O-GlcNAcylation regulates extracellular signal-regulated kinase (ERK) activation in Alzheimer's disease.

Introduction: Aberrant activation of Extracellular Signal-Regulated Kinase (ERK) signaling is associated with Alzheimer's disease (AD) pathogenesis. For example, enhanced ERK signal activation mediated by Apolipoprotein E4 (APOE4), which is a critical genetic risk factor for AD, increases the transcription of amyloid precursor protein (APP). We hypothesize that O-linked N-acetylglucosamine (O-GlcNAc) regulates the phosphorylation and activation of ERK. O-GlcNAc is a single sugar post-translational modification that dynamically cycles on and off proteins in response to nutrient changes by the action of the enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. However, O-GlcNAc quickly returns to a baseline level after stimulus removal (called O-GlcNAc homeostasis). Methods: We did a serum reactivation time-course followed by western blot in SH-SY5Y neuroblastoma cells after long-term O-GlcNAcase (OGA) inhibition by Thiamet-G (TMG) treatment, O-GlcNAc transferase (OGT) knock-down (KD) and OGA KD. Brain tissues of C57BL6/J mice and 5XFAD Alzheimer's disease mice intra-peritoneally injected with TMG for 1 month and C57BL6/J mice intra-peritoneally injected with TMG for 6 months were also used for western blot. Results: We found that ERK1/2 phosphorylation at Thr 202/Tyr204 and Thr183/Tyr185 (p-ERK) are amplified and hence ERK1/2 are activated after long-term OGA inhibition in SH-SY5Y cells. In addition to pharmacological treatment, genetic disruption of O-GlcNAc by OGT KD and OGA KD also increased p-ERK in SH-SY5Y cells suggesting O-GlcNAc homeostasis controls ERK signaling. To determine how O-GlcNAc regulates p-ERK, we probed the expression of phosphorylated mitogen-activated protein kinase-kinase (p-MEK) which phosphorylates and activates ERK and Dual specificity phosphatase-4 (DUSP4) which dephosphorylates and inactivates ERK in SH-SY5Y cells. p-MEK increases in TMG treated and OGT KD cells whereas total DUSP4 decreases in OGT KD and OGA KD cells with serum reactivation time course. Next, we probed the role of OGA inhibition in regulating ERK activation using mice brain-tissue samples. Interestingly, 6-month intra-peritoneal TMG injection in C57BL/6J mice showed an increase in amplitude of p-ERK and APP protein levels, indicating long-term OGA inhibition potentially contributes to AD progression. Furthermore, 1-month TMG injection was sufficient to increase the amplitude of p-ERK in 5XFAD AD mice brains suggesting AD phenotype contributes to the acceleration of ERK activation mediated by OGA inhibition. Conclusion: Together, these results indicate that disruptions to O-GlcNAc homeostasis amplify ERK signal activation in AD.

OGA Inhibition Alters Energetics and Nutrient Sensing in Alzheimer's Disease Cytoplasmic Hybrids.

BACKGROUND: Alzheimer's disease (AD) features reductions in key bioenergetic fluxes and perturbed mitochondrial function. Cytoplasmic hybrids (cybrids) generated through the transfer of AD subject mitochondria to mtDNA-depleted SH-SY5Y neuroblastoma cells recapitulate some of these features in an in vitro setting. OBJECTIVE: For this study, we used the AD cybrid model to assess the impact of a nutrient-excess like-state via increasing O-GlcNAcylation on whole cell and mitochondrial homeostasis. METHODS: We induced increased O-GlcNAc by treating AD and control cybrid cell lines with Thiamet G (TMG), an inhibitor of the O-GlcNAcase enzyme that mediates removal of the nutrient-dependent O-GlcNAc modification. RESULTS: Relative to control cybrid cell lines, AD cybrid lines showed a blunted response to TMG-induced O-GlcNAcylation. At baseline, AD cybrid cell line mitochondria showed partial activation of several proteins that help maintain bioenergetic homeostasis such as AMP-Regulated Kinase suggesting that AD mitochondria initiate a state of nutrient stress promoting energetic compensation; however, this compensation reduces the capacity of cells to respond to additional nutrient-related stresses such as TMG treatment. Also, TMG caused disruptions in acetylation and Sirtuin 3 expression, while lowing total energetic output of the cell. CONCLUSION: Together, these findings suggest that modulation of O-GlcNAc is essential for proper energetic function of the mitochondria, and AD mitochondrial capacity to handle nutrient-excess is limited.

