Guar gum consumption in adolescent and adult rats: short- and long-term metabolic effects

Metabolic responses to short- and long-term guar gum consumption were studied in adolescent and adult rats. For the long-term study, male adolescent rats were divided into four groups (n = 60/group) and fed guar gum, cellulose, or bran diet for 67 weeks. Metabolic studies (food--water intake, feces--urine output, body weight, carbohydrate tolerance) were performed eight times during the 67 weeks. The guar gum group consumed less diet throughout the entire study and gained less weight over the first 20 weeks compared with the cellulose and bran groups. A second bran-fed group was food restricted over the first 20 weeks to match the reduced weight gain of the guar gum group and then fed ad libitum. Reduced plasma glucose excursions were measured for only the guar gum group after both fibre-free glucose and sucrose challenges at weeks 6, 12, and 18; from 24 to 64 weeks all four groups had similar glucose tolerance responses. Twenty-four hour urinary glucose excretion was similar during all eight metabolic studies up to 64 weeks for guar gum and cellulose groups. In the short-term study, male adolescent (200 g; n = 10/group) and adult (630 g; n = 15/group) rats were divided into five and four groups, respectively, and fed guar gum, guar by-product (GBP), cellulose, or bran diet for 6 weeks. A metabolic study was performed during the 6th week. Adolescent rats fed guar gum or GBP diets gained less weight than the cellulose group; only the guar gum group displayed improved carbohydrate tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Daily exercise vs. caloric restriction for prevention of nonalcoholic fatty liver disease in the OLETF rat model

The maintenance of normal body weight either through dietary modification or being habitually more physically active is associated with reduced incidence of nonalcoholic fatty liver disease (NAFLD). However, the means by which weight gain is prevented and potential mechanisms activated remain largely unstudied. Here, we sought to determine the effects of obesity prevention by daily exercise vs. caloric restriction on NAFLD in the hyperphagic, Otsuka Long-Evans Tokushima Fatty (OLETF) rat. At 4 wk of age, male OLETF rats (n = 7-8/group) were randomized to groups of ad libitum fed, sedentary (OLETF-SED), voluntary wheel running exercise (OLETF-EX), or caloric restriction (OLETF-CR; 70% of SED) until 40 wk of age. Nonhyperphagic, control strain Long-Evans Tokushima Otsuka (LETO) rats were kept in sedentary cage conditions for the duration of the study (LETO-SED). Both daily exercise and caloric restriction prevented obesity and the development of type 2 diabetes observed in the OLETF-SED rats, with glucose tolerance during a glucose tolerance test improved to a greater extent in the OLETF-EX animals (30-50% lower glucose and insulin areas under the curve, P < 0.05). Both daily exercise and caloric restriction also prevented excess hepatic triglyceride and diacylglycerol accumulation (P < 0.001), hepatocyte ballooning and nuclear displacement, and the increased perivenular fibrosis and collagen deposition that occurred in the obese OLETF-SED animals. However, despite similar hepatic phenotypes, OLETF-EX rats also exhibited increased hepatic mitochondrial fatty acid oxidation, enhanced oxidative enzyme function and protein content, and further suppression of hepatic de novo lipogenesis proteins compared with OLETF-CR. Prevention of obesity by either daily exercise or caloric restriction attenuates NAFLD development in OLETF rats. However, daily exercise may offer additional health benefits on glucose homeostasis and hepatic mitochondrial function compared with restricted diet alone.     

The effects of diet on the esterification of glycerol phosphate, dihydroxyacetone phosphate and 2-hexadecylglycerol by homogenates of rat adipose tissue.

