Davina H. Rhodes

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.

Genome-Wide Association Study of Grain Polyphenol Concentrations in Global Sorghum [Sorghum bicolor (L.) Moench] Germplasm

Identifying natural variation of health-promoting compounds in staple crops and characterizing its genetic basis can help improve human nutrition through crop biofortification. Some varieties of sorghum, a staple cereal crop grown worldwide, have high concentrations of proanthocyanidins and 3-deoxyanthocyanidins, polyphenols with antioxidant and anti-inflammatory properties. We quantified total phenols, proanthocyanidins, and 3-deoxyanthocyanidins in a global sorghum diversity panel (n = 381) using near-infrared spectroscopy (NIRS), and characterized the patterns of variation with respect to geographic origin and botanical race. A genome-wide association study (GWAS) with 404,628 SNP markers identified novel quantitative trait loci for sorghum polyphenols, some of which colocalized with homologues of flavonoid pathway genes from other plants, including an orthologue of maize (Zea mays) Pr1 and a homologue of Arabidopsis (Arabidopsis thaliana) TT16. This survey of grain polyphenol variation in sorghum germplasm and catalog of flavonoid pathway loci may be useful to guide future enhancement of cereal polyphenols.

Role of leptin receptor-induced STAT3 signaling in modulation of intestinal and hepatic inflammation in mice

Leptin‐deficient ob/ob mice are resistant to dextran sulfate sodium (DSS)‐induced colitis and Concanavalin A (Con A)‐induced hepatitis. However, the signal transduction pathways involved have not been identified. The present study investigated the effect of leptin‐induced STAT3 signaling in the DSS and Con A models. Mice carrying a leptin receptor (LEPR) gene mutant for Y1138 (s/s mice), with abrogated leptin‐induced STAT3 signaling, were compared with wild‐type (WT) and LEPR‐deficient db/db mice. Administration of DSS to s/s mice resulted in a clinical score and colon shortening of intermediate severity compared with disease induced in WT and db/db mice—the latter group having the lowest disease severity. A comparable degree of inflammatory infiltrate and epithelial damage was observed in the colon of WT and s/s mice, and these parameters were reduced in db/db mice. Levels of IFN‐γ, IL‐6, IL‐10, and TNF‐α were comparable in the colon of s/s and db/db mice, and a similar trend was observed for CXCL2. s/s and WT mice developed severe liver disease in response to Con A, whereas db/db mice were protected. However, Con A‐induced serum IL‐6 and TNF‐α levels in s/s mice mimicked levels observed in db/db rather than WT mice. In conclusion, lack of leptin‐induced STAT3 signaling is associated with reduced cytokine production following DSS and Con A administration, but it appears to sensitize mice to the effects of proinflammatory mediators.

Dissecting genome-wide association signals for loss-of-function phenotypes in sorghum flavonoid pigmentation traits

Genome-wide association studies are a powerful method to dissect the genetic basis of traits, although in practice the effects of complex genetic architecture and population structure remain poorly understood. To compare mapping strategies we dissected the genetic control of flavonoid pigmentation traits in the cereal grass sorghum by using high-resolution genotyping-by-sequencing single-nucleotide polymorphism markers. Studying the grain tannin trait, we find that general linear models (GLMs) are not able to precisely map tan1-a, a known loss-of-function allele of the Tannin1 gene, with either a small panel (n = 142) or large association panel (n = 336), and that indirect associations limit the mapping of the Tannin1 locus to Mb-resolution. A GLM that accounts for population structure (Q) or standard mixed linear model that accounts for kinship (K) can identify tan1-a, whereas a compressed mixed linear model performs worse than the naive GLM. Interestingly, a simple loss-of-function genome scan, for genotype-phenotype covariation only in the putative loss-of-function allele, is able to precisely identify the Tannin1 gene without considering relatedness. We also find that the tan1-a allele can be mapped with gene resolution in a biparental recombinant inbred line family (n = 263) using genotyping-by-sequencing markers but lower precision in the mapping of vegetative pigmentation traits suggest that consistent gene-level resolution will likely require larger families or multiple recombinant inbred lines. These findings highlight that complex association signals can emerge from even the simplest traits given epistasis and structured alleles, but that gene-resolution mapping of these traits is possible with high marker density and appropriate models.

