Low- and high-carbohydrate diets: body composition differences in rats

The assessment of serum trace element levels as the diagnostic biomarkers of functional state of broiler chickens

Background and Aim

Elemental analysis is a useful technique for predicting metabolic disorders in broiler chickens. Elemental imbalances are also important for the development of new methods to diagnose the health status of birds that can be implemented on a farm-wide scale. This study aimed to identify elemental markers related to pre-nosological diagnoses of metabolic disorders in broiler chickens.

Materials and Methods

We compared birds given high-protein, high-carbohydrate, and high-fat diets. A control group received the standard diet recommended by the All-Russian Research and Technological Institute of Poultry, while experimental Group I received a diet with high-protein content, Group II received a diet with high-carbohydrate content, and Group III received a diet with high-fat content. At the end of the experiment, blood samples were taken for biochemical and elemental analysis. Biochemical analysis was carried out using an automated biochemical analyzer, and the levels of trace elements in the serum were assessed using inductively coupled plasma spectrometry.

Results

We found that the high-protein diet was accompanied by a decrease in chicken body weight, cholesterol, and several elements (i.e., P, Cr, Cu, Zn, and B) as well as an increase in the levels of Ca, Co, and Si. The high-carbohydrate diet led to a significant increase in glucose levels as well as a decrease in the levels of albumin, triglycerides, and Cr, Mn, Se, I, and Cu. Finally, the high-fat diet led to an increase in body weight, glucose, cholesterol, triglycerides, and the elements Cu, Zn, and Si as well as a decrease in the levels of Mg, Cr, and Fe.

Conclusion

The determination of the levels of trace elements such as Co, Cr, Mn, Fe, and Cu in chicken blood serum may be an important indicator of the state of protein, carbohydrate, and lipid metabolism of poultry stock.

Differential response of rat strains to obesogenic diets underlines the importance of genetic makeup of an individual towards obesity

Obesity, a multifactorial disorder, results from a chronic imbalance of energy intake vs. expenditure. Apart from excessive consumption of high calorie diet, genetic predisposition also seems to be equally important for the development of obesity. However, the role of genetic predisposition in the etiology of obesity has not been clearly delineated. The present study addresses this problem by selecting three rat strains (WNIN, F-344, SD) with different genetic backgrounds and exposing them to high calorie diets. Rat strains were fed HF, HS, and HFS diets and assessed for physical, metabolic, biochemical, inflammatory responses, and mRNA expression. Under these conditions: significant increase in body weight, visceral adiposity, oxidative stress and systemic pro-inflammatory status; the hallmarks of central obesity were noticed only in WNIN. Further, they developed altered glucose and lipid homeostasis by exhibiting insulin resistance, impaired glucose tolerance, dyslipidemia and fatty liver condition. The present study demonstrates that WNIN is more prone to develop obesity and associated co-morbidities under high calorie environment. It thus underlines the cumulative role of genetics (nature) and diet (nurture) towards the development of obesity, which is critical for understanding this epidemic and devising new strategies to control and manage this modern malady.

Energy dense, protein restricted diet increases adiposity and perturbs metabolism in young, genetically lean pigs

Animal models of obesity and metabolic dysregulation during growth (or childhood) are lacking. Our objective was to increase adiposity and induce metabolic syndrome in young, genetically lean pigs. Pre-pubertal female pigs, age 35 d, were fed a high-energy diet (HED; n = 12), containing 15% tallow, 35% refined sugars and 9.1–12.9% crude protein, or a control corn-based diet (n = 11) with 12.2–19.2% crude protein for 16 wk. Initially, HED pigs self-regulated energy intake similar to controls, but by wk 5, consumed more (P<0.001) energy per kg body weight. At wk 15, pigs were subjected to an oral glucose tolerance test (OGTT); blood glucose increased (P<0.05) in control pigs and returned to baseline levels within 60 min. HED pigs were hyperglycemic at time 0, and blood glucose did not return to baseline (P = 0.01), even 4 h post-challenge. During OGTT, glucose area under the curve (AUC) was higher and insulin AUC was lower in HED pigs compared to controls (P = 0.001). Chronic HED intake increased (P<0.05) subcutaneous, intramuscular, and perirenal fat deposition, and induced hyperglycemia, hypoinsulinemia, and low-density lipoprotein hypercholesterolemia. A subset of HED pigs (n = 7) was transitioned back to a control diet for an additional six weeks. These pigs were subjected to an additional OGTT at 22 wk. Glucose AUC and insulin AUC did not improve, supporting that dietary intervention was not sufficient to recover glucose tolerance or insulin production. These data suggest a HED may be used to increase adiposity and disrupt glucose homeostasis in young, growing pigs.

