Experimental Diabetology

In the Laboratory of Experimental Diabetology, research activities are mainly focused on the cellular and molecular mechanisms underlying development of long-term complications of diabetes mellitus, and on the potential pharmacologic prevention and treatment of these conditions. In the Lab, expertise from multiple disciplines converge, including clinical medicine and basic research methods.

Worldwide, diabetes mellitus is progressively growing with epidemic diffusion. Its prevalence reaches 5-7% of the general population in Western countries, and is even higher in the developing world. Importantly, diabetes is associated with a shortened life expectancy. Diabetes develops as a consequence of a complex interplay between genes and environment. The metabolic alterations observed in diabetes (hyperglycemia, radical species overproduction, etc.) may induce the appearance and progressions of chronic complications within several organs, including the arteries, heart, kidneys, nerves and eyes. The ongoing research projects of this lab are specifically devoted to:

i) assessing the role of both mesenchymal and hemopoietic stem cells in the long-term diabetic complications, and to verify possible pharmacologic modulation of these cells to interrupt the pathologic processes leading to diabetic complications;

ii) determining the pathophysiological contribution of exaggerated oxidative stress in the glucometabolic regulation and its role in the progression of both macro- and microvascular complications, such as vascular disease and diabetic wounds;

iii) evaluating the significance and mechanisms of endothelial dysfunction in relation to insulin resistance and its associated metabolic abnormalities, such as arterial hypertension, dyslipidemia, and obesity;

iv) defining the relationships between longevity-associated genes, metabolic disturbances, and long-term diabetic complications. We aim to understand why diabetes shortens life span and how to circumvent the pathological processes leading to this sort of "precocious ageing".

The specific commitment of this Lab is to integrate basic science activities with clinical activities and observations, thus creating a unique environment, ideal to provide significant advancement in the field, through approaches of "translational medicine". The group comprises a set of medical doctors, research fellows, as well as lab personnel with extensive experience in cell culture, tissue analysis, and animal models of disease.

Specific Aims and Results

In the last 10 years our group has achieved important results in the following research areas.

•  We have extensively characterized alterations of bone marrow-derived progenitor/stem cells in vitro as well as in vivo in humans and animals with diabetes. The endothelial progenitor cell (EPCs) population is indeed believed to represent a determinant of vascular health and their alteration in the setting of diabetes is likely to have important implications. We have related the number and function of EPCs to development of long-term diabetic cardiovascular complications. These studies have allowed to define a new model for the development of both micro- and macrovascular long term complications, that emphasizes the crucial role of the progressive shortage of bone-marrow derived stem cells, a condition, this, similar to that observed in the ageing process. We have also identified some pharmacologic approaches able to restore the stem cell population. We have identified some new clinical markers of diabetic complications. Future scopes are devoted to the study of further potential molecular mechanisms and therapeutic implications. The use of new animal models will allow to further assess the regulation of vascular progenitor cells in the presence of diabetes. We are currently moving to consider the biology of circulating progenitor cells from a wider pathophysiological perspective, taking into account the potential roles of these cells in the cardiovascular system, through differentiation into pro-calcific cells and smooth muscle cells. Application of our knowledge on progenitor cell shortage in diabetes is close to identification of clinical application and therapies.

•  We have identified new relationships between hyperglycemia and the exaggerated production of reactive oxygen species within the vascular endothelial cells, and how these free radicals may potentially affect the pathogenesis of diabetic complications. We specifically studied the role of Nicotinamide adenine dinucleotide phosphate (NADPH) and of src homology 2 domain-containing transforming protein C1 (p66Shc). The role of p66Shc has been specifically assessed also in vivo, as we found that this protein is an important mediator of impaired diabetic ulcer healing (see figure: from Fadini et al. Diabetes 2010).

•  We also assessed other potential mechanisms of endothelial dysfunction by using novel experimental approaches both in vivo and in vitro. We have modelled the kinetic of nitric oxide production by using stably labeled infusion of 15N arginine and its conversion to 15N labeled nitric oxide. Nitric oxide (NO) is crucial to endothelial function and this experimental approach can provide valuable information on NO bioavailability and regulation in vivo. We are also assessing the role of cell-to-cell interactions by using a bioreactor approach, which allows to study mutual inter-relationships among cell types involved in the development of diabetic complications, such as endothelial cells and adipocytes.

•  In the context of the relationship between aging and diabetes, we have demonstrated a contribution of the longevity-related protein silent information regulation 2 homolog (Sirt) -1 in humans mononuclear cells expression ex vivo to diabetes condition. Sirt1 regulates gene silencing, DNA repair, and life span. The most-studied function, gene silencing, involves the inactivation of chromosome domains containing key regulatory genes by packaging them into a specialized chromatin structure that is inaccessible to DNA-binding proteins. The nuclear SIRT1 has been shown to target the p53 tumor suppressor protein for deacetylation to suppress DNA damage. We hypothesized that this protein may play an important role in the pathogenesis of diabetic complication by inducing both insulin resistance and endothelial dysfunction. We are now assessing its role in the diabetes-mediated organ damage, and specifically we dissect out its relationships with other protein such as p66shc and p53 tumor suppressor protein.

