Genetically Mediated Lipid Metabolism and Risk of Insulin Resistance: Insights from Mendelian Randomization Studies

Comparative Analysis of Omega-3, Omega-6, and Endocannabinoid Content of Human, Cattle, Goat, and Formula Milk

Human milk is the primary source of infant nutrition, although breastfeeding rates are declining today, and human milk is often replaced by animal milk-based infant formula. Infant formula is intended to replicate the composition of human milk, albeit significant differences remain in the physiological responses to breastfeeding and formula feeding in offspring. More research is needed on the composition of human milk and other milk types, especially regarding their lipid content. A comparative analysis of different milk samples was carried out in this study. The amount of omega-3 fatty acids, omega-6 fatty acids, and endocannabinoids was measured in human, cattle, and goat milk as well as in goat milk- and cow milk-based infant formulas using chromatography coupled to mass spectrometry. Significant differences between the human and animal milks were observed in the case of omega-6 fatty acid and endocannabinoid content, with higher omega-6 fatty acid and lower endocannabinoid levels in human milk than in animal milk samples and infant formulas. Goat milk shares the highest similarity to human milk in terms of the analyzed lipid species. However, our results indicate that the levels of the examined bioactive lipid species in human milk failed to be replaced by goat milk- and cow milk-derived infant formulas.

Daytime napping and risk of incident main adverse cardiovascular events and mortality among adults with type 2 diabetes

AIMS

To explore the link between daytime napping and the risk of major adverse cardiovascular events (MACE) and mortality in individuals with type 2 diabetes.

METHODS

This prospective study included 21,129 participants with diabetes from the UK Biobank, all of whom were free of MACE and cancer at baseline. Data on habitual daytime napping and sleep duration were collected via a baseline questionnaire. Cox proportional hazards regression models were employed to assess the relationship between daytime napping and MACE, all-cause mortality, and cardiovascular disease (CVD) specific mortality. MACE was defined as a composite of myocardial infarction, heart failure, and stroke.

RESULTS

Over an average 11.9-year follow-up, 5,611 MACE cases, 3,854 all-cause deaths, and 1,839 CVD deaths were identified. Compared to those who never/rarely napped, the multivariable-adjusted hazard ratios for usually napping were: 1.39 (1.08, 1.65) for MACE; 1.44 (1.01, 1.92) for myocardial infarction; 1.33 (1.07, 1.64) for heart failure; 1.57 (1.06, 2.33) for stroke; 1.28 (1.01, 1.60) for all-cause mortality; 1.33 (0.97, 1.94) for CVD mortality.

CONCLUSIONS

Frequent daytime napping is significantly associated with an increased risk of MACE and mortality among individuals with diabetes, particularly those who have extended sleep durations of more than 10 h and severe diabetes.

Laminaria japonica polysaccharide protects against liver and kidney injury in diabetes mellitus through the AhR/CD36 pathway

The lipid accumulation associated with diabetes causes continuous liver and kidney damage. Laminaria japonica polysaccharide (fucoidan) has been shown to regulate the disorder in lipid metabolism caused by diabetes. Herein, we established a diabetes mellitus (DM) rat model through a high-fat and high-sugar diet combined with streptozotocin. An automatic biochemical analyzer was used to detect serum lipid content, and hematoxylin and eosin, Masson, periodic acid-silver-methenamine, and Oil Red O staining were used to observe changes in the structure of the kidney and liver, including fibrosis and lipid accumulation. We confirmed that fucoidan could ameliorate renal injury, lipid metabolism, and oxidative stress in streptozotocin-induced diabetic rat models. Metabolomics analysis demonstrated that amino acid metabolism is an important process. We further demonstrated a novel role of fucoidan in regulating kidney and liver lipid metabolism through the aryl hydrocarbon receptor (AhR)-mediated CD36 signaling pathway. Similar results were found in DM rats treated with an AhR inhibitor, as well as in those treated with a combination of both an AhR inhibitor and fucoidan. Importantly, we observed a higher expression of AhR/CD36 in the kidneys and liver of rats with DM, and the level of AhR/CD36 correlated with lipid accumulation and kidney function, suggesting that AhR/CD36 signaling could be a promising therapeutic target for fucoidan in treating lipid metabolism in DM. PRACTICAL APPLICATION: As the main component of Laminaria japonica, fucoidan has excellent antioxidant properties and protective effects against liver and kidney damage in diabetes mellitus. It can play a protective role in the daily diet of diabetic patients. Alternatively, it could be developed as a potential therapeutic drug for the treatment of diabetes.

