A chronic metabolic disease called diabetes mellitus is typified by persistently high blood sugar levels brought on by either decreased insulin action or production, or both. Acute metabolic disorders and chronic microvascular and macrovascular problems are caused by inadequate glycaemic management. Therefore, glycaemic parameter measurement is crucial for diabetes mellitus diagnosis, monitoring, and treatment.^1,2The metabolic condition known as type 2 diabetes mellitus (T2DM) is characterized by persistently high blood sugar levels that result from a combination of insulin resistance, deteriorating pancreatic β-cell function, and impaired incretin signalling. Obesity and accompanying metabolic disorders, such as dyslipidaemia, oxidative stress, and chronic low-grade inflammation, are directly linked to its fast-rising global occurrence.³ As an endocrine organ that secretes inflammatory cytokines including interleukin-6, interleukin-1β, and tumour necrosis factor-α, visceral adipose tissue plays a crucial pathogenic role. By interfering with insulin receptor substrate function and downstream pathways, these mediators hinder insulin signalling. Prolonged inflammatory stress also damages β-cells by causing oxidative damage and increasing the production of advanced glycation end products, which worsens glycaemic control.^4,5,6

One of the most widely used markers of glucose homeostasis is fasting blood sugar (FBS), which measures basal insulin function and hepatic glucose production. High fasting blood sugar levels are frequently used to diagnose and track diabetes mellitus because they are a sign of poor glucose control. A persistently elevated FBS is linked to a higher risk of complications from diabetes.⁷

Glycated haemoglobin (HbA1c), the gold standard marker for long-term glycaemic control, gives an estimate of the average blood glucose levels over the previous 8–12 weeks. HbA1c levels correlate strongly with the risk of diabetic microvascular complications and are widely used to assess treatment efficacy. Since HbA1c is unaffected by transient variations in blood glucose levels, it is a more accurate measure of chronic hyperglycaemia than FBS.^8,9 Because changes in hemoglobin concentration or red blood cell lifetime might affect HbA1c readings, hemoglobin (Hb) is essential for interpreting HbA1c findings. It is crucial to take hemoglobin levels into account when assessing glycaemic management since conditions like anemia might have an impact on HbA1c regardless of glycaemic status.¹⁰ Previously recognized for its function in the metabolism of calcium and bone, vitamin D₃ is now more well acknowledged for its role in the metabolism of glucose. Adipose tissue, skeletal muscle, and pancreatic β-cells all contain vitamin D receptors, which may be involved in insulin sensitivity and secretion. The pathophysiology of diabetes mellitus is influenced by insulin resistance, decreased insulin secretion, and chronic inflammation, all of which have been linked to vitamin D₃ insufficiency.^11,12Low vitamin D₃ levels have been linked in a number of studies to poor glycaemic management, and hypovitaminosis D is quite common around the world, even in tropical nations. Nonetheless, there is still variation in the association between vitamin D₃ levels and glycaemic indicators as FBS and HbA1c among populations.¹³The goal of the current study was to compare the results with those of healthy controls and assess the relationship between serum vitamin D₃ levels and glycaemic markers, such as fasting blood sugar and HbA1c, in patients with diabetes mellitus.

This case-control study was carried out over a 6-month period at Government Medical College Anantnag (GMC A) and its affiliated hospital on 50 confirmed diabetic patients (both from OPD and IPD) and 50 healthy controls with institutional ethical and scientific committee approval. Patients who were willing to take part in the study gave their informed written consent. Inclusion criteria: confirmed diabetics of both the genders attending OPD and IPD of GMC A irrespective of age, ethnicity, duration and treatment of diabetes or any other comorbidities were included in the study. People who appear to be in good health and have normal glycaemic readings (controls). Exclusion criteria: Individuals suffering from malabsorption disorders, liver disease, and chronic kidney disease, Individuals using vitamin D supplements, Women who are nursing or pregnant, Individuals suffering from either acute or chronic inflammatory diseases, diabetics (type2) of either gender who refused to take part in the study, all non-diabetics and type 1 diabetics.Venous blood samples were taken aseptically following an overnight fast. Standard laboratory techniques were used to estimate the following parameters:FBS, or fasting blood sugar, HbA1c, ABG, or average blood glucose, was calculated from HbA1c and levels of serum vitamin D₃ Statistics Analysis: SPSS software was used to analyze the data. Mean ± standard deviation was used to express the results.The parameters of the cases and controls were compared using the Independent Student's t-test.The relationship between vitamin D₃ levels and glycaemic markers was evaluated using Pearson correlation analysis. Statistical significance was defined as a p-value of less than 0.05.

