Glucose Regulates the Expression of the Apolipoprotein A5 Gene

The apolipoprotein A5 gene (APOA5) is a key player in determining triglyceride concentrations in humans and mice. Since diabetes is often associated with hypertriglyceridemia, this study explores whether APOA5 gene expression is regulated by alteration in glucose homeostasis and the related pathways. D-glucose activates APOA5 gene expression in a time- and dose-dependent manner in hepatocytes, and the glycolytic pathway involved was determined using D-glucose analogs and metabolites. Together, transient transfections, electrophoretic mobility shift assays and chromatin immunoprecipitation assays show that this regulation occurs at the transcriptional level through an increase of USF1/2 binding to an E-box in the APOA5 promoter. We show that this phenomenon is not due to an increase of mRNA or protein expression levels of USF. Using protein phosphatases 1 and 2A inhibitor, we demonstrate that D-glucose regulates APOA5 gene via a dephosphorylation mechanism, thereby resulting in an enhanced USF1/2-promoter binding. Last, subsequent suppressions of USF1/2 and phosphatases mRNA through siRNA gene silencing abolished the regulation. We demonstrate that APOA5 gene is up regulated by D-glucose and USF through phosphatase activation. These findings may provide a new cross talk between glucose and lipid metabolism

Selective Peroxisome Proliferator-Activated Receptor Alpha Modulators (SPPARMα): New Opportunities to Reduce Residual Cardiovascular Risk in Chronic Kidney Disease?

PURPOSE OF REVIEW: Chronic kidney disease (CKD) poses a major global challenge, which is exacerbated by aging populations and the pandemic of type 2 diabetes mellitus. Much of the escalating burden of CKD is due to cardiovascular complications. Current treatment guidelines for dyslipidemia in CKD prioritize low-density lipoprotein cholesterol management, but still leave a high residual cardiovascular risk. Targeting elevated triglycerides and low plasma high-density lipoprotein cholesterol, a common feature of CKD, could offer additional benefit. There are, however, safety issues with current fibrates (peroxisome proliferator-activated receptor alpha [PPARα] agonists), notably the propensity for elevation in serum creatinine, indicating the need for new approaches. RECENT FINDINGS: Interactions between the ligand and PPARα receptor influence the specificity and potency of receptor binding, and downstream gene and physiological effects. The peroxisome proliferator-activated receptor alpha modulator (SPPARMα) concept aims to modulate the ligand structure so as to enhance binding at the PPARα receptor, thereby improving the ligand's selectivity, potency, and safety profile. This concept has led to the development of pemafibrate, a novel SPPARMα agent. This review discusses evidence that differentiates pemafibrate from current fibrates, especially the lack of evidence for elevation in serum creatinine or worsening of renal function in high-risk patients, including those with CKD. SUMMARY : Differentiation of pemafibrate from current fibrates aims to address unmet clinical needs in CKD. The ongoing PROMINENT study will provide critical information regarding the long-term efficacy and safety of pemafibrate in patients with type 2 diabetes mellitus, including those with CKD, and whether the favorable lipid-modifying profile translates to reduction in residual cardiovascular risk

Selective Peroxisome Proliferator-Activated Receptor Alpha Modulators (SPPARMα) in the Metabolic Syndrome: Is Pemafibrate Light at the End of the Tunnel?

