3-isobutyl-1-methylxanthine Research Articles

Aggregated chromosomes/chromatin transfer: a novel approach for mitochondrial replacement with minimal mitochondrial carryover: the implications of mouse experiments for human aggregated chromosome transfer.

Nuclear transfer techniques, including spindle chromosome complex (SC) transfer and pronuclear transfer, have been employed to mitigate mitochondrial diseases. Nevertheless, the challenge of mitochondrial DNA (mtDNA) carryover remains unresolved. Previously, we introduced a method for aggregated chromosome (AC) transfer in human subjects, offering a potential solution. However, the subsequent rates of embryonic development have remained unexplored owing to legal limitations in Japan, and animal studies have been hindered by a lack of AC formation in other species. Building upon our success in generating ACs within mouse oocytes via utilization of the phosphodiesterase inhibitor 3-isobutyl 1-methylxanthine (IBMX), this study has established a mouse model for AC transfer. Subsequently, a comparative analysis of embryo development rates and mtDNA carryover between AC transfer and SC transfer was conducted. Additionally, the mitochondrial distribution around SC and AC structures was investigated, revealing that in oocytes at the metaphase II stage, the mitochondria exhibited a relatively concentrated arrangement around the spindle apparatus, while the distribution of mitochondria in AC-formed oocytes appeared to be independent of the AC position. The AC transfer approach produced a marked augmentation in rates of fertilization, embryo cleavage, and blastocyst formation, especially as compared to scenarios without AC transfer in IBMX-treated AC-formed oocytes. No significant disparities in fertilization and embryo development rates were observed between AC and SC transfers. However, relative real-time PCR analyses revealed that the mtDNA carryover for AC transfers was one-tenth and therefore significantly lower than that of SC transfers. This study successfully accomplished nuclear transfers with ACs in mouse oocytes, offering an insight into the potential of AC transfers as a solution to heteroplasmy-related challenges. These findings are promising in terms of future investigation with human oocytes, thus advancing AC transfer as an innovative approach in the field of human nuclear transfer methodology.

FRI018 A Novel Truncating Variant Of EBF2 Disrupts Human Adipocyte Differentiation In Lipodystrophy Syndromes: An Example Of A Discovery From A Clinical Translational Pipeline

Abstract Disclosure: M.C. Foss de Freitas: Advisory Board Member; Self; PTC Therapeutics. N. Wys: None. M. Udler: None. L. Pais: None. A. Monteiro da Rocha: None. O.A. MacDougald: None. E.A. Oral: Consulting Fee; Self; Regeneron Pharmaceuticals, Aegerion Pharmaceuticals, Ionis Pharmaceuticals Inc., Third Rock Ventures, Rejuvenate Inc. Grant Recipient; Self; Regeneron Pharmaceuticals, Aegerion Pharmaceuticals, Ionis Pharmaceuticals Inc., Novo Nordisk, Fractyl Laboratories, Rhythm pharmaceuticals, GID Dynamics. Other; Self; Aegerion Pharmaceuticals. T. Chun: None. Objective/Goals: Partial Lipodystrophy is characterized by the gradual loss of adipose tissues, which progresses after birth. The genetic and molecular underpinning of many cases of partial lipodystrophy have not been fully understood. Aiming to better understand the molecular pathogenesis of familial partial lipodystrophy, we initiated deep sequencing for our patients with partial lipodystrophy syndromes. A novel variant of early B cell factor 2 (EBF2) was identified. Here we report the biological impact of a novel truncating EBF2 variant. Methods: We performed loss-of-function and gene rescue experiments using 3T3-L1 and human primary subcutaneous preadipocytes. All cells were cultured in DMEM with 10% bovine calf serum (Invitrogen). After lentivirus transfection (Full-length EBF2 or truncated variant EBF2), cells were grown to confluence and then exposed to adipogenesis induction media containing dexamethasone, insulin and isobutyl methylxanthine. Total RNA was extracted using RNeasy Mini Kit (Qiagen), and cDNA was synthesized using IScript (Bio-Rad). Real-time qPCR was performed using TaqMan probes for Pparg and Fabp4, two key adipogenesis markers. Results: The patient was found to carry a heterozygous nonsense mutation in exon 6 of 16 (NM_022659.4) of EBF2, causing the premature termination of the protein at amino acid position 165 (EBF2 8:26033143 C>A (hg38), c.493G>T, p.Glu165Ter). Adipogenesis was significantly suppressed in 3T3-L1 cells when endogenous Ebf2 was suppressed with siRNA and lentiviral shRNA. Adipocytes with suppressed Ebf2 expression showed a marked reduction of intracellular lipid content and Pparg and Fabp4 expression (>80% reduction). With lentiviral gene transfer, EBF2 fully rescued adipogenic potential, whereas the truncated variant EBF2 p.Glu165Ter did not. Of note, 3T3-L1 cells transfected with the EBF2 variant impaired adipogenesis, suggesting an inhibitory effect of the EBF2 variant on adipogenesis. We next confirmed the inhibition in adipogenesis with the EBF2 variant in primary human preadipocytes from subcutaneous adipose tissues. Using lentiviral gene transfer in human preadipocytes, we observed that the full-length EBF2 increased the gene expression of PPARg and FABP4 while the truncated EBF2 variant did not. Conclusion: Our data suggest that EBF2 is indispensable for adipogenesis of mouse and human preadipocytes. The truncating variant of EBF2 p.Glu165Ter likely plays a pathogenic role in the partial lipodystrophy presentation of this patient. Whole genome (or exome) sequencing undertaken in patients with partial lipodystrophy and subsequent biological functional analysis may lead to identification of novel mechanisms driving novel discoveries. Presentation: Friday, June 16, 2023

