Maternal eicosapentaenoic acid feeding promotes placental angiogenesis through a Sirtuin-1 independent inflammatory pathway

Maternal overnutrition or obesity is associated with a wide range of metabolic disorders and may impair placental angiogenesis. Previous studies have shown that n-3 polyunsaturated fatty acids (PUFA) promote fetal growth in both rodents and humans. Whether n-3 PUFA impacts on placental angiogenesis in vivo remains unclear. Sirtuin-1 (SIRT1) is a protein deacetylase that plays an important role in regulating inflammation and endothelial function. Little information is available on a putative role of SIRT1 in placental angiogenesis. The goal of this study was to examine the capability of eicosapentaenoic acid (EPA) to regulate angiogenesis and inflammation in SIRT1-deficient placentas. In the present study, male and female SIRT1^+/− mice were mated overnight, then primiparous SIRT1^+/− mice were fed a 60% kcal HFD or equienergy EPA diet (4.4% EPA-ethyl ester). We found that the EPA diet significantly improved maternal insulin sensitivity and decreased plasma levels of inflammatory factors IL-6 and TNFα concentration. Moreover, EPA treatment promoted fetus growth and placental angiogenesis, and inhibited the hypoxia inducible factor-1α(HIF1α) pathway. SIRT1 deficiency exhibited an opposite effect, leading to decrease in placental angiogenesis and fetal weight. No significant effect was observed between diet and genotype. Here, we reported for the first time that EPA treatment increased the expression of placental inflammatory genes and promoted translocation of NFκB into the nucleus. On the contrary, SIRT1-deficient placentas showed a decreased inflammation state. Together, these data demonstrate a previously unknown role of EPA to promote placental angiogenesis through a SIRT1 independent inflammatory pathway.     

Insulin Stimulated-Glucose Transporter Glut 4 Is Expressed in the Retina

The vertebrate retina is a very metabolically active tissue whose energy demands are normally met through the uptake of glucose and oxygen. Glucose metabolism in this tissue relies upon adequate glucose delivery from the systemic circulation. Therefore, glucose transport depends on the expression of glucose transporters. Here, we show retinal expression of the Glut 4 glucose transporter in frog and rat retinas. Immunohistochemistry and in situ hybridization studies showed Glut 4 expression in the three nuclear layers of the retina: the photoreceptor, inner nuclear and ganglionar cell layers. In the rat retina immunoprecipitation and Western blot analysis revealed a protein with an apparent molecular mass of 45 kDa. ¹⁴C-glucose accumulation by isolated rat retinas was significantly enhanced by physiological concentrations of insulin, an effect blocked by inhibitors of phosphatidyl-inositol 3-kinase (PI3K), a key enzyme in the insulin-signaling pathway in other tissues. Also, we observed an increase in ³H-cytochalasin binding sites in the presence of insulin, suggesting an increase in transporter recruitment at the cell surface. Besides, insulin induced phosphorylation of Akt, an effect also blocked by PI3K inhibition. Expression of Glut 4 was not modified in retinas of a type 1 diabetic rat model. To our knowledge, our results provide the first evidence of Glut4 expression in the retina, suggesting it as an insulin- responsive tissue.     

Pregestational diet transition to normal-fat diet avoids the deterioration of pancreatic β-cell function in male offspring induced by maternal high-fat diet

Novel progress has been made to understand the adverse pathophysiology in the pancreas of offspring exposed to overnutrition in utero. Our study is the first to evaluate whether the adverse effects of maternal overnutrition on offspring β-cell function are reversible or preventable through preconception maternal diet interventions. Herein, offspring mice were exposed in utero to one of the following: maternal normal-fat diet (NF group), maternal high-fat diet (HF group) or maternal diet transition from an HF to NF diet 9 weeks before pregnancy (H9N group). Offspring mice were subjected to postweaning HF diet for 12 weeks. HF offspring, but not H9N, displayed glucose intolerance and insulin resistance. HF male offspring had enlarged islet β-cells with reduced β-cell density, whereas, H9N male offspring did not show these changes. Co-immunofluorescent (Co-IF) staining of glucose transporter 2 (Glut2) and insulin (Ins) revealed significantly more Glut2⁺Ins⁻ cells, indicative of insulin degranulation, in HF male offspring but not H9N. In addition, Co-IF of insulin and p-H3S10 indicated that β cells of HF male offspring, but not H9N, had proliferation defects likely due to inhibited protein kinase B (AKT) phosphorylation. In summary, our study demonstrates that maternal H9N diet effectively prevents functional deterioration of β cells seen in HF male offspring by avoiding β-cell proliferation defects and degranulation.     