1. Male rats were fed for 5 weeks after weaning on a diet containing (by weight) 59% of starch or on diets that contained 39% of starch and 20% of either sucrose, beef tallow or corn oil. 2. The rats fed on the beef tallow consumed more energy than did the rats fed on the starch and sucrose diets. The rats fed on the corn oil drank less water than did the other groups of rats. 3. There were no significant differences between the four groups in terms of body-weight gain, epididymal-fat-pad weight and in the size, number and triacylglycerol content of the adipocytes in the fat-pads. 4. There was a significant correlation (P less than 0.001) between the activities of glycerol phosphate acyltransferase and monoacylglycerol acyltransferase in individual rats. Both of these activities were highest in the group fed on the high-starch diet and both correlated with the consumption of glucose by individual rats in the four groups. 5. The percentage of glycerol phosphate converted into diacylglycerol and triacylglycerol was positively correlated with the mean diameters, surface area and triacylglycerol content of the adipocytes for individual rats and was greates in the sucrose-fed rats. 6. The specific activity of dihydroxyacetone phosphate acyltransferase was highest in the rats fed on beef tallow. This activity was positively correlated with the energy intake for all dietary groups over the 5-week feeding period. 7. The results are discussed in terms of the functions of the three routes of glycerolipid synthesis in adipose tissue.     

Subdiaphragmatic vagal deafferentation affects body weight gain and glucose metabolism in obese male Zucker (fa/fa) rats

We investigated the effect of subdiaphragmatic vagal deafferentation (SDA) on food intake, body weight gain, and metabolism in obese (fa/fa) and lean (Fa/?) Zucker rats. Before and after recovery from surgery, food intake and body weight gain were recorded, and plasma glucose and insulin were measured in tail-prick blood samples. After implantation of a jugular vein catheter, an intravenous glucose tolerance test (IVGTT) was performed, followed by minimal modeling to estimate the insulin sensitivity index. Food intake relative to metabolic body weight (g/kg(0.75)) and daily body weight gain after surgery were lower (P < 0.05) in SDA than in sham obese but not lean rats. Before surgery, plasma glucose and insulin concentrations were lower (P < 0.05) in lean than in obese rats but did not differ between surgical groups within both genotypes. Four weeks after surgery, plasma glucose and insulin were still similar in SDA and sham lean rats but lower (P < 0.05) in SDA than in sham obese rats. IVGTT revealed a downward shift of the plasma insulin profile by SDA in obese but not lean rats, whereas the plasma glucose profile was unaffected. SDA decreased (P < 0.05) area under the curve for insulin but not glucose in obese rats. The insulin sensitivity index was higher in lean than in obese rats but was not affected by SDA in both genotypes. These results suggest that elimination of vagal afferent signals from the upper gut reduces food intake and body weight gain without affecting the insulin sensitivity index measured by minimal modeling in obese Zucker rats.     

Regulation of UCP1, UCP2, and UCP3 mRNA expression in brown adipose tissue, white adipose tissue, and skeletal muscle in rats by estrogen

The effects of ovariectomy (OVX) and estrogen substitution on body weight, body composition, food intake, weight gain, and expression of uncoupling proteins (UCPs) in brown adipose tissue (BAT), white adipose tissue (WAT), and skeletal muscle were studied in four groups of rats: (1) Sham-operated rats (N = 8), (2) ovariectomized rats (OVX - E) (N = 8), (3) estrogen-treated OVX rats (OVX + E) (N = 8), and (4) OVX rats on energy restriction (OVX - E + D) (N = 8). OVX was associated with an increase in food intake and body weight gain during a 5-week study period compared to sham-operated rats. The estrogen-substituted rats had a significantly lower food intake and weight gain during the 5 weeks compared to the sham-operated group. However, we also included a nontreated OVX group that was allowed to eat only enough chow to match the weight gain of the sham-operated group. To match the weight gain in the two groups, the OVX group had to consume 16% less chow than the sham-operated group. In BAT, the UCP1 expression was significantly lower in estrogen-deficient rats compared to either intact rats or estrogen-substituted rats, whereas UCP2 and UCP3 mRNA expression was similar in BAT from all four groups. In WAT, both estrogen-deficient groups had significantly lower UCP2 mRNA expression compared to the control rats and estrogen-treated rats; In contrast, the UCP3 mRNA expression in WAT was similar in all four groups. Finally, in skeletal muscle the OVX group on mild energy restriction had reduced UCP3 mRNA expression compared to control, OVX, and estrogen-treated rats. In contrast, the UCP2 mRNA expression in skeletal muscle was similar in all four groups. Thus, the findings that estrogen deficiency is followed by reduced UCP1 expression in BAT and reduced UCP2 expression in WAT in association with weight gain probably caused by a decrease in energy expenditure might indicate that UCPs play a role for the estrogen-mediated changes in body weight and energy expenditure.     

