Effects of peroxidized polyunsaturated fatty acids on mitochondrial function and structure: pathogenetic implications for Reye's syndrome

Linoleic acid, a polyunsaturated fatty acid, is a constituent of margosa oil which has been implicated as a cause of Reye's syndrome (RS) in infants. Increased concentrations of polyunsaturated fatty acids have been found in sera from patients with RS. Isolated rat liver mitochondria exposed to the peroxidized (but not unperoxidized) methyl esters of linoleic (C18:2) or linolenic (C18:3) acids showed decreases in state 3 and uncoupled respiratory rates and in respiratory control and ADP/O ratios. In addition, they caused mitochondrial swelling as demonstrated spectrophotometrically. Between the two, the peroxidized methyl ester of linolenic acid was more toxic and was capable of inducing high amplitude swelling ultrastructurally similar to that seen in the hepatocytes of RS victims. The ability of rat liver mitochondria to oxidize glutamate was inversely related to the peroxide concentration in the medium. This accords with the reports of reduced glutamic dehydrogenase activities in the livers of both patients with Reye's syndrome and rats treated with margosa oil.     

Hydroxypropylated distarch phosphate versus unmodified tapioca starch: fat oxidation and endurance in C57BL/6J mice

An RS4-type resistant starch is a chemically modified starch that shows reduced availability in comparison to the corresponding unmodified starch. Hydroxypropylated distarch phosphate (HDP) is an RS4-type resistant starch that increases energy expenditure and prevents high-fat diet-induced obesity through increased hepatic fatty acid oxidation. The aim of this study was to clarify the acute effects of HDP from tapioca starch (HPdTSP) on physical performance in mice. Male C57BL/6J mice were used to examine the effects of a single administration of 2 mg/g body weight HPdTSP or unmodified tapioca starch (TS) on postprandial responses in serum metabolic parameters, running endurance capacity on a treadmill, whole-body energy metabolism during exercise, activity of enzymes involved in fatty acid oxidation, liver and gastrocnemius muscle glycogen content, and serum glucose, insulin, non-esterified fatty acid, lactate, and triglyceride levels after exercise. Running time to fatigue was significantly greater in HPdTSP mice than in TS mice. Furthermore, HPdTSP maintained higher fat oxidation and this was associated with a greater activity of enzymes in fatty acid oxidation in the muscle during exercise. The blood lactate and serum insulin levels after exercise was significantly lower in HPdTSP mice than in TS mice. Liver glycogen was significantly higher in HPdTSP mice than in TS mice. These results suggest that acute oral administration of the RS4-type resistant starch, HPdTSP, maintained higher fat oxidation and reduced liver glycogen consumption during exercise and increased running endurance capacity in mice.     

Metformin regulates palmitate-induced apoptosis and ER stress response in HepG2 liver cells

The excessive supply of fatty acids to the liver contributes to hepatic insulin resistance and endoplasmic reticulum (ER) stress associated with obesity or type 2 diabetes mellitus. Furthermore, excess and/or prolonged ER stress contributes to hepatic cell death deteriorating nonalcoholic fatty liver disease to steatohepatitis. The aim of this study was to investigate the effects of metformin on palmitate-induced ER stress and hepatic insulin resistance in HepG2 cells. Metformin significantly inhibited palmitate-induced cell death and apoptosis via caspase-3 activation. Metformin also blocked the induction of ER stress proteins (GRP78, Chop, Cleaved ATF-6, p-eIF2 alpha and XBP-1) and regulated serine phosphorylation of IRS-1. Metformin may therefore protect hepatocytes from death induced by saturated fatty acids. These data may also provide a further rationale for exploring the use of metformin in the treatment of non-alcoholic fatty liver disease, revealing its blocking effect for hepatic insulin resistance evoked by saturated fatty acids.     

