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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 5  |  Issue : 3  |  Page : 116-120

Vitamin D and liver enzymes' levels in Libyans with type 2 diabetes


1 Department of Genetic Engineering, Biotechnology Research Center, Tripoli, Libya
2 Department of Environment, Food, and Biological Applications, Biotechnology Research Center, Tripoli, Libya
3 Department of Biochemistry, Faculty of Medicine, University of Tripoli, Tripoli, Libya

Date of Submission18-Mar-2021
Date of Acceptance04-Aug-2021
Date of Web Publication11-Oct-2021

Correspondence Address:
Dr. Mouna Mohamed ElJilani
Department of Genetic Engineering, Biotechnology Research Center, Alfornaj, Tripoli
Libya
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ljms.ljms_18_21

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  Abstract 


Background: Many epidemiological studies reported the association of Vitamin D deficiency and abnormal liver enzymes' levels with type 2 diabetes (T2D) and their findings remain inconsistent. Aim: The study investigated the status of both Vitamin D levels and liver enzymes' activity in a Libyan population with T2D. Materials and Methods: A total of 180 individuals of both genders whose ages ranged between 25 and 62 years were enrolled. Fasting blood sugar, (FBS), Vitamin D, aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT) were measured in patients' serum. The association of both Vitamin D and liver enzymes levels with T2D was evaluated by Chi-square analyses. Results: 55.6% of the study subjects were diabetics and 44.4% were healthy controls. 100% of T2D patients had deficient Vitamin D level (<20 ng/ml) (P = 0.000). The mean Vitamin D level was higher in nondiabetics (39.1 ± 4.0) ng/ml than in T2D patients (7.4 ± 1.8) ng/ml. 98% (P = 0.068), 97% (P = 0.118), and 100% of T2D patients had normal levels of AST, ALP, and ALT enzymes, respectively. The mean AST, ALP, and ALT enzymes levels for nondiabetics were 30.3 ± 4.1, 58.7 ± 8.0, and 24.8 ± 4.9 U/L, respectively. The mean AST, ALP, and ALT enzymes levels for T2D patients were 11.3 ± 2.9, 125.0 ± 11.5, and 10.3 ± 1.7 U/L, respectively. Conclusions: Vitamin D deficiency may be related to T2D in the Libyan population, while the liver enzymes showed no significant differences between diabetics and nondiabetics.

Keywords: Libyans, liver enzymes, type 2 diabetes, Vitamin D


How to cite this article:
ElJilani MM, Alemam HA, Bashein A. Vitamin D and liver enzymes' levels in Libyans with type 2 diabetes. Libyan J Med Sci 2021;5:116-20

How to cite this URL:
ElJilani MM, Alemam HA, Bashein A. Vitamin D and liver enzymes' levels in Libyans with type 2 diabetes. Libyan J Med Sci [serial online] 2021 [cited 2021 Dec 5];5:116-20. Available from: https://www.ljmsonline.com/text.asp?2021/5/3/116/328083




  Introduction Top


Diabetes is a chronic metabolic illness characterized by elevated glucose levels resulting in serious damage to the heart, blood vessels, eyes, nerves, and kidneys. The most common is type 2 diabetes (T2D), typically in adults, which occurs when the body becomes resistant to insulin. According to the WHO, about 422 million people worldwide have diabetes, the majority living in low- and middle-income countries, and 1.6 million deaths are directly attributed to diabetes annually.[1] By 2016, the percentage of diabetic patients in Libya was 13.7%.[2]

Vitamin D plays a critical role in the regulation of glucose through effects on insulin secretion and action.[3] Ecological evidence has shown higher rates of metabolic disorders including diabetes with increasing distance from the equator, suggesting potential associations of Vitamin D insufficiency in areas with less exposure to sunlight.[4] However, recently, there was accumulating evidence to suggest that altered Vitamin D and calcium homeostasis might play a role in the development of T2D.[5] While many studies have reported a protecting association of Vitamin D and T2D, the current results are inconsistent. A previous meta-analysis of eight observational studies showed that Vitamin D intake or status was associated with decreased risk of T2D, whereas pooled analysis of seven clinical trials of Vitamin D supplementation did not display an effect on incident diabetes.[6]

On the other hand, previous studies reported that T2D is a well-known inducer for abnormal liver function tests (LFTs).[7],[8],[9] However, the markers for liver dysfunction, such as aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT), have been shown as good indicators to measure liver health and involved with insulin resistance (IR)[10] and risk of T2D.[11] Studies have been conducted worldwide to evaluate the relationship between liver enzymes and T2D and their findings were different.[12],[13] The aim of the present study was to investigate the association of both Vitamin D status and liver enzymes levels (AST, ALT, and ALP) with T2D since data for this study are so far not available in Libya.


