Improving the accuracy of the SRK/T formula in Chinese with implanting less than 10 D IOL calculated by the SRK/T formula: the SRK/T-Li formula.

PURPOSE: To explore the accuracy of the improved SRK/T-Li formula in eyes following implantation of intraocular lens (IOL) of less than 10 D as calculated by using the SRK/T formula in Chinese. METHODS: A total of 489 eyes from 489 patients with cataracts were included in this study. These patients were divided into a training set (271 patients) and a testing set (218 patients). The IOL power calculated by using SRK/T was less than 10 D. We evaluated the accuracy of the modified SRK/T-Li formula (P = PSRK/T × 0.8 + 2 (P = implanted IOL power; PSRK/T = IOL power calculated by SRK/T)). We evaluated the mean absolute error (MAE), percentage of prediction error (PE) within ± 0.25, ± 0.50, and ± 1.00 D, and the percentage of postoperative hyperopia. RESULTS: The MAE values in order of lowest to highest were as follows: 0.412 D (SRK/T-Li), 0.414 D (Barrett Universal II, (BUII)), 0.814 D (SRK/T), and 1.039 D (Holladay 1). The percentage of PE within ± 0.25 D, ± 0.50 D, and ± 1.00 D was 38.99%, 69.27% and 92.66% (BUII), 40.83%, 69.27% and 94.04% (SRK/T-Li), 20.64%, 41.28% and 71.56% (SRK/T), and 7.34%, 16.51% and 53.21% (Holladay 1), respectively. SRK/T-Li had the smallest postoperative hyperopic shift. CONCLUSIONS: For Chinese patients with an IOL power of less than 10 D as calculated by using the SRK/T, the SRK/T-Li has good accuracy and is the best choice to reduce postoperative hyperopic shift.

Hepatic Fibroblast Growth Factor 21 Is Involved in Mediating Functions of Liraglutide in Mice With Dietary Challenge.

BACKGROUND AND AIMS: Several studies have shown that expression of hepatic fibroblast growth factor 21 (FGF21) can be stimulated by glucagon-like peptide 1 (GLP-1)-based diabetes drugs. As GLP-1 receptor (GLP-1R) is unlikely to be expressed in hepatocytes, we aimed to compare such stimulation in mice and in mouse hepatocytes, determine the involvement of GLP-1R, and clarify whether FGF21 mediates certain functions of the GLP-1R agonist liraglutide. APPROACH AND RESULTS: Liver FGF21 expression was assessed in mice receiving a daily liraglutide injection for 3 days or in mouse primary hepatocytes (MPHs) undergoing direct liraglutide treatment. The effects of liraglutide on metabolic improvement and FGF21 expression were then assessed in high-fat diet (HFD)-fed mice and compared with the effects of the dipeptidyl-peptidase 4 inhibitor sitagliptin. Animal studies were also performed in Glp1r-/- mice and liver-specific FGF21-knockout (lFgf21-KO) mice. In wild-type mouse liver that underwent RNA sequencing and quantitative reverse-transcription PCR, we observed liraglutide-stimulated hepatic Fgf21 expression and a lack of Glp1r expression. In MPHs, liraglutide did not stimulate Fgf21. In mice with HFD-induced obesity, liraglutide or sitagliptin treatment reduced plasma triglyceride levels, whereas their effect on reducing body-weight gain was different. Importantly, increased hepatic FGF21 expression was observed in liraglutide-treated mice but was not observed in sitagliptin-treated mice. In HFD-fed Glp1r-/- mice, liraglutide showed no beneficial effects and could not stimulate Fgf21 expression. In lFgf21-KO mice undergoing dietary challenge, the body-weight-gain attenuation and lipid homeostatic effects of liraglutide were lost or significantly reduced. CONCLUSIONS: We suggest that liraglutide-stimulated hepatic Fgf21 expression may require GLP-1R to be expressed in extrahepatic organs. Importantly, we revealed that hepatic FGF21 is required for liraglutide to lower body weight and improve hepatic lipid homeostasis. These observations advanced our mechanistic understanding of the function of GLP-1-based drugs in NAFLD.