Adoption of poor lifestyles (inactivity and energy-dense diets) has driven the worldwide increase in the metabolic syndrome, type 2 diabetes mellitus and non-alcoholic steatohepatitis (NASH). Of the defining features of the metabolic syndrome, an atherogenic dyslipidaemia characterised by elevated triglycerides (TG) and low plasma concentration of high-density lipoprotein cholesterol is a major driver of risk for atherosclerotic cardiovascular disease. Beyond lifestyle intervention and statins, targeting the nuclear receptor peroxisome proliferator-activated receptor alpha (PPARα) is a therapeutic option. However, current PPARα agonists (fibrates) have limitations, including safety issues and the lack of definitive evidence for cardiovascular benefit. Modulating the ligand structure to enhance binding at the PPARα receptor, with the aim of maximising beneficial effects and minimising adverse effects, underlies the SPPARMα concept. This review discusses the history of SPPARM development, latterly focusing on evidence for the first licensed SPPARMα, pemafibrate. Evidence from animal models of hypertriglyceridaemia or NASH, as well as clinical trials in patients with atherogenic dyslipidaemia, are overviewed. The available data set the scene for therapeutic application of SPPARMα in the metabolic syndrome, and possibly, NASH. The outstanding question, which has so far eluded fibrates in the setting of current evidence-based therapy including statins, is whether treatment with pemafibrate significantly reduces cardiovascular events in patients with atherogenic dyslipidaemia. The PROMINENT study in patients with type 2 diabetes mellitus and this dyslipidaemia is critical to evaluating this

The orphan nuclear receptor RORα is a negative regulator of the inflammatory response

Retinoid-related orphan receptor α (RORα) (NR1F1) is a member of the nuclear receptor superfamily whose biological functions are largely unknown. Since staggerer mice, which carry a deletion in the RORα gene, suffer from immune abnormalities, we generated an adenovirus encoding RORα1 to investigate its potential role in control of the inflammatory response. We demonstrated that RORα is expressed in human primary smooth-muscle cells and that ectopic expression of RORα1 inhibits TNFα-induced IL-6, IL-8 and COX-2 expression in these cells. RORα1 negatively interferes with the NF-κB signalling pathway by reducing p65 translocation as demonstrated by western blotting, immunostaining and electrophoretic mobility shift assays. This action of RORα1 on NF-κB is associated with the induction of IκBα, the major inhibitory protein of the NF-κB signalling pathway, whose expression was found to be transcriptionally upregulated by RORα1 via a ROR response element in the IκBα promoter. Taken together, these data identify RORα1 as a potential target in the treatment of chronic inflammatory diseases, including atherosclerosis and rheumatoid arthritis

Apolipoprotein A5 is an inflammatory responsive gene down-regulated by tumor necrosis factor alpha and interleukin-1

Several epidemiological studies have established that elevated plasma triglyceride concentrations constitute an independent risk factor for cardiovascular diseases. In addition, systemic inflammation is associated with severe hypertriglyceridemia and previous studies have demonstrated that cytokines such as tumor necrosis factor alpha (TNFalpha;) and interleukin-1 (IL-1) can elevate plasma triglyceride levels. Recently, we identified a new apolipoprotein, APOA5, selectively expressed in the liver and showed that this gene is a crucial determinant of plasma triglyceride levels. In this study, we sought to determine whether inflammatory cytokines regulate APOA5 and consequently influence plasma triglyceride levels. We found initially that treatment of human hepatocytes with TNFalpha; or IL-1 reduced the expression of APOA5 mRNA. Subsequent, we demonstrated through transient transfection experiments that both TNFalpha; and IL-1 down-regulate human APOA5 at the transcriptional level. Further deletion analyses of the APOA5 promoter and binding assays revealed the presence of a promoter sequence, containing a PPARalpha; Response Element, responsive to cytokine stimulation. In vivo, treatment of hAPOA5 transgenic mice with TNFalpha; down-regulated the hAPOA5 gene expression in hepatocytes. In patients displaying systemic inflammation, plasma concentrations of triglycerides and ApoAV were inversely correlated. These findings demonstrate that APOA5 is an inflammatory responsive gene and constitutes a link between inflammation and triglyceride-associated cardiovascular risk

Transcriptional Regulation of Apolipoprotein A5 Gene Expression by theNuclear Receptor ROR alpha

Apolipoprotein A5 has recently been identified as a crucial determinant of plasma triglyceride levels. Our results showed that RORa up-regulates human APOA5 but has no effect on mouse apoa5 promoter. These data suggest an additional important physiological role for RORa in the regulation of genes involved in plasma triglyceride homeostasis in human and probably in the development of atherosclerosi