Fructose Levels Are Markedly Elevated in Cerebrospinal Fluid Compared to Plasma in Pregnant Women

Background

Fructose, unlike glucose, promotes feeding behavior in rodents and its ingestion exerts differential effects in the human brain. However, plasma fructose is typically 1/1000th of glucose levels and it is unclear to what extent fructose crosses the blood-brain barrier. We investigated whether local endogenous central nervous system (CNS) fructose production from glucose via the polyol pathway (glucose→sorbitol→fructose) contributes to brain exposure to fructose.

Methods

In this observational study, fasting glucose, sorbitol and fructose concentrations were measured using gas-chromatography-liquid mass spectroscopy in cerebrospinal fluid (CSF), maternal plasma, and venous cord blood collected from 25 pregnant women (6 lean, 10 overweight/obese, and 9 T2DM/gestational DM) undergoing spinal anesthesia and elective cesarean section.

Results

As expected, CSF glucose was ~60% of plasma glucose levels. In contrast, fructose was nearly 20-fold higher in CSF than in plasma (p < 0.001), and CSF sorbitol was ~9-times higher than plasma levels (p < 0.001). Moreover, CSF fructose correlated positively with CSF glucose (ρ 0.45, p = 0.02) and sorbitol levels (ρ 0.75, p < 0.001). Cord blood sorbitol was also ~7-fold higher than maternal plasma sorbitol levels (p = 0.001). There were no differences in plasma, CSF, and cord blood glucose, fructose, or sorbitol levels between groups.

Conclusions

These data raise the possibility that fructose may be produced endogenously in the human brain and that the effects of fructose in the human brain and placenta may extend beyond its dietary consumption.     

Relation of Body Fat Distribution to Reproductive Factors in Pre- and Postmenopausal Women

TROISI, REBECCA J, ANNE M WOLF, JOANN E MANSON, KELLY M. KLINGLER AND GRAHAM A. COLDITZ. Relation of body fat distribution to reproductive factors in pre- and postmenopausal women. Obes Res. 1995;3:143–151. The cross-sectional relations of several reproductive characteristics with self-reported waist-to-hip circumference ratio were evaluated in 44, 487 pre- and postmenopausal women 40 to 65 years of age who were free of cancer, cardiovascular disease, and diabetes. All results were adjusted for age, body mass index, cigarette smoking, physical activity, and alcohol intake. Current use of postmenopausal hormones was associated with a significantly lower waist-to-hip ratio than either past or never use independent of type of menopause (0.778 versus 0.784, p=0.0001 and 0.787, p=0.0001, respectively), although associations with type (unopposed estrogens versus combined estrogen and progesterone) and duration of hormone therapy were not noted. Waist-to-hip ratio did not differ between pre- and postmenopausal women, but demonstrated weak positive associations with age at menarche, parity, and age at first birth, and a weak inverse association with past duration of breast-feeding. These data confirm relations of several reproductive factors and use of hormone replacement therapy with body fat distribution. Epidemiologic studies relating body fat distribution to disease outcomes in women should consider these factors as potential confounders.     

Psychiatric III-Health of Women and Its Relationship to Obesity and Body Fat Distribution