The developmental Wnt signaling pathway effector ß-catenin/TCF mediates hepatic functions of the sex hormone estradiol in regulating lipid metabolism.

The bipartite transcription factor ß-catenin (ß-cat)/T cell factor (TCF), formed by free ß-cat and a given TCF family member, serves as the effector of the developmental Wnt signaling cascade. ß-cat/TCFs also serve as effectors of certain peptide hormones or growth factors during adulthood. We reported that liver-specific expression of dominant-negative Transcription factor 7 like 2 (TCF7L2DN) led to impaired glucose disposal. Here we show that, in this LTCFDN transgenic mouse model, serum and hepatic lipid contents were elevated in male but not in female mice. In hepatocytes, TCF7L2DN adenovirus infection led to stimulated expression of genes that encode lipogenic transcription factors and lipogenic enzymes, while estradiol (E2) treatment attenuated the stimulation, associated with Wnt-target gene activation. Mechanistically, this E2-mediated activation can be attributed to elevated ß-cat Ser675 phosphorylation and TCF expression. In wild-type female mice, ovariectomy (OVX) plus high-fat diet (HFD) challenge impaired glucose disposal and insulin tolerance, associated with increased hepatic lipogenic transcription factor sterol regulatory element-binding protein 1-c (SREBP-1c) expression. In wild-type mice with OVX, E2 reconstitution attenuated HFD-induced metabolic defects. Some of the attenuation effects, including insulin intolerance, elevated liver-weight gain, and hepatic SREBP-1c expression, were not affected by E2 reconstitution in HFD-fed LTCFDN mice with OVX. Finally, the effects of E2 in hepatocytes on ß-cat/TCF activation can be attenuated by the G-protein-coupled estrogen receptor (GPER) antagonist G15. Our study thus expanded the scope of functions of the Wnt pathway effector ß-cat/TCF, as it can also mediate hepatic functions of E2 during adulthood. This study also enriches our mechanistic understanding of gender differences in the risk and pathophysiology of metabolic diseases.

Current understanding and controversies on the clinical implications of fibroblast growth factor 21.

Metabolic functions of the hepatic hormone fibroblast growth factor 21 (FGF21) have been recognized for more than a decade in studying the responses of human subjects and rodent models to nutritional stresses such as fasting, high-fat diet or ketogenic diet consumption, and ethanol intake. Our interest in the beneficial metabolic effects of FGF21 has risen due to its potential ability to serve as a therapeutic agent for various metabolic disorders, including type 2 diabetes, obesity, and fatty liver diseases, as well as its potential to act as a diagnostic or prognostic biomarker for metabolic and other disorders. Here, we briefly review the FGF21 gene and protein structures, its expression pattern, and cellular signaling cascades that mediate FGF21 production and function. We mainly focus on discussing experimental and clinical literature pertaining to FGF21 as a therapeutic agent. Furthermore, we present several lines of investigation, including a few studies conducted by our team, suggesting that FGF21 expression and function can be regulated by dietary polyphenol interventions. Finally, we discuss the literature debating FGF21 as a potential biomarker in various disorders.

Estrogen-Wnt signaling cascade regulates expression of hepatic fibroblast growth factor 21.

