Exercise reverses the harmful effects of consumption of a high-fat diet on synaptic and behavioral plasticity associated to the action of brain-derived neurotrophic factor

A diet high in total fat (HF) reduces hippocampal levels of brain-derived neurotrophic factor (BDNF), a crucial modulator of synaptic plasticity, and a predictor of learning efficacy. We have evaluated the capacity of voluntary exercise to interact with the effects of diet at the molecular level. Animal groups were exposed to the HF diet for 2 months with and without access to voluntary wheel running. Exercise reversed the decrease in BDNF and its downstream effectors on plasticity such as synapsin I, a molecule with a key role in the modulation of neurotransmitter release by BDNF, and the transcription factor cyclic AMP response element binding protein (CREB), important for learning and memory. Furthermore, we found that exercise influenced the activational state of synapsin as well as of CREB, by increasing the phosphorylation of these molecules. In addition, exercise prevented the deficit in spatial learning induced by the diet, tested in the Morris water maze. Furthermore, levels of reactive oxygen species increased by the effects of the diet were decreased by exercise. Results indicate that exercise interacts with the same molecular systems disrupted by the HF diet, reversing their effects on neural function. Reactive oxygen species, and BDNF in conjunction with its downstream effectors on synaptic and neuronal plasticity, are common molecular targets for the action of the diet and exercise. Results unveil a possible molecular mechanism by which lifestyle factors can interact at a molecular level, and provide information for potential therapeutic applications to decrease the risk imposed by certain lifestyles.

Prostate cancer: another aspect of the insulin-resistance syndrome?

Insulin resistance and compensatory hyperinsulinaemia are thought to be the underlying factors in the metabolic or insulin-resistance syndrome and can be controlled by diet and exercise. Hyperinsulinaemia has been shown to have a direct effect on the live, suppressing the production of sex hormone-binding globulin (SHBG) and insulin-like growth factor-binding proteins 1 and 2 (IGFBP-1, -2) while stimulating the production of insulin-like growth factor 1 (IGF-1). These factors have been proposed to be important modulators of hormone-related cancers, such as prostate cancer. Men adopting a low-fat diet and daily exercise reduced their levels of serum insulin and IGF-1, while increasing their levels of IGFBP-1 and sex hormone-binding globulin (SHBG). Cell-culture studies with LNCaP prostate cancer cells showed apoptosis of tumour cells and a reduction in serum-stimulated cell growth in the post diet and exercise serum. These results suggest that prostate cancer may be another aspect of the insulin-resistance syndrome and that adopting a low-fat diet combined with regular exercise may reduce the risk for prostate and other hormone-related cancers. This needs to be tested with prospective studies.

A high-fat, refined sugar diet reduces hippocampal brain-derived neurotrophic factor, neuronal plasticity, and learning

We have investigated a potential mechanism by which a diet, similar in composition to the typical diet of most industrialized western societies rich in saturated fat and refined sugar (HFS), can influence brain structure and function via regulation of neurotrophins. We show that animals that learn a spatial memory task faster have more brain-derived neurotrophic factor (BDNF) mRNA and protein in the hippocampus. Two months on the HFS diet were sufficient to reduce hippocampal level of BDNF and spatial learning performance. Consequent to the action of BDNF on synaptic function, downstream effectors for the action of BDNF on synaptic plasticity were reduced proportionally to BDNF levels, in the hippocampus of rats maintained on the HFS diet between 2 and 24 months. In particular, animals maintained on the HFS diet showed a decrease in levels of: (i) synapsin I mRNA and protein (total and phosphorylated), important for neurotransmitter release; (ii) cyclic AMP-response element-binding protein (CREB) mRNA and protein (total and phosphorylated); CREB is required for various forms of memory and is under regulatory control of BDNF; (iii) growth-associated protein 43 mRNA, important for neurite outgrowth, neurotransmitter release, and learning and memory. Diet-related changes were specific for the hippocampus consequent to its role in memory formation, and did not involve neurotrophin-3, another member of the neurotrophin family. Our results indicate that a popularly consumed diet can influence crucial aspects of neuronal and behavioral plasticity associated with the function of BDNF.

Changes in sex hormone-binding globulin, insulin, and serum lipids in postmenopausal women on a low-fat, high-fiber diet combined with exercise

Dietary factors including fat and fiber have been reported to play a role in the development of breast cancer, possibly mediated by changes in estradiol. Diet and exercise have been shown to affect levels of sex hormone-binding globulin (SHBG), which in turn regulate the bioavailability of estradiol. Diet and exercise also affect insulin levels, which play a role in the synthesis of SHBG, and the hormone itself is a potent mitogen for many cancer cell lines. This study was designed to measure the effects of a low-fat, high-fiber diet, combined with regular aerobic exercise, on the levels of SHBG, insulin, and serum lipids in postmenopausal women with or without hormone replacement therapy (HRT). Two groups of postmenopausal women, 11 on HRT and 11 not on HRT, underwent a low-fat (1O% fat calories), high-fiber (65-70 g/day) diet-and-exercise intervention for three weeks. Serum SHBG, insulin, and lipids were measured before and after the regimen. After the intervention, SHBG levels were significantly increased for the women on HRT (44.5 +/- 3.4 vs. 62 +/- 6.4 nmol/l) and the women not on HRT (32.1 +/- 4.6 vs. 45.5 +/- 6.1 nmol/l, both changes p < 0.01). Also after the intervention, insulin levels were significantly reduced for the women on HRT (196 +/- 44.4 vs. 119.8 +/- 28.7 pmol/l) and the women not on HRT (144.2 +/- 17.9 vs. 115.5 +/- 20.8 pmol/l, both changes p < 0.01). Body mass index and total cholesterol were significantly reduced for both groups of women (all changes p < 0.01). Although the exact mechanism for the change in SHBG is not known, the increases in SHBG and reductions in insulin as a result of this lifestyle intervention should reduce the risk for breast cancer in postmenopausal women.

Impaired insulin-receptor autophosphorylation is an early defect in fat-fed, insulin-resistant rats

High-fat feeding results in impaired insulin signaling in skeletal muscle, but the role of the insulin receptor (IR) remains controversial. In the present study, female Fischer 344 rats were fed diets either low in fat [low fat, complex carbohydrate (LFCC)] or high in fat and sucrose (HFS). Insulin-stimulated skeletal muscle glucose transport, measured in purified sarcolemmal vesicles, was lower in rats consuming the HFS diet for 2 and 8 wk compared with LFCC controls (72.9 +/- 3.5, 67.6 +/- 3.5, and 86.1 +/- 3.5 pmol x mg(-1) x 15 s(-1), respectively; P < 0.05). Muscle IR content was unchanged in 2-wk HFS animals but was 50% lower in the 8-wk HFS group (P < 0.001). However, compared with LFCC, insulin-stimulated IR autophosphorylation was 26% lower in 2-wk HFS and 40% lower in 8-wk HFS animals (P < 0.005). Total muscle content of the proposed IR inhibitors cytokine tumor necrosis factor-alpha and membrane glycoprotein PC-1 was not significantly changed in HFS animals at either 2 or 8 wk. These results demonstrate that high-fat feeding induces insulin resistance in muscle concomitant with a diminished IR signaling capacity, although the mechanism remains unknown.

