CAPOT: A flexible rapid assessment model to estimate local deposition of fish cage farm wastes.

The Cage Aquaculture Particulate Output and Transport (CAPOT) model is an easy to use and flexible farm-scale model that can rapidly estimate particulate waste deposition from fish cage production. This paper describes and tests the model and demonstrates its use for Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua). The spreadsheet-based model gives outputs for waste distribution in a variety of spatial modelling software formats, used for further analysis. The model was tested at a commercial Atlantic cod farm and commercial Atlantic salmon farm under full production conditions. Sediment trap data showed predictions, using actual recorded feed and biomass data, to be 96% (±36%) similar for Atlantic cod beyond 5 m from the cage edge, giving a satisfactory estimate of local benthic impact in the vicinity of the farm. For Atlantic salmon, using estimated production biomass and FCR (Feed Conversion Ratio) to calculate feed input, the model overestimated wastes directly beneath the cages (120% ± 148%) and underestimated beyond 5 m from the cage edge, being 48% (±42%) similar to sediment trap data. CAPOT is a suitable initial, rapid assessment model to give an overview of potential impact of particulate waste from new or expanded fish cage farms, with little operator expertise by a wide range of stakeholders.

Variability in parathyroid hormone assays confounds clinical practice in chronic kidney disease patients.

BACKGROUND: Intact parathyroid hormone (iPTH) measurements are used to guide therapy in renal patients, but variability in results can occur depending on the assay used. This study has investigated iPTH assay variation in North West England and paired data with regional audit data to determine clinical relevance of assay variability. METHODS: Thirty-seven haemodialysis patients had blood taken (EDTA plasma, and serum), and samples were processed at 17 laboratories that analyse iPTH for North West dialysis patients. Correction factors were calculated and applied to the iPTH assay results to enable direct comparisons. These correction factors were also applied to Regional Audit data to determine if iPTH assay variability explains the variation in unit performance in achieving PTH targets. RESULTS: The iPTH results from the 37 patients were significantly different when either analysed by different assays and/or different laboratories (P < 0.001). The Abbott Architect method consistently produced the highest iPTH results. Of the 37 patients, between 49% and 65% would achieve the Kidney Disease: Improving Global Outcomes (KDIGO) iPTH target depending on the assay used. When results were adjusted using correction factors, 21% of the patients would require a change of management according to guidelines. Data from all haemodialysis units submitted for the regional audit were adjusted to the Roche assay and this led to a small change in achievement of KDIGO iPTH targets in individual units when compared to each other. CONCLUSIONS: A combination of iPTH assay variability and diversity in clinical management leads to variation in achieving iPTH targets. Both need to be improved and/or standardized to improve patient care.

Insulin-like growth factor-II and insulin-like growth factor binding protein-2 prospectively predict longitudinal elevation of HDL-cholesterol in type 2 diabetes.

INTRODUCTION: Associations of insulin-like growth factor-II (IGF-II) and insulin-like growth factor binding protein-2 (IGFBP-2) with cardiovascular risk have been inadequately studied. We hypothesized that IGF-II and IGFBP-2 associate with longitudinal trends in lipid profiles in type 2 diabetes patients. SUBJECTS AND METHODS: Four hundred and eighty nine subjects with type 2 diabetes (age 27-87 years) from the Salford Diabetes Cohort were studied. Longitudinal clinical information was extracted for an eight-year period (2002-2009) from an integrated electronic dataset of primary care and hospital data. RESULTS: There were 294 male subjects and mean age was 62.9 years. At baseline, IGF-II concentration was 602 ng/mL. HDL cholesterol at baseline was associated with log-IGF-II concentration in a model adjusted for age, gender, baseline body-mass index (BMI), estimated glomerular filtration rate (eGFR) and lipid-lowering therapy. IGFBP-1 and IGFBP-2 were associated with high HDL-cholesterol. A higher circulating IGF-II concentration at baseline was also associated with longitudinal increase in HDL-cholesterol in mixed-effects regression analyses independent of IGF-I, IGFBP-1, IGFBP-2, IGFBP-3, age, gender, eGFR, BMI and lipid-lowering therapy. Log-transformed baseline concentrations of IGFBP-1 and IGFBP-2 were also associated with longitudinal elevation in HDL-cholesterol. No association was observed for IGF-II or IGFBP-2 with longitudinal LDL cholesterol trends. CONCLUSION: Our analyses based on 'real world' data demonstrate that higher baseline IGF-II and IGFBP-2 predict increased HDL concentration over time, implicating IGF-II in modulation of circulating HDL-cholesterol concentrations.

Atorvastatin administration is associated with dose-related changes in IGF bioavailability.