Objective : Abdominal obesity is associated with serious, prevalent diseases. Previously, psychiatric symptoms and ill-health has been found in this condition in men. The results of a similar study in women is reported herein. Research Methods and Procedures : A cohort of 1464 women, aged 40 years and recruited by systematic sampling, was examined (77.7% participation rate). Items regarding use of anxiolytics, hypnotics, and antidepressive drugs were registered, as well as symptoms of dyspepsia, sleeping disturbances, melancholy, and degree of life satisfaction. Smoking and alcohol consumption, as well as self-measured weight, height, waist, and hip circumferences, were reported, from which body mass index [BMI; weight (kg)/height² (m²), kg/m²] and the waist/hip circumference ratio (WHR) were calculated. Results : In bivariate analyses, BMI was associated with use of anxiolytics, antidepressive drugs, various sleeping disturbances, and a low degree of life satisfaction. After controlling for “the WHR, alcohol, and tobacco use in multivariate analysis, the associations between BMI and use of anxiolytics and sleeping disturbances remained significant. The WHR correlated with dyspepsia, sleeping problems, and use of antidepressive drugs. After adjustments for BMI, smoking, and alcohol, the relationship to dyspepsia and antidepressants remained significant. Discussion : The results suggest that elevated BMI (obesity) and elevated WHR (central fat distribution) are associated in different ways with symptoms of psychiatric ill-health in women. Obesity alone shows no such relationships to psy chiatric ill-health in men, whereas central fat distribution shows independent associations to all of the measured variables studied in this report in women, suggesting gender differences in these associations.     

Serum Uric Acid Is More Strongly Associated with Impaired Fasting Glucose in Women than in Men from a Community-Dwelling Population

Serum uric acid (SUA) levels are associated with metabolic syndrome (MetS) and its components such as glucose intolerance and type 2 diabetes. It is unknown whether there are gender-specific differences regarding the relationship between SUA levels, impaired fasting glucose (IFG) and newly detected diabetes. We recruited 1,209 men aged 60±15 (range, 19–89) years and 1,636 women aged 63±12 (range, 19–89) years during their annual health examination from a single community. We investigated the association between SUA levels and six categories according to fasting plasma glucose (FPG) level {normal fasting glucose (NFG), <100 mg/dL; high NFG-WHO, 100 to 109 mg/dL; IFG-WHO, 110 to 125 mg/dL; IFG-ADA, 100 to 125 mg/dL; newly detected diabetes, ≥126 mg/dL; known diabetes} SUA levels were more strongly associated with the different FPG categories in women compared with men. In women, the associations remained significant for IFG-WHO (OR, 1.23, 95% CI, 1.00–1.50) and newly detected diabetes (OR, 1.33, 95% CI, 1.03–1.72) following multivariate adjustment. However, in men all the associations were not significant. Thus, there was a significant interaction between gender and SUA level for newly detected diabetes (P = 0.005). SUA levels are associated with different categories of impaired fasting glucose in participants from community-dwelling persons, particularly in women.     

Associations of Green Tea and Rock Tea Consumption with Risk of Impaired Fasting Glucose and Impaired Glucose Tolerance in Chinese Men and Women

Objective

To explore the associations of green tea and rock tea consumption with risk of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT).

Methods

A multistage, stratified, cluster, random-sampling method was used to select a representative sample from Fujian Province in China. In total, 4808 subjects without cardiovascular disease, hypertension, cancer, or pancreatic, liver, kidney, or gastrointestinal diseases were enrolled in the study. A standard questionnaire was used to gather data on tea (green, rock, and black) consumption and other relevant factors. The assessment of impaired glucose regulation (IGR) was using 75-g oral glucose tolerance test (OGTT), the diagnostic criteria of normal glucose tolerance was according to American Diabetes Association.

Results

Green tea consumption was associated with a lower risk of IFG, while rock tea consumption was associated with a lower risk of IGT. The adjusted odds ratios for IFG for green tea consumption of <1, 1–15, 16–30, and >30 cups per week were 1.0 (reference), 0.42 (95% confidence intervals (CI) 0.27–0.65), 0.23 (95% CI, 0.12–0.46), and 0.41 (95% CI, 0.17–0.93), respectively. The adjusted odds ratios for IGT for rock tea consumption of <1, 1–15, 16–30, and >30 cups per week were 1.0 (reference), 0.69 (95% CI, 0.48–0.98), 0.59 (95% CI, 0.39–0.90), and 0.64 (95% CI, 0.43–0.97), respectively. A U-shaped association was observed, subjects who consumed 16–30 cups of green or rock tea per week having the lowest odds ratios for IFG or IGT.