We have generated the transgenic mouse line LTCFDN in which dominant negative TCF7L2 (TCF7L2DN) is specifically expressed in the liver during adulthood. Male but not female LTCFDN mice showed elevated hepatic and plasma triglyceride (TG) levels, indicating the existence of estrogen-ß-cat/TCF signaling cascade that regulates hepatic lipid homeostasis. We show here that hepatic fibroblast growth factor 21 (FGF21) expression was reduced in male but not in female LTCFDN mice. The reduction was not associated with altered hepatic expression of peroxisome proliferator-activated receptor α (PPARα). In mouse primary hepatocytes (MPH), Wnt-3a treatment increased FGF21 expression in the presence of PPARα inhibitor. Results from our luciferase-reporter assay and chromatin immunoprecipitation suggest that evolutionarily conserved TCF binding motifs (TCFBs) on Fgf21 promoter mediate Wnt-3a-induced Fgf21 transactivation. Female mice showed reduced hepatic FGF21 production and circulating FGF21 level following ovariectomy (OVX), associated with reduced hepatic TCF expression and ß-catenin S675 phosphorylation. Finally, in MPH, estradiol (E2) treatment enhanced FGF21 expression, as well as binding of TCF7L2 and ribonucleic acid (RNA) polymerase II to the Fgf21 promoter; and the enhancement can be attenuated by the G-protein-coupled estrogen receptor 1 (GPER) antagonist G15. Our observations hence indicate that hepatic FGF21 is among the effectors of the newly recognized E2-ß-cat/TCF signaling cascade.NEW & NOTEWORTHY FGF21 is mainly produced in the liver. Therapeutic effect of FGF21 analogues has been demonstrated in clinical trials on reducing hyperlipidemia. We show here that Fgf21 transcription is positively regulated by Wnt pathway effector ß-cat/TCF. Importantly, hepatic ß-cat/TCF activity can be regulated by the female hormone estradiol, involving GPER. The investigation enriched our understanding on hepatic FGF21 hormone production, and expanded our view on metabolic functions of the Wnt pathway in the liver.

Glucagon-like peptide-1 receptor mediates the beneficial effect of liraglutide in an acute lung injury mouse model involving the thioredoxin-interacting protein.

Repurposing clinically used drugs is among the important strategies in drug discovery. Glucagon-like peptide-1 (GLP-1) and its diabetes-based drugs, such as liraglutide, possess a spectrum of extra-pancreatic functions, while GLP-1 receptor (GLP-1R) is most abundantly expressed in the lung. Recent studies have suggested that GLP-1-based drugs exert beneficial effects in chronic, as well as acute, lung injury rodent models. Here, we show that liraglutide pretreatment reduced LPS induced acute lung injury in mice. It significantly reduced lung injury score, wet/dry lung weight ratio, bronchoalveolar lavage fluid immune cell count and protein concentration, and cell apoptosis in the lung, and it was associated with reduced lung inflammatory cytokine and chemokine gene expression. Importantly, these effects were virtually absent in GLP-1R-/- mice. A well-known function of GLP-1 and GLP-based drugs in pancreatic ß-cells is the attenuation of high-glucose stimulated expression of thioredoxin-interacting protein (TxNIP), a key component of inflammasome. LPS-challenged lungs showed elevated TxNIP mRNA and protein expression, which was attenuated by liraglutide treatment in a GLP-1R-dependent manner. Hence, our observations suggest that GLP-1R is essential in mediating beneficial effects of liraglutide in acute lung injury, with the inflammasome component TxNIP as a potential target.

Dietary Cyanidin-3-Glucoside Attenuates High-Fat-Diet-Induced Body-Weight Gain and Impairment of Glucose Tolerance in Mice via Effects on the Hepatic Hormone FGF21.

BACKGROUND: Dietary polyphenols including anthocyanins target multiple organs. OBJECTIVE: We aimed to assess the involvement of glucagon-like peptide 1 (GLP-1), leptin, insulin and fibroblast growth factor 21 (FGF21) in mediating metabolic beneficial effects of purified anthocyanin cyanidin-3-glucoside (Cy3G). METHODS: Intestinal proglucagon gene (Gcg; encoding GLP-1) and liver Fgf21 expression were assessed in 6-wk-old male C57BL-6J mice fed a low-fat-diet (LFD; 10% of energy from fat), alone or with 1.6 mg Cy3G/L in drinking water for 3 wk [experiment (Exp.) 1; n = 5/group]. Similar mice were fed the LFD or a high-fat diet (HFD; 60% energy from fat) with or without Cy3G for 20 wk. Half of the mice administered Cy3G also received 4 broad-spectrum antibiotics (ABs) in drinking water between weeks 11 and 14, for a total of 6 groups (n = 8/group). Metabolic tolerance tests were conducted between weeks 2 and 16. Relevant hormone gene expression and plasma hormone concentrations were assessed mainly at the end of 20 wk (Exp. 2). RESULTS: In Exp. 1, Cy3G administration increased ileal but not colonic Gcg level by 2-fold (P < 0.05). In Exp. 2, Cy3G attenuated HFD-induced body-weight gain (20.3% at week 16), and improved glucose tolerance (26.5% at week 15) but not insulin tolerance. Although Cy3G had no effect on glucose tolerance in LFD mice, LFD/Cy3G/AB mice showed better glucose tolerance than LFD/Cy3G mice (23%). In contrast, HFD/Cy3G/AB mice showed worse glucose tolerance compared with HFD/Cy3G mice (15%). Beneficial effects of Cy3G in HFD mice were not associated with changes in plasma leptin, insulin or GLP-1 concentrations. However, Cy3G increased hepatic Fgf21 expression in mice in Exp. 1 by 4-fold and attenuated Fgf21 overexpression in HFD mice (Exp. 2, 22%), associated with increased expression of genes that encode FGFR1 and ß-klotho (>3-fold, P < 0.05). CONCLUSIONS: Dietary Cy3G may reduce body weight and exert metabolic homeostatic effects in mice via changes in hepatic FGF21.

