Mogrol Derived from Siraitia grosvenorii Mogrosides Suppresses 3T3-L1 Adipocyte Differentiation by Reducing cAMP-Response Element-Binding Protein Phosphorylation and Increasing AMP-Activated Protein Kinase Phosphorylation

Siraitia grosvenorii As a Homologue of Food and Medicine: A Review of Biological Activity, Mechanisms of Action, Synthetic Biology, and Applications in Future Food

Siraitia grosvenorii (SG), also known as Luo Han Guo or Monk fruit, boasts a significant history in food and medicine. This review delves into SG's historical role and varied applications in traditional Chinese culture, examining its phytochemical composition and the health benefits of its bioactive compounds. It further explores SG's biological activities, including antioxidant, anti-inflammatory, and antidiabetic properties and elucidates the mechanisms behind these effects. The review also highlights recent synthetic biology advances in enhancing the production of SG's bioactive compounds, presenting new opportunities for broadening their availability. Ultimately, this review emphasizes SG's value in food and medicine, showcasing its historical and cultural importance, phytochemistry, biological functions, action mechanisms, and the role of synthetic biology in its sustainable use.

Mogrol stimulates G-protein-coupled bile acid receptor 1 (GPBAR1/TGR5) and insulin secretion from pancreatic β-cells and alleviates hyperglycemia in mice

Target identification is a crucial step in elucidating the mechanisms by which functional food components exert their functions. Here, we identified the G-protein-coupled bile acid receptor 1 (GPBAR1, also known as TGR5) as a target of the triterpenoid mogrol, a class of aglycone mogroside derivative from Siraitia grosvenorii. Mogrol, but not mogrosides, activated cAMP-response element-mediated transcription in a TGR5-dependent manner. Additionally, mogrol selectively activated TGR5 but not the other bile acid-responsive receptors (i.e., farnesoid X receptor, vitamin D receptor, or muscarinic acetylcholine receptor M3). Several amino acids in TGR5 (L71A2.60, W75AECL1, Q77AECL1, R80AECL1, Y89A3.29, F161AECL2, L166A5.39, Y240A6.51, S247A6.58, Y251A6.62, L262A7.35, and L266A7.39) were found to be important for mogrol-induced activation. Mogrol activated insulin secretion under low-glucose conditions in INS-1 pancreatic β-cells, which can be inhibited by a TGR5 inhibitor. Similar effects of mogrol on insulin secretion were observed in the isolated mouse islets. Mogrol administration partially but significantly alleviated hyperglycemia in KKAy diabetic mice by increasing the insulin levels without affecting the β-cell mass or pancreatic insulin content. These results suggest that mogrol stimulates insulin secretion and alleviates hyperglycemia by acting as a TGR5 agonist.

Establishment of a novel experimental system using single cell-derived pleomorphic rhabdomyosarcoma cell lines expressing K-RasG12V and deficient in p53

Pleomorphic rhabdomyosarcoma (PRMS) predominantly arises in adult skeletal musculature and is usually associated with poor prognosis. Thus, effective treatments must be developed. PRMS is a rare tumor; therefore, it is critical to develop an experimental system to understand the cellular and molecular mechanisms of PRMS. We previously demonstrated that PRMS develops after p53 gene deletion and oncogenic K-Ras expression in the skeletal muscle tissue. In that study, oncogenic K-Ras-expressing cells were diverse and the period until disease onset was difficult to control. In this study, we developed an experimental system to address this problem. Single cell-derived murine cell lines, designated as RMS310 and RMSg2, were established by limiting the dilution of cells from a lung metastatic tumor colony that were positive for various cancer stem cells and activated skeletal muscle-resident stem/progenitor cell marker genes by RT-PCR. All cell lines stably recapitulated the histological characteristics of human PRMS as bizarre giant cells, desmin-positive cells, and lung metastases in C57BL/6 mice. All subclones of the RMSg2 cells by the limiting dilution in vitro could seed PRMS subcutaneously, and as few as 500 RMSg2 cells were sufficient to form tumors. These results suggest that the RMSg2 cells are multipotent cancer cells that partially combine the properties of skeletal muscle-resident stem/progenitor cells and high tumorigenicity. Thus, our model system's capacity to regenerate tumor tissue in vivo and maintain stable cells in vitro makes it useful for developing therapeutics to treat PRMS.

