Polygenic scores of diabetes-related traits in subgroups of type 2 diabetes in India: a cohort study

Clinical use of polygenic scores in type 2 diabetes: challenges and possibilities

Resulting from a combination of genetic and environmental factors, type 2 diabetes is highly heterogeneous in manifestation and disease progression, with the only common feature being chronic hyperglycaemia. In spite of vigorous efforts to elucidate the pathogenetic origins and natural course of the disease, there is still a lack of biomarkers and tools for prevention, disease stratification and treatment. Genome-wide association studies have reported over 1200 variants associated with type 2 diabetes, and the decreased cost of generating genetic data has facilitated the development of polygenic scores for estimating an individual's genetic disease risk based on combining effects from most-or all-genetic variants. In this review, we summarise the current knowledge on type 2 diabetes-related polygenic scores in different ancestries and outline their possible clinical role. We explore the potential applicability of type 2 diabetes polygenic scores to quantify genetic liability for prediction, screening and risk stratification. Given that most genetic risk loci are determined from populations of European origin while other ancestries are under-represented, we also discuss the challenges around their global applicability. To date, the potential for clinical utility of polygenic scores for type 2 diabetes is limited, with such scores outperformed by clinical measures. In the future, rather than predicting risk of type 2 diabetes, the value of polygenic scores may be in stratification of the severity of disease (risk for comorbidities) and treatment response, in addition to aiding in dissecting the pathophysiological mechanisms involved.

Distinct Roles of Common Genetic Variants and Their Contributions to Diabetes: MODY and Uncontrolled T2DM

Type 2 diabetes mellitus (T2DM) encompasses a range of clinical manifestations, with uncontrolled diabetes leading to progressive or irreversible damage to various organs. Numerous genes associated with monogenic diabetes, exhibiting classical patterns of inheritance (autosomal dominant or recessive), have been identified. Additionally, genes involved in complex diabetes, which interact with environmental factors to trigger the disease, have also been discovered. These genetic findings have raised hopes that genetic testing could enhance diagnostics, disease surveillance, treatment selection, and family counseling. However, the accurate interpretation of genetic data remains a significant challenge, as variants may not always be definitively classified as either benign or pathogenic. Research to date, however, indicates that periodic reevaluation of genetic variants in diabetes has led to more consistent findings, with biases being steadily eliminated. This has improved the interpretation of variants across diverse ethnicities. Clinical studies suggest that genetic risk information may motivate patients to adopt behaviors that promote the prevention or management of T2DM. Given that the clinical features of certain monogenic diabetes types overlap with T2DM, and considering the significant role of genetic variants in diabetes, healthcare providers caring for prediabetic patients should consider genetic testing as part of the diagnostic process. This review summarizes current knowledge of the most common genetic variants associated with T2DM, explores novel therapeutic targets, and discusses recent advancements in the pharmaceutical management of uncontrolled T2DM.

Beyond BMI: Exploring obesity trends in the south Asian region

Background

Obesity is a global health challenge affecting individuals across all demographics. In South Asia, the traditional method of assessing obesity using Body Mass Index (BMI), may not account for factors such as fat distribution, muscle mass, or ethnic variations.

Objective

This narrative review explores the multifaceted nature of obesity in South Asia, focusing on the region's demographic profiles and the socio-cultural and economic determinants shaping obesity trends. Additionally, the review critiques the limitations of BMI as an accurate measure of obesity in this diverse population.

Methods

A comprehensive literature search was conducted to identify studies that address obesity trends in South Asia, with a focus on regional variations, influencing factors, and the limitations of BMI.

Results

The review identifies significant variations in obesity prevalence across South Asian countries, influenced by cultural norms, economic disparities, and urbanization. The limitations of BMI as a tool for assessing obesity are highlighted, particularly in its inability to capture fat distribution and muscle mass variations specific to South Asian populations.

Conclusions

Obesity in South Asia is shaped by complex demographic, cultural, and economic factors. While BMI is commonly used, it is insufficient for accurately assessing obesity in this population. More refined, context-specific measures are needed to better understand and address the growing obesity epidemic in South Asia.

