Purpose

To quantitatively assess pancreatic fat content in patients with essential hypertension and to investigate the association of average fat fraction(FF) of pancreas with age, and hypertension duration using MRI-based noninvasive IDEAL-IQ.

Introduction

Essential hypertension is characterized by unexplained chronic hypertension, accounting for approximately 95% of patients with hypertension. Insulin resistance(IR) is an independent risk factor for essential hypertension, which is closely related to the occurrence, development and prognosis of essential hypertension. The extension of hypertension course aggravates IR [1]. Reaven[2] first proposed metabolic X syndrome as being a series of metabolic disorders related to insulin resistance in 1988, including hyperlipidemia, primary hypertension, and coronary heart disease. A vicious cycle involving insulin resistance and ectopic deposition of lipids occurs commonly[3-4]. Overproduction of Free Fatty Acids (FFAs) that exceeds the oxidative capacity of the tissues causes ectopic deposition of lipids and results in overspill of FFAs from fat tissue to non-fat cells, such as liver, heart, skeletal muscle and islet beta cells. Ectopic deposition of lipids can cause injury to the affected tissues, and thus, lead to IR. On the other hand, IR will further promote fat ectopic deposition as a positive feedback to form this vicious cycle. In recent years, relevant literatures revealed that IR is closely related to pancreatic fat infiltration, which may be a common manifestation of metabolic syndrome [5].Relevant studies showed that pancreatic fat infiltration can lead to poor prognosis of pancreatitis, pancreatic cancer and postoperative pancreatic fistula [6-8]. Therefore, the quantitation of pancreatic fat has important clinical significance. In this study, IDEAL-IQ is used to assess correlation between hypertension and pancreatic fat quantification.

Methods

A total amount of forty-four patients with essential hypertension were included in the present study. Inclusion criteria were as follows: 1) essential hypertension diagnosed in clinic, 2) with complete records of laboratory indicators and clinical parameters, including both clinical history and laboratory examination results, 3) IDEAL-IQ sequence included in upper abdomen MRI examination history and laboratory examination results, 4) MRI images were clear, 5) medium build. Exclusion criteria were as follows: 1) suspected secondary hypertension patients, 2) diabetes mellitue, 3) fatty liver, 4) evidence of alcohol consumption: ≥20 g alcohol/day for women and ≥30 g alcohol/day for men, 5) pancreatic lesions. Meanwhile, thirty healthy participants were included in the control group, whose age and gender were matched with that of patients with essential hypertension. Pancreatic lesions and fat liver were excluded according to the T1WI, T2WI and DWI images. Written consents were achieved from all participants in accordance with the guidance of our hospital ethical committee. 1.5T MRI scanner (GE 1.5t Signa HDXT, Milwaukee, United States) was used in the present study with an eight-channel phased-array body coil . The patients fasted for 4-6 hours and were trained to exhale and hold their breath for more than 20 seconds before scanning. The subjects were examined in the supine position. A three-plane localization imaging gradient-echo sequence was performed at the beginning of acquisition. All data were analyzed using SPSS Ver.19.0 (SPSS Inc., Chicago, IL, USA). A two-tailed P value less than 0.05 was considered to be statistically significant.

Results

The data measured by two independent radiologists were in good agreement. For all three regions, the average FF of the pancreas was significantly higher in the essential hypertension group compared with that in control group (Z= 5.841;P<0.05). Among all the participants, the average FF of the pancreas was weakly correlated with age (r=0.283, P<0.05). In patient group, the average FF of pancreas was moderately correlated with the duration of hypertension (r=0.558, P<0.05).

Conclusion

IDEAL-IQ technique corrects many confounding factors that interfere with fat quantification, such as T2* decay, fat peak distribution, and so on,Finally, to generate accurate fat fraction image and R2* map. It has been applied to quantitative analysis of fat in several parts of the body[9-10].IDEAL-IQ is a new way to evaluate the pancreatic fat quantification in patients with hypertension. The fat fraction of the pancreas in patients with hypertension is significantly higher than that in normal subjects,and the longer the length of the course of the disease is.

Acknowledgements

No acknowledgement found.

References

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