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J Lovejoy

Publications and source records attributed to J Lovejoy.

10 recordsLinked to original sources
PubMed1999

Prevalence of self-reported nutrition-related health problems in the Lower Mississippi Delta.

OBJECTIVES: The purpose of this study was to assess demographic and geographic differences in prevalence of self-reported nutrition-related health problems in Arkansas, Louisiana, and Mississippi. METHODS: The authors analyzed 1991 and 1993 Behavioral Risk Factor Surveillance System data for adults 18 years or older. RESULTS: Less educated African American women and women of other minority groups who were aged 35 to 64 years reported the highest prevalence of health problems. Geographic differences involved prevalence of hypertension, health status, and insurance status. CONCLUSIONS: Specific demographic subgroups and geographic areas with a high risk of health problems are in particular need of targeted interventions.

Adult↗
PubMed1995

Insulin sensitivity accounts for glucose and lactate kinetics after intravenous glucose injection.

Mathematical modeling was used to explore the interaction between glucose, insulin, and lactate during the frequently sampled intravenous glucose tolerance test (FSIGTT). Insulin-modified FSIGTs were performed in 25 lean volunteers, and an additional 5 volunteers underwent FSIGTs with glucose injection alone to illustrate the effect of insulin on both glucose and lactate kinetics. The model chosen as the best representation of the system extended the minimal model of glucose kinetics (MM) by including a two-compartment model of lactate kinetics. The model accounted for both glucose and lactate kinetics, provided traditional MM parameters of insulin sensitivity and glucose effectiveness, and descriptive parameters of lactate kinetics. Modeling suggested that lactate production was limited by the rate of glucose disappearance, with no indication of direct effects of insulin on lactate. Inclusion of lactate kinetics had no adverse effect on MM parameters (SG: 0.023 +/- 0.009 vs. 0.023 +/- 0.010 min-1, SI: 1.01 +/- 0.70 vs. 1.03 +/- 0.71 x 10(4).min-1.pmol-1.1; P > 0.50, lactate model vs. MM), and indicated that approximately 1.2% min-1 of total glucose disappearance during the FSIGT is converted to lactate. An additional benefit of including lactate kinetics was the significant improvement in precision in MM parameter estimates as reflected by the fractional standard deviations (FSDs). This effect was most prominent for SG, in which a threefold improvement in parameter precision was observed (FSD: 13.5 +/- 3.1 vs. 42.5 +/- 48.5; means +/- SD).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Insulin resistance in obesity is associated with elevated basal lactate levels and diminished lactate appearance following intravenous glucose and insulin.

Lactate metabolism is altered in obesity. Increasing obesity is associated with increased blood lactate levels after an overnight fast. In contrast, we have recently shown a marked decrease in the capacity for acute lactate generation in obese subjects following an oral glucose load, which we postulated might be linked to altered insulin sensitivity. In the present study, we systematically analyzed the relationship between insulin sensitivity (the Sensitivity Index [SI] derived using the minimal model), body mass index (BMI), and glucose, insulin, and lactate levels in the basal state and following intravenous (IV) glucose and insulin administration in lean and obese subjects. The results showed that SI and BMI were inversely related, as expected. Insulin sensitivity was more tightly associated with glucose, insulin, and lactate levels (both basal and integrated) than obesity per se. A significant inverse relationship was found between SI and basal lactate levels (r = -.56). Moreover, a significant and positive relationship was found between SI and incremental lactate area under the curve (reflecting acute lactate production) (r = .41). In a multiple regression analysis to separate the independent effects of obesity (BMI) and insulin sensitivity, after adjusting for age, sex, and race, SI accounted for 34% of the variance in basal lactate and 24% of the variance in incremental lactate area. Obesity independently accounted for 10% of the variance in basal lactate and 11% of the variance in incremental lactate area, neither of which were statistically significant. We conclude that elevations in basal lactate are associated with the development of insulin resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Habitual dietary intake and insulin sensitivity in lean and obese adults.

Studies in rodents have shown that short-term increases in dietary fat result in fat cell enlargement and insulin resistance. In humans, although high-fat diets have been associated with obesity, little is known about the specific metabolic effects of these diets. In this study we explored possible associations between habitual dietary composition and insulin sensitivity. Twenty-two lean and 23 obese subjects were characterized by dietary history (food frequency questionnaire), anthropometrics, oral glucose tolerance, and insulin sensitivity (SI, from the minimal model). As shown previously, body mass index was positively correlated with percent of energy intake as fat (r = 0.47, P = 0.001). Increasing fat intake was also associated with diminished SI (r = -0.41, P = 0.01). In contrast, SI was positively correlated with fiber intake (r = 0.43, P = 0.007). Multivariate analysis confirmed the importance of dietary fiber for SI. We conclude that habitually low dietary fiber intake, along with elevated dietary fat, correlates with diminished SI in otherwise healthy lean and obese subjects.

