Site-specific transgenesis of the Drosophila melanogaster Y-chromosome using CRISPR/Cas9.

Despite the importance of Y-chromosomes in evolution and sex determination, their heterochromatic, repeat-rich nature makes them difficult to sequence (due, in part, to ambiguities in sequence alignment and assembly) and to genetically manipulate. Therefore, they generally remain poorly understood. For example, the Drosophila melanogaster Y-chromosome, one of the most extensively studied Y-chromosomes, is widely heterochromatic and composed mainly of highly repetitive sequences, with only a handful of expressed genes scattered throughout its length. Efforts to insert transgenes on this chromosome have thus far relied on either random insertion of transposons (sometimes harbouring 'landing sites' for subsequent integrations) with limited success or on chromosomal translocations, thereby limiting the types of Y-chromosome-related questions that could be explored. Here, we describe a versatile approach to site-specifically insert transgenes on the Y-chromosome in D. melanogaster via CRISPR/Cas9-mediated homology-directed repair. We demonstrate the ability to insert, and detect expression from, fluorescently marked transgenes at two specific locations on the Y-chromosome, and we utilize these marked Y-chromosomes to detect and quantify rare chromosomal nondisjunction effects. Finally, we discuss how this Y-docking technique could be adapted to other insects to aid in the development of genetic control technologies for the management of insect disease vectors and pests.

Loneliness Predicts Progression of Frailty in Married and Widowed, but Not Unmarried Community Dwelling Older Adults.

BACKGROUND: Loneliness is highly prevalent among older adults and is associated with frailty. Most studies consider loneliness in isolation without consideration for structural and functional measures of social relationships - and longitudinal studies are scarce. OBJECTIVES: This study examined longitudinal associations between loneliness and frailty and analyzed how structural and functional social measures influence these associations. DESIGN: Linear mixed effects models examined longitudinal associations between loneliness and frailty assessed with the frailty index (scale 0-100). Models were adjusted for baseline age, gender, education, depressive symptoms, global cognition, and structural (e.g., social network, marital status), and functional social measures (e.g., social, cognitive, and physical activity, and social support). PARTICIPANTS: Loneliness and frailty data from 1,931 older adults without dementia at baseline from the Rush Memory and Aging Project were examined (mean age 79.6 ± 7.7 years, 74.9% female). MEASUREMENTS: Baseline loneliness assessed by the de Jong Gierveld Loneliness Scale was the predictor of interest. RESULTS: Frailty increased significantly over a mean follow-up period of 4.6 years. Effects of loneliness on frailty were modified by marital status. Loneliness predicted an additional accumulation of 0.37 and 0.34 deficits on the frailty index per year in married and widowed individuals respectively, compared to those who were not lonely (married: p=0.009, CI 0.09, 0.64; widowed: p=0.005, CI 0.1, 0.58). Loneliness did not predict frailty progression in unmarried individuals. CONCLUSIONS: Loneliness predicts frailty progression, highlighting the importance of social determinants on physical health in aging.

Genetic susceptibility for ischemic infarction and arteriolosclerosis based on neuropathologic evaluations.

