Effect of sucrose on lipogenesis of rats chronically treated with ethanol

Summary The effect of chronic ethanol administration with and without sucrose on the lipogenic enzymes of liver and adipose tissue of rats was studied. Ethanol markedly influenced the adipose lipogenic enzymes at 28 days. Sucrose caused a 2-10fold increase in lipogenic enzymes of both adipose and liver.Acknowledgment. This work was supported in part by a grant from the North Carolina Alcohol Research Authority.     

Effect of PGE1 on lipogenesis in perfused rat liver.

In perfused livers of 24 hour-fasted rats, PGE1 (prostaglandin E1) infused continuously into the perfusate, was found to cause a 45% increase in the incorporation of 1-14C acetate into liver fatty acids. PGE1 was found to have no effect, however, on the activity of the key lipogenic enzymes.     

Effect of PGE1 on lipogenesis in perfused rat liver

Summary In perfused livers of 24 hour-fasted rats, PGE₁ (prostaglandin E₁) infused continuously into the perfusate, was found to cause a 45% increase in the incorporation of 1-¹⁴C acetate into liver fatty acids. PGE₁ was found to have no effect, however, on the activity of the key lipogenic enzymes.     

Triacylglycerol hydrolase: role in intracellular lipid metabolism

Recent scientific advances have revealed the identity of several enzymes involved in the synthesis, storage and catabolism of intracellular neutral lipid storage droplets. An enzyme that hydrolyzes stored triacylglycerol (TG), triacylglycerol hydrolase (TGH), was purified from porcine, human and murine liver microsomes. In rodents, TGH is highly expressed in liver as well as heart, kidney, small intestine and adipose tissues, while in humans TGH is mainly expressed in the liver, adipose and small intestine. TGH localizes to the endoplasmic reticulum and lipid droplets. The TGH genes are located within a cluster of carboxylesterase genes on human and mouse chromosomes 16 and 8, respectively. TGH hydrolyzes stored TG, and in the liver, the lipolytic products are made available for VLDL-TG synthesis. Inhibition of TGH activity also inhibits TG and apolipoprotein B secretion by primary hepatocytes. A role for TGH in basal TG lipolysis in adipocytes has been proposed. TGH expression and activity is both developmentally and hormonally regulated. A model for the function of TGH is presented and discussed with respect to tissue specific functions.     

Changes in mammary tissue lipid metabolism in the goats during the first 2 months of lactation]

5 French Alpine Goats were studied after normal or premature parturition. Mammary tissue acetyl-C oA carboxylase, glucose-6-phosphate dehydrogenase, malic enzyme and lipoprotein lipase (LPL) activities varied in parallel with milk fat secretion from the 3rd to the 9th week of lactation. Variations of mammary LPL activity and of long chain fatty acid secretion were positively highly correlated during that period. In goats with normal parturition, lipogenic activities seemed to reach a maximum level shortly after parturition. There was a positive correlation between mammary Ll activities and plasma non esterified fatty acid contents, possibly reflecting a relationship between adipose tissue mobilisation and mammary metabolism.     

Revisiting the metabolic syndrome: the emerging role of aquaglyceroporins

The metabolic syndrome (MetS) includes a group of medical conditions such as insulin resistance (IR), dyslipidemia and hypertension, all associated with an increased risk for cardiovascular disease. Increased visceral and ectopic fat deposition are also key features in the development of IR and MetS, with pathophysiological sequels on adipose tissue, liver and muscle. The recent recognition of aquaporins (AQPs) involvement in adipose tissue homeostasis has opened new perspectives for research in this field. The members of the aquaglyceroporin subfamily are specific glycerol channels implicated in energy metabolism by facilitating glycerol outflow from adipose tissue and its systemic distribution and uptake by liver and muscle, unveiling these membrane channels as key players in lipid balance and energy homeostasis. Being involved in a variety of pathophysiological mechanisms including IR and obesity, AQPs are considered promising drug targets that may prompt novel therapeutic approaches for metabolic disorders such as MetS. This review addresses the interplay between adipose tissue, liver and muscle, which is the basis of the metabolic syndrome, and highlights the involvement of aquaglyceroporins in obesity and related pathologies and how their regulation in different organs contributes to the features of the metabolic syndrome.     

Selective effect of noradrenaline on superoxide dismutase activity in the brown adipose tissue and liver of the rat

Summary Noradrenaline treatment results in a significant increase of superoxide dismutase activity in the intrascapular brown adipose tissue but not in the liver.     

Pseudocholinesterase in obesity: Hypercaloric diet induced changes in experimental obese mice

Summary Pseudocholinesterase activity is significantly higher in liver and serum, but lower in adipose tissue of genetically obese, diabetic and gold thioglucose treated mice. Similar enzyme changes were also observed in lean mice on a high carbohydrate diet. A marked reduction (40%) in PChE activity occurred in the liver of genetically diabetic mice when starved for 24 h. These observations suggest that pseudocholinesterase induction in the liver and repression in the adipose tissue is affected by excessive calorie intake in obesity. This provides a model to study the biological function of PChE in health and disease.Acknowledgments. We thank Dr Charles A. Janeway Child Health Centre and Faculty of Medicine, Memorial University of Newfoundland for financial support.     

