The bone marrow stroma consists of a heterogeneous population of cells which participate in osteogenic, adipogenic, and hematopoietic events. The murine stromal cell line, BMS2, exhibits the adipocytic and osteoblastic phenotypes in vitro. BMS2 differentiation was examined in response to cytokines which share the gp130 signal transducing protein within their receptor complex. Four of the cytokines (interleukin 6, interleukin 11, leukemia inhibitory factor, and oncostatin M) inhibited hydrocortisone-induced adipocyte differentiation in a dose dependent manner based on lipid accumulation and lipoprotein lipase enzyme activity. Inhibition occurred only when the cytokines were present during the initial 24 h of the induction period; after 48 h their effects were diminished. Likewise, these cytokines increased alkaline phosphatase enzyme activity twofold in preadipocyte BMS2 cells. Both leukemia inhibitory factor and oncostatin M induced early active gene expression in resting preadipocyte BMS2 cells and decreased the steady state mRNA level of a unique osteoblastic gene marker, osteocalcin. A fifth cytokine whose receptor complex shares the gp130 protein, ciliary neurotrophic factor, did not significantly regulate stromal cell differentiation when added by itself. However, with the addition of a missing component of its receptor complex, ciliary neurotrophic factor receptor alpha protein, this cytokine also inhibited BMS2 adipogenesis. Together, these data indicate that the cytokines whose receptors share the gp130 protein can modulate stromal cell commitment to the adipocyte and osteoblast differentiation pathways.

The molecular mechanism involved in altered regulation of the rate-limiting enzyme in hepatic gluconeogenesis, phosphoenolpyruvate carboxykinase (PEPCK), during endotoxemia is not completely understood. We examined, therefore, the effect of a nonlethal dose of Escherichia coli endotoxin on PEPCK gene expression in fasted rats. 5 h after endotoxin treatment, the PEPCK transcription rate and the amount of mRNAPEI'K were significantly decreased at a time when the insulin/glucagon (I/ G) molar ratio and plasma corticosterone levels were significantly increased. Similar results were observed in a time course study, in which altered cAMP induction of PEPCK gene expression paralleled changes in the I/G molar ratio. In diabetic rats treated with endotoxin, PEPCK gene expression was decreased in the absence, however, of an increased I/G molar ratio. This finding indicates that other factors, such as inflammatory mediators or cytokines, alter PEPCK gene transcription during endotoxemia. IL-6, a putative mediator of endotoxin action in the liver, had no effect on PEPCK gene expression in fasted rats, but did decrease cAMP induction of PEPCK gene expression. These results indicate that, during endotoxemia, regulation of PEPCK gene expression is influenced by inflammatory mediators in addition to the classical endocrine hormones. IL-6, however, does not appear to be involved directly in the altered regulation ofthe PEPCK gene during endotoxemia. (J. Clin. Invest. 1991. 88:811-816.)

Background: It is critical that medical students develop self-directed, lifelong learning skills to navigate medical school successfully and to become competent healthcare professionals. Moreover, the Liaison Committee on Medical Education (LCME), the USA medical school accrediting body, requires activities designed to help students develop self-directed learning (SDL) skills in the preclinical years. Objective: We evaluated the feasibility and effectiveness of a self-directed learning activity in a 6-week first-year medical student course. Design: The course director assigned infectious disease case studies to teams of first-year medical students who individually assessed their knowledge gaps of the case, identified scholarly sources to fill their knowledge gaps, shared the information with their teammates, and reflected on their ability to guide their own learning. Students were asked to rate workload, team effort, acquisition of new clinical knowledge, and lifelong learning skills. Students were also asked to reflect on how this assignment affected their perception of their SDL skills. Descriptive statistics were used to analyze responses to the Likert scale questions. Thematic analysis was applied to the comments. Results: Survey response rate was 80% (131/163). Students strongly or moderately agreed that 1) they spent an appropriate amount of time on the project (94%), 2) the workload was evenly distributed among their teammates (95%), 3) their teammates made significant and timely contributions to the project (97%), 4) the project contributed to learning new clinical knowledge (92%), and 5) the project contributed to the acquisition of lifelong learning skills (85%). The analysis team identified four themes from student reflections on their perception of their self-directed learning skills: self-learning skills, collaboration, application, and metacognition, Conclusions: Study results demonstrated that we successfully implemented a case-based SDL activity in a first-year medical school course and that students perceived the activity as a valuable learning experience.

Inflammatory mediators orchestrate the host immune and metabolic response to acute bacterial infections and mediate the events leading to septic shock. Tumor necrosis factor (TNF) has long been identified as one of the proximal mediators of endotoxin action. Recent studies have implicated peroxisome proliferator-activated receptor alpha (PPARα) as a potential target to modulate regulation of the immune response. Since PPARα activators, which are hypolipidemic drugs, are being prescribed for a significant population of older patients, it is important to determine the impact of these drugs on the host response to acute inflammation. Therefore, we examined the role of PPARα activators on the regulation of TNF expression in a mouse model of endotoxemia. CD-1 mice treated with dietary fenofibrate or Wy-14,643 had fivefold-higher lipopolysaccharide (LPS)-induced TNF plasma levels than LPS-treated control-fed animals. Higher LPS-induced TNF levels in drug-fed animals were reflected physiologically in significantly lower glucose levels in plasma and a significantly lower 50% lethal dose than those in LPS-treated control-fed animals. Utilizing PPARα wild-type (WT) and knockout (KO) mice, we showed that the effect of fenofibrate on LPS-induced TNF expression was indeed mediated by PPARα. PPARα WT mice fed fenofibrate also had a fivefold increase in LPS-induced TNF levels in plasma compared to control-fed animals. However, LPS-induced TNF levels were significantly decreased and glucose levels in plasma were significantly increased in PPARα KO mice fed fenofibrate compared to those in control-fed animals. Data from peritoneal macrophage studies indicate that Wy-14,643 modestly decreased TNF expression in vitro. Similarly, overexpression of PPARα in 293T cells decreased activity of a human TNF promoter-luciferase construct. The results from these studies suggest that any anti-inflammatory activity of PPARα in vivo can be masked by other systemic effects of PPARα activators.