In Vivo Monitoring of Glycerolipid Metabolism in Animal Nutrition Biomodel-Fed Smart-Farm Eggs.

Although many studies have examined the biochemical metabolic pathways by which an egg (egg yolk) lowers blood lipid levels, data on the molecular biological mechanisms that regulate and induce the partitioning of hepatic glycerolipids are missing. The aim of this study was to investigate in vivo monitoring in four study groups using an animal nutrition biomodel fitted with a jugular-vein cannula after egg yolk intake: CON (control group, oral administration of 1.0 g of saline), T1 (oral administration of 1.0 g of pork belly fat), T2 (oral administration of 1.0 g of smart-farm egg yolk), and T3 (oral administration of T1 and T2 alternately every week). The eggs induced significant and reciprocal changes in incorporating 14C lipids into the total glycerolipids and releasing 14CO2, thereby regulating esterification and accelerating oxidation in vivo. The eggs increased phospholipid secretion from the liver into the blood and decreased triacylglycerol secretion by regulating the multiple cleavage of fatty acyl-CoA moieties' fluxes. In conclusion, the results of the current study reveal the novel fact that eggs can lower blood lipids by lowering triacylglycerol secretion in the biochemical metabolic pathway of hepatic glycerolipid partitioning while simultaneously increasing phospholipid secretion and 14CO2 emission.

The roles of DGAT1 and DGAT2 in human myotubes are dependent on donor patho-physiological background.

The roles of DGAT1 and DGAT2 in lipid metabolism and insulin responsiveness of human skeletal muscle were studied using cryosections and myotubes prepared from muscle biopsies from control, athlete, and impaired glucose regulation (IGR) cohorts of men. The previously observed increases in intramuscular triacylglycerol (IMTG) in athletes and IGR were shown to be related to an increase in lipid droplet (LD) area in type I fibers in athletes but, conversely, in type II fibers in IGR subjects. Specific inhibition of both diacylglycerol acyltransferase (DGAT) 1 and 2 decreased fatty acid (FA) uptake by myotubes, whereas only DGAT2 inhibition also decreased fatty acid oxidation. Fatty acid uptake in myotubes was negatively correlated with the lactate thresholds of the respective donors. DGAT2 inhibition lowered acetate uptake and oxidation in myotubes from all cohorts whereas DGAT1 inhibition had no effect. A positive correlation between acetate oxidation in myotubes and resting metabolic rate (RMR) from fatty acid oxidation in vivo was observed. Myotubes from athletes and IGR had higher rates of de novo lipogenesis from acetate that were normalized by DGAT2 inhibition. Moreover, DGAT2 inhibition in myotubes also resulted in increased insulin-induced Akt phosphorylation. The differential effects of DGAT1 and DGAT2 inhibition suggest that the specialized role of DGAT2 in esterifying nascent diacylglycerols and de novo synthesized FA is associated with synthesis of a pool of triacylglycerol, which upon hydrolysis results in effectors that promote mitochondrial fatty acid oxidation but decrease insulin signaling in skeletal muscle cells.

Impact of the Combination of Probiotics and Digital Poultry System on Behavior, Welfare Parameters, and Growth Performance in Broiler Chicken.

Recently, applied technology in the form of the combination of a probiotics and a digital poultry system, with the convergence of Information and Communications Technology and farm animals, has enabled a new strategy to overcome the livestock production crisis caused by climate change, while maintaining sustainable poultry farming in terms of care, feeding, and environmental management systems for poultry. The aim of this study was to investigate the biological mechanisms of animal behavioral welfare and production improvement using the combination of a probiotics and a digital poultry system in broiler chickens. A total of 400 one-day-old male broilers (ROSS 308) were randomly divided into four treatment groups, with five replicates each (20 birds/replicate pen) in a completely randomized design: control group with a conventional poultry system without probiotics (CON), conventional poultry system with 500 ppm of probiotics (CON500), digital poultry control system without probiotics (DPCS), and digital poultry system with 500 ppm of probiotics (DPS500). All experimental animals were reared for 35 days under the same standard environmental conditions. The experimental results indicated that the animal behavioral welfare, which includes drinking, eating, locomotion, grooming, and resting, in addition to foot pads, knee burns, plumage, and gait scores, as well as the growth performance of the broiler chickens, were improved by maintaining immune function and cecal microbiota balance via interaction between the combination of a probiotics and a digital poultry system. In conclusion, it was found that the combined system showed improved broiler growth performance and animal behavioral welfare. Thus, further studies of molecular biological mechanisms by the use of such a combined system to improve the nutritional composition and quality of chicken meats are recommended.