Involvement of a battery of investigated genes in lipid droplet pathophysiology and associated comorbidities

Lipid droplets (LDs) are highly specialized energy storage organelles involved in the maintenance of lipid homoeostasis by regulating lipid flux within white adipose tissue (WAT). The physiological function of adipocytes and LDs can be compromised by mutations in several genes, leading to NEFA-induced lipotoxicity, which ultimately manifests as metabolic complications, predominantly in the form of dyslipidemia, ectopic fat accumulation, and insulin resistance. In this review, we delineate the effects of mutations and deficiencies in genes - CIDEC, PPARG, BSCL2, AGPAT2, PLIN1, LIPE, LMNA, CAV1, CEACAM1, and INSR - involved in lipid droplet metabolism and their associated pathophysiological impairments, highlighting their roles in the development of lipodystrophies and metabolic dysfunction.

Evaluating Triglyceride and Glucose Index as a Simple and Easy-to-Calculate Marker for All-Cause and Cardiovascular Mortality

OBJECTIVE

The triglyceride and glucose (TyG) index is a useful marker of insulin resistance and is a predictor of several metabolic diseases. The aim of this study was to evaluate the association between the TyG index and all-cause or cardiovascular mortality using a large population-based cohort study database.

METHODS

A total of 255,508 subjects in the Kangbuk Samsung Health Study cohort were enrolled. Cox proportional hazards models were used to analyze the risk of mortality.

RESULTS

During a median 5.7-year follow-up, the cumulative all-cause and cardiovascular mortality was 0.47% and 0.07%. There was a nonlinear relationship between the TyG index and death, and moving from moderate to high, the TyG index levels were associated with an increase in the risk of death. The hazard ratio (HR) for all-cause and cardiovascular mortality of the TyG index was 1.21 [95% confidence interval (CI) 1.14-1.28] and 1.45 (95% CI 1.26-1.66) in the unadjusted model, respectively. After adjustment for covariates, the association between the TyG index and all-cause and cardiovascular mortality was attenuated. In the multivariable-adjusted model, the TyG index was associated with an elevated risk of all-cause mortality in women (HR 1.13, 95% CI 1.02-1.26) and a decreased risk in men (HR 0.92, 95% CI 0.85-0.99). The association between cardiovascular mortality and the TyG index was not statistically significant among either men or women in the multivariable-adjusted model.

CONCLUSIONS

The TyG index in a young, relatively healthy, population is associated with an elevated risk of all-cause and cardiovascular mortality. This association between the TyG index and all-cause mortality persists in women after multivariable adjustment.

Triglyceride and glucose index is a simple and easy-to-calculate marker associated with nonalcoholic fatty liver disease

OBJECTIVE

The aim of this study was to evaluate the relationship between the triglyceride and glucose (TyG) index and nonalcoholic fatty liver disease (NAFLD) using a large, population-based cohort study database.

METHODS

A total of 52,575 participants were enrolled from 2007 to 2013 in the Kangbuk Samsung Health Study cohort. The presence of NAFLD was ascertained by ultrasonography in the absence of other known liver diseases.

RESULTS

Over a median 5.1 years of follow-up, 7,292 participants (13.87%) were diagnosed with NAFLD. In a multivariate-adjusted model, the hazard ratio for NAFLD of the TyG index was 1.413 (95% CI: 1.349-1.480) in the first 6 months, 1.480 (95% CI: 1.408-1.556) in months 6 to 12, 1.427 (95% CI: 1.370-1.485) in months 12 to 18, and 1.246 (95% CI: 1.159-1.339) in months >18. The hazard ratios of triglycerides, glucose, fatty liver index, and homeostatic model assessment of insulin resistance for NAFLD in months >18 were 1.124 (95% CI: 1.061-1.190), 1.037 (95% CI: 0.970-1.109), 1.508 (95% CI: 1.417-1.605), and 1.177 (95% CI: 1.116-1.242), respectively. The NAFLD-free rate decreased with increasing TyG index quartile (p < 0.001). The TyG index level from which the risk of NAFLD increased appeared to be 8.24.

CONCLUSIONS

This study found that the TyG index is a simple and easy-to-calculate marker associated with NAFLD.

Lipid traits and type 2 diabetes risk in African ancestry individuals: A Mendelian Randomization study

BACKGROUND

Dyslipidaemia is highly prevalent in individuals with type 2 diabetes mellitus (T2DM). Numerous studies have sought to disentangle the causal relationship between dyslipidaemia and T2DM liability. However, conventional observational studies are vulnerable to confounding. Mendelian Randomization (MR) studies (which address this bias) on lipids and T2DM liability have focused on European ancestry individuals, with none to date having been performed in individuals of African ancestry. We therefore sought to use MR to investigate the causal effect of various lipid traits on T2DM liability in African ancestry individuals.