P-197 Nuclear transfer with almost nonexistent mitochondrial carryover -a mouse model-

Abstract Study question Can the transfer of aggregated chromosomes (AC) as compared to spindle-chromosome transfer (SCT) reduce mitochondrial DNA (mtDNA) carryover and improve development rates? Summary answer The rate of mtDNA carryover after AC transfer was only 0.1%, which was much less than that of 2.0% after SCT. What is known already Nuclear transfer techniques such as SCT and pronuclear transfer have been applied to prevent mitochondrial diseases and to treat early embryonic arrest, however, the problem of mtDNA carryover has not yet been resolved. We previously reported on an AC transfer (ACT) method in humans which could overcome the above problem, however, consequent embryonic development rates have not been investigated in Japan due to legal restrictions and no animal study has been conducted, as the formation of ACs has not been found in any other species. Study design, size, duration Following our success in the creation of ACs in mouse oocytes using IBMX (3-Isobutyl 1-methylxanthine), a phosphodiesterase inhibitor, a mouse model of ACT was established. This was followed by a comparison of the rates of embryo development and mtDNA carryover in both ACT and SCT in over 100 oocytes. The distribution of mitochondria around SC and AC were also examined by confocal laser microscope (FV3000, Olympus, Japan). Participants/materials, setting, methods GV stage oocytes were collected from 8-12 week B6D2F1 mice. After GVBD, oocytes were incubated in KSOM medium, containing 3 mM IBMX, for 10-14 hours until AC is formed. ACs and SCs were injected into enucleated MII stage donor oocytes and then fertilized at the MII stage. Embryos were cultured for 5 days to compare the rates of embryo development. Enucleated ACs and SCs were subjected to real-time PCR, to analyze the carryover of mtDNA. Main results and the role of chance The rates of fertilization, embryo cleavage and blastocyst formation in AC oocytes without AC transfer (control), in ACT and in SCT were 60.7%, 55.9%, 13.2% (control), 82.5%, 80.8% and 30.8% (ACT), and 81.0%, 74.5% and 31.4% (SCT) respectively. The ACT group showed a significant increase in fertilization (P = 0.007), embryo cleavage (p = 0.008) and blastocyst formation (p = 0.034) rates, as compared to those in the control group. There were no significant differences between ACT and SCT regarding the rates of fertilization, embryo cleavage and blastocyst formation. The relative, real-time PCR showed that mtDNA carryover in the ACT group was 0.1% ± 0.07%, which was significantly lower than that in the SCT group of 2.0% ± 0.6% (p = 0.027). 3D confocal laser microscopy revealed that mitochondria were not localized around either SCs or ACs, as they were around pronuclei. Limitations, reasons for caution Although we succeeded in establishing a mouse model of ACT, validation in human oocytes is required to confirm the benefit of this method. Further experiments are required to confirm if healthy offspring can be obtained after ACT. Wider implications of the findings ACT could reduce the amount of mtDNA carryover and overcome heteroplasmy. As ACT improved the low embryo development rate caused by IBMX and had similar embryo development rates to SCT, the findings of this study may give rise to ACT being employed as a novel method for human nuclear transfer. Trial registration number not applicatable

231-OR: Reduced NKX2-2 Expression Enhances Insulin Secretion by Primary Human ß-Cells