Molecular Mechanism for Hepatic Glycerolipid Partitioning of n-6/n-3 Fatty Acid Ratio in an Obese Animal Biomodels.

The n-6/n-3 metabolic pathway associated with hepatic glycerolipid portioning plays a key role in preventing obesity. In this nutrition metabolism study, we used in vivo monitoring techniques with 40 obese male Sprague-Dawley strain rats attached with jugular-vein cannula after obesity was induced by a high-fat diet to determine the molecular mechanism associated with hepatic glycerolipid partitioning involving the n-6/n-3 metabolic pathway. Rats were randomly assigned to four groups (10 animals per group), including one control group (CON, n-6/n-3 of 71:1) and three treatment groups (n-6/n-3 of 4:1, 15:1 and 30:1). They were fed with experimental diets for 60 days. Incorporation rates of [14C]-labeling lipid into glycerolipid in the liver were 28.87−37.03% in treatment groups fed with diets containing an n-6/n-3 ratio of 4:1, 15:1 and 30:1, which were significantly (p < 0.05) lower than that in the CON (40.01%). However, 14CO2 emission % of absorbed dose showed the opposite trend. It was significantly (p < 0.05) higher in a treatment groups (n-6/n-3 of 4:1, 15:1 and 30:1, 30.35−45.08%) than in CON (27.71%). Regarding the metabolic distribution of glycerolipid to blood from livers, phospholipid/total glycerolipid (%) was significantly (p < 0.05) lower in CON at 11.04% than in treatment groups at 18.15% to 25.15%. Moreover, 14CO2/[14C]-total glycerolipid (%) was significantly (p < 0.05) higher in treatment groups at 44.16−78.50% than in CON at 39.50%. Metabolic distribution of fatty acyl moieties flux for oxidation and glycerolipid synthesis in the liver were significantly (p < 0.05) better in order of 4:1 > 15:1 > 30:1 than in the CON. Our data demonstrate that n-6/n-3 of 4:1 could help prevent obesity by controlling the mechanism of hepatic partitioning through oxidation and esterification of glycerolipid in an obese animal biomodel.

Treatment of human skeletal muscle cells with inhibitors of diacylglycerol acyltransferases 1 and 2 to explore isozyme-specific roles on lipid metabolism.

Diacylglycerol acyltransferases (DGAT) 1 and 2 catalyse the final step in triacylglycerol (TAG) synthesis, the esterification of fatty acyl-CoA to diacylglycerol. Despite catalysing the same reaction and being present in the same cell types, they exhibit different functions on lipid metabolism in various tissues. Yet, their roles in skeletal muscle remain poorly defined. In this study, we investigated how selective inhibitors of DGAT1 and DGAT2 affected lipid metabolism in human primary skeletal muscle cells. The results showed that DGAT1 was dominant in human skeletal muscle cells utilizing fatty acids (FAs) derived from various sources, both exogenously supplied FA, de novo synthesised FA, or FA derived from lipolysis, to generate TAG, as well as being involved in de novo synthesis of TAG. On the other hand, DGAT2 seemed to be specialised for de novo synthesis of TAG from glycerol-3-posphate only. Interestingly, DGAT activities were also important for regulating FA oxidation, indicating a key role in balancing FAs between storage in TAG and efficient utilization through oxidation. Finally, we observed that inhibition of DGAT enzymes could potentially alter glucose-FA interactions in skeletal muscle. In summary, treatment with DGAT1 or DGAT2 specific inhibitors resulted in different responses on lipid metabolism in human myotubes, indicating that the two enzymes play distinct roles in TAG metabolism in skeletal muscle.

In vivo monitoring of hepatic glycolipid distribution of n-6 ∕ n-3 in jugular-vein-cannulated rats as a nutritional research model for monogastric animal.

