This document discusses ectopic fat deposition in non-adipose tissues and the concept of lipotoxicity. It begins by outlining the physiological roles of fat tissue and triglycerides in energy storage. It then discusses the negative effects of excess fat accumulation, describing how too much visceral fat is associated with metabolic complications. The document explores how lipid accumulation in the liver, muscles, pancreas and other tissues can impair organ function and insulin sensitivity through lipotoxicity. It examines the mechanisms of lipotoxicity and discusses lifestyle and pharmacological interventions that may help treat lipotoxicity and non-alcoholic fatty liver disease.

1. Mohamed Kamar
Professor Of Diabetes And Endocrinology
Faculty Of Medicine
Zagazig University
Aswan February 2012
ECTOPIC FAT

2. FAT AROUND THE BODY
IS IT ALL THE SAME?

3. FAT AROUND THE BODY
• Physiological role of fat----------
The Good
• Too much fat in fat tissue---------
The Bad
• Fat in non-fat tissue-----------------
The Ugly

4. PHYSIOLOGIC ROLE OF FAT: TRIGLYCERIDE
• Energy dense macromoloecules: 9 kcal/g
• Stored without water
• A 72 kg person has 12 kg fat =110,000 kcal= 60 days (vs 1
day from glycogen)
• 12 kg fat = 126 kg glycogen

5. • Triglycerides are stored
in specialized fat cells
(adipocytes)
• The adipose tissue is
not just a fat depot
PHYSIOLOGIC ROLES OF FAT: TRIGLYCERIDE

6. AdiposeAdipose
TissueTissue UnknownUnknown
FactorsFactors
Agouti proteinAgouti protein
RetinolRetinol
PAI-1PAI-1
LeptinLeptin
ASPASP
AngiotensinAngiotensin
ANG-IIANG-II
AdiponectinAdiponectin
AdipsinAdipsin
ResistinResistin
Bone Morphogenic ProteinBone Morphogenic Protein
IGF-1IGF-1
IGFBPIGFBP
TNF-TNF-αα InterleukinsInterleukins
TGFTGF ββ
FGFFGF
EGFEGF
Fatty AcidsFatty Acids
LysophospholipidLysophospholipid
LactateLactate
AdenosineAdenosine
ProstaglandinsProstaglandins
GlutamineGlutamine
EstrogenEstrogen
PHYSIOLOGIC ROLES OF FAT: TRIGLYCERIDE

7. TOO MUCH FAT IN FAT TISSUE
How much is too much?

9. TOO MUCH OF A GOOD THING IS BAD
Oral E: A Review Of Endocr Metab Disord 2003

10. ANDROID (APPLE) VS. GYNOID (PEAR) OBESITY
AA
TributeTribute
to ato a
PioneerPioneer
Jean Vague (1947)
Adapted from Vague J. Presse Med 1947; 30: 339–40
The amount of Visceral fat
determines the risk of
developing T2DM and
CVD

11. TOO MUCH FAT IN FAT TISSUE
• Functional consequences of regional differences
Large viscreal adipocytes:
• Enhanced secretion of FFA
• Lower capavity to stiore fat
• Altered adipokine secretion (leptin, adipnvectin, resistin,
viscefatin)
• Inflammation (TNFα. IL6)

12. 12
Wellen K and Hotamisligil G. J Clin Invest 2003; 112:1785
Wellen K and Hotamisligil G.
J Clin Invest 2003; 112:1785
Too Much Fat In Fat Tissue
Adipose tissue (AT) expansion during
weight gain leads to recruitment of
macrophages through local hypoxia.
These localize around dead
adipocytes and secrete inflammaiory
cytokines

13. THE UGLY
FAT IN NON-FAT TISSUE

14. LIPOTOXICITY
• LIVER Non-alcoholic steatohepatitis
• MUSCLE
• Skeletal (insulin resistance, major impact because the
muscle is the major site of insulin stimulated glucose
disposal)
• Cardiac muscle cardiomyopathy
• Pancreatic beta cells defective insulin secretion

15. Florence (Italy),
September 30 and October 1, 2005
15
NAFLD and NASH
Pure fatty liver
HCC
Fibrosis +
necroinflammation
Cirrhosis
N
A
F
L
D
NASHNASHNASHNASH
No fatNo fatNo fatNo fat
Time
25-30% of US adults
10%
30%
AASLD Single Topic Conference, Hepatology 2003

16. Florence (Italy),
September 30 and October 1, 2005
16
NAFLD - steatosis

17. Florence (Italy),
September 30 and October 1, 2005
17
NAFLD - steatonecrosis

18. DIAGNOSIS OF NAFLD & NASH
• Clinical findings
• Few clinical symptoms (upper right quadrant discomfort)
• Requires a high degree of clinical suspicion
• Laboratory
• May be associated with elevation of liver transaminases (ALT>AST)
• May NOT be associated with an elevation of ALT/AST
• Imaging
• U/S: (↑ echogenicity) 65-80% sensitivity for NAFLD
• Magnetic imaging streptoscopy
• Gold standard
• Very precise and reproducible measure of liver fat
• Restricted to research setting
• Liver biopsy: only way to make a diagnosis of NASH

