Changes in plasma lipids and lipoproteins in humans during a 2-year period of dietary restriction in Biosphere 2.

BACKGROUND: A cohort study was performed of 8 people sealed inside Biosphere 2 to evaluate the effects of dietary restriction in humans on lipid and lipoprotein levels and the relationship of these levels to energy, fat, and protein content of the diet, and body weight, weight change, and energy expenditure. METHODS: Eight healthy people aged 27 to 67 years, 4 women and 4 men, were sealed inside Biosphere 2 from September 26, 1991, to September 26, 1993, the longest sustained period in an "isolated confined environment" on record. They were studied throughout confinement and for more than 2 years after their exit and return to an ad libitum diet. Food available was severely restricted during most of the 2-year period inside Biosphere 2. High work output was maintained and food quality remained high, resulting in prolonged restriction of energy intake without malnutrition. RESULTS: Fasting plasma cholesterol, triglyceride, and high-density lipoprotein (HDL) cholesterol levels; HDL subfraction distribution; dietary energy, fat, and protein content intake; and height, weight, weight change, and energy expenditure were measured. Total plasma cholesterol and triglyceride levels decreased 30% and 45%, respectively. The HDL and low-density lipoprotein levels also decreased and, in some participants, levels of HDL2 subfractions were increased. Multivariate analysis showed that the major cause of these changes was energy restriction. CONCLUSIONS: Energy restriction was the major factor leading to low lipid and lipoprotein levels. Energy restriction with adequate nutrition of young and middle-aged people may substantially reduce risk for atherosclerosis and consequent coronary artery and cerebrovascular disease.

Clinical evaluation of failure to thrive in older people.

The purpose of this article is to outline a clinical approach to patients with failure to thrive in old age. The article starts with a hypothetical clinical case presentation epitomizing the problem seen in an outpatient clinic by geriatricians. This case is then used as a basis to discuss salient features of failure to thrive which may be different from patient to patient. The focus is on using standard outpatient evaluation methods to identify common problems causing failure to thrive.

Caloric restriction increases HDL2 levels in rhesus monkeys (Macaca mulatta).

Caloric restriction (CR) prolongs the life of rodents and other small animals, but the benefits of CR for primates and people are as yet unknown, and mechanisms by which CR may slow aging remain unidentified. A study of rhesus monkeys, Macaca mulatta, is underway to determine if CR might prolong life span in primates and to evaluate potential mechanisms for life prolongation. Thirty rhesus monkeys in three age cohorts, restricted to 70% of ad libitum calorie intake for 6-7 yr, were compared with 30 controls. Plasma lipid, lipoprotein, and high-density lipoprotein (HDL) apolipoproteins and subfractions were measured and compared with weight, percent fat, glucose, and insulin level. CR caused decreased triglyceride levels in adult monkeys and increased levels of HDL2b, the HDL subfraction associated with protection from atherosclerosis. Multivariate statistical analyses showed that differences in lipid and lipoprotein levels occurring with CR could be accounted for, at least in part, by decreased body mass and improved glucose regulation. These studies have used a novel dietary modification paradigm in nonhuman primates focused on calorie reduction. Results suggest that CR, as mediated by its beneficial effect on body composition and glucose metabolism, could prolong human life by decreasing the incidence of atherosclerosis.

Failure to thrive in the elderly.

Failure to thrive in the elderly is a syndrome and not a diagnosis. It encompasses a number of conditions characterized by progressive weight loss and decrease in function. For purposes of diagnosis and treatment, failure to thrive can be divided into nonorganic and organic causes. Nonorganic causes include psychosocial problems and difficulties with physical function. Organic causes include known diseases and, possibly, unknown age-associated changes in nutrition, regulation of inflammation, and anabolic and catabolic hormones.

High density lipoprotein cholesterol subfractions in older people.

