Molecular cloning, tissue expression pattern, and copy number variation of porcine SCUBE3.

The signal peptide CUB EGF-like domain-containing protein 3 (SCUBE3) gene is a member of SCUBE gene family and plays important roles in bone cell biology and the determination of limb bone length. In this study, the full-length transcript of porcine SCUBE3 was cloned using reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends. The full-length sequence of porcine SCUBE3 cDNA was 4131 base pairs and included 21 exons. The SCUBE3 gene contained a 2895-base pair open reading frame that encoded a peptide of 965 amino acids. Comparison of the deduced amino acid sequences of porcine SCUBE3 with those of human, mouse, zebrafish, and rat showed 96, 95, 73, and 95% identities, respectively. Porcine SCUBE3 mRNA expression levels were highest in the backfat, bone marrow, and cartilage tissues. Copy number variation was detected in porcine SCUBE3 and validated by real-time quantitative polymerase chain reaction. Different copy number variations were present in randomly selected individuals and may, therefore, be a good marker for identifying phenotypic traits. Our findings provide a basis for further investigation of the functions and regulatory mechanisms of SCUBE3 in pigs.

Regulation of glucose-dependent insulinotropic polypeptide release by protein in the rat.

Glucose-dependent insulinotropic polypeptide (GIP) release has been demonstrated predominantly after ingestion of carbohydrate and fat. These studies were conducted to determine the effects of protein on GIP expression in the rat. Whereas no significant changes in duodenal mucosal GIP mRNA levels were detected in response to peptone, the duodenal GIP concentration increased from 8.4+/-1.5 to 19.8+/-3.2 ng GIP/mg protein at 120 min (P<0.01). Plasma GIP levels also increased from 95+/-5.2 pg/ml to a peak of 289+/-56.1 pg/ml at 120 min (P<0.01). To determine whether the effects of protein on GIP were due to stimulation of acid secretion, rats were pretreated with 10 mg/kg omeprazole, after which mucosal and plasma GIP concentrations were partially attenuated. To further examine the effects of luminal acid, rats were administered intraduodenal 0.1 M HCl for 120 min, which significantly enhanced GIP expression. These studies indicate that nutrient protein provides a potent stimulus for GIP expression in the rat, an effect that occurs at the posttranslational level and may be mediated in part through the acid-stimulatory properties of protein. The effects of acid on GIP are consistent with a role for GIP as an enterogastrone in the rat.