Altered Hypothalamic Signaling and Responses to Food Deprivation in Rats Fed a Low‐Carbohydrate Diet

Objective: To model how consuming a low‐carbohydrate (LC) diet influences food intake and body weight. Research Methods and Procedures: Food intake and body weight were monitored in rats with access to chow (CH), LC‐high‐fat (HF), or HF diets. After 8 weeks, rats received intracerebroventricular injections of a melanocortin agonist (melanotan‐II) and antagonist (SHU9119), and feeding responses were measured. At sacrifice, plasma hormones and hypothalamic expression of mRNA for proopiomelanocortin (POMC), melanocortin‐4 receptor, neuropeptide Y (NPY), and agouti related protein (AgRP) were assessed. A second set of rats had access to diet (chow or LC‐HF) for 4 weeks followed by 24 h food deprivation on two occasions, after which food intake and hypothalamic POMC, NPY, and AgRP mRNA expression were measured. Results: HF rats consumed more food and gained more weight than rats on CH or LC‐HF diets. Despite similar intakes and weight gains, LC‐HF rats had increased adiposity relative to CH rats. LC‐HF rats were more sensitive to melanotan‐II and less sensitive to SHU9119. LC‐HF rats had increased plasma leptin and ghrelin levels and decreased insulin levels, and patterns of NPY and POMC mRNA expression were consistent with those of food‐deprived rats. LC‐HF rats did not show rebound hyperphagia after food deprivation, and levels NPY, POMC, and AgRP mRNA expression were not affected by deprivation. Discussion: Our results demonstrate that an LC diet influences multiple systems involved in the controls of food intake and body weight. These data also suggest that maintenance on an LC‐HF diet affects food intake by reducing compensatory responses to food deprivation.     

Newly Identified HNP‐F from Human Neutrophil Peptide‐1 Promotes Hemostasis

Active hemostatic agents can play a crucial role in saving patients’ lives during surgery. Active hemostats have several advantages including utilization of natural blood coagulation and biocompatibility. Among them, although human neutrophil peptide‐1 (HNP‐1) has been previously reported with the hemostatic mechanism, which part of HNP‐1 facilitates the hemostatic activity is not known. Here, a partial peptide (HNP‐F) promoting hemostasis, originating from HNP‐1, has been newly identified by the blood coagulation ability test. HNP‐F shows the best hemostatic effect between the anterior half and posterior half of peptides. Moreover, microscopic images show platelet aggregation and an increase in the concentration of platelet factor 4, and the scanning electron microscope image of platelets support platelet activation by HNP‐F. Thromboelastography indicates decreased clotting time and increased physical properties of blood clotting. Mouse liver experiments demonstrate improved hemostatic effect by treatment of peptide solution. Cell viability and hemolysis assays confirm the HNP‐F's biosafety. It is hypothesized that the surface charge and structure of HNP‐F could be favorable to interact with fibrinogen or thrombospondin‐1. Collectively, because HNP‐F as an active peptide hemostat has many advantages, it could be expected to become a potent hemostatic biomaterial, additive or pharmaceutical candidate for various hemostatic applications.     

Normal Distribution of Body Weight Gain in Male Sprague‐Dawley Rats Fed a High‐Energy Diet

Objective: To investigate the effect of a high‐energy (HE) diet on caloric intake, body weight, and related parameters in outbred male Sprague‐Dawley (SD) rats. Research Methods and Procedures: Twenty‐eight SD rats were fed either chow (C) for 19 weeks or HE diet for 14 weeks and then C for 5 weeks. Blood hormones and metabolites were assayed, and expression of uncoupling protein‐1 and hypothalamic energy‐balance‐related genes were determined by Northern blotting and in situ hybridization, respectively. Results: HE rats gained body weight more rapidly than C animals with a range of weight gains, but there was no evidence that weight gain was bimodally distributed. Caloric intake was transiently elevated after introduction of the HE diet. Transfer of HE rats back to C resulted in a drop in caloric intake, but a stable body weight. In terminal analysis, two of four dissected adipose tissue depots were heavier in rats that had previously been fed HE diet. Blood leptin, insulin, glucose, and nonesterified fatty acids were not different between the groups. Uncoupling protein‐1 mRNA was elevated in interscapular brown adipose tissue from HE rats. There was a trend for agouti‐related peptide mRNA in the hypothalamic arcuate nucleus to be higher in HE rats. Discussion: Contrary to other studies of the SD rat on HE diet, body weight and other measured parameters were normally distributed. There was no segregation into two distinct populations on the basis of susceptibility to diet‐induced obesity. This characteristic may be dependent on the breeding colony from which animals were sourced.     

