Effect of acarbose on glucose homeostasis, lipogenesis and lipogenic enzyme gene expression in adipose tissue of weaned rats

Diabetologia, Jun 1993

Acarbose is a potent intestinal glucosidase inhibitor which could have an anti-obesity property by reducing postprandial plasma glucose and insulin levels, potentially responsible for high rates of lipid synthesis in adipose tissue. We have tested this hypothesis by studying rats during the weaning period, when the lipogenic capacity of the adipose tissue develops. Rats were treated from age 19 days onwards with acarbose (10 mg/100 g diet) and studied at age 30 days. Acarbose was efficient in reducing postprandial excursions of both blood glucose and plasma insulin. Acarbose-treated rats behave like rats continuously infused with glucose with no metabolic signs of carbohydrate deprivation since gluconeogenesis was not activated. There was no massive caecal fermentation of carbohydrate since volatile fatty acids did not significantly increase in the portal blood. One of the most striking features of the acarbose-treated rats was the reduction of adipose tissue weight due to a reduced adipocyte size. This was concomitant with a reduced lipogenic capacity from glucose in isolated adipocytes under insulin stimulation. The activity of fatty acid synthase and acetyl-CoA carboxylase was decreased concomitantly with a reduced expression of their specific mRNA. This study allows the conclusion of postprandial hyperinsulinaemia and hyperglycaemia have a major role in the control of expression of lipogenic enzymes and thus on adipose tissue lipogenic capacity.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://link.springer.com/content/pdf/10.1007%2FBF02743265.pdf

Effect of acarbose on glucose homeostasis, lipogenesis and lipogenic enzyme gene expression in adipose tissue of weaned rats

Diabetologia Effect o f acarbose o n glucose homeostasis, lipogenesis and lipogenic enzyme gene expression in adipose tissue o f w e a n e d rats J. M a u r y 0 T. Issad 0 D . P e r d e r e a u 0 B. G o u h o t 0 P. Ferr 0 J. Girard 0 0 Centre de Recherche sur l'EndocrinologieMoldculaire,et le Drveloppement CNRS, Meudon,France 2Unit6 342INSERM, Hrpital SaintVincentde Paul , Paris , France Summary. Acarbose is a potent intestinal glucosidase inhibitor which could have an anti-obesity property by reducing postprandial plasma glucose and insulin levels, potentially responsible for high rates of lipid synthesis in adipose tissue. We have tested this hypothesis by studying rats drying the weaning period, when the lipogenic capacity of the adipose tissue develops. Rats were treated from age 19 days onwards with acarbose (10 rag/100 g diet) and studied at age 30 days. Acarbose was efficient in reducing postprandial excursions of both blood glucose and plasma insulin. Acarbose-treated rats behave like rats continuously infused with glucose with no metabolic signs of carbohydrate deprivation since gluconeogenesis was not activated. There was no massive caecal fermentation of carbohydrate since volatile fatty acids did not significantly increase in the portal blood. One of the most a-Glucosidase inhibitor; glucose absorption; gluconeogenesis; plasma insulin; isolated adipocytes; lipogenesis - ct-Glucoside hydrolases are key enzymes of carbohydrate digestion [ 1 ]. Acarbose is a potent intestinal glucosidase inhibitor with excellent affinity for sucrase, glucoamylase and maltase [ 2-4 ]. By its anti-sucrase and anti-maltase properties, acarbose reduces the availability of glucose for intestinal absorption, delays starch digestion and reduces postprandial plasma glucose and insulin levels in normal subjects [ 1, 5 ]. Such modulation of the absorptive pattern of carbohydrates and resulting insulin secretion could be considered as an adjunct to specific therapy such as in diabetes. Indeed, acarbose is efficient in reducing postprandial plasma glucose and insulin levels in diabetic subjects [ 6, 7 ] and in non-diabetic and diabetic rats fed with a carbohydrate diet containing this inhibitor [ 4, 8 ]. Similarly, acarbose could also be efficient in obesity