Ectopic and Visceral Fat Deposition in Lean and Obese Patients With Type 2 Diabetes

Abstract

Background: Type 2 diabetes (T2D) and obesity are associated with nonalcoholic fatty liver disease, cardiomyopathy, and cardiovascular mortality. Both show stronger links between ectopic and visceral fat deposition, and an increased cardiometabolic risk compared with subcutaneous fat.

Objectives: This study investigated whether lean patients (Ln) with T2D exhibit increased ectopic and visceral fat deposition and whether these are linked to cardiac and hepatic changes.

Methods: Twenty-seven obese patients (Ob) with T2D, 15 Ln-T2D, and 12 normal-weight control subjects were studied. Subjects underwent cardiac computed tomography, cardiac magnetic resonance imaging (MRI), proton and phosphorus MR spectroscopy, and multiparametric liver MR, including hepatic proton MRS, T1- and T2*-mapping yielding "iron-corrected T1" [cT1].

Results: Diabetes, with or without obesity, was associated with increased myocardial triglyceride content (p = 0.01), increased hepatic triglyceride content (p = 0.04), and impaired myocardial energetics (p = 0.04). Although cardiac structural changes, steatosis, and energetics were similar between the T2D groups, epicardial fat (p = 0.04), hepatic triglyceride (p = 0.01), and insulin resistance (p = 0.03) were higher in Ob-T2D. Epicardial fat, hepatic triglyceride, and insulin resistance correlated negatively with systolic strain and diastolic strain rates, which were only significantly impaired in Ob-T2D (p < 0.001 and p = 0.006, respectively). Fibroinflammatory liver disease (elevated cT1) was only evident in Ob-T2D patients. cT1 correlated with hepatic and epicardial fat (p < 0.001 and p = 0.01, respectively).

Conclusions: Irrespective of body mass index, diabetes is related to significant abnormalities in cardiac structure, energetics, and cardiac and hepatic steatosis. Obese patients with T2D show a greater propensity for ectopic and visceral fat deposition.

Keywords: diabetic cardiomyopathy; epicardial fat deposition; fatty liver disease; magnetic resonance imaging; magnetic resonance spectroscopy.

Central Illustration

The Role of Fat Deposition in Type 2 Diabetes: Examples of ¹H-MRS, and Transaxial Liver ShMOLLI T₁ Map in a Healthy Volunteer, a Lean Patient With T2D, and an Obese Patient With T2D (A) Proton magnetic resonance spectroscopy (¹H-MRS) of healthy volunteer with hepatic triglyceride (TG) 2.5%. (B)¹H-MRS of lean patient with type 2 diabetes (T2D) with hepatic TG 7.6%. (C) Obese patient with T2D with hepatic TG 16.1%. (D) Healthy volunteer with liver Shortened Modified Look-Locker Inversion recovery (ShMOLLI) T₁ map with corrected T₁ (cT₁) 748 ms. (E) Lean patient with T2D with liver ShMOLLI T₁ map with cT₁ 772 MS. (F) Obese patient with T2D with liver ShMOLLI T₁ map with cT₁ 1244 ms. BMI = body mass index.

Figure 1

Study Protocol for Patients With T2D Suitability of patients with type 2 diabetes (T2D) was assessed during the first hospital visit. Those patients who consented to have a cardiac computed tomography (CT) scan were then invited for the second hospital visit. The third hospital visit included magnetic resonance imaging (MRI) and magnetic resonance spectroscopy scans (3T). Multiparametric liver MRI included proton magnetic resonance spectroscopy (¹H-MRS) for hepatic triglyceride; T₁ and T₂* mapping yielded iron-corrected T₁ (cT₁). This was followed by cardiac magnetic resonance, which included cine imaging to assess left ventricular (LV) volumes, mass, and ejection fraction; myocardial tagging for assessment of peak circumferential systolic strain and diastolic strain rate; cardiac ¹H-MRS for myocardial triglyceride; and late gadolinium enhancement (LGE) imaging for exclusion of myocardial scarring. Control subjects underwent identical MRI protocols. ³¹P-MRS = phosphorus magnetic resonance spectroscopy; ECG = electrocardiogram; HLA = horizontal long axis; PCr/ATP = myocardial phosphocreatine to adenosine triphosphate concentration ratio; SA = short axis.

Figure 2

Representative Examples of CT Epicardial Fat Volumes in a Lean and an Obese Patient With T2D (Top) Lean patient with T2D with epicardial fat volume 37.75 cm³. (Bottom) Obese patient with T2D with epicardial fat volume 192.59 cm³. Abbreviations as in Figure 1.

Figure 3

Differences in Cardiac Function, Hepatic Steatosis, and Hepatic cT₁ Among the Study Cohorts (A) Peak circumferential systolic strain; (B) diastolic strain rate; (C) hepatic triglyceride content (%); and (D) hepatic corrected T₁ map (ms). The dots indicate values outside the interquartile range. Abbreviations as in Figure 1.