The Pathophysiology of Type 2 Diabetes Mellitus in Non-obese Individuals: An Overview of the Current Understanding

Effects of tumor necrosis factor-α rs1800629 and interleukin-10 rs1800872 genetic variants on type 2 diabetes mellitus susceptibility and metabolic parameters among Jordanians

OBJECTIVES

Diabetes mellitus (DM) is a complex chronic illness with diverse pathogenesis and associations with health complications. Genetic factors significantly contribute to DM development, and tumor necrosis factor alpha (TNF-α) and interleukin-10 (IL-10) genes play major roles. This study aims to explore the influence of TNF-α rs1800629 and IL-10 rs1800872 genetic variants on T2DM development in Jordanian patients at Jordan University Hospital.

METHODS

One-hundred and 60 diabetic and 159 non-diabetic subjects were genotyped for TNF-α rs1800629. Additionally, 181 diabetic and 191 non-diabetic subjects were genotyped for IL-10 rs1800872 using PCR-RFLP genotyping method. The demographic, lipid, and glycemic parameters of the patients were obtained from the computer records in the hospital.

RESULTS

TNF-α rs1800629 and IL-10 rs1800872 genetic variants exhibited significant different frequencies in non-T2DM subjects and T2DM patients. The difference in TNF-α rs1800629 genotype frequency between non-T2DM and T2DM participants was significant under the dominant model, while the IL-10 rs1800872 genotype frequency was significant under the recessive model. A significant association (p<0.05) was observed between TNF-α rs1800629 and total cholesterol levels, and between IL-10 rs1800872 polymorphism and glycosylated hemoglobin (HbA1c) and creatinine levels among T2DM patients.

CONCLUSIONS

TNF-α rs1800629 and IL-10 rs1800872 are identified as genetic risk factors for T2DM. These variants also correlate with variations in cholesterol, HbA1c, and creatinine levels among T2DM patients. Larger clinical studies are warranted to validate these findings.

Effects of Excessive High-fructose Corn Syrup Drink Intake in Middle-aged Mice

BACKGROUND/AIM

The global prevalence of type 2 diabetes (T2D) continues to increase, necessitating the need for understanding the causes of its development. The widespread use of high-fructose corn syrup (HFCS) in drinks and diets is suspected to play a role in metabolic disorders. Although many studies have reported on the effects of excessive HFCS and excessive energy intakes in middle-aged individuals, few have focused on energy restriction. This study aimed to investigate the effects of excessive HFCS drink intake under energy restriction on developing T2D in early middle-aged mice.

MATERIALS AND METHODS

Early middle-aged mice were divided in HFCS and control groups; they were provided either 10% HFCS water or deionized water ad libitum for 12 weeks, respectively. Total energy intake was controlled using a standard rodent diet. Oral glucose tolerance test (OGTT), insulin tolerance test (ITT), tissue weight measurements, serum parameter analyses, and mRNA expression assessments were performed.

RESULTS

No increase in body and adipose tissue weight was observed with excessive HFCS intake under energy restriction. Moreover, serum lipid parameters did not differ from those of controls. However, in the OGTT and ITT, the HFCS group showed higher blood glucose levels than the control group. Moreover, the pancreatic weight and insulin II mRNA expression were reduced.

CONCLUSION

The excessive HFCS drink intake under energy restriction did not induce obesity; however, it induced impaired glucose tolerance, indicating its negative effects on the pancreas in early middle-aged mice. When translated in human physiology, our results show that even if one does not become obese, excessive HFCS may affect the overall metabolic mechanism; these effects may vary depending on age.

Periodontitis is associated with insulin resistance in adults living with diabetes mellitus in Uganda: a cross- sectional study

INTRODUCTION

Evidence suggests that majority of patients with diabetes mellitus in Uganda have poor glycaemic control as well as periodontal disease. This study set out to determine the association between periodontitis and insulin resistance in adult patients with diabetes mellitus in Uganda using the triglyceride glucose index.

