The role of PPARs in the microvascular dysfunction in diabetes.
There is a major defect in skin blood flow (SkBF) in people with type 2 diabetes (T2DM). This defect is associated with relatively normal nitric oxide (NO) production in the skin. The abnormal blood flow cosegregates with hypertension, dyslipidemia, abnormal fatty acid composition, a proinflammatory state, and insulin resistance. Since these covariates are an integral part of the insulin resistance syndrome, we examined the effects of the thiazoledindiones (TZDs) as insulin sensitizers for their ability to correct the abnormal blood flow. The PPARgamma rosiglitazone improved NO production to normal levels, but had a small effect on SKBF. In contrast, pioglitazone had a small effect on skin neurovascular function but a dramatic effect on reducing nitrosative stress. These effects do not appear to be due to the insulin sensitizing properties of these compounds but are associated with a reduction in indices of inflammation, hemodilution, and are likely to be due to one of the many "vascular" effects of TZDs. The role of inflammation in the disordered neurovascular function in diabetes cannot be underplayed and the possible contribution of PPARalpha agonists to alter the inflammatory state needs to be explored further. Since blood flow regulation is mediated by mechanisms other than NO, such as prostaglandins and endothelial derived hyperpolarizing factor, which, in turn, are compromised by the inflammatory state, we anticipate that activation of both the PPARgamma as well as PPARalpha should ameliorate the disordered blood flow in type 2 diabetes. While it now appears that the PPARs may have a major role to play in protection from macrovascular disease, their contribution to amelioration of the microvascular defects in type 2 diabetes has fallen short of spectacular success. In this respect, the combinations of PPARalpha, PPARbeta and PPARgamma may better serve the unique requirements for improving the microvascular defect in diabetes.
Vinik
Aaron
A
Strelitz Diabetes Institute, Eastern Virginia Medical School, Norfolk, VA 23510, United States. vinikai@evms.edu
Parson
Henri
H
Ullal
Jagdeesh
J
D000818:Animals; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology*; D005227:Fatty Acids / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology / Q000627:therapeutic use; D007333:Insulin Resistance; D008833:Microcirculation / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism; D047492:Peroxisome Proliferator-Activated Receptors / Q000819:agonists / Q000378:metabolism*; D000077205:Pioglitazone; D000077154:Rosiglitazone; D012867:Skin / Q000098:blood supply*; D045162:Thiazolidinediones / Q000494:pharmacology / Q000627:therapeutic use; D014657:Vasculitis / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology
D005227:Fatty Acids; D007004:Hypoglycemic Agents; D047492:Peroxisome Proliferator-Activated Receptors; D045162:Thiazolidinediones; D000077154:Rosiglitazone; D009569:Nitric Oxide; D000077205:Pioglitazone