Influence of a Mediterranean Diet Combined With a Physical Activity Intervention, on NAFLD and Inflammation Parameters.

BACKGROUND Chronic liver diseases are among the main causes of morbidity and mortality. Increasing liver disease mortality has been associated with increasing prevalence of NAFLD. The term "fatty liver disease" is the hallmark of NAFLD and refers to a fat deposit in liver cells greater than 5% that is not related to alcohol intake, viral infections, or drug use. Hepatic steatosis is an independent risk factor for all liver alterations that characterize NAFLD and, in particular, inflammation and fibrosis.

The percentage of NAFLD tends to increase with increasing BMI, Age, Presence of metabolic diseases such as dyslipidemia, Type 2 diabetes.

The following are involved in the onset and progression of NAFLD:

• insulin resistance
• generalized inflammation;
• intestine-liver pathways
• intestinal microbiota. In the absence of officially approved pharmacological therapies for the treatment of NAFLD, the guidelines recommend lifestyle-based interventions, both in quantitative and qualitative terms in diet and increased physical exercise. Diet can improve NAFLD by reducing the amount of liver fat and insulin resistance, while exercise promotes weight loss and improves liver function.

Limiting calorie intake in diets, reducing alcohol consumption, and reducing consumption of highly processed foods have proven to be the most important factor in the management of NAFLD.

Regarding the Mediterranean diet, although there are studies demonstrating its effectiveness in improving NAFLD, there are no publications that have examined which Mediterranean diet model is best for NAFLD with regards to macronutrient content. In the Mediterranean diet, carbohydrates are mainly supplied by foods rich in fiber and with a low glycemic index or low glycemic load, while lipids are mainly supplied by foods rich in monounsaturated fatty acids (mainly olive oil) and polyunsaturated fatty acids (mainly dried fruit, fish and vegetables). It is not known whether variations in the proportion of carbohydrates and lipids, which characterize the Mediterranean diet, can favorably or unfavorably influence the development of NAFLD and NASH.

It has been shown that physical exercise, reduces the amount of liver fat and this change is associated with changes in body weight and cardiorespiratory capacity.

Recent studies suggest that changes in the gut microbiota may represent a new strategy to prevent or treat NAFLD.

A recent prospective study observed that NAFLD is associated with a 20% increased risk of developing irritable bowel syndrome (IBS), a disease characterized by abdominal pain and bloating, frequent diarrhea or prolonged constipation, often alternating periodic.

Since NAFLD and IBS share changes in circulating levels of proinflammatory cytokines, increased (TNF)-α, interleukin (IL)-6, and decreased IL-10, alterations in the intestinal barrier, and alterations in intestinal motility, one cannot exclude that improvement or worsening of NFLD could influence improvement or worsening of IBS.

Inflammation associated with obesity may in turn play a significant role in the development of gastrointestinal disorders. It is a chronic state of low intensity that involves the entire organism. Obesity is related to an increase in inflammatory cytokines in tissues that activate immune responses, altering cellular metabolic pathways. Chronic low intensity inflammation and the variation in the concentration of metabolic hormones, together with the distribution of adipose tissue in the abdominal cavity and alterations in the bacterial populations of the intestinal microbiota, represent the main factors involved in the development of gastrointestinal diseases. Pathologies that develop precisely through alterations of the intestinal barrier. When evaluating the integrity of the intestinal barrier, it is important to consider zonulin, a GI peptide capable of modulating the functionality of tight junctions.

Serum zonulin levels have been shown to correlate with the extent of damage to the mucosal barrier. Cellular and/or TJ damage can impact proper leaky gut function. I-FABPs are cytosolic proteins present in epithelial cells responsible for the transport of fatty acids and are released into circulation following the loss of membrane integrity and eliminated in the urine and represent a non-invasive marker of damage at the epithelial level intestinal.

Alterations in the barrier function can favor the entry of bacteria and their products. Lipopolysaccharide (LPS) has been found to influence barrier function. Under physiological conditions, LPS is unable to cross intact epithelium, but in the presence of reduced epithelial integrity it is able to cross the gastrointestinal barrier.

Tryptophan, an essential amino acid for humans, is catabolized by commensal bacteria into various derivatives, which are absorbed by the intestine and eliminated in the urine. Two of these compounds, indole and skatole, are currently used to diagnose dysbiosis of the small intestine and colon, respectively.

CLINICAL STUDY DESIGN The study, conducted on patients with both obesity (BMI > 30.0) and NAFLD (diagnosed by FLI (fatty liver index) and/or Fibroscan will be a two-arm interventional study, with nutritional and increased physical exercise. The enrolled patients, who meet the inclusion criteria, will be randomly assigned to one of the two study arms and will be asked to follow a personalized diet based on anthropometric characteristics, following the percentage of macronutrients in their arm. All patients will be asked to follow a low-calorie diet, with ¾ of the calories of an isocaloric diet. The exercise program administered to patients will be the same for everyone. Having established common criteria for patient recruitment (presence of obesity and NAFLD), type of low-calorie diet (3/4 of an isocaloric diet) and type of physical exercise, patients will be enrolled and randomly assigned to the two intervention arms. Arm 1 involves a low-calorie diet, meeting the criteria of the Mediterranean diet, with the following percentage of macronutrients: carbohydrates 50% of total calories, lipids 30%, proteins 20%; Arm 2 involves a low-calorie diet, meeting the criteria of the Mediterranean diet, with the following percentage of macronutrients: carbohydrates 30% of total calories, lipids 50%, proteins 20%.