A low-fat, high-complex carbohydrate diet supplemented with long-chain (n-3) fatty acids alters the postprandial lipoprotein profile in patients with metabolic syndrome

Dietary fat intake plays a critical role in the development of metabolic syndrome (MetS). This study addressed the hypothesis that dietary fat quantity and quality may differentially modulate postprandial lipoprotein metabolism in MetS patients. A multi-center, parallel, randomized, controlled trial conducted within the LIPGENE study randomly assigned MetS patients to 1 of 4 diets: high-SFA [HSFA; 38% energy (E) from fat, 16% E as SFA], high-monounsaturated fatty acid [HMUFA; 38% E from fat, 20% E as MUFA], and 2 low-fat, high-complex carbohydrate [LFHCC; 28% E from fat] diets supplemented with 1.24 g/d of long-chain (LC) (n-3) PUFA (ratio 1.4 eicosapentaenoic acid:1 docosahexaenoic acid) or placebo (1.24 g/d of high-oleic sunflower-seed oil) for 12 wk each. A fat challenge with the same fat composition as the diets was conducted pre- and postintervention. Postprandial total cholesterol, triglycerides (TG), apolipoprotein (apo) B, apo B-48, apo A-I, LDL-cholesterol, HDL-cholesterol and cholesterol, TG, retinyl palmitate, and apo B in TG-rich lipoproteins (TRL; large and small) were determined pre- and postintervention. Postintervention, postprandial TG (P < 0.001) and large TRL-TG (P = 0.009) clearance began earlier and was faster in the HMUFA group compared with the HSFA and LFHCC groups. The LFHCC (n-3) group had a lower postprandial TG concentration (P < 0.001) than the other diet groups. Consuming the LFHCC diet increased the TG (P = 0.04), large TRL-TG (P = 0.01), TRL-cholesterol (P < 0.001), TRL-retinyl palmitate (P = 0.001), and TRL-apo B (P = 0.002) area under the curve compared with preintervention values. In contrast, long-term ingestion of the LFHCC (n-3) diet did not augment postprandial TG and TRL metabolism. In conclusion, postprandial abnormalities associated with MetS can be attenuated with LFHCC (n-3) and HMUFA diets. The adverse postprandial TG-raising effects of long-term LFHCC diets may be avoided by concomitant LC (n-3) PUFA supplementation to weight-stable MetS patients.

Longitudinal adaptations to very low-carbohydrate weight-reduction diet in obese rats: body composition and glucose tolerance

Longitudinal effects of a very low-carbohydrate (VLC) and a calorie-matched high-carbohydrate (HC) weight reduction diet were compared in dietary obese Sprague-Dawley rats exhibiting impaired glucose tolerance and insulin resistance. Obese rats were divided into weight-matched groups: (i) VLC rats consumed an energy-restricted 5% carbohydrate, 60% fat diet for 8 weeks, (ii) HC rats consumed an isocaloric 60% carbohydrate, 15% fat diet, and (iii) HF rats consumed a high-fat diet ad libitum. HC and VLC rats showed similar reductions in body fat and hepatic lipid at the midpoint of the weight-reduction program, indicating effects due to energy deficit. At the end point, however, HC rats showed greater reductions in total and percent body fat, hepatic lipid and intramuscular lipid than did VLC rats, suggesting that diet composition induced changes in the relative efficiencies of the HC and VLC diets over time. HC rats showed marked improvement in glucose tolerance at the midpoint and end point, whereas VLC rats showed no improvement. Impaired glucose tolerance in VLC rats at the end point was due to insulin resistance and an attenuated insulin secretory response. Glucose tolerance in energy-restricted rats correlated negatively with hepatic and intramuscular lipid levels, but not visceral or total fat mass. These findings demonstrate that adaptations to diet composition eventually enabled HC rats to lose more body fat than VLC rats even though energy intakes were equal, and suggest that the elevated levels of hepatic and intramuscular lipid associated with VLC diets might predispose to insulin resistance and impaired glucose tolerance despite weight loss.

