Research Summary

Dr. Andrew Posselt, a bariatric and transplant surgeon, is director of the Pancreatic Islet Transplantation Program at UCSF Medical Center. He specializes in adult and pediatric kidney, liver and pancreas transplantation, laparoscopic and open (traditional) bariatric surgery, robotic surgery and performed the first robotic donor nephrectomy at UCSF in May, 2023.

In addition to caring for patients, Posselt conducts research on pancreatic islet transplantation, a procedure that can allow people with type 1 diabetes to discontinue insulin therapy. He also investigates mechanisms by which a transplant recipient's body rejects or tolerates tissue from a donor who isn't genetically identical, and he studies the metabolic and biochemical consequences of bariatric surgery.

Posselt earned his medical degree and a doctorate in immunology from the University of Pennsylvania. He completed residencies in internal medicine and general surgery as well as a transplant fellowship at UCSF, before joining the staff in 2003.

Posselt is a member of several professional and honorary societies, and has given presentations on transplant issues related to patient care and research. At UCSF, he supervises residents and fellows in transplant services and general surgery.

Research Funding

  • July 14, 2021 - May 31, 2024 - Vertical Sleeve Gastrectomy for Treatment of NASH: a pilot randomized control , Co-Principal Investigator . Sponsor: NIH, Sponsor Award ID: R01DK128325
  • May 1, 2014 - April 30, 2021 - Treatment of Type I Diabetes by Islet Transplantation into the Gastric Submucosa , Principal Investigator . Sponsor: NIH, Sponsor Award ID: R01DK098581
  • September 30, 2009 - July 31, 2013 - "Advancing Islet Transplant for Type 1 Diabetes Care" , Principal Investigator . Sponsor: NIH, Sponsor Award ID: U01DK085531
  • September 21, 2009 - June 30, 2012 - Effect of Obesity on Long-Term Clinical Outcomes after Kidney Donation , Principal Investigator . Sponsor: NIH, Sponsor Award ID: R21DK078702

Education

PhD, 1993 - Immunology, University of Pennsylvania
M.D., 1993 - School of Medicine, University of Pennsylvania
Residency, - Internal Medicine, University of California, San Francisco

