Troglitazone and Δ2Troglitazone enhance adiponectin expression in monocytes/macrophages through the AMP-activated protein kinase pathway

Circulating adiponectin levels, expression of adiponectin receptors, and methylation of adiponectin gene promoter in relation to Alzheimer's disease

BACKGROUND

The role of adiponectin (ADIPOQ) in Alzheimer's disease (AD) has been documented, however, demonstrating controversial results. In this study, we investigated blood serum ADIPOQ levels, methylation of the adiponectin gene promoter, and adiponectin receptors (AdipoR1 and AdipoR2) expression in blood samples isolated from AD patients and healthy controls.

METHODS

We performed a case-control study including 248 subjects (98 AD patients and 150 healthy controls); ADIPOQ serum levels, AdipoR1, and AdipoR2 levels in PBMC were measured by ELISA Kits, and ADIPOQ gene methylation was analyzed using methyl-specific PCR.

RESULTS

Serum adiponectin levels were threefold higher in the AD group compared to the controls. We have also found a positive correlation between adiponectin and MMSE scores and high-density lipoprotein cholesterol (HDL-C) in AD patients. A significant difference in the proportion of methylation of the CpG sites at - 74 nt of the ADIPOQ gene promoter was detected in AD cases, and the levels of adiponectin in blood serum were significantly higher in methylated samples in the AD group compared to controls. The amount of AdipoR1 was significantly higher among AD subjects, while the expression of AdipoR2 did not vary between AD patients and controls.

CONCLUSION

These findings may contribute to a deeper understanding of the etiological factors leading to the development of dementia and may serve as a basis for the development of predictive biomarkers of AD.

Role of Adiponectin in Cardiovascular Diseases Related to Glucose and Lipid Metabolism Disorders

Lifestyle changes have led to increased incidence of cardiovascular disease (CVD); therefore, potential targets against CVD should be explored to mitigate its risks. Adiponectin (APN), an adipokine secreted by adipose tissue, has numerous beneficial effects against CVD related to glucose and lipid metabolism disorders, including regulation of glucose and lipid metabolism, increasing insulin sensitivity, reduction of oxidative stress and inflammation, protection of myocardial cells, and improvement in endothelial cell function. These effects demonstrate the anti-atherosclerotic and antihypertensive properties of APN, which could aid in improving myocardial hypertrophy, and reducing myocardial ischemia/reperfusion (MI/R) injury and myocardial infarction. APN can also be used for diagnosing and predicting heart failure. This review summarizes and discusses the role of APN in the treatment of CVD related to glucose and lipid metabolism disorders, and explores future APN research directions and clinical application prospects. Future studies should elucidate the signaling pathway network of APN cardiovascular protective effects, which will facilitate clinical trials targeting APN for CVD treatment in a clinical setting.

AMPK: An odyssey of a metabolic regulator, a tumor suppressor, and now a contextual oncogene

Metabolic reprogramming is a unique but complex biochemical adaptation that allows solid tumors to tolerate various stresses that challenge cancer cells for survival. Under conditions of metabolic stress, mammalian cells employ adenosine monophosphate (AMP)-activated protein kinase (AMPK) to regulate energy homeostasis by controlling cellular metabolism. AMPK has been described as a cellular energy sensor that communicates with various metabolic pathways and networks to maintain energy balance. Earlier studies characterized AMPK as a tumor suppressor in the context of cancer. Later, a paradigm shift occurred in support of the oncogenic nature of AMPK, considering it a contextual oncogene. In support of this, various cellular and mouse models of tumorigenesis and clinicopathological studies demonstrated increased AMPK activity in various cancers. This review will describe AMPK's pro-tumorigenic activity in various malignancies and explain the rationale and context for using AMPK inhibitors in combination with anti-metabolite drugs to treat AMPK-driven cancers.

Adiponectin as a potential therapeutic target for the treatment of restenosis

Restenosis is a pathologic re-narrowing of a coronary artery lesion after mechanical injury. Its pathophysiological mechanisms have not been fully elucidated at present, but are thought to include inflammation, vascular smooth muscle cell (VSMC) proliferation, and matrix remodeling, beginning with insufficient endothelium healing. Restenosis presents with angina symptoms or acute coronary syndromes and lead to a revascularization, either with coronary artery bypass or repeat percutaneous coronary intervention. Some studies have reported that hypoadiponectinemia has been an independent risk factor for the onset of acute coronary syndromes and restenosis. Accumulating evidence shows that low concentrations of adiponectin may be involved in impairing endothelium functions, inflammation, and VSMC proliferation that lead to restenosis. Preclinical studies have proven that adiponectin promotes endothelium healing, effectively inhibits inflammation, and maintains contractile phenotypes of VSMCs, indicating that it may be developed as a new therapeutic target for the treatment of restenosis.

Methods to Evaluate AMPK Regulation of Macrophage Cholesterol Homeostasis

Macrophages are a driving force in the development and progression of atherosclerosis, a chronic condition that can lead to cardiovascular disease. In this chapter we describe methods that monitor macrophage cholesterol homeostasis such as cholesterol synthesis, uptake, and efflux, all with the use of AMPK activators and potential genetic models that could help shed light on the role of this metabolic regulator in atherosclerosis and other chronic diseases.

AMPK as a Therapeutic Target for Treating Metabolic Diseases

The AMP-activated protein kinase (AMPK) is a central regulator of multiple metabolic pathways and may have therapeutic importance for treating obesity, insulin resistance, type 2 diabetes (T2D), non-alcoholic fatty liver disease (NAFLD), and cardiovascular disease (CVD). Given the ubiquitous expression of AMPK, it has been a challenge to evaluate which tissue types may be most beneficially poised for mediating the positive metabolic effects of AMPK-centered treatments. In this review we evaluate the metabolic phenotypes of transgenic mouse models in which AMPK expression and function have been manipulated, and the impact this has on controlling lipid metabolism, glucose homeostasis, and inflammation. This information may be useful for guiding the development of AMPK-targeted therapeutics to treat chronic metabolic diseases.

Evolving role of adiponectin in cancer-controversies and update

Adiponectin (APN), an adipokine produced by adipocytes, has been shown to have a critical role in the pathogenesis of obesity-associated malignancies. Through its receptor interactions, APN may exert its anti-carcinogenic effects including regulating cell survival, apoptosis and metastasis via a plethora of signalling pathways. Despite the strong evidence supporting this notion, some work may indicate otherwise. Our review addresses all controversies critically. On the whole, hypoadiponectinaemia is associated with increased risk of several malignancies and poor prognosis. In addition, various genetic polymorphisms may predispose individuals to increased risk of obesity-associated malignancies. We also provide an updated summary on therapeutic interventions to increase APN levels that are of key interest in this field. To date efforts to manipulate APN levels have been promising, but much work remains to be done.