Marja-Riitta Taskinen

Secondary lymphedema (LE) following breast cancer‐related surgery is a life‐long complication, which currently has no cure. LE induces significant regional adipose tissue deposition, requiring liposuction as a treatment. Here, we aimed to elucidate the transcriptional, metabolomic, and lipidomic signature of the adipose tissue developed due to the surgery‐induced LE in short‐ and long‐term LE patients and compared the transcriptomic landscape of LE adipose tissue to the obesity‐induced adipose tissue. Adipose tissue biopsies were obtained from breast cancer‐operated females with LE from the affected and non‐affected arms ( n = 20 patients). To decipher the molecular properties of the LE adipose tissue, we performed RNA sequencing, metabolomics, and lipidomics combined with bioinformatics analyses. Differential gene expression data from a cohort of lean and obese patients without LE was used for comparisons. Integrative analysis of functional genomics revealed that inflammatory response, cell chemotaxis, and angiogenesis were upregulated biological processes in the LE arm, indicating a sustained inflammation in the edematous adipose tissue; whereas, epidermal differentiation, cell–cell junction organization, water homeostasis, and neurogenesis were downregulated in the LE arm. Surprisingly, only a few genes were found to be the same in the LE‐induced and the obesity‐induced adipose tissue expansion, indicating a different type of adipose tissue development in these two conditions. In metabolomics analysis, we found reduced levels of a branched‐chain amino acid valine in the LE arm and downregulation of the mRNA levels of its transporter SLC6A15 . Lipidomics analyses did not show any significant differences between the LE and non‐LE arms, suggesting that other factors affect the lipid composition of the adipose tissue more than the LE in these patients. Our results provide a detailed molecular characterization of adipose tissue in secondary LE after breast cancer‐related surgery. We also show distinct differences in transcriptomic signatures between LE‐induced adipose tissue and obesity‐induced adipose tissue, but only minor differences in metabolome and lipidome between the LE and the non‐LE arm.

Objective: Secondary lymphedema (LE) following breast cancer surgery is a life-long complication, which currently has no cure. LE induces significant regional adipose tissue deposition, requiring liposuction as a treatment. Here, we aimed to elucidate the transcriptional, metabolomic, and lipidomic signature of the adipose tissue developed due to the surgery-induced LE in short- and long-term LE patients, and compared the transcriptomic landscape in LE to the obesity-induced adipose tissue. Methods: Adipose tissue biopsies were obtained from breast cancer-operated females with LE from the affected and non-affected arms (n=20 patients). To decipher molecular properties of the LE adipose tissue, we performed RNA sequencing, metabolomics, and lipidomics combined with bioinformatics analyses. Results: Integrative analysis of functional genomics revealed that inflammatory response, cell chemotaxis and angiogenesis were upregulated biological processes in the LE arm, indicating a sustained inflammation in the edematous adipose tissue, whereas, epidermal differentiation, cell-cell junction organization, water homeostasis and neurogenesis were, in turn, downregulated in the LE arm. Surprisingly, only few genes were found to be the same in the LE-induced and the obesity-induced adipose tissue expansion, indicating a different type of adipose tissue development in these two diseases. In metabolomics analysis, the concentration of a branched-chain amino acid valine was found to be reduced in the edematous arm together with downregulation of mRNA levels of its transporter SLC6A15 . Lipidomics analyses did not show any significant differences between the diseased and healthy arm, suggesting that diet affects the lipid composition of the adipose tissue more than the LE. Conclusions: Our results provide a detailed molecular characterization of adipose tissue in secondary LE of breast cancer patients vs individuals with obesity. The results show distinct differences in transcriptomic signatures between LE patients vs individuals with obesity, but only minor differences in metabolome and lipidome between the diseased and the healthy arm.

