A novel natural PPARγ agonist, Gypenoside LXXV, ameliorates cognitive deficits by enhancing brain glucose uptake via the activation of Akt/GLUT4 signaling in db/db mice

Gypenosides alleviate oxidative stress in the hippocampus, promote mitophagy, and mitigate depressive-like behaviors induced by CUMS via SIRT1

ETHNOPHARMACOLOGICAL RELEVANCE

The use and efficacy of Gynostemma [Gynostemma pentaphyllum (Thunb.) Makino], a versatile traditional Chinese herb, was first documented in the renowned pharmacopoeia, "Compendium of Materia Medica". Gypenosides (Gps), saponin components are the primary constituents responsible for its biological activities and clinical effects, which include antioxidant, immunoregulatory, antitumor, and neuroprotective properties. Pharmacological studies have shown that Gps has the potential to combat depression. However, the exact molecular mechanisms underlying its antidepressant effects remain unclear.

AIM OF THE STUDY

This study aims to elucidate the mechanisms underlying the antidepressant effects of Gps through antioxidative stress, utilizing an integrated approach that includes network pharmacology, molecular simulations, and experimental validation.

MATERIALS AND METHODS

Sprague-Dawley rats were subjected to chronic unpredictable mild stress (CUMS) and were orally administered doses of Gps (50 and 100 mg/kg) and fluoxetine (10 mg/kg). The regulatory effects of Gps on depression-like behaviors in CUMS rats and their impact on oxidative stress levels in the hippocampus region were evaluated. Network pharmacology was used to investigate the mechanisms by which Gps affects oxidative stress in depression, and was accompanied by molecular docking and dynamics simulations. CUMS rats were treated orally with Gps (100 mg/kg) and injected with EX527 for rescue experiments to validate the role of SIRT1 in antioxidative stress and evaluate the impact of Gps on mitophagy.

RESULTS

Gps ameliorated depression-like behaviors induced by CUMS in rats. The improvements observed included an increased sucrose preference, reduced immobility time in the tail suspension and forced swim tests, and an increased movement distance in the open-field test. Additionally, Gps effectively reduced reactive oxygen species, malondialdehyde, and 8-hydroxy-2'-deoxyguanosine levels in the hippocampus, while increasing the contents of ATP, catalase, superoxide dismutase, and glutathione, indicating an increased capacity for antioxidative stress in the hippocampus. Furthermore, Gps increased the number of neuronal cells in the hippocampal CA1 region and the level of mitochondrial autophagy, with SIRT1 as a potential key target. Inhibition of SIRT1 expression by exposure to EX527 reversed the beneficial effects of Gps, further validating the critical role of SIRT1 in the regulation of oxidative stress and improving depression-like behavior.

CONCLUSION

Gps improved the antioxidative stress capacity of the hippocampus and promoted mitophagy in CUMS rats through SIRT1, thus protecting hippocampal neurons and improving depression-like behavior.

Neuroprotective effects of Gypenosides: A review on preclinical studies in neuropsychiatric disorders

Gynostemma pentaphyllum (Thunb.) Makino is a perennial creeping herb belonging to the Cucurbitaceae family that has a long history of usage in traditional oriental medicine. Gypenosides are the primary bioactive compounds in Gynostemma pentaphyllum. Because of the medicinal value of gypenosides, functional food and supplements containing gypenosides have been promoted and consumed with popularity, especially among Asian communities. This review presented the progress made in the research of pharmacological properties of gypenosides on diseases of the nervous system and their possible mechanism of action. To date, preclinical studies have demonstrated the therapeutic effects of gypenosides in alleviating neuropsychiatric disorders like depression, Parkinson's disease, Alzheimer's disease, secondary dementia, stroke, optic neuritis, etc. Pharmacological studies have discovered that gypenosides can modulate various major signaling pathways like NF-κB, Nrf2, AKT, ERK1/2, contributing to the neuroprotective properties. However, there is a dearth of clinical research on gypenosides, with current investigations on the compounds being mainly conducted in vitro and on animals. Future studies focusing on isolating and purifying novel gypenosides and investigations on exploring the potential molecular mechanism underlying their biological activities are warranted, which may serve as a foundation for further clinical trials for the betterment of human health.

The activation of AMPK/PGC-1α/GLUT4 signaling pathway through early exercise improves mitochondrial function and mitigates ischemic brain damage

Mitochondria play a crucial role in maintaining cellular energy supply and serve as a source of energy for repairing nerve damage following a stroke. Given that exercise has the potential to enhance energy metabolism, investigating the impact of exercise on mitochondrial function provides a plausible mechanism for stroke treatment. In our study, we established the middle cerebral artery occlusion (MCAO) model in Sprague-Dawley rats and implemented early exercise intervention. Neurological severity scores, beam-walking test score, and weight were used to evaluate neurological function. The volume of cerebral infarction was measured by MRI. Nerve cell apoptosis was detected by TUNEL staining. Mitochondrial morphology and structure were detected by mitochondrial electron microscopy. Mitochondrial function was assessed using membrane potential and ATP measurements. Western blotting was used to detect the protein expression of AMPK/PGC-1α/GLUT4. Through the above experiments, we found that early exercise improved neurological function in rats after MCAO, reduced cerebral infarction volume and neuronal apoptosis, promoted the recovery of mitochondrial morphology and function. We further examined the protein expression of AMPK/PGC-1α/GLUT4 signaling pathway and confirmed that early exercise was able to increase its expression. Therefore, we suggest that early exercise initiated the AMPK/PGC-1α/GLUT4 signaling pathway, restoring mitochondrial function and augmenting energy supply. This, in turn, effectively improved both nerve and body function in rats following ischemic stroke.

