AMP-activated Protein Kinase Activation Research Articles

The pro-drug C13 activates AMPK by two distinct mechanisms.

The AMP-activated protein kinase (AMPK) is a sensor of cellular energy status that is expressed in almost all eukaryotic cells. In the canonical activation mechanism, it is activated by increases in AMP:ATP and ADP:ATP ratios that signify declining cellular energy status. Once activated, AMPK phosphorylates numerous targets that promote catabolic pathways generating ATP, while inhibiting anabolic and other processes that consume ATP, thus acting to restore energy homeostasis. Pharmacological agents that activate AMPK have been useful in identifying downstream targets and have potential as drugs for treatment of metabolic disorders such as Type 2 diabetes and non-alcoholic fatty liver disease. One such agent is C13, a pro-drug with a phosphonate bis(isobutyryloxymethyl) ester moiety, with the isobutyryloxymethyl groups increasing membrane permeability. Following cellular uptake, C13 is cleaved to release C2, an AMP analogue and potent AMPK activator that is specific for complexes containing the α1 (but not the α2) catalytic subunit isoform. This has previously been assumed to be the sole mechanism by which C13 activates AMPK, with potential roles for the isobutyryloxymethyl groups being ignored. We now report that, following cleavage from C13, these protective groups are metabolized to formaldehyde, an agent that inhibits mitochondrial function and increases cellular AMP:ATP ratios, thus providing additional AMPK activation by the canonical mechanism.

AMP-activated protein kinase in the amygdala and hippocampus contributes to enhanced fear memory in diabetic mice.

Diabetic patients have an increased risk of psychiatric disorders. Because hyperglycaemia increases L-lactate in the brain and L-lactate inhibits AMP-activated protein kinase (AMPK), this study investigated the role of L-lactate and AMPK in strengthened fear memory, a model for human psychiatric disorders, in diabetic mice. The diabetic model was mice injected with streptozotocin. Fear memory was measured using the conditioned fear test with low (0.45 mA) or high (0.50 mA) foot shock to cause low and high freezing, respectively. Protein levels of AMPK and phosphorylated AMPK (pAMPK) were measured by western blotting and immunohistochemistry. At 0.45 mA, the AMPK inhibitor dorsomorphin increased freezing, which was inhibited by the AMPK activator acadesine. In contrast, at 0.50 mA, acadesine decreased freezing, which was inhibited by dorsomorphin. In diabetic mice, pAMPK was decreased in the amygdala and hippocampus. Diabetic mice showed increased freezing at 0.45 mA, which was inhibited by acadesine. In the amygdala and hippocampus, L-lactate was increased in diabetic mice and injection of L-lactate into non-diabetic mice increased freezing at 0.45 mA. In addition, L-lactate decreased pAMPK in the hippocampus, but not the amygdala, and increase in freezing induced by L-lactate was inhibited by acadesine. Dorsomorphin-induced increase in freezing was inhibited by the AMPA receptor antagonist NBQX. In diabetic mice, L-lactate is increased in the amygdala and hippocampus, possibly through hyperglycaemia, which strengthens fear memory through inhibition of AMPK and activation of glutamatergic function.

Influence of different types of dietary sugars on the intestinal mucosa and hepatic lipid metabolism in germ-free mice

The excessive consumption of dietary sugar induces changes in gut microbiota, which is associated with obesity and metabolic dysregulation. This study investigated the effects of monosaccharide and fructooligosaccharide (FOS) intake on metabolic function and intestinal environment in germ-free (GF) mice lacking gut microbiota. GF mice were provided with a chow diet and administered a water solution containing 15 % glucose, fructose, or FOS for 4 weeks. Compared with FOS, glucose, and fructose induced increased hepatic lipid accumulation, increased adipocyte size in white adipose tissue, and upregulated hepatic lipogenic gene expression. FOS exhibited notably higher activation of hepatic AMP-activated protein kinase compared with those consuming glucose or fructose. Moreover, the number of goblet cells in the intestinal mucosa increased significantly with FOS consumption. Collectively, these findings indicate that while monosaccharides caused metabolic disorders in GF mice, FOS alleviated these disorders and increased the number of goblet cells in the intestinal mucosa. These results provide evidence for the occurrence of these effects independently of the gut microbiota.

