1

Genetic Basis of Lipodystrophies

Abhimanyu Garg, M.D.

Professor of Internal Medicine

Chief, Division of Nutrition and Metabolic Diseases

Distinguished Chair in Human Nutrition Research

UT Southwestern Medical Center

Dallas, Texas

Lipodystrophies

Disorders characterized by

selective loss of adipose tissue.

2

Metabolic Complications of

Lipodystrophies

• Insulin resistance, Premature DM

• Hypertriglyceridemia, low HDL cholesterol

• Polycystic ovarian syndrome

• Acanthosis nigricans

• Hepatic Steatosis

• Hypertension (rare)

Etiological Classification

GENETIC

• Autosomal recessive

• Autosomal dominant

• De novo mutations

ACQUIRED

• Autoimmune

• HAART-induced in HIV-

infected patients

• Others

HAART: Highly active antiretroviral therapy

HIV: Human immunodeficiency virus

3

Phenotypic Classification

GENERALIZED LIPODYSTROPHY

• Congenital generalized lipodystrophy (CGL)

• Acquired generalized lipodystrophy (AGL)

PARTIAL LIPODYSTROPHY

• Familial partial lipodystrophy (FPL)

• Acquired partial lipodystrophy (APL)

• HAART-induced in HIV-infected patients (LD-HIV)

LOCALIZED LIPODYSTROPHY

Genetic LipodystrophiesAutosomal Recessive

• Congenital generalized lipodystrophy (CGL)

• Mandibuloacral dysplasia (MAD)-associated

• Autoinflammatory (JMP)

• Other types– FPL

– SHORT syndrome

– Neonatal Progeroid syndrome

– MDP syndrome

Autosomal Dominant• Familial partial lipodystrophy

(FPL)

• Atypical progeroid

syndrome

• Hutchinson-Gilford progeria

syndrome

• SHORT syndrome

Garg, A. JCEM, 2011 Nov; 96(11):3313-25

4

Congenital Generalized Lipodystrophy(Berardinelli-Seip Syndrome)

• Autosomal recessive

• Prevalence < 1 in 10 million

• Reported in ~300 patients of

various ethnicities

Congenital Generalized Lipodystrophy

(Clinical Characteristics)

• Generalized lack of body fat and extreme

muscularity from birth (essential criterion)

• Acanthosis nigricans

• Hepatomegaly due to steatosis

• Acromegaloid features, umbilical hernia

• Clitoromegaly and hirsutism in women

• Lytic lesions in appendicular skeleton

Garg A. Am J Med 108; 143-52, 2000

5

Characterization of CGL Phenotype(Laboratory Characteristics)

• Fasting or postprandial hyperinsulinemia

• Marked insulin resistance

• IGT or DM during teenage years

• Hypertriglyceridemia and low HDL cholesterol

• Characteristic body fat distribution on MRI

• Markedly reduced leptin and adiponectin levels

Simha & Garg. JCEM, 2003;88(11):5433-7

Haque et al. JCEM 2002;87:2395-2398

Garg et al. Diabetes Care 1995

CGL

www.lipodystrophy.info

6

• Hyperinsulinemia at or shortly after birth

• IGT during childhood

• DM usually in teenage years (onset 1-37 y)

• Severe amyloidosis of islets (90% affected) with

ß cell atrophy

• Resistant to ketosis

• Requires high dose of insulin (100-3000 u/d)

DM in CGL Patients

Garg et al. Diabetes Care 1995

Garg A. N Engl J Med 350; 1220-34, 2004

Serum Leptin Levels in CGL

Median

~7th %ile for M

F

Haque et al. JCEM 87:2395-8, 2002

Leptin (ng/m

L)

0

1

2

3

4

5

(APGAT2) (SEIPIN)CGL1 CGL2

M MF F

(AGPAT2)

7

CGL

Molecular Basis

Subtype Gene

• CGL1 AGPAT2

• CGL2 BSCL2

• CGL3 CAV1

• CGL4 PTRF

AGPAT2 mutations in CGL, type 1

(TG biosynthetic pathway)