Soluble Fermentable Dietary Fibre (Pectin) Decreases Caloric Intake,Adiposity and Lipidaemia in High-Fat Diet-Induced Obese Rats

Consumption of a high fat diet promotes obesity and poor metabolic health, both of which may be improved by decreasing caloric intake. Satiety-inducing ingredients such as dietary fibre may be beneficial and this study investigates in diet-induced obese (DIO) rats the effects of high or low fat diet with or without soluble fermentable fibre (pectin). In two independently replicated experiments, young adult male DIO rats that had been reared on high fat diet (HF; 45% energy from fat) were given HF, low fat diet (LF; 10% energy from fat), HF with 10% w/w pectin (HF+P), or LF with 10% w/w pectin (LF+P) ad libitum for 4 weeks (n = 8/group/experiment). Food intake, body weight, body composition (by magnetic resonance imaging), plasma hormones, and plasma and liver lipid concentrations were measured. Caloric intake and body weight gain were greatest in HF, lower in LF and HF+P, and lowest in the LF+P group. Body fat mass increased in HF, was maintained in LF, but decreased significantly in LF+P and HF+P groups. Final plasma leptin, insulin, total cholesterol and triglycerides were lower, and plasma satiety hormone PYY concentrations were higher, in LF+P and HF+P than in LF and HF groups, respectively. Total fat and triglyceride concentrations in liver were greatest in HF, lower in LF and HF+P, and lowest in the LF+P group. Therefore, the inclusion of soluble fibre in a high fat (or low fat) diet promoted increased satiety and decreased caloric intake, weight gain, adiposity, lipidaemia, leptinaemia and insulinaemia. These data support the potential of fermentable dietary fibre for weight loss and improving metabolic health in obesity.     

Changes in glucose tolerance and leptin responsiveness of rats offered a choice of lard, sucrose, and chow

Rats offered chow, lard, and 30% sucrose solution (choice) rapidly become obese. We tested metabolic disturbances in rats offered choice, chow+lard, or chow+30% sucrose solution [chow+liquid sucrose (LS)] and compared them with rats fed a composite 60% kcal fat, 7% sucrose diet [high-fat diet (HFD)], or a 10% kcal fat, 35% sucrose diet [low-fat diet (LFD)]. Choice rats had the highest energy intake, but HFD rats gained the most weight. After 23 days carcass fat was the same for choice, HFD, chow+lard, and chow+LS groups. Glucose clearance was the same for all groups during an intraperitoneal glucose tolerance test (GTT) on day 12, but fasting insulin was increased in choice, LFD fed, and chow+LS rats. By contrast, only choice and chow+LS rats were resistant to an intraperitoneal injection of 2 mg leptin/kg on day 17. In experiment 2 choice rats were insulin insensitive during an intraperitoneal GTT, but this was corrected in an oral GTT due to GLP-1 release. UCP-1 protein was increased in brown fat and inguinal white fat in choice rats, and this was associated with a significant increase in energy expenditure of choice rats during the dark period whether expenditure was expressed on a per animal or a metabolic body size basis. The increase in expenditure obviously was not great enough to prevent development of obesity. Further studies are required to determine the mechanistic basis of the rapid onset of leptin resistance in choice rats and how consumption of sucrose solution drives this process.     

Insulin and glucagon secretion and the insulin sensitivity of peripheric organs of colony-bred sand rats fed with pellet diet after weaning.