by decreasing plasma insulin levels since metabolic abnormalities can be partly ascribed to hyperinsulinaemia [9]. During the suckling period, which corresponds to a high-fat low-carbohydrate diet, the lipogenic capacity in basal conditions or after stimulation by insulin is very low in white adipose tissue and it considerably increases after weaning to a high-carbohydrate diet. Indeed it has been striking features of the acarbose-treated rats was the reduction of adipose tissue weight due to a reduced adipocyte size. This was concomitant with a reduced lipogenic capacity from glucose in isolated adipocytes under insulin stimulation. The activity of fatty acid synthase and acetyl-CoA carboxylase was decreased concomitantly with a reduced expression of their specific mRNA. This study allows the conclusion that postprandial hyperinsulinaemia and hyperglycaemia have a major role in the control of expression of lipogenic enzymes and thus on adipose tissue lipogenic capacity. shown that weaning to a high-carbohydrate diet is followed by a rapid increase in lipogenic enzyme m R N A and activities [ 10 ]. These results suggest that the appearance of peaks of plasma glucose and insulin concentrations concomitant with the adult high-carbohydrate meals may be involved in the development of the lipogenic capacity observed in white adipose tissue. Thus, the sucklingweaning transition is a good model with which to study whether acarbose, by its anti-hyperglycaemic and anti-hyperinsulinaemic properties, affects the development of the lipogenic capacity of white adipose tissue. We have thus addressed the following questions: is it possible to use acarbose in weaned rats to slow down glucose absorption? Has it any consequence on the metabolism of white adipose tissue? Materials and m e t h o d s Chemicals: Acarbose was a gift of Bayer Laboratories (Wtippertat, FRG). Cotlagenase (0.44U/mg) and chemicals for enzyme assays were from Boehringer Mannheim (Meylan,France). Phenol, chloroform, and ethanol were from Farmitalia (Carlo Erba, Milan, Italy). Formamide (deionized before use by treatment with Bio-Rad A G 501-X8 resin), formaldehyde, and pentanol-2 [isoamyl alcohoI (IAA)] were from Prolabo (Paris, France). Dextran sulphate, agarose and serum bovine albumin fraction V fatty acid-free (BSA) were purchased from Sigma (St Louis, Mo., USA). Nylon Hybond-N filters, multiprime D N A labelling system, [a-32P] dCTP (specific activity 3,000 Ci/mmol), and hyperfilms MP were supplied by Amersham International (Amersham, Bucks, UK). [3-3H] glucose, [U14C]glucose, and NaH[14C] CO3were from the C E A (Gif-sur-Yvette, France). Animals: Wistar rats bred in our laboratory were used. They were housed in a room in which the temperature was maintained at 240C, with light from 07.00 to 19.00 hours. The studies were performed on 14/15-day-old suckling rats, and on 28/32 day-old rats weaned at 19 days to a high carbohydrate (HC) diet (% of energy: 62 % carbohydrate, 12 % fat and 26 % protein) with or without acarbose. In order to assess the most efficient dose of acarbose, a group of rats (24/25-day-old) was anaesthetized with pentobarbital (1.3 mg/g body weight). Rats were then force-fed with 20 mg/g body weight of a carbohydrate mixture containing sucrose and raw starch (1/5 weight/weight) and 0, 5 or 20 mg acarbose/100 g of carbohydrate. Blood was sampled at different times after the garage and blood glucose concentration was measured. Blood glucose and plasma insulin concentrations were also measured at 0, 20, 40 and 60 min after a spontaneous meal in 23-day-old rats, fasted for 12 h and treated or not treated with acarbose from 19 days of age. In order to evaluate the importance of gluconeogenesis for glucose homeostasis, anaesthetized 30-day-old weaned rats treated or not treated with acarbose were injected with 3-mercaptopicolinate (3-MPA) (75 mg/kg i.p.), a specific inhibitor of the key enzyme of gluconeogenesis, phosphoenolpyruvate carboxykinase (PEPCK) (EC. 41.1.32), at the end of the absorptive period (07.00 hours). The blood glucose concentration was followed for 60 min after the drug injection. The