Difference in nutrient accumulation patterns between diapause-destined and non-diapause-destined larvae of Hyphantria cunea

Nutrient accumulation is crucial in insect diapause preparation because insufficient nutrient accumulation can shorten the diapause period, interfere with diapause development completion, and decrease the probability of surviving the overwintering period. The amounts of lipids and carbohydrates stored in diapausing pupae of Hyphantria cunea (Drury) (Lepidoptera: Erebidae, Arctiinae) are greater than those in the non-diapausing pupae. In this study, we tested the hypothesis that diapause-destined (DD) and non-diapause-destined (NDD) larvae of H. cunea have different nutrient accumulation patterns in penultimate and final instars. The body mass, as well as lipid, carbohydrate, and soluble protein contents, and the efficiency of converting digested food and ingested food into body matter were greater in the DD penultimate and final instars than in the NDD penultimate and final instars. Larger amounts of lipids, carbohydrates, and proteins were absorbed by DD penultimate and final instars and the final instar development period in the DD larvae was prolonged relative to NDD larvae. The activities of fatty acid synthase and glycogen synthase of DD penultimate and final instars were significantly higher than those of NDD larvae. These results suggest that the changes in nutrient accumulation patterns between DD and NDD larvae occur in penultimate and final instars, and that the DD larvae increase their nutrient accumulation during diapause preparation by the combined effect of extending their final-instar development period and improving their digestive efficiency; they increase their lipid and carbohydrate stores by increasing the activities of fatty acid synthase and glycogen synthase in the fat body.     

Astragaloside IV ameliorates fat metabolism in the liver of ageing mice through targeting mitochondrial activity

Astragaloside IV (AST) is a major bioactive compound of Radix Astragali with medical and health benefits. Previous studies have found that AST can reduce the body weights of high-fat diet fed mice. However, the effect of AST on fat metabolism of ageing mice is unclear. In this study, naturally ageing mice were administered intragastrically with AST at 30 mg/kg/day (ageing + AST-L group) and 90 mg/kg/day (ageing + AST-H group) for 16–20 months. Adult (4 months old) and ageing mice were given 1% sodium carboxyl methylcellulose as vehicle. Energy metabolism-related biological parameters of living mice were examined. Moreover, mRNA and protein levels of key enzymes/proteins involved in triglyceride (TG) lipolysis, fatty acid β-oxidation (FAO), ketone body (KB) production and mitochondrial respiratory chain were also examined after sacrifice. Results demonstrated that treatment with AST significantly reduced body weight, white fat and liver/body weight ratio of ageing mice, significantly reduced serum/hepatic TG levels, respiratory quotient, promoted fatty acid mobilization in white adipose tissue, mitochondrial FAO and KB production and mitochondrial biosynthesis/functions in the liver of ageing mice. AST also up-regulated the expression of phosphorylated AMP-activated protein kinase, acetyl-CoA carboxylase, acetyl-coenzyme A synthetase, carnitine palmitoyltransferase 1a/1b, enoyl coenzyme A hydratase-short chain, acyl-CoA dehydrogenase medium chain and mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase-2 involved in fat metabolism. These results indicated that mitochondrial activity could be the target of AST to treat abnormal fat metabolism during ageing.     

Both substrate availability and utilisation contribute to the defence of core temperature in response to acute cold

