Our objective was to establish a diabetes mellitus type 2 (DM2) model in rats using a high-fat diet and streptozotocin (HF-STZ). Male Wistar rats (240-250g) were divided into a control group ...(commercial feed), and HF-STZ group, (66.5%-commercial feed, 13.5%-lard, and 20%-sugar). STZ (40mg/kg i.p.) or vehicle was administered on the 13th day. An oral glucose tolerance test (OGTT) was performed (2.5mg of glucose/kg v.o.) on both groups. After 39 days of treatment, blood and tissue samples were collected for analyses. The weight gain after STZ administration was lower in the HF-STZ group than in the control group with reductions in muscle mass and adipose tissue. The HF-STZ group showed hyperglycemia after STZ administration (glucose on day 39: HF-STZ: 499 ± 60; control: 134 ± 9mg/dL). Serum glucagon was 23% lower, and insulin levels were unaltered. The HOMA index was 4-times higher in the HF-STZ. The HF-STZ group showed increased post-prandial (330%) and fasting (125%) triglycerides, and while glycogen content in the liver and muscles decreased (70-80%). The area under the curve (OGTT) was 282% higher in the HF-STZ group. The combination of high-fat diet with STZ (i.p) generated rats with hyperglycemia associated with hypertriglyceridemia and introduced many other alterations present in human DM2.
The aim of this study was investigate the effects of a low-protein, high-carbohydrate (LPHC) diet introduced to rats soon after weaning. The animals were distributed in the following groups: LPHC45: ...fed an LPHC diet (6%-protein, 74%-carbohydrate) for 45 days; C45: fed a control (C) diet (17%-protein, 63%-carbohydrate) for 45 days; R (Reverse): fed with LPHC for 15 days followed by C diet for 30 days. The LPHC45 group showed alterations in the energetic balance with an increase in brown adipose tissue, and in glucose tolerance, and lower final body weight, muscle mass and total protein in blood when compared with C45 group. The HOMA-IR index was similar between LPHC45 and C45 groups, but this parameter was lower in LPHC45 compared with R groups. Serum adiponectin was higher in LPHC45 group than C45 and R groups. The R group presented higher fed insulin than C45 and LPHC45 and higher T4 compared with C45 group. Total cholesterol in R group was higher when compared with LPHC45 group. Thus, the data show that the change of the diet LPHC for a balanced diet led to different metabolic evolution and suggest that the different response can be due to different levels of adiponectin.
The aim of this study was to evaluate thermogenesis in the interscapular brown adipose tissue (IBAT) of rats submitted to low-protein, high-carbohydrate (LPHC) diet and the involvement of adrenergic ...stimulation in this process. Male rats (~100 g) were submitted to LPHC (6 %-protein; 74 %-carbohydrate) or control (C; 17 %-protein; 63 %-carbohydrate) isocaloric diets for 15 days. The IBAT temperature was evaluated in the rats before and after the administration of noradrenaline (NA) (20 µg 100 g b w⁻¹ min⁻¹). The expression levels of uncoupling protein 1 (UCP1) and other proteins involved in the regulation of UCP1 expression were determined by Western blot (Student’s t test, P ≤ 0.05). The LPHC diet promoted a 1.1 °C increase in the basal temperature of IBAT when compared with the basal temperature in the IBAT of the C group. NA administration promoted a 0.3 °C increase in basal temperature in the IBAT of the C rats and a 0.5 °C increase in the IBAT of the LPHC group. The level of UCP1 increased 60 % in the IBAT of LPHC-fed rats, and among the proteins involved in its expression, such as β3-AR and α1-AR, there was a 40 % increase in the levels of p38-MAPK and a 30 % decrease in CREB when compared to the C rats. The higher sympathetic flux to IBAT, which is a consequence of the administration of the LPHC diet to rats, activates thermogenesis and increases the expression of UCP1 in the tissue. Our results suggest that the increase in UCP1 content may occur via p38 MAPK and ATF2.
A low-protein, high-carbohydrate (LPHC) diet for 15 days increased the lipid content in the carcass and adipose tissues of rats. The aim of this work was to investigate the mechanisms of this lipid ...increase in the retroperitoneal white adipose tissue (RWAT) of these animals. The LPHC diet induced an approximately two- and tenfold increase in serum corticosterone and TNF-α, respectively. The rate of de novo fatty acid (FA) synthesis in vivo was reduced (50%) in LPHC rats, and the lipoprotein lipase activity increased (100%). In addition, glycerokinase activity increased (60%), and the phosphoenolpyruvate carboxykinase content decreased (27%). Basal U-
14
C-glucose incorporation into glycerol-triacylglycerol did not differ between the groups; however, in the presence of insulin, U-
14
C-glucose incorporation increased by 124% in adipocytes from only control rats. The reductions in IRS1 and AKT content as well as AKT phosphorylation in the RWAT from LPHC rats and the absence of an insulin response suggest that these adipocytes have reduced insulin sensitivity. The increase in NE turnover by 45% and the lack of a lipolytic response to NE in adipocytes from LPHC rats imply catecholamine resistance. The data reveal that the increase in fat storage in the RWAT of LPHC rats results from an increase in FA uptake from circulating lipoproteins and glycerol phosphorylation, which is accompanied by an impaired lipolysis that is activated by NE.