CMI: CRISPR/Cas9 Based Efficient Multiplexed Integration in Saccharomyces cerevisiae

Genomic integration is the preferred method for gene expression in microbial industrial production. However, traditional homologous recombination based multiplexed integration methods often suffer from low integration efficiency and complex experimental procedures. Here, we report a CRISPR/Cas9 based multiplexed integration (CMI) system in Saccharomyces cerevisiae, which can achieve quadruple integration at an individual locus without pre-engineering the host. A fused protein, Cas9-Brex27, was used as a bait to attract Rad51 recombinase to the proximity of the double-strand breaks introduced by the CRISPR/Cas9 system. The efficiency of quadruple integration was increased to 53.9% with 40 bp homology arms (HAs) and 78% with 100 bp HAs. CMI was applied to integrate a heterologous mogrol biosynthetic pathway consisting of four genes in a one-step transformation and offered an efficient solution for multiplexed integration. This method expands the synthetic biology toolbox of S. cerevisiae.

Pharmacological Activities of Mogrol: Potential Phytochemical against Different Diseases

Recently, mogrol has emerged as an important therapeutic candidate with multiple potential pharmacological properties, including neuroprotective, anticancer, anti-inflammatory, antiobesity, antidiabetes, and exerting a protective effect on different organs such as the lungs, bone, brain, and colon. Pharmacokinetic studies also highlighted the potential of mogrol as a therapeutic. Studies were also conducted to design and synthesize the analogs of mogrol to achieve better activities against different diseases. The literature also highlighted the possible molecular mechanism behind pharmacological activities, which suggested the role of several important targets, including AMPK, TNF-α, and NF-κB. These important mogrol targets were verified in different studies, indicating the possible role of mogrol in other associated diseases. Still, the compilation of pharmacological properties, possible molecular mechanisms, and important targets of the mogrol is missing in the literature. The current study not only provides the compilation of information regarding pharmacological activities but also highlights the current gaps and suggests the precise direction for the development of mogrol as a therapeutic against different diseases.

Effect of different sweeteners on the quality, fatty acid and volatile flavor compounds of braised pork

This study aimed to assess how several sweeteners (white sugar, Siraitia grosvenorii fruit, mogrosides, and stevia glycoside) affected the flavor, fatty acid composition, and quality of braised pork. The findings indicated that braised meat prepared with sweeteners differed from typical braised pork. When simmered for 60 min, the typical braised pork with white granulated sugar exhibited a significant cooking loss (CL) and little water content. Significantly more than in the group containing Siraitia grosvenorii, mogroside, and stevia glycoside, the Thiobarbituric acid (TBARS) value increased by 14.39% (P < 0.05). The sample in the group that included mogroside had a low CL rate. After 40 min of stewing, the lean pork has the highest L* value, but the 60-min stew sample is nicely colored and stretchy. Mogroside can prevent protein, and lipid oxidation, is thermally stable and reduces CL during stewing. Additionally, Siraitia grosvenorii and stevia glycosides help prevent oxidation from intensifying during stewing. When Siraitia grosvenorii is added, lipid oxidation is significantly inhibited, and stevia glycosides are more beneficial for enhancing meat color. With an increase in heating time, the fatty acids in braised pork reduced; the unsaturated fatty acid (UFA) of the Siraitia grosvenorii fruit (SF) and mg group also fell somewhat, and the UFA: SFA ratio was higher than that of the white sugar (WS) group. The SFA content of the braised meat in the stevia glycoside group was higher than that of the WS group. In all, 75 volatile flavor elements in braised pork were discovered by Gas chromatography-ion mobility spectrometry (GC-IMS). The sweetener increased alcohols, esters, and acids in the braised pork. As stewing time increased, ketones decreased, but aldehydes and esters increased. The pork formed antioxidant peptides with great nutritional value after cooking. Braised pork with mogroside and stevia glycoside additions primarily have some protein color protection and antioxidant effects. This study may offer fresh perspectives on applying natural sweeteners and enhancing braised pork’s flavor.