Lessons Learned From Epidemiology of Type 2 Diabetes in South Asians: Kelly West Award Lecture 2024

South Asia has high prevalence rates of type 2 diabetes (T2D). Until the 1990s, the prevalence of T2D within South Asia was low but much higher in the South Asian diaspora living abroad. Today, high prevalence rates of T2D are reported among those living in South Asia. T2D in South Asians presents with unique clinical features described as the "South Asian phenotype" that include younger age at onset of diabetes than in White Europeans, much lower BMI, hyperinsulinemia and greater insulin resistance, rapid decline in β-cell function resulting in low insulin reserve, low muscle mass, and greater ectopic fat deposition, especially in the liver. Also, prevalence of impaired fasting glucose is higher among South Asians than prevalence of impaired glucose tolerance. Genetic predisposition combined with intrauterine fetal programming (low vitamin B12 intake and high folate intake) increases susceptibility to T2D, from birth. In later life, overnutrition, especially a high carbohydrate intake with refined grains of higher glycemic index, coupled with low physical activity likely triggers the T2D epidemic in South Asians. Additionally, there are emerging risk factors like air pollution. Preventing T2D in South Asians requires a multifactorial approach, including improvements in maternal and fetal nutrition with special reference to vitamin B12 and folate intake, decreasing refined carbohydrate and increasing protein and fiber intake in the diet, increasing physical activity, and control of air pollution. Lessons learned from epidemiology of T2D in South Asians could be useful to other developing countries that are in earlier stages of epidemiological transition.

Integrating Polygenic Risk Scores (PRS) for Personalized Diabetes Care: Advancing Clinical Practice with Tailored Pharmacological Approaches

The rising global prevalence of diabetes poses a serious threat to public health, national economies, and the healthcare system. Despite a high degree of disease heterogeneity and advancing techniques, there is still an unclear diagnosis of patients with diabetes compounded by the array of long-term microvascular and macrovascular complications associated with the disease. In addition to environmental variables, diabetes susceptibility is significantly influenced by genetic components. The risk stratification of genetically predisposed individuals may play an important role in disease diagnosis and management. Precision medicine methods are crucial to reducing this global burden by delivering a more personalised and patient-centric approach. Compared to the European population, genetic susceptibility variants of type 2 diabetes mellitus (T2DM) are still not fully understood in other major populations, including South Asians, Latinos, and people of African descent. Polygenic risk scores (PRS) can be used to identify individuals who are more susceptible to complex diseases such as diabetes. PRS is selective and effective in developing novel diagnostic interventions. This comprehensive predictive approach facilitates the understanding of distinct response profiles, resulting in the development of more effective management strategies. The targeted implementation of PRS is especially advantageous for people who fall into a higher-risk category for diabetes. Through early risk assessment and the creation of individualised diabetes treatment plans, the integration of PRS in clinical practice shows potential for reducing the prevalence of diabetes and its complications. Diabetes self-management depends significantly on patient empowerment, with behavioural monitoring emerging as a vital facilitator. The main aim of this review article is to formulate a more structured intervention strategy by advocating for increased awareness of the clinical utility of PRS and counseling among healthcare practitioners, patients, and individuals at risk of diabetes.

Type 2 diabetes: a contemporary view from the Asian lens

PURPOSE OF REVIEW

The aim of this article was to review the up-to-date evidence with regards to the unique features of the Type 2 diabetes (T2D) pathophysiology, complications, response to therapy with the possibility of precision medicine guiding therapeutic decision making in Asia.

RECENT FINDINGS

Asia is the epicenter of diabetes. There have been marked advances with genotyping and phenotyping of the Asian patient with T2D, particularly with young onset diabetes where early beta cell failure and rapid progression of complications are more frequent. As Asians have lower muscle mass and higher adiposity, sarcopenia is increasingly associated with diabetes. Response to lifestyle and pharmacotherapy are generally similar, but unique features exist with different populations. Across Asia, use of guideline directed medical therapy for cardio-renal protection are recommended, but uptake of these newer agents are suboptimal and barriers exist with regards to standardized care.

SUMMARY

Although many similarities have been observed across Asia, due to the heterogeneity of populations within Asia, further research is required to streamline and pave the way towards precision medicine. There is an urgent need for region wide consensus to minimize barriers to diabetes care and stigma in diabetes terminology across Asia.

