Regulation of glycolysis and fatty acid synthesis from glucose in sheep adipose tissue

Robertson, James P.; Faulkner, Anne; Vernon, Richard G.

doi:10.1042/bj2060577

Cited by 57 publications

(47 citation statements)

References 39 publications

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“…Adipocytes were prepared by collagenase digestion, and the adipocyte mean cell volume and number of adipocytes per gram adipose tissue were determined (57).…”

Section: Methodsmentioning

confidence: 99%

Leptin secretion and hypothalamic neuropeptide and receptor gene expression in sheep

Sørensen

Adam²,

Findlay³

et al. 2002

American Journal of Physiology-Regulatory, Integrative and Comp

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Sheep were fed ad libitum and killed at 6 and 18 days of lactation; ad libitum-fed nonlactating sheep were killed as controls. Despite increased food intake, lactating ewes were in negative energy balance. Lactation decreased plasma leptin and adipose tissue leptin mRNA concentrations. OB-Rb gene expression, determined by in situ hybridization, was increased in the hypothalamic arcuate nucleus (ARC) and ventromedial hypothalamic nucleus (VMH) at both stages of lactation. Neuropeptide Y (NPY) was increased by lactation in both the ARC and dorsomedial hypothalamus (DMH), although increased gene expression in the DMH was only apparent at day 18 of lactation. Gene expression was decreased for cocaine-and amphetamine-regulated transcript (CART) in the ARC and VMH and for proopiomelanocortin in ARC during lactation. Agouti-related peptide gene expression was increased in the ARC, and melanocortin receptor expression was unchanged in both the ARC and VMH with lactation. Thus the hypoleptinemia of lactation may activate NPY orexigenic pathways and attenuate anorexigenic melanocortin and CART pathways in the hypothalamus to promote the hyperphagia of lactation. hypothalamic neuropeptides; appetite NUTRIENT REQUIREMENTS ARE markedly increased during lactation to meet the demands for milk production (7,70). In most mammals, these additional requirements are met primarily by increasing food intake (7,20,70), but factors regulating the hyperphagia of lactation are not well understood. In addition, in many species, the increased intake is insufficient to meet the metabolic demands, resulting in a state of negative energy balance during early lactation when body lipid reserves are mobilized (7,69). In some species such as the rat, the degree of negative energy balance is usually slight, with animals mobilizing ϳ1 g fat/day (7). Domestic ruminants, however, usually exhibit a greater degree of negative energy balance during early lactation (7, 11), which can impact on their welfare and productivity (28), yet the regulatory mechanisms have not been elucidated.It is postulated that leptin, a peptide hormone secreted by adipose tissue (75), could play a role in the hyperphagia of lactation. Leptin acts on hypothalamic neuronal systems to regulate energy balance and neuroendocrine function; in particular, a reduction in circulating leptin is a potent signal of negative energy balance, activating compensatory orexigenic pathways in the hypothalamus (3-5, 35, 64). Key targets are neurons in the hypothalamic arcuate nucleus (ARC) expressing the signaling form of the leptin receptor (OB-Rb); these are the orexigenic peptides neuropeptide Y (NPY) and agouti-related peptide (AGRP) and the anorexigenic peptides proopiomelanocortin (POMC, precursor for melanocortins) and cocaine-and amphetamine-regulated transcript (CART) (4,5,31,62,64,72). Adipose leptin gene expression and serum leptin concentrations are reported to be reduced during lactation in the monogastric rat in most (16,36,39,56,65,74), but not all (17,19,61), studies. NPY (18,21,...