Protective effects of estrogen on gender-specific development of diet-induced hypertension

Dietary and humoral factors are thought to be involved in the development of hypertension. This study investigated the interaction between diet and gonadal hormone status in the development and reversibility of hypertension. Normal male and female and ovariectomized (OVX) female Fischer rats were placed on either a high-fat (primarily saturated), refined carbohydrate (sucrose) (HFS) or a low-fat, complex carbohydrate (LFCC) diet at 2 mo of age, and body weight and systolic blood pressure (BP) were measured. Male and OVX female rats were initially on the diets for 7 mo, whereas normal female rats were on the diets for 2 yr. After this initial phase, a group of rats from each of the normal HFS groups were converted to the LFCC diet for a period of 1 mo (males) and 2 mo (females). The OVX females were subcutaneously implanted with a 0.5-mg estradiol (E2) pellet for 1 mo. A significant rise in arterial BP occurred within 12 mo in female and only 2 mo in male rats on the HFS diet, exceeding 140 mmHg after 24 and 7 mo, respectively. Conversion from the HFS to the LFCC diet led to a normalization of BP in both female and male rats. HFS diet-induced hypertension was accelerated by OVX in female rats, approaching the pattern seen in male rats. The effect of OVX was completely reversed by E2 replacement. BP did not significantly change in any of the LFCC groups at any time point, and E2 replacement had no effect on BP in the OVX LFCC group. All HFS groups had significantly greater body weight, with differences occurring sooner in the male and OVX rats compared with the female rats. Diet modification resulted in a partial but significant reduction of body weight, but E2 replacement did not. These results demonstrate that long-term consumption of HFS diet induces hypertension in both genders and is reversible by diet modification. Hypertension is significantly delayed in females with functional ovaries. This protection is lost by OVX and restored by estrogen replacement. Thus hormone status contributes to the delayed onset of diet-induced hypertension in females compared with males.

SNARE-complex disassembly by NSF follows synaptic-vesicle fusion

Soluble N-ethylmaleimide-sensitive fusion attachment protein receptor (SNARE)-mediated fusion of synaptic vesicles with the presynaptic-plasma membrane is essential for communication between neurons. Disassembly of the SNARE complex requires the ATPase N-ethylmaleimide-sensitive fusion protein (NSF). To determine where in the synaptic-vesicle cycle NSF functions, we have undertaken a genetic analysis of comatose (dNSF-1) in Drosophila. Characterization of 16 comatose mutations demonstrates that NSF mediates disassembly of SNARE complexes after synaptic-vesicle fusion. Hypomorphic mutations in NSF cause temperature-sensitive paralysis, whereas null mutations result in lethality. Genetic-interaction studies with para demonstrate that blocking evoked fusion delays the accumulation of assembled SNARE complexes and behavioral paralysis that normally occurs in comatose mutants, indicating NSF activity is not required in the absence of vesicle fusion. In addition, the entire vesicle pool can be depleted in shibire comatose double mutants, demonstrating that NSF activity is not required for the fusion step itself. Multiple rounds of vesicle fusion in the absence of NSF activity poisons neurotransmission by trapping SNAREs into cis-complexes. These data indicate that NSF normally dissociates and recycles SNARE proteins during the interval between exocytosis and endocytosis. In the absence of NSF activity, there are sufficient fusion-competent SNAREs to exocytose both the readily released and the reserve pool of synaptic vesicles.

Evidence of an inhibitory effect of diet and exercise on prostate cancer cell growth

PURPOSE

A high fat diet and sedentary lifestyle may predispose men to prostate cancer through effects on serum factors such as hormones. We evaluated the effects of a low fat, high fiber diet and exercise intervention on serum stimulated growth of established prostate cancer cell lines.

MATERIALS AND METHODS

Fasting serum was obtained from 13 overweight men before and after undergoing an 11-day low fat, high fiber diet and exercise intervention. Serum was also obtained from 8 men who had complied with the regimen for a mean of 14.2 years. Hormone dependent LNCaP and independent PC-3 prostate cancer cell lines were grown in culture medium containing 10% of subject pre-intervention or post-intervention serum and viable cells were counted after 48 hours. Anthropometry, serum free testosterone, lipids and glucose were measured in all subjects.

RESULTS

Post-intervention serum from each of the 11-day intervention subjects reduced LNCaP cell growth by a mean of 30% compared with pre-intervention serum from each (p <0.01). LNCaP cell growth in serum from long-term subjects was 15% below that of post-intervention serum (p <0.01). There was no difference in the growth of PC-3 cells when cultured with serum from either intervention group. Serum free testosterone, body weight, glucose and lipids were significantly reduced in 11-day subjects.

CONCLUSIONS

A low fat, high fiber diet and exercise intervention resulted in serum changes that significantly reduced the growth of androgen responsive LNCaP prostate cancer cells in vitro.

Reversibility of Chronic Experimental Syndrome X by Diet Modification

Abstract —This study was designed to examine whether abnormalities that comprise the metabolic syndrome, including insulin resistance, hyperinsulinemia, hypertension, hyperlipidemia, and obesity, are reversible by diet. Female Fischer rats were placed on either a high-fat, refined-carbohydrate (HFS) diet or low-fat, complex-carbohydrate (LFCC) diet for a period of 20 months. After 20 months, a group of HFS rats were switched to the LFCC diet (HFS/LFCC) for a period of 2 months. Skeletal muscle glucose transport, plasma insulin, systolic blood pressure, and plasma lipids were measured in all groups after 22 months. Energy intake and body weight were measured weekly. In the HFS group, insulin-stimulated glucose transport was significantly reduced (67±4 versus 98±4 pmol · mg − 1 · 15 s − 1 ), whereas plasma insulin (300±49 versus 82±8 pmol/L), blood pressure (147±4 versus 123±4 mm Hg), plasma triglycerides (2.58±0.31 versus 0.39±0.04 mmol/L), LDL cholesterol (C) (3.45±0.40 versus 0.89±0.06 mmol/L), LDL-C to HDL-C ratio (2.9±0.1 versus 2.2±0.1), VLDL-C (1.53±0.23 versus 0.37±0.07 mmol/l), Total-C (5.56±0.58 versus 1.49±0.10 mmol/L), and body weight (360±11 versus 260±5 g) were all significantly elevated compared with the LFCC. Energy intake did not differ significantly; however, the LFCC had a much poorer feed efficiency. Conversion to a LFCC diet for 2 months led to normalization of glucose transport, blood pressure, plasma insulin, and VLDL-C and significant amelioration of obesity and other lipid abnormalities. These results demonstrate that syndrome X induced by an inappropriate diet is reversed with implementation of a low-fat, unrefined-carbohydrate diet without caloric restriction and suggest that diet may be a possible treatment for multiple simultaneous cardiovascular risk factors.