Synoptic CV

2001–present	Associate Professor of Endocrinology and Metabolism, University of Padova, School of Medicine, Italy
1996–2001	Specialty in Internal Medicine, University of Padova, School of Medicine, Italy
1988–2001	House Staff, General Hospital City of Padova, Italy
1985–1988	Ph.D. in Endocrinology and Metabolism, University of Modena, School of Medicine, Italy
1980	Graduation in Medicine Summa cum laude, University of Padova, School of Medicine, Italy

Honours

2008	EASD Castelli-Pedroli Prize. Golgi Lecture
1994	Italian Society for the Study of Diabetes Price for the best work presented at Italian National Meeting for the Study of Diabetes
1990	Sigma-Tau Price for a study on diabetic cardiomyopathy
1986	Fogarty International Award from the National Institute of Health
1986	University of Padova Price for a research on "diabetic cardiomyopathy"
1985	Nato CNR grant
1984	Lilly price for the best presentation at Italian Diabetes Meeting

Additional Publications

• Fadini GP, Maruyama S, Ozaki T, Taguchi A, Meigs J, Dimmeler S, Zeiher AM, de Kreutzenberg S, Avogaro A, Nickenig G, Schmidt-Lucke C, Werner N (2010) Circulating progenitor cell count for cardiovascular risk stratification: a pooled analysis. PLoS ONE 5:e11488.
• Fadini GP, Albiero M, Menegazzo L, Boscaro E, Pagnin E, Iori E, Cosma C, Lapolla A, Pengo V, Stendardo M, Agostini C, Pelicci PG, Giorgio M, Avogaro A (2010) The Redox Enzyme p66Shc Contributes to Diabetes and Ischemia-Induced Delay in Cutaneous Wound Healing. Diabetes 59:2306-14.
• Fadini GP, Avogaro A (2010) Cell-based methods for ex vivo evaluation of human endothelial biology. Cardiovasc. Res. 87:12-21.
• Bolego C, Rossoni G, Fadini GP, Vegeto E, Pinna C, Albiero M, Boscaro E, Agostini C, Avogaro A, Gaion RM, Cignarella A (2010) Selective estrogen receptor-alpha agonist provides widespread heart and vascular protection with enhanced endothelial progenitor cell mobilization in the absence of uterotrophic action. FASEB J. 24:2262-72.
• de Kreutzenberg SV, Ceolotto G, Papparella I, Bortoluzzi A, Semplicini A, Dalla Man C, Cobelli C, Fadini GP, Avogaro A (2010) Downregulation of the longevity-associated protein sirtuin 1 in insulin resistance and metabolic syndrome: potential biochemical mechanisms. Diabetes 59:1006-15.
• Fadini GP, de Kreutzenberg S, Albiero M, Coracina A, Pagnin E, Baesso I, Cignarella A, Bolego C, Plebani M, Nardelli GB, Sartore S, Agostini C, Avogaro A (2008) Gender differences in endothelial progenitor cells and cardiovascular risk profile: the role of female estrogens. Arterioscler. Thromb. Vasc. Biol. 28:997-1004.
• Avogaro A, de Kreutzenberg SV, Fadini GP (2008) Oxidative stress and vascular disease in diabetes: is the dichotomization of insulin signaling still valid? Free Radic. Biol. Med. 44:1209-15.
• Fadini GP, Sartore S, Schiavon M, Albiero M, Baesso I, Cabrelle A, Agostini C, Avogaro A (2006) Diabetes impairs progenitor cell mobilisation after hindlimb ischaemia-reperfusion injury in rats. Diabetologia 49:3075-84.
• Fadini GP, Sartore S, Albiero M, Baesso I, Murphy E, Menegolo M, Grego F, Vigili de Kreutzenberg S, Tiengo A, Agostini C, Avogaro A (2006) Number and function of endothelial progenitor cells as a marker of severity for diabetic vasculopathy. Arterioscler. Thromb. Vasc. Biol. 26:2140-6.
• Fadini GP, Miorin M, Facco M, Bonamico S, Baesso I, Grego F, Menegolo M, de Kreutzenberg SV, Tiengo A, Agostini C, Avogaro A (2005) Circulating endothelial progenitor cells are reduced in peripheral vascular complications of type 2 diabetes mellitus. J. Am. Coll. Cardiol. 45:1449-57.

Contact

Angelo Avogaro Venetian Institute of Molecular Medicine Via Orus 2 35129 Padua — Italy

Tel.:  (+39) 049 7923 220