H2C

H2C

HC

OH

OH

OPO32-

H2C

H2C

HC

O

OH

OPO32-

C

O

R1

Glycerol-

3-Phosphate

1-Acylglycerol-

3-Phosphate

(Lysophosphatidic Acid)

GPAT AGPAT

Acyl-

CoACoA Acyl-

CoACoA

AGPAT2

mutated

in CGL1

2-Monoacylglycerol

1,2 Diacylglycerol

Phosphate

(Phosphatidic Acid)

H2C

H2C

HC

O

O

O

C

O

R1

C

O

R2

C R3

O

1,2 Diacylglycerol Triacylglycerol

DGATPPH2C

H2C

HC

O

O

OPO32-

C

O

R1

C

O

R2

H2C

H2C

HC

O

O

OH

C

O

R1

C

O

R2

H2O PiAcyl-

CoACoA

Phosphatidyl Inositol

Cardiolipin

Phosphatidyl Choline

Phosphatidyl Ethanolamine

Phosphatidyl Serine

MGATAcyl-CoA

CoA

8

• BSCL2 located on chromosome 11q13

• Encodes a 462 amino acid transmembrane ER

protein, seipin

• Seipin has a CAAX motif at C-terminal and

an N-glycosylation site

• Role in lipid droplet formation and adipocyte

differentiation

BSCL2 Mutations in CGL, Type 2

Magre et al. Nat Genet 2001;28:365-70

Windpassinger et al. Nat. Genet. 2004; 36:271-6

Agarwal & Garg. Trends Mol. Med. 2004;10:440-4

Szymanski et al. PNAS 104:20890-20895, 2007

Fei et al. J Cell Biol 180:473-482, 2008

Payne et al. Diabetes 57:2055-2060, 2008

Lipid dropletGlycerol-3-P

LPA

PA

Pi

DAG

TG

CoAFA-CoA

CoA

FA-CoA

CoA

FA-CoA

fusion

ER

Nucleus

Nuclear pore

GPATs

AGPATs

PAPs

DGATs

Normal

ER

Lipid droplet

Nucleus

Nuclear pore

Seipin Deficiency

Seipin Deficiency Impairs Lipid Droplet Fusion

Garg and Agarwal. BBA: 1791:507-13. 2009

9

Phenotypic Differences in CGL Patients

with AGPAT2 and BSCL2 Mutations

CGL1

(AGPAT2)

CGL2

(BSCL2)

Mental Retardation

Cardiomyopathy

Lytic bone lesions

Loss of Mechanical Fat

Metabolic Abnormalities

–

–

++

–

+++

+

+

–

++

+++

Magre´ J, et al. Nat Genet 2001;28:365-70

Agarwal, Simha et al. JCEM 2003; 88:4840-47

van Meldergem et al. J Hum Genet 2003;39:722-33

Caveolin 1 mutation in CGL, Type 3

Kim, CA et al. JCEM 2008;93:1129-1134

Garg and Agarwal, JCEM 2008;93:1183-1185

Caveolin-1

ER

Caveolae

Lipid droplet

Caveolin

vesicle

Nucleus

Nuclear pore

Perilipin

CIDEC

PTRF/Cavin

• 22-year-old F from Brazil

• Homozygous p.Glu38X

mutation

• Poor growth, short stature

• Generalized lipodystrophy,

hepato-splenomegaly, HTG,

acanthosis and hirsutism

• Diabetes mellitus – age 13

• Vitamin D resistance

• Amenorrhea - age 20

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CGL, Type 4• ~ 30 patients reported

• Generalized loss of fat

• Congenital myopathy, elevated serum creatine

kinase levels

• Percussion induced muscle mounding

• Congenital pyloric stenosis

• Long QT interval, arrhythmias, sudden death

• Atlanto-axial instability

Hayashi et al. J Clin Invest 119: 2623-33; 2009.

