Barry R. Goldin

L-Glutamate Dehydrogenases*

Publisher Summary Glutamate dehydrogenases, as a class, catalyze the reversible oxidative deamination of L-glutamate to α -ketoglutarate and ammonia. The description of the characteristics of this reaction from a variety of sources show that, although all classed as glutamate dehydrogenase, the enzymes are different in terms of kinetic characteristics, metabolic function, and molecular properties. The animal enzymes are sensitive to the concentration of purine nucleotides, can catalyze the reaction using either Nicotinamide adenine dinucleotide (NAD) or Nicotinamide adenine dinucleotide phosphate (NADP), and undergo a reversible polymerization reaction, which might influence the allosteric characteristics of the enzyme. The non-animal sources are specific either for NAD or for NADP, are in general not influenced by purine nucleotides, and do not appear to undergo a reversible polymerization reaction. These differences are related to the metabolic role of the reaction, which in animal tissues serves as an important link between carbohydrate and protein metabolism utilizing either α-ketoglutarate or glutamate depending on the condition of the cell, but which in non-animal organisms might act unidirectionally.

Soybean phytoestrogen intake and cancer risk.

Because many Western diseases are hormone-dependent cancers, we have postulated that the Western diet, compared with a vegetarian or semi-vegetarian diet, may alter hormone production, metabolism or action at the cellular level. Recently, our interest has been focused on the cancer-protective role of some hormone-like diphenolic phytoestrogens of dietary origin, the lignans and isoflavonoids. The precursors of the biologically active compounds originate in soybean products (mainly isoflavonoids but also lignans), as well as whole grain cereals, seeds, probably berries and nuts (mainly lignans). The plant lignan and isoflavonoid glycosides are converted by intestinal bacteria to hormone-like compounds with weak estrogenic and antioxidative activity; they have now been shown to influence not only sex hormone metabolism and biological activity but also intracellular enzymes, protein synthesis, growth factor action, malignant cell proliferation, differentiation and angiogenesis, making them strong candidates for a role as natural cancer protective compounds. Epidemiological investigations support this hypothesis, because the highest levels of these compounds are found in countries or regions with low cancer incidence. This report is a review of results that suggest that the diphenolic isoflavonoids and lignans are natural cancer-protective compounds.

Survival of Lactobacillus species (strain GG) in human gastrointestinal tract

A newly isolated strain of a species ofLactobacillus of human origin, designated GG (Lactobacillus GG), has been studied to determine its ability to survive in the human gastrointestinal tract. When fed to 76 volunteers as a frozen concentrate or as a fermented preparation in milk or whey,Lactobacillus GG was recovered in the feces of all subjects receiving the fermented milk or whey and in 86% receiving the frozen concentrate when a single fecal specimen was cultured. The organism was also present in the feces of subjects concurrently receiving ampicillin. After terminating feeding of the organism,Lactobacillus GG persisted in the feces of 87% of volunteers four days later and in 33% of subjects seven days later.Lactobacillus GG lowered fecal bacterial β-glucuronidase activity by approximately 80% in volunteers given the organism for four weeks. These studies demonstrate thatLactobacillus GG can survive and temporarily colonize the human gastrointestinal tract and can affect the metabolic activity of the resident microflora.

Estrogen Excretion Patterns and Plasma Levels in Vegetarian and Omnivorous Women

We studied 10 vegetarian and 10 nonvegetarian premenopausal women on four occasions approximately four months apart. During each study period, the participants kept three-day dietary records, and estrogens were measured in plasma, urinary, and fecal samples. Vegetarians consumed less total fat than omnivores did (30 per cent of total calories, as compared with 40 per cent) and more dietary fiber (28 g per day, as compared with 12 g). There was a positive correlation between fecal weight and fecal excretion of estrogens in both groups (P less than 0.001), with vegetarians having higher fecal weight and increased fecal excretion of estrogens. Urinary excretion of estriol was lower in vegetarians (P less than 0.05), and their plasma levels of estrone and estradiol were negatively correlated with fecal excretion of estrogen (P = 0.005). Among the vegetarians the beta-glucuronidase activity of fecal bacteria was significantly reduced (P = 0.05). We conclude that vegetarian women have an increased fecal output, which leads to increased fecal excretion of estrogen and a decreased plasma concentration of estrogen.

Immunologic effects of national cholesterol education panel step-2 diets with and without fish-derived N-3 fatty acid enrichment.

