Tetrahydrobiopterin deficiency and dopamine loss in a genetic mouse model of Lesch-Nyhan disease

Hypoxanthine-guanine phosphoribosyltransferase (HPRT) is an enzyme that catalyses the conversion of hypoxanthine and guanine into their respective nucleotides. Inherited deficiency of the enzyme is associated with a loss of striatal dopamine in both mouse and man. Although HPRT is not directly involved in the metabolism of dopamine, it contributes to the supply of GTP, which is used in the first and rate-limiting step in the synthesis of tetrahydrobiopterin (BH4). Since BH4 is required as a cofactor for tyrosine hydroxylase in the synthesis of dopamine, any limitation in the supply of GTP could interfere with the synthesis of dopamine. The current studies were designed to address the hypothesis that the reduced striatal dopamine in mice with HPRT deficiency results from reduced availability of BH4. The mutant mice had small reductions in striatal BH4, with normal BH4 levels in other brain regions. Liver BH4 was normal in HPRT-deficient mutant mice, and a phenylalanine challenge test failed to reveal any evidence for impaired hepatic phenylalanine hydroxylase, another BH4-dependent enzyme. Although striatal BH4 content is not normal, supplementation with BH4 or L-dopa failed to correct the striatal dopamine deficiency of the mutant mice, suggesting that BH4 limitation is not responsible for the dopamine loss.     

The association of non-alcoholic fatty liver disease and metabolic syndrome in a Chinese population

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is associated with features of metabolic syndrome. The aim of this study was to investigate the association between NAFLD and metabolic syndrome in a Chinese population.METHODS: Data from subjects were retrospectively collected from 2006 to 2009. The exclusion criteria included significant consumption of alcohol and chronic hepatitis B and C. The patients were assigned to two groups according to ultrasound findings: normal group and fatty liver group. The liver func-tion of patients was determined by assessing serum alanine aminotransferase (ALT). Metabolic syndrome was diagnosed based on the 2005 International Diabetes Federation criteria.RESULTS: A total of 7568 subjects were enrolled and 5736 (75.8%) and 1832 (24.2%) patients were assigned to the nor-mal and fatty liver groups, respectively. The fatty liver group had significant male predominance (69.7% vs 56.0%), higher body mass index (mean, 26.67 vs 23.55 kg/m2) compared with the normal group. There were 441 (7.7%) and 377 (20.6%) cases with metabolic syndrome in the normal and fatty liver groups, respectively, with significant difference (P=0.001), and the subgroup of 385 cases with fatty liver and elevated ALT had higher prevalence (28.8%) of metabolic syndrome. The strongest association of an individual component of meta-bolic syndrome with NAFLD was hyperlipidemia (adjusted OR=2.55, 95% CI: 2.22-2.94).CONCLUSION: The individuals with NAFLD had a higher ra-tio of metabolic syndrome. Hyperlipidemia had the strongest positive association with NAFLD.     

Lower number of cerebellar Purkinje neurons in psychosis is associated with reduced reelin expression

Reelin is an extracellular matrix protein synthesized in cerebellar granule cells that plays an important role in Purkinje cell positioning during cerebellar development and in modulating adult synaptic function. In the cerebellum of schizophrenia (SZ) and bipolar (BP) disorder patients, there is a marked decrease (≈50%) of reelin expression. In this study we measured Purkinje neuron density in the Purkinje cell layer of cerebella of 13 SZ and 17 BP disorder patients from the McLean 66 Cohort Collection, Harvard Brain Tissue Resource Center. The mean number of Purkinje neurons (linear density, neurons per millimeter) was 20% lower in SZ and BP disorder patients compared with nonpsychiatric subjects (NPS; n = 24). This decrease of Purkinje neuron linear density was unrelated to postmortem interval, pH, drugs of abuse, or to the presence, dose, or duration of antipsychotic medications. A comparative study in the cerebella of heterozygous reeler mice (HRM), in which reelin expression is down-regulated by ≈50%, showed a significant loss in the number of Purkinje cells in HRM (10–15%) compared with age-matched (3–9 months) wild-type mice. This finding suggests that lack of reelin impairs GABAergic Purkinje neuron expression and/or positioning during cerebellar development.     

Cyclin-dependent kinase 5 is a mediator of dopaminergic neuron loss in a mouse model of Parkinson's disease

Recent evidence indicates that cyclin-dependent kinases (CDKs, cdks) may be inappropriately activated in several neurodegenerative conditions. Here, we report that cdk5 expression and activity are elevated after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a toxin that damages the nigrostriatal dopaminergic pathway. Supporting the pathogenic significance of the cdk5 alterations are the findings that the general cdk inhibitor, flavopiridol, or expression of dominant-negative cdk5, and to a lesser extent dominant-negative cdk2, attenuates the loss of dopaminergic neurons caused by MPTP. In addition, CDK inhibition strategies attenuate MPTP-induced hypolocomotion and markers of striatal function independent of striatal dopamine. We propose that cdk5 is a key regulator in the degeneration of dopaminergic neurons in Parkinson's disease.     