METHODS

Using univariable and multivariable two-sample MR, we leveraged summary-level data for lipid traits and T2DM liability from the African Partnership for Chronic Disease Research (APCDR) (N = 13,612, 36.9% men) and from African ancestry individuals in the Million Veteran Program (Ncases = 23,305 and Ncontrols = 30,140, 87.2% men), respectively. Genetic instruments were thus selected from the APCDR after which they were clumped to obtain independent instruments. We used a random-effects inverse variance weighted method in our primary analysis, complementing this with additional sensitivity analyses robust to the presence of pleiotropy.

FINDINGS

Increased genetically proxied low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels were associated with increased T2DM liability in African ancestry individuals (odds ratio (OR) [95% confidence interval, P-value] per standard deviation (SD) increase in LDL-C = 1.052 [1.000 to 1.106, P = 0.046] and per SD increase in TC = 1.089 [1.014 to 1.170, P = 0.019]). Conversely, increased genetically proxied high-density lipoprotein cholesterol (HDL-C) was associated with reduced T2DM liability (OR per SD increase in HDL-C = 0.915 [0.843 to 0.993, P = 0.033]). The OR on T2DM per SD increase in genetically proxied triglyceride (TG) levels was 0.884 [0.773 to 1.011, P = 0.072] . With respect to lipid-lowering drug targets, we found that genetically proxied 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) inhibition was associated with increased T2DM liability (OR per SD decrease in genetically proxied LDL-C = 1.68 [1.03-2.72, P = 0.04]) but we did not find evidence of a relationship between genetically proxied proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition and T2DM liability.

INTERPRETATION

Consistent with MR findings in Europeans, HDL-C exerts a protective effect on T2DM liability and HMGCR inhibition increases T2DM liability in African ancestry individuals. However, in contrast to European ancestry individuals, LDL-C may increase T2DM liability in African ancestry individuals. This raises the possibility of ethnic differences in the metabolic effects of dyslipidaemia in T2DM.

FUNDING

See the Acknowledgements section for more information.

A network pharmacology study to investigate bioactive compounds and signaling pathways of garlic (Allium sativum L.) husk against type 2 diabetes mellitus

During garlic harvest, much husk has been generated, nearly all husk is discarded as unnecessary by-products. However, in Korean folk remedies, Allium sativum L. husk (ASLH) extracts have been used as a reliever against type 2 diabetes mellitus (T2DM). Currently, its significant mechanisms against T2DM remain unclear. Thus, the aim of this study is to investigate the characteristics of its key signaling pathways, targets, and compounds. The compounds in ASLH were analyzed by gas chromatography-mass spectrum (GC-MS) and confirmed drug-like compounds (DLCs) in silico. Then, protein-protein interaction (PPI) networks and signaling pathways, targets, compounds are constructed, visualized by using RStudio. Finally, we performed a molecular docking test (MDT) to identify the key mechanism(s), target(s), and compound(s) of ASLH on T2DM. A total of 23 compounds in ASLH were identified by GC-MS, and all compounds were accepted by Lipinski's rule. The 23 compounds were associated with 521 targets and retrieved 4,736 T2DM-related targets by Online Mendelian Inheritance in Man (OMIM) and DisGeNET. The final overlapping 87 targets were obtained between compounds-targets and T2DM-related targets. The number of 13 signaling pathways, 33 targets, and 19 compounds of ASLH were associated with T2DM. In parallel, MDT revealed four potential compounds: (1) 9-hexacosene, (2) 2-(([2-ethylhexyl]oxy)carbonyl)benzoic acid, (3) clionasterol, (4) 4-methyl-2-phenylpyrimidine on PPAR signaling pathway. Overall, the four compounds from ASLH might show an anti-T2DM synergistic effect by activating the PPAR signaling pathway or inactivating the phospholipase D signaling pathway. In this study, we suggest that ASLH might be considered a health-promising resource from both nutraceutical and pharmaceutical perspectives. PRACTICAL APPLICATIONS: Allium sativum L. husk (ASLH) has been regarded as wastes that come from garlic (Allium sativum L.). During the harvesting period of garlic, a considerable amount of ASLH is a severe problem in farm communities. Particularly, garlic bioactive compounds are well documented including organosulfur compounds. Conversely, at present, no information is available on chemical compounds of ASLH to use in health industries. Taking this matter into consideration, our analysis approach was to select drug-like compounds (DLCs) from ASLH via GC-MS, thereby we can explore the compounds with high cell permeability. The screened compounds can be used as nutraceutical or medicinal or even cosmetical resources. In this study, we described the significant compounds via the network pharmacology concept to uncover the pharmaceutical mechanism(s) of ASLH against T2DM. Eventually, this work provides nutraceutical or medicinal value of ASLH and suggests that ASLH might be used as an upcycling resource to relieve T2DM.

