Sex and body-type interactions in the regulation of renal sodium transporter levels, urinary excretion, and activity in lean and obese zucker rats

BACKGROUND

Female humans and rodents are relatively protected against the development of hypertension and renal disease. Whether this protection is modified during insulin resistance and obesity, however, is not known.

OBJECTIVE

Because renal sodium reabsorption has a central role in determining blood pressure, we hypothesized that lean female rats would bave reduced renal expression, activity, and urinary excretion of 8 major sodium transporters/channels.

METHODS

Lean and obese, male and female Zucker rats (n = 4-8 per group) were fed progressively higher levels of dietary NaCl over a period of 54 days. Urinary excretion of renal sodium transport proteins was determined for 3 different dietary levels (0.04%, 0.4%, and 4%) of NaCl. With the high-NaCl diet, natriuretic responses to benzamil, furosemide, and thiazide were used as in vivo markers for activity of the epithelial sodium channel (ENaC), the bumetanide-sensitive Na-K-2C1 cotransporter (NKCC2), and the thiazide-sensitive NaCl cotransporter (NCC), respectively.

RESULTS

Female rats (of both body types) had lower plasma renin activity and insulin levels than their male counterparts. Likewise, immunoblotting revealed female rats had increased whole kidney abundance of NCC and of the alpha, beta, and gamma subunits of ENaC, as well as decreased abundance of the type 3 sodium hydrogen exchanger (NHE3), type 2 sodium phosphate cotransporter (NaPi-2), and alpha-1 sodium-potassium-adenosine triphosphatase (Na-K-ATPase), compared with males. Obese rats had reduced levels of NKCC2, NHE3, and gamma-ENaC, but higher levels of NaPi-2 and NCC. Urine excretion of sodium transporters in lean female rats was nearly undetectable, whereas obese rats of both sexes excreted markedly more NKCC2 and NCC, which agreed with greater natriuretic responses to thiazide and furosemide.

CONCLUSIONS

Obese female rats are similar to lean female rats with regard to the sex-distinct pattern of renal sodium transporters. However, obese female rats are more like obese male rats with regard to increased natriuretic response tofurosemide and thiazide, and to urine excretion of several transporters including NCC. Our results suggest that, with obesity, there is some loss of the protective female advantage.

Assessment and mathematical modeling of glucose turnover and insulin sensitivity in lean and obese cats

Insulin sensitivity (SI) of glucose disposal can be quantified with the euglycemic hyperinsulinemic clamp (EHC) with tracer glucose infusion. True steady state is, however, difficult to achieve, and non-steady state analysis of EHC data is preferred. This analysis requires information on glucose kinetics that can be obtained from bolus injection of cold and tracer glucose. The aim of this study was to assess glucose kinetics in cats. Mathematical modeling and non-steady state analysis was applied to assess effects of obesity on glucose turnover, glycolysis/glycogen synthesis, SI, and inhibition of endogenous glucose production (EGP) in lean cats (L) and obese cats (O). D-[3-(3)H]-glucose kinetics and 3H-H2O production were analyzed in 4 L and 4 O with three-compartment modeling. Frequently sampled insulin-modified intravenous glucose tolerance tests (FSIGT) with minimal model analysis were performed in 5L and 3 O to assess glucose kinetics and SI. EHC was performed in 10 L and 10 O with primed-constant infusion of 3H-glucose. Data were analyzed with a modified minimal model segregating suppression of EGP by insulin using a non-linear mixed-effects population approach. FSIGT provided estimates of SI, glucose effectiveness SG, and distribution volume. EHC provided estimates of SI, SG, glycolysis, and suprabasal insulin concentration for 50% EGP inhibition. Obesity appears to affect glucose distribution but not utilization at basal insulin, and reduces SI estimated by FSIGT and EHC. Differences in SI between FSIGT and EHC depend on different descriptions of EGP inhibition by insulin. Finally, glucose disposal at basal insulin appears to occur entirely through glycolysis, whereas significant amounts of glucose are sequestrated from oxidation during EHC.

JNK1 deficiency does not enhance muscle glucose metabolism in lean mice

Mice deficient in c-jun-NH(2)-terminal kinase 1 (JNK1) exhibit decreased fasting blood glucose and insulin levels, and protection against obesity-induced insulin resistance, suggesting increased glucose disposal into skeletal muscle. Thus, we assessed whether JNK1 deficiency enhances muscle glucose metabolism. Ex vivo insulin or contraction-induced muscle [(3)H]2-deoxyglucose uptake was not altered in JNK1 knockout mice, demonstrating that JNK1 does not regulate blood glucose levels via direct alterations in muscle. In vivo muscle [(3)H]2-deoxyglucose uptake in response to a glucose injection was also not enhanced by JNK1 deficiency, demonstrating that a circulating factor was not required to observe altered muscle glucose uptake in the knockout mice. JNK1 deficiency did not affect muscle glycogen levels or the protein expression of key molecules involved in glucose metabolism. This study is the first to directly demonstrate that enhanced skeletal muscle glucose metabolism does not underlie the beneficial effects of JNK1 deficiency in lean mice.

Comparison of anthropometric, metabolic and dietary fatty acids profiles in lean and obese dyslipidaemic Asian Indian male subjects

OBJECTIVES

To compare obesity measures, metabolic profiles and dietary fatty acids in lean and obese dyslipideamic Asian Indian male subjects.

