Induction and reversibility of an obesity syndrome by intracerebroventricular neuropeptide Y administration to normal rats

Diabetologia, Dec 1994

Summary Intracerebroventricular neuropeptide Y (NPY) administration to normal rats for 7 days produced a sustained, threefold increase in food intake, resulting in a body weight gain of more than 40 g. Basal plasma insulin and triglyceride levels were increased in NPY-treated compared to vehicle-infused rats by about four- and two-fold, respectively. The glucose utilization index of white adipose tissue, measured by the labelled 2-deoxy-d-glucose technique was four times higher in NPY-treated rats compared to controls. This change was accompanied by an increase in the insulin responsive glucose transporter protein (GLUT 4). In marked contrast, muscle glucose utilization was decreased in NPY-treated compared to vehicle-infused animals. This change was accompanied by an increase in triglyceride content. When NPY-treated rats were prevented from overeating, there was no decrease in muscle glucose uptake, nor was there an increase in muscle triglyceride content. This suggests that muscle insulin resistance of ad libitum-fed NPY-treated rats is due to a glucose-fatty acid (Randle) cycle. When intracerebro-ventricular NPY administration was stopped and rats kept without any treatment for 7 additional days, all the abnormalities brought about by the neuropeptide were normalized. A tonic central effect of NPY is therefore needed to elicit and maintain most of the hormonal and metabolic abnormalities observed in the present study. Such abnormalities are analogous to those seen in the dynamic phase of obesity syndromes in which high hypothalamic NPY levels have been reported.

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Induction and reversibility of an obesity syndrome by intracerebroventricular neuropeptide Y administration to normal rats

Diabetologia Induction and reversibility of an obesity syndrome by intracerebroventricular neuropeptide Y administration to normal rats R. Vettor 0 N. Zarjevski 0 . Cusin 0 E Rohner-Jeanrenaud 0 B. Jeanrenaud 0 0 Laboratoires de Recherches M~taboliques,Faculty and Department of Medicine, University of Geneva , Geneva , Switzerland Summary Intracerebroventricular neuropeptide Y (NPY) administration to normal rats for 7 days produced a sustained, threefold increase in food intake, resulting in a body weight gain of m o r e than 40 g. Basal plasma insulin and triglyceride levels were increased in NPY-treated compared to vehicle-infused rats by about four- and two-fold, respectively. The glucose utilization index of white adipose tissue, measured by the labelled 2-deoxy-D-glucose technique was four times higher in NPY-treated rats compared to controls. This change was accompanied by an increase in the insulin responsive glucose transporter protein ( G L U T 4). In marked contrast, muscle glucose utilization was decreased in NPY-treated compared to vehicle-infused animals. This change was accompanied by an increase in triglyceride content. When NPY-treated rats were prevented from overeating, there was no decrease in muscle glucose up- Intracerebroventricular (i; c; v; ); neuropeptide Y (NPY); food intake; body weight gain; in vivo glucose uptake; muscle insulin resistance - 9 Springer-Verlag1994 Obesity is a pathological condition characterized by an imbalance between caloric intake and total energy expenditure. Hyperinsulinaemia and insulin resistance are the most prominent facets of this syndrome. The initial cause(s) that ultimately lead to obesity are yet to be determined. In man, cross-sectional studies suggested the existence of a progressive evolution of the obese subjects to hyperinsulinAbbreviations: NPY, Neuropeptide Y; icv,intracerebroventricular; GLUT 4, glucose transporter 4. take, nor was there an increase in muscle triglyceride content. This suggests that muscle insulin resistance of ad libitum-fed NPY-treated rats is due to a glucose-fatty acid (Randle) cycle. When intracerebroventricular NPY administration was stopped and rats kept without any treatment for 7 additional days, all the abnormalities brought about by the neuropeptide were normalized. A tonic central effect of NPY is therefore n e e d e d to elicit and maintain most of the hormonal and metabolic abnormalities observed in the present study. Such abnormalities