed into a new antimalarial drug.

Bioavailability of recombinant human growth hormone in different concentrations and formulations

Whether the bioavailability of growth hormone depends on the concentration or formulation of the preparation was evaluated in 18 growth hormone-deficient patients. The design was a single-blinded, randomized cross-over study, where the patients were given a single, fixed dose subcutaneous injection of growth homrone (3 IU/m2) of 3 different preparations: (1) 4 IU/ml in a bicarbonate buffer dissolved in 0.9% benzyl alcohol (approximately 1.37 mg/ml), (2) 5.9 IU/ml in a phosphate buffer dissolved in 1.5% benzyl alcohol (approximately 2 mg/ml) and (3) 11 7 IU/ml in a phosphate buffer dissolved in 1.5% benzyl alcohol (approximately 4 mg/ml). Conventional growth hormone-therapy was withdrawn 2 days before each study period. Blood samples were drawn over a 24-hr period and assessed for growth hormone, serum insulin-like growth factor I (IGF-I), insulin and glucose. The geometric mean values (+/- geometric S.D) of the relative absorption fractions were F5.9 IU/4 IU = AUC5.9 IU/AUC4 IU = (+/- 1.139) (P = 0.66), F11.7 IU/AUC4 IU = AUC11.7 IU/AUC4 IU (1.14 +/- 1.21) (P = 0.009) AND F11.7 IU/5.9 IU = AUC11.7 IU/AUC5.9 IU = 1.12 (+/- 1.17) (P = 0.005), respectively. The 90% confidence intervals were contained within the limits of 0.80-1.25 accepted for bioequivalence. Geometric mean values (+/- geometric S.D.) of the relative observed maximum concentration, Cmax was for Cmax 5.9 IU/Cmax 4 IU = 1.04 (+/- 1.19) (P = 0.32), Cmax 11.7 IU/Cmax 4 IU = 1.24 (+/- 1.21) (P = 0.0002) and Cmax 11.7 IU/Cmax 5.9 IU = 1.19 (+/- 1.29) (P = 0.012). The median and the range values for the observed time to reach Cmax was tmax 5.9 IU/tmax 4 IU = 0.63 (0.04-1.00), tmax 11.7 IU/tmax 4 IU = 0.59 (0.06-1.0) and tmax 11.7 IU/tmax 5.9 IU = 0.90 (0.51-18.00). There were no significant differences in IGF-I, glucose and insulin profiles. Based on the upper limits of the 90% confidence intervals for relative AUC's the conclusion is that the three different preparations were bioequivalent.

Growth, growth hormone and final height after BMT. Possible recovery of irradiation-induced growth hormone insufficiency

The aim of the present study was to assess growth, final height, growth hormone (GH) secretion and growth factors after BMT including TBI in childhood. The median age of the 25 participants was 11.3 years at BMT, and a median of 7.5 years had elapsed since BMT. The median height standard deviation score (SDS) declined significantly from diagnosis until 4 years after BMT (n = 25, P = 0.015), and decreased 1.08 SDS from diagnosis until final height (n = 14, P = 0.030). Sitting height to standing height ratio was impaired, -0.64 SDS, P < 0.05. GH insufficiency was found in 32% at follow-up. Repeated assessments of GH production over the years indicated improvement in GH secretion in nine individuals. Evaluation of spontaneous 24-h GH secretion indicated a secretory pattern similar to controls, although the total amount of GH secreted was lower. Neither insulin-like growth factor-1 (IGF-1) nor IGF binding protein-3 (IGFBP-3) alone could be used as a marker of GH insufficiency. IGF-1 was low: -1.18 SDS; (P < 0.001). In conclusion, our study demonstrated the impact on growth, final height, body proportions, GH secretion and growth factors after BMT including TBI. We hypothesize that children who receive BMT at a younger age are more at risk of loss of final height and abnormal body proportions. Our data indicate that some improvement in GH production may occur over the years.

[Clinical consequences of intranasal insulin therapy in insulin-dependent diabetes mellitus]

Metabolic control, hypoglycaemia frequency and nasal mucosal physiology were evaluated in 31 insulin-dependent diabetics treated with intranasal insulin at mealtimes for one month and with subcutaneous fast-acting insulin for another month in a randomized crossover trial. During both periods the patients were treated with intermediate-acting insulin at bedtime. Six of the patients were withdrawn from the study during intranasal insulin therapy due to metabolic dysregulation. Insulin concentrations increased more rapidly and decreased more quickly during intranasal as compared with subcutaneous insulin administration. Metabolic control, assessed by haemoglobin A1c concentrations, deteriorated after intranasal as compared with subcutaneous insulin therapy. The bioavailability of intranasally applied insulin was low, since intranasal insulin doses were approximately 20 times higher than subcutaneous doses. The frequency of hypoglycemia was similar during intranasal and subcutaneous insulin therapy, and nasal mucosal physiology was unaffected after intranasal insulin. We conclude that due to low bioavailability and to a high rate of therapeutic failure, intranasal insulin treatment is not a realistic alternative to subcutaneous insulin injections at the present time.