METHODS

Two hundred and twenty-three adult study participants with confirmed diabetes mellitus were enrolled in a cross-sectional study. Oral examination was carried with the aid of a periodontal probe to determine the periodontal status and findings recorded using the WHO Oral Health Assessment Tool for Adults, 2013. We recorded clinical details for body mass index (BMI in kg/m2) and laboratory parameters including fasting blood sugar (mmol/L), glycated hemoglobin levels (HbA1c, %) and serum triglycerides (mmol/L) using a study questionnaire. Data were analyzed using R version 4.10. The glucose triglyceride index was used as a measure of insulin resistance. Logistic regression analysis carried out to determine the factors associated insulin resistance.

RESULTS

The majority of the study participants was female (70%) with an average age of 48.5 years (SD+/- 11.1). The mean body mass index was 29.6 kg/m2 (SD+/- 5.82). The mean serum triglyceride index was 9.48 (SD+/- 0.675). Eighty-six-point 1% of the participants had periodontal disease. Bivariate analysis revealed high odds for male sex (OR = 1.31, 95% C.I = 0.44-4.84, p = 0.65) and periodontitis (OR = 3.65, 95% C.I = 0.79-26.15, p = 0.13) but low odds for a high BMI (OR = 0.45. 95% C.I = 0.07-1.67, p = 0.30). Multivariate regression revealed a significant association between insulin resistance and periodontitis. (AOR = 3.52, 95% C.I = 1.19-1.83, p = 0.03).

CONCLUSION

Insulin resistance is highly prevalent in patients with diabetes mellitus in Uganda and is associated with periodontitis and low body weight.

Incidence and temporal trends in type 2 diabetes by weight status: A systematic review and meta-analysis of prospective cohort studies

Background

Diabetes is more prevalent among overweight/obese individuals, but has become a significant public health challenge among normal weight populations. In this meta-analysis, we aimed to estimate diabetes/prediabetes incidence and its temporal trends by weight status.

Methods

PubMed, Embase, Web of Science, and Cochrane Library were searched until 8 December 2021. Prospective cohort studies reporting diabetes incidence by baseline body mass index (BMI) categories in adults were included. The median year of data collection was used to assess the temporal trends. Subgroup analyses and meta-regression were also performed.

Results

We included 94 studies involving 3.4 million adults from 22 countries. The pooled diabetes incidence in underweight, normal-weight, and overweight/obese adults was 4.5 (95% confidence interval (CI) = 2.8-7.3), 2.7 (95% CI = 2.2-3.3), and 10.5 (95% CI = 9.3-11.8) per 1000 person-years, respectively. The diabetes incidence in low- and middle-income countries (LMICs) was higher than in high-income countries among normal-weight (5.8 vs 2.0 per 1000 person-years) or overweight/obese (15.9 vs 8.9 per 1000 person-years) adults. European and American regions had a higher diabetes incidence than the non-Western areas, regardless of weight status. Underweight diabetes incidence decreased significantly from 1995-2000 to 2005-2010. Diabetes incidence in normal-weight populations has increased continuously since 1985 by an estimated 36% every five years. In overweight/obese adults, diabetes incidence increased between 1985-1990 and 1995-2000, stabilised between 2000 and 2010, and spiked suddenly after 2010.

Conclusions

Diabetes incidence and its temporal trends differed by weight status. The continuous upward trend of diabetes incidence among overweight/obese individuals requires urgent attention, particularly in LMICs. Furthermore, diabetes among normal-weight individuals is becoming a significant public health problem.

Registration

PROSPERO (CRD42020215957).