Curcumin and other dietary polyphenols: potential mechanisms of metabolic actions and therapy for diabetes and obesity.

Recent controversy regarding the therapeutic potential of curcumin indicates the challenges to research in this field. Here, we highlight the investigations of curcumin and other plant-derived polyphenols that demonstrate their application to metabolic diseases, in particular, obesity and diabetes. Thus, a number of preclinical and clinical investigations have shown the beneficial effect of curcumin (and other dietary polyphenols) in attenuating body weight gain, improving insulin sensitivity, and preventing diabetes development in rodent models and prediabetic subjects. Other intervention studies with dietary polyphenols have also found improvements in insulin resistance. Recent studies suggest that the metabolic effects of curcumin/polyphenols are linked to changes in the gut microbiota. Thus, research into curcumin continues to provide novel insights into metabolic regulation that may ultimately translate into effective therapy.

Curcumin and dietary polyphenol research: beyond drug discovery.

Numerous natural products available over the counter are commonly consumed by healthy, sub-healthy or ill people for the treatment and prevention of various chronic diseases. Among them, a few dietary polyphenols, including the curry compound curcumin, have been attracting the most attention from biomedical researchers and drug developers. Unlike many so-called "good drug candidates", curcumin and several other dietary polyphenols do not have a single known therapeutic target or defined receptor. In addition, the bioavailability of these polyphenols is usually very low due to their poor absorption in the gut. These recently debated features have created enormous difficulties for drug developers. In this review, I do not discuss how to develop curcumin, other dietary polyphenols or their derivatives into pharmaceutical agents. Instead, I comment on how curcumin and dietary polyphenol research has enriched our knowledge of insulin signaling, including the presentation of my perspectives on how these studies will add to our understanding of the famous hepatic insulin function paradox.

Hepatic functions of GLP-1 and its based drugs: current disputes and perspectives.

GLP-1 and its based drugs possess extrapancreatic metabolic functions, including that in the liver. These direct hepatic metabolic functions explain their therapeutic efficiency for subjects with insulin resistance. The direct hepatic functions could be mediated by previously assumed "degradation" products of GLP-1 without involving canonic GLP-1R. Although GLP-1 analogs were created as therapeutic incretins, extrapancreatic functions of these drugs, as well as native GLP-1, have been broadly recognized. Among them, the hepatic functions are particularly important. Postprandial GLP-1 release contributes to insulin secretion, which represses hepatic glucose production. This indirect effect of GLP-1 is known as the gut-pancreas-liver axis. Great efforts have been made to determine whether GLP-1 and its analogs possess direct metabolic effects on the liver, as the determination of the existence of direct hepatic effects may advance the therapeutic theory and clinical practice on subjects with insulin resistance. Furthermore, recent investigations on the metabolic beneficial effects of previously assumed "degradation" products of GLP-1 in the liver and elsewhere, including GLP-128-36 and GLP-132-36, have drawn intensive attention. Such investigations may further improve the development and the usage of GLP-1-based drugs. Here, we have reviewed the current advancement and the existing controversies on the exploration of direct hepatic functions of GLP-1 and presented our perspectives that the direct hepatic metabolic effects of GLP-1 could be a GLP-1 receptor-independent event involving Wnt signaling pathway activation.

