Patients with type 1 diabetes show signs of vascular dysfunction in response to multiple high-fat meals

Association of Endotoxemia with Low-Grade Inflammation, Metabolic Syndrome and Distinct Response to Lipopolysaccharide in Type 1 Diabetes

The association of endotoxemia with metabolic syndrome (MS) and low-grade inflammation in type 1 diabetes (T1D) is little-studied. We investigated the levels of lipopolysaccharide (LPS), lipopolysaccharide-binding protein (LBP), endogenous anti-endotoxin core antibodies (EndoCAb IgG and IgM) and high-sensitivity C-reactive protein (hsCRP) in 74 T1D patients with different MS statuses and 33 control subjects. Within the T1D group, 31 patients had MS. These subjects had higher levels of LPS compared to patients without MS (MS 0.42 (0.35-0.56) or no MS 0.34 (0.3-0.4), p = 0.009). MS was associated with LPS/HDL (OR = 6.5 (2.1; 20.0), p = 0.036) and EndoCAb IgM (OR = 0.32 (0.11; 0.93), p = 0.036) in patients with T1D. LBP (β = 0.30 (0.09; 0.51), p = 0.005), EndoCAb IgG (β = 0.29 (0.07; 0.51), p = 0.008) and the LPS/HDL ratio (β = 0.19 (0.03; 0.41, p = 0.084) were significantly associated with log-transformed hsCRP in T1D. Higher levels of hsCRP and EndoCAb IgG were observed in T1D compared to the control (p = 0.002 and p = 0.091, respectively). In contrast to the situation in the control group, LPS did not correlate with LBP, EndoCAb, leukocytes or HDL in T1D. To conclude, endotoxemia is associated with low-grade inflammation, MS and a distinct response to LPS in T1D.

Dietary treatment of type 1 diabetes: Beyond carbohydrate counting to fight cardiovascular risk

AIMS

Type 1 diabetes (T1D) is tied to an increased risk of cardiovascular morbidity and mortality. Dietary treatment would be an elective therapeutic strategy to fight this risk. However, it is not known what the best dietary approach is. We revisited the currently available literature on the nutritional treatment of T1D in the light of their potential comprehensive effects on the management of cardio-metabolic risk factors (body weight, fasting and postprandial glucose and lipid metabolism).

DATA SYNTHESIS

Nutritional research in T1D is mainly focused on blood glucose control, with most of the trials aiming at evaluating the acute effects of nutrients on postprandial glycemic response. The effects of the quantity and quality of nutrients and some specific foods on other metabolic risk factors have been explored mainly in cross-sectional analysis. Very few well-designed nutritional trials evaluated the best dietary approach to comprehensively manage cardiovascular risk by targeting along with blood glucose control, overweight, fasting and postprandial dyslipidemia. Therefore, the current best practice guidance for the dietary management of cardiovascular risk in T1D is generally based on evidence from patients with type 2 diabetes.

CONCLUSIONS

Well-conducted nutritional trials specifically designed for T1D are needed to identify the best dietary treatment to fight cardiovascular risk in these patients.

Whole-exome sequencing identifies novel protein-altering variants associated with serum apolipoprotein and lipid concentrations

BACKGROUND

Dyslipidemia is a major risk factor for cardiovascular disease, and diabetes impacts the lipid metabolism through multiple pathways. In addition to the standard lipid measurements, apolipoprotein concentrations provide added awareness of the burden of circulating lipoproteins. While common genetic variants modestly affect the serum lipid concentrations, rare genetic mutations can cause monogenic forms of hypercholesterolemia and other genetic disorders of lipid metabolism. We aimed to identify low-frequency protein-altering variants (PAVs) affecting lipoprotein and lipid traits.

METHODS

We analyzed whole-exome (WES) and whole-genome sequencing (WGS) data of 481 and 474 individuals with type 1 diabetes, respectively. The phenotypic data consisted of 79 serum lipid and apolipoprotein phenotypes obtained with clinical laboratory measurements and nuclear magnetic resonance spectroscopy.