are analogous to those seen in the dynamic phase of obesity syndromes in which high hypothalamic NPY levels have been reported. [Diabetologia (1994) 37: 1202-1208] aemia, subsequent glucose intolerance and diabetes due to pancreatic decompensation. Such studies failed, however, to pin-point any initial cause(s) in such series of events [ 1, 2 ]. Investigation carried out in animal models potentially allows for an understanding of the aetiology of obesity syndromes. In this respect, it is noteworthy that chronic intracerebroventricular (i.c.v.) neuropeptide Y (NPY) administration to normal rats produced several of the behavioral, hormonal, and metabolic changes observed in the dynamic phase of the genetic or hypothalamic obesity syndromes [ 3-8 ]. Thus, as in young genetically obese animals, chronic i. c. v. NPY administration to normal rats for 7 days resulted in increased food intake, body weight, liver and adipose tissue lipogenic activity, together with a state of muscle insulin resistance [ 9, 10 ]. These considerations, together with the reports showing that hypothalamic NPY m R N A and protein expression were both increased during the dynamic phase of these syndromes [ 11-13 ] lead to the proposal that N P Y could play a role in the establishment and maintenance of obesity syndromes. To further substantiate this viewpoint, N P Y was administered i. c.v. to normal rats for 7 days, then the administration of the peptide was stopped and the hormonalmetabolic consequences of such cessation of N P Y infusion were determined. To try to distinguish between the effects of NPY per se and those due to NPY-induced hyperphagia, metabolic parameters were d e t e r m i n e d in NPY-treated rats prevented from overeating (pair-feeding). Materials and methods Twelve-week-old lean female rats of the Zucker (FA/?) strain were used throughout the study. The animals were initially purchased from the "Centre de S61ection et d'Elevage d'Animaux de Laboratoire" (Orldans, France). They were bred and housed in our animal quarter, submitted to a 12-h light cycle (lights on from 07.00-19.00 hours) and kept at a constant temperature (23 ~ They were fed a standard laboratory chow (carbohydrate 57.7 %; fat 2.5 %; protein 20.6 %; ash 7.5 %; water 11.7 %, Provimi Lacta, Cossonay, Switzerland). Three days before the implantation of the intracerebroventricular (i. c. v.) guiding cannulas, the rats were placed into individual cages. Body weight and food intake were then measured daily until the end of the experimental period. The i. c. v. cannulation and the subsequent experiments were approved by the Ethical Committee for Animal Experimentation of the Geneva Faculty of Medicine, as well as by the Swiss Federal and Geneva Cantonal Veterinarian Offices. Surgical procedure and experimental designs: After three days of habituation to their new housing conditions, the animals were anaesthetized with sodium pentobarbital (60 mg/kg) for the placement of guiding cannulas (outer diameter 0.7 mm) into the right lateral cerebral ventricle according to coordinates previously reported [ 14 ]. Guiding cannulas were then filled with a stylet and fixed on the skull with dental cement [ 14 ]. After a week of recovery, the stylets were removed and replaced by injecting cannulas connected, via a polyethylene catheter, to osmotic minipumps (Model2001; Alza Corp., Palo Alto, Calif., USA) containing either porcine Neuropeptide Y, NPY (Bachem, Bubendorf, Switzerland), or its vehicle (0.04 mol/1 phosphate-buffered saline with 0.1% bovine serum albumin and 0.01% ascorbic acid). The minipumps were placed subcutaneously in the interscapular region, as previously described [ 15 ]. The animals infused with i. c. v. NPY received 10 ~tg/day of the peptide for 7 days. One group of control and NPY-treated animals were allowed to eat ad libitum throughout the 7-day experimental period. A second group of i. c. v. NPY-treated animals and their vehicle-infused controls, were, at day 7, submitted to a light ether anaesthesia for removal of minipumps (cessation of NPY administration). Food intake and body weight were again measured daily for 7 additional days. In a third group of control and i. c. v. NPY-treated rats, a pair-feeding experimental design previously described [ 9 ] was adopted: animals were allowed to eat ad libitum for the first 3 days. Subsequently, and for the next 