Aims: The strength of the relationship of triglyceride-rich lipoproteins (TRL) with risk of coronary heart disease (CHD) compared with low-density lipoprotein (LDL) is yet to be resolved. Methods and results: Single-nucleotide polymorphisms (SNPs) associated with TRL/remnant cholesterol (TRL/remnant-C) and LDL cholesterol (LDL-C) were identified in the UK Biobank population. In a multivariable Mendelian randomization analysis, TRL/remnant-C was strongly and independently associated with CHD in a model adjusted for apolipoprotein B (apoB). Likewise, in a multivariable model, TRL/remnant-C and LDL-C also exhibited independent associations with CHD with odds ratios per 1 mmol/L higher cholesterol of 2.59 [95% confidence interval (CI): 1.99–3.36] and 1.37 [95% CI: 1.27–1.48], respectively. To examine the per-particle atherogenicity of TRL/remnants and LDL, SNPs were categorized into two clusters with differing effects on TRL/remnant-C and LDL-C. Cluster 1 contained SNPs in genes related to receptor-mediated lipoprotein removal that affected LDL-C more than TRL/remnant-C, whereas cluster 2 contained SNPs in genes related to lipolysis that had a much greater effect on TRL/remnant-C. The CHD odds ratio per standard deviation (Sd) higher apoB for cluster 2 (with the higher TRL/remnant to LDL ratio) was 1.76 (95% CI: 1.58–1.96), which was significantly greater than the CHD odds ratio per Sd higher apoB in cluster 1 [1.33 (95% CI: 1.26–1.40)]. A concordant result was obtained by using polygenic scores for each cluster to relate apoB to CHD risk. Conclusion: Distinct SNP clusters appear to impact differentially on remnant particles and LDL. Our findings are consistent with TRL/remnants having a substantially greater atherogenicity per particle than LDL.

Nicotinamide adenine dinucleotide (NAD ⁺ ) precursor nicotinamide riboside (NR) has emerged as a promising compound to improve obesity-associated mitochondrial dysfunction and metabolic syndrome in mice. However, most short-term clinical trials conducted so far have not reported positive outcomes. Therefore, we aimed to determine whether long-term NR supplementation boosts mitochondrial biogenesis and metabolic health in humans. Twenty body mass index (BMI)–discordant monozygotic twin pairs were supplemented with an escalating dose of NR (250 to 1000 mg/day) for 5 months. NR improved systemic NAD ⁺ metabolism, muscle mitochondrial number, myoblast differentiation, and gut microbiota composition in both cotwins. NR also showed a capacity to modulate epigenetic control of gene expression in muscle and adipose tissue in both cotwins. However, NR did not ameliorate adiposity or metabolic health. Overall, our results suggest that NR acts as a potent modifier of NAD ⁺ metabolism, muscle mitochondrial biogenesis and stem cell function, gut microbiota, and DNA methylation in humans irrespective of BMI.

Objectives: We studied apolipoprotein C‐III (apoC‐III) in relation to diabetic kidney disease (DKD), cardiovascular outcomes, and mortality in type 1 diabetes.Methods: The cohort comprised 3966 participants from the prospective observational Finnish Diabetic Nephropathy Study. Progression of DKD was determined from medical records. A major adverse cardiac event (MACE) was defined as acute myocardial infarction, coronary revascularization, stroke, or cardiovascular mortality through 2017. Cardiovascular and mortality data were retrieved from national registries.Results: ApoC‐III predicted DKD progression independent of sex, diabetes duration, blood pressure, HbA_1c, smoking, LDL‐cholesterol, lipid‐lowering medication, DKD category, and remnant cholesterol (hazard ratio [HR] 1.43 [95% confidence interval 1.05–1.94], p = 0.02). ApoC‐III also predicted the MACE in a multivariable regression analysis; however, it was not independent of remnant cholesterol (HR 1.05 [0.81–1.36, p = 0.71] with remnant cholesterol; 1.30 [1.03–1.64, p = 0.03] without). DKD‐specific analyses revealed that the association was driven by individuals with albuminuria, as no link between apoC‐III and the outcome was observed in the normal albumin excretion or kidney failure categories. The same was observed for mortality: Individuals with albuminuria had an adjusted HR of 1.49 (1.03–2.16, p = 0.03) for premature death, while no association was found in the other groups. The highest apoC‐III quartile displayed a markedly higher risk of MACE and death than the lower quartiles; however, this nonlinear relationship flattened after adjustment.Conclusions: The impact of apoC‐III on MACE risk and mortality is restricted to those with albuminuria among individuals with type 1 diabetes. This study also revealed that apoC‐III predicts DKD progression, independent of the initial DKD category.

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.