Inhibition of Dexamethasone-induced Fatty Liver Development by Reducing miR-17-5p Levels.

Steatosis is a pivotal event in the initiation and progression of nonalcoholic fatty liver disease (NAFLD) which can be driven by peroxisome proliferator-activated receptor-α (PPAR-α) dysregulation. Through examining the effect of PPAR-α on fatty liver development, we found that PPAR-α is a target of miR-17-5p. Transgenic mice expressing miR-17 developed fatty liver and produced higher levels of triglyceride and cholesterol but lower levels of PPAR-α. Ectopic expression of miR-17 enhanced cellular steatosis. Gain-of-function and loss-of-function experiments confirmed PPAR-α as a target of miR-17-5p. On the other hand, PPAR-α bound to the promoter of miR-17 and promoted its expression. The feed-back loop between miR-17-5p and PPAR-α played a key role in the induction of steatosis and fatty liver development. Mice with high levels of miR-17-5p were sensitive to Dexamethasone-induced fatty liver formation. Inhibition of miR-17-5p suppressed this process and enhanced PPAR-α expression in mice treated with Dexamethasone. Clofibrate, Ciprofibrate, and WY-14643: three agents used for treatment of metabolic disorders, were found to promote PPAR-α expression while decreasing miR-17-5p levels and inhibiting steatosis. Our studies show that miR-17-5p inhibitor and agents used in metabolic disorders may be applied in combination with Dexamethasone in the treatment of anti-inflammation, immunosuppression, and cancer patients.

Short-Term Curcumin Gavage Sensitizes Insulin Signaling in Dexamethasone-Treated C57BL/6 Mice.

BACKGROUND: Long-term dietary curcumin (>12 wk) improves metabolic homeostasis in obese mice by sensitizing insulin signaling and reducing hepatic gluconeogenesis. Whether these occur only secondary to its chronic anti-inflammatory and antioxidative functions is unknown. OBJECTIVE: In this study, we assessed the insulin sensitization effect of short-term curcumin gavage in a rapid dexamethasone-induced insulin resistance mouse model, in which the chronic anti-inflammatory function is eliminated. METHODS: Six-week-old male C57BL/6 mice received an intraperitoneal injection of dexamethasone (100 mg/kg body weight) or phosphate-buffered saline every day for 5 d, with or without simultaneous curcumin gavage (500 mg/kg body weight). On day 7, insulin tolerance tests were performed. After a booster dexamethasone injection and curcumin gavage on day 8, blood glucose and insulin concentrations were measured. Liver tissues were collected on day 10 for quantitative polymerase chain reaction and Western blotting to assess gluconeogenic gene expression, insulin signaling, and the expression of fibroblast growth factor 21 (FGF21). Primary hepatocytes from separate, untreated C57BL/6 mice were used for testing the in vitro effect of curcumin treatment. RESULTS: Dexamethasone injection impaired insulin tolerance (P < 0.05) and elevated ambient plasma insulin concentrations by ~2.7-fold (P < 0.01). Concomitant curcumin administration improved insulin sensitivity and reduced hepatic gluconeogenic gene expression. The insulin sensitization effect of curcumin was demonstrated by increased stimulation of S473 phosphorylation of protein kinase B (P < 0.01) in the dexamethasone-treated mouse liver, as well as the repression of glucose production in primary hepatocytes (P < 0.001). Finally, curcumin gavage increased FGF21 expression by 2.1-fold in the mouse liver (P < 0.05) and curcumin treatment increased FGF21 expression in primary hepatocytes. CONCLUSION: These observations suggest that the early beneficial effect of curcumin intervention in dexamethasone-treated mice is the sensitization of insulin signaling, involving the stimulation of FGF21 production, a known insulin sensitizer.

p21-Activated protein kinases and their emerging roles in glucose homeostasis.