Clinical predictive score for detecting nonalcoholic fatty liver disease with significant fibrosis in patients with metabolic syndrome

Patients with metabolic syndrome are at a higher risk of nonalcoholic fatty liver disease (NAFLD) and liver fibrosis than the general population. Still, accessibility of screening method for NAFLD with significant fibrosis, such as transient elastography (FibroScan) are limited in some settings. This study aimed to develop a simple clinical predictive score for detecting NAFLD with significant fibrosis in patients with metabolic syndrome.A cross-sectional study was designed to obtain the data from medical records of all relevant patients who underwent transient elastography between January 2011 and December 2020 at Siriraj Hospital, Thailand. A liver stiffness cutoff value of 7.0 kilopascal was used to define the presence of significant liver fibrosis. To examine potential predictors, medical history and clinical data commonly assessed in routine practice were selected by following expert opinions and univariable statistical analysis. Backward and forward stepwise logistic regression was performed to acquire a final prediction model. To simplify the model, a weighted score was assigned for each categorized predictor. In addition, eligible cutoff values of the score and their predictive performances were determined.A total of 745 medical records were reviewed. The prevalence of NAFLD with significant fibrosis in patients with metabolic syndrome was 12.6%. Most clinical characteristics of patients with NAFLD with significant fibrosis and those non-NAFLD and NAFLD with no/mild fibrosis were quite disparate. The most practical model comprised globulin, aspartate transaminase, platelet count, and type 2 diabetes. It provided a good predictive performance with an area under the receiver operating characteristic curve of 0.828 (95% confidence interval [CI]: 0.782, 0.874). At the proper cutoff value, sensitivity and specificity were 76.6% (95% CI: 66.7%, 84.7%) and 72.4% (95% CI: 68.7%, 75.8%), respectively. The likelihood ratio of testing positive for NAFLD with significant fibrosis was 2.8 (95% CI: 2.34, 3.27) among patients with scores above the cutoff value.The first score for detecting of NAFLD with significant fibrosis in patients with metabolic syndrome was developed. This practical score, providing a good predictive performance, should be useful to help clinicians prioritize needs for further investigations among high-risk patients, especially in resource-limited settings.     

Selective inhibition of NF-kappaB activation prevents dopaminergic neuronal loss in a mouse model of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder. Despite intense investigations, no effective therapy is available to stop its onset or halt its progression. The present study evaluates the ability of peptide corresponding to the NF-κB essential modifier-binding domain (NBD) of IκB kinase α (IKKα) or IKKβ to prevent nigrostriatal degeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD and establish a role for NF-κB in human parkinsonism. First, we found that NF-κB was activated within the substantia nigra pars compacta of PD patients and MPTP-intoxicated mice. However, i.p. injection of wild-type NBD peptide reduced nigral activation of NF-κB, suppressed nigral microglial activation, protected both the nigrostriatal axis and neurotransmitters, and improved motor functions in MPTP-intoxicated mice. These findings were specific because mutated NBD peptide had no effect. We conclude that selective inhibition of NF-κB activation by NBD peptide may be of therapeutic benefit for PD patients.     

乌鲁木齐地区脂肪肝发病率及非酒精性脂肪肝与代谢综合征的关系

目的了解乌鲁木齐地区机关汉族成人非酒精性脂肪肝及酒精性脂肪肝的流行状况,并分析非酒精性脂肪肝与代谢综合征的关系。方法对1037例体检者的问卷调查、体格检查、生化、肝脏超声检查等相关资料进行分析。结果乌鲁木齐地区成人脂肪肝检出278例,脂肪肝发生率为检出率为26.8%,非酒精性脂肪肝188例,占18.1%,其中男性161例,女性27例;酒精性脂肪肝90例,占8.7%,其中男性84例,女性6例,男性NAFLD高于女性。NAFLD患者合并MS共计115例,伴有率为61.2%。结论乌鲁木齐地区机关汉族成人脂肪肝（NAFLD及AFLD）患病率远高于国内以及世界范围平均患病率,体现了低龄化趋势及中年年龄段的患病高峰特点;年龄、BMI、WHR、TG以及FPG为NAFLD的相关危险因素,NAFLD可以作为MS组成成分之一。     

