Eur J Endocrinol
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

DOI: 10.1530/eje.1.02229
European Journal of Endocrinology, Vol 155, Issue 3, 461-468
Copyright © 2006 by European Society of Endocrinology
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (1)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Moldes, M.
Right arrow Articles by Clément, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Moldes, M.
Right arrow Articles by Clément, K.
CLINICAL STUDY

Adiponutrin gene is regulated by insulin and glucose in human adipose tissue

Marthe Moldes1,2,3,4, Geneviève Beauregard5, May Faraj5, Noël Peretti6, Pierre-Henri Ducluzeau6, Martine Laville6, Rémi Rabasa-Lhoret5, Hubert Vidal6 and Karine Clément7,8,9

1 Institut Cochin, Department of Endocrinology, Cancer and Metabolism, Paris F-75014, France, 2 Inserm, U567, Paris F-75014, France, 3 CNRS, UMR 8104, Paris F-75014, France, 4 Faculty of Medicine René Descartes, University of Paris 5, UM 3, Paris F-75014, France, 5 Laboratory of Metabolic Dysfunction, Department of Nutrition, University of Montréal, Pavillon Liliane de Stewart H3T1A8 Montréal, Québec, Canada, 6 INSERM U.449, INRA U.1235, Lyon Centre of Research into Human Nutrition, Faculty of Medicine R. Laennec, University Claude Bernard-Lyon, Lyon, France, 7 INSERM, U755 Nutriomique, Paris F-75004, France, 8 Faculty of Medicine, University Pierre and Marie Curie-Paris 6, Les Cordeliers, Paris 75004, France, and 9 Nutrition Department, AP-HP, Hôtel-Dieu Hospital, Paris 75004, France

(Correspondence should be addressed to K Clément at AP-HP, Hôtel-Dieu Hospital, Paris; Email: karine.clement{at}htd.ap-hop-paris.fr)


   Abstract
Top
 Abstract
Introduction
 Materials and methods
 Results
 Discussion
 References
 
Objective: Adiponutrin is a new transmembrane protein specifically expressed in adipose tissue. In obese subjects, short- or long-term calorie restriction diets were associated with a reduction in adiponutrin gene expression. Adiponut.rin mRNA level was previously shown to be negatively correlated with fasting glucose plasma levels and associated with insulin sensitivity of non-diabetic obese and non-obese subjects. The purpose of the present work was to get more insight into the regulation of adiponutrin gene expression by insulin and/or glucose using clamp studies and to examine its potential dysregulation in subjects with a deterioration of glucose homeostasis.

Methods: Adiponutrin gene expression was quantified by reverse transcriptase-quantitative PCR in s.c. adipose tissue of healthy lean subjects after an euglycemic hyperinsulinemic clamp (EGHI), a hyperglycemic euinsulinemic clamp, and a hyperglycemic hyperinsulinemic (HGHI) clamp. Adiponutrin gene expression was also analyzed in patients with different levels of insulin resistance.

Results: During EGHI, insulin infusion induced adiponutrin gene expression 8.4-fold (P = 0.008). Its expression was also induced by glucose infusion, although to a lesser extend (2.2-fold, P = 0.03). Infusion of both insulin and glucose (HGHI) had an additive effect on the adiponutrin expression (tenfold, P = 0.008). In a pathological context, adiponutrin gene was highly expressed in the adipose tissue of type-1 diabetic patients with chronic hyperglycemia compared with healthy subjects. Conversely, adiponutrin gene expression was significantly reduced in type-2 diabetics (P = 0.01), but remained moderately regulated in these patients after the EGHI clamp (2.5-fold increased).

Conclusion: These results suggest a strong relationship between adiponutrin expression, insulin sensitivity, and glucose metabolism in human adipose tissue.


   Introduction
Top
 Abstract
 Introduction
Materials and methods
 Results
 Discussion
 References
 
Adipose tissue plays a central role in the regulation of metabolic homeostasis via its dual role as an energy storage and endocrine organ. Indeed, fat cells produce and secrete a number of endocrine and paracrine factors, called adipokines (such as leptin and adiponectin), which profoundly influence metabolism, energy expenditure, and insulin sensitivity (1). Many unsecreted proteins are also expressed in adipose tissue (2), but a lot remains to be identified regarding their role in metabolism.

The recently cloned adiponutrin gene encodes a new unsecreted protein specifically synthesized by the adipocytes. This transmembrane protein is highly induced during adipocyte differentiation (3). Adiponutrin possesses a ‘patatin-like’ domain, and belongs to a family of enzymes bearing a transacylase/lipase activity such as for desnutrin/adipose triglyceride lipase (ATGL), GS2 proteins (4–7). Despite the structural homology, the precise biological function of the adiponutrin in adipose tissue remains unclear (8). Several lines of evidence suggest that this protein has no lipase activity (7–9). Furthermore, adiponutrin displays a pattern of expression distinct from the other family members (5, 9). Highly regulated by the nutritional status in rodents, adiponutrin gene expression decreases upon fasting and increases during refeeding in animals fed with a high-carbohydrate diet (3, 10, 11) conversely to the desnutrin/ATGL lipase (5, 9). These observations led to the concept that adiponutrin is more likely involved in the anabolic pathway rather than the lipolytic pathway in adipose tissue (8, 9).

