Association between skeletal muscle fat content and very-low-density lipoprotein-apolipoprotein B-100 transport in obesity: effect of weight loss.

AIMS: Ectopic deposition of fat in skeletal muscle is a feature of metabolic syndrome, but its specific association with very-low-density lipoprotein (VLDL)-apolipoprotein (apo) B-100 metabolism remains unclear. METHODS: We examined the association between skeletal muscle fat content and VLDL-apoB-100 kinetics in 25 obese subjects, and the responses of these variables to weight loss. The fat contents of liver, abdomen and skeletal muscle were determined by magnetic resonance imaging, and VLDL-apoB-100 kinetics were assessed using stable isotope tracers. RESULTS: In obese subjects who were insulin sensitive (homeostasis model assessment, HOMA, score ≤ 2.6, n = 12), skeletal muscle fat content was significantly associated with hepatic fat content (r = 0.636), energy intake (r = 0.694), plasma triglyceride (r = 0.644), apoB-100 (r = 0.529), glucose (r = 0.622), VLDL-apoB-100 concentrations (r = 0.860), VLDL-apoB-100 fractional catabolic rate (FCR; r = -0.581) and VLDL-apoB-100 secretion rate (r = 0.607). These associations were not found in obese subjects who were insulin resistant (HOMA score >2.6, n = 13). Of these 25 subjects, 10 obese subjects underwent a 16-week weight loss program. The low-fat diet achieved significant reduction (p < 0.05) in body weight, visceral and subcutaneous fat areas, liver and skeletal muscle fat, energy intake, triglyceride, insulin, HOMA score, VLDL-apoB100 concentrations and VLDL-apoB100 secretion rate. The percentage reduction of skeletal muscle fat with weight loss was significantly associated with the corresponding changes in VLDL-apoB100 concentration (r = 0.770, p = 0.009) and VLDL-apoB-100 secretion (r = 0.682, p = 0.030). CONCLUSIONS: Skeletal muscle fat content is associated with VLDL-apoB-100 transport. Weight loss lowers skeletal muscle fat and VLDL-apoB-100 secretion.

Circulating fatty acids, non-high density lipoprotein cholesterol, and insulin-infused fat oxidation acutely influence whole body insulin sensitivity in nondiabetic men.

Circulating lipids and tissue lipid depots predict insulin sensitivity. Associations between fat oxidation and insulin sensitivity are variable. We examined whether circulating lipids and fat oxidation independently influence insulin sensitivity. We also examined interrelationships among circulating lipids, fat oxidation, and tissue lipid depots. Fifty-nine nondiabetic males (age, 45.4 +/- 2 yr; body mass index, 29.1 +/- 0.5 kg/m(2)) had fasting circulating nonesterified fatty acids (NEFAs) and lipids measured, euglycemic-hyperinsulinemic clamp for whole body insulin sensitivity [glucose infusion rate (GIR)], substrate oxidation, body composition (determined by dual energy x-ray absorptiometry), and skeletal muscle triglyceride (SMT) measurements. GIR inversely correlated with fasting NEFAs (r = -0.47; P = 0.0002), insulin-infused NEFAs (n = 38; r = -0.62; P < 0.0001), low-density lipoprotein cholesterol (r = -0.50; P < 0.0001), non-high-density lipoprotein cholesterol (r = -0.52; P < 0.0001), basal fat oxidation (r = -0.32; P = 0.03), insulin-infused fat oxidation (r = -0.40; P = 0.02), SMT (r = -0.28; P < 0.05), and central fat (percentage; r = -0.59; P < 0.0001). NEFA levels correlated with central fat, but not with total body fat or SMT. Multiple regression analysis showed non-high-density lipoprotein cholesterol, fasting NEFAs, insulin-infused fat oxidation, and central fat to independently predict GIR, accounting for approximately 60% of the variance. Circulating fatty acids, although closely correlated with central fat, independently predict insulin sensitivity. Insulin-infused fat oxidation independently predicts insulin sensitivity across a wide range of adiposity. Therefore, lipolytic regulation as well as amount of central fat are important in modulating insulin sensitivity.

Hypertension in young adults--an under-estimated problem.

