Patricia Monteiro Seraphim

Calorie restriction reduces pinealectomy‐induced insulin resistance by improving GLUT4 gene expression and its translocation to the plasma membrane

Abstract: The present study aimed to investigate insulin sensitivity and GLUT4 expression protein in pinealectomized rats, as well as to determining the effects of melatonin and calorie restriction on the changes induced by pinealectomy. Wistar rats were pinealectomized (Pinx) or sham operated (Sham), and studied 30 days later. Melatonin replacement treatment (50 g/100 g body weight) was continued for 30 days after pinealectomy. Calorie restriction was performed by offering 60% of the standard food intake. In vivo insulin sensitivity was evaluated using the glucose disappearance constant (kITT) during an insulin tolerance test, and GLUT4 mRNA and protein were assessed by Northern and Western blotting, respectively. The in vitro effect of melatonin on GLUT4 protein content in plasma membrane was investigated in adipocytes isolated from intact rats. Compared with Sham rats, Pinx rats showed decreased kITT (40%), GLUT4 expression in white adipose tissue (WAT, ∼70%), and unchanged GLUT4 expression in skeletal muscle. Melatonin treatment in Pinx rats restored the kITT and GLUT4 protein to control values. No in vitro effects of melatonin (10−9 m) upon GLUT4 protein were observed. Calorie restriction of Pinx rats increased their kITT value (∼40%), total GLUT4 protein content (∼240%) and its translocation to the plasma membrane (∼80%) in WAT. The results show that pinealectomy, for lack of melatonin, decreased insulin sensitivity as well as GLUT4 gene expression. Calorie restriction improved insulin sensitivity in Pinx rats, and this was related to increased GLUT4 gene expression and insulin‐induced GLUT4 translocation to the plasma membrane in WAT.

The effects of lesions of the thalamic intergeniculate leaflet on the pineal metabolism

The aim of the present work was to study, in rats, the effects of lesions of the thalamic intergeniculate leaflet (IGL) and the deep pineal/lamina intercalaris region (DP) on the diurnal profile of N-acetylserotonin (NAS) and on the nocturnal pineal reactivity to acute retinal light stimulation (1 or 15 min). The 24-h experiment shows that there is no phase-shifting on the diurnal NAS curve of groups of rats with bilateral IGL lesion compared to the controls. On the other hand there is a significant reduction on the amplitude of pineal NAS content observed in every nocturnal point of the curve. The pineal glands of IGL-lesioned rats, after 1 min of retinal light stimulation, keep their NAS content equal to the lesioned dark-killed rats. Nonetheless, after 15 min of photostimulation, the pineal NAS content is reduced to nearly zero equally to the control animals. DP lesion does not modify the content of NAS in the pineal gland of rats killed in the dark. However, the pineal photo-inhibition process induced by 1 min of light exposure is impaired. These results suggest that: (1) the intergeniculate leaflet has a role in regulating the amplitude of the diurnal rhythm of pineal NAS production rather than its phase entrainment to light-dark cycle. This effect is not dependent on the direct geniculo-pineal connections. (2) The nocturnal pineal photo-inhibition phenomenon could be decomposed in two processes. One, triggered by short pulses of light and totally dependent on the IGL and partially dependent on the direct monosynaptic pathway between this structure and the pineal gland.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute and short-term insulin-induced molecular adaptations of GLUT2 gene expression in the renal cortex of diabetic rats.

Increased GLUT2 gene expression in the renal proximal tubule of diabetic rats is an adaptive condition, which may be important in the diabetic nephropathy development. We investigated the effects of insulin treatment upon the renal GLUT2 overexpression of diabetic rats. Acute treatment, surprisingly, induced a rapid further increase in GLUT2 mRNA content. Twelve hours after insulin injection, GLUT2 mRNA was twice the value of saline-injected rats (P<0.001), when GLUT2 protein remained unchanged. In response to short-term treatment, both GLUT2 mRNA and protein were increased in 1-day treated rats (P<0.05 versus saline-injected), decreasing after that, and reaching, within 6 days, values close to those of non-diabetic rats. Concluding, insulin treatment induced: initially, an additional upregulation of GLUT2 gene expression, involving posttranscriptional modulation; thereafter, downregulation of GLUT2 expression, which returns to non-diabetic levels. The former may be related to increased insulin concentration, the latter may be due to glycemic control.

