Cell shrinkage follows, rather than mediates, the short-term effects of glucagon on carbohydrate metabolism.
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ABSTRACT:
SUBMITTER: Gaussin V
PROVIDER: S-EPMC1133117 | biostudies-other | 1992 Oct
REPOSITORIES: biostudies-other
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Project description:Plants are often challenged by an array of unfavorable environmental conditions. During cold exposure, many changes occur that include, for example, the stabilization of cell membranes, alterations in gene expression and enzyme activities, as well as the accumulation of metabolites. In the presented study, the carbohydrate metabolism was analyzed in the very early response of plants to a low temperature (2 °C) in the leaves of 5-week-old potato plants of the Russet Burbank cultivar during the first 12 h of cold treatment (2 h dark and 10 h light). First, some plant stress indicators were examined and it was shown that short-term cold exposure did not significantly affect the relative water content and chlorophyll content (only after 12 h), but caused an increase in malondialdehyde concentration and a decrease in the expression of NDA1, a homolog of the NADH dehydrogenase gene. In addition, it was shown that the content of transitory starch increased transiently in the very early phase of the plant response (3-6 h) to cold treatment, and then its decrease was observed after 12 h. In contrast, soluble sugars such as glucose and fructose were significantly increased only at the end of the light period, where a decrease in sucrose content was observed. The availability of the monosaccharides at constitutively high levels, regardless of the temperature, may delay the response to cold, involving amylolytic starch degradation in chloroplasts. The decrease in starch content, observed in leaves after 12 h of cold exposure, was preceded by a dramatic increase in the transcript levels of the key enzymes of starch degradation initiation, the α-glucan, water dikinase (GWD-EC 2.7.9.4) and the phosphoglucan, water dikinase (PWD-EC 2.7.9.5). The gene expression of both dikinases peaked at 9 h of cold exposure, as analyzed by real-time PCR. Moreover, enhanced activities of the acid invertase as well as of both glucan phosphorylases during exposure to a chilling temperature were observed. However, it was also noticed that during the light phase, there was a general increase in glucan phosphorylase activities for both control and cold-stressed plants irrespective of the temperature. In conclusion, a short-term cold treatment alters the carbohydrate metabolism in the leaves of potato, which leads to an increase in the content of soluble sugars.
| S-EPMC8268532 | biostudies-literature
Project description:Hypoenergetic diets and resistance training (RT) have been suggested to be important components of weight loss strategy programs; however, there is little evidence as to the chronic effects of different macronutrient compositions on strength performance and muscle mass with RT. The purpose of this study was to compare the effects of carbohydrate restrictive (CRD) and conventional (CONV) diets combined with RT on strength performance and muscle thicknesses in overweight and obese participants already involved in RT programs. Twenty-one volunteers engaged in an eight-week progressive RT program three times per week were assigned to a CRD (< 30 g carbohydrate; n = 12; 30.7 ± 3.9 km·m-2) or a CONV (30% energy deficit; 55%, 15% and 30% energy from carbohydrate, protein and fat, respectively; n=9; 27.7±2.5 km·m-2).At baseline and week 8, the participants underwent body composition assessment by anthropometry, measurement of muscle thickness by ultrasound, and three strength tests using isotonic equipment. Both groups had similar reductions in body mass and fat mass as well as maintenance of fat-free mass. Muscle strength increased 14 ± 6% in the CRD group (p = 0.005) and 19 ± 9% in the CONV group (p = 0.028), with no significant differences between the groups. No significant differences were detected in muscle thicknesses within or between the groups. In conclusion, hypoenergetic diets combined with RT led to significant increases in muscle strength and were capable of maintaining muscle thicknesses in the upper and lower limbs of overweight and obese participants, regardless of the carbohydrate content of the diets.
