A comparison of the properties of the phosphofructokinases of the fat body and flight muscle of the adult male desert locust

1. Phosphofructokinase was isolated, and partially purified by ammonium sulphate fractionation, from the fat body and flight muscle of the desert locust. 2. Ammonium sulphate appears to stabilize the enzymes, but does not activate them. 3. Both flight-muscle and fat-body enzymes give sigmoidal hexose monophosphate concentration-activity curves, which are characteristic of regulatory enzymes. 4. At low ATP concentrations both the enzyme activities increase rapidly with increasing ATP concentrations, but above an optimum concentration ATP becomes inhibitory. This optimum concentration is 0.2mm for the fat-body enzyme and 0.1mm for the flight-muscle enzyme. 5. AMP activates both the enzymes; half-maximal activation occurs at 10mum in each case, the effect being independent of substrate concentration. 6. 3',5'-(cyclic)-AMP (0.5mm) and P(i) (1mm) activate the flight-muscle enzyme, but have no effect on the fat-body enzyme. 7. FDP (1mm) inhibits both enzymes, and with the flight-muscle enzyme this inhibition is increased by increasing the ATP concentration. 8. Citrate, phosphoenolpyruvate and alpha-glycerophosphate have no effect on either enzyme under the assay conditions used. 9. The properties of phosphofructokinases from the locust are compared with those of phosphofructokinases from other sources.     

A comparison of the properties of the pyruvate kinases of the fat body and flight muscle of the adult male desert locust

1. The pyruvate kinases of the desert locust fat body and flight muscle were partially purified by ammonium sulphate fractionation. 2. The fat-body enzyme is allosterically activated by very low (1mum) concentrations of fructose 1,6-diphosphate, whereas the flight-muscle enzyme is unaffected by this metabolite at physiological pH. 3. Flight-muscle pyruvate kinase is activated by preincubation at 25 degrees for 5min., whereas the fat-body enzyme is unaffected by such treatment. 4. Both enzymes require 1-2mm-ADP for maximal activity and are inhibited at higher concentrations. With the fat-body enzyme inhibition by ADP is prevented by the presence of fructose 1,6-diphosphate. 5. Both enzymes are inhibited by ATP, half-maximal inhibition occurring at about 5mm-ATP. With the fat-body enzyme ATP inhibition can be reversed by fructose 1,6-diphosphate. 6. The fat-body enzyme exhibits maximal activity at about pH7.2 and the activity decreases rapidly above this pH. This inactivation at high pH is not observed in the presence of fructose 1,6-diphosphate, i.e. maximum stimulating effects of fructose 1,6-diphosphate are observed at high pH. The flight-muscle enzyme exhibits two optima, one at about pH7.2 as with the fat-body enzyme and the other at about pH8.5. Stimulation of the enzyme activity by fructose 1,6-diphosphate was observed at pH8.5 and above.     

The relationships between corpora allata and fat body and haemolymph lipids in the adult female desert locust

Allatectomy of 1-day-old female desert locusts resulted in an accumulation of lipid in the fat body. This accumulation of lipid was due to the continuation of lipid deposition in the fat body after the period of somatic growth. Somatic growth and feeding activity were unaffected by allatectomy, and so could not be indirect causes of fat body lipid accumulation. Lipid accumulation in allatectomized locusts is more likely to be related directly to a lack of juvenile hormone. Implantation of active corpora allata into 1-day-old adult female locusts resulted in a premature development of oöcytes and a decrease in fat body lipid accumulation; somatic growth was not inhibited. Implantation of active corpora allata into old allatectomized locusts resulted in a decrease in the fat body lipid content and the onset of oöcyte development. The lipid synthetic activity of the fat body, measured by the incorporation of ¹⁴C-actate into total fat body lipid, was greatly increased in allatectomized locusts after the period of somatic growth. The protein synthetic activity of the fat body, measured by the incorporation of ³H-leucine into total fat body protein, remained low after the period of somatic growth in allatectomized insects. Juvenile hormone might thus have a dual effect on fat body metabolism, that is suppressing lipid synthesis and stimulating vitellogenic protein synthesis. Increased synthesis of lipid by the fat body would then account for the accumulation of lipid in the fat body after allatectomy. Inhibition of release of lipid from the fat body is unlikely to play a part in the accumulation as allatectomy had no effect on haemolymph lipid concentrations.     

Effect of caffeine on the body fat and lipid metabolism of rats fed on a high-fat diet

The intake of caffeine (CF) at 0.025, 0.05 or 0.1% for 21 days progressively reduced the body fat mass and body fat percentage in Sprague-Dawley (SD) rats fed on a high-fat diet with increasing administration level. Moreover, CF increased the serum concentrations of catecholamines and free fatty acids in SD rats orally administered with CF (5 mg/kg). These results suggest that the intake of CF reduced body fat by lipolysis via catecholamines. CF has potential as a functional food ingredient with an anti-obesity action.     

Effects of tea catechins on lipid metabolism and body fat accumulation

Long-term feeding of tea catechins suppressed body fat accumulation in high-fat diet-induced obesity in mice, and that their effects might be attributed, at least in part, to the activation of hepatic lipid metabolism. Consecutive intake of tea catechins (588 mg/day) reduced body fat, especially abdominal fat in humans. These results demonstrate that intake of tea catechins is beneficial for body fat accumulation.     

