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Articles by A Vaag
Total Records ( 3 ) for A Vaag
  B Mortensen , P Poulsen , L Wegner , K. L Stender Petersen , R Ribel Madsen , M Friedrichsen , J. B Birk , A Vaag and J. F. P. Wojtaszewski
 

The protein complex AMP-activated protein kinase (AMPK) is believed to play an important role in the regulation of skeletal muscle glucose and lipid metabolism. Defects in the AMPK system might therefore be an important factor in the pathogenesis of type 2 diabetes. We aimed to identify genetic and environmental mechanisms involved in the regulation of AMPK expression and activity and to examine the association between AMPK protein levels and activity on the one hand, and glucose and fat metabolism on the other. We investigated skeletal muscle biopsies from 100 young and 82 older mono- and dizygotic nondiabetic twins excised during the basal and insulin-stimulated states of a physiological hyperinsulinemic-euglycemic clamp. AMPK1, -2, and -3 mRNA expression was investigated using real-time PCR, and Western blotting was employed to measure protein levels. Multiple regression analyses indicated that skeletal muscle AMPK mRNA and protein expression as well as activity were regulated by sex, age, obesity, and aerobic capacity. Comparison of intraclass correlations on AMPK measurements from mono- and dizygotic twins suggested that skeletal muscle AMPK expression was under minor genetic influence. AMPK3 protein expression and activity were negatively related to whole body glucose uptake through the nonoxidative metabolic pathway and positively related to phosphorylation of glycogen synthase. Our results suggest that skeletal muscle AMPK expression is under minor genetic control but regulated by age and sex and associated with obesity and aerobic capacity. Furthermore, our results indicate a role for 3-containing AMPK complexes in downregulation of insulin-stimulated nonoxidative glucose metabolism possibly through inhibition of glycogen synthase activity.

  J Naukkarinen , E Nilsson , H. A Koistinen , S Soderlund , V Lyssenko , A Vaag , P Poulsen , L Groop , M. R Taskinen and L. Peltonen
 

Background— The upstream transcription factor 1 (USF1) gene is associated with familial combined hyperlipidemia, the most common genetic dyslipidemia in humans, as well as with various dyslipidemic changes in numerous other studies. Typical of complex disease-associated genes, neither the explicit mutations have been described nor the functional consequences for risk allele carriers been reported at the cellular or tissue level.

Methods and Results— In this study, we aimed at describing the molecular mechanism through which the strongest associating intronic single-nucleotide polymorphism variant in USF1 is involved in the development of dyslipidemia. The effects of the risk variant on gene expression were studied in 2 relevant human tissues, fat and muscle. Global transcript profiles of 47 fat biopsies ascertained for carriership of the risk allele were tested for differential expression of known USF1 target genes as well as for broader effects on the transcript profile. Allelic imbalance of USF1 in fat was assessed using a quantitative sequencing approach. The possible allele-specific effect of insulin on the expression of USF1 was studied in 118 muscle biopsies before and after a euglycemic hyperinsulinemic clamp. The risk allele of single-nucleotide polymorphism rs2073658 seems to eradicate the inductive effect of insulin on the expression of USF1 in muscle and fat. The expression of numerous target genes is in turn perturbed in adipose tissue.

Conclusions— In risk allele carriers, a defective response of USF1 to insulin results in the suboptimal response of relevant target genes that contributes to the enhanced risk of developing dyslipidemia and coronary heart disease.

  T Sparso , A Bonnefond , E Andersson , N Bouatia Naji , J Holmkvist , L Wegner , N Grarup , A. P Gjesing , K Banasik , C Cavalcanti Proenca , M Marchand , M Vaxillaire , G Charpentier , M. R Jarvelin , J Tichet , B Balkau , M Marre , C Levy Marchal , K Faerch , K Borch Johnsen , T Jorgensen , S Madsbad , P Poulsen , A Vaag , C Dina , T Hansen , O Pedersen and P. Froguel
  OBJECTIVE

Genome-wide association studies have identified several variants within the MTNR1B locus that are associated with fasting plasma glucose (FPG) and type 2 diabetes. We refined the association signal by direct genotyping and examined for associations of the variant displaying the most independent effect on FPG with isolated impaired fasting glycemia (i-IFG), isolated impaired glucose tolerance (i-IGT), type 2 diabetes, and measures of insulin release and peripheral and hepatic insulin sensitivity.

RESEARCH DESIGN AND METHODS

We examined European-descent participants in the Inter99 study (n = 5,553), in a sample of young healthy Danes (n = 372), in Danish twins (n = 77 elderly and n = 97 young), in additional Danish type 2 diabetic patients (n = 1,626) and control subjects (n = 505), in the Data from the Epidemiological Study on the Insulin Resistance Syndrome (DESIR) study (n = 4,656), in the North Finland Birth Cohort 86 (n = 5,258), and in the Haguenau study (n = 1,461).

RESULTS

The MTNR1B intronic variant, rs10830963, carried most of the effect on FPG and showed the strongest association with FPG (combined P = 5.3 x 10–31) and type 2 diabetes. The rs10830963 G-allele increased the risk of i-IFG (odds ratio [OR] 1.64, P = 5.5 x 10–11) but not i-IGT. The G-allele was associated with a decreased insulin release after oral and intravenous glucose challenges (P < 0.01) but not after injection of tolbutamide. In elderly twins, the G-allele associated with hepatic insulin resistance (P = 0.017).

CONCLUSIONS

The G-allele of MTNR1B rs10830963 increases risk of type 2 diabetes through a state of i-IFG and not through i-IGT. The same allele associates with estimates of β-cell dysfunction and hepatic insulin resistance.

 
 
 
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