Karla J. Castellanos

Increased Adiposity, Dysregulated Glucose Metabolism and Systemic Inflammation in Galectin-3 KO Mice

Obesity and type 2 diabetes are associated with increased production of Galectin-3 (Gal-3), a protein that modulates inflammation and clearance of glucose adducts. We used Lean and Diet-induced Obese (DIO) WT and Gal-3 KO mice to investigate the role of Gal-3 in modulation of adiposity, glucose metabolism and inflammation. Deficiency of Gal-3 lead to age-dependent development of excess adiposity and systemic inflammation, as indicated by elevated production of acute-phase proteins, number of circulating pro-inflammatory Ly6Chigh monocytes and development of neutrophilia, microcytic anemia and thrombocytosis in 20-week-old Lean and DIO male Gal-3 KO mice. This was associated with impaired fasting glucose, heightened response to a glucose tolerance test and reduced adipose tissue expression of adiponectin, Gal-12, ATGL and PPARγ, in the presence of maintained insulin sensitivity and hepatic expression of gluconeogenic enzymes in 20-week-old Gal-3 KO mice compared to their diet-matched WT controls. Expression of PGC-1α and FGF-21 in the liver of Lean Gal-3 KO mice was comparable to that observed in DIO animals. Impaired fasting glucose and altered responsiveness to a glucose load preceded development of excess adiposity and systemic inflammation, as demonstrated in 12-week-old Gal-3 KO mice. Finally, a role for the microflora in mediating the fasting hyperglycemia, but not the excessive response to a glucose load, of 12-week-old Gal-3 KO mice was demonstrated by administration of antibiotics. In conclusion, Gal-3 is an important modulator of glucose metabolism, adiposity and inflammation.

Adipose tissue-specific modulation of galectin expression in lean and obese mice: evidence for regulatory function.

Galectins (Gal) exert many activities, including regulation of inflammation and adipogenesis. We evaluated modulation of Gal‐1, ‐3, ‐9 and ‐12 in visceral (VAT) and subcutaneous (SAT) adipose tissue in mice.

Role of IL-6 in the resolution of pancreatitis in obese mice

Obesity increases severity of acute pancreatitis and risk of pancreatic cancer. Pancreatitis and obesity are associated with elevated IL‐6, a cytokine involved in inflammation and tumorigenesis. We studied the role of IL‐6 in the response of lean and obese mice to pancreatitis induced by IL‐12 + IL‐18. Lean and diet‐induced obese (DIO) WT and IL‐6 KO mice and ob/ob mice pretreated with anti‐IL‐6 antibodies were evaluated at Days 1, 7, and 15 after induction of pancreatitis. Prolonged elevation of IL‐6 in serum and visceral adipose tissue was observed in DIO versus lean WT mice, whereas circulating sIL‐6R declined in DIO but not lean mice with pancreatitis. The severe inflammation and lethality of DIO mice were also observed in IL‐6 KO mice. However, the delayed resolution of neutrophil infiltration; sustained production of CXCL1, CXCL2, and CCL2; prolonged activation of STAT‐3; and induction of MMP‐7 in the pancreas, as well as heightened induction of serum amylase A of DIO mice, were blunted significantly in DIO IL‐6 KO mice. In DIO mice, production of OPN and TIMP‐1 was increased for a prolonged period, and this was mediated by IL‐6 in the liver but not the pancreas. Results obtained in IL‐6 KO mice were confirmed in ob/ob mice pretreated with anti‐IL‐6 antibodies. In conclusion, IL‐6 does not contribute to the increased severity of pancreatitis of obese mice but participates in delayed recovery from acute inflammation and may favor development of a protumorigenic environment through prolonged activation of STAT‐3, induction of MMP‐7, and sustained production of chemokines.

