Association between liver insulin resistance and cardiovascular risk factors

Abstract. Vangipurapu J, Stan?áková A, Kuulasmaa T, Soininen P, Kangas AJ, Ala‐Korpela M, Kuusisto J, Laakso M (University of Eastern Finland and Kuopio University Hospital, Kuopio; University of Oulu and Biocenter Oulu, Oulu, Finland). Association between liver insulin resistance and cardiovascular risk factors. J Intern Med 2012; 272: 402–408. Objectives. The objective of this study was to examine the associations between indices of liver insulin resistance (IR) and whole‐body insulin sensitivity and different cardiovascular disease (CVD) risk factors. Design and subjects. A total of 8750 nondiabetic men (age 57.2 ± 7.1 years, body mass index 26.8 ± 3.8 kg m^?2) were included in this study from the population‐based cross‐sectional Metabolic Syndrome In Men (METSIM) cohort. Liver IR index and Matsuda insulin sensitivity index (ISI) were used as markers of liver IR and whole‐body insulin sensitivity, respectively. Pearson correlation analysis was performed to examine the associations between these indices and various CVD risk factors. Results. Total cholesterol (r = ?0.088 vs. r = 0.020; P < 0.0019), high‐sensitivity C‐reactive protein (CRP) (r = 0.284 vs. r = ?0.219; P < 0.0019) and total triglycerides (r = 0.507 vs. r = ?0.477; P < 0.05) were more highly correlated with liver IR index than with Matsuda ISI. By contrast, Matsuda ISI was nominally more highly correlated with systolic and diastolic blood pressure (r = ?0.234 and r = ?0.275 vs. r = 0.202 and r = 0.239, respectively) compared to liver IR index. Furthermore, the variance explained by liver IR index was larger than that explained by Matsuda ISI for the majority of CVD risk factors measured. Conclusions. Liver IR index correlated more strongly than Matsuda ISI with levels of total cholesterol, CRP and triglycerides. Therefore, liver IR might be a significant indicator of CVD risk amongst men.     

A lineshape fitting model for 1H NMR spectra of human blood plasma.

A lineshape fitting model was constructed for classifying the overlapping information in the 1H NMR spectrum of human blood plasma. A reliable assignment of the overlapping fatty acid (-CH2-)n and -CH3 resonances of the various lipoproteins (VLDL, very low density lipoprotein; LDL, low density lipoprotein; HDL high density lipoprotein) is introduced, and for the first time detailed characteristics (chemical shifts, half linewidths, and relative intensities) of the individual lipoprotein components were obtained directly from the whole plasma spectrum. This was achieved by combining the constructed lineshape fitting model and the proper 400 MHz proton NMR measurements from blood plasma of a healthy donor, from fractions of the different lipoproteins, and from plasma samples in which the lipoprotein fractions were separately added. The results suggest fair promise of future applications of the rapid and easy NMR analysis of lipoprotein distribution in various research and clinical situations.     

Proton nuclear magnetic resonance lineshape studies on human blood plasma lipids from newborn infants, healthy adults, and adults with tumors.

The usefulness of proton NMR spectroscopy of human blood plasma for cancer research has been extensively studied in recent years. Two main starting points have been offered by Fossel et al. (N. Engl. J. Med. 315, 1369 (1986)) and Mountford et al. (FEBS Lett. 203, 164 (1986)). In this work the experimental proton NMR spectra of blood plasma were analyzed with the aid of the multivariate lineshape fitting method. An appropriate model structure, in terms of the various lipoprotein (VLDL, LDL, and HDL) signals, for the methylene region was used. Neonates, healthy adults, and adults with nonmalignant and malignant tumors were studied. The linewidth of the methylene region was found to be linearly dependent on the relative concentrations of the lipoproteins. The correlation coefficient was -0.89 (P less than 0.001) for VLDL and 0.88 (P less than 0.001) for HDL. A correlation between VLDL concentration and age, 0.76 (P less than 0.001), was also established. VLDL was modeled using two components. The half-linewidth of the lower field component was slightly elevated for the adults with large metastases. This might be in association with the fucose-containing proteolipid complex detected earlier in cancer cells or in sera of cancer patients. Some signals of this complex may fall in the same region of the spectra. The spectra for the neonates were indicated to be totally different from the adults. This and other related questions were explained by means of the model parameters and the relative concentrations of the lipoproteins VLDL, LDL, and HDL. The presented technique can be used as a rapid research tool for figuring out the relative concentrations of the lipoproteins in blood plasma and explaining the reasons behind the changes in the spectra.     