4 days of NPY administration, rats were pair-fed to the amount of food eaten by vehicle-treated animals. This was performed to rule out the role of hyperphagia on glucose metabolism together with ensuring successful NPY treatment by the occurrence of an initial hyperphagia (i. e. during the first 3 days). Pair-feeding (four meals per day at identical time intervals) consisted in providing all rats with 85 % of the amount of food consumed by normal rats in a usual ad libitum situation. The aim of this feeding protocol was to increase the avidity of control animals for food, thereby partially mimicking the behaviour of the NPY-treated group. Euglycaemic-hyperinsulinaemic clamps and measurement of overall glucose metabolism. The fi/st two groups mentioned were tested using the euglycaemic-hyperinsulinaemic clamp technique. They were fasted for 12 h, then anaesthetized with sodium pentobarbital (60 mg/kg) and two indwelling catheters were inserted, one into the right jugular vein for the respective infusion of glucose, human insulin (Actrapid, Novo, Copenhagen, Denmark) and tracers; the other into the left carotid artery for blood sampling, as detailed elsewhere [ 16 ]. Body temperature was maintained at 37 ~ with a heating blanket connected to a rectal probe. Primed-continuous infusion of U-14C D-glucose (10 ~tCi/h, New England Nuclear Boston, MA, USA) was initiated to allow for the establishment of a steady state of glucose tracer. Blood samples were taken to determine basal insulinaemia and basal glucose turnover. Insulin was then infused to reach a new steady state of glucose turnover and blood samples were taken for the determination of plasma insulin and glucose specific activity. Hepatic glucose production and rate of total glucose utilization in basal and insulin-stimulated states were calculated as described previously [ 16 ]. Determination of insulin-stimulated glucose utilization index in white adipose tissue and in muscles. In the three groups of rats, the glucose utilization index (in vivo glucose uptake) of inguinal white adipose tissue as well as that of eight different muscle types (white and red gastrocnemius, white and red quadriceps, soleus, extensor digitorum longus, tibialis, and diaphragm) was measured during the euglycaemic hyperinsulinaemic clamps associated with the 2-deoxy-D-[13H]-glucose technique as described previously [ 17, 18 ]. Analytical procedures relative to clamp studies. Blood samples (50 91) used for determination of U14C-D-glucose and 2deoxy-D-[13H]-glucose ([3H]2DG) SPECIFICACTIVITIESWEREDEPROTEINIZED WITH 250~tl ZnSO 4 (0.3mol/1) and 250~tl Ba(OH)2 (0.3 mol/1) and immediately centrifuged. The supernatant was used to measure glucose concentration, Ua4C glucose and [3H]2DG PLASMARADIOACTIVITY. For the measurement of basal and insulin-stimulated glucose turnover rate, 200 ~l of supernatant was submitted to an ion exchange resin (AG2 x 8; Bio-Rad Laboratories, Richmond, Calif., USA) to avoid concomitant lactate measurement. Plasma glucose levels were measured by the glucose oxidase method (Glucose analyser 2; Beckman, Palo Alto, Calif., USA). Basal plasma insulin concentrations from the tail tip as well as in samples obtained during the euglycaemic-hyperinsulinaemic clamps (human insulin infusion) were determined in the same assay by a charcoal precipitation radioimmunoassay technique using an antibody directed against both rat and human insulins [ 19 ]. Non-esterified fatty acids (NEFA) and trigtycerides were measured spectrophotometrically by enzymatic methods using commercial kits (Bio-Mdrieux, Marcy l'Etoile, France). Preparation of total membranes from adipose tissue and measurement of G L U T 4 protein. Inguinal white adipose tissue taken from both i. c. v. NPY or vehicle-administered animals af(days) "0 0 0 ,, 0 1 2 3 4 5 6 7 1 2 3 4 5 6 7 (days) ter 7 days of treatment and from animals 7 days after cessation of NPY treatment, was immediately frozen. A total membrane preparation containing both plasma membranes and microsomes was then obtained as previously described [ 20, 21 ]. Protein concentration in the resulting membrane preparation was measured as previously reported [22]. Western blots were carried out to measure the relative abundance of the insulin responsive glucose transporter (GLUT 4) protein using a polyclonal antibody against G L U T 4 R820 (Biogenesis