BACKGROUND: High density lipoprotein (HDL) may be an important risk factor for cardiovascular disease in older people. HDL is heterogeneous with several subfractions. This article describes the distribution and correlates of HDL2 cholesterol (C) and HDL3-C in older people. METHODS: HDL subfraction cholesterols were measured in 1,127 females and 825 males > or = 65 years old who participated in the Cardiovascular Health Study. Distributions of HDL subfraction cholesterols and bivariate and multivariate relationships were determined in cross-sectional analyses. RESULTS: Mean (+/- SD) concentrations of HDL subfractions were: HDL3-C (M .98 +/- .25, F 1.2 +/- .29 mmol/l), HDL2-C (M .09 +/- .08, F .13 +/- .09 mmol/l). HDL2-C, but not HDL3-C, was slightly higher with age. Using multivariate analysis, both HDL2-C and HDL3-C (in females) were inversely correlated with triglyceride, body weight, and fasting insulin; HDL3-C was inversely correlated with central fat distribution in women. Both HDL2-C and HDL3-C were lower in participants with prevalent cardiovascular disease. However, only HDL3-C was significantly inversely related to carotid stenosis, as measured by ultrasound. CONCLUSIONS: The slight increase in HDL-C with age appears to be due to an increase in the HDL2-C subfraction. HDL-C subfractions are independently related to triglyceride levels, body weight, and insulin concentrations in older people, all potentially modifiable risk factors. Both HDL2-C and HDL3-C are lower in older people with prevalent cardiovascular disease, although only HDL3-C was correlated with carotid atherosclerosis. These findings are consistent with the hypothesis that HDL subfractions are important risk factors for atherosclerotic cardiovascular disease in the elderly.

Cytokines decrease apolipoprotein accumulation in medium from Hep G2 cells.

Cytokines, important biochemical mediators of inflammation, cause a rapid fall in the plasma concentration of cholesterol in vivo. One mechanism by which cytokines may cause acquired hypocholesterolemia is by decreasing the hepatic synthesis and secretion of apolipoproteins. To test this hypothesis, we incubated Hep G2 cells with human recombinant tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6. Each of the cytokines resulted in a dose-related reduction in the concentrations of apolipoprotein (apo) A-I, apoB, and lecithin:cholesterol acyltransferase (LCAT) activity in the medium after 24 hours of incubation. The effect of cytokines on apolipoprotein accumulation was not affected by preincubation of Hep G2 cells with fatty acids. Cytokines decreased the concentration of cellular apoA-I mRNA in a dose-related fashion but did not affect cellular concentrations of apoB mRNA. The concentrations of triglyceride and cholesterol were also reduced in the medium of cells incubated with cytokines. Total cell sterol synthesis rates were calculated by [14C]acetate incorporation. Cells incubated with interleukin-6 had a 31% increase in sterol synthesis rate but a 41% decrease in sterol secretion. These data suggest that these cytokines can decrease the hepatic synthesis and/or secretion of apolipoproteins and that this may explain, in part, the acquired hypocholesterolemia seen during acute and chronic inflammation.

Hypertriglyceridemia and cholesteryl ester transfer protein interact to dramatically alter high density lipoprotein levels, particle sizes, and metabolism. Studies in transgenic mice.

