Cultured fetal rat hepatocytes derived from 12, 15 and 19-day gestation rats are capable of secre... more Cultured fetal rat hepatocytes derived from 12, 15 and 19-day gestation rats are capable of secreting transferrin. When dexamethasone is added to the medium an increased secretion rate is observed. The changes in secretion rates in control as well as dexamethasone-treated cells during culture have been shown to correlate with the level of mRNA coding for transferrin. Immunocytochemical experiments show that initially all hepatocytes contain transferrin which is localized in the lumina of the perinuclear space, rough endoplasmic reticulum and in the saccules and vesicles of the Golgi apparatus. During culture, particularly in control cells, the intensity of labelling varies from cell to cell. In addition, adjacent cells are observed to label more intensely in different intracellular organelles.
Worldwide there are over 46 million people living with dementia, and this number is expected to d... more Worldwide there are over 46 million people living with dementia, and this number is expected to double every 20 years reaching about 131 million by 2050. The cost to the community and government health systems, as well as the stress on families and carers is incalculable. Over three decades of research into this disease have been undertaken by several research groups in Australia, including work by our original research group in Western Australia which was involved in the discovery and sequencing of the amyloid-β peptide (also known as Aβ or A4 peptide) extracted from cerebral amyloid plaques. This review discusses the journey from the discovery of the Aβ peptide in Alzheimer's disease (AD) brain to the establishment of pre-clinical AD using PET amyloid tracers, a method now serving as the gold standard for developing peripheral diagnostic approaches in the blood and the eye. The latter developments for early diagnosis have been largely achieved through the establishment of the ...
Retinal imaging has the potential to be used as an early diagnostic tool in Alzheimer’s disease (... more Retinal imaging has the potential to be used as an early diagnostic tool in Alzheimer’s disease (AD). However, direct visualisation of AD related hallmark proteins in the live human retina is challenging and may require the inclusion of additional factors to be effective. This mini review gathers evidence to understand the associations and underlying mechanisms between beta‐amyloid (Aβ, a hallmark feature found in the AD brain), the retina and sleep as collectively they would enhance the diagnostic accuracy of the retinal markers in AD.
Testosterone replacement therapy (TRT) has been investigated in older men as a preventative treat... more Testosterone replacement therapy (TRT) has been investigated in older men as a preventative treatment against Alzheimer's disease and dementia. However, previous studies have been contradictory. We assessed TRT physiological effects in 44 older men (aged 61 ± 7.7 years) with subjective memory complaints using a double blind, randomized, crossover, placebo-controlled study. Participants were randomized into 2 groups, one group received transdermal testosterone (50 mg) daily for 24 weeks, followed by a 4 week wash-out period, then 24 weeks of placebo; the other group received the reverse treatment. Blood evaluation revealed significant increases in total testosterone, free (calculated) testosterone, dihydrotestosterone, and a decrease in luteinizing hormone levels (p<0.001) following TRT. Although there were significant increases in red blood cell counts, hemoglobin and prostate specific antigen levels following TRT, they remained within normal ranges. No significant differences in plasma amyloid beta, estradiol, sex hormone binding globulin, insulin levels, body fat percentage, or body mass index were detected. This is the first carefully controlled study that has investigated the influence of TRT in Indonesian men on blood biomarkers linked to dementia risk. Our study suggests TRT is safe and well-tolerated in this Indonesian cohort, yet longitudinal studies with larger cohorts are needed to assess TRT further, and to establish whether TRT reduces dementia risk.
Animal experiments and cell biology studies have provided evidence that both estrogens and androg... more Animal experiments and cell biology studies have provided evidence that both estrogens and androgens can play a protective role against Alzheimer's disease (AD) related neurodegeneration. Males who become hypogonadal in later life often report problems with their memory. Lower than normal testosterone levels have also been detected in patients prior to the onset of AD, as well as in younger late-onset male AD patients, when compared to appropriate controls. The results of some small clinical trials suggest that testosterone can improve cognitive function in andropause. Although such improvement in cognitive function is subtle, patients on testosterone replacement therapy have reported memory improvements in both declarative and procedural domains. In contrast, there is no clinical evidence to date which suggest that the hormone dihydroepiandrosterone (DHEA) can improve cognitive function. Rises in the levels of the gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (LH), have been associated with AD, but the clinical effects of reducing their levels remain to be determined. We hypothesize that androgens, gonadotropin modulators, or perhaps selective androgen receptor modulators may be useful components of therapy aimed at preventing the onset or delaying the progression of AD in male patients.
A growing body of evidence links type-2 diabetes (T2D) with dementia and neurodegenerative diseas... more A growing body of evidence links type-2 diabetes (T2D) with dementia and neurodegenerative diseases such as Alzheimer's disease (AD). AD is the most common form of dementia and is characterised neuropathologically by the accumulation of extracellular beta amyloid (Aβ) peptide aggregates and intracellular hyper-phosphorylated tau protein, which are thought to drive and/or accelerate inflammatory and oxidative stress processes leading to neurodegeneration. Although the precise mechanism remains unclear, T2D can exacerbate these neurodegenerative processes. Brain atrophy, reduced cerebral glucose metabolism and CNS insulin resistance are features of both AD and T2D. Cell culture and animal studies have indicated that the early accumulation of Aβ may play a role in CNS insulin resistance and impaired insulin signalling. From the viewpoint of insulin resistance and impaired insulin signalling in the brain, these are also believed to initiate other aspects of brain injury, including i...
