Decreased insulin-mediated but not non-insulin-dependent glucose disposal rates in glucose intolerance and type II diabetes in African (Ghanaian) immigrants

Maintaining cultural identity: A systematic mixed studies review of cultural influences on the self-care of African immigrants living with non-communicable disease

AIM

To understand and identify cultural factors influencing the self-care practices of African immigrants living with chronic illness in countries outside Africa.

BACKGROUND

The influence of cultural factors on self-care is relatively unexplored in African immigrants with non-communicable diseases (NCDs).

DESIGN

Systematic Mixed Studies review.

DATA SOURCES

PubMed, Psych Info, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Anthropology Plus and Sociological Abstract computerized databases. No limit was placed on publication date.

REVIEW METHODS

Results-based convergent design was used. The Mixed Method Appraisal Tool was used to evaluate the studies. Quantitative studies were synthesized narratively while qualitative studies were synthesized using thematic synthesis.

RESULTS

We identified 251 articles and nine fulfilled our inclusion criteria. The studies were published between 2006 and 2019, with six qualitative and three quantitative studies. Studies were conducted in the United States, Australia, Sweden, the Netherlands and the United Kingdom. Most studies examined the influence of culture on self-care of diabetes (n = 6), while the rest focused on hypertension (n = 3). Findings highlight that cultural norms and practices, non-Western approaches to interpreting and managing illness, cultural connotations of health behaviours and structural challenges influencing self-care. Cultural food preferences made adherence to prescribed diets challenging. Family support facilitated self-care. Maintaining cultural identity was both a driver and constraint to engaging in self-care.

CONCLUSION

The complex interplay of cultural and structural factors influences the willingness of Africans who have immigrated to a developed country to follow recommended self-care practices. Considering these cultural norms and structural barriers can help to explain the self-care behaviours of African immigrant populations.

IMPACT

Clinicians and policymakers who account for structural factors and integrate cultural factors into care facilities, treatment protocols and policy can be influential in promoting self-care in African immigrant populations.

comparative study of glucose homeostasis, lipids and lipoproteins, HDL functionality, and cardiometabolic parameters in modestly severely obese African Americans and White Americans with prediabetes: implications for the metabolic paradoxes

OBJECTIVE

To determine whether modestly severe obesity modifies glucose homeostasis, levels of cardiometabolic markers, and HDL function in African Americans (AAs) and white Americans (WAs) with prediabetes.

RESEARCH DESIGN AND METHODS

We studied 145 subjects with prediabetes (N = 61 WAs, N = 84 AAs, mean age 46.5 ± 11.2 years, mean BMI 37.8 ± 6.3 kg/m(2)). We measured fasting levels of lipids, lipoproteins, and an inflammatory marker (C-reactive protein [CRP]); HDL functionality (i.e., levels of paraoxonase 1 [PON1]); and levels of oxidized LDL, adiponectin, and interleukin-6 (IL-6). We measured serum levels of glucose, insulin, and C-peptide during an oral glucose tolerance test. Values for insulin sensitivity index (Si), glucose effectiveness index (Sg), glucose effectiveness at zero insulin (GEZI), and acute insulin response to glucose (AIRg) were derived using a frequently sampled intravenous glucose tolerance test (using MINMOD software).

RESULTS

Mean levels of fasting and incremental serum glucose, insulin, and C-peptide tended to be higher in WAs versus AAs. The mean Si was not different in WAs versus AAs (2.6 ± 2.3 vs. 2.9 ± 3.0 × 10(-4) × min(-1) [μU/mL](-1)). Mean values for AIRg and disposition index as well as Sg and GEZI were lower in WAs than AAs. WAs had higher serum triglyceride levels than AAs (116.1 ± 55.5 vs. 82.7 ± 44.2 mg/dL, P = 0.0002). Mean levels of apolipoprotein (apo) A1, HDL cholesterol, PON1, oxidized LDL, CRP, adiponectin, and IL-6 were not significantly different in obese AAs versus WAs with prediabetes.

CONCLUSIONS

Modestly severe obesity attenuated the ethnic differences in Si, but not in Sg and triglyceride levels in WAs and AAs with prediabetes. Despite the lower Si and PON1 values, AAs preserved paradoxical relationships between the Si and HDL/apoA1/triglyceride ratios. We conclude that modestly severe obesity has differential effects on the pathogenic mechanisms underlying glucose homeostasis and atherogenesis in obese AAs and WAs with prediabetes.

Cross-sectional and longitudinal changes of glucose effectiveness in relation to glucose tolerance: the insulin resistance atherosclerosis study

OBJECTIVE

Glucose effectiveness (S(G)), the capacity of glucose to enhance its own disposition, is an independent predictor of future diabetes. However, there are data on cross-sectional and longitudinal changes of S(G) and its components, basal insulin effect on S(G) (BIE) and S(G) at zero insulin (GEZI), but the natural course of S(G) has not been described in a large population.

RESEARCH DESIGN AND METHODS

S(G) was measured at baseline in 1,265 participants (aged 40-69 years) and at the 5-year examination in 827 participants in the Insulin Resistance Atherosclerosis Study (IRAS) using the frequently sampled intravenous glucose tolerance test. None of these participants were treated with glucose-lowering agents.

