A polymerase chain reaction-based method for isolating clones from a complimentary DNA library in sheep.

The sheep (Ovis aries) is favored by many musculoskeletal tissue engineering groups as a large animal model because of its docile temperament and ease of husbandry. The size and weight of sheep are comparable to humans, which allows for the use of implants and fixation devices used in human clinical practice. The construction of a complimentary DNA (cDNA) library can capture the expression of genes in both a tissue- and time-specific manner. cDNA libraries have been a consistent source of gene discovery ever since the technology became commonplace more than three decades ago. Here, we describe the construction of a cDNA library using cells derived from sheep bones based on the pBluescript cDNA kit. Thirty clones were picked at random and sequenced. This led to the identification of a novel gene, C12orf29, which our initial experiments indicate is involved in skeletal biology. We also describe a polymerase chain reaction-based cDNA clone isolation method that allows the isolation of genes of interest from a cDNA library pool. The techniques outlined here can be applied in-house by smaller tissue engineering groups to generate tools for biomolecular research for large preclinical animal studies and highlights the power of standard cDNA library protocols to uncover novel genes.

The role of liver fructose-1,6-bisphosphatase in regulating appetite and adiposity.

Liver fructose-1,6-bisphosphatase (FBPase) is a regulatory enzyme in gluconeogenesis that is elevated by obesity and dietary fat intake. Whether FBPase functions only to regulate glucose or has other metabolic consequences is not clear; therefore, the aim of this study was to determine the importance of liver FBPase in body weight regulation. To this end we performed comprehensive physiologic and biochemical assessments of energy balance in liver-specific transgenic FBPase mice and negative control littermates of both sexes. In addition, hepatic branch vagotomies and pharmacologic inhibition studies were performed to confirm the role of FBPase. Compared with negative littermates, liver-specific FBPase transgenic mice had 50% less adiposity and ate 15% less food but did not have altered energy expenditure. The reduced food consumption was associated with increased circulating leptin and cholecystokinin, elevated fatty acid oxidation, and 3-ß-hydroxybutyrate ketone levels, and reduced appetite-stimulating neuropeptides, neuropeptide Y and Agouti-related peptide. Hepatic branch vagotomy and direct pharmacologic inhibition of FBPase in transgenic mice both returned food intake and body weight to the negative littermates. This is the first study to identify liver FBPase as a previously unknown regulator of appetite and adiposity and describes a novel process by which the liver participates in body weight regulation.

Adipose tissue from pregnant women with and without gestational diabetes mellitus: insulin-sensitive but resistant to hyperosomolarity.

OBJECTIVE: We sought to determine the contribution of adipose tissue to the insulin resistance of pregnancy. We also investigated whether hyperosmolar stress (induced by sorbitol) stimulates glucose uptake in human adipose tissue and, if so, whether this effect is altered in pregnancy and gestational diabetes mellitus. STUDY DESIGN: Subcutaneous and omental adipose tissue biopsy specimens were obtained at elective abdominal surgery or cesarean delivery from 16 normal glucose-tolerant pregnant women, 13 pregnant women with gestational diabetes mellitus, and 19 body mass index-matched nonpregnant control subjects. Basal, insulin (100 nmol/L)-, and sorbitol (250 mmol/L)-stimulated glucose uptake levels were measured. RESULTS: Basal and insulin-stimulated glucose uptake into adipose tissue was not impaired in pregnancy or gestational diabetes mellitus compared with control subjects. Hyperosmolarity stimulated glucose uptake in human adipose tissue from the subcutaneous, but not omental depot, and not in adipose tissue from pregnant subjects. CONCLUSION: There is no significant difference in insulin sensitivity in adipose tissue from pregnant or nonpregnant women; hyperosmolarity stimulates glucose uptake in subcutaneous adipose tissue from nonpregnant women, and adipose tissue from pregnant women is sorbitol resistant. These findings suggest the phosphotidylinositol 3-kinase-independent pathway may have pathophysiologic relevance to glucose uptake in human adipose tissue and may be impaired in pregnancy.

Fibroblast growth factor 1: a key regulator of human adipogenesis.

Obesity, with its related problems, is recognized as the fastest growing disease epidemic facing the world, yet we still have limited insight into the regulation of adipose tissue mass in humans. We have previously shown that adipose-derived microvascular endothelial cells (MVECs) secrete a factor(s) that increases proliferation of human preadipocytes. We now demonstrate that coculture of human preadipocytes with MVECs significantly increases preadipocyte differentiation, evidenced by dramatically increased triacylglycerol accumulation and glycerol-3-phosphate dehydrogenase activity compared with controls. Subsequent analysis identified fibroblast growth factor (FGF)-1 as an adipogenic factor produced by MVECs. Expression of FGF-1 was demonstrated in MVECs but not in preadipocytes, while preadipocytes were shown to express FGF receptors 1-4. The proliferative effect of MVECs on human preadipocytes was blocked using a neutralizing antibody specific for FGF-1. Pharmacological inhibition of FGF-1 signaling at multiple steps inhibits preadipocyte replication and differentiation, supporting the key adipogenic role of FGF-1. We also show that 3T3-L1 cells, a highly efficient murine model of adipogenesis, express FGF-1 and, unlike human preadipocytes, display no increased differentiation potential in response to exogenous FGF-1. Conversely, FGF-1-treated human preadipocytes proliferate rapidly and differentiate with high efficiency in a manner characteristic of 3T3-L1 cells. We therefore suggest that FGF-1 is a key human adipogenic factor, and these data expand our understanding of human fat tissue growth and have significant potential for development of novel therapeutic strategies in the prevention and management of human obesity.