Conclusions

Consumption of green or rock tea may protect against the development of type 2 diabetes mellitus in Chinese men and women, particularly in those who drink 16–30 cups per week.     

Hyperuricemia Is a Risk Factor for the Onset of Impaired Fasting Glucose in Men with a High Plasma Glucose Level: A Community-Based Study

Background

It is not clear whether elevated uric acid is a risk factor for the onset of impaired fasting glucose after stratifying by baseline fasting plasma glucose levels. We conducted a community-based retrospective longitudinal cohort study to clarify the relationship between uric acid levels and the onset of impaired fasting glucose, according to baseline fasting plasma glucose levels.

Methods

We enrolled 6,403 persons (3,194 men and 3,209 women), each of whom was 18–80 years old and had >2 annual check-ups during 2003–2010. After excluding persons who had fasting plasma glucose levels ≥6.11 mM and/or were currently taking anti-diabetic agents, the remaining 5,924 subjects were classified into quartiles according to baseline fasting plasma glucose levels. The onset of impaired fasting glucose was defined as fasting plasma glucose ≥6.11 mM during the observation period.

Results

In the quartile groups, 0.9%, 2.1%, 3.4%, and 20.2% of the men developed impaired fasting glucose, respectively, and 0.1%, 0.3%, 0.5%, and 5.6% of the women developed impaired fasting glucose, respectively (P trend <0.001). After adjusting for age, body mass index, systolic blood pressure, triacylglycerols, high density lipoprotein-cholesterol, creatinine, fatty liver, family history of diabetes, alcohol consumption, and current smoking, uric acid levels were positively associated with onset of impaired fasting glucose in men with highest-quartile fasting plasma glucose levels (adjusted hazard ratio, 1.003; 95% confidence interval, 1.0001–1.005, P = 0.041).

Conclusions

Among men with high fasting plasma glucose, hyperuricemia may be independently associated with an elevated risk of developing impaired fasting glucose.     

No Specific Effect of Fluoxetine Treatment on Fasting Glucose,Insulin, Lipid Levels,and Blood Pressure in Healthy Men with Abdominal Obesity

In this paper we investigated the effect of fluoxetine (60 mg/d) on serum lipids, glucose and insulin concentrations and blood pressure by means of a randomized, double-blind placebo controlled trial. Thirty-eight overweight BMI: 26–30 kg/m²), nondiabetic, nonhypertensive men with an abdominal fat distribution (waist/hip ratio: >0.97) received dietary advice and placebo or fluoxetine for 12 weeks. The changes in serum parameters and blood pressure in the fluoxetine treated group were not different from the placebo treated group, despite a significantly larger weight loss in the fluoxetine group. In both groups serum total-cholesterol concentrations, serum LDL-cholesterol concentrations and tlie HDL/LDL ratio were significantly improved after treatment. Reductions in fasting glucose concentration and systolic blood pressure were only significant in the placebo group. A reduction of serum triglycerides and an increase of HDL-cholesterol were found in the fluoxetine treated group. In the total study population the changes in serum lipids seemed to be more strongly related to the change in total body fat or subcutaneous abdominal fat (assessed by MRI) compared to the change in visceral fat. The improvement of most of the serum lipids was related to tlie change in total body fat independent of the mechanism for attaining this fat loss. Our results indicate that fluoxetine treatment has no specific effect beyond that expected for weight loss on serum lipid, glucose and insulin concentrations, and blood pressure in overweight men.     

Changes in Total Body Water and Body Fat in Young Women in the Course of Menstrual Cycle

This paper reports on the changes in total body water and body fat in young women in during the course of the menstrual cycle. We followed 40 young women with an average age of 21.52 years, and took bioelectrical impedance measurements during two menstrual cycles. The measurements were taken in three phases of the menstrual cycle. We found that body mass and total body water fluctuate during the menstrual cycle. Both parameters are highest in the luteal phase and lowest in the late folicular phase; 65% of the young women demonstrated these changes. The presence or absence of premenstrual symptoms had no influence on these values.     