Real Talk: The Inter-play Between the mTOR, AMPK, and Hexosamine Biosynthetic Pathways in Cell Signaling.

O-linked N-acetylglucosamine, better known as O-GlcNAc, is a sugar post-translational modification participating in a diverse range of cell functions. Disruptions in the cycling of O-GlcNAc mediated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively, is a driving force for aberrant cell signaling in disease pathologies, such as diabetes, obesity, Alzheimer's disease, and cancer. Production of UDP-GlcNAc, the metabolic substrate for OGT, by the Hexosamine Biosynthetic Pathway (HBP) is controlled by the input of amino acids, fats, and nucleic acids, making O-GlcNAc a key nutrient-sensor for fluctuations in these macromolecules. The mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) pathways also participate in nutrient-sensing as a means of controlling cell activity and are significant factors in a variety of pathologies. Research into the individual nutrient-sensitivities of the HBP, AMPK, and mTOR pathways has revealed a complex regulatory dynamic, where their unique responses to macromolecule levels coordinate cell behavior. Importantly, cross-talk between these pathways fine-tunes the cellular response to nutrients. Strong evidence demonstrates that AMPK negatively regulates the mTOR pathway, but O-GlcNAcylation of AMPK lowers enzymatic activity and promotes growth. On the other hand, AMPK can phosphorylate OGT leading to changes in OGT function. Complex sets of interactions between the HBP, AMPK, and mTOR pathways integrate nutritional signals to respond to changes in the environment. In particular, examining these relationships using systems biology approaches might prove a useful method of exploring the complex nature of cell signaling. Overall, understanding the complex interactions of these nutrient pathways will provide novel mechanistic information into how nutrients influence health and disease.

Replication of genetic loci for ages at menarche and menopause in the multi-ethnic Population Architecture using Genomics and Epidemiology (PAGE) study.

STUDY QUESTION: Do genetic associations identified in genome-wide association studies (GWAS) of age at menarche (AM) and age at natural menopause (ANM) replicate in women of diverse race/ancestry from the Population Architecture using Genomics and Epidemiology (PAGE) Study? SUMMARY ANSWER: We replicated GWAS reproductive trait single nucleotide polymorphisms (SNPs) in our European descent population and found that many SNPs were also associated with AM and ANM in populations of diverse ancestry. WHAT IS KNOWN ALREADY: Menarche and menopause mark the reproductive lifespan in women and are important risk factors for chronic diseases including obesity, cardiovascular disease and cancer. Both events are believed to be influenced by environmental and genetic factors, and vary in populations differing by genetic ancestry and geography. Most genetic variants associated with these traits have been identified in GWAS of European-descent populations. STUDY DESIGN, SIZE, DURATION: A total of 42 251 women of diverse ancestry from PAGE were included in cross-sectional analyses of AM and ANM. MATERIALS, SETTING, METHODS: SNPs previously associated with ANM (n = 5 SNPs) and AM (n = 3 SNPs) in GWAS were genotyped in American Indians, African Americans, Asians, European Americans, Hispanics and Native Hawaiians. To test SNP associations with ANM or AM, we used linear regression models stratified by race/ethnicity and PAGE sub-study. Results were then combined in race-specific fixed effect meta-analyses for each outcome. For replication and generalization analyses, significance was defined at P < 0.01 for ANM analyses and P < 0.017 for AM analyses. MAIN RESULTS AND THE ROLE OF CHANCE: We replicated findings for AM SNPs in the LIN28B locus and an intergenic region on 9q31 in European Americans. The LIN28B SNPs (rs314277 and rs314280) were also significantly associated with AM in Asians, but not in other race/ethnicity groups. Linkage disequilibrium (LD) patterns at this locus varied widely among the ancestral groups. With the exception of an intergenic SNP at 13q34, all ANM SNPs replicated in European Americans. Three were significantly associated with ANM in other race/ethnicity populations: rs2153157 (6p24.2/SYCP2L), rs365132 (5q35/UIMC1) and rs16991615 (20p12.3/MCM8). While rs1172822 (19q13/BRSK1) was not significant in the populations of non-European descent, effect sizes showed similar trends. LIMITATIONS, REASONS FOR CAUTION: Lack of association for the GWAS SNPs in the non-European American groups may be due to differences in locus LD patterns between these groups and the European-descent populations included in the GWAS discovery studies; and in some cases, lower power may also contribute to non-significant findings. WIDER IMPLICATIONS OF THE FINDINGS: The discovery of genetic variants associated with the reproductive traits provides an important opportunity to elucidate the biological mechanisms involved with normal variation and disorders of menarche and menopause. In this study we replicated most, but not all reported SNPs in European descent populations and examined the epidemiologic architecture of these early reported variants, describing their generalizability and effect size across differing ancestral populations. Such data will be increasingly important for prioritizing GWAS SNPs for follow-up in fine-mapping and resequencing studies, as well as in translational research.

