Exploratory Data Analysis of Cell and Mitochondrial High-Fat, High-Sugar Toxicity on Human HepG2 Cells

Non-alcoholic steatohepatitis (NASH), one of the deleterious stages of non-alcoholic fatty liver disease, remains a significant cause of liver-related morbidity and mortality worldwide. In the current work, we used an exploratory data analysis to investigate time-dependent cellular and mitochondrial effects of different supra-physiological fatty acids (FA) overload strategies, in the presence or absence of fructose (F), on human hepatoma-derived HepG2 cells. We measured intracellular neutral lipid content and reactive oxygen species (ROS) levels, mitochondrial respiration and morphology, and caspases activity and cell death. FA-treatments induced a time-dependent increase in neutral lipid content, which was paralleled by an increase in ROS. Fructose, by itself, did not increase intracellular lipid content nor aggravated the effects of palmitic acid (PA) or free fatty acids mixture (FFA), although it led to an up-expression of hepatic fructokinase. Instead, F decreased mitochondrial phospholipid content, as well as OXPHOS subunits levels. Increased lipid accumulation and ROS in FA-treatments preceded mitochondrial dysfunction, comprising altered mitochondrial membrane potential (ΔΨm) and morphology, and decreased oxygen consumption rates, especially with PA. Consequently, supra-physiological PA alone or combined with F prompted the activation of caspase pathways leading to a time-dependent decrease in cell viability. Exploratory data analysis methods support this conclusion by clearly identifying the effects of FA treatments. In fact, unsupervised learning algorithms created homogeneous and cohesive clusters, with a clear separation between PA and FFA treated samples to identify a minimal subset of critical mitochondrial markers in order to attain a feasible model to predict cell death in NAFLD or for high throughput screening of possible therapeutic agents, with particular focus in measuring mitochondrial function.

Effects of diet and water supply on energy intake and water loss in a mygalomorph spider in a fluctuating environment of the central Andes

The metabolic and water evaporation strategies in spiders may be part of a set of physiological adaptations to tolerate low or unpredictable food availability, buffering spiders against environmental fluctuations such as those of the high mountains of the central Andes. The aim of this study is to analyze experimentally the variations in metabolic rate and the rate of evaporative water with food and/or water restriction in a high mountain mygalomorph spider population (Paraphysa sp.). We found that the low metabolism of this spider was not affected by water restriction, but its metabolism was depressed after 3 weeks of food deprivation. The spider did not show seasonal metabolic changes but it presented seasonal changes in the rate of evaporative water loss at high temperatures. Females with egg sacs reduced their metabolic rate and evaporative water at high temperatures. These findings constitute a set of possible adaptations to a highly fluctuating Mediterranean environment, which is completely covered with snow for many months and then progresses rapidly to a very dry climate with high temperatures.

Participation of book lungs in evaporative water loss in Paraphysa parvula, a migalomorph spider from Chilean Andes

Small animals need efficient water conservation mechanisms for survival and reproduction, which is relevant for the spiders that have large book lungs with large respiratory surface. If lung evaporation is relevant to limit water loss, adjustments of the spiracle opening to metabolic demands should be expected. In this study, we measured the metabolic rate and total evaporative water loss mediated by the opening of the spiracles in the migalomorph spider Paraphysa parvula, a resident of fluctuating Mediterranean environments of the mountains of central Chile. We found that the metabolism of P. parvula was similar to other Theraphosidae and low compared to other arthropods. Carbon dioxide production and evaporative water loss increased with temperature, particularly at 40 degrees C. The total evaporative water loss at 40 degrees C increased dramatically to about 10 times that found with the lower temperatures. Thus, 40 degrees C will be the limit temperature for this species after which evaporative water loss starts to become damaging, so it has to avoid it. The exposition to hypercapnic environments had as a consequence an increase in evaporative water loss and the involvement of the book lungs in this loss was about 60%. The possibility of losing water could condition this species to seek temperate and oxygenated shelters under rocks.