In humans, the regulation of adiponutrin gene expression was unknown until our first study in obese individuals (12). Although adiponutrin mRNA level in adipose tissue was similar in non-obese and in morbidly obese subjects, short- or long-term calorie restriction diets were associated with a marked reduction in adiponutrin mRNA level suggesting an interaction between this adipose-specific protein and metabolic events occurring during modifications of the energy balance. Adiponutrin mRNA level was also negatively correlated with plasma levels of glucose and mildly associated with subject’s insulin sensitivity (12). Energy deprivation is classically associated with modulation of insulin sensitivity and glucose metabolism. Interactions between adiponutrin and glucose metabolism were also reported in cellular and animal studies. In vitro, the adiponutrin gene is regulated by glucose in 3T3-L1 adipocytes and mildly by insulin (3). In vivo, adiponutrin gene expression rapidly increases in the white adipose tissue of rats fed with a high-sucrose diet (10, 11). These studies suggest a regulation between adiponutrin, and glucose and insulin.

Our goal herein was to get more insight into the regulation of adiponutrin expression by glucose and insulin in humans, as well as to investigate its potential abnormal regulation in pathologic conditions associated with altered glucose and insulin homeostasis. To this end, we examined adiponutrin mRNA levels in s.c. adipose tissue during three acute clamp studies with different insulin and/or glucose infusions in healthy males. Adiponutrin gene expression was also investigated in obesity, and type-1 and type-2 diabetes.


   Materials and methods
Top
 Abstract
 Introduction
 Materials and methods
Results
 Discussion
 References
 
Baseline and stimulated adiponutrin gene expression

Clamp studies in healthy lean subjects  Twenty-three lean male volunteers participated in the clamp study (Table 1Go). Subjects underwent medical examination and routine biological testing. None had a familial or personal history of diabetes and obesity. Subjects were not engaged in physical training (i.e. had < 2 h of structured exercise per week) and did not practice exercise for 48 h before the clinical investigation. The study was conducted in the post-absorptive state after an overnight fast. Three groups of lean subjects underwent a 3-h either euglycemic hyperinsulinemic (EGHI), hyperglycemic euinsulinemic (HGEI) or hyperglycemic hyperinsulinemic clamp (HGHI). Subjects who agreed to repeat the clamp study were included in both HGEI and HGHI clamps (N = 5). The EGHI clamp was performed as described previously (13). Briefly, plasma insulin was elevated to a plateau concentration using primed-constant exogenous insulin infusion at 75 mU/m per minute. Plasma glucose was maintained at fasting levels using 20% dextrose infusion adjusted every 5 min according to the repeated plasma glucose measurements. The HGEI and HGHI clamps were a modification of the technique described by De Fronzo et al. (14). The objective of the hyperglycemic clamps was to increase plasma glucose 5.5 mmol/l above the fasting level (measured as the average of three fasting values obtained in 15 min) (15). To achieve that, 20% dextrose was infused in two phases: (i) bolus dose to increase the glycemia to the desired elevated target and (ii) continuous infusion dose to maintain the glycemia at the desired target, which is adjusted every 5–10 min according to the measured plasma glucose concentration. In order to create, simultaneous to hyperglycemia, either euinsulinemic (HGEI) or hyperinsulinemic (HGHI) conditions, endogenous insulin secretion was inhibited using somatostatin analog (Sandostatin, Novartis Pharma, S.A., Switzerland). Sandostatin was infused in two phases: (i) a bolus dose of 25 µg over 1 min given 5 min before the bolus of glucose and (ii) a maintenance dose of 1.0 µg/min (16). Insulin concentration was then replaced either at basal values (HGEI, constant exogenous insulin infusion at a rate of 3.45 mU/m per minute) or a value comparable to that obtained in the EGHI condition (HGHI, primed-constant exogenous insulin infusion at a rate of 75 mU/m per minute) started at the same time of glucose infusion. Potassium phosphate was added to the dextrose in order to maintain normal potassium values under all three clamp conditions.


View this table:
[in this window]
[in a new window]
  		Table 1 Biological parameters of healthy lean subjects before and after the clamps.
 