The effect of gonadotropin on glucose transport and apoptosis in rat ovary

Although the effects of Gonadotropin on ovarian physiology have been known for many decades, its action on glucose uptake in the rat ovary remained poorly understood. Evidence also suggests that glucose uptake is mediated by a number of glucose transporter proteins (Glut). Therefore, we examined the rat ovary for the presence of Glut1-4 and blood glucose level after eCG (equine chorionic gonadotropin) and anti-eCG antiserum treatment. All of the glucose transports were present in the ovarian oocyte, granulosa cells and theca cells in different stage follicles. The expression of Glut in ovary was up-regulated by eCG, however, anti-eCG antiserum reversed eCG action. Western blot analysis also demonstrated the content of Glut1 was higher in eCG treatment group compared with anti-eCG antiserum and control group. The same tendency was shown in other glut isoforms. Moreover, there were no significant difference between the anti-eCG antiserum and control group. In additional, the level of serum glucose in eCG treatment group was significantly higher than others, which is similar with glut expression pattern. High glucose level in blood is correlated with increased expression of glucose transporter proteins in rat ovary. Meanwhile, anti-eCG antiserum increased granulosa cell apoptosis in antral follicle compared with those in eCG group. Our observations provide potential explanation for the effects of Glut on follicular development in rat ovary and a role for eCG in the regulation of ovarian glucose uptake.     

Glucose transporter 1-mediated glucose uptake is limiting for B-cell acute lymphoblastic leukemia anabolic metabolism and resistance to apoptosis