19. 19
Glucose disposal in NAFLD
Sanyal et al. Gastroenterology 2001
5
10
15
CONT NAFLD NASH
Glucoseinfusion
(mgkg-1min-1)
CONT NAFLD NASH
10 mU kg -1
min -1
40 mU kg -1
min -1

20. Fat in the liver is inversely related
to
insulin sensitivity

21. LIFESTYLE INTERVENTION THERAPIES FOR NASH
• Lifestyle intervention/weight loss
• Reduce ALT, steatosis, less well proven for on
necroinflammation, fibrosis
• Need better standardization, RCTs
• Briatric surgery
• Shown in long-term trials to decrease diabetes and CVD
• In short-term studies, surgery improves histological parameters
in NASH
• Need better long-term RCTs

22. • Not effective
• Not effective
• Effective (PIVENS)
• Overall not effective
• Overall not effective
• Moderate efficacy
• Moderate efficacy
• Moderate efficacy
• Moderate efficacy
• Effective
• Ursodeoxycholic acid
• Pentoxyphilline
• Antioxidanta (vit E)
• Orlistat
• Lipid lowering agents (statins fibratem, omega-3
FA)
• Glucose lowerin agents
• Metformin
• Intensive insulin therapy (NAFLD)
• Exenatide added to insulin (NAFLD)
• Rosiglitazone
• Pioglitazone
PHARMACOLOGICAL INTERVENTIONS FOR NASH
Intervention Outcome
Adapted from Cusi K, Current Opinion Endo,diabetes, Obesity, 2009

28. EFFECT OF VTAMIN E, PIOGLITAZONE OR
PLACEBO IN PATIENTS WITH NASH
• PIVENS, NEJM, 2010. (247 non DM patients divided in 3 gps)
• Primary endpoint reached in
• 43% on vit E (p<0.01)
• 34% with PIO, 30 mg/d (<0.04)
• 18% with PBO
• Resolution NASH PIO 47%, vit E, 36%
• Similar response for low dose PIO and vitamin E

29. LIPOTOXICITY: SKELETAL MUSCLE
Hyperinsulinemic-euglycemic clamp and
intramyocellular lipid content
Morino K et al J Clin Invest 2004

30. Mitochondria
IMC Lipid
ECTOPIC FAT INFILTRATION
Muscle triglyceride:
obesity, insulin resistance
trained athletes

31. 31
Ectopic lipid storage and insulin resistance
IMCL (% H2O)
0
8
12
16
0.60
4
r = - 0.692
p < 0.002
0.84 1.08 1.32 1.56 1.80
Insulinsensitivity
(mg·kg-1
·min-1
)
Muscle
M. tibialis ant.
M. soleus
IMCL
IMCL
Anderwald et al. Diabetes 2002; 51:3025
0
2
4
6
8
10
0 10 20 30 40
Insulinsensitivity
(mg·kg-1
·min-1
)
HCL (% H2O)
r = - 0.598
p < 0.04
H2O
HCL
5 4 3 2 1 0 ppm
Liver
Krssak et al. Diabetologia 1999; 42:113
Extensor
Type IIa,b
Fast
Glycolytic
Flexor
Type I
Slow
Oxidative

32. 32
MUSCLE FAT AND INSULIN
RESISTANCE
SUMMARY
• Muscle lipids correlate variably with insulin resistance (IR) depending on
nutritional and excercise status.
• Increased availability of free fatty acids inhibits insulin signalling by
activating PKC/NFκB and serine phosphorylation of IRS-1. Consequently,
FFA decrease glucose transport and induce IR.
• Impaired lipid oxidation is required to raise intracellular availability of FFA
and IMCL in obesity.
• Reduced mitochondrial function is tightly associated with IR. Defective
muscle ATP synthesis might be responsible for hereditary IR or result from
increased availability of FFA in acquired (nutritional/obesity induced) forms
of IR.

33. LIPOTOXICITY: CARDIAC MUSCLE
Zhou Y-T et al Proc National Acad Science 2000

34. LIPOTOXICITY: CARDIAC MUSCLE

35. EXCESS FAT IN THE PANCREATIC
ISLETS

37. LIPOTOXICITY: PACREATIC BETA CELL
Unger RH Biochimie 2005
The Zucker diabetic fatty rat

38. LIPOTOXICITY: PANCREATIC BETA CELL
Unger et al PNAS 1999

39. Role Of Pancreatic Fat In Beta Cell
Dysfunction And Diabetes

40. Ildiko Lingvay: Lipids in and out of context OP Stockholm 2010

41. LIPOTOXICITY: MECHANISMS
•The hallmark of lipotoxicity is the accumulation
of fat in non-fat tissue
•But is fat the cause, or merely a marker?