RESULTS

The single-variant analysis identified an association between the LIPC p.Thr405Met (rs113298164) and serum apolipoprotein A1 concentrations (p=7.8×10^-8). The burden of PAVs was significantly associated with lipid phenotypes in LIPC, RBM47, TRMT5, GTF3C5, MARCHF10, and RYR3 (p<2.9×10^-6). The RBM47 gene is required for apolipoprotein B post-translational modifications, and in our data, the association between RBM47 and apolipoprotein C-III concentrations was due to a rare 21 base pair p.Ala496-Ala502 deletion; in replication, the burden of rare deleterious variants in RBM47 was associated with lower triglyceride concentrations in WES of >170,000 individuals from multiple ancestries (p=0.0013). Two PAVs in GTF3C5 were highly enriched in the Finnish population and associated with cardiovascular phenotypes in the general population. In the previously known APOB gene, we identified novel associations at two protein-truncating variants resulting in lower serum non-HDL cholesterol (p=4.8×10^-4), apolipoprotein B (p=5.6×10^-4), and LDL cholesterol (p=9.5×10^-4) concentrations.

CONCLUSIONS

We identified lipid and apolipoprotein-associated variants in the previously known LIPC and APOB genes, as well as PAVs in GTF3C5 associated with LDLC, and in RBM47 associated with apolipoprotein C-III concentrations, implicated as an independent CVD risk factor. Identification of rare loss-of-function variants has previously revealed genes that can be targeted to prevent CVD, such as the LDL cholesterol-lowering loss-of-function variants in the PCSK9 gene. Thus, this study suggests novel putative therapeutic targets for the prevention of CVD.

Periodontitis and cardiometabolic disorders: The role of lipopolysaccharide and endotoxemia

Lipopolysaccharide is a virulence factor of gram-negative bacteria with a crucial importance to the bacterial surface integrity. From the host's perspective, lipopolysaccharide plays a role in both local and systemic inflammation, activates both innate and adaptive immunity, and can trigger inflammation either directly (as a microbe-associated molecular pattern) or indirectly (by inducing the generation of nonmicrobial, danger-associated molecular patterns). Translocation of lipopolysaccharide into the circulation causes endotoxemia, which is typically measured as the biological activity of lipopolysaccharide to induce coagulation of an aqueous extract of blood cells of the assay. Apparently healthy subjects have a low circulating lipopolysaccharide activity, since it is neutralized and cleared rapidly. However, chronic endotoxemia is involved in the pathogenesis of many inflammation-driven conditions, especially cardiometabolic disorders. These include atherosclerotic cardiovascular diseases, obesity, liver diseases, diabetes, and metabolic syndrome, where endotoxemia has been recognized as a risk factor. The main source of endotoxemia is thought to be the gut microbiota. However, the oral dysbiosis in periodontitis, which is typically enriched with gram-negative bacterial species, may also contribute to endotoxemia. As endotoxemia is associated with an increased risk of cardiometabolic disorders, lipopolysaccharide could be considered as a molecular link between periodontal microbiota and cardiometabolic diseases.

The effect of a high fat meal on heart rate variability and arterial stiffness in adolescents with or without type 1 diabetes

AIM

Type 1 diabetes (T1D) is associated with increased arterial stiffness and cardiac autonomic neuropathy. We tested whether those variables are acutely affected by a high fat meal (HFM).

METHODS

Responses to a HFM were measured in adolescents with T1D (N = 14) or without T1D (Control, N = 21). Heart rate variability (HRV), arterial stiffness, blood pressure (BP), and energy expenditure (EE) were measured before (baseline) and four times over 180 min postprandially.

RESULTS

T1D had higher blood glucose and insulin, but the suppression of fatty acids (~40%) and rise in triglycerides (~60%) were similar between groups. T1D had 9% higher EE, but postprandial increase in EE was similar to Controls. T1D had ~7 to 24% lower baseline HRV but a similar postprandial decline of ~8 to 25% as Controls. Both groups had a similar 2 to 5% increase in BP after the meal. Rate pressure product increased postprandially in both groups and was higher in T1D. Pulsewave velocity and augmentation index did not differ between groups or change postprandially.

