Remodeling glucose and lipid metabolism through AMPK activation: relevance for treating obesity and Type 2 diabetes

Mangiferin Ameliorates HFD-Induced NAFLD through Regulation of the AMPK and NLRP3 Inflammasome Signal Pathways

Nonalcoholic fatty liver disease (NAFLD) is closely related to glycolipid metabolism and liver inflammation. And there is no effective drug approved for its clinical therapy. In this study, we focused on mangiferin (Man) and explored its effects and mechanisms on NAFLD treatment based on the regulation of glycolipid metabolism and anti-inflammatory in vivo and in vitro. The results exhibited that Man can significantly attenuate liver injury, insulin resistance, and glucose tolerance in high-fat diet- (HFD-) induced NAFLD mice and significantly reduce fat accumulation and inflammation in hepatic tissue of NAFLD mice. The transcriptome level RNA-seq analysis showed that the significantly different expression genes between the Man treatment group and the HFD-induced NAFLD model group were mainly related to regulation of energy, metabolism, and inflammation in liver tissue. Furthermore, western blots, real-time PCR, and immunohistochemistry experiments confirmed that Man significantly activated the AMPK signal pathway and inhibited NLRP3 inflammasome activation and pyroptosis in NAFLD mice. In in vitro cell experiments, we further confirmed that Man can promote glucose consumption and reduce intracellular triglyceride (TG) accumulation induced by free fatty acids in HepG2 cells and further that it can be blocked by AMPK-specific inhibitors. Western blot results showed that Man upregulated p-AMPKα levels and exhibited a significant AMPK activation effect, which was blocked by compound C. At the same time, Man downregulated the expression of NLRP3 inflammasome-related proteins and inhibited the activation of NLRP3 inflammasome, alleviating cell pyroptosis and inflammation effects. These results indicate that Man anti-NAFLD activity is mediated through its regulation of glucolipid metabolism by AMPK activation and its anti-inflammatory effects by NLRP3 inflammasome inhibition. Our study indicates that Man is a promising prodrug for the therapy of NAFLD patients.

A Box-Behnken Design for Optimal Green Extraction of Compounds from Olive Leaves That Potentially Activate the AMPK Pathway

Olive leaves contain bioactive compounds that have been shown to activate AMP-activated protein kinase (AMPK), which decreases intracellular lipid accumulation. Microwave-assisted extraction (MAE) is a green extraction technique that is frequently used in the recovery of phenolic compounds from plants. Thus, in this study, a Box-Behnken design was used to optimize MAE conditions such as temperature, percentage of ethanol and extraction time to obtain the maximum content of total compounds and compounds that activate AMPK. To this end, all extracts were characterized by High-Performance Liquid Chromatography Coupled to Electrospray Ionization Time-of-Flight Mass Spectrometry (HPLC-ESI-TOF-MS). The optimum conditions to obtain the highest content of total compounds were 123 °C, 100% of ethanol/water (v/v) and 23 min, whereas the optimum conditions for the highest amount of compounds that activate AMPK were 111 °C, 42% of ethanol/water (v/v) and 23 min. Thus, a multi-analysis by desirability was carried out to establish MAE optimal conditions for both responses. The optimum conditions were 111 °C, 100% EtOH and 23 min with a desirability of 0.97, which means that the responses are close to their individual optimal values. As a result, the olive leaf extract obtained at these optimal MAE conditions has great potential to be effective in the treatment of obesity.

Efficiently Anti-Obesity Effects of Unsaturated Alginate Oligosaccharides (UAOS) in High-Fat Diet (HFD)-Fed Mice

