This short-term, randomized, placebo-controlled, investigator-initiated trial aims to establish metabolic improvements in NAFLD subjects by dietary supplementation with cofactors N-acetylcysteine, L-carnitine tartrate, nicotinamide riboside and serine. Concomitant use of pivotal metabolic cofactors via simultaneous dietary supplementation will stimulate three different pathways to enhance hepatic β-oxidation and this study's hypothesis is that this will result in decreased amount of fat in the liver.

In this study, investigators aim to lower liver fat content in obese patients with NAFLD by increasing the hepatic levels of pivotal metabolic cofactors via simultaneous dietary supplementation of serine, L-carnitine, N-acetylcysteine (NAC) and nicotinamide riboside (NR).

The study is based on a three-step strategy to increase the amount of fat oxidization in liver: (1) First, the investigators will include L-carnitine to enhance the transport of fatty acids across the mitochondrial membrane (by forming a long chain acetylcarnitine ester and being transported by carnitine palmitoyltransferase (CPT) I and CPT II). Carnitine also plays a role in stabilizing coenzyme A (CoA) and acetyl-CoA levels through the ability to receive or give an acetyl group. (2) Second, the investigators will include nicotinamide riboside, precursor of nicotinamide adenine dinucleotide (NAD+) to boost the level of hepatic β-oxidation of fatty acids in mitochondria. Decreased electron transport chain function combined with impaired rates of fatty acid β-oxidation leads to the accumulation of incomplete products of β-oxidation, which combined with increased levels of reactive oxygen species (ROS) contribute to insulin resistance. Furthermore, as L-carnitine, nicotinamide

riboside stimulate the transfer of fatty acids from cytosol to mitochondria.(3) Finally, they will include the two glutathione precursors serine and N-acetylcysteine to increase glutathione levels in the hepatocytes. Increased glutathione levels will also protect against free radical-mediated oxidative stress generated by the increased β-oxidation of fatty acids in mitochondria.

Previous studies showed that each agent is able to decrease liver fat amount separately and a proof-of-concept study using serine supplementation, and a phase I study using this three-step approach resulted in a significant decrease in plasma metabolites associated with liver fat without significant side effect. Concomitant use of pivotal metabolic cofactors via simultaneous dietary supplementation will stimulate three different pathways to enhance hepatic β-oxidation. The novel design with this study is to give the L-carnitine, NR, serine and NAC as a cocktail. Based on investigators' hypothesis is that this will result in decreased amount of fat in the liver.

The study population will consist of 45 male and female adult overweight and obese subjects diagnosed with NAFLD. Eligible subjects must have signed an informed consent, meet all inclusion criteria and have none of the exclusion criteria. Patients will be randomized on a 2:1 basis to the cofactor mixture or placebo.

The subjects will take a mixture of cofactors or matching placebo as powder dissolved in water by mouth. Subjects in active treatment will receive dietary supplementation with N-acetylcysteine, L-carnitine tartrate, nicotinamide riboside, and serine, administered as a mixture. Half dosage of the co-factors will be given for two weeks (one dose taken just after dinner), and full dosage for 8 weeks (two equal doses taken just after breakfast and dinner). Patients who can tolerate the study agents will start to take half dose of co-factors supplementation (i.e., 1 dosage daily just after dinner) for two weeks.