Baseline adiponutrin gene expression in different pathologic conditions

Subjects  Since insulin sensitivity and glucose tolerance vary with age, we explored two independent groups of age-matched subjects. Group 1 (Table 2Go) comprised ten lean subjects (with no family history of either obesity or type-2 diabetes), nine non-diabetic obese subjects (with no familial history of type-2 diabetes and characterized for glucose tolerance by a classical 75 g 2-h oral glucose tolerance test) and nine type-1 diabetic patients (with no familial antecedent of type-2 diabetes, duration of diabetes being 16 ± 3 years, HbAlc = 9.2% ± 0.3, C peptide < 0.05 ng/ml) with the same age range (22–44) (Table 2Go). The type-1 diabetic subjects were treated with multiple daily injections of insulin (45 ± 5 IU/day). The last dose of insulin was administered the day before the study. On the morning of the experiment, type-1 diabetic patients showed marked hyperglycemia (12.6 ± 0.8 mM).


View this table:
[in this window]
[in a new window]
  		Table 2 Clinical characteristics of younger lean, obese and type-1 diabetics.
 
Group 2 (Table 3Go) comprised age-matched older subjects (41–68). We explored seven lean subjects (with no family history of either obesity or type-2 diabetes), seven non-diabetic obese subjects (with no familial history of type-2 diabetes and were characterized for glucose tolerance by a classical 75 g 2-h oral glucose tolerance test) and eight type-2 diabetic patients (duration of diabetes being 7 ± 1 years, HbAlc = 10.9% ± 0.3). These subjects interrupted their usual treatment of oral anti-diabetic agents at least 1 week before the investigation.


View this table:
[in this window]
[in a new window]
  		Table 3 Clinical characteristics of older lean, obese and type-2 diabetics.
 
Clamp studies in type-2 diabetic subjects  Four type-2 diabetic patients from group 2 agreed to perform a 3-h EGHI.

In all subjects, fasting blood samples were obtained for biochemical and hormonal evaluation. All subjects involved in the different investigation groups gave written consent after being informed of the nature, purpose and possible risks of the study. The experimental protocol was approved by the ethics committee of University of Montreal (Canada) and Hospices Civiles de Lyon (France).

Adipose tissue biopsy  The adipose tissue pieces were sampled, after an overnight fast, in the s.c. peri-umbilical by needle biopsy under local anesthesia (1% xylocaïne). In the clamp study, the s.c. adipose tissue samples were obtained 30 min before the clamp started and at the end (13). Insulin and sandostatin (when applicable) infusions were maintained at the same infusion rate during the post-clamp biopsy. Adipose tissue specimens were immediately frozen in liquid nitrogen and stored at 80 °C until analysis.

Analytical procedures  Plasma glucose concentrations were measured with a glucose-analyzer (Beckman Glucose analyzer, Mississauga, ON, Canada). Plasma insulin was measured in duplicate with a commercial RIA (Linco Research, St-Charles, MO, USA). In the three clamp conditions, all fasting and post-clamp values were an average of the three time point measurements taken over the period of 30 min. Fasting plasma cholesterol and triglycerides were analyzed on the COBAS INTEGRA 400 (Roche). Serum-free fatty acid values were measured using commercially available kits (WAKO Chemicals, Rich-mond, VA, USA).

Analysis of mRNA in adipose tissue biopsy  Total RNAwas extracted from adipose tissue biopsies using the RNeasy total RNA minikit (Qiagen). Adiponutrin mRNA contents were determined by reverse transcriptase-quantitative PCR (RT-qPCR) using a light cycler (Roche), as previously described (17). Results were expressed as the ratio of adiponutrin mRNA to hypoxanthine phosphoribosyltransferase (HPRT) mRNA, a housekeeping gene, used as an internal control. The primer sequences are for the adiponutrin sense 5'-GATGGAGGAGTGAGTGACAA-3' and the adiponutrin antisense 5'-CTGAATGCATCCAAATATCC-3', and for the hypoxanthine phosphoribosyl transferase (HPRT) sense 5'-TTGCTGACCTGCTGGATTAC-3' and HPRT antisenses 5'-AGTTGAGAGATCATCTCCAC-3'. The analysis was performed using the LightCycler software (Roche).

Insulin sensitivity calculation  Insulin sensitivity was evaluated using the quantitative insulin sensitivity check index (QUICKI) method, which correlated well with the hyperinsulinemic euglycemic clamp method. Calculations were performed using fasting glucose and insulin as described (18–20).

Statistics analysis  The data are expressed as mean ± S.E.M. Statistical analysis was performed using JMP statistical software (SAS Institute, Inc., Cary, NC, USA). Wilcoxon non-parametric paired test was used to examine the effect of the clamps on adiponutrin mRNA levels and the clinical and metabolic characteristics of the subjects. We used Kruskal–Wallis or Wilcoxon rank test for comparison between independent groups. Non-parametric Spearman’s rank correlation was used to examine the correlations of the adiponutrin mRNA levels with the clinical and metabolic characteristics and significance was set at P < 0.05.