Triglyceride Glucose-Waist Circumference Is Superior to the Homeostasis Model Assessment of Insulin Resistance in Identifying Nonalcoholic Fatty Liver Disease in Healthy Subjects

The triglyceride glucose (TyG) index has been suggested as a marker for insulin resistance; however, few studies have investigated the clinical implications of markers that combine obesity markers with the TyG index. This study aimed to investigate the associations between non-alcoholic fatty liver disease (NAFLD) and TyG-related markers in healthy subjects in Korea. We enrolled 21,001 asymptomatic participants who underwent hepatic ultrasonography. The homeostasis model assessment of insulin resistance (HOMA-IR), TyG index, TyG-body mass index, and TyG-waist circumference (WC) were subsequently analyzed. NAFLD was diagnosed using hepatic ultrasonography. A multiple logistic regression analysis was performed to evaluate the associations between the quartiles of each parameter and the risk of NAFLD. The increase in the NAFLD risk was most evident when the TyG-WC quartiles were applied; the multivariate-adjusted odds ratios for NAFLD were 4.72 (3.65–6.10), 13.28 (10.23–17.24), and 41.57 (31.66–54.59) in the 2nd, 3rd, and 4th TyG-WC quartiles, respectively, when compared with the lowest quartile. The predictability of the TyG-WC for NAFLD was better than that of the HOMA-IR using the area under the curve. The TyG-WC index was superior to the HOMA-IR for identifying NAFLD in healthy Korean adults, especially in the non-obese population.

Triglyceride Glucose-Waist Circumference Better Predicts Coronary Calcium Progression Compared with Other Indices of Insulin Resistance: A Longitudinal Observational Study

The triglyceride glucose (TyG) index, a product of triglyceride and fasting glucose, is a reliable marker for insulin resistance. We aimed to investigate the association between the TyG-related markers and coronary artery calcification (CAC) progression. We enrolled 1145 asymptomatic participants who underwent repeated CAC score measurements during routine health examinations. Homeostasis model assessment of insulin resistance (HOMA-IR), TyG index, TyG-BMI (body mass index), and TyG-WC (waist circumference) were calculated. Progression of CAC was defined as (1) incident CAC in a CAC-free population, or an (2) increase of ≥2.5 units between the baseline and final square root of the CAC scores in participants with detectable CAC. According to the quartiles of parameters, we stratified the subjects into four groups. The prevalence of progression increased with the TyG-WC quartile (15.0%, 24.1%, 31.0%, and 32.2% for each of the groups; p < 0.001). The multivariate-adjusted odds ratio (95% confidence interval) for CAC score progression was 1.66 (1.01–2.77) when the highest and lowest TyG-WC index quartiles were compared. Furthermore, the predictability of TyG-WC for CAC progression was better than the other indices in terms of the area under the curve. The TyG-WC index predicted CAC progression better than other indices and could be a potential marker of future coronary atherosclerosis.

Causal relationships between lipid and glycemic levels in an Indian population: A bidirectional Mendelian randomization approach

BACKGROUND

Dyslipidemia and abnormal glycemic traits are leading causes of morbidity and mortality. Although the association between the two traits is well established, there still exists a gap in the evidence for the direction of causality.

OBJECTIVE

This study aimed to examine the direction of the causal relationship between lipids and glycemic traits in an Indian population using bidirectional Mendelian randomization (BMR).

METHODS

The BMR analysis was conducted on 4900 individuals (2450 sib-pairs) from the Indian Migration Study. Instrument variables were generated for each lipid and glycemic trait (fasting insulin, fasting glucose, HOMA-IR, HOMA-β, LDL-cholesterol, HDL-cholesterol, total cholesterol and triglycerides) to examine the causal relationship by applying two-stage least squares (2SLS) regression in both directions.

RESULTS

Lipid and glycemic traits were found to be associated observationally, however, results from 2SLS showed that only triglycerides, defined by weighted genetic risk score (wGRS) of 3 SNPs (rs662799 at APOAV, rs780094 at GCKR and rs4420638 at APOE/C1/C4), were observed to be causally effecting 1.15% variation in HOMA-IR (SE = 0.22, P = 0.010), 1.53% in HOMA- β (SE = 0.21, P = 0.001) and 1.18% in fasting insulin (SE = 0.23, P = 0.009). No evidence for a causal effect was observed in the reverse direction or between any other lipid and glycemic traits.

CONCLUSION

The study findings suggest that triglycerides may causally impact various glycemic traits. However, the findings need to be replicated in larger studies.