Krzysztof Łabuzek

Quantification of metformin by the HPLC method in brain regions, cerebrospinal fluid and plasma of rats treated with lipopolysaccharide

Recently, it has been reported that metformin may attenuate inflammation and directly act on the central nervous system. Using the HPLC method, in Wistar rats, we assessed the changes in metformin concentrations in various brain regions (pituitary gland, olfactory bulb, hypothalamus, cerebellum, hippocampus, striatum, frontal cortex), cerebrospinal fluid and plasma after single and chronic oral administration, in the model of systemic inflammation induced by lipopolysaccharide (ip). Regarding the influence of systemic inflammation on metformin distribution, the pituitary gland demonstrated the highest its level after single and chronic administration (28.8 ± 3.5 nmol/g and 24.9 ± 3.2 nmol/g, respectively). We concluded that orally-dosed metformin rapidly crosses the blood-brain barrier and differently accumulates in structures of the central nervous system.

Effect of atorvastatin and fenofibric acid on adipokine release from visceral and subcutaneous adipose tissue of patients with mixed dyslipidemia and normolipidemic subjects

Because of methodological limitations and conflicting results of studies conducted thus far, the possible involvement of human adipose tissue in pleiotropic effects of statins and fibrates requires better understanding. Samples of visceral and subcutaneous adipose tissue obtained from 23 mixed dyslipidemic patients and 23 normolipidemic subjects were treated in vitro for 48 h with atorvastatin, fenofibric acid or both these agents. Visceral and subcutaneous fat of mixed dyslipidemic patients released more leptin, resistin, interleukin-6, tumor necrosis factor alpha (TNFalpha and plasminogen activator inhibitor-1 (PAI-1), and less adiponectin than respective adipose tissue of patients without lipid abnormalities. In both groups of patients, visceral and subcutaneous tissue varied in the amount of secreted adipokines. In dyslipidemic patients both drugs administered alone affected adipose tissue adiponectin and resistin secretion. Additionally, atorvastatin decreased PAI-1 while fenofibric acid reduced leptin release. A combined administration of atorvastatin and fenofibric acid changed the release of all studied markers by visceral fat but did not affect interleukin-6 and TNFalpha release by subcutaneous tissue. In normolipidemic subjects the effect on adipokine release was more pronounced in visceral fat, in which it was strongest if the drugs were given together. Adipose tissue hormonal activity differs between mixed dyslipidemic and normolipidemic patients and between visceral and subcutaneous adipose tissue. Atorvastatin and fenofibrate exhibit their pleiotropic effects in part by changing the adipokine release by human adipose tissue, regardless of its origin. These effects are stronger in patients with mixed dyslipidemia and are particularly pronounced if atorvastatin and fenofibric acid are given together.

Metformin has adenosine-monophosphate activated protein kinase (AMPK)-independent effects on LPS-stimulated rat primary microglial cultures

The results of recent studies suggest that metformin, in addition to its efficacy in treating type 2 diabetes, may also have therapeutic potential for the treatment of neuroinflammatory diseases in which reactive microglia play an essential role. However, the molecular mechanisms by which metformin exerts its anti-inflammatory effects remain largely unknown. Adenosine-monophosphate-activated protein kinase (AMPK) activation is the most well-known mechanism of metformin action; however, some of the biological responses to metformin are not limited to AMPK activation but are mediated by AMPK-independent mechanisms. In this paper, we attempted to evaluate the effects of metformin on unstimulated and LPS-activated rat primary microglial cell cultures. The presented evidence supports the conclusion that metformin-activated AMPK participates in regulating the release of TNF-α. Furthermore, the effects of metformin on the release of IL-1β, IL-6, IL-10, TGF-β, NO, and ROS as well as on the expression of arginase I, iNOS, NF-κB p65 and PGC-1α were not AMPK-dependent, because pretreatment of LPS-activated microglia with compound C, a pharmacological inhibitor of AMPK, did not reverse the effect of metformin. Based on the present findings, we propose that the shift of microglia toward alternative activation may underlie the beneficial effects of metformin observed in animal models of neurological disorders.

Metformin affects macrophages' phenotype and improves the activity of glutathione peroxidase, superoxide dismutase, catalase and decreases malondialdehyde concentration in a partially AMPK-independent manner in LPS-stimulated human monocytes/macrophages.

