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Host Metabolism (host + metabolism)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Screening method to identify inhibitors of siderophore biosynthesis in the opportunistic fungal pathogen, Aspergillus fumigatus

LETTERS IN APPLIED MICROBIOLOGY, Issue 1 2009
L.J. Pinto
Abstract Aims:,Aspergillus fumigatus is the most common cause of airborne mould infections in immunocompromised patients worldwide. Our aim was to develop a method to identify agents that inhibit siderophore biosynthesis because this pathway is unique to the fungus and is essential for virulence. Methods and Results:, A high-throughput two-step screening assay was developed using 96-well plates in which fungal growth and siderophore production is assessed spectrophotometrically. If a compound inhibits growth only in iron-limited medium (screen 1), its effect on siderophore production is then determined (screen 2). The proof of concept was demonstrated using a known antifungal agent, amphotericin B, and a strain of A. fumigatus deficient in siderophore production. Conclusions:, The two-stage screening method clearly identified growth defects in A. fumigatus related specifically to siderophore biosynthesis. Significance and Impact of the Study:, The increasing incidence of life-threatening fungal infections has produced an urgent need for novel antifungal agents. The method described in this report will facilitate the identification of novel antifungal compounds that inhibit a pathway critical for A. fumigatus virulence and have a reduced probability of affecting host metabolism. [source]

Infection of Arabidopsis thaliana leaves with Albugo candida (white blister rust) causes a reprogramming of host metabolism

MOLECULAR PLANT PATHOLOGY, Issue 2 2000
Hsueh-Mei Chou
Albugo candida (Pers.) (O.) Kunze is a biotrophic pathogen which infects the crucifer Arabidopsis thaliana (L.) Heynh forming discrete areas of infection. Eight days after inoculation of leaves, white blisters became visible on the under surface of the leaf although no symptoms were apparent on the upper surface. By day 14, the region of leaf invaded by fungal mycelium had become chlorotic. Recently it has been hypothesized that an accumulation of soluble carbohydrates, following an increase in invertase activity, may trigger sugar signal transduction pathways leading to the repression of photosynthetic gene expression and to the induction of defence proteins. This hypothesis was investigated by quantifying localized changes in carbohydrate and photosynthetic metabolism and the expression of genes encoding photosynthetic and defence proteins. Quantitative imaging of chlorophyll fluorescence revealed that the rate of photosynthesis declined progressively in the invaded regions of the leaf. However, in uninfected regions of the infected leaf the rate of photosynthesis was similar to that measured in the control leaf until late on during the infection cycle when it declined. Images of nonphotochemical fluorescence quenching (NPQ) suggested that the capacity of the Calvin cycle had been reduced in infected regions and that there was a complex metabolic heterogeneity within the infected leaf. A. candida also caused localized changes in the carbohydrate metabolism of the leaf; soluble carbohydrates accumulated in the infected region whereas the amount of starch declined. The reverse was seen in uninfected regions of the infected leaf; carbohydrates did not accumulate until late on during infection and the amount of starch increased as the infection progressed. There was an increase in the activity of invertases which was confined to regions of the leaf invaded by the fungal mycelium. The increase in apoplastic invertase activity was of host origin, as mRNA levels of the AT,FRUCT1 gene (measured by semiquantitative RT-PCR) increased 40-fold in the infected region. The increase in soluble invertase activity resulted from the appearance of a new isoform in the invaded region of the leaf. Current evidence suggests that this was of fungal origin. Northern blot analysis of cab and rbcS showed that photosynthetic gene expression was repressed in the infected leaf from 6 days after inoculation (DAI) when compared to control leaves. In contrast, there was no detectable induction of defence proteins in the infected leaf. These data are discussed in the context of the sugar-sensing hypothesis presented above. [source]

Type III effectors orchestrate a complex interplay between transcriptional networks to modify basal defence responses during pathogenesis and resistance