About 50 people with type 2 diabetes mellitus (cases) and 50 healthy people (controls) participated in the study. The following glycaemic parameters were evaluated: serum vitamin D₃ levels, HbA1c, average blood glucose (ABG), and fasting blood sugar (FBS).

Pearson Correlation Analysis (Within Groups)

Group A: With Diabetes

Serum vitamin D₃ levels and glycaemic indices in diabetes individuals were found to be negatively correlated by Pearson's correlation analysis. Comparing vitamin D₃ with HbA1c
A negative association was found, meaning that greater HbA1c values were linked to lower Vitamin D₃ levels. This suggests that those with Vitamin D deficiency had worse long-term glycaemic management. FBS and ABG vs vitamin D₃. The connection between serum vitamin D₃ and average blood glucose and fasting blood sugar was inverse, suggesting that as vitamin D₃ levels decreased, glycaemic status deteriorated.
This implies that poor glycaemic management in diabetes mellitus is significantly correlated with hypovitaminosis D.

Group B: Healthy Control

There was no discernible or robust relationship between vitamin D₃ levels and glycaemic markers in healthy controls. Regardless of vitamin D₃ levels, HbA1c, FBS, and ABG readings stayed within acceptable physiological ranges. This suggests that in those without diabetes, a vitamin D₃ deficit may not have a substantial impact on glycaemic indices.

Table 1: Study Variable Descriptive Statistics for Patients with Diabetes:

Interpretation: Glycaemic markers were high and varied widely in diabetic subjects. A high prevalence of insufficiency and inadequacy is shown by mean vitamin D₃ levels.

The descriptive data of serum vitamin D₃ levels and glycaemic parameters in diabetic patients are compiled in Table 1. The study population's mean HbA1c value of 7.62 ± 1.64% suggests less than ideal long-term glycaemic management. Both the average blood glucose (158.20 ± 62.07 mg/dL) and the mean fasting blood sugar (134.92 ± 42.61 mg/dL) showed substantial fluctuation and inadequate glycaemic regulation in diabetes patients.
With a broad standard deviation and a mean serum vitamin D₃ level of 26.42 ± 18.67 ng/mL, diabetic individuals' vitamin D₃ status varied widely, ranging from shortage to sufficiency.

Table 2: Study Variables' Descriptive Statistics in Healthy Controls:

Interpretation: Normal glycaemic parameters and relatively lower mean vitamin D₃ levels were shown by healthy controls.

The descriptive statistics for healthy controls are shown in Table 2. The controls had normal glycaemic status, as evidenced by their mean HbA1c (5.03 ± 0.50%), fasting blood sugar (87.30 ± 7.37 mg/dL), and average blood glucose (93.76 ± 11.75 mg/dL) all falling within normal physiological bounds. Although glycaemic indicators were unaltered, the mean serum Vitamin D₃ level was 14.28 ± 9.31 ng/mL, indicating that Vitamin D₃ insufficiency and inadequacy were also found in healthy persons.

Table 3: Vitamin D₃ and HbA1c, Pearson Correlation:

* Statistically significant at p < 0.05

Interpretation: In diabetes patients, there is a moderate and statistically significant link between HbA1c and vitamin D₃, whereas in healthy controls, there is no significant correlation. The Pearson connection between blood vitamin D₃ levels and HbA1c is seen in Table 3. Vitamin D₃ levels and long-term glycaemic management were shown to be connected in diabetes individuals in a substantial and statistically significant way (r = 0.497, p = 0.00024). Conversely, there was no significant link between vitamin D₃ status and HbA1c in non-diabetic persons, as seen by the weak and statistically insignificant correlation shown by healthy controls (r = −0.145, p = 0.316).