  Materials and Methods Top


Subjects and data collection

This study was carried out in the period from September to December 2019 at public health-care centers in Tripoli, Ghadames, and Al-Zawiya in the Western region of Libya. One hundred and eighty Libyan citizens from both genders have participated, included 100 confirmed T2D patients by a self-reported history of taking of antidiabetic medications, and randomly selected 80 controls who came to centers for regular checks. Subjects (age range 25–62 years) were divided into group one (25–34 years), group two (35–44) years, group three (45–53 years), and group four (54–62 years). Each participant was informed about the study's nature, gave consent for participation, and completed a self-reported questionnaire before the study was commenced. Health-related factors including individuals' body weight and height were measured to calculate the body mass index (BMI) (which was calculated as weight in kilogram divided by height in meters squared). Education level, smoking habit, physical activity, and place of residence were among the questionnaire as well. The study was approved by the Bioethics Committee of Biotechnology Research Center, Tripoli, Libya, and conducted in accordance with the Helsinki Declaration.

Blood sample collection and laboratory measurements

Measurement of fasting blood glucose (FBG) level was conducted by collecting 5 ml of blood by venipuncture from each subject after 8 h of fasting, transferred into a tube contained no additives, and centrifuged for 15 min at 8000 rpm; afterward, the serum was transferred to a clean specimen tube and stored at −20°C until analysis. 5 ml of venous blood was withdrawn from each participant, and each sample was placed in a sterilized plain tube made of polystyrene. These tubes, with their contents of blood, were incubated in a water bath at 37°C for 15 min and afterward centrifuged for 10 min at 3000 cycles/min. The serum of each sample was obtained with a mediated micropipette, and then liver enzymes and Vitamin D levels were measured in the obtained serum. Measurement of Vitamin D was performed using ichroma™ II (Boditech Med Incorporated, Gangwon-do, Korea), which is an in vitro diagnostic device that measures the concentration of analytes, contained in blood, urine, or other samples. The levels of liver enzymes (AST, ALT, and ALP) were measured using Biolabo SAS, Maizy kit, France, and the analysis was performed according to the kit instructions using a semiautomatic biochemistry analyzer, Kenza Max BioChemistry (Biolabo Diagnostics, Kenza Biochemistry TM, France). The two applied methods were based on fluorescence immunoassay technology, which was carried out according to the manufacturer's protocol.

Definition of fasting blood glucose levels, elevated Vitamin D, and liver enzymes

T2D was defined as fasting glucose level of ≥120 mg/dL. Both FBG and liver enzymes were defined according to the accredited upper normal limits of laboratories of the health-care centers. Vitamin D deficiency was defined as a serum circulating 25(OH) D level of <20 ng/ml based on the recent Endocrine Society Clinical Practice guidelines.[14] Elevated liver enzymes were defined as one or more measurement of AST >48 U/L in men/>38U/L in women, ALT >40 U/L in men/>38 U/L in women, and ALP >140 U/L in both genders.

Statistical analysis

Descriptive analyses were performed to describe the general characteristics of the study population. Chi-squared analyses were used to assess the correlations between both Vitamin D and liver enzyme levels and serum fasting glucose levels and also to assess the correlation between health-related factors and T2D. P < 0.05 was considered statistically significant. All statistical analyses were performed using SPSS Version 22 statistical software package for Windows (SPSS Inc. Chicago, IL, USA).


