Effects of Rat C-peptide-II on Lipolysis and Glucose Consumption in Cultured Rat Adipose Tissue

Existing data show that C-peptide (CP) prevents or ameliorates diabetes-related complications mainly by improving microcirculation and perhaps metabolism. Although effects of CP on muscle glucose consumption are relatively well studied, its effects on adipose tissue, a key organ involved in metabolism, are not well known. Therefore, the aim of this study was to examine the effects of CP on basal and stimulated lipolysis and glucose consumption in rat retroperitoneal (RP) adipose tissue, using an ex-vivo organ culture setting. The RP adipose tissue was excised from adult male rats, minced and subjected to ex-vivo culture for 24h. The tissue fragments were then weighted and distributed into a 24-well culture plate. The wells were left untreated (basal) or treated with insulin or isoproternol (ISO, stimulated) and incubated in the absence or presence of CP, insulin or a combination of the both peptides. Levels of lipolysis and tissue glucose consumption were determined by glycerol and glucose concentrations measurement in the infranatant conditioned media collected from each well. The CP, like insulin, induced an insignificant reduction in basal lipolysis. While insulin significantly reduced the ISO-stimulated lipolysis, CP was ineffective. Tissue glucose consumption was significantly stimulated by insulin, but was not affected by CP. However, in the presence of CP, inhibitory effect on ISO-stimulated lipolysis and stimulatory effect on glucose consumption of insulin were significantly diminished. Our data suggest that CP may conditionally modulate certain metabolic actions of insulin in RP adipose tissue. These modulations may contribute to fine-tuning of body metabolism under physiologic or pathologic conditions.