Hematological and acute-phase responses to diet-induced obesity in IL-6 KO mice

Obesity is associated with chronic inflammation and elevated levels of IL-6. The role of IL-6 in induction of acute-phase proteins and modulation of hematological responses has been demonstrated in models of inflammation and aging, but not in obesity. We hypothesized that IL-6 is necessary to regulate the acute-phase response and hematological changes associated with diet-induced obesity (DIO) in mice. Feeding a 60%kcal/fat diet for 13 weeks to C57BL6 WT male mice induced a significant increase in IL-6 expression in visceral adipose tissue (VAT), but not liver, compared to mice fed chow diet. Significantly elevated IL-6 levels were present in the peritoneal lavage fluid, but not plasma, of DIO compared to lean mice. A comparable degree of obesity, hepatomegaly, hyperleptinemia, VAT inflammation and insulin resistance was observed in DIO WT and IL-6 KO mice compared to WT and KO mice fed chow diet. Significant leukocytosis was observed in DIO WT but not DIO KO mice compared to lean groups. A significant reduction in platelet counts, without alterations in platelet size, percentage of circulating reticulated platelets and number of bone marrow megakaryocytes, was present in DIO KO mice compared to each other group. Hepatic expression of thrombopoietin was comparable in each group, with DIO WT and KO mice having reduced VAT expression compared to lean mice. Lean KO mice had significantly elevated plasma levels of thrombopoietin compared to each other group, whereas liver-associated thrombopoietin levels were comparable in each group. Deficiency of IL-6 resulted in blunted hepatic induction of the acute-phase protein serum amyloid A-1, whereas expression of hepcidin-1 and -2, LPS-binding protein, ceruloplasmin, plasminogen activator inhibitor-1 and thrombospondin-1 was IL-6-independent. In conclusion, in the absence of overt metabolic alterations, IL-6 modulates leukocytosis, thrombopoiesis and induction of SAA-1, but not other acute-phase proteins in obese 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.

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.

Genetic architecture of kernel composition in global sorghum germplasm

BackgroundSorghum [Sorghum bicolor (L.) Moench] is an important cereal crop for dryland areas in the United States and for small-holder farmers in Africa. Natural variation of sorghum grain composition (protein, fat, and starch) between accessions can be used for crop improvement, but the genetic controls are still unresolved. The goals of this study were to quantify natural variation of sorghum grain composition and to identify single-nucleotide polymorphisms (SNPs) associated with variation in grain composition concentrations.ResultsIn this study, we quantified protein, fat, and starch in a global sorghum diversity panel using near-infrared spectroscopy (NIRS). Protein content ranged from 8.1 to 18.8%, fat content ranged from 1.0 to 4.3%, and starch content ranged from 61.7 to 71.1%. Durra and bicolor-durra sorghum from Ethiopia and India had the highest protein and fat and the lowest starch content, while kafir sorghum from USA, India, and South Africa had the lowest protein and the highest starch content. Genome-wide association studies (GWAS) identified quantitative trait loci (QTL) for sorghum protein, fat, and starch. Previously published RNAseq data was used to identify candidate genes within a GWAS QTL region. A putative alpha-amylase 3 gene, which has previously been shown to be associated with grain composition traits, was identified as a strong candidate for protein and fat variation.ConclusionsWe identified promising sources of genetic material for manipulation of grain composition traits, and several loci and candidate genes that may control sorghum grain composition. This survey of grain composition in sorghum germplasm and identification of protein, fat, and starch QTL contributes to our understanding of the genetic basis of natural variation in sorghum grain nutritional traits.