Adiponectin : muscular regulation during stress and pathophysiological implications
(2006)
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- Authors
- Supervisors
- Brichard, Sonia M.
- Abstract
- Adiponectin is a hormone secreted exclusively by adipocytes under normal conditions. It exhibits insulin-sensitizing, fat-burning and anti-inflammatory properties as well as a modulatory effect on oxidative stress thereby thwarting several disorders belonging to the metabolic syndrome. Due to these potential beneficial effects of adiponectin, the regulation of its gene has been extensively investigated in the adipocyte. However, emerging studies are questioning the specificity of adiponectin expression in adipocytes and point out its presence in non-adipose tissues. We examined whether adiponectin could be induced in skeletal muscle in response to an inflammatory stress or in response to metabolic and/or oxidative aggression. Our data provide evidence that adiponectin is upregulated in vivo and in vitro in human and rodent myotubes in response to inflammatory stimuli evoked by LPS injection or a cytokine mix. The underlying mechanism seems to involve a NO-dependent pathway. To study a metabolic stress, we used leptin-deficient ob/ob mice as a model of obesity and type 2 diabetes. Adiponectin was paradoxically upregulated in the skeletal muscle of these mice. This induction may result from lipotoxicity and related oxidative stress. Adiponectin regulation in muscle appears to be fully distinct from that described in adipose tissue, introducing the concept of tissue-specific regulation. The physiological relevance of the upregulation of muscle adiponectin in response to diabetes or inflammatory injury is still under investigation. However, we hypothesize that it could be viewed as a local protective mechanism to counteract deleterious inflammatory reactions, oxidative damage, ectopic lipid storage and insulin resistance due to the anti-oxidant, anti-inflammatory, anti-diabetic and anti-obesity properties of adiponectin via an autocrine or paracrine way. Recently, skeletal muscle has been recognized as a secretory organ able to secrete factors acting on itself or other tissues. In the light of our results, adiponectin might be viewed not only as an adipokine, but also as one of the newly discovered myokines . Skeletal muscle turns out to modulate adipose tissue development and metabolism. Thus, a reciprocal regulation may exist between muscle and fat, and may participate, in particular, in the control of body weight, by regulating the normal balanced deposition of fat and protein in adipose and skeletal muscle tissue, respectively. In conclusion, the comprehensive understanding of the association between obesity, insulin resistance and other components of the metabolic syndrome has not yet been fully elucidated. However, studying the role of adipokines and myokines provides insights into these inter-relationships. Adiponectin with its numerous beneficial properties for health, plays a central and unique role in this context. It certainly warrants further investigation but is already increasingly proposed as a biomarker of obesity-related diseases and for potential clinical therapy against the metabolic syndrome.
- Affiliations
Citations
Delaigle, A. (2006). Adiponectin : muscular regulation during stress and pathophysiological implications. https://hdl.handle.net/2078.5/112182