Alcohol, HIV, ART, & Bone Metabolism

1. Alcohol, HIV, ART, & Bone Metabolism Robert W. Siggins 24 February 2012 rsiggi@lsuhsc.edu

2. Metabolic Bone Disorders Overview • Origin in disrupted bone remodeling process • Osteomalacia & rickets  bone softening from ↓ bone mineralization; Ca3(PO4)2 deficiency • Osteoporosis ↑ loss total bone mass; resorption > formation

3. Osteopenia and Osteoporosis • Osteopenia • Decreased bone • Not a diagnosis; Radiographic description • Etiology  Osteoporosis, osteomalacia, cancers, endocrine disorders • Osteoporosis • Decreased bone mass • Decreased cancellous (spongy) bone strength

4. Osteoporosis • Porous bone • Poorly mineralized bone • Bone density • Normal bone • 833 mg/cm2 • Osteopenic bone • 648 – 833 mg/cm2 • Osteoporosis • < 648 mg/cm2 • Diagnosis = 2.5 SD from normal female Femoral Head

5. 3-D Micro CT:Healthy vs Osteoporotic Bone 84 year old Female (w/ vertebral fracture) 52 year old Female Borah et al Anat. Rec.(2001)

6. Osteoporosis • Potential causes • Decreased levels of estrogen and testosterone • Alcohol Abuse • HIV / HAART • Inadequate levels of vitamins D and C, or Mg++ • Demonstrated by reduced bone mass / density and an imbalance of bone resorption and formation • Bone histology is usually normal but it lacks structural integrity

7. Osteoporosis

8. Superficial Anatomy of a Long Bone

9. Osteoporoses of Long Bones Postmenopausal = cancellous bone; vertebrae, metaphyses; endocrtical surfaces of long bone Alcoholic = decreased total remodeling of both cancellous and cortical (compact) bone

10. Ca++ Regulation http://www.endocrinesurgery.net.au/parathyroidfunction/

11. Normal Bone Remodeling • Osteoblasts “bone building” cells • They control bone remodeling by: • Laying down new bone • Secrete RANK ligand (RANKL) that controls osteoclasts “bone breaking” cells • Normally, bone formation and breakdown are balanced: • Replace damaged bone • Maintain amount & density of bone

12. Bone Growth • Bone cells and bone marrow cells produce osteoprotegerin (OPG)  inhibited by PTH • Blocks RANKL • Prevents osteoclast development & function • Bone breakdown decreases • Bones grow

13. http://www.medscape.com/viewarticle/479893_2

14. Dogma of Remodeling

15. X-Section of Long Bone

16. Remodeling

17. Remodeling

18. Osteocytes  50 cellular projections; extend throughout bone matrix; connect osteocytes to osteocytes & to cells at the bone surface  form the lacunocanalicular network Nat med 17(10):1235, 2011

19. Matrix Embedded BM Cells • Osteocytes • Floxed RANKL mouse crossed with osteocyte specific Cre mouse • No change in total bone RANKL mRNA or circulationg RANKL • >70% decrease in OC number Nat med 17(10):1235, 2011

20. Alcohol and Bone Metabolism • Osteoblast #, osteoid synthesis, osteoid mineralization rate ↓ in human alcoholics compared to nonalcoholic controls; Impaired polyamine pathway (Klein and Carlos, 1995) • Cortical bone loss  decreased bone formation rate (BFR) (Hogan et al., 1997) • Young adult-to-adult rats  starting age of ethanol feeding increases, cancellous bone loss > cortical bone • Bone marrow in osteoporotic bone ↓ osteogenic cells, ↑ adipocytes (Burkhardt et al., 1987) ACER 29(12):2077, 2005

22. Alterations in the immuno-skeletal interface drive bone destruction in HIV-1 transgenic rats Tatyana Vikulina, et. al. PNAS 107(31):13848 2010

23. PNAS 107(31):13848 2010

24. Bone Mineral Density n = 4 n = 4 n = 6 Average ± SD, *P ≤ 0.05 by Mann-Whitney test

25. Longitudinal trabecular X-sectional trabecular Cortical Scale bar = 1 mm

26. A. CTx = C-terminal telopeptide (n = 4) B. Serum osteocalcin (n = 4) TRAP = Tartrate resistant acid phosphatase

27. G. OCs / BS (n = 4) H. OCs Surface / BS (n = 4) Mineralized bone stains orange/pink (H & E Stain)

28. A. In vitro OC formation; TRAP staining

29. C. Role of TNFα in OCgenesis D. OC precursors E. Histogram = macrophages; Bar graph RT-qPCR for M-CSF

30. RT-qPCR analysis of OPG and RANKL expression from total Spleen and Bone Marrow

31. RT-qPCR analysis of OPG and RANKL expression from B cells and B cell-depleted tissues

32. Antiretroviral Therapies

33. http://aidsinfo.nih.gov/guidelines

36. HAART Effects • N(n)RTIs inhibit mitochondria  • Ox Stress? • Chronic lactic acidosis? • Protease Inhibitors  • Enhance OCgenesis and activity • Decrease OBgenesis and activity • Impaired Vit D metabolism  • Osteomalacia  Osteopenia AIDS 23:1297-1310, 2009

37. Alcohol too! AIDS 23:1297-1310, 2009

38. Questions and Break Time!

39. Healing—Hematoma Formation Blood vessels tear and bleedHematoma HematomaFibrin meshwork Inflammatory cell, influx, fibroblast ingrowth, and capillary bud formation

40. Healing—Fibrous Callus Infiltrating capillaries procallus Fibroblasts (periosteum, endosteum, red marrow) fibrocartilaginous “glue” 2-3 weeks

41. Healing—Bony Callus Osteogenic cells (MSCs)  Osteoblasts Osteoblasts  spongy bone trabeculae Bony sheath covers fibrous callus Spongy bone calcifies 3-4 weeks to months

42. Healing—Remodeling Osteoclasts remove dead bone Compact replaces spongy bone (fracture periphery) Thickened area remains