Abstract Objective To evaluate the browning and the origin of fatty acids (FAs) in the maintenance of triacylglycerol (TAG) storage and/or as fuel for thermogenesis in perirenal adipose tissue ...(periWAT) and inguinal adipose tissue (ingWAT) of rats treated with a low-protein, high-carbohydrate (LPHC) diet. Methods LPHC (6% protein, 74% carbohydrate) or control (C; 17% protein, 63% carbohydrate) diets were administered to rats for 15 days. The tissues were stained with H&E for histological analysis. The content of uncoupling protein 1 (UCP1) was determined by immunofluorescence. Levels of T-box transcription factor (TBX1), PR domain containing 16 (PRDM16), adipose triglyceride lipase (ATGL), hormone-sensitive lipase, lipoprotein lipase (LPL), glycerokinase, phosphoenolpyruvate carboxykinase (PEPCK), glucose transporter 4, β3 -adrenergic receptor (AR), β1 -AR, protein kinase A (PKA), AMP-activated protein kinase (AMPK), and phospho-AMPK were determined by immunoblotting. Serum fibroblast growth factor 21 (FGF21) was measured using a commercial kit (Student’s t -tests, P < 0.05). Results The LPHC diet increased FGF21 levels by 150-fold. The presence of multilocular adipocytes, combined with the increased contents of UCP1, TBX1, and PRDM16 in periWAT of LPHC-fed rats, suggested the occurrence of browning. The contents of β1 -AR and LPL were increased in the periWAT. The ingWAT showed higher ATGL and PEPCK levels, phospho-AMPK/AMPK ratios, and reduced β3 -AR and PKA levels. Conclusion These findings suggested that browning occurred only in the periWAT and that higher utilization of FAs from blood lipoproteins acted as fuel for thermogenesis. Increased G3P generation by glyceroneogenesis increased FAs re-esterification from lipolysis, explaining the increased TAG storage in the ingWAT.
Objectives
The objective of the study was to evaluate whether a twice‐daily instillation of 0.45% preservative‐free ketorolac tromethamine (FKT) or 0.4% benzalkonium chloride‐preserved ketorolac ...tromethamine (BACKT), every 12 h for 30 days may affect tear film parameters and the meibography in healthy dogs. Additionally, we assessed whether the same treatments irritated the ocular surface, affected goblet cell density (GCD), and the levels of oxidative stress biomarkers (OSB) in the conjunctiva of the same dogs.
Procedures
Experimental and masked comparison study. In 11 healthy dogs baseline values of the lipid layer thickness, tear meniscus height, non‐invasive tear breakup time (NI‐TFBT), and the meibomian gland (MG) loss were assessed by OSAvet®. For each dog, one eye received 40 μL of BACKT, while the other received 40 μL FKT, every 12 h for 30 consecutive days. Tear parameters and meibography were repeated 15, 30, and 60 days post‐treatments. Conjunctival hyperemia and blepharospasm were monitored at the same time points. At baseline and Day 30, a conjunctival biopsy was collected for GCD and OSB determination.
Results
Conjunctival hyperemia and blepharospasm were not observed. At Day 15, the MG loss increased only in FKT‐treated eyes (p < .001). On Day 30, both treatment groups showed increased MG loss, shortened NI‐TFBT, and reduced GCD and catalase (p < .05). At Day 30, BACKT‐treated eyes showed lower levels of superoxide dismutase (SOD) (p = .006) and higher levels of malondialdehyde (MDA) (p = .02). Differences between treatments were not observed for any parameter at any time point (p > .05). 60 days after treatment, OSAvet® parameters tended to return to values assessed at baseline; however, significant differences remained for MG loss (p < .05).
Conclusions
Twice‐daily instillation of KT, containing or not BAC, for 30 consecutive days shortened NI‐TFBT, decreased GCD, and increased the MG loss in healthy dogs. KT should be used with caution when prescribed for long periods, particularly in patients with tear film abnormalities. However, future controlled studies using KT, BAC, and other topical NSAIDs are indicated to further support this finding.