Construction and Optimization of the de novo Biosynthesis Pathway of Mogrol in Saccharomyces Cerevisiae

Mogrol plays important roles in antihyperglycemic and antilipidemic through activating the AMP-activated protein kinase pathway. Although the synthesis pathway of mogrol in Siraitia grosvenorii has been clarified, few studies have focused on improving mogrol production. This study employed a modular engineerin g strategy to improve mogrol production in a yeast chassis cell. First, a de novo synthesis pathway of mogrol in Saccharomyces cerevisiae was constructed. Then, the metabolic flux of each synthetic module in mogrol metabolism was systematically optimized, including the enhancement of the precursor supply, inhibition of the sterol synthesis pathway using the Clustered Regularly Interspaced Short Palindromic Repeats Interference system (CRISPRi), and optimization of the expression and reduction system of P450 enzymes. Finally, the mogrol titer was increased to 9.1 μg/L, which was 455-fold higher than that of the original strain. The yeast strains engineered in this work can serve as the basis for creating an alternative way for mogrol production in place of extraction from S. grosvenorii.

Mogroside-Rich Extract From Siraitia grosvenorii Fruits Ameliorates High-Fat Diet-Induced Obesity Associated With the Modulation of Gut Microbiota in Mice

Siraitia grosvenorii is a kind of medicinal food plant. The mogroside-rich extract (MGE) of its fruits can effectively ameliorate obesity, but the underlying mechanisms remain underexplored. In this study, we aimed to determine whether MGE can ameliorate obesity by protecting against the divergences of gut microbiota. Mice were challenged with a high-fat diet (HFD) and treated with MGE by oral gavage. Then, the characteristics of the gut microbiota were determined by 16S rDNA analysis. Our findings showed that MGE could significantly reduce body weight gain and fat tissue weight of the mice fed with HFD. Moreover, MGE markedly attenuated fatty liver, and improved glucose tolerance and insulin sensitivity. We further found that the gut microbiota structures were disturbed by HFD feeding. In particular, the abundance of Firmicutes was increased and the abundance of Bacteroidetes was decreased, resulting in an increased proportion of Firmicutes to Bacteroidetes (F/B), which contributes to obesity. Interestingly, the abnormal proportion of F/B of HFD feeding mice was restored to the level of control mice by MGE treatment. Additionally, the abundances of obesogenic microbiota, such as Ruminiclostridium and Oscillibacter were also decreased after MGE treatment. In summary, our findings demonstrate that MGE can modulate gut microbiota in obese mice and shed new light on how it alleviates obesity.

Effect of synbiotic yogurt fortified with monk fruit extract on hepatic lipid biomarkers and metabolism in rats with type 2 diabetes

Monk fruit extract (MFE) is widely used as a sweetener in foods. In this study, the effects of the consumption of MFE-sweetened synbiotic yogurt on the lipid biomarkers and metabolism in the livers of type 2 diabetic rats were evaluated. The results revealed that the MFE-sweetened symbiotic yogurt affected the phosphatidylcholines, phosphatidylethanolamines, phosphatidylglycerol, lysophosphatidic acids, lysophosphatidylcholines, lysophosphatidylethanolamines, lysophosphatidylglycerols, lysophosphatidylinositols, lysophosphatidylserines, and fatty acid-hydroxy fatty acids biomarkers in the livers of type 2 diabetic rats. In addition, the consumption of the MFE-sweetened synbiotic yogurt significantly altered 12 hepatic metabolites, which are involved in phenylalanine metabolism, sphingolipid metabolism, bile secretion, and glyoxylate and dicarboxylate metabolism in the liver. Furthermore, a multiomics (metabolomic and transcriptomic) association study revealed that there was a significant correlation between the MFE-sweetened synbiotic yogurt and the metabolites and genes involved in fatty acid biosynthesis, bile secretion, and glyoxylate and dicarboxylate metabolism. The findings of this study will provide new insights on exploring the function of sweeteners for improving type 2 diabetes mellitus liver lipid biomarkers.