Age related obesity-induced shortening of GLUT4 mRNA poly(A) tail length in rat gastrocnemius skeletal muscle

Obese insulin resistant animals and humans have shown reduced GLUT4 gene expression. Yet, in skeletal muscle, discrepancy between mRNA and protein regulation has been frequently observed, suggesting a post-transcriptional modulation. We investigated the GLUT4 expression in adipose tissue and muscle of obese 12-month-old (12-mo) rats, comparing with lean 2-month-old (2-mo) animals. Obesity was accompanied by insulin resistance, and 65% reduction (P<0.01) in GLUT4 mRNA and protein in adipose tissue. However, in muscle, despite increased (P<0.05) mRNA content, GLUT4 protein was unchanged. RNase H and poly(A) test assays showed a reduction (P<0.01) of approximately 80 adenines in the GLUT4 mRNA poly(A) tail of muscle from 12-mo rats, recognizing that the poly(A) tail length correlates with translation efficiency. Concluding, age related obesity of 12-mo rats involves suppression of GLUT4 expression in adipose tissue; however, in muscle, GLUT4 mRNA content increases, but with a shorter poly(A) tail, thus unchanging the protein content.

GLUT4 protein expression in obese and lean 12-month-old rats: insights from different types of data analysis

GLUT4 protein expression in white adipose tissue (WAT) and skeletal muscle (SM) was investigated in 2-month-old, 12-month-old spontaneously obese or 12-month-old calorie-restricted lean Wistar rats, by considering different parameters of analysis, such as tissue and body weight, and total protein yield of the tissue. In WAT, an approximately 70% decrease was observed in plasma membrane and microsomal GLUT4 protein, expressed as microg protein or g tissue, in both 12-month-old obese and 12-month-old lean rats compared to 2-month-old rats. However, when plasma membrane and microsomal GLUT4 tissue contents were expressed as g body weight, they were the same. In SM, GLUT4 protein content, expressed as microg protein, was similar in 2-month-old and 12-month-old obese rats, whereas it was reduced in 12-month-old obese rats, when expressed as g tissue or g body weight, which may play an important role in insulin resistance. Weight loss did not change the SM GLUT4 content. These results show that altered insulin sensitivity is accompanied by modulation of GLUT4 protein expression. However, the true role of WAT and SM GLUT4 contents in whole-body or tissue insulin sensitivity should be determined considering not only GLUT4 protein expression, but also the strong morphostructural changes in these tissues, which require different types of data analysis.

β‐Adrenergic activity preserves GLUT4 protein in glycolytic fibers in fasting

Glucose transporter 4 (GLUT4) expression in adipose tissue decreases during fasting. In skeletal muscle, we hypothesized that GLUT4 expression might be maintained in a β‐adrenergic–dependent way to ensure energy disposal for contractile function. Herein we investigate β‐blockade or β‐stimulation effects on GLUT4 expression in oxidative (soleus) and glycolytic [extensor digitorum longus (EDL)] muscles of fasted rats. Fasting increased GLUT4 mRNA in soleus (24%) and EDL (40%), but the protein content increased only in soleus (30%). β1–β2‐, and β1–β2–β3‐blockade decreased (20–30%) GLUT4 mRNA content in both muscles, although GLUT4 protein decreased only in EDL. When mRNA and GLUT4 protein regulations were discrepant, changes in the mRNA poly(A) tail length were detected, indicating a posttranscriptional modulation of gene expression. These results show that β‐adrenergic activity regulates GLUT4 gene expression in skeletal muscle during fasting, highlighting its participation in preservation of GLUT4 protein in glycolytic muscle. Muscle Nerve, 2009

A glândula pineal e o metabolismo de carboidratos

For decades, the influence of the pineal gland on carbohydrate metabolism has been investigated. However, contradictory results have not yet elucidated the role played by melatonin in carbohydrate homeostasis. In our recent studies, we have contributed to characterize the role of the pineal gland as a modulator of carbohydrate metabolism. In addition, based on present-day knowledge, we have demonstrated the steps of insulin action mechanism involved in this modulation. Our studies reveal that pinealectomy causes a condition of obesity-free insulin resistance. The maximum uptake of 2-deoxi-glucose prompted by insulin in isolated adipocytes is diminished, without however changing the insulin capacity to bind to its receptor, and to stimulate the phosphorilation of intracellular substrates represented by pp 185. Conversely, in several insulin-sensitive tissues, our studies detected a decrease in the amount of glucose transporter protein GLUT4, and a decrease in GLUT4 mRNA in only some of these tissues, suggesting a tissue-specific regulation. Additionally, it was demonstrated that the pineal gland regulation influences carbohydrate metabolism through melatonin, by our demonstration that the hormone increased insulin sensitivity of isolated adipocytes, and that melatonin replacement therapy restored the amount of GLUT4 in white adipose tissue. In summary, the studies reported here evidence an important role played by the pineal gland in the modulation of carbohydrate homeostasis. This regulation seems to be melatonin-dependent and can be described, so far, as an increase in tissue sensitivity to insulin, which involves changes in GLUT4 gene expression.