Low-carbohydrate high-fat diets: regulation of energy balance and body weight regain in rats

The aim of the current investigations was to examine the effects of a low-carbohydrate high-fat diet (LC-HFD) on body weight, body composition, growth hormone (GH), IGF-I, and body weight regain after stopping the dietary intervention and returning the diet back to standard laboratory chow (CH). In study one, both adolescent and mature male Wistar rats were maintained on either an isocaloric LC-HFD or CH for 16 days before having their diet switched. In study two, mature rats were maintained on either LC-HFD or CH for 16 days to determine the effects of the LC-HFD on fat pad weight. LC-HFD leads to body weight loss in mature rats (P < 0.01) and lack of body weight gain in adolescent rats (P < 0.01). Despite less body weight, increased body fat was observed in rats maintained on LC-HFD (P < 0.05). Leptin concentrations were higher (P < 0.05), and IGF-I (P < 0.01) concentrations were reduced in the LC-HFD rats. When the diet was returned to CH following LC-HFD, body weight regain was above and beyond that which was lost (P < 0.01). The LC-HFD resulted in increased body fat and had a negative effect upon both GH and IGF-I concentrations, which might have implications for the accretion and maintenance of lean body mass (LBM), normal growth rate and overall metabolic health. Moreover, when the LC-HFD ceases and a high-carbohydrate diet follows, more body weight is regained as compared to when the LC-HFD is consumed, in the absence of increased energy intake.

Low-carbohydrate diet versus caloric restriction: effects on weight loss, hormones, and colon tumor growth in obese mice

Our objective was to compare the effects of a low-carbohydrate diet to a high-carbohydrate/calorie-restricted diet on weight loss, hormones, and transplanted colon tumor growth. Eighty male C57BL/6 mice consumed a diet-induced obesity regimen (DIO) ad libitum for 7 weeks. From Weeks 8 to 14, the mice consumed a 1) DIO diet ad libitum (HF); 2) low-carbohydrate diet ad libitum (LC); 3) high-carbohydrate diet ad libitum (HC); or 4) HC calorie restricted diet (HC-CR). MC38 cells were injected at Week 15. At the time of injection, the HC-CR group displayed the lowest body weight (25.5 +/- 0.57 g), serum insulin-like growth factor I (IGF-I; 135 +/- 56.0 ng/ml), and leptin (1.0 +/- 0.3 ng/ml) levels. This group also exhibited the longest time to palpable tumor (20.1 +/- 0.9 days). Compared to the HF group, the HC group exhibited lower body weight (39.4 +/- 1.4 vs. 32.9 +/- 0.7 g, respectively), IGF-I (604 +/- 44.2 vs. 243.4 +/- 88.9 ng/ml, respectively), and leptin (15.6 +/- 2.2 vs. 7.0 +/- 0.7 ng/ml, respectively) levels but similar tumor growth. IGF-I levels were lower in the LC group (320.0 +/- 39.9 ng/ml) than the HF group, but tumor growth did not differ. These data suggest LC diets do not slow colon tumor growth in obese mice.

Carbohydrate versus energy restriction: effects on weight loss, body composition and metabolism

BACKGROUND/AIMS

To compare weight loss, body composition, and metabolic changes in response to carbohydrate versus dietary energy restriction (DER) in obese mice.

METHODS

One hundred C57BL/6 mice were randomized into five groups of 20. The group of high-carbohydrate (HC) mice consumed an HC diet ad libitum and the group of high-fat (HF) mice consumed an HF diet ad libitum for 14 weeks. Additional groups consumed the HF diet for 7 weeks ad libitum and during weeks 8-14 were switched to either a low-carbohydrate diet (LC) consumed ad libitum, the HC diet pair-fed (PF) to the energy intake of the LC group, or an HC DER regimen providing 70% of the energy intake of the HF group.

RESULTS

At 14 weeks, the LC and HF groups weighed more and exhibited higher percent fat mass and lower bone mineral density than the HC, PF, and DER groups. Relative to the DER group, the LC group displayed comparable serum ketone bodies but higher serum glucose, triglycerides, cholesterol, leptin, insulin, and insulin-like growth factor-1.

CONCLUSIONS

In contrast to DER, the LC diet did not cause weight loss or reduce serum markers associated with obesity-related diseases other than diabetes in obese mice, suggesting that carbohydraterestriction without reduced energy intake does not induce weight loss.