Abstract Objective The aim of this study was to assess the effects of protein restriction in growing rats. Methods Rats (approximate weight, 100 g) were maintained with low-protein (LP; 6%) or ...normoproteic (control; 17%) diets, and at the end of the 15th day, hormonal and biochemistry parameters and energetic balance were evaluated. Data were analyzed using Student's t test (with statistical significance set at P ≤ .05). Results LP animals were hyperphagic and showed increased energetic gain (24%) and energy expenditure (EE) compared with controls. The increase in EE was followed by increased sympathetic activity in brown adipose tissue, evidenced by increased norepinephrine turnover, suggesting increased thermogenesis. In spite of hyperphagia, protein ingestion in LP animals was lower than that of controls ( P < 0.01). The LP diet impaired body growth and caused deep alterations in body chemical composition, with an increase in carcass lipid content (64%) and reductions of protein and water. In LP animals, postprandial glycemia was unchanged, and insulinemia was lower than in controls ( P ≤ .01). Reduction in fasting glycemia without changes in insulinemia also was detected ( P < .01), suggesting increased insulin sensitivity. The LP diet caused a 100% increase in serum leptin ( P < .01). Conclusions Protein restriction led to an increase in EE, with probable activation of thermogenesis in brown adipose tissue, evidenced by an increase in catecholamines levels. Despite the higher EE, energetic gain and lipids increased. The high level of leptin associated with hyperphagia led to the supposition that these animals are leptin resistant, and the increase in insulin sensitivity, suggested by the relation between insulin and glycemia in fasting and fed animals, might contribute to lipid accumulation.
The low-protein, high-carbohydrate (LPHC) diet administered to growing rats soon after weaning, for 15 days, promoted an increase in energy expenditure by uncoupling protein 1 (UCP1) in interscapular ...brown adipose tissue, and also due to the occurrence of the browning process in the perirenal white adipose tissue (periWAT). However, we believe that inguinal white adipose tissue (ingWAT) may also contribute to energy expenditure through other mechanisms. Therefore, the aim of this work is to investigate the presence of the futile creatine cycle, and the origin of lipids in ingWAT, since that tissue showed an increase in the lipids content in rats submitted to the LPHC diet for 15 days. We observed increases in creatine kinase and alkaline phosphatase activity in ingWAT, of the LPHC animals. The mitochondrial Nicotinamide adenine dinucleotide reduced/nicotinamide adenine dinucleotide oxidized ratio is lower in ingWAT of LPHC animals. In the LPHC animals treated with β-guanidinopropionic acid, the extracellular uptake of creatine in ingWAT was lower, as was the rectal temperature. Regarding lipid metabolism, we observed that in ingWAT, lipolysis in vitro when stimulated with noradrenaline is lower, and there were no changes in baseline levels. In addition, increases in the activity of enzymes were also observed: malic, glucose-6-phosphate dehydrogenase, and ATP-citrate lyase, in addition to an increase in the PPARγ content. The results show the occurrence of the futile creatine cycle in ingWAT, and that the increase in the relative mass may be due to an increase in de novo fatty acid synthesis.
The our objective was to investigate the adaptations induced by a low-protein, high-carbohydrate (LPHC) diet in growing rats, which by comparison with the rats fed a control (C) diet at displayed ...lower fasting glycemia and similar fasting insulinemia, despite impairment in insulin signaling in adipose tissues. In the insulin tolerance test the LPHC rats showed higher rates of glucose disappearance (30%) and higher tolerance to overload of glucose than C rats. The glucose uptake by the soleus muscle, evaluated in vivo by administration of 2-deoxy-
14
Cglucose, increased by 81%. The phosphoenolpyruvate carboxykinase content and the incorporation of 1-
14
Cpyruvate into glucose was also higher in the slices of liver from the LPHC rats than in those from C rats. The LPHC rats showed increases in
l
-lactate as well as in other gluconeogenic precursors in the blood. These rats also had a higher hepatic production of glucose, evaluated by in situ perfusion. The data obtained indicate that the main substrates for gluconeogenesis in the LPHC rats are
l
-lactate and glycerol. Thus, we concluded that the fasting glycemia in the LPHC animals was maintained mainly by increases in the hepatic gluconeogenesis from glycerol and
l
-lactate, compensating, at least in part, for the higher glucose uptake by the tissues.
The aim of this study was to investigate tumor necrosis factor alpha (TNF-α)- and noradrenaline (NE)-stimulated lipolysis in retroperitoneal (RWAT) and epididymal (EAT) white adipose tissue as a ...means of understanding how low-protein, high-carbohydrate (LPHC) diet-fed rats maintain their lipid storage in a catabolic environment (marked by increases in serum TNF-α and corticosterone and sympathetic flux to RWAT and EAT), as previously observed. Adipocytes or tissues from the RWAT and EAT of rats fed an LPHC diet and rats fed a control (C) diet for 15 days were used in the experiments. The adipocytes from both tissues of the LPHC rats exhibited lower TNF-α- stimulated lipolysis compared to adipocytes from the C rats. The intracellular lipolytic agents IBMX, DBcAMPc and FSK increased lipolysis in both tissues from rats fed the C and LPHC diets compared to basal lipolysis; however, the effect was approximately 2.5-fold lower in adipocytes from LPHC rats. The LPHC diet induced a marked reduction in the β
3
and α
2
-AR, adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) content in RWAT and EAT. The LPHC diet did not affect TNF-α receptor 1 content but did induce a reduction in ERK p44/42 in both tissues. The present work indicates that RWAT and EAT from LPHC rats have an impairment in the lipolysis signaling pathway activated by NE and TNF-α, and this impairment explains the reduced response to these lipolytic stimuli, which may be fundamental to the maintenance of lipid storage in LPHC rats.
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