PPARγ signaling and metabolism: the good, the bad and the future
TL;DR: This review highlights key advances in understanding PPARγ signaling in energy homeostasis and metabolic disease and also provides new explanations for adverse events linked to TZD-based therapy.
Abstract: Thiazolidinediones (TZDs) are potent insulin sensitizers that act through the nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) and are highly effective oral medications for type 2 diabetes. However, their unique benefits are shadowed by the risk for fluid retention, weight gain, bone loss and congestive heart failure. This raises the question as to whether it is possible to build a safer generation of PPARγ-specific drugs that evoke fewer side effects while preserving insulin-sensitizing potential. Recent studies that have supported the continuing physiologic and therapeutic relevance of the PPARγ pathway also provide opportunities to develop newer classes of molecules that reduce or eliminate adverse effects. This review highlights key advances in understanding PPARγ signaling in energy homeostasis and metabolic disease and also provides new explanations for adverse events linked to TZD-based therapy.
Citations
More filters
TL;DR: This review focuses on biochemical concepts of lipidPeroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting geneexpression and promoting cell death.
Abstract: Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.
3,647 citations
Additional excerpts
...Mario F. Muñoz was supported by Consejeria de Economı́a, Innovacion y Ciencia de la Junta de Andalucia (Spain) postdoctoral fellowship (P10-CTS-6494)....
[...]
TL;DR: New perspective is gained on the roles played by adipocyte in a variety of homeostatic processes and on the mechanisms used by adipocytes to communicate with other tissues and how these relationships are altered during metabolic disease and how they might be manipulated to restore metabolic health.
1,746 citations
Cites background from "PPARγ signaling and metabolism: the..."
..., 2003), but TZD use causes weight gain, not weight loss (Ahmadian et al., 2013)....
[...]
...Thiazolidinediones have been reported to increase the browning of white fat (Petrovic et al., 2010; Qiang et al., 2012; Teruel et al., 2003), but TZD use causes weight gain, not weight loss (Ahmadian et al., 2013)....
[...]
...Unfortunately, the clinical utility of TZDs has been limited by their unfavorable side effect profile, including fluid retention, osteoporosis, and (possibly) increased risk of cardiovascular events (Ahmadian et al., 2013)....
[...]
TL;DR: The pathophysiological link between macrophages, obesity, and insulin resistance is discussed, highlighting the dynamic immune cell regulation of adipose tissue inflammation and the new therapeutic targets that have emerged.
593 citations
Cites background from "PPARγ signaling and metabolism: the..."
...PPARg activation broadly inhibits proinflammatory pathways, leading to decreased ATM content, increased adipose tissue eosinophil numbers, and increased differentiation of anti-inflammatory Treg cells (Ahmadian et al., 2013; Hamaguchi and Sakaguchi, 2012)....
[...]
TL;DR: A significant research effort has recently been undertaken to explore the PPARγ-activating potential of a wide range of natural products originating from traditionally used medicinal plants or dietary sources.
497 citations
TL;DR: The roles of innate immune cells involved in secreting inflammatory factors in the obese state, including proinflammatory adipose tissue macrophages and natural killer cells are reviewed.
Abstract: Low-grade tissue inflammation induced by obesity can result in insulin resistance, which in turn is a key cause of type 2 diabetes mellitus. Cells of the innate immune system produce cytokines and other factors that impair insulin signalling, which contributes to the connection between obesity and the onset of type 2 diabetes mellitus. Here, we review the innate immune cells involved in secreting inflammatory factors in the obese state. In the adipose tissue, these cells include proinflammatory adipose tissue macrophages and natural killer cells. We also discuss the role of innate immune cells, such as anti-inflammatory adipose tissue macrophages, eosinophils, group 2 innate lymphoid cells and invariant natural killer T cells, in maintaining an anti-inflammatory and insulin-sensitive environment in the lean state. In the liver, both Kupffer cells and recruited hepatic macrophages can contribute to decreased hepatic insulin sensitivity. Proinflammatory macrophages might also adversely affect insulin sensitivity in the skeletal muscle and pancreatic β-cell function. Finally, this Review provides an overview of the mechanisms for regulating proinflammatory immune responses that could lead to future therapeutic opportunities to improve insulin sensitivity.
496 citations
References
More filters
TL;DR: The development of brown adipose tissue with its characteristic protein, uncoupling protein-1 (UCP1), was probably determinative for the evolutionary success of mammals, as its thermogenesis enhances neonatal survival and allows for active life even in cold surroundings.
Abstract: Cannon, Barbara, and Jan Nedergaard. Brown Adipose Tissue: Function and Physiological Significance. Physiol Rev 84: 277–359, 2004; 10.1152/physrev.00015.2003.—The function of brown adipose tissue i...
5,470 citations
TL;DR: Patients and providers should consider the potential for serious adverse cardiovascular effects of treatment with rosiglitazone for type 2 diabetes mellitus as well as the availability of outcome data for myocardial infarction and death from cardiovascular causes.
Abstract: �Rosiglitazone was associated with a significant increase in the risk of myocardial infarction and with an increase in the risk of death from cardiovascular causes that had borderline significance. Our study was limited by a lack of access to original source data, which would have enabled time-to-event analysis. Despite these limitations, patients and providers should consider the potential for serious adverse cardiovascular effects of treatment with rosiglitazone for type 2 diabetes.
4,570 citations
TL;DR: It is reported that thiazolidinediones are potent and selective activators of peroxisome proliferator-activated receptor γ (PPARγ), a member of the nuclear receptor superfamily recently shown to function in adipogenesis, and raised the intriguing possibility that PPARγ is a target for the therapeutic actions of this class of compounds.
3,635 citations
TL;DR: The results suggest that the physiologic role of PPAR gamma 2 is to regulate development of the adipose lineage in response to endogenous lipid activators and that this factor may serve to link the process of adipocyte differentiation to systemic lipid metabolism.
3,420 citations
TL;DR: A molecular explanation why SARS-CoV infections cause severe and often lethal lung failure and suggest a rational therapy for SARS and possibly other respiratory disease viruses is provided.
Abstract: During several months of 2003, a newly identified illness termed severe acute respiratory syndrome (SARS) spread rapidly through the world. A new coronavirus (SARS-CoV) was identified as the SARS pathogen, which triggered severe pneumonia and acute, often lethal, lung failure. Moreover, among infected individuals influenza such as the Spanish flu and the emergence of new respiratory disease viruses have caused high lethality resulting from acute lung failure. In cell lines, angiotensin-converting enzyme 2 (ACE2) has been identified as a potential SARS-CoV receptor. The high lethality of SARS-CoV infections, its enormous economic and social impact, fears of renewed outbreaks as well as the potential misuse of such viruses as biologic weapons make it paramount to understand the pathogenesis of SARS-CoV. Here we provide the first genetic proof that ACE2 is a crucial SARS-CoV receptor in vivo. SARS-CoV infections and the Spike protein of the SARS-CoV reduce ACE2 expression. Notably, injection of SARS-CoV Spike into mice worsens acute lung failure in vivo that can be attenuated by blocking the renin-angiotensin pathway. These results provide a molecular explanation why SARS-CoV infections cause severe and often lethal lung failure and suggest a rational therapy for SARS and possibly other respiratory disease viruses.
2,983 citations