Showing papers in "Current Opinion in Clinical Nutrition and Metabolic Care in 2001"
TL;DR: There is abundant evidence that the proportion of energy derived from fat during exercise is higher in women than in men, and this finding seems counterintuitive, as percentage body fat is increased in women.
Abstract: Women generally have a higher percentage of body fat than men. Also, women store more fat in the gluteal-femoral region, whereas men store more fat in the visceral (abdominal) depot. This review focuses on differences in regional fatty acid storage, mobilization and oxidation that may contribute to gender-related differences in body fat distribution. There are pronounced regional differences in the regulation of regional fatty acid metabolism between men and women. Firstly, there is evidence that in vivo, catecholamine mediated leg free fatty acid release is lower in women than in men, whereas free fatty acid release from the upper body depots is comparable. These data correspond to in-vitro adipose tissue biopsy data, which indicate a more pronounced difference in catecholamine mediated lipolysis between upper body and lower body fat depots in women than in men. Secondly, free fatty acid release by the upper body subcutaneous fat depots is higher in men than in women, indicating a higher resistance to the antilipolytic effect of meal ingestion in the upper body fat depots in men. Thirdly, there are indications that basal fat oxidation (adjusted for fat free mass) is lower in females as compared to males, thereby contributing to a higher fat storage in women. Finally, postprandial fat storage may be higher in subcutaneous adipose tissue in women than in men, whereas storage in visceral adipose tissue has been hypothesized to be higher in men. All the above differences may play a role in the variation in net regional fat storage between men and women, but the number of in-vivo studies on gender-related differences in fatty acid metabolism is very limited and most findings require confirmation. Furthermore, there is abundant evidence that the proportion of energy derived from fat during exercise is higher in women than in men. With respect to total body fat, this finding seems counterintuitive, as percentage body fat is increased in women. Further studies are necessary to investigate the significance of differences in exercise-induced fat oxidation on 24-h fat balance.
579 citations
TL;DR: This review focuses on the many gaps in the understanding of the functioning of the ubiquitin-proteasome pathway in muscle atrophy, and highlights the strengths and limitations of the different experimental approaches used in such studies.
Abstract: Studies of many different rodent models of muscle wasting have indicated that accelerated proteolysis via the ubiquitin-proteasome pathway is the principal cause of muscle atrophy induced by fasting, cancer cachexia, metabolic acidosis, denervation, disuse, diabetes, sepsis, burns, hyperthyroidism and excess glucocorticoids. However, our understanding about how muscle proteins are degraded, and how the ubiquitin-proteasome pathway is activated in muscle under these conditions, is still very limited. The identities of the important ubiquitin-protein ligases in skeletal muscle, and the ways in which they recognize substrates are still largely unknown. Recent in-vitro studies have suggested that one set of ubquitination enzymes, E2(14K) and E3(alpha), which are responsible for the 'N-end rule' system of ubiquitination, plays an important role in muscle, especially in catabolic states. However, their functional significance in degrading different muscle proteins is still unclear. This review focuses on the many gaps in our understanding of the functioning of the ubiquitin-proteasome pathway in muscle atrophy, and highlights the strengths and limitations of the different experimental approaches used in such studies.
440 citations
TL;DR: This brief review examines the influence of aging on skeletal muscle mass and strength and specifically highlights sex-related differences and points toward greater declines in muscle quality in older women.
Abstract: This brief review examines the influence of aging on skeletal muscle mass and strength and specifically highlights sex-related differences. It is well established that aging is associated with a significant decline in muscle strength that becomes functionally important by the seventh decade of life. Age-related strength losses are mainly secondary to decline in skeletal muscle mass in men and women. While women may experience earlier strength losses than men, overall, age associated decreases in strength are similar when controlling for muscle mass. Although men may experience greater losses of total muscle mass, recent evidence, however, points toward greater declines in muscle quality in older women. The implications and potential mechanisms for these differences are discussed.
266 citations
TL;DR: The use of phytosterols as supportive therapies in certain chronic conditions has been tested under clinical trial conditions and their direct immune modulatory activity on human lymphocytes has been proven and the mechanism of action in cancer cells has been elucidated.