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid accumulation. The transmembrane 6 superfamily member 2 ( TM6SF2 ) E167K genetic variant associates with NAFLD and with reduced plasma triglyceride levels in humans. However, the molecular mechanisms underlying these associations remain unclear. We hypothesized that TM6SF2 E167K affects hepatic very low-density lipoprotein (VLDL) secretion and studied the kinetics of apolipoprotein B100 (apoB100) and triglyceride metabolism in VLDL in homozygous subjects. In 10 homozygote TM6SF2 E167K carriers and 10 matched controls, we employed stable-isotope tracer and compartmental modeling techniques to determine apoB100 and triglyceride kinetics in the 2 major VLDL subfractions: large triglyceride-rich VLDL ₁ and smaller, less triglyceride-rich VLDL ₂ . VLDL ₁ -apoB100 production was markedly reduced in homozygote TM6SF2 E167K carriers compared with controls. Likewise, VLDL ₁ -triglyceride production was 35% lower in the TM6SF2 E167K carriers. In contrast, the direct production rates for VLDL ₂ -apoB100 and triglyceride were not different between carriers and controls. In conclusion, the TM6SF2 E167K genetic variant was linked to a specific reduction in hepatic secretion of large triglyceride-rich VLDL ₁ . The impaired secretion of VLDL ₁ explains the reduced plasma triglyceride concentration and provides a basis for understanding the lower risk of cardiovascular disease associated with the TM6SF2 E167K genetic variant.

Previous research has shown that using population-specific reference panels has a significant effect on downstream population genomic analyses like haplotype phasing, genotype imputation, and association, especially in the context of population isolates. Here, we developed a high-resolution recombination rate mapping at 10 and 50 kb scale using high-coverage (20–30×) whole-genome sequenced data of 55 family trios from Finland and compared it to recombination rates of non-Finnish Europeans (NFE). We tested the downstream effects of the population-specific recombination rates in statistical phasing and genotype imputation in Finns as compared to the same analyses performed by using the NFE-based recombination rates. We found that Finnish recombination rates have a moderately high correlation (Spearman’s ρ = 0.67–0.79) with NFE, although on average (across all autosomal chromosomes), Finnish rates (2.268 ± 0.4209 cM/Mb) are 12–14% lower than NFE (2.641 ± 0.5032 cM/Mb). Finnish recombination map was found to have no significant effect in haplotype phasing accuracy (switch error rates ~2%) and average imputation concordance rates (97–98% for common, 92–96% for low frequency and 78–90% for rare variants). Our results suggest that haplotype phasing and genotype imputation mostly depend on population-specific contexts like appropriate reference panels and their sample size, but not on population-specific recombination maps. Even though recombination rate estimates had some differences between the Finnish and NFE populations, haplotyping and imputation had not been noticeably affected by the recombination map used. Therefore, the currently available HapMap recombination maps seem robust for population-specific phasing and imputation pipelines, even in the context of relatively isolated populations like Finland.

Identification of biomarkers associated with protection from developing diabetic complications is a prerequisite for an effective prevention and treatment. The aim of the present study was to identify clinical and plasma metabolite markers associated with freedom from vascular complications in people with very long duration of type 1 diabetes (T1D). Individuals with T1D, who despite having longer than 30 years of diabetes duration never developed major macro- or microvascular complications (non-progressors; NP) were compared with those who developed vascular complications within 25 years from diabetes onset (rapid progressors; RP) in the Scandinavian PROLONG (n = 385) and DIALONG (n = 71) cohorts. The DIALONG study also included 75 healthy controls. Plasma metabolites were measured using gas and/or liquid chromatography coupled to mass spectrometry. Lower hepatic fatty liver indices were significant common feature characterized NPs in both studies. Higher insulin sensitivity and residual ß-cell function (C-peptide) were also associated with NPs in PROLONG. Protection from diabetic complications was associated with lower levels of the glycolytic metabolite pyruvate and APOCIII in PROLONG, and with lower levels of thiamine monophosphate and erythritol, a cofactor and intermediate product in the pentose phosphate pathway as well as higher phenylalanine, glycine and serine in DIALONG. Furthermore, T1D individuals showed elevated levels of picolinic acid as compared to the healthy individuals. The present findings suggest a potential beneficial shunting of glycolytic substrates towards the pentose phosphate and one carbon metabolism pathways to promote nucleotide biosynthesis in the liver. These processes might be linked to higher insulin sensitivity and lower liver fat content, and might represent a mechanism for protection from vascular complications in individuals with long-term T1D.