Into the future: prevention of diabetes.

With the increasing prevalence of obesity and an aging population, type 2 diabetes mellitus (T2DM) is rapidly becoming the most common chronic disease in the US. In the US alone, over 1.5 million new cases by the Center for Disease Control are diagnosed per year. Concomitant with the rising epidemic in diabetes are the resulting severe complications such as renal and cardiac dysfunction, amputations, impairment in vision and increased mortality. Since T2DM has such an enormous cost in terms of quality of life and mortality as well as economic cost, prevention of T2DM is an important and appropriate target. Interventions for T2DM range from lifestyle modifications such as weight loss and diet to pharmacological agents and surgical intervention such as bariatric surgery. Of the various lifestyle modifications studied, weight loss has consistently been shown to be an effective mechanism of T2DM prevention. Regarding dietary interventions, only the increased consumption of green, leafy vegetables reduces the risk of T2DM in contrast to the popular belief that a diet high in fruits and vegetables reduces this risk. Pharmacological agents investigated in preventing diabetes primarily target the same pathological pathways found in T2DM. Metformin has consistently been shown to reduce the incidence of T2DM and improve impaired glucose tolerance. α2-Glucosidase inhibitors are also effective in prevention of T2DM, but are limited by their gastrointestinal side effects. Interestingly, although ramipril showed no effect on development of diabetes, valsartan did reduce the incidence of diabetes in patients with impaired glucose tolerance and cardiovascular disease. Although single intervention studies are important in delineating whether an intervention or agent is effective, a multi-faceted approach has been shown to be more effective. Importantly, such an approach is pragmatic and urgently needed to stem the tide of T2DM and its significant human and financial cost.

The role of obesity in the pathogenesis of hypertension.

The rapid rise in the incidence and prevalence of obesity and the concomitant increase in the incidence and prevalence of hypertension have fueled investigation into the role of obesity in the pathogenesis of hypertension. The genetic background that predisposes obese individuals to hypertension is being elucidated, and the importance of adipose tissue as an endocrine organ in the pathogenesis of hypertension is increasingly being recognized. Visceral adipose tissue is critical in the production of pathologic cytokines that are thought to mediate obesity-induced hypertension. Changes in the types and levels of adipocytokines that result from the accumulation of aberrant adipose tissue directly leads to alterations in systemic vascular resistance, sodium retention and sympathetic nervous system activity. Key changes in adipocytokine levels seen in obesity-induced hypertension include increased leptin and adiponectin levels. Another important mechanism in obesity-induced hypertension is the generation of angiotensin II and direct stimulation of aldosterone production. The increased sympathetic nervous system activity seen in obesity-associated hypertension leads to increased renal sodium retention and increased systemic vascular resistance. Increased systemic vascular resistance can also occur directly in obese individuals through vascular fibrosis and lipid deposition. Obesity should no longer be simply considered as a marker of cardiovascular risk but should be regarded as an important and primary contributor to the pathophysiology of hypertension.

Assessing the benefits and harms of statin treatment in patients with chronic kidney disease.

This Practice Point commentary discusses a meta-analysis by Strippoli et al. that included 50 randomized and quasi-randomized trials of statins in patients with different stages of kidney disease (predialysis, dialysis and transplantation; n = 30,144). The authors found that statins safely reduced lipid concentrations and the risk of cardiovascular events and cardiovascular mortality, but that the agents had no effect on all-cause mortality overall and had uncertain renoprotective effects. The analysis was comprehensive and well executed. A decreased risk of all-cause mortality with statins was found in studies of predialysis patients but not in studies of renal transplant recipients or patients on chronic dialysis. Statin doses used in the trials were well tolerated and safe in all subgroups of patients with chronic kidney disease; therefore, we feel that statin use to maintain LDL cholesterol below 100 mg/dl (2.6 mmol/l) should be initiated to potentially decrease cardiovascular risk in such patients. The benefits of statin therapy on all-cause mortality and the clinically significant benefits of this treatment on progression of kidney disease are still unclear, and additional trial evidence in patients with chronic kidney disease is needed.

Characterization of phosphate transport in rat vascular smooth muscle cells: implications for vascular calcification.