DESIGN

Cross-sectional.

SETTINGS

Asian Indians living in the eastern part of India.

SUBJECTS

One hundred and thirty (Group I: lean control, n=50; Group II: lean dyslipidaemic, n=40 and Group III: obese dyslipidaemic, n=40) Asian Indian male subjects (> or =30 years) living in the eastern part of India.

METHODS

Anthropometric measures namely height, weight, circumferences of waist (WC) and hip, lipids (total cholesterol (TC) and triglycerides (TG)), lipoproteins (high- (HDL) and low-density lipoproteins (LDL)), fasting plasma glucose (FPG) and dietary fatty acids were obtained from each participant. Obesity measures, that is, body mass index (BMI), waist-hip ratio (WHR) and conicity index (CI) were subsequently calculated from anthropometric measures. Obesity was defined as individuals having BMI> or =25 kg/m(2). SUBJECTS with one or more of the following conditions were considered as dyslipidaemic: TG> or =2.3 mmol/l, TC> or =6.2 mmol/l, or TC/HDL> or =4.4 mmol/l. Daily intake of nutrients as well as saturated (SFA), monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA) were estimated by adding together all the foodstuffs consumed on weekly and monthly manner. Conversion of foodstuffs into nutrients was performed according to standard nutritive values of Indian foodstuffs.

RESULTS

Analysis of variance with Scheffe's post hoc test revealed that Group I had significantly lower mean compared to both Group II and Group III for age, WC, WHR, CI, TC, TG, LDL, FPG, total carbohydrates intake and intake of trans fatty acids. On the other hand, Group I had significantly lower mean than Group III only for BMI as well as intake of total proteins, total fats, total energy and erucic acids. Although, Group I had significantly greater mean compared to both Group II and Group III for HDL, UFA/SFA, MUFA/SFA and PUFA/SFA. Pearson's partial correlations (controlling for age and total energy) revealed that central obesity measures (WC, WHR and CI) had significant association with dietary fatty acids and their ratios. Furthermore, partial correlations (controlling for age) also showed that the ratios of unsaturated to SFA had significant negative association with lipids, lipoproteins (except HDL) and plasma glucose. Discriminant function analysis revealed that overall 78% of all entries were positively (correctly) classified in three groups using fatty acids and their ratios.

CONCLUSION

It seems rational to argue that while dealing with dyslipidaemic Asian Indians, clinicians should consider obesity measures, metabolic profiles and dietary fatty acids simultaneously to better comprehend the condition (s).

Body composition and metabolic changes following bariatric surgery: effects on fat mass, lean mass and basal metabolic rate

BACKGROUND

Bariatric surgery has become the method of choice for weight loss in severely obese patients. While the incidence of obesity and its co-morbidities have been well-documented, less is known about the outcomes of the surgery as it relates to body composition and metabolic changes.

METHODS

19 bariatric surgery patients (14 female, 5 male) were assessed for basal metabolic rate (BMR), percent fat, fat mass, and lean body mass (LBM) just prior to surgery and at 1, 3 and 6 months after surgery.

RESULTS

Analysis of Variance (ANOVA) using the general linear model indicated significant changes in all measures of body composition for each time period. Linear regression was developed for each of these measures. Of the 39.7-kg weight loss, 26.4 kg (66.5%) was fat mass loss and 13.3 kg (33.5%) was LBM loss. BMR significantly decreased from pre-surgery (2091 kcals) to 1 month post-surgery (1758 kcals), with no significant changes in subsequent time periods. Repeated measures ANOVA for the ratio of BMR/LBM indicated no significant differences for any comparison of time periods (F=2.29, P=.111), suggesting that there is no adaptation of an energy-conserving mechanism in these patients.

CONCLUSION

Bariatric surgery was highly successful in inducing significant changes in body weight (39.7 kg), fat mass (26.4 kg), % body fat (7.9%) but also lean body mass (13.3 kg). The 440 kcal decrease in BMR, while significant, was not greater than expected due to significant decreases in LBM.

Hypovitaminosis D osteopathy: is it mediated through PTH, lean mass, or is it a direct effect?

Hypovitaminosis D is increasing worldwide and is associated with low bone mass. The effects of hypovitaminosis D on bone might be direct or mediated through decreased muscle mass and function and/or secondary hyperparathyroidism. This study systematically investigated the relative contribution of lean mass, PTH, and the direct effect of vitamin D as predictors of vitamin D mediated osteopathy in elderly individuals. 460 ambulatory subjects aged 65-85 years had their bone mass and lean body mass measured by a dual-energy X-ray absorptiometry. Serum calcium, phosphorus and alkaline phosphatase, intact parathyroid hormone (PTH) and 25-hydroxyvitamin D (25 OHD) were also measured. Serum 25 OHD correlated with lean body mass in men, r = 0.24, P = 0.002, but not in women; and with bone mass at all skeletal sites in men, r = 0.20-0.30, P < 0.02. Correlations were also noted at all skeletal sites in women except for the spine, r = 0.13-0.18, P < 0.04. In both genders, BMD at sites enriched in cortical bone was 0.4-0.7 SD lower in the group with the lowest vitamin D tertile than that in the group in the highest tertile. After controlling for PTH, the magnitude of the correlations between BMD and 25 OHD remained significant in both genders. After controlling for lean body mass, the magnitude of these correlations did not change in women and decreased but remained significant in men. After adjustment for age and height, both lean body mass and PTH had significant independent contributions to BMD variance at all skeletal sites. After adjustment for age, height, lean mass, and PTH, 25 OHD did not have any significant residual contribution to BMD variance except at the trochanter in men. This study demonstrates that vitamin D osteopathy in the elderly is in large part mediated through lean mass in men and through PTH levels in both genders, with a greater contribution of PTH in women than in men. There was little demonstrable independent relation between serum 25 OHD and bone mass.