Association between serum leptin concentrations and homeostasis model assessment-insulin resistance of 2.5 and higher in normal weight Japanese women

Normal weight insulin resistant phenotype was characterized in 251 Japanese female university students using homeostasis model assessment-insulin resistance. Birth weight, body composition at age 20, cardiometabolic traits and dietary intake were compared cross-sectionally between insulin sensitive (< 1.6, n = 194) and insulin resistant (2.5 and higher, n = 16) women. BMI averaged < 21 kg/m² and waist < 72 cm and did not differ between two groups. The percentage of macrosomia and serum absolute and fat-mass corrected leptin concentrations were higher in insulin resistant women although there was no difference in birth weight, fat mass index, trunk/leg fat ratio and serum adiponectin. In addition, resting pulse rate, serum concentrations of free fatty acids, triglycerides and remnant-like particle cholesterol were higher in insulin resistant women although HDL cholesterol and blood pressure did not differ. In multivariate logistic regression analyses, serum leptin (odds ratio:1.68, 95% confidential interval:1.08-2.63, p = 0.02) was associated with normal weight insulin resistance independently of macrosomia, free fatty acids, triglycerides, remnant-like particle cholesterol and resting pulse rate. In conclusion, normal weight IR phenotype may be associated with increased plasma leptin concentrations and leptin to fat mass ratio in young Japanese women, suggesting higher leptin production by body fat unit.

Associations of alanine aminotransferase/aspartate aminotransferase with insulin resistance and β-cell function in women

We tested whether alanine aminotransferase/aspartate aminotransferase (ALT/AST), a marker of hepatosteatosis, associates with insulin resistance, β-cell function and postglucose glycemia. We studied 311 young and 148 middle-aged Japanese women, whose BMI averaged < 23.0 kg/m². Insulinogenic index and Matsuda index were evaluated in 110 young and 65 middle-aged women. In two groups of women, ALT/AST was associated positively with homeostasis model assessment insulin resistance (HOMA-IR) and inversely with Matsuda index. In middle-aged women only, the ratio was also associated positively with fasting and postload glycemia and HbA1c. The ratio showed negative association with disposition index (a product of insulinogenic index and Matsuda index). On multivariate linear regression analysis, HOMA-IR emerged as a single determinant of ALT/AST in young and middle-aged women (standardized β: 0.209, p = 0.003 and 0.372, p = 0.002, respectively). ALT/AST was associated with insulin resistance and β-cell function even in non-obese Japanese women, suggesting a pathophysiologic basis in its prediction of diabetic risk.

Treatment strategy for children and adolescents with type 2 diabetes-based on ISPAD Clinical Practice Consensus Guidelines 2022

The principles of treatment for children and adolescents with type 2 diabetes include dietary and exercise management. For dietary management, a relatively modest dietary regimen with an appropriate energy source composition is recommended. Moderate- to vigorous-intensity aerobic activity is recommended for at least 60 min/d. Family members are encouraged to modify their lifestyles. Some patients fail to improve hyperglycemia through dietary and exercise management and eventually require pharmacological treatment. If the patient is metabolically stable (HbA1c level < 8.5% [69 mmol/mol]), metformin is the first-line treatment of first choice. In a case with ketosis or HbA1c of more than 8.5% (69 mmol/mol), insulin will be required initially with once daily basal insulin (0.25-0.5 units/kg). The goal of the initial treatment is to attain an HbA1c level < 7.0% (53 mmol/mol). If the glycemic goal is not attained, the addition of a second agent should be considered. However, the use of antihyperglycemic drugs in pediatric patients is limited in most countries. Therefore, the efficacy and safety of these drugs used in adult patients, including GLP-1 receptor agonists and SGLT2 inhibitors, should be evaluated in pediatric patients worldwide.

Salivary telomere length and the risks of prediabetes and diabetes among middle-aged and older adults: findings from the Health and Retirement Study

AIM

To assess the association of telomere length (TL) with prediabetes/diabetes and to explore the potential factors affecting TL among individuals with prediabetes/diabetes by weight status.

METHODS

This study included 3,379 eligible adults (aged 45-85 years, males: 42%) from the US Health and Retirement Study in 2008. TL was assayed using quantitative PCR of saliva (T/S ratio). Linear and nonlinear associations between TL and prediabetes/diabetes were assessed using the logistic regression and restricted cubic spline model, respectively, adjusting for TL-plate numbers, age, sex, race, body mass index, lifestyles, diabetes medications, and cardiometabolic parameters (blood pressure, C-reactive protein, and total cholesterol). Multiple linear regression was used for testing any factors associated with TL.