Pancreatic islet endocrine cell phenotype and function are tightly regulated by transcription factor (TF) regulatory networks. In a mouse model of pancreas organogenesis, the key islet-enriched TF NKX2.2 governs both β and α cell specification. Further, loss of NKX2.2 in adult mouse β cells results in glucose intolerance, reduced insulin content, and polyhormonal β cells, demonstrating its importance in the maintenance of β cell phenotype. To understand the undefined role of NKX2.2 in adult human islets, we utilized adenoviral delivery of CRISPR and shRNA constructs in our primary human pseudoislet system to knockout (gNKX2-2) or knockdown (shNKX2-2) NKX2-2 in islet cells, respectively (n=4-6 donors without diabetes). Immunofluorescence analyses of gNKX2-2 pseudoislets demonstrated loss of NKX2.2 signal across β (81 ± 2.0%; p<0.001), α (58 ± 5.5%; p=0.001), and δ cells (83 ± 2.2%; p<0.001) compared to scrambled controls (gSCR). Surprisingly, functional assessment by dynamic perifusion revealed increased insulin secretion in gNKX2-2 versus gSCR pseudoislets measured as area under the curve in response to 16.7 mM glucose (6.64 ± 1.53 vs. 3.55 ± 1.53 ng/100 islet equivalents (IEQs); p=0.007) and cAMP-evoked potentiation with 16.7 mM glucose + 100 μM isobutylmethylxanthine (IBMX) (5.43 ± 0.50 vs. 3.15 ± 0.59 ng/100 IEQs p=0.003) without changes in total insulin content (gNKX2-2 vs. gSCR: 3.64 ± 0.75 vs. 4.78 ± 0.87 ng/IEQ, p=0.45). Furthermore, these findings were recapitulated in shNKX2-2 versus shSCR human pseudoislets (16.7 mM glucose: 10.17 ± 2.46 vs. 6.50 ± 2.51 ng/100 IEQs, p=0.02; 16.7 mM glucose + IBMX: 8.43 ± 1.31 vs. 4.21 ± 1.33 ng/100 IEQs, p=0.0002; insulin content: 6.18 ± 1.05 vs. 7.53 ± 1.26 ng/IEQ, p=0.36), where we observed a reduction in NKX2.2hi β (65 ± 10%; p=0.008), α (52 ± 5.5%; p=0.003), and δ cells (83 ± 4.6%; p=0.003). Collectively, our data indicate a critical role of NKX2-2 in the maintenance of primary adult human β cell function and suggest differential roles in islet function across species. Disclosure Y.D.Pettway: None. S.Parker: Research Support; Pfizer Inc. A.C.Powers: None. M.Brissova: None. J.Walker: None. C.Dai: None. R.Aramandla: None. A.L.Hopkirk: None. C.Reihsmann: None. C.Davis: None. R.Jenkins: None. L.Sussel: None.

386 A novel truncating variant of EBF2 disrupts human adipocyte differentiation in lipodystrophy syndromes: an example of a discovery from a clinical translational pipeline

OBJECTIVES/GOALS: Aiming to better understand the molecular pathogenesis of familial partial lipodystrophy (PL), we initiated whole-exome sequencing for our patients with PL syndromes. A novel variant of early B cell factor 2 (EBF2) was identified. Here we report the biological impact of a novel truncating EBF2 variant. METHODS/STUDY POPULATION: Using 3T3-L1 and human primary subcutaneous preadipocytes, we performed loss-of-function and gene rescue experiments. All cells were cultured in DMEM with 10% bovine calf serum (Invitrogen) at 5% CO2. After lentivirus transfection, cells were grown to confluence and then exposed to adipogenesis induction media containing dexamethasone (0.25µM), insulin (1µg/ml) and isobutyl methylxanthine (0.5 mM). Total RNA was extracted using RNeasy Mini Kit (Qiagen) and cDNA was synthesized using IScript (Bio-Rad). Real-time qPCR was performed using TaqMan probes for Pparg and Fabp4, two key adipogenesis markers. RESULTS/ANTICIPATED RESULTS: Patient was found to carry a heterozygous nonsense mutation in exon 6 of EBF2, causing the premature termination of the protein at amino acid position 165. Adipogenesis was significantly suppressed in 3T3L1 cells when endogenous Ebf2 was suppressed with siRNA and lentiviral shRNA. Adipocytes with suppressed Ebf2 expression showed marked reduction of intracellular lipid content and Pparg and Fabp4 expression (>80% reduction). With lentiviral gene transfer, EBF2 fully rescued adipogenic potential, whereas the truncated variant EBF2 did not. Of note, 3T3-L1 cells transfected with the EBF2 variant displayed impaired adipogenesis, suggesting a dominant-negative effect of the EBF2 variant on adipogenesis. We confirmed the dominant effect of the EBF2 variant in human adipocyte differentiation. DISCUSSION/SIGNIFICANCE: Our data suggest that EBF2 is indispensable for adipogenesis. The loss of function and dominant-negative effect of the truncating variant of EBF2 likely plays a pathogenic role in PL. Whole exome sequencing of PL patients and ex-vivo functional analysis help identify novel gene variants and better understand the molecular pathogenesis of PL.

Cyclic adenosine 3’5’monophosphate (cAMP) regulates meiotic maturation in goldfish oocytes Carassius auratus (Teleostei: Cyprinidae)