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Project description:BACKGROUND: The aim of this study was to evaluate short-term effects of a low-carbohydrate diet in overweight and obese subjects with low HDL-C levels. METHODS: Overweight (BMI between 25-30 kg/m2) or obese (BMI over 30 kg/m2) subjects with low HDL-C levels (men with HDL-C <1.03, women <1.29 mmol/l) were invited to the study. A 1400 kcal 75-gram carbohydrate (CHO) diet was given to women and an 1800 kcal 100-gram CHO diet was given to men for four weeks. The distribution of daily energy of the prescribed diet was 21-22% from CHO, 26-29% from protein and 49-53% from fat. Subjects completed a three-day dietary intake record before each visit. Anthropometric indices, body fat ratio, blood lipids, glucose and insulin were measured. Baseline and week-four results were compared with a Wilcoxon signed ranks test. RESULTS: Twenty-five women and 18 men participated. Basal median LDL-C level of men was 3.11 and basal median LDL-C level of women was 3.00 mmol/l. After four weeks of a low-carbohydrate diet, the median energy intake decreased from 1901 to 1307 kcal/day, daily energy from carbohydrate from 55% to 33%, body weight from 87.7 to 83.0 kg and HDL-C increased from 0.83 to 0.96 mmol/l in men (p < 0.002, for all). After four weeks of a low-carbohydrate diet, the median energy intake tended to decrease (from 1463 to 1243 kcal, p = 0.052), daily energy from carbohydrate decreased from 53% to 30% (p < 0.001) and body weight decreased from 73.2 to 70.8 kg (p < 0.001) in women, but HDL-C did not significantly change (from 1.03 to 1.01 mmol/l, p = 0.165). There were significant decreases in body mass index, waist circumference, body fat ratio, systolic blood pressure, total cholesterol, triglyceride and insulin levels in all subjects. CONCLUSIONS: HDL-C levels increased significantly with energy restriction, carbohydrate restriction and weight loss in men. HDL-C levels didn't change in women in whom there was no significant energy restriction but a significant carbohydrate restriction and a relatively small but significant weight loss. Our results suggest that both energy and carbohydrate restriction should be considered in overweight and obese subjects with low HDL-C levels, especially when LDL-C levels are not elevated.
| S-EPMC2994852 | biostudies-other
Project description:Dietary restriction promotes resistance to surgical stress in multiple organisms. Counterintuitively, current medical protocols recommend short-term carbohydrate-rich drinks (carbohydrate loading) prior to surgery, part of a multimodal perioperative care pathway designed to enhance surgical recovery. Despite widespread clinical use, preclinical and mechanistic studies on carbohydrate loading in surgical contexts are lacking. Here we demonstrate in ad libitum-fed mice that liquid carbohydrate loading for one week drives reductions in solid food intake, while nearly doubling total caloric intake. Similarly, in humans, simple carbohydrate intake is inversely correlated with dietary protein intake. Carbohydrate loading-induced protein dilution increases expression of hepatic fibroblast growth factor 21 (FGF21) independent of caloric intake, resulting in protection in two models of surgical stress: renal and hepatic ischemia-reperfusion injury. The protection is consistent across male, female, and aged mice. In vivo, amino acid add-back or genetic FGF21 deletion blocks carbohydrate loading-mediated protection from ischemia-reperfusion injury. Finally, carbohydrate loading induction of FGF21 is associated with the induction of the canonical integrated stress response (ATF3/4, NF-kB), and oxidative metabolism (PPARγ). Together, these data support carbohydrate loading drinks prior to surgery and reveal an essential role of protein dilution via FGF21.
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Project description:Salmonella is gram-negative foodborne zoonotic bacteria which triggers disease in humans. Our previous studies showed 1,8-cineole possessed remarkable antimicrobial effects on foodborne zoonotic bacteria indicating it could serve as a new source of antibiotic for Salmonella. Present study elucidated the antibacterial mechanism of 1,8-cineole by analyzing serum protein expressed by Salmonella following treatment with 1,8-cineole (0.25 mg/mL, 3 h) using isobaric tags for relative and absolute quantification (iTRAQ) with two-dimensional liquid chromatography/tandem mass spectrometry (2D-LC-MS/MS). 1,8-cineole was found to significantly damage the structure of Salmonella cell walls and membranes. A total of 3011 proteins were extracted from the experimental group, of which 435 were differentially expressed (1.5-fold) with 123 upregulated and 312 downregulated. The expressed proteins were involved in 935 intracellular biological processes, 98 cellular components, 477 molecular functions and 86 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Among them, proteins associated with carbohydrate, nucleotide, amino acid, lipid, and energy metabolism were significantly changed following treatment with 1,8-cineole. Carbohydrate metabolism and membrane protein-related genes was down-regulated at the mRNA level when Salmonella was treated with 1,8-cineole. 1,8-cineole may be a potential antibiotic for Salmonella infections.
