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Association between serum triglycerides and brain mechanical properties in humans

Dyslipidemia, including elevated triglycerides (TGs) and reduced high‐density lipoprotein cholesterol (HDL‐C), is a well‐established clinical risk factor for cardiovascular disease (CVD). Higher consumption of added sugar is associated with production of TGs and has been linked to elevated risk of CVD. Age‐related memory loss shares many of the same risk factors as CVD, especially in mid‐life; however, the underlying mechanisms remain incompletely understood. Accordingly, the aim of this study was to examine the independent associations among serum TGs and the TG/HDL‐C ratio with brain integrity and memory in cognitively normal young and middle‐aged (MA) adults. We hypothesized that elevated TGs would be associated with reduced brain integrity, particularly in the hippocampus which is essential to memory performance and that these associations would be linked to dietary consumption of added sugar. All measures were performed in 27 healthy young to MA adults (12 F/15 M, mean age: 42±15 y; age range: 22–69 y; mean BMI: 26±4 kg/m2; mean BP: 114±9/70±11 mmHg). TG and HDL‐C levels were assessed from a 12‐hour fasted blood draw. Brain integrity was measured from the mechanical viscoelastic properties of the global brain as well as the hippocampus (HC) using magnetic resonance elastography (MRE). MRE data were acquired using a Siemens 3T Magnetom Prisma MRI scanner to image shear waves generated via a pneumatic actuator (Resoundant, Rochester, MN) at 50Hz. Global brain stiffness (GBS) and bilateral HC stiffness were estimated from the viscoelastic shear stiffness maps derived from MRE displacement data using a nonlinear inversion algorithm. Delayed recall memory was assessed using the California Verbal Learning Test (CVLT). Dietary intake was quantified from participant self‐report over 3‐days using the Nutrition Data System for Research (NDSR) software. Associations among TG, TG/HDL‐C ratio, GBS and HC stiffness and memory recall were performed using partial correlations correcting for age. Associations among added sugar, TGs and brain stiffness were assessed using linear regression. HC stiffness tended to be inversely associated with serum TGs (r=−0.36, P=0.07) and the TG/HDL‐C ratio (r=−0.38, P=0.05). Likewise, delayed recall memory tended to be negatively associated with elevated serum TGs (r=−0.36, P=0.07) and was inversely correlated with the TG/HDL‐C ratio (r=−0.42, P=0.03). In contrast, there were no associations between GBS and either serum TGs (r=−0.1, P=0.62) or the TG/HDL‐C ratio (r=0.03, P=0.89). Serum TGs tended to be positively associated with higher dietary intake of added sugar (r=0.37, P=0.05); however, added sugar intake was only associated with GBS (r=−0.40, P=0.04) and was not significantly associated with the reduction in HC stiffness (r=−0.14, P=0.49). Higher intake of added sugar leads to elevated serum TGs, which may be associated with early loss of cognitive function by affecting the integrity of brain regions integral to memory performance. Future studies should explore the mechanisms by which elevated serum TGs contribute to the loss of HC integrity in mid‐life and examine how these events contribute to future risk for age‐related mild cognitive impairment.