Influence of the Time of Day and Fasting Duration on Glucose Level following a 1-Hour, 50-Gram Glucose Challenge Test in Pregnant Women

Background

Previous studies have shown that the time of day (TD) of glucose measurement and the fasting duration (FD) influence the glucose levels in adults. Few studies have examined the effects of the TD and FD on the glucose level following a 1-hour, 50-gram glucose challenge test (GCT) in pregnant women in screening for or diagnosing gestational diabetes mellitus (GDM). The objective of this study was to investigate the influence of the TD (morning, afternoon, night) and the FD (the time of the last food ingestion as follows: ≤1 hour, 1–2 hours, and >2 hours) by examining their combined effects on the glucose levels following a 50-gram GCT in pregnant women.

Methods and Results

We analyzed the data of 1,454 non-diabetic pregnant Taiwanese women in a prospective study. Multiple linear regression and multiple logistic regression were used to estimate the relationships between the 9 TD-FD groups and the continuous and binary glucose levels (cut-off at 140 mg/dL) following a 50-gram GCT, after adjusting for maternal age, nulliparity, pre-pregnancy body mass index, and weight gain. Different TD and FD groups were associated with variable glucose responses to the 50-gram GCT, some of which were significant. The estimate coefficients (β) of the TD-FD groups “night, ≤1 hr” and “night, 1–2 hr” revealed significantly lower glucose concentrations [β (95% confidence interval [CI]): −6.46 (−12.53, −0.38) and −6.85 (−12.50, −1.20)] compared with the “morning, >2 hr” group. The TD-FD groups “afternoon, ≤1 hr” and “afternoon, 1–2 hr” showed significantly lower odds ratios (OR) of a positive GCT; the adjusted ORs (95% CI) were 0.54 (0.31–0.95) and 0.58 (0.35–0.96), respectively.

Conclusions

Our findings demonstrate the importance of standardizing the TD and FD for the 1-hour, 50-gram GCT. In screening for and diagnosing GDM, the TD and FD are modifiable factors that should be considered in clinical practice and epidemiological studies.     

Factors Associated with Excessive Body Fat in Men and Women: Cross-Sectional Data from Black South Africans Living in a Rural Community and an Urban Township

Objective

To determine the factors associated with excessive body fat among black African men and women living in rural and urban communities of South Africa.

Methods

This is a cross-sectional analysis of data from the Prospective Urban and Rural Epidemiology (PURE) study, Cape Town, South Africa conducted in 2009/2010. The study sample included 1220 participants (77.2% women) aged 35–70 years, for whom anthropometric measurements were obtained and risk factors documented through face-to-face interviews using validated international PURE study protocols. Sex-specific logistic regression models were used to evaluate socio-demographic, lifestyle and psychological factors associated with three excessive body fat indicators, namely body mass index (BMI), waist circumference (WC) and body fat percent (BF%).

Results

The prevalence of excessive body fat based on BF%, WC and BMI cut-offs were 96.0%, 86.1%, and 81.6% for women respectively, and 62.2%, 25.9%, and 36.0% for men respectively. The significant odds of excessive body fat among the currently married compared to unmarried were 4.1 (95% CI: 1.3–12.5) for BF% and 1.9 (95% CI: 1.3–2.9) for BMI among women; and 4.9 (95% CI: 2.6–9.6), 3.2 (95% CI: 1.6–6.4) and 3.6 (95% CI: 1.9–6.8) for BF%, WC and BMI respectively among men. Age ≤50 years (compared to age >50 years) was inversely associated with excessive BF% in men and women, and less-than-a-college education was inversely associated with excessive BMI and WC in men. Tobacco smoking was inversely associated with all three excessive adiposity indicators in women but not in men. Unemployment, depression, and stress did not predict excessive body fat in men or women.