Acute cooling significantly increases energy demand in non-hibernators for the defence of core temperature but the contribution of the liver to thermogenesis is poorly understood. A two-tracer method to estimate lipid metabolism in cold-naïve control (CON) and cold-acclimated (CA) rats was employed to quantify hepatic rates of fat metabolism. Both fenofibrate, to increase liver mass and fat oxidation and dichloroacetate (DCA) to inhibit fat oxidation were used to alter lipid metabolism in CON animals. Following acute cooling, CA led to a doubling of the time to reach a core temperature 25 °C (P < 0.001), whereas DCA treatment decreased time of cooling (P < 0.01). DCA-treatment increased the gradient of Arrhenius-transformed rate–pressure product (P < 0.01). CA increased both palmitate uptake (P < 0.001) and β-oxidation (P < 0.01) whilst DCA treatment decreased uptake (P < 0.01) and β-oxidation (P < 0.05). Tissue-specific estimates of metabolism revealed that CA led to a 12-fold increase in β-oxidation for brown adipose tissue (P < 0.001) whilst fenofibrate halved β-oxidation in the liver (P < 0.01) despite doubling the liver mass (P < 0.001) and DCA decreased hepatic β-oxidation to 15% of control levels. Taken together, these results suggest that the liver has minimal contribution to thermogenesis in the rat, with brown adipose tissue significantly increasing both fat uptake and oxidation in response to CA.     

Clues on the function of Manduca sexta perilipin 2 inferred from developmental and nutrition-dependent changes in its expression

Cellular triglycerides (TG) are stored in cytosolic lipid droplets (LDs). Perilipins (PLIN) are a group of LD-proteins that play important roles in the assembly and transport of LDs and in TG metabolism. Two members of the PLIN family are found in insects (PLIN1 & 2 or Lsd1 & 2). We have cloned and expressed Manduca sexta PLIN2 (MsPLIN2), and studied developmental and nutritional changes in the expression of PLIN2. Nutritional changes induced fast alterations in PLIN2 mRNA and protein levels in fat body and midgut of the feeding larvae. The relationship observed between PLIN2 expression and TG synthesis in both larval fat body and midgut suggests that PLIN2 is needed when tissues are accumulating TG. However, when the fat body was storing TG at maximal capacity, MsPLIN2 levels declined. This unexpected finding suggests the occurrence of alternative mechanism/s to shield TG from the action of lipases in M. sexta LDs. In addition, it implies that the cellular level of lipid storage could be modulating MsPLIN2 expression and/or degradation. The study also confirmed that MsPLIN2 was most abundant in the adult fat body, which is characterized by a high rate of TG hydrolysis and lipid mobilization. Whether MsPLIN2 is directly involved in lipolysis and/or the secretion of lipids in the fat body of adult of M. sexta is unknown at this time. Nonetheless, the coexistence of high PLIN2 and lipolysis levels suggests a complex role for MsPLIN2. Altogether, we found that MsPLIN2 is needed when the synthesis of glycerides, DG and TG, is active even if the insect is accumulating or consuming TG.     

Lipophorin and its Receptor in Lepidoptera

Lipophorin (Lp) has an approximate native molecular weight of 730 kDa for Bombyx mori and consists of ApoLp‐I and ApoLp‐II with molecular weights of 250 kDa and 90 kDa for B. mori and 230 kDa and 80 kDa for Hyphantria cunea and 230 kDa and 49 kDa for Lymantria dispar, respectively. Lipid in Lp was mostly composed of neutral lipid. Lp of B. mori maintains constant level during larval and pupal stages but greatly increases during adult stage in both male and female. Lp of H. cunea appeared in great amounts in protein yolk bodies of ovary when vitellogenesis is actively taking place and was present in testicular fluid but not in the peritoneal sheath and cysts of testis. ApoLp‐III of B. mori has a molecular weight of 17 kDa and similar amino acid composition as those of other species Lp. H. cunea apoLp‐III has a molecular weight of 18 kDa and was present in all stages and in the protein body of ovary and in the cyst of testis. ApoLp‐III is synthesized in larval and adult fat body. cDNA sequence of Spodoptera litura apoLp‐III encodes a 188 amino acid polypeptide including a 22 amino acid leader peptide. Galleria mellonella Lp receptor has an approximate molecular weight of 97 kDa and 110 kDa under non‐reducing and reducing conditions, respectively and bound HDLp specifically. Lp receptor cDNA of G. mellonella showed th pattern of the VLDL receptor belonging to the LDL receptor family. The variant Lp receptors were expressed in the fat body of G. mellonella; one is a Lp receptor which lacks 84 bp of O linked sugar domain and the other is a full length form of the Lp receptor. The Lp receptor from the fat body of G. mellonella was differently expressed depending on the tissue and the developmental stages with specific abundance in prepupal stage.     