Evaluation and management of extrahepatic manifestations of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a multisystemic disease and a rapidly growing cause of chronic liver disease in children and adults worldwide. Diagnosis and management of extrahepatic manifestations of NAFLD, including cardiovascular disease (CVD), type 2 diabetes mellitus, metabolic syndrome, chronic kidney disease, obstructive sleep apnea, polycystic ovarian syndrome, hypothyroidism, psoriasis, and extrahepatic malignancy are crucial for the treatment of patients with NAFLD. The leading cause of death in NAFLD is primarily from CVD, followed by liver-related mortality, extrahepatic cancer, liver cancer, and diabetes-related mortality. Therefore, clinicians need to identify high-risk patients earlier in the disease course and be aware of the extrahepatic manifestations of NAFLD to improve liver disease outcomes. In this review, we focus on the monitoring and management of the extrahepatic manifestations of NAFLD.     

Effects of succinate dimethyl ester on the metabolic and hormonal response to exercise in fed and starved rats

This study aims at investigating the possible beneficial effect of succinic acid dimethyl ester (SAD), injected intraperitoneally (5.0 micromol/g body wt.), upon the metabolic and hormonal response to a 60 min exercise in both fed and overnight starved rats. In fed rats, the injection of SAD minimized the fall in plasma D-glucose concentration, and the increase in plasma lactate, beta-hydroxybutyrate, free fatty acid and glycerol concentrations, otherwise provoked by exercise. SAD, however, failed to prevent the decrease in plasma insulin concentration and liver glycogen content caused by exercise. Starved rats displayed lower plasma D-glucose and insulin concentrations and higher plasma beta-hydroxybutyrate and free fatty acid concentrations than fed rats. The body weight, liver weight and paraovarian fat weight, as well as the glycogen content of both liver and heart were also decreased in the starved rats. In the latter animals, the injection of SAD again opposed the exercise-induced increase in plasma beta-hydroxybutyrate, free fatty acid and glycerol concentrations, and again failed to prevent the more modest decreases in plasma insulin concentration and liver glycogen content caused by exercise in the starved, as distinct from fed rats. These findings suggest that, independently of any obvious change in plasma insulin concentration, SAD minimizes the exercise-induced mobilization and enhanced utilization of endogenous nutrients, especially fatty acids and glycerol produced by hydrolysis of triglycerides in adipose tissue, presumably through its capacity to act as an oxidizable nutrient in various cell types and as a gluconeogenic precursor in hepatocytes.     

Scanning microdensitometry of glycogen zonation in the livers of rats adapted to a controlled feeding schedule and to 30, 60, or 90% casein diets

The effect of diet composition on diurnal changes in glycogen zonation patterns in rat liver was investigated in individually-caged male Sprague-Dawley rats adapted to the 2 + 22 controlled feeding and lighting schedule and to diets containing 30% casein/55% carbohydrates, 60% casein/25% carbohydrates, or 90% casein (30 rats/dietary group). Three rats from each dietary group were killed at the following times relative to the onset of feeding (0 min):?60, ?30, 0, 15, 30, 45, 60, 90, 120, and 180 min. Glycogen in cryostat sections from the median and right lateral lobes of the liver was fixed and stained by standard techniques. The optical density of glycogen at points along the path between the central and portal veins of a given lobule was determined, and lobular glycogen gradients of replicate animals were integrated to form a composite lobular glycogen distribution profile. In the period from ?60 to 0 min, liver glycogen levels were similar for rats on any of the diets, and the glycogen concentration was similar in periportal (P), midlobular (M), and centrilobular (C) hepatocytes. During the 0- to 45-min period, diet-related glycogen depletion occurred (90 > 60 ? 30% casein) by asymmetrical glycogen loss (P > M ? C hepatocytes) from the liver lobules. Similar food intake curves occurred for all diets. During the 45- to 180-min period, asymmetrical glycogen accumulation began in lobular parenchymal cells (P > M ? C hepatocytes), and the rate of accumulation was related to dietary composition (30 > 60 ? 90% casein). The differential responses of parenchymal cells within liver lobules to physiological stimuli resulted in glycogen distributional changes that were rapid and of large magnitude. Our results are consistent with the hypothesis that periportal and midlobular hepatocytes are more metabolically responsive and active than centrilobular hepatocytes.     