Conclusion

The sex-differences in the socio-demographic and lifestyle factors associated with the high levels of excessive body fat in urban and rural women and men should be considered in packaging interventions to reduce obesity in these communities.     

Seasonal Fluctuations in Body Fat and Activity Levels in a Rain-Forest Species of Mouse Lemur,Microcebus rufus

Seasonal fattening in preparation for the dry season followed by torpor characterizes some members of the family Cheirogaleidae, a group of < 600-g nocturnal Malagasy primates. These behaviors are associated with extreme seasonality in dry forests, where most studies have been conducted. I aimed to determine if the brown mouse lemur (Microcebus rufus), a rain-forest species of cheirogaleid, exhibited similar changes. Between January 1993 and May 1994 I conducted a mark-recapture study on Microcebus rufus in the rain forest of Ranomafana National Park. I monitored body weight and tail circumference for body fat fluctuations and inferred changes in activity levels from presence or absence in the traps. Some individuals of both sexes increased body fat and entered torpor as suggested by their absence from traps for at least 1 month of the dry season. Activity was resumed with body weight reduced by 5–35 g, and tail circumference by 0.4–1.2 cm. Population-level analysis supports these results; highest weight and tail circumference values occurred just before and at the onset of the dry season. Other individuals, predominantly male, exhibited no change in body fat or activity level, and some mouse lemurs increased their body fat over the course of the dry season. Age, social status, and individual response may influence seasonal behavioral strategies. Dry and rain-forest species of mouse lemur adopt similar behaviors to cope with environmental stresses. Mouse lemurs resemble nonprimate, small-bodied mammals, in which behavioral changes related to maintaining energy balance occur during seasonally unfavorable conditions.     

Role of Fat Body Lipogenesis in Protection against the Effects of Caloric Overload in Drosophila

The Drosophila fat body is a liver- and adipose-like tissue that stores fat and serves as a detoxifying and immune responsive organ. We have previously shown that a high sugar diet leads to elevated hemolymph glucose and systemic insulin resistance in developing larvae and adults. Here, we used stable isotope tracer feeding to demonstrate that rearing larvae on high sugar diets impaired the synthesis of esterified fatty acids from dietary glucose. Fat body lipid profiling revealed changes in both carbon chain length and degree of unsaturation of fatty acid substituents, particularly in stored triglycerides. We tested the role of the fat body in larval tolerance of caloric excess. Our experiments demonstrated that lipogenesis was necessary for animals to tolerate high sugar feeding as tissue-specific loss of orthologs of carbohydrate response element-binding protein or stearoyl-CoA desaturase 1 resulted in lethality on high sugar diets. By contrast, increasing the fat content of the fat body by knockdown of king-tubby was associated with reduced hyperglycemia and improved growth and tolerance of high sugar diets. Our work supports a critical role for the fat body and the Drosophila carbohydrate response element-binding protein ortholog in metabolic homeostasis in Drosophila.     

Serum Uric Acid Levels and the Risk of Impaired Fasting Glucose: A Prospective Study in Adults of North China

Objective

To prospectively investigate the association between serum uric acid (SUA) level and incidence of impaired fasting glucose (IFG) in adult Chinese.

Methods

We evaluated 13,328 women and 41,350 men without diabetes and IFG. The participants were classified into quintile according to baseline level of SUA. Data were analyzed to examine the association between SUA levels and the incidence of IFG. We used Cox regression models to estimate the relative risk of IFG after adjusting for known risk factors.

Results

For men, the second quintile of SUA has the lowest cumulative incidence of IFG (29.9%); the fifth quintile of SUA has the highest cumulative incidence of IFG (35.6%). After corrected with Cox regression, the first quartile and the fourth quartile have higher cumulative incidence of IFG than the second quintile, with the HR of 1.11(1.05-1.17) and 1.07(1.01-1.13), respectively. For women, the first quartile of SUA has the lowest cumulative incidence of IFG (20.7%), while the fifth quintile of SUA has the highest cumulative incidence of IFG (30.0%). However, there is no significant difference in IFG between different quintile after adjusted with Cox regression.