Partial sequence and characterization of nitric oxide synthase gene from Hyphantria cunea

Nitric oxide synthase (NOS) gene has been partially sequenced from Hyphantria cunea and compared with those already determined from insects. Hyphantria cunea NOS possesses putative recognition sites for co‐factors heme, BH₄, CaM, FMN, FAD, and NADPH common to NOS. The deduced amino acid sequence of H. cunea NOS cDNA showed 70.3% identity to Manduca sexta NOS and 57.6–69.5% identity to NOS sequences from other insects. Nitric oxide synthase is expressed in all tissues of H. cunea, except in hemocytes. The NOS expression in midgut, fat body, epidermis, and Malpighian tubule strongly increased against Gram‐positive and Gram‐negative bacterial infection. These results suggest that NOS may play an important role in insect defense system against bacterial infection.     

Hormonally-regulated differential expression of the two duplicated insecticyanin genes,ins-a and ins-b,during development of the tobacco hornworm,Manduca sexta

The effects of juvenile hormone (JH) and 20-hydroxyecdysone (20E) on the developmental expression of the two insecticyanin genes, ins-a and ins-b, were investigated with two gene-specific probes. Removal of the corpora allata (-CA, source of JH) clearly delayed and down-regulated the epidermal expression of these genes but enhanced their expression in the fat body during the early development of the fifth instar. Application of JH I to the -CA larvae at the time of head capsule slippage completely restored the normal epidermal expression pattern of the two genes in the early fifth instar, then INS-a mRNA declined prematurely whereas INS-b mRNA remained similar to that in the intact larvae. By contrast, in the fat body of -CA larvae, the exogenous JH had little effect on the levels of INS-a mRNA, but enhanced expression of INS-b mRNA relative to intact larvae. Culture of epidermis from day 1 fifth instar larvae with 40 ng/ml 20E for up to 24 h accelerated the loss of INS-a mRNA without affecting the levels of INS-b mRNA. Both mRNAs declined in isolated larval abdomens over a 24 h period, and this decline was slowed by 1 g methoprene (a JH analog). Together these results indicate that JH controls the levels of the two mRNAs in both the epidermis and fat body, with additional factors involved in regulating these genes in the fat body during the molt and in the epidermis during the growth phase.     

The effect of trans-10, cis-12 conjugated linoleic acid on gene expression profiles related to lipid metabolism in human intestinal-like Caco-2 cells

We conducted an in-depth investigation of the effects of conjugated linoleic acid (CLA) on the expression of key metabolic genes and genes of known importance in intestinal lipid metabolism using the Caco-2 cell model. Cells were treated with 80 μmol/L of linoleic acid (control), trans-10, cis-12 CLA or cis-9, trans-11 CLA. RNA was isolated from the cells, labelled and hybridized to the Affymetrix U133 2.0 Plus arrays (n = 3). Data and functional analysis were preformed using Bioconductor. Gene ontology analysis (GO) revealed a significant enrichment (P < 0.0001) for the GO term lipid metabolism with genes up-regulated by trans-10, cis-12 CLA. Trans-10, cis-12 CLA, but not cis-9, trans-11 CLA, altered the expression of a number of genes involved in lipid transport, fatty acid metabolism, lipolysis, β-oxidation, steroid metabolism, cholesterol biosynthesis, membrane lipid metabolism, gluconeogenesis and the citrate cycle. These observations warrant further investigation to understand their potential role in the metabolic syndrome.     