Rosiglitazone Improves Survival and Hastens Recovery from Pancreatic Inflammation in Obese Mice

Obesity increases severity of acute pancreatitis (AP) by unclear mechanisms. We investigated the effect of the PPAR-gamma agonist rosiglitazone (RGZ, 0.01% in the diet) on severity of AP induced by administration of IL-12+ IL-18 in male C57BL6 mice fed a low fat (LFD) or high fat diet (HFD), under the hypothesis that RGZ would reduce disease severity in HFD-fed obese animals. In both LFD and HFD mice without AP, RGZ significantly increased body weight and % fat mass, with significant upregulation of adiponectin and suppression of erythropoiesis. In HFD mice with AP, RGZ significantly increased survival and hastened recovery from pancreatic inflammation, as evaluated by significantly improved pancreatic histology, reduced saponification of visceral adipose tissue and less severe suppression of erythropoiesis at Day 7 post-AP. This was associated with significantly lower circulating and pancreas-associated levels of IL-6, Galectin-3, osteopontin and TIMP-1 in HFD + RGZ mice, particularly at Day 7 post-AP. In LFD mice with AP, RGZ significantly worsened the degree of intrapancreatic acinar and fat necrosis as well as visceral fat saponification, without affecting other parameters of disease severity or inflammation. Induction of AP lead to major suppression of adiponectin levels at Day 7 in both HFD and HFD + RGZ mice. In conclusion, RGZ prevents development of severe AP in obese mice even though it significantly increases adiposity, indicating that obesity can be dissociated from AP severity by improving the metabolic and inflammatory milieu. However, RGZ worsens selective parameters of AP severity in LFD mice.

Decreased oligodendrocyte nuclear diameter in Alzheimer's disease and Lewy body dementia.

To better understand the pathogenesis of dementia, it is important to understand histopathologic changes in neurodegenerative diseases because they might highlight key aspects of the degenerative process. In this study, the nuclear diameter of neurons and oligodendrocytes in selected temporal lobe areas were determined in autopsy tissue sections from patients with Alzheimers disease (AD), Lewy body dementia (LBD) and controls. Our morphometric studies targeted neurons in the CA4 region of the pyramidal cell layer of the hippocampus, neurons in the granular layer of the dentate gyrus and oligodendrocytes in parahippocampal white matter. Mean neuronal nuclear diameters were not different among the studied groups. However, our studies revealed a statistically significant reduction of mean oligodendrocyte nuclear diameter in AD and LBD relative to controls. The reduction of the mean nucleus diameter of oligodendrocytes in LBD was independent of the presence of associated AD pathology in LBD. These findings for the first time identify decreased oligodendrocyte nucleus diameter as a morphologic feature of AD and LBD and may lead to a better understanding of the role of oligodendrocytes in AD and LBD pathogenesis.

Chronic progressive deficits in neuron size, density, and number in the trigeminal ganglia of mice latently infected with herpes simplex virus

Numerous epidemiological studies have proposed a link between herpes simplex virus (HSV) infection and several common chronic neuropsychiatric and neurodegenerative diseases. Experimental HSV infection of mice can lead to chronic behavioral and neurological deficits and chronic pain. While neuron injury and loss are well‐documented consequences of the acute phase of infection, the pathologic consequences of latent HSV infection are poorly understood. To determine whether latent HSV infection can cause neuronal injury in mice, trigeminal ganglia (TG) derived from adult BALB/c mice 1, 12 and 31 weeks after corneal HSV type 1 (HSV‐1) inoculation were analyzed for evidence of productive or latent HSV‐1 infection, inflammation and changes in neuron size, density and number. We found that latent HSV‐1 infection between 12 and 31 weeks after corneal virus inoculation was associated with inflammation and progressive deficits in mean neuron diameter, neuronal nucleus diameter, neuron density and neuron number in the TG relative to mock‐infected controls. The extent of neuronal injury during latent infection correlated with the extent of inflammation. These studies demonstrate that latent HSV infection is associated with progressive neuronal pathology and may lead to a better understanding of the role of HSV infections in chronic neurological diseases.

