Hippocampal Subfield Volumes in Middle-Aged Adults at Risk of Dementia.

BACKGROUND: Alzheimer's disease (AD) begins decades before the onset of dementia. There is a need to investigate biomarkers of early AD for use in clinical trials and to facilitate early intervention. OBJECTIVE: We aimed to determine whether changes in hippocampal subfield volumes in healthy middle-aged adults were associated with risk of future dementia. METHODS: We included 150 participants from the PREVENT-Dementia cohort, which recruited subjects aged 40-59 with or without a family history of dementia (FHD; included here were 81 with FHD and 69 without). Hippocampal subfield volumes were segmented from high resolution T2-weighted 3T MRI images taken at baseline and 2-year follow-up. RESULTS: FHD and greater 20 year-risk of dementia due to cardiovascular risk factors were both associated with lower CA1 volume. FHD was also associated with a relative increase in combined CA3, CA4, and dentate gyrus volume between baseline and follow-up. CONCLUSION: CA1 atrophy may commence as early as middle-age in those with a high risk of future dementia, while increases in CA3, CA4, and dentate gyrus volume may be a response to early AD in the form of inflammation or neurogenesis.

Increased colonic propionate reduces anticipatory reward responses in the human striatum to high-energy foods.

BACKGROUND: Short-chain fatty acids (SCFAs), metabolites produced through the microbial fermentation of nondigestible dietary components, have key roles in energy homeostasis. Animal research suggests that colon-derived SCFAs modulate feeding behavior via central mechanisms. In humans, increased colonic production of the SCFA propionate acutely reduces energy intake. However, evidence of an effect of colonic propionate on the human brain or reward-based eating behavior is currently unavailable. OBJECTIVES: We investigated the effect of increased colonic propionate production on brain anticipatory reward responses during food picture evaluation. We hypothesized that elevated colonic propionate would reduce both reward responses and ad libitum energy intake via stimulation of anorexigenic gut hormone secretion. DESIGN: In a randomized crossover design, 20 healthy nonobese men completed a functional magnetic resonance imaging (fMRI) food picture evaluation task after consumption of control inulin or inulin-propionate ester, a unique dietary compound that selectively augments colonic propionate production. The blood oxygen level-dependent (BOLD) signal was measured in a priori brain regions involved in reward processing, including the caudate, nucleus accumbens, amygdala, anterior insula, and orbitofrontal cortex (n = 18 had analyzable fMRI data). RESULTS: Increasing colonic propionate production reduced BOLD signal during food picture evaluation in the caudate and nucleus accumbens. In the caudate, the reduction in BOLD signal was driven specifically by a lowering of the response to high-energy food. These central effects were partnered with a decrease in subjective appeal of high-energy food pictures and reduced energy intake during an ad libitum meal. These observations were not related to changes in blood peptide YY (PYY), glucagon-like peptide 1 (GLP-1), glucose, or insulin concentrations. CONCLUSION: Our results suggest that colonic propionate production may play an important role in attenuating reward-based eating behavior via striatal pathways, independent of changes in plasma PYY and GLP-1. This trial was registered at clinicaltrials.gov as NCT00750438.

Short term arterial remodelling in the aortae of cholesterol fed New Zealand white rabbits shown in vivo by high-resolution magnetic resonance imaging - implications for human pathology.