The metabolic profiles of cancer cells have long been acknowledged to be altered and to provide new therapeutic opportunities. In particular, a wide range of both solid and liquid tumors use aerobic glycolysis to supply energy and support cell growth. This metabolic program leads to high rates of glucose consumption through glycolysis with secretion of lactate even in the presence of oxygen. Identifying the limiting events in aerobic glycolysis and the response of cancer cells to metabolic inhibition is now essential to exploit this potential metabolic dependency. Here, we examine the role of glucose uptake and the glucose transporter Glut1 in the metabolism and metabolic stress response of BCR-Abl+ B-cell acute lymphoblastic leukemia cells (B-ALL). B-ALL cells were highly glycolytic and primary human B-ALL samples were dependent on glycolysis. We show B-ALL cells express multiple glucose transporters and conditional genetic deletion of Glut1 led to a partial loss of glucose uptake. This reduced glucose transport capacity, however, was sufficient to metabolically reprogram B-ALL cells to decrease anabolic and increase catabolic flux. Cell proliferation decreased and a limited degree of apoptosis was also observed. Importantly, Glut1-deficient B-ALL cells failed to accumulate in vivo and leukemic progression was suppressed by Glut1 deletion. Similarly, pharmacologic inhibition of aerobic glycolysis with moderate doses of 2-deoxyglucose (2-DG) slowed B-ALL cell proliferation, but extensive apoptosis only occurred at high doses. Nevertheless, 2-DG induced the pro-apoptotic protein Bim and sensitized B-ALL cells to the tyrosine kinase inhibitor Dasatinib in vivo. Together, these data show that despite expression of multiple glucose transporters, B-ALL cells are reliant on Glut1 to maintain aerobic glycolysis and anabolic metabolism. Further, partial inhibition of glucose metabolism is sufficient to sensitize cancer cells to specifically targeted therapies, suggesting inhibition of aerobic glycolysis as a plausible adjuvant approach for B-ALL therapies.Many cancer cells have elevated rates of glycolysis and lactate production even in the presence of oxygen. This program, termed aerobic glycolysis, occurs in a wide range of both solid and liquid tumors and is driven by oncogenic signals and microenvironmental pressures.¹ Aerobic glycolysis is proposed to allow metabolism in low oxygen tensions and to provide biosynthetic intermediates for cell growth. Indeed, aerobic glycolysis readily supports both generation of ATP and biosynthesis of lipids, nucleic acids, and amino acids.¹ Given the high rates of glucose consumption and aerobic glycolysis in most cancers, targeting glucose metabolism has become of significant interest as an approach to eliminate cancer cells. It is now important to establish mechanisms of aerobic glycolysis and the response of cancer cells to metabolic inhibition.The t(9;22) chromosomal translocation that generates the oncogenic kinase BCR-Abl occurs in ~25% of adult B-cell acute lymphoblastic leukemia cells (B-ALL) and is associated with poor prognosis.² The metabolic program of B-ALL cells is undefined, although diffuse large B-cell lymphoma (DLBCL) can either be highly glycolytic or use oxidative phosphorylation and mitochondrial metabolism.³ It has been suggested that BCR-Abl signaling is associated with elevated glucose metabolism, as BCR-Abl can promote glucose uptake and trafficking of glucose transporter Glut1 to the cell surface. Conversely, inhibition of BCR-Abl in leukemic cells suppresses glucose uptake and glycolysis.^{4, 5, 6, 7} This regulation of glucose metabolism may be critical for survival of BCR-Abl B-ALL, as enforced expression of Glut1 protected B-ALL cells from imatinib-induced apoptosis.⁸ These data show that BCR-Abl promotes glucose uptake and aerobic glycolysis, and BCR-Abl-transformed cells may rely on this pathway.Targeting glucose metabolism can have efficacy against a variety of cancers.⁹ Mechanistic understanding of cancer cell metabolic requirements or response to inhibition using pharmacologic approaches, however, has been limited. It has been shown using the glycolytic inhibitor 2-deoxyglucose (2-DG) or glucose deprivation culture conditions that inhibition of glucose metabolism impacts cancer cell growth and viability through several different mechanisms, including cell cycle arrest or cell death by activating AMPK pathway and inactivating mTOR signaling.¹⁰ Reduced glucose metabolism has also been found to impact the stability and synthesis of Bcl-2 family proteins. Glucose deprivation induces expression of pro-apoptotic molecules, including Bim^{7,11, 12, 13, 14, 15} and can induce apoptosis in cells transformed with oncogenic K-Ras through the unfolded protein response pathway.¹⁶Here we examine the mechanism and role of glucose uptake in B-ALL metabolism and leukemia progression by genetically targeting glucose transport. The Glut family of hexose transporters consists of 14 members¹⁷ and B-ALL cells expressed multiple family members. Conditional deletion of Glut1, however, demonstrated that B-ALL cells are reliant on this specific glucose transporter to sustain anabolic metabolism, proliferation, and resistance to cell death. Consistent with our data showing a key role for glucose uptake, we found that pharmacologic inhibition of glycolysis sensitized B-ALL cells to caspase activation and apoptosis to reduce leukemia burden in vivo. Glut1 and glucose uptake have a key role, therefore, to maintain BCR-Abl B-ALL cell growth and resistance to cell death.     

Serpina3c protects against high-fat diet-induced pancreatic dysfunction through the JNK-related pathway

BackgroundSerpina3 is a member of the serine protease inhibitor family and is involved in the inflammatory response. In this study, we investigated the effect of Serpina3c on pancreatic function in hypercholesterolemic mice.MethodsTo investigate the role of Serpina3c in hyperlipidaemia, Serpina3c knockout mice were bred with Apoe-knockout mice (on a C57BL/6 background) to generate heterozygous Serpina3c-Apoe double knockout (Serpina3c^+/−/Apoe^+/−) mice and were then bred to obtain homozygotes. C57BL/6, Serpina3c^−/−, Apoe^−/−, and Apoe^−/-Serpina3c^−/− mice were fed normal chow, and Apoe^−/− and Apoe^−/-Serpina3c^−/− mice were fed a high-fat diet (HFD). After feeding for 3 months, the mice were monitored for body weight, blood glucose, glucose tolerance, and insulin tolerance test (ITT). ELISA and immunohistochemistry were used to detect insulin levels and glucagon expression. Immunohistochemical staining for macrophages in the pancreas was also performed. Western blot analysis was performed on pancreatic tissues to detect the protein levels of insulin-associated molecules, the metalloproteinase MMP2, the tissue inhibitor TIMP2 and components of the JNK-related pathway.ResultsBlood glucose levels, glucose tolerance, and ITT were not significantly different among the groups. Serpina3c knockout resulted in blood lipid abnormalities in mice under HFD conditions. Insulin secretion was decreased in Apoe^−/-Serpina3c^−/− mice compared with Apoe^−/− mice under normal chow conditions. In addition, Apoe^−/-Serpina3c^−/− mice exhibited increased insulin and glucagon secretion and expression after three months of HFD feeding, but insulin secretion was decreased in Apoe^−/-Serpina3c^−/− mice compared with Apoe^−/− mice after the fifth month of HFD feeding. Serpina3c knockout increased MMP2 protein levels, whereas TIMP2 levels in the pancreas were decreased. Furthermore, Serpina3c knockout significantly upregulated the number of macrophages in the pancreas under HFD conditions. The JNK/AKT/FOXO1/PDX-1 axis was found to be involved in Serpina3c-regulated insulin secretion.ConclusionThese novel findings show that Serpina3c could play a protective role in insulin secretion partly through the JNK-related pathway under HFD conditions.     