Dietary carbohydrate and its effects on metabolism and substrate stores in sedentary and active individuals.

This review of carbohydrate (CHO) ingestion and exercise addresses three major issues: (a) how CHO ingestion influences CHO and fat stores, (b) how exercise, by changing CHO stores, alters the responses to CHO or fat ingestion, and (c) the roles of CHO in exercise performance and metabolism. Dietary manipulation is not a simple issue; increasing the dietary content of any specific nutrient alters the entire diet composition. High CHO diets are often low fat diets, hence changing the metabolism and storage of both fat and CHO. Acute CHO ingestion increases CHO oxidation and the "spared" fats are deposited as fat. Chronic high CHO ingestion (without an active lifestyle) leads to muscle becoming insulin-insensitive, adipose tissue processing CHO to fatty acids, and the liver increasing production of VLDL triglycerides. CHO ingestion prior to and during prolonged exercise can increase endurance. It has been suggested that moderate or low glycemic index forms be used prior to and during the exercise, but there is no consensus as to whether it should be a recommendation. The physiological nature of the regulation of CHO stores is poorly understood, but the recent identification of a key enzyme, glycogenin, and two forms of glycogen (pro- and macroglycogen) show promise of a deeper understanding.     

Metabolic effects of glucose,medium chain triglyceride and long chain triglyceride feeding before prolonged exercise in rats

Summary The purpose of this study was to test the hypothesis that oral ingestion of lipids could increase endurance by slowing the rate of glycogen depletion. Trained rats were killed after a 2 h run on a rodent treadmill, following an intragastric infusion of water, glucose, medium chain triglycerides (MCT) or long chain triglycerides (LCT). Glucose and triglycerides were administered in equicaloric concentrations (50 kJ).The results show that oral ingestion of lipids (MCT or LCT) did not reduce glycogen depletion in liver, heart or skeletal muscle after exercise whereas the fat diet increased muscle and heart glycogen stores in resting conditions. In contrast, glucose feeding induced a significant sparing effect on endogenous carbohydrate utilization and reduced physical exercise lipolysis. These data indicated, firstly, that enhanced lipid availability induced by a single lipid meal before exercise was not able to modify the glycogen depletion occuring after exercise and, secondly, that the glucose/fatty acid cycle was not effective in these conditions. The comparison between lipids indicated that the effect on glycogen use of MCT did not differ from that of LCT, and did not seem to be of any particular importance during physical exercise.     

Fatty liver and sudden death. A review

Alcoholism is associated with increased mortality from violent and nonviolent causes. The increase in nonviolent deaths is usually ascribed, at least in part, to "cirrhosis." In the majority of these deaths this implies fatty liver rather than true Laennec's cirrhosis. Studies of sudden nonviolent deaths illustrate the largely unrecognized and frequent occurrence of sudden death with autopsy findings limited solely to fatty liver. The mechanism(s) of these sudden fatty liver deaths is unknown. Several attractive theories attribute such deaths to ethanol withdrawal induced hypoglycemia or hypomagnesemia, pulmonary fat embolization from fatty liver, or other facets of the alcohol withdrawal syndrome, including ethanol dependent maladaptive derangements of neurotransmitters. All the theories of fatty liver death remain essentially untested, however, owing to uncontrolled postmortem conditions and the lack of awareness of fatty liver deaths within the scientific community.     

Endoplasmic reticulum stress, hepatocyte CD1d and NKT cell abnormalities in murine fatty livers