adipose tissue from the dorsolumbar and pericardiac regions was dissected out as described by Pond and Mattacks and by Cantu and Goodman [ 11, 12 ], and was immediately weighed. Analytical techniques Blood glucose: Blood samples were treated as described previously [ 13 ], and blood glucose was measured by the glucose oxidase method (kit from Boehringer Mannheim). Plasma insulin:Blood samples were treated as described previously [t0] and plasma insulin was determined using a radioimmunoassay kit from Oris Industrie (Gif-sur-Yvette, France). Lactate and volatile fatty acid concentrations: Lactate was deter mined spectrophotometrically at the end of the absorptive period and 6 h after food removal. Volatile fatty acids (acetate, butyrate and propionate) were determined by gas-liquid chromatography after ethanol extractions of samples according to Demign6 et al. [ 14 ]. Glucose metabolism in isolated adipocytes:The subcutaneous white adipose tissue of the inguinal region was removed, cut into small pieces, and digested with collagenase. Krebs-Ringer phosphate buffer containing 1 mmol/1 calcium was used for the digestion of adipose tissue which was performed.in a shaking water-bath (37°C) during i h under oxygenation (OJCOz, 95/5 %). The digested tissue was then filtered through a 200-gin nylon mesh, washed 3 times with the incubation buffer containing i mmol/l calcium and resuspended in the same buffer containing 2 mmol/1 calcium. A sample of the initial cell suspension was used for the determination of cell concentration with a Neubauer haemocytometer. Mean fat-cell diameter was determined on four different preparations in each group (200300 cells in each preparation) using a photomicrographic method. The cells were incubated for 2 h in a shaking water-bath (37°C) with different concentrations of insulin. [U-I4C] Glucose conversion into CO2, acylglycerol fatty acids and acylglycerol glycerol was deterJ. Maury et al.:Effect of acarbose on rat adipose tissue metabolism mined as described by Issad et al [ 13 ]. [U-14C] Glucose conversion into lactate was determined as described by Ferr6 et at. [ 15 ]. Enzymes' activities: The activity of fatty acid synthase (FAS) (EC 2.3.1.85) was determined with the spectrophotometric assay of Linn [ 16 ]. The results were expressed as nanomoles of NADPH oxidized per rain per milligram of protein. The maximal activity of acetylCoA carboxytase (ACC) (EC 6.4.1.2) was determined according to Maeda et al. [ 17 ] after incubation in the presence of 10 mmol/1 citrate, by the incorporation of N a i l [14C]CO3 into malonyl-CoA.The results were expressed as nanomoles of malonyl-CoA formed per min per milligram of protein. The activity of PEPCK was measured by the method of Chang and Lane [ 18 ]. The results were expressed as nanomoles of Nag[14C]CO3 fixed per min per milligram of protein. Total RNA extraction: Total cellular R N A was extracted from the subcutaneous adipose tissue of the inguinal region, using the hotphenol procedure of Scherrer and Darnell [ 19 ]. The concentration of R N A was determined by absorbance at 260 nm, and the R N A solutions were stored in water at - 80°C until use. The integrity of R N A was systematicallychecked by electrophoresis in 0.8% agarose submarine minigel with ethidium bromide and visualized under ultraviolet fluorescence. Dot-blot analysis of total RNA: The dot-blot procedure was used for relative quantification of specific mRNA concentration. Increasing amounts (0.4-3 gg) of each total R N A sample to be analysed were denaturated by heating for 10 min at 65°C, then directly dotted to a nylon membrane using a 96-hole Minifold apparatus (Schleicher&Schuelt, Dassel, FRG), and rinsed out twice with 20 x sodium saline citrate (SSC). RNA was then fixed to the membrane by ultraviolet irradiation for 10 min, The filters were kept at 4°C until hybridization. Dot-blot hybridization." The pFAS 18 cDNA for rat liver FAS mRNA was obtained from Dr. A. G. Goodridge (Iowa City, Iowa, USA). The p181-6 cDNA for rat mammary gland A C C mRNA was obtained from Dr. K. H. Kim (West Lafayette, Ind., USA). Hybridizations