Alcohol, HIV, ART, & Bone Metabolism

Robert W. Siggins

24 February 2012

rsiggi@lsuhsc.edu

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

• Osteopenia– Decreased bone– Not a diagnosis; Radiographic

description– Etiology Osteoporosis,

osteomalacia, cancers, endocrine disorders

• Osteoporosis– Decreased bone mass– Decreased cancellous (spongy)

bone strength

Osteopenia and Osteoporosis

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

3-D Micro CT:Healthy vs Osteoporotic Bone

52 year old Female 84 year old Female(w/ vertebral fracture)

Borah et al Anat. Rec.(2001)

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

Superficial Anatomy of a

Long Bone

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

Ca++ Regulation

http://www.endocrinesurgery.net.au/parathyroidfunction/

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

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

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

Dogma of Remodeling

X-Section of Long

Bone

Remodeling

Remodeling

Nat med 17(10):1235, 2011

Osteocytes 50 cellular projections; extend throughout bone matrix; connect osteocytes to osteocytes & to cells at the bone surface form the lacunocanalicular network

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

Alcohol and Bone Metabolism• Osteoblast #, osteoid synthesis, osteoid mineralization

rate ↓ in human alcoholics compared to nonalcoholic controls; Impaired polyamine pathway 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

Alterations in the immuno-skeletal Alterations in the immuno-skeletal interface drive bone destruction in interface drive bone destruction in

HIV-1 transgenic rats HIV-1 transgenic rats

Tatyana Vikulina, et. al.

PNAS 107(31):13848 2010

PNAS 107(31):13848 2010

Average ± SD, *P ≤ 0.05 by Mann-Whitney test

n = 4 n = 4 n = 6

Bone Mineral DensityBone Mineral Density

Longitudinaltrabecular

X-sectionaltrabecular

Cortical

Scale bar = 1 mm

A. CTx = C-terminal A. CTx = C-terminal telopeptide (n = 4)telopeptide (n = 4)

B. Serum B. Serum osteocalcin (n = 4)osteocalcin (n = 4)

TRAP = Tartrate TRAP = Tartrate resistant acid resistant acid phosphatasephosphatase

G. OCs / BS (n = 4)G. OCs / BS (n = 4)

H. OCs Surface / BS H. OCs Surface / BS (n = 4)(n = 4)

Mineralized bone Mineralized bone stains orange/pink stains orange/pink (H & E Stain)(H & E Stain)

A. In vitro OC formation; TRAP A. In vitro OC formation; TRAP stainingstaining

C. Role of TNFC. Role of TNFαα in OCgenesis in OCgenesis

D. OC precursors D. OC precursors

E. Histogram = macrophages; E. Histogram = macrophages; Bar graph RT-qPCR for M-Bar graph RT-qPCR for M-CSF CSF

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

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

Antiretroviral Therapies

http://aidsinfo.nih.gov/guidelines

HAART EffectsHAART 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

Alcohol too! AIDS 23:1297-1310, 2009

Questions and Break Time!Questions and Break Time!

Healing—Hematoma Formation

1. Blood vessels tear and bleedHematoma

2. HematomaFibrin meshwork

3. Inflammatory cell, influx, fibroblast ingrowth, and capillary bud formation

Healing—Fibrous Callus

1. Infiltrating capillaries procallus

2. Fibroblasts (periosteum, endosteum, red marrow) fibrocartilaginous “glue”

2-3 weeks

Healing—Bony Callus

1. Osteogenic cells (MSCs) Osteoblasts

2. Osteoblasts spongy bone trabeculae

3. Bony sheath covers fibrous callus

4. Spongy bone calcifies 3-4 weeksto months

Healing—Remodeling

1. Osteoclasts remove dead bone

2. Compact replaces spongy bone (fracture periphery)

3. Thickened area remains