Elevated hippocampal copper in cases of type 2 diabetes.

BACKGROUND: Type-2 diabetes (T2D) is characterized by chronic hyperglycaemia and glucose-evoked organ damage, and displays systemic copper overload, elevated risk of impaired cognitive function, and epidemiological links to sporadic Alzheimer's disease (sAD). Contrastingly, sAD exhibits impaired cerebral-glucose uptake, elevation of cerebral glucose but not blood glucose levels, and widespread cerebral-copper deficiency. We hypothesized that sAD-like brain-metal perturbations would occur in T2D. METHODS: We measured nine essential elements in an observational case-control study of T2D without dementia (6 cases and 6 controls) in four brain regions and compared the results with those from our study of brain metals in sAD (9 cases and 9 controls), which employed equivalent analytical methodology. We evaluated intergroup differences by supervised and unsupervised multivariate-statistical approaches to contrast between T2D cases and controls, and to compare them with cerebral-metal patterns in sAD. FINDINGS: Unexpectedly, we found that hippocampal-copper levels in T2D were markedly elevated compared with controls (P = 0.005 and 0.007 by Welch's t-test in two technical-replicate experiments), to levels similar to those in cases of untreated Wilson's disease (WD), wherein elevated cerebral copper causes neurodegeneration. By contrast, hippocampal-copper levels in sAD were markedly deficient. Multivariate analysis identified marked differences in patterns of essential metals between hippocampal datasets from cases of T2D and of sAD. INTERPRETATION: Elevated hippocampal copper could contribute to the pathogenesis of cerebral neurodegeneration and cognitive impairment in T2D, similar to known impacts of elevated brain copper in WD. Therapeutic approaches with copper-lowering agents similar to those currently employed in pharmacotherapy of WD, may also be applicable in patients with T2D and impaired cognitive function. Further studies will be required to replicate and extend these findings and to investigate their potential therapeutic implications. FUNDING: In Acknowledgments, includes Endocore Research Trust; Lee Trust; Oakley Mental Health Research Foundation; Ministry of Business, Innovation & Employment; The Universities of Auckland and Manchester, and others.

Proteomic analysis of the human brain in Huntington's Disease indicates pathogenesis by molecular processes linked to other neurodegenerative diseases and to type-2 diabetes.

BACKGROUND: Huntington's disease (HD) is a neurodegenerative disorder in which the aetiological defect is inherited or spontaneous mutation in the HTT gene, which alters the structure of the corresponding huntingtin protein and initiates a pathogenetic cascade that ultimately leads to or causes dementia. OBJECTIVE: Here our main objective was to elucidate further the pathogenic processes that underlie neurodegeneration in HD. METHODS: By using two-dimensional gel electrophoresis we performed a proteomic case-control study of two brain regions in post-mortem human tissue from seven well-characterized HD patients and eight matched controls. RESULTS: In the middle frontal gyrus we identified twenty-two differentially-expressed proteins whereas by contrast in visual cortex only seven were altered. Twenty of these proteins have not to our knowledge been associated with the pathogenesis of HD before although all functional families implicated have previously been linked to other neurodegenerative diseases. Most of the proteins identified play roles in cell stress responses, apoptosis, metabolic regulation linked to type-2 diabetes, the ubiquitin-proteasome system, or protein trafficking/endocytosis. CONCLUSIONS: We propose that HTT mutations lead to or cause functional impairment of these pathways and that simultaneous restoration of their functions by targeted pharmacotherapy could ameliorate the signs and symptoms of HD. These studies provide a unique illustration of the interlinked disease processes that underpin/contribute to the pathogenesis of neurodegeneration in a genetically-mediated disorder of protein structure, and provide a signpost towards the design of new therapeutic interventions.

Reversal of diabetes-evoked changes in mitochondrial protein expression of cardiac left ventricle by treatment with a copper(II)-selective chelator.

Cardiac disease is the commonest cause of death amongst diabetic patients. Diabetic cardiomyopathy, which has a poor prognosis, is characterized by left ventricular hypertrophy and impaired cardiac function and mitochondrial damage is said to contribute to its development. We recently showed that treatment with the Cu(II) -selective chelator, triethylenetetramine (TETA), improved cardiac structure, and function in diabetic subjects without modifying hyperglycemia. Thus, TETA has potential utility for the treatment of heart disease. To further understand the molecular mechanism by which it causes these effects, we have conducted the first study of the effect of oral TETA on protein abundance in the cardiac left ventricle of rats with severe streptozotocin-induced diabetes. Proteomic methods showed that of 211 proteins changed in diabetes, 33 recovered after treatment. Through MS, 16 proteins were identified which may constitute major targets of drug action. Remarkably, most of these were mitochondrial proteins with roles in energy metabolism. In addition to components of the mitochondrial respiratory chain and enzymes involved in fatty acid oxidation, TETA treatment normalized both myocardial expression and enzymatic activity of carnitine palmitoyltransferase 2. These findings indicate that mitochondria constitute major targets in the mechanism by which TETA restores cardiac structure and function in diabetes.