Cell type-specific expression and coregulation of murine resistin and resistin-like molecule-α in adipose tissue

Adipocytes are the exclusive or predominant source of several secreted proteins that exert profound effects on systemic carbohydrate and lipid metabolism. Resistin, a 10-kDa adipose tissue specific secretory protein, has recently been implicated in exerting a negative effect on systemic insulin sensitivity. It is, however, not known how resistin mediates this insulin-desensitizing effect or what regulatory mechanisms control resistin expression. Resistin-like molecule-α (RELMα), a homolog of resistin originally identified by its upregulation in asthmatic lung, is another secreted protein expressed in adipose tissue. The regulation of RELMα in adipose tissue and its relationship to resistin expression has not been addressed so far. Here, we demonstrate that the expression of resistin and RELMα are similarly regulated in adipose tissue despite the fact that RELMα is exclusively expressed in the stromal vascular fraction of adipose tissue and not in adipocytes. Interestingly, this coregulation is limited to adipose tissue as the expression of RELMα in lung is independent of metabolic regulation. Additionally, we show that resistin and RELMα levels are not subject to regulation by proinflammatory stimuli. Finally, acute hyperglycemia leads to up-regulation of resistin and RELMα transcription in various adipose depots.