Geneviève Beauregard

Claude Bernard University Lyon 1, Villeurbanne, Rhône-Alpes, France

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Publications (4)15.09 Total impact

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    ABSTRACT: AimBoth type 1 and 2 diabetes are associated with differential regulation of leptin, adiponectin and ASP. Our aim was to examine whether or not acute hyperinsulinaemia and/or hyperglycaemia per se have differential regulation of these hormones in healthy subjects.MethodsWe examined changes in leptin, adiponectin and ASP concentrations and subcutaneous white adipose tissue mRNA expression with 3-hour hyperinsulinaemic (HI, n = 10), hyperglycaemic (HG, n = 7) and hyperinsulinaemic-hyperglycaemic (HGHI, n = 8) clamps in healthy lean young men. As somatostatin was used for the HG and HGHI clamps, a control somatostatin clamp was carried out (n = 4). Changes in the expression of HKII and p85α Pi3K were examined as positive controls for the induction of gene expression by the insulin pathway.ResultsHI, HG and HGHI clamps increased expression of HKII and p85α Pi3K while somatostatin did not. The HI clamp decreased serum adiponectin (−15%, P < 0.001) and increased serum leptin (+11%, P = 0.031), while the HG clamp reduced serum leptin (−20%, P = 0.003). The HGHI clamp increased serum ASP (+21%, P = 0.047) and expression of C3 (+26%, P = 0.018) and leptin (+50%, P = 0.024). Interestingly, the control somatostatin clamp suppressed both serum leptin (−17%, P = 0.043) and adiponectin (−7%, P = 0.020).ConclusionHG and/or HI per se regulated the concentrations and expression of leptin, adiponectin and ASP in healthy lean young men, suggesting a contribution to dysregulation of these hormones in diabetes.RésuméObjectifLes concentrations plasmatiques de leptine, d’adiponectine et d’ASP sont fortement modifiées, à la fois dans le diabète de type 1 et le diabète de type 2. L’objectif de cette étude était de vérifier si l’hyperinsulinémie et/ou l’hyperglycémie aiguë pouvaient être des acteurs importants de la régulation de ces hormones chez l’homme.MéthodologieNous avons étudié les modifications des concentrations plasmatiques de leptine, d’adiponectine et d’ASP, ainsi que l’expression de leur ARNm dans le tissu adipeux sous-cutané abdominal, au cours de clamps hyperinsulinémiques (HI, n = 10), hyperglycémiques (HG, n = 7) et hyperinsulinémiques hyperglycémiques (HGHI, n = 8) d’une durée de trois heures. Afin de tenir compte de l’effet de la somatostatine utilisée pour les clamps HG et HGHI, un clamp témoin avec perfusion de somatostatine seule a été réalisé chez quatre sujets. Les clamps ont été réalisés chez des hommes jeunes et en bonne santé. Les variations de l’expression génique de l’hexokinase II (HKII) et de la sous-unité p85a de la Pi3kinase (p85a Pi3K) ont été utilisées comme témoins positifs de l’action de l’insuline dans le tissu adipeux.RésultatsLes clamps HI, HG et HGHI induisent tous l’expression de HKII et de p85a Pi3K. La concentration plasmatique de l’adiponectine diminue (−15 %, P < 0,001) et celle de leptine augmente (+11 %, P = 0,031) au cours du clamp HI. La concentration plasmatique de leptine diminue (−20 %, P = 0,003) aussi au cours du clamp HG. La combinaison HGHI entraîne, pour sa part, une augmentation de la concentration plasmatique d’ASP (+21 %, P = 0,047), ainsi que l’expression génique de son précurseur C3 (+26 %, P = 0,018) et de la leptine (+50 %, P = 0,024) dans le tissu adipeux. La perfusion de somatostatine seule (clamp témoin) entraîne une diminution des concentrations plasmatiques de leptine (−17 %, P = 0,043) et d’adiponectine (−7 %, P = 0,020).ConclusionCes résultats montrent que l’hyperglycémie ou l’hyperinsulinémie per se affectent les concentrations plasmatiques et l’expression génique de la leptine, de l’adiponectine et d’ASP chez l’homme sain. Elles pourraient donc être impliquées dans les modifications de la régulation de ces hormones au cours du diabète.
    Diabetes & Metabolism. 01/2008;
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    ABSTRACT: To define the effects of acute hyperglycemia per se (i.e., without the confounding effect of hyperinsulinemia) in human tissues in vivo, we performed global gene expression analysis using microarrays in vastus lateralis muscle and subcutaneous abdominal adipose tissue of seven healthy men during a hyperglycemic-euinsulinemic clamp with infusion of somatostatin to inhibit endogenous insulin release. We found that doubling fasting blood glucose values while maintaining plasma insulin in the fasting range modifies the expression of 316 genes in skeletal muscle and 336 genes in adipose tissue. More than 80% of them were downregulated during the clamp, indicating a drastic effect of acute high glucose, in the absence of insulin, on mRNA levels in human fat and muscle tissues. Almost all the biological pathways were affected, suggesting a generalized effect of hyperglycemia. The induction of genes from the metallothionein family, related to detoxification and free radical scavenging, indicated that hyperglycemia-induced oxidative stress could be involved in the observed modifications. Because the duration and the concentration of the experimental hyperglycemia were close to what is observed during a postprandial glucose excursion in diabetic patients, these data suggest that modifications of gene expression could be an additional effect of glucose toxicity in vivo.
    Diabetes 05/2007; 56(4):992-9. · 7.90 Impact Factor
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    ABSTRACT: Adiponutrin is a newly described white adipose tissue (WAT)-derived protein whose function and regulation remain widely unclear in humans though it is suggested to be related to insulin sensitivity. Recently, we found that adiponutrin expression is reduced in type 2 diabetic subjects in basal and insulin-stimulated states. To examine adiponutrin regulation by the insulin pathway in relation to other WAT-related proteins with well-known relation to insulin signaling and action, we examined in healthy young men (1) the association of adiponutrin with p85alpha PI3K and HKII, leptin, adiponectin, and acylation-stimulating protein (ASP) and (2) the regulation of adiponutrin and WAT-derived proteins by 3-h hyperinsulinemic euglycemic clamp (HIEG). At baseline (N = 20), adiponutrin expressions were positively correlated with those of p85alpha PI3K (R = 0.54, P = 0.017), HKII (R = 0.58, P = 0.010), and serum leptin (R = 0.51, P = 0.036), but not with any other parameter measured including insulin sensitivity. Hyperinsulinemia (N = 10, +2365% above baseline) significantly increased the expression of adiponutrin (+770%, P = 0.002), p85alpha PI3K (+150%, P = 0.033), HKII (+147%, P = 0.007), and serum leptin (+11%, P = 0.031), while it decreased serum adiponectin (-15%, P = 0.001). In the insulin-stimulated state, adiponutrin mRNA expression levels correlated with basal p85alpha PI3K (R = 0.76, P = 0.018) and HKII (R = 0.86, P = 0.003) expression levels, with percentage increase in insulin (R = 0.73, P = 0.040), and with insulin-stimulated state HKII (R = 0.82, P = 0.007), leptin (R = 0.84, P = 0.005), and adiponectin (R = 0.85, P = 0.004) mRNA levels. In healthy young men, adiponutrin expression is upregulated [corrected] by hyperinsulinemia and is related to basal and/or insulin-stimulated p85alpha PI3K, HKII, adiponectin, and leptin expression levels. We hypothesize that insulin-mediated regulation of adiponutrin expression is under the PI3K pathway. The relevance of the present findings to reduced adiponutrin expression in type 2 diabetes is discussed.
    Journal of Endocrinology 12/2006; 191(2):427-35. · 4.06 Impact Factor
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    ABSTRACT: 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. 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. 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). These results suggest a strong relationship between adiponutrin expression, insulin sensitivity, and glucose metabolism in human adipose tissue.
    European Journal of Endocrinology 10/2006; 155(3):461-8. · 3.14 Impact Factor