Molecular mechanism(s) of insulin action on the expression of the angiotensinogen gene in kidney proximal tubular cells

Diabetic Microvascular Disease: An Endocrine Society Scientific Statement

Both type 1 and type 2 diabetes adversely affect the microvasculature in multiple organs. Our understanding of the genesis of this injury and of potential interventions to prevent, limit, or reverse injury/dysfunction is continuously evolving. This statement reviews biochemical/cellular pathways involved in facilitating and abrogating microvascular injury. The statement summarizes the types of injury/dysfunction that occur in the three classical diabetes microvascular target tissues, the eye, the kidney, and the peripheral nervous system; the statement also reviews information on the effects of diabetes and insulin resistance on the microvasculature of skin, brain, adipose tissue, and cardiac and skeletal muscle. Despite extensive and intensive research, it is disappointing that microvascular complications of diabetes continue to compromise the quantity and quality of life for patients with diabetes. Hopefully, by understanding and building on current research findings, we will discover new approaches for prevention and treatment that will be effective for future generations.

Activation of nuclear factor-kappaB by hyperglycemia in vascular smooth muscle cells is regulated by aldose reductase

Activation of the polyol pathway has been linked to the development of secondary diabetic complications. However, the underlying molecular mechanisms remain unclear. To probe the contribution of this pathway, we examined whether inhibition of aldose reductase, which catalyzes the first step of the pathway, affects hyperglycemia-induced activation of the inflammatory transcription factor nuclear factor (NF)-kappaB. Treatment of vascular smooth muscle cells with the aldose reductase inhibitors tolrestat and sorbinil prevented high-glucose-induced protein kinase C (PKC) activation, nuclear translocation of NF-kappaB, phosphorylation of IKK, and the increase in the expression of intracellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and aldose reductase. High-glucose-induced NF-kappaB activation was also prevented by the PKC inhibitors chelerythrine and calphostin C. Ablation of aldose reductase by small interference RNA (siRNA) prevented high-glucose-induced NF-kappaB and AP-1 activation but did not affect the activity of SP-1 or OCT-1. Stimulation with iso-osmotic mannitol activated NF-kappaB and increased the expression of aldose reductase but not ICAM-1 and VCAM-1. Treatment with aldose reductase inhibitors or aldose reductase siRNA did not affect mannitol-induced NF-kappaB or AP-1 activation. Administration of tolrestat (15 mg . kg(-1) . day(-1)) decreased the abundance of activated NF-kappaB in balloon-injured carotid arteries of diabetic rats. Collectively, these results suggest that inhibition of aldose reductase, which prevents PKC-dependent nonosmotic NF-kappaB activation, may be a useful approach for treating vascular inflammation caused by diabetes.

Normalization of lens protein kinase Cgamma in galactosemic dogs by a novel aldose reductase inhibitor

The purpose of this study was to determine the effects of a novel aldose reductase inhibitor on lens protein kinase Cgamma (PKCgamma) levels in galactosemic dogs. Six-month old Beagles (12 total; 6 male and 6 female) were made galactosemic by feeding a diet of 40% galactose for 6 weeks. Three dogs per group were fed either control, normal diet, 40% galactose diet, 40% galactose diet with aldose reductase inhibitor at 100 mg/kg body weight per day given orally, or a control diet with aldose reductase inhibitor alone (1-H,7-H-5alpha,6,8,9-tetrahydro-1-oxopyran[4,3-beta](1) benzopyran, referred to herein as HAR-1). Lenses were removed and analyzed for toxicity by pathological examination. Lens polyol concentrations were determined by GC/MS. PKCgamma levels were determined by Western blot and by reverse transcriptase-polymerase chain reaction (RT-PCR). No toxicity was observed from the aldose reductase inhibitor when given at 100 mg/kg body weight per day for 6 weeks. Galactosemic dogs showed deterioration of lens cells. Deterioration included vacuole formation in the lens, cell lysis, and loss of cell nuclei. Galactosemic dogs given the HAR-1 appeared identical to control dogs. Polyol concentrations in the lenses were reduced by 50% in dogs fed the 40% galactose diet with the aldose reductase inhibitor, HAR-1. PKCgamma protein levels were reduced in the galactosemic dog lenses, but synthesis of PKCgamma was not affected, as measured by RT-PCR. The PKCgamma protein levels were similar to controls in dogs given the aldose reductase inhibitor, HAR-1, even when polyol concentrations remained 50% elevated above control levels. HAR-1, when given to control dogs, caused a reduction in the synthesis of PKCgamma mRNA but not in total PKCgamma protein levels. This study demonstrates the use of a novel aldose reductase inhibitor to control changes in PKCgamma in dog lens, a PKC that is known to control gap junction activity.