to the labelled probes were performed in solutions containing 42% deionized formamide, 7.5% dextran sulphate, 8 x Denhardt's solution, 40 mmol/1 Tris HCt (pH 7.5)and 1% SDS at 42°C overnight. The membranes were washed twice for 30 rain with 2 x SSC/0.1% SDS at 4TC, and once for 30 rain with 1 SSC/0.1 SDS at 65°C and exposed to Hyperfilm MP for 24-48 h at - 80°C with intensifying screens. Quantification was performed by scanning densitometry. Quantification was linear from 0.4 to 1.5 gg of total RNA. The densitometric value corresponding to 1.5 gg R N A was used for the results shown. The spedficityof the various cDNA probes as well as the validity of the dot-Not procedure for m R N A quantification have been pre~4ously checked by Northern blot analysis [ 10, 20, 21 ]. Statistical analysis Results are expressed as means + SEM. Statistical analysis was performed by Student's t-test for unpaired data or by analysis of variance (F-test) when necessary. Results Efficiency o f acarbose on glucose absorption in weaned rats S i n c e a c a r b o s e h a s n e v e r b e e n u s e d in w e a n e d rats, w e c h e c k e d w h e t h e r it e f f i c i e n t l y r e d u c e s p o s t p r a n d i a l e x c u r s i o n s o f b l o o d g l u c o s e a f t e r a c a r b o h y d r a t e m e a l . I n a d u l t r a t s a n d m i c e , a c a r b o s e w a s e f f e c t i v e at 20 a n d J. Maury et "01.:Effect of acarbose on rat adipose tissue metabolism 3.0 -.~ ~ 2.0 0 I 40 I 50 ltg.1. Effect of acarbose on blood glucose concentration after carbohydrate force-feeding. Rats (24/25-day-old) were anaesthetized and force fed with a carbohydrate mixture (20 mg/g body weight) and different dosages of acarbose. Blood glucose concentration was measured every 10 min for 50 min after the force feeding. ( [] ) Controls, ( O ) 5 rag/100 g acarbose in the diet, ( n ) 20 mg/100 g acarbose in the diet. Each point is the mean +_SEM of four different rats. Statistically significant difference (F-test) for *p < 0.05 between controls and acarbose-treated rats 40 mg/100 g chow [ 4, 22, 23 ]. In the p r e s e n t experiments, we used acarbose at 5 and 20 mg/100 g of diet, and blood glucose was d e t e r m i n e d at different times after force feeding 24/25-day-old rats with carbohydrates. A c a r b o s e was efficient at significantly reducing the postprandial excursion of glycaemia at a dosage o v e r 5 mg/100 g diet (Fig. 1). The next step was to find the dosage which to a lesser extent affected the growth and welfare of the rats. T h e food intake was m e a s u r e d every day f r o m day 19 to day 30 in a c a r b o s e - t r e a t e d rats (5,10 and 20 mg/100 g of diet) and in the control group. N o significant difference in the f o o d int a k e was observed, w h a t e v e r the dosage of a c a r b o s e used ( m e a n food intake m e a s u r e d o v e r 9 days was: 7.1 + 0.2 g/day in control rats (n = 9); 6.6 + 0.4 g/day in acarbose-treated rats 5 mg/100 g diet (n = 9); 7.2 + 0.4 g/day in a c a r b o s e - t r e a t e d rats 1 0 m g / 1 0 0 g diet (n =9); and 6.9 + 0.6 g/day in a c a r b o s e - t r e a t e d rats 20 mg/100 g diet (n = 9). T h e b o d y weight of w e a n e d rats was significantly reduced only at 20 mg acarbose/100 g diet (Table 1). Liver, heart and various fat depots of 30-day-old rats were weighed. B o d y weight, liver and heart we!ght were significantly reduced at 20 m g acarbose. A d i p o s e tissue weight was affected at a smaller dosage of acarbose (Table 1). Effect of acarbose on blood glucose and plasma insulin concentrations after a spontaneous meal and during a 12-h fast in weaned rats In o r d e r to k n o w the extent to which the dosage of acarbose used (10 mg/100 g diet) reduced postprandial glycaemia and insulinaemia u n d e r physiological conditions, we m e a s u r e d these p a r a m e t e r s in 23-day-old rats t r e a t e d or not t r e a t e d with acarbose f r o m 19 days, after a spontaneous m e a l and after a 12-h fast. In a c a r b o s e - t r e a t e d rats, glycaemia and insulinaemia increase only marginally after ingestion of the m e a l (Fig. 