p21-Activated protein kinases (PAKs) are centrally involved in a plethora of cellular processes and functions. Their function as effectors of small GTPases Rac1 and Cdc42 has been extensively studied during the past two decades, particularly in the realms of cell proliferation, apoptosis, and hence tumorigenesis, as well as cytoskeletal remodeling and related cellular events in health and disease. In recent years, a large number of studies have shed light onto the fundamental role of group I PAKs, most notably PAK1, in metabolic homeostasis. In skeletal muscle, PAK1 was shown to mediate the function of insulin on stimulating GLUT4 translocation and glucose uptake, while in pancreatic ß-cells, PAK1 participates in insulin granule localization and vesicle release. Furthermore, we demonstrated that PAK1 mediates the cross talk between insulin and Wnt/ß-catenin signaling pathways and hence regulates gut proglucagon gene expression and the production of the incretin hormone glucagon-like peptide-1 (GLP-1). The utilization of chemical inhibitors of PAK and the characterization of Pak1(-/-) mice enabled us to gain mechanistic insights as well as to assess the overall contribution of PAKs in metabolic homeostasis. This review summarizes our current understanding of PAKs, with an emphasis on the emerging roles of PAK1 in glucose homeostasis.

Gut microbiota metabolism of anthocyanin promotes reverse cholesterol transport in mice via repressing miRNA-10b.

RATIONALE: We and others have demonstrated that anthocyanins have antiatherogenic capability. Because intact anthocyanins are absorbed very poorly, the low level of circulating parent anthocyanins may not fully account for their beneficial effect. We found recently that protocatechuic acid (PCA), a metabolite of cyanidin-3 to 0-ß-glucoside (Cy-3-G), has a remarkable antiatherogenic effect. OBJECTIVE: To investigate whether mouse gut microbiota metabolizes Cy-3-G into PCA and to determine whether and how PCA contributes to the antiatherogenic potency of its precursor, Cy-3-G. METHODS AND RESULTS: PCA was determined as a gut microbiota metabolite of Cy-3-G in ApoE(-/-) mice, verified by the utilization of antibiotics to eliminate gut microbiota and further microbiota acquisition. PCA but not Cy-3-G at physiologically reachable concentrations promoted cholesterol efflux from macrophages and macrophage ABCA1 and ABCG1 expression. By conducting a miRNA microarray screening, we revealed that expression of miRNA-10b in macrophages can be reduced by PCA. Functional analyses demonstrated that miRNA-10b directly represses ABCA1 and ABCG1 and negatively regulates cholesterol efflux from murine- and human-derived macrophages. Further in vitro and ex vivo analyses verified that PCA accelerates macrophage cholesterol efflux, correlating with the regulation of miRNA-10b-ABCA1/ABCG1 cascade, whereas Cy-3-G consumption promoted macrophage RCT and regressed atherosclerotic lesion in a gut microbiotaendependent manner. CONCLUSIONS: PCA, as the gut microbiota metabolite of Cy-3-G, exerts the antiatherogenic effect partially through this newly defined miRNA-10b-ABCA1/ABCG1-cholesterol efflux signaling cascade. Thus, gut microbiota is a potential novel target for atherosclerosis prevention and treatment.

GABA exerts protective and regenerative effects on islet beta cells and reverses diabetes.

Type 1 diabetes (T1D) is an autoimmune disease characterized by insulitis and islet ß-cell loss. Thus, an effective therapy may require ß-cell restoration and immune suppression. Currently, there is no treatment that can achieve both goals efficiently. We report here that GABA exerts antidiabetic effects by acting on both the islet ß-cells and immune system. Unlike in adult brain or islet α-cells in which GABA exerts hyperpolarizing effects, in islet ß-cells, GABA produces membrane depolarization and Ca(2+) influx, leading to the activation of PI3-K/Akt-dependent growth and survival pathways. This provides a potential mechanism underlying our in vivo findings that GABA therapy preserves ß-cell mass and prevents the development of T1D. Remarkably, in severely diabetic mice, GABA restores ß-cell mass and reverses the disease. Furthermore, GABA suppresses insulitis and systemic inflammatory cytokine production. The ß-cell regenerative and immunoinhibitory effects of GABA provide insights into the role of GABA in regulating islet cell function and glucose homeostasis, which may find clinical application.

Characterization of SHP-1 protein tyrosine phosphatase transcripts, protein isoforms and phosphatase activity in epithelial cancer cells.