Abstract: Although plant sterols (phytosterols) were chemically described in 1922, their biological role in human and animal health has been underestimated. Their ability to control cholesterol plasma levels in hypercholesterolimic patients was first described in 1983 when the structure of phytosterols implied that they could, by steric hindrance, inhibit the absorption of cholesterol from our diets. This has led to the development of functional foods containing high contents of these plant molecules or their esters as cholesterol controlling foods. Over the last 15 years, however, several reports have appeared in the literature indicating that phytosterols have some immunological activity as highlighted in animal models of inflammation or even in in-vitro and in-vivo models of cancer (colorectal and breast cancer). These findings were paralleled by epidemiological studies correlating the reduced risk of numerous diseases and the dietary intake of phytosterols. It is only in the last 10 years, however, that their direct immune modulatory activity on human lymphocytes has been proven and the mechanism of action in cancer cells has been elucidated. The use of phytosterols as supportive therapies in certain chronic conditions has been tested under clinical trial conditions. This review presents a summary of the in-vitro and in-vivo studies published to date.
246 citations
TL;DR: The changing rate of sex hormone release during the menstrual cycle modifies thermoregulation in women, so there are differences in resting body temperature and thermal responses to positive or negative heat loads depending on the phase of the cycle.
Abstract: Women differ from men in thermal responses to exogenous heat load and heat loss as well as to endogenous heat load during exercise, because they usually have a larger ratio of body surface to body mass, a greater subcutaneous fat content, and lower exercise capacity. When these differences are eliminated in experimental studies, it appears that women's sweating response to heat load is still smaller than that of men, but they are able to maintain their core body temperature on a similar level to that of men as a result of greater evaporative efficiency of sweating. In addition, the changing rate of sex hormone release during the menstrual cycle modifies thermoregulation in women, so there are differences in resting body temperature and thermal responses to positive or negative heat loads depending on the phase of the cycle. In this review, the changes in thermoregulation in young women taking oral contraceptives and those associated with the menopause and hormonal replacement therapy are also described.
212 citations
TL;DR: A number of double-blind, placebo-controlled trials of γ-linolenic acid and fish oil in rheumatoid arthritis have shown significant improvements in a variety of clinical outcomes, but it is unclear what the optimal dosage of the fatty acids is, or whether there would be extra benefit from using them in combination.
Abstract: Rheumatoid arthritis is characterized by infiltration of T lymphocytes, macrophages and plasma cells into the synovium, and the initiation of a chronic inflammatory state that involves overproduction of proinflammatory cytokines and a dysregulated T-helper-1-type response. Eicosanoids synthesized from arachidonic acid and cytokines cause progressive destruction of cartilage and bone. The n-6 polyunsaturated fatty acid gamma-linolenic acid is the precursor of di-homo-gamma-linolenic acid. The latter and the n-3 polyunsaturated fatty acid eicosapentaenoic acid, which is found in fish oil, are able to decrease the production of arachidonic acid-derived eicosanoids and to decrease the production of proinflammatory cytokines and reactive oxygen species, and the reactivity of lymphocytes. A number of double-blind, placebo-controlled trials of gamma-linolenic acid and fish oil in rheumatoid arthritis have shown significant improvements in a variety of clinical outcomes. These fatty acids should be included as part of the normal therapeutic approach to rheumatoid arthritis. However, it is unclear what the optimal dosage of the fatty acids is, or whether there would be extra benefit from using them in combination.
173 citations
TL;DR: Oral carbohydrate loading before surgery has confirmed previous data, using glucose and insulin infusions, that postoperative insulin resistance is reduced compared with overnight fasted patients before surgery, and this is associated with improved well-being before and after surgery.
Abstract: Insulin resistance is a central feature of the metabolic response after elective surgery as well as other trauma, and has been shown to be a predictor of the length of stay after surgery. Carbohydrate treatment instead of overnight fasting before surgery has been shown to reduce postoperative insulin resistance and to reduce hospital stay approximately 20% after elective surgery. For potential use as a clinical routine before surgery, a carbohydrate-rich drink was developed. Gastric emptying of a 50 g oral carbohydrate load using this drink is complete within 90 min after intake. Oral carbohydrate loading before surgery has confirmed previous data, using glucose and insulin infusions, that postoperative insulin resistance is reduced compared with overnight fasted patients before surgery, and this is associated with improved well-being before and after surgery.
157 citations
TL;DR: In liver, branched-chain amino acids enhance the translation of a particular set of mRNAs typified by those encoding the ribosomal proteins and translation elongation factors, suggesting that brancherised amino acids upregulate the capacity of the tissue to synthesize protein.