Shastry et al. Am J Med Genet 2010;152A:2245-53.

Rajab et al. Plos Genet 2010;6:e1000874.

PTRF mutations in CGL, type 4

• PTRF encodes polymerase I and transcript

release factor

• PTRF contributes to caveolae formation

• PTRF Induces expression of caveolins 1 and 3

• All reported mutations are null

• Loss of PTRF results in mislocalization of

caveolins in skeletal muscles

Hayashi et al. J Clin Invest 119: 2623-33; 2009.

Shastry et al. Am J Med Genet 2010;152A:2245-53.

Rajab et al. Plos Genet 2010;6:e1000874.

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Familial Partial Lipodystrophy

• SC fat loss from the extremities resulting in extreme

muscularity

• Fat accumulation in the neck, face & intra-abdominal

area

• Acanthosis nigricans

• Fasting or postprandial hyperinsulinemia

• Predisposition to DM, HTG and hepatic steatosis

• Low HDL cholesterol levels

Garg, A. JCEM, 2011 Nov; 96(11):3313-25

FPL

Molecular Basis

Subtype Gene

• FPL1 Unknown

• FPL2 LMNA

• FPL3 PPARG

• FPL4 PLIN1

• FPL5 AKT2

• FPL6 CIDEC

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Familial Partial Lipodystrophy, Type 2

(Dunnigan type)

www.lipodystrophy.info

Familial Partial Lipodystrophy, Type 2

(Dunnigan type)

• Autosomal dominant

• Prevalence < 1 in 10 million

• Described in ~ 300 patients

mainly of European ancestry

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Lamin A/C Mutations in FPLD

* Cardiomyopathy

† Emery-Dreifuss Muscular Dystrophy

‡ Limb Girdle Muscular Dystrophy

§ Mild Myopathy

¶ Mild Lipodystrophy

Garg A. N Engl J Med 350; 1220-34, 2004

Cao and Hegele. Hum Mol Genet 9:109-112, 2002

5' // // // 3'

1 2 3 4 75 6 8 10 11

16kb 2kb

129↑

R482Q

Structure of Nuclear Lamina

Garg A. N Engl J Med 2004:350; 1220-34.

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Pathogenesis of lipodystrophy in

FPLD patients

• LMNA mutations induce nuclear dysfunction

resulting in premature death or apoptosis of

adipocytes

• Why fat loss spares the face, neck and intra-

abdominal region?

Agarwal & Garg. JCEM 2002; 87: 408-11

Hegele et al. Diabetes 2002;51:3586-90

Savage et al. Diabetes 2003; 52:910-17

PPARG Mutations in FPL, type 3

Garg A. N Engl J Med 350; 1220-34, 2004

• PPARγ is essential

transcription factor for

adipogenesis

• Milder phenotype than

Dunnigan variety

• More fat loss from distal

extremities

• ~40 patients reported

15

FPL, type 4: PLIN1 mutations

• Perilipin 1 is required for optimal lipid incorporation

and release from the lipid droplets

• Three pedigrees reported with heterozygous null

mutations

• Partial lipodystrophy, severe dyslipidemia, and

insulin-resistant diabetes

• More uniform reduction in all fat depots

• Small-sized adipocytes

• Pattern of fat distribution remains unclear

Gandotra et al. NEJM 364, 740-8; 2011

• AKT2 encodes a phosphatidyl inositol -

dependent Serine-Threonine protein kinase

• Single family reported

• R274H heterozygous mutation in a pedigree

with lipodystrophy, DM and insulin resistance

• Pattern of fat loss unknown

• R274H mutation causes reduced fat

accumulation in 3T3-L1 preadipocytes

FPL, type 5: AKT2 mutations

George S, et al. Science 304; 1325-28, 2004

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Agarwal & Garg. Ann Rev Genomics Human Genet 7: 175-199, 2006.