BACKGROUND Diabetic patients experience accelerated atherosclerosis. Metformin is a cornerstone of the current therapy of type 2 diabetes. Macrophages are the key cells associated with the development of atherosclerotic plaques. Therefore, our aim was to assess the in vitro effects of metformin on macrophages and its influence on the mechanisms involved in the development of atherosclerosis. MATERIALS AND METHODS Peripheral blood mononuclear cells were obtained from the group including 16 age-matched healthy non-smoking volunteers aged 18-40 years. Monocytes were further incubated with metformin, LPS and compound C--a pharmacological inhibitor of AMPK. The impact of metformin on oxidative stress markers, antioxidative properties, inflammatory cytokines and phenotypical markers of macrophages was studied. RESULTS We showed that macrophages treated with metformin expressed less reactive oxygen species (ROS), which resulted from increased antioxidative potential. Furthermore, a reduction in inflammatory cytokines was observed. We also observed a phenotypic shift toward the alternative activation of macrophages that was induced by metformin. All the aforementioned results resulted from AMPK activation, but a residual activity of metformin after AMPK blockade was still noticeable even after inhibition of AMPK by compound C. CONCLUSIONS Authors believe that metformin-based therapy, a cornerstone in diabetes therapy, not only improves the prognosis of diabetics by reducing blood glucose but also by reducing oxidative stress, inflammatory cytokine production and the shift toward alternative activation of macrophages.

Incretin-based therapies in the treatment of type 2 diabetes — More than meets the eye?

A lot of contradictory data regarding the serious side effects of incretin-based therapies are currently available, with more being prepared or published every month. Considering the widespread use of these drugs it should be considered a priority to establish both short- and long-term risks connected with incretin treatment. We performed an extensive literature search of the PubMed database looking for articles dealing with connections between incretin-based therapies and pancreatitis, pancreatic cancer, thyroid cancer and other neoplasms. Data obtained indicate that GLP-1 agonists and DPPIV inhibitors could increase the risk of pancreatitis and pancreatic cancer, possibly due to their capacity to increase ductal cell turnover, which has previously been found to be up-regulated in patients with obesity and T2DM. GLP-1 analogues exenatide and liraglutide seem to be connected with medullary thyroid carcinoma in rat models and, surprisingly, GLP-1 receptors have been found in papillary thyroid carcinoma, currently the most common neoplasm of the thyroid gland in humans. Changes in expression of DPPIV have been described in ovarian carcinoma, melanoma, endometrial adenocarcinoma, prostate cancer, non-small cell lung cancer and in certain haematological malignancies. In most cases loss of DPPIV activity is connected with a higher grading scale, more aggressive tumour behaviour and higher metastatic potential. In conclusion animal and human studies indicate that there could be a connection between incretin-based therapies and pancreatitis, pancreatic cancer, thyroid cancer and other neoplasms. Therefore whenever such therapy is started it would be wise to proceed with caution, especially if personal history of neoplasms is present.

Ezetimibe – a new approach in hypercholesterolemia management

Ezetimibe is the first agent used in hypercholesterolemia treatment known to lower intestinal cholesterol uptake that is able to inhibit NPC1L1 transport proteins in the brush boarder of enterocytes and macrophages. Furthermore, it demonstrates anti-inflammatory and immunomodulatory properties and influences the expression of certain antigens. The drug is rapidly absorbed from the gastrointestinal tract and is then glucuronidated to form the active metabolite. It also undergoes extensive enterohepatic circulation. Various genetic polymorphisms seem to influence the pharmacokinetics of ezetimibe with different effects. The drug also presents a complex impact on cytochrome P450 enzymes, as it is a metabolism-dependent inhibitor of CYP3A4. Ezetimibe does not demonstrate any clinically significant interactions with statins, fibrates, mipomersen sodium, levothyroxine or lopinavir. However, its effect in conjunction with cyclosporine is not neutral. The use of this cholesterol absorption inhibitor has been shown to be safe and effective among patients after cardiac, renal and liver transplants, as well as in HIV patients.