Abstract: Historically, amino acids have been viewed as precursors for protein synthesis as well as metabolic substrates. Recently, a new role for amino acids as regulators of mRNA translation has been identified. In this role, they modulate the phosphorylation state of proteins that represent important control points in translation initiation, including the translational repressor 4E-BP1 and the ribosomal protein S6 kinase S6K1. When administered orally to fasted rats the branched-chain amino acids are particularly effective in stimulating translation initiation. Of the branched-chain amino acids, leucine is most potent. Interestingly, leucine administration stimulates global rates of protein synthesis in skeletal muscle but not in liver. However, in liver, branched-chain amino acids enhance the translation of a particular set of mRNAs typified by those encoding the ribosomal proteins and translation elongation factors, suggesting that branched-chain amino acids upregulate the capacity of the tissue to synthesize protein.
123 citations
TL;DR: The pathogenic role for altered glutathione metabolism in such diseases as protein energy malnutrition, seizures, Alzheimer's disease, Parkinson’s disease, sickle cell anaemia, chronic diseases associated with ageing and the infected state is discussed.
Abstract: Altered glutathione metabolism in association with increased oxidative stress has been implicated in the pathogenesis of many diseases. However, whether strategies aimed at restoring glutathione concentration and homeostasis are effective in ameliorating or modifying the natural history of these states is unknown. In this review we discuss the pathogenic role for altered glutathione metabolism in such diseases as protein energy malnutrition, seizures, Alzheimer's disease, Parkinson's disease, sickle cell anaemia, chronic diseases associated with ageing and the infected state. In addition, we discuss the efficacy of glutathione precursors in restoring glutathione homeostasis both in vitro and in vivo.
120 citations
TL;DR: The findings indicate that nutritional and hormonal control of the activity and expression of branched-chain α-keto acid dehydrogenase kinase provides an important means of control of its activity, with inactivation serving to conserve branching-chain amino acids for protein synthesis in some situations and activation serving to provide carbon for gluconeogenesis in others.
Abstract: Branched-chain alpha-keto acid dehydrogenase kinase is responsible for the inactivation and phosphorylation of the branched-chain alpha-keto acid dehydrogenase complex, the enzyme that catalyses the committed step of branched-chain amino acid catabolism. The activity of the branched-chain alpha-keto acid dehydrogenase complex is inversely correlated with kinase activity, suggesting that the relative activity of the kinase is the primary regulator of the activity of the complex. It has been shown that kinase activity and expression are affected by nutritional states imposed by low-protein diet feeding, starvation, diabetes, and exercise. Evidence has also been presented that certain hormones, particularly insulin, glucocorticoid, thyroid hormone and female sex hormones, affect the activity and expression of the kinase. The findings indicate that nutritional and hormonal control of the activity and expression of branched-chain alpha-keto acid dehydrogenase kinase provides an important means of control of the activity of the branched-chain alpha-keto acid dehydrogenase complex, with inactivation serving to conserve branched-chain amino acids for protein synthesis in some situations and activation serving to provide carbon for gluconeogenesis in others.
117 citations
TL;DR: A comprehensive screening tool for assessment of nutritional status is needed that is clinically relevant and cost-effective to perform and should be supplemented by conventional nutritional assessment before treatment is planned.
Abstract: The prevalence of malnutrition, which is relatively low in free-living elderly persons (5-10%), is considerably higher (30-60%) in hospitalized or institutionalized elderly persons. As a result, nutritional assessment should be part of routine clinical practice in elderly patients who are frail, sick or hospitalized. A comprehensive screening tool for assessment of nutritional status is needed that is clinically relevant and cost-effective to perform. A number of simple and rapid tests for detecting or diagnosing malnutrition in the elderly have recently been developed. If malnutrition is suggested by such screening tests, then they should be supplemented by conventional nutritional assessment before treatment is planned.
TL;DR: This review summarizes the present experience in various forms of diarrhoea, inflammatory bowel disease, and Helicobacter infections, in intensive care patients and in connection with extensive surgery.
Abstract: Approximately 70% of the immune system is localized in the gastrointestinal tract. The saliva and gastrointestinal secretions, as well as flora (probiotics) and supplied fibres (prebiotics), are important for optimal function. Probiotic bacteria have been shown to influence the immune system through several molecular mechanisms. Pre-, pro- and synbiotics (products produced by fermentation) offer both protection against and cure of a variety of endemic and acute diseases. This review summarizes the present experience in various forms of diarrhoea, inflammatory bowel disease, and Helicobacter infections, in intensive care patients and in connection with extensive surgery.