Enhanced NO inactivation and hypertension induced by a high-fat, refined-carbohydrate diet

We have recently demonstrated that long-term consumption of a high-fat, refined-carbohydrate (HFS) diet induces hypertension (HTN) in normal rats compared with a low-fat, complex-carbohydrate (LFCC) diet. Limited evidence suggests that high-fat or high-sugar diets cause enhanced generation of reactive oxygen species (ROS). We therefore hypothesized that by inducing oxidative stress, the HFS diet may promote nitric oxide (NO) inactivation and HTN. To test this hypothesis, female Fischer rats were placed on either the HFS or the LFCC diet starting at 2 months of age. Blood pressure, urinary NO metabolites (NO(x)), and total renal NO synthase activity were monitored, and the tissue abundance of nitrotyrosine (NT), which is the stable "footprint" of NO oxidation by ROS, was determined. The HFS diet group exhibited a gradual rise in arterial blood pressure and were hypertensive by 18 months. This trend was accompanied by a marked accumulation of NT in all tested tissues, an initial rise and a subsequent fall in NO synthase activity, and a fall in urinary NO(x) excretion. The HFS diet-fed animals had a blunted blood pressure response to the NO synthase inhibitor N:(omega)-nitro-L-arginine methyl ester (L-NAME) compared with the LFCC diet group, which showed a marked hypertensive response to L-NAME. L-NAME-induced HTN was reversible with L-arginine in the LFCC diet group; however, HTN was not corrected by L-arginine supplementation in the HFS diet group. These findings point to enhanced ROS-mediated inactivation and sequestration of NO, which may contribute to the reduction of bioactive NO and HTN in the HFS diet-fed animals.

Effects of a high-fat-sucrose diet on enzymes in homocysteine metabolism in the rat

Hyperhomocysteinemia (HH) and hyperinsulinemia are both risk factors for cardiovascular disease. To examine the effects of hyperinsulinemia on homocysteine metabolism, we fed rats a high-fat-sucrose (HFS) diet and then measured the hepatic mRNA and activity of 2 key enzymes involved in this metabolic pathway: 5,10-methylenetetrahydrofolate reductase (MTHFR) and cystathionine-beta-synthase (CbetaS). Fischer rats made insulin-resistant by a HFS diet were examined at 6 months and 2 years of age and compared with control rats fed a low-fat, complex-carbohydrate (LFCC) diet. At the end of 6 months, the HFS rats were heavier than the LFCC rats (214 +/- 3.4 v 188 +/- 1.4 g, P < .01). There were no differences in blood glucose between HFS and LFCC rats; however, plasma insulin and homocysteine concentrations were elevated in HFS rats (insulin, 56 +/- 12 v 14.5 +/- 2.9 microU/mL; homocysteine, 10.77 +/- 0.9 v 6.89 +/- 0.34 micromol/L, P < .01). Hepatic CbetaS enzyme activity was significantly lower in HFS compared with LFCC rats (0.45 v 0.64 U/mg, P = .0001), and this decrease was reflected in a decrease of the CbetaS mRNA concentration. In contrast, hepatic MTHFR enzyme activity and mRNA concentration were significantly elevated in the HFS group compared with controls (HFS and LFCC, 8.62 and 4.8 nmol/h/mg protein, respectively, P = .0001). These changes in plasma homocysteine, CbetaS, and MTHFR were significantly correlated with the degree of obesity and hyperinsulinemia. Fasting plasma insulin correlated significantly and positively with plasma homocysteine (r = .51, P < .01) and MTHFR activity (r = .48, P < .01) and negatively with CbetaS activity (r = -.54, P < .001). CbetaS and MTHFR activities were inversely correlated with each other (r = -.58, P < .001). In conclusion, rats fed a HFS diet are hyperinsulinemic, and the hyperinsulinemia is associated with an elevated homocysteine concentration and changes in 2 key enzymes in homocysteine metabolism.

Acute exercise increases nitric oxide synthase activity in skeletal muscle

This study examined the effects of acute exercise on skeletal muscle nitric oxide synthase (NOS) activity. Female Sprague-Dawley rats were divided into three groups: control, exercise, and exercise + N(G)-nitro-L-arginine methyl ester (L-NAME). In the exercise + L-NAME group, L-NAME was administered in the drinking water (1 mg/ml) for 2 days and subsequently the exercise and exercise + L-NAME groups underwent a 45-min bout of exhaustive treadmill running after which NOS activity and muscle glycogen were measured. In the control and exercise groups, 1-amino-S-methylisothiourea (AMITU), a selective neuronal NOS inhibitor, with and without additional nonselective NOS blockade [with N(G)-monomethyl-L-arginine (L-NMMA)], was used in vitro to assess the contribution of nNOS to total NOS activity. The exercise bout increased NOS activity by 37% in exercise compared with control groups, and both groups had significantly greater NOS activity compared with exercise + L-NAME. AMITU decreased total NOS activity in the control and exercise groups by 31.8 and 30.2%, respectively, and these activities were significantly greater than AMITU + L-NMMA in both control and exercise groups. We conclude that 1) there is basal neuronal NOS and endothelial NOS activity in skeletal muscle, 2) an acute exercise bout increases NOS activity in skeletal muscle, and 3) glycogen depletion during exercise occurs irrespective of NOS activity.

Diet-induced changes in endothelial-dependent relaxation of the rat aorta

PURPOSE

Hypertension (HTN), hyperlipidemia (HLP), and hyperinsulinemia are known risk factors for the development of cardiovascular disease. Each has independently been shown to be associated with impaired endothelial function, as demonstrated by decreased endothelial derived relaxation (EDR). Previous work in our laboratory has shown that rats fed a high-fat sucrose (HFS) diet will become insulin resistant, hypertriglyceridemic, and hypertensive. We hypothesize that the development of these diet-induced risk factors is associated with endothelial dysfunction and a significant decrease in EDR. Furthermore, the endothelial dysfunction will be improved by returning to a normal (low-fat complex carbohydrate (LFCC)) diet.

METHODS

Adult, male Fischer rats were fed either a LFCC or a HFS diet for 6 months (n = 8 in each group). A third group of rats (SWITCH) was fed a HFS diet for 6 months and then changed to a LFCC diet for 4 weeks. Blood pressure was measured via the tail-cuff method weekly. The rats were sacrificed and aortic ring segments were placed in physiologic tissue baths for measurement of vascular reactivity to various agents. Arterial ring segments were constricted with potassium chloride (K) and phenylephrine (PE). Endothelial-dependent vasorelaxation was measured with acetylcholine (Ach), bradykinin (BK), and calcium ionophore (CA). Endothelial-independent relaxation was measured using sodium nitroprusside (NTP).