The use of phenome-wide association studies (PheWAS) for exploration of novel genotype-phenotype relationships and pleiotropy discovery.

The field of phenomics has been investigating network structure among large arrays of phenotypes, and genome-wide association studies (GWAS) have been used to investigate the relationship between genetic variation and single diseases/outcomes. A novel approach has emerged combining both the exploration of phenotypic structure and genotypic variation, known as the phenome-wide association study (PheWAS). The Population Architecture using Genomics and Epidemiology (PAGE) network is a National Human Genome Research Institute (NHGRI)-supported collaboration of four groups accessing eight extensively characterized epidemiologic studies. The primary focus of PAGE is deep characterization of well-replicated GWAS variants and their relationships to various phenotypes and traits in diverse epidemiologic studies that include European Americans, African Americans, Mexican Americans/Hispanics, Asians/Pacific Islanders, and Native Americans. The rich phenotypic resources of PAGE studies provide a unique opportunity for PheWAS as each genotyped variant can be tested for an association with the wide array of phenotypic measurements available within the studies of PAGE, including prevalent and incident status for multiple common clinical conditions and risk factors, as well as clinical parameters and intermediate biomarkers. The results of PheWAS can be used to discover novel relationships between SNPs, phenotypes, and networks of interrelated phenotypes; identify pleiotropy; provide novel mechanistic insights; and foster hypothesis generation. The PAGE network has developed infrastructure to support and perform PheWAS in a high-throughput manner. As implementing the PheWAS approach has presented several challenges, the infrastructure and methodology, as well as insights gained in this project, are presented herein to benefit the larger scientific community.

Mitochondrial DNA variants in schizophrenia: association studies.

The frequency of three selected mitochondrial DNA variations was compared between cases with schizophrenia and two groups of unrelated controls: screened adults and neonates. The comparisons were conducted separately among Caucasians and African-Americans. No significant differences were detected, suggesting that the variants may not be associated with schizophrenia. Limitations of the study are discussed.

Low prevalence of psychoses among the Hutterites, an isolated religious community.

OBJECTIVE: The authors estimated the prevalence of psychoses among the Hutterites in Manitoba, Canada, who lived in 102 communal farms or colonies. The study stemmed from an earlier epidemiological survey of North American Hutterite colonies (1950-1953), in which a low prevalence of psychoses was documented. METHOD: Psychiatrically ill individuals identified during the previous survey were rediagnosed with DSM-IV criteria. A current provincial health insurance claims database was queried anonymously for the period June 1992-May 1997, and the prevalence rate of disease among Hutterites, identified by distinctive surnames and unique postal addresses, was compared with the rate in the entire population of the province of Manitoba and in a comparison group of persons with Hutterite surnames but with addresses outside the Hutterite colonies. RESULTS: The annual prevalence of schizophrenia among the communal Hutterites, estimated from the database search by using ICD-9 criteria, was consistent with the prevalence found in the prior epidemiological survey (annual mean of 1.2/1,000 population, compared with 1.3/1,000 in the prior survey). The database search yielded a significantly lower prevalence for schizophrenia and other functional psychoses among communal Hutterites as well as among the comparison group, compared to the total Manitoba population. There was also lower prevalence for affective psychoses and adjustment reaction disorders among the communal Hutterites, compared to the total Manitoba population. Rates for neurotic disorders were elevated both among the communal Hutterites and the comparison group. CONCLUSIONS: The prevalence of specific psychoses was reduced among the Hutterites, although neurotic disorders were more prevalent. These findings suggest some specificity, although possible artifacts such as ascertainment bias must be considered. Further research is needed to examine genetic and environmental factors that may contribute to reduced prevalence of specific psychoses among the Hutterites.

Whipple's disease can mimic chronic AIDS enteropathy.