Maternal metformin administration during the pre-gestation period improves transient cerebral ischemia injury in male offspring rats

Purpose: It seems that maternal intervention, which may involve epigenetic mechanisms, can affect cerebral ischemia in offspring. Metformin consumption by the mother activates the AMP-activated protein kinase (AMPK) pathway. Metformin has also induced the AMPK and protected neurons in cerebral ischemia. This study investigates the effect of maternal metformin administration, which activates the AMPK pathway, on cerebral ischemia in offspring Methods: Animals were separated into four groups: sham, 2-vessels occlusion (2VO), Met+2VO, Met+compound c (CC)+2VO. Female rats were administrated with metformin at a dose of 200 mg.kg-1 body weight for 2 weeks prior to mating. After the final metformin injection, each female rat was paired with an intact adult male to allow for mating. Sixty-days old offspring underwent cerebral ischemia and then memory-related tests were done. Results: Current data revealed that the neurological deficits score was reduced Met+2VO group (P<0.001), and the memory increased (P<0.001) in comparison to the 2VO. The Bcl-2/Bax ratio declined in the metformin group (P<0.001) while the Brain-Derived Neurotropic Factor (BDNF), c-fos, p-AMPK/AMPK ratio and Histone H3K9 acetylation in the hippocampus augmented significantly compared to the 2VO group (P<0.001). Conclusion: These findings indicated that the metformin intervention via AMPK activation could improve the movement disability, enhance spatial memory, increase neural plasticity, and augment the bioenergetics state and histone acetylation in the hippocampus of the offspring.

Investigation of the physiological effects of uridine on Nile Tilapia (Oreochromis niloticus)

Uridine, an essential nucleoside involved in various physiological and biochemical processes, has been shown to influence hepatic fat accumulation. However, its broader physiological roles in aquaculture species like Nile tilapia remain underexplored. This study aimed to systematically assess the effects of uridine on Nile tilapia physiology. Nile tilapia (3.58 ± 0.02 g) were fed with different levels (0, 1, and 4 g/kg) of uridine for 10 weeks. The supplementation with 4 g/kg uridine significantly increased the carcass ratio and total protein of whole fish by 4.18 % and 4.08 %, respectively, and reduced the viscerosomatic index and total lipid of whole fish by 12.76 % and 20.48 %, respectively. Supplementation with 4 g/kg uridine increased the expression of protein synthesis genes. The supplementation of uridine suppressed the expression of fatty acid synthesis genes and promoted the expression of lipolysis-related genes by the activation of AMP-activated protein kinase (AMPK). This activation led to a significant decrease in both liver and serum triglyceride levels. The administration of 4 g/kg uridine significantly reduced hepatic cholesterol levels by inhibiting the expression of cholesterol synthesis-related genes. Additionally, 4 g/kg uridine notably augmented the liver's antioxidant capacity, thereby promoting the hepatic health. Furthermore, addition of uridine elevated the intestinal villi height, improved intestinal barrier integrity, and reduced intestinal inflammation response. Therefore, this study suggested that dietary supplementation of uridine can promote protein deposition and improve hepatic and intestinal health in Nile tilapia.

β-Caryophyllene, a dietary phytocannabinoid, alleviates high-fat diet-induced hepatic steatosis in mice via AMPK activation.