Obesity and IL-6 interact in modulating the response to endotoxemia in mice

Obesity is associated with elevated levels of IL-6. High IL-6 is prognostic of mortality in sepsis, while controversial data link obesity to sepsis outcome. We used Lean and diet-induced obese (DIO) WT and IL-6 KO mice to investigate the interaction between obesity and IL-6 in endotoxemia. Circulating levels of IL-6 were significantly higher in WT DIO versus WT Lean mice receiving LPS (2.5 μg/mouse, ip). Obesity lead to greater weight loss in response to LPS, with IL-6 deficiency being partially protective. Plasma TNFα, IFNγ, Galectin-3 and leptin were significantly elevated in response to LPS and were each differentially affected by obesity and/or IL-6 deficiency. Plasma Galectin-1 and adiponectin were significantly suppressed by LPS, with obesity and IL-6 deficiency modulating the response. However, LPS comparably increased IL-10 levels in each group. Leukopenia with relative neutrophilia and thrombocytopenia developed in each group after injection of LPS, with obesity and genotype affecting the kinetics, but not the magnitude, of the response. Hepatic induction of the acute-phase protein SAA by LPS was not affected by obesity or IL-6 deficiency, although baseline levels were highest in WT DIO mice. Injection of LPS significantly increased hepatic mRNA expression of PAI-1 in Lean WT and Lean KO mice, while it suppressed the high baseline levels observed in the liver of DIO WT and DIO KO mice. Thus, both IL-6 and obesity modulate the response to endotoxemia, suggesting a complex interaction that needs to be considered when evaluating the effect of obesity on the outcome of septic patients.

Inhibition of the nucleotide-binding domain, leucine-rich containing family, pyrin-domain containing 3 inflammasome reduces the severity of experimentally induced acute pancreatitis in obese mice

Acute pancreatitis (AP), although most often a mild and self-limiting inflammatory disease, worsens to a characteristically necrotic severe acute pancreatitis (SAP) in about 20% of cases. Obesity, affecting more than one-third of American adults, is a risk factor for the development of SAP, but the exact mechanism of this association has not been identified. Coincidental with chronic low-grade inflammation, activation of the nucleotide-binding domain, leucine-rich containing family, pyrin-domain containing 3 (NLRP3) inflammasome increases with obesity. Lean mice genetically deficient in specific components of the NLRP3 inflammasome are protected from experimentally induced AP, indicating a direct involvement of this pathway in AP pathophysiology. We hypothesized that inhibition of the NLRP3 inflammasome with the sulfonylurea drug glyburide would reduce disease severity in obese mice with cerulein-induced SAP. Treatment with glyburide led to significantly reduced relative pancreatic mass and water content and less pancreatic damage and cell death in genetically obese ob/ob mice with SAP compared with vehicle-treated obese SAP mice. Glyburide administration in ob/ob mice with cerulein-induced SAP also resulted in significantly reduced serum levels of interleukin 6, lipase, and amylase and led to lower production of lipopolysaccharide-stimulated interleukin 1β release in cultured peritoneal cells, compared with vehicle-treated ob/ob mice with SAP. Together, these data indicate involvement of the NLRP3 inflammasome in obesity-associated SAP and expose the possible utility of its inhibition in prevention or treatment of SAP in obese individuals.

Vitamin D, inflammation, and relations to insulin resistance in premenopausal women with morbid obesity

In this study, the associations between vitamin D, insulin sensitivity, and inflammation and their relationships with adipose tissue expression of vitamin D receptor (VDR) and inflammatory markers in women with morbid obesity were determined.

Therapeutic administration of orlistat, rosiglitazone, or the chemokine receptor antagonist RS102895 fails to improve the severity of acute pancreatitis in obese mice

Objective Currently, there is no therapy for severe acute pancreatitis (AP) except for supportive care. The lipase inhibitor orlistat, the peroxisome proliferator-activated receptor &ggr; agonist rosiglitazone, and the chemokine receptor 2 antagonists attenuate the severity of AP in rodents if administered before or at the time of induction of pancreatitis. However, it is unknown whether these treatments are effective if administered therapeutically after induction of pancreatitis. Methods Male C57BL6 mice with diet-induced obesity received 2 injections of mrIL-12 (150 ng per mouse) and mrIL-18 (750 ng per mouse) intraperitoneally at 24-hour intervals. The mice were injected 2, 24, and 48 hours after the second injection of IL-12 + IL-18 with orlistat (2 mg per mouse), rosiglitazone (0.4 mg per mouse), RS102895 (0.3 mg per mouse), or vehicle (20 &mgr;L of DMSO and 80 &mgr;L of canola oil) and euthanized after 72 hours. Results Orlistat decreased intra-abdominal fat necrosis compared with vehicle (P < 0.05). However, none of the drug treatments produced significant decreases in pancreatic edema, acinar necrosis, or intrapancreatic fat necrosis. Conclusions Drugs previously shown to improve the severity of AP when given before or at the time of induction of pancreatitis failed to do so when administered therapeutically in the IL-12 + IL-18 model.