Search Results
Search for other papers by Mohamed Asrih in
Google Scholar
PubMed
Search for other papers by François R Jornayvaz in
Google Scholar
PubMed
Nonalcoholic fatty liver disease (NAFLD) has become a major health problem in developed countries. It has affected more than 30% of the general population and is commonly associated with insulin resistance, which is a major risk factor for the development of type 2 diabetes and a central feature of the metabolic syndrome. Furthermore, accumulating evidences reveal that NAFLD as well as insulin resistance is strongly related to inflammation. Cytokines and adipokines play a pivotal role in inflammatory processes. In addition, these inflammatory mediators regulate various functions including metabolic energy balance, inflammation, and immune response. However, their role in modulating ectopic lipids involved in the development of insulin resistance, such as diacylglycerols and ceramides, remains unknown. The aim of this review is first to describe the pathophysiology of insulin resistance in NAFLD. In particular, we discuss the role of ectopic lipid accumulation in the liver. Secondly, we also summarize recent findings emphasizing the role of main inflammatory markers in both NAFLD and insulin resistance and their potential role in modulating hepatic fat content in NAFLD and associated hepatic insulin resistance.
Division of Metabolic and Vascular Health, Warwickshire Institute for the Study of Diabetes, Clinical Sciences Research Laboratories, Warwick Medical School, University Hospital Site, University of Warwick, Coventry CV2 2DX, UK
Search for other papers by M K Piya in
Google Scholar
PubMed
Search for other papers by P G McTernan in
Google Scholar
PubMed
Division of Metabolic and Vascular Health, Warwickshire Institute for the Study of Diabetes, Clinical Sciences Research Laboratories, Warwick Medical School, University Hospital Site, University of Warwick, Coventry CV2 2DX, UK
Search for other papers by S Kumar in
Google Scholar
PubMed
Adipose tissue is an active endocrine organ, and our knowledge of this secretory tissue, in recent years, has led us to completely rethink how our body functions and becomes dysregulated with weight gain. Human adipose tissue appears to act as a multifunctional secretory organ with the capacity to control energy homoeostasis through peripheral and central regulation of energy homoeostasis. It also plays an important role in innate immunity. However, the capability to more than double its original mass to cope with positive energy balance in obesity leads to many pathogenic changes. These changes arise within the adipose tissue as well as inducing secondary detrimental effects on other organs like muscle and liver, including chronic low-grade inflammation mediated by adipocytokines (adipokine inflammation). This inflammation is modulated by dietary factors and nutrients including glucose and lipids, as well as gut bacteria in the form of endotoxin or LPS. The aim of this current review is to consider the impact of nutrients such as glucose and lipids on inflammatory pathways, specifically within adipose tissue. Furthermore, how nutrients such as these can influence adipokine inflammation and consequently insulin resistance directly through their effects on secretion of adipocytokines (TNFα, IL6 and resistin) as well as indirectly through increases in endotoxin is discussed.
Search for other papers by A P Santos-Silva in
Google Scholar
PubMed
Search for other papers by E Oliveira in
Google Scholar
PubMed
Search for other papers by C R Pinheiro in
Google Scholar
PubMed
Search for other papers by A L Nunes-Freitas in
Google Scholar
PubMed
Search for other papers by Y Abreu-Villaça in
Google Scholar
PubMed
Search for other papers by A C Santana in
Google Scholar
PubMed
Search for other papers by C C Nascimento-Saba in
Google Scholar
PubMed
Search for other papers by J F Nogueira-Neto in
Google Scholar
PubMed
Search for other papers by A M Reis in
Google Scholar
PubMed
Search for other papers by E G Moura in
Google Scholar
PubMed
Search for other papers by P C Lisboa in
Google Scholar
PubMed
Exposure to tobacco smoke is related to changes in energy balance regulation and several endocrine dysfunctions. Previously, we showed that maternal nicotine (the main addictive compound of tobacco) exposure exclusively during lactation affects biochemical profiles in mothers, milk, and pups. As the possible consequences for mothers and offspring of maternal smoking during lactation are still unknown, we evaluated the effects of tobacco smoke exposure on nutritional, biochemical, and hormonal parameters in dams and pups at weaning. After 72 h from birth, lactating rats were divided into two groups: smoke-exposed (S) in a cigarette-smoking machine, 4×1 h per day throughout the lactation period without pups; control (C), rats were treated the same as the experimental group but exposed to filtered air. Dams and pups were killed at weaning (21 days of lactation). Body weight and food intake were evaluated. Milk, blood, visceral fat, adrenal, and carcass were collected. S dams showed hyperprolactinemia (+50%), hypoinsulinemia (−40%), hypoleptinemia (−46%), as well as lower triglycerides (−53%) and very low-density lipoprotein cholesterol (−50%). Milk of S dams had higher lactose (+52%) and triglycerides (+78%). S pups presented higher body protein (+17%), lower total (−24%) and subcutaneous fat contents (−25%), hypoglycemia (−11%), hyperinsulinemia (+28%), hypocorticosteronemia (−40%), lower adrenal catecholamine content (−40%), hypertriglyceridemia (+34%), higher high-density lipoprotein cholesterol (+16%), and lower low-density lipoprotein cholesterol (−45%). In conclusion, tobacco smoke exposure leads to changes in nutritional, biochemical, and hormonal parameters in dams and, passively through the milk, may promote several important metabolic disorders in the progeny.