Animal experiments and cell biology studies have provided evidence that both estrogens and androg... more Animal experiments and cell biology studies have provided evidence that both estrogens and androgens can play a protective role against Alzheimer's disease (AD) related neurodegeneration. Males who become hypogonadal in later life often report problems with their memory. Lower than normal testosterone levels have also been detected in patients prior to the onset of AD, as well as in younger late-onset male AD patients, when compared to appropriate controls. The results of some small clinical trials suggest that testosterone can improve cognitive function in andropause. Although such improvement in cognitive function is subtle, patients on testosterone replacement therapy have reported memory improvements in both declarative and procedural domains. In contrast, there is no clinical evidence to date which suggest that the hormone dihydroepiandrosterone (DHEA) can improve cognitive function. Rises in the levels of the gonadotropins, follicle stimulating hormone (FSH) and luteinizin...
The physiological importance of the insulin responsive glucose transporter GLUT4 in adipocytes an... more The physiological importance of the insulin responsive glucose transporter GLUT4 in adipocytes and muscle in maintaining glucose homeostasis is well established. A key protein associated with this process is the aminopeptidase IRAP which co-localizes with GLUT4 in specialized vesicles, where it plays a tethering role. In this study, we investigated the distribution of both GLUT4 and IRAP in the kidney to gain insights into the potential roles of these proteins in this organ. Both IRAP and GLUT4 immunostaining was observed in the epithelial cells of the proximal and distal tubules and thick ascending limbs in the cortex, but very little overlap between GLUT4 and IRAP immunoreactivity was observed. GLUT4 staining was consistent with a vesicular localization, whereas IRAP staining was predominantly on the luminal surface. In the principal cells of the inner medulla collecting duct (IMCD), IRAP immunoreactivity was detected throughout the cell, with limited overlap with the vasopressin responsive water channel aquaporin-2 (AQP-2). AQP-2 levels were observed to be two-fold higher in IRAP knockout mice. Based on our results, we propose that GLUT4 plays a role in shunting glucose across epithelial cells. In the kidney cortex, IRAP, in concert with other peptidases, may be important in the generation of free amino acids for uptake, whereas in the principal cells of the inner medulla IRAP may play a localized role in the regulation of vasopressin bioactivity.
Cultured fetal rat hepatocytes derived from 12, 15 and 19-day gestation rats are capable of secre... more Cultured fetal rat hepatocytes derived from 12, 15 and 19-day gestation rats are capable of secreting transferrin. When dexamethasone is added to the medium an increased secretion rate is observed. The changes in secretion rates in control as well as dexamethasone-treated cells during culture have been shown to correlate with the level of mRNA coding for transferrin. Immunocytochemical experiments show that initially all hepatocytes contain transferrin which is localized in the lumina of the perinuclear space, rough endoplasmic reticulum and in the saccules and vesicles of the Golgi apparatus. During culture, particularly in control cells, the intensity of labelling varies from cell to cell. In addition, adjacent cells are observed to label more intensely in different intracellular organelles.
Worldwide there are over 46 million people living with dementia, and this number is expected to d... more Worldwide there are over 46 million people living with dementia, and this number is expected to double every 20 years reaching about 131 million by 2050. The cost to the community and government health systems, as well as the stress on families and carers is incalculable. Over three decades of research into this disease have been undertaken by several research groups in Australia, including work by our original research group in Western Australia which was involved in the discovery and sequencing of the amyloid-β peptide (also known as Aβ or A4 peptide) extracted from cerebral amyloid plaques. This review discusses the journey from the discovery of the Aβ peptide in Alzheimer's disease (AD) brain to the establishment of pre-clinical AD using PET amyloid tracers, a method now serving as the gold standard for developing peripheral diagnostic approaches in the blood and the eye. The latter developments for early diagnosis have been largely achieved through the establishment of the ...
Retinal imaging has the potential to be used as an early diagnostic tool in Alzheimer’s disease (... more Retinal imaging has the potential to be used as an early diagnostic tool in Alzheimer’s disease (AD). However, direct visualisation of AD related hallmark proteins in the live human retina is challenging and may require the inclusion of additional factors to be effective. This mini review gathers evidence to understand the associations and underlying mechanisms between beta‐amyloid (Aβ, a hallmark feature found in the AD brain), the retina and sleep as collectively they would enhance the diagnostic accuracy of the retinal markers in AD.
