Blood Flow and Salivary Gland Function in Diabetes

University Of The Pacific-Stockton, Stockton CA

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Abstract

DESCRIPTION (provided by applicant): Several lines of evidence suggest that there is a fundamental relationship between blood flow and secretory function in salivary glands, and it has been hypothesized that salivary hypofunction in diabetic patients results in part from abnormalities in blood flow. Initial studies demonstrate that neural regulation of submandibular gland (SMG) blood flow is compromised in streptozotocin-diabetic (STZ) rats, a model of insulin-dependent diabetes mellitus (Type 1). Endothelium-dependent mechanisms play a significant role in this phenomenon, but the specific pathways affected were influenced by gender. In males, prostacyclin (PGI2) and nitric oxide (NO) pathways are impaired, whereas in females NO-dependent responses are maintained and endothelium-derived hyperpolarizing factor (EDHF) mechanisms are impaired. However, non-insulin- dependent diabetes mellitus (Type 2) accounts for more than 90% of the disease seen in patient populations. More importantly, the onset and mechanisms underlying endothelial dysfunction in Type 2 diabetes may differ significantly from those in Type 1 diabetes. For example, in contrast to patients with Type 1 diabetes impaired endothelium-dependent vasodilatation is common in early and otherwise uncomplicated Type 2 diabetes. It has even been suggested that there is a reciprocal relationship between the development of insulin-resistance and endothelial dysfunction in Type 2 diabetes. Salivary gland function in models of Type 2 diabetes remains virtually unexplored, and therefore we propose to examine its effects on vascular and secretory function using a rat model (Zucker Obese Rat). The Goals of this application are to: 1. Characterize the relationship between blood flow and salivary secretion in a rat model of Type 2. 2. Determine the relative contributions of NO, PGI2, EDHF to impaired vasodilatation in the SMG in Type 2. 3. Investigate the relationship between impaired vasodilatation and the expression of endothelial NO synthase (eNOS), phosphorylated eNOS (p-eNOS), cyclooxygenase 1 and 2 (COX1, COX2), and 2C and 4A family of cytochrome P450 enzymes (CYP 2C11, 2C23, 2J3, 2J4, 4A2 and 4A3) and soluble epoxide hydrolase (sEH) enzyme using Real-time PCR and Western blotting. 4. Examine the effects of two different therapeutic strategies on endothelial function in the submandibular gland: " increasing insulin sensitivity (treatment of diabetic animals with rosglitazone) " inactivation of protein kinase C 2 (treatment of diabetic animals with ruboxistaurin). In addition to significantly increasing our understanding of salivary gland physiology in diabetes, a greater understanding of the mechanisms underlying microvascular abnormalities may contribute to the development of new therapeutic strategies for the prevention and treatment of diabetic microvascular disease. PUBLIC HEALTH RELEVANCE: These studies will add significantly to our understanding of salivary gland physiology. Further, understanding the mechanisms underlying microvascular abnormalities in the diabetic SMG may contribute to the development of new therapeutic strategies for the prevention and treatment of diabetic microvascular disease.