BACKGROUND: Recent genetic studies of stroke and related risk factors have identified a growing number of susceptibility loci; however, the relationship of these alleles to ischemic stroke is unknown. The challenge in finding reproducible loci of ischemic stroke susceptibility may be in part related to the etiologic heterogeneity in clinically defined stroke subtypes. In this study, we tested whether known single nucleotide polymorphisms (SNPs) associated with stroke or putative stroke risk factors are associated with neuropathologically defined micro- or macroscopic infarcts and with arteriolosclerosis. METHODS: Measures of neuropathology and genotyping were available from 755 deceased participants from the Religious Orders Study and the Rush Memory and Aging Project. All donated brains were examined by a board-certified neuropathologist using standardized protocol for the presence of microscopic infarct, macroscopic infarct and arteriolosclerosis (lipohyalinosis). In primary analysis, 74 candidate SNPs previously associated (p < 5 × 10(-8)) with ischemic stroke or known risk factors, including atrial fibrillation (AF), hypertension, diabetes, low-density lipoprotein (LDL) level and carotid artery stenosis, were evaluated for association with neuropathologic endpoints. We performed a secondary exploratory analysis to include 93 additional SNPs associated with putative ischemic stroke risk factors including SNPs associated with high-density lipoprotein (HDL), triglyceride serum levels, myocardial infarction (MI), coronary artery disease and cerebral white matter disease. Regression models relating SNPs to cerebrovascular neuropathology were adjusted for age at death, gender and cohort membership. RESULTS: The strongest associations seen for both macroscopic and microscopic infarcts were risk variants associated with diabetes. The diabetes risk variant rs7578326 located near the IRS1 locus was associated with both macroscopic (OR = 0.73, p = 0.011) and microscopic (OR = 0.71, p = 0.009) infarct pathology. Another diabetes susceptibility locus (rs12779790) located between the calcium/calmodulin-dependent protein kinase ID (CAMK1D) and cell division cycle 123 homolog (CDC123) genes is also associated with both macroscopic (OR = 1.40, p = 0.0292) and microscopic infarcts (OR = 1.43, p = 0.0285). The diabetes risk variant rs864745 within JAZF1 was associated with arteriolosclerosis (OR = 0.80, p = 0.014). We observed suggestive associations with the diabetes risk variant rs7961581 (p = 0.038; between TSPAN8 and LGR5) and rs5215 (p = 0.043; KCNJ11), the LDL risk variant rs11206510 (p = 0.045; PCSK9), as well as the AF risk locus ZFHX3. The CDKN2A/B locus (rs2383207, 9p21), identified initially as a susceptibility allele for MI and recently implicated in large vessel stroke, was associated with macroscopic infarct pathology in our autopsy cohort (OR = 1.26, p = 0.031). CONCLUSION: Our results suggest replication of the candidate CDKN2A/B stroke susceptibility locus with directly measured macroscopic stroke neuropathology, and further implicate several diabetes and other risk variants with secondary, pleiotropic associations to stroke-related pathology in our autopsy cohort. When coupled with larger sample sizes, cerebrovascular neuropathologic phenotypes will likely be powerful tools for the genetic dissection of susceptibility for ischemic stroke.

Treatment of cholera-like diarrhoea with oral rehydration.

Cholera diarrhoea remains a major global health problem that has caused seven pandemics. The pathogenesis of cholera is attributable to the production of cholera toxin by the causative pathogen, Vibrio cholerae. The toxin causes increased production of cyclic adenosine monophosphate and this results in massive water and electrolyte secretion into the intestinal lumen. These changes manifest clinically as the painless defecation of voluminous stools that resemble 'rice water', leading to severe dehydration. The cornerstone in the management of cholera diarrhoea is the use of oral rehydration solutions (ORS) to replace the water and electrolytes lost as stools. The World Health Organization recommends the use of ORS of 'reduced osmolarity' for the treatment of acute non-cholera diarrhoea and the use of rice-based ORS for the management of cholera diarrhoea. Although several attempts have been made to improve ORS, studies to evaluate some of the modifications, which include the addition of amylase-resistant starch, the use of amino acids (such as glycine, alanine and glutamine) as sodium cotransporters, and zinc-supplemented ORS, are still needed.

Change in frailty and risk of death in older persons.

The authors developed and validated a continuous composite measure of frailty and examined its rate of change in 832 older persons with annual evaluations for up to 8 years. In generalized estimating equation models adjusted for age, sex, and education, there was a significant increase in frailty during follow-up. In a proportional hazards model controlling for age, sex, education, and baseline frailty, each 1-unit increase in annual change in frailty was associated with an almost 5 times the risk of mortality. Using a continuous measure, the authors document that frailty is progressive in some older persons and that its rate of progression is associated with mortality.

A new central venous catheter cap: decreased microbial growth and risk for catheter-related bloodstream infection.