TL;DR: Although solid conclusions are difficult to make given the paucity of studies focusing on gender differences in human protein metabolism, it seems that the sex hormones may play an important role.
Abstract: Adult male and female humans have clear differences in muscle mass and there is mounting evidence that substrate metabolism differs between genders. These facts suggest that there are gender differences in protein metabolism between males and females. Studies utilizing stable isotopically labeled amino acids show little indication that whole body protein synthesis or breakdown is different between genders. There is evidence that leucine oxidation may be different, both at rest and during exercise, but this evidence is not unequivocal and more, properly controlled studies need to be undertaken to clarify this controversy. Muscle hypertrophy results from positive net muscle protein balance, thus, adult males must have greater net muscle protein synthesis than females, at least at some point in development. Although there is a paucity of data, no gender differences in the basal level net muscle protein balance have been found. It is possible that there are small differences that cannot be distinguished with current methods due to small sample sizes and the sensitivity of the methods. It is more likely, however, that sex hormones contribute to the clear differences in musculature by influencing muscle protein metabolism, especially during puberty. Testosterone increases muscle protein synthesis and net muscle protein balance, resulting in increased muscle mass. Males and females have similar amounts of testosterone until puberty, then testosterone levels increase much more dramatically in males, as does muscle mass. Furthermore, although no evidence exists in humans, in-vitro and rat data suggest that ovarian hormones inhibit muscle protein synthesis. Whereas solid conclusions are difficult to make given the paucity of studies focusing on gender differences in human protein metabolism, it seems that the sex hormones may play an important role. Certainly, more studies need to be conducted to ascertain what gender differences in whole body and muscle protein metabolism exist and how these differences result in different phylogenetic characteristics.
TL;DR: Exercise training has positive anabolic effects even in the frail elderly, and may improve the effect of re-nutrition in malnourished elderly patients.
Abstract: Because of the metabolic changes caused by ageing, malnutrition is accompanied by a preferential loss of fat-free mass in the elderly, and it exaggerates the physiological loss of body cell mass, muscle mass and muscle function observed in the aged. Exercise training has positive anabolic effects ev
TL;DR: Adequate and unbiased scientific data on body fat among ethnic population groups are necessary for a better understanding of the aetiology of obesity and its co-morbidities.
Abstract: Body-composition methodologies rely on assumptions that are not constant across ethnic groups. The consequence is that the methods used need to be population specific to guarantee unbiased conclusions. Alternatively, assumption-free methods such as chemical multiple-compartment models or scanning techniques should be used. Adequate and unbiased scientific data on body fat among ethnic population groups are necessary for a better understanding of the aetiology of obesity and its co-morbidities. The World Health Organization cut-off points for underweight, overweight, obesity and fat distribution, now universally defined, may need revision because the relationship between body mass index and body composition, and between indices of fat distribution and the actual amount of visceral fat, differ across ethnic groups. The need for ethnically specific cut-off points for obesity and fat distribution is substantiated, for example, by elevated disease risks at low levels of body mass index in several populations. Properly designed and conducted studies are needed to obtain unbiased information on these topics.
TL;DR: Investigations using animal models show that estrogen is related to enzyme release, specifically creatine kinase, from exercised skeletal muscle, and research on exercise responses in women with different circulating levels of estrogen has not found estrogen to be related to indicators of muscle damage.
Abstract: Investigations using animal models show that estrogen is related to enzyme release, specifically creatine kinase, from exercised skeletal muscle. In humans, women have lower resting blood creatine kinase levels than men and have an attenuated blood creatine kinase response after prolonged endurance exercise. These results have led to the common belief that women may be protected from exercise-induced muscle damage due to circulating estrogen. Studies using laboratory models to examine gender differences in exercise-induced muscle damage, however, have not consistently documented that women have an attenuated response compared with men. Furthermore, research on exercise responses in women with different circulating levels of estrogen has not found estrogen to be related to indicators of muscle damage. Recent studies, in fact, have reported that women may experience more muscle damage, based on indirect measures, than men. Although some data exist that women may have a faster recovery from exercise-induced muscle damage, these results are tentative at this time.
TL;DR: This review explores the puzzle of how dietary nucleotides modulate immune function, promote faster intestinal healing and have trophic effects on the intestine of parenterally-fed rats which are similar to those resulting from glutamine supplementation, but at much lower intakes.