A good understanding of the mechanism of oocyte development and maturation, and the regulatory factors involved therein are important for the success of a breeding program especially of species used in aquaculture. It is crucial in a breeding program for females to supply high quality mature oocytes, which is generally achieved by fine-tuning oocyte meiotic arrest and resumption progression. Therefore, knowledge of the oocyte maturation process is fundamental for the development of methodologies to increase the success of fish production in aquaculture. TheFigure regulations of oocyte maturation still are not totally understood. The hypothesis whether elevated levels or a drop in intraoocyte cAMP triggers resumption of meiotic maturation was investigated in denuded goldfish oocytes. In the presence of agents that elevate cAMP like forskolin, dibutyryl cAMP, isobutyl methylxanthine, maturation of denuded oocytes was inhibited. Whereas 2’deoxyadenosine-3-monophosphate, an inhibitor of adenylate cyclase promoted oocyte maturation. Forskolin decreased spontaneous maturation as well as hormone-induced maturation of goldfish oocytes. At 10 µM forskolin added up to 4 h after hormonal stimulation completely inhibited oocyte maturation. Beyond 4 h, however, when oocyte maturation had already started, forskolin can no longer inhibit maturation. Intraoocyte cAMP assayed in denuded oocytes with or without hormonal stimulation decreased immediately within 30 minutes. With forskolin, it did not cause a significant decrease in cAMP not until at 4 h. The results were consistent with the findings that elevated levels of cAMP maintain meiotic arrest while a decrease in cAMP is necessary and sufficient to trigger resumption of meiotic maturation.

Antidiabetic Actions of Ethanol Extract of Camellia sinensis Leaf Ameliorates Insulin Secretion, Inhibits the DPP-IV Enzyme, Improves Glucose Tolerance, and Increases Active GLP-1 (7-36) Levels in High-Fat-Diet-Fed Rats.

Camellia sinensis (green tea) is used in traditional medicine to treat a wide range of ailments. In the present study, the insulin-releasing and glucose-lowering effects of the ethanol extract of Camellia sinensis (EECS), along with molecular mechanism/s of action, were investigated in vitro and in vivo. The insulin secretion was measured using clonal pancreatic BRIN BD11 β cells, and mouse islets. In vitro models examined the additional glucose-lowering properties of EECS, and 3T3L1 adipocytes were used to assess glucose uptake and insulin action. Non-toxic doses of EECS increased insulin secretion in a concentration-dependent manner, and this regulatory effect was similar to that of glucagon-like peptide 1 (GLP-1). The insulin release was further enhanced when combined with isobutylmethylxanthine (IBMX), tolbutamide or 30 mM KCl, but was decreased in the presence of verapamil, diazoxide and Ca2+ chelation. EECS also depolarized the β-cell membrane and elevated intracellular Ca2+, suggesting the involvement of a KATP-dependent pathway. Furthermore, EECS increased glucose uptake and insulin action in 3T3-L1 cells and inhibited dipeptidyl peptidase IV (DPP-IV) enzyme activity, starch digestion and protein glycation in vitro. Oral administration of EECS improved glucose tolerance and plasma insulin as well as inhibited plasma DPP-IV and increased active GLP-1 (7-36) levels in high-fat-diet-fed rats. Flavonoids and other phytochemicals present in EECS could be responsible for these effects. Further research on the mechanism of action of EECS compounds could lead to the development of cost-effective treatments for type 2 diabetes.

Polyphenol-Rich Leaf of Annona squamosa Stimulates Insulin Release from BRIN-BD11 Cells and Isolated Mouse Islets, Reduces (CH2O)n Digestion and Absorption, and Improves Glucose Tolerance and GLP-1 (7-36) Levels in High-Fat-Fed Rats.

Annona squamosa, commonly known as custard apple, is traditionally used for the treatment of various diseases including diabetes, cardiovascular disease (CVD), and gastritis. This study was undertaken to investigate the effects of an ethanolic (80% v/v) extract of A. squamosa (EEAS) leaves in vitro on insulin secretion from clonal pancreatic BRIN BD11 β-cells and mouse islets, including mechanistic studies on the effect of EEAS on membrane potential and intracellular calcium ion concentration. Additional in vitro glucose-lowering actions were assessed. For in vivo studies, high-fat-fed (HFF) obese/normal rats were selected. EEAS increased insulin secretion in vitro in a dose-dependent manner. This effect was linked to β-cell membrane depolarisation and cytoplasmic Ca2+ influx. In the presence of isobutyl methylxanthine (IBMX), tolbutamide, or KCl, the insulin-releasing effect of EEAS was increased, suggesting its effect was also mediated via a KATP-independent pathways. EEAS inhibited insulin glycation, glucose absorption, and DPP-IV enzyme activity in vitro and enhanced glucose uptake and insulin action in 3T3L1 cells. In vivo, gut motility, food intake, glucose tolerance, plasma insulin, and active GLP-1 (7-36) levels were improved, whereas plasma DPP-IV levels were reduced in HFF rats. EEAS attenuated the absorption of sucrose and glucose as well as decreased serum glucose levels after sucrose loading and in situ intestinal perfusion in non-diabetic rats. Rutin, proanthocyanidin, and squafosacin G were putatively identified as the anti-hyperglycaemic phytomolecules in EEAS using HPLC followed by LC-MS analysis. This study illustrates the potential of A. squamosa and its phytoconstituents as a source of potential antidiabetic agents.

Insulin Secretory Actions of Ethanol Extract of Eucalyptus citriodora Leaf, including Plasma DPP-IV and GLP-1 Levels in High-Fat-Fed Rats, as Well as Characterization of Biologically Effective Phytoconstituents.