Conclusions

The results of this prospective study suggest that there is a higher risk of developing IFG in association with low or high SUA concentrations for men. These relationships were independent of other known risk factors. There is no significant correlation in the risk of developing IFG in association with SUA concentrations for women. Analyses excluding participants with hypertension or with hyperlipidemia and analyses with participants stratified by age reached similar conclusion.     

A Role for Testosterone in the Maintenance of Seasonally Appropriate Body Mass but not in Lipectomy-Induced Body Fat Compensation in Siberian Hamsters

The purpose of this study was to test whether serum testosterone (T) concentrations characteristic of reproductively active, long-day-housed Siberian hamsters are necessary for compensatory increases in nonexcised fat pads following removal of epididy-mal white adipose tissue (EWAT) and/or for the maintenance of seasonally appropriate body weights in these hamsters. Long-day-housed hamsters were castrated or left intact, sham or EWAT lipectomized, and given T or cholesterol (C) implants. All groups had ad libitum food access except for two castrated T-treated groups that were pair-fed to their C-treat-ed counterparts to control for effects of T on food intake. C-treated castrates had decreased body weights compared with all other groups, suggesting a role of T in the maintenance of seasonally appropriate body mass. Since the T-treated hamsters pair-fed to these T-deficient animals exhibited seasonally appropriate body weights and fat pad masses, T does not appear to affect these parameters through the modulation of food intake. All fat pads of C-treated animals were smaller than those of ad libitum- or pair-fed, T-treated castrates; however, EWAT was the only fat pad that was smaller in the C-treated sham-lipectomized group than in gonad-intact sham-lipectomized hamsters. This result may indicate an enhanced sensitivity of EWAT to T. The effects of T on fat pad mass were not associated with proportionate changes in lipoprotein lipase activity, suggesting that the major effect of T on fat accumulation occurs through other mechanisms in this species. C-treated lipectomized hamsters compensated for the body fat deficit 8 weeks after lipectomy via statistically nonsignificant increases in retroperitoneal and inguinal WAT mass. This finding suggests that, whereas T is necessary for maintenance of seasonally-appropriate body weight, it is not necessary for fat pad compensation after EWAT lipectomy.     

Perceived Stress and Coping Strategies in Relation to Body Mass Index: Cross-Sectional Study of 12,045 Japanese Men and Women

BackgroundAccumulated evidence suggests a weak positive relationship between psychosocial stress and body mass index (BMI), but little is known about stress coping strategies and BMI.ObjectiveWe aimed to examine if perceived stress and coping strategies are related to BMI, with any of their mutual interactions on BMI.MethodsThis cross-sectional study included 5,063 men and 6,982 women aged 40-69 years. A self-administered questionnaire ascertained perceived stress and 5 items of coping strategies (emotion expression, emotional support seeking, positive reappraisal, problem solving, and disengagement). Analyses were performed by gender with adjustment for age, socioeconomic status, and lifestyle factors.ResultsNo significant associations were detected between perceived stress and BMI in either men (P_trend = 0.09) or women (P_trend = 0.58). In men, however, ‘disengagement’ showed an inverse association with BMI (P_trend < 0.001), and ‘positive reappraisal’ and ‘problem solving’ revealed a positive association with BMI (P_trend = 0.04 and 0.007, respectively) even after controlling for perceived stress. A possible interaction between perceived stress and ‘disengagement’ on BMI was found in men (P_interaction = 0.027); the inverse association between ‘disengagement’ and BMI was more evident in higher levels of stress (β = −0.13, P_trend = 0.21 in low; β = −0.22, P_trend = 0.01 in medium; and β = −0.24, P_trend = 0.06 in high). In men, ‘disengagement’ was inversely associated with overweight/obesity (odds ratio 0.79, 95% confidential interval 0.67-0.95), and “positive reappraisal” was positively associated with it (1.25, 1.02-1.54).ConclusionsCoping strategies may have an important role in developing overweight/obesity, particularly in men.     