OBJECTIVE: IGF levels, their binding proteins (IGFBPs) and high-dose statin therapy have been linked to the development of diabetes. We aimed to identify whether atorvastatin caused dose-related changes in IGF proteins. DESIGN AND METHODS: We measured IGF1, IGF2, IGFBP1 and IGFBP3 concentrations at baseline, 6 and 12 months in Protection Against Nephropathy in Diabetes with Atorvastatin trial participants with type 2 diabetes randomised to 10 mg (n=59) vs 80 mg (n=60) of atorvastatin (n=119; mean (S.D.): age 64 (10) years; 83% male; HbA1c 61 (10) mmol/mol; blood pressure 131/73 mmHg). RESULTS: Atorvastatin was associated with overall reductions in circulating IGF1, IGF2 and IGFBP3 concentrations (P<0.05 for all changes). The adjusted mean (95% CI) between-group differences that indicate dose-related changes in IGF proteins were not significant for IGF1: -3 (-21 to 14) ng/ml; IGF2: -23 (-65 to 18) ng/ml and IGFBP3: -0.34 (-0.71 to 0.03) µg/ml, negative values indicating numerically greater lowering with high dose. The IGFBP1 concentration did not change with atorvastatin therapy overall but the adjusted mean (95% CI) between-group difference indicating a dose-related change in log IGFBP1 was highly significant -0.41 (-0.69 to 0.13, P=0.004). CONCLUSION: IGF1, IGF2 and IGFBP3 concentrations decreased following atorvastatin therapy. A differential effect of low- vs high-dose atorvastatin on IGFBP1 concentrations was observed with likely implications for IGF bioavailability. The dose-related differential impact of atorvastatin treatment on concentration of IGF proteins merits investigation as a mechanism to explain the worsening of glucose tolerance with statin therapy.

IGFBP2 is a biomarker for predicting longitudinal deterioration in renal function in type 2 diabetes.

OBJECTIVE: Insulin-like growth factors are implicated in the development of diabetic nephropathy. IGF-binding protein 2 (IGFBP2) and IGF2 are expressed in the kidney, but their associations with diabetic nephropathy are unclear. We therefore tested the hypothesis that circulating levels of IGF2 and IGFBP2 predict longitudinal renal function in individuals with type 2 diabetes. DESIGN AND METHODS: IGFBP2 and IGF2 measurements were performed in 436 individuals (263 males) with type 2 diabetes. Linear mixed-effect regression analysis was used to model the relationship between plasma IGFBP2 concentration and longitudinal changes in estimated glomerular filtration rate (eGFR) over an 8-year period. Analyses were also performed for IGF1, IGF2, IGFBP1 and IGFBP3 concentrations as predictors of longitudinal renal outcomes. RESULTS: High IGFBP2 concentration at baseline was associated with a decreased eGFR over an 8-year period (ß=-0.02, (95% confidence interval -0.03 to -0.01), P<0.001). High IGFBP1, IGFBP2 and IGFBP3 were also associated with low baseline eGFR concentration. CONCLUSION: This study demonstrates that IGFBP2 is a predictor of longitudinal deterioration of renal function in type 2 diabetes.

Mutations in the amino-terminal region of proopiomelanocortin (POMC) in patients with early-onset obesity impair POMC sorting to the regulated secretory pathway.

CONTEXT: Mutations in the proopiomelanocortin (POMC) gene that impair the synthesis or structure of POMC-derived peptides predispose to human obesity. OBJECTIVE: Our objective was to identify and characterize novel mutations in the POMC gene found in patients with early-onset obesity. DESIGN AND PATIENTS: The POMC gene was screened in 500 patients with severe early-onset obesity. The biosynthesis, processing, sorting, and secretion of wild-type POMC and two newly identified POMC mutants was studied using metabolic labeling, Western blotting, and immunoassay analysis of lysates and conditioned media of transiently transfected beta-TC3 cells. RESULTS: Two novel heterozygous missense mutations in POMC (C28F and L37F) were identified in unrelated probands with early-onset obesity and their overweight or obese family members. Both mutations lie in a region of the N terminus of POMC that has been suggested to be involved in its sorting to the regulated secretory pathway. Metabolic labeling studies indicate that whereas the mutations do not reduce intracellular levels of POMC, both mutations (C28F>L37F) impair the ability of POMC to be processed to generate bioactive products. Studies of the secretion of POMC products suggest, particularly with C28F, that the impaired propeptide processing of these mutations results, at least in part, from a mistargeting of mutant POMC to the constitutive rather than the regulated secretory pathway. CONCLUSION: These mutations in patients with early-onset obesity represent a novel molecular mechanism of human POMC deficiency whereby naturally occurring mutations in its N-terminal sequence impair the ability of POMC to enter the trafficking pathway in which serial propeptide processing normally occurs.

Proopiomelanocortin (POMC), the ACTH/melanocortin precursor, is secreted by human epidermal keratinocytes and melanocytes and stimulates melanogenesis.