Search for other papers by SE Snyder in
Google Scholar
PubMed
Search for other papers by B Peng in
Google Scholar
PubMed
Search for other papers by JE Pintar in
Google Scholar
PubMed
Search for other papers by SR Salton in
Google Scholar
PubMed
Analysis of knockout mice suggests that the neurotropin-inducible secreted polypeptide VGF (non-acronymic) plays an important role in the regulation of energy balance. VGF is synthesized by neurons in the central and peripheral nervous systems (CNS, PNS), as well as in the adult pituitary, adrenal medulla, endocrine cells of the stomach and pancreatic beta cells. Thus VGF, like cholecystokinin, leptin, ghrelin and other peptide hormones that have been shown to regulate feeding and energy expenditure, is synthesized in both the gut and the brain. Although detailed developmental studies of VGF localization in the CNS and PNS have been completed, little is known about the ontogeny of VGF expression in endocrine and neuroendocrine tIssues. Here, we report that VGF mRNA is detectable as early as embryonic day 15.5 in the developing rat gastrointestinal and esophageal lumen, pancreas, adrenal, and pituitary, and we further demonstrate that VGF mRNA is synthesized in the gravid rat uterus, together supporting possible functional roles for this polypeptide outside the nervous system and in the enteric plexus.
Search for other papers by EE Onal in
Google Scholar
PubMed
Search for other papers by P Cinaz in
Google Scholar
PubMed
Search for other papers by Y Atalay in
Google Scholar
PubMed
Search for other papers by C Turkyilmaz in
Google Scholar
PubMed
Search for other papers by A Bideci in
Google Scholar
PubMed
Search for other papers by A Akturk in
Google Scholar
PubMed
Search for other papers by N Okumus in
Google Scholar
PubMed
Search for other papers by S Unal in
Google Scholar
PubMed
Search for other papers by E Koc in
Google Scholar
PubMed
Search for other papers by E Ergenekon in
Google Scholar
PubMed
Ghrelin is a newly discovered orexigenic peptide originating from the stomach. Circulating ghrelin levels reflect acute and chronic energy balance in humans. However, it is not known whether ghrelin also plays a role in energy homeostasis during fetal life. Forty-one small-for-gestational age (SGA) and 34 appropriate-for-gestational age (AGA) infants were studied in order to determine whether cord blood ghrelin concentrations were different in SGA infants compared with AGA infants and the relationship to anthropometric measurements at delivery. The cord blood ghrelin concentrations of SGA infants (means+/-S.E.M.; 15.20+/-3.08 ng/ml) were significantly greater than of AGA infants (2.19+/-0.24 ng/ml) (P<0.0001). They were negatively correlated with the infants' birth weights (r=-0.481, P<0.0001) and with body mass index values (r=-0.363, P<0.001). The higher ghrelin concentrations were found in female infants (20.42+/-4.55 ng/ml) than in males (7.05+/-2.27 ng/ml) in the SGA group (P=0.042). These data provide the first evidence that cord ghrelin levels of SGA infants are greater than those of AGA infants and it is suggested that ghrelin is also affected by nutritional status in the intrauterine period.