   Results
Top
 Abstract
 Introduction
 Materials and methods
 Results
Discussion
 References
 
Adiponutrin gene expression is regulated by insulin and glucose in adipose tissue of healthy lean males

To get insight into the regulation of adiponutrin by insulin and/or glucose in the adipose tissue, healthy lean males were subjected to three types of clamps: HGEI, EGHI, or HGHI. This methodology allowed the investigation of an independent and/or additive effect of glucose and insulin on adiponutrin gene expression. The biological parameters observed before and after the three clamps in these groups of age-matched subjects are shown in Table 1Go. Some differences in insulinemia in the fasting state were observed in the EGHI group.

Adiponutrin gene expression was significantly enhanced in s.c. adipose tissue of lean subjects in the three clamp conditions (Fig. 1Go). Compared with each individual basal values, adiponutrin mRNA levels increased during the HGEI clamp 2.2-fold (mean fold change 2.2 ± 0.4; P = 0.03, Fig. 1AGo), and 8.4-fold during the EGHI clamp (8.4 ± 1.5; P = 0.008, Fig. 1BGo). The HGHI clamp led to a tenfold enhancement of adiponutrin gene expression level (10.0 ± 1.78 compared with basal value; P = 0.008, Fig. 1CGo).


Figure 1
View larger version (20K):
[in this window]
[in a new window]
  		Figure 1 Adiponutrin gene expression in response to three acute clamps in s.c. adipose tissue of lean subjects. Adiponutrin mRNA level (µg adiponutrin mRNA/µg hypoxanthine phosphoribosyl-transferase (HPRT) mRNA) were quantified by real-time reverse transcriptase (RT)-PCR before or after the 3-h clamps in lean males. A paired Wilcoxon signed rank test is performed. The individual induction of Adiponutrin mRNA levels is shows during (A) the hyperglycemic euinsulinemic clamp (HGEI) *P = 0.03, (B) the euglycemic hyperinsulinemic clamp (EGHI) {dagger}P = 0.008 and (C) the hyperglycemic hyperinsulinemic clamp (HGHI) {ddagger}P = 0.008. Adiponutrin mRNA level (µg adiponutrin mRNA/µg HPRT mRNA) were quantified by real time RT-PCR in total preparations.

 
Adiponutrin gene expression is modified in subjects with altered insulin resistance and/or glucose homeostasis

We further investigated adiponutrin gene expression in the adipose tissue of subjects with different levels of insulin sensitivity and glucose tolerance. For appropriate analysis, two independent groups were formed based on significant age differences between lean, obese, and type-1 and type-2 diabetic subjects. Clinical and biological features of young type-1 diabetic patients and age-matched non-diabetic obese and lean subjects (group 1) are presented in Table 2Go, while those of older non-diabetic obese, type-2 diabetic, and lean subjects (group 2) are shown in Table 3Go. In both age-matched groups, adiponutrin mRNA expression was similar in lean subjects and obese patients (P = n.s., Fig. 2A and BGo), despite the expected decreased insulin sensitivity in obese subjects as evaluated by QUICKI (Tables 2Go and 3Go). This finding is in agreement with our previous data (12). We observed a twofold increase in adiponutrin gene expression in type-1 diabetic subjects when compared either with lean controls or obese subjects (P = 0.02, Fig. 2AGo). In contrast, adiponutrin gene expression was significantly reduced by 50% in the adipose tissue of type-2 diabetic subjects (Fig. 2BGo). In the group of older lean, obese, and type-2 diabetic subjects, we found a negative correlation between adiponutrin mRNA levels and fasting glycemia (r = –0.43, P = 0.03). Adjustment for age and sex using multivariate analysis showed similar findings.


Figure 2
View larger version (15K):
[in this window]
[in a new window]
  		Figure 2 Adiponutrin mRNA levels in s.c. adipose tissue of age-matched lean, obese and type-1 diabetic subjects (A) and type-2 diabetic subjects (B). Adiponutrin mRNA levels (µg adiponutrin mRNA/µg HPRT mRNA) were quantified by real time RT-PCR in total preparations from lean, obese and type-1 diabetic subjects. (A) *P = 0.007 when comparing levels of adiponutrin gene expression between type-1 diabetic patients and lean subjects and P = 0.004 after comparison with obese subjects (Sum rank test). The comparison of Adiponutrin mRNA levels between lean and obese showed no difference. (B) *P = 0.03 when comparing levels of adiponutrin gene expression between type-2 diabetics and lean subjects and P = 0.01 after comparison with obese subjects despite a similar body mass index (BMI) (Sum rank test).

 
Adiponutrin gene expression in type-2 diabetics during an hyperinsulinemic clamp study

We evaluated whether the adiponutrin gene expression remained regulated by insulin in the adipose tissue of four type-2 diabetic men (age, 59 ± 3 years; body mass index, 29.9 ± 2.6 kg/m; QUICKI, 0.304 + 0.01; Glucose infusion 3.5 ± 2.3 mg glucose/kg per minute; duration of diabetes = 7 ± 1 years, HbAlc = 10.9% ± 0.3). Despite the decreased expression of adiponutrin found in type-2 diabetic patients, adiponutrin gene expression was enhanced 2.5-fold after the EGHI clamp (Fig. 3Go). Although this increase was less than that found in younger lean subjects, the induction in adiponutrin gene expression was significant (mean fold increase, 2.5 ± 0.5, compared with individual basal values, P = 0.04) (Fig. 1Go).