Insulin regulation of the two glucose transporters in 3T3-L1 adipocytes

The amounts of the brain type and muscle type glucose transporters (designated Glut 1 and 4, respectively) in 3T3-L1 adipocytes have been determined by quantitative immunoblotting with antibodies against their carboxyl-terminal peptides. There are about 950,000 and 280,000 copies of Glut 1 and 4, respectively, per cell. Insulin caused the translocation of both types of transporters from an intracellular location to the plasma membrane. The insulin-elicited increase in cell surface transporters was assessed by labeling the surface transporters with a newly developed, membrane-impermeant, photoaffinity labeling reagent for glucose transporters. The increases in Glut 1 and 4 averaged 6.5- and 17-fold, respectively, whereas there was a 21-fold in hexose transport. These results indicate that the translocation of Glut 4 could largely account for the insulin effect on transport rate, but only if the intrinsic activity of Glut 4 is much higher than that of Glut 1. The two transporters are colocalized intracellularly: vesicles (average diameter 72 nm) isolated from the intracellular membranes by immunoadsorption with antibodies against Glut 1 contained 95% of the Glut 4 and, conversely, vesicles isolated with antibodies against Glut 4 contained 85% of the Glut 1.     

Maternal cigarette smoke exposure contributes to glucose intolerance and decreased brain insulin action in mice offspring independent of maternal diet

Background

Maternal smoking leads to intrauterine undernutrition and is associated with low birthweight and higher risk of offspring obesity. Intrauterine smoke exposure (SE) may alter neuroendocrine mediators regulating energy homeostasis as chemicals in cigarette smoke can reach the fetus. Maternal high-fat diet (HFD) consumption causes fetal overnutrition; however, combined effects of HFD and SE are unknown. Thus we investigated the impact of combined maternal HFD and SE on adiposity and energy metabolism in offspring.

Method

Female Balb/c mice had SE (2 cigarettes/day, 5 days/week) or were sham exposed for 5 weeks before mating. Half of each group was fed HFD (33% fat) versus chow as control. The same treatment continued throughout gestation and lactation. Female offspring were fed chow after weaning and sacrificed at 12 weeks.

Results

Birthweights were similar across maternal groups. Faster growth was evident in pups from SE and/or HFD dams before weaning. At 12 weeks, offspring from HFD-fed dams were significantly heavier than those from chow-fed dams (chow-sham 17.6±0.3 g; chow-SE 17.8±0.2 g; HFD-sham 18.7±0.3 g; HFD-SE 18.8±0.4 g, P<0.05 maternal diet effect); fat mass was significantly greater in offspring from chow+SE, HFD+SE and HFD+sham dams. Both maternal HFD and SE affected brain lactate transport. Glucose intolerance and impaired brain response to insulin were observed in SE offspring, and this was aggravated by maternal HFD consumption.

Conclusion

While maternal HFD led to increased body weight in offspring, maternal SE independently programmed adverse health outcomes in offspring. A smoke free environment and healthy diet during pregnancy is desirable to optimize offspring health.     