Adult↗
PubMed1992

Lactate production in adipose tissue: a regulated function with extra-adipose implications.

Estimates of the quantitative contribution of adipose tissue to whole-body glucose metabolism, previously reported as 1-3%, have been revised to be on the order of 10-30%. These revised estimates come, in part, from a recognition that adipose tissue uses glucose to produce lactate and pyruvate, in addition to CO2 and triglycerides. Lactate production by adipose tissue is modulated in vitro by changes in glucose, insulin, and epinephrine concentrations. In vivo, lactate production is regulated acutely by the animal's nutritional state (fed or fasted) and chronically by the degree of obesity. A strong positive correlation exists between rat fat cell size and relative conversion of glucose to lactate (r = 0.89, P less than 0.001). Diabetes is also associated with markedly increased lactate production in adipocytes. Fat cells from obese or diabetic rats (or humans) can metabolize to lactate as much as 50-70% of the glucose taken up. From these recent studies, a picture is emerging in which the adipose organ may provide lactate for hepatic gluconeogenesis during fasting, and also lactate for hepatic glycogen synthesis after food ingestion. Modulation of adipocyte lactate production and contribution of adipose tissue lactate to the body's fuel economy in physiological and pathological states are the focus of this review.

Adipose Tissue↗
PubMed1990

Adrenal suppression and sexual initiation in group-living female rhesus monkeys.

Eight female rhesus monkeys living in an outdoor social group were studied for two menstrual cycles during the breeding season. During one cycle, adrenal steroids were suppressed for an average of 24 days using dexamethasone (0.6 mg/day) administered via subcutaneous osmotic minipumps. During the other cycle females were implanted with control pumps containing sterile water. Observers were blind to the treatments and treatment order was counterbalanced. Female sexual behavior was observed daily with each of two adult rhesus males. During dexamethasone treatment, cortisol levels were suppressed to less than 10% of control levels, and testosterone and androstenedione levels were suppressed to less than 50% of control, suggesting nearly total elimination of adrenal contribution to circulating androgen. All females showed hormonal evidence of ovulation. Adrenal suppression had no significant effect on female behavior, including approaches to the male and sexual solicits. In addition, no differences in any male behavior, including number of ejaculations, were seen between the two treatments. The continued cyclic copulation during adrenal suppression demonstrates that ovarian hormones are sufficient to modulate female rhesus sexual behavior and that adrenal androgens have little effect on the sexual behavior of intact, group-living rhesus females.

Adrenal Glands↗
PubMed1990

Lactate generation following glucose ingestion: relation to obesity, carbohydrate tolerance and insulin sensitivity.

To examine early metabolic abnormalities in obesity prior to the development of carbohydrate intolerance, we studied 14 lean and 37 obese subjects with normal glucose tolerance. All subjects underwent a standard 75 g oral glucose tolerance test (OGTT) with the addition of lactate measurement. As expected, there was a positive relationship between basal insulin and body mass index (BMI kg/m2;r=0.64, P less than 0.0001). In addition, even though the subjects had normal glucose tolerance, both basal glucose and sum of glucose during OGTT showed significant positive associations with obesity. Basal lactate correlated significantly and positively with obesity (r = 0.29, P = 0.04). When incremental areas during OGTT were examined, glucose area during OGTT was positively associated with BMI and insulin area was positively associated with both BMI and sum of glucose. Conversely, the incremental area of lactate decreased as BMI increased (r = -0.41, P = 0.003), despite the increasing glucose area. The results indicate that even prior to frank carbohydrate intolerance, progressive changes in basal levels of glucose, insulin, and lactate, as well as sum of glucose, accompany the expansion of adipose mass in obesity. Two different aspects of lactate metabolism have been examined in obesity. First, the association of increased basal lactate levels with increased obesity may reflect increased lactate production from enlarged adipocytes and an increased fat mass. Secondly, the inverse association between acute lactate generation following glucose ingestion and obesity, despite the increased sum of glucose in obese subjects, may reflect a decreased ability of adipose and/or extra-adipose tissues to convert glucose to lactate due to insulin resistance.

Adult↗
PubMed1976

The effectiveness of drug education programs: a critical review.

Twenty-seven studies were reviewed to determine whether school-based drug abuse prevention efforts have succeeded. Most of the studies reviewed either did not examine program impact on actual drug using behavior or were not designed with a degree of scientific rigor sufficient to warrant acceptance of their findings as valid. Those studies leading to reliable results regarding program effect on drug use were contradictory in their conclusions. In view of the possibility that educational efforts aimed at drug abuse prevention may be counterproductive, it is suggested that school-based programs henceforward be designed and conducted as experiments with controlled manipulation of relevant variables.

Adolescent↗