Diet Impact on Hepatic Transcriptomics and Lipidomics in Pre-diabetes

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, affecting 25% to 30% of the global population and nearly one third of the population in North America. NAFLD is defined as an excessive accumulation of lipids within hepatocytes in the absence of significant alcohol consumption or other causes of chronic liver disease. These patients usually present with hepatic steatosis observed on imaging studies and elevated liver enzymes with clinical features of insulin resistance (IR), including pre-diabetes, type 2 diabetes mellitus (T2DM), arterial hypertension, dyslipidemia, and visceral obesity. The minimum criterion for a histologic diagnosis of NAFLD is \>5 percent steatotic hepatocytes in a liver tissue section. The exact mechanism for the development of NAFLD is unclear, although the current evidence indicates that it is likely a complex interplay among neurohormones, intestinal dysbiosis, nutrition, and genetics. IR plays a crucial role in NAFLD pathophysiology mainly by increasing adipocyte lipolysis, resulting in the circulation of more free fatty acids available for hepatic uptake and increasing hepatic de novo lipogenesis. There is yet no approved pharmacologic option for the treatment of NAFLD. Current international guidelines on NAFLD emphasize the importance of lifestyle modifications for all patients with NAFLD and recommend 7-10% of weight loss and a "healthy diet", without suggesting any particular diet. Recent data provide some support for the beneficial role of low carbohydrate (CHO)/high unsaturated fatty acid (both monounsaturated (MUFAs) and polyunsaturated (PUFAs)) dietary patterns for decreasing hepatic steatosis. This proposal addresses this important research gap by leading to advances regarding the impact of a short-term low CHO/high PUFAs/MUFAs dietary intervention on improving hepatic gene expression profiles and lipid composition in individuals with pre-diabetes. The proposed study is unique because all meals and foods will be provided to participants under carefully controlled isocaloric conditions to maintain a constant bodyweight with optimal energy and macronutrient intake control. The primary objective of the proposed research is to investigate how replacement of dietary CHOs by unsaturated fatty acids (both PUFAs and MUFAs) affects liver fat composition and liver transcriptomics in subjects with pre-diabetes.

Inclusion Criteria: * Males and females 18 to 60 years of age. * Non-smoker * Waist circumference \> 102 cm for men and \> 88 cm for women. * Plasma triglyceride levels \> 1,7 mmol/L at the screening visit. * Fasting plasma glucose levels \> 6,1 mmol/L at the screening visit. * Fasting plasma insulin levels above the upper limit of normal at the screening visit. * Subjects must be willing to give written informed consent and able to adhere to the diet schedule and visit schedule. * Patients should be otherwise healthy, without abnormal renal function or coagulation. Exclusion Criteria: * Patients with extreme dyslipidemias, such as familial hypercholesterolemia will be excluded. * Subjects will be excluded if they have cardiovascular disease (CHD, cerebrovascular disease or peripheral arterial disease) or if they are taking other medications known to affect lipoprotein metabolism (eg. steroids, beta blockers, thiazide diuretics, other lipid lowering agents, significant alcohol intake etc.). * Subjects who are in a situation or have any condition that, in the opinion of the investigator, may interfere with optimal participation in the study. * Individuals with a history of mental instability, drug or alcohol abuse within the past 2 years or individuals who have been treated or are being treated for severe psychiatric illness that, in the opinion of the investigator, may interfere with optimal participation in the study. * Disorders of the hematologic, digestive, or central nervous systems, including cerebrovascular disease and degenerative disease, that would limit study evaluation or participation. * Known impairment of renal function (creatinine \>2.0 mg/dL), dysproteinemia, nephrotic syndrome, or other renal disease. * Subjects with coagulopathy (prothrombin time \[PT\] or partial thromboplastin time \[PTT\] at Visit 1 higher than 1.5 times control). * Patients who are known to have tested positive for human immunodeficiency virus (HIV). * Patients who have used any investigational drug within 30 days of the first clinic visit. * Diabetic patients are excluded from the study. Uncontrolled endocrine or metabolic disease known to influence serum lipids or lipoproteins. Clinically euthyroid subjects on replacement doses of thyroid hormone are eligible for enrollment.