Role of AKT2 in Insulin Signaling

P

P

P

P

P

P P85 P110

P1P2 P1P3

PH

Kinase Regulatory

P P

PDK1

GSK3β

FKHR

(Cell Survival Mode)

Active AKT2

(PKB)

Transcriptional Activation

(adipogenesis)

Insulin

Insulin receptor

P P P PP

Autosomal recessive FPL, type 6

(CIDEC mutation)

Vessels

Patient

Control

Perilipin Staining

Rubio-Cabezas et al. EMBO Mol Med 1: 280-287, 2009

• 19-y-old Ecuadorian girl

• Recurrent diabetic

ketoacidosis

• Homozygous p.E186X

mutation

• CIDEC required for

unilocular lipid droplet

formation

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Mandibuloacral Dysplasia (MAD)(Clinical characteristics)

• Skeletal abnormalities

– Mandibular and clavicular hypoplasia

– Acro-osteolysis

• Progeroid manifestations

– Cutaneous atrophy with prominent superficial vasculature and

mottled hyperpigmentation

– Thin beaked nose

– Hair loss

• Delayed dentition and closure of cranial sutures, crowded

teeth

• Joint stiffness

• Lipodystrophy: partial (type A) or generalized (type B)

Garg, A. JCEM, 2011 Nov; 96(11):3313-25

• Diabetes, glucose intolerance, insulin

resistance

• Mild hypertriglyceridemia and low levels of

HDL cholesterol have been reported in some

patients with MAD

Mandibuloacral Dysplasia(Laboratory characteristics)

Garg, A. JCEM, 2011 Nov; 96(11):3313-25

18

MAD

Molecular Basis

Subtype Gene

• MAD A LMNA

• MAD B ZMPSTE24

Role of ZMPSTE24 in Post-translational

Processing of Prelamin A

Agarwal et al. Hum

Mol Genet 12: 1994-

2001, 2003

19

Phenotypic Differences in MAD type A and B

with LMNA and ZMPSTE24 Mutations

MAD A

(LMNA)

MAD B

(ZMPSTE24)

Onset

Progeroid features

Premature at birth

SC calcified nodules

Focal segmental glomerulosclerosis

2-4 y

++

–

–

–

<2 y

+++

+

++

++

Ahmad et al. Am J Med Genet 2010;152A(11):2703-10

Mandibular Hypoplasia, Deafness and Progeroid (MDP) Syndrome

• Generalized loss of subcutaneous fat

• Mandibular hypoplasia

• Short stature

• Joint contractures

• Sclerodermatous skin with mottled pigmentation

• Hypogonadism and undescended testes in males

• Molecular genetic basis unknown

Shastry et al. JCEM 2010;95:E192-7.

20

Clinical FeatureMAD (LMNA)

n=28

MAD (ZMPSTE24)

n=8

MDP

n=7

Mandibular hypoplasia + + +

Sclerodermatous skin + + +

Lipodystrophy Partial Partial Partial/generalized

Clavicular hypoplasia + + -

Acro-osteolysis + + -

Deafness - - +

Undescended testes,

male hypogonadism- - +

Mandibular Hypoplasia, Deafness and Progeroid

(MDP) Syndrome

Shastry et al. JCEM 2010;95:E192-7.

Atypical Progeroid Syndrome due

to LMNA mutations

• Progeroid features

– Short stature, beaked nose, premature graying,

partial alopecia, high-pitched voice, skin atrophy

over the hands and feet

• Diabetes

• Partial or generalized lipodystrophy

• Skin pigmentation

• Mandibular hypoplasia

Garg et al. JCEM, 94(12), 4971-83 (2009)

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• Severe panniculitis-induced lipodystrophy (face, arms, thorax)

• No acanthosis nigricans or hyperinsulinemia

• Mild hypertriglyceridemia

• Low HDL cholesterol

• Mild elevations of liver enzymes

• Limb muscle atrophy, joint contractures (hands and feet)

• Microcytic hypochromic anemia

• Hypergammaglobulinemia

Garg et al. JCEM, 95, E58-63 (2010)

Joint Contractures, Microcytic Anemia, and Panniculitis-

induced (JMP) Autoinflammatory Lipodystrophy

PSMB8 mutations in JMP syndrome(Nakajo-Nishimura or Chronic atypical neutrophilic dermatosis with

lipodystrophy and elevated temperature [CANDLE] syndromes)

Agarwal et al. AJHG 2010;87:866-72.