Mogrol suppresses lung cancer cell growth by activating AMPK-dependent autophagic death and inducing p53-dependent cell cycle arrest and apoptosis

Lung carcinoma is the leading cause of cancer-related death worldwide. Chemotherapy remains the cornerstone of lung cancer treatment. Unfortunately, most types of cancer will develop resistance to chemotherapies over the time. One of the efforts to prevent the chemotherapy resistance is to find alternative chemotherapy drugs. Mogrol has been found to have antitumor activity. However, little is known about the pharmacological mechanisms underlying the suppression of mogrol on lung cancers. In this study, we observed that mogrol exposure significantly reduced the tumor volume and weight in tumor-bearing nude mice without obvious effect on body weight and cardiac function. Mogrol also significantly inhibited the proliferation and migration of lung cancer cells, including non-small-cell lung carcinoma cells, A549, H1299, H1975 and SK-MES-1 cells, with no obvious effect on control human bronchial epithelial cells (HBE). Further studies revealed that mogrol stirred excessive autophagy and autophagic flux, and finally, autophagic cell death, in lung cancer cells, which could be attenuated by autophagy inhibitors, 3-MA and chloroquine. Furthermore, mogrol significantly activated AMPK to induce autophagy and autophagic cell death, which could be abrogated by Compound C, an AMPK inhibitor. In addition, mogrol induced a significant increase in p53 activity in lung cancer cells, accompanied with cell cycle arrest and apoptosis, which could be weakened by p53 silence. Our results indicated that mogrol effectively suppressed lung cancer cells in vivo and in vitro by inducing the excessive autophagy and autophagic cell death via activating AMPK signaling pathway, as well as cell cycle arrest and apoptosis via activating p53 pathway.

Synthesis and Antiproliferative Activity of Ester Derivatives of Mogrol through JAK2/STAT3 Pathway

In attempt to enhance the antiproliferative activity of mogrol, two series of ester derivatives modified at C₃ -OH and C₁₁ -OH were designed and synthesized. The activity against human cancer cells including A549, NCI-H460 and CNE1 was screened by Cell Counting Kit-8 (CCK8) assay. According to the results, modifications of the mogrol core through introduction of different ester scaffolds drastically improved the cytotoxicity, and some of the derivatives exhibited even higher activity than the positive drug. Among them, compound M2h exhibited nearly 4 times more cytotoxic than 5-Fu against CNE1 cells, derivative M6c showed ten times higher activity with the IC₅₀ value of 10.59 μM than mogrol against NCI-H460 cells, and compound M6a which contained one 1,2,3-triazole motif showed the strongest activity with an three folds lower IC₅₀ value than mogrol. Furthermore, the most potent compound M2h could lead to cell cycle arrest at G2 phase on CNE1 cell lines and M6a induced G1 phase arrest on A549 cell lines. It was noteworthy that both M2h and M6a regulated signal transducer and activator of transcription 3 (STAT3) signal pathway through inhibiting phosphorylation of Janus Kinase 2 (JAK2) and STAT3, and simultaneously increasing the protein level of downstream cyclin p21.

Research progress of pharmacological effects of Siraitia grosvenorii extract

OBJECTIVES

To summarise the ingredients of Luo Han Guo extract and the different pharmacological activity of the different ingredients. Find and evaluate the research value of Luo Han Guo extract as a therapeutic drug.