The exercise will be structured and organised. An effective prescription includes an exercise program that is systematically designed and personalized in terms of frequency, intensity, time, type, volume and progression.

Frequency. Physical activity (walking) will be carried out outdoors on an urban route 3 times a week, on non-consecutive days, for 12 weeks.

Intensity. The intensity of the exercise (50/75% of max HR) Type. The type of exercise is moderate aerobic with a speed ranging from 5 to 10 km/h.

Time. Outing lasting 60 minutes The treatment will last 3 months and, in addition to the V0 (Screening Visit), a further 3 visits are planned (V1-V2-V3).

Patients with obesity (BMI > 30.0) and NAFLD, who are not stably taking drugs, will be considered potentially eligible for enrollment.

At V0 potentially enrollable patients, will undergo:

• Anamnesis;
• Fibroscan, to assess the degree of hepatic steatosis;
• Survey of anthropometric characteristics
• Bioimpedance examination;
• Body composition assessment by DEXA
• Delivery of the accelerometer to the patient, on loan for use for the next 7 days.
• Completion of IPAQ-SF and sports history. If the inclusion criteria are met, the enrolled patients will be invited to return for V1, after 7 days to receive the dietary plan and will be asked to complete two questionnaires assessing gastrointestinal symptoms, Irritable Bowel Syndrome - Severity Scoring System (IBS-SSS), specific to IBS symptoms, and Gastrointestinal Symptom Rating Scale (GSRS), which evaluates gastrointestinal symptoms more generally. Patients will also be asked to complete the Morningness-Eveningness Questionnaire (MEQ-SA). Intestinal characteristics will be assessed using the Bristol scale before, during and after the intervention period.

At V1 patients will also undergo a blood sample via venipuncture. They will be asked to bring two stool samples for the evaluation of intestinal microbiota, fecal zonulin and fecal metabolome. You will also be asked to bring two urine samples. Stool and urine samples will be requested for each visit (V1-V2-V3) Microbiome characterization will be performed using a DNA metabarcoding and metatranscriptomics approach. DNA metabarcoding analysis will be conducted using the V5-V6 hypervariable regions of 16S rRNA for bacteria (MiSeq-Illumina platform). The samples found to be significant in the DNA metabarcoding analysis will be subjected to metatracryptomic analysis (NextSeq 500 platform - Illumina). Metagenomic and metatracryptomic data will be analyzed using bioinformatics pipelines.

Metabolomics examinations will be performed on stool and urine samples. Barrier peptide assay: assays of faecal and serum Zonulin, as well as I-FABP, DAO and circulating LPS in serum will be performed using commercially available ELISA methods.

Dosage of indole and skatole in urine: indole is dosed with a colorimetric analytical method while skatole is determined with a chromatographic method with fluorometric detection on urine collected early in the morning. When urinary indole and skatole values exceed the normal threshold they express fermentative (in the small intestine) and putrefactive (in the colon) dysbiosis respectively.

During V1 patients will also be given a GI Symptom Diary to fill in until the next visit, as well as for subsequent visits.

Additionally there will be:

• Muscle strength measurement test: HandGripp test;
• Test for measuring physical performance: SPPB;
• Dynamic balance test: (TGUG, Time Get Up and Go test)
• 2 km walking test.
• Sit and Reach Test Finally, four questionnaires will be administered to assess levels of anxiety, depression and stress. Specifically, the Hospital Anxiety and Depression Scale (HADS) and Perceived Stress Scale (PSS), the Rotter Locus of Control Scale (Q_LOC), and the Delaying Gratification Inventory (DGI).

Patients will be recalled after 45 days (V2) and 90 days (V3).

During these visits they will be subjected to:

• blood sampling by venipuncture;
• GSRS questionnaire;
• IBS-SSS questionnaire;
• Detection of anthropometric characteristics;
• Bioimpedance test

In V3 alone, patients will also undergo:

• Completion of the HADS questionnaire (Hospital Anxiety and Depression Scale);
• Completion of the PSS (Perceived Stress Scale) questionnaire;
• Completion of Rotter's locus of control scale (Q_LOC) questionnaire
• Completion of the Delaying Gratification Inventory (DGI) questionnaire.
• Test for measuring muscle strength HandGripp Test;
• Test for measuring physical performance: SPPB;
• Dynamic balance test: (TGUG, Time Get Up and Go test)
• 2-Km Walking Test.
• Sit and Reach Test The blood sample taken at the V1-V2-V3 examinations will be used for the dosage of routine haematochemical parameters and nutritional, metabolic and cardiovascular risk parameters (Glycaemia, insulin glycated haemoglobin, triglycerides, total cholesterol, HDL and LDL cholesterol, transaminases (AST and ALT), γGT, creatininemia, uricinemia, blood count, ferritin, 25-OH-vitamin D, calcemia, IGF-I, TSH, FT3, FT4, proBNP). Based on the results, the degree of insulin resistance (HOMA index) and the degree of hepatic steatosis FLI, (fatty liver index) will be calculated, based on anthropometric (BMI, abdominal circumference) and haematochemical (triglycerides and γGT) parameters.) and liver fibrosis (FIB-4).

Major adipokines (leptin, adiponcetin, RBP-4, resistin, visfatin, chemerin), major hepatic growth factors (HGF, Fetuin-A, FGF21, FGF19, PAI-1), major pro-inflammatory cytokines (high-sensitivity C-reactive protein, IL-6, IL-8 and TNF-α) and anti-inflammatory cytokines (IL-4) will also be measured.