Liu et al. (2012) Arthritis & Rheumatism, 64(3), 895–907

Kitamura et al. (2011) JCI, 121(10), 4150–4160

Arima K et al. (2011) PNAS, 108, 14914-14919

• PSMB8 encodes β5i subunit of immunoproteasomes

• Immunoproteasomes are induced by γ-interferon in

lymphoid tissues

• Abnormal processing of autoantigens for MHC-class

1 presentation

• Altered immune response to a common pathogen

triggering autoinflammation

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SHORT SyndromeAutosomal dominant and recessive

• Short stature

• Hyperextensibility of joints

• Ocular depression

• Rieger anomaly

• Teething delay

• Premature onset of DM

• Lipodystrophy

Neonatal Progeroid Syndrome(Wiedemann-Rautenstrauch)

• Premature birth

• Oligoohydroamnios and IUGR

• Dry, deeply wrinkled skin

• Large, low set ears, and beaked nose

• Generalized loss of SC fat sparing gluteal region

• Normal glucose and lipids

• 25 patients reported, early death

O’Neill et al . Am J Med Genet A. 2007;143A(13):1421-30

23

AGPAT,

Myocytes Osteoblasts

Mesenchymal

Stem cells

Pre-adipocyte

Fasting

Feeding

Adipocyte Mature adipocyte Cell Death

C/EBPβ

C/EBPδ

C/EBPα

PPARγ / RXRα

Transcription

factors?

Adipogenic factors

(Insulin, cortisol, etc.)SREBP1c Lipogenesis

(FAS, ACC,

GPAT, DGAT)

Apoptosis

(Lamin A/C,

ZMPSTE24)

Development Differentiation Death/Apoptosis

Interstitial tissue

(PSMB8)

Seipin/AKT2

LipodystrophiesDisorders of Adipose Tissue Development, Differentiation and Death

Garg, A. JCEM, 2011 Nov; 96(11):3313-25

Caveolin-1(PTRF)

ER

Caveolae

Lipid droplet

Caveolin vesicle

Perilipin1

CIDEC

Lamin A/C(ZMPSTE24)

Nucleus

Seipin

Nuclear Lamina

Glycerol-3-P

LPA

PA

Pi

DAG

TG

CoA

FA-CoAGPATs

AGPATs

PAPs

DGATs

CoA FA-CoA

MGATsMAG

CoA

FA-CoA

CoA

FA-CoA

Lipid droplet formation in adipocytes and lipodystrophy genes

Garg, A. JCEM, 2011 Nov; 96(11):3313-25

24

Lipodystrophy in HIV-infected patients

(LD-HIV)

• Loss of sc fat from the extremities and

face

• ↑ Fat deposition in the neck and

abdomen

• ↑↑ TG and ↓ HDL cholesterol

• ↑ Insulin levels

Lipodystrophy in HIV-infected Patients

(MRI images of fat distribution)

PI (-) PI (+)

Head and Neck

PI (-) PI (+)

Thigh

Calf

25

Risk Factors for Lipodystrophy in

HIV-infected Patients

• HIV-1 protease inhibitors (PIs)

• Nucleoside Reverse Transcriptase

inhibitors (NRTIs)

• Duration of HIV infection

• Others

– Aging

– Total body fat mass, nutritional status

– Previous viral load, AIDS

Lipodystrophy in HIV+ Patients

• Characterization of phenotype of PI-induced

lipodystrophy

• Characterize NRTI-induced fat loss and its

associations

• Identify molecular mechanisms underlying

these syndromes

• Development of new antiretrovirals not

associated with development of lipodystrophy

26

Acquired Generalized Lipodystrophy

• About 80 cases reported

• Onset in childhood or adolescence

• Female-to-male ratio: 3:1

• Autoimmune mechanism

Misra and Garg. Medicine 82:129-146, 2003

Panniculitis

Variety

(Type 1)