The metabolic distribution via blood from liver of glycerolipids by omega-6 to omega-3 fatty acid ( n -6  /   n -3) ratio in monogastric animal nutrition is very important. In vivo monitoring technique using jugular-vein-cannulated rats as a nutritional model for monogastric animal can yield important insights into animal nutrition. This study was conducted to determine the effect of different n -6  /   n -3 ratios ( 71 : 1 , 4 : 1 , 15 : 1 , 30 : 1 ) on metabolic distribution of glycerolipids newly synthesized and secreted in the liver of the rats and explore the mechanism involved. Regarding 14 CO 2 released from oxidation of glycerolipid metabolism, it was the highest (22.5 %) in groups with a n -6  /   n -3 ratio of 4 : 1 ( P < 0.05 ). The control group showed the highest total glycerolipid level, followed by the 30 : 1 , 15 : 1 , and 4 : 1 groups in order ( P < 0.05 ). When secreted triacylglycerol level of each group was compared with that of the control group, the 4 : 1 , 15 : 1 , and 30 : 1 groups were decreased by 36.3 %, 20.9 %, and 13.3 %, respectively ( P < 0.05 ). Regarding the distribution of phospholipid against total glycerolipid compared to the control group, the 4 : 1 , 15 : 1 , and 30 : 1 groups were 1.38, 1.29, and 1.17 times higher, respectively ( P < 0.05 ). In the comparison of 14 CO 2 emission against total glycerolipid compared with the control group, the 4 : 1 , 15 : 1 , and 30 : 1 groups were 1.61, 1.52, and 1.29 times higher, respectively ( P < 0.05 ). These results demonstrate that a dietary n -6  /   n -3 fatty acid ratio of 4 : 1 could significantly decrease harmful lipid levels in the blood by controlling the mechanism of metabolic distribution via blood from triglyceride and phospholipid newly synthesized in the liver of cannulated rat.

Hepatic VLDL secretion: DGAT1 determines particle size but not particle number, which can be supported entirely by DGAT2.

We investigated whether, in view of its activity being expressed on both aspects of the endoplasmic reticulum (ER; dual membrane topology), diacylglycerol acyltransferase 1 (DGAT1) plays a distinctive role in determining the triglyceride (TAG) content of VLDL particles secreted by the liver. Mice in which the DGAT1 gene was specifically ablated in hepatocytes (DGAT1-LKO mice) had the same number of VLDL particles (apoB concentration) in the plasma 1 h after Triton 1339 treatment, but these particles were approximately half the size of VLDL particles secreted by control mice and had a proportionately decreased content of TAG, with normal cholesterol and cholesteryl ester contents. Analyses of purified microsomal fractions prepared from 16 h fasted control and DAGT1-LKO mice showed that the TAG/protein ratio in the ER was significantly lower in the latter. Electron micrographs of these livers showed that those from DGAT1-LKO mice did not show the increased lipid content of the smooth ER shown by control livers. The effects of DGAT1- and DGAT2-specific inhibitors on apoB secretion by HepG2 cells showed that DGAT1 is not indispensable for apoB secretion and demonstrated redundancy in the ability of the two enzymes to support apoB secretion. Therefore, our findings show that DGAT1 is essential for the complete lipidation and maturation of VLDL particles within the lumen of the ER, consistent with its dual topology within the ER membrane. In the mouse, DGAT2 can support apoB secretion (particle number) even when TAG availability for full VLDL lipidation is restricted in the absence of DGAT1.

Effect of stocking density on behavioral traits, blood biochemical parameters and immune responses in meat ducks exposed to heat stress.