RESULTS

In cross-sectional analyses, S(G), BIE, and GEZI deteriorated with worsening of glucose tolerance (P < 0.001 for all three associations). In longitudinal analyses among subjects with normal glucose tolerance (NGT) at baseline, S(G), BIE, and GEZI declined in those who progressed to impaired glucose tolerance (IGT) or diabetes (P < 0.001 for all three measures). More modest longitudinal changes were demonstrated in individuals with IGT. The transition back to NGT (as opposed to no change) compared with the transition to diabetes was statistically significant for S(G) (P = 0.049) and BIE (P = 0.042) and was not a statistically significant trend for GEZI (P = 0.332). In individuals with diabetes, only BIE had a significant decline (P = 0.003).

CONCLUSIONS

S(G), BIE, and GEZI decline in subjects whose glycemic status worsens. S(G) and GEZI deteriorate more in the initial stages of the disease process.

Glucose intolerance in the West African Diaspora: a skeletal muscle fibre type distribution hypothesis

In the United States, Black Americans are largely descendants of West African slaves; they have a higher relative proportion of obesity and experience a higher prevalence of diabetes than White Americans. However, obesity rates alone cannot explain the higher prevalence of type 2 diabetes. Type 2 diabetes is characterized by insulin resistance and beta-cell dysfunction. We hypothesize that the higher prevalence of type 2 diabetes in African Americans (as compared to White Americans) is facilitated by an inherited higher percentage of skeletal muscle fibre type II and a lower percentage of skeletal muscle fibre type I. Skeletal muscle fibre type II is less oxidative and more glycolytic than skeletal muscle fibre type I. Lower oxidative capacity is associated with lower fat oxidation and a higher disposal of lipids, which are stored as muscular adipose tissue in higher amounts in Black compared to White Americans. In physically active individuals, the influence of muscle fibre composition will not be as detrimental as in physically inactive individuals. This discrepancy is caused by the plasticity in the skeletal muscle fibre characteristics towards a higher activity of oxidative enzymes as a consequence of physical activity. We suggest that a higher percentage of skeletal muscle fibre type II combined with physical inactivity has an impact on insulin sensitivity and high prevalence of type 2 diabetes in Blacks of West African ancestry.

Impaired insulin sensitivity, insulin secretion, and glucose effectiveness predict future development of impaired glucose tolerance and type 2 diabetes in pre-diabetic African Americans: implications for primary diabetes prevention

OBJECTIVE

We examined the determinants of impaired glucose tolerance (IGT) and type 2 diabetes in first-degree relatives of African-American type 2 diabetic patients over 5-8 years (median 6).

RESEARCH DESIGN AND METHODS

A total of 81 healthy subjects (age 41.5 +/- 4.8 years; BMI 31.3 +/- 3.6 kg/m(2)) participated in the study. Each subject underwent an oral glucose tolerance test (OGTT) and a frequently sampled intravenous glucose tolerance test at baseline. Insulin sensitivity index (S(i)) and glucose effectiveness index (S(g)) were determined by the minimal model method. Homeostasis model assessment (HOMA) was used to estimate insulin resistance (HOMA-IR) and beta-cell function (HOMA-%B). A total of 18 subjects progressed to either IGT or type 2 diabetes (progressors), whereas 19 subjects maintained normal glucose tolerance (nonprogressors).

RESULTS

Comparing the progressors and nonprogressors, mean fasting serum glucose levels (95 +/- 8 vs. 80 +/- 14 mg/dl, P < 0.01) and 2-h serum glucose levels (149 +/- 27 vs. 100 +/- 60 mg/dl, P < 0.01) as well as 2-h serum insulin levels (117 +/- 81 vs. 72 +/- 87 microU/ml, P < 0.01) during OGTT were higher at baseline. Mean acute first-phase insulin secretion (205 +/- 217 vs. 305 +/- 230 microU/ml), HOMA-%B (148 +/- 60 vs. 346 +/- 372, P < 01), S(i) (1.61 +/- 1.13 vs. 2.48 +/- 1.25 x 10(-4). min(-1) [microU/ml](-1)), and S(g) (1.48 +/- 0.61 vs. 2.30 +/- 0.97 x 10(-2). min(-1)) were lower in the progressors than in the nonprogressors at baseline. Mean HOMA-IR (3.31 +/- 1.64 vs. 2.36 +/- 1.64) was significantly greater in the progressors than the nonprogressors. At the time of diagnosis of glucose intolerance (IGT + diabetes), HOMA-%B (101 +/- 48 vs. 148 +/- 60, P < 0.001) and HOMA-IR (5.44 +/- 2.55 vs. 3.31 +/- 1.64, P < 0.003) deteriorated in the progressors versus baseline.

CONCLUSIONS

We conclude that nondiabetic, first-degree relatives of African-American type 2 diabetic patients who progressed to IGT and type 2 diabetes manifest triple defects (decreased insulin secretion, insulin action, and glucose effectiveness) that antecede the disease.