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Morgan J.L.L.,NASA | Zwart S.R.,NASA | Heer M.,University of Bonn | Heer M.,NASA | And 4 more authors.
Journal of Applied Physiology | Year: 2012

Bone metabolism and nutritional status during 30-day headdown- tilt bed rest. J Appl Physiol 113: 1519-1529, 2012. First published September 20, 2012; doi:10.1152/japplphysiol.01064.2012.-Bed rest studies provide an important tool for modeling physiological changes that occur during spaceflight. Markers of bone metabolism and nutritional status were evaluated in 12 subjects (8 men, 4 women; ages 25-49 yr) who participated in a 30-day -6° head-down-tilt dietcontrolled bed rest study. Blood and urine samples were collected twice before, once a week during, and twice after bed rest. Data were analyzed using a mixed-effects linear regression with a priori contrasts comparing all days to the second week of the pre-bed rest acclimation period. During bed rest, all urinary markers of bone resorption increased ̃20% (P < 0.001), and serum parathyroid hormone decreased ̃25% (P < 0.001). Unlike longer (̃60 days) bed rest studies, neither markers of oxidative damage nor iron status indexes changed over the 30 days of bed rest. Urinary oxalate excretion decreased ̃20% during bed rest (P < 0.001) and correlated inversely with urinary calcium (R = -0.18, P < 0.02). These data provide a broad overview of the biochemistry associated with shortduration bed rest studies and provide an impetus for using shorter studies to save time and costs wherever possible. For some effects related to bone biochemistry, short-duration bed rest will fulfill the scientific requirements to simulate spaceflight, but other effects (antioxidants/ oxidative damage, iron status) do not manifest until subjects are in bed longer, in which case longer studies or other analogs may be needed. Regardless, maximizing research funding and opportunities will be critical to enable the next steps in space exploration. Copyright © 2012 the American Physiological Society. Source


Plum L.,Columbia University | Plum L.,Profil Institute for Metabolic Research | Lin H.V.,Columbia University | Lin H.V.,Lilly China Research and Development Center | And 3 more authors.
PLoS ONE | Year: 2012

Insulin receptor (InsR) signaling through transcription factor FoxO1 is important in the development of hypothalamic neuron feeding circuits, but knowledge about underlying mechanisms is limited. To investigate the role of InsR/FoxO1 signaling in the development and maintenance of these circuits, we surveyed the pool of hypothalamic neurons expressing Pomc mRNA in different mouse models of impaired hypothalamic InsR signaling. InsR ablation in the entire hypothalamus did not affect Pomc-neuron number at birth, but resulted in a 25% increase, most notably in the middle arcuate nucleus region, in young adults. Selective restoration of InsR expression in POMC neurons in these mice partly reversed the abnormality, resulting in a 10% decrease compared to age-matched controls. To establish whether FoxO1 signaling plays a role in this process, we examined POMC neuron number in mice with POMC-specific deletion of FoxO1, and detected a 23% decrease in age-matched animals, consistent with a cell-autonomous role of InsR/FoxO1 signaling in regulating POMC neuron number, distinct from its established role to activate Pomc transcription. These changes in Pomc cells occurred in the absence of marked changes in humoral factors or hypothalamic NPY neurons. © 2012 Plum et al. Source


Stirban A.,Profil Institute for Metabolic Research
Current diabetes reports | Year: 2014

Microvascular dysfunction in diabetes plays a crucial role in the development of diabetic complications. The skin, as one of the most accessible organs, serves as a model for the investigation of microvascular dysfunction. Several non-invasive, mostly laser-Doppler-based methods have been developed lately to assess microvascular function in the skin. Microvascular functional changes occur even in the prediabetic state and become more complex with overt diabetes, being exacerbated by the presence of peripheral and/or autonomic diabetic neuropathy. The present article aims at shedding light on the implication of endothelial and neurovascular dysfunction in microvascular changes in diabetes, highlighting the contribution of different forms of diabetic neuropathy. Source


