Anti diabetic effect of CL 316,243 (a β3-adrenergic agonist) by down regulation of tumour necrosis factor (TNF-α) expression.

OBJECTIVE: Obesity is a risk factor for the development of insulin resistance and is one of the most important contributors to the pathogenesis of type 2 diabetes, which acts mainly through the secretion of adipokines such as TNF-α that may influence insulin sensitivity. TNF-α affects many aspects of adipocyte function, such as adipocyte development and lipid metabolism. MATERIAL AND METHODS: We demonstrated that there is a correlation between the expressions of TNF-α in retroperitoneal WAT and insulin-resistance in 8 genetically obese fa/fa rats. Treatment of animals with CL 316,243, a β3-adrenergic agonist, showed an improvement of insulin-resistance that was linked with the suppression of TNF-α mRNA expression in WAT. RESULTS: These results confirm the association between TNF-α expression and the insulin-resistant condition in rats. Our finding indicates that the hyperglycaemia and hyperinsulinemia induced by insulin-resistance correlated positively with the expression of TNF-α mRNA in an abdominal WAT depot. CONCLUSION: We conclude that CL 316,243 possesses both anti-diabetic effects and anti-obesity effects in rodents

Serum glucose concentration.

<p>CL-<i>fa/fa vs</i> S-<i>fa/fa</i> after 4 weeks of treatment, <i>P<0.001</i>, and <i>vs fa/fa</i> week 0, <i>P<0.05</i>. CL-lean <i>vs</i> lean at week 0 and S-lean after 4 weeks of treatment, is not significant. Glucose is higher in <i>fa/fa</i> than lean at week 0, <i>P<0.05</i>, and in S-<i>fa/fa</i> than in S-lean after 4 weeks of treatment, <i>P<0.001</i>. There is no significant difference between CL-<i>fa/fa</i> and CL-lean after 4 weeks of treatment.</p

Effect of CL 316,243 on serum FAs concentration.

<p>*<i>P<0.05</i>, compares the significant differences between the two groups of lean and <i>fa/fa</i> rats.</p

Serum insulin concentration.

<p>CL-<i>fa/fa vs</i> S-<i>fa/fa</i> after 4 weeks of treatment, <i>P<0.001</i>. CL-lean <i>vs</i> S-lean after 4 weeks of treatment, <i>P<0.001</i>. Serum insulin level is higher in <i>fa/fa</i> rats than in lean rats at week 0 and in S-<i>fa/fa</i>, <i>P<0.001</i>. Serum insulin level decreased significantly in CL-lean as compared with S-lean, <i>P<0.001</i>. There is no significant difference between CL-<i>fa/fa</i> CL-lean rats after 4 weeks treatment.</p

Densitometry of the TNF-α mRNA bands as compared to 18S bands in the same lane.

<p>All values are means± SEM. There are significant differences as follow: CL-<i>fa/fa vs</i> S-<i>fa/fa</i>, <i>P<0.001</i>. CL-<i>fa/fa vs</i> S-lean, <i>P<0.05</i>. CL-lean <i>vs</i> S-lean and lean week 0, is not significant. There is nosignificant difference between CL-<i>fa/fa</i> and CL-lean rats at 4 weeks after treatment.</p

Northern blot analysis of TNF-α mRNA expression in the RWAT of lean and <i>fa/fa</i> rats.

<p>Northern hybridization of TNF-α mRNA and 18S ribosomal RNA (as control) was performed using the standard protocol. Briefly, total RNA from retroperitoneal WAT was extracted by Chomczynski method (Chomczynski 1993). Total RNA (∼20 µg) was denatured and separated on formaldehyde gel. Lane 1, L0, lean-pretreatment at week 0; lanes 2 and 3, S-lean; lanes 4 and 5, CL-lean; lane 6, F0, <i>fa/fa</i>-pretreatment at week 0; lanes 7 and 8, S-<i>fa/fa</i> and lanes 9 and 10, CL-<i>fa/fa</i> rats.</p

Body weight of both Lean and <i>fa/fa</i> rats.

<p>Body weight was measured at week 0 and after 4 weeks treatment with either saline (S) or CL316,243 (CL). <b>*S</b>ignificant effect of CL compared with pretreated state at week 0.</p