Incremental predictive value of genetic risk and functional brain connectivity in determining antipsychotic response in schizophrenia

We aimed to assess the incremental value of schizophrenia polygenic risk score (PgRS) and resting-state functional brain connectivity (rsFC) when added to clinical data in predicting the six-week response to oral risperidone (Risperdal) in schizophrenia. Fifty-seven, 54, and 43 individuals in a group of never-before-treated first-episode schizophrenia had good quality whole-genome sequencing (10x), rsFC, and both genomic and rsFC data, respectively, at baseline. Symptom severity ratings were obtained at baseline and six-weeks of oral risperidone (Risperdal) treatment. The primary outcome was the percentage change in the Positive and Negative Syndrome Scale Total scores after risperidone (Risperdal) treatment. Clinical, PgRS, and rsFC determinants of treatment response were first evaluated independently. Subsequently, three blocks of hierarchical multiple regression analyses with leave-one-out cross-validation (n = 43), were implemented to study clinical, clinical + PgRS and clinical + PgRS + rsFC determinants of treatment response. While the combined clinical variables did not show a statistically significant prediction of treatment response, adding PgRS (9 % R2 change) and rsFC (26 % R2 change) in hierarchical steps, significantly improved the overall proportion of variance explained in treatment response. This proof-of-concept investigation underscores the incremental benefits offered by genetic and neuroimaging metrics over clinical measures in determining prospectively-ascertained short-term treatment response in first-episode schizophrenia.

Estimation of genetic variation in vitiligo associated genes: Population genomics perspective

BACKGROUND

Vitiligo is an auto-immune progressive depigmentation disorder of the skin due to loss of melanocytes. Genetic risk is one of the important factors for development of vitiligo. Preponderance of vitiligo in certain ethnicities is known which can be analysed by understanding the distribution of allele frequencies across normal populations. Earlier GWAS identified 108 risk alleles for vitiligo in Europeans and East Asians. In this study, 64 of these risk alleles were used for analysing their enrichment and depletion across populations (1000 Genomes Project and IndiGen) with reference to 1000 Genomes dataset. Genetic risk scores were calculated and Fisher's exact test was performed to understand statistical significance of their variation in each population with respect to 1000 Genomes dataset as reference. In addition to SNPs reported in GWAS, significant variation in allele frequencies of 1079 vitiligo-related genes were also analysed. Two-tailed Chi-square test and Bonferroni's multiple adjustment values along with fixation index (≥ 0.5) and minimum allele frequency (≥ 0.05) were calculated and used to prioritise the variants based on pairwise comparison across populations.

RESULTS

Risk alleles rs1043101 and rs10768122 belong to 3 prime UTR of glutamate receptor gene SLC1A2 are found to be highly enriched in the South Asian population when compared with the 'global normal' population. Intron variant rs4766578 (ATXN2) was found to be deleted in SAS, EAS and AFR and enriched in EUR and AMR1. This risk allele is found to be under positive selection in SAS, AMR1 and EUR. From the ancillary vitiligo gene list, nonsynonymous variant rs16891982 was found to be enriched in the European and the Admixed American populations and depleted in all others. rs2279238 and rs11039155 belonging to the LXR-α gene involved in regulation of metalloproteinase 2 and 9 (melanocyte precursors) were found to be associated with vitiligo in the North Indian population (in earlier study).

CONCLUSION

The differential enrichment/depletion profile of the risk alleles provides insight into the underlying inter-population variations. This would provide clues towards prioritisation of SNPs associated with vitiligo thereby elucidating its preponderance in different ethnic groups.

Phenotypic characterization of nonautoimmune diabetes in adult Ugandans with low body mass index

Background

Type 2 diabetes is common in relatively lean individuals in sub-Saharan Africa. It is unclear whether phenotypic differences exist between underweight and normal-weight African patients with type 2 diabetes. This study compared specific characteristics between underweight (body mass index <18.5 kg/m2) and normal-weight (body mass index of 18.5-24.9 kg/m2) adult Ugandans with new-onset nonautoimmune diabetes.

Methods

We collected the demographic, clinical, anthropometric, and metabolic characteristics of 160 participants with nonobese new-onset type 2 diabetes (defined as diabetes diagnosed <3 months, body mass index <25 kg/m2, and absence of islet-cell autoimmunity). These participants were categorized as underweight and normal weight, and their phenotypic characteristics were compared.