β-Caryophyllene (BCP), a dietary phytocannabinoid, significantly suppresses palmitate-induced lipid accumulation in human HepG2 hepatocytes via activation of AMP-activated protein kinase (AMPK) signaling. The objective of the preset research was to assess whether oral administration of BCP alleviates obesity-induced hepatic steatosis in mice through AMPK activation. We examined the protective action of supplementation of 0.3% BCP (w/w) in a high-fat diet (HFD) on C57BL/6J mice for 12 weeks. BCP supplementation evidently ameliorated histological hepatic steatosis features, and significantly reduced triglycerides and cholesterol levels in liver, and serum levels of aspartate aminotransferase and alanine aminotransferase as compared with non-supplemented HFD-fed mice. Immunoblotting revealed that BCP supplementation in HFD-fed mice also caused hepatic AMPK activation. Furthermore, treatment with BCP in HFD-fed mice significantly suppressed body weight gain and attenuated obesity-related phenotypes relative to the HFD mice. Our results suggest the usefulness of BCP in the prevention of obesity-related liver steatosis and liver injury.

Suppression of neuronal AMPKβ2 isoform impairs recognition memory and synaptic plasticity

AMP-activated protein kinase (AMPK) is an αβγ heterotrimer protein kinase that functions as a molecular sensor to maintain energy homeostasis. Accumulating evidence suggests a role of AMPK signaling in the regulation of synaptic plasticity and cognitive function; however, isoform-specific roles of AMPK in the central nervous system (CNS) remain elusive. Regulation of the AMPK activities has focused on the manipulation of the α or γ subunit. Meanwhile, accumulating evidence indicates that the β subunit is critical for sensing nutrients such as fatty acids and glycogen to control AMPK activity. Here, we generated transgenic mice with conditional suppression of either AMPKβ1 or β2 in neurons and characterized potential isoform-specific roles of AMPKβ in cognitive function and underlying mechanisms. We found that AMPKβ2 (but not β1) suppression resulted in impaired recognition memory, reduced hippocampal synaptic plasticity, and altered structure of hippocampal postsynaptic densities and dendritic spines. Our study implicates a role for the AMPKβ2 isoform in the regulation of synaptic and cognitive function.

Morin promotes autophagy in human PC3 prostate cancer cells by modulating AMPK/mTOR/ULK1 signaling pathway

AMP-activated protein kinase (AMPK) suppresses tumorigenesis by modulating autophagy and apoptosis. This study evaluated the impact of Morin on PC3 prostate cancerous cells by examining the AMPK/ mechanistic target of rapamycin (mTOR)/ ULK1 (UNC-51-like kinase 1) pathway and autophagy process. The PC3 cells were treated with Morin (50 µg/ml) and AICAR (an AMPK activator). Cell viability, apoptosis, autophagy, and level of phosphorylated and non-phosphorylated ULK1, AMPK, and mTOR, as well as LC3B/LC3A, have been investigated. Through DAPI staining, measurement of Bax/Bcl-2 ratio, Caspase activity, and Annexin V/PI method, it has been revealed that Morin induces apoptosis and reduces the growth of PC3 cells. Morin enhanced the protein level of phosphorylated AMPK (p-AMPK) and ULK1 (p-ULK1) and decreased the expression of phosphorylated mTOR (p-mTOR) in the PC3 cells. Morin could also increase the LC3B/LC3A ratio, Acridine Orange-positive cells, expression of Beclin-1 and ATG5 genes, and decrease the p62 protein level indicating autophagy-inducing. AICAR (an AMPK activator) enhanced the impact of Morin on apoptosis, cell growth, and expression of LC3B, p-AMPK, p-ULK1, and p-mTOR proteins in the PC3 cells. These findings suggest that Morin induces apoptotic and autophagic cell death by activating AMPK and ULK1 and suppressing mTOR pathways.

