Current Pharmaceutical Design - Volume 17, Issue 4, 2011

Rev-erbs are members of the nuclear receptor (NR) transcription factor superfamily and are widely expressed, but are most prevalent in liver, adipose tissue, skeletal muscle and brain. Rev-erbs are key regulators of the circadian rhythm and are expressed in a circadian manner. The discovery that Rev-erbs are ligand-regulated receptors, whose repressive activity is regulated by the endogenous porphyrin ligand, heme, as well as the recent report of the first synthetic Rev-erb ligand, GSK4112/SR6452, suggests that pharmacological modulation through Rev-erb may provide new routes to treat metabolic diseases. Here, we review the work leading to the discovery that Rev-erbs are indeed ligand-regulated and the role that both natural and synthetic Rev-erb ligands have on adipogenesis.

Since storage of excess fat in peripheral tissues is a contributing factor leading to obesity and type II diabetes, many investigators are studying the key lipid metabolizing enzymes found in adipose tissue as drug targets to reduce excess fat. The availability of cultured cell lines and primary stem cells, preadipocyetes, and adipocytes has facilitated therapeutic approaches aimed at targeting fat storage. This includes developing inhibitors for enzymes regulating lipogenesis in these cells, such as acetyl-CoA carboxylase, fatty acid synthase, diacylgycerol acyl transferase, and stearoyl CoA desaturase. High level expression of each protein is often used to confirm stem cells have undergone adipogenesis. Inhibition of these enzymes often leads to reduced fat cell fat differentiation and lipid synthesis and may also contribute to increased fat oxidation and energy expenditure. This article reviews developments in pharmaceutical research on these enzymes, with particular emphasis on the role of the enzymes in adipose tissue metabolism.

Information relating to the biology, culture expansion, and mechanisms relating to adipose-derived cells has advanced significantly in the past decade. Both the heterogeneous stromal vascular fraction (SVF) and more homogeneous adipose-derived stem cells (ASC) offer unique opportunities as novel cell-based therapeutics and as traditional pharmaceutical discovery tools. This review highlights the cytokine secretory functions of ASC and SVF cells as well as their potential use as immunomodulators and gene delivery vehicles. These functions make it feasible to exploit adipose-derived cells in the treatment of ischemic, musculoskeletal, and oncological disorders. With appropriate commercial development and in vivo validation, ASC and SVF cells will have a significant therapeutic impact in the future.

Gp130 cytokines are involved in the regulation of numerous biological processes, including hematopoiesis, immune response, inflammation, cardiovascular action, and neuronal survival. These cytokines share glycoprotein 130 as a common signal transducer in their receptor complex and typically activate STAT3. Most gp130 cytokines have paracrine or endocrine actions, and their levels can be measured in circulation in rodents and humans. In recent years, various laboratories have conducted studies to demonstrate that gp130 cytokines can modulate adipocyte development and function. Therefore, these studies suggest that some gp130 cytokines may be viable anti-obesity therapeutics. In this review, we will summarize the reported effects of gp130 cytokines on adipocyte differentiation and adipocyte function. In addition, the modulation of gp130 cytokines in conditions of obesity, insulin resistance, and Type 2 diabetes will be presented.

There is a dramatic increase in the number of elderly persons on a worldwide scale with an increase in chronic comorbidities, especially type 2 diabetes (T2DM) and dementia. Although cognitive faculties commonly deteriorate in non-diabetic persons as they age, several studies have concluded that diabetes is uniquely associated with cognitive decline and is associated with a two-fold risk of Alzheimer's Disease (AD). Studies have also suggested that good glycemic has shown to improve cognitive status, however whether the use of specific anti-diabetic oral agents may play an additional role in controlling against cognitive deterioration is unknown. In addition, excitotoxicity from the overstimulation of glutamate receptors is considered a major cause of neuron death in AD and statins may be promising agents for protecting against memory loss. Possible pathophysiologic mechanisms common to both T2DM and AD are glucose toxicity and a direct effect of insulin on amyloid metabolism. In fact, AD and T2DM have comparable pathological features in the islet and brain (amyloid derived from amyloid β protein (β-amyloid) in the brain in AD and islet amyloid derived from islet amyloid polypeptide in the pancreas in T2DM). Evidence is growing linking precursors of amyloid deposition in the brain and pancreas to the pathogenesis of AD and T2DM, respectively. Indeed, the need to identify agents capable of correcting such pathological features may in turn significantly protect against the accumulation of β-amyloid in the brain, known to interfere with correct cognitive function. Cholesterol may also be directly involved in β-amyloid aggregation: abnormal oxidative metabolites such as cholesterol-derived aldehydes can modify β-amyloid, firstly promoting Schiff base formation, then accelerating the early stages of amyloidogenesis. At the moment, genome-wide association studies (GWAS) have begun to elucidate the genetic architecture of chronic diseases including, T2DM and AD. Thus, one of the challenges for a successful GWAS in the future will be to identify a genotype in older persons with T2DM for good drug response, which in turn may protect against cognitive decline and AD. The literature has suggested that the use of insulin sensitizers and statins is correlated with a lower rate of cognitive decline in older persons. In this paper, we will explore recent findings regarding diverse single nucleotide polymorphisms from GWAS on T2DM, AD and both. We will also shed light on future pathways, as the basis of improving drug and diagnostics development for a better integration of genetic studies for precise drugdevelopment focusing on the role of genetic variation in maintaining metabolic control and cognitive performance.

Herbal medicines, an important group of multicomponent therapeutics, are widely and increasignly used worldwide. Despite the popularitiy of herbal medicines, the clinical evidence that support the use of most herbal medicines is weak. Pharmacokinetic and absorption, distribution, metabolism and excretion (ADME) studies have been integrated into modern drug development, but ADME studies are generally not needed for herbal remedy discovery and development. For the majority of herbal medicines, data on their ADME and pharmacokinetic properties in humans are lacking or scant. An extensive literature search indicates that there are limited data on ADME properties of herbal medicines in humans. Many herbal compounds undergo Phase I and/or Phase II metabolism in vivo, with cytochrome P450s (CYPs) and uridine diphosphate glucuronosyltransferases (UGTs) playing a major role. Some herbal ingredients are substrates of P-glycoprotein (P-gp/MDR1/ABCB1) which is highly expressed in the intestine, liver, brain and kidney. As such, the activities of these drug metabolizing enzymes and drug transporters are critical determining factors for the in vivo ADME processes of herbal remedies. There are increasing ADME studies of herbal remedies, but these studies are mainly focused on a small number of herbal medicines including St John's wort, milk thistle, curcumin, echinacea, ginseng, ginkgo, and ginger. For an herbal medicine, the pharmacological activity is gained when the active agents or the active metabolites reach and sustain proper levels at their sites of action. Both the dose levels and ADME processes of active herbal components in the body govern their target-site concentrations and thus the therapeutic responses. In this regard, a safe and optimal use of herbal medicines requires a full understanding of their ADME profiles. To optimize the use of herbal remedies, further studies to explore their ADME properties in humans are certainly warranted.