Colony-bred sand rats were fed with rat pellet chow in restricted quantities or ad libitum for 8--10 or 28--31 weeks after weaning. The changes of glucose metabolism were characterized by an intraperitoneal glucose tolerance test. The daily food intake and the average weight gain differed only in the first 5--7 weeks of pellet nutrition. In the impaired glucose tolerance tests of all sand rats the high basal plasma IRI levels were not significantly increased by the grossly enhanced blood glucose concentrations. The insulin secretion of either acutely incubated or for 8 days cultivated isolated pancreatic islets, however, was stimulated already by low (1.7 and 5 mM) glucose concentrations in all diet groups. Otherwise the glucagon secretion of isolated islets was not suppressed by high glucose concentrations. No changes of insulin or glucagon contents of islets were found in the different diet groups. The adipocytes of all animals revealed a complete ineffectiveness of insulin on the glucose utilization to CO2 and triglycerides. The basal glucose conversion to CO2 and glycogen in skeletal muscle and the stimulatory potency of insulin was low and not distinctly different in all groups. In liver glycogen and triglyceride contents as well as gluconeogenic enzyme activities were not influenced by feeding of different quantities of pellet diet at the investigated time points. The time course of the metabolic and clinical alterations demonstrates that the peripheral organs become insensitive to insulin in the first weeks after weaning.     

Effect of High Sucrose Feeding on Fat Accumulation in the Male Wistar Rat

High sucrose intake is generally thought to be a risk factor for obesity and insulin resistance. We examined the effects of feeding sucrose on fat accumulation and insulin release in male rats. Six-week-old male Wistar rats were maintained on a high sucrose diet for 4 or 12 weeks. Control rats were fed a diet based on starch. No significant difference in daily caloric intake or weight gain existed between the two dietary groups. There was no difference between the two dietary groups in the gain of abdominal subcutaneous fat (SC) at 4-week. In contrast, rats fed the high sucrose diet had significantly more mesenteric fat (MES) than controls (p<0.01). At 12 weeks, rats fed the high sucrose diet had significantly more SC and MES than controls (SC:p<0.05, MES:p<0.01). Basal immunoreactive insulin (IRI) concentrations in the portal vein (PV) of rats fed the high sucrose diet was significantly higher compared to those of controls (4 wk: p<0.05, 12 wk: p<0.05). No difference between the two dietary groups in basal IRI concentrations in the inferior vena cava (TVC) existed at 4 weeks; whereas at 12 weeks, the basal IRI concentrations in the IV C in rats fed the high sucrose diet were significantly higher than in controls (p<0.05). The mesenteric and subcutaneous fat accumulations were closely related to hyperinsulinemia in the portal vein and inferior vena cava, respectively. Twelve weeks of high sucrose feeding caused accumulation of abdominal adipose tissue with marked hyperinsulinemia and hyperlipidemia. Our study is the first to demonstrate that abdominal fat induced by high sucrose intake in male rats is accompanied by an abnormal metabolic state similar to an insulin-resistant state.     

Effects of corticocerebellar lesions on taste preferences, body weight gain, food and fluid intake in the rat.

The experiments reported here attempted to examine in two groups of rats the effects on the taste preferences, food and fluid intake, energy balance and body weight gain of corticocerebellar lesions involving, primarily, the Lobulus VI (LVI) or the Lobulus Paramedianus (LP). The results showed that the lesions of LVI or LP did not affect the daily intake of total fluid and salty solution. The intake of sweet solution increased in both groups of lesioned rats, while the intake of deionized water and acid and bitter solutions decreased only in the LVI lesioned rats. Food intake decreased in the LVI-lesioned rats but not in the LP-lesioned animals. Body weight gain, efficiency of food utilization, caloric intake and body surface gain decreased in both groups. It seems therefore that the cerebellar cortex, which probably receives taste fibers, somehow influences taste preferences and water intake, and that it may be involved in the mechanisms of food intake, its utilization and body energy balance.     

Excessive Energy Intake Does Not Modify Fed‐state Tissue Protein Synthesis Rates in Adult Rats