We identified 7 SHP-1 (PTPN6) transcripts using epithelial cancer-derived cell lines. Four were shown to utilize the epithelial promoter 1 to transcribe a full-length, a partial (exon 3) or complete (exons 3 & 4) deletion of the N-SH2 domain, and also a non-coding transcript having a stop codon caused by a frame shift due to intron 2 retention. Three additional transcripts were shown to utilize the hematopoietic promoter 2 to transcribe a full-length, a partial (exon 3) deletion of the N-SH2 domain and a non-coding transcript with intron 2 retention. We show that endogenous proteins corresponding to the open-reading-frame (ORF) transcripts are produced. Using GST-fusion proteins we show that each product of the ORF SHP-1 transcripts has phosphatase activity and isoforms with an N-SH2 deletion have increased phosphatase activity and novel protein-protein interactions. This study is the first to document utilization of promoter 2 by SHP-1 transcripts and a noncoding transcript in human epithelial cells.

GLP-1-derived nonapeptide GLP-1(28-36)amide represses hepatic gluconeogenic gene expression and improves pyruvate tolerance in high-fat diet-fed mice.

Certain "degradation" products of GLP-1 were found to possess beneficial effects on metabolic homeostasis. Here, we investigated the function of the COOH-terminal fragment of GLP-1, the nonapeptide GLP-1(28-36)amide, in hepatic glucose metabolism. C57BL/6 mice fed a high-fat diet (HFD) for 13 wk were injected intraperitoneally with GLP-1(28-36)amide for 6 wk. A significant reduction in body weight gain in response to HFD feeding was observed in GLP-1(28-36)amide-treated mice. GLP-1(28-36)amide administration moderately improved glucose disposal during glucose tolerance test but more drastically attenuated glucose production during pyruvate tolerance test, which was associated with reduced hepatic expression of the gluconeogenic genes Pck1, G6pc, and Ppargc1a. Mice treated with GLP-1(28-36)amide exhibited increased phosphorylation of PKA targets, including cAMP response element-binding protein (CREB), ATF-1, and ß-catenin. In primary hepatocytes, GLP-1(28-36)amide reduced glucose production and expression of Pck1, G6pc, and Ppargc1a, which was associated with increased cAMP content and PKA target phosphorylation. These effects were attenuated by PKA inhibition. We suggest that GLP-1(28-36)amide represses hepatic gluconeogenesis involving the activation of components of the cAMP/PKA signaling pathway. This study further confirmed that GLP-1(28-36)amide possesses therapeutic potential for diabetes and other metabolic disorders.

GLP-1(28-36) improves ß-cell mass and glucose disposal in streptozotocin-induced diabetic mice and activates cAMP/PKA/ß-catenin signaling in ß-cells in vitro.

Recent studies have demonstrated that the COOH-terminal fragment of the incretin hormone glucagon-like peptide-1 (GLP-1), a nonapeptide GLP-1(28-36)amide, attenuates diabetes and hepatic steatosis in diet-induced obese mice. However, the effect of this nonapeptide in pancreatic ß-cells remains largely unknown. Here, we show that in a streptozotocin-induced mouse diabetes model, GLP-1(28-36)amide improved glucose disposal and increased pancreatic ß-cell mass and ß-cell proliferation. An in vitro investigation revealed that GLP-1(28-36)amide stimulates ß-catenin (ß-cat) Ser(675) phosphorylation in both the clonal INS-1 cell line and rat primary pancreatic islet cells. In INS-1 cells, the stimulation was accompanied by increased nuclear ß-cat content. GLP-1(28-36)amide was also shown to increase cellular cAMP levels, PKA enzymatic activity, and cAMP response element-binding protein (CREB) and cyclic AMP-dependent transcription factor-1 (ATF-1) phosphorylation. Furthermore, GLP-1(28-36)amide treatment enhanced islet insulin secretion and increased the growth of INS-1 cells, which was associated with increased cyclin D1 expression. Finally, PKA inhibition attenuated the effect of GLP-1(28-36)amide on ß-cat Ser(675) phosphorylation and cyclin D1 expression in the INS-1 cell line. We have thus revealed the beneficial effect of GLP-1(28-36)amide in pancreatic ß-cells in vitro and in vivo. Our observations suggest that GLP-1(28-36)amide may exert its effect through the PKA/ß-catenin signaling pathway.

