Increased hepatic triacylglycerol secretion in fasted rats with ventromedial hypothalamic lesions.

Adult female rats with lesions in the ventromedial hypothalamic area and sham-operated controls were given Triton WR 1339 intravenously after 24 h without food for measurement of liver triacylglycerol secretion rate. Tritiated water was injected for measurement of lipogenesis in liver, perirenal and subcutaneous adipose tissues in vivo. The experiments were performed on unrestrained animals with a chronically implnted venous heart cannula after 24 h without food. By the use of this technique, anesthesia and handling of the animals during the experiments was avoided. The following differences in the lesioned animals compared to the sham-operated controls were found: relative hypertriglyceridemia. A significant increase of triacylglycerol accumulation in the plasma. Increased incorporation of 3H FROM 3H20 into liver fatty acids. The experiments demonstrate that hepatic lipid synthesis during fasting is greater in the lesioned than in the control animals, but not high enough to account for the increased triacylglycerol secretion. A shift in the hepatic metabolism of fatty acids, leading to greater triacylglycerol formation at the expense of other processes is therefore suggested. The possible role of insulin in these metabolic changes is discussed.

Protein depletion and energy retention in rats with ventromedial hypothalamic lesions.

The catabolic effect of bilateral lesions in the ventromedial are of the hypothalamus (VMH) was studied in nitrogen-balance experiments and compared with the effect of a sham-operation in control animals. A transitory (24 h) increase in urine nitrogen was found in the controls, while in the lesioned animals, a persistent increase was found as long as the animals were fed. Fasting (48 h) eliminated the difference in urea excretion between the groups. Food-dependent effects of the VMH lesion are suggested. The changes in body and organ composition of VMH-lesioned animals, kept for 4 months on a food intake close to normal, were studied. The massive increase of body lipids and marked decrease of body protein and water was primarily due to increased subcutaneous-and abdominal-fat, and reduced skeletal and skin protein. An almost normal composition of the liver and close to normal amounts of protein in the viscera demonstrate that at least some tissues in VMH animals are able to maintain a normal protein content. Hyperphagia as a means to counteract the increased amino acid catabolism and to sustain the lean body mass is discussed.

The effect of ventromedial hypothalamic lesions on metabolism and insulin secretion in rats on a controlled feeding regimen.

The metabolic effect of ventromedial hypothalamic (VMH) lesions, which are known to cause hyperphagia and obesity, has been studied in rats kept on a controlled light and food regimen. The animals were sacrificed at 4 different times during the second postoperative day. A feeding-induced hypersecretion of insulin was found to the VMH-lesioned animals. It was accompanied by a marked hypoglycemia as compared to the control groups during the feeding period. The glycogen content of liver and diaphragm in the lesioned groups is increased as compared to the controls during the same period. The VMH-lesioned animals showed hypertriglyceridemia both in the fed and fasted state, whereas the postabsorptive plasma levels of free fatty acids and glycerol were decreased. An increased level of urea was observed in all lesioned groups. This is in accordance with the demonstrated protein catabolism which follows VMH lesions.

Protein metabolism in rats with ventromedial hypothalamic lesions: dietary effects on nitrogen retention.

The protein metabolism of rats bearing bilateral lesions in the ventromedial area of hypothalamus (VMH) was studied in nitrogen balance experiments employing high protein and high fat diets. The catabolic effect of VMH destruction was to a great extent counterbalanced by increased protein intake. This indicates that increased amino acid catabolism, rather than impaired mechanisms for protein synthesis, is responsible for the poor nitrogen retention of VMH-lesioned rat fed normal amounts of protein. A trend of increasing nitrogen excretion with increasing dietary fat was found when the caloric intake of VMH-lesioned animals was elevated by substitution of dietary carbohydrates with fat. Persistent liponeogenesis in spite of the high fat intake, is suggested as a possible explanation for this observation.

Validation of energy intake estimated from a food frequency questionnaire: a doubly labelled water study.