RESULTS

The HFS diet group developed HTN compared to LFCC group. Vasoconstriction to K and PE were similar in all groups. Vasorelaxation to Ach, BK, and CA was significantly decreased in the HFS group, but returned to baseline in the diet-switched group, as did the systolic blood pressure. There were no differences in relaxation to NTP.

CONCLUSIONS

HFS diet-induced HTN is associated with significantly decreased EDR. Switching to a low-fat diet reverses this effect. The vascular smooth muscle contraction and endothelial-independent relaxation are not affected by the diet-induced risk factors. There is a direct and reversible effect of an HFS diet on endothelial function and blood pressure.

Effect of diet on fat cell size and hormone-sensitive lipase activity

This study was designed to examine the relationship between diet-induced insulin resistance/hyperinsulinemia, fat cell hypertrophy, and hormone-sensitive lipase (HSL) to elucidate whether an attenuated HSL activity leads to obesity. Female Fischer 344 rats were fed either a low-fat, complex-carbohydrate diet or a high-fat, refined-sugar (HFS) diet for 2 wk, 2 mo, or 6 mo. Adipose tissue morphology and HSL activity as well as plasma free fatty acid and glycerol levels were determined at these times. No differences between groups were seen after 2 wk except the previously reported hyperinsulinemia in the HFS animals. At both 2 and 6 mo, the HFS animals demonstrated adipocyte hypertrophy. Basal and stimulated HSL activities and plasma glycerol were significantly elevated in the HFS group. There was a positive correlation between adipocyte size and HSL activity for both basal and stimulated states. These results demonstrate that an attenuated HSL activity is not observed with the onset of insulin resistance/hyperinsulinemia and therefore does not play a role in the development of obesity.

Prognostic relevance of micro-vessel density in cancer of the urinary bladder

Angiogenesis is an important factor in tumour growth and metastasis. Degree of angiogenesis (microvascular density-MVD) has been found to correlate with tumour progression and disease outcome in a number of different malignancies. We studied 88 patients undergoing cystectomy for transitional cell bladder cancer to determine if angiogenesis was associated with cancer specific survival. Microvessels were identified by immunostaining of endothelial cells for CD31. Active areas of angiogenesis ("hot spots") were selected using low magnification. The vessel count was performed using a Chalkley point graticule. The mean of 3 counts was used for statistical analysis. The median count was 3.4. Univariate analysis revealed that higher MVD was associated with worsening prognosis (p = 0.02). When adjusted for clinical stage MVD continued to predict worsening prognosis (p = 0.02). MVD was not affected by age or sex or by previous radiotherapy. MVD was associated with the risk of patients dying following pelvic recurrence (p = 0.03) and MVD was significantly higher in patients with lymph node metastasis at surgery. In conclusion, microvessel density proved to be an independent prognostic marker in transitional cell carcinoma of bladder.

Effects of an intensive diet and exercise program on lipids in postmenopausal women

An intensive diet and exercise program resulted in significant reductions in serum lipids and reduced the susceptibility of low-density lipoprotein to oxidation in postmenopausal women.

Application of molecular typing methods to dermatophyte species that cause skin and nail infections

Typing methods utilising DNA technology were applied to a collection of Trichophyton mentagrophytes and T. rubrum isolates from skin and nail infections. The methods included restriction enzyme analysis (REA), hybridisation with the DNA probe poly (dG-dT), randomly amplified polymorphic DNA (RAPD) by PCR and restriction analysis of a segment of PCR-amplified rDNA. All these tests successfully differentiated the species, but few intra-species differences were detected. REA demonstrated some isolate variation, but this was limited and difficult to interpret, making it unsuitable as a typing tool. RAPD demonstrated few variations amongst T. mentagrophytes and none in T. rubrum.

Effects of diet and exercise on insulin, sex hormone-binding globulin, and prostate-specific antigen

A diet high in fat has been linked to prostate cancer, possibly through an influence on hormones. Sex hormone-binding globulin (SHBG) binds androgens and is regulated in part by insulin. Diet and exercise can modify insulin levels, potentially affecting SHBG and the biologically available levels of androgens. To determine the effects of a low-fat (< 10% of calories), high-fiber diet plus daily exercise on insulin, SHBG, prostate-specific antigen (PSA), and serum lipids, we measured the levels of these factors in the serum of 27 obese men undergoing a three-week diet-and-exercise program. Insulin decreased from 222 +/- 30 to 126 +/- 21 pmol/l (p < 0.01), and SHBG increased from 18 +/- 2 to 25 +/- 3 nmol/l (p < 0.01). Body mass index decreased from 35 +/- 1.9 to 33.4 +/- 1.8 kg/m2 (p < 0.01). PSA levels were normal and did not change significantly, although in a small subset of men (n = 3) with slightly elevated PSA levels (> 2.5 ng/ml) all showed a decrease. The three-week diet-and-exercise intervention decreased insulin and lipid levels while increasing SHBG. The increase in SHBG would result in more testosterone being bound and, therefore, less of the androgen available to act on the prostate. The decrease in insulin might also decrease mitogenic activity in the prostate. The diet-and-exercise regimen did not have a significant impact on normal PSA levels. Although modest, these changes may be protective against the development of prostate cancer.

Stimulation of NSF ATPase activity during t-SNARE priming

N-Ethylmaleimide-sensitive factor (NSF) plays a key role in vesicular traffic by disassembling and priming SNARE proteins for their function in docking and fusion. We demonstrate that the ATPase activity of NSF is activated by alpha-soluble NSF attachment protein (alpha-SNAP) in a complex with syntaxin 1A. In addition, we show that a construct consisting of the H3 domain of syntaxin IA (GST-synt(195-263), which does not support NSF disassembly in the presence of MgATP gave a larger stimulation. NSF ATPase activation was specific and did not occur using mutant alpha-SNAPs unable to bind GST-synt or with mutated C-termini. We suggest that activation of NSF ATPase activity in the SNARE complex may be essential to allow SNARE priming.

Diet-induced insulin resistance precedes other aspects of the metabolic syndrome

This study was designed to examine the effects of a high-fat refined-sugar (HFS) or a low-fat complex-carbohydrate (LFCC) diet on insulin-stimulated skeletal muscle glucose transport, plasma insulin, blood pressure, plasma triglycerides, plasma glycerol, body weight, and body fat in female Fischer rats. Insulin-stimulated glucose transport was significantly reduced in the HFS group at 2 wk, 2 mo, and 2 yr, whereas serum insulin was significantly elevated at all time points. Blood pressure was not significantly elevated in the HFS group until 12 mo, and all HFS animals were hypertensive by 18 mo. Glycerol, triglycerides, and abdominal fat cell size were not significantly different at 2 wk but were significantly elevated in the HFS rats at 2 and 6 mo. Body weight was similar in both groups until 20 wk on the diet, when the HFS rats started to gain more weight. These results demonstrate that insulin resistance and hyperinsulinemia occur before the other manifestations of the metabolic syndrome and that diet, not obesity, is the underlying cause.