Distinct impaired regulation of SOCS3 and long and short isoforms of the leptin receptor in visceral and subcutaneous fat of lean and obese women

Animal studies have illustrated the importance of the expression in adipose tissue of the leptin receptor (OB-R), and of SOCS3 an inhibitor of the leptin signaling pathway, in body weight regulation. The aim of the present study was to investigate in human adipose tissues of the same patients the OB-R isoforms and SOCS3 expression. Subcutaneous and omental adipose tissues were obtained from 6 lean and 18 morbidly obese women. The long isoform OB-Rb mRNA mediating leptin signaling, and SOCS3 mRNA are abundantly present in the subcutaneous fat of lean women, but are 90% and 70% decreased (P<0.0001) in obese women. In visceral fat from lean and obese women, both OB-Rb and SOCS3 mRNA are detected at very low levels. Subcutaneous/visceral ratios for OB-Ra the short OB-R isoform, OB-Rb, and SOCS3 mRNA abundance strongly correlate with the insulin sensitivity index, HOMA-% S, (r=0.49, P<0.0001, r=0.42, P=0.0002 and r=0.38, P=0.0002, respectively) in both lean and obese patients without type 2 diabetes. The near absence of OB-Rb mRNA and the similarly decreased SOCS3 expression in obese adipose tissue may reflect a defective leptin signaling pathway that could play a role in the impairment of insulin sensitivity associated with excess adiposity.

Enigma interacts with adaptor protein with PH and SH2 domains to control insulin-induced actin cytoskeleton remodeling and glucose transporter 4 translocation

APS (adaptor protein with PH and SH2 domains) initiates a phosphatidylinositol 3-kinase-independent pathway involved in insulin-stimulated glucose transport. We recently identified Enigma, a PDZ and LIM domain-containing protein, as a partner of APS and showed that APS-Enigma complex plays a critical role in actin cytoskeleton organization in fibroblastic cells. Because actin rearrangement is important for insulin-induced glucose transporter 4 (Glut 4) translocation, we studied the potential involvement of Enigma in insulin-induced glucose transport in 3T3-L1 adipocytes. Enigma mRNA was expressed in differentiated adipocytes and APS and Enigma were colocalized with cortical actin. Expression of an APS mutant unable to bind Enigma increased the insulin-induced Glut 4 translocation to the plasma membrane. By contrast, overexpression of Enigma inhibited insulin-stimulated glucose transport and Glut 4 translocation without alterations in proximal insulin signaling. This inhibitory effect was prevented with the deletion of the LIM domains of Enigma. Using time-lapse fluorescent microscopy of green fluorescent protein-actin, we demonstrated that the overexpression of Enigma altered insulin-induced actin rearrangements, whereas the expression of Enigma without its LIM domains was without effect. A physiological link between increased expression of Enigma and an alteration in insulin-induced glucose uptake was suggested by the increase in Enigma mRNA expression in adipose tissue of diabetic obese patients. Taken together, these data strongly suggest that the interaction between APS and Enigma is involved in insulin-induced Glut 4 translocation by regulating cortical actin remodeling and raise the possibility that modification of APS/Enigma ratio could participate in the alteration of insulin-induced glucose uptake in adipose tissue.

Retinol-binding protein 4 and insulin resistance in lean, obese, and diabetic subjects

BACKGROUND

Insulin resistance has a causal role in type 2 diabetes. Serum levels of retinol-binding protein 4 (RBP4), a protein secreted by adipocytes, are increased in insulin-resistant states. Experiments in mice suggest that elevated RBP4 levels cause insulin resistance. We sought to determine whether serum RBP4 levels correlate with insulin resistance and change after an intervention that improves insulin sensitivity. We also determined whether elevated serum RBP4 levels are associated with reduced expression of glucose transporter 4 (GLUT4) in adipocytes, an early pathological feature of insulin resistance.

METHODS

We measured serum RBP4, insulin resistance, and components of the metabolic syndrome in three groups of subjects. Measurements were repeated after exercise training in one group. GLUT4 protein was measured in isolated adipocytes.

RESULTS

Serum RBP4 levels correlated with the magnitude of insulin resistance in subjects with obesity, impaired glucose tolerance, or type 2 diabetes and in nonobese, nondiabetic subjects with a strong family history of type 2 diabetes. Elevated serum RBP4 was associated with components of the metabolic syndrome, including increased body-mass index, waist-to-hip ratio, serum triglyceride levels, and systolic blood pressure and decreased high-density lipoprotein cholesterol levels. Exercise training was associated with a reduction in serum RBP4 levels only in subjects in whom insulin resistance improved. Adipocyte GLUT4 protein and serum RBP4 levels were inversely correlated.