  Results Top


Out of 180 patients, 80 (44.4%) were nondiabetics (43 males and 37 females) and 100 (55.6%) were T2D (50 males and 50 females). The mean age for nondiabetic subjects was 41.2 ± 7.5 years and 45.6 ± 8.5 years for T2D subjects. Thirty-five percent of the T2D group were within the age range (45–53) years and the majority of them (82%) were obese with a higher mean BMI (26.1 ± 1.9 kg/m2) than the participant of the nondiabetic category (23.3 ± 0.8 kg/m2). Seventy-nine percent of T2D patients were married and 74% of them had a diploma. However, the majority of T2D patients (63%) were nonsmokers and (84%) of them had no physical activity of any kind, and in addition, the majority of them (58%) live in Tripoli. A statistically significant association was detected in variables of age groups (P = 0.002), BMI (P = 0.000), education level (P = 0.002), smoking status (P = 0.000), and physical activity (P = 0.000). No significant difference (P ≥ 0.05) was observed in variables of gender, marital status, type of physical activity, and residency. The lifestyle and health characteristics of the study participants are displayed in [Table 1].
Table 1: Lifestyle and health characteristics of nondiabetics and diabetic patients (95% confidence interval)

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The mean glucose level was 84.9 ± 2.9 (mg/dL) for nondiabetic participants and 144.7 ± 18.4 (mg/dL) for T2D diabetic patients. Vitamin D status and liver enzymes' levels in nondiabetics and T2D patients are displayed in [Table 2]. A significant relation was detected between glucose and Vitamin D levels (P < 0.05). One hundred percent of T2D patients had deficient Vitamin D levels (<20 ng/ml). The mean Vitamin D level was higher in the nondiabetic group (9.1 ± 4.0) ng/ml than in T2D patients (7.5 ± 1.8) ng/ml. On the other hand, no significant correlation between liver enzymes and glucose levels was observed. Ninety-eight percent (P = 0.068), 97% (P = 0.118), and 100% of T2D patients had normal levels of AST, ALP, and ALT enzymes, respectively. The mean AST, ALP, and ALT enzymes' levels for nondiabetics were 30.3 ± 4.1, 58.7 ± 8.0, and 24.8 ± 4.9 U/L, respectively. The mean AST, ALP, and ALT enzymes levels for T2D patients were 11.3 ± 2.9, 125.0 ± 11.5, and 10.3 ± 1.7 U/L, respectively.
Table 2: Vitamin D and liver enzymes levels in nondiabetics and Type 2 diabetic patients (95% confidence interval)

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  Discussion Top


Deficient Vitamin D levels were obvious in T2D patients, while there were no significant differences in liver enzymes' levels between nondiabetic subjects and T2D patients. The number of literature work explaining the various functions of vitamin D along with calcium metabolism and bone integrity is increasing. According to epidemiologic studies, Vitamin D deficiency is related to the development of metabolic syndromes such as T2D due to its involvement in several important physiological pathways.[15] Vitamin D is involved in pancreatic β-cell dysfunction,[16] and IR,[17] the main underlying disorder characterizing T2D. The effect of Vitamin D on diabetes became more obvious after the detection of Vitamin D receptor in the pancreas, adipose tissue, skeletal muscle cells, and immune cells, which indicates a regulatory role of Vitamin D on glucose homeostasis. Vitamin D can directly enhance insulin synthesis and its release from pancreatic β-cells, in addition, to increase the expression of the insulin receptor in peripheral tissues. It also has an indirect antidiabetic effect by acting on the immune system cells that secrete pro-inflammatory cytokines as mediators affecting systemic inflammation contribute to IR and autoimmune-mediated destruction of pancreatic β-cells.[18] All these factors may explain the findings of this study, which agrees with a review study by Wimalawansa who stated that the majority of cross-sectional, observational, and ecological studies reported inverse correlations between Vitamin D status and hyperglycemia in T2D patients.[19] However, a cohort study based on a large survey in East China showed that T2D patients had higher levels of serum 25(OH) D than nondiabetics, which makes the relationship between Vitamin D and T2D intriguing.[20] Many observational studies support improving T2D, obesity, and metabolic syndrome with Vitamin D adequacy. Nevertheless, validation of the hypothesis that hypovitaminosis D worsens these disorders is beneficial.