LTD, Bournemouth, Dorset, UK) [ 23-25 ]. Blots were then submitted to autoradiography. Quantification of G L U T 4 was performed by counting the radioactivity corresponding to the G L U T 4 signal of the autoradiogram, from which background radioactivity was subtracted, from excised pieces of membranes. Muscle triglyceride assay. One hundred to 200 mg of frozen ( - 70 ~ tibialis were homogenized in chloroform-methanol (2 : 1 vol : vol). After 4 h of gentle shaking at room temperature, the extract was washed twice with 1 mol/1 H2SO4 and finally dried in the presence of 100 mg anhydrous Na2S20 4. Phoi.c.v. NPY I A s s h o w n b y F i g u r e 1, i n t r a c e r e b r o v e n t r i c u l a r (i. c. v.) N P Y a d m i n i s t r a t i o n to n o r m a l r a t s r e s u l t e d in a n initially r a p i d , t h e n s u s t a i n e d i n c r e a s e in f o o d i n t a k e rela t i v e to controls. A t d a y 7, t h e daily f o o d i n t a k e was 55.4 + 4.9 g in N P Y - t r e a t e d r a t s a n d 18.1 + 0.4 g in v e h i c l e - i n f u s e d r a t s (p < 0.0001). T h a t s u c h i n c r e a s e in f o o d i n t a k e w a s d u e t o i.c.v. N P Y is f u r t h e r s h o w n b y F i g u r e 1. I n d e e d , w i t h i n 1 d a y o f N P Y w i t h d r a w al, f o o d i n t a k e r e t u r n e d to c o n t r o l v a l u e s a n d s u b s e q u e n t l y r e m a i n e d n o r m a l . I n c r e a s e d f o o d i n t a k e r e s u l t e d , as d e p i c t e d b y Figure 2, in a p r o g r e s s i v e i n c r e a s e in b o d y w e i g h t in t h e i.c.v. N P Y - t r e a t e d g r o u p r e l a t i v e to controls. This was elicited b y t h e p r e s e n c e of i.c.v. N P Y as evid e n c e d b y t h e o b s e r v a t i o n t h a t b o d y weight, a f t e r c e s s a t i o n of c e n t r a l N P Y a d m i n i s t r a t i o n , p r o g r e s s i v e ly r e t u r n e d to n o r m a l c o n t r o l v a l u e s (Fig. 2). A s s h o w n b y T a b l e 1, p r o m i n e n t i n c r e a s e s in b a s a l p l a s m a insulin a n d t r i g l y c e r i d e levels w e r e f o u n d in 8-h f a s t e d i. c. v. N P Y - t r e a t e d r a t s r e l a t i v e to controls, o f a b o u t f o u r a n d t w o fold, respectively. I. c.v. N P Y a d m i n i s t r a t i o n did n o t c h a n g e p l a s m a g l u c o s e a n d N E F A levels. T h e i n c r e a s e d p l a s m a insulin a n d triglyc e r i d e levels o f t h e i. c. v. N P Y - a d m i n i s t e r e d a n i m a l s R. Vettor et al,: Intracerebroventricular NPY: peripheral, reversible effects 100 50 0 N ** Fig. 3. Inguinal white adipose tissue glucose utilization index (upper panel) and insulin responsive glucose transporter (GLUT 4) protein levels (lower panel) measured in tissues from vehicle-infused normal rats (controls, [-~); normal rats administered i.c.v. NPY for 7 days ([~); i.c.v. NPY-administered rats for 7 days studied 7 days after cessation of the NPY administration (removal of minipumps delivering the neuropeptide, m). Glucose utilization index was measured via the labelled 2-deoxyglucose technique during euglycaemic-hyperinsulinaemic clamps (See Materials and Methods). Means _+SEM of six-seven animals per group. Intergroup differences, ** p < 0.01 r e t u r n e d to n o r m a l values 7 days a f t e r cessation of i. c.v. N P Y a d m i n i s t r a t i o n . C l a m p s w e r e p e r f o r m e d in two groups o f rats. T h e first r e c e i v e d i. c. v. N P Y or its vehicle for 7 days, the o t h e r was first a d m i n i s t e r e d for 7 days with i.c.v. N P Y or its vehicle, t h e n k e p t for a n a d d i t i o n a l 7-day p e r i o d following r e m o v a l of m i n i p u m p s delivering the n e u r o p e p t i d e . T h e s e d a t a are s h o w n in Table 2. It m a y be seen t h a t all groups w e r e c o m p a r e d at similar s t e a d y - s t a t e levels of g l y c a e m i a a n d insulinaemia. Insulin i n h i b i t e d h e p a t i c glucose p r o d u c t i o n n o r m a l ly in all groups. T h e w h o l e - b o d y glucose disappearance r a t e was significantly d e c r e a s e d in the g r o u p o f rats t h a t h a d b e e n a d m i n i s t e r e d w i t h i. c. v. N P Y for 7 days relative to respective controls a n d w h e n expressed p e r kg b o d y w e i g h t while it was u n a l t e r e d w h e n expressed p e r a n i m a l ( d a t a n o t shown). R a t e s of glucose d i s a