Beta cell function, insulin resistance and vitamin D status among type 2 diabetes patients in Western Kenya

Abstract

Serum vitamin D status exerts effects on glucose-insulin-homeostatic states underlying Diabetes-Mellitus, Type 2 (T2DM). This has been described in white and Asian population where low Vitamin D levels predicted future impairments in beta cell function and worsening of insulin resistance. This study aimed to examine the relationship between serum vitamin D, insulin resistance and beta cell function in a sub population of black Kenyan T2DM patients. The primary objective was to determine the levels of serum 25 hydroxy (25-OH) vitamin D, and estimate the insulin resistance, and beta cell function among T2DM patients at Moi Teaching and Referral Hospital (MTRH). This was a cross sectional study. 124 T2DM patients attending the MTRH Diabetes clinic between February and May 2016 were enrolled. Patients on insulin therapy and/or thiazolidinediones were excluded. Anthropometric, clinical and demographic data was obtained. Samples were drawn for estimation of serum 25-OH vitamin D, fasting insulin levels and fasting blood glucose levels. HOMA (Homeostatic model of assessment) model was used to estimate Beta cell secretion (HOMA-B) and insulin resistance (HOMA-IR); while the Disposition index {(DI) hyperbola product of insulin sensitivity (1/HOMA-IR) and beta cell secretion} was used to estimate the beta cell function. The relationships between serum vitamin D, insulin resistance and beta cell function were explored using a linear regression model. The study participants had a mean age of 56.2 (± 9.2) years, and a mean BMI of 26.9 kg/m2 (4.3). Forty nine percent (n = 61) were males. Vitamin D deficiency was present in 71.1% (n = 88) of the respondents. Relatively low levels of insulin resistance and higher levels of beta cell dysfunction were observed {median HOMA-IR of 2.3 (0.7, 6.5) and Disposition Index (DI) of 25.5 (14.3, 47.2)}. Vitamin D levels exhibited a low positive correlation with DI [r = 0.22 (95% CI: 0.03, 0.37)], but was not significantly correlated with HOMA-IR [r = 0.07(95% CI: − 0.11, 0.25)]. These results indicate that beta cell dysfunction rather than insulin resistance as the predominant defect among black T2DM patients seeking care at the MTRH diabetes clinic. Vitamin D deficiency is also prevalent among them and exhibits a low positive correlation with beta cell dysfunction. There was no correlation observed between Vitamin D deficiency and insulin resistance.

Effects of Probiotic Supplementation during Pregnancy on the Future Maternal Risk of Metabolic Syndrome

“…Chronic inflammatory reaction increases IR, disrupts the function of pancreatic β cells and insulin secretion. Vitamin D deficiency can also worsen the function of β cells in the pancreas [ 57 , 58 , 59 , 60 ].…”

Clinical, metabolic, and immunological characterisation of adult Ugandan patients with new-onset diabetes and low vitamin D status

“…Using the Leslie Kish formula (1965. Survey Sampling, New York: John Wiley and Sons, Inc.) of sample size calculation for cross-sectional studies, n = Z 2 Pq/d 2 where n = sample size, Z = 1.96, the normal value corresponding to the 95% confidence interval, d = 5% as the margin of error and a prevalence (P) of vitamin D deficiency of 71.1% in 124 adult patients with type 2 diabetes attending an outpatient diabetes clinic in Western Kenya [26], we estimated a sample size of a minimum of 316 participants.…”

“…The median (IQR) age, BMI, HbA1c, and vitamin D concentration of the participants was 48 years (39-58), 27 kg/m 2 (23-31), 11% (8)(9)(10)(11)(12)(13) or 96 mmol/mol (67-115), and 24 ng/ml (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), respectively. About 54% of the participants were females.…”

“…Vitamin D deficiency, vitamin D insufficiency, and normal vitamin D status were noted in 105 participants (32.1%), 140 participants (42.8%), and 82 participants (25.1%), respectively. Female participants had statistically lower serum vitamin D concentrations compared with male participants (23 [18][19][20][21][22][23][24][25][26][27][28][29] ng/ml vs 24 [19][20][21][22][23][24][25][26][27][28][29][30][31][32] ng/ml, p = 0.05).…”

“…Compared with those with normal vitamin D status, participants with vitamin D deficiency and insufficiency had higher circulating concentrations of interleukin (IL) 6 (29 pg/ml, 23 pg/ml vs 18 [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] pg/ ml, p = 0.01), and IL-8 (24 [86-655] pg/ml, 207 [81-853] pg/ml vs 98 [67-224], p = 0.03) (Fig. 1).…”