"Fatty acid dysregulation in NAFLD" Studying the fasting to fed state transition. Outline

Transcription

1 "Fatty acid dysregulation in NAFLD" STOPNASH Symposium on the Origins and Pathways of Nonalcoholic Steatohepatitis October 7, 25 Elizabeth J Parks, PhD, FAHA Division of Gastroenterology/Hepatology Department of Nutrition/Exercise Physiology University of Missouri School of Medicine Columbia, MO Studying the fasting to fed state transition The ability to appropriately fast is maintained in obesity and insulin resistance. The metabolism that causes disease occurs at the transition from the fasting to fed state. Outline Lipogenesis in health subjects and those with insulin resistance: - effect of sugars - circadian patterns Is liver energy metabolism limited in NAFLD? Changes in fatty acid fluxes with weight loss in NAFLD A case study of weight loss

2 Liver- fatty acid sources, fluxes, and fates Intestine 2 Chylomicron Dietary sugars de novo lipogenesis hepatic lipid droplets Liver 3 fatty acid fatty acid Muscle synthesis Lipoprotein assembly FFA FFA H VLDL Adipose Liver s synthesis of de novo fatty acids from dietary CHO Meal Meal 2 de novo lipogenesis (%) Time (h) Continuously fed Elevated lipogenesis: Obesity, insulin resistance, diabetes Schwarz, AJCN, 23 Marques-Lopes, AJCN, 2 VLDL de novo fatty acids (%) 2% High-fat diet P<.5 High-CHO diet 5% % 5% % Lean Obese Obese Lean Obese Normal Normal HyperIns Normal HyperIns Ins Ins Ins 8% CHO test meal 53% sucrose 27% lactose BMI = 3.8 kg/m 2 BMI = 2.8 kg/m 2 Vedala, JLR, 26 Day Day 2 Obese non-db Obese Db Fractional DNL (%) Hudgins, JLR, 2 Lean controls clock time meals 2

3 lipogenesis in healthy subjects Constant, elevated lipogenesis In Caucasian NAFLD patients 3% 3% 2% 2% % % % % meal meal Timlin, Db 27 Donnelly, JCI 25 NAFLD Clinical Trial A study of subjects with a wide range of liver fat and insulin sensitivities To determine the relationships between nutrient metabolism during the fasted and fed states and liver (and whole body) fatty acid flux. Determine the metabolic mechanisms that reduce liver fat during weight loss. Subject characteristics Glucose (mg/dl) Insulin (mu/l) Low IH 9.3 ± ± 4 High IH 98. ± 4.4 ± 4 P-value No of subjects 3 IH (%) 3. ± ± 3.6 <. BMI (kg/m 2 ) 35.3 ± ± Body weight (kg) 2.9 ± ± Body fat (%) 39.7 ± ± FFA (mmol/l).57 ±.5.66 ±.2.6 (mg/dl) ± 5 34 ± HOMA.67 ± ±..24 SI ( -4 * min - per U/mL) 3. ± ±.4.36 ALT (U/L) 47 ± ±

4 TRL- from lipogenesis Higher de novo lipogenesis in NAFLD. Less suppression with fasting. 4% 35% 3% 25% 2% 5% % 5% % 4 PM PM Time * * ** * * NAFLD Obese control Significantly lower than AM * de novo lipogenesis and dietary sugars 5 Lipogenesis (% of TRL- fatty acids) P =. Dietary total sugars 2. ±.3% Dietary total sugars 5.6 ±.8% P =.3 Low IH High IH Outline Lipogenesis in health subjects and those with insulin resistance: - effect of sugars - circadian patterns Is liver energy metabolism limited in NAFLD? Changes in fatty acid fluxes with weight loss in NAFLD A case study of weight loss 4

5 The role of mitochondrial energy metabolism Chylomicron HGP Dietary sugars de novo lipogenesis fatty acid hepatic lipid droplets fatty acid synthesis FFA FFA H VLDL Current controversy Few mitochondria in NAFLD? More mitochondria, but dysfunction? ROS? Liver TCA cycle activity 2 P =.2 Hepatic TCA cycle flux mol / kg BM / min Low IH High IH Sunny/Parks, Cell Metabolism, 2 5

6 Is mitochondrial activity limiting in NAFLD? Dietary- fatty acids Adipose Glucose Glucose GNG Lipogenesis ER/Golgi FACoA FACoA -oxidation TCA cycle ATP Liver Cell VLDL Ketones Hepatic TCA cycle flux mol / kg BM / min NAS score 3 2 r =.7, P = % IH Sunny/Parks, Cell Metabolism, 2 Fasting hepatic substrate fluxes in humans Iozzo, AJG, 2 C-palmitate infused, quantitated by PET FA mol/min ml liver Yes, energy generation is limited Cortez-Pinto 3 P-MRS ATP recovery after fructose in biopsy-proven NASH compared to leaner controls Perez-Carreras in vitro ETC, biopsy mito resp chain activity lower in NASH Schmid 3 P-MRS Flux thru ATP syn lower in T2DM (not NAFLD) No, energy metabolism is not limited Sanyal in vitro ox from biopsies in NASH Sunny U- 3 C-propionate, NMR in hepatic TCA cycle activity Iozzo Miele 3 C-palmitate, PET in hepatic FAO in obesity (not NAFLD) 3 C-8: breath test cumulative ox in NASH compared to controls Plasma HB concentrations as a biomarker? just don't do it 6