DHA regulates lipogenesis and lipolysis genes in mice adipose and liver

Docosahexaenoic acid (DHA) is one kind of ω-3 polyunsaturated fatty acids (PUFAs) and plays an important role in lipid metabolism. In this research, mice were daily intragastric administrated with DHA for 3 weeks. Subcutaneous adipose tissue and liver were separated every week, RNA was extracted. Peroxisome proliferator-activated receptor (PPARγ), Sterol regulatory element binding protein-1c (SREBP-1c), Fatty acid synthetase (FAS), Hormone sensitive lipase (HSL) and triglyceride hydrolase TGH genes expression were detected by quantitative PCR. Data showed that, DHA up-regulated PPARγ, HSL and TGH in adipose tissue, but it had no effect on SREBP-1c and FAS expression. However, in liver there were some differences in regulating these genes. PPARγ, SREBP-1c and FAS were down-regulated, HSL was up-regulated and TGH had no change. These results indicated that DHA played different regulating roles in lipid metabolism in different tissues. In adipose tissue, DHA increased the expression of lipogenesis and lipolysis genes. In liver lipogenesis genes were decreased, but lipolysis genes were increased by DHA. In conclusion, DHA could reduce body fat mass through regulating lipogenesis and lipolysis genes.     

Susceptibility of Hyphantria cunea to a granulosis virus isolated from Diacrisia virginica

The dosage-mortality response of Hyphantria cunea larvae to a granulosis virus isolated from Diacrisia virginica was studied. Serial decimal dilutions of the D. virginica granulosis virus were fed to early second-instar H. cunea larvae. the LD₅₀ for this virus (7.9 × 10⁵ capsules/larva) was significantly greater than the LD₅₀ calculated for the H. cunea granulosis virus (7.06 × 10⁴ capsules/larva) against the same instar of H. cunea. Time mortality studies demonstrated that the LT₅₀ values for the D. virginica granulosis were four to six times greater than for comparable dosages of H. cunea granulosis virus. Based on the mortality response of assayed H. cunea, it is possible to distinguish between the D. virginica granulosis virus and the H. cunea granulosis virus.     

Adrenalectomy Reduces Adiposity by Decreasing Feed Efficiency,Not Direct Effects on White Adipose Tissue

EDENS, N. K., A. MOSHIRFAR, G. M. POTTER, S. K. FRIED, AND T. W. CASTONGUAY. Adrenalectomy reduces adiposity by decreasing feed efficiency, not direct effects on white adipose tissue. Obes Res. Objective: This study was conducted to establish the effects of adrenalectomy (ADX) on adipose tissue metabolism in male Sprague—Dawley rats fed a standard chow diet. Research Methods and Procedures: The effects of adrenalectomy on adipose cell size, lipoprotein lipase activity, and basal and insulin-stimulated glucose conversion to lipid and lipolysis were measured. Results: ADX decreased body weight gain during the postoperative period in the absence of changes in food intake; feed efficiency was decreased significantly. ADX decreased adipocyte size by 30%. ADX increased adipocyte response to the effect of submaximal concentrations of insulin on lipid synthesis and lipolysis. ADX decreased maximally insulin-stimulated lipid synthesis, but this effect was accounted for by decreased adipocyte size. In contrast, ADX had no effect on maximally insulin-inhibited lipolysis. ADX did not affect heparin-releasable LPL. The small effect of ADX on residual extractable adipose tissue LPL activity was accounted for by decreased fat cell size. Discussion: ADX decreased adiposity in the absence of changes in food intake, lipoprotein lipase activity, and adipocyte lipid metabolism. The effect is best attributed to decreased feed efficiency.     

Regulation of Lipolysis and Lipoprotein Lipase after Weight Loss in Obese,Postmenopausal Women