Differential regulation of two glucose transporters by chronic growth hormone treatment of cultured 3T3-F442A adipose cells

New methods for the analysis of glucose transporters were used to analyze the molecular mechanisms involved in the insulin-antagonistic effects of growth hormone (GH), which is known as a diabetogenic hormone. The ability of GH to alter the number and mRNA levels of two different glucose transporters in cultured 3T3-F442A adipocytes was investigated using specific antibodies and cDNA probes. At concentrations of GH as low as 0.5 and 5 ng/ml and at incubation times as short as 4 h, GH decreased rates of 2-deoxyglucose uptake in 3T3-F442A adipocytes. 3-O-Methyl-D-glucose uptake was inhibited to an extent similar to that of 2-deoxyglucose uptake (60-80%) after a 24-h incubation with GH (500 ng/ml), indicating that GH inhibits glucose metabolism specifically at the step of glucose transport. To determine whether reduced rates of glucose transport might result from reduced numbers of glucose transporters, whole cell lysates were prepared from GH-treated cells and subjected to immunoblotting using antibodies that identify Glut 1 (HepG2/rat brain) and Glut 4 (muscle/adipose) transporters. GH caused a time- and dose-dependent decrease in the number of Glut 1 transporters in the cell. Northern and slot-blot analyses showed a GH-induced dose-dependent decrease in levels of Glut 1 mRNA. In contrast, levels of Glut 4 transporter and mRNA were unchanged by GH. These data suggest that GH regulates Glut 1 and Glut 4 transporters differentially and that it exerts its inhibitory effect on glucose uptake at least in part by decreasing the synthesis of Glut 1 transporters. These studies provide the first evidence that GH regulates a key gene in metabolic regulation and can interfere with gene expression.     

Slc2a5 (Glut5) Is Essential for the Absorption of Fructose in the Intestine and Generation of Fructose-induced Hypertension

The identity of the transporter responsible for fructose absorption in the intestine in vivo and its potential role in fructose-induced hypertension remain speculative. Here we demonstrate that Glut5 (Slc2a5) deletion reduced fructose absorption by ∼75% in the jejunum and decreased the concentration of serum fructose by ∼90% relative to wild-type mice on increased dietary fructose. When fed a control (60% starch) diet, Glut5^-/- mice had normal blood pressure and displayed normal weight gain. However, whereas Glut5^+/+ mice showed enhanced salt absorption in their jejuna in response to luminal fructose and developed systemic hypertension when fed a high fructose (60% fructose) diet for 14 weeks, Glut5^-/- mice did not display fructose-stimulated salt absorption in their jejuna, and they experienced a significant impairment of nutrient absorption in their intestine with accompanying hypotension as early as 3–5 days after the start of a high fructose diet. Examination of the intestinal tract of Glut5^-/- mice fed a high fructose diet revealed massive dilatation of the caecum and colon, consistent with severe malabsorption, along with a unique adaptive up-regulation of ion transporters. In contrast to the malabsorption of fructose, Glut5^-/- mice did not exhibit an absorption defect when fed a high glucose (60% glucose) diet. We conclude that Glut5 is essential for the absorption of fructose in the intestine and plays a fundamental role in the generation of fructose-induced hypertension. Deletion of Glut5 results in a serious nutrient-absorptive defect and volume depletion only when the animals are fed a high fructose diet and is associated with compensatory adaptive up-regulation of ion-absorbing transporters in the colon.Fructose is a monosaccharide and is one of the three most important blood sugars along with glucose and galactose (1–3). It plays an essential role in vital metabolic functions in the body, including glycolysis and gluconeogenesis (4–6). Fructose is predominantly metabolized in the liver. A high flux of fructose to the liver perturbs glucose metabolism and leads to a significantly enhanced rate of triglyceride synthesis. In addition, fructose can be metabolized in the liver to uric acid, a potent antioxidant (7, 8).The classic model of sugar absorption indicates that sodium glucose cotransporter 1 (Sglt1)³ and Glut5 absorb glucose and fructose, respectively, from intestinal lumen to cytosol, and Glut2 transports both glucose and fructose from the cytosol to the blood (9–19). Glut2 has high affinity for glucose and a moderate affinity for fructose, whereas Glut5 predominantly transports fructose with very low affinity for glucose (9–19; reviews in Refs. 14, 17–19). The expression of Glut5 or Glut2 in the small intestine increases in rats or mice fed a diet high in fructose or perfused with increased fructose concentration (11–14, 18, 19).Glut2 is predominantly found on the basolateral membrane and in the cytoplasm of enterocytes at basal state but is thought to be recruited to the apical membrane in the presence of increased glucose or fructose in the intestinal lumen (11, 19). Given the fact that both Glut5 and Glut2 can transport fructose in vitro and given the ability of Glut2 to traffic to the apical membrane, the contribution of Glut5 to the absorption of fructose in vivo and systemic fructose homeostasis remains speculative.The marked increase in dietary fructose consumption in the form of high fructose corn syrup, a common sweetener used in the food industry, table sugar, and fruits correlates with the increased incidence of metabolic syndrome, which is reaching an epidemic proportion in developed countries and is a major contributor to premature morbidity and mortality in our society (20–22). Increased dietary fructose intake recapitulates many aspects of metabolic syndrome, including dyslipidemia, insulin resistance, and hypertension in rat and mouse (23–26). Recent studies demonstrate that fructose-induced hypertension is initiated by increased absorption of salt and fructose in the intestine (27); however, the one or more molecules (Glut2, Glut5, Glut7, or Sglt1) that are responsible for the absorption of fructose in the intestine remain speculative. Further, although Glut7, Glut5, and Glut2 can transport fructose in vitro, the role of Glut5 in in vivo fructose absorption remains unknown. To ascertain the role of Glut5 in fructose absorption in the intestine in vivo and fructose-induced hypertension, mice lacking the Glut5 gene (Glut5^-/-) were placed on either high fructose or normal diet and compared with their wild-type littermates (Glut5^+/+).     