The liver regulates lipid homeostasis and is enriched with natural killer T (NKT) cells that respond to lipid antigens. Optimal maturation and activation of NKT cells requires their interaction with lipid antigens that are presented by cluster of differentiation-1 (CD-1) molecules on antigen-presenting cells. Hepatocytes express CD1d and present lipid antigens to NKT cells. Depletion and dysregulation of hepatic NKT cells occurs in mice with fatty livers. Herein, we assess whether reduced CD1d content on steatotic hepatocytes contributes to fatty liver-associated NKT cell abnormalities. We show that despite expressing normal levels of CD1d mRNA, fatty hepatocytes from ob/ob mice have significantly less CD1d on their plasma membranes than normal hepatocytes. This has functional significance because ob/ob hepatocytes are less able to activate CD1d-restricted T-cell responses in vitro, and CD1d-reactive NKT cells are reduced in ob/ob livers. Events in the endoplasmic reticulum (ER) normally regulate CD1d trafficking to plasma membranes. Hepatic steatosis has been associated with ER stress. To determine if ER stress reduces CD-1 accumulation on hepatocytes, we evaluated hepatic ER stress in ob/ob mice and treated cultured hepatocytes and lean mice with tunicamycin to induce ER stress. Lipid accumulation and ER stress occurred in the livers of both ob/ob and tunicamycin-treated mice. Tunicamycin caused dose-dependent decreases in hepatocyte CD1d, inhibited hepatocyte activation of CD1d-restricted T-cell responses, depleted liver populations of CD1d-reactive NKT cells and promoted Th-1 polarization of hepatic cytokine production. In conclusion, ER stress-related decreases in hepatocyte CD1d contribute to NKT cell dysregulation in fatty livers.     

Costaining for keratins 8/18 plus ubiquitin improves detection of hepatocyte injury in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is a global health dilemma. The gold standard for diagnosis is liver biopsy. Ballooned hepatocytes are histologic manifestations of hepatocellular injury and are characteristic of steatohepatitis, the more severe form of nonalcoholic fatty liver disease. Definitive histologic identification of ballooned hepatocytes on routine stains, however, can be difficult. Immunohistochemical evidence for loss of the normal hepatocytic keratin 8/18 can serve as an objective marker of ballooned hepatocytes. We sought to explore the utility of a keratin 8/18 plus ubiquitin double immunohistochemical stain for the histologic evaluation of adult nonalcoholic fatty liver disease. Double immunohistochemical staining for keratin 8/18 and ubiquitin was analyzed using 40 adult human nonalcoholic fatty liver disease core liver biopsies. Ballooned hepatocytes lack keratin 8/18 staining as previously shown by others, but normal-size hepatocytes with keratin loss are approximately 5 times greater in number than keratin-negative ballooned hepatocytes. Keratin-negative ballooned hepatocytes, normal-size hepatocytes with keratin loss, and ubiquitin deposits show a zonal distribution, are positively associated with each other, and are frequently found adjacent to or intermixed with fibrous matrix. All 3 lesions correlate with fibrosis stage and the hematoxylin and eosin diagnosis of steatohepatitis (all P < .05). Compared with hematoxylin and eosin staining, immunohistochemical staining improves the receiver operating characteristics curve for advanced fibrosis (0.77 versus 0.83, 0.89, and 0.89 for keratin-negative ballooned hepatocytes, normal-size hepatocytes with keratin loss, and ubiquitin, respectively) because immunohistochemistry is more sensitive and specific for fibrogenic hepatocellular injury than hematoxylin and eosin staining. Keratin 8/18 plus ubiquitin double immunohistochemical stain improves detection of hepatocyte injury in nonalcoholic fatty liver disease. Thus, it may help differentiate nonalcoholic steatohepatitis from nonalcoholic fatty liver.     

Lipopeliosis: fat induced sinusoidal dilatation in transplanted liver mimicking peliosis hepatis.

A distinct peliosis-like lesion arose in the liver allograft of a 51 year old man. This lesion was caused by necrotic, fat-laden hepatocytes that released fat globules into the sinusoids. These then became strikingly distended with cysts, thus mimicking peliosis hepatitis. It is suggested that this lesion be called lipopeliosis.     

