The metabolic syndrome

Inhibition of a novel Dickkopf-1-LDL receptor-related proteins 5 and 6 axis prevents diabetic cardiomyopathy in mice

BACKGROUND AND AIMS

Anti-hypertensive agents are one of the most frequently used drugs worldwide. However, no blood pressure-lowering strategy is superior to placebo with respect to survival in diabetic hypertensive patients. Previous findings show that Wnt co-receptors LDL receptor-related proteins 5 and 6 (LRP5/6) can directly bind to several G protein-coupled receptors (GPCRs). Because angiotensin II type 1 receptor (AT1R) is the most important GPCR in regulating hypertension, this study examines the possible mechanistic association between LRP5/6 and their binding protein Dickkopf-1 (DKK1) and activation of the AT1R and further hypothesizes that the LRP5/6-GPCR interaction may affect hypertension and potentiate cardiac impairment in the setting of diabetes.

METHODS

The roles of serum DKK1 and DKK1-LRP5/6 signalling in diabetic injuries were investigated in human and diabetic mice.

RESULTS

Blood pressure up-regulation positively correlated with serum DKK1 elevations in humans. Notably, LRP5/6 physically and functionally interacted with AT1R. The loss of membrane LRP5/6 caused by injection of a recombinant DKK1 protein or conditional LRP5/6 deletions resulted in AT1R activation and hypertension, as well as β-arrestin1 activation and cardiac impairment, possibly because of multiple GPCR alterations. Importantly, unlike commonly used anti-hypertensive agents, administration of the anti-DKK1 neutralizing antibody effectively prevented diabetic cardiac impairment in mice.

CONCLUSIONS

These findings establish a novel DKK1-LRP5/6-GPCR pathway in inducing diabetic injuries and may resolve the long-standing conundrum as to why elevated blood DKK1 has deleterious effects. Thus, monitoring and therapeutic elimination of blood DKK1 may be a promising strategy to attenuate diabetic injuries.

Effect of omega-3 ethyl esters on the triglyceride-rich lipoprotein response to endotoxin challenge in healthy young men

Oxylipins are produced enzymatically from polyunsaturated fatty acids, are abundant in triglyceride-rich lipoproteins (TGRL), and mediate inflammatory processes. Inflammation elevates TGRL concentrations, but it is unknown if the fatty acid and oxylipin composition change. In this study, we investigated the effects of prescription ω-3 acid ethyl esters (P-OM3; 3.4 g/d EPA + DHA) on the lipid response to an endotoxin challenge (lipopolysaccharide (LPS); 0.6 ng/kg body weight). Healthy young men (N=17) were assigned 8-12 weeks of P-OM3 and olive oil control in a randomized order crossover study. Following each treatment period, subjects received endotoxin challenge, and the time-dependent TGRL composition was observed. Post-challenge, arachidonic acid (AA) was 16% [95% CI: 4%, 28%] lower than baseline at 8 hours with control. P-OM3 increased TGRL ω-3 fatty acids (EPA 24% [15%, 34%]; DHA 14% [5%, 24%]). The timing of ω-6 oxylipin responses differed by class; AA-derived alcohols peaked at 2 hrs, while linoleic acid (LA)-derived alcohols peaked at 4 hrs (p_int = 0.006). P-OM3 increased EPA alcohols by 161% [68%, 305%] and DHA epoxides by 178% [47%, 427%] at 4 hrs compared to control. In conclusion, this study shows that TGRL fatty acid and oxylipin composition changes following endotoxin challenge. P-OM3 alters the TGRL response by increasing availability of ω-3 oxylipins for resolution of the inflammatory response.

Trafficking of nonesterified fatty acids in insulin resistance and relationship to dysglycemia

In adipose, insulin functions to suppress intracellular lipolysis and secretion of nonesterified fatty acid (NEFA) into plasma. We applied glucose and NEFA minimal models (MM) following a frequently sampled intravenous glucose tolerance test (FSIVGTT) to assess glucose-specific and NEFA-specific insulin resistance. We used total NEFA and individual fatty acids in the NEFA MM, comparing the model parameters in metabolic syndrome (MetSyn) subjects (n = 52) with optimally healthy controls (OptHC; n = 14). Results are reported as mean difference (95% confidence interval). Using the glucose MM, MetSyn subjects had lower [-73% (-82, -57)] sensitivity to insulin (S_i) and higher [138% (44, 293)] acute insulin response to glucose (AIR_g). Using the NEFA MM, MetSyn subjects had lower [-24% (-35, -13)] percent suppression, higher [32% (15, 52)] threshold glucose (g_s), and a higher [81% (12, 192)] affinity constant altering NEFA secretion (ϕ). Comparing fatty acids, percent suppression was lower in myristic acid (MA) than in all other fatty acids, and the stearic acid (SA) response was so unique that it did not fit the NEFA MM. MA and SA percent of total were increased at 50 min after glucose injection, whereas oleic acid (OA) and palmitic acid (PA) were decreased (P < 0.05). We conclude that the NEFA MM, as well as the response of individual NEFA fatty acids after a FSIVGTT, differ between OptHC and MetSyn subjects and that the NEFA MM parameters differ between individual fatty acids.