OBJECTIVE: Catheter-related blood stream infection (CRBI) is a major cause of morbidity and mortality, and is a source of significant healthcare expenditures in patients that require central venous catheters for intravenous nutrition, chemotherapy, and other products. The source of many catheter-related infections is contamination of the catheter hub. Herein an antimicrobial catheter cap, the AB Cap is described. METHODS: The AB Cap device is a catheter cleaning device designed to keep needleless luer valves clean by encapsulating them in a cleaning solution. This device was evaluated using an in vitro model of hub contamination with Staphylococcus aureus, Staphylococcus epidermidis (S. epidermidis), Klebsiella pneumonia (K. pneumonia), Pseudomonas aeruginosa, Escherichia coli and Candida albicans (C. albicans). Following hub contamination on days 1, 3, 5 and 7, saline was infused through the AB Cap and effluent collected from the efferent end. The effluent fluid was cultured for the index organisms, and allowed to incubate in culture for up to 7 days. Negative control caps were not contaminated and positive controls lacked cleaning solution and were contaminated. RESULTS: Microbial growth developed for all index organisms, and generally within 1 day of culture growth following the first day of contamination (day 1) in effluent from all positive controls, while no growth occurred in effluent from negative controls. No growth of any organism occurred in any of the test items after the first day of contamination. Growth of three organisms was detected in two of the three test AB Caps following contamination day 3, after 1-4 days of incubation. All organisms could be cultured in the effluent from two of the three test items at contamination day 5, generally by the second day of incubation. One test item remained free of growth for the entire test period except for one organism. By day 7, this particular test item grew an additional organism and the testing was concluded. All positive growth test items remained positive on subsequent inoculations during culture of newly obtained effluent with the exception of test item A, from which effluent following inoculation on day 3 showed growth of S. epidermidis and K. pneumonia, but no growth for these organisms from effluent obtained on inoculation day 5. In addition, effluent from test item C showed growth of C. albicans from inoculation day 5, but no growth from effluent obtained on inoculation day 7. The growth of S. epidermidis from effluent of test item A from the day 3 inoculation, and C. albicans from effluent of test items B and C did not occur until day 4 of incubation, suggesting a very small amount of contamination. CONCLUSION: An antimicrobial catheter cap is not a complete substitute for a proper catheter cleaning technique and other anti-infection precautions. However, we describe a unique catheter cap that significantly decreased the likelihood of a catheter-related infection from a non-cleaned cap in an in vitro model.

Multiple functions of nucleosomes and regulatory factors in transcription.

The in vivo packaging of DNA with histone proteins to form chromatin makes its transcription a difficult process. Biochemical and genetic studies are beginning to reveal mechanistic details of how transcriptional regulatory factors confront at least two hurdles created by nucleosomes, the primary structural unit of chromatin. Regulatory factors must gain access to their respective binding sites and activate the formation of transcription complexes at core promoter elements. Distinct regulatory factors may be specialized to perform these functions.

Pulmonary function, muscle strength and mortality in old age.

Numerous reports have linked extremity muscle strength with mortality but the mechanism underlying this association is not known. We used data from 960 older persons without dementia participating in the Rush Memory and Aging Project to test two sequential hypotheses: first, that extremity muscle strength is a surrogate for respiratory muscle strength, and second, that the association of respiratory muscle strength with mortality is mediated by pulmonary function. In a series of proportional hazards models, we first demonstrated that the association of extremity muscle strength with mortality was no longer significant after including a term for respiratory muscle strength, controlling for age, sex, education, and body mass index. Next, the association of respiratory muscle strength with mortality was attenuated by more than 50% and no longer significant after including a term for pulmonary function. The findings were unchanged after controlling for cognitive function, parkinsonian signs, physical frailty, balance, physical activity, possible COPD, use of pulmonary medications, vascular risk factors including smoking, chronic vascular diseases, musculoskeletal joint pain, and history of falls. Overall, these findings suggest that pulmonary function may partially account for the association of muscle strength and mortality.

Respiratory muscle strength predicts decline in mobility in older persons.

OBJECTIVES: To test the hypothesis that respiratory muscle strength is associated with the rate of change in mobility even after controlling for leg strength and physical activity. METHODS: Prospective study of 890 ambulatory older persons without dementia who underwent annual clinical evaluations to examine change in the rate of mobility over time. RESULTS: In a linear mixed-effect model adjusted for age, sex, and education, mobility declined about 0.12 unit/year, and higher levels of respiratory muscle strength were associated with a slower rate of mobility decline (estimate 0.043, SE 0.012, p < 0.001). Respiratory muscle strength remained associated with the rate of change in mobility even after controlling for lower extremity strength (estimate 0.036, SE 0.012, p = 0.004). In a model that included terms for respiratory muscle strength, lower extremity strength and physical activity together, all three were independent predictors of mobility decline in older persons. These associations remained significant even after controlling for body composition, global cognition, the development of dementia, parkinsonian signs, possible pulmonary disease, smoking, joint pain and chronic diseases. CONCLUSION: Respiratory muscle strength is associated with mobility decline in older persons independent of lower extremity strength and physical activity. Clinical interventions to improve respiratory muscle strength may decrease the burden of mobility impairment in the elderly.