Figure 3
View larger version (13K):
[in this window]
[in a new window]
  		Figure 3 Adiponutrin gene expression in s.c. adipose tissue of type-2 diabetic patients before and after an acute euglycemic hyperinsulinemic clamp. Adiponutrin mRNA levels (µg adiponutrin mRNA/µg HPRT mRNA) were quantified by real time RT-PCR in total preparations from type-2 diabetic subjects before or after the 3 h-hyperinsulinemic clamp. *P = 0.04.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
References
 
The present investigation of different pathophysiological situations suggests a combined role of insulin and glucose in regulating the adiponutrin gene expression in human adipose tissue. Insulin markedly stimulated adiponutrin gene expression and further enhanced the moderate induction by glucose. Chronic hyperglycemia in type-1 diabetics was associated with an increased adiponutrin gene expression, whereas its expression was diminished in the type-2 diabetic state, and not in obesity. Insulin infusion was nevertheless able to stimulate adiponutrin gene expression in diabetic subjects but with less efficiency than in healthy ones.

In a previous investigation, we suggested a potential role for the adiponutrin protein to control energy balance in adipocytes in response to substrate availability. We showed that adiponutrin gene expression positively correlated with the level of insulin sensitivity and negatively with fasting glucose both in obese and non-obese subjects (12). The three clamp conditions performed here allowed some clarifications of the respective in vivo effects of insulin and glucose on adiponutrin gene expression. The apparent predominant role of insulin in inducing adiponutrin gene expression in human adipose tissue is in close agreement with the two recent papers showing that (i) in isolated human adipocytes, glucose induction of adiponutrin expression requires insulin and (ii) in mice with insulin or insulin receptor deficiency, lack of insulin stimulation on adipose tissue resulted in impaired adiponutrin expression (9, 21). Interestingly, the levels of insulin reached in our clamp study remained in the range of peak values that would be expected after a large meal and thus could be physiologically relevant (22). In vitro experiments in murine 3T3-L1 adipocytes showed that adiponutrin gene expression depended more on glucose than on insulin (3). The moderate glucose induction could be related to a potential effect of sandostatin, which was used to suppress endogenous insulin secretion during the HGEI and HGHI clamp studies. Furthermore, subjects from these two clamp studies also presented higher fasting insulinemia than in subjects from EGHI clamp, which could possibly modulate glucose induced adiponutrin response. Nevertheless, besides species differences regarding the predominant effector, both in vivo and in vitro studies suggest that glucose and insulin are important regulators of adiponutrin gene expression in adipocytes. The effect of these effectors on adiponutrin protein expression could not be explored in our study because of the amount of tissues.

Our study also suggests a relationship between the degree of insulin-sensitivity and the modulation of adiponutrin gene expression. A high induction in adiponutrin gene expression was observed in adipose tissue of young type-1 diabetic patients with marked hyperglycemia, but expected unaltered insulin-signaling pathway. Conversely, in type-2 diabetic patients, the deterioration of insulin sensitivity could account for the impaired adiponutrin gene expression in s.c. adipose tissue. Whether genetic variations of adiponutrin also contribute to its gene modulation in diabetics as described in obese subjects is yet to be investigated (21). This could be an attractive hypothesis regarding contribution of an impaired adiponutrin production in insulin resistance process. Clamp studies provide tracks for the role of several adipose tissue-produced proteins in this context. Clearly, the biological function of adiponutrin is an important issue that remains to be elucidated. A number of studies already evoke that adiponutrin does not exhibit lipase activity (7–9). Although these findings will need further studies, our results and those of others argue that adiponutrin may favor the anabolic pathway.

Insulin is the principal regulatory hormone involved in the tight regulation of fuel metabolism. A major action of insulin is the regulation of anabolic responses in fat cells, as it stimulates glucose and FFA uptake, inhibits lipolysis, and stimulates de novo fatty acid synthesis, through the activation of the insulin-signaling pathway. In clamp studies, mRNA contents of key protein contributors of the insulin action, such as p85{alpha} regulatory subunit of phosphatidylinositol 3-kinase (p85{alpha} PI3-kinase), hexokinase II, the glucose-transporter GLUT4, and the transcription factor sterol regulatory element binding protein-1c (SREBP-1c) also increased after an insulin infusion in adipose tissue of healthy subjects (23). The effect of insulin on these genes has provided arguments for the involvement of the PI3-kinase pathway as a mediator of insulin action together with evidences obtained in cell culture experiments (24–26). Adiponutrin could belong to this class of genes acutely regulated by insulin infusion in human adipose tissue. In type-2 diabetic patients, the regulatory effect of insulin on p85{alpha} PI3Kinase, hexokinase II, GLUT4, and SREBP-1c is altered in the adipose tissue (23) in agreement with an altered PI3-kinase signaling pathway (27–29). GLUT4 and SREBP-1c are also significantly decreased in the adipose tissue of obese non-diabetic subjects (23). Adiponutrin showed a different pattern with a reduction of its basal expression in the adipose tissue of type-2 diabetic patients, but not in obese subjects, and an induction upon insulin infusion in type-2 diabetic patients. These data also suggest that adiponutrin gene dysregulation may be associated with impaired insulin sensitivity and also a defective glucose tolerance in adipose tissue as observed in type-2 diabetics, but not in obese patients.