Circulating amino acids and the risk of macrovascular,microvascular and mortality outcomes in individuals with type 2 diabetes: results from the ADVANCE trial

Aims/hypotheses

We aimed to quantify the association of individual circulating amino acids with macrovascular disease, microvascular disease and all-cause mortality in individuals with type 2 diabetes.

Methods

We performed a case-cohort study (N?=?3587), including 655 macrovascular events, 342 microvascular events (new or worsening nephropathy or retinopathy) and 632 all-cause mortality events during follow-up, in a secondary analysis of the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) study. For this study, phenylalanine, isoleucine, glutamine, leucine, alanine, tyrosine, histidine and valine were measured in stored plasma samples by proton NMR metabolomics. Hazard ratios were modelled per SD increase in each amino acid.

Results

In models investigating associations and potential mechanisms, after adjusting for age, sex and randomised treatment, phenylalanine was positively, and histidine inversely, associated with macrovascular disease risk. These associations were attenuated to the null on further adjustment for extended classical risk factors (including eGFR and urinary albumin/creatinine ratio). After adjustment for extended classical risk factors, higher tyrosine and alanine levels were associated with decreased risk of microvascular disease (HR 0.78; 95% CI 0.67, 0.91 and HR 0.86; 95% CI 0.76, 0.98, respectively). Higher leucine (HR 0.79; 95% CI 0.69, 0.90), histidine (HR 0.89; 95% CI 0.81, 0.99) and valine (HR 0.79; 95% CI 0.70, 0.88) levels were associated with lower risk of mortality. Investigating the predictive ability of amino acids, addition of all amino acids to a risk score modestly improved classification of participants for macrovascular (continuous net reclassification index [NRI] +35.5%, p?<?0.001) and microvascular events (continuous NRI +14.4%, p?=?0.012).

Conclusions/interpretation

We report distinct associations between circulating amino acids and risk of different major complications of diabetes. Low tyrosine appears to be a marker of microvascular risk in individuals with type 2 diabetes independently of fundamental markers of kidney function.

     

Circulating metabolite predictors of glycemia in middle-aged men and women

OBJECTIVE

Metabolite predictors of deteriorating glucose tolerance may elucidate the pathogenesis of type 2 diabetes. We investigated associations of circulating metabolites from high-throughput profiling with fasting and postload glycemia cross-sectionally and prospectively on the population level.

RESEARCH DESIGN AND METHODS

Oral glucose tolerance was assessed in two Finnish, population-based studies consisting of 1,873 individuals (mean age 52 years, 58% women) and reexamined after 6.5 years for 618 individuals in one of the cohorts. Metabolites were quantified by nuclear magnetic resonance spectroscopy from fasting serum samples. Associations were studied by linear regression models adjusted for established risk factors.

RESULTS

Nineteen circulating metabolites, including amino acids, gluconeogenic substrates, and fatty acid measures, were cross-sectionally associated with fasting and/or postload glucose (P < 0.001). Among these metabolic intermediates, branched-chain amino acids, phenylalanine, and α1-acid glycoprotein were predictors of both fasting and 2-h glucose at 6.5-year follow-up (P < 0.05), whereas alanine, lactate, pyruvate, and tyrosine were uniquely associated with 6.5-year postload glucose (P = 0.003–0.04). None of the fatty acid measures were prospectively associated with glycemia. Changes in fatty acid concentrations were associated with changes in fasting and postload glycemia during follow-up; however, changes in branched-chain amino acids did not follow glucose dynamics, and gluconeogenic substrates only paralleled changes in fasting glucose.