Intermittent resistance exercise and obesity, considered separately or combined, impair spermatic parameters in adult male Wistar rats

Obesity and absence of physical exercise are global problems that affect concentration and sperm quality in the male reproductive system. The purpose of this study was to examine the effect of obesity and resistance training, considered separately or in association, on testicular function and reproductive capacity. Twenty pubertal male Wistar rats were distributed into four groups: control (C) and exercise (E) groups that received standard rat chow; and obese (O) and obese with exercise (OE) groups that received a high‐fat diet. All the groups received filtered water during the experimental conditions. Groups E and OE were submitted to 8 weeks of high‐intensity intermittent training. Afterwards, testes were collected for sperm count, spermatogenic kinetics, histopathology, morphometry and immunodetection of androgen receptors (AR). The vas deferens was collected for sperm morphology. The results showed that obesity increased body weight, naso‐anal length, liver and epididymal fat weight, abnormal spermatozoa and immunodetectable AR. Intermittent exercise decreased daily sperm production (DSP), sperm count and normal spermatozoa, whereas the number of tubules with immunodetectable AR increased. The combination of obesity and intermittent training led to reduced sperm count and DSP, although abnormal spermatozoa and the number of tubules with immunodetectable AR increased. Thus, in conclusion, both obesity and resistance training impaired testicular function during puberty in rats; and this type of exercise has also been shown to be detrimental to testicular physiology.

Can the Intermittent Training Generate Alterations on the Liver Tissue of Rats Submitted to a Hyperlipidic Diet

Estudios indican que el aumento de la actividad fisica y la disminucion de los niveles de grasa en el higado ayudan a reducir el riesgo de morbilidad por enfermedades hepaticas. El objetivo fue evaluar el efecto de un programa de entrenamiento intermitente de ocho semanas en el tejido hepatico de ratas con dieta alta en grasa. Treinta ratas Wistar machos fueron divididas en grupos Control Sedentario (SC), Control Ejercicio (CE) (con fuente de alimentacion que consiste en la racion estandar y agua), Obeso Sedentario (OS) y Obeso Ejercicio (OE) (con alimentacion compuesta por tocino, mortadela, salchichas, galletas, refrescos y racion estandar), sometidas a un entrenamiento intermitente a traves de saltos mediante estimulacion electrica con tres series de 12 repeticiones, tres veces por semana durante ocho semanas. Al final del periodo de entrenamiento, los animales fueron sacrificados; se extrajeron sus higados para el procesamiento histologico y tincion con hematoxilina y eosina (HE). Luego se realizo el analisis cariometrico de los nucleos de los hepatocitos. Se observo que los nucleos de los hepatocitos fueron menores en los animales obesos en comparacion con los nucleos de hepatocitos de los animales de control, pues el ejercicio combinado con una dieta adecuada se mostro eficiente para que causar alteraciones en los nucleos de hepatocitos, y esa combinacion puede retener la funcion normal de las celulas y disminuir las posibilidades de la aparicion de danos en los tejidos. Ademas, el ejercicio aislado no puede ser considerado como un factor de proteccion contra la alteracion las celulas del higado.

Morphometric and Fractal Analysis of Injured Skeletal Muscle Tissue Subjected to A Combination of Treatments; Cryotherapy and Therapeutic Ultrasound

El objetivo del estudio fue evaluar los efectos de la asociacion de las tecnicas de crioterapia y ultrasonido terapeutico en el tratamiento de la lesion muscular por impacto. Fueron utilizadas 55 ratas Wistar, expuestas a lesion y separadas en grupos (n = 11): Lesion aguda (LA), Lesion (L), Crioterapia (CR), Ultrasonido Terapeutico (UT) y Crioterapia + Ultrasonido Terapeutico (CRUT). Los grupos CR y CRUT recibieron la aplicacion, durante 20 minutos, en tres momentos (inmediatamente, 24 y 48 horas, despues de la lesion). Los grupos UT y CRUT, recibieron UT por siete dias, con una duracion de cinco minutos, en modo pulsado, con una intensidad de 0,5 W/cm2 y frecuencia de 1 MHz. Fueran medidos el peso corporal y el peso de los musculos gastrocnemios y se realizaron cortes histologicos del musculo gastrocnemio, los cuales fueron tenidos con hematoxilina-eosina (HE) para el analisis morfometrico y con picrosirius para el analisis del colageno por dimension fractal (DF). Los resultados de los analisis intragrupo demostraron una menor disminucion de la masa coporal y muscular en el grupo CRUT. Ademas, fue observado un valor inferior en la morfometria en el grupo CRUT en comparacion a los grupos LA (p = 0,001), L (p = 0,001), CR (p = 0,001) y UT (p = 0,001), y un menor valor de la DF con respecto al colageno en el grupo CRUT en comparacion a los grupos LA (p = 0,007) y CR (p = 0,014). En sintesis, el presente estudio demostro que el protocolo de asociacion de las tecnicas de CR y UT causaron mayores respuestas beneficas en los aspectos analizados en comparacion a los protocolos con los tratamientos aplicados de forma aislada.