The specific molecular mechanisms regulating the adiponutrin gene expression in human adipose tissue are unknown. Tracks might be provided by future studies of transcription factors targeted by insulin. Indeed, the adiponutrin gene exhibits features of lipogenic genes (3), being mainly regulated by the SREBP-1c factor in adipose tissue (30–32). The new transcription factor, carbohydrate responsive element binding protein (ChREBP) has been suggested to mediate glucose action in liver. In adipose tissue, its expression is subjected to combined regulation by glucose and insulin (33, 34). Noteworthy computer analysis has provided evidence for the presence of sterol response element and carbohydrate response element consensus sites in the mouse adiponutrin promoter (unpublished observation), suggesting that both SREBP-1c and ChREBP could transactivate the adiponutrin promoter. Some degree of regulation by peroxisome proliferator-activated receptor {gamma} has also been suggested since it was reported that adiponutrin gene expression is suppressed by troglitazone in 3T3-L1 adipocytes (35). Molecular studies are needed to identify the molecular mechanisms involved in the regulation at the level of gene and protein expression.

In conclusion, the adiponutrin gene is strongly and rapidly regulated by insulin and/or glucose in humans. Although the physiological role of this protein is not established, in vivo and in vitro results suggest that adiponutrin may participate more likely in the anabolic pathway in adipose tissue. Further investigations are needed to clarify the function of this new protein in the modulation of whole body glucose homeostasis.


   Acknowledgements
 
We thank Drs Anne-Francoise Burnol and Danièle Lacasa for critical reading of the manuscript, Emmanuelle Loizon and Christine Rouault for technical help in the RT-qPCR assay of adiponutrin mRNA and Isabelle Vignault for the technical help in clamp studies. Marthe Moldes was granted by the Association pour la Recherche contre le cancer (ARC). The AFERO-ROCHE association provided fundings of UMR 7079. R Rabasa-Lhoret holds a scholarship from Fonds de Recherche en Santé du Québec (FRSQ) and M Faraj holds a postdoctoral fellowship from the Canadian Institute for Health Research (CIHR). This study was supported in part by CIHR (R Rabasa-Lhoret, pilot project grant # 119352), ADQ (R Rabasa-Lhoret, Quebec diabetes association start-up fund 2003–2004), ALFEDIAM-ROCHE (H Vidal) and a research grant from the Programme National de Recherche en Nutrition Humaine (H Vidal, K Clément).


   References
Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 

    1. Trayhurn P & Wood IS. Adipokines: inflammation and the pleiotropic role of white adipose tissue. British Journal of Nutrition 2004 92 347–355.[CrossRef][ISI][Medline]

    2. Clement K, Viguerie N, Poitou C, Carette C, Pelloux V, Curat CA, Sicard A, Rome S, Benis A, Zucker JD, Vidal H, Laville M, Barsh GS, Basdevant A, Stich V, Cancello R & Langin D. Weight loss regulates inflammation-related genes in white adipose tissue of obese subjects. FASEB Journal 2004 18 1657–1669.[Abstract/Free Full Text]

    3. Baulande S, Lasnier F, Lucas M & Pairault J. Adiponutrin, a transmembrane protein corresponding to a novel dietary- and obesity-linked mRNA specifically expressed in the adipose lineage. Journal of Biological Chemistry 2001 276 33336–33344.[Abstract/Free Full Text]

    4. Jenkins CM, Mancuso DJ, Yan W, Sims HF, Gibson B & Gross RW. Identification, cloning, expression, and purification of three novel human calcium-independent phospholipase A2 family members possessing triacylglycerol lipase and acylglycerol transacylase activities. Journal of Biological Chemistry 2004 279 48968–48975.[Abstract/Free Full Text]

    5. Villena JA, Roy S, Sarkadi-Nagy E, Kim KH & Sul HS. Desnutrin, an adipocyte gene encoding a novel patatin domain-containing protein, is induced by fasting and glucocorticoids: ectopic expression of desnutrin increases triglyceride hydrolysis. Journal of Biological Chemistry 2004 279 47066–47075.[Abstract/Free Full Text]