Abstract: Dietary nucleotides, like glutamine, have attracted attention as a key ingredient missing from nutritional formulae for many years. They are the building blocks of tissue RNA and DNA and of ATP and their presence in breast milk has stimulated research in babies which has indicated that supplementation of infant formula milk leads to improved growth and reduced susceptibility to infection. Animal studies have confirmed some of these data. In particular, dietary nucleotides modulate immune function, promote faster intestinal healing and have trophic effects on the intestine of parenterally-fed rats which are similar to those resulting from glutamine supplementation, but at much lower intakes. Nucleotide supplementation has also been shown to improve some aspects of tissue recovery from ischaemia/reperfusion injury or radical resection. There is, however, a fundamental paradox. The intestine and liver possess powerful homeostatic mechanisms which degrade intake of purines and pyrimidines (i.e. salvage) and replace it with de novo synthesised output. It is possible that peripheral tissues receive only small amounts of nucleotides of dietary origin. Previously, nucleotides have been proposed as being conditionally-essential nutrients that provide an adequate supply of purines and pyrimidines for nucleic acid synthesis in neonates or in the stressed patient. This review explores this puzzle in the light of recent data from nutritional studies and from research into purinergic signalling in the intestine, heart and cells of the immune system. We propose that dietary nucleotides should be considered within a pharmacological and metabolic framework.
TL;DR: This review focuses on recent advances in the understanding of the ubiquitin-proteasome-dependent pathway, which is involved in the control of many major biological functions and may also interfere or cooperate with other proteolytic pathways.
Abstract: The mechanisms of proteolysis remain to be fully defined. This review focuses on recent advances in our understanding of the ubiquitin-proteasome-dependent pathway, which is involved in the control of many major biological functions. The ubiquitinylation/deubiquitinylation system is a complex machin
TL;DR: The review covers several very recent publications shedding new light on and expanding the authors' knowledge of the interaction between inflammation and the decrease in serum retinol and carotenoids.
Abstract: Inflammation causes a decrease in serum retinol and carotenoids as a consequence of the acute phase response of the organism. Under normal conditions both the acute phase response and the alterations in dynamics of retinol and carotenoids are transient. For both retinoids and carotenoids the adaptiv
TL;DR: Animal and preliminary human study evidence suggests that 17-β-estradiol may be a major determinant of the sex dimorphic response in carbohydrate metabolism during exercise and may have future implications for the care of patients with diabetes and inborn errors of lipid metabolism.
Abstract: During submaximal endurance exercise, women oxidize more lipid and less carbohydrate as metabolic substrates than men. This is reflected in a lower glycogen utilization in skeletal muscle and lower hepatic glucose production for women compared with men. These latter observations may explain the lower leucine oxidation observed during endurance exercise in women. Animal and preliminary human study evidence suggests that 17-beta-estradiol may be a major determinant of the sex dimorphic response in carbohydrate metabolism during exercise. From a practical standpoint, it appears necessary for women to increase their dietary energy intake (and percentage derived from carbohydrates) for four days before a sporting event in order to supercompensate muscle glycogen concentrations. Sex differences in carbohydrate metabolism may have future implications for the care of patients with diabetes and inborn errors of lipid metabolism.
TL;DR: The potential role of enteral nutrition as primary therapy for Crohn's disease is particularly addressed in this review, and recent data on the in-vivo anti-inflammatory actions of butyrate merit special mention.
Abstract: Nutritional derangements are frequent in inflammatory bowel disease. In the past year significant work has been published examining the mechanisms of impaired food intake in animal models of inflammatory bowel disease, which allow a better understanding of these processes. Data from the same laboratory have shed further light on the relative role of underfeeding and inflammation on the growth retardation associated with intestinal inflammation. Other studies have provided further data on the risk factors and predictive biomarkers of bone loss in patients with inflammatory bowel disease. The potential role of enteral nutrition as primary therapy for Crohn's disease is particularly addressed in this review. Recent contributions to the field emphasized the special importance of this modality of therapy in paediatric patients. The possible mechanisms for such a therapeutic action are not well understood. Other nutrients may have a therapeutic potential in inflammatory bowel disease. In particular, recent data on the in-vivo anti-inflammatory actions of butyrate merit special mention. Finally, novel nutritional therapeutic strategies for inflammatory bowel disease, such as transforming growth factor-beta2-enriched enteral feeding, or hydrothermally processed cereals have recently been explored.