THE PLANT JOURNAL, Issue 1 2006
William Truman
Summary To successfully infect a plant, bacterial pathogens inject a collection of Type III effector proteins (TTEs) directly into the plant cell that function to overcome basal defences and redirect host metabolism for nutrition and growth. We examined (i) the transcriptional dynamics of basal defence responses between Arabidopsis thaliana and Pseudomonas syringae and (ii) how basal defence is subsequently modulated by virulence factors during compatible interactions. A set of 96 genes displaying an early, sustained induction during basal defence was identified. These were also universally co-regulated following other bacterial basal resistance and non-host responses or following elicitor challenges. Eight hundred and eighty genes were conservatively identified as being modulated by TTEs within 12 h post-inoculation (hpi), 20% of which represented transcripts previously induced by the bacteria at 2 hpi. Significant over-representation of co-regulated transcripts encoding leucine rich repeat receptor proteins and protein phosphatases were, respectively, suppressed and induced 12 hpi. These data support a model in which the pathogen avoids detection through diminution of extracellular receptors and attenuation of kinase signalling pathways. Transcripts associated with several metabolic pathways, particularly plastid based primary carbon metabolism, pigment biosynthesis and aromatic amino acid metabolism, were significantly modified by the bacterial challenge at 12 hpi. Superimposed upon this basal response, virulence factors (most likely TTEs) targeted genes involved in phenylpropanoid biosynthesis, consistent with the abrogation of lignin deposition and other wall modifications likely to restrict the passage of nutrients and water to the invading bacteria. In contrast, some pathways associated with stress tolerance are transcriptionally induced at 12 hpi by TTEs. [source]

Body composition and time course changes in regional distribution of fat and lean tissue in unselected cancer patients on palliative care,Correlations with food intake, metabolism, exercise capacity, and hormones

CANCER, Issue 10 2005
Marita Fouladiun M.D.
Abstract BACKGROUND Several investigations that yielded different results in terms of net changes in body composition of weight-losing cancer patients have been reported that employed a variety of methods based on fundamentally different technology. Most of those reports were cross-sectional, whereas to the authors' knowledge there is sparse information available on longitudinal follow-up measurements in relation to other independent methods for the assessment of metabolism and performance. METHODS For the current report, the authors evaluated time course changes in body composition (dual-energy X-ray absorptiometry) with measurements of whole body and regional distribution of fat and lean tissue in relation to food and dietary intake, host metabolism (indirect calorimetry), maximum exercise capacity (walking test), and circulating hormones in cancer patients who were receiving palliative care during 4,62 months of follow-up. The entire cohort comprised 311 patients, ages 68 years ± 3 years who were diagnosed with solid gastrointestinal tumors (84 colorectal tumors, 74 pancreatic tumors, 73 upper gastrointestinal tumors, 51 liver-biliary tumors, 3 breast tumors, 5 melanomas, and 21 other tumor types). RESULTS Decreased body weight was explained by loss of body fat, preferentially from the trunk, followed by leg tissue and arm tissue, respectively. Lean tissue (fat-free mass) was lost from arm tissue, whereas trunk and leg tissue compartments increased, all concomitant with declines in serum albumin, increased systemic inflammation (C-reactive protein, erythrocyte sedimentation rate), increased serum insulin, and elevated daily caloric intake; whereas serum insulin-like growth factor 1 (IGF-1), resting energy expenditure, and maximum exercise capacity remained unchanged in the same patients. Serum albumin levels (P < 0.001), whole body fat (P < 0.02), and caloric intake (P < 0.001) predicted survival, whereas lean tissue mass did not. Daily intake of fat and carbohydrate was more important for predicting survival than protein intake. Survival also was predicted by serum IGF-1, insulin, leptin, and ghrelin levels (P < 0.02 , P < 0.001). Serum insulin, leptin, and ghrelin (total) levels predicted body fat (P < 0.001), whereas IGF-1 and thyroid hormone levels (T3, free T3) predicted lean tissue mass (P < 0.01). Systemic inflammation primarily explained variation in lean tissue and secondarily explained loss in body fat. Depletion of lean arm tissue was related most to short survival compared with the depletion of lean leg and trunk tissue. CONCLUSIONS The current results demonstrated that body fat was lost more rapidly than lean tissue in progressive cancer cachexia, a phenomenon that was related highly to alterations in the levels of circulating classic hormones and food intake, including both caloric amount and diet composition. The results showed importance in the planning of efficient palliative treatment for cancer patients. Cancer 2005. © 2005 American Cancer Society. [source]