Relation of glucocorticosteroids and testosterone to the annual cycle of free-living degus in semiarid central Chile

We investigated seasonal patterns of plasma glucocorticosteroids (GCs) in both sexes and testosterone (T) in males in relation to the annual cycle in central Chile of a natural population of the degu (Octodon degus), a caviomorph rodent. We wanted to find out which GCs are present in degus, whether their seasonal variation suggests suppressive or synergistic interrelationships with T, and whether seasonal variation in GC levels indicates a relationship with energy mobilization and demands of reproduction. Degus mated in late autumn, and female body mass increased in pregnancy and remained high during lactation and throughout spring. Over the subsequent period of summer drought both sexes declined to a minimal body mass before the next mating season. Cortisol appears to be the principal GC in degus. In fact cortisol levels were so high that the extremely low levels of corticosterone measured were probably largely due to the cross-reactivity of our corticosterone antiserum with cortisol. Titers of cortisol in females exceeded 1000 ng/ml at lactation in the spring of 2 years; cortisol declined greatly following lactation and during the summer and reached its lowest mean level of about 500 ng/ml at mating. Males were more difficult to capture than females and thus our sampling was limited, but male cortisol levels were similar to those of females during the times of year when we measured them. Male T levels remained within a low range all year, but at mating, when mean T was highest (0.16 ng/ml) and when most males had detectable T, degus showed their lowest cortisol levels. The minimal cortisol level of males during mating represents a possible suppressive effect of T, as described in other mammals. At the time of their spring emergence, 60% of juvenile males had detectable T levels comparable to those of adults, suggesting important organizational effects of T at that time in their maturation. Peak cortisol titers in both sexes were associated with lactation in females, when energy mobilization, production, and body mass were at their greatest.

Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy

Animals must match their foraging and digestion to seasonal changes in availability and quality of food. When these parameters decline, the animal's performance limits for extracting energy and nutrients may be challenged. In the laboratory, we investigated daily patterns of food processing on a low-quality (high-fiber) diet of alfalfa in an herbivorous, day-active rodent, the degu (Octodon degus), which inhabits semiarid central Chile. We manipulated timing of food availability, from continuous availability down to as little as 5 h/d. Degus maintained weight while digesting only 53% of dry-matter consumption. With food continuously available in a metabolic cage, the animals ate more food and deposited about twice as much feces in the day as at night. Continuous 24-h behavioral observation revealed that degus were actually defecating at the same rate both night and day but then ingesting most of the feces they produced at night. Further experimental treatments challenged animals with limited periods of food availability that matched natural foraging patterns. With either 11 h of daytime food availability or only 5 h (in morning and afternoon periods of 2.5 h each), degus consumed as much food as those with 24-h food availability. Continuous 24-h behavioral observations revealed in the 11-h group that nearly all feces produced at night were reingested and nearly none were reingested in the day, whereas the 5-h group resorted to further coprophagy during the 6-h midday interval with no food. Despite these differences in timing of food intake and coprophagy in response to the three experimental treatments, the degus were defecating at the same rate both night and day, which indicated a constant rate of output from the colon. This suggests a range of adjustments of digestive physiology to the timing of gut function by balancing coprophagy with ingestion of food. Overall, 38% of 24-h feces production was reingested, and 87% of this coprophagy occurred at night. The ingestion of feces during parts of the day when food is unavailable provides for continued intake into the digestive tract and appears to represent an increase in overall efficiency of gut use.

A putative pyruvate dehydrogenase alpha subunit gene from Trypanosoma cruzi

A full-length DNA clone encoding a putative pyruvate dehydrogenase alpha subunit (E1 alpha) gene was isolated from a Trypanosoma cruzi (RA strain) DNA library. Sequencing of this clone revealed it to encode a 378 amino acid protein (M(r) 42774) with high sequence similarity to E1 alpha obtained from different sources. The highest score is obtained with human E1 alpha: 43,3% similarity. Southern blot analysis is consistent with the existence of a single copy of this putative T. cruzi E1 alpha gene per haploid genome in different parasite strains. Expression of this gene was demonstrated by Northern blot analysis and its trans-splicing acceptor site was identified by Polymerase Chain Reaction-mediated amplification of its cDNA.

Diagnostic value of detecting specific IgA and IgM with recombinant Trypanosoma cruzi antigens in congenital Chagas' disease

The present study compares the early diagnosis of congenital Chagas' disease with a DOT assay using recombinant antigens with immunofluorescence antibody testing (IFAT) and an enzyme-linked immunosorbent assay (ELISA). The studies were performed using cord blood and sera of 12 infected newborns (group I) and 12 uninfected ones born to Trypanosoma cruzi-infected mothers (group II). Conventional IFAT and ELISA showed positive results for IgG at high titers, in infants and mothers of both groups; IgA antibodies were detected by ELISA in four of the infected infants and IgM was detected in two of them. All sera of the uninfected infants were negative for IgA and IgM in the ELISA. Application of a DOT assay using eight recombinant T. cruzi antigens allowed detection of specific IgA in the cord blood of six of the infected cases and IgM in eight of them. Repetition of these serologic tests in samples obtained during a monthly follow-up gave positive results for IgA in two of the initially negative infants of group I and for IgM in four of them. This means that diagnosis of congenital T. cruzi infection was confirmed, through demonstration of specific IgM, in all infected infants, and of IgA in eight of them. The importance of late detection of IgM in siblings born of infected mothers is discussed. The detection of IgM and IgA in sera obtained after birth is believed to be due to a congenital transmission of the parasite that occurred late in pregnancy. No IgA or IgM antibodies could be detected by the DOT assay in the sera of the negative controls.(ABSTRACT TRUNCATED AT 250 WORDS)