Objective: To test the hypothesis that the greater β‐adrenoceptor (β‐AR)‐stimulated lipolysis and sensitivity (half‐maximal lipolytic response) in abdominal (ABD) adipocytes, greater gluteal (GLT) adipose tissue‐lipoprotein lipase (AT‐LPL) activity, and dyslipidemia associated with obesity in older women are modifiable by weight loss (WL) and are not due to menopause or aging. Research Methods and Procedures: The metabolic effects of 6 months of hypocaloric diet and low‐intensity walking WL program on the regional regulation of in vitro lipolysis and AT‐LPL activity in subcutaneous ABD and GLT adipocytes were measured in 34 obese (48.7 ± 0.7% body fat, mean ± SE) postmenopausal (59 ± 1 years) white women. Results: The lipolytic responsiveness to the β‐AR agonist isoproterenol and basal lipolysis in the presence of 1 U/mL adenosine deaminase‐uninhibited (lipolysis) were greater (p < 0.01) in ABD than GLT adipocytes before and after WL, but there were no regional differences in postreceptor (dibutyryl 3′, 5′‐cyclic adenosine monophosphate)‐stimulated lipolysis. β‐AR sensitivity was greater in ABD than GLT adipocytes before (p < 0.01) but not after WL. Regional AT‐LPL did not change after WL, but the change in the activity of ABD (but not GLT) AT‐LPL correlated with the baseline adenosine deaminase‐uninhibited lipolysis (r = 0.38, p = 0.03). There were no relationships between the declines in plasma triglyceride or increases in high‐density lipoprotein cholesterol associated with WL and the changes in regional fat cell metabolism. Discussion: Thus, despite improving lipoprotein lipid profiles in obese, postmenopausal women, WL does not affect the regulation of regional fat metabolism, and a greater tonic inhibition of basal lipolysis by endogenous adenosine may increase the activity of AT‐LPL after WL and predispose older women to develop ABD adiposity.     

Dietary Restriction during Development Enlarges Intestinal and Hypodermal Lipid Droplets in Caenorhabditis elegans

Dietary restriction (DR) extends lifespan in man species and modulates evolutionary conserved signalling and metabolic pathways. Most of these studies were done in adult animals. Here we investigated fat phenotypes of C. elegans larvae and adults which were exposed to DR during development. This approach was named “developmental-DR” (dDR). Moderate as well as stringent dDR increased the triglyceride to protein ratio in L4 larvae and adult worms. This alteration was accompanied by a marked expansion of intestinal and hypodermal lipid droplets. In comparison to ad libitum condition, the relative proportion of fat stored in large lipid droplets (>50 µm³) was increased by a factor of about 5 to 6 in larvae exposed to dDR. Microarray-based expression profiling identified several dDR-regulated genes of lipolysis and lipogenesis which may contribute to the observed fat phenotypes. In conclusion, dDR increases the triglyceride to protein ratio, enlarges lipid droplets and alters the expression of genes functioning in lipid metabolism in C. elegans. These changes might be an effective adaptation to conserve fat stores in animals subjected to limiting food supply during development.     

Inhibition of the actions of peroxisome proliferator-activated receptor alpha on obesity by estrogen

Objective: To determine whether the major ovarian factor estrogen modulates peroxisome proliferator‐activated receptor (PPAR) α actions on obesity and to investigate the mechanism by which estrogen regulates PPARα actions. Research Methods and Procedures: Female ovariectomized mice were randomly divided into four groups (n = 8/group). After they were treated with combinations of high fat, fenofibrate (FF), or 17β‐estradiol (E) for 13 weeks, variables and determinants of obesity and lipid metabolism were measured using in vivo and in vitro approaches. Results: When female ovariectomized mice were given a high‐fat diet with either FF or E, body weight gain and white adipose tissue mass were significantly reduced and serum lipid profiles were improved compared with control mice fed a high‐fat diet alone. When mice were concomitantly treated with FF and E, however, E reversed the effects of FF on body weight gain, serum lipid profiles, and hepatic PPARα target gene expression. Consistent with the in vivo data, E not only decreased basal levels of PPARα reporter gene activation but also significantly decreased Wy14,643‐induced luciferase reporter activity. In addition, inhibition of PPARα functions by E did not seem to occur by interfering with the DNA binding of PPARα. Discussion: Our results demonstrate that in vivo and in vitro treatment of estrogen inhibited the actions of FF‐activated PPARα on obesity and lipid metabolism through changes in the expression of PPARα target genes, providing evidence that FF does not regulate obesity in female mice with functioning ovaries.