Resistin is an adipocyte-secreted
hormone proposed to link
obesity with
insulin resistance and diabetes, but no previous study has performed a joint quantitative evaluation of white adipose tissue (WAT)
resistin mRNA expression and serum levels in relation to insulinemia and glycemia in mice. We have thus comparatively assessed WAT
resistin mRNA expression and serum
resistin levels in lean C57BL/6J mice and various mouse models of
obesity, including diet-induced obese (DIO) C57BL/6J mice, high fat-fed
TNF-alpha-/- mice, and brown adipose tissue (BAT)-deficient
uncoupling protein-
diphtheria toxin A chain (UCP1-DTA) mice. We also studied whether treatment with the weight-reducing and
insulin-sensitizing compounds, MTII, an
alpha-melanocyte-stimulating hormone analog, or
CNTF(Ax15), a
ciliary neurotrophic factor analog, alters
resistin mRNA expression and/or circulating levels in lean and DIO C57BL/6J mice. We find that
resistin mRNA expression is similar in DIO and lean C57BL/6J mice, as well as in
TNF-alpha-/- and wild-type (WT) mice. Circulating
resistin levels, however, are higher in DIO C57BL/6J, high fat-fed
TNF-alpha-/-, and UCP1-DTA mice compared with lean controls. Moreover, although
resistin mRNA expression is upregulated by MTII treatment for 24 h and downregulated by
CNTF(Ax15) treatment for 3 or 7 days, circulating
resistin levels are not altered by MTII or
CNTF(Ax15) treatment. In addition, serum
resistin levels, but not
resistin mRNA expression levels, are correlated with
body weight, and neither
resistin mRNA expression nor serum
resistin levels are correlated with serum
insulin or
glucose levels. We conclude that transcriptional regulation of
resistin in WAT does not correlate with circulating
resistin levels and that circulating
resistin is unlikely to play a major endocrine role in
insulin resistance or glycemia in mice.