Previous case reports have demonstrated that the intestinal pathology of Mycobacterium avium-intracellulare (MAI) infection in the acquired immune deficiency syndrome (AIDS) has a light microscopic appearance similar to Whipple's disease. This case report describes a 52-yr-old male patient with a clinical picture suggestive of AIDS, including diarrhea, weight loss, oral thrush, and intestinal cryptosporidiosis. The intestinal biopsy showed light microscopic features compatible with either MAI or Whipple's disease, but electron microscopy confirmed the presence of the Whipple bacillus. Markers of human immunodeficiency virus (HIV) infection were absent. Although immune abnormalities have been reported in Whipple's disease, this is the first report of opportunistic infections complicating this condition. A useful clinical pearl emerges from this and other cases: AIDS can mimic Whipple's disease; Whipple's disease can mimic AIDS.

Endoscopic variceal ligation in patients who have failed endoscopic sclerotherapy.

Endoscopic variceal ligation has been developed as an alternative to endoscopic sclerotherapy. We report a series of 12 men with a history of bleeding esophageal varices who were treated with endoscopic variceal ligation after they had failed sclerotherapy. Hemostasis was achieved in all 10 patients who were bleeding at the time of initial endoscopy and again in those who subsequently re-bled. Over a follow-up period of up to 22 months, varices have been and remain eradicated in five patients; in four others, a reduction in grade was noted before death (two patients), liver transplant, or loss to follow-up (one patient each); two patients died before they could be re-evaluated, while in the remaining patient, no reduction in variceal grade was noted before loss to follow-up. No complication was recorded after 35 endoscopic treatment sessions involving a total of 245 rubber band ligations. Our results indicate that endoscopic variceal ligation may be used with success in patients who fail sclerotherapy.

Chronic viral hepatitis.

Chronic viral hepatitis is a common clinical problem; it must be differentiated from other forms of chronic liver disease by history, laboratory data, and liver biopsy. This article reviews the treatment of chronic hepatitis B, delta hepatitis, and nonA and nonB viral hepatitis and emphasizes the controlled trials when available.

High-affinity interleukin-2 receptors on blood lymphocytes are decreased during active rheumatoid arthritis.

The expression of receptors for interleukin-2 (IL-2R) was examined in patients with active or inactive rheumatoid arthritis (RA) and in control subjects. Unstimulated blood lymphocytes from patients with active RA had increased levels of total IL-2R, as measured by Tac-positive cells, compared with the levels found in the other 2 groups. Mitogen-stimulated cells from patients with active RA expressed less IL-2R per cell, but the most striking feature was the failure to express high-affinity IL-2R. These changes could reflect persistent antigenic stimulation and explain the defective cell-mediated immunity in RA patients.

Interleukin 2 inhibitor in synovial fluid.

Since evidence for the presence of IL-2 activity in rheumatoid synovial fluid is conflicting, we have assayed IL-2 activity in synovial fluid from patients with rheumatoid arthritis (RA) and other articular diseases (OAD). Using the IL-2-dependent murine T cell line CTLL, IL-2 activity was not demonstrable in synovial fluid tested at concentrations ranging from 50% to 0.02%. There was an inhibitory effect on IL-2 activity in the bioassay of synovial fluid from 16 of the 22 patients with RA and 15 of the 16 with OAD. This inhibitory activity was heat-labile, precipitable by ammonium sulphate, reversible with excess IL-2 and was not significantly altered by preincubation of synovial fluid with CTLL. The mean inhibitory activity of synovial fluid from patients with RA was significantly reduced in comparison with that of synovial fluid from patients with OAD. Sera also had an inhibitory effect on IL-2 activity; however sera from patients with RA were less inhibitory than control sera but were more inhibitory than sera from patients with systemic lupus erythematosus. The deficiency in synovial fluid of an inhibitor of IL-2 activity may be relevant to the pathogenesis of RA.

Deficiency of the suppressor inducer subset of T lymphocytes in rheumatoid arthritis.

New monoclonal antibodies allow CD4 lymphocytes to be categorized into helper/inducer (HI) CD4+ 4B4+, and suppressor inducer (SI) CD4+ 2H4+ subpopulations. Blood and synovial lymphocytes from 30 patients with rheumatoid arthritis (RA), 13 patients with other articular diseases, and 24 control subjects were exposed to these monoclonal antibodies and analyzed by flow cytometry. CD4:CD8 ratios were similar for the 3 groups. In RA patients, there was a depletion of SI cells in blood and synovial fluid, and the ratio of HI cells to SI cells was elevated, particularly in the synovial lymphocytes. These data provide new evidence for T cell dysregulation in the perpetuation of RA.