CONCLUSION

Adolescents with T1D have evidence of cardiac autonomic dysfunction and increased EE, but those variables, along with arterial stiffness, are not acutely made worse by a HFM.

Exercise and nutrition in type 1 diabetes: Insights from the FinnDiane cohort

Type 1 diabetes is a challenging disease, characterized by dynamic changes in the insulin need during life periods, seasons of the year, but also by everyday situations. In particular, changes in insulin need are evident before, during and after exercise and having meals. In the midst of different life demands, it can be very burdensome to achieve tight glycemic control to prevent late diabetes complications, and at the same time, to avoid hypoglycemia. Consequently, many individuals with type 1 diabetes are faced with diabetes distress, decreasing profoundly their quality of life. Today, the nationwide Finnish Diabetic Nephropathy (FinnDiane) Study, launched in 1997, has gathered data from more than 8,000 well-characterized individuals with type 1 diabetes, recruited from 93 centers all over Finland and has established its position as the world's leading project on studying complications in individuals with type 1 diabetes. Studying risk factors and mechanisms of diabetes complications is inconceivable without trying to understand the effects of exercise and nutrition on glycemic control and the development of diabetes complications. Therefore, in this paper we provide findings regarding food and exercise, accumulated during the 25 years of studying lives of Finnish people with type 1 diabetes.

Remnant cholesterol predicts progression of diabetic nephropathy and retinopathy in type 1 diabetes

BACKGROUND

We aimed to assess whether remnant cholesterol concentration and variability predict the progression of diabetic nephropathy (DN) and severe diabetic retinopathy (SDR) in type 1 diabetes.

METHODS

This observational prospective study covered 5150 FinnDiane Study participants. Remnant cholesterol was calculated as total cholesterol - LDL cholesterol - HDL cholesterol and variability as the coefficient of variation. DN category was based on consensus albuminuria reference limits and the progression status was confirmed from medical files. SDR was defined as retinal laser treatment. For 1338 individuals, the severity of diabetic retinopathy (DR) was graded using the ETDRS classification protocol. Median (IQR) follow-up time was 8.0 (4.9-13.7) years for DN and 14.3 (10.4-16.3) for SDR.

RESULTS

Remnant cholesterol (mmol L^-1 ) was higher with increasing baseline DN category (P < 0.001). A difference was also seen comparing non-progressors (0.41 [0.32-0.55]) with progressors (0.55 [0.40-0.85]), P < 0.001. In a Cox regression analysis, remnant cholesterol predicted DN progression, independently of diabetes duration, sex, HbA_1c , systolic blood pressure, smoking, BMI, estimated glucose disposal rate and estimated glomerular filtration rate (HR: 1.51 [1.27-1.79]). Remnant cholesterol was also higher in those who developed SDR (0.47 [0.36-0.66]) than those who did not (0.40 [0.32-0.53]), P < 0.001, and the concentration increased stepwise with increasing DR severity (P < 0.001). Regarding SDR, the HR for remnant cholesterol was 1.52 (1.26-1.83) with the most stringent adjustment. However, remnant cholesterol variability was not independently associated with the outcomes.

CONCLUSIONS

Remnant cholesterol concentration, but not variability, predicts DN progression and development of SDR. However, it remains to be elucidated whether the associations are causal or not.

Dyslipidemia in Type 1 Diabetes: AMaskedDanger

Type 1 diabetes (T1D) patients show lipid disorders which are likely to play a role in their increased cardiovascular (CV) disease risk. Quantitative abnormalities of lipoproteins are noted in T1D with poor glycemic control. In T1D with optimal glycemic control, triglycerides and LDL-cholesterol are normal or slightly decreased whereas HDL-cholesterol is normal or slightly increased. T1D patients, even with good glycemic control, show several qualitative and functional abnormalities of lipoproteins that are potentially atherogenic. An association between these abnormalities and CV disease risk has been reported in recent studies. Although the mechanisms underlying T1D dyslipidemia remain unclear, the subcutaneous route of insulin administration, that is responsible for peripheral hyperinsulinemia, is likely to be an important factor.

