Gene Polymorphisms and Carbohydrate Diets James M. Ntambi Ph.D
Fatty Acids that Flux into Tissue Lipids are from Dietary Sources or are Made De novo from Glucose or Fructose Glucose Fructose Acetyl-CoA ACC Malonyl-CoA FAS Diet Palmitate (C16:0) ElovI6 Stearate (C18:0) Diet SCD Palmitoleate (C16:1 9) Oleate (C18:1 9) GPAT AGPAT2 Lipin DGAT GPAT AGPAT-2 WS LRAT DGAT ACAT AGAT TG PL WE RE CE ADG
The Stearoyl-CoA Desaturase (SCD) Reaction CoA S O 9 10 Stearoyl-CoA NAD(P)H+H + Cytochrome b 5 reductase (FADH 2 ) 2 cytochrome b 5 Fe 2+ O 2 SCD NAD(P) Cytochrome b 5 reductase (FAD) 2 cytochrome b 5 Fe 3+ 2H 2 O CoA S O 9 10 Oleoyl-CoA
Mouse has 4 and Human has 2 SCD Gene Isoforms
Inducers Glucose Fructose Insulin Cholesterol LXR Agonists Vitamin A Vitamin D Growth hormone Estrogen Androgen Peroxisome proliferators Low temperature Iron TGF-β KGF β-amyloid Repressors PUFA (w-3, w6) Leptin Thyroid Hormone Glucagon TZDs Dehydroepiandrosterone Cadmium TNF-α
??? 16 12 8 4 0 0 10 20 30 Time of feeding (h)
Fold change in mrna 25 20 15 10 5 SCD1 actin 0 Diabetic contro 24 hour trilinolenin triarachidonin + insulin
Fructose Induces SCD1: PUFAs Repress 30 Fold change in mrna 25 20 15 10 5 SCD1 actin 0 Diabetic contro 24 hour trilinolenin triarachidonin + frucose
18:1/18:0 Ratio vs. Diet Low-carbohydrate diet High-carbohydrate diet
Desaturation Ratio in FCHL Subjects
Fatty Acids that Flux into Tissue Lipids are from Dietary Sources or are Made De novo from Glucose or Fructose Glucose Fructose Acetyl-CoA ACC Malonyl-CoA FAS Diet Palmitate (C16:0) ElovI6 Stearate (C18:0) Diet SCD Palmitoleate (C16:1 9) Oleate (C18:1 9) GPAT AGPAT2 Lipin DGAT GPAT AGPAT-2 WS LRAT DGAT ACAT AGAT TG PL WE RE CE ADG
Gene Knockout Technology produced SCD1-/- mice which look leaner but weigh more than SCD1+/+ Mice (At the University of Wisconsin-Madison) SCD1-/- mice 24.9 grams SCD1+/+ mice 22.6 grams
SCD1 Deletion Prevented HF and CHO- Induced Weight Gain: Mice Hyperphagic 50 45 40 35 30 25 20 15 8week old 3 6 9 12 Feeding (wk WT-LF WT-HF SCD1 KO-LF SCD1 KO-HF Food intake (g/g BW/day) 0.25 0.2 0.15 0.1 0.05 0 Food Intake WT-LF WT-HF SCD1 KO-LF SCD1 KO-HF
Lipids from Liver of SCD1 / Mice Fed CHO + Oleate / Chow / CHO / CHO + 18:1 Cholesterol ester Triglyceride Cholesterol
Mouse models of obesity Ob/ob (B6) Leptin deficient Hyperphagic Insulin resistant Agouti obese (A y /a) (B6) Expresses leptin Hyperphagic Leptin and Insulin resistant Diet-induced obesity (DIO) (B6) 60% kcals from fat (32% by weight) 16 wk feeding Leptin and Insulin Sampath, Miyazaki & Ntambi et al., (unpublished)
SCD1 Deficiency Prevents Liver Steatosis: Reduced VLDL Production Sampath, Miyazaki & Ntambi et al.
SCD1 Deficiency Completely Prevents Leptin Resistance-induced Adiposity and Liver Enlargement Growth curve (n=12~18) **p<0.001 vs WT, #p<0.005 vs Agouti
SCD1 Deficiency Completely Prevents Leptin Resistance-induced Adiposity Weight of adipose tissue (n=12~18) **p<0.001 vs WT, #p<0.005 vs Agouti
Skin SCD1 deficiency protects agouti mice against insulin and leptin resistances A Gluocse tolerance test B Leptin tolerance test (n=5~7) #p<0.01 vs Agouti mice
SCD1 Conditional Knockout 1 2 3 4 5 6 Cre-Recombinase 1 2 4 5 6 = loxp site Liver Adipose Albumin Cre Muscle SCD1 flox/flox Skin Brain FABP4 Cre Liver Creatine Kinase Cre K14 Cre Nestin Cre Adipo/Liver Cre
Challenge Lox and LKO with Lard and High Carbohydrate Diets
LKO Blocked CHO-induced Lipogenesis: Rescued by Oleate not Saturated Fat
SREBP and Lipogenic Enzymes in Liver of SCD1 -/- Mice Fed a High Fructose Diet (A) SCD1 +/+ +/+ Diet Chw Fru Fat Feeding Period 7d SREBP-1 SCD1 FAS ACC FK 2.3 16.3 9.8 13.3 +/+ / / Fru Chw Fru 18:1 7d 7d 3.6 15.3 14.0 16.8 / Fru 18:1 2d / Fru 18:1 7d 4.3 3.5 7.0 / Fru 18:0 7d (C) SCD1 +/+ +/+ Diet Chw Fru Fat SREBP-1 FAS ACC rrna / Chw / Fru / / / Fru Fru Fru 16:0 18:218:1 1.9 3.5 12.3 3.8 10.5 6.2 2.8 3.0 2.2 2.8 2.4 Aldolase B 3.3 3.0 3.3 3.2 3.8 3.3 rrna (B) SCD1 Diet Fat Feeding Period psrebp-1 msrebp-1 psrebp-2 (D) +/+ +/+ +/+ / / / / / SCD1 +/+ +/+ / Chw Fru Fru ChwFru Fru Fru Fru Diet Chw Fru Chw 18:1 18:1 18:1 18:0 Fat 7d 7d 7d 2d 7d 7d msrebp-1 1.8 1.8 4.0 6.7 5.3 / Fru / / / Fru Fru Fru 16:0 18:218:1 4.6 3.3 msrebp-2
Liver steatosis is Reduced on HCHO, but not on Lard Diet LOX LKO Chow HF HC
Carbohydrate-Induced Lipogenesis
Glucose + Glucose High Fat L I P O G E N E S I S High carbohydrate- Induced Lipogenesis Pyru ChREBP Acetyl-CoA Malonyl-CoA 16:0 18:0 16:1 18:1 ACC FAS LCE SCD GPAT AGPAT-2 Lipin DGAT TRIGLYCERIDES VLDL HMG-CoA synthase HMG-CoA reductase GPAT AGPAT-2 PL, CL Pgc1-b SREBP1c WE WS CHOLESTEROGENESIS ADG GPAT SREBP2 Oxysterols LXR Pgc1-b Pgc1-b Cholesterol storage CHOLESTERYL ESTER VLDL excretion Bile acids
FUNDING SOURCES NATIONAL INSTITUTES OF HEALTH (NIDDK) AMERICAN HEART ASSOCIATION UNITED STATES DEPARTMENT OF AGRICULTURE STEENBOCK ENDOWED PROFESSORSHIP