The effect of a combination of short-chain fatty acids on glycometabolic control in men

[摘要] English: Dietary fibre has revealed benefits for health maintenance and disease prevention and as acomponent of medical nutrition therapy. Dietary fibre forms an important part of theWestemised diet, which is characterised by low-fat, low-carbohydrate and low-fibreintake. A high-fibre diet may favourably influence glycometabolic control. It is believedthat short-chain fatty acids (SCF As) may partially be responsible for some of thebeneficial effects of dietary fibre on metabolism. These SCFAs namely, acetate,propionate and butyrate arc the major products of colonic fibre fermentation. Some ofthe SCFAs have been shown to improve blood glucose and insulin levels. However, theeffect of a combination of SCFAs on glycometabolic control is still unclear.The main aim of the study was to determine the effect of a combination of SCFAs(acetate: propionate: butyrate in the ratio of 70: 15: 15, respectively) and (acetate &propionate: in the ratio of 50:50, respectively) on glycometabolic control in men. The study was a randomised, placebo-controlled, double-blinded clinical trial. Voluntarysubjects were recruited for this study using a very strict set of inclusion criteria. Allsubjects received a placebo for a period of one week following the collection of baselineblood samples and other information. A second baseline blood sample was collectedfrom each individual at the end of this period to ensure accurate reflection of the variablesand a stable baseline. Subjects were randomly assigned to three different interventiongroups and consumed the different mixtures of either placebo, acetate-propionatebutyrateor acetate-propionate supplement for a period of four weeks following thesecond baseline blood collection. Supplementation of eight capsules daily was sustainedfor four weeks. Metabolic indicators (serum glucose, serum insulin, serum albumin, totalprotein, total cholesterol (TC), high-density lipoprotein (HDL) cholesterol, low-densitylipoprotein (LDL) cholesterol, non-esterified fatty acids (NEF A), anthropometric statusand blood pressure were measured at baseline two (day 8) and after supplementation (day36). A wash-out period of one week following the supplementation period measured anychanges in the metabolic indicators (day 43). The usual dietary intake of the subjects wasobtained using a food frequency questionnaire (FFQ) at baseline one (day 0) and after supplementation (day 36). Anthropometric status included body mass index (BMI) andwaist-to-hip ratio (WHR), which were measured by means of standardised methods (ondays 1, 8 and 36). The BMI and WHR fell within the normal range, and remained withinthe normal range during the study. This indicated that the subjects were apparentlyhealthy. The study group was also of homogeneous nature, mainly as a result of the strictinclusion criteria applied at the time of recruitment of the subjects. The fasting serum glucose levels were within the higher normal range (5.1 - 5.7mmollL).No statistically significant changes were observed in any of the glycometabolicparameters following supplementation with the different SCFAs regimens (acetate,propionate and butyrate; acetate and propionate). Total cholesterol (TC) levels of thesubject group as a whole fell within the normal range of the population (3.0 -5.2mmollL). However, the observed levels fell in the higher normal range (4.1 -4.8mmol/L). The HDL-C levels increased slightly in group three (acetate andpropionate) and slightly decreased in group two (acetate, propionate and butyrate),however not significantly. The LDL-C significantly decreased in group two (acetate,propionate and butyrate). The observed decreased in systolic blood pressure werestatistically significant after the intervention period in group two (acetate, propionate andbutyrate). However, observed changes in LDL-C and systolic blood pressure were of noclinical importance. The FFQ indicated a tendency towards the adoption of anatherogenic Westenised diet. This study could not shown that a combination of short chain fatty acids have a beneficialeffect on glycometabolic control. The findings of this study are supported by otherstudies, which indicate that acetate, propionate and butyrate do not improve glucosemetabolism in healthy subjects. In contrast, other studies indicated a decrease in fastingserum glucose concentration from propionate (Todesco et aI., 1991) and acetate (Jenkinset aI., 1991) as well as from a combination of acetate, propionate and butyrate (De Wet,1999). The controversial results regarding the effect of short chain fatty acids on glucosemetabolism emphasize the importance of further investigation about the associationbetween physical characteristics and formation of SCFAs, as well as the differentcombinations of SCFAs over a longer period of time.

[发布机构] University of the Free State