The active treatment duration will be 10 weeks for each subject and the total study duration is estimated as 14 months. The study comprises seven clinical visits; (1) pre-screening visit, (2) screening visit, (2) randomization visit, (3) post-treatment visit (day 14); (4) post-treatment visit (day 28); (5) post-treatment visit (day 42) and (4) end of treatment visit (day 70). At visit 1 informed consent will be signed, all procedures including clinical and physical examination, assessment of inclusion and exclusion criteria, genetic analysis and transient elastography will be done. At visit 2 and visit 7, all procedures including review of 3-day diet records, clinical and physical examination; body composition analysis with Bioelectrical Impedance Analysis (BIA), ECG evaluation, blood, urine and stool sampling for routine laboratory tests, lipidomics, metabolomics and gut microbiota analysis and magnetic resonance imaging and MR spectroscopy will be carried out. At visit 3, eligible study subjects will be randomized to active therapy or placebo groups and study agents will be dispensed as half-of therapy. At visit 4, and 6, clinical and physical examination, ECG evaluation, blood, urine and stool sampling for routine laboratory tests, lipidomics, metabolomics and gut microbiota analysis, magnetic resonance imaging and MR spectroscopy and initiation of full dose therapy (i.e. taking cocktails two times just after breakfast and dinner) will be realized. At visit 5, visit 4 and 6 will be repeated excluding magnetic resonance imaging and MR spectroscopy. After the visit 7, participants will stop taking study agents.

A subject will be considered as having completed the study if he/she has completed all assessments at the End of Treatment Visit (Visit 7) and has been followed up until 10 weeks after initiation of the study drugs.

Statistics for the primary outcome parameter will be tested by Mann-Whitney U test or t-test depending on the results of normality test. For the secondary and third outcome parameters one-way repeated measures ANOVA will be performed.

Inclusion Criteria:

• Men and women (18-70 years old)
• Body mass index >27kg/m2
• Triglyceride levels ≤354 mg/dl and LDL chol ≤175 mg/dl
• No history of medication use for hepatic steatosis
• Increased liver fat (>5.5%)

Exclusion Criteria:

• Inability or unwillingness to give written informed consent

• Systolic blood pressure >160 mm Hg and/or diastolic blood pressure > 105 mm Hg

• Type 1 or type 2 diabetes

• Chronic liver disease other than NAFLD (i.e. chronic infection with hepatitis C virus [HCV] or hepatitis B virus [HBV], autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, Wilson s disease, alpha-1 antitrypsin deficiency).

• Previous gastric or small bowel surgery

• Active gastric ulcer

• Inflammatory bowel disease

• ALT or AST >3× ULN (upper limit of normal)

• Detection of cirrhosis by transient elastography or other imaging modalities

• Diarrhea (defined as more than 2 stool per day) within 7 days before enrollment

• Chronic kidney disease with an estimated glomerular filtration rate <60 ml/min/1.73m2

• Significant cardiovascular co-morbidity (i.e. heart failure, documented coronary artery disease, valvular heart disease)

• Patients with active bronchial asthma

• Patients with phenylketonuria (contraindicated for NAC)

• Patients with histamine intolerance

• Clinically significant TSH level outside the normal range (0.04-6 mU/L)

• Known allergy for substances used in the study

• Concomitant medication use:

  1. Lipid-lowering drugs within 3 months
  2. Oral antidiabetics given for insulin resistance of obesity (metformin, liraglutide etc.) within 3 months
  3. Thiazide diuretics with a dose >25 mg/d
  4. Postmenopausal estrogen therapy
  5. Any medication acting on nuclear hormone receptors or inducing Cytochromes P450 (CYPs)
  6. Self-administration of dietary supplements such as any vitamins, omega-3 products, or plant stanol/sterol products within 1 month
  7. Treatment with medications known to cause fatty liver disease such as atypical neuroleptics, tetracycline, methotrexate or tamoxifen
  8. Use of an antimicrobial agent in the 4 weeks preceding randomization

• Active smokers consuming >10 cigarettes/day

• Alcohol consumption over 192 grams for men and 128 grams for women per week

• Patients considered as inappropriate for this study for any reason (patients unable to undergo MRI study, noncompliance etc.)

• Subjects with Patatin-like phospholipase domain-containing protein 3( PNPLA3) I148M (homozygous for I148M)

• Women who are pregnant, are planning pregnancy, or who are breast-feeding

• Women of childbearing potential not protected by effective birth control method

• Active participation in another clinical study