RESULTS

Among 3,379 participants, 868 (25.7%) had prediabetes with a mean TL of 1.34 ± 0.37 (T/S ratio) and 858 (25.4%) had diabetes with a mean TL of 1.36 ± 0.43 (T/S ratio). Neither linear nor nonlinear association of TL with prediabetes/diabetes was significant by weight status. Age was negatively associated with TL in both normal-weight (β = - 0.002, p = 0.025) and overweight/obese (β = - 0.002, p = 0.006) prediabetes, but non-significant in normal-weight and overweight/obese diabetes. BMI and cardiometabolic parameters were not associated with TL in prediabetes/diabetes by weight status.

CONCLUSIONS

Salivary TL was not associated with prediabetes/diabetes among the US middle-aged and older adults. Further longitudinal studies are required to establish the link between TL and diabetes development and to identify potential factors affecting TL shortening, particularly in normal-weight diabetic patients.

Insulin secretion and action with increasing age - A comparison between Middle Eastern immigrants and native Swedes

Aims

Little is known how insulin secretion and action change over time in populations of different ethnicities. We studied changes in insulin secretion and action with increasing age in Iraqi-born immigrants and native Swedes, and investigated if the changes were modified by region of origin.

Methods

Residents of Malmö, 30–75 years of age born in Iraq or Sweden, were invited to participate in this population-based, cross-sectional study. Health examination, medical history, lifestyle, sociodemographic data, and fasting blood samples were assessed. Oral glucose tolerance tests were performed and insulin secretion (disposition index, DIo) and insulin sensitivity index (ISI) calculated using the Matsuda indices.

Results

In total 1881 people participated; 1193 Iraqi- and 688 Swedish born. DIo decreased with increasing age in the total study population (β for the effect of age on ln DIo: ^-0.018, 95% CI ^-0.023 to ^-0.013, P < 0.001), adjusted for origin, lifestyle and anthropometric measures. DIo was generally lower in Iraqis vs. Swedes (median: 12,712.9 vs. 14,659.2, P = 0.004), but the difference disappeared when adjusted for BMI.

Further, ISI declined with increasing age in both Iraqis and Swedes. ISI was generally lower among Iraqis compared to Swedes, (median: 76.9 vs. 102.3, p < .001). The difference could not be fully explained by age, sex, lifestyle, and anthropometric measures. No significant interactions were observed.

Conclusions

The levels of DIo and ISI were lower among Iraqis compared to Swedes and declined with increasing age, irrespective of origin.

Maternal low protein diet and fetal programming of lean type 2 diabetes

Maternal nutrition is found to be the key factor that determines fetal health in utero and metabolic health during adulthood. Metabolic diseases have been primarily attributed to impaired maternal nutrition during pregnancy, and impaired nutrition has been an immense issue across the globe. In recent years, type 2 diabetes (T2D) has reached epidemic proportion and is a severe public health problem in many countries. Although plenty of research has already been conducted to tackle T2D which is associated with obesity, little is known regarding the etiology and pathophysiology of lean T2D, a variant of T2D. Recent studies have focused on the effects of epigenetic variation on the contribution of in utero origins of lean T2D, although other mechanisms might also contribute to the pathology. Observational studies in humans and experiments in animals strongly suggest an association between maternal low protein diet and lean T2D phenotype. In addition, clear sex-specific disease prevalence was observed in different studies. Consequently, more research is essential for the understanding of the etiology and pathophysiology of lean T2D, which might help to develop better disease prevention and treatment strategies. This review examines the role of protein insufficiency in the maternal diet as the central driver of the developmental programming of lean T2D.