High stocking density (HSD) and heat stress (HS) caused by climate change can lower blood homeostasis and negatively impact the behavioral traits of animals. The objective of this study was to explore the influence of stocking densities on behavioral traits, blood parameters, immune responses, and stress hormones in meat ducks (Cherry valley, Anas platyrhynchos) exposed to HS. A total of 320 meat ducks were assigned to four groups with different stocking densities using a randomized complete block design. The ducks were then reared for 42 days. The assigned density groups were as follows: (1) control group (CON, three birds m - 2 , normal environmental heat conditions); (2) low stocking density (LSD, three birds m - 2 , heat stress conditions); (3) medium stocking density (MSD, four birds m - 2 , heat stress conditions); and (4) high stocking density (HSD, six birds m - 2 , heat stress conditions). To induce HS, the environment of the poultry house was set to a temperature of 34 ± 2 ∘ C with a relative humidity of 70 % from 11:00 to 16:00 for the finisher period (from day 22 to day 42 of the rearing period). Concentrations of blood triacylglycerol, total cholesterol, low-density lipoprotein cholesterol (LDL-C), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were higher in the HS groups compared with the CON group, with HSD showing the highest levels ( P < 0.05 ). The concentrations of high-density lipoprotein cholesterol (HDL-C) and glucose were lower in the HSD groups than in the CON group ( P < 0.05 ). Red blood cell (RBC) and platelet (PLT) counts were lower in HS groups compared with the CON group, with the HSD group displaying the lowest counts ( P < 0.05 ). Blood pH values were also higher in the HS groups than in the CON group, with the highest values observed in the HSD group ( P < 0.05 ). Concentrations of blood p CO 2 , HCO 3 , and T CO 2 were higher in the HS groups than in the CON group, with HSD showing the lowest levels ( P < 0.05 ). The concentration of PO 2 was higher in CON than in any of the HS groups, with the lowest levels found in the HSD group ( P < 0.05 ). The concentrations of blood IgG and corticosterone were increased in the HS groups compared with the CON group ( P < 0.05 ). Animal behavioral trait scores were also higher in HS groups than in the CON group ( P < 0.05 ); these scores were the highest in the HSD group. Overall, animal behavioral traits, blood biochemical parameters, and immune responses in meat ducks exposed to heat stress were highest in the HSD group, but not significantly different between the LSD or MSD groups.

Differential activation of Fyn kinase distinguishes saturated and unsaturated fats in mouse macrophages.

Diet-induced obesity is associated with increased adipose tissue activated macrophages. Yet, how macrophages integrate fatty acid (FA) signals remains unclear. We previously demonstrated that Fyn deficiency (fynKO) protects against high fat diet-induced adipose tissue macrophage accumulation. Herein, we show that inflammatory markers and reactive oxygen species are not induced in fynKO bone marrow-derived macrophages exposed to the saturated FA palmitate, suggesting that Fyn regulates macrophage function in response to FA signals. Palmitate activates Fyn and re-localizes Fyn into the nucleus of RAW264.7, J774 and wild-type bone marrow-derived macrophages. Similarly, Fyn activity is increased in cells of adipose tissue stromal vascular fraction of high fat-fed control mice, with Fyn protein being located in the nucleus of these cells. We demonstrate that Fyn modulates palmitate-dependent oxidative stress in macrophages. Moreover, Fyn catalytic activity is necessary for its nuclear re-localization and downstream effects, as Fyn pharmacological inhibition abolishes palmitate-induced Fyn nuclear redistribution and palmitate-dependent increase of oxidative stress markers. Importantly, mono-or polyunsaturated FAs do not activate Fyn, and fail to re-localize Fyn to the nucleus. Together these data demonstrate that macrophages integrate nutritional FA signals via a differential activation of Fyn that distinguishes, at least partly, the effects of saturated versus unsaturated fats.

Diacylglycerol acyltransferase 2 links glucose utilization to fatty acid oxidation in the brown adipocytes.

Brown adipose tissue uptake of glucose and fatty acids is very high during nonshivering thermogenesis. Adrenergic stimulation markedly increases glucose uptake, de novo lipogenesis, and FA oxidation simultaneously. The mechanism that enables this concerted response has hitherto been unknown. Here, we find that in primary brown adipocytes and brown adipocyte-derived cell line (IMBAT-1), acute inhibition and longer-term knockdown of DGAT2 links the increased de novo synthesis of fatty acids from glucose to a pool of TAG that is simultaneously hydrolyzed, providing FA for mitochondrial oxidation. DGAT1 does not contribute to this pathway, but uses exogenous FA and glycerol to synthesize a functionally distinct pool of TAG to which DGAT2 also contributes. The DGAT2-dependent channelling of 14C from glucose into TAG and CO2 was reproduced in ß3-agonist-stimulated primary brown adipocytes. Knockdown of DGAT2 in IMBAT-1 affected the mRNA levels of UCP1 and genes important in FA activation and esterification. Therefore, in ß3-agonist activated brown adipocytes, DGAT2 specifically enables channelling of de novo synthesized FA into a rapidly mobilized pool of TAG, which is simultaneously hydrolyzed to provide substrates for mitochondrial fatty acid oxidation.