Mice with Low Metabolic Rates Are Not Susceptible to Weight Gain When Fed a High‐Fat Diet

Objective: Mice divergently selected for high or low food intake (FI) at constant body mass differ in their resting metabolic rates (RMRs). Low‐intake individuals (ML) have significantly lower RMR (by 30%) compared with those from the high‐intake line (MH). We hypothesized that MLs might, therefore, be more likely to increase their body and fat mass when exposed to a high‐fat diet (HFD). Research Methods and Procedures: We exposed both lines to a diet with 44.9% calories from fat for 3 weeks while measuring FI, fecal production, and body mass and then returned the mice to standard chow. Results: When exposed to the HFD, both lines significantly decreased their FI (MH, 40% to 45%; ML, 31% to 35%). This decrease occurred simultaneously with a significant increase in apparent energy absorption efficiency (AEAE). When returned to chow, FI and AEAE returned to the levels observed prior to HFD exposure. Because of the adjustments in FI, the absorbed energy was maintained in the MLs and, thus, body mass remained constant. The MH individuals overcompensated for the elevated energy content and AEAE on the HFD and, therefore, absorbed lower energy than when feeding on chow. These mice also did not significantly change their body mass when on the HFD and must have made adjustments in their energy expenditures. Both lines and both sexes increased in fat content on the HFD, but these effects were not different between lines or sexes. Discussion: We found no support for the hypothesis that mice with low RMRs were more susceptible to weight gain when fed the HFD.     

Intramyocellular Lipid Content and Molecular Adaptations in Response to a 1‐Week High‐Fat Diet

Objective: To investigate molecular adaptations that accompany the elevation of intramyocellular lipid (IMCL) content on a high‐fat (HF) diet for 1 week. Research Methods and Procedures: Ten subjects consumed a normal‐fat (NF) diet for 1 week, followed by an HF diet for another week. After both dietary periods, we determined the IMCL content by proton magnetic resonance spectroscopy in the vastus lateralis muscle and quantified changes in gene expression, protein content, and activity in biopsy samples. We investigated genes involved in carbohydrate and fatty acid handling [lipoprotein lipase, acetyl‐coenzyme A carboxylase (ACC) 2, hormone‐sensitive lipase, hexokinase II, and glucose transporter 4] and measured protein levels of CD36 and phosphorylated and unphosphorylated ACC2 and the activity of adenosine monophosphate‐activated kinase. Results: IMCL content was increased by 54% after the HF period. Lipoprotein lipase mRNA concentration was increased by 33%, whereas ACC2 mRNA concentration tended to be increased after the HF diet. Hexokinase II, glucose transporter 4, and hormone‐sensitive lipase mRNA were unchanged after the HF diet. ACC2 and CD36 protein levels, phosphorylation status of ACC2, and adenosine monophosphate‐activated kinase activity did not change in response to the HF diet. Discussion: We found that IMCL content in skeletal muscle increased after 1 week of HF feeding, accompanied by molecular adaptations that favor fat storage in muscle rather than oxidation.     

High‐Fat Diet Feeding Elevates Skeletal Muscle Uncoupling Protein 3 Levels But Not Its Activity in Rats

Objective: The objective of this study is to test the impact of high‐fat diet (HFD) feeding on skeletal muscle (SM) uncoupling protein 3 (UCP3) expression and its association with mitochondrial ion permeability and whole‐body energy homeostasis. Research Methods and Procedures: Sprague–Dawley rats were fed ad libitum either a HFD (60% of energy from fat, n = 6) or a low‐fat diet (12% of energy from fat, n = 6) for 4 weeks. Twenty‐four‐hour energy expenditure was measured by indirect calorimetry in the last week of the dietary treatment. Blood samples were collected for plasma leptin and free fatty acid assays, and mitochondria were isolated from hindlimb SM for subsequent determinations of UCP3 levels and mitochondrial ion permeability. Results: Plasma leptin levels were higher in rats fed the HFD despite the same body weight in two groups. The same dietary treatment also rendered a 2‐fold increase in plasma free fatty acid and SM UCP3 protein levels (Western blot) compared with the group fed the low‐fat diet. However, the elevated UCP3 protein levels did not correlate with mitochondrial swelling rates, a measure of mitochondrial chloride, and proton permeability, or with 24‐hour energy expenditure. Discussion: The high correlation between the levels of plasma free fatty acid levels and SM UCP3 suggests that circulating free fatty acid may play an important role in UCP3 expression during the HFD feeding. However, the dissociation between the UCP3 protein levels and 24‐hour energy expenditure as well as mitochondrial ion permeability suggests that mitochondrial proton leak mediated by muscle UCP3 may not be a major contributor in energy balance in HFD feeding, and other regulatory mechanisms independent of gene regulation may be responsible for the control of UCP3‐mediated uncoupling activity.     

