Amjad Kanaan

Neuronal death during combined intermittent hypoxia/hypercapnia is due to mitochondrial dysfunction

Breathing-disordered states, such as in obstructive sleep apnea, which are cyclical in nature, have been postulated to induce neurocognitive morbidity in both pediatric and adult populations. The oscillatory nature of intermittent hypoxia, especially when chronic, may mimic the paradigm of ischemia-reperfusion in that tissues and cells are exposed to episodes of low and high O(2) and this may lead to oxidant stress. Therefore, we decided to explore the potential contribution of oxidant stress in our intermittent hypoxia/hypercapnia animal model and the role that mitochondria might play in this stress. Neonatal mice were exposed to intermittent hypoxia/hypercapnia for 10 days and 2 wk. Combined intermittent hypoxia/hypercapnia led to a marked increase in apoptotic cell death in the cerebral cortex. Oxygen consumption studies in isolated mitochondria from intermittent hypoxia/hypercapnia-exposed brains demonstrated significant reductions in both state 4 and state 3 respiratory activities by approximately 60% and 75%, respectively. Electron paramagnetic resonance spectroscopy registered a significant increase in superoxide production during nonphosphorylating state 4 by 37%, although superoxide leakage during state 3 did not increase upon treatment. Neuronal superoxide-specific dihydroethidium oxidation was also greater in exposed animals. These studies indicate that intermittent hypoxia/hypercapnia leads to oxidative stress due to mitochondrial response within the mouse central nervous system.

Enhanced Glucose Uptake in Phenylbutyric Acid-Treated 3T3-L1 Adipocytes

Diabetes Mellitus is a chronic metabolic disease marked by altered glucose homeostasis and insulin resistance. The phosphatase PTEN antagonizes the insulin-induced-PI3K-driven cascade that normally leads to GLUT4 membrane translocation. This study investigates the effect of Phenylbutyric Acid (PBA), a chemical chaperone and a potential mediator of PTEN activity, on glucose uptake in differentiated 3T3-L1 adipocytes. Adipocyte differentiation status was quantified by Oil Red O staining and the expression of AP2. Baseline and insulin-induced adipocyte glucose uptake were assayed with and without PBA treatment. Expression of GLUT1, GLUT4, PIP3, pAkt, pPTEN, and PARK-7 was examined by western blot. Plasma membrane expression of GLUT4 was determined using immunofluorescence. Leptin and adiponectin secretion was measure by enzyme-linked immunosorbent assay. PBA treatment, alone or with insulin induction, significantly increased glucose uptake in 3T3-L1 adipocytes. PBA significantly increased GLUT1 but not GLUT4 total protein expression. However, a significant increase in membrane GLUT4 protein translocation was observed. The expression of PIP3 and pAkt increased indicating enhanced PI3k pathway activity. There was a significant decrease in PTEN activity as evident by a rise in the phosphorylated form of this protein. PARK7 protein expression increased with PBA. Treating differentiated adipocytes with PBA did not alter their differentiation status, but decreased the leptin to adiponectin ratio. Conclusion: this study showed that PBA enhances adipocyte glucose uptake potentially through its effect on glucose transporter expression and/or trafficking via the PI3K signaling pathway; suggesting PBA as a possible candidate for the ancillary management of diabetes.

Metformin Treatment Inhibits Motility and Invasion of Glioblastoma Cancer Cells

Glioblastoma multiforme (GBM) is one of the most common and deadliest cancers of the central nervous system (CNS). GBMs high ability to infiltrate healthy brain tissues makes it difficult to remove surgically and account for its fatal outcomes. To improve the chances of survival, it is critical to screen for GBM-targeted anticancer agents with anti-invasive and antimigratory potential. Metformin, a commonly used drug for the treatment of diabetes, has recently emerged as a promising anticancer molecule. This prompted us, to investigate the anticancer potential of metformin against GBMs, specifically its effects on cell motility and invasion. The results show a significant decrease in the survival of SF268 cancer cells in response to treatment with metformin. Furthermore, metformins efficiency in inhibiting 2D cell motility and cell invasion in addition to increasing cellular adhesion was also demonstrated in SF268 and U87 cells. Finally, AKT inactivation by downregulation of the phosphorylation level upon metformin treatment was also evidenced. In conclusion, this study provides insights into the anti-invasive antimetastatic potential of metformin as well as its underlying mechanism of action.

Colectomy induces an aldosterone-mediated increase in jejunal glucose uptake in rats

Aims: The main function of the colon is water and electrolyte absorption. Total colectomy eliminates this colonic function and may alter the absorptive capacity of the small intestine for nutrients. This study examines the effect of total colectomy on jejunal glucose absorption and investigates the potential role of aldosterone in mediating the alterations in glucose uptake post‐colectomy using the aldosterone antagonist spironolactone. Main methods: Total colectomy with ileo‐rectal anastomosis was performed on anesthetized rats. Sham rats were identically handled without colon resection. Two days post‐surgery, groups of colectomized rats were injected with either a daily subcutaneous dose of spironolactone or sesame oil for 12 days. Body weight changes and food and water intake were measured in all experimental groups. Glucose absorption was measured by in‐vivo single pass perfusion in the rat jejunum of control, sham, colectomized, colectomized with spironolactone, and colectomized with sesame oil treatment. Na/K ATPase, SGK1, SGLT1 and GLUT2 expressions were determined in jejunal mucosa in control, colectomized and colectomized/spironolactone injected rats by Western blot analysis. Histological assessment was performed on jejunal sections in control and colectomized groups. Key findings: Glucose absorption significantly increased in colectomized rats with an observed increase in Na/K ATPase and SGK1 expression. No significant expression change in SGLT1 and GLUT2 was detected in the jejunum in colectomized rats. Spironolactone, however, significantly decreased the glucose uptake post‐colectomy and normalized Na/K ATPase and SGK1 expression. Significance: Our results suggest that jejunal glucose uptake increases post‐colectomy as a possible consequence of an aldosterone‐mediated function.