Extra-nuclear telomerase reverse transcriptase (TERT) regulates glucose transport in skeletal muscle cells.

Telomerase reverse transcriptase (TERT) is a key component of the telomerase complex. By lengthening telomeres in DNA strands, TERT increases senescent cell lifespan. Mice that lack TERT age much faster and exhibit age-related conditions such as osteoporosis, diabetes and neurodegeneration. Accelerated telomere shortening in both human and animal models has been documented in conditions associated with insulin resistance, including T2DM. We investigated the role of TERT, in regulating cellular glucose utilisation by using the myoblastoma cell line C2C12, as well as primary mouse and human skeletal muscle cells. Inhibition of TERT expression or activity by using siRNA (100nM) or specific inhibitors (100nM) reduced basal 2-deoxyglucose uptake by ~50%, in all cell types, without altering insulin responsiveness. In contrast, TERT over-expression increased glucose uptake by 3.25-fold. In C2C12 cells TERT protein was mostly localised intracellularly and stimulation of cells with insulin induced translocation to the plasma membrane. Furthermore, co-immunoprecipitation experiments in C2C12 cells showed that TERT was constitutively associated with glucose transporters (GLUTs) 1, 4 and 12 via an insulin insensitive interaction that also did not require intact PI3-K and mTOR pathways. Collectively, these findings identified a novel extra-nuclear function of TERT that regulates an insulin-insensitive pathway involved in glucose uptake in human and mouse skeletal muscle cells.

Hepatic triacylglycerol synthesis and secretion: DGAT2 as the link between glycaemia and triglyceridaemia.

lThe liver regulates both glycaemia and triglyceridaemia. Hyperglycaemia and hypertriglyceridaemia are both characteristic of (pre)diabetes. Recent observations on the specialised role of DGAT2 (diacylglycerol acyltransferase 2) in catalysing the de novo synthesis of triacylglycerols from newly synthesized fatty acids and nascent diacylglycerols identifies this enzyme as the link between the two. This places DGAT2 at the centre of carbohydrate-induced hypertriglyceridaemia and hepatic steatosis. This function is complemented, but not substituted for, by the ability of DGAT1 to rescue partial glycerides from complete hydrolysis. In peripheral tissues not normally considered to be lipogenic, synthesis of triacylglycerols may largely bypass DGAT2 except in hyperglycaemic/hyperinsulinaemic conditions, when induction of de novo fatty acid synthesis in these tissues may contribute towards increased triacylglycerol secretion (intestine) or insulin resistance (adipose tissue, and cardiac and skeletal muscle).

Diacylglycerol acyltransferase 2 acts upstream of diacylglycerol acyltransferase 1 and utilizes nascent diglycerides and de novo synthesized fatty acids in HepG2 cells.

The two diacylglycerol acyltransferases, DGAT1 and DGAT2, are known to have non-redundant functions, in spite of catalysing the same reaction and being present in the same cell types. The basis for this distinctiveness, which is reflected in the very different phenotypes of Dgat1(-/-) and Dgat2(-/-) mice, has not been resolved. Using selective inhibitors of human DGAT1 and DGAT2 on HepG2 cells and gene silencing, we show that, although DGAT2 activity accounts for a modest fraction (< 20%) of overall cellular DGAT activity, inhibition of DGAT2 activity specifically inhibits (and is rate-limiting for) the incorporation of de novo synthesized fatty acids and of glycerol into cellular and secreted triglyceride to a much greater extent than it affects the incorporation of exogenously added oleate. By contrast, inhibition of DGAT1 affects equally the incorporation of glycerol and exogenous (preformed) oleate into cellular and secreted triacylglycerol (TAG). These data indicate that DGAT2 acts upstream of DGAT1, largely determines the rate of de novo synthesis of triglyceride, and uses nascent diacylglycerol and de novo synthesized fatty acids as substrates. By contrast, the data suggest that DGAT1 functions in the re-esterification of partial glycerides generated by intracellular lipolysis, using preformed (exogenous) fatty acids. Therefore, we describe distinct but synergistic roles of the two DGATs in an integrated pathway of TAG synthesis and secretion, with DGAT2 acting upstream of DGAT1.

