Hydroxymethylglutaryl–CoA reductase inhibitor inhibits induction of nitric oxide synthase in 3T3–L1 preadipocytes

Drugs Involved in Dyslipidemia and Obesity Treatment: Focus on Adipose Tissue

Metabolic syndrome can be defined as a state of disturbed metabolic homeostasis characterized by visceral obesity, atherogenic dyslipidemia, arterial hypertension, and insulin resistance. The growing prevalence of metabolic syndrome will certainly contribute to the burden of cardiovascular disease. Obesity and dyslipidemia are main features of metabolic syndrome, and both can present with adipose tissue dysfunction, involved in the pathogenic mechanisms underlying this syndrome. We revised the effects, and underlying mechanisms, of the current approved drugs for dyslipidemia and obesity (fibrates, statins, niacin, resins, ezetimibe, and orlistat; sibutramine; and diethylpropion, phentermine/topiramate, bupropion and naltrexone, and liraglutide) on adipose tissue. Specifically, we explored how these drugs can modulate the complex pathways involved in metabolism, inflammation, atherogenesis, insulin sensitivity, and adipogenesis. The clinical outcomes of adipose tissue modulation by these drugs, as well as differences of major importance for clinical practice between drugs of the same class, were identified. Whether solutions to these issues will be found in further adjustments and combinations between drugs already in use or necessarily in new advances in pharmacology is not known. To better understand the effect of drugs used in dyslipidemia and obesity on adipose tissue not only is challenging for physicians but could also be the next step to tackle cardiovascular disease.

AICAR Attenuates TNFα-Induced Inappropriate Secretion of Monocyte Chemoattractant Protein-1 and Adiponectin in 3T3-L1 Adipocytes

Aim: The increase in monocyte chemoattractant protein-1 (MCP-1) and the decrease in adiponectin production from hypertrophic adipocytes are associated with adipose tissue inflammation and its metabolic complications. The aim of this study was to determine whether 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR), an adenosine monophosphate-activated protein kinase (AMPK) activator, modulates these adipocytokine productions in tumor necrosis factor-α (TNFα)-treated adipocytes.

Methods: AICAR and/or other reagents were added to the culture medium, and then, TNFα was added to fully differentiated 3T3-L1 adipocytes. The MCP-1 and adiponectin production in the culture supernatant was measured by ELISA. AMPK, phosphatidylinositol 3-kinase (PI3K), and nuclear factor-κB (NF-κB) activities were also assayed.

Results: Treatment with TNFα increased MCP-1 and decreased adiponectin secretion dose-dependently in the 3T3-L1 adipocytes, and AICAR significantly inhibited these TNFα-mediated changes. Interestingly, metformin, another AMPK activator, did not have such effects on these adipocytokines. Both the AMPK and PI3K systems in the cells were significantly activated by the AICAR treatment, but the effects of AICAR on adipocytokines were not weakened by the addition of dorsomorphin, an AMPK inhibitor, or LY294002, a PI3K inhibitor. Pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor, showed protective effects similar to those as AICAR. AICAR, but not metformin, significantly inhibited the TNFα-stimulated activation of NF-κB, and dorsomorphin did not change AICAR's effect.

Conclusion: AICAR attenuates the TNFα-induced secretion of MCP-1 and adiponectin in 3T3-L1 adipocytes. The observed effects of AICAR seem to be mainly due to the inhibition of NF-κB activation rather than the activation of the AMPK pathway, at least in TNFα-treated adipocytes.

Neuroprotective potential of fasudil mesylate in brain ischemia-reperfusion injury of rats

We previously reported that inhibition of Rho-kinase (ROCK) by hydroxyl fasudil improves cognitive deficit and neuronal damage in rats with chronic cerebral ischemia (Huang et al., Cell Mol Neurobiol 28:757-768, 2008). In this study, fasudil mesylate (FM) was investigated for its neuroprotective potential in rats with ischemia following middle cerebral artery occlusion (MCAO) and reperfusion. The effect of fasudil mesylate was also studied in rat brain cortical and hippocampal slices treated with oxygen-glucose deprivation (OGD) injury. Gross anatomy showed that cerebral infarct size, measured with 2,3,5-triphenyltetrazolium chloride (TTC) staining, was significantly smaller in the FM-treated than in the non-FM-treated ischemic rats. In the brain regions vulnerable to ischemia of ischemic rats, fasudil mesylate was also found to significantly restore the enzyme protein expression level of endothelial nitric oxide synthase (eNOS), which was decreased in ischemia. However, it remarkably reduced the protein synthesis of inducible nitric oxide synthase (iNOS) that was induced by ischemia and reperfusion. In rat brain slices treated with OGD injury, fasudil mesylate increased the neuronal cell viability by 40% for cortex and by 61% for hippocampus, respectively. Finally, in the presence of OGD and fasudil mesylate, superoxide dismutase (SOD) activity was increased by 50% for cortex and by 58% for hippocampus, compared to OGD only group. In conclusion, our in vivo study showed that fasudil mesylate not only decreased neurological deficit but also reduced cerebral infarct size, possibly and at least partially by augmenting eNOS protein expression and inhibiting iNOS protein expression after ischemia-reperfusion.

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Background

Fenofibrate, a PPAR alpha agonist, has been widely used in clinics as lipid-regulating agent. PPAR alpha is known to be expressed in many organs including pancreatic beta cells and regulate genes involved in fatty acid metabolism. Some reports based on cell lines or animals have provided evidences that PPAR alpha agonists may affect (increased or suppressed) beta cell insulin secretion, and several studies are producing interesting but still debated results.

Methods

In this research, we investigated the long term effects of fenofibrate on beta cell function in a metabolic syndrome animal model, monosodium glutamate (MSG) induced obese rats. Obese MSG rats were administered by gavage with fenofibrate at a dose of 100 mg/kg for 12 weeks. Oral glucose tolerance and insulin tolerance tests were performed to evaluate glucose metabolism and insulin sensitivity. We have used the hyperglycemic clamp technique to evaluate the capacity of beta cell insulin secretion. This technique provides an unbiased approach to understand the beta cell function in vivo. The changes of gene and protein expression in the pancreas and islets were also analyzed by Real-Time-PCR, Western blot and immunostaining.

Results

Fenofibrate reduced the plasma lipid levels within a few days, and showed no beneficial effects on glucose homeostasis or insulin sensitivity in obese MSG rats. But the animals treated with fenofibrate exhibited significantly decreased fasting plasma insulin and impaired insulin secretory response to glucose stimulation. Further studies confirmed that fenofibrate increased MDA level and decreased total ATPase activity in pancreatic mitochondrion, accompanied by the upregulation of iNOS and NF-kappa B and TNF alpha expression in pancreatic islets of obese MSG rats.

Conclusions

Long-term fenofibrate treatment disrupted beta cell function, and impaired glucose-stimulated insulin secretion in obese MSG rats, perhaps to some extent associated with the activated inflammatory pathway and increased formation of oxidative products, especially the up-regulation of NF-kappa B and iNOS expression in islets.