The Effect of a Hypocaloric Diet Containing Olive Oil on Hepatic Steatosis Grading Using Tissue Elastography: A Randomized Controlled Trial

INTRODUCTION

Metabolic-associated fatty liver disease (MAFLD) , formly known as non-alcoholic fatty liver disease (NAFLD)is the most common chronic liver disease worldwide it is known as presence of hepatic steatosis in the absence of any secondary causes of hepatic fat accumulation [1].

In a high proportion of cases, MAFLD is related to "metabolic syndrome" (hyperglycemia, dyslipidemia, high blood pressure, and abdominal obesity) [1].

Peripheral insulin resistance affects carbohydrate and fat metabolism resulting in triglyceride (TG) accumulation in the liver. Resistance to insulin stimulation of glucose uptake via glucose transporter-4 by skeletal muscle and adipose tissue, in conjunction with the inhibition of lipolysis in adipose tissue by insulin, redirects glucose to the liver where the insulin continues to stimulate de novo lipogenesis and increase the flow of fatty acids from adipose tissue to the liver. This lead to increase consentration of TG in the liver. It is unclear how impairment in lipid export via very low density lipoprotein (VLDL) secretion, β-oxidation of free fatty acids (FFAs), or other metabolic pathways results in an inability to maintain fat balance, which leads to the development of fatty liver[2].

Dietary factors are thought to play a significant role in the development of MAFLD. The amount and type of dietary fat seem to affect fatty infiltration and lipid peroxidation in MAFLD, yet there is limited information on the effects of the type of dietary fat in MAFLD., the Mediterranean diet has  recently  gained attention as a diet that protect against MAFLD and cardiovascular disease. we known that olive oil is rich in monounsaturated fatty acids (MUFAs), olive oil responsible for the major part of the beneficial effects of the Mediterranean diet [3].‎

Hepatic steatosis can be assessed by using the Fibro Scan® device with the controlled attenuation parameter (CAP) facility. Ultrasound signals are attenuated by liver fat which can be measured using a conventional probe, giving a value between 100 and 400 dB/m [4].

The purpose of study was to determine the effect of a hypocaloric diet containing olive oil on hepatic steatosis grading using tissue elastography controlled attenuation parameter (CAP).

Patients‎ AND METHODS

This study was designed as a prospective open labelled randomized clinical trial. It was conducted at the Department of Tropical Medicine and Infectious diseases in Tanta University hospital from October 2018 to November 2019. Seventy- six patients with hepatic steatosis were enrolled, of these, 60 patients wererandomly divided into two groups: Group 1: 30 patients with hepatic steatosis on a hypocaloric diet including olive oil and Group 2: 30 patients with hepatic steatosis on an olive oil-free hypocaloric diet. Two patients in group 2 dropped out during follow up ( figure 1). The two groups were matched as regard physical activity and caffeine intake ( 1 cup /day).

Patients included in the study were 18 years of age or older, capable of giving an informed consent, with a BMI of 30-40 kg/m2 and diagnosed with hepatic steatosis by transient elastography (fibroscan®) (CAP)  (>222 dB/m).

None of the patients took mineral or multivitamin supplements or lipid reduction medications within 3 months before the study was included or consumed olive products last month before the trial was included.

Exclusion criteria: Patients with fibrosis, cirrhosis, alcoholic steatohepatitis, or increased liver enzymes, as well as patients with secondary causes of hepatic fat buildup (heavy alcohol intake). The study excluded individuals with liver diseases that cause steatosis, such as hepatitis C or B, Wilson disease, starvation, total parenteral nutrition, or bariatric surgery, as well as those taking specific medications (amiodarone, methotrexate, tamoxifen, corticosteroids, valproate, antiretroviral agents, or oral contraceptives). Individuals with diabetes mellitus or impaired glucose tolerance, hypothyroidism, pregnancy, breastfeeding, or who had a recent weight loss during the preceding six months were also excluded from the study.

At each visit, complete measurements were taken (height, weight, mid-arm circumference, waist circumference, and BMI) (at baseline, 3 months and 6 months from the beginning).

Determination of total daily calorie needs for weight loss: The total calories required to maintain weight for each patient was calculated by multiplying the appropriate activity factor by the basal metabolic rate(BMR) using the Harris Benedict Equation

For men :BMR = 10 x weight( kg) + 6.25 x height (cm) – 5 x age + 5

For women :BMR = 10 x weight( kg) + 6.25 x height (cm) – 5 x age -161. The required calories for maintenance decreased by 500 calories[5]. 

Determination of total daily amount of olive oil in the diet for patients from group 1:

Olive oil amount was calculated for each patient to provide 20% of the daily calories,considering that eachtablespoon of olive oil (14g) gives 120 kcal. The remaining 10% of daily fat calories were obtained from various sources, in keeping with the Mediterranean diet's emphasis on unsaturated fat, which accounts for around 30% of total calories. Each patient is prescribed a balanced eating plan that is unique to them. Patients were advised to take the olive oil first thing in the morning or to incorporate it into their salad.

   The BMI, calorie requirements, and daily consumption of olive oil were re-calculated at each follow up, and the patient was given a new diet plan.

In group 11 patients were received 10% of total fat as MUFA , 10% as PUFA , 9% saturated fat and 1% transfat.

The 2 groups were matched as regard percent of macronutrients. They received 50% carbohydrate and 20% protein.