AIM: To study the prevalence of hypertension and "white coat hypertension" in young adult Asian males, and identify the associated risk factors. METHODS: Population-based descriptive analysis of 3,352 Singapore military conscripts presenting consecutively for medical screening, followed by case-control study of subjects with elevated blood pressure. A standard protocol for assessing elevated blood pressure, 24-hour ambulatory monitoring and detailed interviews were performed. Main study outcomes are prevalence rate of hypertension and "white coat hypertension", mean blood pressure readings, and adjusted odds ratios for associated variables. RESULTS: Prevalence of hypertension and "white coat hypertension" was 1.6% (95% CI 1.2, 2.0) and 2.0% (95% CI 1.5, 2.5) respectively. Twenty-four-hour ambulatory monitoring was required to differentiate the two conditions, with a fall of 22.5 mmHg (95% CI 19.7, 25.3) observed between first visit and day-time ambulatory mean systolic blood pressures. There was strong association between hypertension and obesity (adjusted odds ratio using Body Mass Index: 1.19, p<0.001). Other important variables included parental history of hypertension, Malay ethnicity and low socio-economic status, although there was no significant correlation in our regression model. CONCLUSION: This study provides population-based data on hypertension in young Asian adults. While the prevalence of hypertension is low compared to older age groups, it remains important to detect cases early, as appropriate treatment may mitigate long-term cardiovascular risks and reduce target organ damage. There is a clear role for ambulatory blood pressure monitoring for differentiating true hypertension from "white coat hypertension". There may be a role for targeted screening of high-risk groups, particularly the obese.

The adaptor protein BLNK is required for b cell antigen receptor-induced activation of nuclear factor-kappa B and cell cycle entry and survival of B lymphocytes.

B lymphocytes lacking the adaptor protein B cell linker (BLNK) do not proliferate in response to B cell antigen receptor (BCR) engagement. We demonstrate here that BCR-activated BLNK(-)/- B cells fail to enter the cell cycle, and this is due to their inability to induce the expression of the cell cycle regulatory proteins such as cyclin D2 and cyclin-dependent kinase 4. BCR-stimulated BLNK(-)/- B cells also do not up-regulate the cell survival protein Bcl-x(L), which may be necessary for the cells to complete the cell cycle. In addition, BLNK(-)/- B cells exhibit a high rate of spontaneous apoptosis in culture. Examination of the various BCR-activated signaling pathways in mouse BLNK(-)/- B cells reveals the intact activation of Akt and mitogen-activated protein kinases but the impaired activation of nuclear factor (NF)-kappaB that is known to regulate genes involved in cell proliferation and survival. The inability to activate NF-kappaB in BCR-stimulated BLNK(-)/- B cells is due to a failure to induce the degradation of the inhibitory kappaB protein. In all these aspects, BLNK(-)/- B cells resemble xid B cells that have a mutation in Bruton's tyrosine kinase (Btk). Recently, phospholipase C (PLC)-gamma2 has also been demonstrated to be essential for NF-kappaB activation. Since BLNK has been shown separately to interact with both Btk and PLC-gamma2, our finding of normal Btk but impaired PLC-gamma2 activation in BCR-stimulated BLNK(-)/- B cells strongly suggests that BLNK orchestrates the formation of a Btk-PLC-gamma2 signaling axis that regulates NF-kappaB activation. Taken together, the NF-kappaB activation defect may be sufficient to explain the similar defects in BCR-induced B cell proliferation and T cell-independent immune responses in BLNK(-)/-, Btk(-)/-, and PLC-gamma2(-)/- mice.

Paget's disease: acquired resistance to one aminobisphosphonate with retained response to another.