OBJECTIVE: The validation of dietary assessment methods is critical in the evaluation of the relation between dietary intake and health. The aim of this study was to assess the validity of a food frequency questionnaire by comparing energy intake with energy expenditure measured with the doubly labelled water method. DESIGN: Total energy expenditure was measured with the doubly labelled water (DLW) method during a 10 day period. Furthermore, the subjects filled in the food frequency questionnaire about 18-35 days after the DLW phase of the study was completed. SUBJECTS: Twenty-one healthy, non-pregnant females volunteered to participate in the study; only 17 subjects completed the study. RESULTS: The group energy intake was on average 10% lower than the energy expenditure, but the difference was not statistically significant. However, there was a wide range in reporting accuracy: seven subjects were identified as acceptable reporters, eight as under-reporters and two were identified as over-reporters. The width of the 95% confidence limits of agreement in a Bland and Altman plot for energy intake and energy expenditure varied from -5 to 3 MJ. CONCLUSION: The data showed that there was substantial variability in the accuracy of the food frequency questionnaire at the individual level. Furthermore, the results showed that the questionnaire was more accurate for groups than individuals.

Accuracy of a quantitative food frequency questionnaire applied in elderly Norwegian women.

The accuracy (reproducibility and relative validity) of a self-administered quantitative food frequency questionnaire including 180 food items was evaluated. A total of 38 elderly women kept multiple weighed diet records for a total of 14 days over a 6-week period and filled in the questionnaire both before and after this period. Spearman rank correlations between the nutrient intakes from the two questionnaires varied from 0.43 for carbohydrate to 0.88 for energy percentage from alcohol. The median correlation was 0.70. Seven women whose recorded average energy intake was less than 1.17 times their measured basal metabolic rate were excluded from the analysis comparing the questionnaire and the diet records. The first questionnaire gave on the average 10% higher nutrient median values than the records, while the second questionnaire did not in general produce higher values. Unadjusted correlation coefficients comparing intakes measured by the two methods ranged from 0.31 for vitamin C to 0.79 for energy percentage from carbohydrate, the median coefficient being 0.61. On the average 77% of the subjects were classified in the same (+/- 1) quintile in the first food frequency questionnaire and the diet records. The present study indicates that the self-administered quantitative food frequency questionnaire is useful for measuring individual or group intakes for a variety of nutrients.

Early effects of feeding upon hormonal and metabolic alterations in adult rats with ventromedial (VMH) lesions.

The importance of the nutritional state for the development of metabolic alterations after ventromedial hypothalamic (VMH) destructions has been investigated. In the first experiment, groups of fed and 12 hours fasted animals were operated, given an intraperitoneal injection of 3H2O (1 mCi), and left without food until sacrificed 12 hours postoperatively. The lipogenesis in liver and adipose tissue, and the plasma levels of insulin, glucose, urea, free fatty acids (FFA) and triglycerides (TG) were measured. Animals operated in the fed state had increased lipogenesis in parametrial adipose tissue and hypoglycemia compared to their controls, whereas we found no differences between the groups which had been fasted 12 hours before surgery. In the second experiment, animals were deprived of food for 12 hours before being lesioned or sham-operated, and for 12 more hours postoperatively. They were then given one meal by stomach tube, and groups were killed 2, 4, 8 and 12 hours later. The following differences between groups were observed: 2 hours after feeding, the lesioned animals had increased plasma TG levels, but decreased liver lipogenesis. 4 hours after feeding, animals with lesions were hypoglycemic, and had lower plasma levels of FFA and TG than the controls. Hypoglycemia in lesioned animals was found also 8 hours after feeding, together with increased plasma TG levels. 12 hours after feeding, increased liver lipogenesis in lesioned animals was the only difference observed between the groups. The third and last experiment investigated the effect of three meals given 12, 18 and 24 hours postoperatively. Lesioned animals sacrificed 4 hours after the third meal had hypoglycemia, increased plasma TG levels, and increased lipogenesis, both in liver and adipose tissue. The metabolic differences between lesioned and sham-operated animals persisted also 8 hours after the last meal, except for the lipogenesis in adipose tissue. No differences in plasma insulin levels between animals with lesions or sham-operations were observed in these experiments.