Results

Of the 160 participants with nonobese new-onset type 2 diabetes, 18 participants (11.3%) were underweight. Compared with those with normal weight, underweight participants presented with less co-existing hypertension (5.6% versus 28.2%, p = 0.04) and lower median visceral fat levels [2 (1-3) versus 6 (4-7), p < 0.001], as assessed by bioimpedance analysis. Pathophysiologically, they presented with a lower median 120-min post-glucose load C-peptide level [0.29 (0.13-0.58) versus 0.82 (0.39-1.50) nmol/l, p = 0.04] and a higher prevalence of insulin deficiency (66.7% versus 31.4%, p = 0.003).

Conclusion

This study demonstrates that nonautoimmune diabetes occurs in underweight individuals in sub-Saharan Africa and is characterized by the absence of visceral adiposity, reduced late-phase insulin secretion, and greater insulin deficiency. These findings necessitate further studies to inform how the prevention, identification, and management of diabetes in such individuals can be individualized.

Prediabetes in rural adolescent girls from DERVAN cohort: data from the KONKAN region of the state of Maharashtra, India (DERVAN-4)

Background

India is witnessing an epidemic of type 2 diabetes. Overweight/obesity, overnutrition, physical inactivity, and family history are well-known risk factors for diabetes. We investigated the role of undernutrition in the development of diabetes among rural adolescent girls.

Methods

DERVAN cohort study was set up in the KONKAN region of the western Indian state of Maharashtra. It enrolled 1,520 adolescent girls (16-18 years old at the time of enrollment). We measured glycemic parameters (glucose, insulin, and HbA1C) and body size using anthropometry and body composition using bioimpedance. Prediabetes was diagnosed using the American Diabetic Association (ADA) criteria. We also calculated various HOMA indices for insulin resistance (HOMA-IR), β-cell function (HOMA-β), insulin sensitivity (HOMA-S), and compensatory β-cell response using a homeostasis model. BMI, body fat%, and waist circumferences were treated as exposures and all the glycemic parameters and indices as outcomes.

Results

The median age of the subjects was 16.6 years. The median weight, height, and BMI were 40.7 kg, 151.7 cm, and 17.5 kg/m2, respectively. Prevalence of underweight was 28.8%, and stunting was observed in 30.4%. Thinness and obesity using BMI were observed in 58.4% and 4.2%, respectively. The median body fat% was 22.5, and excess body fat (>35%) was observed in 5.7%. The prevalence of prediabetes was 39.4%. Fasting insulin concentrations, HOMA-IR, and HOMA-β showed a positive trend across body composition quartiles (p < 0.001). HOMA-S and compensatory β-cell response showed an inverse trend (p < 0.001). Compared with prediabetic girls in the overweight/obese group, girls most undernourished group had lower median insulin concentrations (8.1 μIU/ml vs. 17.1 μIU/ml), lower HOMA-IR (1.1 vs. 2.3), and lower HOMA-β (75.6 vs. 129.2) but higher sensitivity (87.4 vs. 43.7) (p < 0.001) for all.

Conclusion

We have reported a high prevalence of prediabetes among rural adolescent girls with a very low prevalence of obesity. Prediabetes in obesity is driven by hyperinsulinemia and overworking of the pancreas while poor β-cell function and poor insulin secretion are major drivers in the undernourished group. The high-risk diabetes screening programs are much needed for the undernourished populations. Caution should be exercised for planning the interventions as overfeeding (or overnutrition) is likely to put the populations at risk of development of obesity and insulin resistance.

The role of structural racism and geographical inequity in diabetes outcomes

Diabetes is pervasive, exponentially growing in prevalence, and outpacing most diseases globally. In this Series paper, we use new theoretical frameworks and a narrative review of existing literature to show how structural inequity (structural racism and geographical inequity) has accelerated rates of diabetes disease, morbidity, and mortality globally. We discuss how structural inequity leads to large, fixed differences in key, upstream social determinants of health, which influence downstream social determinants of health and resultant diabetes outcomes in a cascade of widening inequity. We review categories of social determinants of health with known effects on diabetes outcomes, including public awareness and policy, economic development, access to high-quality care, innovations in diabetes management, and sociocultural norms. We also provide regional perspectives, grounded in our theoretical framework, to highlight prominent, real-world challenges.