Twenty-five years after the first paper on etidronate in Paget's disease, there are few published papers that address bisphosphonate resistance as a specific clinical phenomenon. We report our data from two studies. Study 1 is a retrospective study of 20 patients with moderate to severe disease who were treated with intravenous (iv) pamidronate (221 +/- 18 mg [SEM]; range 60-360 mg), and after biochemical remission and relapse were retreated with generally larger iv dosage (293 +/- 28 mg; range 180-600 mg). The nadir bone turnover values were similar: plasma alkaline phosphatase (pAP) in 20 patients was 243 +/- 40 IU/l (mean +/- SEM) after the first course, and 267 +/- 44 IU/l after the second (reference range [RR] 35-135 IU/l). Likewise, fasting urinary hydroxyproline excretion (HypE) in 14 of the 20 patients was 4.5 +/- 1.1 micromol/LGF and 4.1 +/- 0.9 micromol/LGF, respectively (RR 0.40-1.92 micromol/LGF). However the minimum duration of biochemical remission was significantly shorter after the second course-10.9 +/- 1.7 months (first) and 5.6 +/- 0.9 months (second) (p < 0.03; Friedman's ANOVA n = 17). A subgroup of 10 patients who were followed for three courses showed a significantly higher pAP nadir in the third course. Study 2 is a prospective study of 40 patients, 23 previously untreated (NILPREV) and 17 previously treated with iv pamidronate (PAMPREV) and in biochemical relapse, who were randomly allocated to either oral alendronate 40 mg daily in 3 month units, or iv pamidronate 60 mg every 3 months. Treatment was continued until pAP and fasting urinary deoxypyridinoline/creatinine (Dpy/Cr) ratios (RR 5-27 micromol/mol) were both in the reference range, or a clear plateau in each marker developed. At baseline, there were no significant differences in either marker between the two NILPREV groups and between the two PAMPREV groups. Using log-transformed data, in NILPREV the pAP reductions were significant and similar over the first 6 months. However, although each Dpy/Cr reduction was also significant, the difference in responses favored alendronate (p < 0.015). In PAMPREV both markers showed no significant response to pamidronate; comparison showed a significantly greater response to alendronate (pAP p < 0.02; Dpy/Cr p < 0.002). Using two-way ANOVA, the pAP responses to alendronate in NILPREV and PAMPREV were similar and those to pamidronate were different (p = 0.034). The percentage of patients with both markers in the RR at 6 months or earlier were identical in NILPREV patients: alendronate 87% and pamidronate 87%. However in PAMPREV they were different: alendronate 83% and pamidronate 0% (p = 0.003). These data indicate: 1) patients treated with the same aminobisphosphonates for two courses show similar nadir values of bone turnover markers but a shorter remission time after the second course. In a third course the nadirs are significantly higher; and 2) in the alendronate/pamidronate comparison, NILPREV and PAMPREV patients showed similar pAP responses to alendronate, but significantly different responses to pamidronate. Thus, patients showing acquired partial resistance to one aminobisphosphonate (usually after two or more previous courses) are still capable of remission after exposure to another compound of the same class.

Fine needle aspiration cytology of the thyroid--a review of experience in 1853 cases.

1853 thyroid lesions subjected to cytological sampling (either by the fine needle aspiration or fine needle capillary sampling technique) from January 1992 to December 1997 at the University Hospital, Kuala Lumpur, were reviewed. Nodular goitre was the most common thyroid lesion needled (67.35%). Among the neoplastic lesions, follicular neoplasms predominated (64%), followed by papillary carcinoma (29.4%). In 325 cases, partial or total thyroidectomy had been done, providing material for histological review and cyto-histological correlation. Cytological diagnosis was found to have high sensitivity and specificity rates of over 75%. Besides, most non-neoplastic thyroid lesions could be diagnosed on cytology. The scope of cytology in the diagnosis of lymphomas, anaplastic and metastatic tumours rendered diagnostic biopsies (or thyroidectomy) unnecessary in these cases. Being a cost-effective technique and having the capacity to provide exact morphological diagnosis in a large variety of thyroid lesions, cytology is obviously the method of choice in the assessment of thyroid nodules.

Immunolabelling of prolactin at ultrastructural level using the protein A-gold technique on Epon-embedded tissue.

