Ariane Boivin

Publications (2)5.72 Total impact

• Article: Androgens and body fat distribution.

  Karine Blouin, Ariane Boivin, André Tchernof
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  ABSTRACT: An important sex difference in body fat distribution is generally observed. Men are usually characterized by the android type of obesity, with accumulation of fat in the abdominal region, whereas women often display the gynoid type of obesity, with a greater proportion of their body fat in the gluteal-femoral region. Accordingly, the amount of fat located inside the abdominal cavity (intra-abdominal or visceral adipose tissue) is twice as high in men compared to women. This sex difference has been shown to explain a major portion of the differing metabolic profiles and cardiovascular disease risk in men and women. Association studies have shown that circulating androgens are negatively associated with intra-abdominal fat accumulation in men, which explains an important portion of the link between low androgens and features of the metabolic syndrome. In women, the low circulating sex hormone-binding globulin (SHBG) levels found in abdominal obesity may indirectly indicate that elevated free androgens are related to increased visceral fat accumulation. However, data on non SHBG-bound and total androgens are not unanimous and difficult to interpret for total androgens. These studies focusing on plasma levels of sex hormones indirectly suggest that androgens may alter adipose tissue mass in a depot-specific manner. This could occur through site-specific modulation of preadipocyte proliferation and/or differentiation as well as lipid synthesis and/or lipolysis in mature adipocytes. Recent results on the effects of androgens in cultured adipocytes and adipose tissue have been inconsistent, but may indicate decreased adipogenesis and increased lipolysis upon androgen treatment. Finally, adipose tissue has been shown to express several steroidogenic and steroid-inactivating enzymes. Their mere presence in fat indirectly supports the notion of a highly complex enzymatic system modulating steroid action on a local basis. Recent data obtained in both men and women suggest that enzymes from the aldoketoreductase 1C family are very active and may be important modulators of androgen action in adipose tissue.
  The Journal of Steroid Biochemistry and Molecular Biology 03/2008; 108(3-5):272-80. · 3.05 Impact Factor
• Article: Regional differences in adipose tissue metabolism in obese men.

  Ariane Boivin, Gaétan Brochu, Simon Marceau, Picard Marceau, Frédéric-Simon Hould, André Tchernof
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  ABSTRACT: We examined omental and subcutaneous adipose tissue adipocyte size, and lipolysis and lipoprotein lipase (LPL) activity in a sample of 33 men aged 22.6 to 61.2 years and with a body mass index ranging from 24.6 to 79.1 kg/m2. We tested the hypothesis that lipolysis rates would be higher in the omental fat depot than in subcutaneous adipose tissue and that this difference would persist across the spectrum of abdominal adiposity values. Omental and subcutaneous adipose tissue samples were obtained during surgery. Adipocytes were isolated by collagenase digestion. Adipocyte size and LPL activity as well as basal, isoproterenol-, forskolin-, and dibutyryl cyclic adenosine monophosphate-stimulated lipolysis were measured. Although adipocytes from both fat compartments were larger in obese subjects, no difference was observed in the size of omental vs subcutaneous fat cells. Lipoprotein lipase activity, expressed as a function of cell number, was significantly higher in omental than in subcutaneous fat tissue (P<.005). Basal lipolysis and lipolytic responses to isoproterenol, forskolin, or dibutyryl cyclic adenosine monophosphate, expressed either as a function of cell number or as a fold response over basal levels, were not significantly different in omental vs subcutaneous fat cells. When stratifying the sample in tertiles of waist circumference, adipocyte diameter was similar in the omental and subcutaneous depots for all adiposity values. Omental adipocyte size reached a plateau in the 2 upper tertiles of waist circumference, that is, from a waist circumference of 125 cm and above. Lipoprotein lipase activity was significantly higher in omental cells in the middle tertile of waist circumference (P=.05), and no regional difference was noted in lipolysis values across waist circumference tertiles. In conclusion, in normal-weight to morbidly obese men, although adipocyte size and lipolysis tended to increase with higher waist circumference, no difference was observed between the omental and subcutaneous fat depot.
  Metabolism 05/2007; 56(4):533-40. · 2.66 Impact Factor