Circadian Neuroendocrine Role in Age-Related Changes in Body Fat Stores and Insulin Sensitivity of the Male Sprague-Dawley Rat

A role for circadian neuroendocrine rhythms in the age-related development of obesity and insulin resistance was investigated in the male Sprague-Dawley rat. The phases and amplitudes of the plasma rhythms of several metabolic hormones (i.e. corticosterone, prolactin, insulin, and triiodothyronine) differed in lean, insulin-sensitive (3-week-old rats). insulin-resistant (8-week-old rats) and obese, insulin-resistant (44-week-old rats) animals. Simulation of the daily rhythms of endogenous corticosterone and prolactin by daily injections of the hormones at times corresponding to the peak levels found in 3-week-old rats reversed age-related increases in insulin resistance and body fat in older (5-6-month-old) rats. Ten such daily injections of corticosterone and prolactin in 12-14-week-old rats produced long-term reductions in body fat stores (30%). plasma insulin concentration (40%″). and insulin resistance (60%) (determined by a glucose tolerance test) measured 11-14 weeks after the treatment. Alterations in circadian neuroendocrine rhythms may account for age-related changes in carbohydrate and lipid metabolism in the male Sprague-Dawley rat, and resetting of these rhythms by appropriately timed daily injections of corticosterone and prolactin may help maintain metabolism characteristic of younger animals.     

Circadian Neuroendocrine Role in Age-Related Changes in Body Fat Stores and Insulin Sensitivity of the Male Sprague-Dawley Rat

A role for circadian neuroendocrine rhythms in the age-related development of obesity and insulin resistance was investigated in the male Sprague-Dawley rat. The phases and amplitudes of the plasma rhythms of several metabolic hormones (i.e. corticosterone, prolactin, insulin, and triiodothyronine) differed in lean, insulin-sensitive (3-week-old rats). insulin-resistant (8-week-old rats) and obese, insulin-resistant (44-week-old rats) animals. Simulation of the daily rhythms of endogenous corticosterone and prolactin by daily injections of the hormones at times corresponding to the peak levels found in 3-week-old rats reversed age-related increases in insulin resistance and body fat in older (5-6-month-old) rats. Ten such daily injections of corticosterone and prolactin in 12-14-week-old rats produced long-term reductions in body fat stores (30%). plasma insulin concentration (40%'). and insulin resistance (60%) (determined by a glucose tolerance test) measured 11-14 weeks after the treatment. Alterations in circadian neuroendocrine rhythms may account for age-related changes in carbohydrate and lipid metabolism in the male Sprague-Dawley rat, and resetting of these rhythms by appropriately timed daily injections of corticosterone and prolactin may help maintain metabolism characteristic of younger animals.     

Role of the Liver in Regulation of Body Cysteine and Taurine Levels: A Brief Review

The first-pass metabolism of dietary sulfur amino acids by the liver and the robust upregulation of hepatic cysteine dioxygenase activity in response to an increase in dietary protein or sulfur amino acid level gives the liver a primary role in the removal of excess cysteine and in the synthesis of taurine. Hepatic taurine synthesis is largely restricted by the low availability of cysteinesulfinate as substrate for cysteinesulfinate decarboxylase, and taurine production is increased when cysteinesulfinate increases in response to an increase in the hepatic cysteine concentration and the associated increase in cysteine dioxygenase activity. The upregulation of cysteine dioxygenase in the presence of cysteine is a consequence of diminished ubiquitination of cysteine dioxygenase and a slower rate of degradation by the 26S proteasome.