Colchicine-induced inhibition of fat globule development in hepatocytes of rats injected with ethionine

To examine the effect of colchicine on ethionine-induced fatty liver, adult female rats were starved overnight and then injected i.p. with 1 g/kg ethionine at 11th hour of fasting; then a half of the rats were also injected i.p. with 2.5 mg/kg colchicine twice at 3 and 6 h after the single administration of ethionine. Similarly, fasted control rats were injected i.p. with vehicle alone at the above times. All of the rats were sacrificed after a 20-h fast, and the hepatocytes in periportal areas were observed ultrastructurally. In addition, total lipids in the liver tissue were extracted and determined biochemically. Although similar significant increases of triglyceride were observed in the liver tissue of all ethionine-injected rats, the hepatocytes in the group treated with both chemicals had fewer cytoplasmic fat globules (CFG) than those in the group treated with ethionine only. On the other hand, the diameters of markedly increased membrane-bound lipid particles (MLP) in the double-treated group were distributed mainly in the range 0.2-0.4 micron, compared with those (0.1-0.2 micron) in the other groups. These findings indicate that colchicine inhibits the development of CFG in ethionine-injured hepatocytes.     

Smooth endoplasmic reticulum proliferation and increased cell multiplication in cultured hepatocytes of the newborn rat in the presence of phenobarbital

Twenty-eight-day old male Sprague-Dawley rats were fed diets containing 2, 5, 10, 15, 25, or 50% protein and varying levels of fat and energy for 8 weeks and were then killed. The livers of rats fed the 2% lactalbumin protein diet ad libitum but not the others showed visible fat. This difference was confirmed histologically. Chemical analyses of the livers indicated that the rats fed the 2% protein diets ad libitum had experienced a substantial reduction in liver cell size but only a very slight reduction in the lipid content of each cell. As a consequence, their livers showed a net increase in the amount of lipid per g of tissue and this gave them a fatty appearance. The lipids formed large fat globules suspended in a greatly reduced amount of protoplasm; there were no fat globules outside the cells. Therefore, the fatty liver of protein deficiency was a physical phenomenon rather than a metabolic defect. Rats fed the 2% protein diets in restricted amounts also had shrunken cells but they did not manifest fatty liver because there was a relatively greater reduction in liver cell lipid than in liver cell size. There was a reduced amount of protein in the livers of rats fed 2 and 5% protein diets which can be explained by a reduction in liver RNA and in Protein/RNA ratio. Protein/RNA ratio was enhanced by starvation. Liver protein content showed a biphasic response to variation in dietary fat level with its lowest value in rats fed diets containing 11.9% fat.     

Liver composition and histology of rainbow trout fed cyclopropenoid fatty acids.

Rainbow trout were fed 200 ppm cyclopropenoid fatty acids (CPFA) in a semipurified casein-gelatin-dextrin diet for 8 months. Liver weights, liver fat, and glycogen levels were measured during the course of the exepriment and compared with those of control fish. The effect of CPFA on liver histology was also monitored and was found to produce necrosis of hepatocytes, unusual glycogen deposition, appearance of “fibers” in the cytoplasm of many cells, and fibrotic bile ducts and blood vessels. Most of these histological abberations remained after MS was removed from the diet. Liver size, expressed as a percentage of body weight, in CPFA-fed fish became significantly larger (P < 0.05) after 7 months and remained higher until the feeding trial was terminated. Percentage of liver lipids was significantly higher (P < 0.05) in CPFA-fed fish, but returned to normal when the fish were returned to control diet.     

Reye综合征24例尸检报道

Reye综合征(Reye syndrome,RS)是一种急性非炎性脑病—内脏脂肪变性综合征,主要累及儿童和青少年,常发生在前驱疾病的恢复期,其病因和发病机理仍不清楚。本文对24例RS尸检资料进行了回顾性研究,并对本病的诊断标准、RS肝脏的病理学、肝穿刺活检的重要性和成人RS等进行讨论。     

Phlorizin induced autophagocytosis during hepatocytic glycogenolysis

The naturally occurring glucoside, phlorizin, produces massive hepatic glycogenolysis. The mechanism by which glycogen breakdown occurs is unknown. This treatment induces acute glycogenolysis which is limited to the hepatocytes of the portal third of the liver lobule. Electron microscopic examination of these hepatocytes revealed rapid sequestration of masses of glycogen as well as mitochondria within cytoplasmic membranes. These cytosegresomes rapidly acquired acid phosphatase by fusion with lysosomes. Glucose administration did not inhibit this process. These data indicated that a large portion of glycogen degradation induced by phlorizin results from lysosomal reaction. It is suggested that phlorizin produces glycogenolysis by blockade of glucose transport, resulting in a pseudohypoglycemia.     