Uncovering crosstalk between AMPK and the ATF4-Integrated Stress Response

The reprograming of cellular metabolism in cancer cells is directly inter-related to their capacity for uncontrolled growth. As such, targeting of mitochondrial function has been explored as a therapeutic strategy in cancer. However, inhibition of mitochondria inevitably leads to activation of cellular stress pathways including the integrated stress response (ISR). The ISR includes as a key feature, increased activity of activating transcription factor 4 (ATF4), which goes on to up-regulate a range of gene targets to restore cellular homeostasis. Inhibition of mitochondria also can impair bioenergetic and biosynthetic capacity, which might activate AMP-activated protein kinase (AMPK), a cellular energy sensor that also orchestrates metabolic homeostasis. While the ISR and AMPK both critically regulate metabolism in cancer cells, the link between these mechanisms remains unclear. To address this gap, we tested effects of various energetic stress conditions in MEF cell systems deficient in AMPK activity. To comprehensively impair metabolic networks, we used nutrient starvation treatments in combination with silencing of the protein OPA1 which maintains organisational integrity of the mitochondrial cristae. Our results suggest that AMPK may be involved in suppressing the ISR upon mitochondrial disruption. To further explore, we took the alternative approach to test a range of mitochondrial targeting drugs in wildtype or AMPK-deficient MEF. To gain insight into roles of AMPK in the ISR and related adaptive gene responses, we analysed resulting transcriptomes. These results further revealed a regulatory link between AMPK and the ATF4-ISR, showing that AMPK loss hypersensitizes the cell to energetic stress. Our work uncovering the crosstalk between AMPK and the ATF4-ISR has potential to reveal novel interactions that could suggest metabolic liabilities that may be relevant for targeting in cancer cells.

Glucose-Dependent Insulinotropic Polypeptide Inhibits AGE-Induced NADPH Oxidase-Derived Oxidative Stress Generation and Foam Cell Formation in Macrophages Partly via AMPK Activation.

Glucose-dependent insulinotropic polypeptide (GIP) of the incretin group has been shown to exert pleiotropic actions. There is growing evidence that advanced glycation end products (AGEs), senescent macromolecules formed at an accelerated rate under chronic hyperglycemic conditions, play a role in the pathogenesis of atherosclerotic cardiovascular disease in diabetes. However, whether and how GIP could inhibit the AGE-induced foam cell formation of macrophages, an initial step of atherosclerosis remains to be elucidated. In this study, we address these issues. We found that AGEs increased oxidized low-density-lipoprotein uptake into reactive oxygen species (ROS) generation and Cdk5 and CD36 gene expressions in human U937 macrophages, all of which were significantly blocked by [D-Ala2]GIP(1-42) or an inhibitor of NADPH oxidase activity. An inhibitor of AMP-activated protein kinase (AMPK) attenuated all of the beneficial effects of [D-Ala2]GIP(1-42) on AGE-exposed U937 macrophages, whereas an activator of AMPK mimicked the effects of [D-Ala2]GIP(1-42) on foam cell formation, ROS generation, and Cdk5 and CD36 gene expressions in macrophages. The present study suggests that [D-Ala2]GIP(1-42) could inhibit the AGE-RAGE-induced, NADPH oxidase-derived oxidative stress generation in U937 macrophages via AMPK activation and subsequently suppress macrophage foam cell formation by reducing the Cdk5-CD36 pathway.

8-Prenylgenistein Isoflavone in Cheonggukjang Acts as a Novel AMPK Activator Attenuating Hepatic Steatosis by Enhancing the SIRT1-Mediated Pathway.

8-Prenylgenistein (8PG), a genistein derivative, is present in fermented soybeans (Glycine max), including cheonggukjang (CGJ), and exhibits osteoprotective, osteogenic, and antiadipogenic properties. However, the hepatoprotective effects of 8PG and its underlying molecular mechanisms remain largely unexplored. Here, we identified the high binding affinity of 8PG with AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1), which acts as a potent AMPK activator that counteracts hepatic steatosis. Notably, 8PG exhibited better pharmacokinetics with greater absorption and higher plasma binding than the positive controls for the target proteins. Moreover, 8PG exerted non-carcinogenic activity in rats and significantly increased AMPK phosphorylation. Compound C, an AMPK inhibitor, did not antagonize 8PG-activated AMPK in HepG2 cells. 8PG significantly attenuated palmitate-induced lipid accumulation and enhanced phosphorylated AMPK and its downstream target, acetyl-CoA carboxylase. Further, 8PG activated nuclear SIRT1 at the protein level, which promoted fatty acid oxidation in palmitate-treated HepG2 cells. Overall, 8PG acts as a potent AMPK activator, further attenuating hepatic steatosis via the SIRT1-mediated pathway and providing new avenues for dietary interventions to treat metabolic dysfunction-associated steatotic liver disease (MASLD).

