The acute effects of inulin and resistant starch on postprandial serum short-chain fatty acids and second-meal glycemic response in lean and overweight humans

Abstract

Background/ObjectivesColonic-fermentation of dietary-fibre to short-chain fatty-acids (SCFA) may protect against obesity and diabetes, but excess production of colonic SCFA has been implicated in the promotion of obesity. We aimed to compare the effects of two fermentable-fibres on postprandial SCFA and second-meal glycaemic response in healthy overweight or obese (OWO) vs lean (LN) participants.Methodsusing a randomized cross-over design, 13 OWO and 12 LN overnight fasted participants were studied for 6h on 3 separate days after consuming 300mL water containing 75g glucose(GLU) as control or with 24g inulin(IN) or 28g resistant-starch(RS). A standard lunch was served 4h after the test-drink.ResultsWithin the entire group, compared to control, IN significantly increased serum SCFA (p<0.001) but had no effect on FFA or second-meal glucose and insulin responses. In contrast, RS had no significant effect on SCFA but reduced FFA rebound (p<0.001) and second-meal glucose (p=0.002) and insulin responses (p=0.024). OWO had similar postprandial serum SCFA and glucose concentrations but significantly greater insulin and FFA than LN. However, the effects of IN and RS on SCFA, glucose, insulin and FFA responses were similar in LN and OWO.ConclusionsResistant-starch has favorable second-meal effects, likely related to changes in FFA rather than SCFA concentrations. However, a longer study may be needed to demonstrate an effect of RS on SCFA. We found no evidence that acute increases in SCFA after IN reduce glycaemic responses in humans, and we were unable to detect a significant difference in SCFA responses between OWO vs LN subjects.

Review article: short chain fatty acids as potential therapeutic agents in human gastrointestinal and inflammatory disorders

“…It has been estimated that 36% of colonic‐derived acetate becomes systemically available, in contrast to only 9% of propionate and 2% of butyrate . In healthy subjects, fasting levels of acetate in peripheral blood have been reported to rise from a mean of 54 to 169 μmol/L, 6‐8 h after consumption of a 24‐h high resistant starch diet, although this rise of >100 μmol/L has not been achieved through the use of inulin, guar gum or XOS fibre supplements . Circulating concentrations of SCFA levels are likely to be tightly controlled by energy levels within the body, as SCFA are known substrates for the production of glucose, fatty acids and ketone bodies, outlined in Figure .…”

“…Highly fermentable fibres, such as inulin and guar gum can produce a significant rise in plasma SCFA levels within 6 h when consumed as a 20‐30 g supplement . Furthermore, longer term consumption in studies ranging from days to weeks, of a similar dose of resistant starch increases faecal levels of total SCFA and butyrate .…”

Effect of resistant starch supplementation on blood lipids in metabolic&ensp;disorder adults: A meta analysis of randomized controlled trials

“…35 Recent research showed that butyrate could regulate the release of GLP-1 through its central and peripheral targets. 32,34,36 However, Castillo et al reported that consumption of native banana starch supplementation (24 g/d) as a rich source ofRS2 for 4 weeks did not affect the lipid profile, HbA1c and FBS and insulin resistance in obeseT2DM patients. 37 Therefore, it is meaningful to investigate the effect of RS on blood lipids to obtain relatively reliable evidence.…”

“…25 From the previous studies, RS played a useful role in health by some potential mechanisms include: ① changes in intestinal microbiota, ② a reduction in insulin, ③ resistance rise in HDL-c concentrations, and ④ an increase in SCFAs production. [3][4][5][6][26][27][28][29][30][31][32][33][34] RS could produce SCFAs through two pathways: directly (RS fermentation) or indirectly (increasing colonic butyrate-producing microbiota such as Lachnospiraceae and Ruminococcaceae). Butyrate can control macrophage activity and expression of NF-κB which is the main inflammatory and immune response.…”

“…Because some studies had reported that SCFA does not discount a change in fecal/luminal concentrations, which may be involved in the increased stimulation of GLP1 through the FFAR 2/3 receptor. 32,34,38 Additionally, some researches had reported that RS2 could not improve human health as expected because of its instability by gelatinization as natural starch granules. 31,39 The result suggested that the supplementation of RS was not useful to control blood lipids in overweight people with no drug treatment, which may be due to the shorter duration of fewer than 8 weeks.…”