Post-exposure targeting of specific epitopes on ricin toxin abrogates toxin-induced hypoglycemia, hepatic injury, and lethality in a mouse model

Effects in the liver of fatal intoxication with the binary toxin ricin are unclear. We report a robust neutrophil influx into the liver of C57BL/6 mice after lethal parenteral ricin challenge, occurring in peri-portal and centro-lobular hepatic areas within 2 h, followed by the abrupt disappearance of hepatic macrophages/Kupffer cells. Chemokine profiles determined by microarray, ribonuclease protection assays, northern blotting, and enzyme-linked immunosorbent assays showed rapid (2 h) upregulation and persistence of those for neutrophils (CXCL1/KC, CXCL2/MIP-2) and monocytes (CCL2/MCP-1). Red blood cell pooling (8-12 h), loss of hepatocyte glycogen (8-48 h) associated with progressive hypoglycemia, fibrin deposition (24-48 h), and death (72-96 h) followed. Monoclonal antibody to ricin A chain, administered intravenously, blunted hypoglycemia, and abrogated death. This outcome was observed when anti-ricin antibody was given before toxin exposure as well as when administered approximately 10 h after toxin exposure. Targeting antibody to specific amino-acid sequences on the ricin A chain (HAEL and QXXWXXA) was critical to the therapeutic effect. Re-emergence of liver macrophages/Kupffer cells and replenishment of glycogen in previously depleted hepatocytes preceded full recovery of the host. These data identify critical events for liver injury and healing in ricin intoxication, as well as a new means and specific targets for post-exposure therapeutic intervention.     

Reaction of the liver to the effects of hexachlorocyclohexane (experimental study)]

The effects of hexachlorocyclohexane (HCHCH) on the weight of the liver, content of protein, glycogen, total lipids as well as morphological and ultrastructural changes in the liver were studied. It was established that HCHCH caused a considerable increase in the weight of the liver, as well as in the levels of protein, glycogen and total lipids, which was particularly pronounced following prolonged administration of HCHCH in the dose 1/50 LD50. Large doses of HCHCH (1/3 LD50) brought about marked dystrophic changes in the liver similar to the type of hydropic degeneration, accumulation of fatty drops in hepatocytes Application of a dose 1/50 LD50 of HCHCH resulted in an increased size of hepatocytes, dystrophic changes being noted only in individual cells. Histochemisally there were revealed high levels of RNA and glycogen in hepatocytes. An-Electron-microscopy study of hepatic cells showed the most manifested changes in the endoplasmatic network of hepatocytes, which were seen in an enlargement of the elements of the smooth endoplasmatic reticulum. A suggestion was put forward that the changes indicated above were associated with a stimulating effect of HCHCH on the microsomic system of hepatocytes, i.e. on the enzymatic systems localized in the smooth endoplasmatic network.     

The diagnosis of fatal pulmonary fat embolism using quantitative morphometry and confocal laser scanning microscopy

The postmortem diagnosis of fat embolism syndrome (FES), traditionally based on the histological demonstration of fat globules, needs a quantitative analysis of both the size and localization of the fat emboli, which is essential for a reliable grading of the pulmonary fat embolism. The clinical data and the autopsy records of 2738 autopsies were retrospectively evaluated, and 21 cases in which FES was pointed out as cause of death were selected and compared with 21 fatal cases referred to as major trauma in which the cause of death was not attributed to fat embolism, and with 47 fatal cases as control group, respectively. The following parameters were investigated: the total area of the embolized tissue; the total number of emboli; the mean area of the emboli; the mean percentage of the embolized tissue area as compared with the total tissue area of each sample; the total percentage of the embolized tissue area as compared with the total tissue area of all slides. The most reliable parameters seem to be the ratio between embolized tissue areas as compared with the total tissue area of each sample. These parameters showed a good correlation with the clinical data.