TL;DR: Over the lifespan there is a decline in food intake, including alterations in the gastrointestinal satiating system, the effect of elevated leptin levels, especially in men, and a variety of changes in central nervous system neurotransmitters.
Abstract: Over the lifespan there is a decline in food intake. This has been termed the physiological anorexia of aging. It has many causes, including alterations in the gastrointestinal satiating system, the effect of elevated leptin levels, especially in men, and a variety of changes in central nervous system neurotransmitters. Beyond the age of 70 years body mass declines. This includes both loss of adipose tissue and muscle mass. The loss of muscle mass in older individuals is termed sarcopenia. There is increasing evidence that this is caused, in men, partly by the decline in testosterone. Illness results in an increase of cytokines that produce both anorexia and cause protein wasting. Many of the causes of cachexia in older individuals are treatable. Depression is the most common cause of weight loss in older individuals. Dieting in older individuals is associated with a loss of skeletal tissue as well as fat mass. This can place older individuals at risk of becoming the 'fat frail'.
TL;DR: The central role of alanine aminotransferase in the coupling of glutamine and glucose metabolisms in the small intestine is emphasized, and the production of glucose by thesmall intestine may be acutely blunted upon insulin infusion.
Abstract: Both glutamine and glucose are highly utilized by the small intestine in various animal species. They are, however, very partially oxidized, the major known fate of glucose being lactate and alanine, and that of glutamine being citrulline or proline. At variance with the current view that only the liver and kidney are gluconeogenic organs, because both are the only tissues to express the glucose-6 phosphatase gene, this gene is also expressed in the small intestine in rats and humans, and is strongly induced in insulinopenic states, such as fasting and diabetes. Under the latter conditions, the small intestine contributes 20-25% of whole-body endogenous glucose production. The main small intestine gluconeogenic substrate is glutamine and, to a lesser extent, glycerol. Accounting for these fluxes, the phosphoenolpyruvate carboxykinase gene is strongly induced in insulinopenia and, although up to now it had been considered absent from this tissue, the glycerokinase gene is expressed in the small intestine. The production of glucose by the small intestine may be acutely blunted upon insulin infusion. These new data also emphasize the central role of alanine aminotransferase in the coupling of glutamine and glucose metabolisms in the small intestine.
TL;DR: The present review describes the latest developments in the field of peroxisome proliferator-activated receptor isotypes, including their implication in the control of proliferation and differentiation of normal and malignant cells, and on the mechanisms implicated in the regulation of sterol regulatory element binding protein type 1 activity by polyunsaturated fatty acids.
Abstract: Over the past 10 years it has become evident that fatty acids regulate cellular functions by modulating gene expression. Fatty acids and fatty acid metabolites exert some of their effects on gene expression by affecting the activity of nuclear transcription factors, peroxisome proliferator-activated receptors and sterol regulatory element binding protein type 1. The present review describes the latest developments in the field, with particular emphasis on the physiological roles of the various peroxisome proliferator-activated receptor isotypes, including their implication in the control of proliferation and differentiation of normal and malignant cells, and on the mechanisms implicated in the regulation of sterol regulatory element binding protein type 1 activity by polyunsaturated fatty acids.
TL;DR: Therapy with very high pharmacological doses of the vitamin K2 menatetrenone has impressively been used to prevent further bone mineral loss and fracture risk in osteoporotic patients and to reduce the percentage of undercarboxylated osteocalcin in the circulation.
Abstract: The K vitamins, a group of napthoquinones, are required for the carboxylation of a limited number of proteins including the bone matrix protein osteocalcin. Vitamin K1 (phylloquinone) and vitamin K2 (menaquinones), differ regarding food source (green vegetables and fermented products, respectively), bioavailability and intermediate metabolism. Epidemiological studies provide evidence for an association between a low vitamin K intake and an enhanced osteoporotic fracture risk. Doses of vitamin K1 up to 15 times the current recommended dietary allowance have successfully been used to reduce the percentage of undercarboxylated osteocalcin in the circulation. Studies demonstrating clear beneficial effects on bone health, however, are still lacking. In contrast, therapy with very high pharmacological doses of the vitamin K2 menatetrenone has impressively been used to prevent further bone mineral loss and fracture risk in osteoporotic patients.
TL;DR: Future developments should be aimed at both educational intervention and biomaterials research, which will probably lead to a new set of catheters that are more resistant to infection and thrombosis.