2). Moreover, after a 12-h fast, basal glycaemia and basal insulinaemia were 1.8-fold higher in a c a r b o s e - t r e a t e d rats. Indeed, b l o o d glucose and p l a s m a insulin concentrations at 0, 6 or 12 h after food rem o v a l decreased continuously during the 12-h fast in the control rats but r e m a i n e d unchanged in a c a r b o s e - t r e a t e d rats (Fig. 2). Fermentation products in acarbose-treated rats In o r d e r to d e t e r m i n e if c a r b o h y d r a t e f e r m e n t a t i o n in the colon provides volatile fatty acids (butyrate, propionate, acetate), their concentrations were d e t e r m i n e d in the portal b l o o d of post-absorptive rats. Volatile fatty acids w e r e not significantly higher in a c a r b o s e - t r e a t e d rats t h a n in control rats (results not shown). Is hepatic gluconeogenesis stimulated by the acarbose treatment? If acarbose induces m a r k e d reductions in the a m o u n t of glucose absorbed, gluconeogenesis should be activated in acarbose-treated rats. This hypothesis was tested by using 3-MPA, an inhibitor of P E P C K , at the end of the absorpRats were weaned at 19 days. Each rat in the acarbose-treated group was paired with a control of the same weight in the same litter. Body weight and organ weight were measured at 30 days. Results are the mean _+SEM of four determinations, ap < 0.05 between control and acarbose-treated rats (t-test) e~ 8 Fig.2. Effect of acarbose treatment on glycaemia and insulinaemia during a 12-h fast and after a spontaneous meal in 23-day-old rats. Rats were treated or not with acarbose (10 mg/100 g diet) from 19 days. Blood glucose and plasma insulin concentrations were measured during a 12-h fast and after a normal diet meal. ( [] ) Controls, ( • ) acarbose-treated (10 rag/100 g diet). Each point is the mean _+SEM of four different rats. Statistically significant difference (Ftest) respectively for *p < 0.05 and ***p < 0.01 between controls and acarbose-treated rats tive period. 3-MPA induced an i m p o r t a n t hypoglycaemic effect in control rats fasted for 24 h (Fig. 3). In contrast, 3M P A did not significantly decrease blood glucose concentration in fed control rats and a c a r b o s e - t r e a t e d rats. We c o m p l e t e d this e x p e r i m e n t by m e a s u r i n g the activity of P E P C K in control and a c a r b o s e - t r e a t e d rats after sampling the liver of the rats at the end of the absorptive period. T h e activity of liver P E P C K was similar in control and a c a r b o s e - t r e a t e d rats (126 + 50, n = 4 vs 163 + 50 n m o l x m i n - i x g - ~of liver, n = 4). F r o m this set of experiments, we can conclude that acarbose indeed reduces the gtycaemia and insulinaemia excursions following m e a l s and that a c a r b o s e - t r e a t e d rats b e h a v e like rats infused continuously with glucose with no m e t a b o l i c signs of c a r b o h y d r a t e deprivation. The next 8 o = Ng.3. Effect of 3-mercaptopicolinate (3-MPA), an inhibitor of gluconeogenesis, on blood glucose concentrations in absorptive rats. Rats treated or not treated with acarbose (10 mg/100 g diet) were injected with 3-MPA at the end of the absorptive period. A group of control rats was fasted for 24 h before the injection of 3-MPA. The pattern of blood glucose concentration was followed for 60 min after 3-MPA injection. ( [] ) 24-h fasted controls, ( [] ) fed controls, ( [] ) acarbose-treated (10 mg/100 g diet). Each point is the mean + SEM of four different rats. Statistically significant difference (F-test), respectively for ***p < 0.00t between 24-h fasted controls and the two other experimental groups question was to assess whether it had an impact on adipose tissue metabolism. Fatpad weight and adipocyte size For this series of experiments the subcutaneous inguinal fat p a d was sampled. As for other fat depots (Table 1), the fat p a d weight was significantly lower in a c a r b o s e - t r e a t e d rats t h a n in controls, respectively 0 . 6 9 + 0 . 