p p e a r a n c e r e t u r n e d to n o r m a l values w h e n N P Y a d m i n i s t r a t i o n was s t o p p e d for 7 days. Similar o b s e r v a t i o n s w e r e m a d e for the c a l c u l a t e d glucose c l e a r a n c e rates (Table 2). The insulin-stimul a t e d in vivo glucose u p t a k e (or glucose utilization index, as m e a s u r e d by t h e l a b e l l e d 2-deoxy-D-glucose t e c h n i q u e ) by adipose tissue is s h o w n in F i g u r e 3. It m a y be s e e n t h a t the inguinal w h i t e adipose tissue f r o m 7-day i.c.v. N P Y - a d m i n i s t e r e d rats was m u c h m o r e insulin responsive t h a n t h a t of vehicle-infused controls. This was a c c o m p a n i e d b y an increase in the t o t a l a m o u n t of the insulin responsive glucose transp o r t e r ( G L U T 4) p r o t e i n (Fig. 3). T h a t t h e s e changes w e r e p r o d u c e d b y the p r e s e n c e of N P Y w i t h i n the brain was s h o w n by the o b s e r v a t i o n o f a r e t u r n to c o n t r o l values of b o t h the in vivo adipose tissue glucose utilization i n d e x a n d adipose tissue G L U T 4 p r o t e i n levels 7 days a f t e r cessation of N P Y administ r a t i o n (Fig. 3). A s s h o w n in Table 3 glucose utilization i n d e x by total i n t e r s c a p u l a r b r o w n adipose tissue was unc h a n g e d in i.c.v. N P Y - a d m i n i s t e r e d rats as comp a r e d to controls. A f t e r cessation of N P Y t r e a t m e n t glucose u p t a k e t e n d e d to be l o w e r t h a n t h a t of controls w i t h o u t r e a c h i n g statistical significance. The i n s u l i n - s t i m u l a t e d in vivo glucose utilization i n d e x b y several d i f f e r e n t muscle types is s h o w n b y Figure 4. R e l a t i v e to t h e glucose utilization i n d e x observed in muscles f r o m vehicle-infused rats, the insulin responsiveness of muscles o b t a i n e d f r o m i.c.v. N P Y - t r e a t e d rats was significantly a n d o f t e n m a r k e d ly decreased. The d e c r e a s e d insulin responsiveness of muscles f r o m i.c.v. N P Y - a d m i n i s t e r e d animals was n o r m a l i z e d a f t e r 7 d a y s of cessation of N P Y adminisI.c.v. NPY T h e p r e s e n t s t u d y e x t e n d s p r e v i o u s o b s e r v a t i o n s s h o w i n g t h a t i.c.v. N P Y a d m i n i s t r a t i o n t o n o r m a l r a t s f o r 7 d a y s r e s u l t e d in h y p e r p h a g i a , i n c r e a s e d b o d y w e i g h t gain, h y p e r i n s u l i n a e m i a , i n c r e a s e d w h i t e a d i p o s e tissue m e t a b o l i c a c t i v i t y c o n c o m i t a n t T SOL EDL TIB W. GAST R, GAST W. QUAD R. QUAD DIA Fig. 4. Muscle glucose utilization index measured in eight different muscle types obtained, respectively, from vehicle-infused normal rats (controls, [ ] ); normal rats administered i.c.v. NPY for 7 days (~'~); i.c.v. NPY-administered rats for 7 days studied 7 days after cessation of i. c. v. NPY administration (removal of minipumps delivering the neuropeptide, [ ] ). Glucose utilization index was measured via the labelled 2-deoxyglucose technique during euglycaemic-hyperinsulinaemic clamps (See Materials and Methods). SOL, soleus; EDL, extensor digitorum longus; TIB, tibialis; W. GAST, R. GAST, white or red gastrocnemius; W. QUAD, R. QUAD, white or red quadriceps; DIA, diaphragm. Means + SEM of six-seven animals per group. Intergroup differences indicated by ** p < 0.01. Other intergroup values, NS w i t h insulin r e s i s t a n c e at t h e level o f the m u s c l e m a s s [ 4, 9, 10 ]. T h e h o r m o n a l a n d m e t a b o l i c a l t e r a tions o b s e r v e d a f t e r i. c. v. N P Y a d m i n i s t r a t i o n a r e int e r e s t i n g l y s i m i l a r to t h o s e o b s e r v e d d u r i n g t h e dyn a m i c p h a s e o f h y p o t h a l a m i c o r g e n e t i c o b e s i t y synd r o m e s [ 3, 5-8 ]. A s g e n e t i c a l l y o b e s e r o d e n t s are c h a r a c t e r i z e d b y e a r l y o v e r e x p r e s s i o n o f t h e i r h y p o thalamic N P Y protein and m R N A levels [ 11-13 ], it was of additional interest to investigate whether cessation of i.c.v. N P Y administration would result in the reversal of the metabolic defects brought about by the peptide. If such was the case, it would suggest that attempts at altering N P Y levels in young genetically obese rodents (via central N P Y antagonist, N P Y antibody, or antisense N P Y oligonucleotide administration) could possibly prevent the development of their syndrome. Indeed, down-regulation of food intake and of basal insulin levels have already been shown when antisense N P Y oligonucleotides were administered directly into the arcuate nucleus of normal rats [ 27 ]. The present study shows that 7 days after the cessation of i. c. v. N P Y administration to normal rats, increased food intake and body weight gain, hyperinsulinaemia and hypertriglyceridaemia as well as the insulin over-responsiveness of white adipose tissue and the insulin under-responsiveness of all muscles studied had all returned to normal values. Such was also the case for the total glucose disappearance rate that was slightly lower in i. c. v. NPY-treated rats than in controls when expressed per kg body weight (but not when expressed per animal). For white adipose tissue from i. c.v. NPY-infused rats the sequence of events proposed could be: increase in basal and substrate-induced insulinaemia, over-expression of white adipose tissue G L U T 4 m R N A and protein with resultant increase in glucose transport activity in this tissue. This sequence is in keeping with data obtained upon administering normal rats with insulin for 4 days while maintaining euglycaemia by superimposed glucose infusion [ 28, 29 ]. This view is also strengthened by the observation of a normalization of basal insulinaemia, as well as of white adipose tissue G L U T 4 protein and glucose transport, 7 days after cessation of i.c.v. N P Y administration. The mechanism of the effect of i. c. v. N P Y on the establishment of muscle insulin resistance of the glucose transport process is less clear, as muscle G L U T 4 expression is unaltered by i.c.v. N P Y administration. It could conceivably be due to an increased glucose-fatty acid cycle [ 30 ]. Indeed, in an overweight condition, excess body fat is not limited to adipose tissue but is also present in muscles [ 31 ]. Additionally, muscle lipid substrate is supplied by hydrolysis of triglycerides inside the muscle fibers [ 32 ]. Several observations have thus shown that a large proportion of the increase in lipid oxidation of obese subjects is accounted for by an increase in intramuscular triglyceride mobilization [ 31, 33-36 ]. Finally, muscle insulin resistance has been shown to be directly related to the accumulation of muscle triglycerides [ 26, 37 ]. This view is substantiated, in the present study, by the observation that in i. c.v. NPY-treated rats prevented from overeating (i. e. pair-feeding experiments), there was no significant increase in muscle triglyceride content (judged by that of tibialis), in contrast to what was observed in muscles of ad libitum-fed NPY-treated rats (Fig.5). W h e n no triglyceride accumulation was noted in pair-fed NPY-administered rats (presumably due to lesser substrate availability), there was no defect in muscle glucose utilization index (Table 4), while all muscles of hyperphagic NPY-treated animals that had a high triglyceride content were resistant to the in vivo effect of insulin on glucose uptake (Fig. 4). This difference is consistent with the hypothesis that the degree of hyperinsulinaemia (meal-induced insulin responses, in particular) was probably unequal in the two groups of i. c. v. NPY-treated rats. It was probably much m o r e m a r k e d in hyperphagic than in pair-fed NPY-treated rats, bringing about muscle insulin resistance by yet another mechanism; i. e., hyperinsulinaemia, also known to produce muscle insulin resistance [ 28, 29, 38 ]. I. c. v. N P Y treatment of normal rats produced no change in total interscapular brown adipose tissue glucose uptake. This was the result of both an increase in tissue weight and a decrease in glucose utilization as expressed per milligram of tissue in i.c.v. NPY-treated animals compared to controls. Seven days after cessation of N P Y treatment, tissue weight had decreased while glucose utilization index expressed per milligram of tissue had remained unaltered compared to NPY-treated rats. U n d e r these conditions, total brown adipose tissue glucose uptake was decreased, although such decrease failed to reach statistical significance compared to vehicle-infused rats. To conclude, when i.c.v. NPY-administered rats are fed ad libitum and therefore