Saroglitazar is non-inferior to fenofibrate in reducing triglyceride levels in hypertriglyceridemic patients in a randomized clinical trial

PPARs in atherosclerosis: The spatial and temporal features from mechanism to druggable targets

BACKGROUND

Atherosclerosis is a chronic and complex disease caused by lipid disorder, inflammation, and other factors. It is closely related to cardiovascular diseases, the chief cause of death globally. Peroxisome proliferator-activated receptors (PPARs) are valuable anti-atherosclerosis targets that showcase multiple roles at different pathological stages of atherosclerosis and for cell types at different tissue sites.

AIM OF REVIEW

Considering the spatial and temporal characteristics of the pathological evolution of atherosclerosis, the roles and pharmacological and clinical studies of PPARs were summarized systematically and updated under different pathological stages and in different vascular cells of atherosclerosis. Moreover, selective PPAR modulators and PPAR-pan agonists can exert their synergistic effects meanwhile reducing the side effects, thereby providing novel insight into future drug development for precise spatial-temporal therapeutic strategy of anti-atherosclerosis targeting PPARs.

KEY SCIENTIFIC

Concepts of Review: Based on the spatial and temporal characteristics of atherosclerosis, we have proposed the importance of stage- and cell type-dependent precision therapy. Initially, PPARs improve endothelial cells' dysfunction by inhibiting inflammation and oxidative stress and then regulate macrophages' lipid metabolism and polarization to improve fatty streak. Finally, PPARs reduce fibrous cap formation by suppressing the proliferation and migration of vascular smooth muscle cells (VSMCs). Therefore, research on the cell type-specific mechanisms of PPARs can provide the foundation for space-time drug treatment. Moreover, pharmacological studies have demonstrated that several drugs or compounds can exert their effects by the activation of PPARs. Selective PPAR modulators (that specifically activate gene subsets of PPARs) can exert tissue and cell-specific effects. Furthermore, the dual- or pan-PPAR agonist could perform a better role in balancing efficacy and side effects. Therefore, research on cells/tissue-specific activation of PPARs and PPAR-pan agonists can provide the basis for precision therapy and drug development of PPARs.

Safety and Efficacy of the Novel RNA Interference Therapies for Hypertriglyceridemia and Mixed Hyperlipidemia Management: A Systematic Review and Meta-analysis

BACKGROUND

No meta-analysis has holistically analyzed and summarized the safety and therapeutic efficacy of the newer RNA interference (RNAi) therapies, olezarsen, plozasiran, and zodasiran, in managing conditions associated with hypertriglyceridemia (HTG).

METHODS

Randomized controlled trials (RCTs) involving patients with HTG or mixed hyperlipidemia (MHL) receiving either olezarsen, plozasiran, or zodasiran in the intervention arm and a placebo in the control arm were searched through electronic databases. The primary outcome was the safety profile of the drugs studied; secondary outcomes included the percent change from baseline (CFB) in the lipid levels, including triglyceride (TG).

RESULTS

Six RCTs with 334 participants were evaluated. Olezarsen, plozasiran, and zodasiran were well-tolerated with no higher risk of serious adverse events or injection-site reactions. After 24 weeks, plozasiran increased alanine aminotransferase and HbA1c more than placebo, although the difference was insignificant at 48 weeks. Plozasiran and zodasiran had little effect on hyperglycemia worsening. Olezarsen increased the likelihood of mild platelet count decreases without clinical harm. At their longest clinical trial follow-up, the highest doses of olezarsen, plozasiran, and zodasiran lowered TG by 55.2%, 50.57%, and 51.2% of baseline levels. All three drugs decreased non-HDL-C and remnant cholesterol. Olezarsen and plozasiran lowered ApoC-III and increased HDL-C, whereas zodasiran reduced HDL-C. Zodasiran decreased LDL-C, whereas olezarsen and plozasiran had no effects on LDL-C. Plozasiran and zodasiran lowered apolipoprotein B, but not olezarsen.

CONCLUSION

The newer RNA interference (RNAi) therapies appear safe and have excellent TG-lowering efficacy in patients with HTG and MHL.

Management of triglycerides, non-high density lipoprotein cholesterol and high density lipoprotein cholesterol

Dyslipidaemia characterised by elevated total cholesterol/LDL-C, triglyceride or both or decreased HDL-C is an important risk factor for the development of ASCVD. Atherogenic dyslipidaemia characterised by high TG, low HDL-C and elevated small dense LDL (sdLDL) is more prevalent in Asian Indians. Normal level of TG is generally considered as <150 mg/dl. Hypertriglyceridemia is closely associated with obesity, metabolic syndrome and diabetes mellitus. Goals of management of hypertriglyceridemia are to lower the risk of atherosclerotic cardiovascular events and reduce the risk of pancreatitis. Lifestyle modification is important. In severe hypertriglyceridemia, TG lowering pharmacotherapy is important to prevent pancreatitis. In mild to moderate hypertriglyceridemia, pharmacotherapy is employed only if associated with ASCVD or high risk factors and not controlled with lifestyle modifications and statins. Non-High Density Lipoprotein Cholesterol which estimates the cholesterol content of the atherogenic apoB containing lipoproteins, measured as total cholesterol minus HDL-C is equivalent to LDL-C in ASCVD risk assessment and superior to it in those with mild to moderate hypertriglyceridemia. Some international guidelines, have included measurement of non-HDL-C as primary therapeutic target for patients with ASCVD. Low HDL cholesterol is common in Indians. Despite evidence of inverse relationship between HDL-C and cardiovascular events, HDL-C as a causative factor for development of atherosclerosis is unproven. Therapeutic strategies directed at increasing HDL-C levels have not been shown to have cardiovascular benefits and hence HDL-C is currently not a target for drug-based treatment.