KEY FINDINGS

Siraitia grosvenorii is a fruit native to China and has many years of medicinal history. Because of its low-calorie and sugar-free properties, it is approved as a sweetener substitute in foods for obese and diabetic patients. Experiments have shown that this sweetener is non-toxic. This article summarises much literature on S. grosvenorii extracts, briefly introduces their chemical composition and metabolic distribution and summarises the possible pharmacological effects of each S. grosvenorii extract. Siraitia grosvenorii extract has anti-diabetic, anti-tumour, anti-inflammatory, antioxidant, neuroprotective and lipogenic inhibitory effects. These pharmacological activities suggest the medicinal value of S. grosvenorii.

SUMMARY

Luo Han Guo extract is a low-calorie, non-toxic substance, and its pharmacological activity and its potential medicinal properties support its further utilisation and research.

Mogroside V Alleviates Oocyte Meiotic Defects and Quality Deterioration in Benzo(a)pyrene-Exposed Mice

Accumulating evidence has demonstrated that benzo(a)pyrene (BaP) exposure adversely affects female reproduction, especially oocyte meiotic maturation and subsequent embryo development. Although we previously found that mogroside V (MV), a major bioactive component of S. grosvenorii, can protect oocytes from quality deterioration caused by certain stresses, whether MV can alleviate BaP exposure-mediated oocyte meiotic defects remains unknown. In this study, female mice were exposed to BaP and treated concomitantly with MV by gavage. We found that BaP exposure reduced the oocyte maturation rate and blastocyst formation rate, which was associated with increased abnormalities in spindle formation and chromosome alignment, reduced acetylated tubulin levels, damaged actin polymerization and reduced Juno levels, indicating that BaP exposure results in oocyte nucleic and cytoplasmic damage. Interestingly, MV treatment significantly alleviated all the BaP exposure-mediated defects mentioned above, indicating that MV can protect oocytes from BaP exposure-mediated nucleic and cytoplasmic damage. Additionally, BaP exposure increased intracellular ROS levels, meanwhile induced DNA damage and early apoptosis in oocytes, but MV treatment ameliorated these defective parameters, therefore it is possible that MV restored BaP-mediated oocyte defects by reducing oxidative stress. In summary, our findings demonstrate that MV might alleviate oocyte meiotic defects and quality deterioration in BaP-exposed mice.

Mogrol, an aglycone of mogrosides, attenuates ulcerative colitis by promoting AMPK activation

BACKGROUND

Ulcerative colitis (UC) is a non-specific chronic inflammatory disease. The incidence of UC in China has been increasing in recent years. Mogrol is an aglycone of mogrosides. Studies have shown that mogrosides have anti-oxygenation, anti-inflammatory, and laxative effects as well as other biological activities.

PURPOSE

To investigate the beneficial effects of mogrol on UC and identify its underlying mechanisms.

STUDY DESIGN

We used the dextran sodium sulphate (DSS)-induced UC model in mice, TNF-α-damaged NCM460 colonic epithelial cells, macrophage cells THP-M stimulated with lipopolysaccharide (LPS) / adenosine triphosphate (ATP) and compound C (an AMPK inhibitor) to confirm the key role of AMPK (AMP-activated protein kinase) activation.

METHODS

Histological evaluation, immunohistochemical staining, Western blot analysis, immunofluorescence assay and quantitative real time-PCR were used in the study.

RESULTS

Oral administration of mogrol (5 mg/kg/daily) in vivo significantly attenuated pathological colonic damage, inhibited inflammatory infiltration and improved the abnormal expression of NLRP3 inflammasome in colonic mucosa via the AMPK and NF-κB signaling pathways. In vitro, mogrol protected against intestinal epithelial barrier dysfunction by activating AMPK in TNF-α-treated NCM460 cells and inhibited the production of inflammatory mediator in LPS-stimulated THP-M cells. Furthermore, mogrol's effects were reversed by compound C intervention in DSS-induced UC model.

CONCLUSION

Mogrol exerts protective effects in experimental UC and inhibits production of inflammatory mediators through activation of AMPK-mediated signaling pathways.