Lipidomics of infant mesenchymal stem cells associate with the maternal milieu and child adiposity.

Our objective was to interrogate mesenchymal stem cell (MSC) lipid metabolism and gestational exposures beyond maternal body mass that may contribute to child obesity risk. MSCs were cultured from term infants of mothers with obesity (n = 16) or normal weight (n = 15). In MSCs undergoing myogenesis in vitro, we used lipidomics to distinguish phenotypes by unbiased cluster analysis and lipid challenge (24-hour excess fatty acid [24hFA]). We measured MSC AMP-activated protein kinase (AMPK) activity and fatty acid oxidation (FAO), and a composite index of maternal glucose, insulin, triglycerides, free fatty acids, TNF-α, and high-density lipoprotein and total cholesterol in fasting blood from mid and late gestation (~17 and ~27 weeks, respectively). We measured child adiposity at birth (n = 29), 4-6 months (n = 29), and 4-6 years (n = 13). Three MSC clusters were distinguished by triacylglycerol (TAG) stores, with greatest TAGs in Cluster 2. All clusters increased acylcarnitines and TAGs with 24hFA, although Cluster 2 was more pronounced and corresponded to AMPK activation and FAO. Maternal metabolic markers predicted MSC clusters and child adiposity at 4-6 years (both highest in Cluster 3). Our data support the notion that MSC phenotypes are predicted by comprehensive maternal metabolic milieu exposures, independent of maternal BMI, and suggest utility as an at-birth predictor for child adiposity, although validation with larger longitudinal samples is warranted.

Ginsenoside Rh4 prevents endothelial dysfunction as a novel AMPK activator.

The AMP-activated protein kinase (AMPK) signalling pathway is a desirable target for various cardiovascular diseases (CVD), while the involvement of AMPK-mediated specific downstream pathways and effective interventions in hyperlipidaemia-induced endothelial dysfunction remain largely unknown. Herein, we aim to identify an effective AMPK activator and to explore its efficacy and mechanism against endothelial dysfunction. Molecular docking technique was adopted to screen for the potent AMPK activator among 11 most common rare ginsenosides. In vivo, poloxamer 407 (P407) was used to induce acute hyperlipidaemia in C57BL/6J mice. In vitro, palmitic acid (PA) was used to induce lipid toxicity in HAEC cells. We discovered the strongest binding of ginsenoside Rh4 to AMPKα1 and confirmed the action of Rh4 on AMPK activation. Rh4 effectively attenuated hyperlipidaemia-related endothelial injury and oxidative stress both in vivo and in vitro and restored cell viability, mitochondrial membrane potential and mitochondrial oxygen consumption rate in HAEC cells. Mechanistically, Rh4 bound to AMPKα1 and simultaneously up-regulated AKT/eNOS-mediated NO release, promoted PGC-1α-mediated mitochondrial biogenesis and inhibited P38 MAPK/NFκB-mediated inflammatory responses in both P407-treated mice and PA-treated HAEC cells. The AMPK inhibitor Compound C treatment completely abrogated the regulation of Rh4 on the above pathways and weakened the lowering effect of Rh4 on endothelial impairment markers, suggesting that the beneficial effects of Rh4 are AMPK dependent. Rh4 may serve as a novel AMPK activator to protect against hyperlipidaemia-induced endothelial dysfunction, providing new insights into the prevention and treatment of endothelial injury-associated CVD.

Promising Influences of Moringa oleifera in Functional Foods against Metabolic Syndrome: A Comprehensive and Mechanistic Review.