An environment-dependent structural switch underlies the regulation of carnitine palmitoyltransferase 1A.

The enzyme carnitine palmitoyltransferase 1 (CPT1), which is anchored in the outer mitochondrial membrane (OMM), controls the rate-limiting step in fatty acid ß-oxidation in mammalian tissues. It is inhibited by malonyl-CoA, the first intermediate of fatty acid synthesis, and it responds to OMM curvature and lipid characteristics, which reflect long term nutrient/hormone availability. Here, we show that the N-terminal regulatory domain (N) of CPT1A can adopt two complex amphiphilic structural states, termed Nα and Nß, that interchange in a switch-like manner in response to offered binding surface curvature. Structure-based site-directed mutageneses of native CPT1A suggest Nα to be inhibitory and Nß to be noninhibitory, with the relative Nα/Nß ratio setting the prevalent malonyl-CoA sensitivity of the enzyme. Based on the amphiphilic nature of N and molecular modeling, we propose malonyl-CoA sensitivity to be coupled to the properties of the OMM by Nα-OMM associations that alter the Nα/Nß ratio. For enzymes residing at the membrane-water interface, this constitutes an integrative regulatory mechanism of exceptional sophistication.

Packing of transmembrane domain 2 of carnitine palmitoyltransferase-1A affects oligomerization and malonyl-CoA sensitivity of the mitochondrial outer membrane protein.

The purpose of this study was to investigate the sequence-dependence of oligomerization of transmembrane domain 2 (TM2) of rat carnitine palmitoyltransferase 1A (rCPT1A), to elucidate the role of this domain in the function of the full-length enzyme. Oligomerization of TM2 was studied qualitatively using complementary genetic assays that facilitate measurement of helix-helix interactions in the Escherichia coli inner membrane, and multiple quantitative biophysical methods. The effects of TM2-mutations on oligomerization and malonyl-CoA inhibition of the full-length enzyme (expressed in the yeast Pichia pastoris) were quantified. Changes designed to disrupt close-packing of the GXXXG(A) motifs reduced the oligomeric state of the corresponding TM2 peptides from hexamer to trimer (or lower), a reduction also observed on mutation of the TM2 sequence in the full-length enzyme. Disruption of these GXXXG(A) motifs had a parallel effect on the malonyl-CoA sensitivity of rCPT1A, reducing the IC(50) from 30.3 ± 5.0 to 3.0 ± 0.6 µM. For all measurements, wild-type rCPT1A was used as a control alongside various appropriate (e.g., molecular mass) standards. Our results suggest that sequence-determined, TM2-mediated oligomerization is likely to be involved in the modulation of malonyl-CoA inhibition of CPT1A in response to short- and long-term changes in protein-protein and protein-lipid interactions that occur in vivo.

Evidence that diacylglycerol acyltransferase 1 (DGAT1) has dual membrane topology in the endoplasmic reticulum of HepG2 cells.