AICAR (5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside) increases the production of toxic molecules and affects the profile of cytokines release in LPS-stimulated rat primary microglial cultures

AICAR (5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside, Acadesine, AICA riboside) is an activator of AMP-activated protein kinase (AMPK). The results of recent studies suggest that AICAR, in addition to its application for treating metabolic disorders, may also have therapeutic potential for treating neuroinflammatory diseases where reactive microglia play an etiological role. However, the molecular mechanisms of action by which AICAR exerts its anti-inflammatory effects still remain unclear or controversial. In this paper we attempt to evaluate the effects of AICAR on non-stimulated and LPS-activated rat primary microglial cell cultures. The presented evidence supports the conclusion that AMPK activated by AICAR is involved in regulation of ROS and cytokine production (IL-1 beta, TNF-alpha (6h), IL-10 and TGF-beta) as well as arginase I and PGC-1alpha expression. Furthermore, we found that the effects of AICAR on IL-6 and TNF-alpha (12, 24h) release and on the expression of iNOS and NF-kappaB p65 are not AMPK-dependent because the pre-treatment of LPS-activated microglia with compound C (a pharmacological inhibitor of AMPK) did not reverse the effect of AICAR. The results of the presented study provide additional data about AMPK-dependent and -independent mechanisms whereby AICAR may modulate inflammatory response of microglia.

AMP‐activated protein kinase is involved in induction of protective autophagy in astrocytes exposed to oxygen‐glucose deprivation

AMP‐activated kinase (AMPK) acts as the intracellular ATP depletion sensor, which detects and limits increases in the AMP/ATP ratio. AMPK may be significantly activated under stress conditions that deplete cellular ATP levels such as ischemia/hypoxia or glucose deprivation. Recent studies strongly suggest that AMPK participates in autophagy regulation, but it is not known whether AMPK activated by ischemia regulates autophagy in astrocytes and the consequence of autophagy activation in ischemic astrocytes are unclear. We have investigated the contribution of AMPK to autophagy activation in rat primary astrocyte cultures subjected to ischemia‐simulating conditions (combined oxygen glucose deprivation, OGD) and its potential effects on astrocyte damage induced by OGD (1–12 h). The evidence supports the conclusion that AMPK activation at early stages of OGD is involved in induction of protective autophagy in astrocytes. Inhibition of AMPK, either by siAMPKα1 or by compound C, significantly attenuated the expression of autophagy‐related proteins and decrease of astrocyte viability following OGD. The findings provide additional data about the role of AMPK in ischemic astrocytes and downstream responses that may be involved in OGD‐induced protective autophagy.

Eplerenone promotes alternative activation in human monocyte-derived macrophages

BACKGROUND In this study, we have analyzed the response of human monocyte-derived macrophages to mineralocorticoid axis modulators. METHODS Human monocyte-derived macrophages were incubated with aldosterone alone, eplerenone alone, and the combination of aldosterone and eplerenone. The analyzed variables were nitric oxide and reactive oxygen species production, and the gene and protein expression of inducible nitric oxide synthase, arginase I, and mannose receptor. RESULTS We showed that aldosterone promotes a classic inflammatory response in macrophages, whereas its antagonist, eplerenone, attenuates aldosterone-induced activity. CONCLUSION Eplerenone did not quantitatively weaken the response of macrophages to aldosterone but instead qualitatively changed their behavior.

Atorvastatin and fenofibric acid differentially affect the release of adipokines in the visceral and subcutaneous cultures of adipocytes that were obtained from patients with and without mixed dyslipidemia

In this study, we compared the effects of atorvastatin and fenofibric acid, which were administered alone or in combination, on the secretory function of human adipocytes that were obtained from the visceral and subcutaneous adipose tissues of 19 mixed dyslipidemic patients and 19 subjects with a normal lipid profile. The adipocytes were incubated in vitro in the presence of atorvastatin and/or fenofibric acid. The secretory function of the cells was determined using ELISA assays. The visceral adipocytes released significantly more adiponectin and IL-6 and less PAI-1 than those that were obtained from subcutaneous tissue. The levels and patterns of adipokine release differed between the patients with or without lipid abnormalities and between the adipocytes that were obtained from visceral or subcutaneous adipose tissue. The culture that contained hypolipidemic drugs resulted in the significant changes of the release of adipokines. The effects of atorvastatin and fenofibric acid on the hormonal function of human adipocytes may be, in part, responsible for the clinical efficacy of these drugs in the prevention and treatment of dyslipidemia-related cardiovascular and metabolic disorders. The study supports the concept that the pleiotropic effects of fenofibrate and atorvastatin may be, in part, a result of their impact on the secretory function of adipocytes.