Mediators between oral dysbiosis and cardiovascular diseases

Clinical periodontitis is associated with an increased risk for cardiovascular diseases (CVDs) through systemic inflammation as the etiopathogenic link. Whether the oral microbiota, especially its quality, quantity, serology, and virulence factors, plays a role in atherogenesis is not clarified. Patients with periodontitis are exposed to bacteria and their products, which have access to the circulation directly through inflamed oral tissues and indirectly (via saliva) through the gastrointestinal tract, resulting in systemic inflammatory and immunologic responses. Periodontitis is associated with persistent endotoxemia, which has been identified as a notable cardiometabolic risk factor. The serology of bacterial biomarkers for oral dysbiosis is associated with an increased risk for subclinical atherosclerosis, prevalent and future coronary artery disease, and incident and recurrent stroke. In addition to species-specific antibodies, the immunologic response includes persistent, cross-reactive, proatherogenic antibodies against host-derived antigens. Periodontitis may affect lipoprotein metabolism at all levels, and all lipoprotein classes are affected. Periodontitis or its bacterial signatures may be involved not only in increased storage of proatherogenic lipids but also in attenuation of the anti-atherogenic processes, thereby putatively increasing the net risk of atherosclerosis. In this review we summarize possible molecular mediators between the dysbiotic oral microbiota and atherosclerotic processes.

Intestinal alkaline phosphatase at the crossroad of intestinal health and disease - a putative role in type 1 diabetes

BACKGROUND

Patients with type 1 diabetes have shown an increase in circulating cytokines, altered lipoprotein metabolism and signs of vascular dysfunction in response to high-fat meals. Intestinal alkaline phosphatase (IAP) regulates lipid transport and inflammatory responses in the gastrointestinal tract. We therefore hypothesized that changes in IAP activity could have profound effects on gut metabolic homeostasis in patients with type 1 diabetes.

METHODS

Faecal samples of 41 nondiabetic controls and 46 patients with type 1 diabetes were analysed for IAP activity, calprotectin, immunoglobulins and short-chain fatty acids (SCFAs). The impact of oral IAP supplementation on intestinal immunoglobulin levels was evaluated in C57BL/6 mice exposed to high-fat diet for 11 weeks.

RESULTS

Patients with type 1 diabetes exhibited signs of intestinal inflammation. Compared to controls, patients with diabetes had higher faecal calprotectin levels, lower faecal IAP activities accompanied by lower propionate and butyrate concentrations. Moreover, the amount of faecal IgA and the level of antibodies binding to oxidized LDL were decreased in patients with type 1 diabetes. In mice, oral IAP supplementation increased intestinal IgA levels markedly.

CONCLUSION

Deprivation of protective intestinal factors may increase the risk of inflammation in the gut - a phenomenon that seems to be present already in patients with uncomplicated type 1 diabetes. Low levels of intestinal IgA and antibodies to oxidized lipid epitopes may predispose such patients to inflammation-driven complications such as cardiovascular disease and diabetic nephropathy. Importantly, oral IAP supplementation could have beneficial therapeutic effects on gut metabolic homeostasis, possibly through stimulation of intestinal IgA secretion.

The effect of standardized food intake on the association between BMI and 1H-NMR metabolites

Multiple studies have shown that levels of ¹H-NMR metabolites are associated with disease and risk factors of disease such as BMI. While most previous investigations have been performed in fasting samples, meta-analysis often includes both cohorts with fasting and non-fasting blood samples. In the present study comprising 153 participants (mean age 63 years; mean BMI 27 kg/m²) we analyzed the effect of a standardized liquid meal (SLM) on metabolite levels and how the SLM influenced the association between metabolites and BMI. We observed that many metabolites, including glycolysis related metabolites, multiple amino acids, LDL diameter, VLDL and HDL lipid concentration changed within 35 minutes after a standardized liquid meal (SLM), similarly for all individuals. Remarkable, however, is that the correlations of metabolite levels with BMI remained highly similar before and after the SLM. Hence, as exemplified with the disease risk factor BMI, our results suggest that the applicability of ¹H-NMR metabolites as disease biomarkers depends on the standardization of the fasting status rather than on the fasting status itself. Future studies are required to investigate the dependency of metabolite biomarkers for other disease risk factors on the fasting status.