7 Hepatic energy metabolism NAS Sunny Sanyal Miele Cortez-Pinto Perez-Carreras Iozzo in hepatic FAO in obesity Roden and colleagues T2DM has lower liver metabolism Koliaki and Roden, Mol Cell Endo, 23 Outline Lipogenesis in health subjects and those with insulin resistance: - effect of sugars - circadian patterns Is liver energy metabolism limited in NAFLD? Changes in fatty acid fluxes with weight loss in NAFLD A case study of weight loss Phase metabolic tests Phase 2 Weight loss and follow-up Consent & Screening IVGTT tests +/- Liver biopsy NMR Study Liver- by H-MRS Glucose and ketone metabolism, and TCA cycling GC/MS Lipid Study Liver- fatty acid sources Fasting / fed lipogenesis Adipose metabolism Follow-up Tests IVGTT NMR glucose/ketones Weight stability Clinic visits Dietary Therapy Weight stability GC/MS lipid study +/- Liver biopsy Time in months 7

8 Changes due to caloric restriction BW (kg) P < Insulin Sensitivity P =.3 4. > 2.5 normal Post Wt-Loss Post Wt-Loss Liver- by MRS 6% 4% 2% % 8% 6% 4% 2% %.9 % P = % Post Wt -Loss < 5.6% normal Plasma ALT (U/L) P =.6 2 Post Wt-Loss < 3 U/L normal n=25, mean ± SEM Fasting and fed concentrations Glucose (mg/dl) Evmeal Lunch 2 Post weight loss resting/sleeping FFA (mmol/l) Evmeal Lunch Insulin (uu/ml) Plasma (mg/dl) Hours relative to midnight Hours relative to midnight VLDL Sources (mmol/l).4 Obese Control NAFLD DNL FFA EvMeal.35.3 Treatment P-value Treatment P-value P =.42 PostWL.524 PostWL 8

9 Outline Lipogenesis in health subjects and those with insulin resistance: - effect of sugars - circadian patterns Is liver energy metabolism limited in NAFLD? Changes in fatty acid fluxes with weight loss in NAFLD A case study of weight loss Case Study: Subject #8 33 yo Hispanic female Body weight = 68.8 kg BMI = 3.8 kg/m 2 Body fat = 4.7 % W:H =.99 Liver fat = 27.3 % Glucose = 93 mg/dl Insulin = mu/l HbAc = 6.2 % Ins Res (DI 992) ALT = 63 mu/l Subject #8 Histology. Histology Trichrome 2x Mild pericellular fibrosis adjacent to central veins. Ballooning degeneneration of hepatocytes. central vein Trichrome 2x Post-Wt loss Body weight: kg Liver fat: 27.3%.8% Plasma ALT: 63 U/L Nash Score: Ins Res (DI 992) Ins Res (DI 947) Plasma mg/dl 2 2. Follow-up Histology Trichrome 2x Healthy liver demonstrating resolution of steatosis and fibrosis. central vein Trichrome 2x 9

10 Summary Metabolic derangments of the fasted to fed state transition lead to the development of disease. These preliminary data suggest that the metabolic environment of the liver in metabolic syndrome is characterized by an increase in lipogenesis from sugars. Weight loss significantly lowers liver fat content. It can do so by improving all of these pathways to reduce the burden of fatty acids in the liver. Of the 22 outcomes measured, the primary improvement in patients regressing their liver fat was a significant reduction in hepatic de novo lipogenesis. Parks Lab moto, "Panta Rei" ~ all things are in flux ~ Appreciation goes to the research subjects who volunteered their time. University of Missouri Qiong Hu, PhD Miriam Jacome-Sosa, PhD Nhan Le, BS Army of Undergrads Camila Manrique, MD John Thyfault, PhD Paul Fadel, PhD Daniel Credeur, PhD Robert Restaino, MS Charla Jay, RN Drew Jett, PharmD Heather Leidy, PhD Lana Merrick, BS CRC nurses and staff UTSW Jennifer Lambert, PhD Shawn Burgess, PhD Jeff Browning, MD Jay Horton, PhD Lilly Research Labs Sudha Shankar, MD Funding R DK887 5PLDK883 CTRC: Grant Number UL RR24982 ADA grant Environmental weight loss strategy