CONCLUSIONS

RBP4 is an adipocyte-secreted molecule that is elevated in the serum before the development of frank diabetes and appears to identify insulin resistance and associated cardiovascular risk factors in subjects with varied clinical presentations. These findings provide a rationale for antidiabetic therapies aimed at lowering serum RBP4 levels.

Prediction Equation of Resting Energy Expenditure in an Adult Spanish Population of Obese Adult Population

OBJECTIVE

The aim of our study was to evaluate the accuracy of the equations to estimate REE in obese patents and develop a new equation in our obese population.

SUBJECTS AND METHODS

A population of 200 obesity outpatients was analyzed in a prospective way. The following variables were specifically recorded: age, weight, body mass index (BMI), waist circumference, and waist-to-hip ratio. Basal glucose, insulin, and TSH (thyroid-stimulating hormone) were measured. An indirect calorimetry and a tetrapolar electrical bioimpedance were performed. REE measured by indirect calorimetry was compared with REE obtained by prediction equations to obese or nonobese patients.

RESULTS

The mean age was 44.8 +/- 16.81 years and the mean BMI 34.4 +/- 5.3. Indirect calorimetry showed that, as compared to women, men had higher resting energy expenditure (REE) (1,998.1 +/- 432 vs. 1,663.9 +/- 349 kcal/day; p < 0.05) and oxygen consumption (284.6 +/- 67.7 vs. 238.6 +/- 54.3 ml/min; p < 0.05). Correlation analysis among REE obtained by indirect calorimetry and REE predicted by prediction equations showed the next data; Berstein's equation (r = 0.65; p < 0.05), Harris Benedict's equation (r = 0.58; p < 0.05), Owen's equation (r = 0.56; p < 0.05), Ireton's equation (r = 0.58; p < 0.05) and WHO's equation (r = 0.57; p < 0.05). Both the Berstein's and the Ireton's equations overpredicted REE and showed nonsignificant mean differences form measured REE. The Owen's, WHO's, and Harris Benedict's equations underpredicted REE. Our male prediction equation was REE = 58.6 + (6.1 x weight (kg)) + (1,023.7 x height (m)) - (9.5 x age). The female model was REE = 1,272.5 + (9.8 x weight (kg)) - (61.6 x height (m)) - (8.2 x age). Our prediction equations showed a nonsignificant difference with REE measured (-3.7 kcal/day) with a significant correlation coefficient (r = 0.67; p < 0.05).

CONCLUSION

Previously developed prediction equations overestimated and underestimated REE measured. WHO equation developed in normal weight individuals provided the closest values. The two new equations (male and female equations) developed in our study had a good accuracy.

Adipose gene expression response of lean and obese mice to short-term dietary restriction

Overweight and obesity lead to higher morbidity risks, which are alleviated even by mild weight loss. To gain insight in the molecular effects of weight loss in adipose tissue, we analyzed the effects of short-term dietary restriction (DR) on mice fed a low-fat diet (lean mice) or a high-fat diet (obese mice). Female C57Bl6/J mice on both diets were on DR until an average body weight loss of 20%, which was achieved in 8 to 12 days depending on body weight at the start of DR. Plasma free fatty acids and blood glucose levels decreased significantly on DR. In the (restricted) low-fat diet groups, gene expression analysis using adipose-enriched cDNA microarrays revealed only two transcripts to be significant differentially expressed by DR: up-regulation of malic enzyme (Mod1) and down-regulation of major urinary protein 1 (Mup1). Real-time polymerase chain reaction analysis confirmed these findings and showed, for the high-fat diet groups, an identical expression pattern for Mup1, whereas Mod1 showed an opposed gene expression pattern for the high-fat diet groups. In conclusion, initial weight loss induces transcriptional changes only in a very small number of adipose genes, which also depends on the (restricted) diet used.

Subcutaneous adipose tissue cytokine production is not responsible for the restoration of systemic inflammation markers during weight loss

CONTEXT

It has been suggested that weight loss can improve systemic inflammation associated with obesity by decreasing the adipose production of pro-inflammatory cytokines. This suggestion, however, remains controversial.

OBJECTIVE

To analyse the effect of weight loss on peripheral inflammatory markers and subcutaneous adipocytokine production.

DESIGN

Patients were studied at baseline, at the end of the weight loss period, and after 2 weeks of weight stabilisation.

SUBJECTS

Nineteen morbid obese non-diabetic patients and 20 lean control subjects.

INTERVENTION

During the weight loss period patients followed a 6-week low-calorie diet.

MEASUREMENTS

Plasma levels of inflammatory markers, maximal in vitro whole-blood cytokine production, subcutaneous adipose tissue expression and content of several cytokines.

RESULTS

Obese subjects had higher circulating levels of C reactive protein (CRP), serum amyloid A (SAA), interleukin IL-6, IL-1 and soluble tumor necrosis factor receptors (sTNFR). Weight loss was associated with a significant decrease in CRP, SAA, leucocytes and plasma IL-6. Maximal in vitro cytokine production of IL-1 and sTNFR1 increased during this period. Weight loss did not induce significant changes in the adipose concentrations of IL-6, IL-1 or sTNF-receptors. However, adipose expression of IL-6, IL-1, TNFalpha, membrane cofactor protein-1 and adiponectin increased at the end of the weight loss period. During weight maintenance, circulating inflammatory parameters increased and in some cases returned to baseline.