CONCLUSIONS

Alterations in branched-chain and aromatic amino acid metabolism precede hyperglycemia in the general population. Further, alanine, lactate, and pyruvate were predictive of postchallenge glucose exclusively. These gluconeogenic precursors are potential markers of long-term impaired insulin sensitivity that may relate to attenuated glucose tolerance later in life.Type 2 diabetes is characterized by a long progression period before overt disease onset (1,2). Metabolic perturbations characterizing and contributing to the disease development may be observed already in the prediabetic state (3,4). Knowledge on systemic metabolites associated with deteriorating glucose tolerance may elucidate the pathogenesis of diabetes and holds potential for prevention. Comprehensive metabolic profiling is therefore increasingly used to provide hypotheses implicating novel pathways in the disease etiology (5).Using high-throughput metabolite quantification, we have demonstrated metabolic signatures of insulin resistance in young adults beyond the traditional characteristics of the metabolic syndrome (6). Further, metabolite profiling in the Framingham Heart Study recently linked five branched-chain (leucine, isoleucine, and valine) and aromatic (phenylalanine and tyrosine) amino acids with the risk for future diabetes (7). A lipid signature of triacylglycerols with lower carbon number and double-bond content was also associated with increased risk for diabetes (8). Nonetheless, it remains unknown whether these metabolites are associated with the development of hyperglycemia in nondiabetic individuals and whether the effects would be more specific to fasting or postload glycemia.Elevated fasting and postchallenge glucose both increase the risk for diabetes; however the mechanisms regulating fasting and stimulated glycemia are partly distinct and the glucose measures have different consequences in terms of risk for cardiovascular mortality (9–11). Pathophysiological differences related to insulin sensitivity and secretion have been suggested to underpin the dissimilarities in glucose tolerance (1,3,11,12). Here, we studied metabolite profiles of glycemia in the general population. The aim was to investigate associations of circulating metabolites from high-throughput profiling separately for fasting and 2-h glucose cross-sectionally and prospectively in middle-aged Finnish men and women. We further assessed whether changes in metabolite levels paralleled changes in glycemia during the 6.5-year follow-up period.     

MR spectroscopy quantitation: a review of frequency domain methods.

There has been a vast increase in applications of magnetic resonance spectroscopy (MRS) in biomedical research during the last few years. This is not surprising since MRS provides both in vivo and in vitro a non-invasive tool for various biochemical and biomedical studies. There are also expectations that clinical MRS will have an important role as a diagnostic tool. An essential prerequisite for the future success of MRS for applicability in biomedical sciences will be accurate and biochemically relevant data analysis (at as high a level of automation as possible). This review briefly describes principles of the methodology available for advanced quantitative data analysis in the frequency domain. Various biomedical applications are discussed in order to illustrate the practical aspects of the analyses and to show the applicability and power of biochemical prior knowledge-based lineshape fitting analysis.     

Evidence for altered hepatic gluconeogenesis in patients with cirrhosis using in vivo 31-phosphorus magnetic resonance spectroscopy

BACKGROUND AND AIMS: Alterations in gluconeogenesis in the diseased liver can be assessed non-invasively using magnetic resonance spectroscopy by measuring changes in phosphomonoester resonance which contains information regarding several metabolites, including the phosphorylated intermediates of the gluconeogenic pathway. METHODS: 31P magnetic resonance spectroscopy was used to determine changes in phosphomonoesters following bolus infusions of 2.8 mmol/kg L-alanine in five patients with functionally compensated cirrhosis and in five patients with functionally decompensated cirrhosis. RESULTS: Compared with six healthy volunteers, baseline phosphomonoester values were elevated by 35% (p<0.05) in the compensated cirrhosis group and by 57% (p<0.01) in the decompensated cirrhosis group. Following alanine infusion, phosphomonoesters in healthy volunteers increased by 46% from baseline values (p<0.01), in patients with compensated cirrhosis by 27% (p<0.02) but those with decompensated cirrhosis showed no increase from baseline. There was a reduction in the percentage of inorganic phosphate signal in all subjects. CONCLUSIONS: By analysing changes in phosphomonoester and inorganic phosphate resonances it is possible to discern clear metabolic differences between healthy volunteers and patients with cirrhosis of varying severity using magnetic resonance spectroscopy. Those patients with functionally decompensated cirrhosis have higher percentage baseline phosphomonoester values but the absence of phosphomonoester elevation following L-alanine infusion suggests that they are unable to mount a significant metabolic response with a progluconeogenic stimulus.     