Pertaining liver enzymes, high prevalence of abnormal serum AST and ALT in Chinese,[8] and Bangladeshi[9] and ALP in Bangladeshi[9] T2D patients were found. Both studies concluded that T2D has been a risk factor for abnormal LFTs and hepatic diseases, while the present study showed a negative association of AST, ALP, and ALT with T2D. Most of the previous studies analyzed ALT, AST, and GGT in T2D individuals; however, not many of them included ALP.[9] Glucose is crucial for liver function and fatty acid metabolism and vice versa.[21] Enzymes and signaling pathways involved in hepatic glucose homeostasis contribute to insulin sensitivity. Reciprocally peripheral IR and lipolysis contribute to hepatic steatosis.[22] The mechanism of T2 diabetes mellitus (T2DM) to cause liver enzymes abnormalities remains unclear. The potential hypothesis is that elevated enzymes' levels reflect an excess fat deposition in the liver, a condition termed nonalcoholic fatty liver disease (NAFLD). This NAFLD is considered to be involved with metabolic syndrome, which is related to several cardiovascular risk factors associated with IR and T2D.[23] On the other hand, a large population-based cohort study by Kälsch et al. concluded that normal liver enzymes are correlated with the severity of the metabolic syndrome. They found that transaminase levels within normal ranges were closely associated with BMI and diabetes risk, which is the main key feature of metabolic syndrome besides IR, which agrees with our findings. Kälsch et al. suggested reassessment of current normal range limits of transaminases, which was already discussed in previous studies, to provide a more exact indicator for chronic metabolic liver injury, particularly to reflect the situation in diabetics or obese individuals.[24] Liver transaminases are the main indicator for further diagnostics for liver injury in clinicians daily routine. Therefore, current normal values might miss a significant amount of individuals already developing chronic metabolic liver disease and presenting with transaminase values in the upper normal levels.[25]

We also adjusted our analyses with matched control subjects for a number of other factors including age, BMI, marital status, education level, smoking, physical activity, and location of residence. Our results showed no significant association between T2D and gender differences, which agrees with the results of the Iranian study by Rahmanian et al.[26] and disagrees with the Finnish study by Aregbesola et al. who suggested a gender difference in T2D, with an increased T2D risk in males.[27] T2D was significantly associated with age in our study, which was consistent with previous studies conducted in Bangladesh and Iran.[9],[26] Moreover, BMI is a well-known risk factor for T2D; the majority of T2D patients were obese which agreed with a study on the Swedish population,[28] while disagreeing with the Bangladeshi study.[9] T2D patients were similar to control subjects in terms of marital status, but had less education which conformed with the Iranian and Swedish studies.[26],[28] Observational studies have suggested a relation between smoking and the risk of T2D. A meta-analysis of prospective observational studies to investigate the association of smoking status with the risk of T2DM was conducted in Japan; they suggested that smoking is associated with an increased risk of T2D.[29] However, 63% of T2D patients in our study were nonsmokers, but the percentage in the nondiabetic control group was 100%. In terms of physical activity, inconsistent results were reported as well. A study on physical disability trajectories in older Americans with and without diabetes highlighted the consistently greater development of disability over time in adults with diabetes which agrees with our findings, however disagrees with Islam et al.'s finding.[9] At the level of the location of residence, previous studies also showed inconsistent findings. A study conducted in Nigeria concluded that urban residence is a risk factor for new-onset diabetes among elderlies,[30] which disagrees with the results of our study besides a Polish study which concluded that the sociodemographic differences between groups depending on the place of living did not exert a significant influence on the level of metabolic control of diabetes.[31]

The study has several limitations. First, it was a descriptive cross-sectional study with limited capacity to investigate any association relationship between Vitamin D levels and abnormal LFT's. Second, the study included only the Western region of Libya; therefore, the results may not be applicable to the eastern region of the country. Third, due to its cross-sectional design, the results may not indicate the long-term profile.


  Conclusions Top


We studied the relation of both Vitamin D and liver enzymes with T2D in a Libyan population. The essential role of Vitamin D in T2D and the inverse association of lower Vitamin D status with a higher risk of incident of the disease were found in the present study and reported in many previous observational studies. The liver enzymes showed no significant differences between subjects having T2D and nondiabetic subjects. Confirmation of a potential association of Vitamin D and liver enzymes with T2D requires specifically designed clinical studies conducted in well-defined populations to obtain proper insights into the involvement of liver enzymes and Vitamin D in T2D.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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