Serum growth hormone-binding protein in obesity: effect of a short-term, very low calorie diet and diet-induced weight loss

GH-binding protein (GHBP) is increased in obesity. It is not known whether the increase in GHBP is reversible with weight loss or modulated by acute changes in nutritional intake. To address these questions, we measured GHBP in 18 obese subjects [body mass index (BMI), 40.9 +/- 1.1 kg/m2 (mean +/-SEM)] before and after an average weight loss of 30.3 +/- 4.6 kg and in 18 age- and sex matched normal subjects (BMI, 23.0 +/- 0.4 kg/m2) and studied the effects of a very low calorie diet over 4 days in 5 normal subjects and a subgroup of obese subjects before (n = 6) and after (n = 5) weight loss. GHBP was elevated in the obese subjects compared to levels in age- and sex-matched normal controls (1.48 +/- 0.1 vs. 0.53 +/- 0.1 nmol/L; P < 0.0001). GHBP was positively correlated to BMI and waist circumference (r = 0.71; P < 0.00001 and r = 0.73; P < 0.00001, respectively). In addition, GHBP was positively correlated to insulin as well as proinsulin levels (r = 0.60; P < 0.001 and r = 0.55; P < 0.001, respectively). After diet-induced massive weight loss, GHBP levels were restored to normal in obese subjects (BMI, 27.8 +/- 1.4 kg/m2). Multiple stepwise regression analysis revealed that changes in waist circumference and abdominal sagittal diameter during weight loss were the major determinants of and accounted for 54% of the fall in GHBP levels. Neither insulin nor proinsulin was an independent predictor. No changes were observed in GHBP in normal, obese, or reduced weight obese subjects after 4 days of a very low calorie diet, although mean insulin levels fell significantly in the normal subgroup as well as in the obese subgroup studied after weight loss. In summary, GHBP levels are elevated in obesity, are restored to normal by massive weight loss, and are unaffected by short term hypocaloric feeding. We conclude that GHBP may be regulated by the same or closely related factors that regulate fat mass and abdominal fat mass in particular, but not by insulin or acute changes in nutrition.

An unusual type of familial lipodystrophy

A mother and her daughter with a novel type of familial partial lipodystrophy were studied. Both had atrophy of fat in the face, chest, and upper and lower limbs and abdominal obesity caused by intraabdominal fat accumulation. The mother had severe insulin resistance and impaired glucose tolerance, whereas the daughter had normal glucose tolerance and normal insulin sensitivity. Both had metabolic rates about 30% above normal levels, but normal thyroid function and plasma lipids.

Collagen metabolism in obesity: the effect of weight loss

OBJECTIVE

To investigate the impact of obesity, fat distribution and weight loss on collagen turnover using serum concentrations of the carboxyterminal propeptide of type I procollagen (S-PICP) and the aminoterminal propeptide of type III pro-collagen (S-PIIINP) as markers for collagen turnover.

DESIGN

Blood samples were obtained once at baseline, and after 8 and 16 weeks of dietary treatment (5.0 MJ/day diet).

SETTING

Outpatient clinic of Hvidovre University Hospital.

MAIN OUTCOME MEASURES

S-PICP, S-PIIINP, fat distribution and weight loss.

RESULTS

S-PIIINP was associated with body weight (r = 0.37; P = 0.004), height (r = 0.27; P = 0.04), waist circumference (r = 0.35; P = 0.007), as well as with WHR (r = 0.33; P = 0.01) and was inversely correlated to age (r = -0.40; P = 0.002). Compared with randomly selected controls from a large pool of healthy volunteers, the obese patients had elevated S-PIIINP values before as well as during weight loss, whereas S-PICP levels were within the normal range and did not correlate with any anthropometric measures. The average weight loss after 16 weeks dietary treatment was 8.1 kg (s.d. = 0.8). S-PIIINP decreased during the 16 weeks of energy restriction (P < 0.05) and changes in S-PIIINP was correlated to body weight loss (r = 0.32; P < 0.05) and to changes in waist circumference (r = 0.34; P < 0.05) as well as changes in WHR (r = 0.30; P < 0.05).

CONCLUSION

S-PIIINP is elevated in obesity and associated with body fat distribution, suggesting an increased turnover of type III collagen related to obesity in general and to abdominal obesity in particular. S-PIIINP levels decreases during weight loss in obese subjects, whereas S-PICP levels seems un-related to obesity and weight loss.

