Lipid-induced glucose intolerance is driven by impaired glucose kinetics and insulin metabolism in healthy individuals

Alterations in Adipose Tissue Distribution, Cell Morphology, and Function Mark Primary Insulin Hypersecretion in Youth With Obesity

Excessive insulin secretion independent of insulin resistance, defined as primary hypersecretion, is associated with obesity and an unfavorable metabolic phenotype. We examined the characteristics of adipose tissue of youth with primary insulin hypersecretion and the longitudinal metabolic alterations influenced by the complex adipo-insular interplay. In a multiethnic cohort of adolescents with obesity but without diabetes, primary insulin hypersecretors had enhanced model-derived β-cell glucose sensitivity and rate sensitivity but worse glucose tolerance, despite similar demographics, adiposity, and insulin resistance measured by both oral glucose tolerance test and euglycemic-hyperinsulinemic clamp. Hypersecretors had greater intrahepatic and visceral fat depots at abdominal MRI, hypertrophic abdominal subcutaneous adipocytes, higher free fatty acid and leptin serum levels per fat mass, and faster in vivo lipid turnover assessed by a long-term 2H2O labeling protocol. At 2-year follow-up, hypersecretors had greater fat accrual and a threefold higher risk for abnormal glucose tolerance, while individuals with hypertrophic adipocytes or higher leptin levels showed enhanced β-cell glucose sensitivity. Primary insulin hypersecretion is associated with marked alterations in adipose tissue distribution, cellularity, and lipid dynamics, independent of whole-body adiposity and insulin resistance. Pathogenetic insight into the metabolic crosstalk between β-cell and adipocyte may help to identify individuals at risk for chronic hyperinsulinemia, body weight gain, and glucose intolerance.

ARTICLE HIGHLIGHTS

Insulin resistance potentiates the effect of remnant cholesterol on cardiovascular mortality in individuals without diabetes

BACKGROUND AND AIMS

Remnant cholesterol (RC) and insulin resistance (IR) have been independently associated with cardiovascular risk. Here, we evaluated the role of IR and RC on cardiovascular disease (CVD) mortality.

METHODS

We conducted an analysis of 16,113 individuals ≥20 years without diabetes from the National Health and Nutrition Examination Survey (NHANES-III/IV). RC levels were calculated using total cholesterol, non-HDL-c, and LDL-c; IR was defined as HOMA2-IR≥2.5 and CVD mortality as a composite of cardiovascular and cerebrovascular mortality. Multiple linear regression was used to assess the relationship between HOMA2-IR and RC and Cox regression models to assess their joint role in CVD mortality. Causally ordered mediation models were used to explore the mediating role of IR in RC-associated CVD mortality.

RESULTS

We identified an association between higher HOMA2-IR and higher RC levels. The effect of IR on CVD mortality was predominant (HR 1.32, 95%CI 1.18-1.48) and decreased at older ages (HR 0.934, 95%CI 0.918-0.959) compared to RC (HR 0.983, 95%CI 0.952-1.014). Higher risk of CVD mortality was observed in individuals with IR but normal RC (HR 1.37, 95%CI 1.25-1.50) and subjects with IR and high RC (HR 1.24, 95%CI 1.13-1.37), but not in subjects without IR but high RC. In mediation models, HOMA2-IR accounted for 78.2% (95%CI 28.11-98.89) of the effect of RC levels on CVD mortality.

CONCLUSIONS

Our findings suggest that RC potentiates the risk of CVD mortality through its effect on whole-body insulin sensitivity, particularly among younger individuals.

Proteomic predictors of individualized nutrient-specific insulin secretion in health and disease

Population level variation and molecular mechanisms behind insulin secretion in response to carbohydrate, protein, and fat remain uncharacterized despite ramifications for personalized nutrition. Here, we define prototypical insulin secretion dynamics in response to the three macronutrients in islets from 140 cadaveric donors, including those diagnosed with type 2 diabetes. While islets from the majority of donors exhibited the expected relative response magnitudes, with glucose being highest, amino acid moderate, and fatty acid small, 9% of islets stimulated with amino acid and 8% of islets stimulated with fatty acids had larger responses compared with high glucose. We leveraged this insulin response heterogeneity and used transcriptomics and proteomics to identify molecular correlates of specific nutrient responsiveness, as well as those proteins and mRNAs altered in type 2 diabetes. We also examine nutrient-responsiveness in stem cell-derived islet clusters and observe that they have dysregulated fuel sensitivity, which is a hallmark of functionally immature cells. Our study now represents the first comparison of dynamic responses to nutrients and multi-omics analysis in human insulin secreting cells. Responses of different people's islets to carbohydrate, protein, and fat lay the groundwork for personalized nutrition.