    6. Zimmermann R, Strauss JG, Haemmerle G, Schoiswohl G, Birner-Gruenberger R, Riederer M, Lass A, Neuberger G, Eisenhaber F, Hermetter A & Zechner R. Fat mobilization in adipose tissue is promoted by adipose triglyceride lipase. Science 2004 306 1383–1386.[Abstract/Free Full Text]

    7. Lake AC, Sun Y, Li JL, Kim JE, Johnson JW, Li D, Revett T, Shih HH, Liu W, Paulsen JE & Gimeno RE. Expression, regulation, and triglyceride hydrolase activity of adiponutrin family members. Journal of Lipid Research 2005 46 2477–2487.[Abstract/Free Full Text]

    8. Zechner R, Strauss JG, Haemmerle G, Lass A & Zimmermann R. Lipolysis: pathway under construction. Current Opinion in Lipidology 2005 16 333–340.[ISI][Medline]

    9. Kershaw EE, Hamm JK, Verhagen LA, Peroni O, Katic M & Flier JS. Adipose triglyceride lipase: function, regulation by insulin, and comparison with adiponutrin. Diabetes 2006 55 148–157.[Abstract/Free Full Text]

    10. Polson DA & Thompson MP. Adiponutrin mRNA expression in white adipose tissue is rapidly induced by meal-feeding a high-sucrose diet. Biochemical and Biophysical Research Communications 2003 301 261–266.[CrossRef][ISI][Medline]

    11. Polson DA & Thompson MP. Macronutrient composition of the diet differentially affects leptin and adiponutrin mRNA expression in response to meal feeding. Journal of Nutritional Biochemistry 2004 15 242–246.

    12. Liu YM, Moldes M, Bastard JP, Bruckert E, Viguerie N, Hainque B, Basdevant A, Langin D, Pairault J & Clement K. Adiponutrin: a new gene regulated by energy balance in human adipose tissue. Journal of Clinical Endocrinology and Metabolism 2004 89 2684–2689.[Abstract/Free Full Text]

    13. Laville M, Auboeuf D, Khalfallah Y, Vega N, Riou JP & Vidal H. Acute regulation by insulin of phosphatidylinositol-3-kinase, Rad, Glut 4, and lipoprotein lipase mRNA levels in human muscle. Journal of Clinical Investigation 1996 98 43–49.[ISI][Medline]

    14. DeFronzo RA, Tobin JD & Andres R. Glucose clamp technique: a method for quantifying insulin secretion and resistance. American Journal of Physiology 1979 237 E214–E223.

    15. Meneilly GS, Ryan EA, Radziuk J, Lau DC, Yale JF, Morais J, Chiasson JL, Rabasa-Lhoret R, Maheux P, Tessier D, Wolever T, Josse RG & Elahi D. Effect of acarbose on insulin sensitivity in elderly patients with diabetes. Diabetes Care 2000 23 1162–1167.[Abstract/Free Full Text]

    16. Giugliano D, Marfella R, Verrazzo G, Acampora R, Coppola L, Cozzolino D & D’Onofrio F. The vascular effects of L-Arginine in humans. The role of endogenous insulin. Journal of Clinical Investigation 1997 99 433–438.[ISI][Medline]

    17. Rome S, Meugnier E & Vidal H. The ubiquitin-proteasome pathway is a new partner for the control of insulin signaling. Current Opinion in Clinical Nutrition and Metabolic Care 2004 7 249–254.[CrossRef][ISI][Medline]

    18. Chen H, Sullivan G & Quon MJ. Assessing the predictive accuracy of QUICKI as a surrogate index for insulin sensitivity using a calibration model. Diabetes 2005 54 1914–1925.[Abstract/Free Full Text]

    19. Katz A, Nambi SS, Mather K, Baron AD, Follmann DA, Sullivan G & Quon MJ. Quantitative insulin sensitivity check index: a simple, accurate method for assessing insulin sensitivity in humans. Journal of Clinical Endocrinology and Metabolism 2000 85 2402–2410.[Abstract/Free Full Text]

    20. Rabasa-Lhoret R, Bastard JP, Jan V, Ducluzeau PH, Andreelli F, Guebre F, Bruzeau J, Louche-Pellissier C, MaItrepierre C, Peyrat J, Chagne J, Vidal H & Laville M. Modified quantitative insulin sensitivity check index is better correlated to hyperinsulinemic glucose clamp than other fasting-based index of insulin sensitivity in different insulin-resistant states. Journal of Clinical Endocrinology and Metabolism 2003 88 4917–4923.[Abstract/Free Full Text]

    21. Johansson LE, Hoffstedt J, Prikh H, Carlsson E, Wabitsch M, Bondeson AG, Hedenbro J, Tronqvist H, Groop L & Ridderstrale M. Variation in the adiponutrin gene influences its expression and associates with obesity. Diabetes 2006 55 826–833.[Abstract/Free Full Text]

    22. Lafrance L, Rabasa-Lhoret R, Poisson D, Ducros F & Chiasson JL. Effects of different glycaemic index foods and dietary fibre intake on glycaemic control in type 1 diabetic patients on intensive insulin therapy. Diabetic Medicine 1998 15 972–978.