Intranasal insulin therapy: the clinical realities

To evaluate metabolic control and safety parameters (hypoglycaemia frequency and nasal mucosa physiology), 31 insulin-dependent diabetic patients were treated with intranasal insulin at mealtimes for 1 month and with subcutaneous fast-acting insulin at meals for another month in an open, crossover randomized trial. During both treatment periods the patients were treated with intermediate-acting insulin at bedtime. Six of the patients were withdrawn from the study during intranasal insulin therapy due to metabolic dysregulation. Serum insulin concentrations increased more rapidly and decreased more quickly during intranasal as compared with subcutaneous insulin administration. Metabolic control deteriorated, as assessed by haemoglobin A1c concentrations, slightly but significantly after intranasal as compared with subcutaneous insulin therapy. The bioavailability of intranasally applied insulin was low, since intranasal insulin doses were approximately 20 times higher than subcutaneous doses. The frequency of hypoglycaemia was similar during intranasal and subcutaneous insulin therapy, and nasal mucosa physiology was unaffected after intranasal insulin. We conclude that due to low bioavailability and to a high rate of therapeutic failure, intranasal insulin treatment is not a realistic alternative to subcutaneous insulin injections at the present time.

Massive weight loss restores 24-hour growth hormone release profiles and serum insulin-like growth factor-I levels in obese subjects

In the present study, we 1) determined whether the impaired spontaneous 24-h GH secretion as well as the blunted GH response to provocative testing in obese subjects are persistent disorders or transient defects reversed with weight loss and 2) investigated 24-h urinary GH excretion and basal levels of insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP-3), as well as insulin in obese subjects before and after a massive weight loss. We studied 18 obese subjects (age, 26 +/- 1 yr; body mass index, 40.9 +/- 1.1 kg/m2); 18 normal age-, and sex-matched control subjects; and 9 reduced weight obese subjects after a diet-induced average weight loss of 30.3 +/- 4.6 kg. Twenty-four-hour spontaneous GH secretion was estimated by obtaining 3240 integrated 20-min blood samples using a constant blood withdrawal technique and computerized algorithms. Body composition was determined using anthropometric measurements and dual energy x-ray absorptiometry scanning (DXA). In the obese subjects, 24-h spontaneous GH release profiles and the GH responses to insulin-induced hypoglycemia and L-arginine as well as basal IGF-I levels and the IGF-I/IGFBP-3 molar ratio were decreased, whereas insulin levels were elevated compared to those in normal subjects. In obese subjects, 24-h spontaneous GH secretion and serum IGF-I levels were inversely related to abdominal fat (r = -0.67; P < 0.01) and percent body fat (r = -0.69; P < 0.01), respectively. The decreased 24-h spontaneous GH release profiles, the decreased GH responses to insulin-induced hypoglycemia and L-arginine, the decreased basal IGF-I levels and IGF-I/IGFBP-3 molar ratio, as well as the elevated insulin levels were returned to normal after a massive weight loss in the obese subjects. In conclusion, the present study has shown reversible defects in 24-h spontaneous GH release profiles, basal IGF-I levels, and the IGF-I/IGFBP-3 molar ratio in obese subjects. The recovery of the 24-h GH release points to an acquired transient defect rather than a persistent preexisting disorder.

Lack of stimulation of 24-hour growth hormone release by hypocaloric diet in obesity

Obesity is associated with a marked reduction in the spontaneous secretion of GH. To investigate the effect of acute alterations in calorie intake on GH release, 24-hr spontaneous GH release was measured during habitual calorie intake as well as during a short term, very low calorie diet (VLCD) in 6 obese subjects, 5 obese subjects after weight loss, and 5 normal, age- and sex-matched control subjects. Integrated 20-min samples were obtained over 24-h on two occasions in each subject using a constant blood withdrawal technique. In addition, basal levels of serum insulin-like growth factor-I (IGF-I), IGF-binding protein-1 (IGFBP-1), IGF-binding protein-3 (IGFBP-3), insulin, pro-insulin, and blood glucose were measured during habitual energy intake as well as during the hypocaloric diet. Twenty-four-hour GH release profiles and IGFBP-1 were decreased, and insulin as well as proinsulin levels were elevated in obese subjects compared to those in normal age- and sex-matched controls. No differences between obese subjects and normal controls were present regarding IGF-I, IGFBP-3, or IGF-I/IGFBP-3 molar ratio. In the last 24 h during the 96-h VLCD, an increase in 24-h GH release and basal IGFBP-1 levels and a decrease in basal insulin levels occurred in the normal controls, whereas no such changes were observed in the obese subjects. After caloric restriction 24-hr GH release, IGFBP-1 levels and insulin levels were similar in control subjects and obese subjects after weight loss. This suggests a reversible defect in GH release, rather than a persistent preexisting disorder. It is hypothesized that enhanced bioavailability of IGF-I, acting in concert with elevated proinsulin and insulin levels, may account for the lack of stimulation of 24-hr GH release by the hypocaloric diet in obese subjects. We conclude that the increase in 24-h spontaneous GH release and IGFBP-1 levels observed in normal subjects during the last 24 h of a 96-h VLCD is abolished in obese subjects. The lack of short term hypocaloric stimulation of spontaneous GH release may promote the retention of body fat and perpetuate the obese state.