The impact of chronic excessive energy intake on protein metabolism is still controversial. Male Wistar rats were fed ad libitum during 5 weeks with either a high‐fat high‐sucrose diet (HF: n = 9) containing 45% of total energy as lipids (protein 14%; carbohydrate 40% with 83.5% sucrose) or a standard diet (controls: n = 10). Energy intake and body weight were recorded. At the end of the experiment, we measured body composition, metabolic parameters (plasma amino acid, lipid, insulin, and glucose levels), inflammatory parameter (plasma α2‐macroglobulin), oxidative stress parameters (antioxidant enzyme activities, lipoperoxidation (LPO), protein carbonyl content in liver and muscle), and in vivo fed–state fractional protein synthesis rates (FSRs) in muscle and liver. Energy intake was significantly higher in HF compared with control rats (+28%). There were significant increases in body weight (+8%), body fat (+21%), renal (+41%), and epidydimal (+28%) fat pads in HF compared with control rats. No effect was observed in other tissue weights (liver, muscle, spleen, kidneys, intestine). Liver and muscle FSRs, plasma levels of lipids, glucose, insulin and α2‐macroglobulin, soleus and liver glutathione reductase and peroxidase acitivities, MnSOD activity, LPO, and protein carbonyl content were not altered by the HF diet. Only soleus muscle and liver Cu/ZnSOD activity and soleus muscle catalase activities were reduced in HF rats compared with control rats. Thus, chronic excessive energy intake and increased adiposity, in the absence of other metabolic alterations, do not stimulate fed‐state tissue protein synthesis rates.     

Citrate diminishes hypothalamic acetyl-CoA carboxylase phosphorylation and modulates satiety signals and hepatic mechanisms involved in glucose homeostasis in rats

The hypothalamic AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) pathway is known to play an important role in the control of food intake and energy expenditure. Here, we hypothesize that citrate, an intermediate metabolite, activates hypothalamic ACC and is involved in the control of energy mobilization. Initially, we showed that ICV citrate injection decreased food intake and diminished weight gain significantly when compared to control and pair-fed group results. In addition, we showed that intracerebroventricular (ICV) injection of citrate diminished (80% of control) the phosphorylation of ACC, an important AMPK substrate. Furthermore, citrate treatment inhibited (75% of control) hypothalamic AMPK phosphorylation during fasting. In addition to its central effect, ICV citrate injection led to low blood glucose levels during glucose tolerance test (GTT) and high glucose uptake during hyperglycemic-euglycemic clamp. Accordingly, liver glycogen content was higher in animals given citrate (ICV) than in the control group (23.3+/-2.5 vs. 2.7+/-0.5 microg mL(-1) mg(-1), respectively). Interestingly, liver AMPK phosphorylation was reduced (80%) by the citrate treatment. The pharmacological blockade of beta3-adrenergic receptor (SR 59230A) blocked the effect of ICV citrate and citrate plus insulin on liver AMPK phosphorylation. Consistently with these results, rats treated with citrate (ICV) presented improved insulin signal transduction in liver, skeletal muscle, and epididymal fat pad. Similar results were obtained by hypothalamic administration of ARA-A, a competitive inhibitor of AMPK. Our results suggest that the citrate produced by mitochondria may modulate ACC phosphorylation in the hypothalamus, controlling food intake and coordinating a multiorgan network that controls glucose homeostasis and energy uptake through the adrenergic system.     

The effects of chronic central administration of corticotropin-releasing factor on food intake, body weight, and hypothalamic-pituitary-adrenocortical hormones.

The effects of chronic central administration of corticotropin-releasing factor (CRF) on food intake, body weight, and hypothalamic-pituitary-adrenocortical hormones were investigated in rats. The infusion of ovine CRF at doses of 0.3 and 1.0 microgram/h continuously induced decrease in food intake and a suppression of body-weight gain for 7 days. The inhibition of body weight gain induced by CRF could not be accounted for solely by a decreased food intake since the suppression of body-weight gain in CRF-infused rats was significantly greater than that observed in rats which received the same amount of food as the CRF-infused rats. The content of proopiomelanocortin (POMC) -derived peptides in the anterior lobe of the pituitary as well as the plasma levels of ACTH and corticosterone (B) were significantly elevated in CRF-treated rats, and the CRF content in the hypothalamus was significantly decreased. These results suggest that chronic intracerebroventricular (icv) administration of CRF stimulates the synthesis and secretion of POMC-related peptides in the pituitary and suppresses food intake accompanied by inhibition of body weight gain. The results are similar to clinical and laboratory findings observed in patients with stress-induced anorexia.     