CONCLUSIONS

A low-calorie diet is associated with an improvement in the systemic inflammatory status. This seems to be due to energy restriction rather than to adipose mass loss, since inflammatory levels return to baseline soon after weight stabilisation. Furthermore, a negative energy balance and fat mobilisation are associated with increased subcutaneous cytokine adipose expression.

Angiotensin II type 2 receptor agonist directly inhibits proximal tubule sodium pump activity in obese but not in lean Zucker rats

We have reported recently that the renal angiotensin II type 2 (AT2) receptors are upregulated and involved in promoting natriuresis/diuresis in obese but not in lean Zucker rats. In the present study, we tested the hypothesis that there is an enhanced AT2 receptor signaling via NO/cGMP pathway leading to greater inhibition of the Na(+), K(+)-ATPase (NKA) activity in the proximal tubules (PT) of obese rather than lean Zucker rats. The AT2 agonist CGP42112 (0.1 to 100 nmol/L) inhibited (33% at 100 nmol/L) the NKA activity in the PTs of obese but not in lean Zucker rats. The AT2 antagonist PD123319 (1 micromol/L), not the angiotensin II type 1 antagonist losartan (1 micromol/L), significantly diminished the CGP42112-induced inhibition of the NKA activity in obese rats. The AT2 agonist (10 nmol/L)-induced NKA inhibition was abolished by the soluble guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo-[4,3-a] quinoxalin-1-one (10 micromol/L), the NO synthase inhibitor NG-nitro-L-arginine methyl ester (100 micromol/L), and the protein kinase G inhibitor K1388 (2 micromole/L). CGP42112 (10 nmol/L) caused an increase in serine phosphorylation of NKA alpha1-subunit in PT of obese rats. Measurement of cGMP and NO revealed that CGP42112 (0.1 to 100 nmol/L) increased cGMP and NO accumulation in the PTs of obese but not lean rats. The CGP42112-induced stimulation of NO and cGMP was blocked by PD123319 (1 micromol/L), NG-nitro-L-arginine methyl ester (100 micromol/L), and 1H-[1,2,4] oxadiazolo-[4,3-a] quinoxalin-1-one (10 micromol/L) but not by losartan (1 micromol/L). The data suggest that the AT2 receptor activation via stimulation of the NO/cGMP/protein kinase G pathway directly inhibits the tubular NKA activity that provides as a mechanism responsible for the AT2 receptor-mediated natriuresis in obese but not in lean Zucker rats.

Energy expenditure in underweight chronic obstructive pulmonary disease patients before and during a physiotherapy programme

OBJECTIVE

To investigate how total daily energy expenditure (TEE) changes when underweight patients with chronic obstructive pulmonary disease (COPD) enters a physiotherapy programme.

DESIGN

Prospective intervention study.

SETTING

Sahlgrenska University Hospital, Göteborg, Sweden.

SUBJECTS

Fifteen patients with severe COPD and BMI<21 kg/m(2) were recruited consecutively at the outpatient COPD unit at the Department of Respiratory Medicine. Fourteen patients completed the whole study.

INTERVENTION

TEE was assessed by the doubly labelled water method in a 2-week control period and during 2 weeks of physiotherapy. Energy intake was assessed using 7-day dietary record during control and physiotherapy period.

RESULTS

Mean TEE during physiotherapy period was 500 kJ (6%) lower than during control period but the difference was not statistically significant. Ten of the 14 patients had lower and four had higher TEE. Mean energy intake during the physiotherapy period did not change from the control period (7700 vs 7600 kJ/day).

CONCLUSIONS

Since underweight patients with COPD may show variable TEE during physiotherapy compared to a control period, an assessment of individual energy requirements is recommended.

Association of body mass index with suicide mortality: a prospective cohort study of more than one million men

The authors investigated the association of body mass index (BMI) with suicide in a record linkage study based on the Swedish Military Service Conscription Register, the Population and Housing Censuses, and the Cause of Death Register. The cohort studied consisted of 1,299,177 Swedish men who were conscripted in 1968-1999, had their BMI measured at age 18-19 years, and were followed up for as long as 31 years. A strong inverse association was found between BMI and suicide. For each 5-kg/m2 increase in BMI, the risk of suicide decreased by 15% (95% confidence interval: 9, 21). The association was similar when subjects with mental disorder at baseline were excluded from the analysis. BMI-suicide associations were similar in relation to suicide deaths occurring in the first 5 years of follow-up (hazard ratio for each 5-kg/m2 increase in BMI = 0.84, 95% confidence interval: 0.73, 0.96) compared with associations > or = 10 years after baseline (hazard ratio = 0.87, 95% confidence interval: 0.79, 0.96), indicating that weight loss as a consequence of mental illness does not explain the BMI-suicide association and that factors influencing BMI may be causally implicated in the etiology of mental disorders leading to suicide.