Reductions in dietary fat, saturated fat, and cholesterol have been recommended to reduce the risk of heart disease in our society. The effects of these modifications on human cytokine production and immune responses have not been well studied. 22 subjects > 40 yr of age were fed a diet approximating that of the current American (14.1% of calories as saturated fatty acids, [SFA], 14.5% monounsaturated fatty acids [MUFA], 6.1% [n-6] polyunsaturated fatty acids [PUFA], 0.8% [n-3] PUFA, and 147 mg cholesterol/1,000 calories) for 6 wk, after which time they consumed (11 in each group) one of the two low-fat, low-cholesterol, high-PUFA diets based on National Cholesterol Education Panel (NCEP) Step 2 recommendations (4.0-4.5% SFA, 10.8-11.6% MUFA, 10.3-10.5% PUFA, 45-61 mg cholesterol/1,000 calories) for 24 wk. One of the NCEP Step 2 diets was enriched in fish-derived (n-3) PUFA (low-fat, high-fish: 0.54% or 1.23 g/d eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA] [121-188 g fish/d]) and the other low in fish-derived (n-3) PUFA (low-fat, low-fish [0.13% or 0.27 g/d EPA and DHA] [33 g fish/d]). Measurements of in vivo and in vitro indexes of immune responses were taken after each dietary period. Long-term feeding of low-fat, low-fish diet enriched in plant-derived PUFA increased blood mononuclear cell mitogenic response to the T cell mitogen Con A, IL-1 beta, and TNF production and had no effect on delayed-type hypersensitivity skin response, IL-6, GM-CSF, or PGE2 production. In contrast, the low-fat, high-fish diet significantly decreased the percentage of helper T cells whereas the percentage of suppressor T cells increased. Mitogenic responses to Con A and delayed-type hypersensitivity skin response as well as the production of cytokines IL-1 beta, TNF, and IL-6 by mononuclear cells were significantly reduced after the consumption of the low-fat, high-fish diet (24, 40, 45, 35, and 34%, respectively; P < 0.05 by two-tailed Students t test except for IL-1 beta and TNF, which is by one-tailed t test). Our data are consistent with the concept that the NCEP Step 2 diet that is high in fish significantly decreases various parameters of the immune response in contrast to this diet when it is low in fish. Such alterations may be beneficial for the prevention and treatment of atherosclerotic and inflammatory diseases but may be detrimental with regard to host defense against invading pathogens.

EXCRETION OF THE LIGNANS ENTEROLACTONE AND ENTERODIOL AND OF EQUOL IN OMNIVOROUS AND VEGETARIAN POSTMENOPAUSAL WOMEN AND IN WOMEN WITH BREAST CANCER

Dietary studies and assays of urinary lignans in postmenopausal women showed that lignan excretion is significantly lower in urine of women with breast cancer than in normal omnivorous and vegetarian women and confirmed that there is a significant correlation between fibre intake and lignan excretion. It is suggested that the precursors of the human lignans enterolactone and enterodiol formed by the intestinal microflora are to be found in fibre-rich foods such as grains, nuts, and legumes. Excretion of equol, which has antioestrogenic properties, was similar in all groups studied and did not correlate with fibre intake, but occasional high values were found in some subjects.

A randomized, double-blind trial of lactobacillus GG versus placebo in addition to standard maintenance therapy for children with Crohn's disease

&NA; Probiotics are widely used by patients with Crohns disease (CD) in an attempt to improve their health, but few controlled studies have been done to evaluate the efficacy of these therapies. We conducted a randomized, placebo‐controlled trial of the probiotic Lactobacillus rhamnosus strain GG (LGG) to see if the addition of LGG to standard therapy prolonged remission in children with CD. Concomitant medications allowed in the study included aminosalicylates, 6‐mercaptopurine, azathioprine, and low‐dose alternate day corticosteroids. Seventy‐five children (age range, 5‐21 yr) with CD in remission were randomized to either LGG (n = 39) or placebo (n = 36) and followed for up to 2 years. The median time to relapse was 9.8 months in the LGG group and 11.0 months in the placebo group (P = 0.24); 31% (12/39) of patients in the LGG group developed a relapse compared with 6/36 (17%) of the placebo group (P = 0.18). The LGG was well tolerated, with a side effect profile comparable with placebo. This study suggests that LGG does not prolong time to relapse in children with CD when given as an adjunct to standard therapy.

Clinical Indications for Probiotics: An Overview

Probiotic bacteria are used to treat or prevent a broad range of human diseases, conditions, and syndromes. In addition, there are areas of medical use that have been proposed for future probiotic applications. Randomized double-blind studies have provided evidence of probiotic effectiveness for the treatment and prevention of acute diarrhea and antibiotic-induced diarrhea, as well as for the prevention of cow milk-induced food allergy in infants and young children. Research studies have also provided evidence of effectiveness for the prevention of travelers diarrhea, relapsing Clostridium difficile-induced colitis, and urinary tract infections. There are also studies indicating that probiotics may be useful for prevention of respiratory infections in children, dental caries, irritable bowel syndrome, and inflammatory bowel disease. Areas of future interest for the application of probiotics include colon and bladder cancers, diabetes, and rheumatoid arthritis. The probiotics with the greatest number of proven benefits are Lactobacillus rhamnosus strain GG and Saccharomyces boulardii.

Probiotics for humans

This chapter will review the current status of probiotics in the area of human health and nutrition, including some reference of the use of probiotics in foods. The development of new strains of bacteria that can either improve current medical use or be used for medical problems in which probiotics have not been previously considered applicable or effective will be discussed. In this regard a review of both selective procedures and bio engineering techniques will be discussed.

Alterations in fecal microflora enzymes related to diet, age, lactobacillus supplements, and dimethylhydrazine.

The bacterial enzymes, β‐glucuronidase, azoreductase, and nitroreductase, have been measured in the fecal microflora of rats. The effects of diet, advanced age, Lactobacillus acidophilus supplements, and dimethylhydrazine on these microbial enzyme activities have been determined. The shift from a grain to a meat diet resulted in 1.5‐2.5‐fold increase in the activity of all three enzymes. Animals over 20 months of age, consuming a meat diet, showed further increases in fecal β‐glucuronidase activity, while the levels of all three microbial enzymes increased in old rats fed a grain diet. Feeding supplement of L. acidophilus significantly lowered the activity of fecal nitroreductase and azoreductase in meat‐eating animals, but had no effect on nitroreductase activity in grain‐fed animals. Dimethylhydrazine increased the fecal β‐glucuronidase activity in both grain‐ and meat‐fed animals, but the carcinogen had no effect on nitroreductase or azoreductase activity. These findings have relevance to known features of the epidemiology and etiology of large bowel cancer, and suggest certain approaches to prevention.