Molecular and Translational Medicine - (Head Eugenia Carvalho)
Metabolism, Insulin Resistance and Complications - Research highlights:
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Mechanisms of insulin resistance, pathogenesis of type 2 diabetes and obesity
Signal transduction and cross talk pathways in the cardiovascular system
The adipocyte as a source and target for inflammation and atherosclerosis
The effects of glucocorticoids and immunosuppressive agents on insulin action and metabolism
The complications of diabetes
The view of the adipocyte as a passive reservoir for energy storage is no longer valid it is emerging as participant in regulating
physiologic and pathologic processes, including immunity and inflammation, as a secretory and endocrine organ, modulating
appetite, energy expenditure, insulin sensitivity, endocrine, reproductive systems and bone metabolism. It stores excess energy in
the form of lipids and is able to dramatically change its size in agreement with changing metabolic needs, with obesity as the result,
increasing in both adipocyte number and size. An excess of adipose tissue increases the risk for obesity, coronary artery disease,
hypertension, lipid abnormalities, type 2 diabetes and even cancer. The obese state has been characterized by a deregulation of the
adipose tissue that can cause a state of low-grade, chronic, systemic inflammation that can link both the metabolic and vascular
pathologies. Studies in healthy first-degree relatives of type 2 diabetic patients have shown that abdominal obesity, waist-hip ratio,
and fat cell size are important markers of insulin resistance and already show deregulated adipose tissue at the molecular level.
Better understanding of the mechanisms of
adipose tissue regulation and identification
Secretory Organ
Endocrine Gland
Inert Storage Depot
of the molecular basis of the deregulated
Brain
adipose tissue may provide new insights into
Fatty
Glucose
ANS
acids
the causes of insulin resistance, diabetes and
the associated complications.
Fed
Leptin
Triglyceride
• Mechanisms of insulin resistance. We
have been interested in the study of the
Fasted
homeostasis model assessment (HOMA) and
Liver
Fatty
the quantitative insulin sensitivity check
FFA, Cytokines,
Glycerol
acids
index (QUICKI) as markers of insulin
TNF-
-1, ILT cell
Gonad
resistance. Serum samples from 5711
6,
Pancre
Adipokines, Adipsin
subjects were collected for measurements of
Muscle
as
Leptin, Adiponectin,
glucose, cholesterol, and triglycerides to
Resistin, etc.
assess the prevalence of impaired glucose
tolerance and diabetes. We found that 11% of the population is hyperglycemic, and that these models can be used to assess insulin
sensitivity in the population at large. In addition, we studied glycogen metabolism in primary adipocytes. Our results demonstrate
that the standard method of glycogen extraction and isolation does not completely exclude glucose. With tissues that contain high
glycogen levels such as liver and muscle, a residual amount of glucose may not significantly alter the estimates of glycogen
concentrations. However, with adipocytes and other cells with low glycogen levels, the presence of a residual amount of glucose in
the isolated glycogen preparation can inflate the estimate of glycogen concentration. Glucose oxidase treatment provides a
convenient and quantitative means for scavenging residual glucose before glycogen is hydrolyzed
• The role of neuropeptides in wound healing in diabetes. Impaired wound healing is a major clinical problem in diabetes.
Peripheral neuropathy is a major contributing factor to tissue ischemia. We studied wound healing in a model that mimics the
human condition by using NK-1R deficient mice and CJ, the NK-1R antagonist. The NK-1R deficiency was associated with 17%
reduction in skin oxygenation at baseline and 24% ten days after wound induction. These mice showed a significant reduction of the
wound area. Wound area reduction was impaired by 25% in the CJ treated wild-type mice when compared to the saline-treated
mice. These results indicate that SP plays a crucial role in wound healing and that a major pathway is the reduction of tissue
oxygenation. Manipulation of the SP pathway may prove a potential new therapeutic approach in treating diabetic foot ulceration.
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Cs
In
A
su
10
lin
a
Cs
A
10
Cs
In
A
su
30
lin
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A
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l
In
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sa
Fold increase
600
• Role of glucocorticoids (GCs) and immunosuppressive agents (IA) in the impairment
of glucose and lipid metabolism in the metabolic syndrome. The induction of insulin
resistance by GCs and IA is a process that is still poorly understood. The main hypothesis is
that GCs and IA are associated with insulin resistance, causing major metabolic chages in
adipocytes leading to impaired insulin sensitivity. If IA induce changes in whole body
glucose and lipid metabolism leading to abnormal insulin signaling and the accumulation of
lipid in skeletal muscle, this is likely to contribute to the development of whole-body
insulin resistance, glucose intolerance and fasting hyperglycemia.
Our preliminary results indicate that the treatment of isolated rat fat cells with IA causes a significant decrease in the insulin
stimulated glucose uptake. Glucose uptake was measured for 30 minutes in the presence of insulin (6.9 nM). As shown with cells
treated with CsA, in the adjacent picture, insulin stimulated glucose uptake was 7 fold increased in relation to basal uptake. When
cells were treated with cyclosporin A (CsA) at 10 and 30 uM concentrations in the presence of insulin, the insulin stimulated
glucose uptake was decreased by 35-45% (*p≤0.05 different from basal, #p≤0.05 different from insulin). Similar results were
obtained for cells treated with tacrolimus (FK), Prednisolone (P) and Dexamethasone (D). These results demonstrate that both CsA,
FK, P and D can inhibit insulin stimulated glucose uptake ex-vivo, promoting insulin resistance and causing major metabolic chages
in adipocytes. Increased knowledge on the mechanisms responsible for the development of insulin resistance caused by GCs and
IA is of great importance to find new and more efficient treatments for post-transplant diabetes. Identification of new
biomarkers would be valuable in the treatment of insulin resistance and vascular complications.
Group members:
Ermelindo Leal, Post-Doc
Maria Joao Pereira, PhD Student
Sara Goncalves, PhD Student
Ana Tellechea, PhD Student
Marta Passadouro, Technician
Joana Pedro, Technician
Alice Melao, Technician
Key references
 Carvalho E, Wu S, Pradhan L, Kokkotou, E, and Veves A. The role of substance P in wound healing in diabetes.
Manuscrit in preparation. Oral presentation at ADA 2008 242-OR.

Pereira MJ, Mergulhão AP, Carvalho E and Aureliano M. HOMA and QUICKI as markers for insulin resistance in the
south of Portugal. in preparation.

Nunes PM, Carvalho E, Jones JG. Elimination of glucose contamination from adipocyte glycogen extracts. Carbohydr
Res. 2008 343(9):1486-1489
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Karagiannides I, Torres D, Tseng Y-H, Bowe C, Carvalho E, Espinoza D, Pothoulakis C and Kokkotou E. Substance P as
a novel anti-obesity target. Gastroenterology. 2008 134(3):747-55.

Carvalho E. (2006) O adipócito: vítima ou vilão. Endoc Metab & Nutrição. 15(5):249-251

Carvalho E, Kotani K, Peroni OD, Kahn BB.Adipose-specific overexpression of GLUT4 reverses insulin resistance and
diabetes in mice lacking GLUT4 selectively in muscle. Am J Physiol Endocrinol Metab. 2005, 289(4):E551-61
Funding Sources:
Foundation for Science and Technology POCTI/SAU-MMO/57598/2004 (FCT2006-2009)
European Foundation for the Study of Diabetes (EFSD/JDRF/Novo Nordisk) European Programme in Type 1 Diabetes Research
(2009-2010)