Stimulation of NSF ATPase activity by alpha-SNAP is required for SNARE complex disassembly and exocytosis

N-ethylmaleimide-sensitive fusion protein (NSF) and alpha-SNAP play key roles in vesicular traffic through the secretory pathway. In this study, NH2- and COOH-terminal truncation mutants of alpha-SNAP were assayed for ability to bind NSF and stimulate its ATPase activity. Deletion of up to 160 NH2-terminal amino acids had little effect on the ability of alpha-SNAP to stimulate the ATPase activity of NSF. However, deletion of as few as 10 COOH-terminal amino acids resulted in a marked decrease. Both NH2-terminal (1-160) and COOH-terminal (160-295) fragments of alpha-SNAP were able to bind to NSF, suggesting that alpha-SNAP contains distinct NH2- and COOH-terminal binding sites for NSF. Sequence alignment of known SNAPs revealed only leucine 294 to be conserved in the final 10 amino acids of alpha-SNAP. Mutation of leucine 294 to alanine (alpha-SNAP(L294A)) resulted in a decrease in the ability to stimulate NSF ATPase activity but had no effect on the ability of this mutant to bind NSF. alpha-SNAP (1-285) and alpha-SNAP (L294A) were unable to stimulate Ca2+-dependent exocytosis in permeabilized chromaffin cells. In addition, alpha-SNAP (1-285), and alpha-SNAP (L294A) were able to inhibit the stimulation of exocytosis by exogenous alpha-SNAP. alpha-SNAP, alpha-SNAP (1-285), and alpha-SNAP (L294A) were all able to become incorporated into a 20S complex and recruit NSF. In the presence of MgATP, alpha-SNAP (1-285) and alpha-SNAP (L294A) were unable to fully disassemble the 20S complex and did not allow vesicle-associated membrane protein dissociation to any greater level than seen in control incubations. These findings imply that alpha-SNAP stimulation of NSF ATPase activity may be required for 20S complex disassembly and for the alpha-SNAP stimulation of exocytosis.

Exercise-stimulated glucose transport in skeletal muscle is nitric oxide dependent

It has been suggested that there are separate insulin-stimulated and contraction-stimulated glucose transport pathways in skeletal muscle. This study examined the effects of nitric oxide on glucose transport in rat skeletal muscle by use of an isolated sarcolemmal membrane preparation and the nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME), administered in the drinking water (1 mg/ml). Female Sprague-Dawley rats were divided into five groups: control, acute exercise, acute exercise+L-NAME, insulin stimulated, and insulin stimulated+L-NAME. Exercise (45 min of exhaustive treadmill running) increased glucose transport (37 +/- 2 to 76 +/- 5 pmol.mg-1.15 s-1) and this increase was completely inhibited by L-NAME (40 +/- 4 pmol.mg-1.15 s-1). A maximum dose of insulin increased glucose transport (87 +/- 10 pmol.mg-1.15 s-1), and adding L-NAME had no effect (87 +/- 11 pmol.mg-1.15 s-1). In addition, exercise, but not exercise+L-NAME, increased sarcolemma GLUT-4 content. This study confirms that there are separate pathways for contraction- and insulin-stimulated glucose transport. More importantly, although exercise and insulin both significantly increased glucose transport, L-NAME had no effect on insulin-stimulated glucose transport but blocked the exercise-stimulated transport. We conclude that nitric oxide is involved in the signal transduction mechanism to increase glucose transport during exercise.

Effects of intensive diet and exercise intervention in patients taking cholesterol-lowering drugs

Patients taking cholesterol-lowering drugs were placed on a very low fat, high-complex-carbohydrate diet with daily aerobic exercise and achieved 19%, 20% and 29% reductions in total cholesterol, LDL-cholesterol and triglycerides, respectively. Fifty-one percent of the primary care physicians had not used diet therapy before initiating drugs and 29% did not use diet therapy along with the drugs as recommended by the National Cholesterol Education Program.

Similar effects of alpha- and beta-SNAP on Ca(2+)-regulated exocytosis

Soluble N-ethylmaleimide-sensitive fusion protein attachment proteins (SNAP) proteins function in Ca(2+)-regulated exocytosis. Recent work (Schiavo et al. (1996) Nature 378, 733-736) based on in vitro protein interactions has raised the possibility that alpha- and beta-SNAPs have distinct roles in exocytosis. We have examined this possibility by comparing the activities of recombinant alpha- and beta-SNAPs. Both of these proteins were able to similarly bind NSF and activate its ATPase activity but to a lesser extent than gamma-SNAP. When introduced into digitoninpermeabilised chromaffin cells, both alpha- and beta-SNAP stimulated Ca(2+)-regulated exocytosis in a MgATP-dependent manner. The dose-response relationships for these proteins were essentially the same and addition of both proteins did not lead to any further increase in exocytosis above that due to each protein alone. We conclude that alpha- and beta-SNAPs are interchangeable isoforms with similar functions in regulated exocytosis.

Patch-clamp capacitance analysis of the effects of alpha-SNAP on exocytosis in adrenal chromaffin cells

We have examined the effect of alpha-SNAP on exocytosis in adrenal chromaffin cells by direct assay of exocytosis using patch-clamp capacitance analysis. Cells were recorded using the whole cell patch-clamp configuration and the cells dialysed with control pipette solution or with a pipette solution containing alpha-SNAP or the deletion mutant alpha-SNAP(41–295). The deletion mutant was found to be unable to bind to syntaxin allowing a test of the requirement for syntaxin-binding for any effect of alpha-SNAP on exocytosis. Following cell dialysis for 10 minutes, cells were depolarised five times at 2 minute intervals. At each depolarisation step cells dialysed with alpha-SNAP showed a significant increase in both the initial rate and extent of exocytosis which was seen as a rise in membrane capacitance. This increase in exocytosis was not observed with alpha-SNAP(41–295) which instead produced some inhibition of the extent but had no effect on the initial rate of exocytosis. These results show directly that alpha-SNAP has a specific and marked stimulatory effect on exocytosis in chromaffin cells.