High-resolution, non-invasive imaging methods are required to monitor progression and regression of atherosclerotic plaques. We investigated the use of MRI to measure changes in plaque volume and vessel remodelling during progression and regression of atherosclerosis in New Zealand White rabbits. Atherosclerotic lesions were induced in the abdominal aorta by balloon injury and cholesterol feeding. MR images (2D) of the abdominal aorta were acquired with cardiac and respiratory gating using a fast spin echo sequence with and without fat-suppression. In an initial study on rabbits treated for 30 weeks we imaged the aortae with a spatial resolution of 250x250 micrometers with a slice thickness of 2 mm and achieved a close correlation between MRI-derived measurements and those made on perfusion pressure-fixed histological sections (r(1) = 0.83, slope p(1) < 0.01). We subsequently imaged 18 rabbits before and periodically during 12 weeks of cholesterol feeding (progression) followed by 12 weeks on normal diet (regression). Aortic wall (atherosclerotic lesion) volume increased significantly during progression and decreased during regression. In contrast, lumen volume increased during progression and did not change during regression. In conclusion, this study confirms that non-invasive, high-resolution MRI can be used to monitor progression and regression of atherosclerosis, each within 3 months and shows, for the first time in a short-term model, that positive remodelling occurs early during progression and persists through regression of atherosclerotic lesions.

Validation of MRI measurement of cardiac output in the dog: the effects of dobutamine and minoxidil.

The use of magnetic resonance imaging (MRI) for the measurement of cardiac output parameters in anesthetized adult male beagle dogs has been validated against a widely accepted thermodilution method. Using a multislice cine gradient echo MRI method to acquire images of the entire heart, left ventricular lumen volumes were measured at systole and diastole in seven animals. Cardiac output correlated well (R 2 = 0.88) with thermodilution measurements made in a parallel manner, both before and during acute stimulation with the inotrope dobutamine. In a chronic study of changes in cardiac morphology and function brought about by the antihypertensive minoxidil, MRI reliably detected the expected increases in stroke volume (28%) and cardiac output (58%) resulting from neural reaction to decreased blood pressure. Left ventricular lumen enlarged as well in response to fluid retention and plasma volume increase. Two in four minoxidil-treated animals also developed clear MRI-visible pericardial effusion.

Effect of the TRPV1 antagonist SB-705498 on the nasal parasympathetic reflex response in the ovalbumin sensitized guinea pig.

BACKGROUND AND PURPOSE: Nasal sensory nerves play an important role in symptoms associated with rhinitis triggered by environmental stimuli. Here, we propose that TRPV1 is pivotal in nasal sensory nerve activation and assess the potential of SB-705498 as an intranasal therapy for rhinitis. EXPERIMENTAL APPROACH: The inhibitory effect of SB-705498 on capsaicin-induced currents in guinea pig trigeminal ganglion cells innervating nasal mucosa was investigated using patch clamp electrophysiology. A guinea pig model of rhinitis was developed using intranasal challenge of capsaicin and hypertonic saline to elicit nasal secretory parasympathetic reflex responses, quantified using MRI. The inhibitory effect of SB-705498, duration of action and potency comparing oral versus intranasal route of administration were examined. KEY RESULTS: SB-705498 concentration-dependently inhibited capsaicin-induced currents in isolated trigeminal ganglion cells (pIC50 7.2). In vivo, capsaicin ipsilateral nasal challenge (0.03-1 mM) elicited concentration-dependent increases in contralateral intranasal fluid secretion. Ten per cent hypertonic saline initiated a similar response. Atropine inhibited responses to either challenge. SB-705498 inhibited capsaicin-induced responses by ∼50% at 10 mg·kg⁻¹ (oral), non-micronized 10 mg·mL⁻¹ or 1 mg·mL⁻¹ micronized SB-705498 (intranasal) suspension. Ten milligram per millilitre intranasal SB-705498, dosed 24 h prior to capsaicin challenge produced a 52% reduction in secretory response. SB-705498 (10 mg·mL⁻¹, intranasal) inhibited 10% hypertonic saline responses by 70%. CONCLUSIONS AND IMPLICATIONS: The paper reports the development of a guinea pig model of rhinitis. SB-705498 inhibits capsaicin-induced trigeminal currents and capsaicin-induced contralateral nasal secretions via oral and intranasal routes; efficacy was optimized using particle-reduced SB-705498. We propose that TRPV1 is pivotal in initiating symptoms of rhinitis.