Ketone body metabolism during development

This paper briefly reviews the role of ketone bodies during development in the rat. Regulation of ketogenesis is in part dependent on the supply to the liver of medium- and long-chain fatty acids derived from mother's milk. The partitioning of long-chain fatty acids between the hepatic esterification and oxidation pathways is controlled by the concentration of malonyl-CoA, a key intermediate in the conversion of carbohydrate to lipid. As hepatic lipogenesis is depressed during the suckling period, [malonyl-CoA] is low and entry of long-chain acyl-CoA into the mitochondria for partial oxidation to ketone bodies is not restrained. Removal of ketone bodies by developing tissues is regulated by their availability in the circulation and by the activities of the enzymes of ketone body utilization. The patterns of activities of these enzymes differ among tissues during development so that the neonatal brain is an important site of ketone body utilization. The major role of ketone bodies in development is as an oxidative fuel to spare glucose, but they can also act as lipid precursors.     

In vitro study of lipid metabolism in the mealworm larval fat body

Lipid metabolism in Tenebrio larval fat body has been studied in vitro. Lipid release required the presence of diluted hemolymph in the incubation medium. This time-dependent release of lipid was strongly stimulated in a dose-dependent manner by Tenebrio corpora cardiaca (CC) extracts or synthetic adipokinetic hormone (AKH I). Furthermore, some glycerol was released when larval fat body was incubated without hemolymph, and this phenomenon was also dose dependent for added CC extracts. Lipid synthesis was estimated in vitro by following the incorporation of radioactivity from [6-¹⁴C] glucose into fatty acids. Lipogenesis occurred in the absence of added carbohydrates in the medium, but it was stimulated by the addition of glucose, and especially trehalose (10 mg ml^?1). Intestinal insulin-like peptide (ILP) also stimulated in vitro lipogenesis in a dose-dependent fashion. We conclude that lipolytic and lipogenetic activities of larval mealworm fat body in vitro are effectively under hormonal control.     

A role for the adult fat body in Drosophila male courtship behavior

Mating behavior in Drosophila depends critically on the sexual identity of specific regions in the brain, but several studies have identified courtship genes that express products only outside the nervous system. Although these genes are each active in a variety of non-neuronal cell types, they are all prominently expressed in the adult fat body, suggesting an important role for this tissue in behavior. To test its role in male courtship, fat body was feminized using the highly specific Larval serum protein promoter. We report here that the specific feminization of this tissue strongly reduces the competence of males to perform courtship. This effect is limited to the fat body of sexually mature adults as the feminization of larval fat body that normally persists in young adults does not affect mating. We propose that feminization of fat body affects the synthesis of male-specific secreted circulating proteins that influence the central nervous system. In support of this idea, we demonstrate that Takeout, a protein known to influence mating, is present in the hemolymph of adult males but not females and acts as a secreted protein.     

Juvenile hormone binding components of locust fat body

Juvenile hormone (JH) binding components from the fat body of the African migratory locust were analyzed in a search for a potential nuclear JH receptor. Biosynthetically prepared 10R[³H]JH III gave a high proportion of specific binding to isolated nuclei and extracted proteins; data obtained with the JH analogs, [³H]methoprene and [³H]pyriproxyfen, on the other hand, were obscured by abundant non-specific binding. The vast majority of the high affinity JH III binding activity present in cytosolic and nuclear extracts was due to a high molecular weight JH binding protein (JHBP) which has previously been identified in locust hemolymph. This protein has several chromatographic forms which interfered in the search for a nuclear JH receptor. When specific antiserum was used to remove JHBP from nuclear extracts, a novel JH binding activity (NBP) was detected. NBP could be separated from JHBP by precipitation with ammonium sulfate. NBP displayed a high affinity for JH III (Kd = 0.25 nM) and JH I and JH II competed strongly for JH III binding, whereas methoprene and pyriproxyfen showed apparent competition when present in 1,000-fold excess. NBP was present in nuclear extracts at approximately 25,000 sites per cell; levels were similar in male and female locusts and were not greatly affected by the presence or absence of JH. The characteristics of NPB make it a strong candidate for a nuclear JH receptor. © 1995 Wiley-Liss, Inc.     

The architecture of the accessory reproductive glands of the male desert locust. 5: ultrastructure during maturation

The accessory reproductive glands of the male desert locust were studied with the electron microscope from the time of adult emergence until full sexual maturity was attained (10 days). Observations on the changes in the nucleus and the cytoplasm of the glandular epithelium, particularly those organelles involved in the elaboration of cell secretions, were made during the maturation of the accessory glands. Cells of gland 16 (the functional seminal vesicle) exhibit numerous ribosomal aggregates, have a concentration of mitochondria along their luminal surface, and show some secretory activity, even at the time of adult emergence. On the other hand, all other accessory glands show very little development of the secretory apparatus (rough-surfaced endoplasmic reticulum, polyribosomes, Golgi elements, elaborate mitochondria, etc.) until after the fifth adult day. These changes parallel changes in the secretory activity of the adult corpus allatum; and it is suggested that the corpus allatum hormone regulates the maturation of the truly glandular accessory glands of the locust, but not that of the functional vesicle.