Domains of alpha-SNAP required for the stimulation of exocytosis and for N-ethylmalemide-sensitive fusion protein (NSF) binding and activation

The binding of alpha-SNAP to the membrane proteins syntaxin, SNAP-25, and synaptobrevin leads to the recruitment of the N-ethylmaleimide-sensitive fusion protein (NSF). ATP hydrolysis by NSF has been suggested to drive conformational changes in one or more of these membrane proteins that are essential for regulated exocytosis. Functional evidence for a role of alpha-SNAP in exocytosis in adrenal chromaffin cells comes from the ability of this protein to stimulate Ca(2+)-dependent exocytosis in digitonin-permeabilized cells. Here we examine the effect of a series of deletion mutants of alpha-SNAP on exocytosis, and on the ability of alpha-SNAP to interact with NSF, to define essential domains involved in protein-protein interactions in exocytosis. Deletion of extreme N- or C-terminal regions of alpha-SNAP produced proteins unable to bind to syntaxin or to stimulate exocytosis, suggesting that these domains participate in essential interactions. Deletion of C-terminal residues abolished the ability of alpha-SNAP to bind NSF. In contrast, deletion of up to 120 N-terminal residues did not prevent the binding of NSF to immobilized alpha-SNAP and such mutants were also able to stimulate the ATPase activity of NSF. These results suggest that the C-terminus, but not the N-terminus, of alpha-SNAP is crucial for interactions with NSF. The involvement of the C-terminus of alpha-SNAP, which contains a predicted coiled-coil domain, in the binding of both syntaxin and NSF would place the latter two proteins in proximity in a ternary complex whereupon the energy derived from ATP hydrolysis by NSF could induce a conformational change in syntaxin required for exocytosis to proceed.

Primary small cell neuroendocrine carcinoma of the kidney

The histological, immunohistochemical, and ultrastructural features of a primary small cell neuroendocrine carcinoma of the renal parenchyma are described. Tumor cells were positive for cytokeratin, neuron-specific enolase, and Leu 7, but Grimelius- and chromogranin-negative. They also exhibited positivity with anti-MIC2 antibody. By electron microscopy, tonofibrils, primitive desmosomes, and dense-core granules with a neuroendocrine appearance were present. This is only the 7th recorded example of such a tumor at this site, which showed an aggressive course characterized by widespread bony metastases.

Effects of diet and exercise on qualitative and quantitative measures of LDL and its susceptibility to oxidation

The purpose of this study was to investigate the effects of an intensive diet and exercise program on the quantity and quality of LDL as well as its susceptibility to in vitro oxidation. The diet was low in fat (< 10% kcal) and cholesterol (< 100 mg/d), while high in complex, unrefined carbohydrates (> 70% kcal) and fiber (35 g/1000 kcal). The study was composed of 80 participants in a 3-week residential program where food was provided ad libitum and there was daily aerobic exercise, primarily walking. In each subject, preparticipation and postparticipation fasting blood samples were drawn and LDL was isolated via density gradient ultracentrifugation. LDL particle diameter was determined by gradient gel electrophoresis of serum (n = 23). Isolated LDL was either separated into 6 subfractions by saline gradient equilibrium ultracentrifugation (n = 26) or subjected to in vitro copper oxidation (n = 32). Significant reductions (P < .01) in serum levels of cholesterol (20%). LDL-cholesterol (20%), HDL-cholesterol (17%), triglycerides (26%), and glucose (16%) as well as in body weight (4%) were noted for the total population. The mean particle diameter of the LDL increased (24.2 +/- 0.2 to 25.1 +/- 0.14 nm, P < .01) and was correlated with the reduction in serum triglycerides (r = .58, P < .01). Six of 22 subjects changed in LDL phenotype from B (< or = 25.5 nm) to A (> 25.5 nm). The percentage of LDL-cholesterol carried in the more dense subfractions fell significantly, while that carried by the less dense fractions increased. Initial oxidation levels fell (21%), while the lag time before copper-induced oxidation increased (13%). Reductions were observed in both the rate of oxidation (16%) and peak oxidation (20%). All of these changes should result in a dramatic reduction in the risk for atherosclerosis and its clinical sequelae.

Effects of a very low fat, high fiber diet on serum hormones and menstrual function. Implications for breast cancer prevention

BACKGROUND

Low fat, high fiber dietary interventions that decrease blood estrogen levels may reduce breast cancer risk. Asian women consuming their traditional low fat, high fiber diets have lower blood estrogen levels before and after menopause and lower rates of breast cancer compared with Western women. The current controlled feeding study of premenopausal women was designed to determine the effects of a very low fat (10% of calories) and high fiber (35-45 g/day) diet on blood estrogen levels and menstrual function.

METHOD

Twelve healthy premenopausal women with regular ovulatory cycles were followed for 3 months. Subjects consumed a diet providing 30% of their energy from fat and 15-25 g of dietary fiber per day for 1 month, and they consumed a very low fat, high fiber and libitum diet providing 10% of their energy from fat and 25-35 g of dietary fiber per day for 2 months.

RESULTS

At the end of the second month of the very low fat, high fiber diet, there was a significant reduction in serum estrone and estradiol levels during the early follicular and late luteal phases. There were no significant changes observed in serum estrone sulfate, sex hormone binding globulin, or progesterone. Despite a significant decrease in serum estradiol and estrone levels after 2 months of a very low fat, high fiber diet, there was no interference with ovulation or the magnitude of the mid-cycle leuteinizing hormone surge. Small changes in menstrual cycle length of up to 3 days were not ruled out due to the small sample size of the study.

CONCLUSIONS

A very low fat, high fiber diet in healthy premenopausal women can reduce estradiol and estrone levels without affecting ovulation, thereby providing a rationale for the prevention of breast cancer through a very low fat, high fiber diet.

Calcineurin feedback inhibition of agonist-evoked cAMP formation

The effects of immunosuppressant blockers of calcineurin (protein phosphatase 2B) on cAMP formation and hormone release were investigated in mouse pituitary tumor (AtT20) cells. Immunosuppressants enhanced corticotropin-releasing factor- and isoproterenol-evoked cAMP production in proportion with their potency to block calcineurin. Further analysis of cAMP production revealed that intracellular Ca2+ derived through voltage-regulated calcium channels reduces cAMP formation induced by corticotropin releasing-factor or beta 2-adrenergic stimulation and that this effect of Ca2+ is inhibited by blockers of calcineurin. AtT20 cells were found to express at least three species of adenylyl cyclase mRNA-encoding types 1 and 6 as well as a novel isotype, which appeared to be the predominant species. In two cell lines expressing very low or undetectable levels of the novel cyclase mRNA (NCB20 and HEK293 cells respectively), corticotropin-releasing factor-induced cAMP formation was not altered upon blockage of calcineurin activity. These data identify calcineurin as a Ca2+ sensor that mediates the negative feedback effect of intracellular Ca2+ on receptor-stimulated cAMP production. Furthermore, the effect of calcineurin on cAMP synthesis appears to be associated with the expression of a novel adenylyl cyclase isotype, which is highly abundant in AtT20 cells.

Adaptations of immature trabecular bone to exercise and augmented dietary protein

Exercise and diet synergistically influence bone, but it remains unclear whether augmenting dietary protein intake during moderate exercise has a beneficial or negative effect on immature bone mechanical integrity. Thus, we examined lumbar vertebral bodies (L6) and femoral necks (FN) in trained and untrained rats fed either a recommended protein (15%) or higher protein (30%) diet. Male Wistar rats (8 wk old) were assigned to one of two exercise groups (high protein exercise [HPE], recommended protein exercise [RPE], run 3 d.wk-1 on a motor-driven treadmill at approximately 80% of their maximum oxygen capacity) or to one of two sedentary caged-control groups (high protein control [HPC], recommended protein control [RPC]. After 8 wk, in the HPE group, FN maximum normal stress was significantly greater than all other groups, and FN maximum load and energy at maximum load (per unit body mass) were significantly greater than the sedentary control groups. L6 stress at the proportional limit and initial-maximum stress did not differ among groups, but L6 percent ash was significantly greater in the HPE and RPC groups. Thus, coupling high dietary protein with moderate exercise can produce positive effects on immature rat femoral neck mechanical properties and structure.