Obesity and its related complications have become one of the leading problems affecting human health. However, current anti-obesity treatments are limited by high cost and numerous adverse effects. In this study, we investigated the use of a non-toxic green food additive, known as unsaturated alginate oligosaccharides (UAOS) from the enzymatic degradation of Laminaria japonicais, which showed effective anti-obesity effects in a high-fat diet (HFD) mouse model. Compared with acid hydrolyzed saturated alginate oligosaccharides (SAOS), UAOS significantly reduced body weight, serum lipid, including triacylglycerol (TG), total cholesterol (TC) and free fatty acids (FFA), liver weight, liver TG and TC, serum alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels, adipose mass, reactive oxygen species (ROS) formation, and accumulation induced in HFD mice. Moreover, the structural differences in β-d-mannuronate (M) and its C5 epimer α-l-guluronate (G) did not cause significant functional differences. Meanwhile, UAOS significantly increased both AMP-activated protein kinase α (AMPKα) and acetyl-CoA carboxylase (ACC) phosphorylation in adipocytes, which indicated that UAOS had an anti-obesity effect mainly through AMPK signaling. Our results indicate that UAOS has the potential for further development as an adjuvant treatment for many metabolic diseases such as fatty liver, hypertriglyceridemia, and possibly diabetes.

Jwa Kum Whan Attenuates Nonalcoholic Fatty Liver Disease by Modulating Glucose Metabolism and the Insulin Signaling Pathway

Over the last decade, the link between nonalcoholic fatty liver disease (NAFLD) and insulin resistance has attracted considerable attention. Caused by chronic hyperglycemic stress, insulin resistance (IR) impairs insulin signal transduction and leads to the development of NAFLD. Jwa Kum Whan (JKW), a herbal formula in Traditional Korean Medicine, consists of two medicinal herbs that possess notable effects against hyperglycemia and IR. In this study, we sought to determine the pharmacological effects of JKW, and the mechanisms responsible, on hepatic steatosis in free fatty acids (FFAs)-stimulated HepG2 cells and in high-fat diet (HFD)-fed obese mice. Treatment with JKW significantly decreased intracellular lipid accumulation in vitro. Furthermore, JKW significantly triggered the phosphorylation of insulin receptor substrate-1 (IRS-1) and phosphoinositide 3-kinase (PI3K) and modulated glucose and lipid metabolism via an AMP-activated protein kinase (AMPK) signaling pathway. Analysis of serum parameters in HFD-fed mice showed that JKW improved glucose levels and insulin resistance index (HOMA-IR). In addition, JKW successfully reduced hepatic triglyceride (TG) and cholesterol accumulation. Our results suggest that JKW alleviates NAFLD by modulating the insulin signaling pathway and glucose metabolism. These findings provide a scientific rationale for the potential use of JKW for the treatment and prevention of NAFLD.

Inhibition of Adipogenesis by Diphlorethohydroxycarmalol (DPHC) through AMPK Activation in Adipocytes

The purpose of this study was to investigate the antiobesity effect and the mechanism of action of diphlorethohydroxycarmalol (DPHC) isolated from Ishige okamurae in 3T3-L1 cells. The antiobesity effects were examined by evaluating intracellular fat accumulation in Oil Red O-stained adipocytes. Based on the results, DPHC dose-dependently inhibited the lipid accumulation in 3T3-L1 adipocytes. DPHC significantly inhibited adipocyte-specific proteins such as SREBP-1c, PPARγ, C/EBP α, and adiponectin, as well as adipogenic enzymes, including perilipin, FAS, FABP4, and leptin in adipocytes. These results indicated that DPHC primarily acts by regulating adipogenic-specific proteins through inhibiting fat accumulation and fatty acid synthesis in adipocytes. DPHC treatment significantly increased both AMPK and ACC phosphorylation in adipocytes. These results indicate that DPHC inhibits the fat accumulation by activating AMPK and ACC in 3T3-L1 cells. Taken together, these results suggest that DPHC can be used as a potential therapeutic agent against obesity.

AMP-activated protein kinase signaling is upregulated in papillary thyroid cancer

AMP-activated protein kinase (AMPK) is activated by the depletion in cellular energy levels and allows adaptive changes in cell metabolism and cell survival. Recently, our group described that AMPK plays an important role in the regulation of iodide and glucose uptake in thyroid cells. However, AMPK signaling pathway in human thyroid carcinomas has not been investigated so far.

OBJECTIVE

To evaluate the expression and activity of AMPK in papillary thyroid carcinomas.

