Endocrine Abstracts

Background: High levels of mannose-binding lectin (MBL), an activator of complement, have been associated with increased mortality and risk of albuminuria in patients with type 2 diabetes. It is not known if MBL is synthesized in human adipose tissue and the effects of weight loss and changes in insulin sensitivity on MBL levels have been poorly elucidated.

Methods: Of 36 nondiabetic obese subjects received a very low-calorie diet (VLCD) of 800 kcal/day for 8 weeks. Fasting blood samples were obtained at baseline and after 8 weeks of VLCD and concentrations of MBL, glucose, and insulin were measured. Insulin resistance was assessed using the HOMA-IR method. Furthermore, to investigate if MBL is synthesized in adipose tissue MBL real-time RT-PCR was performed on human adipose tissue compared to liver tissue.

Results: After 8 weeks the mean body weight was reduced by 13.5 kg (106.3±2.6 kg (Se) vs 92.8±2.4 kg, P<0.0001). Insulin resistance was reduced by 45.4±7.0%, P < 0.0001. Median MBL at baseline was 746 μg/l (Iqr 316-1190) vs 892 μg/l (IQR 336-1511) at 8 weeks, P=0.23. No correlations were found between weight loss and changes in MBL (r=−0.098, P=0.57) nor between changes in insulin resistance and MBL (r=−0.24, P=0.15). MBL real-time RT-PCR showed no expression of mRNA in adipose tissue but as expected good expression in liver tissue.

Conclusions: Serum MBL levels do not seem to be related to weight or insulin resistance, and the concentrations are not affected by weight loss and changes in insulin resistance. MBL is synthesized in human liver tissue, but not in human adipose tissue. Inter-individual differences in MBL depend primarily on MBL genotype, and may not be modifiable by lifestyle interventions.