The use of the colloidal-gold technique in electron microscopy immunocytochemistry has provided important information on the in situ localisation of intracellular antigens. We have developed a post-embedding technique for prolactin localisation on resin-embedded human pituitary tissue sections by the use of the protein-A gold conjugate. Human pituitary tissue obtained at autopsy was processed for electron microscopical study without post-osmication and then embedded in Epon. The indirect immunoperoxidase method was used for light microscopical targetting of lactotroph cells for subsequent electron microscopical antigen localisation. Ultra-thin sections were labelled with human anti-human prolactin followed by protein-A gold conjugate. Specific labelling was observed over secretory granules with a density of 15-30 particles per granule, as determined by the Quantimet 570 image analysis system. This technique provides a means of studying the pathophysiology of hormonal secretion at ultrastructural level and can be a useful tool in diagnostic and research investigations.

Microwave-stimulated fixation for electron microscopy using a domestic microwave oven.

We investigated microwave-stimulated fixation of tissues for transmission electron microscopy using a domestic microwave oven operating at a frequency of 2.45 GHz with an output power of 500W. Microwave-stimulated fixation, in 4% glutaraldehyde, of fresh rat kidney, liver, heart and brain tissues was compared to conventional fixation. Human renal biopsies were similarly studied. Electron microscopy showed excellent ultrastructural preservation comparable to that obtained by conventional fixation. The optimal temperature range for microwave-stimulated fixation was found to lie between 50 degrees C and 55 degrees C. Our results indicate that microwave-stimulated fixation is a rapid and reproducible technique and can be effectively applied to routine diagnostic pathology.

Fetal tectal or cortical tissue transplanted into brachial lesion cavities in rats: influence on the regrowth of host retinal axons.

Fetal neural tissue was transplanted into suction lesions of the left brachium and pretectal region in young rats. Tectal tissue was grafted into 6-18-day-old rats and cortical tissue was transplanted into 17-20-day-old animals. The aim was to determine whether grafts could potentiate the regrowth of damaged retinal axons and, as a consequence, stimulate the axons to reenter their host target, the superior colliculus (SC). Fifteen to 581 days after transplantation, host retinal projections were traced by injecting the right eye with horseradish peroxidase (HRP). Parallel series of frozen brain sections were stained for HRP histochemistry, acetylcholinesterase, Nissl, or neurofibrils. At all ages studied, grafts survived and grew within the wound cavity; survival was better in the older animals. Most cortical grafts and a small number of tectal grafts filled the wound cavity and formed complete tissue bridges across the lesion. The majority of tectal grafts were attached to one or the other side of the lesion and were connected to the opposite lesion face by glial and connective tissue membranes that formed over the lesion site. In many animals that received tectal transplants, host retinal axons were traced growing into the grafts. Regenerating axons innervated specific, localized areas within the grafts, and it appeared that the axons retained the ability to recognize their appropriate target cells within the graft neuropil. Comparable ingrowth into cortical grafts was not observed. Optic axons were occasionally seen reentering the superficial layers of the host SC; however, compared to fetal tectal grafts, the density of host SC innervation was sparse. The implications of these data are discussed with regard to the possible use of fetal neural tissue grafts as reconstructive tissue bridges in the mammalian central nervous system.

Lack of ingrowth of retinal axons into the visually deafferented superior colliculus in young rats: a horseradish peroxidase study.

Suction lesions of the brachium of the left superior colliculus (SC) and pretectal region were made in 6-11-day-old hooded rats. Central retinal projections were examined 15-261 days later by injecting the right eye of each rat with horseradish peroxidase. Retinal fibres were found to have regrown either within glial and connective tissue membranes which formed over the lesion cavity or across the surface of the lesion itself. The axons sometimes grew up the rostral face of the remaining SC to reach the superficial tectal layers; however, there was no significant penetration into the SC neuropil.

Regrowth of retinal axons after lesions of the brachium and pretectal region in the rat.

Suction lesions of the left rostral superior colliculus (SC) and pretectal area were made in young rats. One to 50 days later, the right eye of each animal was injected with horseradish peroxidase (HRP). Animals were subsequently perfused and the brains processed with tetramethylbenzidine. In many older animals, lesioned areas were covered with thin membranes composed of glial and connective tissue cells. HRP-labelled optic axons were traced running through these membranes for up to 3 mm. On occasion, regrowing retinal fibres reached the rostral border of the remaining SC but did not grow into the tectal neuropil.