Proopiomelanocortin (POMC) can be processed to ACTH and melanocortin peptides. However, processing is incomplete in some tissues, leading to POMC precursor release from cells. This study examined POMC processing in human skin and the effect of POMC on the melanocortin-1 receptor (MC-1R) and melanocyte regulation. POMC was secreted by both human epidermal keratinocytes (from 5 healthy donors) and matched epidermal melanocytes in culture. Much lower levels of alpha-MSH were secreted and only by the keratinocytes. Neither cell type released ACTH. Cell extracts contained significantly more ACTH than POMC, and alpha-MSH was detected only in keratinocytes. Nevertheless, the POMC processing components, prohormone convertases 1, 2 and regulatory protein 7B2, were detected in melanocytes and keratinocytes. In contrast, hair follicle melanocytes secreted both POMC and alpha-MSH, and this was enhanced in response to corticotrophin-releasing hormone (CRH) acting primarily through the CRH receptor 1. In cells stably transfected with the MC-1R, POMC stimulated cAMP, albeit with a lower potency than ACTH, alpha-MSH, and beta-MSH. POMC also increased melanogenesis and dendricity in human pigment cells. This release of POMC from skin cells and its functional activity at the MC-1R highlight the importance of POMC processing as a key regulatory event in the skin.

Proopiomelanocortin-derived peptides in rat cerebrospinal fluid and hypothalamic extracts: evidence that secretion is regulated with respect to energy balance.

Regulation of proopiomelanocortin (POMC) is an important means of controlling the central melanocortin system. It has never been established whether the spectrum of POMC-derived peptides synthesized and secreted from the hypothalamus is altered in response to changes in energy homeostasis in vivo. To monitor secretion, we analyzed peptide content of rat cerebrospinal fluid. Strikingly, both the POMC precursor and ACTH were readily detected. Moreover, levels of both were lower in samples from obese Zucker rats (fa/fa) vs. lean Zucker rats (+/+, fa/+) and from fasted vs. fed rats, whereas alpha MSH could not be detected. POMC levels were also decreased in hypothalamic extracts from obese and fasted animals. In contrast, despite being the most predominant peptide in extracts, alpha MSH levels were not significantly changed in any of the rat models. The ratio of precursor to derived peptides in cerebrospinal fluid was significantly higher in obese vs. lean and fed vs. fasted rats, indicating that secretion of POMC-derived peptides is differentially down-regulated during negative energy balance. In contrast to peptide analysis, we found that POMC gene expression was not significantly decreased in fasted rat hypothalami. We conclude that regulation of peptide secretion is an important mechanism by which the POMC system is controlled.

Characterisation of ACTH related peptides in ectopic Cushing's syndrome.

Adrenocorticotrophin (ACTH) is derived by cleavage from the precursor, pro-opiomelanocortin (POMC), and depending on the degree of processing by the tissue or tumor, there is the potential for a number of ACTH-related peptides to be secreted from POMC expressing cells. Previous chromatographic approaches have indicated the presence of high molecular weight forms of ACTH in the human peripheral circulation. However a quantitative assessment of the degree of processing requires two-site immunoradiometric assays which distinguish ACTH precursors and ACTH. Using this approach, we have previously identified the precursors of ACTH (POMC and proACTH) in the circulation of normal subjects in the range 5-40 pmol/l, which suggests that processing in the normal pituitary cell is incomplete. This study aimed to examine the extent of POMC processing by tumors that give rise to Cushing's Syndrome as a means of evaluating its usefulness as a diagnostic marker. In a retrospective analysis of 86 patients with Cushing's Syndrome, 34/35 patients with pituitary tumors had low levels of ACTH precursors (below 100 pmol/l) and the mean ratio of ACTH precursors:ACTH was 5:1 which indicates that these tumors do process POMC to ACTH relatively efficiently. In ectopic Cushing's Syndrome, it is unlikely that the extra-pituitary tumor cells, process POMC as efficiently. Therefore increased prevalence of ACTH precursors in the circulation would be expected and this was substantiated by the large excess of ACTH precursors (139-18,000 pmol/l) in the circulation of the 51 patients with the ectopic ACTH Syndrome. The diagnostic accuracy of the measurement of ACTH precursors was then prospectively compared with a group of 62 patients undergoing the current "gold standard" test of inferior petrosal sinus sampling (IPSS). All those patients with ACTH precursors below a diagnostic cut-off of 100 pmol/l were subsequently shown to have pituitary tumors, whereas levels of >100 pmol/l were seen in the four patients with ectopic tumors. In comparison the IPSS had a specificity of 100% but a sensitivity of 93% and for these false negative results the ACTH precursors proved diagnostically useful. Therefore measurement of ACTH precursors offers a simple non-invasive diagnostic test for the differential diagnosis of Cushing's Syndrome which compares favourably with IPSS.