overeat, the hormonal and metabolic homeostasis is altered, with high body weight gain and concomitant muscle insulin resistance presumably due to an increased glucose-fatty acid (Randle) cycle. These defects are normalized 7 days after cessation of i. c.v. N P Y treatment. This suggests that a normalization of the high central NPYergic tone of obese rodents in general could result in an amelioration of their obesity-insulin resistance syndrome. Acknowledgements. This work was Supported by Grant 3226405.89 from the SwissNational Science Foundation (Berne, Switzerland), and by a grant-in-aid from Nestl6 S.A. (Vevey, Switzerland). Dr. R. Vettor is the recipient of a grant from the Italian M.U.R.S.T. The excellent technical assistance of Ms. P.Arboit and Ms. E Califano is gratefully acknowledged. We thank Ms. E Touabi and Ms. T.-M.Besson for their excellent secretarial work. We also thank Mr. R Germann for his technical assistance. The authors of this study are members of the Geneva-Diabetes-Group. 1. Jallut D , Golay A , Munger R et al. ( 1990 ) Impaired glucose tolerance and diabetes in obesity: a 6-year follow-up study of glucose metabolism . Metabolism 39 : 1068 - 1075 2. Felber J-P ( 1992 ) From obesity to diabetes. Pathophysiological considerations . Int J Obes 16 : 937 - 952 3. P6nicaud L , Kinebanyan MF , Ferr6 P e t al. ( 1989 ) Development of VMH obesity: in vivo insulin secretion and tissue insulin sensitivity. A m J Physio1257 : E255 - E260 4. Stanley BG , Kyrkouli SE , Lampert S , Leibowitz SF ( 1986 ) Neuropeptide Y chronically injected into the hypothalamus: a powerful neurochemical inducer of hyperphagia and obesity . Peptides 7 : 1189 - 1192 5. P6nicaud L , Ferr6 R Terrettaz J e t al. ( 1987 ) Development of obesity in Zucker rats. Early insulin resistance in muscles but normal sensitivity in white adipose tissue . Diabetes 36 : 626 - 631 6. Stern JS , Johnson PR ( 1977 ) Spontaneous activity and adipose cellularity in the genetically obese Zucker rat (fa/fa) . Metabolism 26 : 371 - 380 7. Rohner-Jeanrenaud F , Jeanrenaud B ( 1985 ) Involvement of the cholinergic system in insulin and glucagon oversecreti0n of genetic preobesity . Endocrinology 116 : 830834 8. P6nicaud L , Ferr6 R Assimacopoulos-Jeannet F et al. ( 1991 ) Increased gene expression of lipogenic enzymes and glucose transporter in white adipose tissue of suckling and weaned obese Zucker rats . Biochem J 279 : 303 - 308 9. Zarjevski N , Cusin I , Vettor R , Rohner-Jeanrenaud F , Jeanrenaud B ( 1993 ) Chronic intracerebroventricular Neuropeptide-Y administration to normal rats mimics hormonal and metabolic changes of obesity . Endocrinology 133 : 1753 - 1758 10. Zarjevski N , Cusin I , Vettor R , Rohner-Jeanrenaud F , Jeanrenaud B ( 1994 ) Intracerebroventricular administration of neuropeptide Y to normal rats has divergent effects on glucose utilization b y adipose tissue and skeletal muscle . Diabetes 43 : 764 - 769 11. Bchini-Hooft van Huijsduijnen O , Rohner-Jeanrenaud F , Jeanrenaud B ( 1993 ) Hypothalamic Neuropeptide Y messenger ribonucleic acid levels in pre-obese and genetically obese (fa/fa) rats; potential regulation thereof by corticotropin-releasing factor . J Neuroendocrinol 5 : 381 - 386 12. Sanacora G , Finkelstein JA , White JD ( 1992 ) Developmental aspect of differences in hypothalamic preproneuropeptide Y messenger ribonucleic acid content in lean and genetically obese Zucker rats . J Neuroendocrinol 4 : 353 - 357 13. Beck B , Burlet A , Bazin R , Nicolas JR Burlet C (1993) Elevated Neuropeptide-Y in the arcuate nucleus of young obese Zucker rats may contribute to the development of their overeating . J Nutr 123 ( 6 ): 1168 - 1172 14. Chaouloff F , Jeanrenaud B ( 1988 ) Hyperinsulinemia of the genetically obese (fa/fa) rat is decreased by a low dose of the 5- HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) . Eur J Pharmacol 147 : 111 - 118 15. Rohner-Jeanrenaud F , Walker CD , Greco-Perotto R , Jeanrenaud B ( 1989 ) Central corticotropin-releasing factor administration prevents the excessi'ge body weight gain of genetically obese (fa/fa) rats . Endocrinology 124 : 733 - 739 16. Terrettaz J , Jeanrenaud B ( 1983 ) In vivo hepatic and peripheral insulin resistance in genetically obese (fa/fa) rats . Endocrinology 112 : 1346 - 1351 17. Ferr6 P , Leturque A , Burnol AF , P6nicaud L , Girard J ( 1985 ) A method to