Selected Publications

  1. Abbasi AB, Posselt A, Orandi BJ, Odorico JS, Stock PG. Obesity management before and after pancreas transplantation. Curr Opin Organ Transplant. 2025 May 05.  View on PubMed
  2. Ku E, McCulloch CE, Roll GR, Adey D, Sood P, Posselt A, Grimes BA, Johansen KL. Association between bariatric surgery after kidney transplantation and graft and survival outcomes. Am J Transplant. 2025 Jan 22.  View on PubMed
  3. Mattke J, Eaton A, Wijkstrom M, Witkowski P, Trikudanathan G, Singh VK, Schwarzenberg SJ, Ramanathan K, Pruett TL, Posselt A, Nathan JD, Morgan K, Mokshagundam SP, Lara L, Gardner TB, Freeman M, Downs E, Chinnakotla S, Beilman GJ, Ahmad S, Adams D, Abu-El-Haija M, Naziruddin B, Bellin MD. Islet Isolation Outcomes in Patients Undergoing Total Pancreatectomy With Islet Autotransplantation in the POST Consortium. Transplantation. 2025 01 01; 109(1):207-216.  View on PubMed
  4. Wu KC, Wu PH, Kazakia G, Patel S, Black DM, Lang TF, Kim TY, King NJ, Hoffmann TJ, Chang H, Linfield G, Palilla S, Rogers SJ, Carter JT, Posselt AM, Schafer AL. Skeletal effects of sleeve gastrectomy, by sex and menopausal status and compared to Roux-en-Y gastric bypass surgery. J Clin Endocrinol Metab. 2024 Nov 27.  View on PubMed
  5. Wu KC, Wu PH, Kazakia G, Patel S, Black DM, Lang TF, Kim TY, King NJ, Hoffman TJ, Chang H, Linfield G, Palilla S, Rogers SJ, Carter JT, Posselt AM, Schafer AL. Skeletal effects of sleeve gastrectomy, by sex and menopausal status and in comparison to Roux-en-Y gastric bypass surgery. medRxiv. 2024 Jun 25.  View on PubMed
  6. Wu KC, McCauley KE, Lynch SV, Nayak RR, King NJ, Patel S, Kim TY, Condra K, Fadrosh D, Nguyen D, Lin DL, Lynch K, Rogers SJ, Carter JT, Posselt AM, Stewart L, Schafer AL. Alteration in the gut microbiome is associated with changes in bone metabolism after laparoscopic sleeve gastrectomy. J Bone Miner Res. 2024 Mar 22; 39(2):95-105.  View on PubMed
  7. Downs EM, Eaton A, Witkowski P, Wijkstrom M, Walsh M, Trikudanathan G, Singh VK, Schwarzenberg SJ, Pruett TL, Posselt A, Naziruddin B, Nathan JD, Mokshagundam SP, Morgan K, Lara LF, Gardner TB, Freeman ML, Ellery K, Chinnakotla S, Beilman GJ, Adams D, Ahmad S, Abu-El-Haija M, Bellin MD. Nutritional Risks in Patients Undergoing Total Pancreatectomy Islet AutoTransplantation in the POST Consortium. J Gastrointest Surg. 2023 09; 27(9):1893-1902.  View on PubMed
  8. Wisel SA, Posselt AM, Szot GL, Nunez M, Santos-Parker K, Gardner JM, Worner G, Roll GR, Syed S, Kelly Y, Ward C, Tavakol M, Johnson K, Masharani U, Stock PG. A Multi-Modal Approach to Islet and Pancreas Transplantation With Calcineurin-Sparing Immunosuppression Maintains Long-Term Insulin Independence in Patients With Type I Diabetes. Transpl Int. 2023; 36:11367.  View on PubMed
  9. Wu KC, Cao S, Weaver CM, King NJ, Patel S, Kim TY, Black DM, Kingman H, Shafer MM, Rogers SJ, Stewart L, Carter JT, Posselt AM, Schafer AL. Intestinal Calcium Absorption Decreases After Laparoscopic Sleeve Gastrectomy Despite Optimization of Vitamin D Status. J Clin Endocrinol Metab. 2023 01 17; 108(2):351-360.  View on PubMed
  10. Santandreu AG, Taheri-Tehrani P, Feinberg B, Torres A, Blaha C, Shaheen R, Moyer J, Wright N, Szot GL, Fissell WH, Vartanian S, Posselt A, Roy S. Characterization of human islet function in a convection-driven intravascular bioartificial pancreas. Bioeng Transl Med. 2023 Mar; 8(2):e10444.  View on PubMed
  11. Wu KC, Cao S, Weaver CM, King NJ, Patel S, Kingman H, Sellmeyer DE, McCauley K, Li D, Lynch SV, Kim TY, Black DM, Shafer MM, Özçam M, Lin DL, Rogers SJ, Stewart L, Carter JT, Posselt AM, Schafer AL. Prebiotic to Improve Calcium Absorption in Postmenopausal Women After Gastric Bypass: A Randomized Controlled Trial. J Clin Endocrinol Metab. 2022 03 24; 107(4):1053-1064.  View on PubMed