Skinfold thickness, body fat percentage and body mass index in obese and non-obese Indian boys

Childhood obesity is presently increasing worldwide and has created enormous concern for researchers working in the field of obesity related diseases with special interest in child health and development. Selected anthropometric measurements including stature, body mass, and skinfolds are globally accepted sensitive indicators of growth patterns and health status of a child. The present study was therefore aimed not only at evaluating the body mass index (BMI), skinfolds, body fat percentage (%fat) in obese school going boys of West Bengal, India, but also aimed to compare these data with their non-obese counterparts. Ten to sixteen year old obese boys (N = 158) were separated from their non-obese counterparts using the age-wise international cut-off points of BMI. Skinfolds were measured using skinfold calipers, BMI and %fat were calculated from standard equations. Body mass, BMI, skinfolds and %fat were significantly (P<0.001) higher for the sample of obese boys when compared to their non-obese counterparts. The obese group also showed progressive age-wise increments in all recorded anthropometric parameters. Stature (cm) showed no significant inter-group variation except in the 10 year age group (P<0.001). All data for the non-obese group were comparable with other national and international studies, but those collected for the obese group could not feasibly be compared because the availability of data on obese children is limited. Current data and prediction equations will not only serve as a reference standard, but also be of vital clinical importance in order to identify or categorize obese boys, and to take preventative steps to minimise serious health problems that appear during the later part of life.

The in vivo cardiac kinetics of Tc-99m N-NOET are accelerated in obese, hyperlipidemic Zucker rats

BACKGROUND

Previous studies demonstrated that the intrinsic myocardial washout of bis(N-ethoxy,N-ethyldithiocarbamato)nitrido technetium(V) (technetium 99m N-NOET) was affected by changes occurring in the intravascular compartment such as variations in circulating lipid levels. We sought to determine whether the myocardial kinetics of Tc-99m N-NOET were affected by hyperlipidemia in a clinically relevant experimental model.

METHODS AND RESULTS

Tc-99m N-NOET (50 MBq/kg) and thallium 201 (12 MBq/kg) were injected intravenously into hyperlipidemic fa/fa Zucker rats (n=6) and their lean, normolipidemic littermates (n=8), and dual-isotope in vivo planar imaging was performed for 60 minutes. In vivo image quantification indicated significantly faster cardiac washout of Tc-99m N-NOET in fa/fa animals versus lean animals (time constant, 411+/-64 minutes vs 1094+/-226 minutes, respectively; P<.05), whereas Tl-201 cardiac washout was not affected (356+/-85 minutes vs 337+/-53 minutes, respectively; P=not significant).

CONCLUSION

The cardiac kinetics of Tc-99m N-NOET, but not those of Tl-201, were accelerated after intravenous injection of the tracer in fa/fa Zucker rats with circulating lipid levels similar to those encountered clinically in hyperlipidemic patients. The relationship between lipidemia and the rate of Tc-99m N-NOET myocardial washout warrants further clinical investigation.

Adiponectin levels during low- and high-fat eucaloric diets in lean and obese women

OBJECTIVE

Adiponectin influences insulin sensitivity (S(I)) and fat oxidation. Little is known about changes in adiponectin with changes in the fat content of eucaloric diets. We hypothesized that dietary fat content may influence adiponectin according to an individual's SI.

RESEARCH METHODS AND PROCEDURES

We measured changes in adiponectin, insulin, glucose, and leptin in response to high-fat (HF) and low-fat (LF) eucaloric diets in lean (n = 10) and obese (n = 11) subjects. Obese subjects were further subdivided in relation to a priori SI.

RESULTS

We found significantly higher insulin, glucose, and leptin and lower adiponectin in obese vs. lean subjects during both HF and LF. The mean group values of these measurements, including adiponectin (lean, HF 21.9 +/- 9.8; LF, 20.8 +/- 6.6; obese, HF 10.0 +/- 3.3; LF, 9.5 +/- 2.3 ng/mL; mean +/- SD), did not significantly change between HF and LF diets. However, within the obese group, the insulin-sensitive subjects had significantly higher adiponectin during HF than did the insulin-resistant subjects. Additionally, the change in adiponectin from LF to HF diet correlated positively with the obese subjects' baseline SI.

DISCUSSION

Although in lean and obese women, group mean values for adiponectin did not change significantly with a change in fat content of a eucaloric diet, a priori measured SI in obese subjects predicted an increase in adiponectin during the HF diet; this may be a mechanism that preserves SI in an already obese group.

Insulin resistance in the Zucker diabetic fatty rat: a metabolic characterisation of obese and lean phenotypes

The Zucker diabetic fatty (ZDF) rat is a commonly used animal model of type 2 diabetes yet complete descriptions of insulin resistance in this model are limited. We present a full characterisation of in vivo insulin resistance in obese (fa/fa) animals compared to lean (+/?) littermates. Anaesthetised, ten-week old, obese ZDF rats and their lean littermates underwent a hyperinsulinaemic euglycaemic glucose clamp. Compared with lean littermates, obese ZDF rats required an 89% lower glucose infusion rate to maintain euglycaemia and showed a 35% decrease in peripheral glucose disposal. Insulin-stimulated glucose uptake (R(g')) in obese animals was also significantly less in all skeletal muscles studied. R(g') in cardiac and white adipose tissue was not different between the two groups. Total glycogen content in skeletal and cardiac muscle was significantly less in obese animals, while total glycogen content in the liver was significantly greater than in lean littermates. Glycogen synthesis was also decreased in skeletal muscle of obese animals. Compared with lean animals, total triglyceride content was significantly greater in skeletal muscle, heart and liver of obese ZDF rats. Obese animals also showed significantly increased glucose incorporation into lipid in all of these tissues, indicating an increase in lipogenesis. Collectively, these results provide an integrated characterisation of in vivo insulin resistance in obese ZDF rats and a direct comparison with lean littermates.