Triacylglycerol (TAG) synthesis and secretion are important functions of the liver that have major impacts on health, as overaccumulation of TAG within the liver (steatosis) or hypersecretion of TAG within very low density lipoproteins (VLDL) both have deleterious metabolic consequences. Two diacylglycerol acyltransferases (DGATs 1 and 2) can catalyze the final step in the synthesis of TAG from diacylglycerol, which has been suggested to play an important role in the transfer of the glyceride moiety across the endoplasmic reticular membrane for (re)synthesis of TAG on the lumenal aspect of the endoplasmic reticular (ER) membrane (Owen, M., Corstorphine, C. C., and Zammit, V. A. (1997) Biochem. J. 323, 17-21). Recent topographical studies suggested that the oligomeric enzyme DGAT1 is exclusively lumen facing (latent) in the ER membrane. By contrast, in the present study, using two specific inhibitors of human DGAT1, we present evidence that DGAT1 has a dual topology within the ER of HepG2 cells, with approximately equal DGAT1 activities exposed on the cytosolic and lumenal aspects of the ER membrane. This was confirmed by the observation of the loss of both overt (partial) and latent (total) DGAT activity in microsomes prepared from livers of Dgat1(-/-) mice. Conformational differences between DGAT1 molecules having the different topologies were indicated by the markedly disparate sensitivities of the overt DGAT1 to one of the inhibitors. These data suggest that DGAT1 belongs to the family of oligomeric membrane proteins that adopt a dual membrane topology.

Effects of diabetes family history and exercise training on the expression of adiponectin and leptin and their receptors.

Daughters of diabetes patients have lower insulin sensitivity than women with no diabetes family history, but increase insulin sensitivity to a greater extent with exercise training. This study aimed to determine whether differences in circulating concentrations of adiponectin and leptin, and adipose tissue expression of their genes and receptors played a role. Women offspring of patients with type 2 diabetes mellitus (n = 34; age, 35.6 ± 7.0 years; body mass index, 28.1 ± 5.1 kg/m²) and matched controls with no diabetes family history (n = 36; age, 33.6 ± 6.1 years; body mass index, 27.3 ± 4.7 kg/m²) participated. Blood and abdominal subcutaneous adipose tissue samples were obtained at baseline and after a controlled 7-week endurance-type exercise intervention (sessions were performed at 65%-80% of maximum heart rate). At baseline, no significant differences were observed between groups in circulating leptin or adiponectin concentrations, or expression of their genes or receptors. In response to exercise, plasma leptin decreased more in offspring than controls (-32.2% vs -7.3%, P = .005 for interaction); and the long isoform of the leptin receptor messenger RNA (mRNA) increased significantly only in the offspring (+39.4%, P = .026 vs +7.7%, P = .892). Leptin mRNA decreased similarly in both groups (-24.7% vs -25.0%, P < .05 for both). Furthermore, changes in plasma leptin (r = -0.432, P < .001) and leptin mRNA (r = -0.298, P = .019) correlated significantly with changes in insulin sensitivity. Plasma adiponectin decreased similarly in both groups (-12.1% vs -15.2%, P < .01 for both), but no significant changes were observed in adiponectin-related gene expression. This work shows that exercise training has differing effects on leptin-related variables between women with and without a diabetes family history and suggests that these molecular differences may contribute to the differential effects of exercise training on insulin sensitivity between these 2 groups.

High glucose and elevated fatty acids suppress signaling by the endothelium protective ligand angiopoietin-1.

Pre-diabetes is characterized by hyperglycemia and dyslipidemia; it is associated with increased cardiovascular disease and endothelial dysfunction. Angiopoietin-1 (Ang1), a ligand for endothelial receptor, is a potent vascular protective factor important in maintaining normal endothelial function. The aim of the study was to examine the influence of elevated glucose and fatty acid concentrations on angiopoietin signaling in human cardiac microvascular endothelial cells. Incubation with 30 mM glucose caused 50% suppression in the ability of Ang1 to activate Tie2-receptor phosphorylation without any decrease in Tie2 expression or increased internalization in microvascular endothelial cells. Examination of downstream signaling revealed inhibition of Ang1-dependent Akt phosphorylation. By contrast, Ang1 activation of Erk1/2 signaling was not affected by hyperglycemia. Similar suppression of Ang1-dependent activation of Akt by hyperglycemia was observed in large vessel human endothelial cells. Incubation of microvascular endothelial cells with 200 microM palmitic acid significantly inhibited Ang1-dependent Akt phosphorylation without affecting phosphorylation of the Tie-2 receptor or of ERK1/2. Therefore, contrary to hyperglycemia, palmitate acted exclusively downstream of the receptor. The present findings suggest a mechanism by which increased glucose or fatty acids may suppress vascular protection by Ang1 and predispose to endothelial dysfunction and vascular disease.