AICAr, a Widely Used AMPK Activator with Important AMPK-Independent Effects: A Systematic Review

AICAR′s ability to activate AMPK makes it useful for studying the cellular responses to metabolic stress and energy demand. AICAR mimics the effects of insulin on the expression of two gluconeogenic genes PEPCK and glucose-6-phosphatase. L-arginine-induced elevations in serum levels of pancreas injury enzymes (amylase and lipase) and the pathological changes as well as pancreatitis scores analyzed in H&E-stained pancreas sections in Nrf2 knockout (KO) mice were higher than those in WT SAP mice (Figures 7A–D). Meanwhile, the beneficial effects of AICAR against L-arginine-induced pancreatic injury reflected by the above indicators were significantly attenuated in Nrf2 KO mice compared with WT littermates (Figures 7A,C). Likewise, the pathological changes in liver sections of the Nrf2 KO SAP mice were more severe than those in the WT SAP groups by H&E staining (Figure 7B). Additionally, treatment of WT SAP mice with AICAR markedly reduced these negative pathological changes (Figure 7B); however, these protective effects mediated by AICAR were weakened in Nrf2 KO mice (Figure 7B).

Exercise Training—Humans

• As MB staining is much more feasible to perform than viable counting of hundreds of microtiter wells, we therefore continued to evaluate growth by the MB assay.
• All rats and mice were fed randomly at 24 ± 2°C and 40–60% humidity with a 12 h dark cycle before the experiment.
• Both human and murine lymphocytes (CD3+CD45+) were characterised as T helper (% CD4+ of CD3+CD45+) and cytotoxic T cells (% CD8+ of CD3+CD45+).
• The present study confirms these findings and provides additional evidence that AMPK is required to fully beget exercise training-induced increases in mitochondrial oxidative phosphorylation complexes.

Although a peptide blocks MUC1 signalling, metabolites targeting MUC1 are not well studied. Cells were seeded in 96-well flat bottom microtiter plates at a density of 1×104 cells per well. The absorbance was measured on a microplate reader (Synergy HT, Bio-Tek, USA) at 570 nm. So far 5-Fluorouracil (5-FU) remains a widely used chemotherapeutic drug in the treatment of colorectal carcinoma. Recently, metformin is reported to have a synergistic effect in combination with some chemotherapeutic agents 17, 18. However, it remains unclear whether metformin or AICAR can be used in combination with 5-FU to enhance the anticancer effect, since there is no study on the correlation between the metformin/AICAR and 5-FU treatment in vitro and in vivo.

For in vitro experiments, two human osteosarcoma cell lines, MG63 and KHOS, were treated with AICAR, and the effects of AICAR on cell growth and mitochondrial apoptosis were assessed by WST assays, TUNEL staining, and immunoblot analyses. In vivo, human osteosarcoma-bearing mice were treated with AICAR, and the mitochondrial proliferation and apoptotic activity in treated tumors were assessed. In vitro experiments revealed that AICAR activated AMPK, inhibited cell growth, and induced mitochondrial apoptosis in both osteosarcoma cell lines. In vivo, AICAR significantly reduced osteosarcoma growth without apparent body weight loss and AICAR increased both mitochondrial proliferation and apoptotic activity in treated tumor tissues.

AICAR and metformin decreased the IL-8 and GROα production stimulated by TNF-α in KGN

The supernatant was collected and mixed with 10% activated charcoal (Sigma-Aldrich), followed by centrifugation at 13,000 rpm for 20 min. 3H2O in the aqueous phase was measured by liquid scintillation counting (Perkin Elmer Trilu, MA, USA) and normalized to protein contents. The cells detect a lower energy of the effort, calculating the concentration of the AMP. To acquire further evidence that AICAR effects on CFB expression are independent of AMPK, we knocked out both catalytic isoforms of AMPK (α1 and α2) genes by CRISPR-Cas9 endonuclease system. First we made sure that TNF-α-induced expression of CFB in AMPK α-knockout cells was comparable to that in negative controls using CRISPR/Cas9 vectors guided by scramble RNA (Fig. 4). AMPKα deletion did not modify the inhibitory effect of AICAR on TNF-α-induced CFB expression (Fig. 4).