Multi-strain probiotic supplement attenuates streptozotocin-induced type-2 diabetes by reducing inflammation and β-cell death in rats

Probiotics are health beneficial bacterial populations colonizing the human gut and skin. Probiotics are believed to be involved in immune system regulation, gut microbiota stabilization, prevention of infectious diseases, and adjustments of host metabolic activities. Probiotics such as Lactobacillus and Bifidobacterium affect glycemic levels, blood lipids, and protein metabolism. However, the interactions between probiotics and metabolic diseases as well as the underlying mechanisms remain unclear. We used streptozotocin (STZ)-induced diabetic animal models to study the effect of Probioglu^TM, a multi-strain probiotic supplement including Lactobaccilus salivarius subsp. salicinius AP-32, L. johnsonii MH-68, L. reuteri GL-104, and Bifidobacterium animalis subsp. lactis CP-9, on the regulation of physiochemical parameters related to type-2 diabetes. Experimental rats were randomly assigned into five groups, control group, streptozotocin (STZ)-treated rats (STZ group), STZ + 1× Probioglu^TM group, STZ + 5× Probioglu^TM group, and STZ + 10× Probioglu^TM group, and physiological data were measured at weeks 0, 2, 4, 6, and 8. Our results indicate that supplementation with Probioglu^TM significantly improved glucose tolerance, glycemic levels, insulin levels, and insulin resistance (HOMA-IR). Furthermore, we observed reduction in urea and blood lipid levels, including low-density lipoprotein (LDL), triglycerides (TG), and total cholesterol (TC). Probioglu^TM administration increased the β-cell mass in STZ-induced diabetic animal models, whereas it reduced the levels of proinflammatory cytokines TNF-α, IL-6, and IL-1β. In addition, the enhancement of oxidative stress biomarkers and superoxide dismutase (SOD) activities was associated with a decrease in malondialdehyde (MDA) levels. We conclude that Probioglu^TM attenuates STZ-induced type-2 diabetes by protecting β-cells, stabilizing glycemic levels, and reducing inflammation. Among all probiotic treating groups, the 10×Probioglu^TM treatment revealed the best results. However, these experimental results still need to be validated by different animal models of type-2 diabetes and human clinical trials in the future.

A Non-obese, Treatment-Naive Japanese Diabetic Patient With Elevated Insulin Clearance and Hyperglycemia Under Enhanced Insulin Sensitivity and Increased Insulin Secretion: Elevated Insulin Clearance as Type 2 Japanese Diabetes Mellitus (T2JDM)

Diabetes mellitus is a heterogeneous and complex metabolic disorder characterized by hyperglycemia secondary to either resistance to insulin actions on the liver and peripheral tissues, insufficient insulin secretion from pancreatic β-cells, or both. An integrated balance between blood insulin levels and whole-body insulin sensitivity could theoretically provide the clinical effectiveness of insulin action. Peripheral blood insulin concentrations might be determined by the capacity of endogenous pancreatic β-cell insulin secretion and the degree of the whole body insulin clearance. Here, we report a non-obese normoinsulinemic Japanese diabetic patient with elevated insulin clearance assessed by a hyperinsulinemic-euglycemic clamp examination and increased insulin secretion measured by daily urinary excretion of C-peptide immunoreactivity. We propose this unique pathogenic condition of diabetes with normoinsulinemia and elevated insulin clearance as "type 2 Japanese diabetes mellitus (T2JDM)."

Impact of High Fat Diet and Ethanol Consumption on Neurocircuitry Regulating Emotional Processing and Metabolic Function

The prevalence of psychiatry disorders such as anxiety and depression has steadily increased in recent years in the United States. This increased risk for anxiety and depression is associated with excess weight gain, which is often due to over-consumption of western diets that are typically high in fat, as well as with binge eating disorders, which often overlap with overweight and obesity outcomes. This finding suggests that diet, particularly diets high in fat, may have important consequences on the neurocircuitry regulating emotional processing as well as metabolic functions. Depression and anxiety disorders are also often comorbid with alcohol and substance use disorders. It is well-characterized that many of the neurocircuits that become dysregulated by overconsumption of high fat foods are also involved in drug and alcohol use disorders, suggesting overlapping central dysfunction may be involved. Emerging preclinical data suggest that high fat diets may be an important contributor to increased susceptibility of binge drug and ethanol intake in animal models, suggesting diet could be an important aspect in the etiology of substance use disorders. Neuroinflammation in pivotal brain regions modulating metabolic function, food intake, and binge-like behaviors, such as the hypothalamus, mesolimbic dopamine circuits, and amygdala, may be a critical link between diet, ethanol, metabolic dysfunction, and neuropsychiatric conditions. This brief review will provide an overview of behavioral and physiological changes elicited by both diets high in fat and ethanol consumption, as well as some of their potential effects on neurocircuitry regulating emotional processing and metabolic function.