METHODS

We examined total and phosphorylated AMPK (tAMPK and pAMPK) and phosphorylated acetyl-CoA-carboxylase (pACC) expressions through imunohistochemistry, using a tissue microarray block composed of 73 papillary thyroid carcinomas (PAP CA) or microcarcinomas (PAP MCA) and six adenoma (AD) samples from patients followed at the Federal University Hospital. The expression levels were compared with the non-neoplastic tissues from the same patient. Two different pathologists analyzed the samples and attributed scores of staining intensity and the proportion of stained cells. A total index was obtained by multiplying the values of intensity and the proportion of stained cells (INTxPROP).

RESULTS

tAMPK, pAMPK, and pACC showed a predominant cytoplasmic staining in papillary carcinomas, adenomas, and non-neoplastic thyroid tissues. However, the intensity and the proportion of stained cells were higher in carcinomas, so that a significant increase was found in the INTxPROP score both in PAP CA and PAP MCA, when compared with their respective controls.

CONCLUSION

Our results show unequivocally that AMPK pathway is highly activated in papillary thyroid carcinomas; however, more studies are necessary to understand the pathophysiological significance of AMPK activation in thyroid carcinogenesis.

The role of AMP-activated protein kinase in regulating white adipose tissue metabolism

AMP-activated protein kinase (AMPK) is a heterotrimeric enzyme that plays a major role in the maintenance of energy homeostasis in various organs and tissues. When activated, AMPK can induce substrate catabolism and shut down energy-consuming anabolic pathways to increase intracellular ATP availability. Even though most of these effects have been described in muscle and liver, several studies have provided compelling evidence that AMPK also plays an important role in the regulation of white adipose tissue (WAT) glucose and lipid metabolism. In fact, the effects of acute and chronic AMPK activation in the WAT induce profound changes in adiposity with important implications for the treatment of obesity and its related metabolic disorders. This review discusses the role of AMPK in the regulation of white adipocyte metabolism with respect to energy storage and release, gene expression, mitochondrial biogenesis, oxidative capacity, cell differentiation, and the potential impact on whole-body adiposity and energy homeostasis.

A novel role for AMP-kinase in the regulation of the Na+/I--symporter and iodide uptake in the rat thyroid gland

The aim of this study was to investigate the role of AMP-kinase (AMPK) in the regulation of iodide uptake by the thyroid gland. Iodide uptake was assessed in PCCL3 follicular thyroid cells exposed to the AMPK agonist 5-aminoimidazole-4-carboxamide-ribonucleoside (AICAR), and also in rat thyroid glands 24 h after a single intraperitoneal injection of AICAR. In PCCL3 cells, AICAR-induced AMPK and acetyl-CoA carboxylase (ACC) phosphorylation decreased iodide uptake in a concentration-dependent manner, while the AMPK inhibitor compound C prevented this effect. In the thyroid gland of rats injected with AICAR, AMPK and ACC phosphorylation was increased and iodide uptake was reduced by ~35%. Under conditions of increased AMPK phosphorylation/activation such as TSH deprivation or AICAR treatment, significant reductions in cellular Na(+)/I(-)-symporter (NIS) protein (~41%) and mRNA content (~65%) were observed. The transcriptional (actinomycin D) and translational (cycloheximide) inhibitors, as well as the AMPK inhibitor compound C prevented AICAR-induced reduction of NIS protein content in PCCL3 cells. The presence of TSH in the culture medium reduced AMPK phosphorylation in PCCL3 cells, while inhibition of protein kinase A (PKA) with H89 prevented this effect. Conversely, the adenylyl cyclase activator forskolin abolished the AMPK phosphorylation response induced by TSH withdrawal in PCCL3 cells. These findings demonstrate that TSH suppresses AMPK phosphorylation/activation in a cAMP-PKA-dependent manner. In summary, we provide novel evidence that AMPK is involved in the physiological regulation of iodide uptake, which is an essential step for the formation of thyroid hormones as well as for the regulation of thyroid function.