Effect of feeding type 2 diabetes mellitus rats with synbiotic yogurt sweetened with monk fruit extract on serum lipid levels and hepatic AMPK (5' adenosine monophosphate-activated protein kinase) signaling pathway

Monk fruit extract (MFE) is a natural sweetener that has been used as an ingredient of food and pharmaceutical products. The effects of feeding synbiotic yogurt fortified with MFE to rats with type 2 diabetes induced by high-fat diet and streptozotocin on serum lipid levels and hepatic AMPK signaling pathway were evaluated. Results showed that oral administration of the synbiotic yogurt fortified with MFE could improve serum lipid levels, respiratory exchange rate, and heat level in type 2 diabetic rats. Transcriptome analysis showed that synbiotic yogurt fortified with MFE may affect the expression of genes involved in binding, catalytic activity, and transporter activity. The Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that these differentially expressed genes were related to AMPK signaling pathway, linoleic acid metabolism, and α-linolenic acid metabolism. Western blotting confirmed that synbiotic yogurt fortified with MFE could activate AMPK signaling and improve the protein level of the hepatic gluconeogenic enzyme G6Pase in diabetic rats. The results indicated that MFE could be a novel sweetener for functional yogurt and related products.

Mogrol attenuates lipopolysaccharide (LPS)-induced memory impairment and neuroinflammatory responses in mice

This study aimed to evaluate whether mogrol, a main bioactive ingredient of Siraitia grosvenorii, could attenuate LPS-induced memory impairment in mice. The behavioral tests and immunohistochemical analysis and Western blot were performed. The present results showed that oral administration of mogrol (20, 40, 80 mg/kg) significantly improved LPS-induced memory impairment in mice. The results also indicated that mogrol treatment significantly reduced the number of Iba1-positive cells, the nuclear NF-κB p65 and levels of TNF-α, IL-1β and IL-6 both in the hippocampus and frontal cortex of LPS-challenged mice. [Formula: see text].

Mogroside V protects porcine oocytes from in vitro ageing by reducing oxidative stress through SIRT1 upregulation

Postovulatory ageing compromises oocyte quality and subsequent development in various manners. We aimed to assay the protective effects of mogroside V on porcine oocyte quality during in vitro ageing and explore the related causes. We observed that mogroside V can effectively maintain normal oocyte morphology and early embryo development competence after prolonged culture for 24 h. Moreover, mogroside V can markedly reduce reactive oxygen species (ROS) levels, alleviate spindle formation and chromosome alignment abnormalities, improve mitochondrial contents, adenosine triphosphate (ATP) levels and the membrane potential (ΔΨm), and reduce early apoptosis in aged oocytes. We examined the molecular changes and found that SIRT1 expression was decreased in in vitro aged oocytes but was maintained by exposure to mogroside V. However, when SIRT1 was successfully inhibited by the specific inhibitor EX-527, mogroside V could not reduce ROS levels or alleviate abnormal spindle organization and chromosome misalignment. In summary, our results demonstrated that mogroside V can alleviate the deterioration of oocyte quality during in vitro ageing, possibly by reducing oxidative stress through SIRT1 upregulation.

AMPK activation is involved in hypoglycemic and hypolipidemic activities of mogroside-rich extract from Siraitia grosvenorii (Swingle) fruits on high-fat diet/streptozotocin-induced diabetic mice

AMPK is involved in hypoglycemic and hypolipidemic activities of mogrosides from Siraitia grosvenorii (Swingle) fruits on diabetic mice.

Neuroprotective effect of mogrol against Aβ1-42 -induced memory impairment neuroinflammation and apoptosis in mice

OBJECTIVES

Cognitive impairment is the main character of Alzheimer's disease (AD). This study mainly focused on whether mogrol, a tetracyclic triterpenoids compound of Siraitia grosvenorii Swingle, can ameliorate the memory impairment induced by Aβ_1-42 .