Saponins derived from Gynostemma pentaphyllum regulate triglyceride and cholesterol metabolism and the mechanisms: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Gynostemma pentaphyllum (Thunb.) Makino (G. pentaphyllum) can be used for both medicinal and tea and has lipid-lowering properties. Modern research has shown that its main bioactive components are flavonoids and saponins. It has many beneficial effects such as hypolipidemic, anti-cancer, cardioprotective, hepatoprotective, neuroprotective, anti-diabetic and anti-inflammatory.

AIMS OF THE REVIEW

This review aimed to summarize its anti-glycolipid metabolic models and mechanisms are reviewed to facilitate a deeper understanding of the mechanism in lowering lipids.

MATERIALS AND METHODS

Information related to lipid lowering in G. pentaphyllum was collated by reviewing the relevant literature in the PubMed database from 1985 to 2023.

RESULTS

Only 101 G. pentaphyllum compounds have been initially explored for their hypolipidemic activity. There are cell models, animal models and human subjects for lipid-lowering of it. It reduced triglyceride level via PPAR/UCP-1/PGC-1α/PRDM16 and (SREBP-1c)-ACC/FAS-CPT1 signal pathways. Cholesterol-lowering effects via (SREBP-2)-HMGCR, PCSK9-LDLR and bile acid biosynthetic pathways. Activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) is a key factor in the regulation of glycolipid metabolism in G. pentaphyllum. Other pathways of action of G. pentaphyllum in regulating glucolipid metabolism are also discussed in this paper.

CONCLUSION

To date, more than 328 saponins have been isolated and identified in Gynostemma. Further studies on these components, including molecular mechanisms and in vivo metabolic regulation, need to be further confirmed. G. pentaphyllum has the potential to be developed into drugs or functional foods, but further research is needed.

Natural products in non-alcoholic fatty liver disease (NAFLD): Novel lead discovery for drug development

With changing lifestyles, non-alcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide. A substantial increase in the incidence, mortality, and associated burden of NAFLD-related advanced liver disease is expected. Currently, the initial diagnosis of NAFLD is still based on ultrasound and there is no approved treatment method. Lipid-lowering drugs, vitamin supplementation, and lifestyle improvement treatments are commonly used in clinical practice. However, most lipid-lowering drugs can produce poor patient compliance and specific adverse effects. Therefore, the exploration of bio-diagnostic markers and active lead compounds for the development of innovative drugs is urgently needed. More and more studies have reported the anti-NAFLD effects and mechanisms of natural products (NPs), which have become an important source for new drug development to treat NAFLD due to their high activity and low side effects. At present, berberine and silymarin have been approved by the US FDA to enter clinical phase IV studies, demonstrating the potential of NPs against NAFLD. Studies have found that the regulation of lipid metabolism, insulin resistance, oxidative stress, and inflammation-related pathways may play important roles in the process. With the continuous updating of technical means and scientific theories, in-depth research on the targets and mechanisms of NPs against NAFLD can provide new possibilities to find bio-diagnostic markers and innovative drugs. As we know, FXR agonists, PPARα agonists, and dual CCR2/5 inhibitors are gradually coming on stage for the treatment of NAFLD. Whether NPs can exert anti-NAFLD effects by regulating these targets or some unknown targets remains to be further studied. Therefore, the study reviewed the potential anti-NAFLD NPs and their targets. Some works on the discovery of new targets and the docking of active lead compounds were also discussed. It is hoped that this review can provide some reference values for the development of non-invasive diagnostic markers and new drugs against NAFLD in the clinic.

Increasing brain glucose uptake by Gypenoside LXXV ameliorates cognitive deficits in a mouse model of diabetic Alzheimer's disease

We have previously reported that Gypenoside LXXV (GP-75), a novel natural PPARγ agonist isolated from Gynostemma pentaphyllum, ameliorated cognitive deficits in db/db mice. In this study, we further investigated the beneficial effects on cognitive impairment in APP/PS1 mice and a mouse model of diabetic AD (APP/PS1xdb/db mice). Interestingly, intragastric administration of GP-75 (40 mg/kg/day) for 3 months significantly attenuated cognitive deficits in APP/PS1 and APP/PS1xdb/db mice. GP-75 treatment markedly reduced the levels of glucose, HbA1c and insulin in serum and improved glucose tolerance and insulin sensitivity in APP/PS1xdb/db mice. Notably, GP-75 treatment decreased the β-amyloid (Aβ) burden, as measured by ¹¹ C-PIB PET imaging. Importantly, GP-75 treatment increased brain glucose uptake as measured by ¹⁸ F-FDG PET imaging. Moreover, GP-75 treatment upregulated PPARγ and increased phosphorylation of Akt (Ser473) and GLUT4 expression levels but decreased phosphorylation of IRS-1 (Ser616) in the hippocampi of both APP/PS1 and APP/PS1xdb/db mice. Furthermore, GP-75-induced increases in GLUT4 membrane translocation in primary hippocampal neurons from APP/PS1xdb/db mice was abolished by cotreatment with the selective PPARγ antagonist GW9662 or the PI3K inhibitor LY294002. In summary, GP-75 ameliorated cognitive deficits in APP/PS1 and APP/PS1xdb/db mice by enhancing glucose uptake via activation of the PPARγ/Akt/GLUT4 signaling pathways.