Vascular disease and dementias: paradigm shifts to drive research in new directions

Vascular disease was once considered the principal cause of aging-related dementia. More recently, however, research emphasis has shifted to studies of progressive neurodegenerative disease processes, such as those giving rise to neuritic plaques, neurofibrillary tangles, and Lewy bodies. Although these studies have led to critical insights and potential therapeutic strategies, interest in the role of systemic and cerebrovascular disease mechanisms waned and has received relatively less attention and research support. Recent studies suggest that vascular disease mechanisms play an important role in the risk for aging-related cognitive decline and disorders. Vascular disease frequently coexists with cognitive decline in aging individuals, shares many risk factors with dementias considered to be of the "Alzheimer type," and is observed more frequently than expected in postmortem material from individuals manifesting "specific" disease stigmata, such as abundant plaques and tangles. Considerable difficulties have emerged in attempting to classify dementias as being related to vascular versus neurodegenerative causes, and several systems of criteria have been used. Despite multiple attempts, a lack of consensus remains regarding the optimal means of incorporating vascular disease into clinical diagnostic, neurocognitive, or neuropathologic classification schemes for dementias. We propose here an integrative, rather than a strictly taxonomic, approach to the study and elucidation of how vascular disease mechanisms contribute to the development of dementias. We argue that, instead of discriminating between, for example, "Alzheimer's disease," "vascular dementia," and other diseases, there is a greater need to focus clinical and research efforts on elucidating specific pathophysiologic mechanisms that contribute to dementia phenotypes and neuropathologic outcomes. We outline a multitiered strategy, beginning with clinical and public health interventions that can be implemented immediately, enhancements to ongoing longitudinal studies to increase their informative value, and new initiatives to capitalize on recent advances in systems biology and network medicine. This strategy will require funding from multiple public and private sources to support collaborative and interdisciplinary research efforts to take full advantage of these opportunities and realize their societal benefits.

Metabolic syndrome and breast cancer in the me-can (metabolic syndrome and cancer) project

BACKGROUND

Few studies have assessed the metabolic syndrome (MetS) as an entity in relation to breast cancer risk, and results have been inconsistent. We aimed to examine the association between MetS factors (individually and combined) and risk of breast cancer incidence and mortality.

METHODS

Two hundred ninety thousand women from Austria, Norway, and Sweden were enrolled during 1974-2005, with measurements of height, weight, blood pressure, and levels of glucose, cholesterol, and triglycerides. Relative risks (RR) of breast cancer were estimated using Cox proportional hazards regression for each MetS factor in quintiles and for standardized levels (z-scores) and for a composite z-score for the MetS.

RESULTS

There were 4,862 incident cases of breast cancer and 633 deaths from breast cancer identified. In women below age 50, there was a decreased risk of incident cancer for the MetS (per 1-unit increment of z-score; RR, 0.83; 95% confidence interval, 0.76-0.90) as well as for the individual factors (except for glucose). The lowest risks were seen among the heaviest women. In women above age 60, there was an increased risk of breast cancer mortality for the MetS (RR, 1.23; 95% confidence interval, 1.04-1.45) and for blood pressure and glucose. The strongest association with mortality was seen for increased glucose concentrations.

CONCLUSIONS

The MetS was associated with a decreased risk of incident breast cancer in women below age 50 with high body mass index, and with an increased risk of breast cancer mortality in women above 60.

IMPACT

Lifestyle interventions as recommended for cardiovascular disease prevention may be of value to prevent breast cancer mortality in postmenopausal women.

Abnormal liver function test results are related to metabolic syndrome and BMI in Taiwanese adults without chronic hepatitis B or C

BACKGROUND

Metabolic syndrome (MS) is considered a cause of abnormal deposition of fat into hepatocytes, which might be associated with hepatic steatosis or abnormal liver function.

OBJECTIVE

The aim of this study was to explore the factors associated with MS and the relationship between MS and abnormal aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyl transferase (GGT) levels in Taiwanese subjects without chronic hepatitis B (CHB) or C (CHC).

SUBJECTS

We enrolled 2539 Taiwanese adults without CHB or CHC (age range: 16-88 years old) and investigated the factors related to MS using the NCEP-ATP (National Cholesterol Education Program-Adult Treatment Panel) III criteria; body mass index (BMI) was measured using Asia-Pacific criteria.

RESULTS

The prevalence rate of MS in Taiwanese adults without CHB or CHC was 16.9% using the modified ATP III criteria and 15.4% using the International Diabetes Federation criteria. Males had a significantly higher prevalence rate than females (P<0.001), and subjects with MS were significantly older and had significantly higher BMI values and AST, ALT and GGT levels (all P<0.001). In univariate analyses, the abnormality of liver function test results were related to gender, level of fasting sugar, systolic blood pressure, triglyceride, high-density lipoprotein, BMI and MS (all P<0.05). Multivariate analysis showed that the male gender, a higher BMI value and MS were related to abnormal liver function test results. The cutoff value for ALT in relation to MS is 31 IU l(-1) for male and 18 IU l(-1) for female.

CONCLUSION

The prevalence of MS in Taiwanese adults without hepatitis B or C was found to be high, and MS and BMI were identified as being related to abnormal liver function test results in these adults.