Maternal obesity impairs brain glucose metabolism and neural response to hyperglycemia in male rat offspring

Hypothalamic appetite regulators neuropeptide Y (NPY) and pro‐opiomelanocortin (POMC) are modulated by glucose. This study investigated how maternal obesity disturbs glucose regulation of NPY and POMC, and whether this deregulation is linked to abnormal hypothalamic glucose uptake‐lactate conversion. As post‐natal high‐fat diet (HFD) can exaggerate the effects of maternal obesity, its additional impact was also investigated. Female Sprague Dawley rats were fed a HFD (20 kJ/g) to model maternal obesity. At weaning, male pups were fed chow or HFD. At 9 weeks, in vivo hypothalamic NPY and POMC mRNA responses to acute hyperglycemia were measured; while hypothalami were glucose challenged in vitro to assess glucose uptake‐lactate release and related gene expression. Maternal obesity dampened in vivo hypothalamic NPY response to acute hyperglycemia, and lowered in vitro hypothalamic glucose uptake and lactate release. When challenged with 20 mM glucose, hypothalamic glucose transporter 1, monocarboxylate transporters, lactate dehydrogenase‐b, NPY and POMC mRNA expression were down‐regulated in offspring exposed to maternal obesity. Post‐natal HFD consumption reduced in vitro lactate release and monocarboxylate transporter 2 mRNA, but increased POMC mRNA levels when challenged with 20 mM glucose. Overall, maternal obesity produced stronger effects than post‐natal HFD consumption to impair hypothalamic glucose metabolism. However, they both disturbed NPY response to hyperglycemia, potentially leading to hyperphagia.

     

Differential expression of glucose transporters in rabbit placenta: effect of hypercholesterolemia in dams

Low birth weight is observed in rabbit offspring when maternal hypercholesterolemia is induced during gestation, but the related etiology is still unknown. Glucose is one of the most important substances during fetal development, and defect in glucose supply to fetus was related to pathophysiological mechanisms in intrauterine growth restriction. Thus, the aim of this work was to evaluate the impact of maternal hypercholesterolemia during rabbit gestation on the glucose metabolism and the routing of glucose transporters (SLC2 and SLC5 [previously known as GLUT and SGLT]) in placenta. In this study, maternal and offspring serum levels of glucose and insulin were evaluated for control and hypercholesterolemic groups, and the mRNA and protein expressions of placental SLCs were quantified by real-time RT-PCR and Western immunoblot, respectively. Our data demonstrate that maternal hypercholesterolemia during gestation: 1) induces offspring hypoglycemia; 2) does not modify the genetic and protein expressions of SLC2A1 and SLC2A4 (previously GLUT1 and GLUT4) in total placental extract; 3) downregulates the placental SLC5A1 (previously SGLT1) protein expression without affecting its mRNA levels; 4) impairs the translocation of SLC2A1 but not SLC2A4 from cytoplasmatic pool to the cell membrane surface. Then we assume that reduction of offspring birth weight in presence of maternal hypercholesterolemia may be related to the offspring's hypoglycemia and the reduction of the cell surface expression of placental SLC2A1.     