Testosterone replacement therapy (TRT) has been investigated in older men as a preventative treat... more Testosterone replacement therapy (TRT) has been investigated in older men as a preventative treatment against Alzheimer's disease and dementia. However, previous studies have been contradictory. We assessed TRT physiological effects in 44 older men (aged 61 ± 7.7 years) with subjective memory complaints using a double blind, randomized, crossover, placebo-controlled study. Participants were randomized into 2 groups, one group received transdermal testosterone (50 mg) daily for 24 weeks, followed by a 4 week wash-out period, then 24 weeks of placebo; the other group received the reverse treatment. Blood evaluation revealed significant increases in total testosterone, free (calculated) testosterone, dihydrotestosterone, and a decrease in luteinizing hormone levels (p<0.001) following TRT. Although there were significant increases in red blood cell counts, hemoglobin and prostate specific antigen levels following TRT, they remained within normal ranges. No significant differences in plasma amyloid beta, estradiol, sex hormone binding globulin, insulin levels, body fat percentage, or body mass index were detected. This is the first carefully controlled study that has investigated the influence of TRT in Indonesian men on blood biomarkers linked to dementia risk. Our study suggests TRT is safe and well-tolerated in this Indonesian cohort, yet longitudinal studies with larger cohorts are needed to assess TRT further, and to establish whether TRT reduces dementia risk.
Animal experiments and cell biology studies have provided evidence that both estrogens and androg... more Animal experiments and cell biology studies have provided evidence that both estrogens and androgens can play a protective role against Alzheimer's disease (AD) related neurodegeneration. Males who become hypogonadal in later life often report problems with their memory. Lower than normal testosterone levels have also been detected in patients prior to the onset of AD, as well as in younger late-onset male AD patients, when compared to appropriate controls. The results of some small clinical trials suggest that testosterone can improve cognitive function in andropause. Although such improvement in cognitive function is subtle, patients on testosterone replacement therapy have reported memory improvements in both declarative and procedural domains. In contrast, there is no clinical evidence to date which suggest that the hormone dihydroepiandrosterone (DHEA) can improve cognitive function. Rises in the levels of the gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (LH), have been associated with AD, but the clinical effects of reducing their levels remain to be determined. We hypothesize that androgens, gonadotropin modulators, or perhaps selective androgen receptor modulators may be useful components of therapy aimed at preventing the onset or delaying the progression of AD in male patients.
A growing body of evidence links type-2 diabetes (T2D) with dementia and neurodegenerative diseas... more A growing body of evidence links type-2 diabetes (T2D) with dementia and neurodegenerative diseases such as Alzheimer's disease (AD). AD is the most common form of dementia and is characterised neuropathologically by the accumulation of extracellular beta amyloid (Aβ) peptide aggregates and intracellular hyper-phosphorylated tau protein, which are thought to drive and/or accelerate inflammatory and oxidative stress processes leading to neurodegeneration. Although the precise mechanism remains unclear, T2D can exacerbate these neurodegenerative processes. Brain atrophy, reduced cerebral glucose metabolism and CNS insulin resistance are features of both AD and T2D. Cell culture and animal studies have indicated that the early accumulation of Aβ may play a role in CNS insulin resistance and impaired insulin signalling. From the viewpoint of insulin resistance and impaired insulin signalling in the brain, these are also believed to initiate other aspects of brain injury, including i...
Animal experiments and cell biology studies have provided evidence that both estrogens and androg... more Animal experiments and cell biology studies have provided evidence that both estrogens and androgens can play a protective role against Alzheimer's disease (AD) related neurodegeneration. Males who become hypogonadal in later life often report problems with their memory. Lower than normal testosterone levels have also been detected in patients prior to the onset of AD, as well as in younger late-onset male AD patients, when compared to appropriate controls. The results of some small clinical trials suggest that testosterone can improve cognitive function in andropause. Although such improvement in cognitive function is subtle, patients on testosterone replacement therapy have reported memory improvements in both declarative and procedural domains. In contrast, there is no clinical evidence to date which suggest that the hormone dihydroepiandrosterone (DHEA) can improve cognitive function. Rises in the levels of the gonadotropins, follicle stimulating hormone (FSH) and luteinizin...
The physiological importance of the insulin responsive glucose transporter GLUT4 in adipocytes an... more The physiological importance of the insulin responsive glucose transporter GLUT4 in adipocytes and muscle in maintaining glucose homeostasis is well established. A key protein associated with this process is the aminopeptidase IRAP which co-localizes with GLUT4 in specialized vesicles, where it plays a tethering role. In this study, we investigated the distribution of both GLUT4 and IRAP in the kidney to gain insights into the potential roles of these proteins in this organ. Both IRAP and GLUT4 immunostaining was observed in the epithelial cells of the proximal and distal tubules and thick ascending limbs in the cortex, but very little overlap between GLUT4 and IRAP immunoreactivity was observed. GLUT4 staining was consistent with a vesicular localization, whereas IRAP staining was predominantly on the luminal surface. In the principal cells of the inner medulla collecting duct (IMCD), IRAP immunoreactivity was detected throughout the cell, with limited overlap with the vasopressin responsive water channel aquaporin-2 (AQP-2). AQP-2 levels were observed to be two-fold higher in IRAP knockout mice. Based on our results, we propose that GLUT4 plays a role in shunting glucose across epithelial cells. In the kidney cortex, IRAP, in concert with other peptidases, may be important in the generation of free amino acids for uptake, whereas in the principal cells of the inner medulla IRAP may play a localized role in the regulation of vasopressin bioactivity.
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