Browsing by Author "Sun, Jun"

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    Decreased microbial co-occurrence network stability and SCFA receptor level correlates with obesity in African-origin women
    (Nature Research, 2018-11-20) Dugas, Lara R.; Bernabé, Beatriz Peñalver; Priyadarshini, Medha; Fei, Na; Park, Seo Jin; Brown, Laquita; Plange-Rhule, Jacob; Nelson, David; Toh, Evelyn C.; Gao, Xiang; Dong, Qunfeng; Sun, Jun; Kliethermes, Stephanie; Gottel, Neil; Luke, Amy; Gilbert, Jack A.; Layden, Brian T.; Microbiology and Immunology, School of Medicine
    We compared the gut microbial populations in 100 women, from rural Ghana and urban US [50% lean (BMI < 25 kg/m2) and 50% obese (BMI ≥ 30 kg/m2)] to examine the ecological co-occurrence network topology of the gut microbiota as well as the relationship of short chain fatty acids (SCFAs) with obesity. Ghanaians consumed significantly more dietary fiber, had greater microbial alpha-diversity, different beta-diversity, and had a greater concentration of total fecal SCFAs (p-value < 0.002). Lean Ghanaians had significantly greater network density, connectivity and stability than either obese Ghanaians, or lean and obese US participants (false discovery rate (FDR) corrected p-value ≤ 0.01). Bacteroides uniformis was significantly more abundant in lean women, irrespective of country (FDR corrected p < 0.001), while lean Ghanaians had a significantly greater proportion of Ruminococcus callidus, Prevotella copri, and Escherichia coli, and smaller proportions of Lachnospiraceae, Bacteroides and Parabacteroides. Lean Ghanaians had a significantly greater abundance of predicted microbial genes that catalyzed the production of butyric acid via the fermentation of pyruvate or branched amino-acids, while obese Ghanaians and US women (irrespective of BMI) had a significantly greater abundance of predicted microbial genes that encoded for enzymes associated with the fermentation of amino-acids such as alanine, aspartate, lysine and glutamate. Similar to lean Ghanaian women, mice humanized with stool from the lean Ghanaian participant had a significantly lower abundance of family Lachnospiraceae and genus Bacteroides and Parabacteroides, and were resistant to obesity following 6-weeks of high fat feeding (p-value < 0.01). Obesity-resistant mice also showed increased intestinal transcriptional expression of the free fatty acid (Ffa) receptor Ffa2, in spite of similar fecal SCFAs concentrations. We demonstrate that the association between obesity resistance and increased predicted ecological connectivity and stability of the lean Ghanaian microbiota, as well as increased local SCFA receptor level, provides evidence of the importance of robust gut ecologic network in obesity.
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    EFFECTS OF ORTHODONTIC MINI-IMPLANT DIAMETER ON MICRODAMAGE.
    (Office of the Vice Chancellor for Research, 2012-04-13) Cruz, Enrique; Liu, Sean; Sun, Jun; Blanchard, Steven B.; Soto, Armando; Stewart, Kelton T.; Allen, Matthew R.; Liu, Sean
    Microdamage reduces bone mechanical properties and thus could possi-bly contribute to implant failure. The objective of this study was to investi-gate whether the diameter of mini-implants (MI) affects microdamage gen-eration and whether this differs between the mandible and maxilla due to their contrasting cortical thicknesses. Methods: Maxillary and mandibular quadrants of 5 dogs were randomly assigned to receive, in situ, no interven-tion (control), pilot drilling only, or pilot drilling plus one of three diameters of MI: 1.4 (n=18), 1.6 (n=18), and 2.0 mm (n=18). Microdamage was as-sessed on basic fuchsin stained sections using epifluorescence microscopy. Results: No microdamage was found in the non-drilling controls. Pilot drill-ing produced only minimal microdamage in the maxilla but more microdamage in the mandible. There was significantly higher microdamage generated in the mandible, compared to the maxilla (p<0.05). In the maxil-la, although insertion of all implants produced higher microdamage than the control and pilot drilling, there were no differences between the 3 MI diame-ters. In the mandible, insertion of implants generated significantly higher microdamage than the control, but it did not produce higher microdamage than pilot drilling. Similarly, no differences in microdamage were found be-tween 3 MI diameters. Conclusion: Insertion of MIs in the mandible pro-duced higher microdamage than in the maxilla, which may explain that the higher MI failure rate in the mandible. Implant diameter did not affect over-all microdamage burden in either jaw. Microdamage was mostly generated by pilot drilling through the cortex in the mandible, while microdamage in the maxilla was mainly produced when manual inserting MIs after pilot drill-ing.