Urinary tract obstruction and nephrostomy drainage in pelvic malignant disease

OBJECTIVE

To determine the survival of patients after percutaneous nephrostomy drainage (PND) for obstructive uropathy secondary to pelvic malignant disease.

PATIENTS AND METHODS

The records of 77 patients undergoing PND for obstructive uropathy were reviewed. Patients were classified according to the nature of the obstructing lesion: Group I (primary untreated malignancy, 31 patients); Group II (recurrent malignancy with further treatment, 15 patients); Group III (recurrent malignancy with no further treatment, 12 patients); and Group IV (benign disease as a consequence of previous treatment, 19 patients). Outcome was assessed by survival over a mean follow-up of 20 months (range 2 days-8.3 years).

RESULTS

Overall median survival was 26 weeks, with a 5-year survival of 22%. The survival in Groups I and II was not significantly different (median survival 27 and 20 weeks, respectively; 5-year survival, 10% and 20%, respectively). Group III patients had a poor prognosis (median survival 6.5 weeks) with no patient surviving beyond one year, whilst Group IV patients fared best with a 5-year survival of 64%. The commonest primary tumour type was carcinoma of the cervix (42 patients), and these patients were analysed as a subset. Benign post-radiation fibrosis was found in 16 of 27 patients (59%). Survival was related to the diagnostic group.

CONCLUSION

The nature and extent of the obstructing lesion and its potential for further treatment are the major determinants of post-nephrostomy survival. Every effort should therefore be made to identify the nature of the obstruction before deciding on PND.

Response of immature diabetic rat bone-ligament junctions to insulin and exercise

The mechanical and morphological characteristics of femur-medial collateral ligament-tibia units and the histomorphometry of medial collateral ligament-tibial insertion were examined in female Sprague-Dawley rats with diabetes mellitus (type I, insulin-dependent diabetes). Diabetes was induced with the streptozotocin, a drug with toxic effects on insulin-producing islet cells in the pancreas. The groups studied included rats with untreated streptozotocin-induced diabetes mellitus (Diabetes), insulin-treated streptozotocin-induced diabetes (Diabetes-Insulin), exercise with streptozotocin-induced diabetes (Diabetes-Exercise), exercise with insulin-treated streptozotocin-induced diabetes (Diabetes-Insulin-Exercise), and age-matched sedentary-control rats (Control). Diabetes and Diabetes-Exercise groups had significantly lower body mass and higher blood glucose than Diabetes-Insulin, Diabetes-Insulin-Exercise, and Control groups, indicating that exercise alone did not prevent growth retardation or improve blood glucose control in the streptozotocin-induced diabetes. The strength of Diabetes femur-medial collateral ligament-tibia units was significantly less than Control, but exercise (with or without insulin treatment) maintained the bone-ligament-bone unit strength at a normal level. The load (per unit body mass) of Diabetes-Exercise femur-medial collateral ligament-tibia unit was significantly greater than Control, Diabetes, and Diabetes-Insulin groups. The tensile stiffness (per unit body mass) of the femur-medial collateral ligament-tibia unit for the Diabetes-Exercise group was also significantly greater than Control and Diabetes-Insulin groups. The fibroblast-like cell density in medial collateral ligament at its tibial-insertion site and medial collateral ligament insertion area was significantly less in Diabetes rats. RELEVANCE--:Diabetes mellitus can have deleterious effects on connective tissues, such as bone and ligament. Thus the bone-ligament junction becomes vulnerable. The results of this experiment suggest, however, that exercise, with or without insulin treatment, can have a positive effect on the bone-ligament interface in the rat with type I diabetes mellitus. Furthermore exercise (with insulin treatments) can mitigate growth retardation and many of the adverse effects of streptozotocin-induced diabetes on the structure and mechanical properties of immature bone-ligament junctions.

Effect of short-term cardiovascular conditioning and low-fat diet on myocardial blood flow and flow reserve

BACKGROUND

Cardiovascular conditioning reduces resting myocardial oxygen demand by lowering systolic blood pressure and heart rate. Lower myocardial oxygen demand at rest would be expected to be associated with a decrease in resting myocardial blood flow and, consequently, an increase in myocardial flow reserve as the ratio of hyperemic to resting blood flow. However, the effect of controlled exercise together with a low-lipid diet on myocardial blood flow and flow reserve has not been examined in humans.

METHODS AND RESULTS

Myocardial blood flow at rest and after dipyridamole-induced hyperemia (0.56 mg/kg i.v.) was quantified with [13N]ammonia and positron emission tomography in 13 volunteers before and upon completion of a 6-week program of cardiovascular conditioning and a low-fat diet. Exercise capacity and serum lipid profiles were also assessed at the start and finish of the program. Eight normal volunteers of similar age not participating in the conditioning program served as a control group. Cardiovascular conditioning lowered the resting rate-pressure product (8859 +/- 2128 versus 7450 +/- 1496, P < .001), serum cholesterol (217 +/- 36 versus 181 +/- 26 mg/dL), LDL cholesterol (140 +/- 32 versus 114 +/- 24 mg/dL), and triglycerides (145 +/- 53 versus 116 +/- 33 mg/dL, all P < .05). Exercise tolerance (metabolic equivalent of the task, METs) improved significantly from 10.0 +/- 3.0 to 14.4 +/- 3.6 (P < .01). Resting blood flow decreased (0.78 +/- 0.18 versus 0.69 +/- 0.14 mL.g-1.min-1, P < .05), whereas hyperemic blood flow increased (2.06 +/- 0.35 versus 2.25 +/- 0.40 mL.g-1.min-1, P < .05), resulting in an improved myocardial flow reserve (2.82 +/- 1.07 versus 3.39 +/- 0.91, P < .05). Overall, the myocardial flow reserve was significantly related to exercise performance (METs). In the control group, no changes in resting rate-pressure product, serum cholesterol levels, exercise performance, resting or hyperemic myocardial blood flow, or flow reserve were observed.

CONCLUSIONS

Short-term cardiovascular conditioning together with a low-fat diet results in an improved myocardial flow reserve by lowering resting blood flow and increasing coronary vasodilatory capacity. These changes are associated with an improved exercise capacity and may offer a protective effect in patients with coronary artery disease.