ONE-SENTENCE SUMMARY

Deep phenotyping and multi-omics reveal individualized nutrient-specific insulin secretion propensity.

Early time-restricted carbohydrate consumption vs conventional dieting in type 2 diabetes: a randomised controlled trial

AIMS/HYPOTHESIS

Early time-restricted carbohydrate consumption (eTRC) is a novel dietary strategy that involves restricting carbohydrate-rich food intake to the morning and early afternoon to align with circadian variations in glucose tolerance. We examined the efficacy, feasibility and safety of eTRC in individuals with type 2 diabetes under free-living conditions.

METHODS

In this randomised, parallel-arm, open label, controlled trial, participants with type 2 diabetes and overweight/obesity (age 67.2±7.9 years, 47.8% women, BMI 29.4±3.7 kg/m2, HbA1c 49±5 mmol/mol [6.6±0.5%]) were randomised, using computer-generated random numbers, to a 12 week eTRC diet or a Mediterranean-style control diet with matched energy restriction and macronutrient distribution (50% carbohydrate, 30% fat and 20% protein). The primary outcome was the between-group difference in HbA1c at 12 weeks. Body composition, 14 day flash glucose monitoring and food diary analysis were performed every 4 weeks. Mixed meal tolerance tests with mathematical beta cell function modelling were performed at baseline and after 12 weeks.

RESULTS

Twelve (85.7%) participants in the eTRC arm and 11 (84.6%) participants in the control arm completed the study, achieving similar reductions in body weight and fat mass. The two groups experienced comparable improvements in HbA1c (-3 [-6, -0.3] mmol/mol vs -4 [-6, -2] mmol/mol, corresponding to -0.2 [-0.5, 0]% and -0.3 [-0.5, -0.1]%, respectively, p=0.386), fasting plasma glucose, flash glucose monitoring-derived glucose variability and mixed meal tolerance test-derived glucose tolerance, insulin resistance, insulin clearance and plasma glucagon levels, without changes in model-derived beta cell function parameters, glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide and non-esterified fatty acid levels. The two diets similarly reduced liver function markers and triglyceride levels, being neutral on other cardiometabolic and safety variables. In exploratory analyses, diet-induced changes in body weight and glucometabolic variables were not related to the timing of carbohydrate intake.

CONCLUSIONS/INTERPRETATION

The proposed eTRC diet provides a feasible and effective alternative option for glucose and body weight management in individuals with type 2 diabetes, with no additional metabolic benefits compared with conventional dieting.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05713058 FUNDING: This study was supported by the European Society for Clinical Nutrition and Metabolism (ESPEN) and the Italian Society of Diabetology (SID).

Postprandial Triglyceride, Glucose and Insulin Levels 10 Years After Bariatric Surgery in Women With Severe Obesity - A Pilot Study: Part 1 - Laparoscopic Greater Curvature Plication

The long-term effects of bariatric surgery on postprandial profiles in patients with obesity and type 2 diabetes (T2D) have not yet been investigated. Therefore, this study examined postprandial profiles before laparoscopic greater curvature plication (LGCP), and then at 2 and 10 years after surgery.The studied cohort included 10 women (mean age= 54.4±5 years) with obesity (mean BMI= 42.5±7.8 kg/m?) and T2D who underwent LGCP. All subjects underwent a standardized liquid mixed-meal test. For statistical evaluation, ANOVA with Bonferroni multiple comparison was used. Mean postprandial levels were significantly decreased 2 years after surgery. Responses 10 years after the surgery also remained significantly lower than before surgery. Changes observed during the follow-up were significant: glucose: F=34.5, p<0.001; insulin: F=49.3, p<0.001; triglycerides F=9.2, p<0.001. The long-term favorable effects of bariatric surgery on cardiometabolic health may be partly mediated by reductions in postprandial glucose, insulin, and triglyceride levels.

Interaction between the GCKR rs1260326 variant and serum HDL cholesterol contributes to HOMA-β and ISIMatusda in the middle-aged T2D individuals