非酒精性脂肪性肝病的靶向治疗研究进展

非酒精性脂肪性肝病（NAFLD）是最常见的进行性疾病,临床上目前尚无疗效确切的治疗药物。介绍了脂肪酸-胆酸偶合物（FABACs）和熊去氧胆酸-溶血磷脂酰乙醇胺偶合物（UDCA-LPE）两种新型的具有NAFLD防治作用的肝靶向药物的研究进展。FABACs通过调节脂代谢,特异性的降低高脂饲料所致NAFLD的肝脏脂肪升高,预防NAFLD的形成;而且对已形成的NAFLD也有治疗作用;Ⅱ期临床研究结果显示其起效快、安全性好。UDCA-LPE在降低NAFLD的肝脏脂肪的同时,能够抑制线粒体损伤和凋亡,促进肝细胞再生,对NAFLD发展过程中的相关炎症具有显著的抑制作用。因此,FABACs和UDCA-LPE对防治NAFLD具有良好的应用前景。     

Mechanism for the inhibition of the carboxyltransferase domain of acetyl-coenzyme A carboxylase by pinoxaden

Acetyl-CoA carboxylases (ACCs) are crucial metabolic enzymes and have been targeted for drug development against obesity, diabetes, and other diseases. The carboxyltransferase (CT) domain of this enzyme is the site of action for three different classes of herbicides, as represented by haloxyfop, tepraloxydim, and pinoxaden. Our earlier studies have demonstrated that haloxyfop and tepraloxydim bind in the CT active site at the interface of its dimer. However, the two compounds probe distinct regions of the dimer interface, sharing primarily only two common anchoring points of interaction with the enzyme. We report here the crystal structure of the CT domain of yeast ACC in complex with pinoxaden at 2.8-Å resolution. Despite their chemical diversity, pinoxaden has a similar binding mode as tepraloxydim and requires a small conformational change in the dimer interface for binding. Crystal structures of the CT domain in complex with all three classes of herbicides confirm the importance of the two anchoring points for herbicide binding. The structures also provide a foundation for understanding the molecular basis of the herbicide resistance mutations and cross resistance among the herbicides, as well as for the design and development of new inhibitors against plant and human ACCs.     

Effects of (+)-octanoylcarnitine in intact myocardium

Summary Fatty acid metabolites (long-chain esters of CoA and carnitine) which collect in ischemic myocardium can form amphiphiles capable of disrupting subcellular performance. It is important to document the role of these amphiphiles in intact tissue. D-Octanoylcarnitine was chosen because of its previously described effects on inhibiting palmitoylcarnitine transferasc (PCT-II) inin vitro andin vivo liver preparations. This inhibition will shift tissue levels of CoA and carnitine intermediates and thus alter amphiphile levels. The compound's actions in cardiac muscle are unknown.Dose response curves were developed in intact hearts to test the influence of D-octanoylcarnitine at pharmacological concentrations. Measurements were obtained in working, extracorporeally perfused, swine hearts. Drug was administered either systemically (IV) or via dircct intracoronary (IC) infusions into the left anterior descending coronary circulation. Excess fatty acids were provided to ensure adequate fatty acid substrate for oxidation. Coronary flow was controlled at aerobic levels. Systemic administration of D-octanoylcarnitine (0.8–6.8 mM) resulted in transient peripheral hypotension which caused correlative decreascs in¹⁴CO₂ production from labeled palmitate. Infusion of D-octanoylcarnitine (0.5–3.9 mM) IC did not cause appreciable hypotension and was not associated with suppression of fatty acid oxidation. No build-up of carnitine esters was noted in treated hearts but acyl CoA levels were reduced (p<-0.002). This latter finding was modestly related to increasing dose schedule of the compound in the IC group. The lack of suppression in fatty acid oxidation argues against significant inhibition of PCT II and lessens the attractiveness of using D-octanoylcarnitine in intact myocardium to selectively bloock fatty acid utilization at this locus.This work was supported in part by PHS Grant HL-21209 and the Rennebohm Foundation of Wisconsin.     

Lean-non-alcoholic fatty liver disease increases risk for metabolic disorders in a normal weight Chinese population