Differential expression of aquaporin 7 in adipose tissue of lean and obese high fat consumers

Aquaporin 7 (AQP7) is an aquaglyceroprotein responsible for the secretion and uptake of glycerol from the adipocyte. The modulation of the expression of this membrane transport protein might play an important role in the susceptibility to the development of obesity. The aim of the present study was to compare the AQP7 gene expression in subcutaneous abdominal fat in lean vs. obese high fat intakers with a similar daily physical activity pattern. Twelve young men, 6 lean (BMI=23.2+/-0.4kg/m(2)) and 6 obese (35.0+/-1.1kg/m(2)) with a similar habitual dietary intake of fat (45.5+/-2.5 vs. 43.5+/-1.7% daily energy from fat for lean and obese, respectively) and physical activity (16.0+/-5.7 vs. 17.2+/-5.1 METsh/week for lean and obese, respectively), were recruited. Subcutaneous abdominal fat biopsies were obtained and total RNA was extracted and purified. Pools of RNA from lean and obese individuals were probed into Affymetrix GeneChip Human U133A. The microarray analysis revealed that AQP7 gene was down-regulated in obese compared to lean subjects. The results of the microarray analysis were confirmed by real-time PCR studies. In summary, our data show that the AQP7 gene is differentially expressed in adipose tissue of lean and obese individuals. The down-regulation of the AQP7 gene could be implicated in the susceptibility to obesity by reducing glycerol release and promoting the accumulation of lipids in the adipose tissue.

Predicted vs measured energy expenditure in critically ill, underweight patients

A retrospective analysis was conducted to compare 4 energy-prediction equations against measured resting energy expenditure (MREE) determined via indirect calorimetry. Data from a heterogeneous group of 42 critically ill, severely underweight (59.50 +/- 17.30 kg; 77.1 +/- 9.7% ideal body weight [IBW]) male patients were assessed. The Hamwi formula was used to determine IBW. The Harris-Benedict (HB) equation was calculated for patients <90% IBW using both current body weight (CBW) and IBW. Energy needs were also estimated with an Ireton-Jones formula for all mechanically ventilated patients (n = 37). For patients <85% IBW (n = 31), an adjusted body weight was determined ([CBW + IBW]/2) and used in the HB formula. The HB formula using the IBW, CBW, and adjusted body weight was significantly different (p < .05) than MREE. The Ireton-Jones equation was not significantly different (p > .05) from MREE but tended to overestimate energy needs (109.3% +/- 16.8% MREE). Conversely, using the CBW or IBW in the HB underestimated the patient's energy needs; 77.0% +/- 11.6% MREE and 90.9 +/- 16.1% MREE, respectively. For patients <85% IBW, use of the adjusted body weight in the HB represented 84.2% +/- 13.9% MREE. The average caloric need was 31.2 +/- 6.0 kcal/kg CBW. Indirect calorimetry remains the best method of determining a patient's energy needs. Until a large prospective trial is conducted, a combination of prediction equations tempered with clinical judgment and monitoring the appropriateness of the nutrition prescription remains the best approach to quality patient care.

Inverse relationship between PGC-1alpha protein expression and triacylglycerol accumulation in rodent skeletal muscle

PGC-1alpha is a key regulator of tissue metabolism, including skeletal muscle. Because it has been shown that PGC-1alpha alters the capacity for lipid metabolism, it is possible that PGC-1alpha expression is regulated by the intramuscular lipid milieu. Therefore, we have examined the relationship between PGC-1alpha protein expression and the intramuscular fatty acid accumulation in hindlimb muscles of animals in which the capacity for fatty acid accumulation in muscle is increased (Zucker obese rat) or reduced [FAT/CD36 null (KO) mice]. Rates of palmitate incorporation into triacylglycerols were determined in perfused red (RG) and white gastrocnemius (WG) muscles of lean and obese Zucker rats and in perfused RG and WG muscles of FAT/CD36 KO and wild-type (WT) mice. In obese Zucker rats, the rate of palmitate incorporation into triacylglycerol depots in RG and WG muscles were 28 and 24% greater than in lean rats (P < 0.05). In FAT/CD36 KO mice, the rates of palmitate incorporation into triacylglycerol depots were lower in RG (-50%) and WG muscle (-24%) compared with the respective muscles in WT mice (P < 0.05). In the obese animals, PGC-1alpha protein content was reduced in both RG (-13%) and WG muscles (-15%) (P < 0.05). In FAT/CD36 KO mice, PGC-1alpha protein content was upregulated in both RG (+32%, P < 0.05) and WG muscles (+50%, P < 0.05). In conclusion, from studies in these two animal models, it appears that PGC-1alpha protein expression is inversely related to components of intramuscular lipid metabolism, because 1) PGC-1alpha protein expression is downregulated when triacylglycerol synthesis rates, an index of intramuscular lipid metabolism, are increased, and 2) PGC-1alpha protein expression is upregulated when triacylglycerol synthesis rates are reduced. Therefore, we speculate that the intramuscular lipid sensing may be involved in regulating the protein expression of PGC-1alpha in skeletal muscle.

