Regulation of nutrient uptake by AMP-activated protein kinase

Therapeutic potential of alkaloid extract from Codonopsis Radix in alleviating hepatic lipid accumulation: insights into mitochondrial energy metabolism and endoplasmic reticulum stress regulation in NAFLD mice

Alkaloids are a class of naturally occurring bioactive compounds that are widely distributed in various food sources and Traditional Chinese Medicine. This study aimed to investigate the therapeutic effects and underlying mechanisms of alkaloid extract from Codonopsis Radix (ACR) in ameliorating hepatic lipid accumulation in a mouse model of non-alcoholic fatty liver disease (NAFLD) induced by a high-fat diet (HFD). The results revealed that ACR treatment effectively mitigated the abnormal weight gain and hepatic injury associated with HFD. Furthermore, ACR ameliorated the dysregulated lipid metabolism in NAFLD mice, as evidenced by reductions in serum triglyceride, total cholesterol, and low-density lipoprotein levels, accompanied by a concomitant increase in the high-density lipoprotein level. ACR treatment also demonstrated a profound anti-oxidative effect, effectively alleviating HFD-induced oxidative stress and promoting ATP production. These effects were achieved through the up-regulation of the activities of mitochondrial electron transfer chain complexes I, II, IV, and V, in addition to the activation of the AMPK/PGC-1α pathway, suggesting that ACR exhibits therapeutic potential in alleviating the HFD-induced dysregulation of mitochondrial energy metabolism. Moreover, ACR administration mitigated HFD-induced endoplasmic reticulum (ER) stress and suppressed the overexpression of ubiquitin-specific protease 14 (USP14) in NAFLD mice. In summary, the present study provides compelling evidence supporting the hepatoprotective role of ACR in alleviating lipid deposition in NAFLD by improving energy metabolism and reducing oxidative stress and ER stress. These findings warrant further investigation and merit the development of ACR as a potential therapeutic agent for NAFLD.

Protein regulation mechanism of cold tolerance in Haemaphysalis longicornis

Ticks are external parasitic arthropods that can transmit a variety of pathogens by sucking blood. Low-temperature tolerance is essential for ticks to survive during the cold winter. Exploring the protein regulation mechanism of low-temperature tolerance of Haemaphysalis longicornis could help to explain how ticks survive in winter. In this study, the quantitative proteomics of several tissues of H. longicornis exposed to low temperature were studied by data independent acquisition technology. Totals of 3 699, 3 422, and 1 958 proteins were identified in the salivary gland, midgut, and ovary, respectively. The proteins involved in energy metabolism, cell signal transduction, protein synthesis and repair, and cytoskeleton synthesis changed under low-temperature stress. The comprehensive analysis of the protein regulation of multiple tissues of female ticks exposed to low temperature showed that maintaining cell homeostasis, maintaining cell viability, and enhancing cell tolerance were the most important means for ticks to maintain vital signs under low temperature. The expression of proteins involved in and regulating the above cell activities was the key to the survival of ticks under low temperatures. Through the analysis of a large amount of data, we found that the expression levels of arylamine N-acetyltransferase, inositol polyphosphate multikinase, and dual-specificity phosphatase were up-regulated under low temperature. We speculated that they might have important significance in low-temperature tolerance. Then, we performed RNA interference on the mRNA of these 3 proteins, and the results showed that the ability of female ticks to tolerate low temperatures decreased significantly.

Integrative approach to uncover antioxidant properties of Bupleuri Radix and its active compounds: Multiscale interactome-level analysis with experimental validation

Acute and chronic liver disease are global problems with high morbidity and mortality. Bupleuri Radix (BR) is an herbal medicine that has been prescribed empirically in traditional Asian medicine to modulate liver metabolism. However, its active compounds and therapeutic mechanisms remain unclear. Here, we integrated a network-based approach and experimental validation to elucidate BR's therapeutic potential in treating oxidative liver injury. Our approach incorporated data collection and network construction utilizing bioinformatics tools, and identified active compounds and key mechanisms based on the multiscale interactome. The proposed mechanisms were validated using an in vitro oxidative stress model and an in vivo carbon tetrachloride-induced model. We found that BR ameliorated the oxidative hepatic damage by acting on multiple proteins (STAT3, TNF, and BCL2) and signaling pathways (AMPK and Hippo signaling pathways). Subsequent in vitro experiments confirmed that BR significantly inhibited oxidative stress and mitochondrial damage. We further validated the effect of BR on the AMPK and Hippo-YAP pathways; a key mechanism for the antioxidant properties of BR. We prioritized the active compounds in BR based on a multiscale interactome-based approach, and further experiments revealed that saikosaponin A was a key active compound involved in hepatocyte protection (EC₅₀ = 50 μM), similar to the result using metformin and 5-aminoimidazole-4-carboxamide ribonucleotide. Histochemistry and blood biochemistry established that BR significantly inhibited carbon tetrachloride-induced oxidative tissue damage in mice. Thus, BR can be used to develop novel therapeutics for oxidative liver injury. Moreover, we suggest a novel strategy to prioritize and validate the active compounds and key mechanisms of herbal medicine based on the multiscale interactome.