Endotoxemia, nutrition, and cardiometabolic disorders

AIMS

Circulating lipopolysaccharides (LPSs), associated with both infection and inflammation, may arise from the gastrointestinal tract microbiota, and the levels may be affected by daily nutrition. We investigated whether nutrient intake affects the association of serum LPS activity with prevalent obesity, metabolic syndrome (MetS), diabetes, and coronary heart disease (CHD) and with the risk of incident CHD events.

METHODS

The nutrition cohort (n = 2,452, mean age ± SD, 52.2 ± 10.1 years) of the FINRISK 1997 Study was followed up for 10 years. Information on macronutrient intake at baseline was collected from 24-h dietary recall. Serum endotoxin activities were determined by the Limulus amebocyte lysate assay.

RESULTS

LPS activity was associated directly with the total energy intake and indirectly with carbohydrate intake in lean, healthy subjects. High LPS was significantly associated with prevalent obesity, MetS, diabetes, and CHD events, independently of established risk factors, CRP, and total energy or nutrient intake. The ORs (95 % CI) were 1.49 (1.21-1.85, p < 0.001, Q2-4 vs. Q1) for obesity, 2.56 (1.97-3.32, p < 0.001, Q2-4 vs. Q1) for MetS, 1.94 (1.06-3.52, p = 0.031, Q2-4 vs. Q1) for CHD, and 1.01 (1.00-1.01, p = 0.032, LPS unit) for diabetes. In the follow-up, high LPS was significantly associated with the risk of CHD events with a hazard ratio of 1.88 (1.13-3.12, p = 0.013, Q2-4 vs. Q1). This association was independent of baseline established risk factors, diet, obesity, MetS, and diabetes.

CONCLUSION

A high serum LPS activity is strongly associated with cardiometabolic disorders, which supports the role of bacterial infections and immune response in their etiology.

High-fat meals induce systemic cytokine release without evidence of endotoxemia-mediated cytokine production from circulating monocytes or myeloid dendritic cells

AIMS

Dietary fats have been shown to promote the translocation of bacterial endotoxins from the gut into circulation, which may induce systemic inflammation and modulate the inflammatory response of circulating immune cells. The aim of this study was to determine the effect of the postprandial milieu on inflammation and the inflammatory response of antigen presenting cells in the context of type 1 diabetes (T1D).

MATERIALS AND METHODS

Eleven patients with T1D and eleven nondiabetic controls were recruited as part of the FinnDiane study and given two fatty meals during 1 day. Cytokine responses in monocytes and myeloid dendritic cells (mDCs) as well as serum lipopolysaccharide activity levels, triglyceride concentrations and cytokine concentrations were measured from fasting and postprandial blood samples.

RESULTS

Postprandially, patients with T1D and controls showed significant increases in eight inflammatory cytokines (IL-6, TNF-α, IL-1β, IFN-α, IL-10, IFN-γ, IL-12 and MIP-1β) without concomitant increase in serum LPS activity. Serum cytokine production was similar in both groups. No postprandial change was seen in the IL-6, TNF-α or IL-1β production of mDCs or monocytes. At fasting, diabetic mDCs exhibited higher LPS-induced IL-6 and IL-1β production than controls.

CONCLUSIONS

Acute high-fat meals increase circulating cytokines but have no effect on serum lipopolysaccharide activity levels or cytokine production in circulating mDCs or monocytes. Our results suggest that postprandial increase in serum cytokine levels is neither mediated by circulating endotoxins nor the activation of circulating innate cells. The production of high-fat meal-induced inflammatory markers is most likely regulated at the tissue level.