There is weight reduction programs by diet modification

There is no any MAFLD affecting drugs as vitamin e, obeticholic acid , steroids , etc. used during the study

Patients were advised to walk for an average 20-30 min / day

Techniques of transient elastography (FibroScan™):

Patients were instructed to fast for at least four hours before examination (since liver stiffness increases significantly following food intake and acoustic radiation force impulse (ARFI) measures are best to be performed under fasting conditions).

To facilitate visualization of the liver's right lobe, patients were asked to lie either in the 30° lateral left or supine position. The right arm was raised above the head to increase the intercostal spaces, and patients were instructed to breathe calmly as deep inspiration and expiration results in an erroneous rise in liver rigidity due to increased central venous pressure.

Liver stiffness was calculated automatically in the selected area, the average of multiple measurements (at least 10 valid measurements) were obtained, and reported with the following criteria; ratio of number of valid measurements to the total number of measurements is ≥ 60% and the interquartile range (IQR), which reflects the variability of measurements, is less than 30% of the median value of liver stiffness measurements.

Examiner used the gel-covered convex ultrasonic elastographic probe in the sixth, seventh, and eighth intercostal spaces of the right liver, as well as the elastography image and quantification box 2-6 cm beneath the liver capsule. We must to confirm that no major blood vessels, gallbladder, or bile ducts were present in the examined area.

Statistical Analysis

Statistical analysis of the present study was done by SPSS V26  (IBM Inc., Chicago,IL,USA)

quantitative variables were presented as mean and standard deviation(SD) and compared between the two groups utilizing unpaired Student's t- test. Repeated measures ANOVA was used to compare measurements compared to baseline. Qualitative variables were presented as frequency and percentage and were analyzed utilizing Chi- square test or fisher's exact test when appropriate. A two tailed P value < 0.05 was considered statistically significant.

RESULTS:

A total number of 76 patients with hepatic steatosis were enrolled in this study and of these patients, 60 patients wererandomized to receive either a hypocaloric diet including olive oil or an olive oil-free hypocaloric diet.

Demographic baseline characteristics of patients of the studied groups were showed in (Table 1)

BMI showed an insignificant difference between both groups at baseline and after 3 months (P = 0.481 and 0.145) while after 6 months, there was a significant decrease in group 1 than in group 2 (P = 0.037) (Table 2)

Waist circumference in group 1 and 2 decreased significantly at 6 months (P <0.001) with no significant difference between both groups at baseline, after 3 months and after 6 months (P = 0.102, 0.286 and 0.512).

Mid-arm circumference in group 1 decreased significantly at 3 and 6 months (P = 0.043 and <0.001) while in group 2, it decreased insignificantly at 3 months but decreased significantly at 6 months (P <0.001). There was an insignificant difference between both groups at baseline, after 3 months and after 6 months (P = 0.269, 0.804 and 0.413). (Table 3)

Serum triglycerides in groups 1 and 2 decreased insignificantly at 3 months but at 6 months the decrease was statistically significant in group 1 (P = 0.006) while in group 2 it remained insignificant. However, on comparison between the two groups regarding serum triglyceride levels at baseline, 3 months and 6 months from starting the diet there was no significant difference (P = 0.756, 0.874 and 0.248 respectively) (table 5)

Serum cholesterol decreased insignificantly 3 months into the study among patients of both groups I and 2, but at 6 months, the cholesterol levels of group 1 decreased significantly (P <0.001) compared to the baseline levels. On the other hand, serum cholesterol in group 2 showed an insignificant difference at 6 months.

The difference in serum cholesterol levels between the patients from both groups was insignificant at baseline and after 3 months (P = 0.343 and 0.487) while after 6 months, the levels were significantly lower in group 1 (P = 0.017). (table 5)

HDL in group 1 decreased significantly at 3 and 6 months (P = 0.043 and <0.001) while in group 2, it showed an insignificant difference at 3 and 6 months compared to baseline.

CAP in group 1 and 2 decreased insignificantly at 3 months but became significantly lower at 6 months (P <0.001). CAP showed an insignificant difference between both groups at baseline and after 3 months (P = 0.906 and 0.120), while after 6 months, there was a more significant decrease in group 1 than group 2 (P = 0.017). The difference between baseline CAP measurements and at 6 months was significantly more in group 1 than group 2 (P = 0.012) (Table 4)

Table (2): Body mass index (BMI) (kg/m2) in both groups at baseline, 3 and 6 months of ‎inclusion in the study.

P1: P value in group 1 at 3 months compared to “baseline”; P2: P value in group 2 at six months ‎compared to the baseline; P3: Comparison between both groups at baseline; P4: Comparison between ‎both groups at 3 months; P5: Comparison between both groups at 6 months, *significant as p value < ‎‎0.05‎

Table (3): Waist circumference (cm) and mid-arm circumference (cm) in patients from both ‎groups‎.‎

P1: P value in group 1 at 3 months compared to “baseline”; P2: P value in group 2 at six ‎months compared to the baseline; P3: Comparison between both groups at baseline; P4: Comparison ‎between both groups at 3 months; P5: Comparison between both groups at 6 months, *significant as p ‎value < 0.05‎‎.

Table (4): Controlled attenuation parameter (CAP) (dB/m) in both groups‎.

P1: P value in group 1 at 3 months compared to “baseline”; P2: P value in group 2 at six months compared to the baseline; P3: Comparison between both groups at baseline; P4: Comparison between both groups at 3 months; P5: Comparison between both groups at 6 months, *significant as p value < 0.05.

 Table (5): Complete lipid profile in both groups.

DISCUSSION