Martin A. Eastwood

Serum 7α-hydroxy-4-cholesten-3-one and selenohomocholyltaurine (sehcat) whole body retention in the assessment of bile acid induced diarrhoea

Objective: To assess the reliability of serum 7α-hydroxy-4-cholesten-3-one (7α-3ox-C) in the differential diagnosis of bile acid induced diarrhoea by comparison with 75selenohomocholyltaurine whole body retention (SeHCAT WBR). Design: One hundred and sixty-four patients with chronic diarrhoea were investigated prospectively in two centres (Edinburgh and Sweden) by two different tests which measure bile acid loss or synthesis: the SeHCAT test which measures the 7-day SeHCAT WBR and serum 7α-3ox-C which reflects the rate of bile acid synthesis. Results: Forty-six patients had SeHCAT WBR of less than 10% (19 with ileal disease or resection, nine with idiopathic bile acid induced diarrhoea and 18 with miscellaneous causes for bile acid induced diarrhoea). All patients with ileal or idiopathic disease showed a favourable response to treatment as did 13 of the miscellaneous group. Serum 7α-3ox-C was raised in all subjects with ileal disease/resection, seven patients with idiopathic disease and all subjects in the miscellaneous group who responded to treatment. Sixteen out of 118 patients with SeHCAT WBR greater than or equal to 10% had raised serum 7α-3ox-C. Conclusion: The positive predictive value of serum 7a-3ox-C was 74%. The high negative predictive value (98%) of serum 7α-3ox-C indicates the possible use of this test for excluding bile acid malabsorption in this population. All but two subjects who responded to treatment had raised serum 7a-3ox-C concentrations. The possibility that the sensitivity of the test can be improved by repeat testing needs to be further investigated. There was a significant correlation between fractional catabolic rate (FCR) SeHCAT and serum 7α-3ox-C (r = 0.63, P< 0.0001). Further data are required to validate the reference range in women over 70 years of age.

The effects of dietary gum tragacanth in man

Following a 7-day control period, 5 male volunteers consumed 9.9 g gum tragacanth (GT) daily for 21 days. The GT was well tolerated and there were no adverse effects in any of the volunteers. The daily intake was very high in relation to the minor amounts of GT (estimated at 2 g per person per annum) likely to be ingested as a foodstuffs additive. The wide range of measurements made before and at the end of the test period show that the ingestion of GT had no significant effect on any of the following: plasma biochemistry; haematological indices; urinalysis parameters; glucose tolerance; serum cholesterol, triglycerides and phospholipids; breath hydrogen and methane concentrations. The intestinal transit time decreased and faecal fat concentration increased (P less than 0.01) for 4 subjects. The faecal wet and dry weights increased in all subjects (P less than 0.01). These changes may be of nutritional and physiological interest but do not reflect any adverse toxicological effects arising from the ingestion of large daily doses of GT.

COLONIC FUNCTION IN PATIENTS WITH DIVERTICULAR DISEASE

Diverticular disease is thought to be associated with prolonged intestinal transit-time, a reduced stool weight, and increased intracolonic pressure. Sixty patients with diverticular disease did not regularly show these features. Variation in colonic function was considerable in these patients and was similar to that in the general population from which the patients were recruited. Constipation may be a complication of diverticular disease and not necessarily part of its aetiology.

A study of the effects of dietary gum arabic in the rat

Gum arabic (GA) is a water-soluble polysaccharide (molecular weight approximately 850 000) containing rhamnose, arabinose, glucuronic acid and galactose. The metabolism of GA has been studied in the rat. Adult male Wistar rats were given GA incorporated into either an Oxoid breeders (OB) diet or an elemental (Elem) diet. Intestinal contents were examined for precipitable GA using acidified ethanol. GA was found from stomach to small intestine but not in the caecum, colon or rectum. Caecal excision and restoration of intestinal continuity resulted in GA recovery from stomach to rectum. Excreted methane, hydrogen and volatile fatty acids (VFA) were measured as indicators of bacterial activity in the caecum and colon. Methane excretion increased on the OB + GA diet and H2 concentrations remained unaltered. The Elem diet abolished gas production. When the animals were given the Elem + GA diet, H2 and methane were only produced after 28 d. Faecal VFA increased with increasing GA intake, acetate concentration increased and butyrate concentration decreased with increasing GA dosage. Significant decreases in concentrations of VFA were found from caecum to left colon and from left colon to faeces. It can be concluded that GA degradation occurs in the caecum and is associated with increased methane excretion, increased VFA concentrations and changes in the proportions of various VFA in the faeces.

The effects of dietary gum karaya (Sterculia) in man

Following a 7-day control period, 5 male volunteers consumed 10.5 g gum karaya (GK) daily for 21 days. Measurements before and at the end of the test period showed that the ingestion of GK had no significant effect on the following: intestinal transit time, faecal wet or dry weight, concentrations of faecal fat, total and individual volatile fatty acids, bile acids, and neutral sterols; breath hydrogen and methane concentrations; glucose tolerance; serum cholesterol, HDL cholesterol, triglycerides and phospholipids; plasma biochemistry; haematological indices; urinalysis parameters. The daily test intake, which was large in relation to the very minor amounts of GK used in foodstuffs, did not cause any toxic effects in terms of the wide range of measurements made; moreover the GK had no metabolic action of any consequence.

The submucosa of the human colon

Full-thickness specimens of colon were obtained at operation or autopsy from 20 patients. The submucosa was isolated from the mucosa and muscularis externa, with confirmation by light microscopy. Submucosal specimens were then fixed and prepared for scanning and transmission electron microscopy, with preservation of their orientation. The submucosa was found to consist of a series of layers of collagen fibres, each layer 0.5-2.0 microns thick. The fibres within each layer were co-directionally orientated. The autopsy specimens were comparable in appearance with the operative ones. The mean diameter of the collagen fibrils was 69 +/- 13 nm, and the mean fibril count per unit area was 159 +/- 58/microns2.

Water, electrolytes, minerals and trace elements

Water is the basic chemical of life, acting both as a bulk and localized solvent for the body. Water is an angular molecule with two vertical planes of symmetry and is an acceptor and donator of protons. Water freezes at 0°C to form a stable phase (ice) with a variety of structural formations. The chemical potential of ice is much lower than that of liquid water. As water is warmed the structure becomes more open and is at its maximum volume at 4°C. Water molecules are held apart by hydrogen bonds between structures.

Specific nutritional requirements

The science of nutrition aims to define the overall quantity and individual constituents of nutrition for all of the human population.

Eating and digestion

The regulation of body weight is dependent upon a balance between nutrient intake and utilization, though there are other important factors (Figure 10.1).

The metabolism of nutrients

The liver is the largest organ in the body, weighing 1200–1500 g — about 2% of the total weight of an adult. In the infant it is relatively larger and contributes to the characteristic rotund abdomen. The liver is important in the metabolism and storage of nutrients, particularly in that it is the first organ to which nutrients are exposed after absorption from the intestine.