A transgenic mouse model reproduces human hereditary systemic amyloidosis.

Amyloidoses are rare life-threatening diseases caused by protein misfolding of normally soluble proteins. The fatal outcome is predominantly due to renal failure and/or cardiac dysfunction. Because amyloid fibrils formed by all amyloidogenic proteins share structural similarity, amyloidoses may be studied in transgenic models expressing any amyloidogenic protein. Here we generated transgenic mice expressing an amyloidogenic variant of human apolipoprotein AII, a major protein of high density lipoprotein. According to amyloid nomenclature this variant was termed STOP78SERApoAII. STOP78SER-APOA2 expression at the physiological level spontaneously induced systemic amyloidosis in all mice with full-length mature STOP78SER-ApoAII identified as the amyloidogenic protein. Amyloid deposits stained with Congo red were extracellular, and consisted of fibrils of approximately 10 nm diameter. Renal glomerular amyloidosis was a major feature with onset of renal insufficiency occurring in mice older than six months of age. The liver, heart and spleen were also greatly affected. Expression of STOP78SER-APOA2 in the liver and intestine in mice of the K line but not in other amyloid-laden organs showed they present systemic amyloidosis. The amyloid burden was a function of STOP78SER-APOA2 expression and age of the mice with amyloid deposition starting in two-month-old high-expressing mice that died from six months onwards. Because STOP78SER-ApoAII conserved adequate lipid binding capacity as shown by high STOP78SER-ApoAII amounts in high density lipoprotein of young mice, its decrease in circulation with age suggests preferential deposition into preformed fibrils. Thus, our mouse model faithfully reproduces early-onset hereditary systemic amyloidosis and is ideally suited to devise and test novel therapies.

D25V apolipoprotein C-III variant causes dominant hereditary systemic amyloidosis and confers cardiovascular protective lipoprotein profile.

Apolipoprotein C-III deficiency provides cardiovascular protection, but apolipoprotein C-III is not known to be associated with human amyloidosis. Here we report a form of amyloidosis characterized by renal insufficiency caused by a new apolipoprotein C-III variant, D25V. Despite their uremic state, the D25V-carriers exhibit low triglyceride (TG) and apolipoprotein C-III levels, and low very-low-density lipoprotein (VLDL)/high high-density lipoprotein (HDL) profile. Amyloid fibrils comprise the D25V-variant only, showing that wild-type apolipoprotein C-III does not contribute to amyloid deposition in vivo. The mutation profoundly impacts helical structure stability of D25V-variant, which is remarkably fibrillogenic under physiological conditions in vitro producing typical amyloid fibrils in its lipid-free form. D25V apolipoprotein C-III is a new human amyloidogenic protein and the first conferring cardioprotection even in the unfavourable context of renal failure, extending the evidence for an important cardiovascular protective role of apolipoprotein C-III deficiency. Thus, fibrate therapy, which reduces hepatic APOC3 transcription, may delay amyloid deposition in affected patients.

Transient micro-elastography: A novel non-invasive approach to measure liver stiffness in mice.

AIM: To develop and validate a transient micro-elastography device to measure liver stiffness (LS) in mice. METHODS: A novel transient micro-elastography (TME) device, dedicated to LS measurements in mice with a range of measurement from 1-170 kPa, was developed using an optimized vibration frequency of 300 Hz and a 2 mm piston. The novel probe was validated in a classical fibrosis model (CCl(4)) and in a transgenic murine model of systemic amyloidosis. RESULTS: TME could be successfully performed in control mice below the xiphoid cartilage, with a mean LS of 4.4 ± 1.3 kPa, a mean success rate of 88%, and an excellent intra-observer agreement (0.98). Treatment with CCl(4) over seven weeks drastically increased LS as compared to controls (18.2 ± 3.7 kPa vs 3.6 ± 1.2 kPa). Moreover, fibrosis stage was highly correlated with LS (Spearman coefficient = 0.88, P < 0.01). In the amyloidosis model, much higher LS values were obtained, reaching maximum values of > 150 kPa. LS significantly correlated with the amyloidosis index (0.93, P < 0.0001) and the plasma concentration of mutant hapoA-II (0.62, P < 0.005). CONCLUSION: Here, we have established the first non-invasive approach to measure LS in mice, and have successfully validated it in two murine models of high LS.

Postprandial metabolic and hormonal responses of obese dyslipidemic subjects with metabolic syndrome to test meals, rich in carbohydrate, fat or protein.

BACKGROUND: The metabolic syndrome (MS) is a cluster of heterogeneous abnormalities conferring increased risk of cardiovascular diseases. Few postprandial studies have been conducted in MS individuals. OBJECTIVES: We aimed to study MS subjects with the same abnormalities: abdominal obesity, hypertriglyceridemia and low plasma HDL. We assessed postprandial variations of metabolic parameters related to obesity, dyslipidemia and glucose homeostasis. METHODS: In this randomized, double-blind, cross-over study, male MS and control subjects consumed, at separate occasions, a high carbohydrate (HC), high fat (HF) or high protein (HP) breakfast meal providing 30% of each subject's resting energy expenditure. RESULTS: Appetite hormones peptide YY and ghrelin did not differ between-subject groups. Interleukin-6 was two-fold higher in MS compared with control subjects, consistently with an inflammatory state. Hypertriglyceridemia of MS subjects was aggravated postprandially with the HF and HP meals and was lowest after the HC meal, arguing against increased hepatic VLDL production. HDL-cholesterol of MS subjects remained low postprandially, whereas apolipoprotein (apo) A-II was higher than in control subjects. Unexpectedly, postprandial insulin and glucose responses were higher in MS compared with control subjects, with the HP meal inducing the greater effects. CONCLUSIONS: The sustained postprandial hypertriglyceridemia of MS subjects after all meals suggests defective catabolism of triglyceride-rich lipoproteins. The greater postprandial increases in plasma insulin and glucose in MS relatively to control subjects indicate decreased insulin sensitivity, not revealed in the fasted state.