Table 4: Glycaemic Parameter Comparison of Healthy Controls and Diabetic Patients:

* Statistically significant at p < 0.05

Interpretation: Glycaemic indices were noticeably higher in diabetic patients than in healthy controls. The independent Student's t-test is used in Table 4 to compare the glycaemic parameters of diabetes patients and healthy controls. The HbA1c, fasting blood sugar, and average blood glucose levels of diabetic patients were considerably higher than those of controls (p < 0.001 for all measures). These findings clearly differentiate diabetic patients from healthy people by confirming a significant deterioration of glycaemic control in these patients.

Table 5: Serum vitamin D₃ levels in diabetic patients and healthy controls are compared:

* Statistically significant at p < 0.05

Interpretation: There was a substantial difference in serum vitamin D₃ levels between diabetic patients and healthy controls. The comparison of the two research groups' blood vitamin D₃ levels is displayed in Table 5. There was a statistically significant difference between the mean levels of Vitamin D₃ in diabetes patients and healthy controls (p = 0.00008).
 The large standard deviation suggests significant variation in vitamin D₃ status between the two groups in spite of this discrepancy.

Table 6: Diabetic Patients' Vitamin D₃ Status:

Interpretation: A high prevalence of hypovitaminosis D was indicated by the fact that over half of the diabetes individuals had vitamin D₃ deficiency.The distribution of vitamin D₃ status among individuals with diabetes is shown in Table 6. Of the patients, 52% had vitamin D₃ insufficiency and 48% had adequate levels. This research indicates that people with diabetes mellitus have a significant frequency of hypovitaminosis D, indicating that vitamin D₃ insufficiency is widespread in this community. In comparison to healthy controls, the study showed that diabetes individuals had noticeably higher glycaemic indices. Vitamin D₃ levels and HbA1c were shown to be statistically significantly correlated in diabetes patients but not in healthy people. Hypovitaminosis D is quite prevalent in diabetes mellitus, as evidenced by the fact that over half of the diabetic patients had vitamin D₃ deficiency.

The current study shows that glycaemic management in individuals with diabetes mellitus is significantly correlated with blood vitamin D₃ levels. In contrast to healthy controls, diabetic patients had noticeably higher HbA1c, fasting blood sugar, and average blood glucose levels, indicating inadequate glycaemic management.14Only diabetic individuals showed a significant association between their vitamin D₃ levels and HbA1c, indicating that vitamin D₃ status may affect glycaemic management when insulin resistance or β-cell dysfunction is present. Through a variety of processes, such as improving insulin sensitivity in peripheral tissues, modulating systemic inflammation, and enhancing insulin secretion via vitamin D receptors on pancreatic β-cells, vitamin D₃ is known to contribute to glucose homeostasis.15,16

Additionally, intracellular calcium regulation—which is necessary for insulin-mediated signal transduction—is influenced by vitamin D₃. Vitamin D₃ deficiency may consequently affect insulin production and action, which might compromise glycaemic control in diabetics.17,18

Unless there is underlying metabolic dysfunction, vitamin D₃ insufficiency alone may not change glucose metabolism, as evidenced by the lack of a significant correlation between vitamin D₃ and glycaemic indices in healthy individuals. Vitamin D insufficiency may have a contributing role in the pathogenesis of diabetes mellitus, as evidenced by the high prevalence of this condition among diabetic patients.19,20

In individuals with diabetes mellitus, the current study shows a substantial correlation between blood vitamin D₃ levels and glycaemic indices. Poor glycaemic control in this group was confirmed by the significantly higher fasting blood sugar, HbA1c, and average blood glucose levels in diabetic patients when compared to healthy controls. Patients with diabetes showed a statistically significant link between their HbA1c and vitamin D₃ levels, but healthy people showed no such correlation. Hypovitaminosis D may be associated with poor glycaemic control, as the significant frequency of vitamin D₃ insufficiency among diabetes patients indicates. Vitamin D₃ and glycaemic markers do not significantly correlate in controls, suggesting that the link only becomes clinically meaningful when metabolic dysfunction is present.

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