AIM: To study the prevalence and clinical biochemical, blood cell and metabolic features of lean-non-alcoholic fatty liver disease (lean-NAFLD) and its association with other diseases.METHODS: Demographic, biochemical and blood examinations were conducted in all the subjects in this study. We classified the subjects into four groups according to their weight and NAFLD status: lean-control, lean-NAFLD [body mass index (BMI) < 24 kg/m²], overweight-obese control and overweight-obese NAFLD. One-way analysis of variance (ANOVA) was used to compare the means of continuous variables (age, BMI, blood pressure, glucose, lipid, insulin, liver enzymes and blood cell counts) and the χ² test was used to compare the differences in frequency of categorical variables (sex, education, physical activity, smoking, alcohol consumption and prevalence of hypertension, hyperlipidemia, diabetes, metabolic syndrome central obesity and obesity). Both univariate and multivariate logistic regression models were adopted to calculate odds ratios (ORs) and predict hyperlipidemia, hypertension, diabetes and metabolic syndrome when we respectively set all controls, lean-control and overweight-obese-control as references. In multivariate logistic regression models, we adjusted potential confounding factors, including age, sex, smoking, alcohol consumption and physical activity.RESULTS: The prevalence of NAFLD was very high in China. NAFLD patients were older, had a higher BMI, waist circumference, blood pressure, fasting blood glucose, insulin, blood lipid, liver enzymes and uric acid than the controls. Although lean-NAFLD patients had lower BMI and waist circumstance, they had significantly higher visceral adiposity index than overweight-obese controls. Lean-NAFLD patients had comparable triglyceride, cholesterin and low-density lipoprotein cholesterin to overweight-obese NAFLD patients. In blood cell examination, both lean and overweight-obese NAFLD was companied by higher white blood cell count, red blood cell count, hemoglobin and hematocrit value. All NAFLD patients were at risk of hyperlipidemia, hypertension, diabetes and metabolic syndrome (MetS). Lean-NAFLD was more strongly associated with diabetes (OR = 2.47, 95%CI: 1.14-5.35), hypertension (OR = 1.72, 95%CI: 1.00-2.96) and MetS (OR = 3.19, 95%CI: 1.17-4.05) than overweight-obese-NAFLD (only OR for MetS was meaningful: OR = 1.89, 95%CI: 1.29-2.77). NAFLD patients were more likely to have central obesity (OR = 1.97, 95%CI: 1.38-2.80), especially in lean groups (OR = 2.17, 95%CI: 1.17-4.05).CONCLUSION: Lean-NAFLD has unique results in demographic, biochemical and blood examinations, and adds significant risk for diabetes, hypertension and MetS in lean individuals.     

MYC inhibition induces metabolic changes leading to accumulation of lipid droplets in tumor cells

The MYC genes are the most frequently activated oncogenes in human tumors and are hence attractive therapeutic targets. MYCN amplification leads to poor clinical outcome in childhood neuroblastoma, yet strategies to modulate the function of MYCN do not exist. Here we show that 10058-F4, a characterized c-MYC/Max inhibitor, also targets the MYCN/Max interaction, leading to cell cycle arrest, apoptosis, and neuronal differentiation in MYCN-amplified neuroblastoma cells and to increased survival of MYCN transgenic mice. We also report the discovery that inhibition of MYC is accompanied by accumulation of intracellular lipid droplets in tumor cells as a direct consequence of mitochondrial dysfunction. This study expands on the current knowledge of how MYC proteins control the metabolic reprogramming of cancer cells, especially highlighting lipid metabolism and the respiratory chain as important pathways involved in neuroblastoma pathogenesis. Together our data support direct MYC inhibition as a promising strategy for the treatment of MYC-driven tumors.     

Castration modifies aortic vasoreactivity and serum fatty acids in a sucrose-fed rat model of metabolic syndrome

Levels of testosterone and estradiol influence the incidence of cardiovascular diseases: generally, estrogens in females are protective before menopause; coronaropathies, hypertension, and dyslipidemias in normal men are more frequent at comparable ages. We investigated the modulation by castration of in vitro vasoreactivity, serum lipid content, and systolic blood pressure (SBP) in rats with sucrose-induced metabolic syndrome. The main characteristics of the rat model are: hypertriglyceridemia, moderately high blood pressure, intra-abdominal accumulation of adipose tissue, hyperinsulinemia, nephropathy, increased oxidative stress, and altered vasoreactivity. Male weanling rats received 30% sucrose solution for 16 weeks (metabolic syndrome; MS), controls (C) had plain water; both had commercial rodent chow. They were subdivided into five groups with two subgroups each: Group 1, intact C and MS rats, Groups 2–5, C and MS rats castrated for periods of 16, 12, 8, and 4 weeks. At the end of the study period, systolic blood pressure was measured, and blood and aortas were obtained for fatty acid determination and vasoreactivity assays, respectively. After 16 weeks’ sucrose treatment MS aortas showed hypercontractility and decreased vasodilation. Palmitic and palmitoleic acids were increased in MS versus C. Arachidonic acid levels in MS were lower than in intact or castrated C. Long-term castration of 16 weeks normalized the levels of palmitic and oleic acids. With the shorter periods of castration, contractility increased and relaxation decreased in C and MS, but it was more significant in C. Regarding fatty acid composition, long-term castration increased polyunsaturated (arachidonic and eicosapentaenoic) fatty acids. The shorter periods did not modify the fatty acid profile in either C or MS. Metabolic syndrome altered SBP, aortic reactivity, and levels of fatty acids; castration of long duration normalized them in some cases.