    23. Ducluzeau PH, Perretti N, Laville M, Andreelli F, Vega N, Riou JP & Vidal H. Regulation by insulin of gene expression in human skeletal muscle and adipose tissue. Evidence for specific defects in type 2 diabetes. Diabetes 2001 50 1134–1142.[Abstract/Free Full Text]

    24. Azzout-Marniche D, Becard D, Guichard C, Foretz M, Ferre P & Foufelle F. Insulin effects on sterol regulatory-element-binding protein-1c (SREBP-1c) transcriptional activity in rat hepatocytes. Biochemical Journal 2000 2 389–393.

    25. Osawa H, Sutherland C, Robey RB, Printz RL & Granner DK. Analysis of the signaling pathway involved in the regulation of hexokinase II gene transcription by insulin. Journal of Biological Chemistry 1996 271 16690–16694.[Abstract/Free Full Text]

    26. Roques M & Vidal H. A phosphatidylinositol 3-Kinase/p70 ribosomal S6 protein kinase pathway is required for the regulation by insulin of the p85alpha regulatory subunit of phosphatidyl-inositol 3-kinase gene expression in human muscle cells. Journal of Biological Chemistry 1999 274 34005–34010.[Abstract/Free Full Text]

    27. Carvalho E, Eliasson B, Wesslau C & Smith U. Impaired phosphorylation and insulin-stimulated translocation to the plasma membrane of protein kinase B/Akt in adipocytes from type II diabetic subjects. Diabetologia 2000 43 1107–1115.[CrossRef][ISI][Medline]

    28. Carvalho E, Jansson PA, Axelsen M, Eriksson JW, Huang X, Groop L, Rondinone C, Sjostrom L & Smith U. Low cellular IRS 1 gene and protein expression predict insulin resistance and NIDDM. FASEB Journal 1999 13 2173–2178.[Abstract/Free Full Text]

    29. Smith U. Impaired (‘diabetic’) insulin signaling and action occur in fat cells long before glucose intolerance–is insulin resistance initiated in the adipose tissue? International Journal of Obesity and Related Metabolic Disorders 2002 26 897–904.

    30. Tontonoz P, Kim JB, Graves RA & Spiegelman BM. ADD1: a novel helix-loop-helix transcription factor associated with adipocyte determination and differentiation. Molecular and Cellular Biology 1993 13 4753–4759.[Abstract/Free Full Text]

    31. Kim JB & Spiegelman BM. ADD1/SREBP1 promotes adipocyte differentiation and gene expression linked to fatty acid metabolism. Genes and Development 1996 10 1096–1107.[Abstract/Free Full Text]

    32. Flier JS & Hollenberg AN. ADD-1 provides major new insight into the mechanism of insulin action. PNAS 1999 96 14191–14192.[Free Full Text]

    33. He Z, Jiang T, Wang Z, Levi M & Li J. Modulation of carbohydrate response element-binding protein gene expression in 3T3-L1 adipocytes and rat adipose tissue. American Journal of Physiology. Endocrinology and Metabolism 2004 287 E424–E430.[Abstract/Free Full Text]

    34. Uyeda K, Yamashita H & Kawaguchi T. Carbohydrate responsive element-binding protein (ChREBP): a key regulator of glucose metabolism and fat storage. Biochemical Pharmacology 2002 63 2075–2080.[CrossRef][ISI][Medline]

    35. Polson D & Thompson M. Adiponutrin gene expression in 3T3-L1 adipocytes is downregulated by troglitazone. Hormone and Metabolic Research 2003 35 508–510.[CrossRef][ISI][Medline]

Received 30 March 2006
Accepted 12 June 2006




This article has been cited by other articles:


Home page
 Eur J EndocrinolHome page
L. E Johansson, U. Lindblad, C. A Larsson, L. Rastam, and M. Ridderstrale
Polymorphisms in the adiponutrin gene are associated with increased insulin secretion and obesity
Eur. J. Endocrinol., November 1, 2008; 159(5): 577 - 583.
[Abstract] [Full Text] [PDF]

Home page
 J EndocrinolHome page
M. Faraj, G. Beauregard, E. Loizon, M. Moldes, K. Clement, Y. Tahiri, K. Cianflone, H. Vidal, and R. Rabasa-Lhoret
Insulin regulation of gene expression and concentrations of white adipose tissue-derived proteins in vivo in healthy men: relation to adiponutrin.
J. Endocrinol., November 1, 2006; 191(2): 427 - 435.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (1)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Moldes, M.
Right arrow Articles by Clément, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Moldes, M.
Right arrow Articles by Clément, K.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS