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Articles by O. D Carlson
Total Records ( 2 ) for O. D Carlson
  P Matt , F Schoenhoff , J Habashi , T Holm , C Van Erp , D Loch , O. D Carlson , B. F Griswold , Q Fu , J De Backer , B Loeys , D. L Huso , N. B McDonnell , J. E Van Eyk , H. C Dietz and the GenTAC Consortium
 

Background— Marfan syndrome (MFS) is caused by mutations in the fibrillin-1 gene and dysregulation of transforming growth factor-β (TGF-β). Recent evidence suggests that losartan, an angiotensin II type 1 blocker that blunts TGF-β activation, may be an effective treatment for MFS. We hypothesized that dysregulation of TGF-β might be mirrored in circulating TGF-β concentrations.

Methods and Results— Serum obtained from MFS mutant mice (Fbn1C1039G/+) treated with losartan was analyzed for circulating TGF-β1 concentrations and compared with those from placebo-treated and wild-type mice. Aortic root size was measured by echocardiography. Data were validated in patients with MFS and healthy individuals. In mice, circulating total TGF-β1 concentrations increased with age and were elevated in older untreated Fbn1C1039G/+ mice compared with wild-type mice (P=0.01; n=16; mean±SEM, 115±8 ng/mL versus n=17; mean±SEM, 92±4 ng/mL). Losartan-treated Fbn1C1039G/+ mice had lower total TGF-β1 concentrations compared with age-matched Fbn1C1039G/+ mice treated with placebo (P=0.01; n=18; 90±5 ng/mL), and circulating total TGF-β1 levels were indistinguishable from those of age-matched wild-type mice (P=0.8). Correlation was observed between circulating TGF-β1 levels and aortic root diameters in Fbn1C1039G/+ and wild-type mice (P=0.002). In humans, circulating total TGF-β1 concentrations were elevated in patients with MFS compared with control individuals (P<0.0001; n=53; 15±1.7 ng/mL versus n=74; 2.5±0.4 ng/mL). MFS patients treated with losartan (n=55) or β-blocker (n=80) showed significantly lower total TGF-β1 concentrations compared with untreated MFS patients (P≤0.05).

Conclusions— Circulating TGF-β1 concentrations are elevated in MFS and decrease after administration of losartan, β-blocker therapy, or both and therefore might serve as a prognostic and therapeutic marker in MFS.

  C. W Chia , O. D Carlson , W Kim , Y. K Shin , C. P Charles , H. S Kim , D. L Melvin and J. M. Egan
  OBJECTIVE

Glucose-dependent insulinotropic polypeptide (GIP), unlike glucagon-like peptide (GLP)-1, lacks glucose-lowering properties in patients with type 2 diabetes. We designed this study to elucidate the underlying pathophysiology.

RESEARCH DESIGN AND METHODS

Twenty-two insulin-naïve subjects with type 2 diabetes were given either synthetic human GIP (20 ng · kg–1 · min–1) or placebo (normal saline) over 180 min, starting with the first bite of a mixed meal (plus 1 g of acetaminophen) on two separate occasions. Frequent blood samples were obtained over 6 h to determine plasma GIP, GLP-1, glucose, insulin, glucagon, resistin, and acetaminophen levels.

RESULTS

Compared with placebo, GIP induced an early postprandial increase in insulin levels. Intriguingly, GIP also induced an early postprandial augmentation in glucagon, a significant elevation in late postprandial glucose, and a decrease in late postprandial GLP-1 levels. Resistin and acetaminophen levels were comparable in both interventions. By immunocytochemistry, GIP receptors were present on human and mouse -cells. In TC1 cell line, GIP induced an increase in intracellular cAMP and glucagon secretion.

CONCLUSIONS

GIP, given to achieve supraphysiological plasma levels, still had an early, short-lived insulinotropic effect in type 2 diabetes. However, with a concomitant increase in glucagon, the glucose-lowering effect was lost. GIP infusion further worsened hyperglycemia postprandially, most likely through its suppressive effect on GLP-1. These findings make it unlikely that GIP or GIP receptor agonists will be useful in treating the hyperglycemia of patients with type 2 diabetes.

 
 
 
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