The Association Between Insulin Resistance, Leptin, and Resistin and Diabetic Nephropathy in Type 2 Diabetes Mellitus Patients with Different Body Mass Indexes

AIM

This study aimed to compare HOMA-IR, leptin, and resistin as the risk factors for diabetic nephropathy in the type 2 diabetes mellitus (T2DM) patients with different BMI classifications.

MATERIALS AND METHODS

A total of 309 patients with T2DM were enrolled in this cross-sectional study. All participants were divided into three groups according to BMI: the normal weight group (18.5 kg/m²≤BMI<24 kg/m²), the overweight group (24kg/m²≤BMI<28 kg/m²) and the obesity group (BMI≥28 kg/m²). The clinical information and laboratory examinations were recorded in detail. Leptin and resistin levels were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Higher HOMA-IR, leptin and resistin levels were found to be the risk factors for diabetic nephropathy when we made comparisons in the total population (P<0.05). In the normal weight group, logistic regression analysis showed that T2DM patients with higher HOMA-IR (OR=4.210, P=0.001), leptin (OR=2.474, P=0.031) and resistin levels (OR=8.299, P<0.001) had nearly 4-fold, 2-fold and 8-fold risk for diabetic nephropathy, respectively, after adjustments. The receiver operating characteristic (ROC) curves indicated that the area under the curves (AUCs) of HOMA-IR and resistin were 0.699 (95% CI 0.617-0.772) and 0.790 (95% CI 0.715-0.854), respectively, which were significantly larger than the AUC of 0.5 (all P<0.001). However, no significant association was observed between HOMA-IR, leptin, and resistin and renal complications (all P>0.05) in the overweight and obesity groups in both logistic regression and AUC analysis.

CONCLUSION

Higher insulin resistance, leptin and resistin levels were observed as risk factors for diabetic nephropathy in T2DM patients with lower BMI. These were not obvious in the overweight and obese patients.

Pyrroloquinoline Quinone Modifies Lipid Profile, but Not Insulin Sensitivity, of Palmitic Acid-Treated L6 Myotubes

Pyrroloquinoline quinone (PQQ) is a novel stimulator of mitochondrial biogenesis and cellular energy metabolism. This is the first study investigating regulatory mechanisms and metabolic responses underlying PQQ’s action in palmitate-exposed L6 myotubes. Particularly, we assessed alterations in lipid content and composition, expression of metabolic enzymes, and changes in glucose transport. The experiments were conducted using muscle cells subjected to short (2 h) and prolonged (24 h) incubation with PQQ in a sequence of pre- and post-palmitic acid (PA) exposure. We demonstrated the opposite effects of 2 and 24 h treatments with PQQ on lipid content, i.e., a decline in the level of free fatty acids and triacylglycerols in response to short-time PQQ incubation as compared to increases in diacylglycerol and triacylglycerol levels observed after 24 h. We did not demonstrate a significant impact of PQQ on fatty acid transport. The analysis of metabolic enzyme expression showed that the vast majority of PQQ-dependent alterations cumulated in the PA/PQQ 24 h group, including elevated protein amount of peroxisome proliferator activated receptor γ co-activator 1α (PGC-1α), sirtuin-1 (SIRT1), phosphorylated 5′AMP-activated protein kinase (pAMPK), carnitine palmitoyltransferase I (CPT1), citrate synthase (CS), fatty acid synthase (FAS), and serine palmitoyltransferase, long chain base subunit 1 (SPT1). In conclusion, the results mentioned above indicate PQQ-dependent activation of both fatty acid oxidation and lipid synthesis in order to adapt cells to palmitic acid-rich medium, although PQQ did not attenuate insulin resistance in muscle cells.