OBJECTIVE: Hyperphosphatemia and inorganic phosphate (Pi) transport by vascular smooth muscle cells (VSMCs) have been implicated in the pathogenesis of vascular calcification. The aim of this work has been to characterize Pi transport in VSMCs. METHODS AND RESULTS: Primary cultures of VSMCs express both high affinity Na-dependent and Na-independent components of Pi transport. Under physiological conditions both transport systems are saturated, show similar activity, and are inhibited by increasing pH. The Na-dependent transport is also weakly inhibited by phosphonoformic acid (PFA) (3.9 mmol/L IC50 at 0.05 mmol/L Pi). Real-time polymerase chain reaction shows that Pit1 and Pit2 are expressed to the same degree, and no other Pi transporters are significantly expressed. When expressed in Xenopus oocytes they are strictly Na-dependent, with high affinities for Pi, and are inhibited by increasing pH, but only weakly inhibited by PFA. We have used RNA interference to demonstrate that Pit1 and Pit2 are the transporters responsible for Na-dependent Pi transport in VSMCs. CONCLUSIONS: Taken together these novel findings suggest new roles of Pi transport in the pathogenesis of VC and have implications as potential future clinical targets.

Delayed therapy of experimental global cerebral ischemia with acetyl-L-carnitine in dogs.

Acetyl-L-carnitine (ALCAR), when administered immediately following restoration of spontaneous circulation (ROSC) from experimental cardiac arrest (CA) has previously been demonstrated to promote normalization of brain energy metabolism and neurologic recovery following 10 min CA. In order to determine ultimate efficacy for this or other drugs, clinical trials must be performed in human subjects. In several human clinical trials, though, drug administration has been significantly delayed following resuscitation from CA. These experiments test the hypothesis that post-resuscitative delay in ALCAR administration will impair the ability of this drug to promote neurologic recovery. Neurological deficit scoring (23 h) as well as frontal cortex lactate levels (2 and 24 h) were compared following resuscitation from 10 min CA in dogs receiving either ALCAR or drug vehicle 30 min following ROSC. Dogs treated with ALCAR 30 min following ROSC from 10 min CA exhibited more normal cerebral cortex lactate levels than did vehicle control animals. There was no difference, however, in neurologic deficit scores between groups, with all animals demonstrating moderate to severe clinical neurologic impairment at 23 h following ROSC. A 30-min delay in ALCAR administration following ROSC from 10 min CA impairs the ability of this drug to promote neurologic recovery despite apparent normalization of brain lactate levels.

Patterns of gene expression differentially regulated by platelet-derived growth factor and hypertrophic stimuli in vascular smooth muscle cells: markers for phenotypic modulation and response to injury.

In vascular smooth muscle cells (VSMC), platelet-derived growth factor (PDGF) suppresses expression of multiple smooth muscle contractile proteins, useful markers of differentiation. Conversely, hypertrophic agents induce expression of these genes. The goal of this study was to employ genomic approaches to identify classes of genes differentially regulated by PDGF and hypertrophic stimuli. Changes in gene expression were determined using Affymetrix RAE-230 GeneChips in rat aortic VSMC stimulated with PDGF. For comparison with a model hypertrophic stimulus, a microarray was performed with VSMC stably expressing constitutively active Galpha(16), which strongly induces smooth muscle marker expression. We identified 75 genes whose expression was increased by exposure to PDGF and decreased by expression of Galpha(16) and 97 genes whose expression was decreased by PDGF and increased by Galpha(16). These genes included many smooth muscle-specific proteins; several extracellular matrix, cytoskeletal, and chemotaxis-related proteins; cell signaling molecules; and transcription factors. Changes in gene expression for many of these were confirmed by PCR or immunoblotting. The contribution of signaling pathways activated by PDGF to the gene expression profile was examined in VSMC stably expressing gain-of-function H-Ras or myristoylated Akt. Among the genes that were confirmed to be differentially regulated were CCAAT/enhancer-binding protein delta, versican, and nexilin. All of these genes also had altered expression in injured aortas, consistent with a role for PDGF in the response of injured VSMC. These data indicate that genes that are differentially regulated by PDGF and hypertrophic stimuli may represent families of genes and potentially be biomarkers for vascular injury.