0 8 g vs 1.30 _+0.2 g (p < 0.01), with a weight ratio control: acarbose of 1.93. In order to d e t e r m i n e w h e t h e r the weight reduction of adipose tissue was related to a decrease in the n u m b e r or in the v o l u m e of adipose cells, adipocytes were isolated and the d i a m e t e r of the adipocytes in each group was measured. T h e m e a n d i a m e t e r of adipocytes was 56.6 _+0.6 g m in control rats and 45.3 + 0.5 g m in acarbose-treated rats (p < 0.001). F r o m the m e a s u r e d m e a n diam e t e r it is possible to calculate the m e a n v o l u m e of adipocytes in each group and the v o l u m e ratio control: acarbose. This ratio is 1.96, which w h e n c o m p a r e d with the weight ratio of 1.93 (see a b o v e ) strongly suggests that it is the adipocyte v o l u m e and not the n u m b e r p e r fat p a d which is modified by the acarbose treatment. Glucose metabolism T h e products of glucose m e t a b o l i s m in isolated adipocytes are a - g l y c e r o p h o s p h a t e for the esterification of fatty acids to triglycerides, lactate released in the incubation m e d i u m , CO2 mainly derived f r o m the decarboxylation of glucose into the pentose p h o s p h a t e p a t h w a y and through the p y r u v a t e d e h y d r o g e n a s e step and fatty agids of triacylglycerols. We studied the utilization of glucose in the various metabolic pathways in isolated adipocytes in the ab40-Results are the mean + SEM of four determinations. Difference significant (t-test), respectivelyfor ap < 0.05 and bp < 0.001 between control and acarbose-treated rats s e n c e o r in t h e p r e s e n c e o f 800 g U / m l insulin ( T a b l e 2). I n c o n t r o l rats, insulin significantly i n c r e a s e d t h e u t i l i z a t i o n o f g l u c o s e in all t h e m e t a b o l i c p a t h w a y s . I n t h e a c a r b o s e t r e a t e d g r o u p t h e s t i m u l a t i o n o f g l u c o s e u t i l i z a t i o n b y insulin was lower. T h e m a i n d i f f e r e n c e in a d i p o c y t e s f r o m a c a r b o s e - t r e a t e d a n d c o n t r o l r a t s was f o u n d in t h e g l u c o s e o x i d a t i o n a n d in t h e l i p o g e n i c c a p a c i t y ( i n c o r p o r a t i o n of g l u c o s e into f a t t y acids) u n d e r insulin s t i m u l a t i o n , l e a d i n g to a d e c r e a s e d t o t a l g l u c o s e u t i l i z a t i o n in t h e a d i p o c y t e s o f a c a r b o s e - t r e a t e d rats. Lipogenic enzyme activities and m R N A concentrations W e t h e n m e a s u r e d t h e activities of t h e t w o m a j o r l i p o g e n i e e n z y m e s , F A S a n d A C C in w h i t e a d i p o s e tissue. T h e activity o f F A S a n d A C C w e r e s i g n i f i c a n t l y l o w e r in a c a r b o s e - t r e a t e d rats (n = 6, p < 0.01) ( F i g . 4 ) . A m a r k e d d e c r e a s e in t h e r e l a t i v e c o n c e n t r a t i o n o f F A S a n d A C C m R N A s was f o u n d in t h e a c a r b o s e - t r e a t e d rats (2.4 a n d I00 -c~ 50 F A S A C C mRNA concentrations 1.8-fold lower, respectively than in control rats, p < 0.05) (Fig. 4). In o r d e r to verify that these changes were specific for lipogenic enzymes, the blots were hybridized with the P E P C K c D N A p r o b e since this e n z y m e changes in an opposite direction to that of lipogenic enzymes [ 10 ]. Bet w e e n 21 days and 30 days, P E P C K m R N A concentration in white adipose tissue was decreased by 30 + 10 % in acarb o s e - t r e a t e d rats (n = 6) and b y 70 + 5 % in control rats (n = 6,p < 0.01). Discussion In the present study, we have shown that acarbose is efficient in significantly reducing the meal-induced excursions of b l o o d glucose and p l a s m a insulin concentrations. This is in a g r e e m e n t with o t h e r studies in genetically obese animals [ 24, 25 ]. A c a r b o s e could reduce or slow down c a r b o h y d r a t e absorption or b o t h f r o m the gastrointestinal tract, as it has b e e n shown in m a n in vivo where acarbose was able to decrease c a r b o h y d r a t e absorption by 30 % and to increase the absorption time up to 1.7-fold in a d o s e - d e p e n d e n t fashion [26]. In our model, the m a i n effect of acarbose