Several types of transgenic mice were used to study the influence of hypertriglyceridemia and cholesteryl ester transfer protein (CETP) expression on high density lipoprotein (HDL) levels, particle sizes, and metabolism. The presence of the CETP transgene in hypertriglyceridemic human apo CIII transgenic mice lowered HDL-cholesterol (HDL-C) 48% and apolipoprotein (apo) A-I 40%, decreased HDL size (particle diameter from 9.8 to 8.8 nm), increased HDL cholesterol ester (CE) fractional catabolic rate (FCR) 65% with a small decrease in HDL CE transport rate (TR) and increased apo A-I FCR 15% and decreased apo A-I TR 29%. The presence of the CETP transgene in hypertriglyceridemic mice with human-like HDL, human apo A-I apo CIII transgenic mice, lowered HDL-C 61% and apo A-I 45%, caused a dramatic diminution of HDL particle size (particle diameters from 10.3 and 9.1 to 7.6 nm), increased HDL CE FCR by 107% without affecting HDL CE TR, and increased apo A-I FCR 35% and decreased apo A-I TR 48%. Moreover, unexpectedly, hypertriglyceridemia alone in the absence of CETP was also found to cause lower HDL-C and apo A-I levels primarily by decreasing TRs. Decreased apo A-I TR was confirmed by an in vivo labeling study and found to be associated with a decrease in intestinal but not hepatic apo A-I mRNA levels. In summary, the introduction of the human apo A-I, apo CIII, and CETP genes into transgenic mice produced a high-triglyceride, low-HDL-C lipoprotein phenotype. Human apo A-I gene overexpression caused a diminution of mouse apo A-I and a change from monodisperse to polydisperse HDL. Human apo CIII gene overexpression caused hypertriglyceridemia with a significant decrease in HDL-C and apo A-I levels primarily due to decreased HDL CE and apo A-I TR but without a profound change in HDL size. In the hypertriglyceridemic mice, human CETP gene expression further reduced HDL-C and apo A-I levels, primarily by increasing HDL CE and apo A-I FCR, while dramatically reducing HDL size. This study provides insights into the genes that may cause the high-triglyceride, low-HDL-C phenotype in humans and the metabolic mechanisms involved.

Dietary fat increases high density lipoprotein (HDL) levels both by increasing the transport rates and decreasing the fractional catabolic rates of HDL cholesterol ester and apolipoprotein (Apo) A-I. Presentation of a new animal model and mechanistic studies in human Apo A-I transgenic and control mice.

In humans, diets high in saturated fat and cholesterol raise HDL-cholesterol (HDL-C) levels. To explore the mechanism, we have devised a mouse model that mimics the human situation. In this model, HuAITg and control mice were studied on low fat (9% cal)-low cholesterol (57 mg/1,000 kcal) (chow) and high fat (41% cal)-high cholesterol (437 mg/1,000 kcal) (milk-fat based) diets. The mice responded to increased dietary fat by increasing both HDL-C and apo A-I levels, with a greater increase in HDL-C levels. This was compatible with an increase in HDL size observed by nondenaturing gradient gel electrophoresis. Turnover studies with doubly labeled HDL showed that dietary fat both increase the transport rate (TR) and decreased the fractional catabolic rate of HDL cholesterol ester (CE) and apo A-I, with the largest effect on HDL CE TR. The latter suggested that dietary fat increases reverse cholesterol transport through the HDL pathway, perhaps as an adaptation to the metabolic load of a high fat diet. The increase in apo A-I TR by dietary fat was confirmed by experiments showing increased apo A-I secretion from primary hepatocytes isolated from animals on the high fat diet. The increased apo A-I production was not associated with any increase in hepatic or intestinal apo A-I mRNA, suggesting that the mechanism of the dietary fat effect was posttranscriptional, involving either increased translatability of the apo A-I mRNA or less intracellular apo A-I degradation. The dietary fat-induced decrease in HDL CE and apo A-I fractional catabolic rate may have been caused by the increase in HDL particle size, as was suggested by our previous studies in humans. In summary, a mouse model has been developed and experiments performed to better understand the paradoxical HDL-raising effect of a high fat diet.

A prospective study of outcome from protein-energy malnutrition in nursing home residents.

To study recovery from protein-energy malnutrition in patients newly admitted to a chronic care facility, biochemical and anthropomorphic malnutrition indicators were measured prospectively over a 2-month period. Subjects were observed for a mean of 76 +/- 18 days after admission. Factors which might affect nutritional status including method of feeding, energy prescribed, use of supplemental feedings, assistance in eating, and amount of diet consumed were recorded. Confounding variables including illness, mental status, functional status, or prescription drugs were evaluated for their impact. On the basis of an empiric nutrition score, 54% of newly admitted residents were malnourished. Improvement in nutritional score occurred in 63% of malnourished patients remaining in the facility whereas 37% remained malnourished. Two related factors, percentage of diet consumed and degree of assistance required in eating, were important differences in the outcome of patients remaining malnourished. Interventional studies to determine whether outcome can be improved by more aggressive feeding methods or by feeding teams need to be undertaken.