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    Effects of PYK2-Deficiency on Midpalatal Suture Expansion in Mice
    (2015-08) Sun, Jun; Bruzzaniti, Angela; Liu, Sean Shih-Yao; Brown, David T.; Chu, Tien Min; Levon, John A.
    Background: Suture expansion is a very important clinical approach to correct maxillary width deficiency, but it has a high potential for treatment relapse. Accelerating bone formation and mineralization in the midpalatal suture during suture expansion is beneficial in preventing relapse of the arch width and reducing the retention period. Pyk2 is tyrosine kinase which has been shown to mediate signaling pathways that are involved in the process of bone remodeling. Pyk2 knock-out (KO) mice have augmented bone formation and increased bone mass, suggesting that therapeutic strategies that inhibit Pyk2 may be useful to enhance bone remodeling and prevent suture relapse during suture expansion. Objectives: To determine if Pyk2-deficiency affects midpalatal suture bone mass and bone remodeling with or without suture expansion in mice. Methods: Thirty-six Pyk2-KO and thirty-six wild type (WT) 6 week-old male mice were randomly assigned into three groups: receiving no expansion force (0 g), 10 g or 20 g force of rapid maxillary expansion for 14 days. Half of the mice in each group were used for histology analysis; the other half was assigned for fluorescence analysis. Suture width, maxilla width and bone volume/tissue volume around suture bone edges were measured using micro-CT. Histological analyses of osteoclasts (tartrate resistant acid phosphatase, TRAP), osteoblasts (alkaline phosphatase, ALP) and chondrocytes (alcian blue) were performed. Results: The BV/TV ratio was significantly higher in Pyk2-KO control mice compared to WT control mice. Suture expansion in WT and Pyk2-KO mice led to an increase in bone marrow spaces around the suture edge and significantly reduced BV/TV. Expansion also led to a significant increase in suture width, suture fibrous area, osteoclast number, cartilage area and hypertrophic chondrocyte number. However, BV/TV in Pyk2-KO mice was significantly higher than in WT mice at both the 10 g and 20 g force levels. In addition, Pyk2-KO exhibited reduced suture width, maxilla width, fibrous area and osteoclast number per bone surface (OC.S/BS) compared to WT mice under expansion forces. Cartilage area and hypertrophic chondrocyte number were increased by force but were independent of mouse genotypes. Conclusion: Pyk2-KO mice have higher BV/TV and narrower suture width compared to WT mice, which may be due to decreased osteoclast activity. The higher BV/TV of the midpalatal sutures of Pyk2-KO mice following suture expansion may suggest the presence of a more stable suture that has a reduced potential for relapse. Therapeutic strategies to inhibit Pyk2 during RME may be beneficial in increasing bone mass and preventing relapse of the suture.
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    Pyk2 deficiency enhances bone mass during midpalatal suture expansion
    (Wiley, 2020-11) Sun, Jun; Eleniste, Pierre P.; Utreja, Achint; Turkkahraman, Hakan; Liu, Sean Shih-Yao; Bruzzaniti, Angela; Prosthodontics, School of Dentistry
    OBJECTIVE: To determine if Pyk2 deficiency increases midpalatal suture bone mass and preserves sutural integrity after maxillary expansion. SETTING AND SAMPLE: Thirty-six male Pyk2 knockout (KO) and control (WT) mice at 6 weeks of age. MATERIALS AND METHODS: Mice received nickel-titanium spring expanders delivering 0 g (no intervention control), 10 or 20 g force for 14 days. High-resolution micro-CT was used to determine bone volume/tissue volume (BV/TV), sutural width and intermolar width. Effects on osteoclasts, chondrocytes and suture morphology were determined by histomorphometry. RESULTS: Pyk2-KO controls (0 g) had 7% higher BV/TV compared with WT controls. Expanded Pyk2-KO maxillae also exhibited 12% (10 g) and 18% (20 g) higher BV/TV than WT mice. Although bone loss following expansion occurred in both genotypes, BV/TV was decreased to a greater extent in WT maxillae (-10% at 10g; -22% at 20 g) compared with Pyk2-KO maxillae (-11% only at 20 g). Expanded WT maxillae also showed a greater increase in sutural width, intermolar width and fibrous connective tissue width compared with expanded Pyk2-KO maxillae. Moreover, osteoclast number was increased 77% (10 g) and 132% (20 g) in expanded WT maxillae, but remained unchanged in expanded Pyk2-KO, compared to their respective controls. Cartilage area and chondrocyte number were increased to the same extent in expanded WT and Pyk2-KO sutures. CONCLUSIONS: These findings suggest that midpalatal suture expansion increases osteoclast formation in WT but not Pyk2-KO mice, leading to higher BV/TV in expanded Pyk2-KO maxillae. These studies suggest Pyk2-targeted strategies may be beneficial to increase bone density and preserve sutural integrity during maxillary expansion.