Search for other papers by C Fernandez-Galaz in
Google Scholar
PubMed
Search for other papers by T Fernandez-Agullo in
Google Scholar
PubMed
Search for other papers by F Campoy in
Google Scholar
PubMed
Search for other papers by C Arribas in
Google Scholar
PubMed
Search for other papers by N Gallardo in
Google Scholar
PubMed
Search for other papers by A Andres in
Google Scholar
PubMed
Search for other papers by M Ros in
Google Scholar
PubMed
Search for other papers by JM Carrascosa in
Google Scholar
PubMed
Leptin interacts with specific receptors in hypothalamic nuclei and modulates energy balance. Growing evidence has shown the association of obesity and hyperleptinaemia with non-insulin-dependent diabetes mellitus and insulin resistance. The aged Wistar rat shows peripheral insulin resistance in the absence of obesity and alterations of glucose homeostasis. However, it is not known whether, in these animals, the leptin action is altered. Here we studied the effect of ageing on plasma leptin concentration and the ability of hypothalamic nuclei to capture i.c.v.-injected digoxigenin-labelled leptin. Our data indicate that 24-month-old animals are hyperleptinaemic. However, daily food intake was greater in old animals, suggesting that they are leptin resistant. Leptin uptake in the hypothalamus was reduced in old rats. This uptake was a receptor-mediated process as demonstrated by displacement. Leptin accumulation in hypothalamic nuclei was partially colocalized with neuropeptide Y fibres. Immunohistochemical and western blot analyses showed a lower amount of the long form of leptin receptors in the hypothalamus of aged rats. Analysis by RT-PCR also demonstrated a decreased expression of leptin receptor mRNA in old animals. We conclude that the lower leptin uptake may be explained, at least in part, by a decreased amount of receptors in hypothalamic neurones of the aged rats.
Search for other papers by B. H. Breier in
Google Scholar
PubMed
Search for other papers by J. J. Bass in
Google Scholar
PubMed
Search for other papers by J. H. Butler in
Google Scholar
PubMed
Search for other papers by P. D. Gluckman in
Google Scholar
PubMed
ABSTRACT
The relationship between plasma GH profiles and circulating concentrations of insulin-like growth factor 1 (IGF-1) at three different planes of nutrition, chosen to represent a high, medium and low level of nutrition (3%, 1·8% and 1% dry matter of liveweight per day) was studied in 15 young Angus steers. All steers were maintained on 3% dry matter for 5 weeks, then on one of the three nutritional planes for 4 weeks and then all were returned to 3% dry matter for 3 weeks. Blood was sampled through jugular catheters at 15-min intervals for 25 h at the end of each phase of the study and additional samples were taken on 2 days each week.
Pulsatile release of GH occurred episodically with a diurnal increase during night and morning hours only in steers on high nutritional intakes. Reduced feeding at both the medium and the low plane abolished the diurnal rhythm and significantly increased mean plasma GH concentrations, the amplitude of GH pulses and the area under the GH profiles. Baseline concentrations of GH and pulse frequency did not change through nutritional manipulation. Upon realimentation, plasma GH concentrations decreased in both previously undernourished groups, with those fed 1% dry matter still having increased levels 10 days after refeeding. Plasma IGF-1 concentrations showed no periodicity. With nutritional deprivation, a decrease in IGF-1 concentration was observed only at negative energy balance (1% group). In this group plasma IGF-1 concentrations were progressively restored within 1 week of realimentation.
The different relationship between GH and IGF-1 release at each plane of nutrition suggests that at both medium and low levels of feed intake, tissue insensitivity to GH may exist peripherally and perhaps centrally. It is suggested that nutritional status may, through modulation of tissue sensitivity to GH, be a primary factor in determining growth and the regulation of the somatotrophic axis in the postnatal ruminant.
J. Endocr. (1986) 111, 209–215
Search for other papers by M J Devlin in
Google Scholar
PubMed
Search for other papers by D J Brooks in
Google Scholar
PubMed
Search for other papers by C Conlon in
Google Scholar
PubMed
Search for other papers by M van Vliet in
Google Scholar
PubMed
Search for other papers by L Louis in
Google Scholar
PubMed
Search for other papers by C J Rosen in
Google Scholar
PubMed
Harvard Medical School, Boston, Massachusetts, USA
Search for other papers by M L Bouxsein in
Google Scholar
PubMed
Starvation induces low bone mass and high bone marrow adiposity in humans, but the underlying mechanisms are poorly understood. The adipokine leptin falls in starvation, suggesting that hypoleptinemia may be a link between negative energy balance, bone marrow fat accumulation, and impaired skeletal acquisition. In that case, treating mice with leptin during caloric restriction (CR) should reduce marrow adipose tissue (MAT) and improve bone mass. To test this hypothesis, female C57Bl/6J mice were fed a 30% CR or normal (N) diet from 5 to 10 weeks of age, with daily injections of vehicle (VEH), 1mg/kg leptin (LEP1), or 2mg/kg leptin (LEP2) (N=6–8/group). Outcomes included body mass, body fat percentage, and whole-body bone mineral density (BMD) via peripheral dual-energy X-ray absorptiometry, cortical and trabecular microarchitecture via microcomputed tomography (μCT), and MAT volume via μCT of osmium tetroxide-stained bones. Overall, CR mice had lower body mass, body fat percentage, BMD, and cortical bone area fraction, but more connected trabeculae, vs N mice (P<0.05 for all). Most significantly, although MAT was elevated in CR vs N overall, leptin treatment blunted MAT formation in CR mice by 50% vs VEH (P<0.05 for both leptin doses). CR LEP2 mice weighed less vs CR VEH mice at 9–10 weeks of age (P<0.05), but leptin treatment did not affect body fat percentage, BMD, or bone microarchitecture within either diet. These data demonstrate that once daily leptin bolus during CR inhibits bone marrow adipose expansion without affecting bone mass acquisition, suggesting that leptin has distinct effects on starvation-induced bone marrow fat formation and skeletal acquisition.