We also investigated the impact of AICAR/Compound C treatment on acetyl-CoA carboxylase (ACC), the downstream target of activated AMPK in T cells. Similarly, AICAR promoted, while Compound C inhibited, phosphorylation of ACC (Ser-79) in Iono-activated CD4+ and CD8+ T cells from WT mice (Figure 1E). Using Western blot analysis, we further confirmed that AICAR enhanced, but Compound C inhibited, the phosphorylation of AMPK and ACC in T cells from WT mice, but not from KO mice (Figure 1F). Altogether, using CD4-Cre-AMPKα1fl/fl mice, our data clearly indicate a specific AMPK activation/inhibition effect of AICAR/Compound C in T cells.

To understand the mechanism responsible for proliferation arrest in response to AICAr, we have to go back to the role of endogenous AICAR in de novo purine synthesis that has been well-known to affect cell growth much before the discovery of the role of AICAr in AMPK activation. As a central metabolic regulator that reacts to an increase in AMP/ATP ratio, AMPK restricts growth and proliferation in response to energetic or nutritional stress. As shown in Figure 2, mTOR is a catalytic subunit of two functionally distinct protein complexes, mTORC1 (mTOR complex 1) and mTORC2 (mTOR complex 2), and both S6K1 and 4E-BP1 lie downstream of mTORC1.

Loss of phosphatase and tensin homologue (PTEN) is the most common mutation of a tumor suppressor gene in prostate cancer, and both cell lines used in this study have inactive PTEN 41. PTEN is a negative regulator of the PI3K-Akt pathway and downstream mTOR signalling and its loss of function leads to dysregulation of this pathway, increasing proliferation, survival, resistance to therapy and altering metabolism 42. Re-introduction of PTEN in PTEN-null prostate cancer or inhibition of the PI3K pathway also decreased expression of fatty acid synthase 43, demonstrating the importance of its role in prostate cancer. Radiation-induced activation of the PI3K/Akt/mTOR pathway may limit the effectiveness of radiotherapy and inhibition of this pro-survival pathway enhanced sensitivity to radiotherapy in glioblastoma and prostate cancer cells 44, 45. Prior studies on anti-inflammatory effects of AICAR and AMPK have not examined effects on complement components. The current study shows the ability of AICAR to inhibit TNF-α-induced CFB expression in human RPE cells.

NFκB what dissociated from IκB and subsequently shepherded to the nucleus, was also thought to be suppressed by AICAR and by metformin. On the basis of present observations, IL-8 and GROα in FF are thought to lead to neutrophil chemoattraction and accumulation. As our results also indicated that IL-8 and GROα are regulated by a mechanism involving TNF-α, it is likely that IL-8 and GROα may play an important role in the accumulation of neutrophils and in the subsequent induction of ovulation https://kingscathedral.com/blog/steroids-understanding-their-use-benefits-and-75/ 33. On the other hand, the elevation of not only white blood count and neutrophil count but also TNF-α, IL-6, CRP in serum levels have been implicated in pathphysiological findings of PCOS compared with age- and /body mass index- matched controls 34-36.

Recent research has shown that the tumour microenvironment has played a vital role in promoting tumour initiation and progression by modulating the extracellular matrix and immune cell homing 102. We noticed that AICAR treatment could block the proliferation of stromal cells, including alveolar macrophages, endothelial cells, and fibroblasts. Tumour-adjacent stromal cells promote tumour initiation and progression by providing paracrine signals 103. Thus, AICAR might concurrently decrease tumour cells’ survival by inhibiting paracrine signalling from these tumour stromal cells. Recent studies showed that blocking JAK-STAT signalling with the JAK inhibitors reduced tumour-promoting inflammation and tumour formation in the lungs 56. Our data showing reduced JAK-STAT signalling after AICAR treatment indicates that AICAR might play a similar role to JAK inhibitors in blocking pro-tumorigenic signals from stromal cells.

In these same double-knockout mice, S6K1 phosphorylation was significantly increased, suggesting that both substrates of TORC1 influence each other (32). The present data also support this finding, given the significant decrease in S6K1 phosphorylation in the AICAR-treated ob/ob mice. Activation of glycogen phosphorylase and glycogenolysis in rat skeletal muscle by AICAR—an activator of AMP-activated protein kinase. AMPK is a heterodimeric protein serine/threonine kinase that regulates the energy status of cells to protect cell from metabolic stress. AMPK phosphorylates various metabolic enzymes to activate catabolic pathways (e.g. ketogenesis) and block anabolic pathways (e.g. protein synthesis). One of the key mechanisms is the upregulation of glucose transporter proteins, such as GLUT4, which translocate to the cell membrane, allowing more glucose to enter the cell.