Elevated Insulin Sensitivity in Low‐protein Offspring Rats Is Prevented by a High‐fat Diet and Is Associated With Visceral Fat

This study tests the hypothesis that a high‐fat postnatal diet increases fat mass and reduces improved insulin sensitivity (IS) found in the low‐protein model of maternal undernutrition. Offspring from Wistar dams fed either a 20% (control (CON)) or 8% (low protein (LP)) protein diet during gestation and lactation were randomly assigned to a control (con) or cafeteria (caf) diet at weaning (21 days) until 3 months of age at which point IS was measured (hyperinsulinemic–euglycemic clamp). Fat mass, growth, energy intake (EI) and expenditure (EE), fuel utilization, insulin secretion, and leptin and adiponectin levels were measured to identify a possible role in any changes in IS. IS was increased in LP‐con in comparison to CON‐con animals. Cafeteria feeding prevented this increase in LP animals but had no effect in CON animals (insulin‐stimulated glucose infusion rates (GIRs; mg/min/kg); CON‐con: 13.9 ± 1.0, CON caf: 12.1 ± 2.1, LP‐con: 25.4 ± 2.0, LP‐caf: 13.7 ± 3.7, P < 0.05). CON‐caf animals had similar percent epididymal white adipose tissue (%EWAT; CON‐con: 1.71 ± 0.09 vs. CON‐caf: 1.66 ± 0.08) and adiponectin (µg/ml: CON‐con: 4.61 ± 0.34 vs. CON‐caf: 3.67 ± 0.18) except hyperinsulinemia and relative hyperleptinemia in comparison to CON‐con. Differently, LP‐caf animals had increased %EWAT (LP‐con: 1.11 ± 0.06 vs. LP‐caf: 1.44 ± 0.08, P < 0.05) and adiponectin (µg/ml: LP‐con: 5.38 ± 0.39 vs. LP‐caf: 3.75 ± 0.35, P < 0.05) but did not show cafeteria‐induced hyperinsulinemia or relative hyperleptinemia. An increased propensity to store visceral fat in LP animals may prevent the elevated IS in LP offspring.     

Effects of Cricket Extract on Lipid Metabolism and Body Fat Content in High- Fat Diet Fed Rats

The effect of cricket extract on high‐fat diet fed rat was observed. It was shown that cricket extract prevented the increment of body weight by high‐fat diet. The extract also decreased the value of AST in liver. The most significant effect of the extract was shown on lipid metabolism. The contents of total lipid and total cholesterol in liver and feces were reduced by the extract on dose‐dependent. These statistically significant results were clear in 3% extract treated group (HFD3) while were slight in 1% extract treated group (HFD1). The same result was also shown in body fat content.     

Decreasing Effect of Chitosan on the Apparent Fat Digestibility by Rats Fed on a High-fat Diet

We investigated the effects of various dietary fibers or their likenesses on the apparent fat digestibility by rats fed on a high-fat diet. Each of 23 different fibers was added at 5% (w/w) to a purified diet containing 20% (w/w) corn oil. The rats were fed these diets for 2 weeks, and the feces were collected from each animal during the last 3 days. When compared with cellulose (control), 10 of the tested fibers significantly increased the fecal lipid excretion. Among these fibers, chitosan markedly increased the fecal lipid excretion and reduced the apparent fat digestibility to about a half relative to the control. The apparent protein digestibility was not greatly affected by chitosan. The fatty acid composition of the fecal lipids closely reflected that of the dietary fat. These results suggest that chitosan has potency for interfering with fat digestion and absorption in the intestinal tract, and for facilitating the excretion of dietary fat into the feces.     

Effect of a High‐fat Diet on 24‐Hour Pattern of Circulating Adipocytokines in Rats

We have shown a significant disruption of 24‐h pattern of plasma pituitary, adrenal, and gonadal hormones in high‐fat‐fed rats. Our objective was to assess the effect of a high‐fat diet (35% fat) on mean levels and 24‐h pattern of several adipocytokines in rats. A normal diet–fed rats (4% fat) were used as controls. When body weight of high‐fat‐fed rats attained values about 25% higher than controls (after 66 days of treatment), the animals were killed at six different time intervals throughout a 24‐h cycle. Plasma concentrations of insulin, adiponectin, interleukin (IL)‐1, leptin, ghrelin, plasminogen activator inhibitor‐1 (PAI‐1), and monocyte chemoattractant protein‐1 (MCP‐1) were measured in a multianalyte profiling by using the Luminex‐100 system. Tumor necrosis factor α (TNFα) and IL‐6 were measured by enzyme‐linked immunosorbent assay. A significant hyperglycemia developed in high‐fat‐fed rats, together with a significant increase in plasma insulin. Mean levels of plasma adiponectin, IL‐1, IL‐6, TNFα, and leptin augmented, and ghrelin decreased, in high‐fat‐fed rats. The normal daily pattern of plasma insulin, adiponectin, IL‐1, IL‐6, TNFα, leptin, ghrelin, and MCP‐1 became disrupted in high‐fat‐fed rats. The results indicate that a high‐fat diet may bring about signs of insulin resistance and mild inflammation in rats, together with the disruption in daily variations of circulating insulin and ghrelin, and of several adipocytokines including leptin, adiponectin, IL‐1, IL‐6, TNFα, and MCP‐1.