Reduced intake of carbohydrate prevents the development of obesity and impaired glucose metabolism in ghrelin O-acyltransferase knockout mice

A close relationship between acylated-ghrelin and sucrose intake has been reported. However, little has been examined about the physiological action of ghrelin on preference for different types of carbohydrate such as glucose, fructose, and starch. The current study was aimed to investigate the role of acylated-ghrelin in the determinants of the choice of carbohydrates, and pathogenesis of chronic disorders, including obesity and insulin resistance. In a two-bottle-drinking test, ghrelin O-acyltransferase (GOAT) knockout (KO) mice consumed a less amount of glucose and maltodextrin, and almost the same amount of fructose and saccharin solution compared to WT littermates. The increased consumption of glucose and maltodextrin was observed when acylated-ghrelin, but not unacylated-ghrelin, was exogeneously administered in normal C57BL/6J mice, suggesting an association of acylated-ghrelin with glucose-containing carbohydrate intake. When fed a diet rich in maltodextrin, starch and fat for 12 weeks, GOAT KO mice showed less food intake and weight gain, as well as improved glucose tolerance and insulin sensitivity than WT mice. Our data suggests that blockade of GOAT activity may offer a therapeutic option for treatment of obesity and its associated metabolic syndrome by preventing from overconsumption of carbohydrate-rich food.     

QUERCETIN EFFECTS ON WEIGHT GAIN AND CALORIC INTAKE IN EXERCISED RATS

Quercetin is a flavonoid which activates oxidative metabolism. Quercetin may reduce weight gain by decreasing feed efficiency. The present study aims to evaluate weight gain, caloric intake and feed efficiency in exercised and sedentary rats supplemented with quercetin. Wistar rats were divided into four groups: quercetin-exercise training (QT), quercetin-sedentary (QS), placebo-exercise training (PT) and placebo-sedentary (PS). Rats were exercised and/or orally supplemented with quercetin (25 mg · kg⁻¹ on alternate days) during six weeks. Weight gain of the QT group decreased when compared with the PT and PS groups. Exercised groups increased cumulative caloric intake during the experimental period. The QT group rats also reduced their feed efficiency when compared with the QS and PS groups. These results suggest that quercetin is not able to decrease weight gain because no differences were found between placebo and quercetin condition either in the sedentary or in the training condition.     

Food Viscosity Influences Caloric Intake Compensation and Body Weight in Rats

Objective: To determine the effects of food viscosity on the ability of rats to compensate for calories in a dietary supplement. Research Methods and Procedures: In a series of four experiments, rats consumed dietary supplements equated for caloric and nutritive content but differing in viscosity. Experiments 1 to 3 examined the ability of the rats to compensate for the calories consumed in low‐ compared with high‐viscosity premeals by reducing intake of a subsequent test meal. Caloric compensation was assessed with a wide range of premeal viscosity levels and with two different non‐nutritive thickening agents. Experiment 4 assessed the effects of consuming daily a low‐viscosity compared with an equicaloric high‐viscosity dietary supplement on longer term body weight gain. Results: Consuming a lower viscosity premeal was followed by significantly more caloric intake (i.e., less caloric compensation) compared with consuming premeals with higher viscosity levels. This effect was not specific to one thickening agent. Furthermore, rats given a low‐viscosity supplement daily gained significantly more weight over a 10‐week period compared with rats given a high‐viscosity supplement. Discussion: The results of these experiments suggest that food viscosity may be an important determinant of short‐term caloric intake and longer term body weight gain.     

Vasopressin deficiency and the modulation of consummatory behavior

This study examined patterns of consummatory behavior in normal and vasopressin-deficient rats under ad lib and food-restricted conditions. Differing patterns of intake of food, water, sucrose, and saccharin were found in the two groups. During the ad lib period, the normal rats gained more weight and ate significantly more food than vasopressin-deficient rats. The vasopressin-deficient animals consumed significantly more sucrose than normal animals during this period. No significant differences in body weight, food intake, sucrose intake, or saccharin intake were noted during the food-restricted period between the two groups. During the food-restricted condition the normal animals showed a cyclic pattern of food, sucrose, and saccharin intake. This cyclic pattern of intake was absent in vasopressin-deficient animals. A vasopressin-serotonin interaction is hypothesized as a possible mechanism producing the differences in the two strains of animals. In addition, the data support the position that food consumption is regulated primarily by caloric and/or nutritional factors.     

