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

English: Dietary fibre has revealed benefits for health maintenance and disease prevention and as a component of medical nutrition therapy. Dietary fibre forms an important part of the Westemised diet, which is characterised by low-fat, low-carbohydrate and low-fibre intake. A high-fibre diet may favourably influence glycometabolic control. It is believed that short-chain fatty acids (SCF As) may partially be responsible for some of the beneficial effects of dietary fibre on metabolism. These SCFAs namely, acetate, propionate and butyrate arc the major products of colonic fibre fermentation. Some of the SCFAs have been shown to improve blood glucose and insulin levels. However, the effect 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. Voluntary subjects were recruited for this study using a very strict set of inclusion criteria. All subjects received a placebo for a period of one week following the collection of baseline blood samples and other information. A second baseline blood sample was collected from each individual at the end of this period to ensure accurate reflection of the variables and a stable baseline. Subjects were randomly assigned to three different intervention groups and consumed the different mixtures of either placebo, acetate-propionatebutyrate or acetate-propionate supplement for a period of four weeks following the second baseline blood collection. Supplementation of eight capsules daily was sustained for four weeks. Metabolic indicators (serum glucose, serum insulin, serum albumin, total protein, total cholesterol (TC), high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, non-esterified fatty acids (NEF A), anthropometric status and blood pressure were measured at baseline two (day 8) and after supplementation (day 36). A wash-out period of one week following the supplementation period measured any changes in the metabolic indicators (day 43). The usual dietary intake of the subjects was obtained using a food frequency questionnaire (FFQ) at baseline one (day 0) and after supplementation (day 36). Anthropometric status included body mass index (BMI) and waist-to-hip ratio (WHR), which were measured by means of standardised methods (on days 1, 8 and 36). The BMI and WHR fell within the normal range, and remained within the normal range during the study. This indicated that the subjects were apparently healthy. The study group was also of homogeneous nature, mainly as a result of the strict inclusion 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 glycometabolic parameters following supplementation with the different SCFAs regimens (acetate, propionate and butyrate; acetate and propionate). Total cholesterol (TC) levels of the subject 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 and propionate) 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 were statistically significant after the intervention period in group two (acetate, propionate and butyrate). However, observed changes in LDL-C and systolic blood pressure were of no clinical importance. The FFQ indicated a tendency towards the adoption of an atherogenic Westenised diet. This study could not shown that a combination of short chain fatty acids have a beneficial effect on glycometabolic control. The findings of this study are supported by other studies, which indicate that acetate, propionate and butyrate do not improve glucose metabolism in healthy subjects. In contrast, other studies indicated a decrease in fasting serum glucose concentration from propionate (Todesco et aI., 1991) and acetate (Jenkins et 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 glucose metabolism emphasize the importance of further investigation about the association between physical characteristics and formation of SCFAs, as well as the different combinations of SCFAs over a longer period of time.