The response of cyclic 3',5'-AMP and cyclic 3',5'-GMP phosphodiesterases to experimental diabetes

Alloxan diabetes caused a decrease in cyclic AMP phosphodiesterase in all affected rat tissues. Cyclic GMP phosphodiesterase activity was, however, decreased in adipose and liver, but increased increased in heart and uterus.     

Studying non-alcoholic fatty liver disease with zebrafish: a confluence of optics, genetics, and physiology

Obesity is a public health crisis. New methods for amelioration of its consequences are required because it is very unlikely that the social and economic factors driving it will be reversed. The pathological accumulation of neutral lipids in the liver (hepatic steatosis) is an obesity-related problem whose molecular underpinnings are unknown and whose effective treatment is lacking. Here I review how zebrafish, a powerful model organism long-used for studying vertebrate developmental programs, is being harnessed to uncover new factors that contribute to normal liver lipid handling. Attention is given to dietary models and individual mutants. I speculate on the possible roles of non-hepatocyte residents of the liver, the adipose tissue, and gut microbiome on the development of hepatic steatosis. The highlighted work and future directions may lead to fresh insights into the pathogenesis and treatment of excess liver lipid states.     

Regulation of liver lipogenic enzymes by dietary fats

Summary The hepatic lipogenic enzyme levels are more in rats on a fatfree diet and less in unsaturated fat-fed rats, the saturated fat-fed ones remaining in between.     

Increase in superoxide dismutase activity induced by thyroid hormones in the brains of neonate and adult rats

Summary The activity of cytoplasmic superoxide dismutase (SOD) in the liver was about twice as high in adult rats as it was in neonates. In the brain and in the interscapular brown adipose tissue (IBAT), SOD activity was not changed during postnatal development, although it was slightly higher in the brain than in the IBAT (p>0.1). Thyroid hormones produced an increase in SOD activity in the brain of newborn rats, as well as in those animals 30 and 60 days old. The same quantity of hormones did not produce any significant changes in the liver or in the IBAT.     

The response of cyclic 3′,5′-AMP and cyclic 3′,5′-GMP phosphodiesterases to experimental diabetes

Summary Alloxan diabetes caused a decrease in cyclic AMP phosphodiesterase in all affected rat tissues. Cyclic GMP phosphodiesterase activity was, however, decreased in adipose and liver, but increased in heart and uterus.This research was supported by U.S. Public Health Service grant RO1-AM19364-O1 and MARC training grant No. 1-TO2-GMO50000.     

Immunochemical identity of dipeptidyl aminopeptidase IV from pig serum, liver, submaxillary gland and kidney.

The enzymes which were extracted by autodigestion from the microsomal fractions of the pig kidney, liver and submaxillary gland and from the serum showed an immunochemical identity by a double immunodiffusion test. But the kidney enzyme had a different pI-value from the pI-values of the enzymes of other organs.     

Diphasic action of 2,2-diphenylpropionic acid N,N-diethylaminoethyl ester hydrochloride on hepatic drug metabolism in the mouse

Summary 2,2-Diphenylpropionic acid N,N-diethylaminoethyl ester hydrochloride, 30 min after a single i.p. dose, inhibits the microsomal drug-metabolizing enzymes of the mouse liver and prolongs the hexobarbital sleeping time; 24 h after the administration, it induces hepatic microsomal drug-metabolizing enzymes and shortens hexobarbital sleeping time.     

A simple method for the preparation of antibodies to the mitochondrial biotin-dependent carboxylases

Heterologous antiserum to the 3 biotin-dependent carboxylases was prepared by selective removal of these enzymes from human liver on an avidin-sepharose column. A carboxylase-avidin-sepharose matrix was used as an antigen to produce anti-carboxylase antibodies. The resultant antisera can be used to purify the specific carboxylases, to prepare monoclonal antibodies to these enzymes or to study inherited carboxylase deficiencies and biotin-dependent intermediary metabolism.     

Immobilized subunits can function as an affinity sorbent to purify oligomeric enzymes: The usefulness of hybridization on the solid support

Summary Immobilized dimers of yeast glyceraldehyde-3-phosphate dehydrogenase covalently bound to sepharose were shown to form hybrids with soluble dimers of the homologous enzymes present in crude tissue extracts (rat skeletal muscle, rat, rabbit and bovine hearts, rat liver, rat brain). Immobilized hybrid tetramers were then dissociated to form purified soluble enzymes.     

Effect of chronic ethanol treatment on peroxisomal acyl-CoA oxidase activity and lipid peroxidation in rat liver and heart

Chronic ethanol administration was shown to increase catalase and acyl-CoA oxidase activities in rat myocardium but did not alter the activity of liver peroxisomal enzymes. As a result of alcohol consumption a 2-3-fold increase in the level of lipid peroxidation was observed in the heart tissue while in the liver the induction was much less pronounced.