Abstract
Consumption of red raspberries has been reported to exert acute beneficial effects on postprandial glycemia, insulinemia, triglyceridemia, and cytokine levels in metabolically disturbed subjects. In a two-arm parallel-group, randomized, controlled trial, 59 subjects with overweight or abdominal obesity and with slight hyperinsulinemia or hypertriglyceridemia were randomized to consume 280 g/day of frozen raspberries or to maintain their usual diet for 8 weeks. Primary analyses measured metabolic differences between the groups. Secondary analyses performed with omics tools in the intervention group assessed blood gene expression and plasma metabolomic changes following the raspberry supplementation. The intervention did not significantly affect plasma insulin, glucose, inflammatory marker concentrations, nor blood pressure. Following the supplementation, 43 genes were differentially expressed, and several functional pathways were enriched, a major portion of which were involved in the regulation of cytotoxicity, immune cell trafficking, protein signal transduction, and interleukin production. In addition, 10 serum metabolites were found significantly altered, among which β-alanine, trimethylamine N-oxide, and bioactive lipids. Although the supplementation had no meaningful metabolic effects, these results highlight the impact of a diet rich in raspberry on the immune function and phospholipid metabolism, thus providing novel insights into potential immune-metabolic pathways influenced by regular raspberry consumption.
Highlights
Both clinical and epidemiological studies highlight the contribution of a plant-food-predominant diet in the maintenance, or even the improvement, of metabolic homeostasis owing to its fiber and phytochemical contents [1]
To be included in the study, subjects had to be men or pre-menopausal women, Caucasian, aged between 18 to 60 years, have a body-mass index (BMI) between 25 and 40 kg/m2 or a waist circumference ≥ 94 cm for men and ≥80 cm for women, as well as meet at least one of the following criteria: Plasma triglycerides (TG) > 1.35 mmol/L, or insulin concentration > 42 pmol/L, using our new analytic method and corresponding to a threshold value of 60 pmol/L with the former method that was predictive of a higher risk of cardiovascular disease in the Quebec population [26]
Findings from two recent studies indicated that acute Rb supplementation, with daily consumptions of 125 and 250 g, may lower postprandial hyperglycemia, hypertriglyceridemia, and inflammatory response (IL-6 and TNF-α), as well as SBP when extended for four weeks, in diabetic or prediabetic individuals [20,21]
Summary
Both clinical and epidemiological studies highlight the contribution of a plant-food-predominant diet in the maintenance, or even the improvement, of metabolic homeostasis owing to its fiber and phytochemical contents [1]. It has been demonstrated that dietary habits are difficult to change over the long term [6], highlighting the need to identify simple nutritional interventions that increase the fiber and phytochemical contents of the diet. In this regard, growing evidence has supported the role of berry fruits in the prevention and management of metabolic disorders [7]. Among the most commonly consumed berries, red raspberry (Rb; Rubus idaeus L.) is low in sugar and rich in both fiber and phenolic compounds, mostly anthocyanins, and ellagitannins [8]
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