Due to the numerous adverse effects of synthetic drugs, researchers are currently studying traditional medicinal plants to find alternatives for diabetes treatment. Eucalyptus citriodora is known to be used as a remedy for various illnesses, including diabetes. This study aimed to explore the effects of ethanol extract of Eucalyptus citriodora (EEEC) on in vitro and in vivo systems, including the mechanism/s of action. The methodology used involved the measurement of insulin secretion from clonal pancreatic β-cells, BRIN BD11, and mouse islets. Other in vitro systems further examined EEEC’s glucose-lowering properties. Obese rats fed a high-fat-fed diet (HFF) were selected for in vivo evaluation, and phytoconstituents were detected via RP-HPLC followed by LC-MS. EEEC induced insulin secretion in a concentration-dependent manner with modulatory effects, similar to 1 µM glucagon-like peptide 1 (GLP-1), which were partly declined in the presence of Ca2+-channel blocker (Verapamil), KATP-channel opener (Diazoxide), and Ca2+ chelation. The insulin secretory effects of EEEC were augmented by isobutyl methylxanthine (IBMX), which persisted in the context of tolbutamide or a depolarizing concentration of KCl. EEEC enhanced insulin action in 3T3-L1 cells and reduced glucose absorption, and protein glycation in vitro. In HFF rats, it improved glucose tolerance and plasma insulin, attenuated plasma DPP-IV, and induced active GLP-1 (7-36) levels in circulation. Rhodomyrtosone B, Quercetin-3-O-β-D-glucopyranoside, rhodomyrtosone E, and quercitroside were identified as possible phytoconstituents that may be responsible for EEEC effects. Thus, these findings revealed that E. citriodora could be used as an adjunct nutritional supplement to manage type 2 diabetes.

Hydrogen sulfide potently promotes neuronal differentiation of adipose tissue-derived stem cells involving nitric oxide-mediated signaling cascade with the aid of cAMP-elevating agents

Neuronal differentiation of adipose tissue-derived stem cells (ASCs) is potently promoted by valproic acid (VPA) through a gaseous signaling molecule, nitric oxide (NO). Here, we investigated the involvement of hydrogen sulfide (H2S), another gaseous signaling molecule, in neuronal differentiation of ASCs. VPA-promoted neuronal differentiation of ASCs was accompanied by increased intracellular H2S and sulfane sulfur with increased mRNA expression of enzymes synthesizing sulfane sulfur including cystathionine β-synthase (CBS), of which inhibition reduced the differentiation efficiency. H2S donors, GYY4137 (GYY) or NaHS, potently promoted neuronal differentiation of ASCs when cAMP-elevating agents, dibutyryl cyclic adenosine monophosphate and isobutyl methyl-xanthine, were added as neuronal induction medium (NIM). Neuronal differentiation of ASCs promoted by NaHS or GYY was accompanied by Ca2+ entry and increased mRNA expression of voltage-gated Ca2+ channels. NaHS or GYY also increased mRNA expression of enzymes of the NO-citrulline cycle including inducible NO synthase (iNOS). It was concluded from these results that H2S potently promoted differentiation of ASCs into neuronal cells expressing functional voltage-gated Ca2+ channels with the aid of cAMP-elevating agents, involving NO-mediated signaling cascade. These effects of H2S were also considered as a partial mechanism for the VPA-promoted neuronal differentiation of ASCs.

Increase in Ca2+-Activated cAMP/PKA Signaling Prevents Hydroxychloroquine-Induced Bradycardia of the Cardiac Pacemaker

Bradycardia or tachycardia are known side effects of drugs that limit their clinical use. The heart pacemaker function which control the heart rate under normal conditions is determined by coupled clock system. Thus, interfering with specific clock mechanism will affect other clock mechanisms through changes in interconnected signaling and can lead to rhythm disturbance. However, upregulation of a different clock components can compensate for this change. We focus here on hydroxychloroquine (HCQ), which has been shown effective in treating COVID-19 patients, however its bradycardic side effect limits its clinical use. We aim to decipher the mechanisms underlying the effect of HCQ on pacemaker automaticity, to identify a potential drug that will eliminate the bradycardia. We used isolated rabbit sinoatrial node (SAN) cells, human-induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs) and mouse SAN cells residing in SAN tissue. Further, we employed SAN cell computational model to suggest mechanistic insights of the effect of HCQ on pacemaker function. HCQ increased mean spontaneous beat interval and variability in all three models in parallel to slower intracellular kinetics. The computational model suggested that HCQ affects the pacemaker (funny) current (If), L-type Ca2+ current (ICa,L), transient outward potassium (Ito) and due to changes in Ca2+ kinetics, the sodium-calcium exchanger current (INCX). Co-application of 3’-isobutylmethylxanthine (IBMX) and HCQ prevented the increase in beat interval and variability in all three experimental models. The HCQ-induced increase in rabbit and mice SAN cell and hiPSC-CM spontaneous beat interval, can be prevented by a phosphodiester inhibitor that restores automaticity due to slower intracellular Ca2+ kinetics.