Psychologic assessment of morbidly obese patients undergoing gastric bypass: a comparison of preoperative and postoperative adjustment.

Thirty-three morbidly obese patients underwent gastric bypass operation after intensive medical and psychiatric evaluation. Five psychometric tests were administered before and after operation. The study patients were found to have less self-esteem and more depressive traits than a normal population. This did not change after operation despite weight loss. High levels of optimism were not associated with better weight loss. However, patients who understood before operation that the success of the operation depended upon changing their eating behavior lost more weight. After operation patients expressed satisfaction with life and a new freedom from constant hunger. There was a reported decrease in organic symptoms, an increase in social activities, an improvement in interpersonal relationships, and a social usefulness not experienced previously. In selected patients with no active psychiatric disease or psychologic instability, gastric bypass, coupled with consistent postoperative reinforcement, produces behavioral changes that can lead to permanent weight loss without concomitant psychologic deterioration.

Gastric bypass for morbid obesity: a medical--surgical assessment.

With the operative modifications and dietary guidelines described in this report, death and complications from gastric bypass were minimal, and weight loss was marked. Ninety per cent of a group of 69 patients lost more than half of their excess weight within the first two years after operation. Stringent preselection of patients for operation was crucial to the success of the operation, and marked alterations of eating behavior was necessary to achieve the weight loss. Mild electrolyte deficiencies and hypovitaminosis occurred in up to one-fourth of the patients. While none of these abnormalities was harmful to the patients, and all were easily corrected, their occurrence demonstrates the importance of long-term follow-up after the operation. We conclude that gastric bypass, with a 50-60 cc pouch and a small (1-1.2 cm) gastrojejunostomy, remains the operation of choice for morbid obesity.

Jejunoileal bypass. Late metabolic sequelae and weight gain.

Of 101 patients originally operated on, the status of 98 is known. Given the mortality and reanastomosis rates, the operation must be considered an absolute failure in 28 percent of the patients. Given the other complications that appear (or persist) late postoperatively, only 18 percent of the entire series of patients have had what can be considered a good result. We therefore conclude that intestinal bypass is not an appropriate operation for morbid obesity and that complete long-term follow-up is essential for all patients who undergo the operation, despite what might seem to be a smooth course in the 1st 2 years postoperatively.

Reanastomosis after jejunoileal bypass.

One hundred and one patients underwent jejunoileal bypass after careful preoperative evaluation. These patients were re-evaluated after operation on a frequent basis, and 23% have required restoration of intestinal continuity (reanastomosis) by a mean postoperative time of 44 months. The most frequent reasons for reanastomosis were liver dysfunction (5% of the entire series), severe malnutrition or weakness (5%), and late electrolyte imbalance (4%). Two patients did not survive reanastomosis, both having liver failure. Of the patients who did survive, weight gain (approaching prebypass weight) and improvement in liver function tests, electrolyte balance, serum vitamin levels, and diarrhea have been the rule. Of the entire series of 101 patients who underwent bypass, 58% either had life-threatening complications, had to be reanastomosed, or died. These morbidity and mortality rates raise the important question of whether jejunoileal bypass is an appropriate procedure for the treatment of morbid obesity.

A contrast of the three more common illnesses with the ten less common in a study and 18-month follow-up of 314 psychiatric emergency room patients.

The present study combines four factors: an initial research interview, a blind follow-up of the patients seen initially, the use of specified diagnostic criteria, and the application of these techniques to a psychiatric emergency room population of 314 patients. Follow-up studies were done in 299 patients (95%) a mean of 18.2 months after the initial interview. The patients were described diagnostically and demographically. There were three more common diagnoses: affective disorder, alcoholism, and antisocial personality. There were ten additional less common diagnoses, as well as an undiagnosed group and a group without diagnosis. There were single diagnoses in 190 patients and multiple diagnoses in the remaining 124 patients. Three diagnoses or less per patient were not uncommon; more than three diagnoses per patient were uncommon. Diagnoses of affective disorder, alcoholism, and antisocial personality occurred in 64% of the total number of diagnoses. The remainder of the diagnoses occurred in 36%. Prompt hospitalization occurred in 14% of the total sample.