Metabolic syndrome (MetS) is now considered a global issue with a growing financial and health impact. Numerous herbal alternatives have been examined and researched due to the ever-increasing demand for new medications to treat metabolic syndrome disorders. People have empirically employed Moringa oleifera (MO), a native plant to several Asian nations, for a variety of diseases. We sought to examine recent research on MO in MetS and its potential mechanism of action in the current review. Four databases, including PubMed, Scopus, Web of Sciences, and Google Scholar, were thoroughly searched, and the data were then compiled. In total, 146 papers covering nonclinical and clinical MO investigations in metabolic syndromerelated disorders are included in this study. Numerous research confirmed MO's positive impact on the control of blood glucose, blood pressure, hyperlipidemia, and obesity. Many molecular processes have been investigated, including increasing glucose transporter type 4 (GLUT4) expression, inhibition of β-Hydroxy-β-methylglutaryl-coenzyme A (HMG-CoA), α-glucosidase inhibiting, AMP-activated protein kinase (AMPK) activation, and other suggested mechanisms. The current review established much data favoring MO's potential advantages in metabolic syndrome. However, further research involving human studies is required in this area to determine whether Moringa can effectively treat metabolic syndrome.

Magnoflorine attenuates Ang II-induced cardiac remodeling via promoting AMPK-regulated autophagy.

Heart failure (HF) remains one of the most common events in the progression of hypertension. Magnoflorine (MNF) has been shown beneficial effects on the cardiovascular system. However, the action of MNF on angiotensin (Ang) II-induced cardiac remodeling and its underlying mechanisms have not yet been characterised. Here, we assessed the action of MNF in the development of hypertension-related HF. C57BL/6 male mice were subjected to Ang II through a micro-osmotic pump infusion continuously for 4 weeks to induce hypertensive HF. MNF (10 and 20 mg/kg) was administered in the final 2 weeks. Ang II content was measured by enzyme-linked immunosorbent assay (ELISA) kit. Values of ejection fraction (EF) and fractional shortening (FS) were detected using an ultrasound diagnostic instrument. The mRNA levels of hypertrophic and fibrotic genes were determined by real-time quantitative polymerase chain reaction (RT-qPCR). Haematoxylin and eosin (H&E), wheat germ agglutinin (WGA), Masson trichrome, and Sirius Red staining were used to analyse pathologic changes in heart tissues. The expression levels of phosphorylated AMP-activated protein kinase (AMPK), light chain 3 microtubule associated protein II (LC3 II) to LC3 I, and p62 were detected by western blot assay. MNF significantly improved cardiac dysfunction and the content of creatine kinase-MB without altering blood pressure in Ang II-challenged mice. MNF obviously corrected the phenotypes of cardiac hypertrophy and fibrosis, including the high mRNA levels of atrial natriuretic peptide (Anp), brain natriuretic peptide (Bnp), collagen1a (Col1a1), transforming growth factor beta (Tgfb1), enlarged myocardial areas, and increased positive areas of Masson trichrome and Sirius Red staining. In addition, MNF alleviated oxidative injury, reflected by the upregulation of glutathione and the downregulation of reactive oxygen species and malondialdehyde. The activation of AMPK was elevated accompanied by an increased level of autophagy by MNF in hypertensive heart tissues. The therapeutic action of MNF was confirmed in Ang II-challenged H9c2 cells. Specifically, the AMPK inhibitor could eliminate the autophagy pathway in which MNF is involved. MNF has benefits in hypertension-induced cardiac remodeling, which was partially associated with the improvement of oxidative stress via the mediation of the AMPK/autophagy axis.

Exercise-Induced cytokines, diet, and inflammation and their role in adipose tissue metabolism.