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“…Adipocytes were prepared by collagenase digestion, and the adipocyte mean cell volume and number of adipocytes per gram adipose tissue were determined (57).…”

Section: Methodsmentioning

confidence: 99%

Leptin secretion and hypothalamic neuropeptide and receptor gene expression in sheep

Sørensen

Adam²,

Findlay³

et al. 2002

American Journal of Physiology-Regulatory, Integrative and Comp

Self Cite

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“…These were maintained in culture in Medium 199 as described previously (Robertson et al 1982) for 72 h in combinations of insulin (17 nM) and dexamethasone (10 nM). Fresh explants of adipose tissue and explants after culture were snap frozen and stored in liquid nitrogen.…”

Section: Tissue Culturementioning

confidence: 99%

Insulin-glucocorticoid interactions in the regulation of acetyl-CoA carboxylase-alpha transcript diversity in ovine adipose tissue

Travers

Barber²

1999

Journal of Molecular Endocrinology

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Transcription of the acetyl-CoA carboxylase (ACC)-gene is initiated from two promoters, promoter I (PI) and promoter II (PII) types when compared with explants prior to culture. PII transcripts, by contrast, were increased 2-fold by culture in insulin plus dexamethasone and this was entirely attributed to an increase in the expression of the E[2/4/5] type. Dexamethasone acts to potentiate the action of insulin on PI and PII transcript abundance and this effect is greatest for PI transcripts. This study has demonstrated that repression of the ACC-gene in adipose tissue during lactation is largely achieved through attenuation of PI transcript abundance and may be related, in part, to a change in the sensitivity of the apparatus that regulates PI transcript steady-state levels to insulin.

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“…Explants weighing about 15 mg were cut using scissors and cultured in Medium 199 with Earle's salts, -glutamine, 25 mM Hepes (pH 7·3) (Gibco Biocult, Paisley, Strathclyde, Scotland, UK), 2·6 mM acetate (final concentration) and antibiotics (Robertson et al 1982). Tissue was preincubated in the culture medium for 22 h after which it was transferred to fresh culture medium plus or minus 4·5 nM GH and other agents as indicated in the text and tables and maintained in culture for a further period of 24 h. Ovine pituitary GH was a gift from NIADDK, Bethesda, MD, USA; H7 was from Scientific Marketing, Barnet, Herts, UK; okadaic acid was from Calbiochem-Novabiochem (UK) Ltd, Nottingham, Notts, UK; phorbol myristyl acetate (PMA) was from Sigma-Aldrich, Poole, Dorset, UK.…”

Section: Tissue Culturementioning

confidence: 99%

Regulation of the GTP-binding protein-based antilipolytic system of sheep adipocytes by growth hormone

Doris¹,

Kilgour²,

Houslay³

et al. 1998

Journal of Endocrinology

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Chronic exposure of sheep adipose tissue to growth hormone (GH) in vitro decreases the ability of the adenosine analogue, N 6 -phenylisopropyladenosine (PIA), to inhibit isoprenaline-stimulated lipolysis by a mechanism which is dependent on both gene transcription and protein serine/threonine phosphorylation. The inhibition is not due to a change in ligand binding to the adenosine receptor, the amounts of the three isoforms of the inhibitory GTP-binding protein, G i , or the maximum (forskolin-stimulated) adenylate cyclase activity. The ability of GH to modulate the PIA-activated adenosine receptor to stimulate dissociation of heterotrimeric G i was assessed by measurement of pertussis toxin-catalysed ADP-ribosylation of G i ; GH does not appear to alter the interaction between the activated receptor and G i . The ability of GH to alter the ability of activated G i to inhibit adenylate cyclase activity was assessed by measuring the ability of a GTP analogue, guanosine 5 -[ -imido]triphosphate (p[NH]ppG), to inhibit forskolinstimulated adenylate cyclase activity; chronic exposure to GH prevented this effect of p [NH]ppG. Thus the attenuation of the inhibition of lipolysis by PIA by chronic exposure of adipocytes to GH appears to be due to an impairment in the interaction between adenylate cyclase and the subunit of one or more isoforms of G i .

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Regulation of glycolysis and fatty acid synthesis from glucose in sheep adipose tissue

Cited by 57 publications

References 39 publications

Leptin secretion and hypothalamic neuropeptide and receptor gene expression in sheep

Leptin secretion and hypothalamic neuropeptide and receptor gene expression in sheep

Insulin-glucocorticoid interactions in the regulation of acetyl-CoA carboxylase-alpha transcript diversity in ovine adipose tissue

Regulation of the GTP-binding protein-based antilipolytic system of sheep adipocytes by growth hormone

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