METHODS

Memory impairment mice model was made by stereotactic intra-hippocampal microinjection of Aβ_1-42 (410 pm/mouse). Mogrol (20, 40, 80 mg/kg) was given to mice by intragastric administration at 3 days after Aβ_1-42 injection for totally 3 weeks. Morris water maze test and Y-maze test were operated to evaluate the therapeutic effect of morgrol on Aβ_1-42 -induced memory impairments. Immunohistochemical analyses and Hoechst 33258 assay were used to evaluate effect of morgrol on Aβ_1-42 -induced microglia overactivation and apoptotic response in hippocampus of mice. Western blotting assay was used to evaluate effect of mogrol on the Aβ_1-42 -activated NF-κB signaling.

KEY FINDINGS

Mogrol could significantly alleviate Aβ_1-42 -induced memory impairments, inhibit Aβ_1-42 -induced microglia overactivation and prevent Aβ_1-42 -triggered apoptotic response in the hippocampus. Mogrol also could suppress Aβ_1-42 -activated NF-κB signaling, reduce the production of proinflammatory cytokines.

CONCLUSIONS

This study suggested that mogrol would ameliorate the memory impairment induced by Aβ_1-42 , which is involved in anti-inflammation and anti-apoptosis in the brain.

Stereoselective effects of lactate enantiomers on the enhancement of 3T3-L1 adipocyte differentiation

Lactate contains a chiral carbon and thus has two optical isomers-d-lactate and l-lactate. l-Lactate is the predominant form that is produced by the body and can be delivered to the organs. On the other hand, gut microbiota produce both isomers, which can then flow into the body. Although both d-lactate and l-lactate can contribute to energy metabolism, their potential roles in adipocyte differentiation remain to be elucidated. Here, we investigated the effects of l-lactate and d-lactate on the differentiation of 3T3-L1 preadipocytes. Both lactate enantiomers were demonstrated to enhance triglyceride accumulation by stimulating the early phase of adipocyte differentiation. Notably, d-lactate was more potent than l-lactate in inducing triglyceride accumulation. The degree of triglyceride accumulation induced by l-lactate was similar to that induced by pyruvate. d-Lactate was more potent than l-lactate in increasing the activity of glycerol-3-phosphate dehydrogenase. Both lactate enantiomers did not affect cell viability. Moreover, both enantiomers upregulated the expression of peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein (C/EBP) α, sterol regulatory element-binding protein-1c, and fatty acid synthase, with d-lactate exerting stronger effects than l-lactate. By contrast, lactate did not influence the expression of C/EBPβ and C/EBPδ. d-Lactate significantly increased and l-lactate tended to increase p38 MAPK phosphorylation, and the p38 MAPK inhibitor SB203580 inhibited the stimulation of adipocyte differentiation by d-lactate and l-lactate. These findings showed that both lactate enantiomers stimulate preadipocyte differentiation, with d-lactate showing more potent effects than l-lactate. In addition, our study demonstrated that d-lactate and l-lactate exert different effects on physiological events.

Implications of glycerol metabolism for lipid production

Triacylglycerol (TAG) is an important product in oil-producing organisms. Biosynthesis of TAG can be completed through either esterification of fatty acids to glycerol backbone, or through esterification of 2-monoacylglycerol. This review will focus on the former pathway in which two precursors, fatty acid and glycerol-3-phosphate (G3P), are required for TAG formation. Tremendous progress has been made about the enzymes or genes that regulate the biosynthetic pathway of TAG. However, much attention has been paid to the fatty acid provision and the esterification process, while the possible role of G3P is largely neglected. Glycerol is extensively studied on its usage as carbon source for value-added products, but the modification of glycerol metabolism, which is directly associated with G3P synthesis, is seldom recognized in lipid investigations. The relevance among glycerol metabolism, G3P synthesis and lipid production is described, and the role of G3P in glycerol metabolism and lipid production are discussed in detail with an emphasis on how G3P affects lipid production through the modulation of glycerol metabolism. Observations of lipid metabolic changes due to glycerol related disruption in mammals, plants, and microorganisms are introduced. Altering glycerol metabolism results in the changes of final lipid content. Possible regulatory mechanisms concerning the relationship between glycerol metabolism and lipid production are summarized.