42. THE PUZZLE OF TRAINED ATHLETES
• Triglycerides accumulate in the muscle tissue of highly
physically trained athletes, who demonstrate enhanced
insulin sensitivity.
• It has been suggested that muscle triglyceride may not have
adverse metabolic consequences in muscle that has the
capacity for efficient lipid utilization

43. GLUCOLIPOTOXICITY
• Either hyperglycemia alone or elevated circulating FFAs alone should not
be so detrimental to a cell
• When glucose levels alone are high, glucose is oxidized, and when FFAs
alone are high, then they are oxidized instead of glucose.
• FFAs are elevated during fasting, but are not toxic to cells under this low
glucose condition.
• When both glucose and FFA levels are high, FFA esters (FACoAs) are
high, and cannot be oxidized because glucose-derived malonyl-CoA is
also elevated.
• Excess Malonyl-CoA results from excessive glucose metabolism in
hyperglycemic hyperinsulinemic diabetic patients
• (Malonyl Co A -->↑FA synthesis & ↓FA oxidation)

44. Increased cellular levels of malonyl-CoA and FACoA as a common mechanism causing
glucolipotoxicity in various tissues in obesity-associated type 2 diabetes.
Prentki M et al. Diabetes 2002;51:S405-S413
Copyright © 2011 American Diabetes Association, Inc.

45. LIPOTOXICITY: MECHANISMS
• Triglyceride accumulation is a marker of fat overload
• The “lipotoxic” molecules are not the triglycerides
themselves but metabolites derived from fat, e.g.,
diglycerides, ceramide, etc…

46. LIPOTOXICITY :MECHANISMS
↑↑ Glucose
oxidation
↑↑
Malonyl
Co A
-
β−oxidation
↑↑ LC FA-
CoA
TG
DAG CERAMIDE
PKC PKB NFκB ROS NOS
Lipotoxicity

47. 47
Relationship between decrease in plasma FFA concentration
and increase in acute insulin response following acipimox
treatment
Paolisso et al. Diabetologia 1998; 41:1127
10 20 30 40
20
30
40
50
60
r = 0.64
p<0.001
Decreaseinplasma
FFAconc.(%)
Increase in acute insulin response (%)

48. LIPOTOXICITY IS IT TREATABLE?

49. DPP – DIABETES PREVENTION PROGRAM
• 3234 in 25 clinical centers with
• BMI >24 (>22 in Asians)
• IGT: FPG 95-125 mg/dl
or 2HPPG 140-199 mg/dl
Randomized to:
• Standard lifestyle + metformin
• Standard lifestyle + placebo
• Intensive Lifestyle Intervention: 7% weight reduction and 150 min
of exercise/wk
• Primary outcome: progression to DM on annual OGTT or
semiannual FPG ≥126 mg/dl or 2HPPG≥200 mg/dl
The DPP Research Group. NEJM 2002; 346: 393–403

50. 0 1 2 3 4
0
10
20
30
40
Years from randomizationYears from randomization
Cumulativeincidence(%)Cumulativeincidence(%)
Placebo (n=1082)Placebo (n=1082)
Metformin (n=1073, p<0.001 vs. PlaceboMetformin (n=1073, p<0.001 vs. Placebo))
Lifestyle (n=1079, p<0.001 vs. Metformin, p<0.001 vs. PlaceboLifestyle (n=1079, p<0.001 vs. Metformin, p<0.001 vs. Placebo))
Incidence of diabetesIncidence of diabetes
Risk reductionRisk reduction
31% by metformin31% by metformin
58% by lifestyle58% by lifestyle
The DPP Research Group. NEJM 2002; 346: 393–403

51. LIPOTOXICITY IS IT TREATABLE?
• Tuomelehto NEJM, 2001
• FINNISH DIABETES PRVENTION STUDY GROUP
• 522 subjects with IGT randomized to a control group and an
intervention group with 5% weight loss and 30 minutes of
exercise daily
• Risk of diabetes reduced by 58%

52. A CENTRAL ROLE FOR AMP KINASE
• Highly sensitive metabolic sensor
• Ubiquitously expressed
• Modulates the activity of numerous proteins and
metabolic pathways

53. LIPOTOXICITY IS IT TREATABLE?
Exercise Leptin Adiponectin TZD Metformin
↑ AMPK
↓ Malonyl CoA
↓ LC CoA
↑ FA oxidation
↑ FA esterifiication
↓ Ceramidesynthesis
↓ Lipolysis
↑ Glucose transport
↓ NFκB ↓ Oxidative stress
Adapted from Rudermam and Pentki, Nature Reviews, Drug Discovery, 2004

54. CONCLUSION I
• Fat is good but too much of a good thing is bad
• Too much fat in fat tissue is bad especially in visceral adipose
depots
• Lipotoxicity affects many tissues
• Skeletal muscle insulin resistance
• Cardiac muscle cardiomyopathy
• Liver NASH and insulin resistance
• Pancreatic beta cell defective insulin secretion ( in the
presence of concomitant hyperglycemia)

55. CONCLUSION II
• Ectopic accumulation of fat is a marker but probably not a
mechanism of lipotoxicity
• Non-oxidative lipid metabolites affect a number of signaling
pathways and tissue function that underlie the mechanisms
of lipotoxicity
• Shifting lipid metabolism toward oxidation may represent a
viable therapeutic option
• AMPK plays a central role in metabolic sensing and is an
attractive therapeutic target

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57. Thank You