Energy metabolism in rats with ventromedial hypothalamic lesions.

Rats with ventromedial hypothalamic lesions (VMH) have increased ability to accumulate energy. The aim of this investigation was to characterize the main processes responsible for the reduced energy expenditure, using indirect calorimetry, nitrogen, and energy balance techniques. Metabolism was studied during different metabolic conditions created by a strict feeding regimen with concentrated feeding periods. A computerized system for indirect calorimetry enabled continuous study of individual animals for prolonged time periods. We found a mean decrease of 15.5% in total energy expenditure and decreased nitrogen retention in VMH rats. Calculation of respiratory quotient (RQ), energy expenditure, and the metabolic mixture demonstrated fluctuations in metabolism in accordance with the feeding regimen. The same percent reduction in resting postabsorptive energy expenditure was found as in total expenditure. Quantitatively, this main finding means that metabolic processes that occurred both in the resting and postabsorptive state were responsible for two-thirds of the total reduction in energy expenditure, whereas only one-third could be attributed to differences in dietary-induced thermogenesis and/or physical activity. It is concluded that VMH-animals spent as much as 10.3% of their total energy expenditure on liponeogenesis compared with 2.5% in controls.

Opposite effect of cold on energetic efficiency in normal and obese Wistar rats with hypothalamic lesions.

Reduced thermogenesis in brown adipose tissue (BAT) may contribute to increased energetic efficiency and obesity in rats with ventromedial hypothalamic (VMH) lesions. Thermogenic activity of BAT is a function of the environmental temperature. If a relationship exists, it follows that the increased energetic efficiency of VMH-lesioned rats likewise should be governed by temperature. We have therefore investigated the energy balance of normal and VMH-lesioned rats housed at 30 degrees C and 10 degrees C. Experiments at differing feeding levels allowed calculation of maintenance energy requirements and the net energetic efficiencies of each group. VMH-lesioned rats at thermoneutrality (30 degrees C) accumulated more body fat at all feeding levels than did normal rats. Maintenance energy requirement was reduced, but the net energetic efficiency did not differ significantly from normal. The reduced maintenance energy requirement of lesioned rats persisted at 10 degrees C. Net energetic efficiency decreased in normal rats acclimated to cold but increased in the lesioned group. The difference was significant (P less than 0.05). The cold-induced increase in interscapular brown adipose tissue (IBAT) oxidative capacity of VMH-lesioned rats was only half that of normal rats. Differences in BAT thermogenesis may be the basis for the differing temperature effects on net energetic efficiency.

Consequences of ventromedial hypothalamic lesions on metabolism of perfused rat liver.

Metabolism of perfused livers from control and ventromedial hypothalamus (VMH)-lesioned rats has been studied. To eliminate the possibility that observed metabolic abnormalities could be realted to hyperphagia, VMH-lesioned rats were placed on restricted diet matching that of controls. Ten days postoperatively, VMH-lesioned rats had hyperinsulinemia, hypertriglyceridemia, increased blood urea nitrogen levels, together with decreased plasma free fatty acid (FFA) and glucose levels. Insulin release produced in vivo by a glucose load was much higher in VMH-lesioned than in control rats. Perfused livers from VMH-lesioned rats secreted more triglycerides and produced more urea than controls, whereas production of glucose and ketone bodies was reduced. Lipogenesis, newly synthesized triglyceride secretion, and the activity of acetyl-CoA carboxylase and fatty acid synthetase were greatest in livers from VMH-lesioned rats. Fasting abolished hyperinsulinemia and most of these observed metabolic alterations. After treatment with anti-insulin serum, the high rate of lipogenesis observed in livers from VMH-lesioned rats was restored toward normal. It is suggested that hyperinsulinemia may be partly responsible for the metabolic disorders observed in livers from nonhyperphagic VMH-lesioned rats.

Significance of hyperinsulinemia in ventromedial hypothalamus-lesioned rats.