Modified LDL - trigger of atherosclerosis and inflammation in the arterial intima

Atherosclerosis is characterized by chronic inflammation of an injured intima. The pathological processes are initiated by accumulation of morphologically distinct, modified forms of LDL, and followed by cellular infiltration and foam cell formation. Activated intimal cells secrete enzymes and agents capable of modifying LDL, and the modified lipids of LDL, in turn, are able to activate intimal cells and to trigger various inflammatory signals. These processes can initiate and maintain a vicious circle in the intima and lead to lesion progression. In this review, we focus on the LDL modifications relevant to the initial lipid accumulation and discuss their pro-inflammatory effects.     

Hyperglycemia and a common variant of GCKR are associated with the levels of eight amino acids in 9,369 Finnish men

We investigated the association of glycemia and 43 genetic risk variants for hyperglycemia/type 2 diabetes with amino acid levels in the population-based Metabolic Syndrome in Men (METSIM) Study, including 9,369 nondiabetic or newly diagnosed type 2 diabetic Finnish men. Plasma levels of eight amino acids were measured with proton nuclear magnetic resonance spectroscopy. Increasing fasting and 2-h plasma glucose levels were associated with increasing levels of several amino acids and decreasing levels of histidine and glutamine. Alanine, leucine, isoleucine, tyrosine, and glutamine predicted incident type 2 diabetes in a 4.7-year follow-up of the METSIM Study, and their effects were largely mediated by insulin resistance (except for glutamine). We also found significant correlations between insulin sensitivity (Matsuda insulin sensitivity index) and mRNA expression of genes regulating amino acid degradation in 200 subcutaneous adipose tissue samples. Only 1 of 43 risk single nucleotide polymorphisms for type 2 diabetes or hyperglycemia, the glucose-increasing major C allele of rs780094 of GCKR, was significantly associated with decreased levels of alanine and isoleucine and elevated levels of glutamine. In conclusion, the levels of branched-chain, aromatic amino acids and alanine increased and the levels of glutamine and histidine decreased with increasing glycemia, reflecting, at least in part, insulin resistance. Only one single nucleotide polymorphism regulating hyperglycemia was significantly associated with amino acid levels.     

Weight change and lipoprotein particle concentration and particle size: a cohort study with 6.5-year follow-up

ObjectiveObesity and overweight are related to unfavourable lipoprotein subclass profiles. Here we studied the relation between weight change and lipoprotein particle concentrations and sizes in a general population cohort in a longitudinal setting.MethodsThe cohort included 683 adults with a 6.5-year follow-up. Lipoprotein particle subclasses and mean particle sizes of VLDL, LDL, and HDL were measured by nuclear magnetic resonance spectroscopy.ResultsDuring the follow-up period, a weight loss of at least 5% was associated with decreased particle concentrations of all apoB-containing subclasses and increased concentrations of large HDL particles. Coherently, weight gain (≥5%) was associated with increases in all apoB-containing subclasses and decreases in total and medium HDL particle concentrations. The relatively largest increase occurred for large HDL particle concentration (24.1%, 95% CI 15.8–32.5) in weight loss and for large VLDL particle concentration (33.0%, 19.6–46.4) in weight gain. Weight change correlated positively with changes in apoB-containing lipoprotein particle concentrations and also with the change in average VLDL particle size. Negative correlations were found between weight change and the change in average LDL (r = ?0.10) and HDL (r = ?0.32) particle size, but not between weight change and total HDL particle concentration.ConclusionModerate weight loss is related to favourable and weight gain to unfavourable changes in lipoprotein subclass profiles. These population level findings underline the importance of weight control as a modifier of cardiovascular risk factors.