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.

Increased axonal expression of nectin-1 in multiple sclerosis plaques.

Nectin-1 is a cell adhesion molecule that plays a role in interneuronal synapse formation, in axonal guidance during development and possibly in neuron-glia interactions. To better understand axonal changes in MS, nectin-1 expression was determined by immunohistochemistry in normal adult human cerebral white matter (n = 4) and in six MS plaques (three active and three inactive). The intensity of axonal nectin-1 expression was scored on a scale of 0 to 4+. In normal adult cerebral white matter, axons showed weak nectin-1 expression with a score of 1.25 ± 0.50. Axonal nectin-1 expression was significantly stronger within both active (score = 3.33 ± 0.289, p = 0.001) and inactive (score = 2.16 ± 0.29, p = 0.038) MS plaques than in normal white matter. Axons in white matter adjacent to MS plaques showed nectin-1 expression (score = 1.5 ± 0.50) that was not statistically different from normal controls (p = 0.542). These findings raise the possibility that increased expression of nectin-1 in MS lesions plays a role in the pathogenesis of MS through participation in axonal responses to injury and mediation of altered neuron-glia interactions relevant to myelination.

Inflammatory markers and tract-based structural connectomics in older adults with a preliminary exploration of associations by race.

Peripheral inflammation has been implicated in cognitive dysfunction and dementia. While studies outline the relationship between elevated inflammation and individual gray or white matter alterations, less work has examined inflammation as related to connectivity between gray and white matter or variability in these associations by race. We examined the relationship between peripheral inflammation and tract-based structural connectomics in 74 non-demented participants (age = 69.19 ± 6.80 years; 53% female; 45% Black) who underwent fasting venipuncture and MRI. Serum was assayed for C-reactive protein, interleukin-6, and interleukin-1ß. Graph theory analysis integrated T1-derived gray matter volumes and DTI-derived white matter tractography into connectivity matrices analyzed for local measures of nodal strength and efficiency in a priori regions of interest associated with cardiovascular disease risk factors and dementia. Linear regressions adjusting for relevant covariates showed associations between inflammatory markers and nodal strength in the isthmus, posterior and caudal anterior cingulate (p's ≤ .042). Adding an inflammatory marker*race term showed race-modified associations between C-reactive protein and efficiency in the thalamus and amygdala, and nodal strength in the putamen (p's ≤ .048), between interleukin-6 and efficiency in the pars triangularis and amygdala (p's ≤ .024), and between interleukin-1ß and nodal strength in the pars opercularis (p = .048). Higher levels of inflammation associated with lower efficiency and higher strength for White participants but higher efficiency and lower strength for Black participants. Results suggest inflammation is associated with tract-based structural connectomics in an older diverse cohort and that differential relationships may exist by race within prefrontal and limbic brain regions.

Inflammation, Cognition, and White Matter in Older Adults: An Examination by Race.

OBJECTIVES: Non-Latino Black adults have greater risk for Alzheimer's dementia compared to non-Latino White adults, possibly due to factors disproportionally affecting Black adults including cardiovascular disease (CVD). Chronic peripheral inflammation is implicated in both Alzheimer's dementia and CVD and is known to impact cognition and cerebral white matter, yet little work has examined these associations by race. This study examined associations between inflammation, cognition, and cerebral white matter generally, and by race. METHODS: Eighty-six non-demented older Black and White participants (age = 69.03; 50% female; 45% Black participants) underwent fasting venipuncture, cognitive testing, and MRI. Serum was assayed for interleukin-6 (IL-6), C-reactive protein (CRP), and interleukin 1-beta. Cognitive domains included memory, executive function, and attention/information processing. MRI measures included white matter hyperintensity volumes (WMH) and quantification of white matter integrity in areas outside WMHs via DTI-derived fractional anisotropy (FA) and mean diffusivity, as well as multi-component relaxometry derived myelin water fraction (MWF). RESULTS: Black and White participants did not differ on age, sex, or CVD risk. Separate linear regression models adjusting for relevant confounders revealed that higher IL-6 associated with lower executive function and higher CRP levels associated with lower FA and MWF. Stratified analyses revealed that these association were significant for Black participants only. DISCUSSION: These findings suggest that peripheral inflammation is inversely associated with select cognitive domains and white matter integrity (but not WMHs), particularly in older Black adults. It is important to consider race when investigating inflammatory associates of brain and behavior.

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

OBJECTIVE: 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. METHODS: An oral glucose tolerance test prior to surgery was completed by healthy premenopausal women (n = 76) seeking bariatric surgery. Abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were collected during surgery. RESULTS: Approximately, 70% of our subjects were vitamin D sufficient or optimal, and 80% had normal glucose tolerance. No significant association between serum 25-hydroxyvitamin D [25(OH)D] with circulating inflammatory markers or insulin sensitivity was identified. In subjects with waist circumference of <139 cm (n = 42), log25(OH)D positively predicted VAT logIL-6 mRNA expression (P = 0.003). LogVDR expression was positively correlated with the expression of inflammatory markers in both SAT (logIL-1ß mRNA: r = 0.95, P < 0.0001; logTNF mRNA: r = 0.82, P < 0.0001) and VAT (logIL-1ß mRNA: r = 0.89, P < 0.0001; logTNF mRNA: r = 0.75, P < 0.0001). VAT logVDR expression positively predicted logHOMA-IR in non-African American subjects (P = 0.05). CONCLUSIONS: The beneficial effects of vitamin D on inflammation and insulin sensitivity were not supported by our findings. VDR does not appear to possess a protective effect in adipose tissue.

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 1ß 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.

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 γ 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 µL of DMSO and 80 µL 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.

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 Ly6C(high) 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.

OBJECTIVE: 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. DESIGN AND METHODS: We used two mouse models of obesity, high-fat diet induced obesity (DIO) and ob/ob mice. We also evaluated the response of Gal-1 KO mice to DIO. RESULTS: Both age and diet modulated expression of galectins, with DIO mice having higher serum Gal-1 and Gal-3 versus lean mice after 13-17 weeks of high-fat diet. In DIO mice there was a progressive increase in expression of Gal-1 and Gal-9 in SAT, whereas Gal-3 increased in both VAT and SAT. Expression of Gal-12 declined over time in VAT of DIO mice, similar to adiponectin. Obesity lead to increased production of Gal-1 in adipocytes, whereas the increased Gal-3 and Gal-9 of obesity mostly derived from the stromovascular fraction. Expression of Gal-12 was restricted to adipocytes. There was increased production of Gal-3 and Gal-9, but not Gal-1, in CD11c(-) and CD11c(+) macrophages from VAT of DIO versus lean mice. Expression of Gal-1, -3 and -12 in VAT and SAT of ob/ob mice followed a trend comparable to DIO mice. Rosiglitazone reduced serum Gal-1, but not Gal-3 and modulated expression of Gal-3 in VAT and Gal-9 and Gal-12 in SAT of DIO mice. High-fat feeding lead to increased adiposity in Gal-1 KO versus WT mice, with loss of correlation between leptin and adiposity and no alterations in glucose and insulin levels. CONCLUSIONS: Obesity leads to differential modulation of Gal-1, 3, 9 and 12 in VAT and SAT, with Gal-1 acting as a modulator of adiposity.

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 Alzheimer's 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.

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.