The significance of the hyperinsulinemia on the altered metabolism in ventromedial hypothalamus (VMH)-lesioned rats was tested. VMH lesions induced increases in fatty acid synthesis, lipoprotein lipase (LPL) activity, and plasma urea levels, and a decrease in plasma triglyceride concentrations. Similarly, in normal rats treated with pharmacological doses of insulin (14 U X rat-1 X day-1), fatty acid synthesis and LPL activity in fat tissue and the plasma urea were considerably elevated and plasma triglyceride was lowered compared with untreated controls. When endogenous insulin production was abolished by streptozotocin treatment, the four metabolic variables in the VMH-lesioned rats did not differ from those in diabetic controls. Substitution with 2 U of insulin X rat-1 X day-1, however, restored the differences in metabolism between VMH-lesioned diabetic and control diabetic rats. Substitution with 3 or 4 U insulin X rat-1 X day-1 showed the same differences. In VMH-lesioned rats the insulin level increased significantly from the 10th to the 70th day postoperatively; however, the rate of fatty acid synthesis, LPL activity, and plasma urea levels decreased, whereas plasma triglyceride concentrations increased. The results strongly suggest that the metabolic changes occurring after VMH lesions are only in part explained by the hyperinsulinemia associated with the VMH syndrome and indicate that other hormonal and/or nervous factors are involved.

The significance of hyperphagia and diet composition on the metabolism in ventromedial hypothalamic lesioned male rats.

The metabolic consequences of ventromedial hypothalamic lesion were studied in a group of aged male rats which were obese and had decreased response to insulin. The effects of hyperphagia and ventromedial hypothalamic lesion per se were separated by comparing experimental animals fed isocalorically with controls and animals fed ad libitum. Ventromedial hypothalamic lesion as such led to increases in the glucose conversion to fatty acid and in lipoprotein lipase activity in adipose tissue. Protein catabolism as reflected by plasma urea levels, was enhanced. The lipoprotein lipase activity in heart tended to be lower after VMH lesion. These metabolic changes were amplified in the VMH lesioned rats fed ad libitum. The liver glycogen content was lowered by VMH lesion, but this effect was abolished by hyperphagia. In parallel experiments the influence of diet composition was studied by feeding similar groups with diet of high fat content. The glucose incorporation in fatty acids was in all groups markedly and similarly inhibited by the high fat diet. The increase in lipoprotein lipase activity in heart and adipose tissue of control rats with high fat intake could not be demonstrated in any of the groups with ventromedial hypothalamic lesion. The plasma urea level in the control group was not affected by the diet, but tended to increase in the ventromedial hypothalamic lesioned groups on high fat intake. These findings demonstrate that the well known metabolic effects of ventromedial hypothalamic lesions are also manifest in obese insulin resistant male rats. Furthermore, the responses to changes in diet composition are different from those of the control rats.

Variations in insulin responsiveness in rat fat cells are due to metabolic differences rather than insulin binding.

Insulin resistance was studied by comparing insulin response and insulin binding in four groups of rats. Glucose metabolism in isolated fat cells from male Wistar rats weighing 340 g was less responsive to a supramaximal dose of insulin than glucose metabolism in fat cells from rats weighing 200 g. Induction of streptozotocin-diabetes in rats weighing 200 g resulted in a marked decrease in the insulin responsiveness of fat cells. Ventromedial hypothalamic lesions of 340 g rats had the opposite effect and restored the insulin responsiveness of fat cells. The responsiveness in the four groups was correlated to the rate of glucose conversion to fatty acids in fat cells. The binding of 125I-insulin was the same in both 340 and 200 g rats. The ventromedial hypothalamic lesioned rats and the diabetic rats showed, in spite of their great difference in insulin responsiveness, the highest binding of 125I-insulin to fat cells. Insulin binding was not correlated to the plasma insulin level which however was reflected in the lipoprotein lipase activity in the adipose tissue. In conclusion, these results indicate that variations in insulin responsiveness in fat cells are due to alterations in cellular metabolism rather than in insulin binding.