Effects of acute and chronic exercise on skeletal muscle glucose transport in aged rats

The purpose of this study was to investigate the effects of acute and chronic exercise on skeletal muscle glucose transport in aged rats by using an isolated sarcolemmal membrane preparation. In 24-mo-old female Fischer 344 rats, a maximum dose of insulin increased glucose transport from 43 +/- 6 to 82 +/- 6 pmol.mg protein-1.15 s-1. A 45-min bout of exhaustive treadmill running increased glucose transport to the same maximum level (88 +/- 5 pmol.mg protein-1.15 s-1). Eight weeks of progressive exercise training resulted in a 65% increase in succinic dehydrogenase activity in hindlimb muscles and a 55% increase in total cellular GLUT-4 content. Despite these biochemical adaptations, there was no change in either basal or maximum insulin-stimulated glucose transport between control (43 +/- 6 and 82 +/- 6 pmol.mg protein-1.15 s-1, respectively) and trained (42 +/- 2 and 82 +/- 8 pmol.mg protein-1.15 s-1, respectively) animals. When hindlimb muscle succinate dehydrogenase activity and GLUT-4 content were compared for both the combined sedentary and trained groups, a significant correlation (r = 0.68) was obtained. This study demonstrates that the skeletal muscle glucose transport system of 24-mo-old rats is fully stimulated by acute exercise and that, although GLUT-4 levels are increased in aged animals after exercise training, this does not result in an enhancement of maximal insulin-stimulated glucose transport. Thus increases in GLUT-4 are not sufficient to improve muscle insulin responsiveness with training.

Long-term, high-fat-sucrose diet alters rat femoral neck and vertebral morphology, bone mineral content, and mechanical properties

Short-term exposure to diets high in fat and sucrose can induce hyperinsulinemia, affect calcium and magnesium metabolism, and alter bone mineralization and mechanical properties. The current study focused on the morphological and structural changes that result from long-term exposure to a high-fat sucrose (HFS) diet. Inbred, female Fischer 344 rats were assigned randomly to a low-fat, complex-carbohydrate (LFCC) diet group or a HFS diet for 24 months. At the end of the 2 years, each femoral neck (FN) was tested to failure in cantilever-bending, the sixth lumbar vertebra (L6) was tested in compression, and geometrical characteristics of the bones were determined. Although the HFS rats were significantly fatter and heavier than the LFCC rats, the HFS L6 had a significantly smaller average cross-sectional area. When L6 structural properties were normalised with respect to body mass, the HFS L6 had significantly lower loads, energies, and stiffnesses. The HFS L6 stress and strain energy density values were also significantly less than the LFCC L6. Compared to the LFCC FN, the HFS FN had a smaller cortical shell and larger trabecular core. The HFS FN also had significantly lower mass-normalised loads, energies, and stiffnesses. These results suggest that a long-term HFS diet has a significant adverse effect on rat bone morphology and mechanics.

Diet, not aging, causes skeletal muscle insulin resistance

The purpose of this study was to compare the effects of raising female Fischer rats on a low-fat, high-complex-carbohydrate diet (LFCC) versus a high-fat, sucrose diet (HFS) on serum glucose and insulin as well as skeletal muscle glucose transport. No significant differences were observed between 6- and 24-month-old rats raised on the LFCC diet for serum glucose (3.6 +/- 0.1 vs. 3.7 +/- 0.2 mM) and insulin (88 +/- 6 vs. 98 +/- 10 pM) or for basal (35 +/- 3 vs. 39 +/- 6 pmol/mg protein/15 s) or insulin-stimulated (74.2 +/- 7.6 vs. 69.4 +/- 3.8 pmol/mg protein/15 s) glucose transport. These data indicate that aging per se does not lead to insulin resistance. When the 24-month-old animals raised on the HFS diet were compared with those on the LFCC diet, major differences were observed. Fasting serum insulin was significantly higher in the HFS group (437 +/- 118 vs. 98 +/- 10 pM) and insulin-stimulated glucose transport was significantly reduced (52.5 +/- 3.7 vs. 69.4 +/- 3.8 pmol/mg protein/15 s). Fasting glucose (3.7 +/- 0.2 vs. 3.6 +/- 0.1 mM) and basal glucose transport (38 +/- 6 vs. 39 +/- 6 pmol/mg protein/15 s) were unchanged. These results indicate that diet and not aging per se caused insulin resistance.

Diet and exercise in the treatment of NIDDM. The need for early emphasis

OBJECTIVE

To investigate the effectiveness of an intensive diet and exercise program for controlling non-insulin-dependent diabetes mellitus (NIDDM) and reducing risk factors associated with macrovascular complications.

RESEARCH DESIGN AND METHODS

Medical charts obtained from 4,587 participants in a lifestyle modification program were screened for patients with NIDDM. A total of 652 patients was identified, and their responses to the 3-week program were analyzed.

RESULTS

Fasting glucose level was reduced from 10.0 to 8.45 mmol/l, and 71% of 197 subjects taking oral hypoglycemic agents and 39% of 212 taking insulin were able to discontinue their medication. Of the 243 not taking medication, 76% reduced their fasting glucose levels to < or = 7.84 mmol/l. Blood pressure was significantly reduced, and of the 319 initially taking antihypertension drugs, 34% had their medication discontinued. Serum total and low-density lipoprotein cholesterol were reduced by 22% and triglycerides by 33%. The ratio of total to high-density lipoprotein cholesterol was reduced by 13%.

CONCLUSIONS

Lifestyle modification consisting of diet combined with aerobic exercise can be effective for controlling NIDDM and reducing risk factors associated with macrovascular complications in both men and women. The program was far more effective in controlling the disease in patients taking no medication or oral agents compared with patients taking insulin. These results stress the need for early emphasis on lifestyle modification in the treatment of NIDDM.

Exercise capacity of rats remains unaffected by a chronic pressure overload

OBJECTIVE

The aim was to determine if the adaptive responses of the myocardium to a chronic pressure overload affected cardiovascular performance when evaluated under conditions of increased functional demand.

METHODS

Selected female rats were made hypertensive by abdominal aortic constriction. After eight weeks of aortic constriction, cardiovascular responses and work performance were measured during a maximal treadmill exercise bout.

RESULTS

Aortic constriction increased mean arterial pressure and the relative quantity of the slow ATPase myosin isoform, V3, relative to untreated controls (p < 0.05). Both groups had similar oxygen consumptions (VO2), heart rates (HR), and oxygen pulses (VO2/HR) at rest and throughout the exercise test. Both groups reached their VO2 max at the same exercise duration and exercise intensity (40.4 m.min-1). Soleus citrate synthase activity was not different between the groups.

CONCLUSIONS

These similarities in work capacity, VO2, oxygen pulse, and muscle oxidative capacity suggest (1) that cardiovascular and exercise capacity can both be maintained in spite of the presence of a chronic pressure overload; (2) that after two months of aortic constriction the heart appears to be in a compensated stage of adaptation; and (3) that the cardiac myosin isoenzyme profile may have little direct effect on cardiovascular functional capacity.