The relationships of adiponectin with insulin and lipids are strengthened with increasing adiposity

CONTEXT

Adipose tissue inflammation has been implicated in the pathogenesis of obesity-related comorbidities. Adiponectin, an antiinflammatory protein, improves insulin sensitivity and lipid levels systemically. Because adiponectin is secreted by adipocytes, it may also act locally to counteract insulin resistance and dyslipidemia worsened by inflammation.

OBJECTIVE

The aim of this study was to determine whether associations between adiponectin and insulin sensitivity and lipids are stronger with increasing adiposity.

DESIGN

This cross-sectional study involved participants in The Princeton School District Study.

SETTING

The study was conducted in the Princeton City schools (Cincinnati, OH) during the 2001-2002 school year.

PARTICIPANTS

A total of 1196 non-Hispanic White and Black students in grades 5-12 participated.

MAIN OUTCOME MEASURE

The relationships between adiponectin and high-density lipoprotein, triglycerides, and insulin were measured. To test our hypothesis, we: 1) compared correlation and regression coefficients of lean and nonlean individuals, and 2) incorporated an adiponectin by adiposity interaction in regression models.

RESULTS

For high-density lipoprotein and triglycerides, the relationship with adiponectin, although present among lean adolescents, strengthened with increasing adiposity. However, with insulin, a relationship with adiponectin was only present among nonlean adolescents.

CONCLUSIONS

These analyses suggest that adiponectin's relationship with insulin and lipids strengthens with increasing adiposity, such that heavier adolescents have a greater benefit from high levels of adiponectin than their lean counterparts.

Proximal femur bone geometry is appropriately adapted to lean mass in overweight children and adolescents

It is unclear if the bones of overweight children are appropriately adapted to increased loads. The objective of this study was to compare bone geometry in 40 overweight (body mass index [BMI] > 85th percentile) and 94 healthy weight (BMI < or = 85th percentile) subjects, ages 4-20 years. Dual energy X-ray absorptiometry (Hologic QDR 2000) scans were analyzed at the femoral shaft (FS) and narrow neck (NN) by the Hip Structure Analysis program. Subperiosteal width, cortical thickness and indices of bone axial and bending strength (bone cross-sectional area [CSA] and section modulus [Z]) were measured from bone mass profiles. Multivariate regression models were used to compare overweight and healthy weight subjects. Z was 11 (95% CI 5, 19) and 13 (7, 20) percent higher at the FS and NN, respectively, in overweight subjects (P < 0.001), adjusted for height, maturation and gender. At the NN, higher Z was due to greater subperiosteal width [4% (2, 7)] and bone CSA [10% (5, 16]) and at the FS, to higher bone CSA [10% (5, 16)] and thicker cortices [9% (3, 15)]. When lean mass was added to the models, bone variables did not differ between overweight and healthy weight subjects (P > 0.22), with the exception of NN subperiosteal width [3% (0, 6), P = 0.04]. Fat mass did not contribute significantly to any model. In summary, proximal femur bone geometric strength in overweight children was appropriately adapted to lean mass and height but greater weight in the form of fat mass did not have an independent effect on bone bending strength. These geometric adaptations are consistent with the mechanostat hypothesis that bone strength adapts primarily to muscle forces, not to static loads represented by body weight.

Negative association between circulating total homocysteine and proinflammatory chemokines MCP-1 and RANTES in prepubertal lean, but not in obese, children

This study investigated in prepubertal obese children (POC), compared with prepubertal lean children (PLC), a possible relation among plasma total homocysteine (tHcy)-an independent risk factor for future atherosclerosis-and MCP-1 and RANTES, two circulating chemokines inducing leukocyte transendothelial migration (TEM), implicated in the initial stages of the inflammatory part of the atherosclerotic process. Seventy-two POC were evaluated for circulating tHcy, MCP-1, and RANTES, and compared with 42 healthy PLC. The mean adjusted (for age, sex as well as log10total insulin, vitB12, folate, total cholesterol, HDL cholesterol, log10triglycerides, and log10glucose levels) differences in tHcy, MCP-1, and RANTES levels between PLC and POC were all significant [1.16 nmol/mL (P = 0.03), 26.6 pg/mL (P = 0.02), and 52.9 pg/mL (P = 0.03), respectively]. In PLC, but not in POC, tHcy levels were negatively associated with both circulating MCP-1 (B = -1.68, P = 0.007) and RANTES (B = -1.16, P = 0.01) after adjusting for age, sex, BMI, as well as log10total insulin, vitB12, folate, total cholesterol, HDL cholesterol, log10triglycerides, and log10glucose levels. In conclusion, in POC there is a lack, in contrast to PLC, of a possibly autoregulatory, negative association of elevated tHcy levels to increased MCP-1 and RANTES levels. This could contribute to future, homocysteine-induced atherosclerosis.