  12. Witkowski P, Philipson LH, Buse JB, Robertson RP, Alejandro R, Bellin MD, Kandeel F, Baidal D, Gaglia JL, Posselt AM, Anteby R, Bachul PJ, Al-Salmay Y, Jayant K, Perez-Gutierrez A, Barth RN, Fung JJ, Ricordi C. Islets Transplantation at a Crossroads - Need for Urgent Regulatory Update in the United States: Perspective Presented During the Scientific Sessions 2021 at the American Diabetes Association Congress. Front Endocrinol (Lausanne). 2021; 12:789526.  View on PubMed
  13. Meier RPH, Kelly Y, Yamaguchi S, Braun HJ, Lunow-Luke T, Adelmann D, Niemann C, Maluf DG, Dietch ZC, Stock PG, Kang SM, Feng S, Posselt AM, Gardner JM, Syed SM, Hirose R, Freise CE, Ascher NL, Roberts JP, Roll GR. Advantages and Limitations of Clinical Scores for Donation After Circulatory Death Liver Transplantation. Front Surg. 2021; 8:808733.  View on PubMed
  14. Nathan JD, Yang Y, Eaton A, Witkowski P, Wijkstrom M, Walsh M, Trikudanathan G, Singh VK, Schwarzenberg SJ, Pruett TL, Posselt A, Naziruddin B, Mokshagundam SP, Morgan K, Lara LF, Kirchner V, He J, Gardner TB, Freeman ML, Ellery K, Conwell DL, Chinnakotla S, Beilman GJ, Ahmad S, Abu-El-Haija M, Hodges JS, Bellin MD. Surgical approach and short-term outcomes in adults and children undergoing total pancreatectomy with islet autotransplantation: A report from the Prospective Observational Study of TPIAT. Pancreatology. 2022 Jan; 22(1):1-8.  View on PubMed
  15. Ku E, McCulloch CE, Roll GR, Posselt A, Grimes BA, Johansen KL. Bariatric surgery prior to transplantation and risk of early hospital re-admission, graft failure, or death following kidney transplantation. Am J Transplant. 2021 11; 21(11):3750-3757.  View on PubMed
  16. Lara LF, Wastvedt S, Hodges JS, Witkowski P, Wijkstrom M, Walsh RM, Singh VK, Schwarzenberg SJ, Pruett TL, Posselt A, Naziruddin B, Nathan JD, Morgan KA, Mitchell R, Kirchner VA, Mokshagundam SL, Hatipoglu B, Gardner TB, Freeman ML, Chinnakotla S, Beilman GJ, Abu-El-Haija M, Conwell DL, Bellin MD, POST study consortium. The Association of Smoking and Alcohol Abuse on Anxiety and Depression in Patients With Recurrent Acute or Chronic Pancreatitis Undergoing Total Pancreatectomy and Islet Autotransplantation: A Report From the Prospective Observational Study of TPIAT Cohort. Pancreas. 2021 07 01; 50(6):852-858.  View on PubMed
  17. Witkowski P, Odorico J, Pyda J, Anteby R, Stratta RJ, Schrope BA, Hardy MA, Buse J, Leventhal JR, Cui W, Hussein S, Niederhaus S, Gaglia J, Desai CS, Wijkstrom M, Kandeel F, Bachul PJ, Becker YT, Wang LJ, Robertson RP, Olaitan OK, Kozlowski T, Abrams PL, Josephson MA, Andreoni KA, Harland RC, Kandaswamy R, Posselt AM, Szot GL, Ricordi C. Arguments against the Requirement of a Biological License Application for Human Pancreatic Islets: The Position Statement of the Islets for US Collaborative Presented during the FDA Advisory Committee Meeting. J Clin Med. 2021 Jun 29; 10(13).  View on PubMed
  18. Witkowski P, Wijkstrom M, Bachul PJ, Morgan KA, Levy M, Onaca N, Chaidarun SS, Gardner T, Shapiro AMJ, Posselt A, Ahmad SA, Daffonchio L, Ruffini PA, Bellin MD. Targeting CXCR1/2 in the first multicenter, double-blinded, randomized trial in autologous islet transplant recipients. Am J Transplant. 2021 11; 21(11):3714-3724.  View on PubMed
  19. Sharpton SR, Terrault NA, Tavakol MM, Posselt AM. Sleeve gastrectomy prior to liver transplantation is superior to medical weight loss in reducing posttransplant metabolic complications. Am J Transplant. 2021 10; 21(10):3324-3332.  View on PubMed
  20. Desai CS, Szempruch KR, Vonderau JS, Chetboun M, Pattou F, Coates T, De Paep DL, Hawthorne WJ, Khan KM, de Koning EJP, Naziruddin B, Posselt A, Schrope BA, Wijkstrom M, Witkowski P, Shapiro AMJ. Anticoagulation practices in total pancreatectomy with autologous islet cell transplant patients: an international survey of clinical programs. Transpl Int. 2021 03; 34(3):593-595.  View on PubMed

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