MIND Diet Associated with Reduced Incidence and Delayed Progression of ParkinsonismA in Old Age.

BACKGROUND: In old age, motor impairments including parkinsonian signs are common, but treatment is lacking for many older adults. In this study, we examined the association of a diet specifically developed to promote brain health, called MIND (Mediterranean-DASH Diet Intervention for Neurodegenerative Delay), to the incidence and progression of parkinsonism in older adults. METHODS: A total of 706 Memory and Aging Project participants aged 59 -97 years and without parkinsonism at baseline were assessed annually for the presence of four parkinsonian signs using a 26-item modified version of the United Parkinson's Disease Rating Scale. Incident parkinsonism was defined as the first occurrence over 4.6 years of follow-up of two or more parkinsonian signs. The progression of parkinsonism was assessed by change in a global parkinsonian score (range: 0-100). MIND, Mediterranean, and DASH diet pattern scores were computed based on a validated food frequency questionnaire including 144 food items. We employed Cox-Proportional Hazard models and linear mixed models, to examine the associations of baseline diet scores with incident parkinsonism and the annual rate of change in global parkinsonian score, respectively. RESULTS: In models adjusted for age, sex, smoking, total energy intake, BMI and depressive symptoms, higher MIND diet scores were associated with a decreased risk of parkinsonism [(HR=0.89, 95% CI 0.83-0.96)]; and a slower rate of parkinsonism progression [(ß= -0.008; SE=0.0037; p=0.04)]. The Mediterranean diet was marginally associated with reduced parkinsonism progression (ß= -0.002; SE=0.0014; p=0.06). The DASH diet, by contrast, was not associated with either outcome. CONCLUSION: The MIND diet created for brain health may be a associated with decreased risk and slower progression of parkinsonism in older adults.

Complex regulation of simian virus 40 early-region transcription from different overlapping promoters.

During simian virus 40 lytic infection there is a shift in initiation sites used to transcribe the early region, which encodes large T and small t antigens. Early in infection, transcription is initiated almost exclusively from sites that are downstream of the origin of DNA replication, whereas transcripts produced later are initiated mainly from sites on the upstream side. We have used mutant virus and specially constructed plasmid DNAs to investigate the factors regulating this transcriptional shift. In our studies simian virus 40 large T antigen appears to mediate the shift in transcription in two ways: first, T antigen represses transcription at the downstream sites late in infection by binding to the region where these RNAs are initiated; second, T antigen promotes transcription from sites on the upstream side by its ability to initiate replication or amplification, or both, of the template DNA. In addition, transcription from the downstream sites is heavily dependent on enhancer sequences located in the 72-base-pair repeat region, whereas transcription from the upstream sites late in infection does not require enhancer sequences. Thus, different overlapping promoters regulate simian virus 40 early-region expression in a manner that apparently coordinates the production of large T antigen with the increase in viral DNA.

Unusual regulation of simian virus 40 early-region transcription in genomes containing two origins of DNA replication.

As part of our efforts to create multifunctional vectors for the transduction of animal cells, a set of simian virus 40 recombinants were constructed which contain an inverted duplication of the region including the origin of viral DNA replication (ori) and the early-region promoter. The unusual aspects of the structure of these recombinant genomes revealed several unexpected features of their function. In particular, transcription from the early-region promoters on these recombinants occurred primarily after the start of DNA replication, and, in that sense, these promoters behaved as if they were late-region promoters. This behavior results from the fact that these genomes contain multiple ori segments, and, therefore, they replicate earlier and faster than wild-type virus DNA, thereby causing a precocious shift in the initiation of early-region transcription from sites downstream of ori to sites located upstream of ori. The abnormal expression from multiple ori genomes is consistent with our present notions regarding the replication-dependent shift in early-region transcriptional start sites (Buchman et al., Mol. Cell. Biol. 4:1900-1914). Since our experiments demonstrate that RNAs initiated upstream of ori contribute to T-antigen formation late in infection, we suggest that the shift in early-region transcription starts modulates large T-antigen production in concert with viral DNA replication.

A yeast ARS-binding protein activates transcription synergistically in combination with other weak activating factors.