Search for other papers by KL Houseknecht in
Google Scholar
PubMed
Search for other papers by CP Portocarrero in
Google Scholar
PubMed
Search for other papers by S Ji in
Google Scholar
PubMed
Search for other papers by R Lemenager in
Google Scholar
PubMed
Search for other papers by ME Spurlock in
Google Scholar
PubMed
Leptin, the product of the ob gene, is secreted from white adipocytes and regulates food intake and whole-body energy metabolism. In rodents and humans, leptin gene expression is under complex endocrine and metabolic control, and is strongly influenced by energy balance. Growth hormone (GH) has myriad effects on adipose tissue metabolism. The primary aim of this study was to determine the ability of GH to regulate leptin mRNA expression in bovine adipose tissue in vitro and in vivo. Incubation of subcutaneous adipose tissue explants for 24 h with GH alone had no effect on bovine leptin gene expression, whereas high concentrations of insulin or dexamethasone (DEX) potently stimulated bovine leptin mRNA abundance. GH, in combination with high concentrations of insulin, DEX, or both, attenuated the ability of insulin or DEX to stimulate leptin expression in vitro. These data indicate that GH can indirectly regulate leptin expression in vitro by altering the adipose tissue response to insulin or DEX. We extended these studies to examine the ability of GH to regulate leptin expression in vivo, using young castrate male cattle treated with no hormone (control) or GH (200 micrograms/kg body weight per day) for 3 days. GH increased plasma GH and insulin concentrations, but not those of cortisol or non-esterified fatty acid (NEFA) concentrations. GH treatment increased adipose tissue leptin and IGF-1 mRNA concentrations (n=9, P>0.001). In addition, leptin abundance was highly correlated with adipose tissue IGF-1 mRNA in GH-treated animals (P>0.001). The timing of GH-induced changes in leptin gene expression preceded measurable GH effects on adiposity.
Search for other papers by M Marie in
Google Scholar
PubMed
Search for other papers by PA Findlay in
Google Scholar
PubMed
Search for other papers by L Thomas in
Google Scholar
PubMed
Search for other papers by CL Adam in
Google Scholar
PubMed
Circulating concentrations of leptin in sheep correlate with body fatness and are affected by level of food intake and photoperiod. The present objective was to elucidate the short-term dynamics of leptin secretion. Frequent blood samples were taken over 48 h from 12 Soay rams after 16 weeks in short-day photoperiod (SD, 16 h darkness:8 h light) with freely available food, and then after 16 weeks in long days (16 h light:8 h darkness) with food freely available (LD) or restricted to 90% maintenance (LDR) (n=6/group). During the second 24 h of sampling, half were food deprived (n=6, SD and LD) and half had their meal times shifted (n=6, SD and LDR). A homologous RIA was developed, using antibodies raised in chicken against recombinant ovine leptin, to measure plasma concentrations. Simultaneous 24 h profiles of plasma insulin, glucose and non-esterified fatty acids (NEFA) were measured. Plasma leptin was higher in LD than SD, and in LD than LDR, associated with higher food intake, liveweight and body condition score (adiposity), but tended to be lower in LDR than SD, associated with lower food intake, liveweight and body condition score. There was no evidence for a circadian rhythm of plasma leptin, but clear evidence for post-prandial peaks of low amplitude (15-36%) 2-8 h after meals given at normal and shifted times. Complete food deprivation caused a dramatic fall in plasma leptin to basal levels within 24 h. There was a positive association of plasma leptin with plasma insulin, and negative association with NEFA, both between meals and during fasting. Thus, plasma leptin concentrations in sheep are sensitive to short-term changes in energy balance, as well as to long-term photoperiod-driven changes in food intake and adiposity.