Sucrose nonfermenting AMPK-related kinase (SNARK) regulates exercise-stimulated and ischemia-stimulated glucose transport in the heart

The signaling mechanisms mediating myocardial glucose transport are not fully understood. Sucrose nonfermenting AMP-activated protein kinase (AMPK)-related kinase (SNARK) is an AMPK-related protein kinase that is expressed in the heart and has been implicated in contraction-stimulated glucose transport in mouse skeletal muscle. We first determined if SNARK is phosphorylated on Thr²⁰⁸, a site critical for SNARK activity. Mice were treated with exercise, ischemia, submaximal insulin, or maximal insulin. Treadmill exercise slightly, but significantly increased SNARK Thr²⁰⁸ phosphorylation. Ischemia also increased SNARK Thr²⁰⁸ phosphorylation, but there was no effect of submaximal or maximal insulin. HL1 cardiomyocytes were used to overexpress wild-type (WT) SNARK and to knockdown endogenous SNARK. Overexpression of WT SNARK had no effect on ischemia-stimulated glucose transport; however, SNARK knockdown significantly decreased ischemia-stimulated glucose transport. SNARK overexpression or knockdown did not alter insulin-stimulated glucose transport or glycogen concentrations. To study SNARK function in vivo, SNARK heterozygous knockout mice (SNARK^+/−) and WT littermates performed treadmill exercise. Exercise-stimulated glucose transport was decreased by ~50% in hearts from SNARK^+/− mice. In summary, exercise and ischemia increase SNARK Thr²⁰⁸ phosphorylation in the heart and SNARK regulates exercise-stimulated and ischemia-stimulated glucose transport. SNARK is a novel mediator of insulin-independent glucose transport in the heart.     

Myocardial macronutrient transporter adaptations in the adult pregestational female intrauterine and postnatal growth-restricted offspring

Associations between exponential childhood growth superimposed on low birth weight and adult onset cardiovascular disease with glucose intolerance/type 2 diabetes mellitus exist in epidemiological investigations. To determine the metabolic adaptations that guard against myocardial failure on subsequent exposure to hypoxia, we compared with controls (CON), the effect of intrauterine (IUGR), postnatal (PNGR), and intrauterine and postnatal (IPGR) calorie and growth restriction (n = 6/group) on myocardial macronutrient transporter (fatty acid and glucose) -mediated uptake in pregestational young female adult rat offspring. A higher myocardial FAT/CD36 protein expression in IUGR, PNGR, and IPGR, with higher FATP1 in IUGR, FATP6 in PNGR, FABP-c in PNGR and IPGR, and no change in GLUT4 of all groups was observed. These adaptive macronutrient transporter protein changes were associated with no change in myocardial [(3)H]bromopalmitate accumulation but a diminution in 2-deoxy-[(14)C]glucose uptake. Examination of the sarcolemmal subfraction revealed higher basal concentrations of FAT/CD36 in PNGR and FATP1 and GLUT4 in IUGR, PNGR, and IPGR vs. CON. Exogenous insulin uniformly further enhanced sarcolemmal association of these macronutrient transporter proteins above that of basal, with the exception of insulin resistance of FATP1 and GLUT4 in IUGR and FAT/CD36 in PNGR. The basal sarcolemmal macronutrient transporter adaptations proved protective against subsequent chronic hypoxic exposure (7 days) only in IUGR and PNGR, with notable deterioration in IPGR and CON of the echocardiographic ejection fraction. We conclude that the IUGR and PNGR pregestational adult female offspring displayed a resistance to insulin-induced translocation of FATP1, GLUT4, or FAT/CD36 to the myocardial sarcolemma due to preexistent higher basal concentrations. This basal adaptation of myocardial macronutrient transporters ensured adequate fatty acid uptake, thereby proving protective against chronic hypoxia-induced myocardial compromise.