Obesity poses a significant global health challenge, necessitating effective prevention and treatment strategies. Exercise and diet are recognized as pivotal interventions in combating obesity. This study reviews the literature concerning the impact of exercise-induced cytokines, dietary factors, and inflammation on adipose tissue metabolism, shedding light on potential pathways for therapeutic intervention. A comprehensive review of relevant literature was conducted to elucidate the role of exercise-induced cytokines, including interleukin-6 (IL-6), interleukin-15 (IL-15), brain-derived neurotrophic factor (BDNF), irisin, myostatin, fibroblast growth factor 21 (FGF21), follistatin (FST), and angiopoietin-like 4 (ANGPTL4), in adipose tissue metabolism. Various databases were systematically searched using predefined search terms to identify relevant studies. Articles selected for inclusion underwent thorough analysis to extract pertinent data on the mechanisms underlying the influence of these cytokines on adipose tissue metabolism. Exercise-induced cytokines exert profound effects on adipose tissue metabolism, influencing energy expenditure (EE), thermogenesis, fat loss, and adipogenesis. For instance, IL-6 activates AMP-activated protein kinase (AMPK), promoting fatty acid oxidation and reducing lipogenesis. IL-15 upregulates peroxisome proliferator-activated receptor delta (PPARδ), stimulating fatty acid catabolism and suppressing lipogenesis. BDNF enhances AMPK-dependent fat oxidation, while irisin induces the browning of white adipose tissue (WAT), augmenting thermogenesis. Moreover, myostatin, FGF21, FST, and ANGPTL4 each play distinct roles in modulating adipose tissue metabolism, impacting factors such as fatty acid oxidation, adipogenesis, and lipid uptake. The elucidation of these pathways offers valuable insights into the complex interplay between exercise, cytokines, and adipose tissue metabolism, thereby informing the development of targeted obesity management strategies. Understanding the mechanisms by which exercise-induced cytokines regulate adipose tissue metabolism is critical for devising effective obesity prevention and treatment modalities. Harnessing the therapeutic potential of exercise-induced cytokines, in conjunction with dietary interventions, holds promise for mitigating the global burden of obesity. Further research is warranted to delineate the precise mechanisms underlying the interactions between exercise, cytokines, and adipose tissue metabolism.

Therapeutic Potential of Quercetin in Diabetic Neuropathy and Retinopathy: Exploring Molecular Mechanisms.

Diabetes mellitus poses a significant health challenge globally, often leading to debilitating complications, such as neuropathy and retinopathy. Quercetin, a flavonoid prevalent in fruits and vegetables, has demonstrated potential therapeutic effects in these conditions due to its antioxidant, anti-inflammatory, and neuroprotective properties. This review summarizes and provides a comprehensive understanding of the molecular mechanisms underlying the efficacy of quercetin in ameliorating diabetic neuropathy and retinopathy. A thorough search was carried out across scientific databases, such as SciFinder, PubMed, and Google Scholar, to gather pertinent literature regarding the effect of quercetin on diabetic neuropathy and retinopathy till February 2024. Preclinical studies indicate that quercetin mitigates neuropathic pain, sensory deficits, and nerve damage associated with diabetic neuropathy by improving neuronal function, reducing DNA damage, regulating pro-inflammatory cytokines, enhancing antioxidant enzyme levels and endothelial function, as well as restoring nerve injuries. In diabetic retinopathy, quercetin shows the potential to preserve retinal structure and function, inhibiting neovascularization, preventing retinal cell death, reducing pro-inflammatory cytokines, and increasing neurotrophic factor levels. Moreover, through modulating key signaling pathways, such as AMP-activated Protein Kinase (AMPK) activation, Glucose Transporter 4 (GLUT 4) upregulation, and insulin secretion regulation, quercetin demonstrates efficacy in reducing oxidative stress and inflammation, thereby protecting nerve and retinal tissues. Despite promising preclinical findings, challenges, such as limited bioavailability, necessitate further research to optimize quercetin's clinical application in order to establish its optimal dosage, formulation, and long-term efficacy in clinical settings.

Metformin as a Modulator of Autophagy and Hypoxia Responses in the Enhancement of Wound Healing in Diabetic Rats.