Autoimmune

Disease Variety

(Type 2)

Juvenile

Dermato-

myositis

Idiopathic Variety

(Type 3)

Acquired Generalized Lipodystrophy

Misra and Garg. Medicine 82:129-146, 2003

27

Variables

Panniculitis

Variety

Autoimmune Disease

Variety

Idiopathic

Variety

Acquired Generalized LipodystrophyClinical Features and Metabolic Abnormalities

* P < 0.05

M : F

Age (y)

Age of onset (y)

Prevalence of DM (%)

Age of onset of DM (y)

Acanthosis nigricans (%)

Hirsutism (%)

Hepatomegaly (%)

Hypertriglyceridemia (%)

Elevated ALT (%)

7 : 11

3 - 59

0.2 - 29

44*

15.8 ±11.4

45

50

71

59*

45

5 : 14

6 - 36

2 – 47*

89

18.8 ±10.0

61.5

33

100

87.5

82

9 : 33

2 - 60

0.6 - 28

87.5

15.8 ±9.1

63

55

84

91

56

Misra and Garg. Medicine 82:129-146, 2003

Acquired Partial Lipodystrophy

(Barraquer-Simons syndrome)

• Progressive fat loss from face, neck, trunk and arms

• Normal or excess fat in hips and legs

• Preceding viral infection

• Duration of fat loss - 18 months to 6 year

• ~250 patients reported

Misra et al. Medicine 83; 18-34, 2004

28

Acquired Partial Lipodystrophy

Age of Onset ~10 Years

Female to Male Ratio 4:1

Low Serum C3 72%

C3NeF Positive 83%

Autoimmune Diseases 11%

Membrano-proliferative

Glomerulonephritis (MPGN) 19%

Misra et al. Medicine 83; 18-34, 2004

Clinical Features of APL

Misra et al. Medicine, 83(1), 18-34, 2004

Variable n n

Age of onset (yr) 10 ± 9.3 32 10.4 ± 7.5 174

Reporting age (yr) 29.9 ± 16.4 35 24.8 ± 13.9 204

Female:male ratio 7.8:1 35 3.5:1 213

Diabetes (%) 13.6 22 11.8 68

Low serum complement 3 (%) 66.6 18 73.6 107

Positive serum complement 3

nephritic factor (%)83 6 83 81

Associated autoimmune disease (%) 20 35 9.1 220

MPGN (%) 3 35 27 166

Present Report Literature Review

29

Alternative Complement Pathway

Misra et al. Medicine 83; 18-34, 2004

Localized Lipodystrophies

• Drug-induced

• Pressure-induced

• Panniculitis

• Centrifugal

• Idiopathic

30

Lipodystrophies(When to suspect)

• “lean or nonobese” patients with:– Premature diabetes

– Insulin resistant diabetes

– Severe hypertriglyceridemia

– Hepatic steatosis

– Acanthosis nigricans

– Polycystic ovarian syndrome

Generalized Lipodystrophies(Differential Diagnosis)

• Malnutrition, starvation

• Anorexia nervosa

• Uncontrolled diabetes mellitus

• Thyrotoxicosis

• Adrenocortical insufficiency

• Cancer cachexia

• HIV-associated wasting

• Chronic infections

• Diencephalic Syndrome

31

Partial Lipodystrophies(Differential Diagnosis)

• Cushing’s syndrome

• Truncal obesity

• Multiple symmetric lipomatosis

(Madelung’s disease)

Conclusions• Adipose tissue serves an important role as an

endocrine organ

• Loss of adipose tissue either due to a genetic

or acquired disorders can lead to several

metabolic complications

• The resulting loss of adipocyte-derived

hormone leptin is a key contributor to

lipodystrophy associated insulin resistance

and lipotoxicity