Current Search:   Kyriazis, George (x)

View All Items

  • CSV Spreadsheet
(1 - 2 of 2)
THE EFFECTS OF A SINGLE EXERCISE BOUT ON PLASMA LEPTIN CONCENTRATION IN OBESE MALES
Title
THE EFFECTS OF A SINGLE EXERCISE BOUT ON PLASMA LEPTIN CONCENTRATION IN OBESE MALES.
Creator
Kyriazis, George, Angelopoulos, Theodore, University of Central Florida
Abstract / Description
Recent findings suggest that leptin may be regulated in response to abrupt changes in energy homeostasis. Therefore, it is conceivable that transient changes in energy balance induced by exercise may also regulate leptin synthesis and secretion. As such, we hypothesized that acute increases energy expenditure (i.e. exercise), may regulate leptin concentrations in obese individuals. Fifteen healthy obese males underwent either a single exercise session of moderate intensity (58.4 % ± 4.0 of...
Show moreRecent findings suggest that leptin may be regulated in response to abrupt changes in energy homeostasis. Therefore, it is conceivable that transient changes in energy balance induced by exercise may also regulate leptin synthesis and secretion. As such, we hypothesized that acute increases energy expenditure (i.e. exercise), may regulate leptin concentrations in obese individuals. Fifteen healthy obese males underwent either a single exercise session of moderate intensity (58.4 % ± 4.0 of VO2max) for 60 min (n=8), or served as controls (n=7). The exercise session elicited an energy expenditure of 567±80 Kcal. No significant changes in plasma leptin (pre 23.5± 30.2; post 24.3± 34.3; 24h-post 34.9± 66.6; 48h-post 33.8±64.0 ng/ml), or insulin levels (pre 16.1± 9.2 vs. post 8.1± 9.1; 24h-post 14.3± 9.9; 48h-post 13.8± 10.2 ?U/ml) were detected immediately after the intervention. Baseline plasma leptin levels were positively correlated with BMI (r=0.65; p<0.01), body weight (r=0.64; p<0.01), % body fat (r=0.90; p<0.01) and were negatively correlated with VO2max (r=-0.82; p<0.01). The results of the present study suggest that acute exercise of moderate intensity and duration may not affect leptin concentration.
Show less
Date Issued
2005
Identifier
CFE0000508, ucf:46459
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000508
THE ENDOCYTIC PROTEIN NUMB REGULATES APP METABOLISM AND NOTCH SIGNALING: IMPLICATIONS FOR ALZHEIMER&amp;#39;S DISEASE
Title
THE ENDOCYTIC PROTEIN NUMB REGULATES APP METABOLISM AND NOTCH SIGNALING: IMPLICATIONS FOR ALZHEIMER'S DISEASE.
Creator
Kyriazis, George, Chan, Sic, University of Central Florida
Abstract / Description
Increased production of amyloid beta (A-beta) peptide, via altered proteolytic cleavage of amyloid protein precursor (APP), and abnormalities in neuronal calcium homeostasis play central roles in the pathogenesis of Alzheimer's disease (AD). Notch1, a membrane receptor that controls cell fate decisions during development of the nervous system, has been linked to AD because it is a substrate for the gamma-secretase protein complex in which mutations cause early-onset inherited AD. Numb is...
Show moreIncreased production of amyloid beta (A-beta) peptide, via altered proteolytic cleavage of amyloid protein precursor (APP), and abnormalities in neuronal calcium homeostasis play central roles in the pathogenesis of Alzheimer's disease (AD). Notch1, a membrane receptor that controls cell fate decisions during development of the nervous system, has been linked to AD because it is a substrate for the gamma-secretase protein complex in which mutations cause early-onset inherited AD. Numb is an evolutionarily conserved endocytic adapter involved in the internalization of transmembrane receptors. Mammals produce four Numb isoforms that differ in two functional domains, a phosphotyrosine-binding domain (PTB) and a proline-rich region (PRR). Recent studies showed that the PTB domain of Numb interacts with the cytoplasmic tails of APP and Notch but the functional relevance of these interactions with respect to AD pathogenesis is not clear. In the current studies, we proposed to investigate the biological consequences of the interaction of the Numb proteins with APP and Notch in neural cells stably overexpressing each of the four human Numb proteins. In the first part of our studies, we found that expression of the Numb isoforms lacking the insert in the PTB (SPTB-Numb) caused the abnormal accumulation of cellular APP in the early endosomes, and increased the levels of C-terminal APP fragments and A-beta. By contrast, expression of the Numb isoforms with the insert in PTB (LPTB-Numb) leads to the depletion of cellular APP and coincides with significantly lower production of APP derivatives and A-beta. The contrasting effects of the Numb isoforms on APP metabolism were not attributed to differences in the expression of APP nor the activities of the various APP-processing secretases. In the second part of our studies, we found that expression of SPTB-Numb protein enhances neuronal vulnerability to serum deprivation-induced cell death by a mechanism involving the dysregulation of cellular calcium homeostasis. Neural cells expressing SPTB-Numb exhibited enhanced Notch activity, which markedly upregulated the expression of transient receptor potential canonical 6 (TRPC6) channels enhancing calcium entry in response to store depletion. We also found that serum deprivation increased TRPC6 expression, mediating the serum deprivation-induced death in neural cells. Interestingly, expression of LPTB-Numb protein suppressed serum deprivation-induced activation of Notch and the subsequent upregulation of TRPC6 and cell death. Finally, we showed that the Numb proteins differentially impact Notch activation by altering the endocytic trafficking and processing of Notch. Taken together, these studies demonstrate that aberrant expression of the Numb proteins may influence APP metabolism and Notch-mediated cellular responses to injury by altering their endocytic trafficking and processing.
Show less
Date Issued
2008
Identifier
CFE0002233, ucf:47917
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002233