seems to b e a slowing down r a t h e r than an overall decrease of carbohydrate absorption. Indeed, very few products of carbohydrate caecal fermentations are found in the portal vein and gluconeogenesis is not increased in a c a r b o s e - t r e a t e d rats. This was not unexpected, since in o u r study, weaned rats received a small dose of acarbose (10 mg/100 g diet). Indeed, Puls and Bishoff [ 3 ] have shown that the increase of liver gluconeogenesis requires high doses ( > 150 mg/100 g diet) of acarbose and was due to the lack of alimentary carbohydrates, since undigested carbohydrates were excreted in faeces. This series of e x p e r i m e n t s suggests that acarbose-treated rats b e h a v e like rats continuously p e r f u s e d with glucose, due to the slowing-down of glucose absorption. This explains why their glycaemia is constant over a 12-h fast and does not increase during the prandial period. We h a v e thus firmly established a m o d e l in which the m a i n alteration in c a r b o h y d r a t e homeostasis is the absence of blood glucose and p l a s m a insulin p e a k s during meals. This has clear effects on adipose tissue m e t a b o l i s m as shown by its weight reduction. T h e decreased lipogenic capacity p r o b a b l y contributes to the decreased adipose cell v o l u m e although a decreased lipoprotein lipase activity cannot b e excluded. T h e o b s e r v e d effect is linked with a decreased gene expression of lipogenic e n z y m e s and indicates a potential role for glucose and insulin excursions in the regulation of these genes as previously suggested [ 10 ]. This study confirms that hyperinsulinaemia and hyperglycaemia h a v e a maj or role in the over-expression of lipogenic enzymes. This fits with in vitro studies [ 27 ] showing that glucose and insulin control FAS and A C C expression and with in vivo studies in obese animals in which hyperinsulinaemia is c o n c o m i t a n t with increased glucose utilization and lipogenic capacity in white adipose tissue in the post-absorptive state [ 28-30 ]. Thus, reductions of hyperinsulinaemia and h y p e r g l y c a e m i a could b e a rational t r e a t m e n t of genetic obesky. Acknowledgements.This work was supported by grants from BayerPharma, France. We acknowledge Drs. H. Bischoff and O. R6gnier for their interest and support during this study. 1. Caspary WF ( 1978 ) Sucrose malabsorption in man after ingestion of a-glucoside hydrolase inhibitor . Lancet I: 1231 - 1233 2. Puls W , Keup U , Krause HP et al. ( 1980 ) Phamacology of a gincosidase inhibitor . Front Hormone Res 7 : 235 - 247 3. Puls W , Bishoff H ( 1983 ) Pharmacology of amylase and glncosidase-inhibitors . In: Creutzfeldt Vv, F6tsch UR (eds) Delaying absorption as a therapeutic principle in metabolic disease . Thieme, Stuttgart New York, pp 70 - 78 4. Lee SM , Bustamante SA , Koldovsky O ( 1983 ) The effect of aglucosidase inhibition on intestinal disacharidase activity in normal and diabetic mice . Metabolism 32 : 793 - 799 5. Keup U , Krause HR Puls W, Thomas G ( 1982 ) Pharmacological studies on acarbose. I) Antihyperglycemic effects . In: Creutzfeldt W (ed) First International Symposium on Acarbose. Excerpta Medica , Amsterdam, pp 147 - 150 6. Willms B , Sachse G , Unger H ( 1980 ) Treatment of diabetes with a glycoside hydrolase inhibitor (Acarbose , Bay g 5421). Front Hormone Res 7 : 276 - 281 7. Reaven GM , Lardinois CM , Greenfield MS , Schwartz HC , Vreman HJ ( 1990 ) Effect of acarbose on carbohydrate and lipid metabolism in NIDDM patients poorly controlled by sulfonylureas . Diabetes Care 13 : 32 - 36 8. Gray SR , Olefsky JM ( 1982 ) Effect of a glucosidase inhibitor on the metabolic response of diabetic rats to a high carbohydrate diet, consisting of starch and sucrose, or glucose . Metabolism 31 : 88 - 92 9. Jeanrenaud B ( 1978 ) Hyperinsulinemiain obesitysyndromes: its metabolic consequences and possible etiology . Metabolism 27 : 1881 - 1892 10. Coup6 C , Perdereau D , Ferr6 P , Hitler Y , Narkewicz M , Girard J ( 1990 ) Lipogenic enzyme activities and mRNA in rat adipose tissue during weaning: role