ABFI (ARS-binding protein I) is a yeast protein that binds specific DNA sequences associated with several autonomously replicating sequences (ARSs). ABFI also binds sequences located in promoter regions of some yeast genes, including DED1, an essential gene of unknown function that is transcribed constitutively at a high level. ABFI was purified by specific binding to the DED1 upstream activating sequence (UAS) and was found to recognize related sequences at several other promoters, at an ARS (ARS1), and at a transcriptional silencer (HMR E). All ABFI-binding sites, regardless of origin, provided weak UAS function in vivo when examined in test plasmids. UAS function was abolished by point mutations that reduced ABFI binding in vitro. Analysis of the DED1 promoter showed that two ABFI-binding sites combine synergistically with an adjacent T-rich sequence to form a strong constitutive activator. The DED1 T-rich element acted synergistically with all other ABFI-binding sites and with binding sites for other multifunctional yeast activators. An examination of the properties of sequences surrounding ARS1 left open the possibility that ABFI enhances the initiation of DNA replication at ARS1 by transcriptional activation.

Identification of a member of a DNA-dependent ATPase family that causes interference with silencing.

DNA in eukaryotic cells is packed in tandem repeats of nucleosomes or higher-order chromatin structures, which present obstacles to many cellular processes that require protein-DNA interactions, such as transcription, DNA repair, and recombination. To find proteins that are involved in increasing the accessibility of specific DNA regions in yeast, we used a genetic approach that exploited transcriptional silencing normally occurring at HML and HMR loci. The silencing is mediated by cis-acting silencer elements and is thought to require the formation of a special chromatin structure that prevents accessibility to the silenced DNA. A previously uncharacterized gene, termed DIS1, was isolated from a screen for genes that interfere with silencing when overexpressed. DIS1 encodes a protein with conserved motifs that are present in a family of DNA-dependent ATPases, the SWI2/SNF2-like proteins. Overproduction of N-terminal half of DIS1 protein interfered specifically with ectopic silencing used in the screen as well as HMR E silencing. Two-hybrid studies revealed a specific interaction between the N terminus of DIS1 and the C-terminal half of SIR4, a protein essential for silencing. Cells with a dis1 knockout mutation had significantly lower mating-type switching rate. These results suggest that DIS1 may contribute to making the silenced DNA template at HM loci more accessible during the mating-type switching process.

Comparison of intron-dependent and intron-independent gene expression.

Recombinant simian virus 40 viruses carrying rabbit beta-globin cDNA failed to express the beta-globin sequence unless an intron was included in the transcription unit. The addition of either beta-globin IVS1 or IVS2 caused a 400-fold increase in RNA production. Stable beta-globin RNA production required sequences in IVS2 that were very close to the splice sites and that coincided with those needed for mRNA splicing. In addition to the recombinant viruses, intron-dependent expression was observed with both replicating and nonreplicating plasmid vectors in short-term transfections of cultured animal cells. Unlike transcriptional enhancer elements, IVS2 failed to increase stable RNA production when it was placed downstream of the polyadenylation site. Using a plasmid vector system to survey different inserted sequences for their dependence on introns for expression, we found that the presence of IVS2 stimulated the expression of these sequences 2- to 500-fold. Sequences from the transcribed region of the herpes simplex virus thymidine kinase gene, a gene that lacks an intervening sequence, permitted substantial intron-independent expression (greater than 100-fold increase) in the plasmid vector system.

Connections between transcriptional activators, silencers, and telomeres as revealed by functional analysis of a yeast DNA-binding protein.

General regulatory factor I (GRFI) is a yeast protein that binds in vitro to specific DNA sequences at diverse genetic elements. A strategy was pursued to test whether GRFI functions in vivo at the sequences bound by the factor in vitro. Matches to a consensus sequence for GRFI binding were found in a variety of locations: upstream activating sequences (UASs), silencers, telomeres, and transcribed regions. All occurrences of the consensus sequence bound both crude and purified GRFI in vitro. All binding sites for GRFI, regardless of origin, provided UAS function in test plasmids. Also, GRFI binding sites specifically stimulated transcription in a yeast in vitro system, indicating that GRFI can function as a positive transcription factor. The stimulatory effect of GRFI binding sites at UASs for the PYK1 and ENO1 genes is significantly enhanced by flanking DNA elements. By contrast, regulatory sequences that flank the GRFI binding site at HMR E convert this region to a transcriptional silencer.