5'AMP-activated protein kinase: an emerging target of phytochemicals to treat chronic inflammatory diseases

Inflammation is a defensive response of the organism to traumatic, infectious, toxic, ischemic, and autoimmune injury. Inflammatory mediators are released to effectively eliminate the inflammatory trigger and restore homeostasis. However, failure of these processes can lead to chronic inflammatory conditions and diseases such as inflammatory bowel diseases, rheumatoid arthritis, inflammatory lung diseases, atherosclerosis, and neurodegenerative diseases. The cure of chronic inflammatory diseases remains challenging as current therapies have various limitations, such as pronounced side effects, progressive loss of efficacy, and high cost especially for biologics. In this context, phytochemicals (such as alkaloids, flavonoids, lignans, phenolic acids, saponins, terpenoids, and other classes) are considered as an interesting alternative approach. Among the numerous targets of phytochemicals, AMP-activated protein kinase (AMPK) can be considered as an interesting target in the context of inflammation. AMPK regulates inflammatory response by inhibiting inflammatory pathways (NF-κB, JAK/STAT, and MAPK) and regulating several other processes of the inflammatory response (oxidative stress, autophagy, and apoptosis). In this review, we summarize and discuss the studies focusing on phytochemicals that showed beneficial effects by blocking different inflammatory pathways implicating AMPK activation in chronic inflammatory disease models. We also highlight elements to consider when investigating AMPK in the context of phytochemicals.

Curcumin alleviates hepatic steatosis by improving mitochondrial function in postnatal overfed rats and fatty L02 cells through the SIRT3 pathway

Postnatal overfeeding could increase the risk of non-alcoholic fatty liver disease (NAFLD) in adulthood. This study investigated the effects of curcumin (CUR) on hepatic steatosis in postnatal overfed rats and elucidated potential mechanisms in mitochondrial functions. Male rats were adjusted to ten (normal litter, NL) or three (small litter, SL) at postnatal day 3. After weaning, NL rats were fed with normal diet (NL) or a high-fat diet (NH) for 10 weeks. SL rats were fed with normal diet (SL), a high-fat diet (SH), a normal diet supplemented with 2% CUR (SL-CUR) or a high-fat diet supplemented with 2% CUR (SH-CUR). At week 13, compared with NL rats, SL and NH rats showed increased body weight, glucose intolerance, dyslipidemia and hepatic lipid accumulation, and these changes were more obvious in SH rats. The opposite trends were observed in SL-CUR and SH-CUR rats. Moreover, CUR could preserve mitochondrial biogenesis and antioxidant response in postnatal overfed rats, and upregulated the mRNA and protein levels of SIRT3. In vitro, L02 cells were exposed to free fatty acids and/or CUR. CUR decreased the levels of cellular lipids and mitochondrial reactive oxygen species, and increased the mitochondrial DNA copy number and superoxide dismutase activity in fatty L02 cells. However, these effects were blocked after SIRT3 silencing. It was concluded that postnatal overfeeding damaged mitochondrial biogenesis and antioxidant response, and increased hepatic lipids and the severity of high-fat-induced NAFLD, while CUR alleviated hepatic steatosis, at least partially, by enhancing mitochondrial function through SIRT3.

Metabolic Therapy of Heart Failure: Is There a Future for B Vitamins?

Heart failure (HF) is a plague of the aging population in industrialized countries that continues to cause many deaths despite intensive research into more effective treatments. Although the therapeutic arsenal to face heart failure has been expanding, the relatively short life expectancy of HF patients is pushing towards novel therapeutic strategies. Heart failure is associated with drastic metabolic disorders, including severe myocardial mitochondrial dysfunction and systemic nutrient deprivation secondary to severe cardiac dysfunction. To date, no effective therapy has been developed to restore the cardiac energy metabolism of the failing myocardium, mainly due to the metabolic complexity and intertwining of the involved processes. Recent years have witnessed a growing scientific interest in natural molecules that play a pivotal role in energy metabolism with promising therapeutic effects against heart failure. Among these molecules, B vitamins are a class of water soluble vitamins that are directly involved in energy metabolism and are of particular interest since they are intimately linked to energy metabolism and HF patients are often B vitamin deficient. This review aims at assessing the value of B vitamin supplementation in the treatment of heart failure.

Nutrient regulation of inflammatory signalling in obesity and vascular disease

Despite obesity and diabetes markedly increasing the risk of developing cardiovascular diseases, the molecular and cellular mechanisms that underlie this association remain poorly characterised. In the last 20 years it has become apparent that chronic, low-grade inflammation in obese adipose tissue may contribute to the risk of developing insulin resistance and type 2 diabetes. Furthermore, increased vascular pro-inflammatory signalling is a key event in the development of cardiovascular diseases. Overnutrition exacerbates pro-inflammatory signalling in vascular and adipose tissues, with several mechanisms proposed to mediate this. In this article, we review the molecular and cellular mechanisms by which nutrients are proposed to regulate pro-inflammatory signalling in adipose and vascular tissues. In addition, we examine the potential therapeutic opportunities that these mechanisms provide for suppression of inappropriate inflammation in obesity and vascular disease.

A new degree of complexi(n)ty in the regulation of GLUT4 trafficking

Loss of the insulin-stimulated glucose uptake in muscle is a crucial event participating in the defect of whole-body metabolism in type 2 diabetes. Therefore, identification by Pavarotti et al. (Biochem. J (2021) 478 (2): 407-422) of complexin-2 as an important contributor to glucose transporter 4 (GLUT4) translocation to muscle cell plasma membrane upon insulin stimulation is essential. The present commentary discusses the biological importance of the findings and proposes future challenges and opportunities.