This study aims to investigate the correlations between islet function/ insulin resistance and serum lipid levels, as well as to assess whether the strength of such correlations is affected by the GCKR rs1260326 variant in healthy and T2D individuals. We performed an oral glucose tolerance test (OGTT) on 4889 middle-aged adults, including 3135 healthy and 1754 T2D individuals from the REACTION population study in the Nanjing region. We also measured their serum lipid levels and genotyped for rs1260326. We found that serum high-density lipoprotein (HDL) cholesterol and triglyceride (TG) levels were independently correlated with indexes of islet function (HOMA-β and IGI [insulinogenic index]) and insulin resistance (HOMO-IR and ISIMatsuda) in both healthy and T2D individuals. The correlations were significantly decreased in T2D individuals, with significant heterogeneities compared to healthy controls (I2 > 75%, Phet < 0.05). Although no correlation was observed between serum total cholesterol (TC) level and islet function/ insulin resistance in healthy controls, significant correlations were found in T2D individuals, with significant heterogeneity to healthy controls in the correlation with ISIMatsuda(I2 = 85.3%, Phet = 0.009). Furthermore, we found significant interactions of the GCKR rs1260326 variant for the correlations between serum HDL cholesterol and HOMA-β/ISIMatsuda in T2D subjects (P = 0.015 and 0.038, respectively). These findings illustrate that distinct correlations between serum lipid levels and islet function/ insulin resistance occurred in T2D subjects compared to healthy individuals. Common gene variants, such as rs1260326, might interact substantially when studied in specific populations, especially T2D disease status.

Association of lipoprotein subfractions with incidence of type 2 diabetes among five U.S. Race and Ethnic groups: The Mediators of Atherosclerosis in South Asians Living in America (MASALA) and Multi-Ethnic study of Atherosclerosis (MESA)

AIMS

We examined associations between lipoprotein subfractions and prevalent and incident T2D in two race/ethnically diverse cohort studies.

METHODS

Adults self-identifying as White, Black, Chinese, Hispanic and South Asian-American without cardiovascular disease, with fasting serum, demographic, and clinical data at enrollment and after 5 years of follow-up were included. Lipoprotein subfractions were measured at enrollment using NMR spectrometry. LASSO regularized logistic regression models adjusted for age, sex, race/ethnicity, lipid-lowering agent use, and waist circumference assessed odds of incident T2D in pooled analyses.

RESULTS

There were 4474 participants with lipoprotein subfraction data at enrollment and 3839 participants without prevalent diabetes, mean age 62 years, 51 % women, with 234 incident T2D cases at 5 years. Triglycerides in small, dense LDL-5 [OR 1.26 (95 % CI 1.11,1.43)], VLDL triglycerides 1.30** [1.16,1.46] and phospholipids in VLDL-1 [OR 1.31 (1.17,1.47)] were associated with higher odds of incident T2D, while free cholesterol in large HDL-1 [OR 0.75 (95 % CI 0.63,0.89)] was inversely associated. The results were similar for prevalent diabetes and did not vary by race/ethnic group.

CONCLUSIONS

Composition of lipoprotein subfractions is differentially associated with prevalent and incident T2D without difference by race/ethnic group. Assessment of lipoprotein composition may enhance targeted risk reduction for T2D.

Atherosclerosis indexes and incident T2DM in middle-aged and older adults: evidence from a cohort study

BACKGROUND

Type 2 diabetes mellitus (T2DM) is an expanding global health problem, requiring effective methods for predicting and diagnosing in its early stages of development. Previous studies reported the prognostic value of the atherosclerosis indexes in both cardiovascular diseases and T2DM. However, the predictive performance of Non-HDL-C, AI, AIP, TG/HDL-C and LCI indexes on the risk of T2DM remains unclear. This study aims to compare the five atherosclerosis indexes for predicting T2DM in middle-aged and elderly Chinese.

METHODS

Data are collected from wave 2011 and wave 2015 of China Health and Retirement Longitudinal Study (CHARLS). Multi-variate logistic regression models were used to estimate odds ratio (OR) with 95% confidence interval (CI) of incident T2DM with five atherosclerosis indexes, and the restricted cubic splines were used to visualize the dose-response relationships. Receiver operating characteristic (ROC) curve was drawn and the areas under the curve (AUC) were used to compare the performance of the five atherosclerosis indexes in predicting T2DM.

RESULTS

A total of 504 (10.97%) participants had T2DM. Multi-variate logistic regression analysis showed that five atherosclerosis indexes were associated with T2DM, with adjusted ORs (95% CIs) of 1.29 (1.15-1.45), 1.29 (1.18-1.42), 1.45 (1.29-1.62), 1.41 (1.25-1.59) and 1.34 (1.23-1.48) for each IQR increment in Non-HDL-C, TG/HDLC, AI, AIP and LCI, respectively. Restricted cubic spline regression showed a nonlinear correlation between five atherosclerosis indexes and the risk of T2DM (p for nonlinear < 0.001). According to the ROC curve analysis, LCI had the highest AUC (0.587 [0.574-0.600]).

CONCLUSION

We found that LCI, compared with other indexes, was a better predictor in the clinical setting for identifying individuals with T2DM in middle-aged and elderly Chinese. LCI monitoring might help in the early identification of individuals at high risk of T2DM.