Tyrosinase suppresses vasculogenic mimicry in human melanoma cells.

Melanoma is a type of skin cancer that derives from melanocytes; this tumor is highly metastatic and causes poor clinical outcomes in patients. Vasculogenic mimicry (VM), a vascular-like network that is formed by tumor cells instead of endothelial cells, promotes the growth and metastasis of tumors by providing tumors with oxygen- and nutrient-containing blood. VM correlates with a poor prognosis in patients with melanoma, but the melanoma-specific mechanisms of VM are unknown. The present study revealed that treatment with the melanogenesis stimulators 3-isobutyl 1-methylxanthine (IBMX) and α-melanocyte-stimulating hormone (α-MSH) significantly inhibited VM in MNT-1 human pigmented melanoma cells. Tyrosinase (TYR), an essential enzyme in melanin production, was upregulated on treatment with α-MSH and IBMX, prompting an examination of the association between TYR and VM. A TYR inhibitor, arbutin, promoted VM in melanoma cells. Furthermore, CRISPR/Cas9-mediated knockout (KO) of TYR increased VM by melanoma cells. Notably, even in non-pigmented melanoma cells, TYR attenuated VM. Although re-expression of wild-type TYR suppressed VM in TYR-KO cells, T373K TYR, a frequently detected mutation in individuals with albinism, failed to inhibit VM. Overall, these results demonstrated that TYR negatively regulates VM, providing novel insights into the antioncogenic function of TYR in melanomas.

Insulin secretory and antidiabetic actions of Heritiera fomes bark together with isolation of active phytomolecules.

In folklore, Heritiera fomes (H. fomes) has been extensively used in treatment of various ailments such as diabetes, cardiac and hepatic disorders. The present study aimed to elucidate the antidiabetic actions of hot water extract of H. fomes (HWHF), including effects on insulin release from BRIN BD11 cells and isolated mouse islets as well as glucose homeostasis in high-fat-fed rats. Molecular mechanisms underlying anti-diabetic activity along with isolation of active compounds were also evaluated. Non-toxic concentrations of HWHF stimulated concentration-dependent insulin release from isolated mouse islets and clonal pancreatic β-cells. The stimulatory effect was potentiated by glucose and isobutyl methylxanthine (IBMX), persisted in presence of tolbutamide or a depolarizing concentration of KCl but was attenuated by established inhibitors of insulin release such as diazoxide, verapamil, and Ca2+ chelation. HWHF caused depolarization of the β-cell membrane and increased intracellular Ca2+. The extract also enhanced glucose uptake and insulin action in 3T3-L1 differentiated adipocytes cells and significantly inhibited in a dose-dependent manner starch digestion, protein glycation, DPP-IV enzyme activity, and glucose diffusion in vitro. Oral administration of HWHF (250 mg/5ml/kg b.w.) to high-fat fed rats significantly improved glucose tolerance and plasma insulin responses and it inhibited plasma DPP-IV activity. HWHF also decreased in vivo glucose absorption and intestinal disaccharidase activity while increasing gastrointestinal motility and unabsorbed sucrose transit. Compounds were isolated from HWHF with similar molecular weights to quercitrin (C21 H20 O11) ranging from 447.9 to 449.9 Da which stimulated the insulin release in vitro and improved both glucose tolerance and plasma insulin responses in mice. In conclusion, H. fomes and its water-soluble phytochemicals such as quercitrin may exert antidiabetic actions mediated through a variety of mechanisms which might be useful as dietary adjunct in the management of type 2 diabetes.

In vitro and in vivo antihyperglycemic activity of the ethanol extract of Heritiera fomes bark and characterization of pharmacologically active phytomolecules.

This study aimed to demonstrate the mechanistic basis of Heritiera fomes, which has traditionally been used to treat diabetes. Clonal pancreatic β-cells and primary islets were used to measure insulin release. 3T3-L1 cells were used to analyse insulin action, and in vitro systems were used to measure further glucose-lowering activity. In vivo assessment was performed on streptozotocin (STZ)-induced type-2 diabetic rats and reversed-phase-HPLC followed by liquid chromatography mass spectrometry (LC-MS) to detect bioactive molecules. Ethanol extract of Heritiera fomes (EEHF) significantly increased insulin release with stimulatory effects comparable to 1 µM glucagon-like peptide 1, which were somewhat reduced by diazoxide, verapamil and calcium-free conditions. Insulin release was stimulated by tolbutamide, isobutyl methylxanthine and KCl. EEHF induced membrane depolarization and increased intracellular Ca2+ levels. EEHF enhanced glucose uptake in 3T3L1 cells and decreased protein glycation. EEHF significantly inhibited postprandial hyperglycaemia following sucrose loading and inversely elevated unabsorbed sucrose concentration in the gut. It suppressed glucose absorption during in situ gut perfusion. Furthermore, EEHF improved glucose tolerance, plasma insulin and gut motility, and decreased plasma dipeptidyl peptidase IV activity. Procyanidins, epicatechin and proanthocyanidins were some of the identified bioactive constituents that may involve in β-cell actions. This study provides some evidence to support the use of H. fomes as an antidiabetic traditional remedy.