Protein Kinases in Obesity, and the Kinase-Targeted Therapy

The action of protein kinases and protein phosphatases is essential for multiple physiological responses. Each protein kinase displays its own unique substrate specificity and a regulatory mechanism that may be modulated by association with other proteins. Protein kinases are classified as dual-specificity kinases and dual-specificity phosphatases. Dual-specificity phosphatases are important signal transduction enzymes that regulate various cellular processes in coordination with protein kinases and play an important role in obesity. Impairment of insulin signaling in obesity is largely mediated by the activation of the inhibitor of kappa B-kinase beta and the c-Jun N-terminal kinase (JNK). Oxidative stress and endoplasmic reticulum (ER) stress activate the JNK pathway which suppresses insulin biosynthesis. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) are important for proper regulation of glucose metabolism in mammals at both the hormonal and cellular levels. Additionally, obesity-activated calcium/calmodulin dependent-protein kinase II/p38 suppresses insulin-induced protein kinase B phosphorylation by activating the ER stress effector, activating transcription factor-4. To alleviate lipotoxicity and insulin resistance, promising targets are pharmacologically inhibited. Nifedipine, calcium channel blocker, stimulates lipogenesis and adipogenesis by downregulating AMPK and upregulating mTOR, which thereby enhances lipid storage. Contrary to the nifedipine, metformin activates AMPK, increases fatty acid oxidation, suppresses fatty acid synthesis and deposition, and thus alleviates lipotoxicity. Obese adults with vascular endothelial dysfunction have greater endothelial cells activation of unfolded protein response stress sensors, RNA-dependent protein kinase-like ER eukaryotic initiation factor-2 alpha kinase (PERK), and activating transcription factor-6. The transcriptional regulation of adipogenesis in obesity is influenced by AGC (protein kinase A (PKA), PKG, PKC) family signaling kinases. Obesity may induce systemic oxidative stress and increase reactive oxygen species in adipocytes. An increase in intracellular oxidative stress can promote PKC-β activation. Activated PKC-β induces growth factor adapter Shc phosphorylation. Shc-generated peroxides reduce mitochondrial oxygen consumption and enhance triglyceride accumulation and lipotoxicity. Liraglutide attenuates mitochondrial dysfunction and reactive oxygen species generation. Co-treatment of antiobesity and antidiabetic herbal compound, berberine with antipsychotic drug olanzapine decreases the accumulation of triglyceride. While low-dose rapamycin, metformin, amlexanox, thiazolidinediones, and saroglitazar protect against insulin resistance, glucagon-like peptide-1 analog liraglutide inhibits palmitate-induced inflammation by suppressing mTOR complex 1 (mTORC1) activity and protects against lipotoxicity.

Immune microenvironment changes of liver cirrhosis: emerging role of mesenchymal stromal cells

Cirrhosis is a progressive and diffuse liver disease characterized by liver tissue fibrosis and impaired liver function. This condition is brought about by several factors, including chronic hepatitis, hepatic steatosis, alcohol abuse, and other immunological injuries. The pathogenesis of liver cirrhosis is a complex process that involves the interaction of various immune cells and cytokines, which work together to create the hepatic homeostasis imbalance in the liver. Some studies have indicated that alterations in the immune microenvironment of liver cirrhosis are closely linked to the development and prognosis of the disease. The noteworthy function of mesenchymal stem cells and their paracrine secretion lies in their ability to promote the production of cytokines, which in turn enhance the self-repairing capabilities of tissues. The objective of this review is to provide a summary of the alterations in liver homeostasis and to discuss intercellular communication within the organ. Recent research on MSCs is yielding a blueprint for cell typing and biomarker immunoregulation. Hopefully, as MSCs researches continue to progress, novel therapeutic approaches will emerge to address cirrhosis.

Targeting PPARs for therapy of atherosclerosis: A review

Atherosclerosis, a chief pathogenic factor of cardiovascular disease, is associated with many factors including inflammation, dyslipidemia, and oxidative stress. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors and are widely expressed with tissue- and cell-specificity. They control multiple genes that are involved in lipid metabolism, inflammatory response, and redox homeostasis. Given the diverse biological functions of PPARs, they have been extensively studied since their discovery in 1990s. Although controversies exist, accumulating evidence have demonstrated that PPAR activation attenuates atherosclerosis. Recent advances are valuable for understanding the mechanisms of action of PPAR activation. This article reviews the recent findings, mainly from the year of 2018 to present, including endogenous molecules in regulation of PPARs, roles of PPARs in atherosclerosis by focusing on lipid metabolism, inflammation, and oxidative stress, and synthesized PPAR modulators. This article provides information valuable for researchers in the field of basic cardiovascular research, for pharmacologists that are interested in developing novel PPAR agonists and antagonists with lower side effects as well as for clinicians.