Abstract: Central vein catheterization is frequently employed for monitoring, administration of drugs and parenteral nutrition in a variety of medical and surgical illnesses. Despite the widespread use of central vein access, both catheter-related infections and mechanical complications remain unacceptably common. In the last few years, data have become available to show that technical innovations and catheter maintenance protocols can reduce both catheter related bloodstream infections as well as mechanical complications. Future developments should be aimed at both educational intervention and biomaterials research. The former incorporates case-based instruction, problem-solving examination, and database analysis; while the latter will probably lead to a new set of catheters that are more resistant to infection and thrombosis.
TL;DR: Estrogen increases the metabolic capacity for both carbohydrate and lipid metabolism, perhaps increasing the overall metabolic flexibility of skeletal muscle, and progesterone negates both these effects, and could therefore result in a state of relative metabolic inflexibility, similar to that observed in the metabolic syndrome.
Abstract: Growing evidence suggests that the ovarian hormones have major effects on lipid and carbohydrate metabolism, and may also play a major role in up-stream molecular signaling mechanisms for regulating substrate metabolism. It appears that the absence of estrogen can impair glucose uptake during exercise. In contrast, progesterone not only impairs contraction-mediated glucose uptake when solely administered, but impairs glucose uptake when physiological concentrations of both estrogen and progesterone are administered. Likewise, progesterone administered to rodents for 14 days decreases glucose transporter (GLUT) 4 protein content in skeletal muscle and adipose tissue. Furthermore removing the ovaries decreases the activity of key oxidative enzymes while estrogen treatment restores the activity of these enzymes. It appears, therefore, that estrogen increases the metabolic capacity for both carbohydrate and lipid metabolism, perhaps increasing the overall metabolic flexibility of skeletal muscle. Conversely, progesterone negates both these effects, and could therefore result in a state of relative metabolic inflexibility, similar to that observed in the metabolic syndrome.
TL;DR: This review will address recent developments in the mechanisms by which hepatic metabolism affects glucose homeostasis in health and disease.
Abstract: The liver plays a central role in the control of glucose production. It is also involved in the regulation of insulin secretion and sensitivity through neural pathways. This review will address recent developments in the mechanisms by which hepatic metabolism affects glucose homeostasis in health and disease. Oral glucose feeding elicits several systemic and hepatic alterations of intermediary metabolism through the activation of neural pathways. How this may affect glucose metabolism will be briefly discussed, and alterations of glucose homeostasis in liver disease will be briefly described. There is evidence that a portion of intrahepatic glucose can be converted into lipids in the process of de-novo lipogenesis. How this may be involved in the control of glycaemia and lipid concentrations will be reviewed. Finally, molecular mechanisms by which the alteration of liver metabolism may affect systemic glucose homeostasis will be outlined.
TL;DR: The work done since the meta-analysis of the trials of nutritional supplementation in all age groups and pathologies until the end of 1999 is considered and the benefits evident to elderly patients using oral supplements are considered.
Abstract: Under-nutrition is common in elderly patients, especially for those in hospital. Hospital stay is often associated with further weight loss. Many authors have considered nutritional supplementation. A recent meta-analysis of the trials of nutritional supplementation in all age groups and pathologies found benefits from supplementation but suggested that further work was required. This review considers the work done since the meta-analysis until the end of 1999 and in particular considers the benefits evident to elderly patients using oral supplements.
TL;DR: A series of potential interactions between herbal and conventional drug therapy that place older people at risk for an adverse drug event are identified and health care professionals need to be aware of.
Abstract: Older people with dementia are often prescribed numerous medications. Use of herbal therapies in addition to these conventional drug therapies may lead to interactions that result in an adverse drug event. We have conducted a systematic review to identify all studies that examined interactions between herbal and conventional drug therapies (i.e. prescription or over-the-counter). Using a MEDLINE search of English-language studies published between 1980 and 2000, we limited our search to those herbal therapies most likely to be used for the treatment of dementia (memory loss and decreased concentration) and related symptoms. We identified 28 articles that describe interactions between these herbal (i.e. St. John's wort, ginkgo biloba, kava, valerian, and ginseng) and conventional drug therapies. Of these articles, 11 examined St. John's wort, four examined ginkgo biloba, five examined kava, one examined valerian, and seven examined ginseng. We identified a series of potential interactions between herbal and conventional drug therapy that place older people at risk for an adverse drug event. Health care professionals need to be aware of these potential interactions.