of the diet . Am J Physio1258: E126 - E133 11. Pond CM , Mattacks CA ( 1991 ) The effects of noradrenaline and insulin on lipolysis in adipocytes isolated from nine different adipose depots of guinea-pigs . Int J Obesity 15 : 60 % 618 12. Cantu RC , Goodman HM ( 1967 ) Effects of denervation and fasting on white adipose tissue . Am J Physio1212: 207 - 212 13. Issad T , Coup6 C , Pastor-Anglada M , Ferr6 R Girard J ( 1988 ) Development of insulin-sensitivity at weaning in the rat . Role of the nutritional transition . Biochem J 251 : 685 - 690 14. Demign6 C , Yacoub C , Rdm6sy C ( 1986 ) Effects of absorption of large amounts of volatile fatty acids on rat liver metabolism . J Nutr 116 : 77 -- 86 15. Ferr6 E P6gorier JP , Marliss EB , Girard J ( 1978 ) Influence of exogenous fat and gluconeogenic substrates on glucose homeostasis in the newborn rat . Am J Physio1234: E129 - E136 16. Linn TC ( 1981 ) Purification and crystallization of rat liver fatty acid synthetase . Arch Biochem Biophys 209 : 613 . 619 17. Maeda H , Ikeda I , Sugano M ( 1975 ) Behavior of the liver key lipogenesis enzymes in rat fed with threonine imbalanced diet . Nutr Rep Int 12 : 61 - 66 18. Chang HC , Lane MD ( 1966 ) Purification and properties of liver mitochondrial phosphoenol pyruvate carboxykinase . J Biol Chem 241 : 2413 - 2420 19. Scherrer K , Darneli J ( 1962 ) Sedimentation characteristics of rapidty labelled RNA from HeLa cells . Biochem Biophys Res Commun 7 : 486 - 490 20. Leturque A , Postic C , Ferr6 P , Girard J ( 1991 ) Nutritional regulation of glucose transporter in muscle and adipose tissue of weaned rats . Am J Physio1260: E588 - E593 21. Foufelle F , Perdereau D , Gouhot B , Ferr6 P , Girard J ( 1992 ) Effect of diets rich in medium-chain and long-chain triglycerides on L Maury et al.: Effect of acarbose on rat adipose tissue metabolism lipogenic-enzymegene expression in liver and adipose tissue of the weaned rat . Eur J Biochem 208 : 381 - 387 22. Koevary SB ( 1990 ) Effects of acarbose on the development of diabetes in BB/Wor rats . Metabolism 39 : 865 - 870 23. Katovich MJ , Meldrum MJ , Vasselli JR ( I991) Beneficial effects of dietary acarbose in the streptozotocin-induced diabetic rat . Metabolism 40 : 1275 - 1282 24. Vasselli JR ; Haraczkiewicz E , Maggio CA , Greenwood MRC ( 1983 ) Effect of an alpha-glucosidaseinhibitor (Acarbose BAY g 5421) on the development of obesity and food motivated behavior in Zucker (fa fa) rats . Pharmacol Biochem Behavior 19 : 85 - 89 25. Le Marchand-Brustel Y , Rochet N , Grtmeaux T , Marot I , Van Obberghen E ( 1990 ) Effect of an a-glucosidase inhibitor on experimentally-inducedobesity in mice . Diabetologia 33 : 24 - 30 26. Radziuk J , Kemmer F , Morishima T , Berchtold R Vranic M ( 1984 ) The effects of an alpha-glucoside hydrolase inhibitor on glycemia and the absorption of sucrose in man determined using a tracer method . Diabetes 33 : 20 % 213 27. Foufelle F , Gouhot B , Ptgorier P e t al. ( 1992 ) Glucose stimulation of lipogenic enzyme gene expression in cultured white adipose tissue . J Biol Chem 267 : 20543 - 20546 28. Ptnicaud L , Ferr6 P , Terretaz J et al. ( 1987 ) Development of obesity in Zucker rats. Early insulin resistance in muscles but normal insulin sensitivity in white adipose tissue . Diabetes 36 : 626 -- 631 29. Krief S , Bazin R , Dupuy E Lavau M ( 1988 ) Increased in vivoglucose utilizationin 30-day-old obese Zucker rat: role of white adipose tissue . Am J Physio1254: E342 - E348 30. Ptnicaud L , Ferr6 P , Assimacopoulos- JeannetF 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 Received: 11 September 1992 and in revised form: 19 February 1993 Dr. J. Girard Centre de Recherche sur l'Endocrinologie Mol6culaire et le Ddveloppement CNRS 9 rue Jules Hetzel F=92190Meudon


This is a preview of a remote PDF: https://link.springer.com/content/pdf/10.1007%2FBF02743265.pdf

J. Maury, T. Issad, D. Perdereau, B. Gouhot, P. Ferré, J. Girard. Effect of acarbose on glucose homeostasis, lipogenesis and lipogenic enzyme gene expression in adipose tissue of weaned rats, Diabetologia, 1993, 503-509, DOI: 10.1007/BF02743265