[The diagnosis of chronic Chagas disease using recombinant antigens of Trypanosoma cruzi]

A panel of eight recombinant Trypanosoma cruzi antigens was used to study the IgG reactivity of sera proceeding from 151 patients with chronic Chagas disease. These samples were reactive against T Cruzi epimastigotes by immunofluorescence and enzyme linked assays. A dot blot assay was performed to evaluate the reactivity against recombinant clones 1, 2, 13, 26, 30, 36, 54 and SAPA (Shed Acute Phase Antigen). Ninety six percent of samples reacted against one or more of these antigens. The most frequently recognized proteins were clones 1, 2, 13, 36 and 26 with 90, 89, 76, 71 and 66 percent of reactivity respectively. Less than 50% of sera reacted against clones 30, 54 and SAPA. Sera from symptomatic patients had a significantly higher frequency of reactivity against clone SAPA than those from asymptomatic patients. This difference suggests that a high reactivity against clone SAPA may be related to acute infections and symptoms. No significant relationship could be established between specific recombinant clone recognitions and particular clinical forms of the disease (cardiological or digestive). It is concluded that these recombinant proteins may become a good tool for the evaluation of the immune response of patients infected with T. cruzi.

Immunodetection of antibodies in sera from symptomatic and asymptomatic Chilean Chagas' disease patients with Trypanosoma cruzi recombinant antigens

A panel of eight Trypanosoma cruzi antigens produced by recombinant DNA techniques was used to compare the reactivity of IgG specificities in the sera from 45 chronic Chagas' disease patients with different clinical symptoms (cardiac disease, gastrointestinal lesions, and combined syndrome) with those present in the sera from 55 asymptomatic patients in Chile. All of the serum samples were first characterized for antibody to T. cruzi epimastigotes by immunofluorescence assay. All of the Chagas' disease sera were reactive, but none of five healthy controls whose sera were also tested had antibodies against the fixed parasites. A dot-blot assay was then performed to evaluate the serum reactivity against recombinant DNA clones 1, 2, 13, 26, 30, 36, 54, and SAPA (shed acute phase antigen). These recombinant antigens were recognized by a large proportion of the sera collected from the Chilean patients. Ninety-five percent of the serum samples reacted with one or more of the recombinant clones. Analysis of the reactivity with individual fusion proteins showed that 88% of these sera reacted with clones 1 and 2, and 78% reacted with clone 13. Differences in reactivity to clones number 13, 30, and SAPA were observed when symptomatic and asymptomatic patients were compared. These differences in reactivity were statistically significant (P less than 0.01) according to Fisher's exact test.

Evaluation of an enzyme-linked immunosorbent assay for the diagnosis of Chagas' disease using synthetic peptides

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect antibodies in human sera to synthetic peptides derived from the repeating amino acid sequence in recombinant Trypanosoma cruzi antigens. Sixty serum samples from patients with chronic Chagas' disease were used to determine the reactivity against the synthetic repeat peptides derived from clones 1, 2, 30, 36, and shed acute phase antigen (SAPA). Ninety-eight percent of the samples had detectable antibodies to one or more of the synthetic peptides at titers greater than 1:100. The percentage of reactive sera increased from 28% with peptide SAPA to 93% with peptide 2. The exposure of patients to T. cruzi was reflected in indirect immunofluorescent antibody titers to fixed epimastigotes. Comparisons between ELISA and immunoradiometric assay data indicated that both tests were of approximately equal sensitivity.

Assay for detection of Trypanosoma cruzi antibodies in human sera based on reaction with synthetic peptides

Synthetic peptides modelled according to the amino acid sequences derived from the repeated domains of five Trypanosoma cruzi antigens were used in an immunoradiometric assay to detect antibodies appearing after natural human infections. An enzyme-linked immunosorbent assay and an indirect immunofluorescence assay performed with a complex antigenic mixture from parasites were used as controls. The results indicate that the synthetic peptides were recognized by a large proportion of serum samples collected from 34 patients with Chagas' disease in Chile and point to their possible use in diagnosis.