The molecular mechanisms underlying delayed wound repair in diabetes involve dysregulation of key cellular processes, including autophagy and hypoxia response pathways. Herein, we investigated the role of topical metformin, an established anti-diabetic drug with potential autophagy-inducing properties, in improving wound healing outcomes under hypoxic conditions. Full-thickness skin wounds were created in streptozotocin-induced diabetic rats, and tissue samples were collected at regular intervals for molecular and histological analysis. The expression levels of autophagy markers LC3B and Beclin-1 were evaluated via immunohistochemistry and qRT-PCR, while the amount of AMP-activated protein kinase (AMPK) and hypoxia-inducible factor-1α (HIF-1α) were determined via ELISA. Our results demonstrated that metformin administration resulted in the upregulation of LC3B and Beclin-1 in the wound bed, suggesting induction of autophagy in response to the treatment. Mechanistically, metformin treatment also led to the increased amount of AMPK, a critical regulator of cellular energy homeostasis, and a subsequent reduction in HIF-1α amount under hypoxic conditions. In conclusion, our findings demonstrate that metformin promotes wound healing in diabetes mellitus by enhancing autophagy through AMPK activation and modulating HIF-1α amount in a hypoxic microenvironment. This study offers a new therapeutic approach by shedding light on the potential benefits of metformin as adjunctive therapy in diabetic wound management.

Dietary Bacillus subtilis benefits meat quality by regulating the muscle fiber type and antioxidant capacity of broilers

The effects of dietary Bacillus subtilis (BS) on the meat quality of broilers were evaluated, with an emphasis on the regulation of muscle fiber types and antioxidant capabilities. One hundred and forty-four Arbor Acres male broilers were divided into 3 treatment groups (0, 300 mg/kg and 500 mg/kg dietary BS) and raised for 35 d. The results suggested that BS improved meat quality by improving the muscular pH, meat color, water holding capacity and shear force. Immunofluorescence staining revealed a positive impact of BS on the muscle fiber transformation in thigh muscles, and the gene/protein expression data from specific muscle fiber types confirmed this finding. BS activated AMP-activated protein kinase (AMPK), silent information regulator 1 and peroxisome proliferator-activated receptor gamma coactivator 1alpha. The postmortem analysis revealed that BS increased the activity of glutathione peroxidase and total antioxidant capacity while decreasing the malondialdehyde content. Additionally, BS increased the gene and protein expression of nuclear factor-like 2 (Nrf2) and activated the Nrf2 signaling pathway, including its downstream factors, such as heme oxygenase-1, catalase, superoxide dismutase and glutathione peroxidase. In conclusion, dietary BS improved meat quality by modifying muscle fiber types and enhancing the antioxidant capacity in broilers.

The effects of Hibiscus sabdariffa Linn. on the levels of FGF21 and AMPK in the Heart of Diabetic Mice

Background : Diabetes Mellitus (DM) is a metabolic disorder characterized by pancreatic cell dysfunction and insulin resistance. Fibroblast Growth Factor 21 (FGF21) is thought to have a cardioprotective role. Through FGF21 signaling, AMP-activated protein kinase (AMPK) activity reduces apoptosis, inflammation, hypertrophy, and fibrosis in the heart. Hibiscus sabdariffa Linn. (HSL) contains flavonoids that have hypoglycemic effects and are anti-inflammatory and antioxidant-active. This study aims to assess the effect of HSL on FGF21 and AMPK levels in the heart of diabetic mice models. Methods : An experimental study using Deutschland Denken Yoken (DDY) mice aged eight weeks were divided into four groups: Control, DM Control, HSL 200, and HSL 400. In the DM control, HSL 200, and HSL 400 groups, diabetes was induced by giving a High Fat Diet(HFD) and STZ 40mg/kgbb. The HSL 200 group was given HSL 200mg/kgBB supplementation for three weeks, and the HSL 400 group was given HSL 400 mg/kgBB supplementation for three weeks. FGF21 and AMPK levels were measured using the enzyme-linked immunosorbent assay (ELISA) method. Results : There was no significant difference between FGF21 and AMPK levels between the control and DM control groups. FGF21 and AMPK levels in the HSL 400 group were higher than in the control, DM control, and HSL 200 groups. Conclusions : These findings suggest that HSL supplementation at specific doses can potentially increase the activation of FGF 21 and AMPK signaling in the heart of diabetic mice models.