Hibiscus sabdariffa Linn fruit derivatives as alternative agents for diabetes mellitus care: A basic insight

This study discusses the effectiveness of methanolic extract and fractions (butanol, ethyl acetate, and n-hexane) of H. sabdariffa Linn fruit towards antidiabetic activities (in vitro). In order to test the efficacy, toxicity and insulin secretion capacity of rat pancreatic β-cell lines (BRIN-BD11) were tested with the methanolic extract and fractions. The outcomes showed that both the extract and the fractions demonstrated significantly lower levels of cytotoxic activities. Furthermore, the methanolic extract and fractions displayed varied sensitivity levels towards insulin release after an incubation period of 30 min. The methanolic extract, at a concentration of 300 µg/mL, significantly stimulated secretion of insulin by 2.85-fold (p<0.001). In addition, butanol, ethyl acetate, and n-hexane fractions revealed a gradual increase in insulin secretion. The stimulated insulin secretion for these fractions had been recorded at 2-fold (p<0.01), 2.67-fold, and 2.31-fold (p<0.001), respectively, at the highest concentrations. The methanolic extract and fractions also appeared to stimulate secretion of insulin with all modulators present, for example, potassium chloride (KCl), insulin secretion inhibitor (verapamil and diazoxide), as well as insulin secretagogue (tolbutamide and isobutylmethylxanthine (IBMX)). These results indicate that H. sabdariffa Linn fruit methanolic extract and fractions could indeed be beneficial for future development of antidiabetic drugs.

CAMP triggers Na+ absorption by distal airway surface epithelium in cystic fibrosis swine.

A controversial hypothesis pertaining to cystic fibrosis (CF) lung disease is that the CF transmembrane conductance regulator (CFTR) channel fails to inhibit the epithelial Na+ channel (ENaC), yielding increased Na+ reabsorption and airway dehydration. We use a non-invasive self-referencing Na+-selective microelectrode technique to measure Na+ transport across individual folds of distal airway surface epithelium preparations from CFTR-/- (CF) and wild-type (WT) swine. We show that, under unstimulated control conditions, WT and CF epithelia exhibit similar, low rates of Na+ transport that are unaffected by the ENaC blocker amiloride. However, in the presence of the cyclic AMP (cAMP)-elevating agents forskolin+IBMX (isobutylmethylxanthine), folds of WT tissues secrete large amounts of Na+, while CFTR-/- tissues absorb small, but potentially important, amounts of Na+. In cAMP-stimulated conditions, amiloride inhibits Na+ absorption in CFTR-/- tissues but does not affect secretion in WT tissues. Our results are consistent with the hypothesis that ENaC-mediated Na+ absorption may contribute to dehydration of CF distal airways.

Effect of selected natural and synthetic substances on rabbit reproduction-A mini review.

Numerous natural and synthetic substances have effects on reproduction through several mechanisms. This review aims to summarize the impact of green tea (GT), yucca schidigera (YS) extract, curcuma longa (CL), adenosine 3',5'-cyclic monophosphate (cAMP) and isobutyl-1-methyl-xanthine (IBMX) stimulators on rabbit reproduction performance. To obtain a comprehensive overview of this topic, the keywords "reproduction," "substances," "spermatogenesis," "embryogenesis,"hormonal profil", "green tea", "yucca schidigera" were searched in such databases as WOS and PubMed to obtain relevant information. Spermatozoa profile was positively effected by the GT and YS, however, cAMP inhibitors stimulated spermatozoa motility resulted in positive or negative effects depending on the doses. Similarly, embryogenesis and hormonal profile were positively influenced by the GT, YS, cAMP and IBMX in a proper administration dose. Further research is needed to improve current knowledge about these substances to identify potential effects on the other reproduction parameters. Furthermore, future studies should combine GT, YS and CL with different plant extracts to determine their effects on spermatozoa status, embryogenesis as well as hormonal profile as key outcomes. This review summarizes current knowledge about effect of natural and synthetic substances on rabbit reproduction.

Novel Facet of an Old Dietary Molecule? Direct Influence of Caffeine on Glucose and Biogenic Amine Handling by Human Adipocytes.