Two DNA-binding factors recognize specific sequences at silencers, upstream activating sequences, autonomously replicating sequences, and telomeres in Saccharomyces cerevisiae.

Two DNA-binding factors from Saccharomyces cerevisiae have been characterized, GRFI (general regulatory factor I) and ABFI (ARS-binding factor I), that recognize specific sequences within diverse genetic elements. GRFI bound to sequences at the negative regulatory elements (silencers) of the silent mating type loci HML E and HMR E and to the upstream activating sequence (UAS) required for transcription of the MAT alpha genes. A putative conserved UAS located at genes involved in translation (RPG box) was also recognized by GRFI. In addition, GRFI bound with high affinity to sequences with the (C1-3A)-repeat region at yeast telomeres. Binding sites for GRFI with the highest affinity appeared to be of the form 5'-(A/G)(A/C)ACCCANNCA(T/C)(T/C)-3', where N is any nucleotide. ABFI-binding sites were located next to autonomously replicating sequences (ARSs) at controlling elements of the silent mating type loci HMR E, HMR I, and HML I and were associated with ARS1, ARS2, and the 2 micron plasmid ARS. Two tandem ABFI binding sites were found between the HIS3 and DED1 genes, several kilobase pairs from any ARS, indicating that ABFI-binding sites are not restricted to ARSs. The sequences recognized by ABFI showed partial dyad-symmetry and appeared to be variations of the consensus 5'-TATCATTNNNNACGA-3'. GRFI and ABFI were both abundant DNA-binding factors and did not appear to be encoded by the SIR genes, whose products are required for repression of the silent mating type loci. Together, these results indicate that both GRFI and ABFI play multiple roles within the cell.

Interaction of GAL4 and GAL80 gene regulatory proteins in vitro.

The GAL80 protein of Saccharomyces cerevisiae, synthesized in vitro, bound tightly to GAL4 protein and to a GAL4 protein-upstream activation sequence DNA complex, as shown by (i) coimmunoprecipitation of GAL4 and GAL80 proteins with anti-GAL4 antiserum, (ii) an electrophoretic mobility shift of a GAL4 protein-upstream activation sequence DNA complex upon the addition of GAL80 protein, and (iii) GAL4-dependent binding of GAL80 protein to upstream activation sequence DNA immobilized on Sepharose beads. Anti-GAL4 antisera were raised against a GAL4-URA3 fusion protein, which could be purified to homogeneity in a single step with the use of an affinity chromatographic procedure for the URA3 gene product.

Neuronal-expressed microRNA-targeted pseudogenes compete with coding genes in the human brain.

MicroRNAs orchestrate brain functioning via interaction with microRNA recognition elements (MRE) on target transcripts. However, the global impact of potential competition on the microRNA pool between coding and non-coding brain transcripts that share MREs with them remains unexplored. Here we report that non-coding pseudogene transcripts carrying MREs (PSG+MRE) often show duplicated origin, evolutionary conservation and higher expression in human temporal lobe neurons than comparable duplicated MRE-deficient pseudogenes (PSG-MRE). PSG+MRE participate in neuronal RNA-induced silencing complexes (RISC), indicating functional involvement. Furthermore, downregulation cell culture experiments validated bidirectional co-regulation of PSG+MRE with MRE-sharing coding transcripts, frequently not their mother genes, and with targeted microRNAs; also, PSG+MRE single-nucleotide polymorphisms associated with schizophrenia, bipolar disorder and autism, suggesting interaction with mental diseases. Our findings indicate functional roles of duplicated PSG+MRE in brain development and cognition, supporting physiological impact of the reciprocal co-regulation of PSG+MRE with MRE-sharing coding transcripts in human brain neurons.

Total parenteral nutrition: challenges and practice in the cirrhotic patient.

Patients with cirrhosis develop metabolic derangements of protein, carbohydrate, and lipid metabolism. Malnutrition is commonplace and is associated with morbidity and mortality. Specific nutrient deficiencies may occur and enteral or parenteral nutritional support may improve outcome in appropriately selected patients. Parenteral nutrition itself has been associated with hepatic dysfunction, although the preponderance of evidence suggests that hepatic dysfunction is more a function of the underlying disorder and malabsorption. Intravenously infused organic nutrients may be metabolized differently than the same nutrient consumed enterally. The pathophysiology of total parenteral nutrition-associated liver disease is discussed as well as potential management options.