Hypocholesterolemia as a predictor of death: a prospective study of 224 nursing home residents.

The relationship of cholesterol, albumin, hemoglobin and glucose levels, and anthropometric variables to risk of death was examined in all residents of a nursing home. Risk of death was a "U-shaped" function of the cholesterol levels. A tenfold increase in relative risk was associated with cholesterol less than 3.4 mmol/l, and the least risk was associated with the middle tertile of cholesterol levels (4.0-5.0 mmol/l). For any level of plasma cholesterol, risk was constant with time for at least 6 months. Low albumin, low hemoglobin, and high fasting glucose levels were also associated with increased mortality; cholesterol levels were nonlinearly related to levels of these risk factors. Proportional hazards models showed that immobility, presence of decubitus ulcers of at least stage II, and use of enteral feeding were also risk factors for death. Because hypocholesterolemia correlated significantly (p less than .05) with the presence of decubiti, elevated white blood cell count, and use of enteral feeding, the association between hypocholesterolemia and risk of death was most likely due to its association with malnutrition and infection.

Changes in lipoprotein concentrations during the development of noninsulin-dependent diabetes mellitus in obese rhesus monkeys (Macaca mulatta).

Abnormalities in plasma lipoprotein concentrations commonly found in subjects with noninsulin-dependent diabetes may be related to insulin resistance, hyperinsulinemia, hyperglycemia, or other metabolic defects. The middle-aged obese rhesus monkey is an animal model in which these defects can be separated in time during the development of diabetes. It is, therefore, a model system for examining the sequence of metabolic changes which occur before and after the onset of diabetes. This sequence of changes was used in the present study to determine if lipoprotein changes occur in association with the development of diabetes in the rhesus monkey. Increases in plasma triglyceride, very low density lipoprotein (VLDL) triglyceride, and VLDL cholesterol, and decreases in high density lipoprotein cholesterol were observed across previously identified groups ranging from normal to diabetic. Plasma triglycerides increased from 0.54 +/- 0.09 (normal) to 1.27 +/- 0.50, 1.93 +/- 0.79, and 4.28 +/- 2.24 in three intermediate groups with progressive hyperinsulinemia and insulin resistance, to 7.59 +/- 2.73 mmol/L in the diabetic monkeys. Increases in VLDL triglyceride and VLDL cholesterol paralleled the plasma triglyceride increases. High density lipoprotein cholesterol decreased across the groups from 2.33 +/- 0.16 (normal) to 1.72 +/- 0.20, 1.17 +/- 0.13, and 1.09 +/- 0.20 mmol/L in the intermediate groups, and was lowest in the diabetic monkeys, 1.00 +/- 0.21. The obese rhesus monkey can therefore be used to study lipoprotein abnormalities as they occur both before and in noninsulin-dependent diabetes.

'Wasting away' of the old old: can it--and should it--be treated?

Asthenia/cachexia, a syndrome which may manifest as a "wasting away," is growing in importance as the number of those ages 75 to 85 and over 85 increases. The syndrome has clearly identifiable laboratory abnormalities, a multitude of etiologic factors, and serious consequences. Accurate diagnosis of the causative agent is often difficult, since asthenia/cachexia is associated with aging, acute disease, and chronic disease. In addition, empiric treatment is often unpleasant and causes grief to families attempting to provide humane care for parents and grandparents at the end of life. The goal of the practitioner is to identify and intervene judiciously in the progressive deterioration of individuals who develop asthenia/cachexia and its complications.