Meier J.J.,Ruhr University Bochum | Pennartz C.,Ruhr University Bochum | Schenker N.,Ruhr University Bochum | Menge B.A.,Ruhr University Bochum | And 4 more authors.
Diabetes, Obesity and Metabolism | Year: 2013

Aim: Postprandial insulin pulsatility is impaired in patients with type 2 diabetes, but the effects of exogenous insulin therapy on pulsatile insulin secretion are not known. We addressed, whether pulsatile insulin secretion is related to glycaemic control, whether basal insulin supplementation increases postprandial insulin secretion, and if so, is this accomplished by a specific improvement in pulsatile insulin secretion? Methods: Fourteen patients with type 2 diabetes underwent a mixed meal test before and after an 8-week treatment period with insulin glargine. Glucose, insulin and C-peptide levels were measured, and insulin pulsatility was determined by deconvolution analysis. Results: Insulin treatment lowered fasting glycaemia from 179.6±7.5mg/dl to 117.6±6.5mg/dl (p<0.001). Postprandial insulin and C-peptide levels increased significantly after the treatment period (p<0.0001). The total calculated insulin secretion rate increased with insulin treatment (p=0.0039), with non-significant increases in both pulsatile and non-pulsatile insulin secretion. Insulin pulse frequency was unchanged by the intervention. There was an inverse relationship between fasting and postprandial glycaemia and insulin pulse mass (r2=0.51 and 0.56, respectively), whereas non-pulsatile insulin secretion was unrelated to either fasting or postprandial glucose concentrations (r2=0.0073 and 0.031). Conclusions: Hyperglycaemia in type 2 diabetes is associated with a reduction in postprandial insulin secretion, specifically through a reduction in insulin pulsatility. Reducing chronic hyperglycaemia by basal insulin therapy enhances endogenous β-cell function in the postprandial state. These data support the use of basal insulin regimens in the pharmacotherapy of overtly hyperglycaemic patients with type 2 diabetes. © 2012 Blackwell Publishing Ltd. Source


Martin S.,Heinrich Heine University Dusseldorf | Herder C.,Heinrich Heine University Dusseldorf | Schloot N.C.,Heinrich Heine University Dusseldorf | Schloot N.C.,University Hospital | And 4 more authors.
PLoS ONE | Year: 2011

Background: Recent evidence suggests that the lipid-lowering agent atorvastatin is also a potent immunomodulator. The aim of this study was to investigate the possible effect of atorvastatin on the decline of residual beta cell function in recent-onset type 1 diabetes. Methods and Findings: The randomised placebo-controlled Diabetes and Atorvastatin (DIATOR) Trial included 89 patients with newly diagnosed type 1 diabetes and islet autoantibodies (mean age 30 years, 40% females), in 12 centres in Germany. Patients received placebo or 80 mg/d atorvastatin for 18 months. As primary outcome stimulated serum C-peptide levels were determined 90 min after a standardized liquid mixed meal. An intent-to-treat analysis was performed. Fasting and stimulated C-peptide levels were not significantly different between groups at 18 months. However, median fasting serum C-peptide levels dropped from baseline to 12 and 18 months in the placebo group (from 0.34 to 0.23 and 0.20 nmol/l, p<0.001) versus a nonsignificant decline in the atorvastatin group (from 0.34 to 0.27 and 0.30 nmol/l, ns). Median stimulated C-peptide concentrations declined between baseline and 12 months (placebo from 0.89 to 0.71 nmol/l, atorvastatin from 0.88 to 0.73 nmol/l, p<0.01 each) followed by a major loss by month 18 in the placebo group (to 0.48 nmol/l, p = 0.047) but not in the atorvastatin group (to 0.71 nmol/l, ns). Median levels of total cholesterol and C-reactive protein decreased in the atorvastatin group only (p<0.001 and p = 0.04). Metabolic control was similar between groups. Conclusions: Atorvastatin treatment did not significantly preserve beta cell function although there may have been a slower decline of beta-cell function which merits further study. Trial Registration: ClinicalTrials.gov NCT00974740. © 2011 Martin et al. Source

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