Interactions between effects of adrenalectomy and diet on insulin secretion in fa/fa Zucker rats

Our objective was to determine if a cafeteria-type diet with increased fat content would block the decrease in insulin secretion induced by adrenalectomy in obese rats. Five week old Zucker (fa/fa) rats were adrenalectomized. One week later, half of the adrenalectomized groups, and age-matched, sham-operated animals were given a diet of 16% fat and 44% carbohydrate. Control animals were maintained on standard rat chow (4.6% fat and 49% carbohydrate). After 4 weeks on the diets, in vivo measurements included caloric intake, weight gain, plasma corticosterone, triglyceride, free fatty acids, and oral glucose tolerance tests. In vitro measurements included glucose-stimulated insulin secretion, glucose phosphorylating activity, islet triglyceride content, and fatty acid oxidizing activity of cultured islets. Generally, the cafeteria diet did not block the effects of adrenalectomy on in vitro insulin secretion parameters, even though in sham-operated animals weight gain and insulin resistance was induced by the diet in vivo. Adrenalectomy and the diet exerted independent effects on glucose phosphorylation and fatty acid oxidation in islets. In conclusion, adrenalectomy decreased the elevated insulin secretion in fa/fa rats. The failure of a cafeteria diet enriched in fat to block the adrenalectomy-mediated changes in B-cell function indicates the importance of glucocorticoids and centrally-mediated effects on insulin secretion and other metabolic parameters.     

Prevention of Obesity in Middle-Aged Monkeys: Food Intake During Body Weight Clamp

Prevention of obesity and increase in longevity in obesity-prone rodents can be achieved by long-term moderate dietary restriction. In order to examine the likelihood that caloric restriction could have similar salutary effects in humans, rhesus monkeys, after reaching mature adult stature, were placed on a protocol to clamp or stabilize body weight by weekly caloric adjustment Further weight gain was prevented by this caloric titration procedure, and thus middle-age onset obesity, which is very common in this species, was prevented. The present study analyzed daily food intake for six weight-clamped monkeys and six ad libitum fed age-matched animals over a 3- year period, ages 18.5 to 21.5 years. After approximately 9 years of caloric restriction the daily calorie load to maintain stable adult body weight proved to be 40% less than the amount ingested by ad libitum fed animals. Calories per kg body weight did not differ significantly between the groups although the ad libitum fed animals were significantly fatter than the weight-clamped group. Prevention of obesity using this weight clamp protocol has also maintained lower insulin levels and higher glucose tolerance in the restricted animals.     

Comparison of Fat Storage between Fischer 344 and Obesity‐Resistant Lou/C Rats Fed Different Diets**

Objective: We aimed to characterize further the Lou/C (LOU) and Fischer 344 (F344) rat strains for nutritional traits to validate their use as contrasting strains for molecular genetic studies. Research Methods and Procedures: Five batches of LOU and F344 rats were used to measure caloric intake, weight gain, and body composition when fed a chow diet, a self‐selection diet (together with the study of preferences for macronutrients), hypercaloric diets, and a chow diet in a cold environment. Results: Despite a higher caloric intake when fed a chow diet, LOU rats showed a lower weight gain, final body weight, and percentage of fat tissue, together with a higher percentage of carcass weight, than F344 rats. When fed a self‐selection diet, LOU males ingested less protein and more fat than F344 males, and the reverse was observed for females. In this condition, feed efficiency was reduced in LOU but increased in F344 rats compared with the chow diet. Diet‐induced obesity was observed in F344 rats but not in LOU rats fed hypercaloric diets. In a cold environment, both LOU and F344 rats displayed an increased percentage of brown adipose tissue compared with control groups, together with a higher caloric intake. Discussion: The study shows robust nutritional differences between the LOU rat, a lean strain with a low feed efficiency and resistant to diet‐induced obesity, and the contrasting F344 rat strain. It also shows the interest in these strains for studying the genetic components of resistance to obesity.