Caffeine is a plant alkaloid present in food and beverages consumed worldwide. It has high lipid solubility with recognized actions in the central nervous system and in peripheral tissues, notably the adipose depots. However, the literature is scant regarding caffeine’s influence on adipocyte functions other than lipolysis, such as glucose incorporation into lipids (lipogenesis) and amine oxidation. The objective of this study was to explore the direct effects of caffeine and of isobutylmethylxanthine (IBMX) on these adipocyte functions. Glucose transport into fat cells freshly isolated from mice, rats, or humans was monitored by determining [3H]-2-deoxyglucose (2-DG) uptake, while the incorporation of radiolabeled glucose into cell lipids was used as an index of lipogenic activity. Oxidation of benzylamine by primary amine oxidase (PrAO) was inhibited by increasing doses of caffeine in human adipose tissue preparations with an inhibition constant (Ki) in the millimolar range. Caffeine inhibited basal and insulin-stimulated glucose transport as well as lipogenesis in rodent adipose cells. The antilipogenic action of caffeine was also observed in adipocytes from mice genetically invalidated for PrAO activity, indicating that PrAO activity was not required for lipogenesis inhibition. These caffeine inhibitory properties were extended to human adipocytes: relative to basal 2-DG uptake, set at 1.0 ± 0.2 for 6 individuals, 0.1 mM caffeine tended to reduce uptake to 0.83 ± 0.08. Insulin increased uptake by 3.86 ± 1.11 fold when tested alone at 100 nM, and by 3.21 ± 0.80 when combined with caffeine. Our results reinforce the recommendation of caffeine’s potential in the treatment or prevention of obesity complications.

Identification of Multiple Pancreatic and Extra-Pancreatic Pathways Underlying the Glucose-Lowering Actions of Acacia arabica Bark in Type-2 Diabetes and Isolation of Active Phytoconstituents.

Acacia arabica is used traditionally to treat a variety of ailments, including diabetes. This study elucidated the antidiabetic actions of A. arabica bark together with the isolation of bioactive molecules. Insulin secretion and signal transduction were measured using clonal β cells and mouse islets. Glucose uptake was assessed using 3T3-L1 adipocytes, and in vitro systems assessed additional glucose-lowering actions. High-fat-fed (HFF) obese rats were used for in vivo evaluation, and phytoconstituents were isolated and characterised by RP-HPLC followed by LC-MS and NMR. Hot-water extract of A. arabica (HWAA) increased insulin release from clonal β cells and mouse islets by 1.3–6.8-fold and 1.6–3.2-fold, respectively. Diazoxide, verapamil and calcium-free conditions decreased insulin-secretory activity by 30–42%. In contrast, isobutylmethylxanthine (IBMX), tolbutamide and 30 mM KCl potentiated the insulin-secretory effects. The mechanism of actions of HWAA involved membrane depolarisation and elevation of intracellular Ca2+ together with an increase in glucose uptake by 3T3-L1 adipocytes, inhibition of starch digestion, glucose diffusion, dipeptidyl peptidase-IV (DPP-IV) enzyme activity and protein glycation. Acute HWAA administration (250 mg/5 mL/kg) enhanced glucose tolerance and plasma insulin in HFF obese rats. Administration of HWAA (250 mg/5 mL/kg) for 9 days improved glucose homeostasis and β-cell functions, thereby improving glycaemic control, and circulating insulin. Isolated phytoconstituents, including quercetin and kaempferol, increased insulin secretion in vitro and improved glucose tolerance. The results indicate that HWAA has the potential to treat type 2 diabetes as a dietary supplement or as a source of antidiabetic agents, including quercetin and kaempferol.

Isolation, Proliferation and Differentiation of Rhesus Macaque Adipose-Derived Stem Cells.

Adipose tissue provides a rich and accessible source of multipotent stem cells, which are able to self-renew. These adipose-derived stem cells (ADSCs) provide a consistent ex vivo cellular system that are functionally like that of in vivo adipocytes. Use of ADSCs in biomedical research allows for cellular investigation of adipose tissue metabolic regulation and function. ADSC differentiation is necessary for adequate adipocyte expansion, and suboptimal differentiation is a major mechanism of adipose dysfunction. Understanding changes in ADSC differentiation is crucial to understanding the development of metabolic dysfunction and disease. The protocols described in this manuscript, when followed, will yield mature adipocytes that can be used for several in vitro functional tests to assess ADSC metabolic function, including but not limited to assays measuring glucose uptake, lipolysis, lipogenesis, and secretion. Rhesus macaques (Macaca mulatta) are physiologically, anatomically, and evolutionarily similar to humans and as such, their tissues and cells have been used extensively in biomedical research and for development of treatments. Here, we describe ADSC isolation using fresh subcutaneous and omental adipose tissue obtained from 4-9-year old rhesus macaques. Adipose tissue samples are enzymatically digested in collagenase followed by filtration and centrifugation to isolate ADSCs from the stromal vascular fraction. Isolated ADSCs are proliferated in stromal media followed by approximately 14-21 days of differentiation using a cocktail of 0.5 μg/mL dexamethasone, 0.5 mM isobutyl methylxanthine, and 50 μM indomethacin in stromal media. Mature adipocytes are observed at approximately 14 days of differentiation. In this manuscript, we describe protocols for ADSC isolation, proliferation, and differentiation in vitro. Although, we have focused on ADSCs from rhesus macaque adipose tissue, these protocols can be utilized for adipose tissue obtained from other animals with minimal adjustments.