quantify glucose utilization in vivo in skeletal muscle and white adipose tissue of the anesthetized rat . Biochem J 228 : 103 - 110 18. James DE , Burleigh KM , Kraegen E W ( 1986 ) In vivo glucose metabolism in individual tissues of the rat . J Biol Chem 261 : 6366 - 6374 19: Herbert V , Lau KS , Gottlieb CW , Bleicher SJ ( 1965 ) Coated charcoal immunoassay of insulin . J Clin Endocrinol 25 : 1375 - 1384 20. Klip A , Ramlal T , Young DA , Holloszy JO ( 1987 ) Insulin-induced translocation of glucose transporters in rat hindlimb muscles . FEBS Lett 224 : 224 - 230 21. Le Marchand-Brustel Y , Olichon-Berthe C , Gremeaux T , Tanti JF , Rochet N , van Obberghen E ( 1990 ) Glucose transporters in insulin sensitive tissues of lean and obese mice . Effects of the thermogenic agent BRL 26830A*. Endocrinology 127 : 2687 - 2695 22. Bradford M ( 1976 ) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding . Anal Biochem 72 : 248 - 254 23. Laemmli UK ( 1970 ) Cleavage of structural proteins during the assembly of the head of bacteriophage T4 . Nature 277 : 680 - 685 24. Haspel HC , Birnbaum MJ , Wilk EW , Rosen OM ( 1985 ) Biosynthetic precursors and in vitro translation products of human hepatocarcinoma cells, human fibroblasts and murine preadipocytes . J Biol Chem 260 : 7219 - 7225 25. James DE , Strube M , Mueckler M ( 1989 ) Molecular cloning and characterization of an insulin-regulatable glucose transporter . Nature 338 : 83 - 87 26. Storlien LH , Jenkins AB , Chisholm DJ et al. ( 1991 ) Influence of dietary fat composition on development of insulin resistance in rats . Diabetes 40 : 280 - 289 27. Akabayashi A , Wahlestedt C , Alexander JT , Leibowitz SF ( 1994 ) Specific inhibition of endogenous neuropeptide Y synthesis in arcuate nucleus by antisense oligonucleotides suppresses feeding behavior and insulin secretion . Mol Brain Res 21 : 55 - 61 28. Cusin I , Terrettaz J , Rohner-Jeanrenaud F , Jeanrenaud B ( 1990 ) Metabolic consequences of hyperinsulinaemia imposed on normal rats on glucose handling by white adipose tissue, muscles and liver . Biochem J 267 : 99 - 103 29. Cusin I , Rohner-Jeanrenaud F , Terrettaz J , Jeanrenaud B ( 1992 ) Hyperinsulinemia and its impact on obesity and insulin resistance . Int J Obes 16 [Suppl 4 ]: S1 -$ 11 30. Randle PJ , Hales CN , Garland PB , Newsholm E A ( 1963 ) The glucose fatty-acid cycle: its role in insulin sensitivity and the metabolic disturbances of diabetes mellitus . Lancet 1 : 785 - 789 31. Felber J-R Acheson KJ , Tappy L ( 1993 ) Obesity and lipid metabolism . In: Felber J-P , Acheson KJ , Tappy L ( eds) From obesity to diabetes . John Wiley, pp 107 - 121 32. Dagenais GR , Tancredi RG , Zierler KL ( 1976 ) Free fatty acid oxidation by forearm muscle at rest, and evidence for an intramuscular lipid pool in the human forearm . J Clin Invest 58 : 421431 33. Groop LC , Bonadonna RC , Shank M , Petrides AS , DeFronzo R A ( 1991 ) Role of free fatty acids and insulin in determining free fatty acid and lipid oxidation in man . J Clin Invest 87 : 83 - 89 34. Bringolf M , Zaragoza N , Rivier D , Felber J-P ( 1972 ) Studies on the metabolic effects induced in the rat by a high-fat diet: inhibition of pyruvate metabolism in diaphragm in vitro and its relation to oxidation of fatty acids . Eur J Biochem 26 : 360 - 367 35. Schindler C , Felber J-P ( 1986 ) Study on the effect of a high-fat diet on diaphragm and liver glycogen and glycerides in the rat . Horm Metab Res 18 : 91 - 93 36. Kiens B , Essen-Gustavson B , Gad R Lithell H ( 1987 ) Lipoprotein lipase activity and intramuscular triglyceride stores after long-term high-fat and high carbohydrate diets in physically trained men . Clin Physiol 7 : 1 - 9 37. Storlien LH , Oakes ND , Pan DA , Kusunoki M , Jenkins AB ( 1993 ) Syndromes of insulin resistance in the rat . Inducement by diet and amelioration with Benfluorex . Diabetes 42 : 457 - 462 38. Takao F , Laury M-C , Ktorza A , Picon L , P6nicaud L ( 1990 ) Hyperinsulinemia increases insulin action in vivo in white adipose tissue but not in muscles . Biochem J 272 : 255 - 257


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R. Vettor, N. Zarjevski, I. Cusin, F. Rohner-Jeanrenaud, B. Jeanrenaud. Induction and reversibility of an obesity syndrome by intracerebroventricular neuropeptide Y administration to normal rats, Diabetologia, 1994, 1202-1208, DOI: 10.1007/BF00399793