Betaine supplement alleviates hepatic triglyceride accumulation of apolipoprotein E deficient mice via reducing methylation of peroxisomal proliferator-activated receptor alpha promoter.

BACKGROUND: Betaine is a methyl donor and has been considered as a lipotropic effect substance. But its mechanism remains unclear. Hepatic steatosis is associated with abnormal expression of genes involved in hepatic lipid metabolism. DNA methylation contributes to the disregulation of gene expression. Here we hypothesized that betaine supplement and subsequent DNA methylation modifications alter the expression of genes that are involved in hepatic lipid metabolism and hence alleviate hepatic triglyceride accumulation. METHODS: Male wild-type (WT) C57BL/6 mice (n = 6) were fed with the AIN-93 G diet. ApoE-/- mice (n = 12), weight-matched with the WT mice, were divided into two groups (n = 6 per group), and fed with the AIN-93 G diet and AIN-93 G supplemented with 2% betaine/100 g diet. Seven weeks after the intervention, mice were sacrificed. Liver betaine, choline, homocysteine concentration were measured by HPLC. Liver oxidants activity and triglyceride level were assessed by ultraviolet spectrophotometry. Finally, hepatic PPAR alpha gene and its target genes expression levels and the methylation status of the PPAR alpha gene were determined. RESULTS: ApoE-/- mice had higher hepatic triglyceride and lower GSH-Px activity when compared with the WT mice. Betaine intervention reversed triglyceride deposit, enhanced SOD and GSH-Px activity in the liver. Interestingly, mice fed on betaine-supplemented diet showed a dramatic increase of hepatic choline concentration and a decrease of betaine and homocysteine concentration relative to the WT mice and the ApoE-/- mice absent with betaine intervention. Expression of PPAR alpha and CPT1 were decreased and expression of FAS was markedly increased in ApoE-/- mice. In parallel, PPAR alpha promoter methylation level were slightly increased in ApoE-/- mice though without significance. Betaine supplement upregulated expression of PPAR alpha and its target genes (CPT1, CYP2E1) and reversed hypermethylation of PPAR alpha promoter of ApoE-/- mice. Furthermore, PPAR alpha methylation was positively correlated with hepatic betaine concentration. CONCLUSIONS: Our findings indicate that betaine supplement could alleviate hepatic triglyceride accumulation and improve antioxidant capacity by decreasing PPAR alpha promoter methylation and upregulating PPAR alpha and its target genes mRNA expression.

An evaluation of the accuracy of toric intraocular lens power calculation based on measured total corneal refractive power.

Purpose: To evaluate a method using measured values of total corneal refractive power (TCRP) for a manufacturer's online calculator by comparing it with the Barrett toric calculator (BTC) and Kane toric calculator (KTC) combined with simulated keratometry values (SimK). Methods: This was a retrospective case series. Patient records were reviewed to identify the patients who had biometry with the IOL Master 700 and Pentacam recorded before toric IOL implantation and refractive follow-up data after implantation. The predicted error in residual astigmatism was calculated by vector analysis according to the calculation methods and the measurements used. Results: A total of 70 eyes of 56 patients were included. The mean absolute astigmatism prediction errors were 0.6 ± 0.32, 0.59 ± 0.35, and 0.61 ± 0.35 D for the ATCTCRP, BTCSimK, and KTCSimK calculators, respectively (P = 0.934), and the centroid of the prediction errors were 0.3 D @ 178°, 0.11 D @ 102°, and 0.09 D @ 147°, respectively (P = 0.23). In the with-the-rule subgroup, the centroid of the prediction error was 0.34 D @ 176° for ATCTCRP and was the highest among the three calculation methods (P = 0.046). Conclusion: The ATCTCRP, BTCSimK, and KTCSimK calculators had similar performance with regards to their astigmatism prediction accuracy. The ATCTCRP calculator combined with 4.0-mm apex/ring readings of TCRP was slightly intended to result in against-the-rule residual astigmatism.