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Project description:Fasting is associated with increased susceptibility to hypoglycemia in people with type 1 diabetes, thereby making it a significant health risk. To date, the relationship between fasting and insulin-induced hypoglycemia has not been well characterized, so our objective was to determine whether insulin-independent factors, such as counterregulatory hormone responses, are adversely impacted by fasting in healthy control individuals. Counterregulatory responses to insulin-induced hypoglycemia were measured in 12 healthy people during 2 metabolic studies. During one study, participants ate breakfast and lunch, after which they underwent a 2-hour bout of insulin-induced hypoglycemia (FED). During the other study, participants remained fasted prior to hypoglycemia (FAST). As expected, hepatic glycogen concentrations were lower in FAST, and associated with diminished peak glucagon levels and reduced endogenous glucose production (EGP) during hypoglycemia. Accompanying lower EGP in FAST was a reduction in peripheral glucose utilization, and a resultant reduction in the amount of exogenous glucose required to maintain glycemia. These data suggest that whereas a fasting-induced lowering of glucose utilization could potentially delay the onset of insulin-induced hypoglycemia, subsequent reductions in glucagon levels and EGP are likely to encumber recovery from it. As a result of this diminished metabolic flexibility in response to fasting, susceptibility to hypoglycemia could be enhanced in patients with type 1 diabetes under similar conditions.
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Project description:The present study concerns short- and long-term effects of interruption of the enterohepatic circulation (EHC) on hepatic cholesterol metabolism and biliary secretion in rats. For this purpose, we employed a technique that allows reversible interruption of the EHC, during normal feeding conditions, and excludes effects of anaesthesia and surgical trauma. [3H]Cholesteryl oleate-labelled human low-density lipoprotein (LDL) was injected intravenously in rats with (1) chronically (8 days) interrupted EHC, (2) interrupted EHC at the time of LDL injection and (3) intact EHC. During the first 3 h after interruption of the EHC, bile flow decreased to 50% and biliary bile acid, phospholipid and cholesterol secretion to 5%, 11% and 19% of their initial values respectively. After 8 days of bile diversion, biliary cholesterol output and bile flow were at that same level, but bile acid output was increased 2-3-fold and phospholipid output was about 2 times lower. The total amount of cholesterol in the liver decreased after interruption of the EHC, which was mainly due to a decrease in the amount of cholesteryl ester. Plasma disappearance of LDL was not affected by interruption of the EHC. Biliary secretion of LDL-derived radioactivity occurred 2-4 times faster in chronically interrupted rats as compared with the excretion immediately after interruption of the EHC. Radioactivity was mainly in the form of bile acids under both conditions. This study demonstrates the very rapid changes that occur in cholesterol metabolism and biliary lipid composition after interruption of the EHC. These changes must be taken into account in studies concerning hepatic metabolism of lipoprotein cholesterol and subsequent secretion into bile.
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Project description:Thirty-two, seven-week old male C57BL/6J mice were obtained from Jackson Labs. Mice were adapted to a 12h/12h reverse light cycle and put on Control diet at 8 weeks of age for 10 days. Food was removed during lights on and restored at lights off. On the day of the experiment, mice were fed Control or MR diet for either 3 or 6 hours. There were 8 mice in each group. Animals were sacrificed using CO2 inhalation and decapitation. The hepatic transcriptome was analyzed for the initial effect of low dietary methionine.
2021-02-22 | GSE158068 | GEO
Project description:Jurkat T cells have been exposed to 9g hypergravity in a custom-built pipette centrifuge for different times (GBF2021). Additionally, Jurkat T cells have been exposed to 300g for 5 minutes in a standard benchtop centrifuge, and waited for different times until adding lysis buffer. For comparison, Jurkat T cells have been exposed to 5 minutes of 42°C.
2023-02-07 | GSE221579 | GEO
Project description:At Aplysia sensory-to-motor neuron synapses, the inhibitory neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFa) produces depression, and serotonin (5-HT) produces facilitation. Short-term depression has been found to result from the activation of a phospholipase A2. The released arachidonate is metabolized by 12-lipoxygenase to active second messengers. We find that FMRFa leads to the phosphorylation and activation of p38 mitogen-activated protein (MAP) kinase. Short-term depression and the release of arachidonate are blocked by the specific p38 kinase inhibitor SB 203580. Both the inhibitor and an affinity-purified antibody raised against recombinant Aplysia p38 kinase injected into sensory neurons prevented long-term depression, which depends on the phosphorylation of translation factors cAMP response element-binding protein 2 (CREB2) and activating transcription factor 2. Facilitation produced by 5-HT, on the other hand, inactivates p38 kinase. Chromatin immunoprecipitation assays indicate that p38 kinase activates CREB2. p38 kinase also is pivotal in the bidirectional regulation of synaptic plasticity: when the kinase is inhibited, brief treatment with 5-HT that normally produces only short-term facilitation now results in long-term facilitation. Conversely, in sensory neurons injected with the activated kinase, long-term facilitation is blocked, and brief exposure to FMRFa, which normally results in short-term depression, results in long-term depression. We conclude that p38 kinase, which itself is bidirectionally regulated by FMRFa and 5-HT, acts as a modulator of synaptic plasticity by positively regulating depression and serving as an inhibitory constraint for facilitation.
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